Method and apparatus for performing an LTM operation

Abstract

A method performed by a UE for performing a layer-1 / layer-2 triggered mobility (LTM) operation is provided. The method receives, from a base station (BS), a configuration message indicating multiple LTM triggering events associated with multiple LTM candidate cells. The method determines whether a radio link failure (RLF) has occurred. The method selects a cell. The method performs, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred. The selected cell is one of the multiple LTM candidate cells that is associated with at least one of the multiple LTM triggering events, and the selected cell is a suitable cell selected by the RRC entity of the UE.

Description

METHOD AND APPARATUS FOR PERFORMING AN LTM OPERATION

[0001] The present disclosure is related to wireless communication and, more specifically, to a User Equipment (UE), Base Station (BS), and method for performing a layer 1 / layer 2 triggered mobility (LTM) operation in the wireless communication networks.

[0002] Various efforts have been made to improve different aspects of wireless communication for the cellular wireless communication systems, such as the 5thGeneration (5G) New Radio (NR), by improving data rate, latency, reliability, and mobility. The 5G NR system is designed to provide flexibility and configurability to optimize network services and types, accommodating various use cases, such as enhanced Mobile Broadband (eMBB), massive Machine-Type Communication (mMTC), and Ultra-Reliable and Low-Latency Communication (URLLC). As the demand for radio access continues to grow, however, there exists a need for further improvements in the next-generation wireless communication systems, such as improvements in a beam management procedure.

[0003] The present disclosure is related to a UE, a BS, and a method for performing a layer 1 / layer 2 triggered mobility (LTM) operation in the wireless communication networks.

[0004] In a first aspect of the present disclosure, a UE for performing an inter-central unit (CU) layer 1 / layer 2 triggered mobility (LTM) or an intra-CU LTM is provided. The UE includes at least one processor and at least one non-transitory computer-readable medium that is coupled to the at least one processor and that stores one or more computer-executable instructions. The computer-executable instructions, when executed by the at least one processor, cause the UE to receive, from a base station (BS), a configuration message indicating multiple LTM triggering events associated with multiple LTM candidate cells, determine whether a radio link failure (RLF) has occurred, select a cell, and perform, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred, where the selected cell is one of the multiple LTM candidate cells that is associated with at least one of the multiple LTM triggering events, and the selected cell is a suitable cell selected by the RRC entity of the UE.

[0005] In some implementations of the first aspect, the selected cell is selected and informed by a medium access control (MAC) entity of the UE when the at least one of the multiple LTM triggering events associated with the selected cell is fulfilled.

[0006] In some implementations of the first aspect, the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to perform the LTM operation without considering the multiple LTM triggering events after determining that the RLF has occurred and an attempt LTM switch indicator indicating the UE to perform the LTM operation is included in the configuration message, where the attempt LTM switch indicator is applied to the selected cell.

[0007] In some implementations of the first aspect, the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to start a Time-To-Trigger (TTT) timer associated with the at least one of the multiple LTM triggering events after determining that the at least one of the multiple LTM triggering events is fulfilled, and perform the LTM operation with the selected cell upon the TTT timer expires, where the at least one of the multiple LTM triggering events remains fulfilled while the TTT timer expires, and the TTT timer is maintained by a medium access control (MAC) entity of the UE.

[0008] In some implementations of the first aspect, the multiple LTM triggering events include one or more Layer-3 cell-level triggering events, one or more Layer-3 beam-level triggering events, and one or more Layer-1 beam-level triggering events, and the one or more Layer-1 beam-level triggering events include at least one of the following events: a first signal quality of a beam associated with a serving cell becomes better than a first absolute threshold, the first signal quality of the beam associated with the serving cell becomes worse than a second absolute threshold, a second signal quality of a beam associated with an LTM candidate cell becomes better than a third signal quality of a beam associated with a primary cell (PCell), a primary secondary cell (PSCell), or the serving cell by a first offset, the second signal quality of the beam associated with the LTM candidate cell becomes better than a third absolute threshold, the first signal quality of the beam associated with the serving cell becomes worse than a fourth absolute threshold and the second signal quality of the beam associated with the LTM candidate cell becomes better than a fifth absolute threshold, and a fourth signal quality of beam associated with a neighbour cell becomes better than a fifth signal quality of a beam associated with a secondary cell (SCell).

[0009] In some implementations of the first aspect, the LTM operation includes at least one of initiating an early synchronization with the selected cell, performing an LTM cell switch procedure with the selected cell, and transmitting, to a serving radio access network, a measurement report associated with the selected cell.

[0010] In some implementations of the first aspect, the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to receive, from the BS, a control message indicating that the at least one of the multiple LTM triggering events is activated or de-activated, determine to activate an evaluation of the at least one of the multiple LTM triggering events after determining that the control message indicates that the at least one of the multiple LTM triggering events is activated, and determine to de-activate the evaluation of the at least one of the multiple LTM triggering events after determining that the control message indicates that the at least one of the multiple LTM triggering events is de-activated.

[0011] In a second aspect of the present disclosure, a method performed by a user equipment (UE) for performing a layer-1 / layer-2 triggered mobility (LTM) operation is provided. The method includes receiving, from a base station (BS), a configuration message indicating multiple LTM triggering events associated with multiple LTM candidate cells, determining whether a radio link failure (RLF) has occurred, selecting a cell, and performing, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred, where the selected cell is one of the multiple LTM candidate cells that is associated with at least one of the multiple LTM triggering events, and the selected cell is a suitable cell selected by the RRC entity of the UE.

[0012] In a third aspect of the present application, a BS for performing a layer-1 / layer-2 triggered mobility (LTM) operation is provided. The BS includes at least one processor and at least one non-transitory computer-readable medium that is coupled to the at least one processor and that stores one or more computer-executable instructions. The computer-executable instructions, when executed by the at least one processor, cause the BS to transmit, to a user equipment (UE), a configuration message indicating multiple LTM triggering events associated with multiple LTM candidate cells, where the configuration message causes the UE to determine whether a radio link failure (RLF) has occurred, select a cell, and perform, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred, where the selected cell is one of the multiple LTM candidate cells that is associated with at least one of the multiple LTM triggering events, and the selected cell is a suitable cell selected by the RRC entity of the UE.

[0013] Aspects of the present disclosure are best understood from the following detailed disclosure when read with the accompanying drawings. Various features are not drawn to scale. Dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

[0014] FIG. 1 is a diagram illustrating an example of associations / mappings between L1 event configurations and LTM candidates, according to an example implementation of the present disclosure.

[0015] FIG. 2 is a diagram illustrating an example of a Time-To-Triggering (TTT) timer counting activity when an entering condition of an L1 event is fulfilled in the UE side, according to an example implementation of the present disclosure.

[0016] FIG. 3 is a diagram illustrating a signaling flow of two-stage activations, according to an example implementation of the present disclosure.

[0017] FIG. 4 is a diagram illustrating the triggering condition of an entering / leaving condition and the associated TimeToTrigger counting activity of a fulfilled entering condition in the UE side, according to an example implementation of the present disclosure.

[0018] FIG. 5A is a diagram illustrating an RRC connection re-establishment procedure, according to an example implementation of the present disclosure.

[0019] FIG. 5B is a diagram illustrating an RRC re-establishment procedure with fallback to an RRC establishment and successful connection, according to an example implementation of the present disclosure.

[0020] FIG. 6 is a diagram illustrating an LTM serving cell switch operation, according to an example implementation of the present disclosure.

[0021] FIG. 7 is a flowchart illustrating a method / process performed by a UE for performing a layer 1 / layer 2 triggered mobility (LTM) operation, according to an example implementation of the present disclosure.

[0022] FIG. 8 is a flowchart illustrating a method / process performed by a BS for performing a layer 1 / layer 2 triggered mobility (LTM) operation, according to an example implementation of the present disclosure.

[0023] FIG. 9 is a block diagram illustrating a node for wireless communication, according to an example implementation of the present disclosure.

[0024] Some of the abbreviations used in the present disclosure include: Abbreviation　　　　Full name 3GPP　　　　3rdGeneration Partnership Project 5G　　　　5thGeneration 5GC　　　　5G Core AMF　　　　Access and Mobility Management Function ARFCN　　　　Absolute Radio-Frequency Channel Number AS　　　　Access Stratum BS　　　　Base Station BWP　　　　Bandwidth Part CA　　　　Carrier Aggregation CAG　　　　Closed Access Group CN　　　　Core Network CU　　　　Central Unit DAPS　　　　Dual Active Protocol Stack DC　　　　Dual Connectivity DCI　　　　Downlink Control Information DL　　　　Downlink DU　　　　Distributed Unit E-UTRA(N)　　　　Evolved Universal Terrestrial Radio Access (Network) EN-DC　　　　E-UTRA NR Dual Connectivity EPC　　　　Evolved Packet Core FR　　　　Frequency Range IAB　　　　Integrated Access and Backhaul ID　　　　Identifier IE　　　　Information Element LAN　　　　Local Area Network LTE　　　　Long Term Evolution LTM　　　　L1 / L2 Triggered Mobility LTM SCS　　　　L1 / L2 Triggered Mobility Serving Cell Switch MAC　　　　Medium Access Control MAC CE　　　　MAC Control Element MCG　　　　Master Cell Group MIB　　　　Master Information Block MN　　　　Master Node MSG　　　　Message MT　　　　Mobile Termination NAS　　　　Non-Access Stratum NE-DC　　　　NR-E-UTRA Dual Connectivity NES　　　　Network Energy Saving NPN　　　　Non-Public Network NR　　　　New Radio NR-U　　　　NR Unlicensed NW　　　　Network NSSAI　　　　Network Slice Selection Assistance Information PCell　　　　Primary Cell PCI　　　　Physical Cell Identity PDCCH　　　　Physical Downlink Control Channel PDSCH　　　　Physical Downlink Shared Channel PDU　　　　Protocol Data Unit PHY　　　　Physical (layer) PLMN　　　　Public Land Mobile Network PNI-NPN　　　　Public Network Integrated Non-Public Network PRACH　　　　Physical Random Access Channel PSCell　　　　Primary SCG Cell / Primary Secondary Cell PUCCH　　　　Physical Uplink Control Channel PUSCH　　　　Physical Uplink Shared Channel RA　　　　Random Access RAN　　　　Radio Access Network RAR　　　　Random Access Response RAT　　　　Radio Access Technology RF　　　　Radio Frequency RNTI　　　　Radio Network Temporary Identifier RRC　　　　Radio Resource Control RS　　　　Reference Signal RSRP　　　　Reference Signal Received Power SCell　　　　Secondary Cell SCG　　　　Secondary Cell Group SI　　　　System Information SIB　　　　System Information Block SL　　　　Sidelink SN　　　　Secondary Node SNPN　　　　Stand-alond Non-Public Network SSB　　　　Synchronization Signal Block TS　　　　Technical Specification UE　　　　User Equipment UL　　　　Uplink V2X　　　　Vehicle-to-Everything WUS　　　　Wake-Up-Signal / Wake-Up-Signaling

[0025] The following contains specific information related to implementations of the present disclosure. The drawings and their accompanying detailed disclosure are merely directed to implementations. However, the present disclosure is not limited to these implementations. Other variations and implementations of the present disclosure will be obvious to those skilled in the art.

[0026] Unless noted otherwise, like or corresponding elements among the drawings may be indicated by like or corresponding reference numerals. Moreover, the drawings and illustrations in the present disclosure are generally not to scale and are not intended to correspond to actual relative dimensions.

[0027] For the purposes of consistency and ease of understanding, like features may be identified (although, in some examples, not illustrated) by the same numerals in the drawings. However, the features in different implementations may be different in other respects and may not be narrowly confined to what is illustrated in the drawings.

[0028] References to “one implementation,” “an implementation,” “example implementation,” “various implementations,” “some implementations,” “implementations of the present application,” etc., may indicate that the implementation(s) of the present application so described may include a particular feature, structure, or characteristic, but not every possible implementation of the present application necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “In some implementations,” or “in an example implementation,” “an implementation,” do not necessarily refer to the same implementation, although they may. Moreover, any use of phrases like “implementations” in connection with “the present application” are never meant to characterize that all implementations of the present application must include the particular feature, structure, or characteristic, and should instead be understood to mean “at least some implementations of the present application” includes the stated particular feature, structure, or characteristic. The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the equivalent.

[0029] The expression “at least one of A, B and C” or “at least one of the following: A, B and C” means “only A, or only B, or only C, or any combination of A, B and C.” The terms “system” and “network” may be used interchangeably. The term “and / or” is only an association relationship for describing associated objects and represents that three relationships may exist such that A and / or B may indicate that A exists alone, A and B exist at the same time, or B exists alone. The character “ / ” generally represents that the associated objects are in an “or” relationship.

[0030] For the purposes of explanation and non-limitation, specific details, such as functional entities, techniques, protocols, and standards, are set forth for providing an understanding of the disclosed technology. In other examples, detailed disclosure of well-known methods, technologies, systems, and architectures are omitted so as not to obscure the present disclosure with unnecessary details.

[0031] Persons skilled in the art will immediately recognize that any network function(s) or algorithm(s) disclosed may be implemented by hardware, software, or a combination of software and hardware. Disclosed functions may correspond to modules which may be software, hardware, firmware, or any combination thereof.

[0032] A software implementation may include computer-executable instructions and / or Artificial Intelligence (AI) / Machine Learning (ML) module(s) stored on a computer-readable medium, such as memory or other type of storage devices. One or more microprocessors or general-purpose computers with communication processing capability may be programmed with corresponding computer-executable instructions and perform the disclosed network function(s), AI / ML module(s), or algorithm(s). The AI / ML module(s) may be implemented with a supervised learning approach, a semi-supervised learning approach, an unsupervised learning approach (e.g., Transductive approach and Inductive approach), a federated learning approach, or a reinforcement learning (RL) approach, but the present disclosure is not limited thereto. The computer-executable instructions associated with the AI module(s) and / or the ML module(s) may include but are not limited to, data management instructions (e.g., collection instructions, validation instructions…etc.), model monitoring and management instructions (e.g., NW KPIs monitoring, model input / output monitoring, model selection / switching / update / upload / download, model (de)activation, model identification, functionality selection…etc.), and / or pre-process input instructions.

[0033] The microprocessors or general-purpose computers may include Application-Specific Integrated Circuits (ASICs), programmable logic arrays, Central Processing Units (CPUs), Tensor Processing Units (TPUs), Graphics Processing Units (GPUs), General-purpose computing on GPUs (GPGPU, or less often GPGP), and / or one or more Digital Signal Processor (DSPs). Although some of the disclosed implementations are oriented to software installed and executing on computer hardware, alternative implementations implemented as firmware, as hardware, or as a combination of hardware and software are well within the scope of the present disclosure. The computer-readable media may include computer-storage media and communication media. Computer-storage media may include both volatile (and / or non-volatile media), and removable (and / or non-removable) media implemented in any method or technology for storage of information such as computer-readable instructions (e.g., computer-readable instructions related to AI module(s) and / or the ML module(s)), data structures, program modules or data.

[0034] The computer-readable medium may include, but is not limited to, Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), High Bandwidth Memory (HBM), Magnetoresistive Random Access Memory (MRAM), Ferroelectric Random Access Memory (FRAM), Resistive Random Access Memory (RRAM), Read-Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), flash memory (or other memory technology), Compact Disc Read-Only Memory (CD-ROM) , Digital Versatile Disks (DVD) (or other optical disk storage), magnetic cassettes, magnetic tape, magnetic disk storage (or other magnetic storage devices), or any other equivalent medium capable of storing computer-readable instructions. Computer-storage media may not include a propagated data signal. Communication media may typically embody computer-readable instructions (e.g., computer-readable instructions related to AI module(s) and / or the ML module(s)), data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transport mechanisms and include any information delivery media.

[0035] A radio communication network architecture such as a Long-Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Pro system, a 5G NR Radio Access Network (RAN), 5G-Advanced (5G-A) system, or an open radio access network (O-RAN) may typically include at least one base station (BS), at least one UE, and one or more optional network elements that provide connection within a network. The BS and one or more optional network elements enable the UE to access a radio network. Thus the UE may communicate with the network, such as a Core Network (CN), an Evolved Packet Core (EPC) network, an Evolved Universal Terrestrial RAN (E-UTRAN), a Next-Generation Core (NGC), a 5G Core (5GC), or an internet via a RAN established by one or more BSs and the network elements / functions.

[0036] A UE may include, but is not limited to, a mobile station, a mobile terminal or device, or a user communication radio terminal. The UE may be a portable radio equipment that includes, but is not limited to, a mobile phone, a tablet, a wearable device, a sensor, a vehicle, a virtual reality (VR) device, an augmented (AR) device, an Internet of Things (IoT) device, an unmanned aerial vehicle (UAV), or a Personal Digital Assistant (PDA) with wireless communication capability. The UE may be configured to receive and transmit signals over an air interface to one or more cells in a RAN. In some implementations, the UE may be an AI / ML-enabled device and / or an AI / ML capable device that is equipped with AI module(s) and / or ML module(s).

[0037] The BS may be configured to provide communication services according to at least a Radio Access Technology (RAT), such as Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM) that is often referred to as 2G, GSM Enhanced Data rates for GSM Evolution (EDGE) RAN (GERAN), General Packet Radio Service (GPRS), Universal Mobile Telecommunication System (UMTS) that is often referred to as 3G based on basic Wideband-Code Division Multiple Access (W-CDMA), High-Speed Packet Access (HSPA), LTE, LTE-A, evolved / enhanced LTE (eLTE) that is LTE connected to 5GC, NR (often referred to as 5G), 5G-A, and / or LTE-A Pro. However, the scope of the present disclosure is not limited to these protocols.

[0038] The BS may include, but is not limited to, a node B (NB) in the UMTS, an evolved node B (eNB) in LTE or LTE-A, a radio network controller (RNC) in UMTS, a BS controller (BSC) in the GSM / GERAN, a next-generation eNB (ng-eNB) in an Evolved Universal Terrestrial Radio Access (E-UTRA) BS in connection with 5GC, a next-generation Node B (gNB) in the 5G-RAN (or in the 5G Access Network (5G-AN)), or any other apparatus capable of controlling radio communication and managing radio resources within a cell. The BS may serve one or more UEs via a radio interface. In some implementations, the BS may be an AI / ML-enabled device and / or an AI / ML capable device that is equipped with AI module(s) and / or ML module(s).

[0039] The BS may be operable to provide radio coverage to a specific geographical area using multiple cells forming the RAN. The BS may support the operations of the cells. Each cell may be operable to provide services to at least one UE within its radio coverage.

[0040] Each cell (may often referred to as a serving cell) may provide services to one or more UEs within the cell’s radio coverage, such that each cell schedules the DL (and optionally UL resources) to at least one UE within its radio coverage for DL (and optionally UL packet transmissions from the UE). The BS may communicate with one or more UEs in the radio communication system via the cells.

[0041] A cell may allocate Sidelink (SL) resources for supporting Proximity Service (ProSe), LTE SL services, LTE / NR sidelink communication services, LTE / NR sidelink discovery services, and / or LTE / NR Vehicle-to-Everything (V2X) services. In addition, a cell may allocate DL and / or UL resources for supporting Multicast / Broadcast Service (MBS) services, Non-Terrestrial Networks (NTN) services, positioning services, power serving services and / or Network Energy Saving (NES) services. Each cell may have overlapped coverage areas with other cells.

[0042] In Multi-RAT Dual Connectivity (MR-DC) cases, the primary cell of a Master Cell Group (MCG) or a Secondary Cell Group (SCG) may be referred to as a Special Cell (SpCell). A Primary Cell (PCell) may include the SpCell of an MCG. A Primary SCG Cell (PSCell) may include the SpCell of an SCG. MCG may include a group of serving cells associated with the Master Node (MN), including the SpCell and optionally one or more Secondary Cells (SCells). An SCG may include a group of serving cells associated with the Secondary Node (SN), including the SpCell and optionally one or more SCells.

[0043] As discussed above, the frame structure for NR may support flexible configurations for accommodating various next generation (e.g., 5G) communication requirements, such as Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC), and Ultra-Reliable and Low-Latency Communication (URLLC), while fulfilling high reliability, high data rate, and low latency requirements. The Orthogonal Frequency-Division Multiplexing (OFDM) technology in the 3GPP may serve as a baseline for an NR waveform. The scalable OFDM numerology, such as adaptive sub-carrier spacing, channel bandwidth, and Cyclic Prefix (CP), may also be used.

[0044] Two coding schemes may be considered for NR, specifically, Low-Density Parity-Check (LDPC) code and Polar Code. The coding scheme adaption may be configured based on channel conditions and / or service applications.

[0045] At least the DL transmission data, a guard period, and UL transmission data should be included in a transmission time interval (TTI) of a single NR frame. The respective portions of the DL transmission data, the guard period, and the UL transmission data should also be configurable based on, for example, the network dynamics of NR. SL resources may also be provided in an NR frame to support ProSe services or V2X services.

[0046] Any two or more than two of the following paragraphs, (sub)-bullets, points, actions, behaviors, terms, or claims described in the present disclosure may be combined logically, reasonably, and properly to form a specific method.

[0047] Any sentence, paragraph, (sub)-bullet, point, action, behaviors, terms, or claims described in the present disclosure may be implemented independently and separately to form a specific method.

[0048] Dependency, e.g., “based on”, “more specifically”, “preferably”, “in one embodiment”, “in some implementations”, etc., in the present disclosure is just one possible example which would not restrict the specific method.

[0049] In some implementations, all the designs / embodiment / implementations introduced within this disclosure are not limited to be applied for dealing with the problems discussed within this disclosure. For example, the described embodiments may be applied to solve other problems that exist in the RAN of wireless communication systems. In some implementations, all of the numbers listed within the designs / embodiment / implementations introduced within this disclosure are just examples and for illustration, for example, of how the described methods are executed.

[0050] The term “A and / or B” within the present disclosure means “A”, “B”, or “A and B”. The term “A and / or B and / or C” within the present disclosure means “A”, “B”, “C”, “A and B”, “A and C”, “B and C”, or “A and B and C”. The term “A / B” within the present disclosure means “A” or “B”.

[0051] The terms, definitions, and abbreviations used in the present disclosure may be either imported from existing documentation (e.g., the European Telecommunications Standards Institute (ETSI), the International Telecommunication Union (ITU), or elsewhere) or newly created by 3GPP experts whenever the need for precise vocabulary is identified.

[0052] In some implementations, the UE may be configured with Layer-1 (L1) measurements with specific reference signal type (e.g., the SSB and / or CSI-RS). In some implementations, the UE may be configured with “periodical reporting” or “event-triggered reporting” to transmit its Layer-1 measurement results to the serving RAN.

[0053] In some implementations, the UE may be configured with one or more of the following Layer-1 (Measurement / Report / Triggering) events (e.g., the Event A1-b to Event A6-b). The one or more Layer-1 (Measurement / Report / Triggering) events may be the triggering events to report the UE’s Layer-1 measurement results.

[0054] Event A1-b: Beam of serving cell becomes better than an absolute threshold. The Event A1-b may also be known as the Event LTM1 in the 3GPP technical specifications, such as the 3GPP TS 38.331.

[0055] Event A2-b: Beam of serving cell becomes worse than an absolute threshold. The Event A2-b may also be known as the Event LTM2 in the 3GPP technical specifications, such as the 3GPP TS 38.331.

[0056] Event A3-b: Beam of candidate cell becomes amount of offset better than beam of PCell / PSCell / serving cell. The Event A3-b may also be known as the Event LTM3 in the 3GPP technical specifications, such as the 3GPP TS 38.331.

[0057] Event A4-b: Beam of candidate cell becomes better than an absolute threshold. The Event A4-b may also be known as the Event LTM4 in the 3GPP technical specifications, such as the 3GPP TS 38.331.

[0058] Event A5-b: Beam of serving cell becomes worse than a first absolute threshold and beam of candidate cell becomes better than a second absolute threshold. The Event A5-b may also be known as the Event LTM5 in the 3GPP technical specifications, such as the 3GPP TS 38.331.

[0059] Event A6-b: Beam of neighbour cell becomes amount of offset better than an SCell.

[0060] In some implementations, a UE may determine one of the following beams (a)-(d) for the “beam of serving cell” in the EventA1-b to EventA6-b.

[0061] (a) The serving beam (e.g., the beam corresponding to the TCI state indicated by the latest DCI).

[0062] (b) The best beam measured in the serving cell which means the beam corresponding to the largest RSRP value among the configured beams.

[0063] (c) The best activated beam measured in the serving cell which means the beam corresponding to the largest RSRP value among the activated beams.

[0064] (d) A beam which is indicated by the serving cell.

[0065] In some implementations, the Layer-1 (measurement / report / triggering) events may be implemented for Layer-1 / Layer-2 Triggered Mobility (LTM) purposes. The LTM operation may include at least one of the following (a)-(c).

[0066] (a) (Action A) Select the candidate beam / cell to trigger the early synchronization.

[0067] (b) (Action B) Select the target beam / cell and trigger the LTM cell switch procedure.

[0068] (c) (Action C) Report Layer-1 measurement result to the serving RAN.

[0069] In some implementations, the Layer-1 (measurement / report / triggering) events may also be used to trigger L3 measurement / report / (conditional) mobility operation. The L3 measurement / report / (conditional) mobility operation may include at least one of the following (d) and (e).

[0070] (d) (Action D) Trigger / leave a Layer-3 cell / beam quality report.

[0071] (e) (Action E) Trigger a conditional handover (CHO) procedure, conditional PSCell addition (CPA), conditional PSCell addition or change (CPAC), and / or Conditional PSCell change (CPC).

[0072] In some implementations, the Layer-1 (measurement / report / triggering) events may combine with one or more L3 report / triggering events to support the triggering / stop of Action D and / or Action E.

[0073] Each action may be associated with one or more LTM candidates (e.g., LTM candidate cells or the (RRC) configurations associated with LTM candidate cells) and one or more L1 events. The Layer-1 (measurement / report / triggering) events may not be used only for the LTM operation.

[0074] In the present disclosure, the designs to enhance the cellular network / UE architecture while the L1 (measurement / report / triggering) events are proposed. Some designs and embodiments nay be based on 3GPP New Radio / E-UTRA technical specifications. However, the proposed designs may not be limited by 3GPP NR / E-UTRA specifications.

[0075] FIG. 1 is a diagram illustrating an example of associations / mappings between L1 event configurations and LTM candidates, according to an example implementation of the present disclosure. As illustrated in FIG. 1, the mapping / association relationship of L1 (measurement / report / triggering) events and LTM candidates for the triggering events design of action A, B, or C for LTM operation enhancements are provided. In some implementations, an LTM candidate may be associated with more than one L1 event. For example, the first L1 event (configuration) 101 may be mapped to or associated with the first LTM candidates 102, the second LTM candidate 104, the third LTM candidate 106, and the fourth LTM candidate 108. The second L1 event (configuration) 103 may be mapped to or associated with the first LTM candidates 102 and the fourth LTM candidate 108. The third L1 event (configuration) 105 may be mapped to or associated with the third LTM candidate 106. The KthL1 event (configuration) 107 may be mapped to or associated with the third LTM candidate 106.

[0076] In some implementations, parameters of L1 (measurement / report / triggering) events may refer to the existing L3 (cell / beam) measurement / report configuration. In addition, the combinations and possible mutual impact of the L1 (measurement / report / triggering) events and L3 measurement / report configurations may also be discussed.

[0077] In some implementations, the L1 (measurement / report / triggering) event and report may be implemented based on the L1 / L2 Triggered Mobility (LTM) configuration and operation.

[0078] In some implementations, the L1 (measurement / report / triggering) events may be configured as part of LTM CSI report configuration (e.g., by referring to the LTM-CSI-ReportConfig IE as specified in the 3GPP TS 38.331).

[0079] In some implementations, a new IE ‘event-riggered’ may be included in the LTM report configuration type IE (e.g., the ltm-ReportConfigType IE). In some implementations, the serving RAN may choose an event-triggered IE with further associated with one Layer-1 measurement report event(s). Table 1 below illustrates an example of the ltm-ReportConfigType IE including the event-triggered IE, according to an example implementation of the present disclosure.

[0080] The serving RAN may configure one or more (Layer-1) report configurations, which may be periodic, semi-persistent on PUCCH, aperiodic, or event-triggered.

[0081] In some implementations, the serving RAN may configure multiple report type configurations to the UE. Therefore, the report type ‘event-triggered’ may be configured to the UE along with other report types, such as ‘periodic’, ‘semi-persistent on PUCCH’, and / or ‘aperiodic’. For example, the ltm-ReportConfigType IE may be configured as ‘sequence’ instead of ‘choice’, and more than one event may be configured jointly.

[0082] In some implementations, the UE may be configured with one or more L1 (measurement / report / triggering) events jointly in a Layer-1 measurement report configuration. Therefore, further information may be provided to be associated with each event, such as the L1 triggering event is {enabled / disabled}, {allowed / not-allowed}, {configured / removed}. In some implementations, the UE may determine the L1 (measurement / report / triggering) events to be applicable (e.g., the event is applied to the evaluation for triggering a report) if they are present in the Event-Triggered IE or they are present with value ‘enabled’ in the Event-Triggered IE. In some implementations, the UE may determine the L1 (measurement / reporting / triggering) events to be not applicable (e.g., the event is not applied to the evaluation for triggering a report) if they are present with value ‘disabled’ in the Event-Triggered IE. Table 2 below illustrates an example of the Event-Triggered IE, according to an example implementation of the present disclosure.

[0083] In some implementations, the Layer-1 measurement report configuration may be an ‘optional’ IE in the (RRC) configuration transmitted to the UE. In some implementations, the Layer-1 measurement report configuration may be designed as the ‘Need M (maintain)’ IE or ‘Need R(Release)’ IE in the (RRC) configuration transmitted to the UE.

[0084] In some implementations, the reference signaling type (e.g., rsType) may be configured with {CSI-RS and / or SSB}. The CSI-RS resource may be associated with the TRS. In some implementations, the quantity of the L1 measurement / report / triggering event (e.g., the rsQuantity) may be implemented on one configured quantity, such as {DL-RSRP, DL-RSRQ, DL-SINR}. In some implementations, the rsType / rsQuantity may be configured in the (LTM) reference configuration as a default setting for the L1 measurement / report / triggering event. In some implementations, an LTM candidate / L1 (measurement / report / triggering) event may be further associated with specific rsType / rsQuantity for UE to perform measurements / evaluations.

[0085] The TimeToTrigger IE may specify 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 the Action A, B, C, D, or E. Value “ms0” may correspond to 0 ms, value “ms40” may correspond to 40 ms, and so on. Table 3 below illustrates an example of the TimeToTrigger IE, according to an example implementation of the present disclosure.

[0086] In some implementations, an L1 (measurement / report / triggering) event may be further configured with a Time-To-Trigger value (e.g., the Tt). Based on the configuration of the Tt, the UE may perform at least one of the Action A, Action B, Action C, Action D, and Action E after the UE detects / observes an L1 (measurement / report / triggering) event (with / without one or more combined conditional (L3) event(s)) is consistently / continuously fulfilled longer than a time period Tt. For example, the UE may set a Time-To-Trigger (TTT) timer, and the initial value of the TTT timer is equivalent to Tt. Upon the UE detects / observes an L1 (measurement / report / triggering) event is fulfilled, the UE may not perform the Action A, B, C, D, or E immediately unless the condition of the L1 (measurement / report / triggering) event (e.g., which activates the Tt counting activity) is still fulfilled during the time period that TTT timer is still running. In addition, the UE may initiate / start / perform the Action A, B, C, D, or E upon / after the TTT timer expires and L1 (measurement / report / triggering) event is still fulfilled. In other words, the TTT timer may be stopped / released when the L1 (measurement / report / triggering) event which triggers the TTT timer running activity becomes not valid / non-fulfilled. In other words, it may mean that the L1 (measurement / report / triggering) event becomes invalid and then the UE may not implement / perform any action associated with the invalid L1 (measurement / report / triggering) event. In other words, the UE may halt / stop / discontinue the action associated with the L1 (measurement / report / triggering) event after the L1 (measurement / report / triggering) event becomes invalid.

[0087] In some implementations, the TTT timer counting mechanism may be associated with the joint combinations of one or more L1 events and one or more L3 events. In this condition, a TTT configuration may be configuration to be associated with the combinations the conditional L1 / L3 events. The TTT timer may be started upon / after all of the combined conditional events are fulfilled. In addition, the TTT may be stopped / reset upon any configured (L1 / L3) event in the combinations is not fulfilled.

[0088] In some implementations, a Time-To-Trigger value may be provided in the reference configuration or in the ltm-Config IE (e.g., the IE configuring all the LTM-related configurations) as one default setting to all the LTM candidates / L1 (measurement / report / triggering) event configuration (e.g., if the LTM candidate / L1 (measurement / report / triggering) event is not configured with the TimeToTrigger value). In some implementations, if an L1 (measurement / reporting / triggering) event configured with a specific Time-To-Trigger value, the UE may ignore the default Time-To-Trigger value.

[0089] In some implementations, the proposed mechanisms about L1 event evaluations / implementations may be included the ltm-Referenceconfiguration IE as specified in the 3GPP New Radio protocols. The configurations related to L1 event evaluations / implementations may be implemented / applied earlier than the LTM SCS operation (e.g., which may be triggered by the receptions of the LTM SCS MAC CE or by conditional LTM operation proposed in the present disclosure). In some implementations, another specific reference configuration for the proposed L1 event evaluations / conditional LTM evaluation (e.g., which is defined as the Conditional-Referenceconfiguration IE) may be configured separately from the (conventional) ltm-ReferenceConfiguration IE. In addition, the UE may evaluate each LTM candidate and L1 event evaluations based on the the Conditional-Referenceconfiguration IE. The Conditional-Referenceconfiguration IE may be applied before the LTM SCS operation is triggered.

[0090] In some implementations, the UE may stop / interrupt the evaluations of conditional LTM operation / proposed L1 event(s) evaluation upon / after the (conditional) LTM operation is triggered by the UE.

[0091] In some other implementations, the UE may keep / continue the evaluations of conditional LTM operation / proposed L1 event(s) evaluation upon / after the (conditional) LTM operation is triggered by the UE.

[0092] In some implementations, the UE may select an LTM candidate for (conditional) LTM operation (e.g., based on the configured the Conditional-Referenceconfiguration IE or the ltm-referenceconfiguration IE) while the timer T311 is counting / running. In some implementations, the UE may not apply / evaluate / measure the configured Conditional-Referenceconfiguration / ltm-Referenceconfiguration IE for the (conditional) LTM operation / proposed L1 event evaluation while the timer T311 is counting / running. In some implementations, the UE may select a suitable cell (e.g., based on the conventional S-criteria / R-criteria) for the LTM SCS operation while the timer T311 is counting / running (e.g., if the UE is allowed / configured to perform the LTM SCS operation during the timer T311 counting period).

[0093] In some implementations, an LTM candidate may be configured with a specific Time-To-Trigger value for the L1 (measurement / report / triggering) event associated with the LTM candidate.

[0094] In some implementations, an LTM candidate may also be configured with an evaluation criteria / parameter (e.g., a Quantity configuration, such as a threshold and / or a TTT timer), and a specific L1 event may also be configured with another evaluation criteria / parameter (e.g., a Quantity configuration, such as a threshold and / or a TTT timer). In this condition, several approaches may be instructed by the serving RAN.

[0095] Case 1: The evaluation criteria / parameters associated with the L1 event (e.g., the configurationeventL1) may always have higher priority than the evaluation criteria / parameters associated with the LTM candidate (e.g., the configurationcandidate). So, the UE may perform the L1 event evaluation (only) based on the configurationeventL1, and may ignore the configurationcandidate.

[0096] Case 2: The evaluation criteria / parameters associated with the LTM candidate (e.g., the configurationcandidate) may always have higher priority than the evaluation criteria / parameters associated with the L1 event (e.g., the configurationeventL1). So, the UE may perform the L1 event evaluation (only) based on the configurationcandidate, and may ignore configurationEventL1.

[0097] Case 3: The UE may determine the evaluation criteria / parameters of an LTM candidate with an L1 event by jointly combining the configured configurationeventL1and configurationcandidate. In addition, when a parameter (e.g., the TTT timer) is found in both configurationeventL1and configurationcandidate, the UE may apply the priority rules based on either the case 1 or case 2 mentioned above.

[0098] In some implementations, an L1 (measurement / report / triggering) event may be configured with a specific Time-To-Trigger value.

[0099] In some implementations, a common Tt value may be configured by a UE to be associated with one or more L1 (measurement / report / triggering) events. In some implementations, ‘common’ may mean that the Tt may be shared by multiple UEs (e.g., the Tt configuration may be provided via broadcasting system information or on-demand SI procedure). In some implementations, ‘common’ may mean that the Tt may be shared by multiple L1 (measurement / report / triggering) events in a UE (e.g., the Tt configuration may be provided via UE-specific control signaling, such as RRC signaling / MAC CE / DCI).

[0100] In some implementations, the UE may evaluate one or more L1 (measurement / report / triggering) events jointly / simultaneously. In some implementations, the one or more L1 (measurement / report / triggering) events evaluated jointly / simultaneously by the UE may be applied to an LTM candidate alone (e.g., in other words, each LTM candidate may be configured with multiple L1 measurement / report / triggering events, and each LTM candidate may be considered independently). In some implementations, the one or more L1 (measurement / report / triggering) events evaluated jointly / simultaneously by the UE may be implemented across all (or a subset of) of the LTM candidates.

[0101] In some implementations, the UE may stop evaluating any L1 (measurement / report / triggering) event when there is already a running / active TTT timer (e.g., associated with one or more fulfilled L1 (measurement / report / triggering) event) or upon / while a TTT timer (e.g., associated with an L1 measurement / report / triggering event) is started by the UE. In some implementations, the UE may still be able to evaluate / measure / detect other L1 (measurement / report / triggering) events even though there is already a running / active TTT timer running. So, the UE may be able to start / count more than one TTT timer jointly / simultaneously. The UE may need to maintain multiple active TTT timers simultaneously in time domain. In some implementations, the UE may maintain multiple active TTT timers associated with an LTM candidate alone (e.g., in other words, each LTM candidate may be configured with multiple L1 measurement / report / triggering events, and each LTM candidate may be considered independently). In some implementations, the UE may maintain multiple active TTT timers across all (or a subset of) of the LTM candidates.

[0102] In some implementations, the UE may stop evaluating / measuring one, some, or all of pending L1 (measurement / report / triggering) event(s) upon / when the UE already performs the action A, B, or C with a target LTM candidate (e.g., due to the TTT timer of an L1 (measurement / report / triggering) event associated with the target LTM candidate expires). The pending L1 (measurement / report / triggering) event may mean that the entering condition / leaving condition of the L1 (measurement / report / triggering) event is not fulfilled yet based on the UE’s measurement and evaluation. In some implementations, the running TTT timer of those L1 (measurement / report / triggering) events may also be stopped / released upon / after the UE performs an action A, B, or C with the target LTM candidate. In some implementations, the UE may stop evaluating / measuring one, some, or all of pending L1 (measurement / report / triggering) event(s) associated with a target LTM candidate upon / when the UE already performs the action A, B, or C to the target LTM candidate (e.g., due to the TTT timer of an L1 (measurement / report / triggering) event expires). In this condition, the UE may still keep evaluating / measuring one, some, or all of pending L1 (measurement / report / triggering) event(s) associated with other LTM candidates. In some implementations, the UE may also stop evaluating / measuring one, some, or all of pending L1 (measurement / report / triggering) event(s) of the rest of LTM candidates upon / when the UE already performs the action A, B, or C with a target LTM candidate (e.g., due to the TTT timer of an L1 (measurement / report / triggering) event associated with the target LTM candidate expires).

[0103] In some implementations, UE may initiate and count multiple TTT timers associated with different L1 (measurement / report / triggering) events / LTM candidates independently. In addition, if a running TTT timer associated with a fulfilled L1 (measurement / report / triggering) event of a target LTM candidate expires, the UE may also trigger the actions associated with the fulfilled L1 (measurement / report / triggering) event accordingly. In addition, the other running TTT timers may be stopped / released by the UE, and so the UE may stop evaluating those pending L1 (measurement / report / triggering) events.

[0104] In some implementations, a common Time-To-Trigger value may be defined for one or more L1 (measurement / report / triggering) events.

[0105] In some implementations, the TTT timer may be activated / counted / stopped / released by the MAC entity. In this condition, the RRC entity may need to configure the LTM candidates / L1 events / TTT values to the MAC entity. In addition, upon the TTT timer expires, the MAC entity may also need to inform the RRC entity that an L1 (measurement / report / triggering) event is fulfilled (and the TTT timer has expired). After receiving the information from the MAC entity, the RRC entity may start performing the action A, B, or C after receiving the indication from the MAC entity. In some other implementations, the MAC entity may start performing the action A, B, or C after determining that an L1 event (e.g., associated with an LTM candidate) is fulfilled (and the TTT timer has expired).

[0106] In some implementations, the TTT timer may be activated / counted / stopped / released by the RRC entity.

[0107] In some implementations, the TTT timer values configured to each different actions (e.g., the action A, B, or C) may be different.

[0108] FIG. 2 is a diagram illustrating an example of a Time-To-Triggering (or TimeToTrigger) (TTT) timer counting activity when an entering condition of an L1 event is fulfilled in the UE side, according to an example implementation of the present disclosure. In some implementations, a UE 20 may start performing the action A (e.g., the early synchronization 202) associated with an LTM candidate immediately when an L1 (measurement / report / triggering) event is fulfilled (206). In addition, a TTT timer associated with the L1 (measurement / report / triggering) event and the same LTM candidate may also be triggered to be counted to zero when the L1 (measurement / report / triggering) event is fulfilled. Then, the UE 20 may start performing the action B (e.g., the LTM cell switch 204) upon / while / after the TTT timer expires (208), as illustrated in FIG. 2.

[0109] The UE procedures as illustrated in FIG. 2 may be associated with a specific LTM candidate. In addition, the UE may maintain multiple UE procedures, and each UE procedure may be associated with a specific LTM candidate, for (conditional) LTM operation. In some implementations, the UE may trigger an LTM cell switch operation associated with an LTM candidate, and there may be also some running TTT timers associated with other LTM candidates. In this condition, the UE may terminate / release / stop / suspended the remaining UE procedures (e.g., which the TTT timers are still running) upon / after the UE triggers an LTM cell switch operation associated with an LTM candidate. In some implementations, the UE may still evaluate / implement L1 (measurement / report / triggering) events even an action is already implemented / triggered (e.g., the action A, B, or C). The UE may stop / release / terminate all the measurement / evaluation of the L1 (measurement / report / triggering) event while / upon / after an LTM cell switch operation is terminated successfully in the UE side (e.g., by referring to the complete condition of the LTM operation).

[0110] In some implementations, a UE may be configured / instructed to start / activate the L1 (measurement / report / triggering) event based on UE-specific control signaling.

[0111] In some implementations, the UE may be pre-configured by UE-specific RRC signaling (e.g., the RRCReconfiguration message or the RRCResume / RRCSetup message) with one or more L1 (measurement / report / triggering) events associated with one or more LTM candidates. In some implementations, the UE may be enabled / authorized to start the evaluation procedure of one or more L1 (measurement / report / triggering) events after receiving the RRC signaling.

[0112] In some implementations, the UE may receive a (conditional) LTM cell switch command (MAC CE), which activates / triggers / enables / configures the UE to start the evaluation / measurement of one or more L1 (measurement / report / triggering) events. In this condition, the LTM cell switch command MAC CE may include further information to activate an L1 (measurement / report / triggering) event evaluation. In some implementations, the UE may also receive an IE (e.g., via the pre-configuration via RRC signaling) which allows / enables the UE to start the evaluation / measurement of one or more L1 (measurement / report / triggering) events upon / after receiving the LTM CSC MAC CE from the serving RAN. In some implementations, the proposed mechanism may also be applicable to the MAC CE which activates the TCI states of an LTM candidate.

[0113] In some implementations, the UE may receive Downlink Control Information (DCI), which instructs the UE to perform an early TA acquisition procedure. Then, after receiving the DCI, the UE may also be authorized / enabled to start performing the evaluation / measurement of one or more L1 (measurement / report / triggering) events to initiate a random access procedure with an LTM candidate for a specific action (e.g., the action B). In this condition, the DCI may further include more information (e.g., one or more index(-ies) associated with the L1 (measurement / report / triggering) event) to authorize / enable the UE to start performing the evaluation procedure. In some implementations, the UE may also receive an IE (e.g., via the pre-configuration via RRC signaling) which allows / enables the UE to start the evaluation / measurement of one or more L1 (measurement / report / triggering) events upon / after receiving the DCI (e.g., for UE TA acquisition) from the serving RAN.

[0114] In some implementations, different LTM candidates may be configured with different activation rules / configurations, and it may be applied to the L1 (measurement / report / triggering) events associated with the LTM candidate.

[0115] In some implementations, the MAC entity in a UE side may be configured by the RRC entity of the UE side with one or more L1 (measurement / report / triggering) events.

[0116] In some implementations, each MAC entity (e.g., the MAC entity associated with master cell group / master node, and / or the MAC entity associated with secondary cell group / secondary node) may be enabled / allowed to be independently configured with one or more L1 (measurement / report / triggering) events. In some implementations, only the MAC entity of the MCG may be configured with L1 (measurement / report / triggering) events.

[0117] In some implementations, the L1 (measurement / report / triggering) events associated with the MCG may be configured by the serving RAN via SRB1 / SRB3. The L1 (measurement / report / triggering) events associated with the SCG may be configured by the serving RAN via SRB1 / SRB3.

[0118] In some implementations, the MAC entity associated with the MCG / SCG may perform the action A, B, or C independently (e.g., based on the Time-To-Trigger Timer counting activity). Therefore, it may be possible that the action A, B, or C associated with MCG / SCG may be performed / implemented jointly (with independent configurations) in time domain.

[0119] In some implementations, the L1 (measurement / report / triggering) events may be allowed to be configured only with the MCG / SCG. In some implementations, if a UE is storing / maintaining one or more L1 (measurement / report / triggering) events for a cell group (e.g., the MCG or SCG), and upon receiving an RRC message configuring the L1 (measurement / report / triggering) event for the other cell group (e.g., the SCG or MCG), the UE may perform one or more of the following actions (1)-(3): (1) release the stored L1 (measurement / report / triggering) events for the cell group (e.g., the MCG or SCG) and store the L1 (measurement / report / triggering) events for the other cell group (e.g., the SCG or MCG), (2) ignore the L1 (measurement / report / triggering) events configured in the RRC message, and (3) initiate the connection re-establishment procedure.

[0120] In some implementations, only one cell group may implement action A, B, or C based on the given L1 (measurement / report / triggering) event in time domain. Therefore, when a MAC entity (e.g., the MAC entity associated with the MCG or SCG) starts performing the action A, B, or C based on the L1 (measurement / report / triggering) event, the UE may stop / suspend / release the evaluation / TTT timer counting activity of another MAC entity.

[0121] In some implementations, the serving RAN may also indicate / instruct the activated TCI state(s) associated with at least one LTM candidate / at least one L1 (measurement / report / triggering) event in the control signaling and / or the specific MAC CE (e.g., the LTM SCS command) / DCI. In some implementations, the serving RAN may configure the candidate TCI-state (e.g., by configuring the CandidateTCI-state and / or CandidateTCI-UL-state) associated with the specific LTM candidate (cell) / L1 event.

[0122] In some implementations, the serving RAN may configure the QCL-information (e.g., the Quasi Co Location) of the LTM candidate as the reference to TCI state. In addition, the serving RAN may transmit the TCIstateToaddModList IE (e.g., by referring to the dl-OrJointTCIStateToAddModList IE) to configure the TCI state list associated with the UE. Then, the serving RAN may transmit the specific MAC CE / DCI to further activate the TCI state(s) associated with the target LTM candidate(s) / L1 event.

[0123] In some implementations, the MAC entity may inform the RRC entity of the UE side when an L1 (measurement / report / triggering) event is fulfilled (e.g., but the TimeToTigger Timer may be counted or be stopped in the MAC entity of the UE side).

[0124] In some implementations, the UE may perform an L1 measurement for an L1 (measurement / report / triggering) event based on the current operating beams (e.g., the SSB burst(s) / CSI-RS / TRS) associated with an LTM candidate cell / current serving cell (e.g., with further TCI state associated with the SSB of the LTM candidate).

[0125] In some implementations, the UE may perform an L1 measurement for an L1 (measurement / report / triggering) event based on the best operating beam (e.g., the best beam direction associated with an SSB / CSI-RS / TRS of an LTM candidate) associated with an LTM candidate cell / current serving cell. In some implementations, the best beam may be based on the L1 (measurement) report (e.g., the largest L1-RSRP / RSRQ / RSSI / SINR value) associated with the candidate cell or the source cell.

[0126] In some implementations, the target CSI-RS configuration of LTM candidates may be configured via current LTM-CSI-ResourceConfig IE as specified in the 3GPP TS 38.331.

[0127] In some implementations, the UE may derive the RS resource for current beam of the serving cell (implicitly) based on the QCL RS indicated by the TCI state (configuration). Therefore, to an activated TCI state of the serving cell, the UE may acquire the RS resource associated with the serving cell through an implicit approach. In some implementations, the serving RAN may also configure the RS resource configuration (e.g., the CSI-RS / SSB / TRS) of the serving cell for the measurement / evaluation of a given L1 (measurement / report / triggering) event. The UE may also need to find the best beam of the serving cell for L1 (measurement / report / triggering) configurations based on the given TCI state configuration / RS resource configuration.

[0128] In some implementations, the L1 event associated with the current serving cell may be associated with (or limited by) current operating beam. In some implementations, the L1 event associated with the current serving cell may be associated with the best beam observed by the UE (e.g., with a given period). In some implementations, the serving RAN may configure which beam (e.g., the current beam or the best beam) for the L1 event triggering / association (e.g., via an indication in the L1 event). In some implementations, both associations (e.g., associated with the current operating beam or associated with the best beam that the UE have measured / observed) may be supported by the UE / serving RAN. In some implementations, both associations (e.g., associated with the current operating beam or associated with the best beam that the UE have measured / observed) may also be applicable to the LTM candidate cell.

[0129] In some implementations, the UE may derive the RS resource for a beam of the LTM candidate cell (implicitly) based on the QCL RS indicated by the TCI state (configuration) configured / activated by the serving RAN. Therefore, to an activated TCI state of the LTM candidate cell, the UE may acquire the RS resource associated with the serving cell through an implicit approach.

[0130] In some implementations, a specific L1 (measurement / report / triggering) event may be pre-configured with the Reference Signal (e.g., the SSB / CSI-RS / TRS) configuration associated with a specific LTM candidate. In some implementations, multiple L1 events may share the same RS configuration.

[0131] FIG. 3 is a diagram illustrating a signaling flow of two-stage activations, according to an example implementation of the present disclosure. In FIG. 3, the UE 30 may receive an LTM configuration from the RAN 32 (as shown in action 301). After receiving the LTM configuration, the UE 30 may receive a first stage (L1 event) activation message (as shown in action 303) and a second stage (L1 event) activation message (as shown in action 305) from the RAN 32. Then, the UE 30 may perform the Action A, B, C, D, or E based on the first stage (L1 event) activation message and the second stage (L1 event) activation message (as shown in action 307).

[0132] In some implementations, the serving RAN may configure / transmit RRC signaling (e.g., via the Reference configuration or via LTM candidate configurations) to define / indicate a set of L1 (measurement / report / triggering) events (e.g., with or without threshold values) associated with an LTM candidate. The (DL) RRC signaling may be defined as a first stage activation message. In some implementations, the first stage activation message may include more than one LTM candidate and multiple sets of L1 (measurement / report / triggering) events. In some implementations, a set of L1 (measurement / report / triggering) events (e.g., with or without threshold values) may also be associated with multiple LTM candidates.

[0133] The serving RAN may configure / transmit another downlink control signaling (e.g., the MAC CE / DCI) to activate one or more specific L1 (measurement / report / triggering) events (e.g., with or without thresholds) associated with an LTM candidate. The (DL) MAC CE / DCI signaling may be defined as a second stage activation message. The second stage activation message may not be the UE TA acquisition DCI or LTM SCS MAC CE shown in conventional LTM operation. The second stage activation message may further include the following information (A)-(C).

[0134] (A) An index value corresponding to the LTM candidate provided in the first stage activation message if multiple LTM candidates are provided in the first stage activation message. Otherwise, this field may be absent.

[0135] (B) An index value corresponding to at least one L1 (measurement / report / triggering) event in the set of L1 (measurement / report / triggering) events given in the first stage activation message. In some implementations, more than one index value may be provided to activate multiple L1 (measurement / report / triggering) events via the second stage activation message.

[0136] (C) Threshold value(s) of the L1 (measurement / report / triggering) event(s) indicated by the second stage activation message. In some implementations, the UE may apply the threshold values pre-configured by the serving RAN (e.g., via reference configuration in LTM operation) if the threshold values of the L1 (measurement / report / triggering) events indicated by the second stage activation message is absent in the second stage activation message.

[0137] In some implementations, the second stage activation message may be implemented by one or more DCI / MAC CE.

[0138] In some implementations, the UE may measure and evaluate the L1 (measurement / report / triggering) events after receiving the second stage activation message. The UE may be enabled to trigger a (conditional) LTM Cell switch operation based on the L1 (measurement / report / triggering) events after receiving the second stage activation message. Specifically, the UE may determine whether to trigger the conditional LTM (SCS / operation) to the candidate cell based on the L1 events.

[0139] In some implementations, there may be more than one LTM candidate for which the L1 (measurement / report / triggering) event is fulfilled. In this condition, the UE may determine which LTM candidate to perform LTM SCS based on UE implementations. In some implementations, the UE may perform at least two actions (e.g., at least two of the actions A, B, C, D, and E) jointly / simultaneously in time domain (e.g., based on UE implementations or based on RAN configuration).

[0140] In some implementations, the serving RAN may pre-configure (e.g., via RRC signaling or the first stage activation message) the priority sequence of LTM candidates for the UE to select for the LTM SCS operation when more than one LTM candidate cell is fulfilled. The UE may perform the LTM SCS operation based on the given priority sequence when more than one LTM candidate cell is fulfilled / qualified (e.g., based on the given L1 (measurement / report / triggering) event associated with the LTM candidate cell). For example, the priority sequence for each LTM candidate cell may be included in the LTM candidate configuration for each LTM candidate cell in the RRC signaling (e.g., the RRC reconfiguration message). Based on the given priority sequence, the UE may only perform an LTM serving cell switch (CSC) operation and the UE may not initiate another LTM serving cell switch operation when a (conditional) LTM SCS operation is still ongoing. In some implementations, the serving RAN may also indicate / instruct the activated TCI state associated with at least one LTM candidate / one L1 (measurement / report / triggering) event in the first stage activation message and / or the second stage activation message. In addition, the UE may perform the measurement / evaluation of one or more L1 events based on the activated TCI state (e.g., the TCI state associated with the serving cell and / or the TCI state associated with LTM candidate).

[0141] In some implementations, the UE may provide / store the L1 measurement results that are triggered by the given L1 (measurement / report / triggering) event in the VarMeasReportList IE.

[0142] In some implementations, the UE may provide / store L1 measurement results that are triggered by the given L1 (measurement / report / triggering) event in another VarMeasReportList-L1 IE. In some implementations, another set of the measId-L1 list may be configured / transmitted by the serving RAN to indicate an L1 measurement configuration (e.g., the measId-L1 may be associated with an L1 measurement object configuration and / or an L1 (measurement / report / triggering) event).

[0143] The UE variable VarMeasReportList may include information about the measurements for which the triggering conditions (e.g., associated with the L1 (measurement / report / triggering) events in the present disclosure) have been met. Table 4 below illustrates an example of the VarMeasReportList-L1 UE variable, according to an example implementation of the present disclosure.

[0144] In some implementations, the UE may not trigger any L1 measurement report to the serving RAN based on the L1 (measurement / report / triggering) report configuration when the timer T311 is counting, even though the UE has been configured with any stored / configured L1 (measurement / report / triggering) event.

[0145] In some implementations, the UE may start the timer T311 upon initiating an RRC connection re-establishment procedure. In some implementations, the UE may stop the running timer T31 upon selecting a suitable NR cell, or upon selecting a suitable L2 U2N Relay UE, or a cell using another RAT. In some implementations, the UE may transition from the RRC Connected state to the RRC idle state when the timer T311 expires.

[0146] In some implementations, a UE may be configured / enabled (e.g., by the serving RAN) to select a candidate beam / cell to trigger early synchronization with a selected LTM candidate which fulfills at least one Layer-1 measurement event.

[0147] In some implementations, the UE may determine whether to perform an LTM execution based on one or more given Layer-1 measurements.

[0148] In some implementations, a UE may be configured with the attemptLTM-Switch IE, which enables the UE to perform the LTM serving cell switch procedure for a selected LTM candidate cell based on the actions as specified in the 3GPP TS 38.331. In some implementations, the UE may select the LTM candidate cell via conventional cell re-selection procedure (e.g., the s-criteria / R-criteria). In some implementations, the UE may select the LTM candidate cell via the L1 (measurement / report / triggering) event, which may be pre-configured by the serving RAN via UE-specific control signaling (e.g., the RRC signaling / MAC CE / DCI) when T311 is counting / running.

[0149] In some implementations, the UE may be configured with an IE to indicate that whether the UE is enabled / allowed (or be disabled) to select an LTM candidate cell based on one or more L1 (measurement / report / triggering) event(s) when the timer T311 is counting / running. In some implementations, the UE may be configured with one or more L1 measurement / report / triggering events (e.g., with or without associated thresholds) that the UE is configured to perform the LTM candidate cell selection when T311 is running.

[0150] In some implementations, the UE may stop / interrupt the evaluations of conditional LTM operation / proposed L1 event(s) upon / after the (conditional) LTM operation is triggered by the UE (e.g., upon / while / after the T311 is triggered / activated / counting). In some implementations, the UE may not stop / interrupt the evaluations of conditional LTM operation / proposed L1 event(s) upon / while / after the timer T311 is triggered / activated / counting).

[0151] In some implementations, the UE may not be allowed to re-evaluate / reselect an LTM candidate cell based on the L1 (measurement / report / triggering) event (and trigger LTM cell switch operation based on the result of L1 (measurement / report / triggering) event) when the timer T311 is running. In this condition, the UE may be configured with L1 (measurement / report / triggering) event for at least one of the following implementations (a) and (b) before the timer T311 is started. In some implementations, the UE may not be configured with L1 (measurement / report / triggering) event for at least one of the following implementations (a) and (b) before the timer T311 is started.

[0152] (a) Select the candidate beam / cell to trigger the early synchronization.

[0153] (b) Select the target beam / cell and trigger the LTM cell switch procedure.

[0154] Therefore, when T311 is running, the UE may still select a suitable cell based on cell (re)selection procedure, and an LTM operation may be implemented (only) when the selected cell is also an LTM candidate cell.

[0155] In some implementations, a UE may be configured / enabled / allowed to evaluate whether an LTM operation (e.g., associated an LTM candidate) can be implemented (e.g., with an LTM candidate cell) based on one or more L1 measurement / report / triggering events (e.g., A1-b, A2-b, A3-b, A4-b, A5-b, and / or A6-b) when the timer T311 is running. In some implementations, the UE may be allowed / enabled to evaluate the L1 (measurement / report / triggering) event only once for the LTM candidate cell selection when the timer T311 is counting / running. In other words, the UE may not be able / allowed to re-evaluate another LTM candidate cell for the LTM operation (e.g., even though the UE may have still valid stored L1 measurement results associated with those LTM candidates) after the UE has already selected an LTM candidate cell and / or initiated an LTM SCS operation when the timer T311 is counting / running.

[0156] In some implementations, the UE may select the candidate (LTM) beam / cell based on the given L1 (measurement / report / triggering) events for the LTM operation.

[0157] In some implementations, the UE may stick on the same LTM candidate cell for (one-shot) LTM operation when the timer T311 is counting / running.

[0158] In some implementations, the UE may already select an LTM candidate (e.g., a first LTM candidate, and the UE may implement the following LTM SCS operation, which is called a first LTM SCS operation, with the first LTM candidate) on Action A or Action B based on the given / configured L1 (measurement / report / triggering) events before the timer T311 is triggered / started to count or before a radio link failure event happens to the UE. Then, upon the UE starts to count T311 to zero or upon the UE considers a radio link failure (RLF) event happens, the UE may ignore / skip / overwrite the selected first LTM candidate, and perform conventional cell (re)selection procedure (e.g., based on the S-criteria and R-criteria in the 3GPP technical specifications) to reselect a cell for the LTM SCS operation, which is called a second LTM candidate and a second LTM SCS operation in this condition (e.g., ‘attemptLTM-Switch’ may or may not be pre-configured to the UE before the RRC re-establishment procedure). In this condition, the UE may give up / interrupt the first LTM SCS operation upon / after the UE initiates an RRC re-establishment procedure (e.g., upon / after the UE starts to count the timer T311 to zero). Then, after the UE re-selects to the second LTM candidate (e.g., when the timer T311 is still counting / running), the UE may start to perform the second LTM SCS operation associated with the second LTM candidate.

[0159] In some implementations, the first LTM candidate and the second LTM candidate may be the same LTM candidate, and the first LTM SCS operation and the second LTM SCS operation may be associated with the same reference configuration / LTM candidate configuration.

[0160] In some implementations, the UE may still need to interrupt the first LTM SCS operation and then re-start the second LTM SCS operation based on the same reference configuration / LTM candidate configuration.

[0161] In some implementations, the first LTM SCS operation may be suspended upon / after the UE initiates an RRC re-establishment procedure. Then, the suspended first LTM SCS operation may be resumed after the cell (re)selection procedure if the re-selected cell is also the first LTM candidate. Otherwise (e.g., the re-selected cell is not the first LTM candidate after cell (re)selection procedure), the UE may release the suspended first LTM SCS operation and start the second LTM SCS operation.

[0162] In some implementations, the serving RAN may configure whether the UE is enabled / disabled to perform the conditional LTM SCS operation (e.g., including the Action A and Action B) during the RRC re-establishment procedure (e.g., when the timer T311 is counting) via UE-specific control signaling (e.g., RRC signaling) or broadcasting control signaling (e.g., via system information broadcasting, on-demand SI procedure or group-common PDCCH transmission).

[0163] In some implementations, the UE may already receive an LTM SCS MAC CE which triggers the UE to perform an LTM SCS operation before a radio link failure event is determined by the UE or before the UE starts to count T311 timer to zero. Then, in these conditions, the UE may be enabled / configured / allowed to evaluate / initiate an L1(measurement / report / triggering) event for LTM SCS operation when the timer T311 is counting / running. In addition, the UE may ignore / overwrite / skip the LTM candidate indicated by the LTM SCS MAC CE (e.g., which is received by the UE when the timer T311 is counting). In addition, the UE may re-select another new LTM candidate (e.g., based on the given L1 (measurement / report / triggering) event), and initiate the LTM SCS operation associated with the new LTM candidate.

[0164] In some implementations, the UE may select the LTM candidate for the LTM operation (e.g., when the timer T311 is still counting / running) based on the cell reselection criteria rather than the L1 conditional event. For example, the UE may select a suitable cell (e.g., based on the S-criteria) and a best ranking cell (e.g., based on the R-criteria).

[0165] In some implementations, the UE may select the LTM candidate for the LTM operation (e.g., when the timer T311 is still counting / running) based on evaluation results of the L1 conditional event rather than the cell reselection criteria.

[0166] In some implementations, the UE may select the LTM candidate for the LTM operation (e.g., when the timer T311 is still counting / running) by jointly considering the evaluation results of the L1 conditional event and the cell reselection criteria.

[0167] In some additional implementations, the UE may be configured / instructed by the serving RAN to perform the L1 event evaluation / LTM candidate selection on one or more frequency carriers (e.g., for the RRC re-establishment procedure when the timer T311 is counting or for (conditional) LTM operation). In some implementations, a frequency list and associated priority sequence (e.g., based on descending / ascending sequence on the associated frequency list) may also be configured to the UE (e.g., via broadcasting system information or UE-specific RRC signaling).

[0168] In some implementations, the MAC entity in a UE side may be configured by the RRC entity of the UE side with one or more L1 events associated with different actions (e.g., action A, B, C, D, or E).

[0169] In some implementations, each MAC entity (e.g., the MAC entity associated with master cell group / master node, and / or the MAC entity associated with secondary cell group / secondary node) may be enabled / allowed to be independently configured with one or more L1 (measurement / report / triggering) events. In some implementations, only the MAC entity of the MCG may be configured with L1 (measurement / report / triggering) events.

[0170] In some implementations, the L1 (measurement / report / triggering) events associated with the MCG may be configured by the serving RAN via SRB1 / SRB3. The L1 (measurement / report / triggering) events associated with the SCG may be configured by the serving RAN via SRB1 / SRB3.

[0171] In some implementations, the MAC entity associated with MCG / SCG may evaluate and trigger the action A, B, or C independently (e.g., based on the Time-To-Trigger Timer counting activity). Therefore, it may be possible that the action A, B, or C associated with the MCG / SCG may be triggered / implemented jointly (e.g., with independent configurations) in time domain.

[0172] In some implementations, the L1 (measurement / report / triggering) events may be allowed to be configured only with MCG / SCG.

[0173] In some implementations, only a cell group may perform action A, B, or C based on the given L1 (measurement / report / triggering) event in time domain. Therefore, while a MAC entity (e.g., the MAC entity associated with the MCG or SCG) starts performing the action A, B, or C based on L1 (measurement / report / triggering) event, the UE may stop / suspend / release the evaluation / TTT timer counting activity of another MAC entity.

[0174] In some implementations, the MAC entities (e.g., the MAC entity associated with the MCG / SCG) may report the L1 event (enter / leave) indication / L1 measurement result to the RRC entity of the UE.

[0175] In some implementations, the UE may be configured with a TimeToTrigger-L1 timer associated with one or more L1 (measurement / report / triggering) events. In addition, the UE may also be configured with a TimeToTrigger timer associated with one or more L3 cell / beam level-measurement reports.

[0176] In this condition, the UE may be triggered to perform the action A, B, or C while / upon / after a running TimeToTrigger-L1 timer expires. In addition, the UE may stop the running TimeToTrigger timer of one or more or all L3 reporting procedures, if any.

[0177] In some implementations, the serving RAN may configure different combinations of L1 (measurement / report / triggering) events to a single LTM candidate. For example, the serving RAN may configure a set of L1 events { Event A2-b (1stL1 event), Event A4-b (2ndL1 event) }, where the 1stL1 event may be associated with the action A (e.g., the early synchronization procedure) and the 2ndL1 event may be associated with the action B (e.g., the LCM SCS operation). In some implementations, the 1stL1 event / 2ndL1 event may be associated with multiple LTM candidates or all of the configure LTM candidates. In some implementations, the 1stL1 event / 2ndL1 event may be associated with a given LTM candidate.

[0178] In some implementations, a specific action (e.g., action A, B, C, D, or E) may be pre-configured to be associated with one or more LTM candidates. In addition, each LTM candidate may be further associated with one or more L1 events for the UE to trigger the given action.

[0179] In some implementations, the EarlySyncUp_conditional IE may be configured to the UE, and the EarlySyncUp_conditional IE may include one or more LTM candidates (e.g., by giving the Physical Cell Identity of the LTM candidate) and one or more L1 events (e.g., by configuring the thresholds of trigger conditions and / or leave conditions, and / or the TimeToTrigger value) for the UE to initiate an early synchronization procedure during the LTM (SCS) preparation.

[0180] In some implementations, another IE (e.g., the LTM_CSC_Switch_Conditional IE) may be configured to the UE, the LTM_CSC_Switch_Conditional IE may include one or more LTM candidates (e.g., by giving the Physical Cell Identity of the LTM candidate) and one or more L1 events (e.g., by configuring the thresholds of trigger conditions and / or leave conditions, and / or the TimeToTrigger value) for the UE to initiate an LTM SCS procedure.

[0181] In some implementations, when a UE starts / initiates an Early Synchronization procedure associated with an LTM candidate (e.g., the LTM Candidate#1), the UE may stop the Early synchronization evaluation procedure of other LTM candidates, if any. Instead, the UE may only monitor / evaluate whether the conditional L1 events of LTM candidate#1 for LTM SCS operation (e.g., the action B) or other actions (e.g., action C, D, and / or E) is fulfilled or not. In some implementations, the UE may start to evaluate the L1 events of Early Synchronization (e.g., the action A) associated with other LTM candidates only upon / after the LTM SCS operation associated with the LTM candidate#1 is terminated successfully, or the LTM SCS operation associated with the LTM candidate#1 is considered fails, or the leave condition of the L1 event which the UE applied / used to trigger the early synchronization (e.g., the Action A) with the LTM candidate#1 is fulfilled.

[0182] In some implementations, the serving RAN may configure an L1 (measurement / report / triggering) event with different threshold values for different actions. In some implementations, the UE may be configured with an L1 Event A3-b and a set of thresholds {Threshold#1 (for action A), Threshold#2(for action B)}. Therefore, the UE may evaluate the L1 event for the actions A and B based on different threshold values. The value of the Threshold#1 may be smaller than or equivalent to the value of the Threshold#2.

[0183] In some implementations, the serving RAN may configure an L1 (measurement / report / triggering) event with a single threshold. In this condition, the UE may perform the action A and action B jointly with an LTM candidate if the L1 event (e.g., associated with one LTM candidate) is fulfilled and the TTT timer expires by referring to the given threshold.

[0184] In some implementations, the serving RAN may configure an L1 (measurement / report / triggering) event with a single threshold and with different TTT values for different actions (e.g., TTT value T1 for action A and TTT value T2 for action B). In this condition, the UE may perform action A when the L1 event is fulfilled for T1 and may perform action B when the L1 event is fulfilled for T2.

[0185] In some implementations, to an LTM candidate, the serving RAN may only be able to configure an L1 event or a set of L1 events (e.g., {Event A2-b, Event A4-b}) to a single LTM candidate. In some implementations, an L1 event may be associated with one or more LTM candidates. To the serving RAN, an L1 event may be associated with a subset of or all of the configured LTM candidates, and the association with an L1 (measurement / report / triggering) event ID and LTM candidate ID / index may be configured by the serving RAN.

[0186] In some implementations, a leave / cancel / stop condition may be configured with an L1 (measurement / report / triggering) event, which triggers the UE to stop an ongoing action A, B, or C after the ongoing action A, B, or C is triggered / activated by the same L1 event.

[0187] In some implementations, an L1 leave / cancel / stop event may be configured to be associated with an L1 (measurement / report / triggering) event, which triggers the UE to stop an ongoing action A, B, or C after the ongoing action A, B, or C is triggered / activated by the same L1 event.

[0188] The format / definition of an L1 (leave / cancel / stop) event may be referred to the existing L1 (measurement / report / triggering) event. In some implementations, a specific L1 (measurement / report / triggering) event may be defined / configured as a leave / cancel / stop event when a specific action is triggered / implemented by the UE. When the leave / cancel / stop event is fulfilled, the UE may cancel / release / stop the ongoing action, and the LTM candidate may not be considered being selected.

[0189] In some implementations, a radio link failure event or a beam failure event associated with the LTM candidate may be defined as a leave / cancel / stop condition.

[0190] In some implementations, the leave / cancel / stop event may include the L3 cell-level / beam-level (report / triggering) event.

[0191] FIG. 4 is a diagram illustrating the triggering condition of an entering / leaving condition and the associated TimeToTrigger counting activity of a fulfilled entering condition in the UE side, according to an example implementation of the present disclosure. As illustrated in FIG. 4, an L1 (measurement / report / triggering) event (e.g., Event A4-b) may be configured with a threshold (e.g., Event A4-b Threshold). The threshold may be presented by DL-RSRP / DL-RSRQ / DL-SINR value.

[0192] As illustrated in FIG. 4, at time point 41, a UE may start to perform a TTT counting activity (e.g., set an initial value of a TTT timer and count the TTT timer to zero) upon / after an L1 event, which is configured to be associated with an action (e.g., the Action B with an LTM candidate), is considered fulfilled by the UE (e.g., at the triggering condition 401, the DL-RSRP measurement result is higher than a trigger threshold 413). Then, the TTT timer associated with the (L1) A4-b event (and the LTM candidate) may be started to count to zero at time point 41. Then, the entering condition of the A4-b event may be considered fulfilled / triggered if the DL-RSRP value keeps higher than the trigger threshold up to the TTT timer expires at time point 43 (otherwise, the UE may stop the TTT timer if the DL-RSRP becomes lower than the triggering threshold during the TTT counting activity). Finally, the UE may start performing the Action B upon, while, or after time point 43. In some implementations, the UE may suspend from implementing action B until the TTT timer expiry at time point 43.

[0193] In some implementations, after the time point 43, the UE may keep monitoring the beam-level measurement result after the action B is implemented. Then, the UE may start to perform another TTT counting activity (e.g., set an initial value of the TTT timer and count the TTT timer to zero) upon / after a leaving condition of the A4-b event is considered fulfilled by the UE (e.g., at the leaving condition 403, the DL-RSRP measurement result is lower than a leaving threshold 415). Then, another TTT timer associated with the L1 A4-b event (and the LTM candidate) may be started at time point 45, and then may be counted to zero at time point 47. Otherwise, the UE may stop another TTT timer if the DL-RSRP becomes higher than the triggering threshold during another TTT counting activity. In some implementations, the UE may initiate another action, which is associated with the leaving condition after the leaving condition is fulfilled / triggered at the time point 47. In some implementations, the UE may stop the ongoing action, which is triggered at the time point 43, after the leaving condition is fulfilled / triggered at the time point 47.

[0194] The Event A4-b threshold value 411 may be decide based on the criteria configured by the L1 event A4-b and the triggering threshold value 413 (e.g., corresponding to the DL-RSRP value of the triggering condition) may be decided by an additional hysteresis value (e.g., the Hysteresis value as shown in FIG. 4), which may also be configured as part of the L1 event A4-b configuration, to prevent an unstable triggering condition decided by the UE. The leave threshold value (e.g., corresponding to the DL-RSRP value of the leaving condition) may be configured for the UE to consider the fulfilled L1 A4-b event is not fulfilled anymore once the monitoring DL-RSRP value becomes lower than the leave threshold value, which is also decide by jointly considering the Event A4-b threshold value and the additional hysteresis value to prevent a leaving condition decided by the UE.

[0195] The UE may measure a DL-RSRP / DL-RSRQ / DL-SINR of one or more LTM candidates. Then, the UE may determine the Event A4-b is triggered / fulfilled upon / after the UE detects one or more LTM candidates whose DL- / DL-RSRQ / DL-SINR values are larger / greater than the Event A4-b Threshold.

[0196] In some implementations, a UE may determine a Trigger threshold (e.g., by adding the Event A4-b threshold with an additional hysteresis threshold) and / or a Leave threshold (e.g., by decreasing the Event A4-b threshold with an additional hysteresis value / threshold) if a hysteresis threshold is configured to be associated with the L1 event (e.g., Event A4-b). The value of hysteresis value may be zero, and it may mean that the value of trigger threshold / leave threshold is the same as the L1 event threshold (e.g., the Event A4-b threshold).

[0197] The UE may trigger a TimeToTrigger (TTT) Timer upon / after the DL-RSRP / DL-RSRQ / DL-SINR values of the same LTM candidate (e.g., the LTM candidate which fulfills the Event A4-b Threshold requirement) is higher than the Trigger threshold. The UE may keep counting the TTT timer to zero if the DL-RSRP / DL-RSRQ / DL-SINR measurement results of the same LTM candidate are still higher than the Trigger threshold. Otherwise, the UE may stop the TTT timer once the DL-RSRP / DL-RSRQ / DL-SINR measurement results of the same LTM candidate become lower than the Trigger threshold. In some implementations, the UE may re-start TTT timer upon / after the UE finds out the DL-RSRP / DL-RSRQ / DL-SINR measurement results of the same LTM candidate become higher than the Trigger threshold again. The UE may repeat the TTT timer stop / reset implementations before the TTT timer is counted to zero successfully or upon the leave condition of the same LTM candidate / L1 event is fulfilled.

[0198] In some implementations, the initial value of TimeToTrigger timer / L1 event threshold / hysteresis value / trigger threshold / leave threshold may be pre-configured to the UE (e.g., with associated L1 event / LTM candidate) as part of the LTM configuration / reference configuration.

[0199] In some implementations, different initial values of TimeToTrigger timer / L1 event threshold / hysteresis value / trigger threshold / leave threshold may be associated with different target LTM candidates. In some implementations, different initial values of TimeToTrigger timer / L1 event threshold / hysteresis value / trigger threshold / leave threshold may be associated with different actions (e.g., action A, B, and C). In some implementations, different initial values of TimeToTrigger timer / L1 event threshold / hysteresis value / trigger threshold / leave threshold may be associated with different L1 events.

[0200] In some implementations, the UE may start / initiate the action A, B, or C upon / after the TTT timer is counted to zero.

[0201] In some implementations, a leave condition may also be defined for the L1 event, and the LTM candidate which triggers the L1 event. As illustrated in FIG. 4, the leave threshold may be determined based on the L1 event threshold (e.g., Event A4-b threshold) with a hysteresis value. Then, in Event A4-b, the UE may stop the triggered action (e.g., action A, B, or C) upon / after the DL-RSRP / DL-RSRQ / DL-SINR measurement results of the same LTM candidate become lower than the leave threshold.

[0202] FIG. 5A is a diagram illustrating an RRC connection re-establishment procedure, according to an example implementation of the present disclosure. In FIG. 5A, the UE 50 may transmit an RRC reestablishment request (e.g., the RRCReestablishmentRequest, as shown in step 501) to the network 52, and the network 52 (e.g., the serving RAN) may reply an RRCReestablishment message (as shown in step 503) to instruct the UE 50 to re-configure the current RRC connection based on the RRCReestablishment message. Finally, the UE 50 may transmit an RRCReestablishmentComplete (as shown in step 505) message after the UE 50 has re-configured the current RRC connection based on the RRCReestablishment message successfully.

[0203] FIG. 5B is a diagram illustrating an RRC re-establishment procedure with fallback to an RRC establishment and successful connection, according to an example implementation of the present disclosure. In FIG. 5B, the UE 50 may transmit an RRC reestablishment request (e.g., the RRCReestablishmentRequest, as shown in step 511) to the network 52, and the network 52 (e.g., the serving RAN) may reply an RRCSetup message (as shown in step 513) to instruct the UE 50 to re-set the current RRC connection (e.g., release the stored configuration of current RRC connection and reset the security key(s) with the serving network). Finally, the UE 50 may transmit an RRCSetupComplete message (as shown in step 515) after the UE 50 has re-set the current RRC connection based on the RRCSetup message successfully.

[0204] In some implementations, a UE may trigger the RRC re-establishment procedure while at least one of the following conditions (a)-(e) is satisfied.

[0205] (a): When Radio Link Failure event happens in the UE.

[0206] (b): When Handover failure happens.

[0207] (c): When mobility from E-UTRA failure happened.

[0208] (d): When integrity check failure indication was received from lower layers.

[0209] (e): When RRC connection reconfiguration failure happens.

[0210] The details of the triggering events for the RRC re-establishment procedure may be referred to the 3GPP TS 38.331.

[0211] In addition, the UE may start to count the timer T311 to zero by setting an initial value to the T311. In some implementations, the UE may perform the cell (re)selection procedure to find out a suitable cell to transmit an RRCReestabishmentRequest message (e.g., via a 2-step / 4-step random access procedure). After receiving the RRCRestablishmentRequest message, the serving network may reply an RRCReestablishment message to the UE, as illustrated in FIG. 5A. The UE may modify / configure UE’s configuration based on the received RRCReestablishment message and the reply a RRCReestablishmentComplege message to the serving network to finish a successful RRC connection re-establishment procedure. In some implementations, the serving network may reply a RRCSetup message to the UE after receiving the RRCReestablishmentRequest message form the UE, as illustrated in FIG. 5B. The procedure in FIG. 5B is a fallback procedure when the serving RAN instructs / configures the UE to reset its UE configuration based on the received RRCSetup message. After receiving the RRCSetup message, the UE may reply an RRCSetupComplete message to the serving network to finish a successful fallback procedure.

[0212] The Start / stop / expiry (UE / RAN) implementations may be referred to the timer T310 and T311 as specified in the 3GPP TS 38.331.

[0213] FIG. 6 is a diagram illustrating an LTM serving cell switch (LTM SCS) Operation, according to an example implementation of the present disclosure. The procedure for LTM may include the following actions 612-626-.

[0214] The UE 60 may send a MeasurementReport message (as shown in action 612) to the RAN 62. The RAN 62 may determine to configure the LTM and initiate the LTM preparation.

[0215] The RAN 62 may transmit an RRCReconfiguration message including the LTM candidate configurations to the UE 60 (as shown in action 614).

[0216] In the action 616, the UE 60 may store the LTM candidate configurations and transmit an RRCReconfigurationComplete message to the RAN 62.

[0217] In the action 618a, the UE 60 may perform DL synchronization with the LTM candidate cell(s) before receiving the cell switch command. The UE 60 may activate and deactivate TCI states of LTM candidate cell(s), as triggered by the RAN 62.

[0218] In the action 618b, the UE 60 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 to the candidate cell, as triggered by the RAN 62. When the UE-based TA measurement is configured, the UE may acquire the TA value(s) of the candidate cell(s) by measurement. The UE may perform the early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command as specified in the 3GPP TS 38.300. This may be done via the CFRA triggered by a PDCCH order from the source cell, following which the UE sends preamble to the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA to the candidate cell(s), the UE may not receive random access response from the network for the purpose of TA value acquisition, and the TA value of the candidate cell may be indicated in the cell switch command. The UE may not maintain the TA timer for the candidate cell, and rely on network implementation to guarantee the TA validity.

[0219] In the action 620, the UE 60 may perform L1 measurements on the configured LTM candidate cell(s) and transmit L1 measurement reports to the RAN 62. The L1 measurement may be performed as long as RRC reconfiguration (e.g., the action 614) is applicable.

[0220] In the action 622, the RAN 62 may determine to execute the cell switch to a target cell and transmit 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 may switch to the target cell and apply the candidate configuration indicated by the target configuration ID.

[0221] In the action 624, the UE 60 may perform the random access procedure to the target cell, if the UE 60 does not have valid TA of the target cell as specified in the 3GPP TS 38.321.

[0222] In the action 626, the UE 60 may complete the LTM cell switch procedure by sending RRCReconfigurationComplete message to the RAN 62 (e.g., the target cell). If the UE 60 has performed an RA procedure in the action 624, the UE 60 may determine that the LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE may determine that the LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0223] The actions 618-626 may be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in the action 614.

[0224] The procedure over the air interface described in FIG. 6 may be applicable to both intra-gNB-DU LTM and inter-gNB-DU LTM. The overall LTM procedures over F1-C interface may refer to the 3GPP TS 38.401.

[0225] The IE MeasConfig may specify measurements to be performed by the UE, and cover intra-frequency, inter-frequency and inter-RAT mobility as well as configuration of measurement gaps, as specified in the 3GPP TS 38.331.

[0226] In 3GPP specification, the serving RAN may associate a measurement object configuration and a report configuration by associating the measObjectId IE (e.g., the measurement object ID of the corresponding measurement object configuration) and the reoprtConfigId IE (e.g., the report configuration ID of the corresponding report configuration) when the measID IE is configured to the UE.

[0227] The MeasIdToAddModList IE may include a list of measurement identities to add or modify, with for each entry the measId, the associated measObjectId and the associated reportConfigId.

[0228] The MeasResults IE may cover measured results for intra-frequency, inter-frequency, inter-RAT mobility and measured results for NR sidelink communication / discovery.

[0229] FIG. 7 is a flowchart illustrating a method / process 700 performed by a UE for performing a layer 1 / layer 2 triggered mobility (LTM) operation, according to an example implementation of the present disclosure.

[0230] In the action 702, the process 700 may start by receiving, from a base station (BS), a configuration message indicating multiple LTM triggering events associated with multiple LTM candidate cells.

[0231] In the action 704, the process 700 may determine whether a radio link failure (RLF) has occurred.

[0232] In the action 706, the process 700 may select a cell.

[0233] In the action 708, the process 700 may perform, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred. The selected cell may be one of the multiple LTM candidate cells that is associated with at least one of the multiple LTM triggering events, and 　　　　the selected cell may be a suitable cell selected by the RRC entity of the UE. The process 700 may then end.

[0234] In some implementations, the selected cell may be selected and informed by a medium access control (MAC) entity of the UE when the at least one of the multiple LTM triggering events associated with the selected cell is fulfilled.

[0235] In some implementations, the process 700 may perform the LTM operation without considering the multiple LTM triggering events after determining that the RLF has occurred and an attempt LTM switch indicator indicating the UE to perform the LTM operation is included in the configuration message, where the attempt LTM switch indicator may be applied to the selected cell that is associated with the at least one of the multiple LTM triggering events.

[0236] In some implementations, the process 700 may start a Time-To-Trigger (TTT) timer associated with the at least one of the multiple LTM triggering events after determining that the at least one of the multiple LTM triggering events is fulfilled, and perform the LTM operation with the selected cell upon the TTT timer expires, where the at least one of the multiple LTM triggering events may remain fulfilled while the TTT timer expires, and the TTT timer may be maintained by a medium access control (MAC) entity of the UE.

[0237] In some implementations, the multiple LTM triggering events may include one or more Layer-3 cell-level triggering events, one or more Layer-3 beam-level triggering events, and one or more Layer-1 beam-level triggering events. The one or more Layer-1 beam-level triggering events may include at least one of the following events: 　　　　a first signal quality of a beam associated with a serving cell becomes better than a first absolute threshold, 　　　　the first signal quality of the beam associated with the serving cell becomes worse than a second absolute threshold, 　　　　a second signal quality of a beam associated with an LTM candidate cell becomes better than a third signal quality of a beam associated with a primary cell (PCell), a primary secondary cell (PSCell), or the serving cell by a first offset, 　　　　the second signal quality of the beam associated with the LTM candidate cell becomes better than a third absolute threshold, 　　　　the first signal quality of the beam associated with the serving cell becomes worse than a fourth absolute threshold and the second signal quality of the beam associated with the LTM candidate cell becomes better than a fifth absolute threshold, and a fourth signal quality of beam associated with a neighbour cell becomes better than a fifth signal quality of a beam associated with a secondary cell (SCell).

[0238] In some implementations, the LTM operation may include at least one of initiating an early synchronization with the selected cell, performing an LTM cell switch procedure with the selected cell, and transmitting, to a serving radio access network, a measurement report associated with the selected cell.

[0239] In some implementations, the process 700 may receive, from the BS, a control message indicating that the at least one of the multiple LTM triggering events is activated or de-activated, determine to activate an evaluation of the at least one of the multiple LTM triggering events after determining that the control message indicates that the at least one of the multiple LTM triggering events is activated, and determine to de-activate the evaluation of the at least one of the multiple LTM triggering events after determining that the control message indicates that the at least one of the multiple LTM triggering events is de-activated.

[0240] The steps / actions shown in FIG. 7 should not be construed as necessarily order dependent. The order in which the process is described is not intended to be construed as a limitation. Moreover, some of the actions shown in FIG. 7 may be omitted in some implementations and one or more actions shown in FIG. 7 may be combined.

[0241] The technical problem addressed by the method illustrated in FIG. 7 is how to efficiently manage the mobility of a user equipment (UE) in a 5G network when a radio link failure (RLF) occurs, particularly by enabling the UE to dynamically select and switch to an appropriate candidate cell based on pre-configured layer 1 / layer 2 triggered mobility (LTM) events, while addressing the challenges of timely cell selection and seamless operation under failure conditions. The advantageous technical effect achieved by the method illustrated in FIG. 7 is the enhanced reliability and responsiveness of the UE in handling LTM operations post-RLF, as it leverages the RRC entity to perform a cell switch to a suitable LTM candidate cell associated with specific triggering events, thereby reducing service interruption and improving network connectivity in dynamic radio environments.

[0242] FIG. 8 is a flowchart illustrating a method / process 800 performed by a BS for performing a layer 1 / layer 2 triggered mobility (LTM) operation, according to an example implementation of the present disclosure.

[0243] In the action 802, the process 800 may start by transmitting, to a user equipment (UE), a configuration message indicating multiple LTM triggering events associated with multiple LTM candidate cells.

[0244] In the action 804, the configuration message causes the UE to determine whether a radio link failure (RLF) has occurred, select a cell, and 　　　　perform, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred. The selected cell may be one of the multiple LTM candidate cells that is associated with at least one of the multiple LTM triggering events, and the selected cell may be a suitable cell selected by the RRC entity of the UE. The process 800 may then end.

[0245] In some implementations, the selected cell may be selected and informed by a medium access control (MAC) entity of the UE when the at least one of the multiple LTM triggering events associated with the selected cell is fulfilled.

[0246] In some implementations, the configuration message may further cause the UE to perform the LTM operation without considering the multiple LTM triggering events after determining that the RLF has occurred and an attempt LTM switch indicator indicating the UE to perform the LTM operation is included in the configuration message, where the attempt LTM switch indicator may be applied to the selected cell.

[0247] In some implementations, the configuration message may further cause the UE to start a Time-To-Trigger (TTT) timer associated with the at least one of the multiple LTM triggering events after determining that the at least one of the multiple LTM triggering events is fulfilled, and perform the LTM operation with the selected cell upon the TTT timer expires, where 　　　　the at least one of the multiple LTM triggering events may remain fulfilled while the TTT timer expires, and the TTT timer may be maintained by a medium access control (MAC) entity of the UE.

[0248] In some implementations, the multiple LTM triggering events may include one or more Layer-3 cell-level triggering events, one or more Layer-3 beam-level triggering events, and one or more Layer-1 beam-level triggering events. The one or more Layer-1 beam-level triggering events may include at least one of the following events: 　　　　a first signal quality of a beam associated with a serving cell becomes better than a first absolute threshold, 　　　　the first signal quality of the beam associated with the serving cell becomes worse than a second absolute threshold, 　　　　a second signal quality of a beam associated with an LTM candidate cell becomes better than a third signal quality of a beam associated with a primary cell (PCell), a primary secondary cell (PSCell), or the serving cell by a first offset, 　　　　the second signal quality of the beam associated with the LTM candidate cell becomes better than a third absolute threshold, 　　　　the first signal quality of the beam associated with the serving cell becomes worse than a fourth absolute threshold and the second signal quality of the beam associated with the LTM candidate cell becomes better than a fifth absolute threshold, and a fourth signal quality of beam associated with a neighbour cell becomes better than a fifth signal quality of a beam associated with a secondary cell (SCell).

[0249] In some implementations, the LTM operation may include at least one of initiating an early synchronization with the selected cell, performing an LTM cell switch procedure with the selected cell, and transmitting, to a serving radio access network, a measurement report associated with the selected cell.

[0250] In some implementations, the configuration message may further cause the UE to receive, from the BS, a control message indicating that the at least one of the multiple LTM triggering events is activated or de-activated, determine to activate an evaluation of the at least one of the multiple LTM triggering events after determining that the control message indicates that the at least one of the multiple LTM triggering events is activated, and determine to de-activate the evaluation of the at least one of the multiple LTM triggering events after determining that the control message indicates that the at least one of the multiple LTM triggering events is de-activated.

[0251] The steps / actions shown in FIG. 8 should not be construed as necessarily order dependent. The order in which the process is described is not intended to be construed as a limitation. Moreover, some of the actions shown in FIG. 8 may be omitted in some implementations and one or more actions shown in FIG. 8 may be combined.

[0252] The method illustrated in FIG. 8 is similar to that in FIG. 7, except that it is described from the perspective of the BS (instead of the UE).

[0253] FIG. 9 is a block diagram illustrating a node 900 for wireless communication in accordance with various aspects of the present disclosure. As illustrated in FIG. 9, a node 900 may include a transceiver 920, a processor 928, a memory 934, one or more presentation components 938, and at least one antenna 936. The node 900 may also include a radio frequency (RF) spectrum band module, a BS communications module, a network communications module, and a system communications management module, Input / Output (I / O) ports, I / O components, and a power supply (not illustrated in FIG. 9).

[0254] Each of the components may directly or indirectly communicate with each other over one or more buses 940. The node 900 may be a UE or a BS that performs various functions disclosed with reference to FIGS. 1 through 8.

[0255] The transceiver 920 has a transmitter 922 (e.g., transmitting / transmission circuitry) and a receiver 924 (e.g., receiving / reception circuitry) and may be configured to transmit and / or receive time and / or frequency resource partitioning information. The transceiver 920 may be configured to transmit in different types of subframes and slots including, but not limited to, usable, non-usable, and flexibly usable subframes and slot formats. The transceiver 920 may be configured to receive data and control channels.

[0256] The node 900 may include a variety of computer-readable media. Computer-readable media may be any available media that may be accessed by the node 900 and include volatile (and / or non-volatile) media and removable (and / or non-removable) media.

[0257] The computer-readable media may include computer-storage media and communication media. Computer-storage media may include both volatile (and / or non-volatile media), and removable (and / or non-removable) media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, Artificial Intelligence (AI) / Machine Learning (ML) module(s), or data.

[0258] Computer storage media may include RAM, DRAM, HBM, MRAM, FRAM, RRAM ROM, EEPROM, flash memory (or other memory technology), CD-ROM, Digital Versatile Disks (DVD) (or other optical disk storage), magnetic cassettes, magnetic tape, magnetic disk storage (or other magnetic storage devices), etc. Computer storage media may not include a propagated data signal. Communication media may typically embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transport mechanism and include any information delivery media.

[0259] The term “modulated data signal” may mean a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. Communication media may include wired media, such as a wired network or direct-wired connection, and wireless media, such as acoustic, RF, infrared, and other wireless media. Combinations of any of the above listed components should also be included within the scope of computer-readable media.

[0260] The memory 934 may include computer-storage media in the form of volatile and / or non-volatile memory. The memory 934 may be removable, non-removable, or a combination thereof. Example memory may include solid-state memory, hard drives, optical-disc drives, etc. As illustrated in FIG. 9, the memory 934 may store a computer-readable and / or computer-executable instructions 932 (e.g., software codes and / or a set of instructions and / or AI / ML module(s)) that are configured to, when executed, cause the processor 928 to perform various functions disclosed herein, for example, with reference to FIGS. 1 through 8. Alternatively, the instructions 932 may not be directly executable by the processor 928 but may be configured to cause the node 900 (e.g., when compiled and executed) to perform various functions disclosed herein. The AI / ML module(s) may be implemented with a supervised learning approach or an unsupervised learning approach (e.g., Transductive approach and Inductive approach).

[0261] The processor 928 (e.g., having processing circuitry) may include an intelligent hardware device, e.g., a Central Processing Unit (CPU), a TPU, a GPU, a GPGPU, a microcontroller, an ASIC, etc. The processor 928 may include memory. The processor 928 may process the data 930 and the instructions 932 received from the memory 934, and information transmitted and received via the transceiver 920, the baseband communications module, and / or the network communications module. The processor 928 may also process information to send to the transceiver 920 for transmission via the antenna 936 to the network communications module for transmission to a CN.

[0262] One or more presentation components 938 may present data indications to a person or another device. Examples of presentation components 938 may include a display device, a speaker, a printing component, a vibrating component, etc.

[0263] In view of the present disclosure, it is obvious that various techniques may be used for implementing the disclosed concepts without departing from the scope of those concepts. Moreover, while the concepts have been disclosed with specific reference to certain implementations, a person of ordinary skill in the art may recognize that changes may be made in form and detail without departing from the scope of those concepts. As such, the disclosed implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the present disclosure is not limited to the particular implementations disclosed and many rearrangements, modifications, and substitutions are possible without departing from the scope of the present disclosure.

Claims

1. A user equipment (UE) for performing a layer 1 / layer 2 triggered mobility (LTM) operation, the UE comprising: 　　　　at least one processor; and 　　　　at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the UE to: 　　　　　　　　receive, from a base station (BS), a configuration message indicating a plurality of LTM triggering events associated with a plurality of LTM candidate cells; 　　　　　　　　determine whether a radio link failure (RLF) has occurred; 　　　　　　　　select a cell; and 　　　　　　　　perform, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred, wherein: 　　　　　　　　　　　　the selected cell is one of the plurality of LTM candidate cells that is associated with at least one of the plurality of LTM triggering events, and 　　　　　　　　　　　　the selected cell is a suitable cell selected by the RRC entity of the UE after determining that the RLF has occurred.

2. The UE of claim 1, wherein the selected cell is selected and informed by a medium access control (MAC) entity of the UE when the at least one of the plurality of LTM triggering events associated with the selected cell is fulfilled.

3. The UE of claim 1, wherein: 　　　　the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to: 　　　　　　　　perform the LTM operation without considering the plurality of LTM triggering events after determining that the RLF has occurred and an attempt LTM switch indicator indicating the UE to perform the LTM operation is included in the configuration message, wherein the attempt LTM switch indicator is applied to the selected cell.

4. The UE of claim 1, wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to: 　　　　start a Time-To-Trigger (TTT) timer associated with the at least one of the plurality of LTM triggering events after determining that the at least one of the plurality of LTM triggering events is fulfilled; and 　　　　perform the LTM operation with the selected cell upon the TTT timer expires, wherein: 　　　　　　　　the at least one of the plurality of LTM triggering events remains fulfilled while the TTT timer expires, and 　　　　　　　　the TTT timer is maintained by a medium access control (MAC) entity of the UE.

5. The UE of claim 1, wherein: 　　　　the plurality of LTM triggering events includes one or more Layer-3 cell-level triggering events, one or more Layer-3 beam-level triggering events, and one or more Layer-1 beam-level triggering events, and 　　　　the one or more Layer-1 beam-level triggering events include at least one of the following events: 　　　　　　　　a first signal quality of a beam associated with a serving cell becomes better than a first absolute threshold, 　　　　　　　　the first signal quality of the beam associated with the serving cell becomes worse than a second absolute threshold, 　　　　　　　　a second signal quality of a beam associated with an LTM candidate cell becomes better than a third signal quality of a beam associated with a primary cell (PCell), a primary secondary cell (PSCell), or the serving cell by a first offset, 　　　　　　　　the second signal quality of the beam associated with the LTM candidate cell becomes better than a third absolute threshold, 　　　　　　　　the first signal quality of the beam associated with the serving cell becomes worse than a fourth absolute threshold and the second signal quality of the beam associated with the LTM candidate cell becomes better than a fifth absolute threshold, and 　　　　　　　　a fourth signal quality of beam associated with a neighbour cell becomes better than a fifth signal quality of a beam associated with a secondary cell (SCell).

6. The UE of claim 1, wherein the LTM operation includes at least one of: 　　　　initiating an early synchronization with the selected cell, 　　　　performing an LTM cell switch procedure with the selected cell, and 　　　　transmitting, to a serving radio access network, a measurement report associated with the selected cell.

7. The UE of claim 1, wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to: 　　　　receive, from the BS, a control message indicating that the at least one of the plurality of LTM triggering events is activated or de-activated; 　　　　determine to activate an evaluation of the at least one of the plurality of LTM triggering events after determining that the control message indicates that the at least one of the plurality of LTM triggering events is activated; and 　　　　determine to de-activate the evaluation of the at least one of the plurality of LTM triggering events after determining that the control message indicates that the at least one of the plurality of LTM triggering events is de-activated.

8. A method performed by a user equipment (UE) for performing a layer-1 / layer-2 triggered mobility (LTM) operation, the method comprising: 　　　　receiving, from a base station (BS), a configuration message indicating a plurality of LTM triggering events associated with a plurality of LTM candidate cells; 　　　　determining whether a radio link failure (RLF) has occurred; 　　　　selecting a cell; and 　　　　performing, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred, wherein: 　　　　　　　　the selected cell is one of the plurality of LTM candidate cells that is associated with at least one of the plurality of LTM triggering events, and 　　　　　　　　the selected cell is a suitable cell selected by the RRC entity of the UE.

9. A base station (BS) for performing a layer 1 / layer 2 triggered mobility (LTM) operation, the BS comprising: 　　　　at least one processor; and 　　　　at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the BS to: 　　　　　　　　transmit, to a user equipment (UE), a configuration message indicating a plurality of LTM triggering events associated with a plurality of LTM candidate cells, wherein the configuration message causes the UE to: 　　　　　　　　　　　　determine whether a radio link failure (RLF) has occurred; 　　　　　　　　　　　　select a cell; and 　　　　　　　　　　　　perform, by a radio resource control (RRC) entity of the UE, an LTM operation associated with the selected cell after determining that the RLF has occurred, wherein: 　　　　　　　　the selected cell is one of the plurality of LTM candidate cells that is associated with at least one of the plurality of LTM triggering events, and 　　　　　　　　the selected cell is a suitable cell selected by the RRC entity of the UE.

10. The BS of claim 9, wherein 　　　　the selected cell is selected and informed by a medium access control (MAC) entity of the UE when the at least one of the plurality of LTM triggering events associated with the selected cell is fulfilled.

11. The BS of claim 9, wherein the configuration message further causes the UE to: 　　　　perform the LTM operation without considering the plurality of LTM triggering events after determining that the RLF has occurred and an attempt LTM switch indicator indicating the UE to perform the LTM operation is included in the configuration message, wherein 　　　　　　　　the attempt LTM switch indicator is applied to the selected cell.

12. The BS of claim 9, wherein the configuration message further causes the UE to: 　　　　start a Time-To-Trigger (TTT) timer associated with the at least one of the plurality of LTM triggering events after determining that the at least one of the plurality of LTM triggering events is fulfilled; and 　　　　perform the LTM operation with the selected cell upon the TTT timer expires, wherein: 　　　　　　　　the at least one of the plurality of LTM triggering events remains fulfilled while the TTT timer expires, and 　　　　　　　　the TTT timer is maintained by a medium access control (MAC) entity of the UE.

13. The BS of claim 9, wherein: 　　　　the plurality of LTM triggering events includes one or more Layer-3 cell-level triggering events, one or more Layer-3 beam-level triggering events, and one or more Layer-1 beam-level triggering events, and 　　　　the one or more Layer-1 beam-level triggering events include at least one of the following events: 　　　　　　　　a first signal quality of a beam associated with a serving cell becomes better than a first absolute threshold, 　　　　　　　　the first signal quality of the beam associated with the serving cell becomes worse than a second absolute threshold, 　　　　　　　　a second signal quality of a beam associated with an LTM candidate cell becomes better than a third signal quality of a beam associated with a primary cell (PCell), a primary secondary cell (PSCell), or the serving cell by a first offset, 　　　　　　　　the second signal quality of the beam associated with the LTM candidate cell becomes better than a third absolute threshold, 　　　　　　　　the first signal quality of the beam associated with the serving cell becomes worse than a fourth absolute threshold and the second signal quality of the beam associated with the LTM candidate cell becomes better than a fifth absolute threshold, and 　　　　　　　　a fourth signal quality of beam associated with a neighbour cell becomes better than a fifth signal quality of a beam associated with a secondary cell (SCell).

14. The BS of claim 9, wherein the LTM operation includes at least one of: 　　　　initiating an early synchronization with the selected cell, 　　　　performing an LTM cell switch procedure with the selected cell, and 　　　　transmitting, to a serving radio access network, a measurement report associated with the selected cell.

15. The BS of claim 9, wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the BS to: 　　　　transmit, to the UE, a control message that indicating that the at least one of the plurality of LTM triggering events is activated or de-activated, wherein the control message causes the UE to: 　　　　　　　　determine to activate an evaluation of the at least one of the plurality of LTM triggering events after determining that the control message indicates that the at least one of the plurality of LTM triggering events is activated; and 　　　　 　　　　determine to de-activate the evaluation of the at least one of the plurality of LTM triggering events after determining that the control message indicates that the at least one of the plurality of LTM triggering events is de-activated.

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