Method and apparatus for layer1 / layer2 triggered mobility (LTM) operation

Abstract

A method performed by a User Equipment (UE) for performing a Conditional Layer1 / Layer2 Triggered Mobility (CLTM) operation is provided. The method receives, from a serving cell, a CLTM configuration indicating a CLTM candidate cell. The method determines whether at least one condition is satisfied. The method starts a first timer in response to determining that the at least one condition is satisfied. The method triggers a CLTM switch to the CLTM candidate cell after the first timer expires.　

Description

METHOD AND APPARATUS FOR LAYER1 / LAYER2 TRIGGERED MOBILITY (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 Conditional Layer 1 / Layer 2 Triggered Mobility (CLTM) 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 LTM operations.

[0003] The present disclosure is related to a UE, a BS, and a method for performing a CLTM operation in the wireless communication networks.

[0004] In a first aspect of the present disclosure, a UE for performing a CLTM operation 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 serving cell, a CLTM configuration indicating a CLTM candidate cell; determine whether at least one condition is satisfied; start a first timer in response to determining that the at least one condition is satisfied; and trigger a CLTM switch to the CLTM candidate cell after the first timer expires.

[0005] In some implementations of the first aspect, the at least one condition includes one or more Layer-1 (L1) conditions. Determining whether the at least one condition is satisfied includes at least one of the following: determining, by a Medium Access Control (MAC) layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L1 beam-level condition based on a first L1 beam-level measurement result of the candidate beam; determining, by the MAC layer of the UE, whether a current beam associated with the serving cell satisfies a second L1 beam-level condition based on a second L1 beam-level measurement result of the current beam; determining, by the MAC layer of the UE, whether the candidate cell satisfies a first L1 cell-level condition based on a first L1 cell-level measurement result of the candidate cell; and determining, by the MAC layer of the UE, whether the serving cell satisfies a second L1 cell-level condition based on a second L1 cell-level measurement result of the serving cell.

[0006] In some implementations of the first aspect, the first timer is started by the MAC layer of the UE. The CLTM switch is triggered by the MAC layer of the UE after the first timer expires. The one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to send, by the MAC layer of the UE, an indication to a Radio Resource Control (RRC) layer of the UE in response to triggering the CLTM switch, where the indication includes a CLTM configuration ID associated with the satisfied at least one condition.

[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: stop, by the MAC layer of the UE, the first timer in response to determining that the at least one condition becomes unsatisfied or in response to performing a MAC reset.

[0008] In some implementations of the first aspect, the at least one condition includes one or more Layer-3 (L3) conditions. Determining whether the at least one condition is satisfied includes at least one of the following: determining, by an RRC layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L3 beam-level condition based on a first L3 beam-level measurement result of the candidate beam; determining, by the RRC layer of the UE, whether a current beam associated with the serving cell satisfies a second L3 beam-level condition based on a second L3 beam-level measurement result of the current beam; determining, by the RRC layer of the UE, whether the candidate cell satisfies a first L3 cell-level condition based on a first L3 cell-level measurement result of the candidate cell; and determining, by the RRC layer of the UE, whether the serving cell satisfies a second L3 cell-level condition based on a second L3 cell-level measurement result of the serving cell.

[0009] In some implementations of the first aspect, the first timer is started by the RRC layer of the UE. Triggering the CLTM switch to the CLTM candidate cell includes instructing, by the RRC layer of the UE, the CLTM switch after the first timer expires. The one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to: stop, by the RRC layer of the UE, the first timer in response to determining that the at least one condition becomes unsatisfied.

[0010] In some implementations of the first aspect, the at least one condition further includes one or more L1 conditions. Determining whether the at least one condition is satisfied further includes at least one of the following: determining, by a MAC layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L1 beam-level condition based on a first L1 beam-level measurement result of the candidate beam; determining, by the MAC layer of the UE, whether a current beam associated with the serving cell satisfies a second L1 beam-level condition based on a second L1 beam-level measurement result of the current beam; determining, by the MAC layer of the UE, whether the candidate cell satisfies a first L1 cell-level condition based on a first L1 cell-level measurement result of the candidate cell; and determining, by the MAC layer of the UE, whether the serving cell satisfies a second L1 cell-level condition based on a second L1 cell-level measurement result of the serving cell.

[0011] 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 second timer, by the MAC layer of the UE, in response to determining that at least one of the one or more L1 conditions is satisfied; and send, by the MAC layer of the UE, an indication to the RRC layer of the UE in response to expiration of the second timer, where the indication includes a CLTM configuration ID associated with the satisfied one or more L1 conditions.

[0012] In some implementations of the first aspect, the CLTM switch is triggered by the RRC layer of the UE after the RRC layer of the UE receives the indication from the MAC layer of the UE and the first timer expires.

[0013] 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 an RRC message for configuring the first timer and a second timer; start, by the RRC layer of the UE, the second timer in response to satisfaction of the at least one condition; and stop the first timer in response to expiration of the second timer.

[0014] In a second aspect of the present application, a BS for configuring a CLTM 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 UE via a serving cell, a CLTM configuration indicating a CLTM candidate cell. The UE determines whether at least one condition is satisfied. The UE starts a first timer in response to determining that the at least one condition is satisfied. The UE triggers a CLTM switch to the CLTM candidate cell after the first timer expires.

[0015] In some implementations of the second aspect, the at least one condition includes one or more L1 conditions and one or more L3 conditions. The UE determines whether at least one of the one or more L1 conditions is satisfied by at least one of the following: determining, by a MAC layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L1 beam-level condition based on a first L1 beam-level measurement result of the candidate beam; determining, by the MAC layer of the UE, whether a current beam associated with the serving cell satisfies a second L1 beam-level condition based on a second L1 beam-level measurement result of the current beam; determining, by the MAC layer of the UE, whether the candidate cell satisfies a first L1 cell-level condition based on a first L1 cell-level measurement result of the candidate cell; and determining, by the MAC layer of the UE, whether the serving cell satisfies a second L1 cell-level condition based on a second L1 cell-level measurement result of the serving cell. The UE determines whether at least one of the one or more L3 conditions is satisfied by at least one of the following: determining, by a Radio Resource Control (RRC) layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L3 beam-level condition based on a first L3 beam-level measurement result of the candidate beam; determining, by the RRC layer of the UE, whether a current beam associated with the serving cell satisfies a second L3 beam-level condition based on a second L3 beam-level measurement result of the current beam; determining, by the RRC layer of the UE, whether the candidate cell satisfies a first L3 cell-level condition based on a first L3 cell-level measurement result of the candidate cell; and determining, by the RRC layer of the UE, whether the serving cell satisfies a second L3 cell-level condition based on a second L3 cell-level measurement result of the serving cell.

[0016] In some implementations of the second aspect, the first timer is started by the MAC layer of the UE. The CLTM switch is triggered by the MAC layer of the UE after the first timer expires. The MAC layer of the UE sends an indication to an RRC layer of the UE in response to triggering the CLTM switch, where the indication includes a CLTM configuration ID associated with the satisfied at least one condition.

[0017] In some implementations of the second aspect, the first timer is started by the RRC layer of the UE. The RRC layer of the UE triggers the CLTM switch to the CLTM candidate cell after the first timer expires. The RRC layer of the UE stops the first timer in response to determining that the at least one condition becomes unsatisfied.

[0018] In a third aspect of the present application, a method performed by a UE for performing a CLTM operation is provided. The method includes receiving, from a serving cell, a CLTM configuration indicating a CLTM candidate cell; determining whether at least one condition is satisfied; starting a first timer in response to determining that the at least one condition is satisfied; and triggering a CLTM switch to the CLTM candidate cell after the first timer expires.

[0019] 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.

[0020] FIG. 1 is a diagram illustrating an LTM procedure, according to an example implementation of the present disclosure.

[0021] FIG. 2A is a flowchart illustrating a method / process performed by a UE for performing a CLTM operation, according to an example implementation of the present disclosure.

[0022] FIG. 2B is a flowchart illustrating a method / process performed by a UE for performing a CLTM operation, according to another example implementation of the present disclosure.

[0023] FIG. 3 is a block diagram illustrating a node for wireless communication, according to an example implementation of the present disclosure.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 key performance indicators (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.

[0032] 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 using one or more Digital Signal Processors (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 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.

[0033] A radio communication network architecture such as a Long-Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Pro system, or 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. 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.

[0034] 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).

[0035] 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.

[0036] 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. Although the gNB is used as an example in some implementations within the present disclosure, it should be noted that the disclosed implementations may also be applied to other types of base stations. 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).

[0037] 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.

[0038] 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 downlink (DL) (and optionally uplink (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.

[0039] A cell may allocate sidelink (SL) resources for supporting the Proximity Services (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.

[0040] 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.

[0041] 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 third generation partnership project (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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The terms, definitions, and abbreviations given in the present disclosure are either imported from existing documentation (e.g., European Telecommunications Standards Institute (ETSI), International Telecommunication Union (ITU), or elsewhere) or newly created by 3GPP experts whenever the need for precise vocabulary is identified.

[0049] Examples of some selected terms in the present disclosure are provided as follows.

[0050] The network (NW), cell, camped cell, serving cell, base station, gNB, eNB, and ng-eNB may be interchangeably in the present disclosure. In some implementations, some of these items may refer to the same network entity.

[0051] The Radio Access Technology (RAT) may include, but not limited to, New Radio (NR), Long Term Evolution (LTE), Evolved Universal Terrestrial Radio Access (E-UTRA) connected to 5G Core Network (5GC), LTE connected to 5GC, E-UTRA connected to Evolved Packet Core (EPC), and LTE connected to EPC. The proposed mechanism may be applied for UEs in public networks or in private networks, such as non-public network (NPN), standalone NPN (SNPN), and public network integrated NPN (PNI-NPN).

[0052] The proposed mechanism may be used for licensed frequency and / or unlicensed frequency. In addition, the proposed mechanism of conditional configuration selection may be applied to cases in which a UE experiences a radio link failure when configured with conditional configurations.

[0053] System information (SI) may refer to Master Information Block (MIB), System Information Block 1 (SIB1), and other SI. Minimum SI may include MIB and SIB1. Other SI may refer to SIB3, SIB4, SIB5, and other SIB(s).

[0054] Dedicated signaling may refer to (but not limited to) RRC message(s). For example, RRC (Connection) Setup Request message, RRC (Connection) Setup message, RRC (Connection) Setup Complete message, RRC (Connection) Reconfiguration message, RRC Connection Reconfiguration message including the mobility control information, RRC Connection Reconfiguration message without the mobility control information inside, RRC Reconfiguration message including the configuration with sync, RRC Reconfiguration message without the configuration with sync inside, RRC (Connection) Reconfiguration Complete message, RRC (Connection) Resume Request message, RRC (Connection) Resume message, RRC (Connection) Resume Complete message, RRC (Connection) Reestablishment Request message, RRC (Connection) Reestablishment message, RRC (Connection) Reestablishment Complete message, RRC (Connection) Reject message, RRC (Connection) Release message, RRC System Information Request message, UE Assistance Information message, UE Capability Enquiry message, and UE Capability Information message.

[0055] The RRC_CONNECTED UE, RRC_INACTIVE UE, and RRC_IDLE UE may apply the proposed implementations.

[0056] The source cell may be a suitable cell or an acceptable cell.

[0057] A suitable cell is a cell on which a UE may camp. The UE may consider a cell as suitable if the following conditions are fulfilled: (1) The cell is part of either the selected Public Land Mobile Network (PLMN) or the registered PLMN or PLMN of the Equivalent PLMN list, and (2) The cell criteria of the cell are fulfilled. Furthermore, according to the latest information provided by Non-Access Stratum (NAS), the suitable cell is not barred. The suitable cell is part of at least one Tracking Area (TA) that is not part of the list of “Forbidden Tracking Areas”, which belongs to a PLMN that fulfils the condition (1).

[0058] An acceptable cell is a cell on which the UE may camp to obtain limited service, such as originating emergency calls and receiving Earthquake and Tsunami Warning System (ETWS) and Commercial Mobile Alert System (CMAS) notifications. An acceptable cell may fulfil the following requirements, which is the minimum set of requirements to initiate an emergency call and to receive ETWS and CMAS notification in an NR network: (1) the cell is not barred, and / or (2) the cell selection criteria are fulfilled.

[0059] Primary Cell (PCell): The MCG cell, operating on the primary frequency, in which the UE either performs the initial connection establishment procedure or initiates the connection re-establishment procedure may be referred to as a primary cell.

[0060] Primary SCG (PSCell): For dual connectivity operation, the SCG cell in which the UE performs random access when performing the Reconfiguration with Sync procedure.

[0061] Serving Cell: For a UE in the RRC_CONNECTED state, that is not configured with Carrier Aggregation (CA) or Dual Connectivity (DC), there is only one serving cell which is a primary cell. For a UE in the RRC_CONNECTED state, that is configured with CA / DC, the term ‘serving cells’ is used to denote a set of cells including the Special Cell(s) and all secondary cells. The serving cell may include a PCell, a PSCell, or an SCell.

[0062] Secondary Cell: For a UE configured with CA, a cell that provides additional radio resources on top of the special cell may be referred to as a secondary cell

[0063] Special Cell (SpCell): For a Dual Connectivity operation, the term Special Cell may include the PCell of the MCG or the PSCell of the SCG depending on whether the MAC entity is associated with the MCG or the SCG, respectively. Otherwise, the term Special Cell may include the PCell.

[0064] Master Cell Group (MCG): In MR-DC, a group of serving cells associated with the master node, including the SpCell (e.g., PCell) and optionally one or more SCells.

[0065] Master node: In MR-DC, the radio access node that provides the control plane connection to the core network. It may be a Master eNB (in E-UTRA-NR Dual Connectivity (EN-DC)), a Master ng-eNB (in NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC)), or a Master gNB (in NR-NR Dual Connectivity (NR-DC) and NR-E-UTRA Dual Connectivity (NE-DC)).

[0066] Secondary Cell Group (SCG): In MR-DC, a group of serving cells associated with the secondary node, including the SpCell (e.g., PSCell) and optionally one or more SCells.

[0067] Secondary node: In MR-DC, the radio access node, with no control plane connection to the core network, providing additional resources to the UE. It may be an en-gNB (in EN-DC), a Secondary ng-eNB (in NE-DC), or a Secondary gNB (in NR-DC and NGEN-DC).

[0068] Source node: The node from which the UE receives a CSC. The source node may be interpreted as a source MN, a source SN, a source PCell, a source PSCell, or a source gNB.

[0069] Source cell: The cell from which the UE receives a CSC. The source cell may be interpreted as a source PCell, or a source PSCell.

[0070] Candidate node: The node that is associated with the LTM candidate configuration stored by the UE. The candidate node may be interpreted as a candidate MN, a candidate SN, a candidate PCell, a candidate PSCell, or a candidate gNB.

[0071] Candidate cell: The cell that is associated with the LTM candidate configuration stored by the UE. The candidate cell may be interpreted as a candidate PCell, or a candidate PSCell.

[0072] Target node: The node that is associated with the LTM candidate configuration ID in the CSC received by the UE. The target node may be interpreted as a target MN, a target SN, a target PCell, a target PSCell, or a target gNB.

[0073] Target cell: The cell that is associated with the LTM candidate configuration ID in the CSC received by the UE. The target cell may be interpreted as a target PCell, or a target PSCell.

[0074] In the present disclosure, the system information may be associated with the serving cell and / or the candidate / target cell.

[0075] Multiple PLMNs may operate on the unlicensed spectrum. Multiple PLMNs may share the same unlicensed carrier. The PLMNs may be public or private. Public PLMNs may include, but not limited to, the operators or virtual operators that provide radio services to the public subscribers. Public PLMNs may own the licensed spectrum and support the radio access technology on the licensed spectrum as well. Private PLMNs may include, but not limited to, the micro-operators, factories, or enterprises that provide radio services to private users (e.g., employees or machines). In some implementations, public PLMNs may support more deployment scenarios (e.g., carrier aggregation between licensed band NR (PCell) and NR-U (SCell), dual connectivity between licensed band LTE (PCell) and NR-U (PSCell), stand-alone NR-U, an NR cell with DL in unlicensed band and UL in licensed band, dual connectivity between licensed band NR (PCell) and NR-U (PSCell)). In some implementations, private PLMNs may mainly support, but not limited to, the stand-alone unlicensed radio access technology (e.g., stand-alone NR-U).

[0076] In the wireless cellular network, mobile devices (e.g., UE) may move from the coverage area of one cell to another cell. To avoid the connection interruption and ensure the service continuity, a handover procedure may be applied for the mobile devices when the handover procedure is triggered under certain conditions, e.g., when the signal quality of the source cell becomes poorer than a threshold for a period.

[0077] A handover procedure may be triggered by Layer 3 (L3) measurements and completed through RRC signaling, which triggers Reconfiguration with Synchronization to change the Primary Cell (PCell) and Primary Secondary Cell (PSCell), as well as to release and add Secondary Cells (SCells). In addition, a conditional handover (CHO) may enhance robustness by allowing the mobile device to receive the target cell configuration in advance, for example, when the signal quality between the mobile device and the source cell is stable. Dual Active Protocol Stack (DAPS) handover may reduce the interruption time because the mobile device may maintain two protocol stacks for simultaneous connections with the source cell and the target cell during handover. For example, one protocol stack is associated with the source cell and the other one is associated with the target cell.These handover procedures, including the conditional handover and the DAPS handover, may require a complete Layer 2 (L2) reset and Layer 1 (L1) reset. L2 may refer to the Medium Access Control (MAC) layer, Radio Link Control (RLC) layer, and Packet Data Convergence Protocol (PDCP) layer, and L1 may refer to the Physical (PHY) layer. Complete L1 / L2 reset may result in longer latency, larger overhead and longer interruption time than beam switch mobility. Thus, L1 / L2 triggered mobility (LTM) has been proposed to enable a serving cell change via L1 / L2 signaling, which may reduce the latency, overhead and interruption time during the handover procedures.

[0078] In addition, LTM may allow the UE to perform early downlink and uplink synchronization to shorten the possible experience of interruption. For early downlink synchronization, the UE may activate the downlink beam of the candidate cell in advance. For early uplink synchronization, the UE may obtain the timing advance (TA) by itself or upon the reception of a cell switch command (CSC) to skip the lengthy random access (RA) procedure.

[0079] To enable faster execution of LTM while potentially reducing signaling overhead, a concept of conditional LTM (CLTM) has been proposed. However, operational details of CLTM remain insufficiently specified. For example, Layer 1 measurements may be evaluated at the MAC layer, whereas Layer 3 measurements may be evaluated at the RRC layer. The interaction mechanism between the MAC layer and the RRC layer for triggering execution of a conditional LTM may need to be further specified.

[0080] LTM Procedure

[0081] FIG. 1 is a diagram illustrating an LTM procedure 100, according to an example implementation of the present disclosure. The LTM procedure 100 may include several stages, including LTM preparation 120, early sync 126, LTM cell switch execution 138, and LTM cell switch completion 142.

[0082] The UE 102 may be in the RRC_CONNECTED state 110. The UE 102 may send a measurement report message 112 to the BS 104 (e.g., a gNB). The BS 104 may decide to configure LTM and initiate LTM preparation, such as LTM candidate preparation 114. The BS 104 may transmit an RRC reconfiguration message 116 to the UE including the LTM candidate configurations. The UE 102 may store the LTM candidate configurations and transmit an RRC reconfiguration complete message 118 to the BS 104.

[0083] In the action 122, the UE 102 may perform DL synchronization with the LTM candidate cell(s) before receiving the cell switch command. The UE may activate and deactivate Transmission Configuration Indicator (TCI) states of LTM candidate cell(s), as triggered by the BS 104. In the action 124, the UE 102 may perform UL synchronization with LTM candidate cell(s) before receiving the cell switch command, by using UE-based TA measurement, if configured, and / or by transmitting a preamble towards the candidate cell, as triggered by the BS 104. When UE-based TA measurement is configured, the UE 102 may acquire the TA value(s) of the candidate cell(s) by measurement. The UE 102 may perform early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command as specified in clause 9.2.6 of the 3GPP TS 38.300. This may be done via Contention Free Random Access (CFRA) triggered by a Physical Downlink Control Channel (PDCCH) order from the source cell, following which the UE 102 may send preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE 102 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 102 may not maintain the TA timer for the candidate cell and may rely on network implementation to guarantee the TA validity.

[0084] The UE 102 may perform L1 measurements on the configured LTM candidate cell(s) and transmit L1 measurement reports 128 to the BS 104. The L1 measurement may be performed as long as RRC reconfiguration 116 is applicable. In the action 130, the BS 104 may decide to execute cell switch to a target cell. The BS 104 may transmit an LTM cell switch command MAC CE 132 triggering cell switch by including a target configuration ID that 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. In the action 134, the UE 102 may detach from the source cell, switch to the target cell, and apply the candidate configuration indicated by the target configuration ID. In the action 136, the UE 102 may perform the random access procedure towards the target cell, if the UE 102 does not have valid TA of the target cell as specified in clause 5.18.35 of the 3GPP TS 38.321. The action 136 may be an optionally omitted in some implementations, such as in a Random Access Channel (RACH)-less LTM procedure.

[0085] In the action 140, the UE 102 may complete the LTM cell switch procedure by sending an RRC reconfiguration complete message to the target cell. If the UE 102 has performed a RA procedure in the action 136 the UE 102 may consider that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE 102 may consider that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0086] In some implementations, the stages including early sync 126, LTM cell switch execution 138, and LTM cell switch completion 142, may be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in the RRC reconfiguration message 116.

[0087] Scenarios

[0088] The following scenarios may be considered in the present disclosure. A network may include multiple cells, and a UE may or may not support the MR-DC configuration. That is, the UE may receive services from at least two Radio Access Network (RAN) nodes or from only one RAN node. The RAN node may be an evolved node B (eNB) or a next generation node B (gNB). The at least two RAN nodes may include an MN associated with an MCG and at least one SN associated with an SCG. The UE may be equipped with multiple receivers and transmitters, and the UE may be capable of supporting the MR-DC dedicated configurations. The network, having the information that the UE is capable of supporting the MR-DC, may configure the UE with the MR-DC configuration (e.g., the SCG configuration), which may be encapsulated in an RRC Reconfiguration message and transmitted from the serving RAN node to the UE.

[0089] In addition, the involved cells may belong to the same gNB distributed unit (gNB-DU) or to different gNB-DUs. Likewise, the involved gNB-DUs may belong to the same gNB centralized unit (gNB-CU) or to different gNB-CUs. It should be noted that, in an MR-DC operation, the UE may transmit or receive signaling (e.g., RRC signaling) to or from the source PCell, where the signaling may include configuration information of the SCG. Similarly, the UE may transmit or receive signaling to or from the source PSCell, where the signaling may include configuration information of the MCG and / or SCG.

[0090] In some implementations, the UE may perform early TCI activation / deactivation for a beam in a candidate cell. In some implementations, the UE may activate / deactivate the beam in response to signaling from the network, where the signaling may be a MAC CE. In some implementations, the UE may activate / deactivate the beam when a preconfigured condition (e.g., the LTM3-like, LTM5-like event) is satisfied. In some implementations, the UE may activate / deactivate the beam by the UE’s implementation.

[0091] In some implementations, the UE may perform early TA acquisition toward a candidate cell. It should be noted that, in this disclosure, “early TA acquisition” and “early UL synchronization” may refer to the same procedure. In some implementations, the UE may obtain a TA value associated with the candidate cell.

[0092] In some implementations, the UE may initiate the early TA acquisition procedure in response to signaling from the network, where the signaling may be Downlink Control Information (DCI). In some implementations, the UE may initiate the early TA acquisition procedure when a preconfigured condition (e.g., the LTM3-like, LTM5-like event) is satisfied. In some implementations, the UE may initiate the early TA acquisition procedure by the UE’s implementation. In some implementations, the UE may obtain the TA value by a measurement performed by the UE (e.g., a UE-based TA measurement). In some implementations, the UE may obtain the TA value via signaling from the serving cell, where the signaling may be a MAC CE. In some implementations, the UE may obtain the TA value via signaling from the candidate cell, where the signaling may be a MAC CE or an RA response.

[0093] In some implementations, an early TA procedure may be initiated by the UE or by the network in a CLTM procedure to enable the UE to obtain, in advance, a TA value associated with a candidate cell before establishing a connection with the candidate cell.

[0094] In some implementations, the early TA procedure may be initiated by the network via DCI (e.g., PDCCH-order RA). For example, the UE may receive, from the BS, a PDCCH order that initiates the early TA procedure. In some implementations, the DCI may indicate the ID of the candidate configuration associated with the candidate cell, the preamble index, and / or the Contention-Free Random Access (CFRA) resource information. In some implementations, upon receiving the DCI, the UE may transmit a preamble on a CFRA resource towards the candidate cell according to the DCI. In some implementations, upon receiving the preamble transmitted from the UE, the candidate cell may obtain a TA value and send the TA value to the serving cell (e.g., via XnAP signaling). In some implementations, upon receiving the TA value from the candidate cell, the serving cell may transmit the TA value to the UE (e.g., via a MAC CE).

[0095] In some implementations, the early TA procedure may be performed by the UE itself. For example, the UE may measure the TA value associated with a candidate cell by its implementation. More specifically, whether the UE is allowed to measure the TA value associated with the candidate cell by its implementation may be configured by the network.

[0096] In some implementations, the early TA procedure may be initiated by the UE. In some implementations, the UE may transmit an early TA request to the serving cell. In some implementations, the early TA request may be transmitted via Uplink Control Information (UCI) or a MAC CE. In some implementations, the early TA request may include an ID associated with the candidate cell, and / or the information of the activated beams or beams with good quality. In some implementations, upon receiving the TA request, the serving cell may transmit DCI to indicate the information of the early TA. In some implementations, upon receiving the DCI, the UE may transmit a preamble on a CFRA resource towards the candidate cell according to the DCI. In some implementations, upon receiving the preamble transmitted from the UE, the candidate cell may obtain a TA value and send the TA value to the serving cell (e.g., via XnAP signaling). In some implementations, upon receiving the TA value from the candidate cell, the serving cell may transmit the TA value to the UE (e.g., via a MAC CE).

[0097] In some implementations, the early TA procedure may be initiated by the UE. In some implementations, the UE may transmit a preamble to the candidate cell. In some implementations, the preamble index of the transmitted preamble may be preconfigured in the LTM configuration (e.g., ltm-Config or ltm-Candidate) and may be determined by the UE according to the activated beams or beams with good quality. In some implementations, after transmitting the preamble, the UE may wait for a period (e.g., an RA-window) for the RA response from the candidate cell. In some implementations, the RA response may include at least the TA value.

[0098] In some implementations, the UE may monitor the PDCCH associated with the RA response according to the search space and Control Resource Set (CORESET) information in the SIB1 of the candidate cell. In some implementations, the UE may monitor the PDCCH associated with the RA response according to the search space and CORESET information in the LTM configuration (e.g., the ltm-Config or the ltm-Candidate).

[0099] Configuration of the Conditions in CLTM

[0100] In some implementations, a beam-level condition may be referred to as the condition evaluated based on the measurement result of a beam. More specifically, the measurement result of a beam may be referred to as the measurement result on a Synchronization Signal Block (SSB) and / or a Channel State Information Reference Signal (CSI-RS). More specifically, the measurement result may be the reference signal received power (RSRP), reference signal received quality (RSRQ), and / or signal to interference plus noise ratio (SINR).

[0101] In some implementations, a cell-level condition may be referred to as the condition evaluated based on the measurement result of a cell. More specifically, the measurement result of a cell may be referred to as the consolidated measurement results on one or more SSBs and / or one or more CSI-RSs associated with the cell. In some implementations, the measurement result of the cell may be referred to as the average of the measurement results of SSBs that are higher than a threshold.

[0102] In some implementations, a beam-level condition may be, but not limited to, one of the following conditions.

[0103] - BeamA1-entering: The quality of the serving beam is better than a first threshold. In some implementations, the first threshold may be configured by the network.

[0104] - BeamA1-leaving: The quality of the serving beam is worse than a second threshold. In some implementations, the second threshold may be configured by the network.

[0105] - BeamA2-entering: The quality of the serving beam is worse than a first threshold. In some implementations, the first threshold may be configured by the network.

[0106] - BeamA2-leaving: The quality of the serving beam is better than a second threshold. In some implementations, the second threshold may be configured by the network.

[0107] - BeamA3-entering: The quality of a candidate beam is better than the quality of the serving beam plus a first offset. In some implementations, the first offset may be configured by the network.

[0108] - BeamA3-leaving: The quality of a candidate beam is worse than the quality of the serving beam plus a second offset. In some implementations, the second offset may be configured by the network.

[0109] - BeamA4-entering: The quality of a candidate beam is better than a first threshold. In some implementations, the threshold may be configured by the network.

[0110] - BeamA4-leaving: The quality of a candidate beam is worse than a second threshold. In some implementations, the second threshold may be configured by the network.

[0111] - BeamA5-entering: The quality of a candidate beam is better than a first threshold, and the quality of the serving beam is worse than a second threshold. In some implementations, the first threshold and the second threshold may be configured by the network.

[0112] - BeamA5-leaving: The quality of a candidate beam is worse than a third threshold, and the quality of the serving beam is better than a fourth threshold. In some implementations, the third threshold and the fourth threshold may be configured by the network.

[0113] It should be noted that the serving beam may be the beam with the best quality in the serving cell. The serving beam may be the beam associated with the indicated TCI state (e.g., currently used for the DL and / or UL transmission).

[0114] In some implementations, a cell-level condition may be, but not limited to, one of the following conditions.

[0115] - CellA1-entering: The quality of the serving cell is better than a first threshold. In some implementations, the first threshold may be configured by the network.

[0116] - CellA1-leaving: The quality of the serving cell is worse than a second threshold. In some implementations, the second threshold may be configured by the network.

[0117] - CellA2-entering: The quality of the serving cell is worse than a first threshold. In some implementations, the first threshold may be configured by the network.

[0118] - CellA2-leaving: The quality of the serving cell is better than a second threshold. In some implementations, the second threshold may be configured by the network.

[0119] - CellA3-entering: The quality of a candidate cell is better than the quality of the serving cell plus a first offset. In some implementations, the first offset may be configured by the network.

[0120] - CellA3-leaving: The quality of a candidate cell is worse than the quality of the serving cell plus a second offset. In some implementations, the second offset may be configured by the network.

[0121] - CellA4-entering: The quality of a candidate cell is better than a first threshold. In some implementations, the first threshold may be configured by the network.

[0122] - CellA4-leaving: The quality of a candidate cell is worse than a second threshold. In some implementations, the second threshold may be configured by the network.

[0123] - CellA5-entering: The quality of a candidate cell is better than a first threshold, and the quality of the serving cell is worse than a second threshold. In some implementations, the first threshold and the second threshold may be configured by the network.

[0124] - CellA5-leaving: The quality of a candidate cell is worse than a third threshold, and the quality of the serving cell is better than a fourth threshold. In some implementations, the third threshold and the fourth threshold may be configured by the network.

[0125] In some implementations, the configuration of the beam-level condition may be configured on a per-beam basis. For example, the MAC layer of the UE may evaluate the beam-level condition of a beam according to the configuration of the beam-level condition associated with the beam. In some implementations, the information element (IE) for the configuration of the beam-level condition may be included in the candidate cell configuration (e.g., the LTM-Candidate), and the IE may include a list of sequences, where each sequence may include an identifier (ID) indicating a beam and an event associated with the beam.

[0126] In some implementations, the configuration of the beam-level condition may be configured on a per-beam-set basis. For example, the MAC layer of the UE may evaluate the beam-level condition of a beam according to the configuration of the beam-level condition associated with a beam set including the beam. In some implementations, the IE for the configuration of the beam-level condition associated with a beam set may be included in the candidate cell configuration (e.g., the LTM-Candidate), and the IE may include a list of sequences, where each sequence may include an ID indicating a beam and an event associated with the beams in the beam set. In some implementations, the IE for the configuration of the beam-level condition associated with a beam set may be included in the LTM configuration (e.g., the LTM-Config), and the IE may include a list of sequences, where each sequence may include an ID indicating a beam and an event associated with the beams in the beam set.

[0127] In some implementations, the configuration of the beam-level condition may be configured on a per-cell basis. For example, the MAC layer of the UE may evaluate the beam-level condition of a beam according to the configuration of the beam-level condition associated with the cell associated with the beam. In some implementations, the IE for the configuration of the beam-level condition associated with a cell may be included in the candidate cell configuration (e.g., the LTM-Candidate), and the IE may include an event associated with the beams associated with the cell.

[0128] In some implementations, the configuration of the beam-level condition may be configured commonly to all the candidate beams. For example, the MAC layer of the UE may evaluate the beam-level condition of a beam according to the configuration of the beam-level condition common to all the candidate beams. In some implementations, the IE for the configuration of the beam-level condition may be included in the LTM configuration (e.g., the LTM-Config), and the IE may include an event associated with all the candidate beams.

[0129] In some implementations, the configuration of the cell-level condition may be configured as a measId IE, which may associate a measurement object (e.g., a measObject IE) including the candidate cell with a report configuration (e.g., a reportConfig IE) including the cell-level condition.

[0130] In some implementations, the configuration of the cell-level condition may be configured on a per-cell basis. For example, the MAC layer of the UE may evaluate the cell-level condition of a cell according to the configuration of the cell-level condition associated with the cell. In some implementations, the IE for the configuration of the cell-level condition may be included in the candidate cell configuration (e.g., the LTM-Candidate) associated with the cell.

[0131] In some implementations, the configuration of the cell-level condition may be configured on a per-cell-set basis. For example, the MAC layer of the UE may evaluate the cell-level condition of a cell according to the configuration of the cell-level condition associated with the cell set including the cell. In some implementations, the IE for the configuration of the cell-level condition may be included in the LTM configuration (e.g., the LTM-Config) associated with the cell.

[0132] In some implementations, the configuration of the cell-level condition may be configured commonly to all the candidate cells. For example, the MAC layer of the UE may evaluate the cell-level condition of a cell according to the configuration of the cell-level condition common to all the candidate cells.

[0133] In some implementations, the UE may obtain the Layer-1 (L1) measurement results (e.g., L1 RSRP, L1 RSRQ, and / or L1 SINR) from the measurement of beam-specific samples (e.g., an SSB and / or a CSI-RS) via specific filtering procedure (e.g., the L1-filtering). More specifically, the L1 measurement results may be derived by the physical (PHY) layer of the UE, and the PHY layer may send the L1 measurement result to the upper layer (e.g., the MAC layer and / or the RRC layer).

[0134] In the present disclosure, the L1 measurement results may be L1 beam-level measurement results or L1 cell-level measurement results; the L3 measurement results may be L3 beam-level measurement results or L3 cell-level measurement results.

[0135] In the present disclosure, an L1 condition may refer to a condition derived from L1 measurement results and may include an L1 beam-level condition and / or an L1 cell-level condition. Similarly, an L3 condition may refer to a condition derived from L3 measurement results and may include an L3 beam-level condition and / or an L3 cell-level condition.

[0136] In the present disclosure, the expression “the cell satisfies the condition” may refer to a case in which the UE considers that a cell-level condition associated with the cell is satisfied. Similarly, the expression “the beam satisfies the condition” may refer to a case in which the UE considers that a beam-level condition associated with the beam is satisfied.

[0137] Interaction between MAC and RRC for CLTM Triggering

[0138] In some implementations, the MAC layer of the UE may evaluate the L1 beam-level conditions associated with each candidate beam. In some implementations, the MAC layer of the UE may evaluate the L1 cell-level conditions associated with each candidate cell.

[0139] In some implementations, when the MAC layer of the UE considers or determines that a candidate beam satisfies the L1 beam-level condition, the MAC layer of the UE may start a timer (e.g., a time-to-trigger, TTT) associated with the beam.

[0140] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the candidate beam (e.g., corresponding to the timer) does not satisfy the L1 beam-level condition.

[0141] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the UE is reconfigured with a configuration related to LTM or conditional LTM (e.g., with an LTM-Config IE) or upon / after the UE starts / triggers a conditional LTM operation.

[0142] In some implementation, the MAC layer may consider that the UE is reconfigured with a configuration related to LTM or conditional LTM when it is indicated by the RRC layer or when the stored configuration related to LTM (e.g., the ltm-Config and / or the ltm-Candidate) is changed.

[0143] For example, the MAC layer of the UE may stop the timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to the cell associated with the timer is reconfigured. It should be noted that the candidate configuration (e.g., the LTM-Candidate IE) may be associated with the CLTM.

[0144] For example, the MAC layer of the UE may stop the timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to a cell other than the cell associated with the timer is reconfigured.

[0145] For example, the MAC layer of the UE may stop the timer if the candidate beam configuration corresponding to the beam associated with the timer is reconfigured.

[0146] For example, the MAC layer of the UE may stop the timer if the candidate beam configuration corresponding to a beam other than the beam associated with the timer is reconfigured.

[0147] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the UE is performing MAC reset or when the UE determines to perform the MAC reset.

[0148] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the UE executes Layer 3 handover and / or conditional handover (e.g., upon reception of an RRCReconfiguration message associated with a cell other than the source cell, or upon application of an RRCReconfiguration message associated with a cell other than the source cell) or when the UE receives an indication from higher layers.

[0149] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the UE executes LTM and / or CLTM (e.g., upon reception of an LTM CSC MAC CE indicating a target cell, upon transmission of an indication related to the LTM CSC from the MAC layer to higher layers such as the RRC layer, or upon application of an RRCReconfiguration message associated with the target cell).

[0150] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the UE performs or triggers an RRC re-establishment procedure.

[0151] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the UE performs a cell selection or reselection procedure.

[0152] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the UE transmits a UE assistance information to indicate the information related to performing a conditional LTM cell switch.

[0153] In some implementations, if the timer expires (e.g., in a case that the candidate beam satisfies the L1 beam-level entering condition for the TTT), the MAC layer of the UE may send an indication to the RRC layer of the UE. In some implementations, the indication may include a beam ID and / or a cell ID. In some implementations, the beam ID may be a TCI state ID. In some implementations, the beam ID may be an SSB Resource indicator (SSBRI) and / or a CSI-RS Resource indicator (CRI). In some implementations, the cell ID may be a Physical Cell ID (PCI), such as the physCellId. In some implementations, the cell ID may be an LTM candidate configuration ID (e.g., the LTM-CandidateId).

[0154] In some implementations, upon receiving the indication from the MAC layer of the UE, the RRC layer of the UE may consider that the beam has satisfied the L1 beam-level condition. The L1 beam-level condition may be an L1 beam-level entering condition or an L1 beam-level leaving condition.

[0155] In some implementations, when the MAC layer of the UE considers or determines that a candidate cell satisfies the L1 cell-level condition, the MAC layer of the UE may start a timer (e.g., TTT) associated with the cell.

[0156] In some implementation, the MAC layer may consider that the UE is reconfigured with a configuration related to LTM or conditional LTM when it is indicated by the RRC layer or when the stored configuration related to LTM (e.g., the ltm-Config and / or the ltm-Candidate) is changed.

[0157] In some implementations, if the timer is running, the MAC layer of the UE may stop the timer when the cell does not satisfy the L1 cell-level condition.

[0158] In some implementations, if the timer expires (e.g., in a case that the candidate cell satisfies the L1 cell-level entering condition for the TTT), the MAC layer of the UE may send an indication to the RRC layer of the UE. In some implementations, the indication may include a cell ID (e.g., the physCellId) to indicate the candidate cell that is associated with the timer. In some implementations, the indication may include a candidate CLTM configuration ID (e.g., the ltm-ConfigId) to indicate the candidate configuration that corresponds to the candidate cell associated with the timer.

[0159] In some implementations, upon receiving the indication from the MAC layer of the UE, the RRC layer of the UE may consider that the cell has satisfied the L1 cell-level condition. The L1 cell-level condition may be an L1 cell-level entering condition or an L1 cell-level leaving condition.

[0160] In some implementations, when the MAC layer of the UE considers or determines that a candidate beam satisfies the L1 beam-level condition, the MAC layer of the UE may send an indication to the RRC layer of the UE. In some implementations, the indication may include a beam ID and / or a cell ID. In some implementations, the beam ID may be a TCI state ID. In some implementations, the beam ID may be an SSBRI and / or a CRI. In some implementations, the cell ID may be a PCI (e.g., physCellId). In some implementations, the cell ID may be an LTM candidate configuration ID (e.g., LTM-CandidateId).

[0161] In some implementations, upon receiving the indication, if the first timer (e.g., the TTT) is not running, the RRC layer of the UE may start / restart the first timer (e.g., the TTT) and / or a second timer. In some implementations, the length of the first timer and the length of the second timer may be configured by the network (e.g., via an RRC message). In some implementations, the second timer may be used to monitor the validity of the satisfied event. For example, if the RRC layer of the UE does not receive the indication from the MAC layer for a period longer than the second timer, the RRC layer may consider that the event is not satisfied and may stop the first timer. In some implementations, the length of the second timer may be shorter than the length of the first timer.

[0162] In some implementations, upon receiving every indication, the RRC layer of the UE may start / restart the second timer.

[0163] In some implementations, when the second timer expires (e.g., the RRC layer of the UE does not receive the indication for more than the length of the second timer), the UE may stop the first timer.

[0164] In some implementations, when the first timer expires (e.g., the RRC layer of the UE keeps receiving indications for more than the length of the first timer), the RRC layer of the UE may consider that the beam has satisfied the L1 beam-level condition. The L1 beam-level condition may be an L1 beam-level entering condition or an L1 beam-level leaving condition.

[0165] In some implementations, if the first timer and / or the second timer is running, the RRC layer of the UE may stop the first timer and / or the second timer when the UE is reconfigured with a configuration related to LTM or conditional LTM (e.g., with an LTM-Config IE) or when the UE starts / triggers a conditional LTM execution.

[0166] For example, the RRC layer of the UE may stop the first timer and / or the second timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to the cell associated with the first timer and / or the second timer is reconfigured.

[0167] For example, the RRC layer of the UE may stop the first timer and / or the second timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to a cell other than the cell associated with the first timer and / or the second timer is reconfigured.

[0168] For example, the RRC layer of the UE may stop the first timer and / or the second timer if the candidate beam configuration corresponding to the beam associated with the first timer and / or the second timer is reconfigured.

[0169] For example, the RRC layer of the UE may stop the first timer and / or the second timer if the candidate beam configuration corresponding to a beam other than the beam associated with the first timer and / or the second timer is reconfigured.

[0170] In some implementations, if the first timer and / or the second timer is running, the RRC layer of the UE may stop the first timer and / or the second timer when the UE executes Layer 3 handover and / or conditional handover (e.g., upon reception of an RRCReconfiguration message associated with a cell other than the source cell, or upon application of an RRCReconfiguration message associated with a cell other than the source cell).

[0171] In some implementations, if the first timer and / or the second timer is running, the RRC layer of the UE may stop the first timer and / or the second timer when the UE executes LTM and / or CLTM (e.g., upon reception of an CSC MAC CE indicating a target cell, upon transmission of an indication related to the LTM CSC from the MAC layer to higher layers such as the RRC layer, or upon application of an RRCReconfiguration message associated with the target cell).

[0172] In some implementations, if the first timer and / or the second timer is running, the RRC layer of the UE may stop the first timer and / or the second timer when the UE performs an RRC re-establishment procedure.

[0173] In some implementations, when the MAC layer of the UE considers that a candidate cell satisfies the L1 cell-level condition, the MAC layer of the UE may send an indication to the RRC layer of the UE. In some implementations, the indication may include a cell ID. In some implementations, the indication may be associated with a cell ID. In some implementations, the cell ID may be a PCI (e.g., physCellId), a serving cell index, or a secondary cell index. In some implementations, the cell ID may be an LTM candidate configuration ID (e.g., LTM-CandidateId).

[0174] In some implementations, upon receiving the indication, if a first timer is not running, the RRC layer of the UE may start / restart the first timer (e.g., the TTT) and / or a second timer. In some implementations, the length of the first timer and the length of the second timer may be configured by the network (e.g., via an RRC message). In some implementations, the length of the second timer may be shorter than the length of the first timer.

[0175] In some implementations, upon receiving every indication, the RRC layer of the UE may start / restart the second timer.

[0176] In some implementations, when the second timer expires (e.g., the RRC layer of the UE does not receive the indication for more than the length of the second timer), the UE may stop the first timer.

[0177] In some implementations, when the first timer expires (e.g., the RRC layer of the UE keeps receiving indications for more than the length of the first timer), the RRC layer of the UE may consider that the cell has satisfied the L1 beam-level condition. The L1 cell-level condition may be an L1 cell-level entering condition or an L1 cell-level leaving condition.

[0178] In some implementations, if the first timer and / or the second timer is running, the RRC layer of the UE may stop the first timer and / or the second timer when the UE is reconfigured with a configuration related to LTM (e.g., with an LTM-Config IE).

[0179] For example, the RRC layer of the UE may stop the first timer and / or the second timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to the cell associated with the first timer and / or the second timer is reconfigured.

[0180] For example, the RRC layer of the UE may stop the first timer and / or the second timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to a cell other than the cell associated with the first timer and / or the second timer is reconfigured.

[0181] For example, the RRC layer of the UE may stop the first timer and / or the second timer if the candidate beam configuration corresponding to the beam associated with the first timer and / or the second timer is reconfigured.

[0182] For example, the RRC layer of the UE may stop the first timer and / or the second timer if the candidate beam configuration corresponding to a beam other than the beam associated with the first timer and / or the second timer is reconfigured.

[0183] In some implementations, if the first timer and / or the second timer is running, the RRC layer of the UE may stop the first timer and / or the second timer when the UE executes Layer 3 handover and / or conditional handover (e.g., upon reception of an RRCReconfiguration message associated with a PCell other than the source PCell, or upon application of an RRCReconfiguration message associated with a PCell other than the source PCell).

[0184] In some implementations, if the first timer and / or the second timer is running, the RRC layer of the UE may stop the first timer and / or the second timer when the UE executes LTM and / or CLTM (e.g., upon reception of an LTM CSC MAC CE indicating a target cell, upon transmission of an indication related to the LTM CSC from the MAC layer to higher layers such as the RRC layer, or upon application of the RRCReconfiguration message associated with the target cell).

[0185] In some implementations, if the first timer and / or the second timer is running, the RRC layer of the UE may stop the first timer and / or the second timer when the UE performs an RRC re-establishment procedure, when the UE triggers the RRC re-establishment procedure, or when the UE performs a cell selection or reselection procedure.

[0186] In some implementations, when the MAC layer of the UE determines that a candidate beam has not satisfied the L1 beam-level condition, if the candidate beam subsequently satisfies the L1 beam-level condition, the MAC layer may send a positive indication to the RRC layer. Conversely, when the MAC layer determines that a candidate beam has satisfied the L1 beam-level condition, if the candidate beam subsequently does not satisfy the L1 beam-level condition, the MAC layer may send a negative indication to the RRC layer.

[0187] In some implementations, the positive and / or negative indication may include a beam ID, a cell ID, and / or an indication of positive or negative status. In some implementations, the beam ID may be a TCI state ID. In some implementations, the beam ID may be an SSBRI and / or a CRI. In some implementations, the cell ID may be a PCI (e.g., physCellId). In some implementations, the cell ID may be an LTM candidate configuration ID (e.g., LTM-CandidateId).

[0188] In some implementations, the indication for positive and negative may include one bit. In some implementations, if the MAC layer considers that the candidate beam does not satisfy the L1 beam-level condition, the MAC layer may set the indication to a first value (e.g., ‘0’); if the MAC layer considers that the candidate beam satisfies the L1 beam-level condition, the MAC layer may set the indication to a second value (e.g., ‘1’). In some implementations, if the indication is set to the first value (e.g., ‘0’), the RRC layer may consider that the candidate beam does not satisfy the L1 beam-level condition; if the indication is set to the second value (e.g., ‘0’), the RRC layer may consider that the candidate beam satisfies the L1 beam-level condition.

[0189] In some implementations, upon receiving the positive indication, if the first timer (e.g., the TTT) is not running, the RRC layer of the UE may start / restart the first timer. In some implementations, the length of the first timer may be configured by the network (e.g., via an RRC message).

[0190] In some implementations, upon receiving a negative indication, if the first timer is running, the RRC layer of the UE may stop the first timer.

[0191] In some implementations, when the first timer expires, the RRC layer of the UE may consider that the beam has satisfied the L1 beam-level condition. The L1 beam-level condition may be an L1 beam-level entering condition or an L1 beam-level leaving condition.

[0192] In some implementations, if the first timer is running, the RRC layer of the UE may stop the first timer when the UE is reconfigured with a configuration related to LTM (e.g., with an LTM-Config IE).

[0193] For example, the RRC layer of the UE may stop the first timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to the cell associated with the first timer is reconfigured.

[0194] For example, the RRC layer of the UE may stop the first timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to a cell other than the cell associated with the first timer is reconfigured.

[0195] For example, the RRC layer of the UE may stop the first timer if the candidate beam configuration corresponding to the beam associated with the first timer is reconfigured.

[0196] For example, the RRC layer of the UE may stop the first timer if the candidate beam configuration corresponding to a beam other than the beam associated with the first timer is reconfigured.

[0197] In some implementations, if the first timer is running, the RRC layer of the UE may stop the first timer when the UE executes Layer 3 handover and / or conditional handover (e.g., upon reception of an RRCReconfiguration message associated with a PCell other than the source PCell, or upon application of an RRCReconfiguration message associated with a PCell other than the source PCell).

[0198] In some implementations, if the first timer is running, the RRC layer of the UE may stop the first timer when the UE executes LTM and / or CLTM (e.g., upon reception of an LTM CSC MAC CE indicating a target cell, upon transmission of an indication related to the LTM CSC from the MAC layer to higher layers such as the RRC layer, or upon application of the RRCReconfiguration message associated with the target cell).

[0199] In some implementations, if the first timer is running, the RRC layer of the UE may stop the first timer when the UE performs an RRC re-establishment procedure, when the UE triggers the RRC re-establishment procedure, or when the UE performs a cell selection or reselection procedure.

[0200] In some implementations, if the first timer is running, the RRC layer of the UE may stop the timer when the UE transmits a UE assistance information to indicate the target cell information.

[0201] In some implementations, when the MAC layer of the UE determines that a candidate cell changes from not satisfying the L1 cell-level condition to satisfying the L1 cell-level condition, the MAC layer may send a positive indication to the RRC layer. Conversely, when the MAC layer determines that a candidate cell changes from satisfying the L1 cell-level condition to not satisfying the L1 cell-level condition, the MAC layer may send a negative indication to the RRC layer.

[0202] In some implementations, the indication may include a cell ID and / or an indication for positive and negative. In some implementations, the cell ID may be a PCI (e.g., physCellId). In some implementations, the cell ID may be an LTM candidate configuration ID (e.g., LTM-CandidateId).

[0203] In some implementations, the indication for positive and negative may include one bit. In some implementations, if the MAC layer considers that the candidate cell does not satisfy the L1 cell-level condition, the MAC layer may set the indication to a first value (e.g., ‘0’); if the MAC layer considers that the candidate cell satisfies the L1 cell-level condition, the MAC layer may set the indication to a second value (e.g., ‘1’). In some implementations, if the indication is set to the first value (e.g., ‘0’), the RRC layer may consider that the candidate cell does not satisfy the L1 cell-level condition; if the indication is set to the second value (e.g., ‘0’), the RRC layer may consider that the candidate cell satisfies the L1 cell-level condition.

[0204] In some implementations, upon receiving the positive indication, if the first timer (e.g., the TTT) is not running, the RRC layer of the UE may start / restart the first timer. In some implementations, the length of the first timer may be configured by the network (e.g., via an RRC message).

[0205] In some implementations, upon receiving a negative indication, if the first timer is running, the RRC layer of the UE may stop the first timer.

[0206] In some implementations, when the first timer expires, the RRC layer of the UE may consider that the cell has satisfied the L1 cell-level condition. The L1 cell-level condition may be an L1 cell-level entering condition or an L1 cell-level leaving condition. The L1 cell-level condition may be based on the L1 measurement result with filtering.

[0207] In some implementations, if the first timer is running, the RRC layer of the UE may stop the first timer when the UE is reconfigured with a configuration related to LTM (e.g., with an LTM-Config IE).

[0208] For example, the RRC layer of the UE may stop the first timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to the cell associated with the first timer is reconfigured.

[0209] For example, the RRC layer of the UE may stop the first timer if the candidate configuration (e.g., the LTM-Candidate IE) corresponding to a cell other than the cell associated with the first timer is reconfigured.

[0210] For example, the RRC layer of the UE may stop the first timer if the candidate beam configuration corresponding to the beam associated with the first timer and / or the second timer is reconfigured.

[0211] For example, the RRC layer of the UE may stop the first timer if the UE determines to apply a beam other than the beam associated with the first timer and / or the second timer.

[0212] For example, the RRC layer of the UE may stop the first timer if the candidate beam configuration corresponding to a beam other than the beam associated with the first timer and / or the second timer is reconfigured.

[0213] In some implementations, if the first timer is running, the RRC layer of the UE may stop the first timer when the UE executes Layer 3 handover and / or conditional handover (e.g., upon reception of an RRCReconfiguration message associated with a cell other than the source cell, or upon application of an RRCReconfiguration message associated with a cell other than the source cell).

[0214] In some implementations, if the first timer is running, the RRC layer of the UE may stop the first timer when the UE executes LTM and / or CLTM (e.g., upon reception of an LTM CSC MAC CE indicating a target cell, upon transmission of an indication related to the LTM CSC from the MAC layer to higher layers such as the RRC layer, or upon application of the RRCReconfiguration message associated with the target cell).

[0215] In some implementations, if the first timer is running, the RRC layer of the UE may stop the first timer when the UE performs an RRC re-establishment procedure.

[0216] In some implementations, when the RRC layer of the UE considers that a candidate beam satisfies the L3 beam-level condition, the RRC layer of the UE may start a timer (e.g., a time-to-trigger, TTT) associated with the beam.

[0217] In some implementations, if the timer is running, the RRC layer of the UE may stop the timer when the beam does not satisfy the L3 beam-level condition.

[0218] In some implementations, if the timer expires (e.g., in a case that the candidate beam satisfies the L3 beam-level entering condition for the TTT), the RRC layer of the UE may consider that the beam has satisfied the L3 beam-level condition. The L3 beam-level condition may be an L3 beam-level entering condition or an L3 beam-level leaving condition.

[0219] In some implementations, when the RRC layer of the UE considers that a candidate cell satisfies the L3 cell-level condition, the RRC layer of the UE may start a timer (e.g., a time-to-trigger, TTT) associated with the cell.

[0220] In some implementations, if the timer is running, the RRC layer of the UE may stop the timer when the cell does not satisfy the L3 cell-level condition.

[0221] In some implementations, if the timer expires (e.g., in a case that the candidate cell satisfies the cell-level entering condition for the TTT), the RRC layer of the UE may consider that the cell has satisfied the cell-level condition. The cell-level condition may be a cell-level entering condition or a cell-level leaving condition.

[0222] In some implementations, if the RRC layer of the UE considers that a candidate cell satisfies the cell-level condition while one or more candidate beams associated with the cell satisfy the beam-level condition, the UE may execute the conditional LTM configuration associated with the candidate cell using one of the candidate beams associated with the candidate cell. More specifically, the UE may select a candidate beam from the one or more candidate beams that satisfy the beam-level condition.

[0223] In some implementations, the UE may select the beam with the highest quality (e.g., the RSRP, RSRQ, and / or SINR). In some implementations, the UE may select the beam by the UE’s implementation. In some implementations, the UE may select the beam that satisfies the beam-level condition for the longest duration.

[0224] Triggering LTM Execution for Mixed L1 and L3 Conditions

[0225] In some implementations, the UE may be simultaneously configured with one or more L1-based conditions and one or more L3-based conditions for a candidate beam and / or a candidate cell in a CLTM configuration. Implementations in which the UE is simultaneously configured with one or more L1-based conditions and one or more L3-based conditions for a candidate beam and / or a candidate cell are provided below.

[0226] In some implementations, the UE may be simultaneously configured with one or more L1-based conditions and one or more L3-based conditions for a candidate beam and / or a candidate cell in a CLTM configuration when a UE capability is reported / transmitted by the UE.

[0227] In some implementations, the UE may trigger a CLTM execution if the UE considers that all the L1-based conditions and all the L3-based conditions are satisfied.

[0228] In some implementations, the UE may trigger a CLTM execution if the UE considers that at least one L1-based condition and at least one L3-based condition are satisfied.

[0229] In some implementations, an indication may be configured to the UE to indicate whether the UE applies the combination of L1-based and L3-based conditions (e.g., the UE triggers a CLTM execution when all the L1-based conditions and all the L3-based conditions are satisfied) or not (e.g., the UE triggers a CLTM execution when all the L1-based conditions or all the L3-based conditions are satisfied). More specifically, the indication may be configured in the same RRC message including the LTM candidate configuration (e.g., the LTM-Candidate IE).

[0230] In some implementations, the indication may be an ENUMERATED format or a Boolean value. If the indication is present with a first specific value (e.g., ‘true’ or 1), the UE may consider that the associated cell and / or the associated beam applies the combination of L1-based and L3-based conditions; if the indication is absent or is present with a second specific value (e.g., ‘false’ or 0), the UE may consider that the associated cell and / or the associated beam does not apply the combination of L1-based and L3-based conditions.

[0231] In some implementations, the indication may be configured commonly to all the candidate cells and / or the candidate beams. For example, the indication may be configured in the LTM configuration (e.g., the LTM-Config IE), and the UE may consider that all the candidate cells and / or all the candidate beams are associated with the indication.

[0232] In some implementations, the indication may be configured on a per candidate cell basis. For example, the indication may be configured in the LTM candidate configuration (e.g., the LTM-Candidate IE), and the UE may consider that the candidate cell and / or all the candidate beams associated with the candidate cell are associated with the indication.

[0233] In some implementations, the indication may be configured on a per candidate beam basis. For example, the indication may be configured in the beam information in an LTM candidate configuration, and the UE may consider that the candidate beam is associated with the indication.

[0234] In some implementations, if the indication indicates that the combination of L1-based and L3-based conditions is applied, the UE may trigger the LTM execution only if the UE considers that all the L1-based conditions and all the L3-based conditions are satisfied.

[0235] In some implementations, if the indication indicates that the combination of L1-based and L3-based conditions is not applied, the UE may trigger the LTM execution if the UE considers that all the L1-based conditions are satisfied, if the UE considers that all the L3-based conditions are satisfied, or if the UE considers that all the L1-based conditions and all the L3-based conditions are satisfied.

[0236] In some implementations, the UE may be configured with only L1-based conditions (e.g., no L3-based condition is configured) for a candidate beam and / or a candidate cell in a CLTM configuration. The UE may trigger the LTM execution if the UE considers that all the L1-based conditions are satisfied.

[0237] In some implementations, the UE may be configured with only L3-based conditions (e.g., no L1-based condition is configured) for a candidate beam and / or a candidate cell in a CLTM configuration. The UE may trigger the LTM execution if the UE considers that all the L3-based conditions are satisfied.

[0238] Triggering and Executing of CLTM for Mixed Beam-Level and Cell-Level Conditions

[0239] In some implementations, if the UE is configured with one or more candidate cells / one or more candidate beams for conditional LTM, where a candidate cell may be associated with one or more L1 and / or L3 cell-level conditions and a candidate beam may be associated with one or more L1 and / or L3 beam-level conditions, the UE may have the following behaviors.

[0240] In some implementations, a candidate cell may be associated with one or more L1 and / or L3 cell-level conditions and a candidate beam may be associated with one or more L1 and / or L3 beam-level conditions when a UE capability is reported / transmitted by the UE.

[0241] In some implementations, the UE may execute the conditional LTM configuration associated with a candidate cell using a candidate beam when the RRC layer of the UE considers that all the beam-level conditions associated with the candidate beam and all the cell-level conditions associated with the candidate cell are satisfied.

[0242] In some implementations, the UE may execute a CLTM configuration associated with a candidate cell using a candidate beam when the RRC layer of the UE considers that at least one beam-level condition associated with the candidate beam and at least one cell-level condition associated with the candidate cell are satisfied.

[0243] In some implementations, the UE may execute the conditional LTM configuration associated with a candidate cell when the RRC layer of the UE considers that all the cell-level conditions associated with the candidate cell are satisfied.

[0244] In some implementations, an indication may be configured to the UE to indicate whether the UE applies the combination of cell-level conditions and beam-level conditions. The indication may be configured in the same RRC message that includes the LTM candidate configuration (e.g., the LTM-Candidate IE).

[0245] In some implementations, the indication may be an ENUMERATED format or a Boolean value. If the indication is present with a first specific value (e.g., ‘true’ or 1), the UE may consider that the associated cell and / or the associated beam applies the combination of cell-level and beam-level conditions; if the indication is absent or is present with a second specific value (e.g., ‘false’ or 0), the UE may consider that the associated cell and / or the associated beam does not apply the combination of cell-level and beam-level conditions.

[0246] In some implementations, if the indication indicates that the combination of cell-level and beam-level conditions is applied, the UE may trigger the LTM execution only if the UE considers that all the cell-level conditions and all the beam-level conditions are satisfied.

[0247] In some implementations, if the indication indicates that the combination of cell-level and beam-level conditions is not applied, the UE may trigger the LTM execution if the UE considers that all the cell-level conditions are satisfied, if the UE considers that all the beam-level conditions are satisfied, or if the UE considers that all the cell-level conditions and all the beam-level conditions are satisfied.

[0248] In some implementations, when the UE considers that all cell-level conditions associated with a candidate cell are satisfied, and for each candidate beam associated with the candidate cell the UE considers that all corresponding beam-level conditions are not satisfied, the UE may check whether any of the beams associated with the candidate cell has a beam-level condition timer (e.g., the TTT) running.

[0249] In some implementations, if at least one beam has a beam-level condition with a running TTT, the UE may check all beams whose beam-level conditions have a running TTT.

[0250] In some implementations, upon a beam satisfying the beam-level condition, the UE may stop the running TTT of the other beams.

[0251] In some implementations, upon a beam satisfying the beam-level condition, the UE may execute the conditional LTM using the beam.

[0252] In some implementations, if an associated candidate beam has a running TTT and the remaining TTT duration is shorter than a threshold, the UE may defer the execution of conditional LTM until the candidate beam satisfies the L1 / L3 beam-level condition. In some implementations, if an associated candidate beam has a running TTT and the remaining TTT duration is longer than the threshold, the UE may execute the conditional LTM without deferring and without using a beam, for example by performing a RACH-based conditional LTM.

[0253] In some implementations, if all the beams do not satisfy the beam-level conditions, the UE may execute the conditional LTM without using a beam.

[0254] In some implementations, if all the beams do not satisfy the beam-level conditions, and there is at least one activated beam associated with the candidate cell, the UE may select an activated beam and execute the conditional LTM with the selected beam. More specifically, the UE may select the activated beam based on the beam quality or by the UE’s implementation.

[0255] In some implementations, if there is no beam whose beam-level condition is running TTT, the UE may execute the conditional LTM towards the candidate cell without using a beam.

[0256] In some implementations, if there is no beam whose beam-level condition is running TTT, the UE may select a beam associated with the candidate cell and execute the conditional LTM towards the candidate cell using the selected beam. In some implementations, the UE may select the beam with the best quality. In some implementations, if there is at least one activated beam associated with the candidate cell, the UE may select an activated beam and execute the conditional LTM with the selected beam. More specifically, the UE may select the activated beam based on the beam quality or by the UE’s implementation. In some implementations, the UE may select the beam by the UE’s implementation.

[0257] In some implementations, when the UE considers that all cell-level conditions associated with a candidate cell are satisfied, and all beam-level conditions corresponding to each candidate beam associated with the candidate cell are not satisfied, the UE may start a timer. In some implementations, the length of the timer may be configured via an RRC message (e.g., in the LTM-Config IE or in the LTM-Candidate IE). In some implementations, the length of the timer may be shorter than the TTT. In some implementations, while the timer is running, if the RRC layer of the UE considers that a candidate beam associated with the candidate cell satisfies the beam-level condition, the UE may stop the timer and execute the conditional LTM using that candidate beam. In some implementations, if the timer expires, the UE may execute the conditional LTM without using a beam. In some implementations, if the timer expires, the UE may execute the conditional LTM using the beam with the best quality. In some implementations, if the timer expires, if there is at least one activated beam associated with the candidate cell, the UE may select an activated beam and execute the conditional LTM using the selected beam.

[0258] It should be noted that the UE’s use of a beam for executing CLTM may include transmitting a configured grant specific to that beam to the candidate cell. It should also be noted that the UE may optionally use the beam for executing CLTM.

[0259] FIG. 2A is a flowchart illustrating a method / process 200 performed by a UE for performing a CLTM operation, according to an example implementation of the present disclosure. In the action 202, the process 200 may start by receiving, from a serving cell, a CLTM configuration indicating a CLTM candidate cell. In the action 204, the process 200 may determine whether at least one condition is satisfied. In some implementations, the at least one condition may include at least one L1 condition and / or at least one L3 condition. For example, the at least one condition may include one or more L1 conditions, one or more L3 conditions, or a combination of one or more L1 conditions and one or more L3 conditions.

[0260] In the action 206, the process 200 may start a first timer in response to determining that the at least one condition is satisfied. In some implementations, the first timer may be referred to as the TTT in the present disclosure. In the action 208, the process 200 may trigger a CLTM switch to the CLTM candidate cell after the first timer expires. In some implementations, the UE may initiate the CLTM switch in response to expiration of the first timer. The process 200 may then end.

[0261] The steps / actions shown in FIG. 2A 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. 2A may be omitted in some implementations and one or more actions shown in FIG. 2A may be combined.

[0262] The method illustrated in FIG. 2A addresses the technical problem of how to reliably and efficiently trigger a CLTM switch while avoiding unstable cell switching caused by transient radio conditions. For example, immediate execution of a cell switch upon satisfaction of a condition may lead to unnecessary mobility actions, increased signaling overhead, or degraded radio performance due to short-term fluctuations in measurements. By introducing a timer (e.g., the TTT) that is started only after the at least one condition is satisfied and by triggering the CLTM switch only after the timer expires, the disclosed method provides a controlled and stable decision mechanism. The advantageous technical effect is that the UE ensures that the triggering condition persists for a sufficient duration before executing the CLTM switch, thereby improving robustness of mobility decisions, reducing unnecessary or oscillatory cell switches, enhancing overall mobility performance, and optimizing radio resource utilization with minimal additional signaling.

[0263] In some implementations, the at least one condition may include one or more L1 conditions. For example, the at least one condition may include at least one L1 beam-level condition and / or at least one L1 cell-level condition. For example, the at least one condition may include multiple L1 conditions, including a first L1 condition associated with a candidate beam and a second L1 condition associated with a current beam.

[0264] In some implementations, the action 204 may be performed by a MAC layer of the UE and the condition in the action 204 may correspond to L1 conditions. Determining whether the at least one condition is satisfied may include at least one of the following: determining, by the MAC layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L1 beam-level condition based on a first L1 beam-level measurement result of the candidate beam; determining, by the MAC layer of the UE, whether a current beam associated with the serving cell satisfies a second L1 beam-level condition based on a second L1 beam-level measurement result of the current beam; determining, by the MAC layer of the UE, whether the candidate cell satisfies a first L1 cell-level condition based on a first L1 cell-level measurement result of the candidate cell; and determining, by the MAC layer of the UE, whether the serving cell satisfies a second L1 cell-level condition based on a second L1 cell-level measurement result of the serving cell.

[0265] In some implementations, the first timer may be maintained by the MAC layer of the UE. In some implementations, the first timer may be started by the MAC layer of the UE. The CLTM switch may be triggered by the MAC layer of the UE after the first timer expires. The MAC layer of the UE may send an indication to an RRC layer of the UE in response to triggering the CLTM switch, where the indication may include a CLTM configuration ID associated with the satisfied at least one condition. In some implementations, the indication may include a candidate CLTM configuration ID (e.g., the ltm-ConfigId) for indicating the candidate configuration that corresponds to the candidate cell associated with the first timer.

[0266] In some implementations, the MAC layer of the UE may stop the first timer in response to determining that the at least one condition becomes unsatisfied or in response to performing a MAC reset. For example, if the first timer is started by the MAC layer due to satisfaction of a first L1 beam-level condition associated with a first candidate beam, the MAC layer of the UE may stop the first timer when the first L1 beam-level condition becomes unsatisfied. In some implementations, the MAC layer of the UE may stop the first timer when the UE is performing MAC reset or when the UE determines to perform the MAC reset.

[0267] In some implementations, the at least one condition may include one or more L3 conditions. For example, the at least one condition may include at least one L3 beam-level condition and / or at least one L3 cell-level condition. For example, the at least one condition may include multiple L3 conditions, including a first L3 condition associated with a candidate beam and a second L3 condition associated with a current beam.

[0268] In some implementations, the action 204 may be performed by an RRC layer of the UE and the condition in the action 204 may correspond to L3 conditions. Determining whether the at least one condition is satisfied may include at least one of the following: determining, by the RRC layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L3 beam-level condition based on a first L3 beam-level measurement result of the candidate beam; determining, by the RRC layer of the UE, whether a current beam associated with the serving cell satisfies a second L3 beam-level condition based on a second L3 beam-level measurement result of the current beam; determining, by the RRC layer of the UE, whether the candidate cell satisfies a first L3 cell-level condition based on a first L3 cell-level measurement result of the candidate cell; and determining, by the RRC layer of the UE, whether the serving cell satisfies a second L3 cell-level condition based on a second L3 cell-level measurement result of the serving cell.

[0269] In some implementations, the first timer may be maintained by the RRC layer of the UE. In some implementations, the first timer may be started by the RRC layer of the UE. Triggering the CLTM switch to the CLTM candidate cell may include instructing, by the RRC layer of the UE, the CLTM switch after the first timer expires. The RRC layer of the UE may stop the first timer in response to determining that the at least one condition becomes unsatisfied. For example, if the first timer is started by the RRC layer due to satisfaction of a second L3 cell-level condition associated with the serving cell, the RRC layer of the UE may stop the first timer when the second L3 cell-level condition becomes unsatisfied.

[0270] In some implementations, the at least one condition may further include one or more L1 conditions. For example, the at least one condition in the action 204 may include at least one L1 condition (e.g., at least one L1 beam-level condition and / or at least one L1 cell-level condition) and at least one L3 condition (at least one L3 beam-level condition and / or at least one L3 cell-level condition). Determining whether the at least one condition is satisfied may further include at least one of the following (e.g., in addition to the determination made by the RRC layer of the UE): determining, by a MAC layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L1 beam-level condition based on a first L1 beam-level measurement result of the candidate beam; determining, by the MAC layer of the UE, whether a current beam associated with the serving cell satisfies a second L1 beam-level condition based on a second L1 beam-level measurement result of the current beam; determining, by the MAC layer of the UE, whether the candidate cell satisfies a first L1 cell-level condition based on a first L1 cell-level measurement result of the candidate cell; and determining, by the MAC layer of the UE, whether the serving cell satisfies a second L1 cell-level condition based on a second L1 cell-level measurement result of the serving cell.

[0271] In some implementations, the MAC layer of the UE may start a second timer in response to determining that at least one of the one or more L1 conditions is satisfied. The MAC layer of the UE may send an indication to the RRC layer of the UE in response to expiration of the second timer, where the indication may include a CLTM configuration ID associated with the satisfied one or more L1 conditions.

[0272] In some implementations, the CLTM switch may be triggered by the RRC layer of the UE after the RRC layer of the UE receives the indication from the MAC layer of the UE and the first timer expires.

[0273] In some implementations, the UE may receive an RRC message for configuring the first timer and a second timer. In some implementations, the second timer may be used to monitor the validity of the satisfied event. It should be noted that the second timer (e.g., for monitoring the validity of the satisfied event) in these implementations is functionally different from the second timer described in other implementations in which the MAC layer of the UE starts a second timer in response to determining that at least one of the one or more L1 conditions is satisfied. Specifically, in the former case, the RRC layer of the UE may start the second timer in response to satisfaction of the at least one condition. In some implementations, the duration of the second timer may be shorter than the duration of the first timer. The UE may stop the first timer in response to expiration of the second timer.

[0274] FIG. 2B is a flowchart illustrating a method / process 210 performed by a UE for performing a CLTM operation, according to another example implementation of the present disclosure. In the process 210, a mixed condition including at least one L1 condition and at least one L3 condition is considered. In the action 212, the process 210 may start by receiving, from a serving cell, a CLTM configuration indicating a CLTM candidate cell. In the action 214, the process 210 may determine whether at least one L3 condition associated with the CLTM candidate cell is satisfied. In the action 216, the process 210 may start a first timer in response to determining that at least one L3 condition is satisfied. In some implementations, the action 214 and the action 216 may be performed by the RRC layer of the UE.

[0275] In the action 218, the process 210 may determine whether at least one L1 condition associated with the CLTM candidate cell is satisfied. In the action 220, the process 210 may start a second timer in response to determining that at least one L1 condition is satisfied. In some implementations, the action 218 and the action 220 may be performed by the MAC layer of the UE.

[0276] In the action 222, the process 210 may trigger a CLTM switch to the LTM candidate cell after the first timer expires and the second timer expires. In some implementations, the action 222 may be performed by the RRC layer of the UE. In some implementations, the RRC layer of the UE may trigger the CLTM switch in response to expiration of both the first timer and the second timer. The process 210 may then end.

[0277] The steps / actions shown in FIG. 2B 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. 2B may be omitted in some implementations and one or more actions shown in FIG. 2B may be combined.

[0278] FIG. 3 is a block diagram illustrating a node 300 for wireless communication, according to an example implementation of the present disclosure. As illustrated in FIG. 3, a node 300 may include a transceiver 320, a processor 328, a memory 334, one or more presentation components 338, and at least one antenna 336. The node 300 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. 3).

[0279] Each of the components may directly or indirectly communicate with each other over one or more buses 340. The node 300 may be a UE or a BS that performs various functions disclosed with reference to FIGS. 1 through 2B.

[0280] The transceiver 320 has a transmitter 322 (e.g., transmitting / transmission circuitry) and a receiver 324 (e.g., receiving / reception circuitry) and may be configured to transmit and / or receive time and / or frequency resource partitioning information. The transceiver 320 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 320 may be configured to receive data and control channels.

[0281] The node 300 may include a variety of computer-readable media. Computer-readable media may be any available media that may be accessed by the node 300 and include volatile (and / or non-volatile) media and removable (and / or non-removable) media.

[0282] 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, AI / ML module(s), or data.

[0283] Computer-storage media may include RAM, ROM, EPROM, 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 (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.

[0284] 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.

[0285] The memory 334 may include computer-storage media in the form of volatile and / or non-volatile memory. The memory 334 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. 3, the memory 334 may store a computer-readable and / or computer-executable instructions 332 (e.g., software codes) that are configured to, when executed, cause the processor 328 to perform various functions disclosed herein, for example, with reference to FIGS. 1 through 2B. Alternatively, the instructions 332 may not be directly executable by the processor 328 but may be configured to cause the node 300 (e.g., when compiled and executed) to perform various functions disclosed herein.

[0286] The processor 328 (e.g., having processing circuitry) may include an intelligent hardware device, e.g., a Central Processing Unit (CPU), a microcontroller, an ASIC, etc. The processor 328 may include memory. The processor 328 may process the data 330 and the instructions 332 received from the memory 334, and information transmitted and received via the transceiver 320, the baseband communications module, and / or the network communications module. The processor 328 may also process information to send to the transceiver 320 for transmission via the antenna 336 to the network communications module for transmission to a CN.

[0287] One or more presentation components 338 may present data indications to a person or another device. Examples of presentation components 338 may include a display device, a speaker, a printing component, a vibrating component, etc.

[0288] 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

A User Equipment (UE) for performing a Conditional Layer 1 / Layer 2 Triggered Mobility (CLTM) 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 serving cell, a CLTM configuration indicating a CLTM candidate cell;　　　　　　　　determine whether at least one condition is satisfied;　　　　　　　　start a first timer in response to determining that the at least one condition is satisfied; and　　　　　　　　trigger a CLTM switch to the CLTM candidate cell after the first timer expires.The UE of claim 1, wherein:　　　　the at least one condition comprises one or more Layer-1 (L1) conditions, and　　　　determining whether the at least one condition is satisfied comprises at least one of the following:　　　　　　　　determining, by a Medium Access Control (MAC) layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L1 beam-level condition based on a first L1 beam-level measurement result of the candidate beam;　　　　　　　　determining, by the MAC layer of the UE, whether a current beam associated with the serving cell satisfies a second L1 beam-level condition based on a second L1 beam-level measurement result of the current beam;　　　　　　　　determining, by the MAC layer of the UE, whether the candidate cell satisfies a first L1 cell-level condition based on a first L1 cell-level measurement result of the candidate cell; and　　　　　　　　determining, by the MAC layer of the UE, whether the serving cell satisfies a second L1 cell-level condition based on a second L1 cell-level measurement result of the serving cell.The UE of claim 2, wherein:　　　　the first timer is started by the MAC layer of the UE,　　　　the CLTM switch is triggered by the MAC layer of the UE after the first timer expires, and　　　　the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to:　　　　　　　　send, by the MAC layer of the UE, an indication to a Radio Resource Control (RRC) layer of the UE in response to triggering the CLTM switch, wherein the indication comprises a CLTM configuration ID associated with the satisfied at least one condition.The UE of claim 3, wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to:　　　　stop, by the MAC layer of the UE, the first timer in response to determining that the at least one condition becomes unsatisfied or in response to performing a MAC reset.The UE of claim 1, wherein:　　　　the at least one condition comprises one or more Layer-3 (L3) conditions, and　　　　determining whether the at least one condition is satisfied comprises at least one of the following:　　　　　　　　determining, by a Radio Resource Control (RRC) layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L3 beam-level condition based on a first L3 beam-level measurement result of the candidate beam;　　　　　　　　determining, by the RRC layer of the UE, whether a current beam associated with the serving cell satisfies a second L3 beam-level condition based on a second L3 beam-level measurement result of the current beam;　　　　　　　　determining, by the RRC layer of the UE, whether the candidate cell satisfies a first L3 cell-level condition based on a first L3 cell-level measurement result of the candidate cell; and　　　　　　　　determining, by the RRC layer of the UE, whether the serving cell satisfies a second L3 cell-level condition based on a second L3 cell-level measurement result of the serving cell.The UE of claim 5, wherein:　　　　the first timer is started by the RRC layer of the UE,　　　　triggering the CLTM switch to the CLTM candidate cell comprises instructing, by the RRC layer of the UE, the CLTM switch after the first timer expires, and　　　　the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to:　　　　　　　　stop, by the RRC layer of the UE, the first timer in response to determining that the at least one condition becomes unsatisfied.The UE of claim 5, wherein:　　　　the at least one condition further comprises one or more Layer-1 (L1) conditions, and　　　　determining whether the at least one condition is satisfied further comprises at least one of the following:　　　　　　　　determining, by a Medium Access Control (MAC) layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L1 beam-level condition based on a first L1 beam-level measurement result of the candidate beam;　　　　　　　　determining, by the MAC layer of the UE, whether a current beam associated with the serving cell satisfies a second L1 beam-level condition based on a second L1 beam-level measurement result of the current beam;　　　　　　　　determining, by the MAC layer of the UE, whether the candidate cell satisfies a first L1 cell-level condition based on a first L1 cell-level measurement result of the candidate cell; and　　　　　　　　determining, by the MAC layer of the UE, whether the serving cell satisfies a second L1 cell-level condition based on a second L1 cell-level measurement result of the serving cell.The UE of claim 7, wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to:　　　　start a second timer, by the MAC layer of the UE, in response to determining that at least one of the one or more L1 conditions is satisfied; and　　　　send, by the MAC layer of the UE, an indication to the RRC layer of the UE in response to expiration of the second timer, wherein the indication comprises a CLTM configuration ID associated with the satisfied one or more L1 conditions.The UE of claim 8, wherein:　　　　 the CLTM switch is triggered by the RRC layer of the UE after the RRC layer of the UE receives the indication from the MAC layer of the UE and the first timer expires.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 a Radio Resource Control (RRC) message for configuring the first timer and a second timer;　　　　start, by the RRC layer of the UE, the second timer in response to satisfaction of the at least one condition; and　　　　stop the first timer in response to expiration of the second timer.A Base Station (BS) for configuring a Conditional Layer 1 / Layer 2 Triggered Mobility (CLTM) 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) via a serving cell, a CLTM configuration indicating a CLTM candidate cell, wherein:　　　　　　　　the UE determines whether at least one condition is satisfied,　　　　　　　　the UE starts a first timer in response to determining that the at least one condition is satisfied, and　　　　　　　　the UE triggers a CLTM switch to the CLTM candidate cell after the first timer expires.The BS of claim 11, wherein:　　　　the at least one condition comprises one or more Layer-1 (L1) conditions and one or more Layer-3 (L3) conditions,　　　　the UE determines whether at least one of the one or more L1 conditions is satisfied by at least one of the following:　　　　　　　　determining, by a Medium Access Control (MAC) layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L1 beam-level condition based on a first L1 beam-level measurement result of the candidate beam;　　　　　　　　determining, by the MAC layer of the UE, whether a current beam associated with the serving cell satisfies a second L1 beam-level condition based on a second L1 beam-level measurement result of the current beam;　　　　　　　　determining, by the MAC layer of the UE, whether the candidate cell satisfies a first L1 cell-level condition based on a first L1 cell-level measurement result of the candidate cell; and　　　　　　　　determining, by the MAC layer of the UE, whether the serving cell satisfies a second L1 cell-level condition based on a second L1 cell-level measurement result of the serving cell, and　　　　the UE determines whether at least one of the one or more L3 conditions is satisfied by at least one of the following:　　　　　　　　determining, by a Radio Resource Control (RRC) layer of the UE, whether a candidate beam associated with the candidate cell satisfies a first L3 beam-level condition based on a first L3 beam-level measurement result of the candidate beam;　　　　　　　　determining, by the RRC layer of the UE, whether a current beam associated with the serving cell satisfies a second L3 beam-level condition based on a second L3 beam-level measurement result of the current beam;　　　　　　　　determining, by the RRC layer of the UE, whether the candidate cell satisfies a first L3 cell-level condition based on a first L3 cell-level measurement result of the candidate cell; and　　　　　　　　determining, by the RRC layer of the UE, whether the serving cell satisfies a second L3 cell-level condition based on a second L3 cell-level measurement result of the serving cell.The BS of claim 11, wherein:　　　　the first timer is started by the MAC layer of the UE,　　　　the CLTM switch is triggered by the MAC layer of the UE after the first timer expires,　　　　the MAC layer of the UE sends an indication to a Radio Resource Control (RRC) layer of the UE in response to triggering the CLTM switch, and　　　　the indication comprises a CLTM configuration ID associated with the satisfied at least one condition.The BS of claim 11, wherein:　　　　the first timer is started by the RRC layer of the UE,　　　　the RRC layer of the UE triggers the CLTM switch to the CLTM candidate cell after the first timer expires, and　　　　the RRC layer of the UE stops the first timer in response to determining that the at least one condition becomes unsatisfied.A method performed by a User Equipment (UE) for performing a Conditional Layer 1 / Layer 2 Triggered Mobility (CLTM) operation, the method comprising:　　　　receiving, from a serving cell, a CLTM configuration indicating a CLTM candidate cell;　　　　determining whether at least one condition is satisfied;　　　　starting a first timer in response to determining that the at least one condition is satisfied; and　　　　triggering a CLTM switch to the CLTM candidate cell after the first timer expires.

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