Method and apparatus for conditional layer 1 / layer 2 triggered mobility in wireless communication systems

Abstract

Methods and apparatuses for conditional Layer 1 / Layer 2 Triggered Mobility (LTM) in wireless communication systems are provided. The method includes receiving, from a source cell, a Radio Resource Control (RRC) configuration that configures a set of conditions for evaluating one or more candidate cells; performing a Layer 1 (L1) measurement on the one or more candidate cells; determining, based on the L1 measurement, which of the one or more candidate cells satisfies at least one condition in the set of conditions; transmitting, to the source cell, a cell switch notification identifying at least one candidate cell determined to satisfy the at least one condition; receiving, from the source cell, a Physical Downlink Control Channel (PDCCH) order that is responsive to the cell switch notification; and performing synchronization with the at least one candidate cell identified in the cell switch notification in response to receiving the PDCCH order.

Description

METHOD AND APPARATUS FOR CONDITIONAL LAYER 1 / LAYER 2 TRIGGERED MOBILITY IN WIRELESS COMMUNICATION SYSTEMS

[0001] The present disclosure is related to wireless communication and, more specifically, to methods and apparatuses for conditional Layer 1 / Layer 2 Triggered Mobility (LTM) in wireless communication systems.

[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) system, 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 increase, however, there exists a need for further improvements in the art.Summery of Invention

[0003] The present disclosure is related to methods and apparatuses for conditional Layer 1 / Layer 2 Triggered Mobility (LTM) in wireless communication systems.

[0004] According to a first aspect of the present disclosure, a User Equipment (UE) is provided. The UE includes 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 source cell, a Radio Resource Control (RRC) configuration that configures a set of conditions for evaluating one or more candidate cells; perform a Layer 1 (L1) measurement on the one or more candidate cells; determine, based on the L1 measurement, which of the one or more candidate cells satisfies at least one condition in the set of conditions; transmit, to the source cell, a cell switch notification identifying at least one candidate cell determined to satisfy the at least one condition; receive, from the source cell, a Physical Downlink Control Channel (PDCCH) order that is responsive to the cell switch notification; and perform synchronization with the at least one candidate cell identified in the cell switch notification in response to receiving the PDCCH order.

[0005] In some implementations of the first aspect of the present disclosure, performing synchronization with the at least one candidate cell includes transmitting a Physical Random Access Channel (PRACH) preamble to the at least one candidate cell identified in the cell switch notification and receiving, from the source cell, Timing Advance (TA) information corresponding to the at least one candidate cell, and where the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to execute, after performing the synchronization with the at least one candidate cell successfully, a cell switch procedure to switch from the source cell to one of the at least one candidate cell based on the TA information.

[0006] In some implementations of the first aspect of the present disclosure, receiving, from the source cell, the TA information includes receiving a Medium Access Control (MAC) Control Element (CE) including the TA information from the source cell.

[0007] In some implementations of the first aspect of the present disclosure, the L1 measurement includes at least one of an L1-Reference Signal Received Power (L1-RSRP) measurement, or an L1-Signal to Interference plus Noise Ratio (L1-SINR) measurement for each of the one or more candidate cells.

[0008] In some implementations of the first aspect of the present disclosure, the set of conditions includes at least one of a first condition that a first L1 measurement result of a candidate cell of the one or more candidate cells becomes better than a second L1 measurement result of the source cell by an offset value, a second condition that the first L1 measurement result of the candidate cell exceeds a first threshold, or a third condition that the second L1 measurement result of the source cell falls below a second threshold while the first L1 measurement result of the candidate cell exceeds a third threshold.

[0009] In some implementations of the first aspect of the present disclosure, the cell switch notification includes, for each candidate cell of the at least one candidate cell determined to satisfy the at least one condition, at least one of a Reference Signal (RS) index, a Transmission Configuration Indicator (TCI) state identifier, or a candidate configuration index.

[0010] In some implementations of the first aspect of the present disclosure, the cell switch notification excludes any of the one or more candidate cells that fails to satisfy any condition in the set of conditions.

[0011] In some implementations of the first aspect of the present disclosure, the RRC configuration includes a Layer 1 / Layer 2 Triggered Mobility (LTM) configuration.

[0012] According to a second aspect of the present disclosure, a method performed by a User Equipment (UE) for conditional Layer 1 / Layer 2 Triggered Mobility (LTM) is provided. The method includes receiving, from a source cell, a Radio Resource Control (RRC) configuration that configures a set of conditions for evaluating one or more candidate cells; performing a Layer 1 (L1) measurement on the one or more candidate cells; determining, based on the L1 measurement, which of the one or more candidate cells satisfies at least one condition in the set of conditions; transmitting, to the source cell, a cell switch notification identifying at least one candidate cell determined to satisfy the at least one condition; receiving, from the source cell, a Physical Downlink Control Channel (PDCCH) order that is responsive to the cell switch notification; and performing synchronization with the at least one candidate cell identified in the cell switch notification in response to receiving the PDCCH order.

[0013] According to a third aspect of the present disclosure, a Base Station (BS) is provided. The BS includes at least one processor and at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the BS to transmit, to a User Equipment (UE), a Radio Resource Control (RRC) configuration that configures a set of conditions for evaluating one or more candidate cells; receive, from the UE, a cell switch notification identifying at least one candidate cell from the one or more candidate cells, where the at least one candidate cell is determined by the UE to satisfy at least one condition in the set of conditions based on a Layer 1 (L1) measurement performed by the UE on the one or more candidate cells; and transmit, to the UE, a Physical Downlink Control Channel (PDCCH) order in response to receiving the cell switch notification, where the PDCCH order causes the UE to perform synchronization with the at least one candidate cell identified in the cell switch notification.

[0014] In some implementations of the third aspect of the present disclosure, the one or more computer-executable instructions, when executed by the at least one processor, further cause the BS to transmit, to the UE, Timing Advance (TA) information corresponding to the at least one candidate cell identified in the cell switch notification.

[0015] In some implementations of the third aspect of the present disclosure, transmitting, to the UE, the TA information includes transmitting a Medium Access Control (MAC) Control Element (CE) including the TA information to the UE.

[0016] In some implementations of the third aspect of the present disclosure, the cell switch notification includes, for each candidate cell of the at least one candidate cell determined to satisfy the at least one condition, at least one of a Reference Signal (RS) index, a Transmission Configuration Indicator (TCI) state identifier, or a candidate configuration index.

[0017] In some implementations of the third aspect of the present disclosure, the set of conditions includes at least one of a first condition that a first L1 measurement result of a candidate cell of the one or more candidate cells becomes better than a second L1 measurement result of a source cell of the UE by an offset value, a second condition that the first L1 measurement result of the candidate cell exceeds a first threshold, or a third condition that the second L1 measurement result of the source cell falls below a second threshold while the first L1 measurement result of the candidate cell exceeds a third threshold.

[0018] In some implementations of the third aspect of the present disclosure, the RRC configuration includes a Layer 1 / Layer 2 Triggered Mobility (LTM) configuration.

[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 schematic diagram illustrating an LTM cell switch procedure with various phases, according to an example implementation of the present disclosure.

[0021] FIG. 2 is a schematic diagram illustrating a conditional LTM procedure without cell switch notification and with RAR from target cell, according to an example implementation of the present disclosure.

[0022] FIG. 3 is a schematic diagram illustrating a conditional LTM procedure without cell switch notification and with TA from source cell, according to an example implementation of the present disclosure.

[0023] FIG. 4 is a schematic diagram illustrating a conditional LTM procedure without cell switch notification and with UE based TA measurement, according to an example implementation of the present disclosure.

[0024] FIG. 5 is a schematic diagram illustrating a conditional LTM procedure with cell switch notification and with RAR from the target cell, according to an example implementation of the present disclosure.

[0025] FIG. 6 is a schematic diagram illustrating a conditional LTM procedure with cell switch notification and with RAR from the source cell, according to an example implementation of the present disclosure.

[0026] FIG. 7 is a schematic diagram illustrating a conditional LTM procedure with cell switch notification and NW synchronization with RAR from candidate cell, according to an example implementation of the present disclosure.

[0027] FIG. 8 is a schematic diagram illustrating a conditional LTM procedure 800 with cell switch notification and NW synchronization with TA value from source cell, according to an example implementation of the present disclosure.

[0028] FIG. 9 is a flowchart illustrating a method / process for conditional LTM in a wireless communication system, according to an example implementation of the present disclosure.

[0029] FIG. 10 is a block diagram illustrating node for wireless communications, in accordance with various aspects of the present disclosure.

[0030] Some of the abbreviations in the present application are defined as follows and, unless otherwise specified, the abbreviations have the following meanings: Abbreviation　　　　　　　　Full name 3GPP　　　　　　　　　　　　3rd Generation Partnership Project 5G　　　　　　　　　　　　　　　　5th Generation ACK　　　　　　　　　　　　Acknowledgment AI　　　　　　　　　　　　　　　　Artificial Intelligence AL　　　　　　　　　　　　　　　　Aggregation Level ARFCN　　　　　　　　　　　　Absolute Radio Frequency Channel Number BFD　　　　　　　　　　　　　　　　Beam Failure Detection BM　　　　　　　　　　　　　　　　Beam Management BWP　　　　　　　　　　　　Band Width Part CA　　　　　　　　　　　　　　　　Carrier Aggregation CORESET　　　　　　　　Control Resource Set CC　　　　　　　　　　　　　　　　Component Carrier CCE　　　　　　　　　　　　　　　　Control Chanel Element CRC　　　　　　　　　　　　Cyclic Redundancy Check C-RNTI　　　　　　　　　　　　Cell Radio Network Temporary Identifier CS-RNTI　　　　　　　　　　　　Configured Scheduling Radio Network Temporary Identifier CSS　　　　　　　　　　　　　　　　Common Search Space CSI　　　　　　　　　　　　　　　　Channel State Information DC　　　　　　　　　　　　　　　　Dual Connectivity DCI　　　　　　　　　　　　　　　　Downlink Control Information DL　　　　　　　　　　　　　　　　Downlink GC-PDCCH　　　　　　　　Group Common Physical Downlink Control Channel HARQ　　　　　　　　　　　　Hybrid Automatic Repeat Request ID　　　　　　　　　　　　　　　　Identifier IE　　　　　　　　　　　　　　　　Information Element IIoT　　　　　　　　　　　　　　　　Industrial Internet of Things LSB　　　　　　　　　　　　　　　　Least Significant Bit LTE　　　　　　　　　　　　　　　　Long Term Evolution L1　　　　　　　　　　　　　　　　Layer 1 L1-RSRP　　　　　　　　　　　　Layer 1 reference signal received power LMF　　　　　　　　　　　　Location Management Function LRR　　　　　　　　　　　　　　　　Link Recovery Request LTM　　　　　　　　　　　　Layer 1 / Layer 2 Triggered Mobility MAC　　　　　　　　　　　　Medium Access Control MCG　　　　　　　　　　　　Master Cell Group MCS-C-RNTI　　　　　　　　Modulation Coding Scheme Cell Radio Network Temporary Identifier mTRP　　　　　　　　　　　　Multiple Transmission Reception Point MIMO　　　　　　　　　　　　Multiple-input Multiple-output MSB　　　　　　　　　　　　Most Significant Bit MSG　　　　　　　　　　　　Message ML　　　　　　　　　　　　　　　　Machine Learning NACK　　　　　　　　　　　　Negative Acknowledgment NDI　　　　　　　　　　　　　　　　New Data Indicator NR　　　　　　　　　　　　　　　　New RAT / Radio NW　　　　　　　　　　　　　　　　Network NUL　　　　　　　　　　　　Normal Uplink PCI　　　　　　　　　　　　　　　　Physical Cell ID PCell　　　　　　　　　　　　Primary Cell PSCell　　　　　　　　　　　　Primary Secondary Cell PBCH　　　　　　　　　　　　Physical Broadcast Channel PDCCH　　　　　　　　　　　　Physical Downlink Control Channel PDSCH　　　　　　　　　　　　Physical Downlink Shared Channel PDU　　　　　　　　　　　　Protocol Data Unit PHY　　　　　　　　　　　　Physical PRACH　　　　　　　　　　　　Physical Random Access Channel PTAG　　　　　　　　　　　　Primary Timing Advance Group PUCCH　　　　　　　　　　　　Physical Uplink Control Channel PUSCH　　　　　　　　　　　　Physical Uplink Shared Channel RA　　　　　　　　　　　　　　　　Random Access RAN　　　　　　　　　　　　Radio Access Network RAR　　　　　　　　　　　　Random Access Response Rel　　　　　　　　　　　　　　　　Release RMSI　　　　　　　　　　　　Remaining Minimum System Information RNTI　　　　　　　　　　　　Radio Network Temporary Identifier RRC　　　　　　　　　　　　Radio Resource Control RRM　　　　　　　　　　　　Radio Resource Measurement RS　　　　　　　　　　　　　　　　Reference Signal RSRP　　　　　　　　　　　　Reference Signal Received Power RV　　　　　　　　　　　　　　　　Redundancy Version SCell　　　　　　　　　　　　Secondary Cell SCG　　　　　　　　　　　　　　　　Secondary Cell Group SCS　　　　　　　　　　　　　　　　Subcarrier Spacing SDM　　　　　　　　　　　　Spatial Division Multiplexing SINR　　　　　　　　　　　　Signal to Interference plus Noise Ratio SpCell　　　　　　　　　　　　Special Cell SR　　　　　　　　　　　　　　　　Scheduling Request SRS　　　　　　　　　　　　　　　　Sounding Reference Signal SRI　　　　　　　　　　　　　　　　SRS Resource Indicator SSB　　　　　　　　　　　　　　　　Synchronization Signal Block STAG　　　　　　　　　　　　Secondary Timing Advance Group STxMP　　　　　　　　　　　　Simultaneous Transmission on Multiple Panels SUL　　　　　　　　　　　　　　　　Supplementary Uplink TA　　　　　　　　　　　　　　　　Timing Advance TAG　　　　　　　　　　　　　　　　Timing Advance Group TB　　　　　　　　　　　　　　　　Transport Block TBS　　　　　　　　　　　　　　　　Transport Block Size TCI　　　　　　　　　　　　　　　　Transmission Configuration Indication TPMI　　　　　　　　　　　　Transmission Precoding Matrix Indicator TR　　　　　　　　　　　　　　　　Technical Report TRP　　　　　　　　　　　　　　　　Transmission Reception Point TS　　　　　　　　　　　　　　　　Technical Specification QCL　　　　　　　　　　　　Quasi-CoLocation UE　　　　　　　　　　　　　　　　User Equipment UL　　　　　　　　　　　　　　　　Uplink URLLC　　　　　　　　　　　　Ultra Reliable Low Latency Communication USS　　　　　　　　　　　　　　　　UE-Specific Search Space WG　　　　　　　　　　　　　　　　Working Group WI　　　　　　　　　　　　　　　　Working Item

[0031] 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.

[0032] 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.

[0033] For 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 shall not be narrowly confined to what is illustrated in the drawings.

[0034] 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 one implementation,” 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] A software implementation may include computer executable instructions 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 executable instructions and perform the disclosed network function(s) or algorithm(s).

[0040] The microprocessors or general-purpose computers may include Application-Specific Integrated Circuits (ASICs), programmable logic arrays, and / or one or more Digital Signal Processor (DSPs). Although some of the disclosed implementations are oriented to software installed and executing on computer hardware, alternative implementations implemented as firmware, as hardware, or as a combination of hardware and software are well within the scope of the present disclosure. The computer-readable medium includes but is not limited to Random Access Memory (RAM), Read Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), flash memory, Compact Disc Read-Only Memory (CD-ROM), magnetic cassettes, magnetic tape, magnetic disk storage, or any other equivalent medium capable of storing computer-readable instructions.

[0041] 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) typically includes at least one base station (BS), at least one UE, and one or more optional network elements that provide connection within a network. The UE communicates with the network such as a Core Network (CN), an Evolved Packet Core (EPC) network, an Evolved Universal Terrestrial RAN (E-UTRAN), a 5G Core (5GC), or an internet via a RAN established by one or more BSs.

[0042] 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, or a Personal Digital Assistant (PDA) with wireless communication capability. The UE is configured to receive and transmit signals over an air interface to one or more cells in a RAN. A UE may be referred to as a PHY / MAC / RLC / PDCP / SDAP entity. The PHY / MAC / RLC / PDCP / SDAP entity may be referred to as the UE.

[0043] 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 LTE (eLTE) that is LTE connected to 5GC, NR (often referred to as 5G), and / or LTE-A Pro. However, the scope of the present disclosure is not limited to these protocols.

[0044] 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, an 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 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.

[0045] 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.

[0046] Each cell (often referred to as a serving cell) may provide services to serve one or more UEs within its radio coverage, such that each cell schedules the DL (and optionally UL resources) to at least one UE within its radio coverage for DL (and optionally UL packet transmissions from the UE). The BS may communicate with one or more UEs in the radio communication system via the plurality of cells.

[0047] A cell may allocate sidelink (SL) resources for supporting the Proximity Service (ProSe) or Vehicle to Everything (V2X) service. Each cell may have overlapped coverage areas with other cells.

[0048] 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.

[0049] As described above, the frame structure for NR supports flexible configurations for accommodating various next generation (e.g., 5G) communication requirements, such as Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC), and Ultra-Reliable and Low-Latency Communication (URLLC), while fulfilling high reliability, high data rate, and low latency requirements. The Orthogonal Frequency-Division Multiplexing (OFDM) technology in the 3GPP may serve as a baseline for an NR waveform. The scalable OFDM numerology, such as adaptive sub-carrier spacing, channel bandwidth, and Cyclic Prefix (CP), may also be used.

[0050] 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.

[0051] 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.

[0052] Any two or more 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.

[0053] 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.

[0054] 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.

[0055] “A and / or B” in the present disclosure may refer to either A or B, both A and B, or at least one of A and B.

[0056] In this disclosure, “X / Y” may encompass the meanings of “X or Y,” “X and Y,” and “X and / or Y,” as indicated by two or more of the sentences, paragraphs, sub-bullets, points, actions, behaviors, terms, alternatives, aspects, examples, embodiments, or claims described in the following invention(s).

[0057] One aspect of the present disclosure may be applied in various contexts, including communications, communication equipment (such as mobile telephone apparatus, base station apparatus, wireless LAN apparatus, and / or sensor devices), integrated circuits (such as communication chips), and software programs, among others.

[0058] The terms “an antenna port” and “antenna ports,” as discussed in the present disclosure, may refer to “an antenna port used for transmission of PUSCH(s) / PUCCH(s)” and “antenna ports used for transmission of PUSCH(s) / PUCCH(s),” respectively.

[0059] Some of the terms, definitions, and / or abbreviations included in the present disclosure may either be sourced from existing documents (such as those from ETSI, ITU, or other sources) or may be newly created by experts from the 3GPP whenever there was a need for a precise vocabulary.

[0060] Examples of some selected terms in the present disclosure are provided as follows.

[0061] Antenna Panel: A conceptual term for a UE antenna implementation. It may be assumed that a panel may be an operational unit for controlling a transmit spatial filter (beam). A panel may typically include multiple antenna elements. In some implementations, a beam may be formed by a panel, and in order to form two beams simultaneously, two panels may be needed. Such simultaneous beamforming by multiple panels may be subject to the UE capability. A similar definition for “panel” may be applicable by applying spatial receiving filtering characteristics.

[0062] Beam: A beam may refer to a spatial (domain) filtering. In some implementations, the spatial filtering may be applied in the analog domain by adjusting a phase and / or an amplitude of a signal before being transmitted by a corresponding antenna element. In some implementations, the spatial filtering may be applied in the digital domain by the Multi-Input Multi-Output (MIMO) technique in the wireless communication system. For example, when a UE makes a PUSCH transmission by using a specific beam, this may imply that the UE makes the PUSCH transmission by using the specific spatial / digital domain filter. The beam may also be, but is not limited to be, represented as an antenna, an antenna port, an antenna element, a group of antennas, a group of antenna ports, or a group of antenna elements. The beam may also be formed by a certain reference signal resource. In short, the beam may be equivalent to a spatial domain filter through which the EM wave is radiated.

[0063] BWP: A subset of the total cell bandwidth of a cell may be referred to as a Bandwidth Part (BWP) and a Bandwidth Adaptation (BA) may be achieved by configuring the UE with BWP(s) and instructing the UE which of the configured BWPs is currently the active one. To enable a BA on the PCell, the gNB may configure the UE with UL and DL BWP(s). To enable the BA on SCells, in case of CA, the gNB may configure the UE with one or more DL BWPs (e.g., there may be no BWP in the UL). For the PCell, the initial BWP may be the BWP used for an initial access. For the SCell(s), the initial BWP may be the BWP configured for the UE to operate after an SCell activation. The UE may be configured with a first active uplink BWP by the firstActiveUplinkBWP IE. If the first active uplink BWP is configured for an SpCell, the firstActiveUplinkBWP IE field may contain the ID of the UL BWP to be activated upon performing the RRC (re-)configuration. If the field is absent, the RRC (re-)configuration may not impose a BWP switching. If the first active uplink BWP is configured for an SCell, the firstActiveUplinkBWP IE field may contain the ID of the uplink bandwidth part to be used upon the MAC-activation of an SCell.

[0064] TCI state: A TCI state may include parameters for configuring a QCL relationship between one or more DL reference signals and a target reference signal set. In some implementations, a target reference signal set may include the DMRS ports of a PDSCH, a PDCCH, a PUCCH, or a PUSCH. The reference signals may include UL or DL reference signals. In NR Rel-15 / 16, the TCI state may be used for a DL QCL indication, whereas the spatial relation information may be used for providing the UL spatial transmission filter information for the UL signal(s) or channel(s). A TCI state may include the information similar to the spatial relation information, which may be used for UL transmission. In other words, from the UL perspective, a TCI state may provide the UL beam information that may indicate the relationship between a UL transmission and the DL or UL reference signals (e.g., the CSI-RS, the SSB, the SRS, and the PTRS).

[0065] DCI: DCI may include downlink control information, and there may be various DCI formats used in a PDCCH. The DCI format may be a predefined format in which the downlink control information may be packed / formed and transmitted in a PDCCH.

[0066] HARQ: A functionality that ensures the delivery between peer entities at Layer 1 (e.g., Physical Layer). A single HARQ process may support one Transport Block (TB) when the physical layer is not configured for the downlink / uplink spatial multiplexing, and when the physical layer is configured for downlink / uplink spatial multiplexing, a single HARQ process may support one or more TBs. There may be one HARQ entity per serving cell. Each HARQ entity may support a parallel (number of) DL and UL HARQ process.

[0067] Network (NW): The NW may be a network node, a TRP, a cell, an eNB, a gNB, and / or a base station. In some implementations, the cell may be a SpCell (Special Cell), a PCell, a PSCell, and / or an SCell.

[0068] Serving Cell: A serving cell may be a PCell (Primary Cell), a PSCell, or an SCell (Secondary Cell). The serving cell may be an activated or a deactivated serving cell.

[0069] Special Cell (SpCell): For Dual Connectivity operation, the term Special Cell may refer to the PCell of the MCG (Master Cell Group) or the PSCell of the SCG (Secondary Cell Group) depending on if the MAC entity is associated to the MCG or the SCG, respectively. Otherwise, the term Special Cell may refer to the PCell. A Special Cell may support PUCCH (Physical Uplink Control CHannel) transmission and contention-based Random Access, and may be always activated.

[0070] In the present disclosure, although the term “gNB” may have been used throughout the document, it should be understood that the term “gNB” may be replaced by any other type of BS (e.g., an eNB).

[0071] A Synchronization Signal Block (SSB) may include, or consist of, a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), and a Physical Broadcast Channel (PBCH) payload. The PSS and the SSS may be pseudo-random sequences with a length equal to 127. The PBCH payload may include a Master Information Block (MIB) (24 bits in total) and an 8 bits payload. The information in the MIB may include: a System Frame Number (SFN), a sub-carrier space (SCS), a DeModulation Reference Signal (DMRS) configuration, an Access Control, and mainly a configuration for a System Information Block 1 (SIB1) acquisition. By decoding the PSS and the SSS, a User Equipment (UE) may be able to identify a Physical Cell Identity (PCI) for a corresponding cell and may determine the symbol boundary. Consequently, with the decoding of the PBCH, the UE may determine the frame boundary and may try to decode the Physical Downlink Control Channel (PDCCH).

[0072] When the UE moves from the coverage area of one cell to another cell, at some point a serving cell change may need to be performed to ensure that the radio connection and the radio quality are beyond a certain level. Currently, the serving cell change may be triggered by L3 measurements and may be done by RRC signaling triggered Reconfiguration with Synchronization for change of PCell and PSCell, as well as release and / or add SCells when applicable. All cases may involve complete L2 (and L1) resets in L3 based mobility, leading to longer latency, larger overhead, and longer interruption time than beam switch mobility. Thus, the goal of L1 / L2 triggered mobility enhancements may be to enable a serving cell change via L1 / L2 signaling, in order to reduce the latency, the overhead and the interruption time. Furthermore, when the UE can determine whether to switch the serving cell based on some defined conditions, the cell switch latency can be reduced dramatically. Hence, conditional Layer 1 / Layer 2 Triggered Mobility (LTM) may be introduced to enhance the handover process.

[0073] In transitioning from LTM procedures to conditional LTM in New Radio (NR), several challenges may emerge due to the differences in operational mechanisms. LTM processes may focus on fixed threshold parameters for triggering handovers and maintaining connectivity, which may not adequately respond to the real-time dynamics of modern mobile environments. This rigidity can lead to suboptimal resource utilization, increased latency, and potential service disruptions as user mobility patterns and network conditions fluctuate.

[0074] The objective of adopting conditional LTM may be to introduce a more dynamic and context-sensitive approach to mobility management. By leveraging adaptive triggers that consider factors such as user behavior, network load, and environmental changes, conditional LTM can optimize handover decisions and enhance the quality of experience for the UE in varying conditions. However, this shift may result in some changes on the measurement, the report, and the synchronization procedure. Thus, the present disclosure aims to address the possible impact on the LTM procedure if conditional LTM is applied.

[0075] When a UE moves from the coverage area of one cell to another cell, a serving cell change may need to be performed due to considering the maintenance of the connection and the quality of service between the serving cell and the UE. The main target of L1 / L2 based mobility may be to reduce latency in mobility, and thus support of L1 beam management and L1 based measurement may be needed to facilitate the scheduling efficiency. Specifically, the UE may receive an RRC pre-configuration to receive some information for candidate cells or at least one target cell before switching to the at least one target cell. Then, the UE may perform the cell switch based on the cell switch command with some mobility latency.

[0076] The mobility latency may include the time from the UE receiving the cell switch command to the UE performing the first DL reception / transmission based on the indicated beam of the target cell. More specifically, the time that the UE processes the cell switch command (Tcmd+Tprocessing,2), the UE executes DL synchronization (Tsearch+TΔ+Tmargin), the UE executes UL synchronization (TIU+TRAR), and the UE performs the first DL reception / transmission after the random access response (RAR) may be considered as handover interruption time, where Tcmdmay refer to time for processing L1 / L2 command, Tprocessing,2may refer to time for UE processing after cell switch command, Tsearchmay refer to time required to search the target cell, TΔmay refer to time for fine tracking and acquiring full timing information, Tmarginmay refer to time for SSB or CSI-RS post-processing, TIUmay refer to interruption uncertainty in acquiring the first available PRACH occasion in the target cell, and TRARmay refer to time for RAR delay. Furthermore, whether to switch the cell may depend on L1 measurement and report, and hence the procedure and method for the L1 measurement and report may be important to specify.

[0077] RRC pre-configuration

[0078] A source cell / BS may transmit a configuration or some information for candidate cells to a UE via RRC signaling. After receiving the RRC pre-configuration (e.g., an RRC reconfiguration message), the UE may store or / and apply the received configuration for the L1 / L2 triggered mobility procedure. In some implementations, the RRC pre-configuration may include resource allocation configuration (e.g., either time domain or frequency domain), DL synchronization specific configuration, UL synchronization specific configuration, BWP configuration, cell group configuration, measurement configuration, report configuration, beam management configuration (e.g., TCI state configuration), mobility scenarios configuration, DL control channel specific configuration, DL data channel specific configuration, UL control channel specific configuration, or / and UL data channel specific configuration.

[0079] In some implementations, the UE may receive RRC pre-configuration(s) of all candidate cells simultaneously. In some implementations, the UE may receive RRC pre-configuration of each candidate cell at different timings. In some implementations, the RRC pre-configuration may be applied by an RRC reconfiguration procedure. In some implementations, the RRC pre-configuration may include a reference configuration and a delta configuration.

[0080] Cell switch command

[0081] During the L1 / L2 triggered mobility procedure, the source cell may inform a UE of cell switching related information with a cell switch command. In some implementations, the cell switch command may refer to a (DL) MAC-CE. In some implementations, the cell switch command may include the IDs of candidate cells (e.g., PCI of candidate cells, additional PCI index, PCI index of serving cell), the ID of target cell (e.g., PCI index of target cell), RRC pre-configuration index associated with the candidate cells or the target cell, BWP information for the candidate cells or the target cell, TA information, associated reference signal information (e.g., SSB index or CSI-RS resource index), or / and TCI state information for the candidate cell(s) or the target cell. After receiving the cell switch command from the source cell, the UE may switch from the serving cell to the target cell indicated in the cell switch command. Preferably, the cell switching may refer to a PCell Change (e.g., switch from the source PCell to the target PCell), SCell change, or / and PSCell change. In some implementations, the target cell may be an SCell before switching. In some implementations, the target cell may be a PSCell before switching. In some implementations, the target cell may be a non-serving cell before switching.

[0082] DL synchronization

[0083] During the L1 / L2 triggered mobility procedure, a UE may execute the DL synchronization process to acquire DL time / frequency synchronization, DL system information, and DL data from the target cell. In some implementations, the UE may perform DL synchronization before processing the cell switch command to reduce the interruption time. In some implementations, the UE may perform DL synchronization after processing the cell switch command when the target cell is specifically indicated. In some implementations, the UE may receive information for DL synchronization from RRC pre-configuration, MAC-CE, or DCI from the source cell. Preferably, the received information may include logical cell ID (e.g., the IDs of the candidate cells (or PCIs of the candidate cells), or / and the ID of the target cell (or PCI of the target cell)), SSB index associated with the candidate cells, SSB index associated with the target cell, time / frequency domain information for the candidate cells, time / frequency domain information for the target cell, CSI resource index associated with the candidate cells, CSI resource index associated with the target cell, TCI state configuration associated with the candidate cells, or / and TCI state configuration associated with the target cell.

[0084] UL synchronization

[0085] During the L1 / L2 triggered mobility procedure, a UE may execute the UL synchronization process to evaluate the exact timing to send UL information / data to the target cell (e.g., timing advance acquisition). In some implementations, the UE may perform UL synchronization after finishing the DL synchronization process. In some implementations, the UE may perform UL synchronization before processing the cell switch command to reduce the interruption time. In some implementations, the UE may perform UL synchronization after processing the cell switch command when the target cell is specifically indicated. In some implementations, the UE may perform a Random Access (RA) procedure, possibly referring to contention-based RA procedure, contention-free RA procedure, 2-step RA procedure, 4-step RA procedure for the candidate cells or the target cell. In some implementations, the UE may perform a Random Access Channel-less (RACH-less) procedure (e.g., without performing RA procedure) for the candidate cells or the target cell. In some implementations, the UE may receive information for UL synchronization from RRC pre-configuration, MAC-CE, or DCI from the source cell. Preferably, the received information may include PRACH resource configuration associated with the candidate cells or the target cell, preamble sequence configuration associated with the candidate cells or the target cell, the RACH procedure indication, timing advance group index associated with the candidate cells or the target cell, UL carrier types (NUL or SUL) for the candidate cells or the target cell, SRS configuration associated with the candidate cells or the target cell, or / and TCI state configuration associated with the candidate cells or the target cell.

[0086] L1 measurement and report

[0087] A UE may perform and report measurement based on the received configuration or indication. L1 measurements may be further classified into L1 intra-frequency measurement or L1 inter-frequency measurement. In some implementations, L1 intra-frequency measurement and L1 inter-frequency measurement may be based on L1-RSRP through measuring SSB (e.g., SS-RSRP) or CSI-RS (e.g., CSI-RSRP). In some implementations, L1 intra-frequency measurement and L1 inter-frequency measurement may be based on L1-SINR through measuring SSB (e.g., SS-SINR) or CSI-RS (CSI-SINR). In some implementations, L1 intra-frequency measurement and L1 inter-frequency measurement may be based on L1-RSRQ through measuring SSB (e.g., SS-RSRQ) or CSI-RS (e.g., CSI-RSRQ).

[0088] In some implementations, the L1 measurement report may include one or some PCIs (e.g., PCIs of the candidate cells, PCI of the source cell, or PCI of the serving cell, or PCI of the target cell). In some implementations, the L1 measurement report may include one or some RS IDs.

[0089] In some implementations, L1 measurement report as UCI transmitted on PUCCH or PUSCH may be considered as the result of measurement from the perspective of the UE. In some implementations, L1 measurement report type may refer to periodic report on PUCCH, semi-persistent report on PUCCH or PUSCH, and aperiodic report on PUSCH. In some implementations, L1 measurement report may be transmitted on a MAC-CE.

[0090] CSI report content

[0091] In some implementations, CSI report may include Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), CSI-RS resource indicator (CRI), SS / PBCH block resource indicator (SSBRI), Layer Indicator (LI), Rank Indicator (RI), Capability Index, L1-RSRP, L1-SINR, or / and L1-RSRQ. In some implementations, the report may contain top K values among a set of measurement results by measuring CSI-RS resource(s) or SSB resource(s).

[0092] Cell term

[0093] In some implementations, a cell in the disclosure may refer to a PCell, a PSCell, a SpCell, an SCell, a candidate cell, a target cell, a neighbor cell, a serving cell or / and a source cell.

[0094] Inter-cell mobility scenarios may include, but not be limited to, intra-node mobility and inter-node mobility. Moreover, each scenario may correspond to intra-DU case, inter-DU case, intra-CU case, or / and inter-CU case. A network node (e.g., BS) may include one central unit (CU) and several distributed units (DUs). A CU may be a logical node hosting RRC, SDAP and PDCP protocols of the BS or RRC and PDCP protocols of the en-gNB that controls the operation of one or more DUs. A DU may be a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and the operation of the DU may be partly controlled by gNB-CU. One DU may support one or multiple cells. The CU may connect to the several DUs via F1 interfaces.

[0095] Intra-node mobility

[0096] In the intra-node mobility scenario, the serving cell and the target cell may operate on the same network node and share the same MAC entity (e.g., carrier aggregation scenario). The intra-node mobility scenario may be further classified into two cases, which are intra-CU with intra-DU case and intra-CU with inter-DU case.

[0097] In the case of intra-CU with intra-DU, the serving cell and the target cell may belong to the same DU and the same CU. In the case of intra-CU with inter-DU, the serving cell and the target cell may belong to the same CU but correspond to different DUs.

[0098] Inter-node mobility

[0099] In the inter-node mobility scenario, the serving cell and the target cell may operate on different network nodes. In other words, the serving cell and the target cell may belong to different CUs. A UE may apply separate MAC entity to the serving cell and the target cell (e.g., dual connectivity scenario). The serving cell may refer to the special cell or PCell and the target cell may refer to special cell, PSCell, or SCell.

[0100] FIG. 1 is a schematic diagram illustrating an LTM cell switch procedure 100 with various phases, according to an example implementation of the present disclosure. For the LTM cell switch procedure, as shown in FIG. 1, the procedure 100 may be divided into different parts such as LTM preparation phase, early synchronization phase, LTM cell switch phase, and LTM cell switch complete phase. Each part in the conditional LTM procedure may be revisited since the UE can determine the timing of performing cell switch when some predefined conditions are met in conditional LTM operation.

[0101] In the LTM preparation phase, the procedure 100 begins in action 102 where the UE may be in RRC_Connected mode with the gNB. In action 104, the UE may transmit a measurement report to the gNB, where the measurement report may contain measurement results of neighboring cells that the UE has measured. In action 106, the gNB may perform LTM candidate preparation based on the received measurement report, and during this preparation, the gNB may determine which cells are suitable candidates for the LTM procedure. In action 108, the gNB may transmit an LTM candidate configuration to the UE, where this configuration may include information about the candidate cells, measurement configurations, and conditions for cell switching. In action 110, the UE may transmit an RRC reconfiguration complete message to the gNB to acknowledge that the LTM candidate configuration has been successfully received and applied.

[0102] Following the preparation phase, the early synchronization phase may begin. In action 112, the UE may perform DL synchronization with candidate cells, where during this process, the UE may acquire downlink timing and frequency synchronization with one or more candidate cells. In action 114, the UE may perform UL synchronization with candidate cells, which may involve performing random access procedures or other synchronization mechanisms to establish uplink timing with the candidate cells.

[0103] The LTM cell switch execution phase may then commence with action 116, where the UE may transmit an L1 measurement report to the gNB, and this report may include Layer 1 measurements such as L1-RSRP or L1-SINR of the candidate cells. In action 118, the gNB may make an LTM cell decision based on the received L1 measurement report, where the gNB may determine which target cell the UE should switch to. In action 120, the gNB may transmit a cell switch command to the UE, where this command may be carried in a MAC CE and may include information about the target cell to switch to. In action 122, the UE may detach from the source cell upon receiving and processing the cell switch command.

[0104] The procedure concludes with the LTM cell switch complete phase. In action 124, the UE may perform a RACH procedure with the target cell if additional synchronization is needed, which may ensure that the UE has proper uplink synchronization with the new serving cell. Finally, in action 126, the UE may transmit an RRC reconfiguration complete message to confirm that the cell switch has been successfully completed and the UE is now connected to the target cell. The dotted boxes in the figure indicate optional or conditional steps that may or may not be performed depending on the specific implementation or scenario, while the solid arrows indicate the main flow of the procedure, showing the sequence of mandatory actions required for completing the LTM cell switch procedure.

[0105] In some implementations, the predefined conditions may include a condition that L1-RSRP / L1-SINR of a candidate cell becomes better by an amount of offset than L1-RSRP / L1-SINR of PCell / PSCell. In some implementations, the predefined conditions may include a condition that L1-RSRP / L1-SINR of a candidate cell becomes better than an absolute threshold. In some implementations, the predefined conditions may include a condition that L1-RSRP / L1-SINR of PCell / PSCell becomes worse than an absolute threshold1 AND L1-RSRP / L1-SINR of a candidate cell becomes better than another absolute threshold2.

[0106] The L1-RSRP / L1-SINR of a candidate cell may be derived from the beam with the highest measured quality (e.g., RSRP / SINR) in the candidate cell. In some implementations, the L1-RSRP / L1-SINR of a candidate cell may be derived from a certain consolidation method on a set of beams in the candidate cell. In some implementations, the L1-RSRP / L1-SINR of the PCell / PSCell may be derived from the beam currently indicated for PDCCH / PDSCH reception in the PCell / PSCell. In some implementations, the L1-RSRP / L1-SINR of the PCell / PSCell may be derived from a certain consolidation method on a set of beams in the PCell / PSCell.

[0107] In some implementations, gNB may be replaced by RAN or Network.

[0108] Cell switch notification

[0109] In some implementations, a UE may transmit a cell switch notification to the source cell to notify which target cell satisfies one or more than one predefined condition. The cell switch notification may include a target cell index, a TCI state ID, an RS index, or / and an LTM candidate configuration ID. Furthermore, the cell switch notification may be carried on a PUSCH (e.g., dynamic PUSCH, CG PUSCH) or a PUCCH (periodic PUCCH, dynamic PUCCH). In some implementations, the cell switch notification may be multiplexed with a CSI report in one PUSCH or PUCCH.

[0110] Switch latency

[0111] In some implementations, if the determined TCI state / RS for the selected candidate cell has been activated by the NW, the switch latency may not include SSB measurement / processing time.

[0112] In some implementations, if the determined TCI state / RS for the selected candidate cell has not been activated by the NW, the switch latency may include SSB measurement / processing time.

[0113] In some implementations, if the determined TCI state / RS for the selected candidate cell is reported as synced / activated in the cell switch request, the switch latency may not include SSB measurement / processing time.

[0114] In some implementations, if the determined TCI state / RS for the selected candidate cell is not reported as synced / activated, the switch latency may include SSB measurement / processing time.

[0115] UE performs early synchronization without cell switch request

[0116] In some implementations, the UE may perform L1 measurement without sending a cell switch notification after receiving an RRC reconfiguration message containing LTM candidate configuration and transmitting an RRC reconfiguration complete message. Then, the UE may evaluate whether the measurement result of one or more than one candidate cells meets the one or more than one conditions.

[0117] In some implementations, whether to perform early synchronization towards the candidate cell may be based on the predefined condition. If a cell satisfies the predefined condition, the UE may perform early synchronization to the cell. In other words, the UE may determine one or more than one candidate cell to perform DL synchronization and UL synchronization based on the one or more than one conditions and the measurement result. For DL synchronization, the UE may determine a TCI state ID / reference signal (RS) index for each of one or more than one candidate cell. For UL synchronization, the UE may perform a RACH procedure to the one or more than one candidate cell based on the determined TCI state / RS index. More specifically, the UE may transmit a PRACH to the one or more than one candidate cell based on the LTM candidate configuration (e.g., the ltm-EarlyUL-SyncConfig-r18 IE) and the one or more than one candidate cell may perform beam sweeping to select a correspondence beam for the UL synchronization (e.g., to receive PRACH from the UE).

[0118] In some implementations, the PRACH may include a specific preamble index / SSB index / CSI-RS index / PRACH configuration index to specify that the RACH procedure is for conditional LTM. In other words, a group of preamble indexes or a group of SSB indexes may be configured for conditional LTM purpose. In some implementations, an RRC parameter (e.g., the prach-ConfigurationIndex-condLTM IE) may be configured in RACH-ConfigGeneric to identify a random access procedure for conditional LTM.

[0119] In some implementations, after the UE transmits the PRACH to the one or more than one candidate cells, the UE may receive a random access response (RAR) with a TA value (or TA command) from the one or more than one candidate cells based on the transmitted PRACH.

[0120] In some implementations, a dedicated search space for configuring RAR of conditional LTM may be configured in the LTM-Candidate configuration. More specifically, the dedicated search space may be a common search space and may be configured to make the UE monitor DCI format 1_0 / DCI format 1_1 / DCI format 2_0 / DCI format 2_1 / dedicated DCI format for LTM with CRC scrambled by RA-RNTI or conditional LTM purpose RA-RNTI. The beams for monitoring RAR may be the same as the TCI state ID / RS index which has been selected in DL synchronization. In some implementations, the dedicated search space may be a target cell specific search space. Thus, the UE may monitor RAR based on the selected / activated TCI state / RS.

[0121] In some implementations, a dedicated DCI format in a common search space to carry a TA value only may be monitored, and the dedicated DCI format may be different from the DCI format carrying RAR. The dedicated DCI format may be with CRC scrambled by a dedicated RNTI (e.g., condLTM-RNTI) or C-RNTI. Furthermore, the dedicated DCI format may include candidate cell information to let the UE know from which candidate cell the TA value is derived. The beams for monitoring RAR may be the same as the TCI state ID / RS index which has been selected in DL synchronization. Thus, the UE may monitor RAR based on the selected / activated TCI state / RS.

[0122] In some implementations, when the UE receives the RAR or the DCI format carrying TA value only, the UL synchronization may be considered as complete. In other words, the UE may not need to transmit message 3 (e.g., MSG3 during a 4-step RA procedure) to proceed in the UL synchronization process, and the UE may be synchronized with the candidate cell.

[0123] In some implementations, after the UE transmits the PRACH to the one or more than one candidate cells, the UE may receive a MAC CE including a TA value from the source cell. In other words, the candidate cells may inform the source cell via an inter-node signaling (e.g., an XnAP message) of the TA values based on the received PRACH, and then the source cell may transmit the TA value to the UE via the MAC CE.

[0124] In some implementations, the MAC CE may be carried in a DG PDSCH or an SPS PDSCH. In some implementations, a DCI format for scheduling the DG PDSCH or activating the SPS PDSCH may be dedicated for conditional LTM.

[0125] In some implementations, the SPS configuration may include an RRC parameter (e.g., the SPS-CondLTM-Configuration IE) to configure the SPS PDSCH resource for conditional LTM.

[0126] In some implementations, the field in the MAC CE may include one or more than one candidate cell ID and the corresponding TA value.

[0127] In some implementations, when the UE receives the MAC CE including the TA value, the UL synchronization may be considered as complete. In other words, the UE may not need to transmit message 3 to proceed in the UL synchronization process, and the UE may be synchronized with the candidate cell.

[0128] In some implementations, the MAC CE may be a TA Command MAC CE which may include a field indicating the TA Group ID and a field indicating the TA value. In some implementations, if the UE receives a TA Command MAC CE after transmitting a preamble towards a target cell for LTM purpose, the UE may consider the TA value indicated in the TA Command MAC CE to be the TA value of the target cell, and the UE may ignore the TAG ID field in the TA Command MAC CE.

[0129] In some implementations, after the synchronization is considered as complete, the UE may switch to one target cell among the candidate cells that finish the UL and / or DL synchronization process.

[0130] In some implementations, after the synchronization is considered as complete, the UE may further evaluate the one or more than one candidate cell based on the predefined conditions again to determine the switching point. More specifically, if one target cell from the candidate cells finishing the synchronization process satisfies the predefined condition, the UE may switch to the target cell immediately. In some implementations, the UE may be configured with separate predefined conditions for the synchronization trigger and for the cell switch trigger. If there are more than one candidate cells satisfying the predefined condition, the UE implementation may determine which candidate cell is to be switched to.

[0131] In some implementations, the UE may be mandated to apply UE based TA measurement after the DL synchronization is completed when conditional LTM is configured.

[0132] In some implementations, the UE may not transmit the L1 measurement report of the candidate cells to the source cell if the conditional LTM is configured for the candidate cells.

[0133] Some exemplary procedures for performing conditional LTM without cell switch notification are shown in FIG. 2, FIG. 3 and FIG. 4.

[0134] FIG. 2 is a schematic diagram illustrating a conditional LTM procedure 200 without cell switch notification and with RAR from target cell, according to an example implementation of the present disclosure. The procedure 200 may be divided into four main phases: LTM preparation, Early synchronization, LTM cell switch execution, and LTM cell switch complete.

[0135] In the LTM preparation phase, the procedure 200 begins in action 202 where the UE may be in RRC_Connected mode with the source gNB. In action 204, the UE may transmit a measurement report to the source gNB, where the measurement report may contain measurement results of neighboring cells. In action 206, the source gNB may perform LTM candidate preparation based on the received measurement report and may coordinate with the target gNB to determine suitable candidate cells for the LTM procedure. In action 208, the source gNB may transmit an LTM candidate configuration to the UE, where this configuration may include information about the candidate cells, measurement configurations, and predefined conditions for cell switching. In action 210, the UE may transmit an RRC reconfiguration complete message to the source gNB to acknowledge that the LTM candidate configuration has been successfully received and applied.

[0136] Following the preparation phase, the early synchronization phase may begin. In action 212, the UE may perform L1 measurement on the candidate cells to obtain measurement results such as L1-RSRP or L1-SINR. In action 214, the UE may evaluate the predefined conditions based on the L1 measurement results to determine whether any candidate cell satisfies the conditions for synchronization. In action 216, the UE may select a TCI state ID / RS index for the candidate cell that satisfies the predefined conditions. In action 218, the UE may transmit a PRACH to the target gNB using the selected TCI state / RS index to initiate the random access procedure. In action 220, the target gNB may transmit a RAR to the UE in response to the received PRACH, where the RAR may contain TA information for uplink synchronization.

[0137] The LTM cell switch execution phase may then commence with action 222, where the UE may evaluate the predefined conditions again to determine whether to perform the actual cell switch. The evaluation at this stage may use the same or different conditions compared to the early synchronization phase. In action 224, the UE may detach from the source cell when the conditions for cell switching are satisfied. In action 226, the UE may perform the cell switch to the target gNB, completing the transition from the source cell to the target cell.

[0138] The procedure concludes with the LTM cell switch complete phase. In action 228, the UE may indicate to the target gNB that the conditional LTM procedure is complete, confirming that the UE has successfully switched to and is now operating with the target cell. The dotted line in action 222 indicates that this evaluation step may be optional or conditional depending on the specific implementation, as the UE may have already determined to switch based on the earlier evaluation.

[0139] FIG. 3 is a schematic diagram illustrating a conditional LTM procedure 300 without cell switch notification and with TA from source cell, according to an example implementation of the present disclosure. The procedure 300 may be divided into four main phases: LTM preparation, Early synchronization, LTM cell switch execution, and LTM cell switch complete.

[0140] In the LTM preparation phase, the procedure 300 begins in action 302 where the UE may be in RRC_Connected mode with the source gNB. In action 304, the UE may transmit a measurement report to the source gNB, where the measurement report may contain measurement results of neighboring cells that the UE has measured. In action 306, the source gNB may perform LTM candidate preparation based on the received measurement report and may coordinate with the target gNB to determine suitable candidate cells for the LTM procedure. In action 308, the source gNB may transmit an LTM candidate configuration to the UE, where this configuration may include information about the candidate cells, measurement configurations, and predefined conditions for cell switching. In action 310, the UE may transmit an RRC reconfiguration complete message to the source gNB to acknowledge that the LTM candidate configuration has been successfully received and applied.

[0141] Following the preparation phase, the early synchronization phase may begin. In action 312, the UE may perform L1 measurement on the candidate cells to obtain measurement results such as L1-RSRP or L1-SINR. In action 314, the UE may evaluate the predefined conditions based on the L1 measurement results to determine whether any candidate cell satisfies the conditions for synchronization. In action 316, the UE may select a TCI state ID / RS index for the candidate cell that satisfies the predefined conditions. In action 318, the UE may transmit a PRACH to the target gNB using the selected TCI state / RS index to initiate the random access procedure.

[0142] A key difference in this procedure occurs in action 320, where the target gNB may transmit TA information to the source gNB through inter-node signaling rather than directly sending a RAR to the UE. Subsequently, in the same action 320, the source gNB may transmit a MAC CE with TA information to the UE, where the MAC CE may contain the TA value received from the target gNB. This approach allows the source gNB to maintain control over the synchronization process and coordinate the TA information delivery to the UE.

[0143] The LTM cell switch execution phase may then commence with action 324, where the UE may evaluate the predefined conditions again to determine whether to perform the actual cell switch. The evaluation at this stage may use the same or different conditions compared to the early synchronization phase. In action 326, the UE may detach from the source cell when the conditions for cell switching are satisfied. In action 328, the UE may perform the cell switch to the target gNB, completing the transition from the source cell to the target cell.

[0144] The procedure concludes with the LTM cell switch complete phase. In action 330, the UE may indicate to the target gNB that the conditional LTM procedure is complete, confirming that the UE has successfully switched to and is now operating with the target cell. The dotted line in action 324 indicates that this evaluation step may be optional or conditional depending on the specific implementation.

[0145] FIG. 4 is a schematic diagram illustrating a conditional LTM procedure 400 without cell switch notification and with UE based TA measurement, according to an example implementation of the present disclosure. The procedure 400 may be divided into four main phases: LTM preparation, Early synchronization, LTM cell switch execution, and LTM cell switch complete.

[0146] In the LTM preparation phase, the procedure 400 begins in action 402 where the UE may be in RRC_Connected mode with the source gNB. In action 406, the UE may transmit a measurement report to the source gNB, where the measurement report may contain measurement results of neighboring cells that the UE has measured. In action 408, the source gNB may perform LTM candidate preparation based on the received measurement report and may coordinate with the target gNB to determine suitable candidate cells for the LTM procedure. In action 410, the source gNB may transmit an LTM candidate configuration to the UE, where this configuration may include information about the candidate cells, measurement configurations, and predefined conditions for cell switching. In action 412, the UE may transmit an RRC reconfiguration complete message to the source gNB to acknowledge that the LTM candidate configuration has been successfully received and applied.

[0147] Following the preparation phase, the early synchronization phase may begin. In action 414, the UE may perform L1 measurement on the candidate cells to obtain measurement results such as L1-RSRP or L1-SINR. In action 416, the UE may evaluate the predefined conditions based on the L1 measurement results to determine whether any candidate cell satisfies the conditions for synchronization. In action 418, the UE may select a TCI state ID / RS index for the candidate cell that satisfies the predefined conditions. A distinctive feature of this procedure occurs in action 420, where the UE may perform UE based TA measurement to determine the timing advance value autonomously without requiring a PRACH transmission or receiving TA information from the network. This approach may reduce signaling overhead and latency as the UE can independently determine the TA value through measurements.

[0148] The LTM cell switch execution phase may then commence with action 422, where the UE may evaluate the predefined conditions again to determine whether to perform the actual cell switch. The evaluation at this stage may use the same or different conditions compared to the early synchronization phase. In action 424, the UE may detach from the source cell when the conditions for cell switching are satisfied. In action 426, the UE may perform the cell switch to the target gNB, completing the transition from the source cell to the target cell using the TA value obtained through the UE based measurement.

[0149] The procedure concludes with the LTM cell switch complete phase. In action 428, the UE may indicate to the target gNB that the conditional LTM procedure is complete, confirming that the UE has successfully switched to and is now operating with the target cell. The dotted line in action 422 indicates that this evaluation step may be optional or conditional depending on the specific implementation.

[0150] UE performs CBRA without cell switch notification

[0151] In some implementations, the UE may perform L1 measurement without sending a cell switch notification after receiving an RRC reconfiguration message containing LTM candidate configuration and transmitting an RRC reconfiguration complete message. Then, the UE may evaluate whether the measurement result of one or more than one candidate cells meets the one or more than one conditions.

[0152] In some implementations, the UE may select one target cell when the target cell satisfies the predefined conditions and may switch to the target cell. After switching to the target cell, the UE may perform contention based random access (CBRA) to do DL and / or UL synchronization.

[0153] In some implementations, the UE may consider this procedure as a fallback mode. More specifically, whether to apply the fallback mode may need to satisfy some conditions.

[0154] UE performs early synchronization with cell switch notification

[0155] In some implementations, the UE may perform L1 measurement and evaluate the predefined conditions, and then the UE may transmit the cell switch notification based on the measurement result and the predefined conditions to the source cell, where the cell switch notification may indicate which candidate cell(s), candidate beam(s) the UE is to be synchronized with / applied to.

[0156] In some implementations, the source cell may transmit one or more than one PDCCH order to instruct the UE to perform a RACH procedure towards the candidate cells in the cell switch notification, where the one or more than one PDCCH order may include the random access preamble index, SS / PBCH index, or / and PRACH mask index.

[0157] In some implementations, after the UE receives the PDCCH order, the UE may transmit a PRACH to the one or more than one candidate cell based on one or more than one PDCCH order.

[0158] In some implementations, the UE may receive RAR or a TA value from the source cell.

[0159] In some implementations, the candidate cell(s) may inform a TA value and other information to the source cell and the source cell may transmit the RAR or TA values to the UE. If the number of candidate cells is more than one, the RAR may include the candidate cell index. On the other hand, if the number of candidate cells is equal to 1, the RAR may not need to include the candidate cell index.

[0160] In some implementations, the UE may receive a MAC CE with TA information from the source cell. The MAC CE may include one or more than one TA information for one or more than one candidate cell.

[0161] In some implementations, the UE may receive RAR from the candidate cell(s).

[0162] In some implementations, a dedicated search space for configuring RAR of conditional LTM may be configured in the LTM-Candidate configuration. More specifically, the dedicated search space may be a common search space and may be configured to make the UE monitor DCI format 1_0 / DCI format 1_1 / DCI format 2_0 / DCI format 2_1 / dedicated DCI format for LTM with CRC scrambled by RA-RNTI or conditional LTM purpose RA-RNTI. The beams for monitoring RAR may be the same as the TCI state ID / RS index which has been indicated in the cell switch notification. Thus, the UE may monitor RAR based on the selected / activated TCI state / RS by the UE.

[0163] In some implementations, a dedicated DCI format in a common search space to carry a TA value only may be monitored, and the dedicated DCI format may be different from the DCI format carrying RAR. The dedicated DCI format may be with CRC scrambled by a dedicated RNTI (e.g., condLTM-RNTI) or C-RNTI. Furthermore, the dedicated DCI format may include candidate cell information to let the UE know from which candidate cell the TA value is derived. The beams for monitoring RAR may be the same as the TCI state ID / RS index which has been indicated in the cell switch notification. Thus, the UE may monitor RAR based on the selected / activated TCI state / RS by the UE.

[0164] In some implementations, when the UE receives the RAR or TA information, the synchronization may be considered as complete. In other words, the UE may not need to transmit message 3 further in the RACH process.

[0165] Alternatively, the UE may transmit the cell switch notification based on the measurement result and the predefined conditions to the source cell, where the cell switch notification may indicate which candidate cell(s), candidate beam(s) the UE is to be synchronized with / applied to, and a preamble index which is to be used in the early TA acquisition procedure.

[0166] More specifically, the candidate cell(s) may be indicated by the LTM candidate ID(s) where the UE may consider a candidate cell is associated with an LTM candidate ID if the cell ID (e.g., the physCellId IE) of the candidate cell and the LTM candidate ID are included in the same LTM-Candidate IE.

[0167] More specifically, the UE may select a preamble index from a set of preamble indexes, where the selected preamble index is the preamble index indicated in the cell switch notification. In some implementations, upon receiving the cell switch notification, the source cell may inform the candidate cell of the preamble index which will be used for early TA acquisition purpose, and the candidate cell may consider the received preamble with preamble index to be used for early TA acquisition purpose.

[0168] Alternatively, if the UE is pre-configured with a preamble index for the early TA acquisition towards the candidate cell, the UE may transmit the cell switch notification without the preamble index. In some implementations, the UE may use the pre-configured preamble index for the random access procedure toward the candidate cell. In some implementations, upon receiving the cell switch notification, the source / candidate cell may consider that the UE may initiate a random access procedure towards the candidate cell with the pre-configured preamble index.

[0169] In some implementations, the UE may be further configured with an offset duration for preamble transmission. The offset duration may last from the UE transmitting the cell switch notification to the UE being allowed to transmit the preamble towards the candidate cell. Upon transmitting the cell switch notification, the UE may initialize a first timer to the value of the offset duration and start the timer. When the first timer expires, the UE may transmit a preamble with the pre-configured / selected preamble index towards the candidate cell on the PRACH of the candidate cell.

[0170] In some implementations, the UE may be further configured with a validity period for preamble transmission. The validity period may last from the UE transmitting the cell switch notification to the UE being not allowed again to transmit the preamble towards the candidate cell. Upon transmitting the cell switch notification, the UE may initialize a second timer to the value of the validity period. When the second timer expires, the UE may consider that the UE is not allowed to use the preamble index for preamble transmission towards the candidate cell for early TA acquisition purpose.

[0171] Alternatively, the validity period may last from the UE being allowed to transmit the preamble towards the candidate cell to the UE being not allowed again to transmit the preamble towards the candidate cell. Upon the first timer expiry, the UE may initialize a third timer to the value of the validity period. When the third timer expires, the UE may consider that the UE is not allowed to use the preamble index for preamble transmission towards the candidate cell for early TA acquisition purpose.

[0172] In some implementations, after the synchronization is considered as complete, the UE may switch to one target cell from the candidate cells that finish the synchronization process.

[0173] In some implementations, after the synchronization is considered as complete, the UE may further evaluate the one or more than one candidate cell based on the predefined conditions again to determine the switching point. More specifically, if one target cell from the candidate cells finishing the synchronization process satisfies the predefined condition, the UE may switch to the target cell immediately. If there are more than one candidate cells satisfying the predefined condition, the UE implementation may determine which candidate cell is to be switched to.

[0174] In some implementations, the predefined conditions may be configured in different LTM configurations. In some implementations, one set of conditions may be configured in the LTM TCI state configuration, one set of conditions may be configured in the Early UL synchronization configuration, and one set of conditions may be configured in the conditional LTM candidate configuration. Thus, the UE may evaluate the predefined conditions based on the respective configuration in different phases (e.g., DL synchronization phase, UL synchronization phase, cell switch phase). In some implementations, the different sets of conditions corresponding to different phases may be same or different.

[0175] Some exemplary procedures for performing conditional LTM with cell switch notification are shown in FIG. 5 and FIG. 6.

[0176] FIG. 5 is a schematic diagram illustrating a conditional LTM procedure 500 with cell switch notification and with RAR from the target cell, according to an example implementation of the present disclosure. The procedure 500 may be divided into four main phases: LTM preparation, Early synchronization, LTM cell switch execution, and LTM cell switch complete.

[0177] The figure illustrates a procedure 500 involving the interaction between a UE, a source gNB, and a target gNB during a conditional LTM procedure with cell switch notification. The procedure may be divided into four main phases: LTM preparation, Early synchronization, LTM cell switch execution, and LTM cell switch complete.

[0178] In the LTM preparation phase, the procedure begins in action 502 where the UE may be in RRC_Connected mode with the source gNB. In action 504, the UE may transmit a measurement report to the source gNB, where the measurement report may contain measurement results of neighboring cells that the UE has measured. In action 506, the source gNB may perform LTM candidate preparation based on the received measurement report and may coordinate with the target gNB to determine suitable candidate cells for the LTM procedure. In action 508, the source gNB may transmit an LTM candidate configuration to the UE, where this configuration may include information about the candidate cells, measurement configurations, and predefined conditions for cell switching. In action 510, the UE may transmit an RRC reconfiguration complete message to the source gNB to acknowledge that the LTM candidate configuration has been successfully received and applied.

[0179] Following the preparation phase, the early synchronization phase may begin. In action 512, the UE may perform L1 measurement on the candidate cells to obtain measurement results such as L1-RSRP or L1-SINR. In action 514, the UE may evaluate the predefined conditions based on the L1 measurement results to determine whether any candidate cell satisfies the conditions for synchronization. A key distinction in this procedure occurs in action 516, where the UE may transmit a cell switch notification to the source gNB, indicating which candidate cell or cells satisfy the predefined conditions and which TCI state or RS index the UE has selected for synchronization.

[0180] In response to the cell switch notification, in action 518, the source gNB may transmit a PDCCH order to the UE, instructing the UE to perform a random access procedure towards the identified candidate cell. The PDCCH order may include parameters such as the random access preamble index, SS / PBCH index, or PRACH mask index. In action 520, the UE may transmit a PRACH to the target gNB based on the information received in the PDCCH order. In action 522, the target gNB may transmit a RAR directly to the UE in response to the received PRACH, where the RAR may contain TA information for uplink synchronization.

[0181] The LTM cell switch execution phase may then commence with action 524, where the UE may evaluate the predefined conditions again to determine whether to perform the actual cell switch. The evaluation at this stage may use the same or different conditions compared to the early synchronization phase. In action 526, the UE may detach from the source cell when the conditions for cell switching are satisfied. In action 528, the UE may perform the cell switch to the target gNB, completing the transition from the source cell to the target cell.

[0182] The procedure concludes with the LTM cell switch complete phase. In action 530, the UE may indicate to the target gNB that the conditional LTM procedure is complete, confirming that the UE has successfully switched to and is now operating with the target cell. The dotted line in action 524 indicates that this evaluation step may be optional or conditional depending on the specific implementation.

[0183] FIG. 6 is a schematic diagram illustrating a conditional LTM procedure 600 with cell switch notification and with RAR from the source cell, according to an example implementation of the present disclosure. The procedure 600 may be divided into four main phases: LTM preparation, Early synchronization, LTM cell switch execution, and LTM cell switch complete.

[0184] In the LTM preparation phase, the procedure 600 begins in action 602 where the UE may be in RRC_Connected mode with the source gNB. In action 604, the UE may transmit a measurement report to the source gNB, where the measurement report may contain measurement results of neighboring cells that the UE has measured. In action 606, the source gNB may perform LTM candidate preparation based on the received measurement report and may coordinate with the target gNB to determine suitable candidate cells for the LTM procedure. In action 608, the source gNB may transmit an LTM candidate configuration to the UE, where this configuration may include information about the candidate cells, measurement configurations, and predefined conditions for cell switching. In action 610, the UE may transmit an RRC reconfiguration complete message to the source gNB to acknowledge that the LTM candidate configuration has been successfully received and applied.

[0185] Following the preparation phase, the early synchronization phase may begin. In action 612, the UE may perform L1 measurement on the candidate cells to obtain measurement results such as L1-RSRP or L1-SINR. In action 614, the UE may evaluate the predefined conditions based on the L1 measurement results to determine whether any candidate cell satisfies the conditions for synchronization. In action 616, the UE may transmit a cell switch notification to the source gNB, indicating which candidate cell or cells satisfy the predefined conditions and which TCI state or RS index the UE has selected for synchronization.

[0186] In response to the cell switch notification, in action 618, the source gNB may transmit a PDCCH order to the UE, instructing the UE to perform a random access procedure towards the identified candidate cell. The PDCCH order may include parameters such as the random access preamble index, SS / PBCH index, or PRACH mask index. In action 620, the UE may transmit a PRACH to the target gNB based on the information received in the PDCCH order. A distinctive aspect of this procedure occurs in action 622, where instead of the target gNB directly transmitting a RAR to the UE, the target gNB may forward the TA information to the source gNB through inter-node signaling, and then the source gNB may transmit the RAR to the UE. This approach allows the source gNB to maintain control over the synchronization process and coordinate the delivery of timing advance information to the UE.

[0187] The LTM cell switch execution phase may then commence with action 624, where the UE may evaluate the predefined conditions again to determine whether to perform the actual cell switch. The evaluation at this stage may use the same or different conditions compared to the early synchronization phase. In action 626, the UE may detach from the source cell when the conditions for cell switching are satisfied. In action 628, the UE may perform the cell switch to the target gNB, completing the transition from the source cell to the target cell.

[0188] The procedure concludes with the LTM cell switch complete phase. In action 630, the UE may indicate to the target gNB that the conditional LTM procedure is complete, confirming that the UE has successfully switched to and is now operating with the target cell. The dotted line in action 624 indicates that this evaluation step may be optional or conditional depending on the specific implementation.

[0189] NW performs early synchronization with cell switch notification

[0190] In some implementations, the UE may perform L1 measurement and evaluate the predefined conditions, and then the UE may transmit the cell switch notification based on the measurement result and the predefined conditions to the source cell, where the cell switch notification may indicate which candidate cell(s), candidate beam(s) the UE is to be synchronized with / applied to.

[0191] In some implementations, for DL synchronization, the UE may receive a TCI state indication MAC CE from the source cell based on the cell switch notification. In some implementations, the MAC CE may include one TCI state ID (DL / joint TCI state or UL TCI state) or two TCI state IDs (DL TCI state and UL TCI state), one field to indicate whether each TCI codepoint has multiple TCI states or a single TCI state, or / and one candidate cell index. In some implementations, the MAC CE may include one RS index (RS index for DL or RS index for UL) or two RS indexes (RS indexes for DL and UL), one field to indicate whether each RS codepoint has multiple RS indexes or a single RS index, or / and one candidate cell index. If there is more than one candidate cell, the UE may receive more than one MAC CE for each candidate cell.

[0192] In some implementations, for UL synchronization, the UE may receive one or more than one PDCCH order from the source cell to perform a RACH procedure towards the candidate cell(s). The received information in the one or more than one PDCCH order may be based on the cell switch notification and the PDCCH order may include the random access preamble index, SS / PBCH index, or / and PRACH mask index.

[0193] In some implementations, after the UE receives the one or more than one PDCCH order, the UE may transmit a PRACH to the one or more than one candidate cell based on one or more than one PDCCH order.

[0194] In some implementations, the UE may receive RAR or a TA value from the source cell.

[0195] In some implementations, the candidate cell(s) may inform a TA value and other information to the source cell and the source cell may transmit the RAR or TA values to the UE. If the number of candidate cells is more than one, the RAR may include the candidate cell index. On the other hand, if the number of candidate cells is equal to 1, the RAR may not need to include the candidate cell index.

[0196] In some implementations, the UE may receive a MAC CE including TA information from the source cell. The MAC CE may include one or more than one TA information for one or more than one candidate cell. In some implementations, the TA information may be a sequence and configured based on the candidate cell list in the LTM configuration (e.g., the LTM-Config IE).

[0197] In some implementations, the UE may receive RAR from the candidate cell(s).

[0198] In some implementations, a dedicated search space for configuring RAR of conditional LTM may be configured in the LTM-Candidate configuration. More specifically, the dedicated search space may be a common search space and may be configured to make the UE monitor DCI format 1_0 / DCI format 1_1 / DCI format 2_0 / DCI format 2_1 / dedicated DCI format for LTM with CRC scrambled by RA-RNTI or conditional LTM purpose RA-RNTI. The beams for monitoring RAR may be the same as the TCI state ID / RS index which has been indicated in the cell switch notification. Thus, the UE may monitor RAR based on the selected / activated TCI state / RS by the UE.

[0199] In some implementations, a dedicated DCI format in a common search space to carry a TA value only may be monitored, and the dedicated DCI format may be different from the DCI format carrying RAR. The dedicated DCI format may be with CRC scrambled by a dedicated RNTI (e.g., condLTM-RNTI) or C-RNTI. Furthermore, the dedicated DCI format may include candidate cell information to let the UE know from which candidate cell the TA value is derived. The beams for monitoring RAR may be the same as the TCI state ID / RS index which has been indicated in the cell switch notification. Thus, the UE may monitor RAR based on the selected / activated TCI state / RS by the UE.

[0200] In some implementations, when the UE receives the RAR or TA information, the synchronization may be considered as complete. In other words, the UE may not need to transmit message 3 further in the RACH process.

[0201] In some implementations, after the synchronization is considered as complete, the UE may switch to one target cell from the candidate cells that finish the synchronization process.

[0202] In some implementations, after the synchronization is considered as complete, the UE may further evaluate the one or more than one candidate cell based on the predefined conditions again to determine the switching point. More specifically, if one target cell from the candidate cells finishing the synchronization process satisfies the predefined condition, the UE may switch to the target cell immediately. If there are more than one candidate cells satisfying the predefined condition, the UE implementation may determine which candidate cell is to be switched to.

[0203] Some exemplary procedures for performing conditional LTM with cell switch notification are shown in FIG. 7 and FIG. 8.

[0204] FIG. 7 is a schematic diagram illustrating a conditional LTM procedure 700 with cell switch notification and NW synchronization with RAR from candidate cell, according to an example implementation of the present disclosure. The procedure 700 may be divided into four main phases: LTM preparation, Early synchronization, LTM cell switch execution, and LTM cell switch complete.

[0205] In the LTM preparation phase, the procedure begins in action 702 where the UE may be in RRC_Connected mode with the source gNB. In action 704, the UE may transmit a measurement report to the source gNB, where the measurement report may contain measurement results of neighboring cells that the UE has measured. In action 706, the source gNB may perform LTM candidate preparation based on the received measurement report and may coordinate with the target gNB to determine suitable candidate cells for the LTM procedure. In action 708, the source gNB may transmit an LTM candidate configuration to the UE, where this configuration may include information about the candidate cells, measurement configurations, and predefined conditions for cell switching. In action 710, the UE may transmit an RRC reconfiguration complete message to the source gNB to acknowledge that the LTM candidate configuration has been successfully received and applied.

[0206] Following the preparation phase, the early synchronization phase may begin. In action 712, the UE may perform L1 measurement on the candidate cells to obtain measurement results such as L1-RSRP or L1-SINR. In action 714, the UE may evaluate the predefined conditions based on the L1 measurement results to determine whether any candidate cell satisfies the conditions for synchronization. In action 716, the UE may transmit a cell switch notification to the source gNB, indicating which candidate cell or cells satisfy the predefined conditions and which TCI state or RS index should be used for synchronization.

[0207] A distinctive aspect of this procedure occurs in action 718, where the source gNB may transmit a TCI / RS indication to the UE based on the cell switch notification. This indication may include TCI state IDs or RS indexes for both downlink and uplink, allowing the network to control the beam selection for synchronization. In action 720, the UE may transmit a PRACH to the target gNB using the TCI state or RS index indicated by the source gNB. In action 722, the target gNB may transmit a RAR directly to the UE in response to the received PRACH, where the RAR may contain TA information for uplink synchronization.

[0208] The LTM cell switch execution phase may then commence with action 724, where the UE may evaluate the predefined conditions again to determine whether to perform the actual cell switch. The evaluation at this stage may use the same or different conditions compared to the early synchronization phase. In action 726, the UE may detach from the source cell when the conditions for cell switching are satisfied. In action 728, the UE may perform the cell switch to the target gNB, completing the transition from the source cell to the target cell.

[0209] The procedure concludes with the LTM cell switch complete phase. In action 730, the UE may indicate to the target gNB that the conditional LTM procedure is complete, confirming that the UE has successfully switched to and is now operating with the target cell. The dotted line in action 724 indicates that this evaluation step may be optional or conditional depending on the specific implementation.

[0210] FIG. 8 is a schematic diagram illustrating a conditional LTM procedure 800 with cell switch notification and NW synchronization with TA value from source cell, according to an example implementation of the present disclosure. The procedure 800 may be divided into four main phases: LTM preparation, Early synchronization, LTM cell switch execution, and LTM cell switch complete.

[0211] In the LTM preparation phase, the procedure 800 may begin in action 802 where the UE may be in RRC_Connected mode with the source gNB. In action 804, the UE may transmit a measurement report to the source gNB, where the measurement report may contain measurement results of neighboring cells that the UE has measured. In action 806, the source gNB may perform LTM candidate preparation based on the received measurement report and may coordinate with the target gNB to determine suitable candidate cells for the LTM procedure. In action 808, the source gNB may transmit an LTM candidate configuration to the UE, where this configuration may include information about the candidate cells, measurement configurations, and predefined conditions for cell switching. In action 810, the UE may transmit an RRC reconfiguration complete message to the source gNB to acknowledge that the LTM candidate configuration has been successfully received and applied.

[0212] Following the preparation phase, the early synchronization phase may begin. In action 812, the UE may perform L1 measurement on the candidate cells to obtain measurement results such as L1-RSRP or L1-SINR. In action 814, the UE may evaluate the predefined conditions based on the L1 measurement results to determine whether any candidate cell satisfies the conditions for synchronization. In action 816, the UE may transmit a cell switch notification to the source gNB, indicating which candidate cell or cells satisfy the predefined conditions and which TCI state or RS index should be used for synchronization.

[0213] In this procedure, the network maintains control over the synchronization process through a series of coordinated actions. In action 818, the source gNB may transmit a TCI / RS indication to the UE based on the cell switch notification, where this indication may include TCI state IDs or RS indexes for both downlink and uplink to control the beam selection. In action 820, the source gNB may transmit a PDCCH order to the UE, instructing the UE to perform a random access procedure towards the identified candidate cell, where the PDCCH order may include parameters such as the random access preamble index, SS / PBCH index, or PRACH mask index. In action 822, the UE may transmit a PRACH to the target gNB based on the information received in the PDCCH order and using the indicated TCI state or RS index. A key distinction in this procedure occurs in action 824, where instead of the target gNB directly transmitting a RAR to the UE, the target gNB may forward the TA information to the source gNB through inter-node signaling, and then the source gNB may transmit a TA indication to the UE. This TA indication may be carried in a MAC CE or other signaling format, allowing the source gNB to maintain control over the timing advance delivery.

[0214] The LTM cell switch execution phase may then commence with action 826, where the UE may evaluate the predefined conditions again to determine whether to perform the actual cell switch. The evaluation at this stage may use the same or different conditions compared to the early synchronization phase. In action 828, the UE may detach from the source cell when the conditions for cell switching are satisfied. In action 830, the UE may perform the cell switch to the target gNB, completing the transition from the source cell to the target cell.

[0215] The procedure concludes with the LTM cell switch complete phase. In action 832, the UE may indicate to the target gNB that the conditional LTM procedure is complete, confirming that the UE has successfully switched to and is now operating with the target cell. The dotted line in action 826 indicates that this evaluation step may be optional or conditional depending on the specific implementation.

[0216] FIG. 9 is a flowchart illustrating method / process 900 for conditional LTM in a wireless communication system, according to an example implementation of the present disclosure. Although actions 902, 904, 906, 908, 910, and 912 are illustrated, as separate actions, represented as independent blocks in FIG. 9, these separately illustrated actions should not be construed as to be necessarily order-dependent. The order in which the actions are performed in FIG. 9 is not intended to be construed as a limitation, and any number of the disclosed blocks may be combined in any order to implement the method, or an alternative method. Each of actions 902, 904, 906, 908, 910, and 912 may be performed independent of the other actions, and may be omitted in some implementations of the present disclosure. Moreover, method / process 900 may be combined with other procedures / methods described in the present disclosure. Process 900 may be performed by a UE, with each action of process 900 corresponding to an operation executed by the UE.

[0217] In action 902, the UE may receive, from a source cell, an RRC configuration that configures a set of conditions for evaluating one or more candidate cells. In action 904, the UE may perform an L1 measurement on the one or more candidate cells. In action 906, the UE may determine, based on the L1 measurement, which of the one or more candidate cells satisfies at least one condition in the set of conditions. In action 908, the UE may transmit, to the source cell, a cell switch notification identifying at least one candidate cell determined to satisfy the at least one condition. In action 910, the UE may receive, from the source cell, a PDCCH order that is responsive to the cell switch notification; and perform synchronization with the at least one candidate cell identified in the cell switch notification in response to receiving the PDCCH order.

[0218] In some implementations, action 912 may include transmitting a PRACH preamble to the at least one candidate cell identified in the cell switch notification, and receiving, from the source cell, TA information corresponding to the at least one candidate cell. Additionally, after performing the synchronization with the at least one candidate cell successfully, the UE may execute a cell switch procedure to switch from the source cell to one of the at least one candidate cell based on the TA information.

[0219] In some implementations, the TA information may be included in MAC signaling. For example, the UE may receive a MAC CE including the TA information from the source cell.

[0220] In some implementations, the L1 measurement may include at least one of the following: an L1-RSRP measurement, or an L1-SINR measurement for each of the one or more candidate cells.

[0221] In some implementations, the set of conditions may include at least one of the following: a first condition that a first L1 measurement result of a candidate cell of the one or more candidate cells becomes better than a second L1 measurement result of the source cell by an offset value, a second condition that the first L1 measurement result of the candidate cell exceeds a first threshold, or a third condition that the second L1 measurement result of the source cell falls below a second threshold while the first L1 measurement result of the candidate cell exceeds a third threshold.

[0222] In some implementations, the cell switch notification may include, for each candidate cell of the at least one candidate cell determined to satisfy the at least one condition, at least one of an RS index, a TCI state identifier, or a candidate configuration index.

[0223] In some implementations, the cell switch notification may exclude any of the one or more candidate cells that fails to satisfy any condition in the set of conditions.

[0224] In some implementations, the RRC configuration may include an LTM configuration.

[0225] The procedures illustrated in FIGS. 1-8 may represent various embodiments and implementations of the method / process 900 described in FIG. 9, demonstrating how the conditional LTM framework may be realized in different network deployment scenarios and operational configurations.

[0226] Specifically, the actions described in Process 900 may be manifested through the detailed procedures shown in FIGS. 1-8. For instance, action 902 of receiving an RRC configuration that configures a set of conditions may correspond to actions 108, 208, 308, 410, 508, 608, 708, and 808 in the respective figures, where the UE receives LTM candidate configuration from the source gNB. Action 904 of performing L1 measurement may be reflected in actions 116, 212, 312, 414, 512, 612, 712, and 812 across the various procedures. Action 906 of determining which candidate cells satisfy the conditions may correspond to the evaluation actions 214, 314, 416, 514, 614, 714, and 814 shown in the respective figures.

[0227] The cell switch notification transmission in action 908 may be specifically implemented in the procedures of FIGS. 5-8 through actions 516, 616, 716, and 816, while the procedures in FIGS. 2-4 may represent alternative implementations where such notification is not required, demonstrating the flexibility of the conditional LTM framework. Action 910 of receiving a PDCCH order and performing synchronization may be embodied in various forms across the figures, such as the PDCCH order reception in actions 518, 618, 720, and 820, followed by PRACH transmission and synchronization procedures.

[0228] The TA information reception described in action 912 may be implemented through different mechanisms as shown in the figures: direct RAR reception from the target cell (actions 220, 522, 622, 722), TA reception via MAC CE from the source cell (actions 320, 824), or UE-based TA measurement (action 420). These variations demonstrate how Process 900 may be adapted to different network architectures and capabilities while maintaining the core principle of conditional LTM.

[0229] Furthermore, the cell switch execution following successful synchronization, as mentioned in Process 900, may correspond to the cell switch actions 226, 328, 426, 528, 628, 728, and 830 in the respective figures, with the final confirmation through RRC reconfiguration complete messages shown in actions 126, 228, 330, 428, 530, 630, 730, and 832.

[0230] This relationship between Process 900 and the procedures in FIGS. 1-8 illustrates that the method may be implemented with varying degrees of network control, different synchronization approaches, and alternative signaling mechanisms while maintaining the fundamental advantages of conditional LTM. The flexibility demonstrated in these implementations may allow network operators to select the most appropriate procedure based on their specific deployment scenarios, network capabilities, and service requirements, thereby enabling optimal adaptation of the conditional LTM framework to diverse operational environments.

[0231] Process 900 may provide significant technical advantages and improvements for conditional LTM in wireless communication systems. Process 900 may enable a UE-centric approach to cell switching that may substantially reduce handover latency, signaling overhead, and service interruption time compared to traditional L3-based mobility procedures. For example, a technical advantage of process 900 may be the reduction in cell switch latency through the use of L1 measurements and conditional evaluation. By allowing the UE to autonomously evaluate predefined conditions based on L1 measurements, process 900 may eliminate the need for time-consuming L3 measurement reporting and RRC reconfiguration procedures that are typically required in conventional handover mechanisms. The L1-based approach may enable sub-millisecond measurement cycles, allowing for more responsive and timely cell switching decisions. Furthermore, process 900 may optimize resource utilization and reduce signaling overhead. The cell switch notification mechanism may ensure that only candidate cells meeting the predefined conditions are reported to the network, thereby avoiding unnecessary signaling for cells that do not satisfy the switching criteria. This selective reporting approach may significantly reduce the uplink signaling load and conserve both UE battery power and network resources.

[0232] It should also be noted that the network device, such as the BS, may perform methods / actions corresponding to those performed by the UE. For example, the receiving actions performed by the UE may correspond to the transmitting / configuring actions of the network device; the transmitting actions performed by the UE may correspond to the receiving actions of the network device. That is, the network device and the UE may have reciprocally aligned roles in transmission and reception. For example, the BS may transmit, to a UE, an RRC configuration that configures a set of conditions for evaluating one or more candidate cells. The BS may receive, from the UE, a cell switch notification identifying at least one candidate cell from the one or more candidate cells, where the at least one candidate cell may be determined by the UE to satisfy at least one condition in the set of conditions based on an L1 measurement performed by the UE on the one or more candidate cells. The BS may then transmit, to the UE, a PDCCH order in response to receiving the cell switch notification, where the PDCCH order may cause the UE to perform synchronization with the at least one candidate cell identified in the cell switch notification.

[0233] FIG. 10 is a block diagram illustrating node 1000 for wireless communications, in accordance with various aspects of the present disclosure. As illustrated in FIG. 10, node 1000 may include transceiver 1020, processor 1028, memory 1034, one or more presentation components 1038, and at least one antenna 1036. Node 1000 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. 10).

[0234] Each of the components may directly or indirectly communicate with each other over one or more buses 1040. Node 1000 may be a UE or a BS that performs various functions disclosed with reference to FIGS. 1-9.

[0235] Transceiver 1020 has transmitter 1022 (e.g., transmitting / transmission circuitry) and receiver 1024 (e.g., receiving / reception circuitry) and may be configured to transmit and / or receive time and / or frequency resource partitioning information. Transceiver 1020 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. Transceiver 1020 may be configured to receive data and control channels.

[0236] Node 1000 may include a variety of computer-readable media. Computer-readable media may be any available media that may be accessed by node 1000 and include volatile (and / or non-volatile) media and removable (and / or non-removable) media.

[0237] 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, or data.

[0238] 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, 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.

[0239] 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 aforementioned listed components should also be included within the scope of computer-readable media.

[0240] Memory 1034 may include computer-storage media in the form of volatile and / or non-volatile memory. Memory 1034 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. 10, memory 1034 may store a computer-readable and / or computer-executable instructions 1032 (e.g., software codes) that are configured to, when executed, cause processor 1028 to perform various functions disclosed herein, for example, with reference to FIGS. 1-9. Alternatively, instructions 1032 may not be directly executable by processor 1028 but may be configured to cause node 1000 (e.g., when compiled and executed) to perform various functions disclosed herein.

[0241] Processor 1028 (e.g., having processing circuitry) may include an intelligent hardware device, e.g., a Central Processing Unit (CPU), a microcontroller, an ASIC, etc. Processor 1028 may include memory. Processor 1028 may process data 1030 and instructions 1032 received from memory 1034, and information transmitted and received via transceiver 1020, the baseband communications module, and / or the network communications module. Processor 1028 may also process information to send to transceiver 1020 for transmission via antenna 1036 to the network communications module for transmission to a CN.

[0242] One or more presentation components 1038 may present data indications to a person or another device. Examples of presentation components 1038 may include a display device, a speaker, a printing component, a vibrating component, etc.

[0243] In view of the present disclosure, it is obvious that various techniques may be used for implementing the disclosed concepts without departing from the scope of those concepts. Moreover, while the concepts have been disclosed with specific reference to certain implementations, a person of ordinary skill in the art may recognize that changes may be made in form and detail without departing from the scope of those concepts. As such, the disclosed implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the present disclosure is not limited to the particular implementations disclosed and many rearrangements, modifications, and substitutions are possible without departing from the scope of the present disclosure.

Claims

1. A User Equipment (UE), 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 source cell, a Radio Resource Control (RRC) configuration that configures a set of conditions for evaluating one or more candidate cells; 　　　　perform a Layer 1 (L1) measurement on the one or more candidate cells; 　　　　determine, based on the L1 measurement, which of the one or more candidate cells satisfies at least one condition in the set of conditions; 　　　　transmit, to the source cell, a cell switch notification identifying at least one candidate cell determined to satisfy the at least one condition; 　　　　receive, from the source cell, a Physical Downlink Control Channel (PDCCH) order that is responsive to the cell switch notification; and 　　　　perform synchronization with the at least one candidate cell identified in the cell switch notification in response to receiving the PDCCH order.

2. The UE of claim 1, wherein performing synchronization with the at least one candidate cell comprises: 　　　　transmitting a Physical Random Access Channel (PRACH) preamble to the at least one candidate cell identified in the cell switch notification; and 　　　　receiving, from the source cell, Timing Advance (TA) information corresponding to the at least one candidate cell, and 　　　　wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to: 　　　　execute, after performing the synchronization with the at least one candidate cell successfully, a cell switch procedure to switch from the source cell to one of the at least one candidate cell based on the TA information.

3. The UE of claim 2, wherein receiving, from the source cell, the TA information comprises receiving a Medium Access Control (MAC) Control Element (CE) comprising the TA information from the source cell.

4. The UE of claim 1, wherein the L1 measurement comprises at least one of: 　　　　an L1-Reference Signal Received Power (L1-RSRP) measurement, or 　　　　an L1-Signal to Interference plus Noise Ratio (L1-SINR) measurement for each of the one or more candidate cells.

5. The UE of claim 1, wherein the set of conditions comprises at least one of: 　　　　a first condition that a first L1 measurement result of a candidate cell of the one or more candidate cells becomes better than a second L1 measurement result of the source cell by an offset value, 　　　　a second condition that the first L1 measurement result of the candidate cell exceeds a first threshold, or 　　　　a third condition that the second L1 measurement result of the source cell falls below a second threshold while the first L1 measurement result of the candidate cell exceeds a third threshold.

6. The UE of claim 1, wherein the cell switch notification comprises, for each candidate cell of the at least one candidate cell determined to satisfy the at least one condition, at least one of: 　　　　a Reference Signal (RS) index, 　　　　a Transmission Configuration Indicator (TCI) state identifier, or 　　　　a candidate configuration index.

7. The UE of claim 1, wherein the cell switch notification excludes any of the one or more candidate cells that fails to satisfy any condition in the set of conditions.

8. The UE of claim 1, wherein the RRC configuration comprises a Layer 1 / Layer 2 Triggered Mobility (LTM) configuration.

9. A method performed by a User Equipment (UE) for conditional Layer 1 / Layer 2 Triggered Mobility (LTM), the method comprising: 　　　　receiving, from a source cell, a Radio Resource Control (RRC) configuration that configures a set of conditions for evaluating one or more candidate cells; 　　　　performing a Layer 1 (L1) measurement on the one or more candidate cells; 　　　　determining, based on the L1 measurement, which of the one or more candidate cells satisfies at least one condition in the set of conditions; 　　　　transmitting, to the source cell, a cell switch notification identifying at least one candidate cell determined to satisfy the at least one condition; 　　　　receiving, from the source cell, a Physical Downlink Control Channel (PDCCH) order that is responsive to the cell switch notification; and 　　　　performing synchronization with the at least one candidate cell identified in the cell switch notification in response to receiving the PDCCH order.

10. A Base Station (BS), the BS comprising: 　　　　at least one processor; and 　　　　at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the BS to: 　　　　transmit, to a User Equipment (UE), a Radio Resource Control (RRC) configuration that configures a set of conditions for evaluating one or more candidate cells; 　　　　receive, from the UE, a cell switch notification identifying at least one candidate cell from the one or more candidate cells, wherein the at least one candidate cell is determined by the UE to satisfy at least one condition in the set of conditions based on a Layer 1 (L1) measurement performed by the UE on the one or more candidate cells; and 　　　　transmit, to the UE, a Physical Downlink Control Channel (PDCCH) order in response to receiving the cell switch notification, wherein the PDCCH order causes the UE to perform synchronization with the at least one candidate cell identified in the cell switch notification.

11. The BS of claim 10, wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the BS to: 　　　　transmit, to the UE, Timing Advance (TA) information corresponding to the at least one candidate cell identified in the cell switch notification.

12. The BS of claim 11, wherein transmitting, to the UE, the TA information comprises transmitting a Medium Access Control (MAC) Control Element (CE) comprising the TA information to the UE.

13. The BS of claim 10, wherein the cell switch notification comprises, for each candidate cell of the at least one candidate cell determined to satisfy the at least one condition, at least one of: 　　　　a Reference Signal (RS) index, 　　　　a Transmission Configuration Indicator (TCI) state identifier, or 　　　　a candidate configuration index.

14. The BS of claim 10, wherein the set of conditions comprises at least one of: 　　　　a first condition that a first L1 measurement result of a candidate cell of the one or more candidate cells becomes better than a second L1 measurement result of a source cell of the UE by an offset value, 　　　　a second condition that the first L1 measurement result of the candidate cell exceeds a first threshold, or 　　　　a third condition that the second L1 measurement result of the source cell falls below a second threshold while the first L1 measurement result of the candidate cell exceeds a third threshold.

15. The BS of claim 10, wherein the RRC configuration comprises a Layer 1 / Layer 2 Triggered Mobility (LTM) configuration.

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