Method and system for handling of secondary cell group (SCG) failure in a wireless communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A user equipment (UE) receives, from a network entity, configuration information for performing conditional handover (CHO) with candidate secondary cell groups (SCGs), performs measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs, detects a SCG failure, stops the evaluation of the conditional reconfiguration for the CHO with the candidate SCGs, transmits, to the network entity, a SCG failure information message.

Description

METHOD AND SYSTEM FOR HANDLING OF SECONDARY CELL GROUP (SCG) FAILURE IN A WIRELESS COMMUNICATION SYSTEM

[0001] The disclosure generally relates to the field of wireless communication and more particularly relates to providing a method and system for handling of Secondary Cell Group (SCG) Failures when Conditional Handover (CHO) with candidate SCG(s) are configured.

[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] In a first aspect of the disclosure, provided herein is a method performed by a user equipment (UE), the method comprising: receiving, from a network entity, configuration information for performing conditional handover (CHO) with candidate secondary cell groups (SCGs); performing measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs; detecting a SCG failure; stopping the evaluation of the conditional reconfiguration for the CHO with the candidate SCGs; and transmitting, to the network entity, a SCG failure information message.

[0009] In a second aspect of the disclosure, provided herein a user equipment (UE) comprising: a transceiver; and at least one processor coupled to the transceiver, configured to: receive, from a network entity, configuration information for performing conditional handover (CHO) with candidate secondary cell groups (SCGs), perform measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs, detect a SCG failure, stop the evaluation of the conditional reconfiguration for the CHO with the candidate SCGs, transmit, to the network entity, a SCG failure information message.

[0010] The features, nature, and advantages of the disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout. Some embodiments of system and / or methods in accordance with embodiments of the subject matter are now described, by way of example only, and with reference to the accompanying Figs., in which:

[0011] Figure 1 depicts an exemplary environment 100 illustrating dual　connectivity wireless network, according to an embodiment of the disclosure;

[0012] Figure 2 depicts an exemplary environment 200 illustrating signal transmission between the UE and the network entity / Base Station with reference to various cells associated with the master and secondary node, according to an embodiment of the disclosure;

[0013] Figure 3 depicts a process flow diagram 300 illustrating the procedure adopted by the UE during the SCG failure, according to an embodiment of the disclosure;

[0014] Figure 4 depicts a block diagram 400 illustrating a system to implement the process being performed by the UE during the SCG failure, according to an embodiment of the disclosure;

[0015] Fig. 5 depicts a flowchart showing steps of a method 500 which is performed by a User Equipment (UE) during an SCG failure, according to an embodiment of the disclosure;

[0016] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the subject matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in a computer readable medium and executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0017] The following description includes information that may be useful in understanding the disclosure. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0018] Handovers in the context of main (primary) cells and secondary cells in 5G are crucial for maintaining seamless connectivity and optimizing network performance. In 5G, a user equipment (UE) can be simultaneously connected to a primary cell (PCell) and multiple secondary cells (SCells) to leverage carrier aggregation and achieve higher data rates. As the UE moves, the signal quality of these cells may fluctuate. Handovers enable the network to dynamically reassign the PCell and SCells to maintain optimal signal quality and performance. This process ensures that users experience uninterrupted service and consistent high-speed connectivity, even as they traverse areas with varying network coverage. Additionally, effective handovers may help balance the load across the network, improve spectrum efficiency, and enhance the overall user experience by minimizing disruptions and maximizing resource utilization.

[0019] However, these handovers present several drawbacks in form of higher latency, increased risk of call drops, limited flexibility with alternatives among others. To mitigate these challenges, the technique of Conditional Handover (CHO) has evolved in recent times. It may be described as an advanced mobility management feature that may pre-emptively prepare multiple potential target cells for the UE to switch to, based on specific conditions like signal quality or network performance. However, this proactive approach reduces latency and increases the likelihood of a successful handover, as the UE can quickly switch to the best available cell without waiting for a new target to be identified and prepared. Consequently, CHO enhances the reliability and efficiency of the handover process, particularly in scenarios with high mobility or fluctuating signal conditions, ensuring smoother transitions and better overall network performance for the user.

[0020] In recent times, a consensus has evolved where it has been agreed that Secondary Cell Group (SCG) failure is one of the most potent challenges associated with CHO in 5G RAN. The SCG failures in the context of CHO in 5G networks occur when the handover process to secondary cells encounters issues, leading to unsuccessful or degraded transitions. These failures may arise due to several factors, including insufficient resource allocation, poor coordination between primary and secondary cells, and unexpected interference or load changes. Additionally, the increased complexity of managing multiple pre-prepared target cells in CHO may strain network resources and signalling capabilities, exacerbating the risk of SCG failures. While CHO aims to enhance handover efficiency and reliability, SCG failures highlight the need for meticulous network planning, robust coordination mechanisms, and adaptive resource management to ensure seamless and successful handovers in a dynamic 5G environment.

[0021] There is therefore a need for a system and method to overcome the challenges associated with the existing technologies and to provide the techniques for maintaining seamless connectivity and optimizing network performance. Addressing these challenges may ensure uninterrupted service, enhanced resource utilization. It may involve improving coordination between primary and secondary cells facilitating enhanced handling of SCG failure in the UE and the network nodes during the CHO with candidate SCG.

[0022] The disclosure overcomes one or more shortcomings of the prior art and provides additional advantages. Embodiments and aspects of the disclosure described in detail herein are considered a part of the claimed disclosure.

[0023] According to an embodiment of the disclosure, a method performed by a User Equipment (UE) during an SCG (Secondary Cell Group) failure has been disclosed. The method comprises receiving configuration for performing Conditional Handover (CHO) with candidate Secondary Cell Groups (SCGs) and performing measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCG(s). Further, it comprises detecting the SCG failure and stopping the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s). After this, the method comprises transmitting a SCG failure information to the network entity.

[0024] According to an embodiment of the disclosure, the disclosed method further comprises stopping measurements for candidate PSCells configured for evaluation of CPA / CPC within the CHO with the candidate SCG(s) upon detecting the SCG Failure.

[0025] According to an embodiment of the disclosure wherein the step of stopping the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s) may be performed upon initiating a SCG failure information procedure.

[0026] According to an embodiment of the disclosure, wherein upon initiating the SCG failure information procedure, the UE may include at least one of: information about whether execution conditions for the CHO were met at the time of the SCG failure and the time elapsed between meeting of the execution conditions for the CHO wherein the execution conditions for CHO are associated with candidate SCG(s); measurement identities of the execution conditions met at the time of the SCG failure; a list of identifiers associated with the conditional reconfiguration for the CHO with the candidate SCG(s); and an associated list of the measurement identities of the conditional execution conditions met at the time of the SCG failure.

[0027] According to an embodiment of the disclosure, wherein upon initiating the SCG failure information procedure, the UE may include at least one of: measurement identifiers of SCG conditional execution conditions for the CHO with the candidate SCG(s); a list of the conditional reconfiguration for the CHO with the candidate SCG(s); and an associated list of the measurement identifiers of the SCG conditional execution conditions and time elapsed between the meeting of the SCG conditions for the CHO with the candidate SCG(s) and the SCG failure.

[0028] According to an embodiment of the disclosure, a system to enable a User Equipment (UE) implement the proposed technique during an SCG (Secondary Cell Group) failure has been disclosed. The system comprises a transceiver, a processing unit and a memory unit. The processing unit in conjunction with the transceiver and the memory unit, during an SCG failure, is configured to receive configuration for performing Conditional Handover (CHO) with candidate Secondary Cell Groups (SCGs) and perform measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCG(s). The processing unit is further configured to detect the SCG failure and subsequently stop the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s). Further, the processing unit may then be configured to transmit a SCG failure information to the network entity.

[0029] According to an embodiment of the disclosure, wherein, during an SCG failure, the processing unit in conjunction with the transceiver and the memory unit is configured to stop the measurements for candidate PSCells configured for evaluation of CPA / CPC within the CHO with the candidate SCG(s) upon detecting the SCG Failure.

[0030] According to an embodiment of the disclosure, wherein the processing unit stops the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s) upon initiating a SCG failure information procedure.

[0031] According to an embodiment of the disclosure, to initiate the SCG failure information procedure, the processing unit in conjunction with the transceiver and the memory unit, during an SCG failure, is configured to transmit at least one of: information about whether executional conditions for the CPA / CPC within the CHO met at the time of the SCG failure; measurement identities of the executional conditions met at the time of the SCG failure; a list of identifiers associated with the conditional reconfiguration for the CHO with the candidate SCG(s); and an associated list of the measurement identities of the conditional execution conditions met at the time of the SCG failure.

[0032] According to an embodiment of the disclosure, to initiate the SCG failure information procedure, the processing unit in conjunction with the transceiver and the memory unit, during an SCG failure, is configured to transmit at least one of: measurement identifiers of SCG conditional execution conditions for the CHO with the candidate SCG(s); a list of the conditional reconfiguration for the CHO with the candidate SCG(s); and an associated list of the measurement identifiers of the SCG conditional execution conditions and time elapsed between the meeting of the SCG conditions for the CHO with the candidate SCG(s) and the SCG failure.

[0033] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

[0034] The following description includes information that may be useful in understanding the disclosure. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0035] Mobility in NR: In wireless technologies like 5G Near Radio (NR), devices may move across different cells. Mobility is performed using a procedure called cell reselection in RRC_IDLE mode. Till NR R17, mobility may be performed using a procedure called handover in RRC_CONNECTED mode. Network controlled mobility applies to User Equipments (UEs) in RRC_CONNECTED. It may require explicit Radio Resource Control (RRC) signaling to be triggered by the Next Generation Node B (gNB) in NR. Handover in NR usually may consist of three steps: handover preparation, handover execution and handover completion. gNB may configure the UE to report measurements and based on the reported measurements or based on its own understanding of the network topology, gNB will send RRC Reconfiguration message to handover the UE to another cell called target cell from the source cell. UE accesses the target cell and sends RRC Reconfiguration complete message. In an alternative way introduced in 3GPP NR release 16 known as Conditional Handover (CHO), gNB may configure the UE with the execution conditions for triggering handover and once the execution conditions are fulfilled, the UE may move to the target cell and may send the RRC Reconfiguration complete.

[0036] Dual Connectivity: Dual connectivity, or more technically multi-radio dual connectivity is specified by 3GPP in specifications such as TS 37.340. A summary of the details on dual connectivity and measurement gap operations with dual connectivity are given below. Next-Generation Radio Access Network (NG-RAN) supports Multi-Radio Dual Connectivity (MR-DC) operation whereby a UE in RRC_CONNECTED is configured to utilize radio resources provided by two distinct schedulers, located in two different NG-RAN nodes connected via a non-ideal backhaul, one providing New Radio (NR) access and the other one providing either Evolved UMTS Terrestrial Radio Access (E-UTRA) or NR access. One node may act as the Master Node (MN) and the other as the Secondary Node (SN). The MN and SN are connected via a network interface and at least the MN is connected to the core network. NG-RAN supports NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), in which a UE may be connected to one NG-eNB (a E-UTRA base station that can connect to 5G core) that acts as a MN and one gNB (5G base station) that acts as a SN. NG-RAN also supports NR-E-UTRA Dual Connectivity (NE-DC), in which a UE is connected to one gNB that acts as a MN and one NG-eNB that acts as a SN.

[0037] PSCell change and PSCell Addition: Primary Secondary Cell (PSCell) change may occur due to mobility and may or may not be associated with the Secondary Node change (SN change). The SN change procedure is initiated either by MN or SN and is used to transfer a UE context from a source SN to a target SN and to change the SCG configuration in UE from one SN to another. Further, a Conditional PSCell Change (CPC) may be defined as a PSCell change that is executed by the UE when execution condition(s) is met. The UE starts evaluating the execution condition(s) upon receiving the CPC configuration and stops evaluating the execution condition(s) once PSCell change is triggered. Intra-SN CPC without MN involvement, inter-SN CPC initiated either by MN or SN are supported. The following principles may apply to CPC:

[0038] ㆍ The CPC configuration contains the configuration of CPC candidate PSCell(s) and execution condition(s) and may contain the MN configuration for inter-SN CPC.

[0039] ㆍ An execution condition may consist of one or two trigger condition(s) (CPC events A3 / A5, as defined in TS 38.331). Only single reference signal (RS) type is supported and at most two different trigger quantities (e.g., RSRP and RSRQ, RSRP and SINR, etc.) can be configured simultaneously for the evaluation of CPC execution condition of a single candidate PSCell.

[0040] ㆍ Before any CPC execution condition is fulfilled, upon reception of PSCell change command or PCell change command, the UE executes the PSCell change procedure as described in clause 10.3 and 10.5 or the PCell change procedure as described in clause 9.2.3.2 in TS 38.300 or clause 10.1.2.1 in TS 36.300, regardless of any previously received CPC configuration. Upon the successful completion of PSCell change procedure or PCell change procedure, the UE releases all stored CPC configurations.

[0041] ㆍ While executing CPC, the UE is not required to continue evaluating the execution condition of other candidate PSCell(s).

[0042] ㆍ Once the CPC procedure is executed successfully, the UE releases all stored CPC configurations.

[0043] ㆍ Upon the release of SCG, the UE releases the stored CPC configurations.

[0044] ㆍ MN adds PSCell during a PSCell addition procedure. A PSCell addition procedure that is executed only when PSCell addition condition(s) are met is called Conditional PSCell Addition (CPA).

[0045] About the SCG Failure and MCG Failure: The following SCG failure cases may occur in NR (based on TS 37.340)

[0046] ㆍ SCG Radio Link Failure (RLF);

[0047] ㆍ SCG beam failure while the SCG is deactivated;

[0048] ㆍ SN addition / change failure;

[0049] ㆍ For EN-DC, NGEN-DC and NR-DC, SCG configuration failure or CPC configuration failure (only for messages on Signaling Radio Bearer 3 (SRB3));

[0050] ㆍ For EN-DC, NGEN-DC and NR-DC, SCG RRC integrity check failure (on SRB3);

[0051] ㆍ For EN-DC, NGEN-DC and NR-DC, consistent uplink (UL) Listen Before Talk (LBT) failure on PSCell;

[0052] ㆍ For Integrated access and backhaul- Mobile Termination (IAB-MT), reception of a Backhaul (BH) RLF indication from SCG;

[0053] ㆍ CPA / CPC execution failure.

[0054] UE may send SCGFailureInformation to report SCG failures to MN. The purpose of this procedure is to inform MN about an SCG failure the UE has experienced i.e. SCG radio link failure, failure of SCG reconfiguration with sync, SCG configuration failure for RRC message on SRB3, SCG integrity check failure, and consistent uplink LBT failures on PSCell for operation with shared spectrum channel access.

[0055] UE behaviour during SCG Failure has been described in 3GPP specification. In NR, this is captured in specifications such as TS 38.331 and TS 37.340 as given below.

[0056] In TS 37.340: In all SCG failure cases, the UE maintains the current measurement configurations from both the MN and the SN and the UE continues measurements based on configuration from the MN and the SN if possible. The SN measurements configured to be routed via the MN will continue to be reported after the SCG failure. NOTE 2: UE may not continue measurements based on configuration from the SN after SCG failure in certain cases (e.g. UE cannot maintain the timing of PSCell). In case of CPA / CPC, upon transmission of the SCGFailureInformation message to the MN, the UE stops evaluating the CPA / CPC execution condition. The UE is not required to continue measurements for candidate PSCell(s) for execution condition upon transmission of the SCGFailureInformation message to the MN.

[0057] TS 38.331: In 5.7.3b.2 section, where upon initiating the procedure, the UE may:

[0058] ㆍ if the procedure was not initiated due to beam failure of the PSCell while the SCG is deactivated:

[0059] ∨ suspend SCG transmission for all SRBs, Data Radio Bearers (DRBs) and, if any, BH Radio Link Control (RLC) channels;

[0060] ∨ reset SCG MAC;

[0061] ㆍ stop T304 for the SCG, if running;

[0062] ㆍ stop conditional reconfiguration evaluation for CPC or CPA, if configured;

[0063] ㆍ if the UE is in (NG)EN-DC:

[0064] ∨ initiate transmission of the SCGFailureInformationNR message as specified in TS 36.331, clause 5.6.13a.

[0065] CHO with candidate SCG(s): In traditional wireless systems, networks cannot configure SCG candidate cells within a CHO configuration. This causes considerable delays for the addition and change of PSCells, which adversely affects the UE performance in dual connectivity scenarios. Hence 3GPP is introducing CHO including target MCG and candidate SCGs in NR release 18. CHO including target MCG and candidate SCGs is a handover procedure in NR-DC scenario that is executed only when execution condition(s) of candidate PCells and execution condition(s) of PSCells are met. This procedure may be also called CHO with candidate SCG(s). For CHO with candidate SCG(s), the network may also configure the UE with one or more candidate target PCells in the conditional reconfiguration and each candidate target PCell is associated with one or more candidate PSCells. The UE starts to evaluate the condition of each candidate target PCell and the condition of each associated candidate PSCell upon reception of the conditional reconfiguration. When one of the target PCells fulfils associated PCell execution condition, and one of its associated candidate PSCells fulfils the associated PSCell execution condition, the UE applies the conditional reconfiguration of the corresponding target PCell and the corresponding candidate PSCell. The network provides the configuration parameters for the target PCell and its associated candidate PSCells in the ConditionalReconfiguration IE. If there are multiple candidate PSCells associated with one candidate target PCell, the NW can provide multiple conditional configurations for the same candidate target PCell, i.e., each one contains one MCG configuration (for the same candidate target PCell) and one SCG configuration (for different candidate PSCell).

[0066] An example specification of the configuration of CHO with candidate SCG(s) are given below: CondReconfigToAddModList

[0067] The IE CondReconfigToAddModList concerns a list of conditional reconfigurations to add or modify, with for each entry the condReconfigId and the associated condExecutionCond / condExecutionCondSCG / condExecutionCondPSCell and condRRCReconfig.

[0068]

[0069]

[0070]

[0071] Hence there exists a need for the handling of SCG Failure in the UE and the network nodes such as gNB when the conditional handover with candidate SCG is configured.

[0072] The information disclosed in this overview section of the disclosure section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

[0073] The foregoing has broadly outlined the features and technical advantages of the disclosure in order that the detailed description of the disclosure that follows may be better understood. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the disclosure.

[0074] The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the disclosure.

[0075] In the realm of 5G networks, handovers are pivotal for maintaining seamless connectivity and optimizing network performance as users move. While traditional handover methods are essential, they can be prone to drawbacks such as latency and increased risk of call drops. To mitigate these challenges, Conditional Handover (CHO) has emerged as an advanced mobility management technique. CHO proactively prepares multiple potential target cells based on specific conditions like signal quality or network performance metrics. This proactive approach significantly reduces latency by enabling quicker transitions to the best available cell without waiting for new targets to be identified and prepared. It aims to enhance the reliability and efficiency of handover processes, particularly in scenarios with high mobility or fluctuating signal conditions. In several deployments, CHO may be implemented with associated Secondary Cell Groups (SCG), and such CHO may be referred to as CHO with candidate SCG(s). Despite its benefits, implementing CHO can introduce complexities when it is configured with SCG, with SCG failures representing a significant challenge. Effectively addressing these challenges demands meticulous network planning, robust coordination mechanisms, and adaptive resource management strategies to ensure seamless and successful handovers in dynamic 5G environments, thereby optimizing user experience and network reliability.

[0076] In order to overcome the above-mentioned challenges, the disclosure provides a method and system for managing Secondary Cell Group (SCG) failures in 5G networks, involving a network entity and UE. The UE may comprise an Input / Output (I / O) unit for user interaction, a transceiver for communication, a memory unit for storing data, a processing unit for task execution, and a fault detection unit for identifying failures. The process may begin with the UE receiving configuration information for CHO with candidate SCG(s) from the network entity. The UE may then perform measurements and evaluations on candidate PCells and associated candidate SCGs, assessing factors like signal strength, quality, beam measurements, and resource availability, in a non-limiting exemplary scenario. If the fault detection unit of the UE identifies an SCG failure, its processing unit may halt the evaluation and initiate an SCG failure information procedure. This procedure may involve two scenarios: in the first, the UE may transmit information on whether CHO conditions were met at failure, elapsed time since these conditions were met, and related measurement identities. In the second, the UE may provide information about measurement identifiers for CHO conditions, conditional reconfiguration parameters, and elapsed time between condition fulfillment and failure detection in the transmitted information. In either of the two scenarios, this information may be then transmitted to the network entity along with the SCG failure information. The disclosed procedure may thus aim to enhance mobility, reliability, and network performance by enabling the UE to adapt quickly to SCG failures, minimizing disruptions and maintaining stable connections.

[0077] In an embodiment of the disclosure, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0078] While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the disclosure.

[0079] The terms "comprise", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device, or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a device or system or apparatus proceeded by "comprises쪋 a" does not, without more constraints, preclude the existence of other elements or additional elements in the device or system or apparatus.

[0080] The terms "an embodiment", "embodiment", "embodiments", "the embodiment", "the embodiments", "one or more embodiments", "some embodiments", and "one embodiment" mean "one or more (but not all) embodiments of the invention(s)" unless expressly specified otherwise.

[0081] The terms "including", "comprising", "having" and variations thereof mean "including but not limited to" unless expressly specified otherwise.

[0082] The terms "network entity", "network", "gNB" and "base station" have been used interchangeably in the disclosure.

[0083] The terms "master node", "main node" and "MN" have been used interchangeably in the disclosure.

[0084] The terms "secondary node" and "SN" have been used interchangeably in the disclosure.

[0085] The terms "Primary Cell" and "PCell" have been used interchangeably in the disclosure.

[0086] The terms "secondary cell" and "SCell" have been used interchangeably in the disclosure.

[0087] The terms "primary secondary cell" and "PSCell" have been used interchangeably in the disclosure.

[0088] Figure 1 depicts an exemplary environment 100 illustrating dual　connectivity wireless network, according to an embodiment of the disclosure. Dual Connectivity (DC) in 5G may refer to a technology where a device, such as a smartphone or other user equipment (UE), may simultaneously connect to and utilize resources from two different types of cell towers or nodes within the network. In this, one node may act as the primary connection (Master Node, MN), typically providing access to the core network, while the other node (Secondary Node, SN) may be used to supplement this connection, thus enhancing data speeds and reliability. This setup may enable seamless switching between nodes based on network conditions, optimizing performance in terms of speed, coverage, and overall user experience by ensuring continuous and efficient data transmission. In the Fig. 1, the Master node (102), the Secondary node (104) and the UE (106) have been illustrated. The detailed configuration and working of these have been explained in the upcoming paragraphs.

[0089] The Master Node (102) is the primary network node that the UE (106) may initially connect to. It may manage the primary control functions and ensure connectivity to the core network. It may provide the main connection to the 5G core network, handling the primary signaling and data transmission. It may further coordinate with the Secondary node (104) to enhance overall network performance. In an exemplary non-limiting scenario, like NR Dual Connectivity both MN and SN may be gNBs. In another exemplary non-limiting scenario, like in NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), the MN may be a NG-eNB (Next Generation E-UTRA Node B), which may support LTE connectivity and interface with the 5G core network. Alternatively, in NR-E-UTRA Dual Connectivity (NE-DC), the MN might be a gNB (5G New Radio Base Station) that provides 5G NR access.

[0090] The Secondary Node (104), on the other hand, is an additional network node that the UE (106) may connect to alongside the MN (102). It may provide supplementary radio resources to boost connectivity and performance. The SN (104) may also work with the MN (102) to offer enhanced data throughput, coverage, and reliability by sharing the load of data transmission and providing additional capacity. In an exemplary non-limiting scenario, in NGEN-DC, the SN (104) might be a gNB providing 5G NR access, while in NE-DC, it might be an ng-eNB supporting LTE connectivity.

[0091] The UE (106), such as a smartphone or any 5G-enabled device, may maintain connections to both MN (102) and SN (104) simultaneously. This may allow the UE (106) to benefit from enhanced data rates, improved coverage, and better network reliability. The dual connectivity setup may therefore dynamically allocate resources between MN (102) and SN (104) based on network conditions, ensuring optimal performance and seamless handovers. In summary, Dual Connectivity (DC) with Multi-Radio Dual Connectivity (MR-DC) in 5G networks may optimize user experience by leveraging the strengths of multiple network nodes simultaneously. It may thereby enhance data speeds, coverage, and reliability by dynamically utilizing resources from two 5G NR networks or both LTE and 5G NR networks, ensuring seamless connectivity and improved performance for UEs across various network conditions. A further elaborative explanation of the master node and secondary node has been provided in the upcoming paragraphs of this disclosure in conjunction with the Fig. 2.

[0092] Fig. 2 depicts an exemplary environment 200 illustrating signal transmission between the UE and the network entity / Base Station with reference to various cells associated with the master and secondary node, according to an embodiment of the disclosure. In this, the master node (202) has been illustrated to have a Master Cell Group (MCG) which comprises non-limiting exemplary cells (208, 210) whereas the secondary node (204) has been illustrated to have a Secondary Cell Group (SCG) which may comprise multiple exemplary cells (212, 214). Both these cell groups i.e., MCG and SCG have been established in connection with the UE (206). As discussed, the MCG may consist of the PCell (Primary Cell, 208) and potentially multiple SCells (Secondary Cells, 210), all managed by the Master Node (202). The MCG may manage the UE's (206) primary connection through the PCell (208) and facilitate optimized performance by adding SCells (210) as and when needed. The MN (202), on the other hand, may further coordinate with the SN (204) to manage dual connectivity, ensuring that the UE (206) may benefit from the combined resources of both the nodes.

[0093] To further elaborate on the components of the MCG, the PCell (208) may be the primary cell in the MCG to which the UE (206) is connected. It may handle the primary control signaling and serve as the anchor point for the UE's (206) connection to the network. Further, within the MCG, the PCell (208) may be responsible for maintaining the UE's (206) connection, managing radio resource control (RRC) signaling, and facilitating the initial attachment to the network. In one of the non-limiting embodiments, even in the scenarios involving carrier aggregation, it is the PCell (208) which may coordinate the use of additional carriers (SCells) to enhance data throughput. The SCell (210), in turn, may be an additional cell in the MCG that the UE (206) may connect to for supplementary radio resources. SCells (210) may be used to boost data rates and improve overall network performance through carrier aggregation, provide extra capacity and enhance the UE's data transmission capabilities by utilizing multiple frequency bands and may further help balance network traffic and reduce congestion. Whereas in the SCG of the secondary node (204), the Primary Secondary Cell (PSCell, 212) is the main cell within the SCG that the UE (206) may connect to when utilizing resources from the secondary node (204). The PSCell (212) may act as the primary cell within the SCG, thus facilitating the management of the connection to the SN (202) and providing essential control signaling for the secondary connection. In another non-limiting embodiment, it may further handle the control plane communication specific to the SCG, including configuration updates and mobility management within the SCG and may be therefore considered central to the management of additional resources provided by the SN (204), facilitating enhanced data throughput and connectivity. The Secondary Cell (SCell, 214), on the other hand, may be regarded as any additional cell within the SCG that provides supplementary radio resources. SCells (214) may work alongside the PSCell (212) to enhance the UE's (206) overall performance through carrier aggregation. They tend to offer advantageous effects by facilitating supplementary resources, carrier aggregation and load balancing.

[0094] By utilizing the master node (202) and secondary node (204), the UE (206) may be configured with a secondary cell group, with primary cell as PSCell (212). This process may be termed as PSCell addition, in one of the non-limiting scenarios, in the context of 5G dual connectivity. PSCell addition may be referred to the process of adding the PSCell (212) to the UE (206) connection. In other words, the PSCell addition may be termed as the process of configuring a new PSCell (212) for the UE (206) within the SN (204) to improve connectivity and resource allocation. In one of the non-limiting exemplary scenarios, the process of PSCell addition may be summarized in the upcoming paragraphs.

[0095] First, the network may continuously monitor the UE's (206) signal quality, data requirements, and mobility. If it detects that the additional resources are needed or a better PSCell is available, it may trigger the PSCell addition process. The decision to add a PSCell is typically made by the MN (202), which may coordinate with the SN (204) to identify the optimal PSCell (212) for the UE (206). The SN (204) may then configure the identified PSCell (212) for the UE (206). This may involve setting up the necessary radio parameters and ensuring that the cell may be able to handle the additional load. The UE (206) may then be informed about the new PSCell (212) through control signaling which, in turn, may update its configuration to connect to the new PSCell (212) while maintaining its connection with the MN (202). The UE (206) may then activate the connection with the new PSCell (212), allowing it to start utilizing the additional radio resources provided by the SN (204). To ensure effective functioning of the PSCell (212) within the SN (204), the technique of PSCell change has evolved which refers to the process of switching the PSCell (212) within the SN (204) that the UE (206) is connected to. This change may be necessary to maintain optimal connectivity and performance as the UE (206) moves or as network conditions fluctuate by ensuring that the UE (206) remains connected to the most suitable cell in terms of signal quality and resource availability within the SN (204). In one of the non-limiting exemplary scenarios, the process of PSCell change may be summarized in the upcoming paragraphs.

[0096] Firstly, the network may be configured to continuously monitor the UE's (206) signal quality, data throughput, and mobility patterns. If the current PSCell's (212) performance degrades or if a better PSCell is available, the network (typically the MN (202) in coordination with the SN (204)) may decide to initiate a PSCell change. The new PSCell may be configured and prepared for the UE, ensuring it is able to handle the additional load and provide the necessary quality of service. The UE (206) may be then notified of the change through control signaling, and it may subsequently update its configuration to connect to the new PSCell. The UE (206) may therefore switch its connection to the new PSCell, ensuring continued optimal performance and connectivity.

[0097] In an embodiment of the disclosure, the process of PSCell change may be achieved by facilitating the technique of Conditional PSCell change (CPC). In this scenario, the CPC may be defined as a mobility management strategy aimed at improving the efficiency and reliability of cell transitions within the SCG associated with the secondary node (204). CPC may operate by preemptively preparing alternative PSCells (212) based on predefined criteria. These criteria, in one of the non-limiting scenarios, may comprise signal quality thresholds or network performance metrics among others. This proactive approach may therefore allow the network entity to swiftly switch the UE (206) to a better-performing PSCell when the current one no longer meets the specified conditions. By reducing the latency associated with handovers and ensuring seamless connectivity, CPC may facilitate enhancing overall network performance, minimizing service disruptions, and optimizing resource utilization thereby providing users with a more consistent and reliable experience. On the similar lines, the process of PSCell addition may be achieved by facilitating the technique of Conditional PSCell addition (CPA) which may be defined as procedure that may be executed only when PSCell addition condition(s) are met.

[0098] To further enhance the efficiency and effectivity of the outcome being achieved by implementing the CPC technique, it may be integrated with the process of Conditional Handover (CHO) popularly used in 5G. In essence, it may be said that the conditional handover with candidate SCG may enhance the mobility management capabilities of 5G networks by anticipating and preparing for handovers based on real-time network conditions and user requirements, ultimately delivering a seamless and reliable connectivity experience. Further, by integrating CHO with CPC, the network may prepare both target SCGs and alternative PSCells simultaneously. This comprehensive approach may ensure that the UE (206) is always connected to the best possible cell configuration, whether it involves switching between SCGs or within a single SCG. The combination of CHO and CPC also enhances handover efficiency by addressing both inter-SCG and intra-SCG mobility scenarios, thereby providing seamless connectivity transitions and improving overall network performance. It may therefore be inferred that together, CHO and CPC contribute to a superior user experience by minimizing disruptions, reducing latency, and optimizing network resources based on real-time conditions and user mobility patterns.

[0099] Despite implementing CHO and CPC, SCG failures may still occur due to several challenges inherent in 5G networks. Resource allocation issues, such as insufficient resources in the target SCGs or dynamic fluctuations in network load, may lead to failed transitions. Additionally, unexpected interference from neighboring cells or external sources and signal propagation issues, like physical obstructions or varying user speeds, may further degrade signal quality, complicating the handover process. Coordination challenges between the MN (202) and SN (204) also play a role. Effective CHO and CPC require seamless cooperation between these nodes, and any lapses may ultimately result in SCG failures. These factors highlight the complexity of maintaining robust connectivity in a dynamic and high-demand 5G environment. As these SCG failures are inevitable, it becomes important for the UE (206) to send SCG failure information to the MN (202) in 5G networks to ensure optimal connectivity and service quality. Reporting SCG failures, such as radio link failures, reconfiguration issues, and integrity check failures, may allow the MN (202) to take immediate corrective actions to restore and maintain the UE's (206) connection, thereby minimizing service disruptions. This information may further help the MN (202) manage handovers more effectively, ensuring smooth transitions between cells or SCGs. Additionally, it may also enable the MN (202) to diagnose and address the root causes of failures, optimize resource allocation, and balance network load, ultimately enhancing the network's reliability and performance. The detailed procedure of reporting the SCG failure by the UE (206) has been explained in the forthcoming paragraphs in conjunction with Fig. 3 of the disclosure.

[0100] In yet another words, the foregoing paragraphs may also be summarized as follows. In an embodiment of the disclosure, during SCG Failure, a User Equipment (UE) that is configured for Conditional Handover (CHO) with candidate SCG(s), may stop conditional reconfiguration evaluation for CHO with candidate SCG(s). During SCG failure Information procedure (for e.g., as described in section 5.7.3 in NR TS 38.331), UE may stop the evaluation of conditional reconfiguration for CHO with candidate SCG(s). This may be performed during the initiation of SCGFailureInformation procedure. This would prevent an unnecessary mobility towards the PCell while the intended SCG is not available and would also help to recover the SCG link quickly through the present serving PCell.

[0101] In view of the extract presented in the overview from TS 38.331, the UE which is configured for the CHO with candidate SCG(s), may stop conditional reconfiguration evaluation for CPA or CPC for the candidate target PSCells which are associated with the candidate PCells in the conditional reconfiguration upon SCGFailure. Alternatively, the UE may stop performing measurements for the candidate PSCells configured for evaluation of CHO with candidate SCG(s) upon SCGFailure. Alternately, UE may continue performing measurements for the candidate PSCells configured for evaluation of CHO with candidate SCG(s) upon SCGFailure.

[0102] In an embodiment of the disclosure, UE may continue performing measurements for the candidate PCells configured for evaluation of CHO with candidate SCG(s) upon SCGFailure. Alternately, UE may stop performing measurements for the candidate PCells configured for evaluation of CHO with candidate SCG(s) upon SCGFailure. Whereas upon SCGFailure, a UE which is configured for the CHO with candidate SCG(s) may inform the network whether conditions for CHO to which one or more of CPA / CPC are associated, were fulfilled at the time of the SCG Failure. If event(s) associated to all measId(s) within conditional execution condition for the PCell were fulfilled at the time of SCG Failure, UE may inform the network that the conditions for CHO were fulfilled at the time of SCG Failure. This information may be provided to the network in NR RRC SCGFailureInformation message.

[0103] Fig. 3 depicts a process flow diagram 300 illustrating the procedure adopted by the UE during the SCG failure, according to an embodiment of the disclosure. In this, a network entity (302) and UE (304) have been illustrated such that the UE (304) may receive (306) the configuration information for performing CHO with candidate SCGs from the network entity (302). In an embodiment of the disclosure, the configuration information may be sent from the network entity (302) to the UE (304) to prepare the UE (304) for potential transitions, enhancing mobility, reliability, network performance, and user experience. It may further facilitate preemptive preparation i.e., by providing the UE (304) with detailed configuration information in advance, the network entity (302) may ensure that the UE (304) is ready to switch to the best available SCG as soon as specific conditions are met, minimizing handover latency and disruption. In an embodiment of the disclosure, this configuration information may comprise the following:

[0104] ㆍ Target Cells Information: It may comprise details about potential Secondary Cell Groups (SCGs) that the UE may switch to, including cell identifiers and connection parameters. It may further include information about the prioritization of candidate SCGs and specific conditions (e.g., signal quality thresholds, load conditions) that must be met for initiating the handover.

[0105] ㆍ Timing and Synchronization: It may comprise timing information to ensure seamless transition without service interruption. It may further include information about data needed to maintain synchronization with the new SCG, crucial for maintaining data integrity and connection stability.

[0106] ㆍ Security Parameters: It may comprise security-related information to ensure that the connection remains secure during and after the handover.

[0107] ㆍ Resource Allocation: It may comprise information about the specific radio resources allocated for the target SCGs, ensuring that the UE can effectively utilize the available spectrum. It may further include QoS parameters to ensure that the UE maintains the required service levels during and after the handover.

[0108] ㆍ Failure Handling Procedures: It may comprise instructions on what actions to take if the handover to a candidate SCG fails, ensuring that the UE can quickly recover and maintain service.

[0109] As and when the configuration information for performing the CHO with the candidate SCGs is received by the UE (304), it may begin executing (308) measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs. In an embodiment of the disclosure, these measurements and evaluations may include:

[0110] ㆍ Signal Strength and Quality Measurements:

[0111] ∨ Reference Signal Received Power (RSRP) for measuring the power level of received signals.

[0112] ∨ Reference Signal Received Quality (RSRQ) for evaluating the quality of received signals.

[0113] ∨ Signal-to-Interference-plus-Noise Ratio (SINR) for assessing the signal quality relative to interference and noise.

[0114] ㆍ Timing and Synchronization:

[0115] ∨ Timing Advance (TA) for measuring the time delay between the UE and the base station to ensure synchronization.

[0116] ∨ Synchronization Signal Block (SSB) Timing for evaluating the timing accuracy of synchronization signals.

[0117] ㆍ Beam Measurements:

[0118] ∨ Beam Reference Signal (BRS) Measurements for assessing the quality and strength of beamforming signals, particularly relevant for high-frequency bands.

[0119] ㆍ Resource Availability and Load Conditions:

[0120] ∨ Resource Block Utilization for monitoring the availability of resource blocks in candidate SCGs.

[0121] ∨ Load Balancing Metrics for evaluating the current load on candidate SCGs to ensure they can handle additional connections.

[0122] ㆍ Quality of Service (QoS) Parameters:

[0123] ∨ Latency and Throughput for measuring the expected latency and data throughput for candidate SCGs.

[0124] ∨ Packet Loss and Jitter for monitoring the stability and reliability of the connection.

[0125] In an embodiment of the disclosure, by continuously evaluating these parameters, the UE (304) may detect (310) early signs of potential SCG failures, such as degrading signal quality, resource shortages, or synchronization issues. This proactive approach may therefore allow the network to take corrective actions promptly, thereby enhancing the reliability and robustness of the handover process and minimizing disruptions to the user's service. Once the SCG failure is detected by the UE (304) then it may stop (312) the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s). In an embodiment of the disclosure, when the evaluation of conditional reconfiguration is stopped / halted after the detection of an SCG failure in a 5G network, it may serve several critical purposes. First and foremost, stopping the evaluation may allow immediate attention to be directed towards stabilizing the connection and recovering from the failure. This prioritization is therefore essential to prevent further network instability and to ensure that resources are efficiently allocated towards resolving the issue at hand. By ceasing the evaluation process, the network entity (302) and the UE (304) may focus on diagnosing the root cause of the SCG failure accurately. This focused approach may aid in determining the exact conditions and factors leading to the failure, facilitating effective troubleshooting and preventive measures to mitigate future occurrences. Additionally, stopping the evaluation may also help in avoiding potentially redundant or ineffective reconfiguration attempts, ensuring that subsequent actions are based on a clear understanding of the current network state. In an embodiment of the disclosure, the stopping of the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s) may be performed upon initiating a SCG failure information procedure. In an embodiment of the disclosure, once the SCG failure is detected, the UE (304) may be prompted to initiate the SCG failure information procedure. This procedure is crucial for informing the network entity (302) (typically the Master Node) about the specific details surrounding the SCG failure, facilitating rapid response and resolution. In an embodiment of the disclosure, the UE (304) may further stop the measurements for candidate PScells configured for evaluation of CPA / CPC within the CHO with the candidate SCG(s) upon detecting the SCG failure. This would help the UE in saving the power and other resources such as processing and memory as the measurements couldn't be used for evaluation. This SCG failure information procedure may comprise of two scenarios, out of which any one is execute at a given time.

[0126] First Scenario: The UE (304), upon stopping of the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s) and stopping the measurements for candidate PScells configured for evaluation of CPA / CPC within the CHO with the candidate SCG(s) may comprise information about at least one of the following in the transmitted (314) SCG failure information to the network entity (302): executing conditions for the CHO i.e., information regarding whether pre-determined execution conditions for Conditional Handover (CHO) were met at the time of the SCG failure. It may further comprise information about the time elapsed which may comprise of the duration between when the execution conditions for CHO were met and when the SCG failure occurred. The transmitted (314) SCG failure information may further comprise measurement identities which may comprise of the identifiers associated with the measurements performed under the pre-determined execution conditions. It may also include a list of identifiers linked to the conditional reconfiguration for CHO with candidate SCGs and the corresponding measurement identities of the pre-determined conditional execution conditions met at the time of the SCG failure.

[0127] Second Scenario: The UE (304), upon stopping of the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s) may comprise information about at least one of the following in the transmitted (314) SCG failure information to the network entity (302): Measurement Identifier which may comprise identifiers specifically related to the SCG conditional execution conditions for CHO with candidate SCGs. It may further comprise a list detailing the conditional reconfiguration parameters for CHO with candidate SCGs and the measurement identities linked to the SCG conditional execution conditions and the time elapsed between meeting these conditions and the detection of the SCG failure.

[0128] Both the scenarios aim to assist the network entity (302) in diagnosing the cause of SCG failures more precisely. They provide crucial data points such as timing of condition fulfilment, specific measurements taken, and configuration details, which aid in troubleshooting and implementing corrective actions swiftly, the difference just lies in the kind of information that may be included by the UE (302) such that in first scenario, the UE (302) may provide at least one of the following comprehensive details such as whether the execution conditions for CHO were met, associated measurement identities, and lists of identifiers and conditions related to conditional reconfiguration. Whereas in the second scenario, the UE (302) may provide at least one of the following comprehensive details such as measurement identifiers related to SCG conditional execution conditions, along with lists detailing conditional reconfiguration parameters and associated measurement identities.

[0129] After stopping the evaluation by the UE (304), the SCG failure information may be transmitted (314) to the network entity (302) by the UE (304). The system to implement the process described in the foregoing paragraphs have been explained in the upcoming paragraphs in conjunction with Fig. 4 of the disclosure.

[0130] The disclosure of the foregoing paragraphs may be further elaborated as follows with the exemplary scenario where a single bit of information such as a flag or an enumerated may be used to inform the network that the conditions for CHO were fulfilled at the time of the SCG Failure. In an embodiment of the disclosure, UE may include the identifier of conditional reconfiguration (such as condReconfigId-r16) corresponding to the CHO condition whose conditions are fulfilled in SCGFailureInformation when conditions for CHO to which one or more of CPA / CPC are associated, were fulfilled at the time of the SCG failure. In an embodiment of the disclosure, UE may include the list of conditional reconfiguration identifiers (such as list of condReconfigId-r16) corresponding to the CHO conditions whose conditions are fulfilled in SCGFailureInformation when conditions for CHO to which one or more of CPA / CPC are associated, were fulfilled at the time of the SCG Failure.

[0131] In an embodiment of the disclosure, upon SCGFailure, a UE which is configured for the CHO with candidate SCG(s) and if the conditions for CHO to which one or more of CPA / CPC are associated is fulfilled, stores and reports the time elapsed between the fulfilment of the conditions for CHO and the SCG Failure. In an embodiment of the disclosure, a UE which is configured for the CHO with candidate SCG(s) and if all the conditions for CHO to which one or more of CPA / CPC are associated are fulfilled, UE may report the time elapsed between the fulfilment of all the conditions in condExecutionCond-r16 and the SCG Failure in SCGFailureInformation message. These additional information would help the network to identify the impacts on the MCG mobility due to SCGFailure.

[0132] Further, if some of the conditions for CHO to which one or more of CPA / CPC are associated were fulfilled at the time of the SCG Failure, UE may include measurement identities of the conditional execution conditions (such as condExecutionCond-r16) which were fulfilled in the SCGFailureInformation message. In an embodiment of the disclosure, if some of the conditions for CHO to which one or more of CPA / CPC are associated were fulfilled at the time of the SCG Failure, UE may include the list of conditional reconfiguration identifiers (such as list of condReconfigId-r16 in the background) and the associated list of measurement identities of the conditional execution conditions (condExecutionCond-r16) which were fulfilled in the SCGFailureInformation message. Furthermore, the list of conditional reconfiguration identifiers may be reported in the order of time. In an embodiment of the disclosure, the first conditional reconfiguration identifier in the list will be the first conditional reconfiguration whose condExecutionCond is fulfilled, the second conditional reconfiguration identifier in the list will be the second conditional reconfiguration whose condExecutionCond is fulfilled, the third conditional reconfiguration identifier in the list will be the third conditional reconfiguration whose condExecutionCond is fulfilled etc. i.e. they are arranged in the chronological order with the oldest entry first and the newest entry last. In an embodiment of the disclosure, the first conditional reconfiguration identifier in the list will be the last conditional reconfiguration whose condExecutionCond is fulfilled, the second conditional reconfiguration identifier in the list will be the second last conditional reconfiguration whose condExecutionCond is fulfilled, the third conditional reconfiguration identifier in the list will be the third conditional reconfiguration whose condExecutionCond is fulfilled etc. i.e. they are arranged in the chronological order with the newest entry first and oldest entry last.

[0133] In an embodiment of the disclosure, the list of conditional reconfiguration identifiers may be reported in the order of time such that the first measurement identity in the list may be the first measurement identity whose condExecutionCond is fulfilled, the second measurement identity in the list may be the second measurement identity whose condExecutionCond is fulfilled, the third measurement identity in the list may be the third measurement identity whose condExecutionCond is fulfilled etc. i.e., they are arranged in the chronological order with the oldest entry first and the newest entry last. In an embodiment of the disclosure, the first measurement identity in the list may be the last measurement identity whose condExecutionCond is fulfilled, the second measurement identity in the list may be the second last measurement identity whose condExecutionCond is fulfilled, the third measurement identity in the list may be the third measurement identity whose condExecutionCond is fulfilled etc. i.e. they are arranged in the chronological order with the newest entry first and oldest entry last.

[0134] In an embodiment of the disclosure, if some of the conditions for CPA / CPC which are associated with CHO conditions were fulfilled at the time of the SCG Failure, UE may inform the network the measurement identifiers of the SCG conditional execution conditions (condExecutionCondSCG-r17) which were fulfilled, in the SCGFailureInformation message. Further, if some of the conditions for CPA / CPC which are associated with CHO conditions were fulfilled at the time of the SCG Failure, UE may include the list of conditional reconfiguration identifiers (such as list of condReconfigId-r16 in the background) and the associated list of measurement identifiers of the SCG conditional execution conditions (condExecutionCondSCG-r17) which were fulfilled in the SCGFailureInformation message. Furthermore, the list of conditional reconfiguration identifiers may be reported in the order of time. In an embodiment of the disclosure, the first conditional reconfiguration identifier in the list may be the first conditional reconfiguration whose condExecutionCondSCG is fulfilled, the second conditional reconfiguration identifier in the list may be the second conditional reconfiguration whose condExecutionCondSCG is fulfilled, the third conditional reconfiguration identifier in the list may be the third conditional reconfiguration whose condExecutionCondSCG is fulfilled etc. i.e., they are arranged in the chronological order with the oldest entry first and the newest entry last. In an embodiment of the disclosure, the first conditional reconfiguration identifier in the list may be the last conditional reconfiguration whose condExecutionCondSCG is fulfilled, the second conditional reconfiguration identifier in the list may be the second last conditional reconfiguration whose condExecutionCondSCG is fulfilled, the third conditional reconfiguration identifier in the list may be the third conditional reconfiguration whose condExecutionCondSCG is fulfilled etc. i.e. they are arranged in the chronological order with the newest entry first and oldest entry last.

[0135] In an embodiment of the disclosure, a UE which is configured for the CHO with candidate SCG(s) and if one of the conditions for CHO to which one or more of CPA / CPC are associated are fulfilled, UE may report the time elapsed between the fulfilment of the fulfilled condition in condExecutionCond-r16 and the SCG Failure in SCGFailureInformation message. Some of the above embodiments may be represented as below in 3GPP TS 38.331.

[0136]

[0137]

[0138] Fig. 4 depicts a block diagram 400 illustrating a system to implement the process being performed by the UE during the SCG failure, according to an embodiment of the disclosure. It comprises a network entity (402), a user equipment (UE, 404). The UE (404) may further comprise an I / O unit (406), a transceiver (408), a memory unit (410), a processing unit (412) and a fault detection unit (414). In this, the I / O unit (406) may be configured to facilitate interaction between the UE (404) and the network entity (402) or any other external devices. In an embodiment of the disclosure, the I / O unit (406) may include components like display screens, keyboards, touchpads, and interfaces for connecting peripherals, allowing users to interact with applications and services offered by the UE (404). The transceiver (408) may be configured to receive signals from nearby base stations / network entity (402) and transmit signals back, establishing and maintaining communication links with the network. In an embodiment of the disclosure, the transceiver (408) may be configured to receive configuration for performing CHO with SCGs which in a non-limiting exemplary scenario may include target cell information, timing and synchronization information, security parameters, failure handling procedures among others. The configuration information received by the transceiver (408) may be stored by the memory unit (410). The memory unit (410) in conjunction with the processing unit (412) may be further configured to execute measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs which in a non-limiting exemplary scenario may include signal strength and quality measurements, beam measurements, resource availability among others. Once the measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs is executed, then the processing unit (412) in conjunction with the fault detection unit (414) may be configured to detect the SCG failure based on the executed measurements and evaluation. In an embodiment of the disclosure, during the SCG failure, the processing unit (412) in conjunction with the transceiver (408) and the memory unit (410) is configured to stop the execution of the measurements for candidate PSCells configured for evaluation of CPA / CPC within the CHO with the candidate SCG(s) upon detecting the SCG failure. Subsequent to detection of the SCG failure, the processing unit (412) may be further configured to stop the evaluation of the conditional reconfiguration for the CHO with the candidate SCGs, wherein the stopping the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s) is performed upon initiating a SCG failure information procedure. This SCG failure information procedure may comprise of two scenarios, out of which any one is execute at a given time.

[0139] First Scenario: The processing unit (412) in conjunction with the memory unit (410) and the transceiver (408), upon stopping of the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s), may be configured to transmit at least one of the following information to the network entity (402): executing conditions for the CHO i.e., information regarding whether pre-determined execution conditions for Conditional Handover (CHO) were met at the time of the SCG failure. It may further comprise information about the time elapsed which may comprise of the duration between when the execution conditions for CHO were met and when the SCG failure occurred. The transmitted SCG failure information may further comprise measurement identities which may comprise of the identifiers associated with the measurements performed under the pre-determined execution conditions. It may also include a list of identifiers linked to the conditional reconfiguration for CHO with candidate SCGs and the corresponding measurement identities of the pre-determined conditional execution conditions met at the time of the SCG failure.

[0140] Second Scenario: The processing unit (412) in conjunction with the memory unit (410) and the transceiver (408), upon stopping of the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s), may be configured to transmit at least one of the following information to the network entity (402): Measurement Identifier which may comprise identifiers specifically related to the SCG conditional execution conditions for CHO with candidate SCGs. It may further comprise a list detailing the conditional reconfiguration parameters for CHO with candidate SCGs and the measurement identities linked to the SCG conditional execution conditions and the time elapsed between meeting these conditions and the detection of the SCG failure.

[0141] Once the evaluation of the conditional reconfiguration for the CHO with the candidate SCGs is stopped then the processing unit (412) in conjunction with the transceiver (408) may be configured to transmit the SCG failure information to the network entity (402).

[0142] Fig. 5 depicts a flowchart showing steps of a method 500 which is performed by a User Equipment (UE) during an SCG failure, according to an embodiment of the disclosure. The method 500 may also be described in the general context of computer executable instructions. Generally, computer executable instructions may include routines, programs, objects, components, data structures, procedures, modules, and functions, which perform specific functions or implement specific abstract data types.

[0143] The order in which the method 500 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the spirit and scope of the subject matter described.

[0144] At step 502, the method 500 may include receiving configuration for performing CHO with candidate SCGs. In an embodiment of the disclosure, the received configuration information may comprise target cell information, timing and synchronization information, security parameters, failure handling procedures, among others. In an embodiment of the disclosure, the transceiver in conjunction with the memory unit may be configured to receive configuration for performing CHO with candidate SCGs.

[0145] At step 504, the method 500 may include executing measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs. In an embodiment of the disclosure, to execute measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs which in a non-limiting exemplary scenario may include signal strength and quality measurements, beam measurements, resource availability, among others. In an embodiment of the disclosure, the processing unit in conjunction with the memory unit may be configured to execute measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs.

[0146] At step 506, the method 500 may include detecting the SCG failure. In an embodiment of the disclosure, the processing unit in conjunction with the fault detection unit may be configured to detect the SCG failure.

[0147] At step 508, the method 500 may include stopping the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s). In an embodiment of the disclosure, the stopping of the evaluation of the conditional reconfiguration for the CHO with the candidate SCG(s) may be performed upon initiating the SCG failure information procedure. In an embodiment of the disclosure, the processing unit in conjunction with the memory unit may be configured to stop the evaluation of the conditional reconfiguration for the CHO with the candidate SCG.

[0148] In an embodiment of the disclosure, after detecting the SCG failure, the method 500 may include stopping measurements for candidate PSCells configured for evaluation of CPA / CPC within the CHO with the candidate SCG(s) upon detecting the SCG Failure. In an embodiment of the disclosure, the processing unit in conjunction with the memory unit may be configured to stop the measurements for candidate PSCells configured for evaluation of CPA / CPC within the CHO with the candidate SCG(s) upon detecting the SCG Failure.

[0149] At step 510, the method 500 may include transmitting the SCG failure information to the network entity. In an embodiment of the disclosure, the processing unit in conjunction with the transceiver may be configured to transmit the SCG failure information to the network entity.

[0150] According to an embodiment of the disclosure, a method performed by a user equipment (UE) comprises stopping the measurements for candidate primary second cells (PSCells) for execution condition upon transmission of the SCG failure information message.

[0151] According to an embodiment of the disclosure, a method performed by a user equipment (UE) comprises transmitting, to the network entity, information whether conditions for the CHO are fulfilled at time of the SCG failure, wherein the information whether the conditions for CHO are fulfilled at the time of the SCG failure is included in the SCG failure information message.

[0152] According to an embodiment of the disclosure, wherein the configuration information comprises information associated with execution condition that needs to be fulfilled in order to trigger execution of the conditional reconfiguration for the CHO.

[0153] According to an embodiment of the disclosure, wherein the SCG failure information message comprises information regarding elapsed time associated with the SCG failure.

[0154] According to an embodiment of the disclosure, wherein in case that conditions for the CHO are fulfilled at time of the SCG failure, the SCG failure information message comprises an identifier of the conditional reconfiguration corresponding to CHO condition fulfilled.

[0155] According to an embodiment of the disclosure, wherein in case that the conditions for the CHO are fulfilled at time of the SCG failure, the SCG failure information message comprises a list of conditional reconfiguration identifiers corresponding to CHO condition fulfilled, and wherein the list of the conditional reconfiguration identifiers is reported in order of time.

[0156] According to an embodiment of the disclosure, a method performed by a user equipment (UE) comprises upon the SCG failure, performing the measurements for candidate PSCells configured for evaluation of Conditional PSCell Addition / Conditional PSCell Change (CPA / CPC) within the CHO with the candidate SCGs.

[0157] According to an embodiment of the disclosure, wherein the at least one processor is further configured to: stop the measurements for candidate primary second cells (PSCells) for execution condition upon transmission of the SCG failure information message.

[0158] According to an embodiment of the disclosure, wherein the at least one processor is further configured to: transmit, to the network entity, information whether conditions for the CHO are fulfilled at time of the SCG failure, wherein the information whether the conditions for CHO are fulfilled at the time of the SCG failure is included in the SCG failure information message.

[0159] According to an embodiment of the disclosure, wherein the configuration information comprises information associated with execution condition that needs to be fulfilled in order to trigger execution of the conditional reconfiguration for the CHO.

[0160] According to an embodiment of the disclosure, wherein the SCG failure information message comprises information regarding elapsed time associated with the SCG failure.

[0161] According to an embodiment of the disclosure, wherein in case that conditions for the CHO are fulfilled at time of the SCG failure, the SCG failure information message comprises an identifier of the conditional reconfiguration corresponding to CHO condition fulfilled.

[0162] According to an embodiment of the disclosure, wherein in case that the conditions for the CHO are fulfilled at time of the SCG failure, the SCG failure information message comprises a list of conditional reconfiguration identifiers corresponding to CHO condition fulfilled, and wherein the list of the conditional reconfiguration identifiers is reported in order of time.

[0163] The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0164] Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Further, any skilled person in the art would appreciate that the reconstruction error mentioned in the foregoing paragraphs may be considered as a value that overshoots the determined threshold value and must not be construed as an error as such.

[0165] Furthermore, one or more computer-readable storage media may be utilized in implementing embodiments consistent with the disclosure. A computer-readable storage medium refers to any type of physical memory on which information or data readable by a processor may be stored. Thus, a computer-readable storage medium may store instructions for execution by one or more processors, including instructions for causing the processor(s) to perform steps or stages consistent with the embodiments described herein. The term "computer- readable medium" should be understood to include tangible items and exclude carrier waves and transient signals, i.e., are non-transitory. Examples include random access memory (RAM), read-only memory (ROM), volatile memory, non-volatile memory, hard drives, CD ROMs, DVDs, flash drives, disks, and any other known physical storage media.

[0166] Suitable processors include, by way of example, a general-purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a graphic processing unit (GPU), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and / or a state machine.

[0167] Advantages of the embodiment of the disclosure are illustrated herein-

[0168] In an embodiment of the disclosure, the disclosure provides techniques of continuously evaluating various parameters thus enabling the UE to detect early signs of potential SCG failures. This proactive approach may enable the network to take corrective actions promptly, enhancing the overall reliability and robustness of the handover process. This pre-emptive preparation thus facilitates the swift transition of the UE to the best available SCG, reducing handover latency and minimizing service disruptions.

[0169] In an embodiment of the disclosure, the disclosure provides techniques for efficient resource utilization as the disclosure proposes the process of stopping the evaluation of conditional reconfiguration upon detecting an SCG failure thus preventing redundant or ineffective reconfiguration attempts. This may thus ensure that UE power, memory, computational resources and network resources are efficiently allocated towards resolving issues and maintaining stable connections.

[0170] In an embodiment of the disclosure, the disclosure provides technique for accurate SCG failure diagnostics by providing for a detailed SCG failure information procedure, which may also include transmitting specific data about measurement identifiers, elapsed time, and conditional reconfiguration parameters, which may eventually help the network entity diagnose the cause of SCG failures more precisely. This may therefore facilitate effective troubleshooting and implementation of corrective actions.

[0171] In an embodiment of the disclosure, the disclosure provides techniques for enhanced scalability by providing a detailed framework for SCG failure detection and response, the disclosed procedure may scale to accommodate increasing numbers of UEs and more complex network topologies. This scalability may be crucial for supporting the growing demand for 5G services.

[0172] In an embodiment of the disclosure, the disclosure provides techniques for enhanced Quality of Service (QoS) by ensuring that the UE maintains required service levels, such as latency, throughput, packet loss, and jitter, during and after the handover. This guarantees that high-priority services and applications continue to perform optimally. It may also provide seamless user experience by managing SCG failures effectively thus contributing to a seamless user experience as it facilitates stable and reliable connections, even in the presence of network changes and potential failures. This reliability is a key factor in user satisfaction with 5G services.

[0173] In an embodiment of the disclosure, the disclosure provides techniques for continuous improvement as it facilitates the process for providing a detailed feedback mechanism by the SCG failure information procedure thus enabling continuous improvement of the network. By analysing the transmitted failure data, network operators may also identify patterns and implement preventive measures to enhance future network performance.

Claims

1.A method performed by a User Equipment (UE), the method comprising:receiving, from a network entity, configuration information for performing conditional handover (CHO) with candidate secondary cell groups (SCGs);performing measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs;detecting a SCG failure;stopping the evaluation of the conditional reconfiguration for the CHO with the candidate SCGs; andtransmitting, to the network entity, a SCG failure information.2.The method of claim 1, further comprising:stopping the measurements for candidate primary second cells (PSCells) for execution condition upon transmission of the SCG failure information message.3.The method of claim 1, further comprising:transmitting, to the network entity, information whether conditions for the CHO are fulfilled at time of the SCG failure,wherein the information whether the conditions for CHO are fulfilled at the time of the SCG failure is included in the SCG failure information message.4.The method of claim 1, wherein the configuration information comprises information associated with execution condition that needs to be fulfilled in order to trigger execution of the conditional reconfiguration for the CHO.5.The method of claim 1, wherein the SCG failure information message comprises information regarding elapsed time associated with the SCG failure.6.The method of claim 1, wherein in case that conditions for the CHO are fulfilled at time of the SCG failure, the SCG failure information message comprises an identifier of the conditional reconfiguration corresponding to CHO condition fulfilled.7.The method of claim 1, wherein in case that the conditions for the CHO are fulfilled at time of the SCG failure, the SCG failure information message comprises a list of conditional reconfiguration identifiers corresponding to CHO condition fulfilled, andwherein the list of the conditional reconfiguration identifiers is reported in order of time.8.The method of claim 1, further comprising:upon the SCG failure, performing the measurements for candidate PSCells configured for evaluation of Conditional PSCell Addition / Conditional PSCell Change (CPA / CPC) within the CHO with the candidate SCGs.9.A user equipment (UE) comprising:a transceiver; andat least one processor coupled to the transceiver, configured to:receive, from a network entity, configuration information for performing conditional handover (CHO) with candidate secondary cell groups (SCGs),perform measurements and evaluation of conditional reconfiguration for the CHO with the candidate SCGs,detect a SCG failure,stop the evaluation of the conditional reconfiguration for the CHO with the candidate SCGs,transmit, to the network entity, a SCG failure information message.10.The UE of claim 9, wherein the at least one processor is further configured to:stop the measurements for candidate primary second cells (PSCells) for execution condition upon transmission of the SCG failure information message.11.The UE of claim 9, wherein the at least one processor is further configured to:transmit, to the network entity, information whether conditions for the CHO are fulfilled at time of the SCG failure,wherein the information whether the conditions for CHO are fulfilled at the time of the SCG failure is included in the SCG failure information message.12.The UE of claim 9, wherein the configuration information comprises information associated with execution condition that needs to be fulfilled in order to trigger execution of the conditional reconfiguration for the CHO.13.The UE of claim 9, wherein the SCG failure information message comprises information regarding elapsed time associated with the SCG failure.14.The UE of claim 9, wherein in case that conditions for the CHO are fulfilled at time of the SCG failure, the SCG failure information message comprises an identifier of the conditional reconfiguration corresponding to CHO condition fulfilled.15.The UE of claim 11, wherein in case that the conditions for the CHO are fulfilled at time of the SCG failure, the SCG failure information message comprises a list of conditional reconfiguration identifiers corresponding to CHO condition fulfilled, andwherein the list of the conditional reconfiguration identifiers is reported in order of time.

Images