Method and apparatus for supporting a subsequent conditional pscell addition and change (CPAC) in a communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The present disclosure relates to methods and User Equipment (UE) for supporting subsequent Conditional PSCell Addition and Change (CPAC). The method comprises receiving an Radio Resource Control (RRC) message comprising of release list for second set of conditional execution conditions for subsequent CPAC by the UE from network entity. The release list includes a list of conditional reconfiguration identifiers and execution conditions associated with them. The method comprises of determining that the conditional reconfiguration identifier is not part of current UE configuration by UE. The method comprises of executing RRC procedure corresponding to the RRC message by the UE. The method comprises of sending an RRC complete message indicating the completion of RRC procedure by the UE to the network entity. The method for supporting subsequent CPAC also comprises of receiving a subsequent CPAC configuration towards a subsequent target PSCell, executing subsequent CPAC and reporting information related to the subsequent CPAC.

Description

METHOD AND APPARATUS FOR SUPPORTING A SUBSEQUENT CONDITIONAL PSCELL ADDITION AND CHANGE (CPAC) IN A COMMUNICATION SYSTEM

[0001] The present disclosure generally relates to telecommunication networks. More particularly, the present disclosure relates to a method for supporting subsequent conditional PScell addition and change (CPAC) and a user equipment (UE), thereof.

[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.

[0008] Aspects of the disclosure are to address at least the above-mentioned problems and / or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide a method and apparatus for supporting a subsequent conditional primary secondary cell (PSCell) addition and change (CPAC) in a communication system.

[0009] Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

[0010] In an embodiment, the present disclosure discloses a method of handling Lower-Layer Triggered Mobility (LTM) candidate configurations. The method comprises receiving a plurality of LTM candidate configurations from a network apparatus. Each LTM candidate configuration of the plurality of LTM candidate configurations is associated with corresponding first identifier. Further, the method comprises receiving an LTM cell switch command from the network apparatus to switch to a cell. The LTM cell switch command includes a second identifier. Furthermore, the method comprises generating a third identifier by incrementing the second identifier by one. Thereafter, the method comprises executing LTM cell switch by applying a LTM candidate configuration from the plurality of LTM candidate configurations, associated with a first identifier that is equal to the third identifier.

[0011] In an embodiment, the present disclosure discloses a method of handling LTM candidate configurations. The method comprises receiving a plurality of LTM candidate configurations from a network apparatus. Further, the method comprises identifying whether the plurality of LTM candidate configurations include configurations for releasing a Secondary Cell Group (SCG). Furthermore, the method comprises determining whether the SCG is configured in a current cell camped on by the UE based on a current configuration of the UE. Thereafter, the method comprises transmitting a reconfiguration complete message, when the SCG is not configured in the current cell.

[0012] In an embodiment, the present disclosure discloses a User Equipment (UE) for handling LTM candidate configurations. The UE comprises a processor and a memory. The processor is configured to receive a plurality of LTM candidate configurations from a network apparatus. Each LTM candidate configuration of the plurality of LTM candidate configurations is associated with corresponding first identifier. Further, the processor is configured to receive an LTM cell switch command from the network apparatus to switch to a cell. The LTM cell switch command includes a second identifier. Furthermore, the processor is configured to generate a third identifier by incrementing the second identifier by one. Thereafter, the processor is configured to execute LTM cell switch by applying a LTM candidate configuration from the plurality of LTM candidate configurations, associated with a first identifier that is equal to the third identifier.

[0013] In an embodiment, the present disclosure discloses a UE for handling LTM candidate configurations. The UE comprises a processor and a memory. The processor is configured to receive a plurality of LTM candidate configurations from a network apparatus. Further, the processor is configured to identify whether the plurality of LTM candidate configurations include configurations for releasing a Secondary Cell Group (SCG). Furthermore, the processor is configured to determine whether the SCG is configured in a current cell camped on by the UE based on a current configuration of the UE. Thereafter, the processor is configured to transmit a reconfiguration complete message, when the SCG is not configured in the current cell.

[0014] In an embodiment, the present disclosure discloses a network apparatus. The network apparatus comprises a processor, a memory, and a communication interface. The processor is configured to transmit a plurality of LTM candidate configurations to a UE. Each LTM candidate configuration is associated with corresponding first identifier. Further, the network apparatus is configured to transmit an LTM cell switch command to the UE. The LTM cell switch command is transmitted to switch to a cell including a second identifier with a value that is equal to a first identifier decremented by one.

[0015] In an embodiment, the present disclosure discloses a method for supporting subsequent Conditional PSCell Addition and Change (CPAC). The method comprises receiving an Radio Resource Control (RRC) message comprising of a release list for a second set of conditional execution conditions for subsequent CPAC. The release list includes a list of conditional reconfiguration identifiers and the execution conditions associated with them. The method further comprises determining, by the UE, that the conditional reconfiguration identifier is not part of a current UE configuration. The method further comprises executing RRC procedure corresponding to the RRC message. The method further comprises sending an RRC complete message indicating the completion of RRC procedure.

[0016] In an embodiment, the present disclosure discloses a method for supporting subsequent CPAC. The method comprises of receiving a subsequent CPAC configuration towards a subsequent target PSCell. The method further comprises executing subsequent CPAC. The method further comprises reporting information related to the subsequent CPAC. The information related to the subsequent CPAC is logged at the network entity.

[0017] In an embodiment, the present disclosure discloses a User Equipment (UE) for supporting subsequent CPAC. The UE comprises a processor and a memory. The processor is configured to receive an Radio Resource Control (RRC) message comprising of a release list for a second set of conditional execution conditions for subsequent CPAC. The release list includes a list of conditional reconfiguration identifiers and the execution conditions associated with them. The UE is configured to determine that the conditional reconfiguration identifier is not part of a current UE configuration. The UE is further configured to execute RRC procedure corresponding to the RRC message. The UE is further configured send to the network entity, an RRC complete message indicating the completion of RRC procedure.

[0018] In an embodiment, the present disclosure discloses a User Equipment (UE) for supporting subsequent CPAC. The UE comprises a processor and a memory. The processor is configured to receive a subsequent CPAC configuration towards a subsequent target PSCell. The UE is configured to execute subsequent CPAC. The UE is further configured to report information related to the subsequent CPAC. The information related to the subsequent CPAC is logged at the network entity.

[0019] Advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

[0020] For more enhanced communication system, there is a need for method and apparatus for supporting a subsequent conditional prminary secondary cell (PSCell) additaion and change (CPAC) in a communication system.

[0021] The novel features and characteristics of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

[0022] Figure 1 illustrates an exemplary environment for handling Lower-Layer Triggered Mobility (LTM) candidate configurations, in accordance with some embodiments of the present disclosure;

[0023] Figure 2 illustrates a detailed diagram of a User Equipment (UE), in accordance with some embodiments of the present disclosure;

[0024] Figure 3 shows an exemplary flow diagrams for handling LTM candidate configurations, in accordance with some embodiments of the present disclosure;

[0025] Figure 4 shows an exemplary flow diagrams for handling LTM candidate configurations, in accordance with some embodiments of the present disclosure;

[0026] Figure 5 shows an exemplary flow diagrams for handling LTM candidate configurations, in accordance with some embodiments of the present disclosure;

[0027] Figure 6 illustrates a diagram of a network apparatus, in accordance with some embodiments of the present disclosure;

[0028] Figure 7 shows an exemplary flow diagram for handling LTM candidate configurations, in accordance with some embodiments of the present disclosure;

[0029] Figure 8 shows exemplary flow charts illustrating method steps for handling LTM candidate configurations, in accordance with some embodiments of the present disclosure;

[0030] Figure 9 shows exemplary flow charts illustrating method steps for handling LTM candidate configurations, in accordance with some embodiments of the present disclosure;

[0031] Figure 10 shows a block diagram of a general-purpose computing system for handling LTM candidate configurations, in accordance with embodiments of the present disclosure;

[0032] Figure 11 shows a representation of a Fifth Generation (5G) system architecture in a non-roaming case, using reference point representation showing how various network functions interact with each other as per conventional systems;

[0033] Figure 12 illustrates a flow representation of signalling procedure for LTM;

[0034] Figure 13a depicts a flow representation of a process of handling ltm-Candidate ToAddModList at UE Radio Resource Control (RRC);

[0035] Figure 13b shows a representation of handling absence of SSB periodicity in LTM SSB candidate configuration;

[0036] Figure 13c is a representation of LTM cell switch trigger upon cell selection performed while T311 is running;

[0037] Figure 13d is a representation of handling RRCBearerRelease;

[0038] Figure 13e is a representation of handling LTM cell switch command reception according to one of the embodiments enclosed;

[0039] Figure 14 illustrates an exemplary environment for supporting subsequent Conditional PSCell Addition and Change (CPAC), in accordance with the embodiments of the present disclosure;

[0040] Figure 15 illustrates a detailed block diagram of the UE configured to support subsequent CPAC, in accordance with some embodiments of the present disclosure;

[0041] Figure 16 illustrates flow diagram 1600 of a method for supporting subsequent CPAC, in accordance with some embodiments of the present disclosure;

[0042] Figure 17 illustrates flow diagram of a method for supporting subsequent CPAC, in accordance with some embodiments of the present disclosure;

[0043] Figure 18 illustrates a diagram of a network entity, in accordance with some embodiments of the present disclosure;

[0044] Figure 19 shows exemplary flow charts illustrating method steps for supporting subsequent CPAC, in accordance with some embodiments of the present disclosure;

[0045] Figure 20 shows exemplary flow charts illustrating method steps for supporting subsequent CPAC, in accordance with some embodiments of the present disclosure;

[0046] Figure 21 shows a block diagram of a general-purpose computing system for supporting subsequent CPAC, in accordance with embodiments of the present disclosure;

[0047] Figure 22 illustrates a procedure for releasing conditional execution conditions for subsequent CPAC in accordance with the embodiments of the present disclosure; and

[0048] Figure 23 illustrates a procedure for SCG Failure Information and subsequent CPAC in accordance with the embodiments of the present disclosure.

[0049] It should be appreciated by those skilled in the art that any block diagram herein represents conceptual views of illustrative systems embodying the principles of the present 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 computer readable medium and executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0050] In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0051] 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 alternatives falling within the scope of the disclosure.

[0052] The terms "comprises", "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 system or apparatus proceeded by "comprises ... a" does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.

[0053] Lower-layer Triggered mobility (LTM) or L1 / L2 based mobility introduced in Release 18 of Third Generation Partnership Project (3GPP) enables a serving cell change via L1 / L2 signalling, while maintaining configuration of upper layers and / or minimizing changes of configuration of the lower layers.

[0054] For LTM, the gNB communicates a candidate identifier to a User Equipment (UE) in a Media Access Layer (MAC) Control Element (CE). Only three bits are allocated by 3GPP to communicate the candidate identifier. Thus, if the index of the LTM candidate cell if communicated in the MAC CE, the base station can configure only 7 candidate cells, even though the index is 1...8, which is not optimal. In the conventional systems, the UE receives the MAC CE containing the candidate identifier configured by the RRC, and the UE directly applies the received identifier. Hence, the configuration is limited to 7 candidate cells.

[0055] For Dual Connectivity (DC), during LTM cell switch, a Master Node (MN) may release a Secondary Cell Group (SCG). In conventional systems, a UE fails RRCReconfiguration procedure and initiates RRCReestablishment, when it receives SCG release when SCG is not configured. Hence, the network needs to reconfigure the subsequent LTM configuration every time after an LTM cell switch, which is not optimal.

[0056] Typically, the LTM configurations received by the UE from the network contains configuration for LTM measurements and reporting, and target configurations. In existing systems, it is not defined when the UE applies each of these configurations.

[0057] A security context is established in Fifth Generation (5G) networks where a security key is generated and stored in both the UE and the network. In the traditional handover procedures, the UE generates or changes a security key whenever there is handover from one cell another cell, based on a "masterkeyUpdate" configured by the network. The configuration of the "masterkeyUpdate" is not defined for the LTM candidate configurations.

[0058] The present disclosure discloses methods, a User Equipment (UE), and a network apparatus for handling LTM candidate configurations. In the present disclosure, when the UE receives LTM candidate cell identifier as N in an LTM cell switch command MAC CE from the network, the UE executes LTM cell switch for LTM candidate N+1. Hence, the claimed invention ensures that UE MAC and UE RRC are synchronised with respect to the value range used for LTM cell switch execution. Thus, the base station can configure for all N candidate cell, thereby ensuring network optimization.

[0059] In the present disclosure, when the UE receives configurations for SCG release, and SCG is not configured in the UE, the UE doesn't consider it as erroneous. Rather, the UE transmits a reconfiguration complete message to the network. Hence, the claimed invention provides a simple method for SCG release during LTM cell switch. In the present disclosure, UE applies a part of LTM configuration at the time of reception of the configuration from the network and a part at the time of LTM cell switch. Hence, the claimed invention defines methods for when to apply which part of the LTM configuration. The claimed invention enables reduction of signalling overhead as a part of the configuration can be stored and applied. In the claimed invention, the network updates a field for configuring "masterKeyUpdate" as optional in a RRC reconfiguration message. The network avoids configuring "masterKeyUpdate" in the LTM candidate configuration. Hence, the claimed invention ensures that security configurations provided by the network is as expected by the UE.

[0060] A handover mechanism is a process in mobile communication in which cellular transmission is transferred from one cell to another neighbouring cell of a network without losing connectivity to the cellular transmission. Lower-layer Triggered mobility (LTM) or L1 / L2 based mobility was introduced in Release 18 of Third Generation Partnership Project (3GPP). LTM enables a serving cell to change via L1 / L2 signalling, while maintaining configuration of upper layers and / or minimizing changes of configuration of the lower layers. The LTM provides improvements in handover latency and interruption time compared to Layer 3 based mobility. However, LTM as introduced in Release 18 has several limitations. Particularly, there are limitations associated with handling of LTM configurations.

[0061] Typically, a base station (for instance, gNodeB (gNB)) configures a range or an index indicating candidate identifiers for the handover. The range indicates a maximum number of candidate cells to which the handover is supported. For conditional configuration-based handovers, the base station configures the range as 1...N. It is desirable to reuse the same range for LTM. This is because it enables reuse in implementation and helps in the interworking with different modes of mobility easier. Hence, 3GPP has agreed to use the candidate identifiers in Radio Resource Control (RRC) from 1...8. However, for LTM, the gNB also communicates a candidate identifier to a User Equipment (UE) in a Media Access Layer (MAC) Control Element (CE). Since the number of bits needed in layer 2 are more valuable, only three bits are allocated by 3GPP to communicate the candidate identifier. Thus, if the index of the LTM candidate cell if communicated in the MAC CE, the base station can configure only 7 candidate cells, even though the index is 1...8, which is not optimal. Due to the limitations of MAC signalling, the number of bits for MAC CE cannot be increased. For instance, if the number of bits of the MAC CE need to be increased, some other field in the MAC CE for LTM cell switch, which provides the information at the time of cell switch needs to be avoided.

[0062] For Dual Connectivity (DC), during LTM cell switch, a Master Node (MN) may release a Secondary Cell Group (SCG). Consider a case where SCG is configured in Cell1 and LTM candidates are Cell2 and Cell3. There needs to be a configuration for releasing SCG (mrdc-SecondaryCellGroupConfig set as release) in RRC configuration for Cell 2 and Cell3. In case, releasing of the SCG is not configured in Cell2 and Cell3, the network needs to reconfigure a subsequent LTM configuration. For instance, consider the UE has moved from cell1 to cell2 through LTM. If the UE moves again from cell2 to cell3 through subsequent LTM, the network needs to reconfigure the subsequent LTM configuration every time after an LTM cell switch, which is not optimal.

[0063] Typically, the LTM configurations received by the UE from the network contains configuration for LTM measurements and reporting, and target configurations. In existing systems, it is not defined when the UE applies each of these configurations.

[0064] A security context is established in Fifth Generation (5G) networks where a security key is generated and stored in both the UE and the network. In the traditional handover procedures, the UE generates or changes a security key whenever there is handover from one cell another cell, based on a "masterkeyUpdate" configured by the network. The configuration of the "masterkeyUpdate" is not defined for the LTM candidate configurations.

[0065] Dual connectivity or particularly multi-radio dual connectivity is specified by Third Generation Partnership Project (3GPP) in specifications such as TS 37.340. Details of the dual connectivity based on v17.1 version of TS 37.340 is provided below. Next Generation-Radio Access Network (NG-RAN) supports Multi-Radio Dual Connectivity (MR-DC) operation whereby a User Equipment (UE) in RRC_CONNECTED state 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 scheduler provides New Radio (NR) access and the other scheduler provides either E-UTRA (Evolved UMTS Terrestrial Radio Access) or NR access. One node acts as a Master Node (MN) and the other node acts as a Secondary Node (SN). The MN and SN are connected via a network interface and at least the MN is connected to a core network. NG-RAN supports NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), in which the UE is connected to one ng-eNB (a E-UTRA base station that connects to 5G core) that acts as the MN and one gNB (5G base station) that acts as the SN. NG-RAN also supports NR-E-UTRA Dual Connectivity (NE-DC), in which the UE is connected to one gNB that acts as the MN and one ng-eNB that act as the SN.

[0066] Master Cell Group in MR-DC is a group of serving cells associated with the MN, comprising of the SpCell (PCell) and optionally one or more SCells. Secondary Cell Group in MR-DC is a group of serving cells associated with the SN, comprising of the SpCell (PSCell) and optionally one or more SCells. SpCell is the primary cell of a master or secondary cell group. PCell is the SpCell of a master cell group and PSCell is the SpCell of a secondary cell group.

[0067] Secondary Node Addition procedure is initiated by the MN and is used to establish UE context at the SN to provide resources from the SN to the UE. PSCell addition takes place during the SN addition procedure. A Conditional PSCell Addition (CPA) is defined as a PSCell addition that is executed by the UE when execution condition(s) is met. Conditional PSCell Addition and Change (CPAC) is selective activation of cell groups supporting subsequent Conditional PSCell Change (CPC) or Conditional PSCell Addition (CPA) after a cell group change. The cell group change is either network initiated or conditional cell group change. The UE starts evaluating the execution condition(s) upon receiving the CPA configuration and stops evaluating the execution condition(s) once PSCell addition or PCell change is triggered.

[0068] In MR-DC, PSCell is changed by network directly using RRC Reconfiguration message or using a Conditional PSCell Change (CPC). CPC is defined as a PSCell change that is executed by the UE when execution condition(s) is met. In the current NR system, the UE starts evaluating the execution condition(s) upon receiving the CPC configuration and stops evaluating the execution condition(s) once PSCell change or PCell change is triggered.

[0069] The principles applied to CPC in current NR specifications are as follows. CPC configuration contains configuration of CPC candidate PSCell(s) and execution condition(s) and may contain MCG configuration for inter-SN CPC, to be applied when CPC execution is triggered. An execution condition consists of one or two trigger condition(s) (CondEvents, as defined in TS 38.331 or TS 36.331). Only single RS type and at most two different trigger quantities (e.g., Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ), RSRP and Signal to Interference plus Noise Ratio (SINR), etc.) are used for the evaluation of CPC execution condition of a single candidate PSCell. Before any CPC execution condition is satisfied, 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. While executing CPC, the UE is not required to continue evaluating the execution condition of other candidate PSCell(s). Once the CPC procedure is executed successfully, the UE releases all stored conditional reconfigurations (i.e., for CPC and for CHO, as specified in TS 38.300 or TS 36.300). In release 18, 3GPP is considering selective activation of cell groups after a PSCell Change (or even a PSCell Addition). UE performs another CPA or CPC without being configured again after a CPA or CPC. Such a CPA or CPC is referred to as subsequent CPAC.

[0070] Therefore, existing systems and UE may not be configured to handle subsequent CPAC. Therefore, there is a need for a method for how a UE behaves when a network entity releases conditional execution conditions for subsequent CPAC, and includes certain conditions which is not available in the existing configuration and how the UE performs the measurements for subsequent CPAC. A PSCell may need to release execution condition to prevent the UE from performing measurements in the cells which are not its immediate neighbours. If the PSCell can release only the execution conditions which are available in the configuration, it needs to inform all the network nodes (SN or MN) about the release of the configurations. Further the network nodes need to update the conditional configuration. This increases the complexity and signalling overhead.

[0071] The information disclosed in this background 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.

[0072] In an embodiment, the present disclosure discloses a method of handling Lower-Layer Triggered Mobility (LTM) candidate configurations. The method comprises receiving a plurality of LTM candidate configurations from a network apparatus. Each LTM candidate configuration of the plurality of LTM candidate configurations is associated with corresponding first identifier. Further, the method comprises receiving an LTM cell switch command from the network apparatus to switch to a cell. The LTM cell switch command includes a second identifier. Furthermore, the method comprises generating a third identifier by incrementing the second identifier by one. Thereafter, the method comprises executing LTM cell switch by applying a LTM candidate configuration from the plurality of LTM candidate configurations, associated with a first identifier that is equal to the third identifier.

[0073] In an embodiment, the present disclosure discloses a method of handling LTM candidate configurations. The method comprises receiving a plurality of LTM candidate configurations from a network apparatus. Further, the method comprises identifying whether the plurality of LTM candidate configurations include configurations for releasing a Secondary Cell Group (SCG). Furthermore, the method comprises determining whether the SCG is configured in a current cell camped on by the UE based on a current configuration of the UE. Thereafter, the method comprises transmitting a reconfiguration complete message, when the SCG is not configured in the current cell.

[0074] In an embodiment, the present disclosure discloses a User Equipment (UE) for handling LTM candidate configurations. The UE comprises a processor and a memory. The processor is configured to receive a plurality of LTM candidate configurations from a network apparatus. Each LTM candidate configuration of the plurality of LTM candidate configurations is associated with corresponding first identifier. Further, the processor is configured to receive an LTM cell switch command from the network apparatus to switch to a cell. The LTM cell switch command includes a second identifier. Furthermore, the processor is configured to generate a third identifier by incrementing the second identifier by one. Thereafter, the processor is configured to execute LTM cell switch by applying a LTM candidate configuration from the plurality of LTM candidate configurations, associated with a first identifier that is equal to the third identifier.

[0075] In an embodiment, the present disclosure discloses a UE for handling LTM candidate configurations. The UE comprises a processor and a memory. The processor is configured to receive a plurality of LTM candidate configurations from a network apparatus. Further, the processor is configured to identify whether the plurality of LTM candidate configurations include configurations for releasing a Secondary Cell Group (SCG). Furthermore, the processor is configured to determine whether the SCG is configured in a current cell camped on by the UE based on a current configuration of the UE. Thereafter, the processor is configured to transmit a reconfiguration complete message, when the SCG is not configured in the current cell.

[0076] In an embodiment, the present disclosure discloses a network apparatus. The network apparatus comprises a processor, a memory, and a communication interface. The processor is configured to transmit a plurality of LTM candidate configurations to a UE. Each LTM candidate configuration is associated with corresponding first identifier. Further, the network apparatus is configured to transmit an LTM cell switch command to the UE. The LTM cell switch command is transmitted to switch to a cell including a second identifier with a value that is equal to a first identifier decremented by one.

[0077] In an embodiment, the present disclosure discloses a method for supporting subsequent Conditional PSCell Addition and Change (CPAC). The method comprises receiving an Radio Resource Control (RRC) message comprising of a release list for a second set of conditional execution conditions for subsequent CPAC. The release list includes a list of conditional reconfiguration identifiers and the execution conditions associated with them. The method further comprises determining, by the UE, that the conditional reconfiguration identifier is not part of a current UE configuration. The method further comprises executing RRC procedure corresponding to the RRC message. The method further comprises sending an RRC complete message indicating the completion of RRC procedure.

[0078] In an embodiment, the present disclosure discloses a method for supporting subsequent CPAC. The method comprises of receiving a subsequent CPAC configuration towards a subsequent target PSCell. The method further comprises executing subsequent CPAC. The method further comprises reporting information related to the subsequent CPAC. The information related to the subsequent CPAC is logged at the network entity.

[0079] In an embodiment, the present disclosure discloses a User Equipment (UE) for supporting subsequent CPAC. The UE comprises a processor and a memory. The processor is configured to receive an Radio Resource Control (RRC) message comprising of a release list for a second set of conditional execution conditions for subsequent CPAC. The release list includes a list of conditional reconfiguration identifiers and the execution conditions associated with them. The UE is configured to determine that the conditional reconfiguration identifier is not part of a current UE configuration. The UE is further configured to execute RRC procedure corresponding to the RRC message. The UE is further configured send to the network entity, an RRC complete message indicating the completion of RRC procedure.

[0080] In an embodiment, the present disclosure discloses a User Equipment (UE) for supporting subsequent CPAC. The UE comprises a processor and a memory. The processor is configured to receive a subsequent CPAC configuration towards a subsequent target PSCell. The UE is configured to execute subsequent CPAC. The UE is further configured to report information related to the subsequent CPAC. The information related to the subsequent CPAC is logged at the network entity.

[0081] 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.

[0082] Wireless technology has been continuously evolving over the years to provide for a growing demand for services and requirements of end users. The earliest generation referred to as Second Generation (2G) of wireless communication provided mobility and voice services while a Third Generation (3G) provided voice and data services. However, with the growing demand for high-speed data, there was a need to further evolve and a Fourth Generation (4G) of wireless communication was developed. In the fourth-generation communication systems, multiple architecture options were designed to provide high-speed data. These systems included aggregating multiple carriers either through carrier aggregation (CA) or through dual connectivity (DC) which allowed operators to provide high data rates per user through the aggregation of the respective radio resources. Furthermore, with growing demands of even higher data rates, ultra-reliability, low latency communication requirements, and machine-type communications, next generation of wireless technology, i.e., Fifth Generation (5G) communication systems were developed. As per TS 38.401, a 5G architecture consists of two parts - a Radio Network (NG-RAN) and a 5G Core network (5GC) which have had major changes compared to earlier technologies as illustrated in Figure 11.

[0083] The NG-RAN consists of a set of next generation NodeBs (gNBs) connected to the 5GC through the NG interface. The gNBs can be interconnected through a Xn interface. A gNB may consist of a gNB-CU and one or more gNB-DU(s). A gNB-CU and a gNB-DU is connected via F1 interface.

[0084]

[0085] In wireless technologies like 5G NR, devices can move across different cells. Mobility is performed using a procedure called cell reselection in RRC_IDLE mode. Till NR R17, mobility is performed using a procedure called handover in RRC_CONNECTED mode.

[0086] Network controlled mobility applies to UEs in RRC_CONNECTED. It requires explicit RRC signalling to be triggered by the gNB in NR. Typically, handover in NR usually consists of three steps: handover preparation, handover execution and handover completion. The gNB may configure the UE to report measurements and based on the reported measurements or based on its own understanding of the network topology, the gNB may send RRC Reconfiguration message to handover the UE to another cell called target cell from a source cell. The UE accesses the target cell and sends RRC Reconfiguration complete message. In an alternative way introduced in 3gpp NR release 16, the gNB may configure the UE with execution conditions for triggering handover and once the execution conditions are satisfied, the UE may move to target cell and sends the RRC Reconfiguration complete. The 3GPP also introduced a new handover called DAPS handover in release 16. In all these methods, the UE performs handover by sending layer 3 (RRC) messages which causes considerable signalling overhead and latency issues. The handover, and conditional handover (CHO) can be referred as layer 3 mobility. In case of dual connectivity, the UE may perform PSCellChange or Conditional PSCellChange. In the context of dual connectivity, the PSCellChange or Conditional PSCellChange can also be referred as layer 3 mobility. i.e. Handover, Conditional Handover, PSCellChange, Conditional PSCellChange etc., refers to L3 mobility. The PSCellChange or Conditional PSCellChange can be referred as SCG layer 3 mobility and the handover and CHO as MCG layer 3 mobility in the context of dual connectivity.

[0087] The 3GPP release 18 considers Lower Layers (L1 / L2 layers) Triggered Mobility, also known as LTM, to solve the problem related to latency, signalling overhead etc., associated with layer 3 mobility. As per 3gpp, the goal of LTM is to enable a serving cell change via L1 / L2 signalling, in order to reduce the latency, overhead and interruption time. Network (gNB) may configure the UE with multiple candidate cells to allow fast application of configurations for candidate cells. Network may further send MAC CE or L1 signalling to dynamically switch the UE from a source cell to one of the configured candidate cells. Further, the LTM can be triggered based on L1 measurements rather than L3 measurements.

[0088] The 3GPP proposes to perform LTM, without reset of lower layers like MAC to avoid data loss and to reduce the additional delay of data recovery wherever it is possible.

[0089] The gNB CU may provide LTMCandidateConfiguration, i.e., configure LTM candidate cells through one RRCReconfiguration message for a candidate target cell. The gNB may further release or modify the candidate configurations. A UE may store the LTM configuration of other candidate cells even after moving to a candidate cell through LTM. The gNB CU also may provide the UE with configuration for performing LTM measurements for different candidate frequencies and candidate cells and reporting based on the performed LTM measurements. The gNB may further release or modify the candidate configurations. A UE may store the LTM configuration of other candidate cells even after moving to a candidate cell through LTM. The gNB also may provide the UE with configuration for performing LTM measurements for different candidate frequencies and candidate cells and reporting based on the performed LTM measurements. The 3gpp supports subsequent LTM, i.e., after one LTM candidate cell becomes a source cell due to LTM, the UE may store LTM candidate configuration and continue to report LTM measurements (L1 measurements for LTM) and the new serving cell may send LTM cell switch command to the UE and UE performs LTM. Such an LTM is called subsequent LTM.

[0090] The UE performs the L1 measurements on the source cell and candidate cell and report L1 measurements through CSI reports to the gNB DU of the source cell. The gNB DU may send a MAC CE (for e.g., LTM MAC CE or cell switch MAC CE) asking the UE to switch to another cell which is an LTM candidate cell. The UE may perform random access during LTM cell switch, or the cell switch may be RACH less. A CellSwitch may be guarded by a timer (referred to as T3xx in this disclosure).

[0091] The UE may be requested to perform random access on a candidate cell before the cell switch, so that the network can calculate the timing advance before the cell switch and inform the UE either through a random-access response or within the MAC CE which is sent for the cell switch. The gNB may configure the UE to perform random access towards one or more LTM candidate cells for receiving the timing advance (TA) before the cell switch is performed (known as Early TA or Early Sync TA or TA for Early Sync). Random access performed on LTM candidate cells for the timing advance reception is known as Random access for early TA. The gNB sends a PDCCH order to initiate RACH for TA measurement for candidate cells. The UE receives PDCCH order from the serving cell. Upon reception of this PDCCH order, the UE initiates RACH for TA measurement for candidate cells on the one or more candidate cell. The UE sends RACH preamble to the candidate cells and receives the Timing Advance (TA) value from the candidate cell. The TA for candidate cells may be received from the source cell as well. Normally, the TA may be received in the random-access response, but it may be also received through a MAC CE. If source DU indicates the UE to retransmit the RACH for early TA, the UE retransmits the same. The gNB may also send PDCCH order to retransmit RACH for TA measurement (also known as RACH for early sync).

[0092] LTM is a procedure in which a gNB receives L1 measurement report(s) from a UE, and on their basis the gNB changes UE's serving cell by a cell switch command signalled via a MAC CE. The cell switch command indicates an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through RRC signalling. Then, the UE switches to the target cell according to the cell switch command. The LTM procedure can be used to reduce the mobility latency as described.

[0093] Network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition is triggered by PDCCH order [or through UE-based TA measurement].

[0094] The network indicates in the cell switch command whether the UE shall access the target cell with a RA procedure if a TA value is not provided or with PUSCH transmission using the indicated TA value. For RACH-less LTM, the UE either monitors PDCCH for dynamic scheduling from the target cell upon LTM cell switch, or the UE selects the configured grant occasion associated with the beam indicated in the cell switch command.

[0095] The following principles apply to LTM:

[0096] a. The UE does NOTupdate its security key in LTM.

[0097] b. Subsequent LTM is supported.

[0098] LTM supports both intra-gNB-DU and intra-gNB-CU inter-gNB-DU mobility. LTM also supports inter-frequency mobility, including mobility to inter-frequency cell that is not a current serving cell. The following scenarios are supported:

[0099] c. PCell change in non-CA scenario,

[0100] d. PCell change in CA scenario,

[0101] e. Dual connectivity scenario, at least for the PSCell change without MN involvement case, i.e., intra-SN PSCell change.

[0102] A supervision timer can be used to detect failure of LTM cell switch procedure, wherein LTM procedure fails if the LTM supervision timer expires, upon which the UE initiates RRC connection re-establishment procedure.

[0103] While the UE has stored LTM candidate cell configurations, the UE can also execute any L3 handover command sent by the network. It is up to the network to avoid any issue due to a collision between LTM execution and L3 handover execution. For e.g., avoiding sending LTM cell switch command and L3 handover command simultaneously.

[0104] Cell switch command is conveyed in a MAC CE, which contains the necessary information to perform the LTM cell switch.

[0105] The overall procedure for LTM is shown in Fig.2. Subsequent LTM is performed by repeating the early synchronization, LTM execution, and LTM completion steps without releasing other LTM candidate cell configurations after each LTM completion.

[0106] The procedure for LTM is as follows:

[0107] 1. The UE sends a MeasurementReport message to the gNB. The gNB decides to configure LTM and initiates candidate cell(s) preparation.

[0108] 2. The gNB transmits an RRCReconfiguration message to the UE including the LTM candidate cell configurations of one or multiple candidate cells.

[0109] 3. The UE stores the LTM candidate cell configurations and transmits an RRCReconfigurationComplete message to the gNB.

[0110] 4a. The UE [may] performs DL synchronization with candidate cell(s) before receiving the cell switch command.

[0111] 4b. The UE [may] performs early TA acquisition with candidate cell(s) requested by the network before receiving the cell switch command. This is done via CFRA triggered by a PDCCH order from the source cell, following which the UE sends preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE does not receive RAR for the purpose of TA value acquisition and the TA value of the candidate cell is indicated in the cell switch command. The UE does not maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.

[0112] 5. The UE performs L1 measurements on the configured candidate cell(s),and transmits lower-layer measurement reports to the gNB. L1 measurement is to be performed as long as apply the RRC reconfiguration in step 2.

[0113] 6. The gNB decides to execute cell switch to a target cell, and transmits a MAC CE triggering cell switch by including the candidate configuration index of the target cell. In NR, the MAC CE is known as LTM cell switch command. The UE switches to the target cell and applies the configuration indicated by candidate configuration index.

[0114] 7. The UE performs the random access procedure towards the target cell, if UE does not have valid TA of the target cell.

[0115] 8. The UE completes the LTM cell switch procedure [by sending RRCReconfigurationComplete message to target cell]. If the UE has performed a RA procedure in step 7, the UE considers that LTM execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE considers that LTM execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0116] Steps 4-8 can be performed multiple times for subsequent LTM cell switch using the LTM candidate cell configuration(s) provided in step 2.

[0117] For the purpose of the present invention, the 3GPP specifications such as TS38.300, TS38.331, TS 38.321 V17.4.0 as relevant background.

[0118] A set of known specification extracts for the LTM with respect to the discussions in 3GPP for TS 38.331 are given below:

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[0152] Upon receiving cell switch command, the UE MAC may perform the following steps:

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[0154]

[0155] The invention proposes various aspects for configuring lower layer triggered mobility by the gNB and handling the configurations by the UE as described in subsequent part of the present disclosure.

[0156] In the following description, any embodiment for gNB is applicable for a Radio Access Node (RAN node) in any wireless technology.

[0157] In an embodiment, upon reception of RRC Reconfiguration or upon execution of the conditional reconfiguration (CHO, CPA or CPC) which adds or modifies LTM candidate configuration (such as by including one or more LTM-Candidate-r18 IEs in LTM-CandidateToAddModList-r18 IE as explained in background), the UE applies a part of the configuration received in LTM candidate configuration immediately and stores another part of configuration received in LTM candidate configuration and applies it during LTM cell switch (which may be triggered upon receiving a DL MAC CE for cell switch or performing LTM based recovery or executing a conditional LTM cell switch).

[0158] In an embodiment, the part of the configuration applied immediately upon adding or modifying LTM candidate configuration includes candidate Id and PCI of the LTM candidate cell, LTM reference signal configuration for measuring LTM candidate cell such as LTM SSB configuration received in LTM candidate cell configuration, configuration for performing early synchronization such as LTM earlySync configuration received in LTM candidate cell configuration and TCI configuration for LTM as received in LTM candidate cell configuration. In NR, the UE may apply the configuration received (or one or more configuration received) in ltm-CandidateId-r18, ltm-CandidatePCI-r18, ltm-SSB-Config-r18, ltm-EarlyUL-SyncConfig-r18, ltm-dl-OrJointTCI-StateToAddModList-r18, ltm-dl-OrJointTCI-StateToReleaseList-r18, ltm-ul-TCI-ToAddModList-r18, ltm-ul-TCI-ToReleaseList-r18 upon receiving the LTM-Candidate-r18 IE. An NR RRC in the NR UE may configure lower layers with any of the received configurations for candidate Id, PCI, SSB configuration, earlySync configuration and TCI configuration in the LTM candidate cell configuration upon reception of LTM candidate cell configuration. The UE RRC does not wait for LTM cell switch to apply these configurations.

[0159] In an embodiment, the part of the configuration which is stored and applied upon cell switch includes ltm-CandidateConfig-r18, ltm-ConfigComplete-r18, ltm-NoResetID-r18 and ltm-ReleaseSCG-r18. The UE RRC defers applying these configurations till the LTM cell switch is completed as illustrated in below table.

[0160]

[0161] In an embodiment, upon LTM candidate cell release, UE RRC configures lower layers to release candidate Id, PCI, SSB configuration, earlySync configuration and TCI configuration, if it is configured earlier. The UE RRC does not wait for LTM cell switch to apply this configuration.

[0162] In an embodiment, upon receiving LTM configuration through ltm-config, the UE RRC configures lower layers with LTM CSI resource configuration. A NR UE RRC configures lower layers with the received information from ltm-CSI-ResourceConfigToAddModList-r18 or ltm-CSI-ResourceConfigToReleaseList-r18 upon receiving LTM configuration. The UE RRC does not wait for LTM cell switch to apply this configuration.

[0163] In an embodiment, if the UE performs LTM cell switch upon performing cell selection while timer T311 is running, the UE avoids performing LTM configuration release (for e.g. UE avoids performing LTM configuration release as described in section 5.3.5.x.7 LTM configuration release in the background). The UE keeps the LTM configuration, generated LTM configuration, ltm-config and LTM CSI report configuration when the UE perform LTM cell switch upon performing cell selection while timer T311 is running. If the UE has selected a LTM candidate cell associated with MCG and the UE is configured to attempt LTM configuration upon performing cell selection while timer T311 is running, the UE keeps the LTM configuration, generated LTM configuration,ltm-config and LTM CSI report configuration. The UE may keep all entries within VarLTM-UE-Config, VarLTM-Config of the applicable cell group for which LTM configuration release is triggered and all entries in ltm-Config and ltm-CSI-ReportConfigToAddModList for all serving cell related to the applicable cell group, as depicted in the table below.

[0164]

[0165] In an embodiment, a gNB avoids configuring masterKeyupdate in a RRCReconfiguration message when that RRCReconfiguration message is configured in ltm-config. This may be represented as below in 3gpp TS 38.331.

[0166]

[0167]

[0168] In an embodiment, a gNB sending RRCReconfiguration message including LTM configuration which contains LTM reference configuration excludes ReconfigurationWithSync in the LTM reference configuration. This may be represented as below in TS 38.331:

[0169] In an embodiment, if the UE receives LTM SSB configuration (such as LTM-SSB-Config-r18) without including SSB periodicity (such as ssb-Periodicity-r18), the UE applies the SSB periodicity as 5ms.

[0170]

[0171]

[0172] In an embodiment, the gNB excludes the field attemptLTM-Switch (or equivalent field which configures the UE to attempt LTM cell switch upon cell selection while timer T311 or equivalent timer is running) while configuring LTM candidate cells for SCG. In an embodiment, if a SN configures a LTM candidate cell in NR-DC, the SN does not include the field attemptLTM-Switch (or equivalent field which configures the UE to attempt LTM cell switch upon cell selection while timer T311 or equivalent timer is running). In an embodiment, if a MN configures LTM candidate cell for SCG, it does not include the field attemptLTM-Switch (or equivalent field which configures the UE to attempt LTM cell switch upon cell selection while timer T311 or equivalent timer is running).

[0173] In an embodiment, Upon an LTM cell switch, the UE releases the radio bearer(s) that are part of the current UE's configuration but not part of the LTM candidate cell configuration indicated by lower layers.

[0174] In an embodiment, if the UE receives RRCReconfiguration including logical channel identifiers in the RLC-BearerToReleaseList which are not part of the current UE configuration, it considers the RRC Reconfiguration procedure as successful and sends RRCReconfigurationComplete.

[0175] In an embodiment, if the UE receives RRCReconfiguration including logical channel identifiers in the RLC-BearerToReleaseList within LTM candidate configuration (such as ltm-CandidateConfig-r18) or within LTM reference configuration and the logical channel identifiers are not part of the current UE configuration, it considers the RRC Reconfiguration procedure as successful and sends RRCReconfigurationComplete.

[0176] In an embodiment, if the UE receives RRCResume including logical channel identifiers in the RLC-BearerToReleaseList which are not part of the current UE configuration, it considers the RRC resume procedure as successful and sends RRCResumeComplete.

[0177] In an embodiment, if the UE receives RRCReconfiguration or RRCResume including logical channel identifiers in the RLC-BearerToReleaseList which are released autonomously by the UE as they are part of the current UE's configuration but not part of the LTM candidate cell configuration which is being applied, UE sends RRCReconfigurationComplete or RRCResumeComplete. This may be represented as below in TS 38.331.

[0178]

[0179] In an embodiment, if the UE receives RRCReconfiguration containing srb3-ToRelease in the RadioBearerConfig and if the SRB3 is not part of the current UE configuration, the UE considers the Reconfiguration procedure as successful and sends RRCReconfigurationComplete.

[0180] In an embodiment, if the UE receives RRCResume containing srb3-ToRelease in the RadioBearerConfig and if the SRB3 is not part of the current UE configuration, the UE considers the Reconfiguration procedure as successful and sends RRCReconfigurationComplete.

[0181] In an embodiment, if the UE receives RRCResume containing srb3-ToRelease in the RadioBearerConfig within LTM candidate configuration (such as ltm-CandidateConfig-r18) or within LTM reference configuration and if the SRB3 is not part of the current UE configuration, the UE considers the Reconfiguration procedure as successful and sends RRCReconfigurationComplete.

[0182] In an embodiment, if the UE receives RRCReconfiguration or RRCResume including srb3-ToRelease in the RadioBearerConfig and the SRB3 is released autonomously by the UE as it is part of the current UE's configuration but not part of the LTM candidate cell configuration which is being applied, the UE sends RRCReconfigurationComplete or RRCResumeComplete and completes the RRC Reconfiguration or RRC Resume procedure successfully. This may be represented as below in TS 38.331.

[0183]

[0184] In an embodiment, if the UE receives a RRC message such as RRCReconfiguration or RRCResume containing ltm-ReleaseSCG-r18 or equivalent field in the LTM candidate configuration such as LTM-Candidate-r18 and if the SCG is not part of the current UE configuration, the UE considers the RRC procedure such as RRC reconfiguration procedure or RRC resume procedure as successful and sends corresponding RRC complete message such as RRCReconfigurationComplete or RRCResumeComplete.

[0185] In an embodiment, if the UE receives a RRC message such as RRCReconfiguration or RRCResume containing mrdc-SecondaryCellGroupConfig or equivalent field set as release and if the SCG is not part of the current UE configuration, the UE considers the RRC procedure such as RRC reconfiguration procedure or RRC resume procedure as successful and sends corresponding RRC complete message such as RRCReconfigurationComplete or RRCResumeComplete.

[0186] In an embodiment, if the UE receives a RRC message such as RRCReconfiguration or RRCResume containing mrdc-SecondaryCellGroupConfig or equivalent field set as release in LTM candidate configuration such as ltm-CandidateConfig-r18 and if the SCG is not part of the current UE configuration, the UE considers the RRC procedure such as RRC reconfiguration procedure or RRC resume procedure as successful and sends corresponding RRC complete message such as RRCReconfigurationComplete or RRCResumeComplete.

[0187] In an embodiment, a gNB (or any RAN node which implements LTM) includes the LTM candidate identifiers in ltm-config from the range 0 to 7. In an embodiment, if the maximum number of LTM candidate cells that may be supported are N, the value of candidate identifiers in ltm-config can be 0, 1, 2...N-1. The minimum value for LTM candidate identifier is 0 and the maximum value is N-1.

[0188] This may be represented as below:

[0189]

[0190] In an embodiment, upon receiving LTM Cell Switch command MAC CE, including Target Configuration ID (i.e., a field which indicates the index of candidate target configuration to apply for LTM cell switch) from the gNB, UE applies the LTM candidate configuration for the LTM candidate cell with the LTM candidate identifier corresponding to the value Target Configuration ID +1.

[0191] For e.g., if the UE has received Target Configuration ID as 0, the UE applies the LTM candidate configuration of the LTM candidate cell with LTM candidate identifier as 1. If the UE has received Target Configuration ID as 1, UE applies the LTM candidate configuration of the LTM candidate cell with LTM candidate identifier as 2. if the UE has received Target Configuration ID as 7, the UE applies the LTM candidate configuration of the LTM candidate cell with LTM candidate identifier as 8. This may be represented as below in TS 38.331:

[0192]

[0193] Alternatively, this may be represented as below in TS 38.321.

[0194]

[0195] Dual connectivity or particularly multi-radio dual connectivity is specified by Third Generation Partnership Project (3GPP) in specifications such as TS 37.340. Details of the dual connectivity based on v17.1 version of TS 37.340 is provided below. Next Generation-Radio Access Network (NG-RAN) supports Multi-Radio Dual Connectivity (MR-DC) operation whereby a User Equipment (UE) in RRC_CONNECTED state 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 scheduler provides New Radio (NR) access and the other scheduler provides either E-UTRA (Evolved UMTS Terrestrial Radio Access) or NR access. One node acts as a Master Node (MN) and the other node acts as a Secondary Node (SN). The MN and SN are connected via a network interface and at least the MN is connected to a core network. NG-RAN supports NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), in which the UE is connected to one ng-eNB (a E-UTRA base station that connects to 5G core) that acts as the MN and one gNB (5G base station) that acts as the SN. NG-RAN also supports NR-E-UTRA Dual Connectivity (NE-DC), in which the UE is connected to one gNB that acts as the MN and one ng-eNB that act as the SN.

[0196] Master Cell Group in MR-DC is a group of serving cells associated with the MN, comprising of the SpCell (PCell) and optionally one or more SCells. Secondary Cell Group in MR-DC is a group of serving cells associated with the SN, comprising of the SpCell (PSCell) and optionally one or more SCells. SpCell is the primary cell of a master or secondary cell group. PCell is the SpCell of a master cell group and PSCell is the SpCell of a secondary cell group.

[0197] Secondary Node Addition procedure is initiated by the MN and is used to establish UE context at the SN to provide resources from the SN to the UE. PSCell addition takes place during the SN addition procedure. A Conditional PSCell Addition (CPA) is defined as a PSCell addition that is executed by the UE when execution condition(s) is met. Conditional PSCell Addition and Change (CPAC) is selective activation of cell groups supporting subsequent Conditional PSCell Change (CPC) or Conditional PSCell Addition (CPA) after a cell group change. The cell group change is either network initiated or conditional cell group change. The UE starts evaluating the execution condition(s) upon receiving the CPA configuration and stops evaluating the execution condition(s) once PSCell addition or PCell change is triggered.

[0198] In MR-DC, PSCell is changed by network directly using RRC Reconfiguration message or using a Conditional PSCell Change (CPC). CPC is defined as a PSCell change that is executed by the UE when execution condition(s) is met. In the current NR system, the UE starts evaluating the execution condition(s) upon receiving the CPC configuration and stops evaluating the execution condition(s) once PSCell change or PCell change is triggered.

[0199] The principles applied to CPC in current NR specifications are as follows. CPC configuration contains configuration of CPC candidate PSCell(s) and execution condition(s) and may contain MCG configuration for inter-SN CPC, to be applied when CPC execution is triggered. An execution condition consists of one or two trigger condition(s) (CondEvents, as defined in TS 38.331 or TS 36.331). Only single RS type and at most two different trigger quantities (e.g., Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ), RSRP and Signal to Interference plus Noise Ratio (SINR), etc.) are used for the evaluation of CPC execution condition of a single candidate PSCell. Before any CPC execution condition is satisfied, 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. While executing CPC, the UE is not required to continue evaluating the execution condition of other candidate PSCell(s). Once the CPC procedure is executed successfully, the UE releases all stored conditional reconfigurations (i.e., for CPC and for CHO, as specified in TS 38.300 or TS 36.300). In release 18,3gpp is considering selective activation of cell groups after a PSCell Change (or even a PSCell Addition). UE performs another CPA or CPC without being configured again after a CPA or CPC. Such a CPA or CPC is referred to as subsequent CPAC.

[0200] A set of IEs used for configuring selective activation of cell groups according to 3gpp TS 38.331 V17.5.0 is given below.

[0201] 6.3.2 Radio resource control information elements

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[0209] Below section based on TS 38.331 V17.5.0 specifies how UE performs measurements including subsequent CPAC.

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[0221] Below section gives some details on how the UE performs conditional reconfiguration for subsequent CPAC.

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[0228] The present disclosure proposes a system and a method for subsequent conditional PScell addition and change (CPAC). In the present disclosure, a UE which stores CPAC configurations and measurement configurations associated to the CPAC configurations performs measurements or performs one or more of the different steps in the measurement procedure such as deriving layer 3 filtered beam measurements or cell measurements for the subsequent CPAC. The present disclosure provides different embodiments of performing the measurements by the UE.

[0229] In the present disclosure, a UE which stores CPAC configurations and the measurement configurations associated to the CPAC configurations (i.e. subsequent CPAC configuration)skips performing measurements or skips performing one or more of the different steps in the measurement procedure (for e.g. as in TS 38.331 step 5.5.3) such as deriving layer 3 filtered beam measurements or cell measurements for the subsequent CPAC. The present disclosure provides different embodiments of skipping performing the measurements by the UE.

[0230] Figure 22 illustrates a procedure for releasing conditional execution conditions for subsequent CPAC in accordance with the embodiments of the present disclosure; and

[0231] Figure 23 illustrates a procedure for SCG Failure Information and subsequent CPAC in accordance with the embodiments of the present disclosure.

[0232] In an embodiment, for a UE which will store the CPAC configurations (for subsequent CPAC), the measurement configurations associated to the CPAC configurations will be skipped while performing measurements or performing one or more of the different steps in the measurement procedure such as deriving layer 3 filtered beam measurements or cell measurements, for the measurement configuration associated only to the CPAC configuration of the PSCell.

[0233] In an embodiment, for a UE which stores the CPAC configurations (for subsequent CPAC),the measurement configurations associated to those CPAC configurations will be skipped while performing measurements or performing one or more of the different steps in the measurement procedure (for e.g. in TS 38.331 step 5.5.3) such as deriving layer 3 filtered beam measurements or cell measurements, when the report configuration is associated to conditional trigger configuration and the measurement configuration is associated to the CPAC configuration of the PSCell.

[0234] This may be captured as below in 3gpp TS 38.331 specification.

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[0240]

[0241] In an embodiment, a UE which stores the CPAC configurations (for subsequent CPAC) and the measurement configurations associated to those CPAC configurations will perform measurements or perform one or more of the different steps in the measurement procedure such as deriving layer 3 filtered beam measurements or cell measurements for the subsequent CPAC, only for the measurement configurations which are associated to the CPAC candidate configuration which are available at the time of performing measurements.

[0242] In an embodiment, a UE which stores the CPAC configurations (for subsequent CPAC) and the measurement configurations associated to those CPAC configurations will perform measurements or perform one or more of the different steps in the measurement procedure such as deriving layer 3 filtered beam measurements or cell measurements for the subsequent CPAC, when the report configuration is associated to conditional trigger configuration, only for the measurement configuration which are associated to the CPAC configuration available at the time of performing measurements.

[0243] In an embodiment, a UE which stores the CPAC configurations (for subsequent CPAC) and the measurement configurations associated to those CPAC configurations will perform measurements or perform one or more of the different steps in the measurement procedure such as deriving layer 3 filtered beam measurements or cell measurements for the subsequent CPAC, only for the measurement configurations which are associated to the CPAC candidate configuration for which subsequent condition for the candidate cell is provided;

[0244] In an embodiment, a UE which stores the CPAC configurations (for subsequent CPAC)and the measurement configurations associated to those CPAC configurations will perform measurements or perform one or more of the different steps in the measurement procedure such as deriving layer 3 filtered beam measurements or cell measurements for the subsequent CPAC, when the report configuration is associated to conditional trigger configuration, only for the measurement configuration which are associated to the CPAC configuration for which subsequent condition for the candidate cell is provided.

[0245] In an embodiment, a UE which stores the CPAC configurations (for subsequent CPAC) and the measurement configurations associated to those CPAC configurations will be skipped while performing measurements or skip performing one or more of the different steps in the measurement procedure such as deriving layer 3 filtered beam measurements or cell measurements for the subsequent CPAC, for the measurement configurations which are only associated to the CPAC candidate configuration for which the subsequent condition (execution condition) is not provided by current serving PSCell.

[0246] In an embodiment, a UE which stores the CPAC configurations (for subsequent CPAC) and the measurement configurations associated to those CPAC configurations will be skipped while performing measurements or skip performing one or more of the different steps in the measurement procedure such as deriving layer 3 filtered beam measurements or cell measurements for the subsequent CPAC, for the measurement configurations which are only associated to the CPAC candidate configuration for which the subsequent condition (execution condition) is not provided by current serving PSCell which is also a subsequent CPAC candidate;

[0247] In an embodiment, UE performs measurements for subsequent CPAC only if the measurement configuration is associated with conditional reconfiguration associated with a valid execution condition. If the stored measurement configuration (such as present in VarMeasConfig) is only for subsequent CPAC and there is no execution condition available for those measurement configurations, UE skips performing measurements (or performing some of the steps in performing measurements as given in TS 38.331 5.5.3). Skipped steps will include deriving L3 measurements for cell measurements, deriving L3 measurements for beam measurements. The valid execution condition will be provided by the current PSCell. Alternatively, the valid execution condition will be provided by the previous PSCell(s) and is still maintained by (not released by) current PSCell.

[0248] In an embodiment, this may be represented as below in TS 38.331.

[0249]

[0250]

[0251]

[0252]

[0253] Alternatively this may be represented as below in the specification TS 38.331.

[0254]

[0255]

[0256]

[0257]

[0258] Thus, UE ignores the measurement configurations present in VarMeasConfig which are configured for subsequent CPAC while performing measurements.

[0259] In an embodiment, for each measId of the MCG measConfig, if configured, and for each measId of the SCG measConfig, if configured, if the associated reportConfig has a reportType set to condTriggerConfig and if the reportConfigId is not associated with any measId indicated by the condExecutionCond or the condExecutionCondSCG of an entry for subsequent CPAC in condReconfigList in VarConditionalReconfig (and also is not associated to any measId indicated by the condExecutionCond or the condExecutionCondSCG other than for subsequent CPAC) , UE skips this report configuration while performing measurements. In an embodiment, previous embodiment is applicable only for the measurements related to subsequent CPAC.

[0260] In an embodiment, for each measId of the MCG measConfig, if configured, and for each measId of the SCG measConfig, if configured, If the associated measObjectId is only associated to a reportConfig with reportType set to condTriggerConfig; and if the measObjectId is not associated with any measId indicated by the condExecutionCond or the condExecutionCondSCG of an entry for subsequent CPAC in condReconfigList in VarConditionalReconfig (and also is not associated to any measId indicated by the condExecutionCond or the condExecutionCondSCG other than for subsequent CPAC), UE skips this report configuration while performing measurements.

[0261] In an embodiment, gNB sends condExecutionCond-r16 or CondReconfigExecCondSCG-r17 in a ASN.1 choice data structure while configuring the UE for subsequent conditional reconfiguration by adding or modifying the execution conditions (such as in CondExecutionCondToAddMod-r18 for SubsequentCondReConfig).

[0262]

[0263]

[0264] In an embodiment, a UE which has received a release list for conditional execution conditions for subsequent CPAC (for e.g. condExecutionCondToReleaseList in the background ) in a RRC message such as RRCReconfiguration or RRCResume, does not consider the message as erroneous if the release list (such as condExecutionCondToReleaseList) includes any condReconfigId value that is not part of the current UE configuration. UE successfully completes the RRC procedure and sends the required complete message (such as RRCReconfigurationComplete or RRCResumeComplete) to the network.

[0265] This may be represented as below based on the background.

[0266]

[0267] Figure 22 illustrates a procedure for releasing conditional execution conditions for subsequent CPAC in accordance with the embodiments of the present disclosure. In an embodiment, a UE which has received a release list for conditional execution conditions for subsequent CPAC in a Radio Resource Control (RRC) message such as RRC Reconfiguration or RRC Resume, does not consider the message as erroneous if the release list includes any identifier identifying the conditional execution condition for subsequent CPAC that is not part of the current UE configuration. UE successfully completes the RRC procedure and sends the required complete message (such as RRC Reconfiguration Complete or RRC Resume Complete) to the network. In an embodiment this identifier is a measurement identifier. In an embodiment this identifier is an identifier for the conditional execution condition. In an embodiment the identifier is a conditional reconfiguration identifier.

[0268] In an embodiment, a UE which has received a release list for conditional execution conditions for subsequent CPAC in a RRC message such as RRC Reconfiguration or RRC Resume, does not consider the message as erroneous if the release list includes any identifier identifying the conditional execution condition or all the conditional execution conditions configured for a conditional reconfiguration or a set of conditional execution conditions for one more conditional reconfigurations etc. for subsequent CPAC that is not part of the current UE configuration. UE successfully completes the RRC procedure and sends the required complete message (such as RRC Reconfiguration Complete or RRC Resume Complete) to the network. In an embodiment this identifier is a measurement identifier. In an embodiment this identifier is an identifier for the conditional execution condition. In an embodiment the identifier is a conditional reconfiguration identifier.

[0269] In an embodiment, UE excludes including the time elapsed between the CPAC execution towards the target PSCell and the corresponding latest CPAC configuration received for the target PSCell in the SCG Failure Information, if the PSCell Change towards the target cell is due to subsequent CPAC. UE doesn't send the time elapsed between the CPAC execution towards the target PSCell and the corresponding latest CPAC configuration received for the target PSCell in the SCG Failure Information.

[0270] In an embodiment, UE includes an information to identify that a CPAC candidate cell has conditional reconfiguration for the CPAC candidate cell but there is no execution condition (or there is no subsequent CPAC execution condition) for the candidate cell, in the SCG Failure Information. In an embodiment, this will be done using a flag in the neighbour cell measurements. In an embodiment, this will be done implicitly by not providing some fields during subsequent CPAC.

[0271] Figure 23 illustrates a procedure for SCG Failure Information and subsequent CPAC in accordance with the embodiments of the present disclosure. In an embodiment, a UE which has experienced SCG Failure while performing PSCell Addition or PSCell Change to a target cell using subsequent CPAC, communicates to the gNB (for e.g., by including in SCG Failure Information) that it has performed PSCell Addition or PSCell Change to a target cell using subsequent CPAC. This information in the SCG failure information will be used for optimization by the network.

[0272] In an embodiment, if the UE logs Successful PSCell Report (SPR) for a PSCell Addition or PSCell Change (UE logs SPR for near failure optimisations based on the thresholds configured by the network and the methods for logging SPR are wellknown in 3gpp), wherein the PSCell Addition or PSCell Change is due to subsequent CPAC, the UE avoids including the field timeSinceCPAC-Reconfig-r18. Ie. For subsequent CPAC, UE doesn't include the time elapsed between the initiation of the last conditional reconfiguration execution towards the target PSCell and the reception of the latest conditional reconfiguration for this target PSCell in SPR. In an embodiment, if the UE logs Successful PSCell Report (SPR) for a PSCell Addition or PSCell Change, wherein the PSCell Addition or PSCell Change is due to subsequent CPAC, the UE sets the field timeSinceCPAC-Reconfig-r18 to the time elapsed between the initiation of the last conditional reconfiguration execution towards the target PSCell and the reception of the latest conditional reconfiguration which is a subsequent CPAC configuration for this target PSCell. This information will be used for optimization by the network.

[0273] In an embodiment, if the UE logs Successful PSCell Report (SPR) for a PSCell Addition or PSCell Change, wherein the PSCell Addition or PSCell Change is due to subsequent CPAC, the UE sets the field timeSinceCPAC-Reconfig-r18 to the time elapsed between the initiation of the last conditional reconfiguration execution towards the target PSCell and the time UE has moved into (for eg. by PSCell Addition or PSCell Change) the source PSCell. The above information will be used for optimization by the network.

[0274] In an embodiment, UE includes an information to identify that a CPAC candidate has conditional reconfiguration for a CPAC candidate cell but there is no execution condition (or there is no subsequent CPAC execution condition) for the candidate PSCell in the SPR. In an embodiment, this will be done using a flag in the neighbor cell measurements which indicates that the CPAC candidate has conditional reconfiguration for a CPAC candidate PSCell but there is no execution condition (or there is no execution condition for subsequent CPAC). The above information will be used for optimization by the network.

[0275] In an embodiment, if the UE logs Successful PSCell Report (SPR) for a PSCell Addition or PSCell Change, the UE sets the field choCandidate in MeasResultNR to true for a candidate PSCell which is configured for subsequent CPAC only if the candidate PSCell has the execution conditions configured. If there is conditional reconfiguration configured for the candidate PSCell, but there is no execution condition available, UE doesn't set the field choCandidate to true. Alternatively, UE sets the field choCandidate in MeasResultNR to true in SPR if the conditional reconfiguration is configured for the candidate PSCell, eventhough there is no associated execution condition configured in the source PSCell. The information will be used for optimization by the network. In an embodiment, the UE sets the field choCandidate in MeasResultNR to true for a candidate PSCell which is configured for subsequent CPAC only if the candidate PSCell has the execution conditions configured in SCGFailureInformation also.

[0276] Figure 1 illustrates an exemplary environment 100 for handling LTM candidate configurations, in accordance with the embodiments of the present disclosure. The exemplary environment 100 comprises a UE 102 and a network apparatus 104. The UE 102 may be any device configured to communicate in a wireless network. Examples of the UE 102 include, but not limited to, mobile phones, smartphones, laptops, wearables, and the like. While the UE 102 is communicating in the wireless, the UE 102 moves between cells to ensure seamless connectivity and continuity of service for a user associated with the UE 102. The UE 102 moves between the cells through a procedure of handover. There are various types of handovers such as Conditional Handover (CHO), Dual Active Protocol Stack (DAPS) handover, LTM handover, and the like. The present disclosure relates to LTM handover. LTM is a procedure in which a network (for instance, gNB) receives L1 measurement report(s) from a UE, and on their basis the network changes UE's serving cell by a cell switch command signalled via a MAC CE. The cell switch command indicates an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through RRC signalling. Then, the UE switches to the target cell according to the cell switch command. The LTM procedure can be used to reduce the mobility latency as described. In an embodiment, the network apparatus 104 is a gNodeB (gNB) as defined in 5G networks. A person skilled in the art will appreciate that the network apparatus 104 may be any other entity in Third-generation (3G) networks, Fourth-generation (4G) networks, and the like.

[0277] In the claimed invention, the UE 102 and the network apparatus 104 are configured to handle the LTM candidate configurations. Herein, the UE 102 is configured to receive LTM candidate configurations from the network apparatus 104. Each LTM candidate configuration is associated with corresponding first identifier. The UE 102 receives an LTM cell switch command from the network apparatus 104 to switch to a cell. The LTM cell switch command includes a second identifier. The UE 102 generates a third identifier by incrementing the second identifier by one. Then, the UE 102 executes LTM cell switch by applying an LTM candidate configuration with a first identifier that is equal to the third identifier.

[0278] In an embodiment, the UE 102 receives LTM candidate configurations from the network apparatus 104, including configurations for releasing a Secondary Cell Group (SCG). When the SCG is not configured in a current cell camped on by the UE 102, the UE 102 transmits a reconfiguration complete message.

[0279] Figure 2 illustrates a detailed diagram 200 of the UE 102 for handling the LTM candidate configurations, in accordance with some embodiments of the present disclosure. The UE 102 may include Central Processing Units 206 (also referred as "CPUs" or "a processor 206"), Input / Output (I / O) interface 202, and a memory 204. In some embodiments, the memory 204 may be communicatively coupled to the processor 206. The memory 204 stores instructions executable by the processor 206. The processor 206 may comprise at least one data processor for executing program components for executing user or system-generated requests. The memory 204 may be communicatively coupled to the processor 206. The memory 204 stores instructions, executable by the processor 206, which, on execution, may cause the processor 206 to handle the LTM candidate configurations. In an embodiment, the memory 204 may include one or more modules 210 and data 208. The one or more modules 210 may be configured to perform the steps of the present disclosure using the data 208, to handle the LTM configurations. In an embodiment, each of the one or more modules 210 may be a hardware unit which may be outside the memory 204 and coupled with the UE 102. As used herein, the term modules 210 refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a Field-Programmable Gate Arrays (FPGA), Programmable System-on-Chip (PSoC), a combinational logic circuit, and / or other suitable components that provide described functionality. The one or more modules 210 when configured with the described functionality defined in the present disclosure will result in a novel hardware. Further, the I / O interface 202 is coupled with the processor 206 through which an input signal or / and an output signal is communicated.

[0280] In one implementation, the modules 210 may include, for example, a communication module 224, a generation module 226, an execution module 228, an identification module 230, a determination module 232, and other modules 234. It will be appreciated that such aforementioned modules 210 may be represented as a single module or a combination of different modules. In one implementation, the data 208 may include, for example, communication data 212, generation data 214. execution data 216, identification data 218, determination data 220, and other data 222.

[0281] In an embodiment, the communication module 224 may be configured to receive a plurality of LTM candidate configurations from the network apparatus 104. In an embodiment, the communication module 224 receives the plurality of LTM candidate configurations in a Radio Resource Control (RRC) reconfiguration message. Each LTM candidate configuration of the plurality of LTM candidate configurations is associated with corresponding first identifier. In an embodiment, first identifiers of the plurality of LTM candidate configurations are defined as a range or an index indicating a maximum number of candidate cells to which the handover is supported. For instance, the first identifiers may range from 1, 2쪋...N. In an exemplary embodiment, the value of 'N' may be 8. Referring to a flow diagram 300 illustrated in Figure 3, at step 1, the UE 102 receives the plurality of LTM candidate configurations with corresponding first identifiers 1,2쪋쪋8. Referring back to Figure 2, the plurality of LTM candidate configurations may be stored as the communication data 212 in the memory 204.

[0282] In an embodiment, the communication module 224 may be configured to receive an LTM cell switch command from the network apparatus 104 to switch to a cell / a target cell. The LTM cell switch command indicates an LTM candidate cell configuration that the network apparatus 104 previously prepared and provided to the UE 102 through RRC signalling. The UE 102 receives the LTM cell switch command to switch to the target cell. The LTM cell switch command includes a second identifier. The second identifier is an identifier associated with LTM candidate configuration of the target cell. Referring again to the flow diagram 300, at step 2, the UE 102 receives the LTM cell switch command indicating the second identifier. In an example, consider the second identifier is '7'. In another example, the second identifier may be '0'. In yet another embodiment, the second identifier may be '1'. Referring back to Figure 2, the second identifier in the LTM cell switch command may be stored as the communication data 212 in the memory 204.

[0283] In an embodiment, the generation module 226 may be configured to receive the communication data 212 from the communication module 224. Further, the generation module 226 may be configured to generate a third identifier by incrementing the second identifier by one. Herein, when the UE 102 receives the second identifier as 'N' in the LTM cell switch command MAC CE from the network apparatus 104, the generation module 226 generates the third identifier by incrementing the second identifier by one i.e., 'N+1'. In an embodiment, the second identifier is a Target Configuration ID (i.e., a field which indicates the index of candidate target configuration to apply for the LTM cell switch). In an exemplary embodiment the length of the field 'Target Configuration ID' is three bits. The generation module 226 generates a value Target Configuration ID +1. Referring again to the flow diagram 300, at step 3, the UE 102 generates the third identifier by incrementing the second identifier by one. The third identifier is generated as '8', when the second identifier is '7'. In another example, when the second identifier is '0', the third identifier is '1'. In yet another example, when the second identifier is '1', the third identifier is '0'. Referring back to Figure 2, the third identifier may be stored as the generation data 214 in the memory 204.

[0284] In an embodiment, the execution module 228 may be configured to receive the generation data 214 from the generation module 226. Further, the execution module 228 may be configured to execute the LTM cell switch. In an embodiment, the execution module 228 may identify an LTM candidate configuration with a first identifier that is equal to the third identifier. Then, the execution module 228 may execute the LTM cell switch by applying the identified LTM candidate configuration. Referring again to Figure 3, at step 4, the UE 102 executes the LTM cell switch by applying the identified LTM candidate configuration. In this example, as the third identifier is '8', the UE 102 executes the LTM cell switch by applying the LTM candidate configuration with the first identifier as '8'. Referring back to Figure 2, data related to the execution of the LTM cell switch may be stored as the execution data 216 in the memory 204. Embodiments of the present disclosure enables the network apparatus 104 to configure all the 'N' cells, even though only three bits are allocated to signal the second identifier.

[0285] The data 208 and the modules 210 are explained with respect to executing the LTM configurations hereafter in the present description.

[0286] In an embodiment, the execution module 228 may be configured to execute a first set of configurations from the plurality of LTM candidate configurations, upon receiving the plurality of LTM candidate configurations from the network apparatus 104. In an embodiment, data related to execution of configurations may be pre-stored ( also referred as pre-stored configuration data). Herein, the pre-stored configuration data may comprise the first set of configurations to be executed upon receiving the plurality of LTM candidate configurations, and the second set of configurations to be executed upon receiving the LTM cell switch command. The first set of configurations may comprise at least one of, but not limited to, configurations including candidate Identity (ID) and Physical Cell Identifier (PCI) of LTM candidate cells, LTM reference signal configuration, configuration for performing early synchronization, and Transmission Configuration Indicator (TCI) state configuration. The second set of configurations comprises at least one of, but not limited to, LTM candidate configurations indicating information whether the LTM candidate configuration is a complete configuration, information to determine whether a Radio Link Control (RLC) reestablishment and Packet Data Convergence Protocol (PDCP) data recovery are applicable at a time of LTM cell switch and whether Secondary Cell Group (SCG) needs to be released at the time of LTM cell switch.

[0287] The execution module 228 identifies the first set of configurations based on the pre-stored configuration data. Then, the execution module 228 executes the first set of configurations. The execution module 228 may store the second set of configurations in the UE 102 until the LTM cell switch command is received. Similarly, the execution module 228 identifies the second set of configurations based on the pre-stored configuration data. Then, the execution module 228 executes the second set of configurations.

[0288] For New Radio (NR), in an embodiment, the execution module 228 may apply the received LTM configurations in ltm-CandidateId-r18, ltm-CandidatePCI-r18, ltm-SSB-Config-r18, ltm-EarlyUL-SyncConfig-r18, ltm-dl-OrJointTCI-StateToAddModList-r18, ltm-dl-OrJointTCI-StateToReleaseList-r18, ltm-ul-TCI-ToAddModList-r18, ltm-ul-TCI-ToReleaseList-r18 upon receiving the LTM-Candidate-r18 IE. An NR RRC in the NR UE may configure lower layers configuration and TCI configuration in the LTM candidate cell configuration upon reception of the LTM candidate configuration. The UE RRC does not wait for LTM cell switch to apply these configurations. In an embodiment, the part of the configuration which is stored and applied upon cell switch includes ltm-CandidateConfig-r18, ltm-ConfigComplete-r18, ltm-NoResetID-r18 and ltm-ReleaseSCG-r18. The UE RRC defers applying these configurations till the LTM cell switch is completed. Referring to a flow diagram 400 in Figure 4, as shown in steps 1 and 2, the UE 102 executes the first set of configurations, upon receiving the plurality of LTM candidate configurations from the UE 102. The UE 102 executes the second set of configurations, upon receiving the LTM cell switch command, as shown in steps 3 and 4. Hence, the claimed invention defines methods for when to apply which part of the LTM configuration. The claimed invention enables reduction of signalling overhead as a part of the configuration can be stored and applied.

[0289] The data 208 and the modules 210 are explained with respect to handling configurations for SCG release hereafter in the present description.

[0290] In an embodiment, the communication module 224 may be configured to receive a plurality of LTM candidate configurations from the network apparatus 104. In an embodiment, the communication module 224 receives the plurality of LTM candidate configurations in a Radio Resource Control (RRC) reconfiguration message. Referring to a flow diagram 500 illustrated in Figure 5, at step 1, the UE 102 receives the plurality of LTM candidate configurations from the network apparatus 104. Referring back to Figure 2, the plurality of LTM candidate configurations may be stored as the communication data 212 in the memory 204.

[0291] In an embodiment, the identification module 230 may be configured to identify whether the plurality of LTM candidate configurations include configurations for releasing the SCG. The plurality of LTM candidate configurations may include configurations for LTM measurements and reporting, and target configurations. The identification module 230 may identify whether the plurality of LTM candidate configurations include "mrdc-SecondaryCellGroupConfig set as release", which indicates configurations for releasing the SCG. The configurations for releasing the SCG may be stored as the identification data 218 in the memory 204.

[0292] In an embodiment, the determination module 232 may be configured to determine whether the SCG is configured in a current cell camped on by the UE 102. The determination module 232 may determine whether the SCG is configured in the current cell based on a current configuration of the UE 102. In an example, consider that the UE 102 was camped on a CellA in which the SCG was configured. The UE 102 may be currently camped on a CellB by performing an LTM cell switch. In such case, the determination module 232 determines whether the SCG is configured in CellB. Referring again to the flow diagram 500 illustrated in Figure 5, at step 2, the UE 102 determines that the SCG is not configured in the current cell. Referring back to Figure 2, data related to the determination may be stored as the determination data 220 in the memory.

[0293] In an embodiment, the communication module 224 may be configured to receive the determination data 220 from the determination module 232. The communication module 224 may be further configured to transmit a reconfiguration complete message, when the SCG is not configured in the current cell. In the conventional systems, when the SCG is not configured in the current cell, the UE 102 fails RRCReconfiguration procedure and initiates RRCReestablishment, when it receives SCG release. Hence, the network needs to reconfigure the subsequent LTM configuration every time including SCG release after identifying whether the SCG is configured, after an LTM cell switch, which is not optimal. In the present disclosure, the UE 102 transmits the reconfiguration complete message (RRCReconfiguration complete) (as shown in step 3 in the flow diagram 500) so that the RRCReconfiguration procedure does not fail and RRCReestablishment is not re-initiated. Hence, the claimed invention provides a simple method to handle SCG release.

[0294] The other data 222 may store data, including temporary data and temporary files, generated by the one or more modules 210 for performing the various functions of the UE 102. The one or more modules 210 may also include the other modules 234 to perform various miscellaneous functionalities of the UE 102. The other data 222 may be stored in the memory 204. It will be appreciated that the one or more modules 210 may be represented as a single module or a combination of different modules.

[0295] Figure 6 illustrates a detailed diagram of the network apparatus 104 for handling the LTM candidate configurations, in accordance with some embodiments of the present disclosure. The network apparatus 104 may include Central Processing Units 602 (also referred as "CPUs" or "a processor 602"), communication interface 606, and a memory 604. In some embodiments, the memory 604 may be communicatively coupled to the processor 602. The memory 604 stores instructions executable by the processor 602. Further, the communication interface 606 is coupled with the processor 602 through which an input signal or / and an output signal is communicated.

[0296] Figure 7 illustrates a flow diagram 700 of handling the LTM candidate configurations by the network apparatus 104, in accordance with embodiments of the present disclosure. In an embodiment, the network apparatus 104 may be configured to transmit the plurality of LTM candidate configurations to the UE 102, as shown in step 1 in the flow diagram 700. Each LTM candidate configuration is associated with corresponding first identifier. For instance, first identifiers may be 1, 2쪋.8. Then, the network apparatus 104 may be configured to transmit an LTM cell switch command to the UE 102, to switch to a cell including a second identifier with a value that is equal to a first identifier decremented by one. In an example, consider that the range for candidate identifiers may be 1-8. The network apparatus 104 cannot transmit the first identifier as 8, as it consumes 4 bits, and only 3 bits are allocated in the LTM. Hence, the network apparatus 104 includes the second identifier with a value that is equal to a first identifier decremented by one, as shown in step 2 of Figure 7. Hence, the range transmitted by the network apparatus 104 may be 0, 1, 2쪋 'N-1' (for example, 0, 2 쪋.7).

[0297] In an embodiment, the network apparatus 104 may be configured to update a field for changing a security key as optional in a RRC reconfiguration message, when the RRC reconfiguration message includes the plurality of LTM candidate configurations. In the traditional handover procedures, the UE 102 generates or changes a security key whenever there is handover from one cell to another cell, based on a "masterkeyUpdate" configured by the network. However, the changing of the security key during LTM cell switch based on the masterkeyUpdate requires a complex design. It may not be also necessary for intra-gNB LTM. Hence, the network apparatus 104 may be configured to update the field for changing a security key as optional in a RRC reconfiguration message.

[0298] Figure 8 shows an exemplary flow chart illustrating method steps for handling the LTM candidate configurations, in accordance with some embodiments of the present disclosure. As illustrated in Figure 8, the method 800 may comprise one or more steps. The method 800 may be described in the general context of computer executable instructions. Generally, computer executable instructions can include routines, programs, objects, components, data structures, procedures, modules, and functions, which perform particular functions or implement particular abstract data types.

[0299] The order in which the method 800 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0300] At step 802, the UE 102 receives a plurality of LTM candidate configurations from the network apparatus 104. In an embodiment, the UE 102 receives the plurality of LTM candidate configurations in a Radio Resource Control (RRC) reconfiguration message. Each LTM candidate configuration of the plurality of LTM candidate configurations is associated with corresponding first identifier.

[0301] At step 802, the UE 102 receives the LTM cell switch command from the network apparatus 104 to switch to a cell / a target cell. The LTM cell switch command indicates an LTM candidate cell configuration that the network apparatus 104 previously prepared and provided to the UE 102 through RRC signalling. The LTM cell switch command includes a second identifier.

[0302] At step 804, the UE 102 generates a third identifier by incrementing the second identifier by one. Herein, when the UE 102 receives the second identifier as 'N' in the LTM cell switch command MAC CE from the network apparatus 104, the UE 102 generates the third identifier by incrementing the second identifier by one i.e., 'N+1',

[0303] At step 806, the UE 102 executes the LTM cell switch. In an embodiment, the UE 102 may identify an LTM candidate configuration with a first identifier that is equal to the third identifier. Then, the UE 102 may execute the LTM cell switch by applying the identified LTM candidate configuration.

[0304] Figure 9 shows an exemplary flow chart illustrating method steps for handling the LTM candidate configurations, in accordance with some embodiments of the present disclosure. As illustrated in Figure 9, the method 900 may comprise one or more steps. The method 900 may be described in the general context of computer executable instructions. Generally, computer executable instructions can include routines, programs, objects, components, data structures, procedures, modules, and functions, which perform particular functions or implement particular abstract data types.

[0305] The order in which the method 900 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0306] At step 902, the UE 102 receives a plurality of LTM candidate configurations from the network apparatus 104. In an embodiment, the UE 102 receives the plurality of LTM candidate configurations in a Radio Resource Control (RRC) reconfiguration message.

[0307] At step 904, the UE 102 identifies whether the plurality of LTM candidate configurations include configurations for releasing the SCG. The plurality of LTM candidate configurations may include configurations for LTM measurements and reporting, and target configurations. The identification module 230 may identify whether the plurality of LTM candidate configurations include "mrdc-SecondaryCellGroupConfig set as release", which indicates configurations for releasing the SCG.

[0308] At step 906, the UE 102 determines whether the SCG is configured in a current cell camped on by the UE 102. The UE 102 may determine whether the SCG is configured in the current cell based on a current configuration of the UE 102.

[0309] At step 908, the UE 102 transmits a reconfiguration complete message, when the SCG is not configured in the current cell. In the present disclosure, the UE 102 transmits the reconfiguration complete message (RRCReconfiguration complete) so that the RRCReconfiguration procedure does not fail and RRCReestablishment is not re-initiated.

[0310] COMPUTER SYSTEM

[0311] Figure 10 illustrates a block diagram of an exemplary computer system 1000 for implementing embodiments consistent with the present disclosure. In an embodiment, the computer system 1000 may be implemented in the UE 102. Thus, the computer system 1000 may be used to handle LTM candidate configurations. The computer system 1000 may comprise a Central Processing Unit 1004 (also referred as "CPU" or "processor"). The processor 1004 may comprise at least one data processor. The processor 1004 may include specialized processing units such as integrated system (bus) controllers, memory management control units, floating point units, graphics processing units, digital signal processing units, etc.

[0312] The processor 1004 may be disposed in communication with one or more input / output (I / O) devices (not shown) via I / O interface 1002. The I / O interface 1002 may employ communication protocols / methods such as, without limitation, audio, analog, digital, monoaural, RCA, stereo, IEEE (Institute of Electrical and Electronics Engineers) -1394, serial bus, universal serial bus (USB), infrared, PS / 2, BNC, coaxial, component, composite, digital visual interface (DVI), high-definition multimedia interface (HDMI), Radio Frequency (RF) antennas, S-Video, VGA, IEEE 802.n / b / g / n / x, Bluetooth, cellular (e.g., code-division multiple access (CDMA), high-speed packet access (HSPA+), global system for mobile communications (GSM), long-term evolution (LTE), WiMax, or the like), etc.

[0313] Using the I / O interface 1002, the computer system 1000 may communicate with one or more I / O devices. For example, the input device 1020 may be an antenna, keyboard, mouse, joystick, (infrared) remote control, camera, card reader, fax machine, dongle, biometric reader, microphone, touch screen, touchpad, trackball, stylus, scanner, storage device, transceiver, video device / source, etc. The output device 1022 may be a printer, fax machine, video display (e.g., cathode ray tube (CRT), liquid crystal display (LCD), light-emitting diode (LED), plasma, Plasma display panel (PDP), Organic light-emitting diode display (OLED) or the like), audio speaker, etc.

[0314] The processor 1004 may be disposed in communication with the communication network 1018 via a network interface 1006. The network interface 1006 may communicate with the communication network 1018. The network interface 1006 may employ connection protocols including, without limitation, direct connect, Ethernet (e.g., twisted pair 10 / 100 / 1000 Base T), transmission control protocol / internet protocol (TCP / IP), token ring, IEEE 802.11a / b / g / n / x, etc. The communication network 1018 may include, without limitation, a direct interconnection, local area network (LAN), wide area network (WAN), wireless network (e.g., using Wireless Application Protocol), the Internet, etc. The network interface 1006 may employ connection protocols include, but not limited to, direct connect, Ethernet (e.g., twisted pair 10 / 100 / 1000 Base T), transmission control protocol / internet protocol (TCP / IP), token ring, IEEE 802.11a / b / g / n / x, etc.

[0315] The communication network 1018 includes, but is not limited to, a direct interconnection, an e-commerce network, a peer to peer (P2P) network, local area network (LAN), wide area network (WAN), wireless network (e.g., using Wireless Application Protocol), the Internet, Wi-Fi, and such. The first network and the second network may either be a dedicated network or a shared network, which represents an association of the different types of networks that use a variety of protocols, for example, Hypertext Transfer Protocol (HTTP), Transmission Control Protocol / Internet Protocol (TCP / IP), Wireless Application Protocol (WAP), etc., to communicate with each other. Further, the first network and the second network may include a variety of network devices, including routers, bridges, servers, computing devices, storage devices, etc.

[0316] In some embodiments, the processor 1004 may be disposed in communication with a memory 1010 (e.g., RAM, ROM, etc. not shown in Figure 10) via a storage interface 1008. The storage interface 1008 may connect to memory 1010 including, without limitation, memory drives, removable disc drives, etc., employing connection protocols such as serial advanced technology attachment (SATA), Integrated Drive Electronics (IDE), IEEE-1394, Universal Serial Bus (USB), fiber channel, Small Computer Systems Interface (SCSI), etc. The memory drives may further include a drum, magnetic disc drive, magneto-optical drive, optical drive, Redundant Array of Independent Discs (RAID), solid-state memory devices, solid-state drives, etc.

[0317] The memory 1010 may store a collection of program or database components, including, without limitation, user interface 1012, an operating system 1014, web browser 1016 etc. In some embodiments, computer system 1000 may store user / application data, such as, the data, variables, records, etc., as described in this disclosure. Such databases may be implemented as fault-tolerant, relational, scalable, secure databases such as Oracle ® or Sybase®.

[0318] The operating system 1014 may facilitate resource management and operation of the computer system 1000. Examples of operating systems include, without limitation, APPLE MACINTOSHR OS X, UNIXR, UNIX-like system distributions (E.G., BERKELEY SOFTWARE DISTRIBUTIONTM (BSD), FREEBSDTM, NETBSDTM, OPENBSDTM, etc.), LINUX DISTRIBUTIONSTM (E.G., RED HATTM, UBUNTUTM, KUBUNTUTM, etc.), IBMTM OS / 2, MICROSOFTTM WINDOWSTM (XPTM, VISTATM / 7 / 8, 10 etc.), APPLER IOSTM, GOOGLER ANDROIDTM, BLACKBERRYR OS, or the like.

[0319] In some embodiments, the computer system 1000 may implement the web browser 1016 stored program component. The web browser 1016 may be a hypertext viewing application, for example MICROSOFTR INTERNET EXPLORERTM, GOOGLER CHROMETM0, MOZILLAR FIREFOXTM, APPLER SAFARITM, etc. Secure web browsing may be provided using Secure Hypertext Transport Protocol (HTTPS), Secure Sockets Layer (SSL), Transport Layer Security (TLS), etc. Web browsers 1016 may utilize facilities such as AJAXTM, DHTMLTM, ADOBER FLASHTM, JAVASCRIPTTM, JAVATM, Application Programming Interfaces (APIs), etc. In some embodiments, the computer system 1000 may implement a mail server (not shown in Figure) stored program component. The mail server may be an Internet mail server such as Microsoft Exchange, or the like. The mail server may utilize facilities such as ASPTM, ACTIVEXTM, ANSITM C++ / C#, MICROSOFTR,.NETTM, CGI SCRIPTSTM, JAVATM, JAVASCRIPTTM, PERLTM, PHPTM, PYTHONTM, WEBOBJECTSTM, etc. The mail server may utilize communication protocols such as Internet Message Access Protocol (IMAP), Messaging Application Programming Interface (MAPI), MICROSOFTR exchange, Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), or the like. In some embodiments, the computer system 1000 may implement a mail client stored program component. The mail client (not shown in Figure) may be a mail viewing application, such as APPLER MAILTM, MICROSOFTR ENTOURAGETM, MICROSOFTR OUTLOOKTM, MOZILLAR THUNDERBIRDTM, etc.

[0320] Furthermore, one or more computer-readable storage media may be utilized in implementing embodiments consistent with the present 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., be non-transitory. Examples include Random Access Memory (RAM), Read-Only Memory (ROM), volatile memory, non-volatile memory, hard drives, Compact　Disc　Read-Only Memory (CD ROMs), Digital Video Disc　(DVDs), flash drives, disks, and any other known physical storage media.

[0321] Figure 14 illustrates an exemplary environment 1400 for supporting subsequent Conditional PSCell Addition and Change (CPAC), in accordance with the embodiments of the present disclosure. The exemplary environment 100 comprises a UE 1402 and a network entity 1404. The UE 1402 may be any device configured to communicate in a wireless network. Examples of the UE 1402 include, but not limited to, mobile phones, smartphones, laptops, wearables, and the like. While the UE 1402 is communicating in the wireless, the UE 1402 moves between cells to ensure seamless connectivity and continuity of service for a user associated with the UE 1402. The UE 1402 moves between the cells through a procedure of handover. There are various types of handovers such as Conditional Handover (CHO), Dual Active Protocol Stack (DAPS) handover, LTM handover, and the like. The present disclosure relates to subsequent CPAC. Subsequent CPAC is a procedure in which a conditional PSCell addition or change procedure that is executed after a PSCell addition, a PSCell change, a PCell change or an SCG release based on pre-configured subsequent CPAC configuration of candidate PSCell(s) without reconfiguration and re-initiation of CPC / CPA. The UE keeps the configured subsequent CPAC configuration (unless the network entity indicates to release it or the UE autonomously releases it upon RRC re-establishment or RRC release) and evaluates the execution conditions of candidate PSCells after completion of a PSCell addition, a PSCell change, a PCell change or an SCG release. In an embodiment, the network entity 1404 may be a gNodeB (gNB) as defined in 5G networks. A person skilled in the art will appreciate that the network entity 1404 may be any other entity in Third-generation (3G) networks, Fourth-generation (4G) networks, and the like.

[0322] In the present disclosure, the UE 1402 and the network entity 1404 are configured to support subsequent CPAC. Herein, the UE 1402 is configured to receive an Radio Resource Control (RRC) message comprising of a release list for a second set of conditional execution conditions for subsequent CPAC from the network entity 1404. The RRC message is one of, without limitation to: RRCReconfiguration or RRCResume. The release list includes a list of conditional reconfiguration identifiers and the execution conditions associated with them.

[0323] In an embodiment, the UE 1402 then determines that the conditional reconfiguration identifier is not part of a current UE configuration. The UE 1402 then executes the RRC procedure corresponding to the RRC message. In an embodiment, the UE 1402 sends an RRC complete message indicating the completion of RRC procedure to the network entity 1404. In an embodiment, the conditional reconfiguration identifiers indicate one of, without limitation to: addition of a configuration of conditional reconfiguration of a PSCell, modification of the configuration of conditional reconfiguration of the PSCell and release of the configuration of conditional reconfiguration of the PSCell.

[0324] In another embodiment, the UE 1402 is configured to receive a subsequent CPAC configuration towards a subsequent target PSCell, from the network entity 1404. The UE 1402 then executes the subsequent CPAC. Upon completion of the subsequent CPAC procedure, the UE 1402 reports to the network entity 1404, information related to the subsequent CPAC. The information related to the subsequent CPAC is logged at the network entity 1404.

[0325] In an embodiment, the UE 1402 excludes a time elapsed between execution of CPAC towards a current target PSCell and reception of a second set of conditional execution conditions for subsequent CPAC in a report sent to the network entity 1404. The report may be included in one of, without limitation to: a Successful PSCell Report (SPR), a Successful PSCell Change Report (SPCR), a Successful PSCell Addition Report (SPAR), or in an SCGFailureInformation.

[0326] In an embodiment, the UE 1402 sets a field which identifies a neighbour cell as a candidate cell as true, if the neighbour cell has both conditional reconfiguration configurations associated with the neighbor cell and conditional execution conditions associated with the neighbor cell, in the report sent to the network entity 1404.

[0327] Figure 15 illustrates a detailed diagram 1500 of the UE 1402 configured to support subsequent CPAC in accordance with some embodiments of the present disclosure. The UE 1402 may include Central Processing Units 15206 (also referred as "CPUs" or "a processor 15206"), Input / Output (I / O) interface 1502, and a memory 1504. In some embodiments, the memory 1504 may be communicatively coupled to the processor 1506. The memory 1504 stores instructions executable by the processor 1506. The processor 1506 may comprise at least one data processor for executing program components for executing user or system-generated requests. The memory 1504 may be communicatively coupled to the processor 1506. The memory 1504 stores instructions, executable by the processor 1506, which, on execution, may cause the processor 1506 to support subsequent CPAC. In an embodiment, the memory 1504 may include one or more modules 1510 and data 1508. The one or more modules 1510 may be configured to perform the steps of the present disclosure using the data 1508, to support subsequent CPAC. In an embodiment, each of the one or more modules 1510 may be a hardware unit which may be outside the memory 1504 and coupled with the UE 1402. As used herein, the term modules 1510 refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a Field-Programmable Gate Arrays (FPGA), Programmable System-on-Chip (PSoC), a combinational logic circuit, and / or other suitable components that provide described functionality. The one or more modules 1510 when configured with the described functionality defined in the present disclosure will result in a novel hardware. Further, the I / O interface 1502 is coupled with the processor 1506 through which an input signal or / and an output signal is communicated.

[0328] In one implementation, the modules 1510 may include, for example, a transceiver module 1522, a determination module 1524, an execution module 1526, a reporting module 1528, and other modules 1530. It will be appreciated that such aforementioned modules 1510 may be represented as a single module or a combination of different modules. In one implementation, the data 1508 may include, for example, transceiver data 1512, determination data 1514, execution data 1516, reporting data 1518, and other data 1520.

[0329] In an embodiment, the transceiver module 1522 may be configured to receive the RRC message comprising of the release list for the second set of conditional execution conditions for subsequent CPAC from the network entity 1404. The RRC message is one of, without limitation to: RRCReconfiguration or RRCResume. The release list includes a list of conditional reconfiguration identifiers and the execution conditions associated with them.

[0330] In an embodiment, the determination module 1524 then determines that the conditional reconfiguration identifier is not part of a current UE configuration. The execution module 1526 is configured to execute the RRC procedure corresponding to the RRC message. In an embodiment, the transceiver module 1522 sends the RRC complete message indicating the completion of RRC procedure to the network entity 1404. In an embodiment, the conditional reconfiguration identifiers indicate one of, without limitation to: addition of a configuration of conditional reconfiguration of a PSCell, modification of the configuration of conditional reconfiguration of the PSCell and release of the configuration of conditional reconfiguration of the PSCell.

[0331] In another embodiment, the transceiver module 1522 is configured to receive a subsequent CPAC configuration towards a subsequent target PSCell, from the network entity 1404. The execution module 1526 is then configured to execute the subsequent CPAC. Upon completion of the subsequent CPAC procedure, the reporting module 1528 reports to the network entity 1404, information related to the subsequent CPAC. The information related to the subsequent CPAC is logged at the network entity 1404, by the reporting module 1528.

[0332] In an embodiment, the reporting module 1528 excludes a time elapsed between execution of CPAC towards a current target PSCell and reception of a second set of conditional execution conditions for subsequent CPAC in a report sent to the network entity 1404. The report may be included in one of, without limitation to: a Successful PSCell Report (SPR), a Successful PSCell Change Report (SPCR), a Successful PSCell Addition Report (SPAR), or in an SCGFailureInformation.

[0333] In an embodiment, the reporting module 1528 sets a field which identifies a neighbour cell as a candidate cell as true, if the neighbour cell has both conditional reconfiguration configurations associated with the neighbor cell and conditional execution conditions associated with the neighbor cell, in the report sent to the network entity 1404.

[0334] Referring to a flow diagram 1600 illustrated in Figure 16, at step 1, the UE 1402 receives receive the RRC message comprising of the release list for the second set of conditional execution conditions for subsequent CPAC from the network entity 1404. The RRC message is one of, without limitation to: RRCReconfiguration or RRCResume. The release list includes a list of conditional reconfiguration identifiers and the execution conditions associated with them.

[0335] At step 2 of the flow diagram 1600, the UE 1402 determines that the conditional reconfiguration identifier is not part of a current UE configuration. At step 3 of the flow diagram 1600, the UE 1402 executes the RRC procedure corresponding to the RRC message.

[0336] At step 4 of the flow diagram 1600, the UE 1402 sends the RRC complete message indicating the completion of RRC procedure to the network entity 1404. In an embodiment, the conditional reconfiguration identifiers indicate one of, without limitation to: addition of a configuration of conditional reconfiguration of a PSCell, modification of the configuration of conditional reconfiguration of the PSCell and release of the configuration of conditional reconfiguration of the PSCell.

[0337] Referring to a flow diagram 1700 illustrated in Figure 17, at step 1, the UE 1402 receive a subsequent CPAC configuration towards a subsequent target PSCell, from the network entity 1404.

[0338] At step 2 of the flow diagram 1700 , the UE 1402 executes the subsequent CPAC. Upon completion of the subsequent CPAC procedure, the UE 1402 at step 3 of the flow diagram 1700, reports to the network entity 1404, information related to the subsequent CPAC. The information related to the subsequent CPAC is logged at the network entity 1404.

[0339] In an embodiment, the UE 1402 excludes a time elapsed between execution of CPAC towards a current target PSCell and reception of a second set of conditional execution conditions for subsequent CPAC in a report sent to the network entity 1404. The report may be included in one of, without limitation to: a Successful PSCell Report (SPR), a Successful PSCell Change Report (SPCR), a Successful PSCell Addition Report (SPAR), or in an SCGFailureInformation.

[0340] In an embodiment, the UE 1402 sets a field which identifies a neighbour cell as a candidate cell as true, if the neighbour cell has both conditional reconfiguration configurations associated with the neighbor cell and conditional execution conditions associated with the neighbor cell, in the report sent to the network entity 1404.

[0341] Figure 18 illustrates a detailed diagram of the network entity 1404 for supporting subsequent CPAC, in accordance with some embodiments of the present disclosure. The network entity 1404 may include Central Processing Units 1802 (also referred as "CPUs" or "a processor 1802"), communication interface 1806, and a memory 1804. In some embodiments, the memory 1804 may be communicatively coupled to the processor 1802. The memory 1804 stores instructions executable by the processor 1802. Further, the communication interface 1806 is coupled with the processor 1802 through which an input signal or / and an output signal is communicated.

[0342] Figure 19 shows an exemplary flow chart illustrating method steps for supporting subsequent CPAC, in accordance with some embodiments of the present disclosure. As illustrated in Figure 19, the method 1900 may comprise one or more steps. The method 1900 may be described in the general context of computer executable instructions. Generally, computer executable instructions can include routines, programs, objects, components, data structures, procedures, modules, and functions, which perform particular functions or implement particular abstract data types.

[0343] The order in which the method 1900 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0344] At step 1902, the UE 1402 receives the RRC message comprising of the release list for the second set of conditional execution conditions for subsequent CPAC from the network entity 1404. The RRC message is one of, without limitation to: RRCReconfiguration or RRCResume. The release list includes a list of conditional reconfiguration identifiers and the execution conditions associated with them.

[0345] At step 1904, the UE 1402 determines that the conditional reconfiguration identifier is not part of a current UE configuration.

[0346] At step 1906, the UE 1402 executes the RRC procedure corresponding to the RRC message.

[0347] At step 1908, the UE 1402 sends the RRC complete message indicating the completion of RRC procedure to the network entity 1404. In an embodiment, the conditional reconfiguration identifiers indicate one of, without limitation to: addition of a configuration of conditional reconfiguration of a PSCell, modification of the configuration of conditional reconfiguration of the PSCell and release of the configuration of conditional reconfiguration of the PSCell.

[0348] Figure 20 shows an exemplary flow chart illustrating method steps for supporting subsequent CPAC, in accordance with some embodiments of the present disclosure. As illustrated in Figure 20, the method 2000 may comprise one or more steps. The method 2000 may be described in the general context of computer executable instructions. Generally, computer executable instructions can include routines, programs, objects, components, data structures, procedures, modules, and functions, which perform particular functions or implement particular abstract data types.

[0349] The order in which the method 2000 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0350] At step 2002, the UE 1402 receive a subsequent CPAC configuration towards a subsequent target PSCell, from the network entity 1404.

[0351] At step 2004, the UE 1402 executes the subsequent CPAC. Upon completion of the subsequent CPAC procedure, the UE 1402 at step At step 2006, reports to the network entity 1404, information related to the subsequent CPAC. The information related to the subsequent CPAC is logged at the network entity 1404.

[0352] In an embodiment, the UE 1402 excludes a time elapsed between execution of CPAC towards a current target PSCell and reception of a second set of conditional execution conditions for subsequent CPAC in a report sent to the network entity 1404. The report may be included in one of, without limitation to: a Successful PSCell Report (SPR), a Successful PSCell Change Report (SPCR), a Successful PSCell Addition Report (SPAR), or in an SCGFailureInformation.

[0353] In an embodiment, the UE 1402 sets a field which identifies a neighbour cell as a candidate cell as true, if the neighbour cell has both conditional reconfiguration configurations associated with the neighbor cell and conditional execution conditions associated with the neighbor cell, in the report sent to the network entity 1404.

[0354] COMPUTER SYSTEM

[0355] Figure 21 illustrates a block diagram of an exemplary computer system 2100 for implementing embodiments consistent with the present disclosure. In an embodiment, the computer system 2100 may be implemented in the UE 1402. Thus, the computer system 1000 may be used to support subsequent CPAC. The computer system 2100 may comprise a Central Processing Unit 2104 (also referred as "CPU" or "processor"). The processor 2104 may comprise at least one data processor. The processor 2104 may include specialized processing units such as integrated system (bus) controllers, memory management control units, floating point units, graphics processing units, digital signal processing units, etc.

[0356] The processor 2104 may be disposed in communication with one or more input / output (I / O) devices (not shown) via I / O interface 2102. The I / O interface 2102 may employ communication protocols / methods such as, without limitation, audio, analog, digital, monoaural, RCA, stereo, IEEE (Institute of Electrical and Electronics Engineers) -1394, serial bus, universal serial bus (USB), infrared, PS / 2, BNC, coaxial, component, composite, digital visual interface (DVI), high-definition multimedia interface (HDMI), Radio Frequency (RF) antennas, S-Video, VGA, IEEE 802.n / b / g / n / x, Bluetooth, cellular (e.g., code-division multiple access (CDMA), high-speed packet access (HSPA+), global system for mobile communications (GSM), long-term evolution (LTE), WiMax, or the like), etc.

[0357] Using the I / O interface 2102, the computer system 2100 may communicate with one or more I / O devices. For example, the input device 2120 may be an antenna, keyboard, mouse, joystick, (infrared) remote control, camera, card reader, fax machine, dongle, biometric reader, microphone, touch screen, touchpad, trackball, stylus, scanner, storage device, transceiver, video device / source, etc. The output device 2122 may be a printer, fax machine, video display (e.g., cathode ray tube (CRT), liquid crystal display (LCD), light-emitting diode (LED), plasma, Plasma display panel (PDP), Organic light-emitting diode display (OLED) or the like), audio speaker, etc.

[0358] The processor 2104 may be disposed in communication with the communication network 2118 via a network interface 2106. The network interface 2106 may communicate with the communication network 2118. The network interface 2106 may employ connection protocols including, without limitation, direct connect, Ethernet (e.g., twisted pair 10 / 100 / 2100 Base T), transmission control protocol / internet protocol (TCP / IP), token ring, IEEE 802.11a / b / g / n / x, etc. The communication network 2118 may include, without limitation, a direct interconnection, local area network (LAN), wide area network (WAN), wireless network (e.g., using Wireless Application Protocol), the Internet, etc. The network interface 2106 may employ connection protocols include, but not limited to, direct connect, Ethernet (e.g., twisted pair 10 / 100 / 2100 Base T), transmission control protocol / internet protocol (TCP / IP), token ring, IEEE 802.11a / b / g / n / x, etc.

[0359] The communication network 2118 includes, but is not limited to, a direct interconnection, an e-commerce network, a peer to peer (P2P) network, local area network (LAN), wide area network (WAN), wireless network (e.g., using Wireless Application Protocol), the Internet, Wi-Fi, and such. The first network and the second network may either be a dedicated network or a shared network, which represents an association of the different types of networks that use a variety of protocols, for example, Hypertext Transfer Protocol (HTTP), Transmission Control Protocol / Internet Protocol (TCP / IP), Wireless Application Protocol (WAP), etc., to communicate with each other. Further, the first network and the second network may include a variety of network devices, including routers, bridges, servers, computing devices, storage devices, etc.

[0360] In some embodiments, the processor 2104 may be disposed in communication with a memory 2110 (e.g., RAM, ROM, etc. not shown in Figure 10) via a storage interface 2108. The storage interface 2108 may connect to memory 2110 including, without limitation, memory drives, removable disc drives, etc., employing connection protocols such as serial advanced technology attachment (SATA), Integrated Drive Electronics (IDE), IEEE-1394, Universal Serial Bus (USB), fiber channel, Small Computer Systems Interface (SCSI), etc. The memory drives may further include a drum, magnetic disc drive, magneto-optical drive, optical drive, Redundant Array of Independent Discs (RAID), solid-state memory devices, solid-state drives, etc.

[0361] The memory 2110 may store a collection of program or database components, including, without limitation, user interface 2112, an operating system 2114, web browser 2116 etc. In some embodiments, computer system 2100 may store user / application data, such as, the data, variables, records, etc., as described in this disclosure. Such databases may be implemented as fault-tolerant, relational, scalable, secure databases such as Oracle ® or Sybase®.

[0362] The operating system 2114 may facilitate resource management and operation of the computer system 2100. Examples of operating systems include, without limitation, APPLE MACINTOSHR OS X, UNIXR, UNIX-like system distributions (E.G., BERKELEY SOFTWARE DISTRIBUTIONTM (BSD), FREEBSDTM, NETBSDTM, OPENBSDTM, etc.), LINUX DISTRIBUTIONSTM (E.G., RED HATTM, UBUNTUTM, KUBUNTUTM, etc.), IBMTM OS / 2, MICROSOFTTM WINDOWSTM (XPTM, VISTATM / 7 / 8, 10 etc.), APPLER IOSTM, GOOGLER ANDROIDTM, BLACKBERRYR OS, or the like.

[0363] In some embodiments, the computer system 2100 may implement the web browser 2116 stored program component. The web browser 2116 may be a hypertext viewing application, for example MICROSOFTR INTERNET EXPLORERTM, GOOGLER CHROMETM0, MOZILLAR FIREFOXTM, APPLER SAFARITM, etc. Secure web browsing may be provided using Secure Hypertext Transport Protocol (HTTPS), Secure Sockets Layer (SSL), Transport Layer Security (TLS), etc. Web browsers 2116 may utilize facilities such as AJAXTM, DHTMLTM, ADOBER FLASHTM, JAVASCRIPTTM, JAVATM, Application Programming Interfaces (APIs), etc. In some embodiments, the computer system 2100 may implement a mail server (not shown in Figure) stored program component. The mail server may be an Internet mail server such as Microsoft Exchange, or the like. The mail server may utilize facilities such as ASPTM, ACTIVEXTM, ANSITM C++ / C#, MICROSOFTR,.NETTM, CGI SCRIPTSTM, JAVATM, JAVASCRIPTTM, PERLTM, PHPTM, PYTHONTM, WEBOBJECTSTM, etc. The mail server may utilize communication protocols such as Internet Message Access Protocol (IMAP), Messaging Application Programming Interface (MAPI), MICROSOFTR exchange, Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), or the like. In some embodiments, the computer system 2100 may implement a mail client stored program component. The mail client (not shown in Figure) may be a mail viewing application, such as APPLER MAILTM, MICROSOFTR ENTOURAGETM, MICROSOFTR OUTLOOKTM, MOZILLAR THUNDERBIRDTM, etc.

[0364] Furthermore, one or more computer-readable storage media may be utilized in implementing embodiments consistent with the present 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., be non-transitory. Examples include Random Access Memory (RAM), Read-Only Memory (ROM), volatile memory, non-volatile memory, hard drives, Compact　Disc　Read-Only Memory (CD ROMs), Digital Video Disc　(DVDs), flash drives, disks, and any other known physical storage media.

[0365] The present disclosure discloses methods, a User Equipment (UE), and a network apparatus for handling LTM candidate configurations. In the present disclosure, when the UE receives LTM candidate cell identifier as N in an LTM cell switch command MAC CE from the network, the UE executes LTM cell switch for LTM candidate N+1. Hence, the claimed invention ensures that UE MAC and UE RRC are synchronised with respect to the value range used for LTM cell switch execution. Thus, the base station can configure for all N candidate cell, thereby ensuring network optimization.

[0366] In the present disclosure, when the UE receives configurations for SCG release, and SCG is not configured in the UE, the UE doesn't consider it as erroneous. Rather, the UE transmits a reconfiguration complete message to the network. Hence, the claimed invention provides a simple method for SCG release during LTM cell switch. In the present disclosure, UE applies a part of LTM configuration at the time of reception of the configuration from the network and a part at the time of LTM cell switch. Hence, the claimed invention defines methods for when to apply which part of the LTM configuration. The claimed invention enables reduction of signalling overhead as a part of the configuration can be stored and applied. In the claimed invention, the network updates a field for configuring "masterKeyUpdate" as optional in a RRC reconfiguration message. The network avoids configuring "masterKeyUpdate" in the LTM candidate configuration. Hence, the claimed invention ensures that security configurations provided by the network is as expected by the UE.

[0367] In the present disclosure, discloses methods and a UE for supporting subsequent Conditional PSCell Addition and Change (CPAC). In an embodiment, in existing systems a PSCell may need to release execution conditions to prevent the UE from performing measurements in the cells which are not its immediate neighbors. In the case that the PSCell can release only the execution conditions which are available in the configuration, it needs to inform all the network nodes (SN or MN) about the release of the configurations. Further network nodes / entities need to update the conditional configuration. This increases the complexity and signalling overhead. The method as described in the present disclosure, i.e., subsequent CPAC, introduces a new behavior for UE reporting in the SON / MDT as the configuration is stored in the UE even before the UE moves to the PSCell.

[0368] 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. The terms "including", "comprising", "having" and variations thereof mean "including but not limited to", unless expressly specified otherwise. The enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms "a", "an" and "the" mean "one or more", unless expressly specified otherwise.

[0369] A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary a variety of optional components are described to illustrate the wide variety of possible embodiments of the invention.

[0370] When a single device or article is described herein, it will be readily apparent that more than one device / article (whether or not they cooperate) may be used in place of a single device / article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be readily apparent that a single device / article may be used in place of the more than one device or article, or a different number of devices / articles may be used instead of the shown number of devices or programs. The functionality and / or the features of a device may be alternatively embodied by one or more other devices which are not explicitly described as having such functionality / features. Thus, other embodiments of the invention need not include the device itself.

[0371] The illustrated operations of Figures 8-9, 19-20 show certain events occurring in a certain order. In alternative embodiments, certain operations may be performed in a different order, modified, or removed. Moreover, steps may be added to the above-described logic and still conform to the described embodiments. Further, operations described herein may occur sequentially or certain operations may be processed in parallel. Yet further, operations may be performed by a single processing unit or by distributed processing units.

[0372] Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

[0373] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.

[0374] Referral Numerals:

[0375]

[0376] A reference to an element in the singular is not intended to mean one and only one unless specifically so stated, but rather one or more. For example, "a" module may refer to one or more modules. An element proceeded by "a," "an," "the," or "said" does not, without further constraints, preclude the existence of additional same elements.

[0377] Headings and subheadings, if any, are used for convenience only and do not limit the disclosure. The word exemplary is used to mean serving as an example or illustration. To the extent that the term "include," "have," or the like is used, such term is intended to be inclusive in a manner similar to the term "comprise" as "comprise" is interpreted when employed as a transitional word in a claim. Relational terms such as first and second and the like may be used to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions.

[0378] Phrases such as an aspect, the aspect, another aspect, some aspects, one or more aspects, an implementation, the implementation, another implementation, some implementations, one or more implementations, an embodiment, the embodiment, another embodiment, some embodiments, one or more embodiments, a configuration, the configuration, another configuration, some configurations, one or more configurations, the subject technology, the disclosure, the present disclosure, other variations thereof and alike are for convenience and do not imply that a disclosure relating to such phrase(s) is essential to the subject technology or that such disclosure applies to all configurations of the subject technology. A disclosure relating to such phrase(s) may apply to all configurations, or one or more configurations. A disclosure relating to such phrase(s) may provide one or more examples. A phrase such as an aspect or some aspects may refer to one or more aspects and vice versa, and this applies similarly to other foregoing phrases.

[0379] A phrase "at least one of" preceding a series of items, with the terms "and" or "or" to separate any of the items, modifies the list as a whole, rather than each member of the list.　 The phrase "at least one of" does not require selection of at least one item; rather, the phrase allows a meaning that includes at least one of any one of the items, and / or at least one of any combination of the items, and / or at least one of each of the items.　 By way of example, each of the phrases "at least one of A, B, and C" or "at least one of A, B, or C" refers to only A, only B, or only C; any combination of A, B, and C; and / or at least one of each of A, B, and C.

[0380] It is understood that the specific order or hierarchy of steps, operations, or processes disclosed is an illustration of exemplary approaches. Unless explicitly stated otherwise, it is understood that the specific order or hierarchy of steps, operations, or processes may be performed in different order. Some of the steps, operations, or processes may be performed simultaneously or may be performed as a part of one or more other steps, operations, or processes. The accompanying method claims, if any, present elements of the various steps, operations or processes in a sample order, and are not meant to be limited to the specific order or hierarchy presented. These may be performed in serial, linearly, in parallel or in different order. It should be understood that the described instructions, operations, and systems may generally be integrated together in a single software / hardware product or packaged into multiple software / hardware products.

[0381] The disclosure is provided to enable any person skilled in the art to practice the various aspects described herein. In some instances, well-known structures and components are shown in block diagram form to avoid obscuring the concepts of the subject technology. The disclosure provides myriad examples of the subject technology, and the subject technology is not limited to these examples. Various modifications to these aspects will be readily apparent to those skilled in the art, and the principles described herein may be applied to other aspects.

[0382] All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using a phrase means for or, in the case of a method claim, the element is recited using the phrase step for.

[0383] The title, background, brief description of the drawings, abstract, and drawings are hereby incorporated into the disclosure and are provided as illustrative examples of the disclosure, not as restrictive descriptions. It is submitted with the understanding that they will not be used to limit the scope or meaning of the claims. In addition, the detailed description provides illustrative examples, and the various features are grouped together in various implementations for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed configuration or operation. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separately claimed subject matter.

[0384] The claims are not intended to be limited to the aspects described herein, but are to be accorded the full scope consistent with the language claims and to encompass all legal equivalents. Notwithstanding, none of the claims are intended to embrace subject matter that fails to satisfy the requirements of the applicable patent law, nor should they be interpreted in such a way.

Claims

1.A method performed by a user equipment (UE) in a communication system, the method comprising:receiving, from a base station, at least one lower-layer triggered mobility (LTM) candidate configuration, wherein each LTM candidate configuration of the at least one LTM candidate configuration is associated with corresponding first identifier;receiving, from the base station, an LTM cell switch command to switch to a cell, wherein the LTM cell switch command includes a second identifier;generating a third identifier by incrementing the second identifier by one; andexecuting, an LTM cell switch by applying a LTM candidate configuration from the at least one LTM candidate configuration, wherein the LTM candidate configuration is associated with a first identifier that is equal to the third identifier.2.The method of claim 1,wherein the at least one LTM candidate configuration is received in a Radio Resource Control (RRC) reconfiguration message.3.The method of claim 1, further comprising:in case that the UE receives the at least one LTM candidate configuration, executing a first set of configurations from the at least one LTM candidate configuration, wherein the first set of configurations are identified based on pre-stored configuration data; andin case that the UE receives the LTM cell switch command from the base station, executing a second set of configurations from the at least one LTM candidate configurations, wherein the second set of configurations are identified based on the pre-stored configuration data.4.The method of claim 3,wherein the first set of configurations includes at least one of, configurations including a candidate Identity (ID) and a Physical Cell Identifier (PCI) of LTM candidate cells, LTM reference signal configuration, configuration for performing an early synchronization, and third configuration information on transmission configuration indicator (TCI) state.5.The method of claim 1,wherein the second set of configurations includes at least one of LTM candidate configurations indicating information whether the LTM candidate configuration is a complete configuration, information to determine whether a radio link control (RLC) reestablishment and packet data convergence protocol (PDCP) data recovery are applicable at a time of LTM cell switch and whether secondary cell group (SCG) needs to be released at the time of LTM cell switch.6.A method performed by a base station in a communication system, the method comprising:transmitting, to a user equipment (UE), at least one lower-layer triggered mobility (LTM) candidate configuration, wherein each LTM candidate configuration of the at least one LTM candidate configuration is associated with corresponding first identifier; andtransmtting, to the UE, an LTM cell switch command to switch to a cell, wherein the LTM cell switch command includes a second identifier,wherein an LTM cell switch is executed by applying a LTM candidate configuration from the at least one LTM candidate configuration, wherein the LTM candidate configuration is associated with a first identifier that is equal to the third identifier which is generated by incrementing the second identifier by one.7.The method of claim 6,wherein the at least one LTM candidate configuration is transmitted in a radio resource control (RRC) reconfiguration message.8.The method of claim 6,wherein in case that the base station transmits the at least one LTM candidate configuration, a first set of configuration from the at least one LTM candidate configuration is executed which are identified based on pre-stored configuration data,wherein in case that the base station transmits the LTM cell switch command, a second set of configurations from the at least one LTM candidate configuration is executed which are identified base on the pre-stored configuration data,wherein the first set of configurations includes at least one of, configurations including a candidate Identity (ID) and a Physical Cell Identifier (PCI) of LTM candidate cells, LTM reference signal configuration, configuration for performing an early synchronization, and third configuration information on transmission configuration indicator (TCI) state, andwherein the second set of configurations includes at least one of LTM candidate configurations indicating information whether the LTM candidate configuration is a complete configuration, information to determine whether a radio link control (RLC) reestablishment and packet data convergence protocol (PDCP) data recovery are applicable at a time of LTM cell switch and whether secondary cell group (SCG) needs to be released at the time of LTM cell switch.9.A user equipment (UE) in a communication system, the UE comprising:a transceiver; anda controller coupled with the transceiver and configured to:receive, from a base station, at least one lower-layer triggered mobility (LTM) candidate configuration, wherein each LTM candidate configuration of the at least one LTM candidate configuration is associated with corresponding first identifier,receive, from the base station, an LTM cell switch command to switch to a cell, wherein the LTM cell switch command includes a second identifier,generate, a third identifier by incrementing the second identifier by one, andexecute, an LTM cell switch by applying a LTM candidate configuration from the at least one LTM candidate configuration, wherein the LTM candidate configuration is associated with a first identifier that is equal to the third identifier.10.The UE of claim 9,wherein the at least one LTM candidate configuration is received in a Radio Resource Control (RRC) reconfiguration message.11.The UE of claim 9, wherein the controller is further configured to:in case that the UE receives the at least one LTM candidate configuration, execute a first set of configurations from the at least one LTM candidate configuration, wherein the first set of configurations are identified based on pre-stored configuration data; andin case that the UE receives the LTM cell switch command from the base station, executing a second set of configurations from the at least one LTM candidate configurations, wherein the second set of configurations are identified based on the pre-stored configuration data.12.The UE of claim 9,wherein the first set of configurations includes at least one of, configurations including a candidate Identity (ID) and a Physical Cell Identifier (PCI) of LTM candidate cells, LTM reference signal configuration, configuration for performing an early synchronization, and third configuration information on transmission configuration indicator (TCI) state.13.The UE of claim 9,wherein the second set of configurations includes at least one of LTM candidate configurations indicating information whether the LTM candidate configuration is a complete configuration, information to determine whether a radio link control (RLC) reestablishment and packet data convergence protocol (PDCP) data recovery are applicable at a time of LTM cell switch and whether secondary cell group (SCG) needs to be released at the time of LTM cell switch.14.A base station in a communication system, the base station comprising:a transceiver; anda controller configured with the transceiver, and configured to:transmit, to a user equipment (UE), at least one lower-layer triggered mobility (LTM) candidate configuration, wherein each LTM candidate configuration of the at least one LTM candidate configuration is associated with corresponding first identifier, andtrasnmit, to the UE, an LTM cell switch command to switch to a cell, wherein the LTM cell switch command includes a second identifier,wherein an LTM cell switch is executed by applying a LTM candidate configuration from the at least one LTM candidate configuration, wherein the LTM candidate configuration is associated with a first identifier that is equal to the third identifier which is generated by incrementing the second identifier by one.15.The base station of claim 14,wherein the at least one LTM candidate configuration is transmitted in a radio resource control (RRC) reconfiguration message,wherein in case that the base station transmits the at least one LTM candidate configuration, a first set of configuration from the at least one LTM candidate configuration is executed which are identified based on pre-stored configuration data,wherein in case that the base station transmits the LTM cell switch command, a second set of configurations from the at least one LTM candidate configuration is executed which are identified base on the pre-stored configuration data,wherein the first set of configurations includes at least one of, configurations including a candidate Identity (ID) and a Physical Cell Identifier (PCI) of LTM candidate cells, LTM reference signal configuration, configuration for performing an early synchronization, and third configuration information on transmission configuration indicator (TCI) state, andwherein the second set of configurations includes at least one of LTM candidate configurations indicating information whether the LTM candidate configuration is a complete configuration, information to determine whether a radio link control (RLC) reestablishment and packet data convergence protocol (PDCP) data recovery are applicable at a time of LTM cell switch and whether secondary cell group (SCG) needs to be released at the time of LTM cell switch.

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