Method and apparatus for l1 measurement for conditional LTM cell switch in a wireless communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The present disclosure relates to methods and devices for reporting measurements in a wireless communication network. The method includes performing a L1 measurement for a candidate cell; and transmitting, to a base station, a medium access control (MAC) control element (CE) for event triggered L1 measurement report including a result of the L1 measurement, wherein a priority of the MAC CE for event triggered L1 measurement report is higher than a priority of a MAC CE for buffer state report (BSR) with exception of BSR included for padding

Description

METHOD AND APPARATUS FOR L1 MEASUREMENT FOR CONDITIONAL LTM CELL SWITCH IN A WIRELESS COMMUNICATION SYSTEM

[0001] This invention provides solutions to extend LTM (L1 / L2-Triggered Mobility) to Conditional L1 / L2 Triggered Mobility (C-LTM), which is a further enhancement of mobility to reduce latency and signalling overheads in a Radio Access Network (RAN). Embodiments find particular utility in Fifth Generation, 5G, network, but may be employed in any suitable system.

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

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

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

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

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

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

[0008] The LTM cell switch procedure is triggered according to network decision, i.e. the network can send UE a MAC Control Element (MAC CE) to trigger the LTM cell switch execution. Unlike this, a Conditional LTM(C-LTM) Cell switch is defined as an LTM cell switch that is executed by the UE when one or more LTM cell switch execution conditions are met.

[0009] According to the first aspect of the present invention, there is provided a method for a user equipment, UE, in a wireless communication system, the method comprising: being configured with at least one candidate cell for a conditional mobility procedure; being configured with an execution condition for a cell switch to the at least one candidate cell, wherein the execution condition is based on Layer 1, L1, measurements; performing L1 measurements for the at least one candidate cell; evaluating the L1 measurements against the execution condition; triggering a cell switch procedure to a target candidate cell from the at least one candidate cell; and in response to the triggering of the cell switch procedure, stopping the evaluation of the execution condition based on the L1 measurements for the target candidate cell.

[0010] In an embodiment, stopping the evaluation comprises stopping the evaluation of the execution condition for all candidate cells associated with a cell group to which the target candidate cell belongs.

[0011] In an embodiment, there is further provided performing a Medium Access Control, MAC, reset in response to the triggering of the cell switch procedure, wherein the MAC reset preserves one or more ltm-Candidate-TimeAlignmentTimers.

[0012] In an embodiment, the MAC reset further comprises cancelling a triggered L1 Event Triggered Measurement Report.

[0013] In an embodiment, there is further provided, prior to the triggering of the cell switch procedure:

[0014] generating a Medium Access Control, MAC, Control Element, CE, comprising the L1 measurement results for the at least one candidate cell.

[0015] In an embodiment, there is further provided, the step of comprising prioritizing the MAC CE comprising the L1 measurement results over a MAC CE for a Buffer Status Report, BSR, and a MAC CE for a Power Headroom Report, PHR.

[0016] In an embodiment, there is further provided, the step of triggering a Scheduling Request, SR, for requesting an uplink resource for transmitting the MAC CE comprising the L1 measurement results.

[0017] In an embodiment, there is further provided, the step of, in response to the triggering of the cell switch procedure, starting synchronization to a downlink, DL, of the target candidate cell.

[0018] In an embodiment the cell switch procedure is a RACH-less procedure, the method further comprising: receiving a cell switch command comprising a Timing Advance, TA, value for the target candidate cell; and applying the TA value for communication with the target candidate cell.

[0019] In an embodiment the MAC CE comprising the L1 measurement results further comprises at least one of: a Report ID, a Satisfied Quantity indicating a number of beams fulfilling a trigger event, or a Reference Signaling Resource Index, RSRI.

[0020] In an embodiment the triggering of the cell switch procedure is based on an indication from lower layers of the UE that a conditional cell switch condition has been met.

[0021] According to a second aspect of the present invention, there is provided apparatus arranged to perform the method of the first aspect.

[0022] Aspects of the present disclosure provide efficient communication methods in a wireless communication system.

[0023] 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.

[0024] FIG. 1 illustrates an overall procedure for LTM according to an embodiment of the disclosure;

[0025] FIG. 2 illustrates an early TCI state (or a downlink BWP) activation (early DL sync) procedure triggered by the network according to an embodiment of the disclosure;

[0026] FIG. 3 illustrates an early TA acquisition (early UL sync) procedure triggered by the network according to an embodiment of the disclosure;

[0027] FIG. 4 is a block diagram of a terminal or user equipment (UE) according to an embodiment of the disclosure;

[0028] FIG. 5 is a block diagram of a base station (BS) according to an embodiment of the disclosure; and

[0029] FIG. 6 is a block diagram of a network entity according to an embodiment of the disclosure.

[0030] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

[0031] It should be appreciated by those skilled in art that any block diagrams herein represent conceptual views of illustrative devices 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.

[0032] Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings.

[0033] In describing the embodiments, while numerous details are set forth for the purpose of illustration, it is understood that some aspects of the disclosure may be practiced with less than all of these details. Numerous variations and alternatives to the details provided herein are possible and are considered within the scope of the disclosure. In some instances, descriptions related to technical contents well-known in the art may be omitted so as to not obscure an understanding of the disclosure, and such omitted descriptions are understood to be within the scope of the disclosure.

[0034] 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.

[0035] The advantages and features of the disclosure and ways to achieve them will be apparent by making reference to embodiments as described herein in detail in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments set forth herein, but may be implemented in various different forms. Other features, aspects, and advantages of the subject matter described herein will become apparent from the disclosure. The following embodiments are merely examples to aid in an understanding of the disclosure and should not be construed to narrow the scope or spirit of the subject matter described herein in any way, but on the contrary, the disclosure covers all modifications, equivalents and alternatives falling within the spirit and scope of the subject matter as defined by the appended claims and equivalents thereof. Throughout the specification, the same or like reference numerals designate the same or like elements. Furthermore, terms which will be described herein 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.

[0036] Herein, it will be understood that each block of 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 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).

[0037] 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.

[0038] 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 / modules” 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 same information and, in some cases, are separate and different information.

[0055] 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.

[0056] For example, the physical layer signaling may be referred to as Layer 1 (L1) signaling and may include downlink control information (DCI). In addition, the higher layer signaling may include a medium access control (MAC) control message, a radio resource control (RRC) signaling message, a non-access stratum (NAS) signaling message, or an application layer message. The RRC signaling message may be referred to as L3 (layer 3) signaling. It should be noted, however, that the higher layer signaling is not limited to the aforementioned examples.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] In the embodiments of the present disclosure described herein, 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.

[0061] The drawings or flowcharts described herein 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 describedherein, 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 the European telecommunications standards institute (ETSI), where appropriate.

[0067] 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 wireless access unit, a BS controller, or a node on a network.

[0068] 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 5th generation (5G) base station architectures in which such CU and DU functional splits are implemented.

[0069] A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, a tablet, a wearable device, an Internet of Things (IoT) device, or any other device / system capable of performing communication functions.

[0070] 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.

[0071] Furthermore, hereinafter, 5G mobile communication technologies (e.g., 5G new radio (NR)), 6th generation (6G) mobile communication technologies 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

[0072] In the following description, the terms physical channel and signal may be used interchangeably with data or control signal. For example, the term physical downlink shared channel (PDSCH) refers to a physical channel through which data is transmitted, but the term PDSCH may also be used to refer to the data itself. That is, in the present disclosure, the expression "transmit a physical channel" may be interpreted as being equivalent to the expression "transmit data or a signal via a physical channel."

[0073] Hereinafter, in the context of the present disclosure, higher layer signaling may refer to signaling corresponding to at least one or any combination of the following: master information block (MIB), system information block (SIB) or SIB M (M = 1, 2, ...), RRC, or MAC control element (CE), or a non-access stratum (NAS) signaling message, or an application layer message. The RRC signaling message may be referred to as Layer 3 (L3) signaling.

[0074] In addition, L1 signaling may refer to signaling corresponding to at least one or any combination of signaling techniques using the at least one or any combination of the following physical layer channels or signaling: physical downlink control channel (PDCCH), DCI, UE-specific DCI, group-common DCI, common DCI, scheduling DCI (e.g., DCI used for scheduling downlink or uplink data), non-scheduling DCI (e.g., DCI not used for scheduling downlink or uplink data) physical uplink control channel (PUCCH), or uplink control information (UCI). The L1 signaling message may be referred to as a physical layer signaling.

[0075] Hereinafter, the expression that information is configured by the BS, as used in the present disclosure or claims, may, in context, be understood to mean that the terminal receives the corresponding information from the BS via a physical layer signaling or a higher layer signaling. Such an expression may be replaced with other terms having the same or substantially equivalent meaning.

[0076] Hereinafter, the operational principle of the present disclosure will be described in detail with reference to the accompanying drawings.

[0077] According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

[0078] Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

[0079] Herein, LTM and C-LTM cell switch procedure is described, including the procedure to facilitate and expedite the cell switch procedure by using L1 measurement report (i.e. L1 event triggered measurement report) from UE. To enable this procedure as intended, there is provided a feature whereby the Scheduling Request (SR) is used for transmission of MAC CE including L1 measurement results and its SR procedures with L1 event triggered measurement report.

[0080] Moreover, to enable this procedure as intended, the MAC entity should prioritize the newly defined MAC CE including L1 measurement results (i.e. L1 measurement report) over other MAC CEs that do not require low latency as the L1 measurement report (i.e. L1 event triggered measurement report) is used for mobility. Based on the proposed logical channel prioritization, the MAC entity can take into account the priority among MAC CEs and MAC Service Data Unit (SDU).

[0081] Further, C-LTM cell switch procedure will apply the target LTM candidate cell configuration to the current UE configuration, which will trigger MAC reset to have a new connection with the target candidate cell. The MAC reset should not reset all timers, configuration, or values because some useful information needs to be maintained, for example, for fall back case or for allowing UE to retry the C-LTM procedure while it needs to cancel unnecessary and outdated reporting. Hence, there is also provided a MAC reset procedures for C-LTM.

[0082] As described, L1 measurement report may be beneficial for the network. However, LTM (or C-LTM) event conditions (i.e. RRC configured conditions) evaluation process based on L1 measurement can cause UE unnecessary processing burden and battery consumption. Therefore, provided is a stop condition for L1 event evaluation process based on L1 measurement, in order to save UE power consumption.

[0083] There are several terms or phrases used extensively herein which may be known to the skilled person, but for the sake of completeness, certain of these are reproduced below:

[0084] PDCCH occasion: A time duration (i.e. one or a consecutive number of symbols) during which the MAC entity is configured to monitor the PDCCH.

[0085] Serving Cell:A PCell, a PSCell, or an SCell.

[0086] Special Cell (SpCell):For Dual Connectivity operation the term Special Cell refers to the PCell of the MCG or the PSCell of the SCG depending on if the MAC entity is associated to the MCG or the SCG, respectively. Otherwise the term Special Cell refers to the PCell. A Special Cell supports PUCCH transmission and contention-based Random Access, and is always activated.

[0087] Timing Advance Group (TAG):A group of Serving Cells that is configured by RRC and that, for the cells with a UL configured, using the same timing reference cell and the same Timing Advance value. A Timing Advance Group containing the SpCell of a MAC entity is referred to as Primary Timing Advance Group (PTAG), whereas the term Secondary Timing Advance Group (STAG) refers to other TAGs.

[0088] Msg3: Message transmitted on UL-SCH containing a C-RNTI MAC CE or CCCH SDU, submitted from upper layer and associated with the UE Contention Resolution Identity, as part of a Random Access procedure.

[0089] LTM candidate cell: A candidate cell configured to the UE as specified by LTM candidate cell configuration (i.e.LTM-CandidateConfig) for LTM in RRC layer.

[0090] Conditional L1 / L2 Triggered Mobility (C-LTM): a LTM cell switch procedure that is executed only when execution condition(s) are met.

[0091] C-LTM candidate cell: A candidate cell configured for conditional LTM

[0092] Multi-Radio Dual Connectivity (MR-DC)is a generalization of the Intra-E-UTRA Dual Connectivity (DC), where a multiple Rx / Tx capable UE may be configured to utilise resources provided by two different nodes connected via non-ideal backhaul, one providing NR access and the other one providing either E-UTRA or NR access. One node acts as the MN(Master Node or MCG(Master Cell Group)) and the other as the SN(Secondary Node or SCG(Secondary Cell Group)). The MN and SN are connected via a network interface and at least the MN is connected to the core network.

[0093] MR-DC with the EPC:E-UTRAN supports MR-DC via E-UTRA-NR Dual Connectivity (EN-DC), in which a UE is connected to one eNB that acts as a MN and one en-gNB that acts as a SN. The eNB is connected to the EPC via the S1 interface and to the en-gNB via the X2 interface. The en-gNB might also be connected to the EPC via the S1-U interface and other en-gNBs via the X2-U interface.

[0094] MR-DC with the 5GC:NG-RAN supports NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), in which a UE is connected to one ng-eNB that acts as a MN and one gNB that acts as a SN. NG-RAN supports NR-E-UTRA Dual Connectivity (NE-DC), in which a UE is connected to one gNB that acts as a MN and one ng-eNB that acts as a SN. NG-RAN supports NR-NR Dual Connectivity (NR-DC), in which a UE is connected to one gNB that acts as a MN and another gNB that acts as a SN. In addition, NR-DC can also be used when a UE is connected to a single gNB, acting both as a MN and as a SN, and configuring both MCG and SCG.

[0095] Throughout, the term “cell switch” is used for the procedure of triggering change of cells via the LTM feature and use the term “Subsequent LTM” for the case when cell switch between L1 / L2 mobility candidates is done without RRC reconfiguration in between.

[0096] Throughout, the reception of LTM triggering MAC CE (i.e. LTE Command MAC CE) indicates the triggering of LTM cell switch execution (i.e. LTM cell switch procedure).

[0097] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which:

[0098] Figures 1, 2 and 3 illustrate message flows according to embodiments of the invention.

[0099] The following relates to general principles for LTM (L1 / L2 Triggered Mobility). LTM is a procedure in which a gNB receives L1 or L3 measurement report(s) from a UE, and on their basis, the gNB may change UE serving cell by a cell switch command signalled via a MAC CE.

[0100] The cell switch command indicates an LTM candidate configuration that the gNB previously prepared and provided to the UE through RRC signalling. Then the UE applies the target configuration according to the cell switch command. The LTM procedure can be used to reduce the mobility latency.

[0101] When configured by the network, it is possible to activate TCI states of one or multiple cells that are different from the current serving cell. For instance, the TCI states of the LTM candidate cells can be activated in advance before any of those cells become the serving cell.

[0102] This allows the UE to be DL synchronized with those cells, thereby facilitating a faster cell switch to one of those cells when cell switch is triggered. All the activated TCI states except those received in the cell switch command are deactivated upon LTM cell switch execution.

[0103] When configured by the network, it is possible to initiate UL TA acquisition (called early TA) procedure of one or multiple cells that are different from the current serving cells. If the cell has the same NTAas the current serving cells or NTA=0, early TA acquisition procedure is not required. The network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition procedure is triggered by PDCCH order or realized through UE-based TA measurement as configured by RRC. In the former case, the gNB / gNB-DU to which the candidate cell belongs calculates the TA value and sends it to the gNB / gNB-DU to which the serving cell belongs via gNB-CU. The serving cell sends the TA value in the LTM cell switch command MAC CE when triggering LTM cell switch. In the latter case, the UE performs TA measurement for the candidate cells after being configured by RRC but the exact time the UE performs TA measurement is up to UE implementation. The UE applies the TA value measured by itself and performs RACH-less LTM upon receiving the cell switch command, if it does not include any valid TA value. The network may also send a TA value in the LTM cell switch command MAC CE without early TA acquisition. The network (e.g. the serving cell or the LTM candidate cells) may also sends UE the TA value in the Timing Advance command MAC CE (e.g. for LTM candidate cell).

[0104] When two TAG IDs are configured for an LTM candidate cell, the gNB-DU to which the LTM candidate cell belongs assigns the same TAG ID pointer values for each TRP to be used by the UEs.

[0105] Depending on the availability of a valid TA value, the UE performs either a RACH-less LTM or RACH-based LTM cell switch. If the valid TA value is provided in the cell switch command, the UE applies the TA value as instructed by the network. In the case where UE-based TA measurement is configured, but no valid TA value is provided in the cell switch command, the UE applies the valid TA value by itself if available. The UE performs RACH-less LTM cell switch upon receiving the cell switch command whenever a valid TA value is available. If no valid TA value is available, the UE performs RACH-based LTM cell switch.

[0106] Regardless of whether the UE is configured for UE-based TA measurement for a certain candidate cell, it will still follow the PDCCH order, which includes performing a random access procedure towards one or more candidate cells. This also applies to the candidate cells for which the UE is capable of deriving TA values by itself. Additionally, regardless of whether the UE has already performed a random access procedure towards the candidate cells, it will still follow the UE-based measurement configuration if configured by the network.

[0107] For RACH-less LTM, the UE accesses the target cell using either a configured grant or a dynamic grant. The configured grant is provided in the LTM candidate configuration, and the UE selects the configured grant occasion associated with the beam indicated in the cell switch command. Upon initiation of LTM cell switch to the target cell, the UE starts to monitor PDCCH on the target cell for dynamic scheduling. Before RACH-less LTM procedure completion, the UE shall not trigger random access procedure if it does not have a valid PUCCH resource for triggered SRs.

[0108] The following principles apply to LTM.

[0109] In embodiments, LTM cell switch can be performed for intra-gNB LTM cell switch cases as well as inter-gNB LTM cell switch cases, which means that security keys may not be able to be maintained upon an LTM cell switch. Given that intra-gNB LTM Cell switch is to change the serving cell within one gNB, there would be no reason to update the security keys because the termination point of user plane entity is the same as before the cell switch. However, the inter-gNB LTM Cell switch would require the security key update as the termination of user plane entity changes. So embodiments therefore restrict the network and UE implementation to maintain security keys for a specific condition. It can be implemented by one of the following options:

[0110] - Option 1. Security keys are maintained upon an LTM cell switch if the source cell and the target LTM candidate cells belong to the same gNB;

[0111] - Option 2. Security keys are maintained upon an LTM cell switch if the LTM cell switch is not a inter-gNB LTM cell switch or if it does not correspond to inter-gNB mobility or if it corresponds to intra-gNB-DU mobility or inter-gNB-DU mobility;

[0112] - Option 3. Security keys are maintained upon an LTM cell switch if the security update is not configured or if the masterKeyupdate is not received (e.g. in RRCReconfiguration message) or if the sk-Counter (e.g. for SCG) is not received (e.g. in RRCReconfiguration message);

[0113] - Option 4. Security keys are maintained upon an LTM cell switch if there is no change of termination point for a radio bearer or if the keyToUse in the RadioBearerConfig is the same as the keyToUse in the current UE configuration.

[0114] If the security keys are not maintained (i.e. the security key is updated) or the masterKeyupdate is received (e.g. in RRCReconfiguration message) or the sk-Counter (e.g. for SCG) is received (e.g. in RRCReconfiguration message), UE should trigger RLC re-establishment or PDCP re-establishment for DRBs or SRBs in the LTM Cell switch procedure.(e.g. upon LTM Cell switch execution)

[0115] Subsequent LTM is supported.

[0116] LTM supports intra-gNB-DU mobility, inter-gNB-DU mobility and inter-gNB mobility. LTM supports both intra-frequency and inter-frequency mobility, including mobility to inter-frequency cell that is not a current serving cell. LTM is supported only for licensed spectrum. The following scenarios are supported:

[0117] - PCell change in non-CA scenario and non-DC scenario;

[0118] - PCell and SCell(s) change in CA scenario;

[0119] - Dual connectivity scenario: including PCell and MCG SCell(s) change and PSCell and SCG SCell(s) change with or without MN involvement. LTM for simultaneous PCell and PSCell change is not supported, i.e Simultaneous LTM for PCell change and LTM for PSCell change is not supported

[0120] While the UE has stored LTM candidate configurations the UE can also execute any L3 handover except for DAPS handover. In the RRC message which the UE applies for any L3 handover (except DAPS), LTM candidate configurations can be added / modified / released by the target cell

[0121] C-plane handling (Control plane handling)

[0122] Cell switch command is conveyed in a MAC CE, which contains the necessary information to perform the LTM cell switch.

[0123] FIG. 1 illustrates an overall procedure for LTM according to an embodiment of the disclosure.

[0124] The overall procedure for LTM is shown in Figure 1. Subsequent LTM is done by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidate configurations after each LTM cell switch completion. The general procedure over the air interface is applicable to SCG LTM.

[0125] The procedure for LTM is as follows, using the step numbers shown in Figure 1:

[0126] Step 1. The UE sends aMeasurementReportmessage to the source gNB. The source gNB decides to configure LTM and initiates LTM preparation.

[0127] Step 1a. In case of inter-gNB LTM, the source gNB requests one or more candidate gNBs to configure LTM for one or more candidate cells. The candidate gNB(s) send LTM candidate configurations to the source gNB.

[0128] Step 2. The source gNB transmits anRRCReconfigurationmessage to the UE including the LTM candidate configurations.

[0129] Step 3. The UE stores the LTM candidate configurations and transmits anRRCReconfigurationCompletemessage to the source gNB.

[0130] Step 4a. The UE performs DL synchronization with the LTM candidate cell(s) before receiving the cell switch command. The UE may activate and deactivate TCI states of LTM candidate cell(s), as triggered by the source gNB.

[0131] Step 4b. The UE may perform UL synchronization with LTM candidate cell(s) before receiving the cell switch command, by using UE-based TA measurement, if configured, and / or by transmitting a preamble towards the candidate cell, as triggered by the source gNB. When UE-based TA measurement is configured, UE acquires the TA value(s) of the candidate cell(s) by measurement. UE performs early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command as specified in clause 9.2.6. This is done via CFRA triggered by a PDCCH order from the source cell, following which the UE sends preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE does not receive random access response from the network for the purpose of TA value acquisition and the TA value of the candidate cell is indicated in the cell switch command. The UE does not maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.

[0132] Step 5. The UE performs L1 measurements on the configured LTM candidate cell(s) and transmits L1 measurement reports to the source gNB. L1 measurement should be performed as long as RRC reconfiguration (step 2) is applicable. To report L1 measurement results quickly, L1 measurement report MAC CE can be defined and sent to the network. The MAC CE can be generated, triggered or sent to the network when a certain condition configured by the network is met. The MAC CE can include L1 measurement results, Report ID indicating corresponding measurement report ID for the configuration identity associated with this event triggered measurement report, Satisfied Quantity indicating the number of beams which fulfil the trigger event in the L1 event triggered measurement report (this field should be absent if the beam(s) not satisfying the event could not be reported), RSRIiindicating the reference signalling resource index of the beam i for the L1 event triggered measurement report (i.e. SS / PBCH Block Resource indicator (SSBRI) or CSI-RS resource indicator (CRI)), etc.

[0133] Step 6. The source gNB decides to execute cell switch to a target cell and informs the target gNB. Source gNB transmits an LTM cell switch command MAC CE triggering cell switch by including a target configuration ID which indicates the index of the candidate configuration of the target cell, a beam indicated with a TCI state or beams indicated with DL and UL TCI states, and a timing advance command for the target cell, if available. The UE switches to the target cell and applies the candidate configuration indicated by the target configuration ID.

[0134] Step 7. The UE performs the random access procedure towards the target cell, if UE does not have valid TA of the target cell as specified in clause 5.18.35 of TS 38.321[6].

[0135] Step 8. The UE completes the LTM cell switch procedure by sendingRRCReconfigurationCompletemessage to target cell. If the UE has performed a RA procedure in step 7 the UE considers that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE considers that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0136] The steps 4-8 can be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in step 2.

[0137] The procedure over the air interface described in Figure 1 is applicable to both intra-gNB-DU LTM and inter-gNB-DU LTM. The overall LTM procedures over F1-C interface are captured in 3GPP document TS 38.401.

[0138] To support the above procedure, the network may configure an RRC_CONNECTED UE to perform L1 beam level measurements for SpCell or SCell or LTM candidate cell(s), including L1 RSRP or SINR. The network may configure the UE to report them in accordance with the L1 event triggered beam level measurement configuration. The measurement report is used for indicating to serving gNB of the L1 beam level measurement results from the serving cell and / or candidate cell(s) when L1 event trigger condition is satisfied. The measurement configuration is provided associated with L1 measurement resource configuration by means of RRC dedicated signalling (e.g. RRCReconfiguration message).

[0139] The network may configure the UE to perform L1 event triggered beam level measurement for the following LTM purpose:

[0140] - Select the candidate beam / cell to trigger early synchronization;

[0141] - Select the target beam / cell and trigger LTM cell switch procedure.

[0142] The network may configure the UE to report the following measurement information based on SS / PBCH block(s):

[0143] - Measurement results per SS / PBCH block;

[0144] - SS / PBCH block(s) resource indicator (SSBRI).

[0145] The network may configure the UE to report the following measurement information based on CSI-RS resources:

[0146] - Measurement results per CSI-RS resource;

[0147] - CSI-RS resource indicator (CRI).

[0148] An RRC_CONNECTED UE obtains L1 beam level measurement results by measuring one or multiple beams as configured by the network. For each L1 beam level measurement result in RRC_CONNECTED, the UE applies the layer 1 filtering , before using the measured results for evaluation of reporting criteria and measurement reporting.

[0149] The MAC entity performs the evaluation of reporting criteria based on the L1 filtered measurement results from lower layer. For L1 beam level event triggered measurements report, the network can configure SS / PBCH block(s) or CSI-RS as event evaluation RS type, and L1-RSRP or SINR as trigger quantity. Reporting quantities can be any combination of quantities (i.e. only L1-RSRP; only SINR; L1-RSRP or SINR), irrespective of the trigger quantity. The purpose of this report is to transfer L1 measurement results from the UE to the network. RRC controls the L1 event triggered beam level measurement reporting by configuring the relevant parameters

[0150] The following relates to early synchronization procedure for LTM cell switch procedure.

[0151] Early Downlink Synchronisation

[0152] When configured by the network, it is possible for a UE in RRC_CONNECTED to be DL synchronized with a cell which is different from the current serving cell. This is possible by activating in advance TCI state(s) or a downlink BWP (Bandwidth Part) that belongs to the cell to which the early DL sync is needed. The downlink BWP can be active or activated as the BWP indicated by thefirstActiveDownlinkBWP-Idin the cell configuration to which the early DL synch is needed (e.g. ServingCellConfig), which can be configured in RRCReconfiguration. The TCI state(s) can be activated on the downlink BWP.

[0153] FIG. 2 illustrates an early TCI state (or a downlink BWP) activation (early DL sync) procedure triggered by the network according to an embodiment of the disclosure.

[0154] Figure 2 describes the early TCI state (or a downlink BWP) activation (early DL sync) procedure triggered by the network. The step numbers below refer to corresponding steps in Figure 2.

[0155] Step 11. The gNB to which Cell A belongs provides a list of TCI states of Cell B to the UE within theRRCReconfigurationmessage. The gNB to which Cell A belongs may provide a list of TCI state(s) for one or multiple cells to which the early TCI state activation procedure may be executed by the UE.

[0156] Step 12. The UE replies with theRRCReconfigurationCompletemessage.

[0157] Step 13. The gNB to which Cell A belongs sends an early TCI state activation MAC CE to the UE in order to initiate an early TCI state activation procedure with Cell B. UE receives the early TCI state activation MAC CE from the current serving cell (i.e. Cell A (SpCell, PCell or PSCell)). The early TCI state activation MAC CE may also indicate TCI state(s) of other cells during the TCI state activation procedure, which may include / indicate index (indices) for TCI state or the corresponding Cell identity or the corresponding downlink BWP identity for early DL synchronization. To indicate these in MAC CE, a bitmap may be used to reduce the overhead of MAC CE, which can be mapped to the configuration information (e.g. cell identifiers or BWP ID) in the ascending order of the values and '1' (or '0') means the indication of the corresponding TCI state or Cell or downlink BWP.

[0158] Step 14-1. (e.g. upon the reception of early TCI state activation MAC CE indicating a cell (e.g. Cell B) and TCI state(s) for the cell,) the UE activates the TCI state(s) of Cell B indicated in the early TCI state activation MAC CE. In other words, the UE activates the TCI state(s) of Cell B indicated in the early TCI state activation MAC CE on the indicated downlink BWP (e.g. by thefirstActiveDownlinkBWP-Idfor Cell B in RRCReconfiguration or by indication in MAC CE). In this case, it would be beneficial for the early uplink synchronization procedure as TCI states between the network and UE get aligned well.

[0159] Step 14-2. In another embodiment, the UE may activate the TCI state(s) of Cell B indicated in the early TCI state activation MAC CE when the UE triggers LTM cell switch procedure (i.e. upon the reception of the first MAC CE (i.e. LTM Cell switch command MAC CE)) to save UE power consumption or UE may activate the TCI state(s) of Cell B indicated in the early TCI state activation MAC CE on the indicated downlink BWP (e.g. by thefirstActiveDownlinkBWP-Idfor Cell B in RRCReconfiguration or by indication in MAC CE) when UE triggers LTM cell switch procedure (i.e. upon the reception of the first MAC CE (i.e. LTM Cell switch command MAC CE)) to save UE power consumption as PDCCH monitoring on active BWP causes unnecessary UE power consumption.

[0160] There are several options concerning how to handle the downlink BWP for Cell B in the early downlink synchronization procedure:

[0161] ○ Option 1: Upon the reception of early TCI state activation MAC CE indicating a cell (e.g. Cell B) and TCI state(s) for the cell, the downlink BWP (e.g. indicated bythe firstActiveDownlinkBWP-Idfor the indicated cell (e.g. Cell B) in RRCReconfiguration or indicated by the MAC CE) is activated or active. The UE activates the downlink BWP and the TCI state(s) of the cell on the downlink BWP in the early downlink synchronization procedure or after completion of the early downlink synchronization procedure.

[0162] ○ Option 2: Upon the reception of early TCI state activation MAC CE indicating a cell (e.g. Cell B) and TCI state(s) for the cell, the UE decides the TCI state(s) of the cell in the early downlink synchronization procedure or after completion of the early downlink synchronization procedure. The downlink BWP (e.g. indicated by the firstActiveDownlinkBWP-Id for the indicated cell (e.g. Cell B) in RRCReconfiguration or indicated by the MAC CE) is activated or active when UE triggers LTM cell switch procedure (i.e. upon the reception of the first MAC CE (i.e. LTM Cell switch command MAC CE)) and UE activates the TCI state(s) of the cell on the downlink BWP. The early TCI state activation MAC CE and LTM Cell switch command MAC CE may be received together in the same MAC PDU.

[0163] - Upon RRC (re-)configuration of firstActiveDownlinkBWP-Id and / or firstActiveUplinkBWP-Id for SpCell except for PSCell when SCG is deactivated or activation of an SCell or early downlink (or uplink) synchronization, the DL BWP and / or UL BWP indicated by firstActiveDownlinkBWP-Id and / or firstActiveUplinkBWP-Id is active without receiving PDCCH indicating a downlink assignment or an uplink grant. Upon RRC (re-)configuration of firstActiveDownlinkBWP-Id for PSCell when SCG is deactivated, the DL BWP is switched to the firstActiveDownlinkBWP-Id. The active BWP for a Serving Cell is indicated by either RRC or PDCCH or MAC CE (early TCI state activation MAC CE or LTM Cell switch command MAC CE). For unpaired spectrum, a DL BWP is paired with a UL BWP, and BWP switching is common for both UL and DL.

[0164] The UE is assumed to have early DL synchronization with the gNB to which Cell B belongs. With this, the gNB to which Cell A belongs may initiate cell switch procedure to Cell B by proving a cell switch command which indicates Cell B as target cell. The cell switch command can be e.g., the LTM cell switch command MAC CE.

[0165] This procedure can be applied to both MCG or SCG separately when UE is configured with dual connectivity.

[0166] The early downlink synchronization can be performed before the early uplink synchronization as the exact TA value can be measured by the network when the TCI states between UE and the network are well aligned, i.e. the network can trigger the early downlink synchronization to UE first and then trigger early uplink synchronization to UE (e.g. after completion of the early downlink synchronization). In other embodiment, the network can skip the early downlink synchronization and trigger early uplink synchronization to UE.

[0167] In another embodiment, the early downlink synchronization and LTM cell switch procedure can be indicated together by two MAC CEs, i.e. early TCI state activation MAC CE and LTM Cell switch command MAC CE. The two MAC CEs can be included in the same MAC PDU and the network send the MAC PDU to UE. In this way, UE activates the indicated TCI states (e.g. on the indicated downlink BWP) and triggers LTM cell switch procedure based on the two MAC CEs.

[0168] Early Uplink Synchronisation

[0169] When configured by the network, it is possible for a UE in RRC_CONNECTED to be UL synchronized with a cell which is different from the current serving cell.

[0170] Figure 3 describes the early TA acquisition (early UL sync) procedure triggered by the network (i.e. herein, early uplink synchronization means early TA acquisition procedure). The step numbers below refer to corresponding steps in Figure 3.

[0171] Step 21. The gNB to which Cell A belongs provides the TA acquisition configuration to the UE within theRRCReconfigurationmessage. The TA acquisition configuration includes RRC configuration information required to send a Random Access Preamble to Cell B so that the gNB to which Cell B belongs can calculate a TA value to be used by the UE, e.g., in case an LTM cell switch procedure is executed to Cell B. The TA acquisition configuration may include information for one or multiple cells to which the TA acquisition procedure may be executed by the UE. UE receives the TA acquisition configuration from the current serving cell (i.e. Cell A or SpCell or PCell or PSCell) byRRCReconfigurationmessage.

[0172] Step 22. The UE replies with theRRCReconfigurationCompletemessage.

[0173] Step 23. The gNB to which Cell A belongs sends a PDCCH order message to the UE in order to initiate a TA acquisition procedure with Cell B. The PDCCH order may include the information required to sends a Random Access Preamble to Cell B and indication whether to perform preamble transmission or preamble retransmission. The gNB to which Cell A belongs may indicate the retransmission of preamble for TA acquisition in case no TA is obtained. UE receives the PDCCH order indicating random access procedure (or preamble (re)transmission) to other cell(s) (e.g. Cell B) from the current serving cell (i.e. Cell A or SpCell or PCell or PSCell).

[0174] Step 24. The UE sends a Random Access Preamble to Cell B so that the gNB to which Cell B belongs can calculate a TA value to be used by the UE, e.g., if an LTM cell switch procedure is triggered to Cell B.

[0175] - There are several options concerning how to handle the uplink BWP for Cell B to transmit the Random Access Preamble to Cell B.

[0176] ○ Option 1: For each LTM candidate cell, the DL BWP and / or UL BWP indicated by firstActiveDownlinkBWP-Id and / or firstActiveUplinkBWP-Id respectively is active when the Random Access procedure on an LTM candidate cell is initiated by a PDCCH order for early uplink synchronization or when early downlink synchronization is initiated (or completed), i.e. UE peforms random access preamble (re)transmission on the UL BWP to the indicated cell (a LTM candidate cell indicated by PDCCH order) in the random access procedure triggered by a PDCCH order (of the serving cell (Spcell or PCell or PSCell)) for early uplink synchronization (e.g. if PRACH occasions or resources are configured on the UL BWP). The DL BWP and / or UL BWP on an LTM candidate cell is deactivated upon reception of LTM Cell Switch Command MAC CE except for the LTM candidate cell indicated by the Target Configuration ID included in the LTM Cell Switch Command MAC CE. The DL BWP and / or UL BWP for the LTM candidate cell indicated by the Target Configuration ID included in the LTM Cell Switch Command MAC CE are active for the Serving Cell.

[0177] ○ Option 2: For each LTM candidate cell, the DL BWP and / or UL BWP indicated by firstActiveDownlinkBWP-Id and / or firstActiveUplinkBWP-Id respectively is active when the Random Access procedure on an LTM candidate cell is initiated by a PDCCH order for early uplink synchronization or when early downlink synchronization is initiated (or completed), i.e. UE peforms random access preamble (re)transmission on the UL BWP to the indicated cell (a LTM candidate cell indicated by PDCCH order) in the random access procedure triggered by a PDCCH order (of the serving cell (Spcell or PCell or PSCell)) for early uplink synchronization (e.g. if PRACH occasions or resources are configured on the UL BWP). The DL BWP and / or UL BWP on an LTM candidate cell is deactivated upon the preamble (re)transmission (i.e. when Random Access procedure initiated by a PDCCH order for early uplink synchronization is completed).

[0178] ○ Option 3: For each LTM candidate cell, the DL BWP and / or UL BWP indicated by firstActiveDownlinkBWP-Id and / or firstActiveUplinkBWP-Id respectively is not active (i.e. deactivated or keep the deactivate state) when the Random Access procedure on an LTM candidate cell is initiated by a PDCCH order for early uplink synchronization or when early downlink synchronization is initiated (or completed), i.e. UE peforms random access preamble (re)transmission on the UL BWP (i.e. on the deactivated UL BWP) to the indicated cell (a LTM candidate cell indicated by PDCCH order) in the random access procedure triggered by a PDCCH order (of the serving cell (Spcell or PCell or PSCell)) for early uplink synchronization (e.g. if PRACH occasions or resources are configured on the UL BWP). In this way, UE is allowed to perform preamble (re)transmission on the deactivated BWP for LTM candidate cells. The DL BWP and / or UL BWP on an LTM candidate cell is activated as SpCell (i.e. PCell or PSCell) when UE successfully completes the LTM cell switch procedure to the LTM candidate cell indicated by the Target Configuration ID included in the LTM Cell Switch Command MAC CE.

[0179] Step 25. The gNB to which Cell A belongs provides the TA value calculated by the gNB to which Cell B belongs during the TA acquisition procedure, e.g. in LTM cell switch command MAC CE which initiate LTM cell switch procedure to Cell B in case an LTM cell switch procedure is triggered to Cell B. UE receives the first MAC CE (i.e. LTM Cell switch command MAC CE) from the current serving cell (i.e. Cell A or SpCell or PCell or PSCell), which triggers LTM cell switch procedure to other cell (e.g. Cell B).

[0180] This procedure can be applied to both MCG or SCG separately when UE is configured with dual connectivity.

[0181] The following concerns User Plane handling.

[0182] After receiving an LTM cell switch command MAC CE, the UE performs MAC reset. For intra-gNB LTM(e.g. intra-gNB-DU mobility), whether the UE performs RLC re-establishment and PDCP data recovery during cell switch is explicitly controlled by the network through RRC signalling. For inter-gNB LTM(e.g. inter-gNB mobility), UE always performs RLC re-establishment and PDCP re-establishment during cell switch.

[0183] In other words, after receiving an LTM cell switch command MAC CE, the UE performs MAC reset. For the case that the security update is not configured or the masterKeyupdate is not received (e.g. in RRCReconfiguration message) or the sk-Counter (e.g. for SCG) is not received (e.g. in RRCReconfiguration message) or there is no change of termination point for a radio bearer or the keyToUse in the RadioBearerConfig is the same as the keyToUse in the current UE configuration, whether the UE performs RLC re-establishment and PDCP data recovery during cell switch is explicitly controlled by the network through RRC signalling.

[0184] For the case that the security update is configured or the masterKeyupdate is received (e.g. in RRCReconfiguration message) or the sk-Counter (e.g. for SCG) is received (e.g. in RRCReconfiguration message) or there is change of termination point for a radio bearer or the keyToUse in the RadioBearerConfig is not the same as the keyToUse in the current UE configuration, the UE always performs RLC re-establishment and PDCP re-establishment during cell switch.

[0185] The following relates to RACH-less handover (LTM Cell switch).

[0186] During intra-gNB HO procedure, RACH-less handover can be configured for a UE. The RACH-less handover procedure applies the following functionality:

[0187] - The UE uses the same timing advance value at the target cell as in the source cell or timing advance value of 0.

[0188] - The handover command for the UE may contain a beam identifier for the beam to be used by the UE at the target cell. The beam may be determined based on a UE measurement report and / or left up to gNB implementation, e.g., using the target cell's knowledge about the beam(s) used by the UE at the co-located source cell.

[0189] - The handover command may include a configured UL grant. UE can fallback to RACH when there is no valid configured uplink grant. Alternatively, an UL grant is dynamically signalled by the target cell.

[0190] - The UE transmits theRRCReconfigurationCompletemessage using the configured or dynamically signalled UL grant. Successful UL data reception on the target cell terminates the RACH-less handover execution.

[0191] The following applies to Conditional L1 / L2 Triggered Mobility.

[0192] A Conditional L1 / L2 Triggered Mobility (C-LTM) is defined as an LTM cell switch that is executed by the UE when one or more LTM cell switch execution conditions are met.

[0193] The following principles apply to C-LTM:

[0194] - Source cell sends the conditional LTM configuration via RRCReconfiguration to UE, which includes the LTM candidate configurations, and the corresponding execution conditions. Source cell and each candidate cell provide their own execution condition for conditional LTM. The resulting C-LTM configuration is included as part of the LTM configuration to the UE.

[0195] - An execution condition can be based on events. Events can be defined and configured by the network

[0196] C-LTM is supported for intra-CU LTM and C-LTM based on inter-CU LTM(inter-gNB LTM) is not supported. C-LTM can be RACH-based or can be configured to be RACH-less. The completion of C-LTM follows the same procedure as LTM cell switch procedure.

[0197] The conditional LTM cell switch procedure is executed (or triggered) upon:

[0198] - the MAC entity determines that the event for conditional LTM is satisfied based on L1 measurements

[0199] - the event for conditional LTM is satisfied based on L3 measurements indicated by upper layers (e.g. RRC layers).

[0200] The network may configure an RRC_CONNECTED UE to perform L1 beam level measurements for SpCell and conditional LTM candidate cell(s) for C-LTM, including L1 RSRP or SINR. The UE may use the L1 measurement for LTM cell switch conditions evaluation in accordance with the reconfiguration for C-LTM. The network may configure the UE to report the L1 measurement results for C- LTM, e.g., to trigger PDCCH ordered early RACH.

[0201] Throughout this application , LTM can also indicate C-LTM, i.e. LTM cell switch can indicate C-LTM cell switch, LTM cell candidate configuration can indicate C-LTM cell candidate configuration, LTM cell switch execution can indicate C-LTM cell switch execution, etc. 2.3.

[0202] Principles for Security protection

[0203] The following high-level principles should be applied in embodiments. Herein, the term security protection implies ciphering or integrity protection. “Ciphering” means not only the ciphering operation but also the deciphering operation because the deciphering should be applied to the data at the receiver if data is ciphered at the transmitter. Likewise, the integrity protection means the integrity verification operation as well as the integrity protection operation because the integrity verification should be applied to the data at the receiver if a data is integrity protected at the transmitter.

[0204] AS security comprises of the integrity protection and ciphering of RRC signalling (SRBs) and user data (DRBs).

[0205] RRC handles the configuration of the AS security parameters which are part of the AS configuration: the integrity protection algorithm, the ciphering algorithm, if integrity protection and / or ciphering is enabled for a DRB and two parameters, namely thekeySetChangeIndicatorand thenextHopChainingCount, which are used by the UE to determine the AS security keys upon reconfiguration with sync (with key change), connection re-establishment and / or connection resume.

[0206] The integrity protection algorithm is common for SRB1, SRB2, SRB3 (if configured), SRB4 (if configured), SRBx (if configured) and DRBs configured with integrity protection, with the samekeyToUsevalue. The ciphering algorithm is common for SRB1, SRB2, SRB3 (if configured), SRB4 (if configured), SRBx (if configured) and DRBs configured with the samekeyToUsevalue. Neither integrity protection nor ciphering applies for SRB0.

[0207] NOTE: All DRBs related to the same PDU session have the same enable / disable setting for ciphering and the same enable / disable setting for integrity protection.

[0208] RRC integrity protection and ciphering are always activated together, i.e. in one message / procedure. RRC integrity protection and ciphering for SRBs are never de-activated. However, it is possible to switch to a 'NULL' ciphering algorithm (nea0).

[0209] For SRBx (if configured), RRC integrity protection and ciphering can be activated and deactivated based on configuration or indication by RRC messages (or MAC CE(Control Elemenent) or PDCP control PDU(Protocol Data Unit)), in order to reduce the UE processing burden. For SRBx (if configured), it is also possible to switch to a 'NULL' ciphering algorithm (nea0) and the 'NULL' integrity protection algorithm (nia0) can be used.

[0210] The 'NULL' integrity protection algorithm (nia0) is used only for SRBs and for the UE in limited service mode and when used for SRBs, integrity protection is disabled for DRBs. In case the 'NULL' integrity protection algorithm is used, 'NULL' ciphering algorithm is also used.

[0211] NOTE: Lower layers discard RRC messages for which the integrity protection check has failed and indicate the integrity protection verification check failure to RRC.

[0212] The AS applies four different security keys: one for the integrity protection of RRC signalling (KRRCint), one for the ciphering of RRC signalling (KRRCenc), one for integrity protection of user data (KUPint) and one for the ciphering of user data (KUPenc). All four AS keys are derived from the KgNBkey. The KgNBkey is based on the KAMFkey, which is handled by upper layers.

[0213] The integrity protection and ciphering algorithms can only be changed with reconfiguration with sync. The AS keys (KgNB, KRRCint, KRRCenc, KUPintand KUPenc) change upon reconfiguration with sync (ifmasterKeyUpdateis included), and upon connection re-establishment and connection resume.

[0214] For each radio bearer an independent counter (COUNTused in PDCP layer) is maintained for each direction. For each radio bearer, theCOUNTis used as input for ciphering and integrity protection.

[0215] It is not allowed to use the sameCOUNTvalue more than once for a given security key. The network is responsible for avoiding reuse of theCOUNTwith the same RB identity and with the same key, e.g. due to the transfer of large volumes of data, release and establishment of new RBs, and multiple termination point changes for RLC-UM bearers and multiple termination point changes for RLC-AM bearer with SN terminated PDCP re-establishment (COUNT reset) due to SN only full configuration whilst the key stream inputs (i.e. bearer ID, security key) at MN have not been updated. In order to avoid such re-use, the network may e.g. use different RB identities for RB establishments, change the AS security key, or an RRC_CONNECTED to RRC_IDLE / RRC_INACTIVE and then to RRC_CONNECTED transition.

[0216] In order to limit the signalling overhead, individual messages / packets include a short sequence number (PDCP SN(Sequence Number)). In addition, an overflow counter mechanism is used: the hyper frame number (HFNused in PDCP layer). The HFN needs to be synchronized between the UE and the network.

[0217] For each SRB, the value provided by RRC to lower layers to derive the 5-bit BEARER parameter used as input for ciphering and for integrity protection is the value of the correspondingsrb-Identitywith the MSBs padded with zeroes.

[0218] For a UE provided with ansk-counter,keyToUseindicates whether the UE uses the master key (KgNB) or the secondary key (S-KeNBor S-KgNB) for a particular DRB. The secondary key is derived from the master key andsk-Counter. Whenever there is a need to refresh the secondary key, e.g. upon change of MN with KgNBchange or to avoid COUNT reuse, the security key update is used. When the UE is in NR-DC, the network may provide a UE configured with an SCG with ansk-Countereven when no DRB is setup using the secondary key (S-KgNB) in order to allow the configuration of SRB3. The network can also provide the UE with ansk-Counter, even if no SCG is configured, when using SN terminated MCG bearers.

[0219] The following relates to MAC / RRC Protocol and associated UE behaviour.

[0220] Multiplexing and assembly for MAC PDU

[0221] Previously, LTM and C-LTM cell switch procedure was described as well as the procedure to facilitate and expedite the cell switch procedure by using L1 measurement report (i.e. L1 event triggered measurement report) from UE. To enable this procedure as intended, the Scheduling Request (SR) need to be used for transmission of MAC CE including L1 measurement results and the following SR procedures with L1 event triggered measurement report (i.e. newly defined MAC CE) are provided :

[0222] The Scheduling Request (SR) is used for requesting UL-SCH resources for new transmission.

[0223] The MAC entity may be configured with zero, one, or more SR configurations. An SR configuration consists of a set of PUCCH resources for SR across different BWPs and cells. For a logical channel or for SCell beam failure recovery, for consistent LBT failure recovery, and for L1 event triggered measurement report, at most one PUCCH resource for SR is configured per BWP. For L1 event triggered measurement report, a dedicated SR configuration could be configured.

[0224] Each SR configuration corresponds to one or more logical channels to L1 event triggered measurement report. Each logical channel, L1 event triggered measurement report, may be mapped to zero or one SR configuration, which is configured by RRC. The SR configuration of the logical channel that triggered L1 event triggered measurement report is considered as corresponding SR configuration for the triggered SR.

[0225] RRC configures the following parameters for the scheduling request procedure:

[0226] -sr-ProhibitTimer(per SR configuration);

[0227] -sr-TransMax(per SR configuration).

[0228] The following UE variables are used for the scheduling request procedure:

[0229] -SR_COUNTER(per SR configuration).

[0230] If an SR is triggered and there are no other SRs pending corresponding to the same SR configuration, the MAC entity shall set theSR_COUNTERof the corresponding SR configuration to 0.

[0231] When an SR is triggered, it shall be considered as pending until it is cancelled.

[0232] All pending SR(s) for BSR triggered according to the BSR procedure (clause 5.4.5) prior to the MAC PDU assembly shall be cancelled and each respectivesr-ProhibitTimershall be stopped when the MAC PDU is transmitted and this PDU includes a Long, Refined Long or Short BSR MAC CE which contains buffer status up to (and including) the last event that triggered a BSR (see clause 5.4.5) prior to the MAC PDU assembly. All pending SR(s) for BSR triggered according to the BSR procedure (clause 5.4.5) shall be cancelled and each respectivesr-ProhibitTimershall be stopped when the UL grant(s) can accommodate all pending data available for transmission.

[0233] The MAC entity shall for each pending SR not triggered according to the BSR procedure for a Serving Cell:

[0234] 1> if this SR was triggered by L1 event triggered measurement report procedure and the L1 event triggered measurement report that triggered the SR has been cancelled:

[0235] 2> cancel the pending SR and stop the correspondingsr-ProhibitTimer, if running.

[0236] To avoid unnecessary Random Access procedure due to a pending SR for L1 event triggered measurement report, we can have the following procedure so that the MAC entity can cancel it when the report is considered to be sent in MAC PDU.

[0237] The MAC entity may stop, if any, ongoing Random Access procedure due to a pending SR for L1 Event Triggered Measurement Report, which has no valid PUCCH resources configured, if:

[0238] - a MAC PDU is transmitted using a UL grant other than a UL grant provided by Random Access Response or a UL grant determined for the transmission of the MSGA payload, and this PDU includes a L1 Event Triggered Measurement Report MAC CE.

[0239] Moreover, to enable this procedure as intended, the MAC entity should prioritize the newly defined MAC CE including L1 measurement results (i.e. L1 measurement report) over other MAC CEs that do not require low latency as the L1 measurement report (i.e. L1 event triggered measurement report) is used for mobility. Therefore, the following prioritization (i.e. logical channel prioritization) is provided on MAC CEs and MAC SDUs when the MAC entity can have room to include them in MAC PDU.

[0240] Logical channels shall be prioritised in accordance with the following order (highest priority listed first) (i.e. For the Logical Channel Prioritization procedure, the MAC entity shall take into account the following relative priority in decreasing order):

[0241] - MAC CE for C-RNTI, or data from UL-CCCH;

[0242] - MAC CE for (Enhanced) BFR, or MAC CE for Configured Grant Confirmation, or MAC CE for Multiple Entry Configured Grant Confirmation;

[0243] - MAC CE for Sidelink Configured Grant Confirmation;

[0244] - MAC CE for LBT failure;

[0245] - MAC CE for SL LBT failure according to clause 5.31.2;

[0246] - MAC CE for Timing Advance Report;

[0247] - MAC CE for L1 measurement report (i.e. L1 event triggered measurement report);

[0248] - MAC CE for Delay Status Report;

[0249] - MAC CE for SL-BSR prioritized according to clause 5.22.1.6;

[0250] - MAC CE for SL-PRS Resource Request;

[0251] - MAC CE for (Extended) BSR, with exception of BSR included for padding;

[0252] - MAC CE for (Enhanced) Single Entry PHR, or MAC CE for (Enhanced) Multiple Entry PHR or MAC CE for Single Entry PHR with assumed PUSCH, or MAC CE for Multiple Entry PHR with assumed PUSCH, or MAC CE for Enhanced Single Entry PHR for multiple TRP or MAC CE for Enhanced Multiple Entry PHR for multiple TRP, or MAC CE for Enhanced Single Entry PHR for multiple TRP STx2P or MAC CE for Enhanced Multiple Entry PHR for multiple TRP STx2P;

[0253] - MAC CE for Positioning Measurement Gap Activation / Deactivation Request;

[0254] - MAC CE for the number of Desired Guard Symbols;

[0255] - MAC CE for Case-6 Timing Request;

[0256] - MAC CE for (Extended) Pre-emptive BSR;

[0257] - MAC CE for SL-BSR, with exception of SL-BSR prioritized according to clause 5.22.1.6 and SL-BSR included for padding;

[0258] - MAC CE for IAB-MT Recommended Beam Indication, or MAC CE for Desired IAB-MT PSD range, or MAC CE for Desired DL Tx Power Adjustment;

[0259] - data from any Logical Channel, except data from UL-CCCH;

[0260] - MAC CE for Recommended bit rate query;

[0261] - MAC CE for BSR included for padding;

[0262] - MAC CE for SL-BSR included for padding.

[0263] NOTE 2: Prioritization among MAC CEs of same priority is up to UE implementation.

[0264] The MAC entity shall prioritize any MAC CE listed in a higher order than 'data from any Logical Channel, except data from UL-CCCH' over NR sidelink transmission.

[0265] For example, the MAC entity shall prioritize the MAC CE for L1 measurement report over other MAC CEs including BSR and PHR. The MAC entity shall prioritize the MAC CE for C-RNTI, or data from UL-CCCH over the MAC CE for L1 measurement report.

[0266] For further enhancement, BSR can be triggered for the case of the L1 measurement report MAC CE to send it quickly. For the L1 event triggered measurement reporting, the detailed procedures of the MAC entity are as follows:

[0267] The MAC entity shall:

[0268] 1> if at least one L1 measurement report has been triggered:

[0269] 2> if UL-SCH resources are available for a new transmission (in the serving cell or the SpCell or SCell) and these UL-SCH resources can accommodate the L1 measurement report MAC CE plus its subheader as a result of logical channel prioritization:

[0270] 3> instruct the Multiplexing and Assembly procedure to generate the L1 measurement report MAC CE;

[0271] 3> increment thenumberOfReportsSentby 1, wherenumberOfReportsSentindicate the number of report;

[0272] 3> stop the periodical reporting timer, if running;

[0273] 3> ifreportAmountis configured in RRC, and thenumberOfReportsSentas defined for thisltm-CSI-ReportConfigIdis less thanreportAmountwherereportAmountindicates the maximum number of the report:

[0274] 4> start the periodical reporting timer with the value ofreportIntervalfor thisltm-CSI-ReportConfigIdas defined within the correspondingLTM-CSI-reportConfig;

[0275] 2> else if the UL-SCH resources are available for a new transmission (in the serving cell or the SpCell or SCell) and these UL-SCH resources can accommodate the Truncated L1 measurement report MAC CE plus its subheader as a result of logical channel prioritization:

[0276] 3> instruct the Multiplexing and Assembly procedure to generate the Truncated L1 measurement report MAC CE;

[0277] 3> increment thenumberOfReportsSentby 1;

[0278] 3> stop the periodical reporting timer, if running;

[0279] 3> ifreportAmountis configured in RRC, and thenumberOfReportsSentas defined for thisltm-CSI-ReportConfigIdis less thanreportAmount:

[0280] 4> start the periodical reporting timer with the value ofreportIntervalfor thisltm-CSI-ReportConfigIdas defined within the correspondingLTM-CSI-reportConfig;

[0281] 2> else (i.e. if there is no uplink resource or no uplink grant to transmit L1 measurement report):

[0282] 3> if the dedicated SR configuration for L1 measurement report MAC CE transmission is configured:

[0283] 4> trigger the SR using the dedicated SR configuration for L1 measurement report;

[0284] 3> else:

[0285] 4> trigger the SR using the SR configuration for L1 measurement report.

[0286] As mentioned above, L1 measurement report would be beneficial for the network but LTM (or C-LTM) event conditions (i.e. RRC configured conditions) evaluation process based on L1 measurement can cause UE unnecessary processing burden and battery consumption. So stop conditions are defined for L1 event evaluation process based on L1 measurement, i.e. if LTM cell switch execution procedure is performed(or triggered) for a LTM candidate cell (i.e. target LTM candidate cell) and execute a reconfiguration with sync, UE can stop L1 event evaluation process based on L1 measurement for the LTM candidate configuration for the LTM candidate cell (i.e. target LTM candidate cell).

[0287] In another embodiment, we can reduce the processing burden further by allowing UE to stop all L1 event evaluation process based on L1 measurement for all the LTM candidate configuration associated with the cell group (e.g. MCG or SCG) if LTM cell switch execution procedure (for MCG or SCG) is performed(or triggered) for a LTM candidate cell (i.e. target LTM candidate cell) and execute a reconfiguration with sync or if UE executes a reconfiguration with sync due to any type of handover.

[0288] To implement this the following procedures are provided:

[0289] The UE shall perform the following actions to execute a reconfiguration with sync.

[0290] 1> if this reconfiguration with sync procedure is performed due to an LTM (or C-LTM) cell switch execution procedure; or

[0291] 1> if LTM (or C-LTM) cell switch execution is triggered upon the indication by lower layers that an LTM cell switch procedure is triggered, or upon performing LTM cell switch following cell selection performed while timer T311 was running or upon the fulfilment of C-LTM cell switch conditions:

[0292] 2> start synchronising to the DL of the indicated LTM candidate cell, if no DL synchronization for the indicated LTM (or C-LTM) candidate cell has been already acquired;

[0293] 2> stop the LTM (or C-LTM) conditions evaluation (e.g. based on L1 measurements), if any, for the LTM (or C-LTM) candidate configuration associated with the target LTM (or C-LTM) candidate cell for which the LTM (or C-LTM) cell switch procedure is triggered;

[0294] To enhance the above procedure, we also propose another procedures:

[0295] The UE shall perform the following actions to execute a reconfiguration with sync.

[0296] 1> if this reconfiguration with sync procedure is performed due to an LTM (or C-LTM) cell switch execution procedure; or

[0297] 1> if LTM (or C-LTM) cell switch execution is triggered upon the indication by lower layers that an LTM cell switch procedure is triggered, or upon performing LTM cell switch following cell selection performed while timer T311 was running or upon the fulfilment of C-LTM cell switch conditions; or

[0298] 2> start synchronising to the DL of the indicated LTM (or C-LTM) candidate cell, if no DL synchronization for the indicated LTM (or C-LTM) candidate cell has been already acquired;

[0299] 2> stop the LTM (or C-LTM) conditions evaluation (e.g. based on L1 measurements), if any, for all the LTM (or C-LTM) candidate configurations (e.g.ltm-Configorltm-ConfigSCG) associated with the cell group (e.g. MCG or SCG) for which the LTM (or C-LTM) cell switch procedure is triggered.

[0300] In another embodiment, UE can simply stop the LTM (or C-LTM) conditions evaluation (e.g. based on L1 measurements), if any, for all the LTM (or C-LTM) candidate configurations (e.g.ltm-Configorltm-ConfigSCG)associated with the cell group (e.g. MCG or SCG) for which the LTM (or C-LTM) cell switch procedure is triggered as an action to be performed in order to execute a reconfiguration with sync.

[0301] In addition to this, UE can stop the LTM conditions evaluation (based on L1 measurements), if any, for all the LTM candidate configurations associated with the MCG if UE initiates the procedure to report SCG failures when neither MCG nor SCG transmission is suspended and when one of the following conditions is met.

[0302] In addition to this, UE can stop the LTM conditions evaluation (based on L1 measurements), if any, for all the LTM candidate configurations associated with the SCG if, in case of MR-DC, a UE configured with split SRB1 or SRB3 initiates the procedure to report MCG failures when neither MCG nor SCG transmission is suspended, the SCG is not deactivated, t316 is configured, and when the following condition is met;

[0303] - upon detecting radio link failure of the MCG while T316 is not running.

[0304] The following relates to MAC reset for C-LTM cell switch.

[0305] As described above, C-LTM cell switch procedure will apply the target LTM candidate cell configuration to the current UE configuration, which will trigger MAC reset to have a new connection with the target candidate cell. The MAC reset should not reset all timers, configuration, or values because some useful information need to be maintained, for example, for fall back case or for allowing UE to retry the C-LTM procedure while it needs to cancel unnecessary and outdated reporting. An embodiment provides the following MAC reset procedures:

[0306] If a reset of the MAC entity is requested by upper layers upon receivingRRCResumeorRRCSetup, the MAC entity shall:

[0307] 1> stop the MBS multicast DRX timers;

[0308] 1> flush the soft buffers for all DL HARQ processes used for MBS multicast;

[0309] 1> for each DL HARQ process used for MBS multicast, consider the next received transmission for a TB as the very first transmission.

[0310] Otherwise, if a reset of the MAC entity is requested by upper layers or the reset of the MAC entity is triggered due to SCG deactivation as defined in clause 5.29, the MAC entity shall:

[0311] 1> if the MAC reset is not due to SCG deactivation:

[0312] 2> initializeBjfor each logical channel to zero;

[0313] 1> initializeSBjfor each logical channel to zero if Sidelink resource allocation mode 1 is configured by RRC;

[0314] 1> if upper layers indicate SCG deactivation andbfd-and-RLMwith valuetrueis configured for the deactivated SCG:

[0315] 2> stop (if running) all timers exceptbeamFailureDetectionTimerassociated with PSCell andtimeAlignmentTimers.

[0316] 1> else if upper layers indicate that MAC reset is triggered by C-LTM cell switch(or C-LTM cell switch is executed):

[0317] 2> stop (if running) all timers, except MBS broadcast DRX timers andltm-Candidate-TimeAlignmentTimers;

[0318] 2> consider alltimeAlignmentTimers,inactivePosSRS-TimeAlignmentTimer, andcg-SDT-TimeAlignmentTimer, andltm-Candidate-TimeAlignmentTimersif configured, as expired and perform the corresponding actions in clause 5.2;

[0319] 1> else:

[0320] 2> stop (if running) all timers, except MBS broadcast DRX timers;

[0321] 2> consider alltimeAlignmentTimers,inactivePosSRS-TimeAlignmentTimer, andcg-SDT-TimeAlignmentTimer, if configured, as expired and perform the corresponding actions in clause 5.2;

[0322] 1> set the NDIs for all uplink HARQ processes to the value 0;

[0323] 1> sets the NDIs for all HARQ process IDs to the value 0 for monitoring PDCCH in Sidelink resource allocation mode 1;

[0324] 1> stop, if any, ongoing Random Access procedure;

[0325] 1> discard explicitly signalled contention-free Random Access Resources for 4-step RA type and 2-step RA type, if any;

[0326] 1> flush Msg3 buffer;

[0327] 1> flush MSGA buffer;

[0328] 1> cancel, if any, triggered Scheduling Request procedure;

[0329] 1> cancel, if any, triggered Buffer Status Reporting procedure;

[0330] 1> cancel, if any, triggered Delay Status Reporting procedure;

[0331] 1> cancel, if any, triggered Power Headroom Reporting procedure;

[0332] 1> cancel, if any, triggered consistent LBT failure;

[0333] 1> cancel, if any, triggered Sidelink consistent LBT failure;

[0334] 1> cancel, if any, triggered BFR;

[0335] 1> cancel, if any, triggered Sidelink Buffer Status Reporting procedure;

[0336] 1> cancel, if any, triggered Pre-emptive Buffer Status Reporting procedure;

[0337] 1> cancel, if any, triggered Timing Advance Reporting procedure;

[0338] 1> cancel, if any, triggered Recommended bit rate query procedure;

[0339] 1> cancel, if any, triggered Configured uplink grant confirmation;

[0340] 1> cancel, if any, triggered configured sidelink grant confirmation;

[0341] 1> clear, if any, configured sidelink grants;

[0342] 1> cancel, if any, triggered Desired Guard Symbol query;

[0343] 1> cancel, if any, triggered Positioning Measurement Gap Activation / Deactivation Request procedure;

[0344] 1> cancel, if any, triggered SDT procedure;

[0345] 1> cancel, if any, triggered IAB-MT Recommended Beam Indication query;

[0346] 1> cancel, if any, triggered Desired DL TX Power Adjustment query;

[0347] 1> cancel, if any, triggered Desired IAB-MT PSD range query;

[0348] 1> cancel, if any, triggered Case-6 Timing Request query;

[0349] 1> cancel, if any, triggered SL-PRS resource request;

[0350] 1> cancel, if any, triggered L1 Event Triggered Measurement Report;

[0351] 1> flush the soft buffers for all DL HARQ processes, except for the DL HARQ process being used for MBS broadcast;

[0352] 1> for each DL HARQ process, except for the DL HARQ process being used for MBS broadcast, consider the next received transmission for a TB as the very first transmission;

[0353] 1> release, if any, Temporary C-RNTI;

[0354] 1> clear, if any, Differential Koffset;

[0355] 1> if upper layers indicate SCG deactivation andbfd-and-RLMwith valuetrueis not configured; or

[0356] 1> if the MAC reset is not due to SCG deactivation:

[0357] 2> reset allBFI_COUNTERs;

[0358] 1> reset allLBT_COUNTERs;

[0359] 1> reset TTT (TimeTrigger value, i.e. the time to trigger) for LTM or TTT for L1 event triggered measurement report triggering condition evaluation, where TimeToTrigger value specifies the value range used for time to trigger parameter, which concerns the time during which specific criteria for the event needs to be met in order to trigger a measurement report, which helps UE apply the criterion correctly;

[0360] 1> reset periodical reporting timer for L1 event triggered measurement report, if any;

[0361] 1> reset allnumberOfReportsSenfor L1 event triggered measurement reportt;

[0362] 1> clear allVarBeamsTriggeredLisfor L1 event triggered measurement reportt;

[0363] 1> clear allVarMeasReportListfor L1 event triggered measurement report.

[0364] The following relates to LTM execution procedure (or LTM command).

[0365] In an embodiment, TA acquisition of candidate cell(s) before LTM cell switch command is supported as described above. By this, as the source cell / DU gets to know the value and the validity of candidate cell TA, it can determine whether it can initiate a RACH-less solution for LTM cell switch and then determine whether it needs to include a beam indication (e.g.TCI state) and TA information in the first MAC CE (i.e. LTM Command MAC CE) as described previously. Therefore, the network can indicate a valid TA to the UE or indicate whether a TA is still valid in the first MAC CE. Upon the reception of the TA information indicated in LTM MAC CE, the UE can apply the TA value and start the TA timer for the target LTM candidate cell upon LTM execution (i.e. LTM cell switch) and UE can perform LTM cell switch without Random access procedure (i.e. with RACH-less solution) if TAT for the target LTM candidate cell is running (i.e. TA value is vaild) or if Beam failure is not detected for the target LTM candidate cell, which means that UE can monitor PDCCH from the target LTM candidate cell or UE can use configured grants the first UL data transmission to the target cell for RACH-less LTM execution (LTM cell switch). Otherwise, UE can perform LTM execution procedure with Random Access procedure.

[0366] In an embodiment, the first MAC CE to be sent to UE can be generated by the source cell (or gNB), i.e. the MAC entity of the source cell (or gNB) generates the first MAC CE including the contents (e.g. TA value or BWP ID, Configuration Identity, etc as described above) and sends it to the UE in order to trigger LTM cell switch procedure.

[0367] In another embodiment, the first MAC CE to be sent to UE can be generated by the target cell (or gNB or CU(Central Unit)), i.e. the MAC entity of the target cell (or gNB or CU(Central Unit)) generates the first MAC CE including the contents (e.g. TA value or BWP ID, Configuration Identity, etc as described above) and forwards it to the source cell (or DU(Distributed Unit)) (e.g. in Xn message via Xn interface or in RRC message or in F1-AP message), and the source cell (or DU) sends it to the UE in order to trigger LTM cell switch procedure.

[0368] To maintain Uplink time alignment efficiently, one of the following options for the behaviours of the MAC entity can be implemented:

[0369] RRC configures the following parameters for the maintenance of UL time alignment:

[0370] -timeAlignmentTimer(per TAG) which controls how long the MAC entity considers the Serving Cells belonging to the associated TAG to be uplink time aligned;

[0371] Option 1: In this option, the Timing Advance Command value (or field) is optional (i.e. can be either present or absent) in the first MAC CE (LTM Command MAC CE). Upon the reception of the first MAC CE (LTM Command MAC CE), the corresponding MAC behaviour is as follows:

[0372] The MAC entity shall:

[0373] 1> if the MAC entity receives an LTM Command MAC CE on a Serving Cell:

[0374] 2> indicate to upper layers that the LTM Command MAC CE is received (triggering the LTM cell switch procedure);

[0375] 2> perform MAC reset;

[0376] 2> indicate to upper layers the Target Configuration ID (i.e. identifier for target LTM candidate cell) included in the MAC CE;

[0377] 2> if Timing Advance Command value is present (or included) or if Timing Advance Command indicates that the Timing Advance value needs to be updated or is not valid anymore or if keeping the Timing Advance or using the TA of the source cell(or Serving cell) is indicated (i.e. the LTM candidate cell indicated by Target Configuration ID (or Serving cell ID) in the first MAC CE, belongs to PTAG) or if Timing Advance Command value is not set as a special value (e.g. 000..0 or 111...1) (e.g. the value indicates RACH-less LTM candidate cell switch) of if RRC parameter indicating RACH-less LTM execution (or indicating the same value as the serving cell) is configured :

[0378] 3> process the received Timing Advance Command. In another embodiment, UE can process the received Timing Advance Command if Timing Advance Command indicates that the Timing Advance value needs to be updated or is not valid anymore or if keeping the Timing Advance or using the TA of the source cell(or Serving cell) is not indicated, in order to avoid unnecessary processing;

[0379] 3> when an LTM Command MAC CE including a Timing Advance Command is received (or if Timing Advance Command indicates that the Timing Advance value needs to be updated or is not valid anymore or if keeping the Timing Advance or using the TA of the source cell(or Serving cell) is not indicated):

[0380] 4> apply the Timing Advance Command for the PTAG or the target LTM candidate cell(or the indicated LTM candidate cell) (i.e. UE can apply and store the Timing Advance value for the PTAG or the taget LTM candidate cell);

[0381] 4> start or restart the timeAlignmentTimer associated with the PTAG or the target LTM candidate cell(or the indicated LTM candidate cell); In another embodiment, UE can start or restart the timeAlignmentTimer associated with the PTAG or the target LTM candidate cell(or the indicated LTM candidate cell) only if thetimeAlignmentTimerassociated with PTAG or the target LTM candidate cell(or the indicated LTM candidate cell)is not running, in order to avoid unnecessary update procedure.

[0382] 3> indicate to upper layers to skip the Random Access procedure for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell). In another embodiment, UE can indicate to upper layers to skip the Random Access procedure for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell) if TAT(timeAlignmentTimer) for the target / indicated LTM candidate cell (or PTAG) is running (i.e. TA value is vaild) or if Beam failure is not detected for the target LTM candidate cell (i.e. ifBFI_COUNTER<beamFailureInstanceMaxCountfor the target / indicated LTM candidate cell (the number of Beam failure Indication is smaller than the maximum number for beam failure detection).

[0383] 2> else (if Timing Advance Command value is absent (or not included) or if keeping the Timing Advance or using the TA of the source cell(or Serving cell) is not indicated (i.e. the LTM candidate cell indicated by Target Configuration ID (or Serving cell ID) in the first MAC CE, does not belong to PTAG) or if Timing Advance Command value is set as a special value (e.g. 000..0 or 111...1) (e.g. the value indicates RACH-based LTM candidate cell switch) or of if RRC parameter indicating RACH-less LTM execution (or indicating the same value as the serving cell) is not configured:

[0384] 3> indicate to upper layers that a Random Access Procedure is needed for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell) or indicate to upper layers to trigger the Random Access procedure for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell); In another embodiment, UE can indicate to upper layers that a Random Access Procedure is needed for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell) if TAT(timeAlignmentTimer) for the target / indicated LTM candidate cell (or PTAG) is not running (i.e. TA value is not vaild) or if Beam failure is detected for the target / indicated LTM candidate cell (i.e. ifBFI_COUNTER>=beamFailureInstanceMaxCountfor the target / indicated LTM candidate cell(or PTAG) (the number of Beam failure Indication is larger than or equal to the maximum number for beam failure detection).

[0385] 3> UE can ignore the received Timinng Advance Command in order to avoid unnecessary update procedure.

[0386] 2> if TCI state information is included:

[0387] 3> consider the SSB corresponding to the indicated TCI state as the selected SSB for the initial uplink transmisision towards the candidate cell;

[0388] 3> indicate to lower layers the information regarding the TCI state information included in the LTM Command MAC CE.

[0389] Option 2: In this option, the Timing Advance Command value (or field) is always present in the first MAC CE (LTM Command MAC CE). Upon the reception of the first MAC CE (LTM Command MAC CE), the corresponding MAC behaviour is as follows:

[0390] The MAC entity shall:

[0391] 1> if the MAC entity receives an LTM Command MAC CE on a Serving Cell:

[0392] 2> indicate to upper layers that the LTM Command MAC CE is received (triggering the LTM cell switch procedure);

[0393] 2> perform MAC reset;2> indicate to upper layers the Target Configuration ID (i.e. identifier for target LTM candidate cell) included in the MAC CE;

[0394] 2> if Timing Advance Command value is not set as a special value (e.g. 000..0 or 111...1) or if Timing Advance Command indicates that the Timing Advance value needs to be updated or is not valid anymore of if RRC parameter indicating RACH-less LTM execution (or indicating the same value as the serving cell) is configured:

[0395] 3> process the received Timing Advance Command;

[0396] 3> when an LTM Command MAC CE including a Timing Advance Command is received:

[0397] 4> apply the Timing Advance Command for the PTAG or the target LTM candidate cell(or the indicated LTM candidate cell) (i.e. UE can apply and store the Timing Advance value for the PTAG or the taget LTM candidate cell);

[0398] 4> start or restart the timeAlignmentTimer associated with the PTAG or the target LTM candidate cell(or the indicated LTM candidate cell); In another embodiment, UE can start or restart the timeAlignmentTimer associated with the PTAG or the target LTM candidate cell(or the indicated LTM candidate cell) only if thetimeAlignmentTimerassociated with PTAG or the target LTM candidate cell(or the indicated LTM candidate cell)is not running, in order to avoid unnecessary update procedure.

[0399] 3> indicate to upper layers to skip the Random Access procedure for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell). In another embodiment, UE can indicate to upper layers to skip the Random Access procedure for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell) if TAT(timeAlignmentTimer) for the target / indicated LTM candidate cell (or PTAG) is running (i.e. TA value is vaild) or if Beam failure is not detected for the target LTM candidate cell (i.e. ifBFI_COUNTER<beamFailureInstanceMaxCountfor the target / indicated LTM candidate cell (the number of Beam failure Indication is smaller than the maximum number for beam failure detection).

[0400] 2> else (if Timing Advance Command value is set as a special value (e.g. 000..0 or 111...1)) of if RRC parameter indicating RACH-less LTM execution (or indicating the same value as the serving cell) is not configured:

[0401] 3> indicate to upper layers that a Random Access Procedure is needed for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell) or indicate to upper layers to trigger the Random Access procedure for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell); In another embodiment, UE can indicate to upper layers that a Random Access Procedure is needed for this LTM cell switch or the target LTM candidate cell(or the indicated LTM candidate cell) if TAT(timeAlignmentTimer) for the target / indicated LTM candidate cell (or PTAG) is not running (i.e. TA value is not vaild) or if Beam failure is detected for the target / indicated LTM candidate cell (i.e. ifBFI_COUNTER>=beamFailureInstanceMaxCountfor the target / indicated LTM candidate cell(or PTAG) (the number of Beam failure Indication is larger than or equal to the maximum number for beam failure detection).

[0402] 3> UE can ignore the received Timinng Advance Command in order to avoid unnecessary update procedure.

[0403] 2> if TCI state information is included:

[0404] 3> consider the SSB corresponding to the indicated TCI state as the selected SSB for the initial uplink transmisision towards the candidate cell;

[0405] 3> indicate to lower layers the information regarding the TCI state information included in the LTM Command MAC CE.

[0406] In an embodiment, alternatively, the TA value (e.g. Timing Advance Command) can be configured in each LTM candidate cell configuration in RRCReconfiguration message and can be applied to UE or the maintenance of TAT timers.

[0407] The network may activate and deactivate the TCI states of LTM candidate cell(s) configured in RRC configuration by sending the fourth MAC CE (i.e. LTM Candidate Cell TCI States Activation / Deactivation MAC CE described in Section 4.1) To enable this, several options are provided to activate and deactivate the TCI states upon LTM execution and one of the options can be implemented:

[0408] - Option 1: In this option, we can restrict the transmission for the fourth MAC CE to the transmission together with the first MAC CE (LTM Command MAC CE described above). For example, the network can send the fourth MAC CE together with the first MAC CE (i.e. both MAC CEs can be included in the same MAC PDU) to activate and deactivate the TCI states for LTM cell switch. If the MAC entity receives a Candidate Cell TCI States Activation / Deactivation MAC CE on a Serving Cell, it indicates to lower layers (i.e. PHY layer (Physical layer)) the information regarding the Candidate Cell TCI States Activation / Deactivation MAC CE for the indicated LTM candidate cell from the first MAC CE. If the fourth MAC CE is not received (e.g. with the first MAC CE), the MAC entity indicates to the lower layers the usage of the indicated (or configured) TCI by RRCReconfiguration for the indicated LTM candidate cell from the first MAC CE, or the lower layers uses the indicated (or configured) TCI by RRCReconfiguration for the indicated LTM candidate cell from the first MAC CE.

[0409] - Option 2: In this option, we do not restrict the transmission for the fourth MAC CE, i.e. the network can send the fourth MAC CE before the transmission of the first MAC CE or regardless of the transmission of the first MAC CE (LTM Command MAC CE described above), in order to activate and deactivate the TCI states for LTM cell switch.. However, even if the MAC entity receives a Candidate Cell TCI States Activation / Deactivation MAC CE on a Serving Cell, it indicates to lower layers (i.e. PHY layer (Physical layer)) the information regarding the Candidate Cell TCI States Activation / Deactivation MAC CE for the indicated LTM candidate cell from the first MAC CE upon the reception of the first MAC CE or upon LTM execution. If the fourth MAC CE was not received, the MAC entity indicates to the lower layers the usage of the indicated (or configured) TCI by RRCReconfiguration for the indicated LTM candidate cell from the first MAC CE or the lower layers uses the indicated (or configured) TCI by RRCReconfiguration for the indicated LTM candidate cell from the first MAC CE upon the reception of the first MAC CE or upon LTM execution.

[0410] FIG. 4 is a block diagram of a terminal or user equipment (UE) 400 according to an embodiment of the disclosure.

[0411] The terminal is an electronic device capable of wireless communication and having various form factors, examples of the 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, or any other device / system capable of performing wireless communication with a base station (BS) and / or another terminal through a wireless channel.

[0412] Referring to FIG. 4, the UE 400 may include at least one transceiver (hereinafter, referred to as simply “transceiver”) 401, at least one processor (hereinafter, referred to as simply “processor”) 402, and at least one memory (hereinafter, referred to as simply “memory”) 403. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 401, the processor 402, and the memory 403 of the UE 400 may operate. However, components of the UE 400 are not limited to the example components illustrated in FIG. 4. In another embodiment, the UE 400 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in some embodiments, any combination of the transceiver 401, the processor 402, or the memory 403 may be integrated in the form of one component.

[0413] The transceiver 401 may be a communication circuit or communication circuitry that enables the UE 400 to perform wireless communication with a node or an entity of a network. For example, the transceiver 401 may enable the UE 400 to transmit or receive a signal to or from a BS through cellular communication, or to transmit or receive a signal to or from another UE through cellular communication. For example, the transceiver 401 may support at least one of various cellular communication technologies including 3rd generation (3G), 4th generation (4G), long term evolution (LTE), 5th generation (5G) NR, 6th generation (6G), and various cellular wireless communication technologies supported by the transceiver (401) may include all subsequent generations of evolved wireless communications.

[0414] According to an embodiment, the UE 400 may include a plurality of transceivers. For example, in the case of supporting evolved-universal terrestrial radio access-new radio (E-UTRA-NR) dual connectivity (EN-DC), the UE 400 may include a first transceiver supporting the 4G LTE wireless communication and a second transceiver supporting the 5G NR wireless communication. According to another embodiment, in the case of supporting NR-dual connectivity (NR-DC), the UE 400 may include a plurality of transceivers supporting the 5G NR wireless communication. According to still another embodiment, in the case of supporting near field wireless communication, the UE 400 may separately include a transceiver supporting at least one standard in the group of wireless communication protocol standards as defined in the protocol standards for Bluetooth®, wireless local area network (WLAN) network (including institute of electrical and electronics engineers (IEEE) 802.11-2016 standard or its amendments, e.g., 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be, without being limited thereto).

[0415] According to an embodiment, the transceiver 401 may include various circuit structures used to transmit or receive signals to or from a BS through a wireless channel. The signals may include control information and data. For example, the transceiver 401 may include a radio frequency (RF) transmitter for up-converting and amplifying the frequency of a transmitted signal and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. The transceiver 401 may output a signal received through a wireless channel to the processor 402 and may transmit, through a wireless channel, a signal output from the processor 402.

[0416] The processor 402 may control general operations of the UE 400 according to embodiments of the disclosure. The processor 402 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 402 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 403, individually, collectively or in any combination thereof. Further, the processor 402 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme.

[0417] The processor 402 may be electrically, operatively, and / or communicatively coupled to the transceiver 401 to control the transceiver 401.

[0418] The processor 402 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. For example, the processor 402 may include a communication processor (CP) configured to control communication operations and an application processor (AP) configured to control execution of an upper layer (for example, an application layer). In a specific embodiment, at least a part of the processor 402 may be included in one chip (or IC) and the other part of the processor 402 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 401 or the memory 403.

[0419] The processor 402 may perform or control or cause an operation of the UE 400 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 402 may control operations of the UE 400 for processing a downlink signal received from a BS or generating and transmitting an uplink signal to a BS. To this end, the processor 402 may execute a computer program, codes, or instructions stored in the memory 403, so as to control other components of the UE 400 to enable execution of various operations.

[0420] The memory 403 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 403 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0421] The memory 403 may be electrically, operatively, and / or communicatively coupled to the processor 402 and may be accessed by the processor 402.

[0422] The memory 403 may store a computer program, codes, or instructions executable by the processor 402. According to an embodiment, a computer program, codes, or instructions executable by the processor 402 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 403, the processor 402 may perform various functions according to an embodiment of the disclosure.

[0423] According to an embodiment of the disclosure, operations of the UE 400 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 403 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0424] FIG. 5 is a block diagram of a base station (BS) 500 according to an embodiment of the disclosure.

[0425] The BS 500 may perform wireless communication with at least one user equipment (UE) located within the area of the BS 500 through a wireless channel. The BS 500 may perform communication with a node or an entity of a network through wired or wireless communication.

[0426] Referring to FIG. 5, the BS 500 may include at least one transceiver (hereinafter, referred to as simply “transceiver”) 501, at least one processor (hereinafter, referred to as simply “processor”) 502, and at least one memory (hereinafter, referred to as simply “memory”) 503. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 501, the processor 502, and the memory 503 of the BS 500 may operate. However, components of the BS 500 are not limited to the example components illustrated in FIG. 5. In another embodiment, the BS 500 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in some embodiments, any combination of the transceiver 501, the processor 502, or the memory 503 may be integrated in the form of one component.

[0427] The transceiver 501 may be a communication circuit or communication circuitry that enables the BS 500 to perform wireless communication with a node or an entity of a network. For example, the transceiver 501 may enable the BS 500 to transmit or receive a signal to or from the UE X00 through cellular communication, or to transmit or receive a signal to or from another network entity through wireless communication. For example, the transceiver 501 may support various cellular communication technologies including 3rd generation (3G), 4th generation (4G), long term evolution (LTE), 5th generation (5G) NR, 6th generation (6G), and various cellular wireless communication technologies supported by the transceiver (501) may include all subsequent generations of evolved wireless communications. According to an embodiment, the transceiver 501 may include various circuit structures used to transmit or receive signals to or from a UE through a wireless channel. The signals may include control information and data. For example, the transceiver 501 may include a radio frequency (RF) transmitter for up-converting and amplifying the frequency of a transmitted signal and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. The transceiver 501 may output a signal received through a wireless channel to the processor 502 and may transmit, through a wireless channel, a signal output from the processor 502.

[0428] Meanwhile, according to an embodiment of the present disclosure, the BS 500 may perform communication with a node or an entity of a network through wired or wireless communication. For example, the BS 500 may perform wired or wireless communication with an adjacent BS, or a node or an entity of a core network through a backhaul network. Although not illustrated in FIG. 5, when the BS 500 performs wired communication, the BS 500 may further include a separate network interface for wired communication in addition to the transceiver 501. The network interface may be referred to as network interface circuitry or communication interface circuitry.

[0429] The processor 502 may control general operations of the BS 500 according to embodiments of the disclosure. The processor 502 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 502 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 503, individually, collectively or in any combination thereof. Further, the processor 502 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme.

[0430] The processor 502 may be electrically, operatively, and / or communicatively coupled to the transceiver 501 to control the transceiver 501.

[0431] The processor 502 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. In a specific embodiment, at least a part of the processor 502 may be included in one chip (or IC) and the other part of the processor 502 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 501 or the memory 503.

[0432] The processor 502 may perform or control or cause an operation of the BS 500 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 502 may control operations of the BS 500 for generating and transmitting a downlink signal to a UE or processing an uplink signal received from a UE. Otherwise, the BS 500 may transmit or receive a signal to or from a neighboring BS, transfer a signal received from a UE to an upper node of the network, or transmit a signal transferred from an upper node of the network to a UE. To this end, the processor 502 may execute a computer program, codes, or instructions stored in the memory 503, so as to control other components of the BS 500 to enable execution of various operations.

[0433] The memory 503 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 503 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0434] The memory 503 may be electrically, operatively, and / or communicatively coupled to the processor 502 and may be accessed by the processor 502.

[0435] The memory 503 may store a computer program, codes, or instructions executable by the processor 502. According to an embodiment, a computer program, codes, or instructions executable by the processor 502 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 503, the processor 502 may perform various functions according to an embodiment of the disclosure.

[0436] According to an embodiment of the disclosure, operations of the BS 500 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 503 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0437] The UE or the base station may perform various communication procedures related to the control plane or the user plane by cooperating with one or more network entities based on wireless communication. For example, the UE may communicate with a network entity (for example, an Access and Mobility Management Function (AMF), a Session Management Function (SMF), rtc.) via the base station, or the base station may perform at least one communication procedure by directly transmitting and receiving signals to / from, or relaying signals between, the network entities.

[0438] The structure of the above-described network entity will be described in more detail with reference to the drawings.

[0439] FIG. 6 is a block diagram of a network entity 600 according to an embodiment of the disclosure.

[0440] The network entity 600 may include an entity (apparatus, device, or server, etc.) that performs one or more network functions (NFs) or a part of a network function constituting a core network (e.g., a 5th generation (5G) core (5GC)) in a communication system. In this case, multiple NFs may be implemented within a single network entity, or a single NF may be distributed and implemented across a plurality of network entities. In addition, when an NF is implemented within the network entity, the NF may be implemented in the form of software, and in such a case, a program for operating the NF may be stored in memory of the network entity 600.

[0441] A single NF may be implemented by one or more instances, which may be deployed on the same network entity or distributed across multiple network entities to operate. The instance may be a software unit that logically executes a specific network function, and may be implemented in a form that is decoupled from physical hardware resources. Further, one or more NFs may be implemented in the form of one network slice to operate to satisfy specifications required by a particular service.

[0442] The NF may include at least one of an access and mobility management function (AMF), a session management function (SMF), a local session management function (L-SMF), a user plane function (UPF), a local user plane function (L-UPF), a policy control function (PCF), a unified data management (UDM), a unified data repository (UDR), a network exposure function (NEF), a network repository function (NRF), an application function (AF), a network slice selection function (NSSF), a network data analytics function (NWDAF), a network slice admission control function (NSACF), an authentication server function (AUSF), or a data network (DN), etc.

[0443] Referring to FIG. 6, the network entity 600 may include at least one network interface 601, at least one processor 602 (hereinafter, “processor”), and at least one memory 603 (hereinafter, “memory”). As described above, a NF may be implemented in the form of a physical device such as the network entity 600, or may be virtualized and executed in the form of an instance. When implemented as an instance, the NF need not necessarily include physical components as illustrated in FIG. 6. In such a case, the instance may be logically represented as comprising one or more logical functional elements.

[0444] According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the network interface 601, the processor 602, and the memory 603 of the network entity 600 may operate. However, components of the network entity 600 are not limited to the example components illustrated in FIG. 6. In another embodiment, the network entity 600 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in an embodiment, the network interface 601, the processor 602, or the memory 603 may be integrated in the form of one component.

[0445] The network interface 601 is a collective term for a transmitter part of the network entity 600 and a receiver part of the network entity 600, and may be a communication circuit for transmitting or receiving a signal to or from a user equipment (UE), a base station (BS), or another network entity. Here, the communication circuit may include both a communication circuit for wireless communication and a communication circuit for a wired communication. For example, the network interface 601 may include a circuit, logic, hardware, etc., configured to exchange a control plane message or a user plane message with a UE, a BS, or other core network entities through wireless communication or wired communication. The network interface 601 may operate using various protocols (e.g., non-access stratum (NAS) protocol). The network interface 601 may also be referred to, for convenience of description or depending on implementation, as communication circuitry, network interface circuitry, or a communication interface circuitry.

[0446] The processor 602 may control general operations of the network entity 600 according to embodiments of the disclosure. The processor 602 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 602 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 603, individually, collectively or in any combination thereof. Further, the processor 602 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme. Further, it should be noted that, according to another embodiment, in a case where NF is implemented in the form of an instance, the network function may be not necessarily configured by physical hardware.

[0447] According to an embodiment, the processor 602 may be electrically, operatively, and / or communicatively coupled to the network interface 601 to control the network interface 601.

[0448] The processor 602 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. In a specific embodiment, at least a part of the processor 602 may be included in one chip (or IC) and the other part of the processor 602 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the network interface 601 or the memory 603.

[0449] The processor 602 may perform or control or cause an operation of the network entity 600 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 602 may control operations of the network entity 600 for exchanging a control plane message or a user plane message with a UE, a BS, or other core network entities through wireless or wired communication, using various protocols (e.g., NAS protocol). To this end, the processor 602 may execute a computer program, codes, or instructions stored in the memory 603, so as to control other components of the network entity 600 to enable execution of various operations.

[0450] The memory 603 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 603 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0451] The memory 603 may be electrically, operatively, and / or communicatively coupled to the processor 602 and may be accessed by the processor 602.

[0452] The memory 603 may store a computer program, codes, or instructions executable by the processor 602. According to an embodiment, a computer program, codes, or instructions executable by the processor 602 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 603, the processor 602 may perform various functions according to an embodiment of the disclosure.

[0453] According to an embodiment of the disclosure, operations of the network entity 600 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 603 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0454] At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware. Terms such as 'component', 'module' or 'unit' used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality. In some embodiments, the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors. These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of others.

[0455] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0456] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0457] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0458] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0459] Meanwhile, although specific embodiments of the present disclosure have been described in detail, various modifications may be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims and equivalents thereof.

[0460] Glossary of terms.

[0461] Throughout this specification, various acronyms are used. The following list includes certain relevant acronyms / abbreviations.

[0462] BCCH Broadcast Control Channel

[0463] BCH Broadcast Channel

[0464] BFD Beam Failure Detection

[0465] C-RNTI Cell RNTI

[0466] CBRA Contention Based Random Access

[0467] CFRA Contention Free Random Access

[0468] CG Configured Grant

[0469] CHO Conditional Handover

[0470] CORESET Control Resource Set

[0471] CPA Conditional PSCell Addition

[0472] CPC Conditional PSCell Change

[0473] DAPS Dual Active Protocol Stack

[0474] DCI Downlink Control Information

[0475] DCP DCI with CRC scrambled by PS-RNTI

[0476] G-CS-RNTI Group Configured Scheduling RNTI

[0477] G-RNTI Group RNTI

[0478] IAB Integrated Access and Backhaul

[0479] L2 Layer-2

[0480] L3 Layer-3

[0481] LTM L1 / L2-Triggered Mobility : a PCell (or PSCell) cell switch procedure that the network triggers via MAC CE based on L1 measurements. RACH-less LTM indicates that a UE skips the Random Access procedure at LTM cell switch. Subsequent LTM indicates LTM between candidate cells without RRC reconfiguration in between MBS Multicast / Broadcast Services

[0482] MCCH MBS Control Channel

[0483] MIB Master Information Block

[0484] MNO Mobile Network Operator

[0485] MRB MBS Radio Bearer

[0486] MT Mobile Termination

[0487] MTCH MBS Traffic Channel

[0488] MUSIM Multi-Universal Subscriber Identity Module

[0489] NB-IoT Narrow Band Internet of Things

[0490] NR NR Radio Access

[0491] NTN Non-Terrestrial Network

[0492] P-RNTI Paging RNTI

[0493] PCH Paging Channel

[0494] PCI Physical Cell Identifier

[0495] PDCCH Physical Downlink Control Channel

[0496] PDSCH Physical Downlink Shared Channel

[0497] PLMN Public Land Mobile Network

[0498] PO Paging Occasion

[0499] PRACH Physical Random Access Channel

[0500] PRB Physical Resource Block

[0501] PS-RNTI Power Saving RNTI

[0502] PSS Primary Synchronisation Signal

[0503] PTM Point to Multipoint

[0504] PTP Point to Point

[0505] PUCCH Physical Uplink Control Channel

[0506] PUSCH Physical Uplink Shared Channel

[0507] PWS Public Warning System

[0508] QAM Quadrature Amplitude Modulation

[0509] QFI QoS Flow ID

[0510] QoE Quality of Experience

[0511] RA Random Access

[0512] RA-RNTI Random Access RNTI

[0513] RACH Random Access Channel

[0514] RMSI Remaining Minimum SI

[0515] RNA RAN-based Notification Area

[0516] RNAU RAN-based Notification Area Update

[0517] RNTI Radio Network Temporary Identifier

[0518] RSRP Reference Signal Received Power

[0519] RSRQ Reference Signal Received Quality

[0520] SDAP Service Data Adaptation Protocol

[0521] SDT Small Data Transmission

[0522] SIB System Information Block

[0523] SI-RNTI System Information RNTI

[0524] SMC Security Mode Command

[0525] SMF Session Management Function

[0526] SMTC SS / PBCH block Measurement Timing Configuration

[0527] SpCell Special Cell (i.e. PCell or PSCell or PCell in MCG or PSCell in SCG)

[0528] SPS Semi-Persistent Scheduling

[0529] SR Scheduling Request

[0530] SRS Sounding Reference Signal

[0531] SS Synchronization Signal

[0532] SSB SS / PBCH block

[0533] SSS Secondary Synchronisation Signal

[0534] TA Timing Advance

[0535] TB Transport Block

[0536] TPC Transmit Power Control

[0537] TRP Transmit / Receive Point

[0538] TRS Tracking Reference Signal

[0539] UCI Uplink Control Information

[0540] UDC Uplink Data Compression

[0541] UL-SCH Uplink Shared Channel

[0542] UPF User Plane Function

[0543] URLLC Ultra-Reliable and Low Latency Communications

Claims

A method performed by a user equipment (UE) in a wireless communication system, the method comprising:performing a L1 measurement for a candidate cell; andtransmitting, to a base station, a medium access control (MAC) control element (CE) for event triggered L1 measurement report including a result of the L1 measurement,wherein a priority of the MAC CE for event triggered L1 measurement report is higher than a priority of a MAC CE for buffer state report (BSR) with exception of BSR included for padding.The method of claim 1, wherein the priority of the MAC CE for event triggered L1 measurement report is lower than a priority of a MAC CE for cell-radio network temporary identifier (C-RNTI) or data from uplink-common control channel (UL-CCCH).The method of claim 1, wherein the priority of the MAC CE for event triggered L1 measurement report is higher than a priority of a MAC CE for power headroom report (PHR).The method of claim 3, wherein the MAC CE for PHR is one of a MAC CE for single entry PHR, a MAC CE for Multiple Entry PHR, a MAC CE for Single Entry PHR with assumed physical uplink shared channel (PUSCH), a MAC CE for Multiple Entry PHR with assumed PUSCH, a MAC CE for Enhanced Single Entry PHR for multiple transmission reception point (TRP), a MAC CE for Enhanced Multiple Entry PHR for multiple TRP, a MAC CE for Enhanced Single Entry PHR for multiple TRP simultaneous transmission with 2 panels (STx2P), or a MAC CE for Enhanced Multiple Entry PHR for multiple TRP STx2P.The method of claim 1, further comprising:identifying that a pending scheduling request (SR) for the event triggered L1 measurement report has no valid physical uplink control channel (PUCCH) resource configured; andinitiating a random access procedure.The method of claim 5, further comprising:identifying that a MAC PDU including the MAC CE for event triggered L1 measurement report is transmitted using a UL grant other than a UL grant provided by random access response or a UL grant determined for a transmission of the MSGA payload; andstopping the random access procedure due to the pending SR for the event triggered L1 measurement report, which has no valid PUCCH resources configured.A user equipment (UE) in a wireless communication system, the UE comprising:at least one transceiver;at least one processor communicatively coupled to the at least one transceiver; andat least one memory, communicatively coupled to the at least one processor, storing instructions executable by the at least one processor individually or in any combination to cause the UE toperform a L1 measurement for a candidate cell, andtransmit, to a base station, a medium access control (MAC) control element (CE) for event triggered L1 measurement report including a result of the L1 measurement,wherein a priority of the MAC CE for event triggered L1 measurement report is higher than a priority of a MAC CE for buffer state report (BSR) with exception of BSR included for padding.The UE of claim 7, wherein the priority of the MAC CE for event triggered L1 measurement report is lower than a priority of a MAC CE for cell-radio network temporary identifier (C-RNTI) or data from uplink-common control channel (UL-CCCH).The UE of claim 7, wherein the priority of the MAC CE for event triggered L1 measurement report is higher than a priority of a MAC CE for power headroom report (PHR).The UE of claim 9, wherein the MAC CE for PHR is one of a MAC CE for single entry PHR, a MAC CE for Multiple Entry PHR, a MAC CE for Single Entry PHR with assumed physical uplink shared channel (PUSCH), a MAC CE for Multiple Entry PHR with assumed PUSCH, a MAC CE for Enhanced Single Entry PHR for multiple transmission reception point (TRP), a MAC CE for Enhanced Multiple Entry PHR for multiple TRP, a MAC CE for Enhanced Single Entry PHR for multiple TRP simultaneous transmission with 2 panels (STx2P), or a MAC CE for Enhanced Multiple Entry PHR for multiple TRP STx2P.The UE of claim 7, wherein the instructions further cause the UE to:identify that a pending scheduling request (SR) for the event triggered L1 measurement report has no valid physical uplink control channel (PUCCH) resource configured, andinitiate a random access procedure.The UE of claim 11, wherein the instructions further cause the UE to:identify that a MAC PDU including the MAC CE for event triggered L1 measurement report is transmitted using a UL grant other than a UL grant provided by random access response or a UL grant determined for a transmission of the MSGA payload, andstop the random access procedure due to the pending SR for the event triggered L1 measurement report, which has no valid PUCCH resources configured.

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