Methods and apparatus for performing cell switch in a communication network

Abstract

The present disclosure generally relates to wireless communication, in particular, to a method for cell switch in a communication network performed by a User Equipment (UE). The method comprises receiving configuration information from a network entity, in which the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. Further, the method comprises performing an evaluation of a CLTM execution condition and detecting mobility event of the UE, based on the configuration information. Furthermore, the method comprises terminating the evaluation of the CLTM execution condition based on the detected mobility event.

Description

METHODS AND APPARATUS FOR PERFORMING CELL SWITCH IN A COMMUNICATION NETWORK

[0001] The present disclosure generally relates to wireless communication, in particular, but not exclusively to methods and apparatus for cell switch in a communication network.

[0002] In 5th Generation (5G) New Radio (NR) technology, mobility procedures traditionally rely on Layer 3 (L3) signalling, which introduces latency and potential data loss during handovers. To address these limitations, the 3GPP has introduced Lower Layer Triggered Mobility (LTM), which enables faster handovers using Layer 1 / Layer 2 (L1 / L2) signaling. LTM allows the User Equipment (UE) to perform early synchronization with a target cell and switch with minimal interruption. However, the existing LTM mechanisms lack flexibility and adaptability in dynamic network conditions.

[0003] To enhance mobility further, Conditional LTM (CLTM) has been proposed, where the UE switches to a target cell only upon satisfying specific execution conditions (e.g., based on Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal to Interference plus Noise Ratio (SINR) thresholds). While CLTM offers improved responsiveness and reduced latency, several challenges remain unaddressed in existing technologies.

[0004] However, existing methods do not define how CLTM should be securely configured. If CLTM is configured before Access Stratum (AS) security activation, there is a risk of UE manipulation by rogue base stations (gNB), such as mobility towards a cell of rogue base station leading to denial of service and other service disruptions. Further, current systems lack a standardized mechanism for the inter-layer communication during CLTM execution, leading to implementation complexity and inefficiency.

[0005] Further, existing methods do not define how CLTM evaluations should be handled when L3 mobility occurs or when Conditional Handover (CHO) configurations are active. This limits applicability of the CLTM in diverse deployment scenarios and affects load balancing capabilities. Especially in split base station architectures, CLTM can not manage load balancing, as the load balancing is typically performed by Centralised Unit (CU).

[0006] CLTM helps the user to perform uplink synchronisation before the cell switch. UE may receive Timing Advance (TA) values while it is connected to the source cell Current systems do not specify how the UE should manage these TA values received for CLTM, especially when the TA remains valid for extended periods. This leads to synchronization issues and resource inefficiencies. Moreover, there is no clear definition of how the UE should behave when CLTM conditions are met, particularly in terms of timer handling, candidate cell identification, and synchronization procedures. This gap hinders consistent implementation across vendors and devices.

[0007] In view of the above, there is a need to address above-mentioned problems.

[0008] 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.

[0009] According to embodiments in the disclosure, a method for cell switch in a communication network performed by a user equipment (UE) is provided. The method comprises receiving, from a network entity, conditional lower layered triggered mobility (CLTM) configuration and at least one or more of a radio resource control (RRC) configuration and lower layered triggered mobility (LTM) cell switch configuration; performing an evaluation of a CLTM execution condition based on the CLTM configuration; and based on detecting mobility event of the UE using at least one or more of RRC configuration information related to handover (e.g., mobility) and the LTM cell switch configuration, terminating the evaluation of the CLTM execution condition.

[0010] According to embodiments in the disclosure, a user equipment (UE) for performing a cell switch procedure in a communication network is provided. The UE comprises at least one processor; and memory coupled with the processor. The at least one processor is configured to receive, from a network entity, a conditional Lower Layered triggered mobility (CLTM) configuration and at least one or more of a radio resource control (RRC) configuration and lower layered triggered Mobility (LTM) cell switch configuration; perform an evaluation of a CLTM execution condition based on the CLTM configuration; and based on detecting mobility event of the UE using at least one or more of RRC configuration information related to handover (e.g., mobility) and the LTM cell switch configuration, terminate the evaluation of the CLTM execution condition.

[0011] In an embodiment the present disclosure provides method for cell switch in a communication network performed by a User Equipment (UE). The method comprises receiving configuration information from a network entity, in which the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. Further, the method comprises performing an evaluation of a CLTM execution condition and detecting mobility event of the UE, based on the configuration information. Furthermore, the method comprises terminating the evaluation of the CLTM execution condition based on the detected mobility event.

[0012] In an embodiment of the present disclosure includes a User Equipment (UE) for performing a cell switch procedure in a communication network. The UE comprises a processor, and a memory coupled with the processor. The processor is configured to receive configuration information from a network entity, in which the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. Further, the processor is configured to perform an evaluation of a CLTM execution condition and detect mobility event of the UE, based on the configuration information. Furthermore, the processor is configured to terminate the evaluation of the CLTM execution condition based on the detected mobility event.

[0013] In an embodiment, the present disclosure includes a method for configuring Conditional Lower-layer Triggered Mobility (CLTM) in a wireless network. The method comprises requesting, by a Central Unit (CU) of a network entity, a Distributed Unit (DU) to configure CLTM for a User Equipment (UE). Further, the method includes configuring, by the DU of the network entity, the CLTM including the LTM candidate cell configuration and informing the CU of the configuration. Furthermore, the method comprises transmitting, by the CU of the network entity, a Radio Resource Control (RRC) reconfiguration message to the UE including the CLTM configuration.

[0014] In an embodiment of the present disclosure includes a network entity for configuring Conditional Lower-layer Triggered Mobility (CLTM) in a communication network. The network entity comprises a processor, and a memory coupled with the processor. The processor is configured to request a Distributed Unit (DU) of the network entity to configure CLTM for a User Equipment (UE), in which the DU configures the CLTM including the LTM candidate cell configuration. Further, the processor is configured to transmit a Radio Resource Control (RRC) reconfiguration message to the UE including the CLTM configuration.

[0015] 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.

[0016] The embodiments of the disclosure itself, 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 drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings in which:

[0017] FIG. 1 illustrates an exemplary environment for performing a cell switch procedure in a communication network, in accordance with some embodiments of the present disclosure;

[0018] FIG. 2 illustrates an internal block diagram of a User Equipment (UE) for performing a cell switch procedure in a communication network, in accordance with some embodiments of the present disclosure;

[0019] FIGs. 3A-3B illustrates an internal block diagram of a network entity for configuring Conditional Lower-layer Triggered Mobility (CLTM) in a communication network, in accordance with some embodiments of the present disclosure;

[0020] FIGs. 4A-4B illustrates data flow representation illustrating performing a cell switch procedure in the communication network, in accordance with some embodiments of the present disclosure;

[0021] FIG. 5 illustrates a flowchart representation of a method for performing a cell switch procedure in a communication network, in accordance with some embodiments of the present disclosure; and

[0022] FIG. 6 illustrates a flowchart representation of a method for configuring Conditional Lower-layer Triggered Mobility (CLTM) in a communication network, in accordance with some embodiments of the present disclosure.

[0023] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the 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.

[0024] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0025] For the purposes of interpreting this specification, the definitions (as defined herein) will apply and whenever appropriate the terms used in singular will also include the plural and vice versa. It is to be understood that the terminology used herein is for the purposes of describing particular embodiments only and is not intended to be limiting. The terms "comprising", "having" and "including" are to be construed as open-ended terms unless otherwise noted.

[0026] The words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.," , "i.e.," are merely used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein using the words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.," , "i.e.," is not necessarily to be construed as preferred or advantageous over other embodiments.

[0027] Embodiments herein may be described and illustrated in terms of blocks which carry out a described function or functions.　These blocks, which may be referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and may optionally be driven by a firmware. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.　The circuits constituting a block may be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block.　Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the disclosure.　Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the disclosure.

[0028] It should be noted that elements in the drawings are illustrated for the purposes of this description and ease of understanding and may not have necessarily been drawn to scale. For example, the flowcharts / sequence diagrams illustrate the method in terms of the steps required for understanding of aspects of the embodiments as disclosed herein. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the present embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Furthermore, in terms of the system, one or more components / modules which comprise the system may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the present embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0029] The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any modifications, equivalents, and substitutes in addition to those which are particularly set out in the accompanying drawings and the corresponding description. Usage of words such as first, second, third etc., to describe components / elements / steps is for the purposes of this description and should not be construed as sequential ordering / placement / occurrence unless specified otherwise.

[0030] Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings.

[0031] In describing the embodiments, descriptions related to technical contents well-known in the art and not associated directly with the disclosure will be omitted. Such an omission of unnecessary descriptions is intended to prevent obscuring of the main idea of the disclosure and more clearly transfer the main idea.

[0032] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted, or schematically illustrated. Further, the size of each element does not completely reflect the actual size. In the drawings, identical or corresponding elements are provided with identical reference numerals or different reference numerals.

[0033] The advantages and features of the disclosure and ways to achieve them will be apparent by making reference to embodiments as described below in detail in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments set forth below, but may be implemented in various different forms. The following embodiments are provided only to completely disclose the disclosure and inform those skilled in the art of the scope of the disclosure, and the disclosure is defined only by the scope of the appended claims. Throughout the specification, the same or like reference numerals designate the same or like elements. Furthermore, in describing the disclosure, a detailed description of known functions or constitution incorporated herein will be omitted in the case that it is determined that the description may make the subject matter of the disclosure unnecessarily unclear. The terms which will be described below are terms defined in consideration of the functions in the disclosure, and may be different according to users, intentions of the operators, or customs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

[0034] Herein, it will be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, may be performed based on computer program instructions. These computer program instructions may be loaded individually or collectively onto at least one processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which perform through any one of, or in any combination of, the at least one processor of the computer or other programmable data processing apparatus, create means for performing the functions specified in the flowchart block(s). These computer program instructions may also be stored in a non-transitory computer usable or computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instruction means that perform the function specified in the flowchart block(s). The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable data processing apparatus to produce a computer executed process such that the instructions that perform on the computer or other programmable data processing apparatus provide steps for executing the functions specified in the flowchart block(s).

[0035] Further, each block may represent a module, segment, or portion of code, which includes one or more executable instructions for executing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order. For example, two blocks (or functions) shown in succession may in fact be performed substantially concurrently or the blocks may sometimes be performed in the reverse order, depending upon the functionality involved.

[0036] As used in embodiments of the disclosure, a "~unit / module" may refer to a software element or a hardware element, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), which performs a predetermined function. However, the term including the word "~unit / module" does not always have a meaning limited to software or hardware. The "~unit / module" may be constructed either to be stored in an addressable storage medium or to execute one or more processors. Therefore, the "~unit / module" includes, for example, software elements, object-oriented software elements, components such as class elements and task elements, processes, functions, properties, procedures, sub-routines, segments of a program code, drivers, firmware, micro-codes, circuits, data, database, data structures, tables, arrays, and parameters. The components and functions provided by the "~unit / module" may be either combined into a smaller number of components and a "~unit / module," or divided into additional components and a "~unit / module." Moreover, the components and "~units / module" may be implemented to reproduce one or more central processing units (CPUs) within a device or a security multimedia card. Further, in the embodiments, the "~unit / module" may include one or more processors.

[0037] The entirety of the one or more computer programs may be stored in a single memory device, or the one or more computer programs may be divided with different portions stored in different multiple memory devices.

[0038] Any of the functions or operations described herein can be processed by one processor or a combination of processors. The one processor or the combination of processors is circuitry performing processing and includes circuitry like an application processor (AP, e.g. a CPU), a communication processor (CP, e.g., a modem), a graphics processing unit (GPU), a neural processing unit (NPU) (e.g., an artificial intelligence (AI) chip), a Wi-Fi chip, a Bluetooth® chip, a global positioning system (GPS) chip, a near field communication (NFC) chip, connectivity chips, a sensor controller, a touch controller, a finger-print sensor controller, a display driver integrated circuit (IC), an audio CODEC chip, a universal serial bus (USB) controller, a camera controller, an image processing IC, microprocessors, microcontrollers, digital　signal processors, FPGA, ASIC, a microprocessor unit (MPU), a system on chip (SoC), an IC, or the like. The one processor or the combination of processors executes instructions that can be stored in a memory, such as the　operating system, in order to control the overall operation of the device.　Also, the one processor or the combination of processors is also capable of executing other processes and programs　resident in the memory, such as processes for the disclosure.

[0039] It will be appreciated that various embodiments of the disclosure according to the claims and description in the specification can be realized in the form of hardware, software or a combination of hardware and software.

[0040] Any such software may be stored in non-transitory computer readable storage media. The non-transitory computer readable storage media store one or more computer programs (software modules), the one or more computer programs include computer-executable instructions that, when executed by one or more processors of an electronic device individually or collectively, cause the electronic device to perform a method of the disclosure. Additionally, or alternatively, such software may be a computer program [product] comprising instructions which, when executed by one or more processors of an electronic device individually or collectively, cause the electronic device to perform a method of the disclosure.

[0041] Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like read only memory (ROM), whether erasable or rewritable or not, or in the form of memory such as, for example, random access memory (RAM), memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a compact disk (CD), digital versatile disc (DVD), magnetic disk or magnetic tape or the like. It will be appreciated that the storage devices and storage media are various embodiments of non-transitory machine-readable storage that are suitable for storing a computer program or computer programs comprising instructions that, when executed, implement various embodiments of the disclosure. Accordingly, various embodiments of the present disclosure may provide a program comprising code for implementing apparatus or a method as claimed in any one of the claims of this specification and a non-transitory machine-readable storage storing such a program.

[0042] Hereinafter, the determination of priority between A and B in the present disclosure may refer to various actions such as selecting the one having a higher priority based on a predefined priority rule and performing an operation corresponding thereto, or omitting or dropping an operation corresponding to the one having a lower priority.

[0043] Hereinafter, "A or B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0044] In addition, "at least one of A, B, and C" as described in the present disclosure may be understood to include A, or B, or C, or any combination of A, B, and C.

[0045] In addition, "at least one of A, B, or C" as described in the present disclosure may be understood to include A, or B, or C, or any combination of A, B, and C.

[0046] Furthermore, "A / B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0047] Furthermore, "A, B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0048] Furthermore, "A and B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0049] Furthermore, "if condition A and condition B are satisfied," as described in the present disclosure, may not be limited to a case where both condition A and condition B are satisfied, but may be understood to include a case where either condition A or condition B is individually satisfied, both condition A and condition B are satisfied, or one or more additional conditions are satisfied in combination.

[0050] Furthermore, throughout this disclosure, ordinal terms such as "first," "second," "third," etc., (and similar qualifiers) are used merely to distinguish between different instances, occurrences, configurations, messages, stages, elements or aspects of elements, operations, or information as described herein. Unless the context clearly dictates otherwise, the use of such ordinal terms does not itself require that the elements, operations, or information distinguished by these terms be structurally different, numerically distinct, or substantively dissimilar. For example, a "first signal" and a "second signal" may refer to instances of the same signal transmitted at different times or containing the same core information despite minor variations, or they may refer to signals with different content or characteristics, depending on the specific context. Similarly, a "first value" and a "second value" may represent the same magnitude but measured or applied in different circumstances, or they may represent different magnitudes. The interpretation should be guided by the specific technical context, function, and relationship described in the relevant portion of the specification and claims.

[0051] Furthermore, the terms "first ~", "second ~", etc., as described in the present disclosure with respect to various elements (e.g., information, objects, operation, sequences, or the like), should not limit those elements. These terms may only be intended to distinguish one element from another, and may not be intended to indicate a specific order. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element.

[0052] Furthermore, even if "first ~" and "second ~" are described in the present disclosure, it may be understood that element(s) referred to by "first ~" and "second ~" may be the same or different. For example, in case of element(s) being information, first information and second information may both be the same information, and, in some cases, are separate and different information.

[0053] In addition, the terms "if ~" and "in case that ~" as used in the disclosure or claims may be interpreted to include the meanings of "when (or upon) ~," "in response to ~," "based on ~," or "according to ~," and may be used interchangeably with these expressions. In addition, expressions other than those exemplified herein may also be used, as long as they have substantially the same meaning and do not impair the technical features of the present disclosure. If a method step (e.g., transmit a signal) is performed according to the disclosure of the application in connection with one of the above terms (such as "in case that ~" or the like), it may be interpreted to include the meanings (disclosure) of a prior determination that a feature has a specific state "~" (e.g., a bit length is above X), and then perform the method step in response to said determination.

[0054] In addition, the term "not perform" as used in the present disclosure or claims may, in context, be understood to mean that the corresponding step is omitted or skipped. Such a term may be replaced with other terms having the same or substantially equivalent meaning.

[0055] In addition, "transmitting a message including A and B" as described in the present disclosure, may be understood as encompassing both (i) transmitting A and B in a single message, and (ii) transmitting A and B separately via multiple messages (e.g., transmitting a first message including A and a second message including B). This interpretation may also apply to messages that include two or more items (e.g., A, B, C), transmitted either together or separately.

[0056] In addition, "transmitting a message including A and transmitting a message including B" may also be interpreted as transmitting a message including A and B in a single message.

[0057] In the specific embodiments of the present disclosure described below, terms or components included in the disclosure may be expressed in singular or plural form depending on the specific embodiments presented. However, such singular or plural expressions are selected appropriately for convenience of description, and the present disclosure is not limited to a singular or plural number of components. A component expressed in the plural form may be implemented as a single component, and a component expressed in the singular form may be implemented as multiple components.

[0058] The drawings or flowcharts described below illustrate example methods that may be implemented according to the principles of the present disclosure, and various modifications may be made to the methods illustrated in the flowcharts of the present disclosure. For example, although illustrated as a series of steps, various steps in each drawing or flowchart may overlap, occur in parallel, occur in a different order, or be repeated. In other examples, any step may be omitted or replaced with another step.

[0059] The process of the flowchart may be performed by a device. One or more of the steps of the　flowchart can be implemented by one or more processors / computer programs executing　instructions to perform the noted functions.

[0060] The methods and apparatuses proposed in the embodiments of the present disclosure may be disclosed in connection with drawings disclosing flowcharts to illustrate example methods that may be implemented according to the principles of the present disclosure. Such flowcharts may contain different branches and / or sub-branches. It is understood that the principles of the present disclosure do not only contain the combination of all branches / sub-branches disclosed in the embodiment, but the present disclosure also contains at least one isolated branch / isolated sub-branch, in particular to a single branch / single sub-branch.

[0061] The methods and apparatuses proposed in the embodiments of the present disclosure are not limited to each embodiment individually, but may also be applied in combination of all or some of the embodiments proposed in the disclosure. Therefore, the embodiments of the present disclosure may be modified and applied without significantly departing from the scope of the present disclosure, as would be understood by those skilled in the art.

[0062] In this case, even if certain wordings are described differently across embodiments, they may be used interchangeably or in substitution or in combination if their underlying concepts are equivalent. For example, for the same or equivalent concept, even if one embodiment uses the expression "A" and another embodiment uses the expression "B", such expressions may be understood interchangeably, in substitution, or in combination.

[0063] The terms used in the following description to refer to access nodes, network entities, messages, interfaces between network entities, various types of identification information, and the like, are provided merely for the convenience of explanation by way of example. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may also be used. Such terms may also be interchangeable with terms defined in any 3rd generation partnership project　(3GPP) technical specifications (TS) or similar technical specifications, e.g., from ETSI, where appropriate.

[0064] Hereinafter, a base station (BS) is an entity that allocates resources to terminals, and may be at least one of a gNode B, an eNode B, a Node B, a 6G base station (sNB), a wireless access unit, a BS controller, or a node on a network.

[0065] Furthermore, the base station of the present disclosure may include a split architecture comprising a central unit (CU) and a distributed unit (DU). In this structure, the CU is configured to process the higher layers of the control and user planes, while the DU is configured to process lower-layer radio resource functions. The embodiments of the present disclosure may be equally applicable to 5G base station architectures in which such CU and DU functional splits are implemented. The embodiments of the present disclosure may be equally applicable to other base station architectures in which such CU and DU functional splits are not implemented.

[0066] A terminal may include a UE, a mobile station (MS), a cellular phone, a smartphone, a computer, a tablet, a wearable device, an Internet of Things (IoT) device, a television, a connected car, or any other device / system capable of performing communication functions.

[0067] In the disclosure, a downlink (DL) refers to a radio link through which a BS transmits a signal to a terminal, and an uplink (UL) refers to a radio link through which a terminal transmits a signal to a BS.

[0068] Furthermore, hereinafter, 5th generation (5G) mobile communication technologies (e.g., 5G new radio (NR)), 6th generation (6G) mobile communication technologies (e.g., 6G Radio (6GR)) may be described by way of example, but the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, newly evolved mobile communication systems developed after 5G and 6G may be included. Furthermore, based on determinations by those skilled in the art, the embodiments of the present disclosure may also be applied to other communication systems (e.g., Wi-Fi systems) through some modifications without significantly departing from the scope of the present disclosure

[0069] The present disclosure relates to Lower Layer Triggered Mobility (LTM). More particularly, the present disclosure relates to conditional LTM and conditional early Random-Access Channel　(RACH) synchronization.

[0070] In wireless technologies such as, Fifth Generation (5G) New Radio (NR), devices can move across different cells. Mobility is performed using a procedure called cell reselection in RRC_IDLE mode. Till NR Release-17 (R17), mobility is performed using a procedure called handover in RRC_CONNECTED mode. Network-controlled mobility applies to User Equipments (UEs) in RRC_CONNECTED mode and requires explicit Radio Resource Control　(RRC) signalling to be triggered by a Next Generation Node B (gNB) in NR. The handover in NR usually consists of three steps: handover preparation, handover execution and handover completion. The gNB may configure the UE to report measurements. Based on the reported measurements, and / or based on its own understanding of the network topology, the gNB will send RRC reconfiguration message to handover the UE from a source cell to another cell called target cell. The UE accesses the target cell and sends RRC reconfiguration complete message. Alternatively, in 3rd Generation Partnership Project　(3GPP) NR release 16, the gNB may configure the UE with the execution conditions for triggering handover. Once the execution conditions are satisfied, the UE may move to target cell and send the RRC reconfiguration complete message. This is known as CHO. The 3gpp also introduced a new handover called Dual Active Protocol Stack (DAPS) handover in release 16. In all these methods, the UE performs handover by sending Layer 3 (L3) (RRC) messages which causes considerable signalling overhead and latency issues. The handover and Conditional Handover (CHO) may be considered as layer 3 mobility. In case of dual connectivity, the UE may perform Primary Secondary Cell Group (SCG) cell　(PSCell) change or conditional PSCellChange. In the context of dual connectivity, the PSCellChange and / or the conditional PSCellChange may also be referred as layer 3 mobility. i.e., handover, conditional handover, PSCellChange, conditional PSCellChange, and the like are referred to L3 mobility. The PSCellChange and / or the conditional PSCellChange may be referred to as SCG layer 3 mobility and the handover and CHO as Master Cell Group　(MCG) layer 3 mobility in the context of dual connectivity.

[0071] The 3gpp release 18 introduced Lower Layers (L1 / L2 layers) triggered mobility, also known as L1 / L2 Triggered Mobility　(LTM) to solve the problem related to latency, signalling overhead, and the like, 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 the candidate cells. The network may further send Medium Access Control (MAC) Control Element (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. LTM may be referred to L1 / L2 Triggered Mobility.

[0072] The gNB Central Unit (CU) may provide LTMCandidateConfiguration, i.e., configure the LTM candidate cells through one RRCReconfiguration message for a candidate target cell. The gNB may further release or modify the candidate configurations. The 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 and the UE may store the LTM configuration of other candidate cells even after moving to a candidate cell through LTM. The gNB may also 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 (e.g. L1 measurements for LTM). The new serving cell may send LTM cell switch command to the UE and UE performs LTM, such an LTM is called subsequent LTM.

[0073] The UE performs the L1 measurements on the source cell and the candidate cell, and reports the L1 measurements through Channel State Information (CSI) reports to the gNB Distributed Unit (DU) of the source cell. The gNB DU may send a MAC CE (for e.g., the LTM MAC CE or cell switch MAC CE) asking the UE to switch to another cell which is a LTM candidate cell. The UE may perform random access during LTM cell switch, or the cell switch may be Random-Access Channel　(RACH) less. The CellSwitch may be guarded by a timer, T304 timer.

[0074] 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 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 synchronization TA or TA for Early Sync). The random access performed on LTM candidate cells for the timing advance reception is known as random access for early TA. The gNB sends a Physical Downlink Control Channel (PDCCH) order to initiate the RACH for TA measurement for the candidate cells. The UE receives the PDCCH order from the serving cell. Upon reception of the PDCCH order, the UE initiates the RACH for the TA measurement for the candidate cells from the one or more candidate cells. The UE sends a RACH preamble to the candidate cells and receives the TA value from the candidate cell. The TA for the candidate cells may be received from the source cell. Generally, the TA will be received in the random access response, but it may be also received through the MAC CE. If a 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 the RACH for the TA measurement (also known as RACH for early sync).

[0075] LTM is a procedure in which the gNB receives L1 measurement report(s) from the UE, and on basis of the reports, the gNB changes the UE's serving cell by a cell switch command signaled via the MAC CE. The cell switch command indicates an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through RRC signaling. 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. UE also may switch to a Master Cell Group (MCG) LTM candidate cell in certain failures using LTM based recovery.

[0076] In an embodiment, the network may request the UE to perform early TA acquisition of the candidate cell before the cell switch. The early TA acquisition is triggered by PDCCH order [or through UE-based TA measurement]. The network indicates in the cell switch command whether the UE shall access the target cell with a Random Access (RA) procedure if a TA value is not provided or with Physical Uplink Shared Channel (PUSCH) transmission using the indicated TA value. For a 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. In an embodiment, the following principles apply to LTM, particularly to intra-CU LTM: (1) the UE doesn't update its security key in LTM and (2) the subsequent LTM is supported.

[0077] 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:

[0078] the PCell change in non-Carrier Aggregation　(CA) scenario,

[0079] the PCell change in CA scenario,

[0080] the dual connectivity scenario, at least for the PSCell change without Master Node　(MN) involvement case, i.e. intra- Secondary Node (SN) PSCell change.

[0081] In an embodiment, a supervision timer can be used to detect failure of LTM cell switch procedure. In this embodiment, LTM procedure fails if the LTM supervision timer expires, upon which the UE initiates the RRC connection re-establishment procedure. 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, e.g., avoiding sending LTM cell switch command and L3 handover command simultaneously.

[0082] The cell switch command is conveyed in a MAC CE, which contains the necessary information to perform the LTM cell switch.

[0083] An event triggered L1 measurement may be applied to select the candidate beam / cell to trigger early synchronization and select the target beam / cell and trigger LTM cell switch procedure. In an embodiment, for event triggered L1 measurements, the beam level measurement result for event evaluation is baseline. In certain cases, cell level measurement also may be considered.

[0084] In an embodiment, for event triggered L1 measurements, the following LTM events based on beam specific quality of serving cell and candidate cells as the L1 LTM measurement events are supported:

[0085] Event LTM2: Beam of serving cell becomes worse than absolute threshold;

[0086] Event LTM3: Beam of candidate cell becomes amount of offset better than beam of serving cell;

[0087] Event LTM4: Beam of candidate cell becomes better than absolute threshold;

[0088] Event LTM5: Beam of serving cell becomes worse than absolute threshold1 and beam of candidate cell becomes better than another absolute threshold2.

[0089] In an embodiment, for event triggered L1 measurements, the UE supports the beam configuration of both Synchronization Signal Block (SSB) and Channel State Information Reference Signal　(CSI-RS) in L1 measurement resource configuration in LTM configuration. Same RS type may be used for both serving and neighboring cell for event LTM3 and event LTM5.

[0090] In an embodiment, for event triggered L1 measurements, the filtering of the L1 measurement results may be performed for the LTM events.

[0091] In an embodiment, for event triggered L1 measurements, for LTM event evaluation, Time-to-Trigger (TTT), hysteresis for entering / leaving, and / or beam specific and / or cell specific offset can be applied.

[0092] Conditional LTM: the UE may be configured with a condition and upon the fulfilment of the condition, the UE executes LTM cell switch.

[0093] Conditions for conditional LTM can be based on measured L1 Reference Signal Received Power (RSRP) or L1 Reference Signal Received Quality　(RSRQ) or L1 Signal to Interference plus Noise Ratio (SINR) of serving cell and neighbor cell. The RSRP, the RSRQ and the SINR may be filtered before using them for conditional LTM. The UE may be configured with an LTM candidate configuration and the conditions for applying the LTM candidate configuration. The conditions can be based on the LTM events such as LTM event LTM3 or LTM5 or other LTM events.

[0094] Conditional early RACH synchronization (also referred as conditional early TA and / or conditional early synchronization or conditional early sync RACH or conditional early synchronization RACH or conditional early synchronization random access or conditional early RACH sync or similar names). The UE may be configured with a condition and upon the fulfilment of the condition the UE initiates random access for receiving the early timing advance (this may be similar to the random access performed for PDCCH ordered RACH). The UE may receive the timing advance in random access response or in a MAC control element. This may be referred to as conditional early RACH synchronization. These conditions can be based on measured L1 RSRP or L1 RSRQ or L1 SINR of serving cell and neighbor cell. These conditions can also be based on measured L3 RSRP or L3 RSRQ or L3 SINR of serving cell and neighbor cell. For e.g., the UE may be configured to perform conditional early RACH synchronization when the serving cell's measured RSRP or RSRQ is below a threshold and that of neighbor cell is above a threshold. In another embodiment, the UE may be configured to perform conditional LTM when the neighbor cell's measured RSRP or RSRQ is better than an offset of that of serving cell.

[0095] In yet another embodiment, the UE may be configured with configuration for early synchronization and the conditions for performing the early synchronization. The conditions can be based on the LTM events such as LTM event LTM3 or LTM5 or other LTM events.

[0096] However, there still exists need for configuration of conditional LTM and conditional early RACH sync, interaction of conditional LTM execution and CHO execution, interaction of conditional LTM execution and conditional early RACH synchronization execution and interaction of MAC reset execution and conditional early RACH synchronization execution.

[0097] With respect to the present invention, v18.2.0 of 3gpp technical specifications 38.331,38.300,38.321,37.340,38.306 and the like may be considered as a background.

[0098] In an embodiment, a network apparatus such as gNB does not configure a CHO and Conditional LTM (CLTM) together. If the network apparatus decides to configure a UE with CHO and the UE is already configured for CLTM, the network apparatus releases CLTM configuration. If the network apparatus decides to configure the UE with CLTM and the UE is already configured for CHO, the network apparatus releases CHO configuration. In another embodiment, the same condition for configuration of CLTM as in the previous embodiment is applicable for configuration of Conditional early RACH synchronization.

[0099] In an embodiment, the network apparatus such as gNB does not configure the CHO and conditional LTM (CLTM) for Master Cell Group　(MCG) together. If the network apparatus such as Master Node (MN) in NR decides to configure the UE with the CHO and the UE is already configured for CLTM for MCG, the network apparatus releases CLTM configuration. If the network apparatus decides to configure the UE with CLTM for MCG and the UE is already configured for CHO, the network apparatus releases CHO configuration. In another embodiment, the condition for configuration of CLTM as in the previous embodiment is applicable for configuration of conditional early RACH synchronization also.

[0100] In an embodiment herein, the network apparatus such as secondary node (SN) gNB does not configure the CHO and CLTM for SCG together. If the network apparatus decides to configure the UE with CHO and the UE is already configured for CLTM for SCG, the network apparatus releases CLTM configuration. If the network apparatus decides to configure the UE with CLTM for SCG and the UE is already configured for CHO, the network apparatus releases CHO configuration. In another embodiment, the condition for configuration of CLTM as in the previous embodiment is applicable for configuration of conditional early RACH synchronization also.

[0101] In an embodiment herein, the network apparatus such as MN gNB does not configure the conditional PSCell Addition (CPA) and CLTM together. If the network apparatus decides to configure the UE with CPA and the UE is already configured for the CLTM, the network apparatus releases CLTM configuration. If the network apparatus decides to configure the UE with CLTM and the UE is already configured for the CPA, the network apparatus releases the CPA configuration. In an embodiment the CLTM is CLTM for MCG. In another embodiment, the condition for configuration of CLTM as in the previous embodiment is applicable for configuration of conditional early RACH synchronization also.

[0102] In an embodiment herein, the network apparatus such as MN gNB or SN gNB does not configure the conditional PSCell Change (CPC) and CLTM together. If the network apparatus decides to configure the UE with the CPC and the UE is already configured for the CLTM, the network apparatus releases the CLTM configuration. If the network apparatus decides to configure the UE with the CLTM and the UE is already configured for CPC, the network apparatus releases CPA configuration. In an embodiment the CLTM is the CLTM for SCG. In an embodiment the CLTM is CLTM for MCG and SCG. In an embodiment, the CLTM can be CLTM for SCG with MN involvement. In another embodiment, the condition for configuration of CLTM as in the previous embodiment is applicable for configuration of conditional early RACH synchronization.

[0103] In an embodiment herein, network apparatus such as gNB configures CLTM for MCG only when AS security has been activated and Signaling Radio Bearer-2 (SRB2) with at least one Data Radio Bearer (DRB) are set up and not suspended. Network apparatus determines whether AS security is activated while configuring CLTM and configures CLTM only if AS security is activated. This allows the UE to verify the authenticity of the network apparatus, thereby preventing the configuration and execution of CLTM by an unauthorised (fake) network apparatus. UE may fail CLTM configuration and the corresponding RRC Reconfiguration procedure if it is configured before AS security activation.Similarly, network apparatus determines whether SRB2 and at least one DRB is configured while configuring CLTM. This reduces the signalling overhead for the configuration of CLTM. In an embodiment herein, the network apparatus such as the gNB configures the CLTM for MCG only when the AS security has been activated and SRB2 with at least one DRB or Multicast Radio Bearer (MRB) are set up and not suspended. In an embodiment herein, the network apparatus such as the gNB configures the CLTM for the MCG only when at least one Radio Link Control　(RLC) bearer is set up in SCG. In an additional embodiment, the same condition for the configuration of CLTM as in the previous embodiment is applicable for configuration of conditional early RACH synchronization.

[0104] In an embodiment herein, the gNB DU includes the conditional LTM configuration (for e.g., in Information Elements (IE) such as CellGroupConfig) for MCG only when AS security has been activated and SRB2 with at least one DRB are set up and not suspended. In an embodiment herein, the gNB DU includes CLTM configuration (for e.g. in IEs such as CellGroupConfig) for MCG only when AS security has been activated. In an embodiment herein, gNB DU includes the CLTM configuration (for e.g., in IEs such as CellGroupConfig) for MCG only when SRB2 with at least one DRB are set up and not suspended. In an embodiment herein, the gNB DU includes conditional LTM configuration (for e.g., in IEs such as CellGroupConfig) for MCG only when the SRB2 with the at least one DRB or MRB are set up and not suspended. In an additional embodiment, the condition for configuration of CLTM as in the previous embodiment is applicable for configuration of Conditional early RACH synchronization.

[0105] In an embodiment, CU may inform DU to configure conditional LTM or Conditional early RACH synchronization through F1AP messages such as F1AP UEContextSetup request or F1AP UEContextModification request and the DU configures conditional LTM configuration or Conditional early RACH synchronization configuration. DU informs CU that conditional LTM configuration or Conditional early RACH synchronization configuration is successful through F1AP messages such as F1AP UEContext Setup Response or F1AP UEContext Modification Response. DU also may send the conditional LTM configuration or Conditional early RACH synchronization configuration to the UE through the CU using F1AP messages. CU includes the received conditional LTM configuration or Conditional early RACH synchronization configuration in the RRC message. As described in the background, conditional LTM configuration provided by DU can include execution condition and the conditions can be based on the LTM events such as LTM event LTM3 or LTM5 or other LTM events.

[0106] In an embodiment herein, the gNB DU includes conditional LTM configuration (for e.g., in IEs such as CellGroupConfig) for SCG only when at least one RLC bearer is set up in SCG. In an additional embodiment, the condition for configuration of CLTM as in the previous embodiment is applicable for configuration of Conditional early RACH synchronization.

[0107] In an embodiment, upon CLTM execution, and the CLTM execution is for MCG, the UE releases the CHO configuration. In an embodiment, upon CLTM execution and the CLTM execution is for MCG, the UE also releases the Conditional PSCell Addition (CPA) and Conditional PSCell Change (CPC) configuration. The UE may keep any subsequent Conditional PSCell Addition and Change (CPAC) configuration.

[0108] In an embodiment, upon CLTM execution and the CLTM execution is for the SCG, the UE keeps the CHO configuration. In an embodiment, the CHO configuration may be CHO configuration stored in the UE for performing subsequent CHO. In an embodiment, upon the CLTM execution and the CLTM execution is for SCG, the UE releases the CPA and the CPC configuration. The UE may keep any subsequent CPAC configuration. Keeping the subsequent CHO or subsequent CPAC configuration upon CLTM execution while releasing the non- subsequent CHO configuration allows reduced signalling for subsequent CHO or subsequent CPAC and a clean handling of other types of mobility.

[0109] In another embodiment, upon CLTM execution and the CLTM execution is for SCG, the UE release the CHO configuration.

[0110] In an embodiment, upon CLTM execution and the CLTM is for the MCG, the UE stops the CHO evaluation. In an embodiment, upon CLTM execution and the CLTM is for the MCG, the UE stops the CPC evaluation. Stopping the CHO evaluation and CPC evaluation avoids collision between CLTM execution and possible triggering of CHO or CPC which complicates the implementation of both the UE and the network apparatus and may also possibly result in the failure of both the procedures. In an embodiment, upon CLTM execution and the CLTM is for the MCG, the UE stops the evaluation of conditional early RACH synchronization for MCG. In an embodiment, upon CLTM execution and the CLTM is for the MCG, the UE stops the evaluation of conditional early RACH synchronization for SCG.

[0111] In an embodiment, upon CHO execution, the UE keeps the CLTM configuration. The UE releases all the conditional reconfigurations and the associated configurations except the conditional reconfiguration for the subsequent CPAC and CLTM. The CLTM configuration in the previous embodiment can be CLTM configuration for the MCG. The CLTM configuration in the previous embodiment can be CLTM configuration for the SCG. This allows the UE to execute CLTM in the new cell without being explicitly configured by the network, which helps in reducing the signalling and executing CLTM quickly.

[0112] In an embodiment, upon CHO execution, the UE keeps the conditional early RACH synchronization configuration.

[0113] In an embodiment, upon CPAC execution, the UE keeps the CLTM configuration for SCG. The UE releases all the conditional reconfigurations and the associated configurations for SCG except for the conditional reconfiguration for the subsequent CPAC and CLTM.

[0114] In an embodiment, upon CPAC execution, the UE keeps the conditional early RACH synchronization the configuration for SCG.

[0115] In an embodiment, upon SCG release, the UE releases the CLTM configuration for the SCG. In an embodiment, upon SCG release, the UE releases the LTM event configuration (configuration for LTM events like LTM2, LTM3,LTM4, LTM5 etc.) for the SCG. In an embodiment, upon SCG release, the UE releases the conditional early RACH synchronization configuration for SCG. This allows the master node to configure the UE with new CLTM configuration, while performing SCG addition.

[0116] In an embodiment, upon CHO execution, the UE stops the evaluation of the CLTM for the MCG. In an embodiment, upon CHO execution, the UE stops the evaluation of the conditional early RACH synchronization for the MCG.

[0117] In an embodiment, upon CPAC execution, the UE stops the evaluation of the CLTM for the SCG. In an embodiment, upon CPAC execution, the UE stops the evaluation of the conditional early RACH synchronization for SCG.

[0118] In an embodiment, upon MAC reset, the UE stops the evaluation of CLTM for the cell group where the MAC reset is executed. In an embodiment, upon the MAC reset of the SCG, the UE stops the evaluation of CLTM for the SCG.

[0119] In an embodiment, upon MAC reset, the UE stops the evaluation of the conditional early synchronization RACH for the cell group where the MAC reset is executed.

[0120] In an additional embodiment, upon MAC reset of the MCG, the UE stops the evaluation of CLTM for the MCG and the SCG. A simple way by which UE can implement this is by resetting time to trigger for the LTM event corresponding to the conditional LTM evaluation. This avoids the concurrency between MAC reset, for e.g. triggered by a RRCReestablishment, and the CLTM evaluation. Concurrency can lead to complex UE and network implementation and the failure of both CLTM and the procedure such as RRCReestablishment which triggeed MAC reset. In an additional embodiment, upon MAC reset of SCG, UE stops the evaluation of the CLTM for the MCG and the SCG.

[0121] In an embodiment, upon stopping the evaluation of CLTM for the MCG or the SCG, the UE also stops the evaluation of conditional early RACH synchronization for the same cell group.

[0122] In an embodiment, upon performing LTM cell switch (for instance by receiving LTM cell switch command or based on LTM based recovery), the UE stops the evaluation of CLTM for the cell group where the LTM cell switch is executed. This avoids the concurrency between non conditional LTM cell switch and the CLTM evaluation. Concurrency can lead to complex UE and network implementation and the failure of both CLTM and the LTM cell switch.

[0123] In an embodiment, upon performing LTM cell switch (for instance by receiving the LTM cell switch command or based on the LTM based recovery), the UE stops the evaluation of conditional early RACH synchronization for the cell group where the LTM cell switch is executed.

[0124] In an embodiment, upon performing LTM cell switch (for instance by receiving LTM cell switch command or based on LTM based recovery) on SCG, UE stops the evaluation of CLTM for the SCG.

[0125] In an additional embodiment, upon performing LTM cell switch (for instance by receiving LTM cell switch command or based on LTM based recovery) on the MCG, the UE stops the evaluation of the CLTM for the MCG and the SCG.

[0126] In an additional embodiment, upon performing the LTM cell switch (for instance by receiving LTM cell switch command or based on the LTM based recovery) on the SCG, the UE stops the evaluation of CLTM for the MCG and the SCG.

[0127] In an embodiment, upon performing Layer3 mobility (for instance by receiving RRC Reconfiguration including ReconfigurationWithSync from the source node or executing CHO / Conditional PSCell Addition / Conditional PSCellChange or performing CHO based recovery) or upon performing RRC reestablishment, the UE stops the evaluation of conditional early RACH synchronization for the cell group where the Layer3 mobility is executed. For example, 'ReconfigurationWithSync' indicates the handover (e.g., handover from a source cell provided by the source node to a target cell provided by the target node).

[0128] In an embodiment, upon performing Layer3 mobility (for instance by receiving RRC reconfiguration including ReconfigurationWithSync from the source node or executing CHO / Conditional PSCell Addition / Conditional PSCellChange or performing CHO based recovery), the UE stops the evaluation of the CLTM for the cell group where the Layer3 mobility is executed. This avoids the concurrency between Layer 3 mobility and the CLTM evaluation. Concurrency can lead to complex UE and network implementation and the failure of both CLTM and the Layer 3 mobility.

[0129] In an embodiment, upon performing the Layer3 mobility on the SCG (for instance by receiving the RRC Reconfiguration including the ReconfigurationWithSync from the source PSCell or executing Conditional PSCell Addition / Conditional PSCellChange), the UE stops the evaluation of the CLTM for the SCG.

[0130] In an additional embodiment, upon performing the Layer3 mobility (for instance by receiving RRC Reconfiguration including ReconfigurationWithSync from the source PCell or executing CHO or performing CHO based recovery) on the MCG, the UE stops the evaluation of CLTM for the MCG and the SCG.

[0131] In an additional embodiment, upon performing the Layer3 mobility on the SCG (for instance by receiving RRC Reconfiguration including ReconfigurationWithSync from the source PSCell or executing Conditional PSCell Addition / Conditional PSCellChange), the UE stops the evaluation of the CLTM for the MCG.

[0132] In an embodiment, upon identifying that the conditions for conditional LTM are met, the UE MAC informs the UE RRC that conditions for conditional LTM are met and the candidate cell identifier (or an information to identify the candidate cell such as the candidate cell identifier minus 1), and the UE RRC executes the LTM cell switch procedure. This allows a modular implementation of the UE, wherein the UE MAC can handle the lower layer specific information / operation for the CLTM, such as the timing advance or the downlink synchronisation related information / operation and the UE RRC can apply the LTM candidate configuration as received from the RRC of network apparatus.

[0133] In an embodiment, upon identifying that the conditions for conditional early synchronization RACH are met for a candidate cell, the UE MAC initiates random access procedure on the candidate cell.

[0134] In an embodiment, If the UE MAC receives random access response including timing advance for the candidate cell or receives the timing advance from the network apparatus in a downlink MAC CE or downlink L1 signaling for the candidate cell, the UE stores the received the timing advance value. Upon executing the LTM cell switch based on the LTM cell switch MAC CE or the conditional LTM cell switch on the same LTM candidate cell, the UE applies the received timing advance value in the previous step. If the UE executes the LTM cell switch based on the LTM cell switch MAC CE and / or the conditional LTM cell switch on a different LTM candidate cell, the UE discards the received timing advance value.

[0135] In another embodiment, if the UE executes the LTM cell switch based on the LTM cell switch MAC CE and / or the conditional LTM cell switch on a different LTM candidate cell, the UE keeps the received timing advance value till a new LTM cell switch occurs to the candidate cell or a timer (such as timing advance timer) expires and applies the timing advance for a LTM cell switch to the same LTM candidate cell. Keeping the TA value avoids the cost of performing random access multiple times, for each of the LTM cell switch.

[0136] In an embodiment, the UE may be configured with a timer, and the UE starts the timer upon receiving the timing advance value through random access response or downlink MAC CE or downlink L1 signaling for a LTM candidate cell (for e.g. after initiating random access procedure for conditional early synchronization random access). Upon the expiry of this timer, UE discards the received timing advance value. Storing the TA value for a very large time can lead to UE losing the synchronisation. Discarding the stored TA based on a timer helps to avoid this loss of synchronisation. As the timer can be configured by the network apparatus, this also ensures that the network can control how long the TA value is kept.

[0137] In an embodiment, upon identifying that the conditions for conditional early synchronization RACH are met for a candidate cell, the UE MAC initiates random access procedure on the candidate cell. The UE may initiate the random access procedure on the uplink or supplementary uplink based on the configuration or internal logic. If the UE MAC receives random access response including timing advance and / or receives the timing advance from the network apparatus in a downlink MAC CE or downlink L1 signaling, the UE stores the received the timing advance value. Upon executing the LTM cell switch based on the LTM cell switch MAC CE or the conditional LTM cell switch on the same LTM candidate cell, and the type of UL for the LTM cell switch is the same (uplink or supplementary uplink), the UE applies the received timing advance value in the previous step. Upon executing the LTM cell switch based on the LTM cell switch MAC CE or the conditional LTM cell switch on the same LTM candidate cell, and the type of UL for the LTM cell switch is different (uplink or supplementary uplink), the UE discards the received timing advance value in the previous step. In another embodiment, upon executing the LTM cell switch based on the LTM cell switch MAC CE or the conditional LTM cell switch on the same LTM candidate cell, and the type of UL for the LTM cell switch is different (uplink or supplementary uplink), the UE keeps the received timing advance value in the previous step till a new LTM cell switch occurs to the candidate cell or a timer (such as timing advance timer) expires and applies the timing advance for a LTM cell switch to the same LTM candidate cell with same type of UL.

[0138] 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.

[0139] While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0140] 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 device or system or apparatus proceeded by "comprises…a" does not, without more constraints, preclude the existence of other elements or additional elements in the device or system or apparatus.

[0141] In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

[0142] In general, a network entity configures User Equipment (UE) with Conditional Lower Layered Triggered Mobility (CLTM) and Conditional Handover (CHO) at the same time. Similarly, when a UE is configured with CLTM, UE may be moved to a target cell through Layer 3 (L3) mobility or LTM cell switch by the network or there may be execution of LTM cell switch to recover from a failure. However, the concept of handling CLTM by the UE in such cases is nowhere defined in existing technologies.

[0143] In 5th Generation (5G) New Radio (NR), when the UE changes from source cell to target cell through LTM cell switch or HO, UE releases CHO configuration. However, the concept of handling CHO configuration during CLTM execution is not clearly defined in existing technologies. Unless these are defined, the interworking between different forms of mobility cannot be performed.

[0144] Embodiments described herein provide a method and User Equipment for performing cell switch procedure in a communication network.

[0145] The method comprises receiving configuration information from a network entity, in which the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. CLTM configuration includes CLTM execution condition and other configurations. Further, the method comprises performing an evaluation of a CLTM execution condition and detecting mobility event of the UE, based on the configuration information. Furthermore, the method comprises terminating the evaluation of the CLTM execution condition based on the detected mobility event.

[0146] The UE comprises a processor, and a memory coupled with the processor. The processor is configured to receive configuration information from a network entity, in which the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. CLTM configuration includes CLTM execution condition and other configurations Further, the processor is configured to perform an evaluation of a CLTM execution condition and detect mobility event of the UE, based on the configuration information. Furthermore, the processor is configured to terminate the evaluation of the CLTM execution condition based on the detected mobility event.

[0147] In another embodiment, the present disclosure includes a method for configuring Conditional Lower-layer Triggered Mobility (CLTM) in a wireless network. The method comprises requesting, by a Central Unit (CU) of a network entity, a Distributed Unit (DU) to configure CLTM for a User Equipment (UE). Further, the method includes configuring, by the DU of the network entity, the CLTM including the CLTM execution condition and / or the LTM candidate cell configuration and informing the CU of the configuration. Furthermore, the method comprises transmitting, by the CU of the network entity, a Radio Resource Control (RRC) reconfiguration message to the UE including the CLTM configuration.

[0148] Another aspect of the present disclosure includes a network entity for configuring Conditional Lower-layer Triggered Mobility (CLTM) in a wireless network. The network entity comprises a processor, and a memory coupled with the processor. The processor is configured to request a Distributed Unit (DU) of the network entity to configure CLTM for a User Equipment (UE), in which the DU configures the CLTM including the CLTM execution condition and / or the LTM candidate cell configuration. Further, the processor is configured to transmit a Radio Resource Control (RRC) reconfiguration message to the UE including the CLTM configuration.

[0149] FIG. 1 illustrates an exemplary environment 100 for performing a cell switch procedure in a communication network, in accordance with some embodiments of the present disclosure.

[0150] In an embodiment, exemplary environment 100 may comprise a User Equipment (UE) 101, a network entity 103, and a communication network 105. In an embodiment, the UE 101 may include, but not limited to, a smartphone, a mobile phone, a personal digital assistant, a tablet computer, a tablet computer, a wearable device, a computer, a laptop computer, an Augmented Reality / Virtual Reality (AR / VR) device, Internet Of Things (IoT) device, a camera, any other device, and the combination thereof.

[0151] Further, in an embodiment, the network entity 103 may include, for example, but not limited to, a base station such as gNodeB (gNB) or eNodeB (eNB) or 6G NodeB (sNB).

[0152] In an embodiment, the UE 101 may communicate with the network entity 103 through the communication network 105. The communication network 105 may include, for example, but not limited to, a direct interconnection, a Local Area Network (LAN), a Wide Area Network (WAN), a wireless network, a point-to-point network, or another configuration.

[0153] The UE 101 may be configured to receive configuration information from the network entity 103, in which the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration.

[0154] Further, the UE 101 may be configured to perform an evaluation of a CLTM execution condition and detect mobility event of the UE 101, based on the configuration information. In an embodiment, the CLTM execution condition may be present in the CLTM configuration. Further, in an embodiment, the mobility event may correspond to event when there is a switch / handover of the UE 101 from one cell, to another cell in the communication network 105. For instance the mobility event may correspond to L3 handover, CHO, LTM cell switch. another conditional LTM cell switch etc.

[0155] In an embodiment, there may be inter-layer interaction between the Media Access Control (MAC) layer and the Radio Resource Control (RRC) layer, in which the MAC layer evaluates the CLTM execution condition 215 and the RRC layer performs the LTM switch execution based on the intimation and information from RRC.

[0156] Furthermore, the UE 101 may be configured to terminate the evaluation of the CLTM execution condition based on the detected mobility event.

[0157] In an embodiment, a Central Unit (CU) of the network entity 103 may request a Distributed Unit (DU) to configure CLTM for the UE 101. Further, the DU of the network entity 103 may configure the CLTM including the CLTM execution condition and / or LTM candidate cell configuration and inform the CU of the configuration. Furthermore, the CU of the network entity 103, may transmit a Radio Resource Control (RRC) reconfiguration message to the UE 101 including the CLTM configuration.

[0158] FIG. 2 illustrates an internal block diagram of a User Equipment (UE) 101 for performing a cell switch procedure in a communication network 105, in accordance with some embodiments of the present disclosure.

[0159] In an embodiment, the UE 101 may include an I / O interface 203, a processor 205 and a memory 207 storing instructions, executable by the processor 205, which, on execution, may cause the UE 101 to perform the cell switch procedure in the communication network 105. In an embodiment, the memory 207 may include data 209 and one or more modules 211. In an embodiment, each of the one or more modules 211 may be a hardware unit which may be outside the memory 207 and coupled with the processor 205.

[0160] In an embodiment, the data 209 may include for example, configuration information 213, CLTM execution condition 215, and other data 217. The configuration information 213, including the CLTM execution condition 215, may be stored in the memory 207 once received from the network entity 103. In an embodiment, the configuration information 213 may comprise Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. Further, in an embodiment, the CLTM execution condition 215 may correspond to conditional data present in the configuration information, indicating the UE 101 to perform CLTM cell switch procedure, when the CLTM execution condition is met.

[0161] In an embodiment, the other data 221 may comprise at least, for example, but not limited to, candidate cell configuration, one or more parameters, LTM cell switch command, and a Radio Resource Control (RRC) signalling message.

[0162] Further in an embodiment, the one or more modules 211 may include a configuration information receiving module 219, an evaluation module 221, and a termination module 223. Each of these modules may be implemented as hardware, firmware, or software components stored in the memory 207 and executed by the processor 205.

[0163] In an embodiment, the configuration information receiving module 219 may be configured to receive the configuration information 213 from the network entity 103, in which the configuration information 213 comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. In an embodiment, the CLTM configuration information 213 may comprise at least one of a candidate cell configuration and the CLTM execution condition 215.

[0164] In an embodiment, the evaluation module 221 may be configured to perform the evaluation of the CLTM execution condition 215 and detect mobility event of the UE 101, based on the configuration information. In an embodiment, the evaluation module 221 may detect the mobility event as LTM cell switch procedure when an LTM cell switch command is received via a Media Access Control (MAC) Control Element (CE) from the network entity 103 or when the UE 101 switches to a Master Cell Group (MCG) LTM candidate cell using LTM based recovery.

[0165] In an embodiment, the evaluation module 221 may detect the mobility event as L3 mobility procedure when an RRC signalling message is received from the network entity 103 including ReconfigurationWithSync or when conditional handover is executed.

[0166] In another embodiment, the evaluation module 221 may perform, periodically, intra-frequency or inter-frequency L1 measurement for at least one candidate cell, in which the intra-frequency or inter-frequency L1 measurement comprises one or more parameters including at least Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal-to-Interference-plus-Noise Ratio (SINR). Further, the evaluation module 221 may determine the mobility event as the CLTM cell switch procedure when at least one parameter of the one of the one or more parameters satisfies respective CLTM execution condition present in CLTM configuration. In an extended embodiment, the CLTM execution may be based on L3 measurements.

[0167] In an embodiment, the termination module 223 may be configured to terminate the evaluation of the CLTM execution condition 215 based on the detected mobility event.

[0168] In an embodiment, the termination module 223 may determine a reception of an LTM cell switch command from the network entity 103 before the fulfilment of the CLTM execution condition 215. Further, the termination module 223 may perform a LTM cell switch procedure to a candidate cell and terminate evaluation of the CLTM execution condition 215, based on the reception of the LTM cell switch command before fulfilment of the CLTM execution condition 215.

[0169] In an embodiment, the termination module 223 may determine the fulfilment of the CLTM execution condition 215 before reception of one of an LTM cell switch command or an RRC signalling message from the network entity 103. Further, the termination module 223 may perform the CLTM cell switch procedure, based on the determined fulfilment of the CLTM execution condition 215, and terminate evaluation of the CLTM execution condition 215, based on completion of the CLTM cell switch procedure.

[0170] In an embodiment, the UE 101 may discard the CLTM configuration, when one of the LTM cell switch procedure or L3 mobility procedure is performed. Further, the UE 101 may discard the CHO configuration and the LTM configuration when the CLTM cell switch procedure is performed.

[0171] In an embodiment, the UE 101 may receive a Timing Advance (TA) value from the network entity 103. Further, the UE 101 may perform an early synchronization with a candidate cell, based on the TA value, in which the UE 101 may synchronize with the candidate cell, before an expiry of a timer pre-set for the TA value. Further, the UE 101 may discard the TA value, upon performing the early synchronization.

[0172] More specifically, the processor 205, upon execution of instructions stored in the memory 207, may be configured to receive configuration information from the network entity 103 via the configuration information receiving module 219. The configuration information 213 may include Conditional Lower Layered Triggered Mobility (CLTM) configuration, Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. Further, the processor 205 may evaluate the CLTM execution condition 215 and detect mobility events of the UE 101 using the evaluation module 221, based on the received configuration information. Furthermore, the processor 205 may terminate the evaluation of the CLTM execution condition 215 using the termination module 223, based on the detected mobility event.

[0173] These modules enable the processor 205 to perform the claimed steps of receiving configuration, evaluating conditions, detecting mobility events, and terminating evaluations.

[0174] FIGs. 3A-3B illustrates an internal block diagram of the network entity 103 for configuring Conditional Lower-layer Triggered Mobility (CLTM) in the communication network 105, in accordance with some embodiments of the present disclosure.

[0175] In an embodiment, as shown in FIG. 3A, the network entity 103 may include an I / O interface 303, a processor 305 and a memory 307 storing instructions, executable by the processor 305, which, on execution, may cause the network entity 103 to configure Conditional Lower-layer Triggered Mobility (CLTM) in the communication network 105. In an embodiment, the memory 307 may include data 309.

[0176] In an embodiment, the data 309 may include for example, the RRC reconfiguration message 313, and the CLTM configuration 315. In an embodiment, the RRC reconfiguration message 313 and the CLTM configuration 315 may be temporarily stored in the memory 307. In other words, without limiting to the data 309, the memory 307 is configured to store other dynamic data for transmission, depending on the requirements of the UE 101.

[0177] In an embodiment, as shown in FIG. 3B, the network entity 103 may comprise a Centralized Unit (CU) 317, and a Distributed Unit (DU) 319. Further, in an embodiment, the processor 205 of network entity 103 may reside either in CU 317 or the DU 319 to perform the recited functionalities.

[0178] In an embodiment, the CU 317, using the processor 205, may request the Distributed Unit (DU) 319 to configure CLTM for the UE 101, in which the DU 319 may configure the CLTM including the CLTM execution conditions and / or the LTM candidate cell configuration.

[0179] In an embodiment, the CU 317, using the processor 205 may transmit a Radio Resource Configuration (RRC) reconfiguration message 313 including the CLTM configuration 315 to the UE 101.

[0180] In an embodiment, the network entity 103 such as gNB configures CLTM for Master Cell Group (MCG) only when Access Stratum (AS) security has been activated and Signaling Radio Bearer-2 (SRB2) with at least one Data Radio Bearer (DRB) are set up and not suspended.

[0181] More specifically, the CU 317 requests DU 319 for conditional LTM configuration. The DU 319 sends the conditional LTM configuration to the UE 101 through the CU 317 using F1 Application Protocol (F1AP) messages. The CU 317 includes the received conditional LTM configuration in the RRC reconfiguration message.

[0182] FIGs. 4A-4B illustrates data flow representation of performing a cell switch procedure in the communication network 105, in accordance with some embodiments of the present disclosure.

[0183] In an embodiment, as shown in FIG. 4A, the UE 101 may receive the configuration information 213 from the network entity 101, in which the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration.

[0184] For example, the CLTM configuration may indicate the UE 101 to undergo a CLTM cell switch procedure when the RSRP value of a candidate cell meets a predefined condition (e.g., falls below or exceeds a threshold such as -80 dB). Additionally, the RRC configuration may instruct the UE 101 to perform L3 mobility upon receiving a specific RRC signaling message from the network entity 103. The LTM cell switch procedure is triggered when the MAC layer evaluates and confirms that the execution condition (based on RSRP or other metrics) is satisfied.

[0185] Further, as shown in block 401, the UE 101 may perform evaluation of CLTM execution condition 215, based on the configuration information 213. For example, let us consider the UE 101 is configured by the network entity 103 with the CLTM configuration that includes a candidate cell Identifier (ID), CLTM execution condition 215 based on L1 measurements such as RSRP threshold: > -80 dBm, RSRQ threshold: > -10 dB, SINR threshold: > 5 dB. The UE 101 performs intra-frequency L1 measurements every 200 ms for the candidate cell, and collects values for RSRP, RSRQ, and SINR.

[0186] For example, At time t1, the UE 101 measures RSRP = -78 dBm, RSRQ = -9 dB, and SINR = 4 dB. Further, the UE 101 evaluates the CLTM execution condition 215 by checking if all the three parameters satisfy the CLTM execution condition 215 defined in the configuration.

[0187] Further, the UE 101 may determine a reception of an LTM cell switch command from the network entity 103 before the fulfilment of the CLTM execution condition 215. For example, when the current measurements of the UE 101 such as RSRP = -78 dBm, RSRQ = -9 dB, and SINR = 4 dB does not satisfy the CLTM execution condition 215, the network entity 103 detects performance degradation or a need for immediate mobility. Apart from the parameters in the example, the network may also configure various offsets and hysteresis for the condition evaluation. Further, the network entity 103 sends the LTM cell switch command to the UE 101 via the MAC CE.

[0188] Upon receiving the LTM cell switch command, the UE 101 immediately performs the LTM cell switch procedure to the candidate cell, as shown in block 402.

[0189] Further, as shown in block 403, the UE 101 terminates the ongoing evaluation of the CLTM execution condition 215, even though the CLTM execution condition 215 was not fulfilled. This ensures that the network entity 103 overrides conditional mobility when necessary, such as in recovery scenarios or urgent handover needs. This also avoids complex concurrency handling which can lead to a complex implementation at the UE and the network and possible failure for all of the CLTM and other procedures.

[0190] In an embodiment, as shown in FIG. 4B, at block 410, the UE 101 may determine the fulfilment of the CLTM execution condition before reception of one of an LTM cell switch command or an RRC signalling message from the network entity 103. Further, as shown in block 411, the UE 101 may perform the CLTM cell switch procedure, based on the determined fulfilment of the CLTM execution condition 215, and terminate evaluation of the CLTM execution condition 215, based on completion of the CLTM cell switch procedure, as shown in block 412.

[0191] For example, let us consider that the UE 101 is configured with a CLTM configuration for a candidate cell, with execution conditions defining RSRP > -80 dBm, RSRQ > -10 dB, SINR > 5 dB. At this stage, the network entity 103 has not yet sent any LTM cell switch command or RRC signalling message for L3 mobility.

[0192] The UE 101 MAC layer performs periodic intra-frequency L1 measurements. That is, at time t1, the UE 101 measures RSRP = -78 dBm, RSRQ = -9 dB, and SINR = 6 dB. These values satisfy the CLTM execution condition. The MAC layer determines that the CLTM condition is fulfilled. Further, the MAC layer informs the RRC layer with the information to identify the candidate cell (candidate cell ID-1).

[0193] The RRC layer initiates and completes the CLTM cell switch procedure to the candidate cell. Upon successful execution of the CLTM switch, the UE 101 stops further evaluation of the CLTM condition for that candidate cell. This entire process occurs before any LTM cell switch command or RRC signalling message is received from the network entity 103. This example demonstrates that the UE 101 autonomously executes CLTM based on local measurements, ensuring low-latency mobility without waiting for network-triggered commands.

[0194] FIG. 5 illustrates a flowchart representation of a method 500 for performing a cell switch procedure in the communication network 105, in accordance with some embodiments of the present disclosure.

[0195] At step 501, the method 500 includes receiving the configuration information 213 from the network entity 103, in which the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration.

[0196] In an embodiment, the configuration information receiving module 219 may be configured to receive the configuration information 213 from the network entity 103, in which the configuration information 213 comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration. In an embodiment, the CLTM configuration information may comprise at least one of a candidate cell configuration and the CLTM execution condition 215.

[0197] At step 502, the method 500 includes performing an evaluation of a CLTM execution condition 215 and detecting mobility event of the UE 101, based on the configuration information 213.

[0198] In an embodiment, the evaluation module 221 may be configured to perform the evaluation of the CLTM execution condition 215 and detect mobility event of the UE 101, based on the configuration information. In an embodiment, the evaluation module 221 may detect the mobility event as LTM cell switch procedure when an LTM cell switch command is received via a Media Access Control (MAC) Control Element (CE) from the network entity 103 or when the UE 101 switches to a Master Cell Group (MCG) LTM candidate cell using LTM based recovery.

[0199] At step 503, the method 500 includes terminating the evaluation of the CLTM execution condition 215 based on the detected mobility event.

[0200] In an embodiment, the termination module 223 may be configured to terminate the evaluation of the CLTM execution condition 215 based on the detected mobility event.

[0201] In an embodiment, the termination module 223 may determine a reception of an LTM cell switch command from the network entity 103 before the fulfilment of the CLTM execution condition 215. Further, the termination module 223 may perform a LTM cell switch procedure to a candidate cell and terminate evaluation of the CLTM execution condition 215, based on the reception of the LTM cell switch command before fulfilment of the CLTM execution condition 215.

[0202] In an embodiment, the termination module 223 may determine the fulfilment of the CLTM execution condition 215 before reception of one of an LTM cell switch command or an RRC signalling message from the network entity 103. Further, the termination module 223 may perform the CLTM cell switch procedure, based on the determined fulfilment of the CLTM execution condition 215, and terminate evaluation of the CLTM execution condition 215, based on completion of the CLTM cell switch procedure.

[0203] FIG. 6 illustrates a flowchart representation of a method 600 for configuring Conditional Lower-layer Triggered Mobility (CLTM) in the communication network 105, in accordance with some embodiments of the present disclosure.

[0204] At step 601, the method 600 includes requesting, by the CU 317 of the network entity 103, the DU 319 to configure CLTM for the UE 101.

[0205] At step 602, the method 600 includes configuring, by the DU 319 of the network entity 103, the CLTM including the CLTM execution condition and / or LTM candidate cell configuration, and informing the CU 317 of the configuration.

[0206] At step 603, the method 600 includes transmitting, by the CU 317 of the network entity 103, a Radio Resource Configuration (RRC) reconfiguration message including the CLTM configuration to the UE 101.

[0207] The present disclosure ensures that CLTM is only configured after Access Stratum (AS) security activation and SRB2 or at least one DRB setup, reducing risks such as fake base station attacks. This enhances trust and reliability in mobility procedures.

[0208] The present disclosure allows CLTM to coexist with Layer 3 mobility (e.g., handovers) and Conditional Handover (CHO), ensuring seamless mobility across diverse scenarios. This is critical for load balancing and recovery in real-world networks.

[0209] The present disclosure supports early uplink synchronization via Timing Advance (TA), improving handover speed and reducing latency.

[0210] According to embodiments in the disclosure, a method for cell switch in a communication network performed by a User Equipment (UE) is provided. The method comprises receiving configuration information from a network entity, wherein the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration; performing an evaluation of a CLTM execution condition and detecting mobility event of the UE, based on the configuration information; and terminating the evaluation of the CLTM execution condition based on the detected mobility event.

[0211] For example, the CLTM configuration information comprises at least one of a candidate cell configuration and the CLTM execution condition.

[0212] For example, the method comprises detecting the mobility event as LTM cell switch procedure when an LTM cell switch command is received via a Medium Access Control (MAC) Control Element (CE) from the network entity or when the UE switches to a Master Cell Group (MCG) LTM candidate cell using LTM based recovery.

[0213] For example, the method comprises detecting the mobility event as L3 mobility procedure when an RRC signalling message is received from the network entity including ReconfigurationWithSync or when conditional handover is executed.

[0214] For example, the method comprises performing, periodically, intra-frequency L1 measurement or inter-frequency L1 measurement for at least one candidate cell, wherein the intra-frequency L1 measurement or inter-frequency L1 measurement comprises one or more parameters including at least Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal-to-Interference-plus-Noise Ratio (SINR); and detecting the mobility event as the CLTM cell switch procedure when at least one parameter of the one of the one or more parameters satisfies respective CLTM execution condition present in CLTM configuration.

[0215] For example, the method comprises determining a reception of an LTM cell switch command from the network entity before the fulfilment of the CLTM execution condition; and performing a LTM cell switch procedure to a candidate cell and terminating evaluation of the CLTM execution condition, based on the reception of the LTM cell switch command before fulfilment of the CLTM execution condition.

[0216] For example, the method comprises determining the fulfilment of the CLTM execution condition before reception of one of an LTM cell switch command or an RRC signalling message from the network entity; performing the CLTM cell switch procedure, based on the determined fulfilment of the CLTM execution condition; and terminating evaluation of the CLTM execution condition, based on completion of the CLTM cell switch procedure.

[0217] For example, the method comprises discarding the CLTM configuration, when one of the LTM cell switch procedure or L3 mobility procedure is performed; and discarding the CHO configuration and the LTM configuration when the CLTM cell switch procedure is performed.

[0218] For example, the method comprises receiving a Timing Advance (TA) value from the network entity; performing an early synchronization with a candidate cell, based on the TA value, wherein the UE synchronizes with the candidate cell, before an expiry of a timer pre-set for the TA value; and discarding the TA value, upon performing the early synchronization.

[0219] For example, the CLTM configuration for the UE and the network entity is applied only when Access Stratum (AS) security has been activated, and a Signalling Radio Bearer (SRB2) with at least one Data Radio Bearer (DRB) is established and not suspended.

[0220] According to embodiments in the disclosure, a method for configuring Conditional Lower-layer Triggered Mobility (CLTM) in a wireless network is provided. The method comprises requesting, by a Central Unit (CU) of a network entity, a Distributed Unit (DU) to configure CLTM for a User Equipment (UE); configuring, by the DU of the network entity, the CLTM including CLTM execution condition and / or LTM candidate cell configuration and informing the CU of the configuration; and transmitting, by the CU of the network entity, a Radio Resource Configuration (RRC) reconfiguration message including the CLTM configuration to the UE.

[0221] According to embodiments in the disclosure, a User Equipment (UE) for performing a cell switch procedure in a communication network is provided. The UE comprises a processor; and a memory coupled with the processor, wherein the processor is configured to receive configuration information from a network entity, wherein the configuration information comprises Conditional Lower Layered Triggered Mobility (CLTM) configuration and at least one or more of a Radio Resource Control (RRC) configuration, and Lower Layered Triggered Mobility (LTM) cell switch configuration; perform an evaluation of a CLTM execution condition and detect mobility event of the UE, based on the configuration information; and terminate the evaluation of the CLTM execution condition based on the detected mobility event.

[0222] According to embodiments in the disclosure, a network entity for configuring Conditional Lower-layer Triggered Mobility (CLTM) in a wireless network is provided. The network entity comprises a processor; and a memory coupled with the processor, wherein the processor is configured to request a Distributed Unit (DU) of the network entity to configure CLTM for a User Equipment (UE), wherein the DU configures the CLTM including CLTM execution condition and / or LTM candidate cell configuration; and transmit a Radio Resource Control (RRC) reconfiguration message to the UE including the CLTM configuration.

[0223] According to embodiments in the disclosure, a method for cell switch in a communication network performed by a user equipment (UE) is provided. The method comprises receiving, from a network entity, conditional lower layered triggered mobility (CLTM) configuration and at least one or more of a radio resource control (RRC) configuration and lower layered triggered mobility (LTM) cell switch configuration; performing an evaluation of a CLTM execution condition based on the CLTM configuration; and based on detecting mobility event of the UE using at least one or more of RRC configuration information related to handover (e.g., mobility) and the LTM cell switch configuration, terminating the evaluation of the CLTM execution condition.

[0224] According to embodiments in the disclosure, a user equipment (UE) for performing a cell switch procedure in a communication network is provided. The UE comprises at least one processor; and memory coupled with the processor. The at least one processor is configured to receive, from a network entity, a conditional Lower Layered triggered mobility (CLTM) configuration and at least one or more of a radio resource control (RRC) configuration and lower layered triggered Mobility (LTM) cell switch configuration; perform an evaluation of a CLTM execution condition based on the CLTM configuration; and based on detecting mobility event of the UE using at least one or more of RRC configuration information related to handover (e.g., mobility) and the LTM cell switch configuration, terminate the evaluation of the CLTM execution condition.

[0225] The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the words "comprising," "having," "containing," and "including," and other similar forms are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items or meant to be limited to only the listed item or items or items. It must also be noted that as used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0226] 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. Accordingly, the embodiments of the disclosure are intended to be illustrative, but not limiting, of the scope of the disclosure.

[0227] While various aspects and embodiments have been disclosed herein, other aspects and embodiments may 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 and spirit being indicated by the following claims.

[0228]

Claims

A method for cell switch in a communication network performed by a user equipment (UE), the method comprising:receiving, from a network entity, conditional lower layered triggered mobility (CLTM) configuration and at least one or more of a radio resource control (RRC) configuration and lower layered triggered mobility (LTM) cell switch configuration;performing an evaluation of a CLTM execution condition based on the CLTM configuration; andbased on detecting mobility event of the UE using at least one or more of RRC configuration information related to handover and the LTM cell switch configuration, terminating the evaluation of the CLTM execution condition.The method as claimed in claim 1, wherein the CLTM configuration information comprises at least one of a candidate cell configuration or the CLTM execution condition.The method as claimed in claim 1, further comprising:detecting the mobility event as LTM cell switch procedure in a case that an LTM cell switch command is received via a medium access control (MAC) control element (CE) from the network entity or in a case that the UE switches to a master cell Group (MCG) LTM candidate cell using LTM based recovery.The method as claimed in claim 3, further comprising:detecting the mobility event as L3 mobility procedure in a case that an RRC signalling message is received from the network entity including information for indicating a handover or in a case that conditional handover is executed.The method as claimed in claim 1, further comprising:performing, periodically, intra-frequency L1 measurement or inter-frequency L1 measurement for at least one candidate cell, wherein the intra-frequency L1 measurement or inter-frequency L1 measurement comprises one or more parameters including at least reference signal received power (RSRP), reference signal received quality (RSRQ), or signal-to-interference-plus-noise ratio (SINR); anddetecting the mobility event as the CLTM cell switch procedure in a case that at least one parameter of the one of the one or more parameters satisfies respective CLTM execution condition present in CLTM configuration.The method as claimed in claim 1, further comprising:determining a reception of an LTM cell switch command from the network entity before the fulfilment of the CLTM execution condition; andperforming a LTM cell switch procedure to a candidate cell and terminating evaluation of the CLTM execution condition, based on the reception of the LTM cell switch command before fulfilment of the CLTM execution condition.The method as claimed in claim 1 further comprising:determining the fulfilment of the CLTM execution condition before reception of one of an LTM cell switch command or an RRC signalling message from the network entity;performing the CLTM cell switch procedure, based on the determined fulfilment of the CLTM execution condition; andterminating evaluation of the CLTM execution condition, based on completion of the CLTM cell switch procedure.The method as claimed in claim 1, further comprising:discarding the CLTM configuration, in a case that one of the LTM cell switch procedure or L3 mobility procedure is performed; anddiscarding the CHO configuration and the LTM configuration in a case that the CLTM cell switch procedure is performed.The method as claimed in claim 1, further comprising:receiving a timing advance (TA) value from the network entity;performing an early synchronization with a candidate cell, based on the TA value, wherein the UE synchronizes with the candidate cell, before an expiry of a timer pre-set for the TA value; anddiscarding the TA value, upon performing the early synchronization.The method as claimed in claim 1, wherein the CLTM configuration for the UE and the network entity is applied only in a case that access stratum (AS) security has been activated, and a signalling radio bearer (SRB2) with at least one data radio bearer (DRB) is established and not suspended.A method for configuring conditional lower-layer triggered mobility (CLTM) in a wireless network, the method comprising:requesting, by a central unit (CU) of a network entity, a distributed unit (DU) to configure CLTM for a User Equipment (UE);configuring, by the DU of the network entity, the CLTM including CLTM execution condition and / or LTM candidate cell configuration and informing the CU of the configuration; andtransmitting, by the CU of the network entity, a radio resource configuration (RRC) reconfiguration message including the CLTM configuration to the UE.A user equipment (UE) for performing a cell switch procedure in a communication network, the UE comprises:at least one processor; andmemory coupled with the processor, wherein the at least one processor is configured to:receive, from a network entity, a conditional Lower Layered triggered mobility (CLTM) configuration and at least one or more of a radio resource control (RRC) configuration and lower layered triggered Mobility (LTM) cell switch configuration;perform an evaluation of a CLTM execution condition based on the CLTM configuration; andbased on detecting mobility event of the UE using at least one or more of RRC configuration information related to handover and the LTM cell switch configuration, terminate the evaluation of the CLTM execution condition.A network entity for configuring conditional lower-layer triggered mobility (CLTM) in a wireless network, the network entity comprises:at least one processor; andmemory coupled with the at least one processor, wherein the at least one processor is configured to:request a distributed unit (DU) of the network entity to configure CLTM for a user equipment (UE), wherein the DU configures the CLTM including CLTM execution condition and / or LTM candidate cell configuration; andtransmit a radio resource control (RRC) reconfiguration message to the UE including the CLTM configuration.

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