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

Abstract

A method performed by a User Equipment (UE) for performing a Layer1 / Layer2 Triggered Mobility (LTM) operation is provided. The method receives, from a serving cell, at least one LTM candidate configuration. The method receives, from the serving cell, an LTM Cell Switch Command (CSC) that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration, the first LTM candidate configuration including an identifier (ID) associated with an LTM candidate cell and an LTM Channel State Information (CSI) report configuration associated with the LTM candidate cell. The method transmits, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC.

Description

METHOD AND APPARATUS FOR LAYER1 / LAYER2 TRIGGERED MOBILITY (LTM) OPERATION

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

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

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

[0004] In a first aspect of the present disclosure, a UE for performing an LTM operation is provided. The UE includes at least one processor and at least one non-transitory computer-readable medium that is coupled to the at least one processor and that stores one or more computer-executable instructions. The computer-executable instructions, when executed by the at least one processor, cause the UE to: receive, from a serving cell, at least one LTM candidate configuration; receive, from the serving cell, an LTM Cell Switch Command (CSC) that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration, the first LTM candidate configuration including an identifier (ID) associated with an LTM candidate cell and an LTM Channel State Information (CSI) report configuration associated with the LTM candidate cell; and transmit, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC.

[0005] In some implementations of the first aspect, the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to perform a Random Access Channel (RACH)-less LTM cell switch to the LTM candidate cell. The uplink resource includes the first Physical Uplink Shared Channel (PUSCH) corresponding to a dynamic grant or a configured grant.

[0006] In some implementations of the first aspect, the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to perform a Random Access Channel (RACH)-based LTM cell switch to the LTM candidate cell. The uplink resource includes a Message 3 (Msg3) PUSCH.

[0007] In some implementations of the first aspect, the at least one LTM candidate configuration is received from the serving cell via a Radio Resource Control (RRC) reconfiguration message.

[0008] In some implementations of the first aspect, the LTM CSI report configuration includes CSI measurement information. The one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to measure a corresponding CSI resource based on the CSI measurement information.

[0009] In a second aspect of the present application, a BS for configuring an LTM operation is provided. The BS includes at least one processor and at least one non-transitory computer-readable medium that is coupled to the at least one processor and that stores one or more computer-executable instructions. The computer-executable instructions, when executed by the at least one processor, cause the BS to: transmit, to a UE, at least one LTM candidate configuration; and transmit, to the UE, an LTM CSC that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration, the first LTM candidate configuration including an ID associated with an LTM candidate cell and an LTM CSI report configuration associated with the LTM candidate cell. The UE transmits, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC.

[0010] In some implementations of the second aspect, the UE performs a RACH-less LTM cell switch to the LTM candidate cell. The uplink resource includes the first PUSCH corresponding to a dynamic grant or a configured grant.

[0011] In some implementations of the second aspect, the UE performs a RACH-based LTM cell switch to the LTM candidate cell. The uplink resource includes a Msg3 PUSCH.

[0012] In some implementations of the second aspect, the at least one LTM candidate configuration is transmitted to the UE via an RRC reconfiguration message.

[0013] In some implementations of the second aspect, the LTM CSI report configuration includes CSI measurement information, and the UE measures a corresponding CSI resource based on the CSI measurement information.

[0014] In a third aspect of the present application, a method performed by a UE for performing an LTM operation is provided. The method includes receiving, from a serving cell, at least one LTM candidate configuration; receiving, from the serving cell, an LTM CSC that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration, the first LTM candidate configuration including an ID associated with an LTM candidate cell and an LTM CSI report configuration associated with the LTM candidate cell; and transmitting, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC.

[0015] 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.

[0016] FIG. 1A is a diagram illustrating a RACH-less LTM procedure, according to an example implementation of the present disclosure.

[0017] FIG. 1B is a diagram illustrating a RACH-based LTM procedure, according to an example implementation of the present disclosure.

[0018] FIG. 2 is a flowchart illustrating a method / process performed by a UE for performing an LTM operation, according to an example implementation of the present disclosure.

[0019] FIG. 3 is a flowchart illustrating a method / process performed by a BS for configuring an LTM operation, according to an example implementation of the present disclosure.

[0020] FIG. 4 is a block diagram illustrating a node for wireless communication, according to an example implementation of the present disclosure.

[0021] Some of the abbreviations used in the present disclosure include: 3GPP　　　　　　　　　　　　3rd Generation Partnership Project 5G　　　　　　　　　　　　5th generation 5GC　　　　　　　　　　　　5G Core Network ACK　　　　　　　　　　　　Acknowledgment AI　　　　　　　　　　　　Artificial Intelligence BWP　　　　　　　　　　　　Bandwidth Part BS　　　　　　　　　　　　Base Station CA　　　　　　　　　　　　Carrier Aggregation CORESET　　　　　　　　　　　　Control resource set CC　　　　　　　　　　　　Component Carrier CCE　　　　　　　　　　　　Control Chanel Element CE　　　　　　　　　　　　Control Element CFRA　　　　　　　　　　　　Contention-Free RA CG　　　　　　　　　　　　Configured Grant CP　　　　　　　　　　　　Cyclic Prefix CQI　　　　　　　　　　　　Channel Quality Indicator CRC　　　　　　　　　　　　Cyclic Redundancy Check CRI　　　　　　　　　　　　CSI-RS resource indicator CSC　　　　　　　　　　　　Cell Switch Command CSI　　　　　　　　　　　　Channel State Information CSS　　　　　　　　　　　　Common Search Space CU　　　　　　　　　　　　Central Unit DC　　　　　　　　　　　　Dual Connectivity DCI　　　　　　　　　　　　Downlink Control Information DG　　　　　　　　　　　　Dynamic Grant DL　　　　　　　　　　　　Downlink DMRS　　　　　　　　　　　　Demodulation Reference Signal DU　　　　　　　　　　　　Distributed Unit EPC　　　　　　　　　　　　Evolved Packet Core E-UTRA　　　　　　　　　　　　Evolved Universal Terrestrial Radio Access FR　　　　　　　　　　　　Frequency Range HARQ　　　　　　　　　　　　Hybrid Automatic Repeat Request ID　　　　　　　　　　　　Identifier IE　　　　　　　　　　　　Information Element L1 / L2 / L3　　　　　　　　　　　　Layer 1 / Layer 2 / Layer 3 LI　　　　　　　　　　　　Layer Indicator LTE　　　　　　　　　　　　Long Term Evolution LTM　　　　　　　　　　　　Layer1 / Layer2 Triggered Mobility MAC　　　　　　　　　　　　Medium Access Control MCG　　　　　　　　　　　　Master Cell Group MIMO　　　　　　　　　　　　Multiple-Input Multiple-Output ML　　　　　　　　　　　　Machine Learning MN　　　　　　　　　　　　Master Node MR-DC　　　　　　　　　　　　Multi-RAT Dual Connectivity Msg3　　　　　　　　　　　　Message 3 NACK　　　　　　　　　　　　Negative Acknowledgment NDI　　　　　　　　　　　　New Data Indicator NR　　　　　　　　　　　　New RAT / Radio NR-DC　　　　　　　　　　　　NR-NR Dual Connectivity NUL　　　　　　　　　　　　Normal Uplink NW　　　　　　　　　　　　Network PBCH　　　　　　　　　　　　Physical Broadcast Channel PCell　　　　　　　　　　　　Primary Cell PCI　　　　　　　　　　　　Physical Cell ID PDCP　　　　　　　　　　　　Packet Data Convergence Protocol PDCCH　　　　　　　　　　　　Physical Downlink Control Channel PDSCH　　　　　　　　　　　　Physical Downlink Shared Channel PHY　　　　　　　　　　　　Physical PMI　　　　　　　　　　　　Precoding Matrix Indicator PRACH　　　　　　　　　　　　Physical Random Access Channel PSCell　　　　　　　　　　　　Primary SCG Cell PTRS　　　　　　　　　　　　Phase Tracking Reference Signal PUCCH　　　　　　　　　　　　Physical Uplink Control Channel PUSCH　　　　　　　　　　　　Physical Uplink Shared Channel QCL　　　　　　　　　　　　Quasi Co-Location RA　　　　　　　　　　　　Random Access RACH　　　　　　　　　　　　Random Access Channel RAN　　　　　　　　　　　　Radio Access Network RAR　　　　　　　　　　　　Random Access Response RAT　　　　　　　　　　　　Radio Access Technology Rel　　　　　　　　　　　　Release RI　　　　　　　　　　　　Rank Indicator RLC　　　　　　　　　　　　Radio Link Control RNTI　　　　　　　　　　　　Radio Network Temporary Identifier RRC　　　　　　　　　　　　Radio Resource Control RS　　　　　　　　　　　　Reference Signal RSRP　　　　　　　　　　　　Reference Signal Received Power RSRQ　　　　　　　　　　　　Reference Signal Received Quality RV　　　　　　　　　　　　Redundancy Version SCell　　　　　　　　　　　　Secondary Cell SCG　　　　　　　　　　　　Secondary Cell Group SDAP　　　　　　　　　　　　Service Data Adaptation Protocol SI　　　　　　　　　　　　System Information SINR　　　　　　　　　　　　Signal to Interference plus Noise Ratio SN　　　　　　　　　　　　Secondary Node SP　　　　　　　　　　　　Semi-Persistent SpCell　　　　　　　　　　　　Special Cell SR　　　　　　　　　　　　Scheduling Request SRS　　　　　　　　　　　　Sounding Reference Signal SS　　　　　　　　　　　　Synchronization Signal SSB　　　　　　　　　　　　SS / PBCH Block SSBRI　　　　　　　　　　　　SS / PBCH Block Resource Indicator SUL　　　　　　　　　　　　Supplementary Uplink TA　　　　　　　　　　　　Timing Advance TB　　　　　　　　　　　　Transport Block TCI　　　　　　　　　　　　Transmission Configuration Indication TR　　　　　　　　　　　　Technical Report TRP 　　　　　　　　　　　　Transmission Reception Point TS　　　　　　　　　　　　Technical Specification UCI　　　　　　　　　　　　Uplink Control Information UE　　　　　　　　　　　　User Equipment UL　　　　　　　　　　　　Uplink URLLC　　　　　　　　　　　　Ultra Reliable Low Latency Communication

[0022] 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.

[0023] 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.

[0024] For the purposes of consistency and ease of understanding, like features may be identified (although, in some examples, not illustrated) by the same numerals in the drawings. However, the features in different implementations may be different in other respects and may not be narrowly confined to what is illustrated in the drawings.

[0025] References to “one implementation,” “an implementation,” “example implementation,” “various implementations,” “some implementations,” “implementations of the present application,” etc., may indicate that the implementation(s) of the present application so described may include a particular feature, structure, or characteristic, but not every possible implementation of the present application necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “In some implementations,” or “in an example implementation,” “an implementation,” do not necessarily refer to the same implementation, although they may. Moreover, any use of phrases like “implementations” in connection with “the present application” are never meant to characterize that all implementations of the present application must include the particular feature, structure, or characteristic, and should instead be understood to mean “at least some implementations of the present application” includes the stated particular feature, structure, or characteristic. The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the equivalent.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] A software implementation may include computer-executable instructions and / or Artificial Intelligence (AI) / Machine Learning (ML) module(s) stored on a computer-readable medium, such as memory or other type of storage devices. One or more microprocessors or general-purpose computers with communication processing capability may be programmed with corresponding computer-executable instructions and perform the disclosed network function(s), AI / ML module(s), or algorithm(s). The AI / ML module(s) may be implemented with a supervised learning approach, a semi-supervised learning approach, an unsupervised learning approach (e.g., Transductive approach and Inductive approach), a federated learning approach, or a reinforcement learning (RL) approach, but the present disclosure is not limited thereto. The computer-executable instructions associated with the AI module(s) and / or the ML module(s) may include but are not limited to, data management instructions (e.g., collection instructions, validation instructions…etc.), model monitoring and management instructions (e.g., NW key performance indicators (KPIs) monitoring, model input / output monitoring, model selection / switching / update / upload / download, model (de)activation, model identification, functionality selection…etc.), and / or pre-process input instructions.

[0030] The microprocessors or general-purpose computers may include Application-Specific Integrated Circuits (ASICs), programmable logic arrays, Central Processing Units (CPUs), Tensor Processing Units (TPUs), Graphics Processing Units (GPUs), General-purpose computing on GPUs (GPGPU, or less often GPGP), and / or using one or more Digital Signal Processors (DSPs). Although some of the disclosed implementations are oriented to software installed and executing on computer hardware, alternative implementations implemented as firmware, as hardware, or as a combination of hardware and software are well within the scope of the present disclosure. The computer-readable medium may include, but is not limited to, Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), High Bandwidth Memory (HBM), Magnetoresistive Random Access Memory (MRAM), Ferroelectric Random Access Memory (FRAM), Resistive Random Access Memory (RRAM), Read-Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), flash memory (or other memory technology), Compact Disc Read-Only Memory (CD-ROM) , Digital Versatile Disks (DVD) (or other optical disk storage), magnetic cassettes, magnetic tape, magnetic disk storage (or other magnetic storage devices), or any other equivalent medium capable of storing computer-readable instructions.

[0031] A radio communication network architecture such as a Long-Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Pro system, or a 5G NR Radio Access Network (RAN), 5G-Advanced (5G-A) system, or an open radio access network (O-RAN) may typically include at least one base station (BS), at least one UE, and one or more optional network elements that provide connection within a network. The BS and one or more optional network elements enable the UE to access a radio network. The UE may communicate with the network, such as a Core Network (CN), an Evolved Packet Core (EPC) network, an Evolved Universal Terrestrial RAN (E-UTRAN), a Next-Generation Core (NGC), a 5G Core (5GC), or an internet via a RAN established by one or more BSs and the network elements / functions.

[0032] A UE may include, but is not limited to, a mobile station, a mobile terminal or device, or a user communication radio terminal. The UE may be a portable radio equipment that includes, but is not limited to, a mobile phone, a tablet, a wearable device, a sensor, a vehicle, a virtual reality (VR) device, an augmented (AR) device, an Internet of Things (IoT) device, an unmanned aerial vehicle (UAV), or a Personal Digital Assistant (PDA) with wireless communication capability. The UE may be configured to receive and transmit signals over an air interface to one or more cells in a RAN. In some implementations, the UE may be an AI / ML-enabled device and / or an AI / ML capable device that is equipped with AI module(s) and / or ML module(s).

[0033] The BS may be configured to provide communication services according to at least a Radio Access Technology (RAT), such as Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM) that is often referred to as 2G, GSM Enhanced Data rates for GSM Evolution (EDGE) RAN (GERAN), General Packet Radio Service (GPRS), Universal Mobile Telecommunication System (UMTS) that is often referred to as 3G based on basic Wideband-Code Division Multiple Access (W-CDMA), High-Speed Packet Access (HSPA), LTE, LTE-A, evolved / enhanced LTE (eLTE) that is LTE connected to 5GC, NR (often referred to as 5G), 5G-A, and / or LTE-A Pro. However, the scope of the present disclosure is not limited to these protocols.

[0034] The BS may include, but is not limited to, a node B (NB) in the UMTS, an evolved node B (eNB) in LTE or LTE-A, a radio network controller (RNC) in UMTS, a BS controller (BSC) in the GSM / GERAN, a next-generation eNB (ng-eNB) in an Evolved Universal Terrestrial Radio Access (E-UTRA) BS in connection with 5GC, a next-generation Node B (gNB) in the 5G-RAN or in the 5G Access Network (5G-AN), or any other apparatus capable of controlling radio communication and managing radio resources within a cell. The BS may serve one or more UEs via a radio interface. Although the gNB is used as an example in some implementations within the present disclosure, it should be noted that the disclosed implementations may also be applied to other types of base stations. In some implementations, the BS may be an AI / ML-enabled device and / or an AI / ML capable device that is equipped with AI module(s) and / or ML module(s).

[0035] 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.

[0036] Each cell (may often referred to as a serving cell) may provide services to one or more UEs within the cell’s radio coverage, such that each cell schedules the downlink (DL) (and optionally uplink (UL) resources) to at least one UE within its radio coverage for DL (and optionally UL packet transmissions from the UE). The BS may communicate with one or more UEs in the radio communication system via the cells.

[0037] A cell may allocate sidelink (SL) resources for supporting the Proximity Services (ProSe), LTE SL services, LTE / NR sidelink communication services, LTE / NR sidelink discovery services, and / or LTE / NR Vehicle-to-Everything (V2X) services. In addition, a cell may allocate DL and / or UL resources for supporting Multicast / Broadcast Service (MBS) services, Non-Terrestrial Networks (NTN) services, positioning services, power serving services and / or Network Energy Saving (NES) services.

[0038] 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.

[0039] As discussed above, the frame structure for NR may support flexible configurations for accommodating various next generation (e.g., 5G) communication requirements, such as Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC), and Ultra-Reliable and Low-Latency Communication (URLLC), while fulfilling high reliability, high data rate, and low latency requirements. The Orthogonal Frequency-Division Multiplexing (OFDM) technology in the third generation partnership project (3GPP) may serve as a baseline for an NR waveform. The scalable OFDM numerology, such as adaptive sub-carrier spacing, channel bandwidth, and Cyclic Prefix (CP), may also be used.

[0040] 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.

[0041] 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.

[0042] Any two or more than two of the following paragraphs, (sub)-bullets, points, actions, behaviors, terms, or claims described in the present disclosure may be combined logically, reasonably, and properly to form a specific method.

[0043] 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.

[0044] 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.

[0045] In some implementations, all the designs / embodiment / implementations introduced within this disclosure are not limited to be applied for dealing with the problems discussed within this disclosure. For example, the described embodiments may be applied to solve other problems that exist in the RAN of wireless communication systems. In some implementations, all of the numbers listed within the designs / embodiment / implementations introduced within this disclosure are just examples and for illustration, for example, of how the described methods are executed.

[0046] The terms, definitions, and abbreviations given in the present disclosure are either imported from existing documentation (e.g., European Telecommunications Standards Institute (ETSI), International Telecommunication Union (ITU), or elsewhere) or newly created by 3GPP experts whenever the need for precise vocabulary is identified.

[0047] Examples of some selected terms in the present disclosure are provided as follows.

[0048] 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.

[0049] BWP: A subset of the total cell bandwidth of a cell is 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 BS (e.g., a gNB) configures the UE with UL and DL BWP(s). To enable the BA on SCells, when CA is deployed, the BS configures the UE with one or more DL BWPs. It should be noted that there may be no BWP in the UL. For the PCell, the initial BWP is the BWP used for an initial access. For the SCell(s), the initial BWP is the BWP configured for the UE to operate after an SCell activation. The UE may be configured with a first active uplink BWP by a 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 such a 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.

[0050] 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. For example, 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).

[0051] Beam: The term “beam” here may be replaced by a spatial filter. A beam may correspond to a spatial (domain) filtering. In one example, 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 another example, 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, “a UE made a PUSCH transmission by using a specific beam” may imply that the UE made 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 electromagnetic (EM) wave is radiated.

[0052] Cell: A cell in the present disclosure may refer to a PCell, a PSCell, an SpCell, an SCell, a candidate cell, a target cell, a neighbor cell, a serving cell, or a source cell.

[0053] The ‘TRP’ in the implementations or the examples may be replaced by ‘beam’ or ‘panel’. The term ‘overlap’ may refer to partial overlap or fully overlap in time domain, frequency domain and / or spatial domain.

[0054] When a UE moves from a coverage area of one cell to a coverage area of another cell, a serving cell change may be performed to maintain radio connectivity and radio quality above a certain level. The serving cell change may be triggered based on L3 measurements and executed through an RRC signaling-triggered Reconfiguration with Synchronization for a change of a PCell and a PSCell, as well as release and / or addition of SCells, when applicable. Such L3-based mobility procedures involve complete L2 and L1 resets, which result in longer latency, larger overhead, and longer interruption time compared to beam switch mobility. LTM enhancements aim to enable serving cell changes through L1 / L2 signaling, thereby reducing latency, signaling overhead, and interruption time.

[0055] In wireless communication, particularly during handover scenarios, acquiring CSI reports is critical to ensuring optimal coding schemes and channel quality for the first transmission in the target cell. This challenge becomes more pronounced in LTM operations, where the procedure for CSI acquisition following a cell switch command may need to be clearly defined. The current practice of performing CSI acquisition for multiple candidate cells imposes significant overhead on the UE, which may degrade system efficiency. Therefore, the present disclosure aims to develop a streamlined CSI acquisition procedure that minimizes UE overhead while ensuring high-quality initial transmissions for the target cell during handover. By addressing these issues, the disclosed implementations aim to enhance the overall performance and reliability of handover operations in advanced wireless networks.

[0056] The main target of L1 / L2 based mobility is to reduce latency in mobility, and thus support of L1 beam management and L1 based measurement may be needed to facilitate the scheduling efficiency. 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.

[0057] The mobility latency may correspond to a time interval between reception of a cell switch command (CSC) by the UE and execution of a first downlink reception or uplink transmission by the UE based on an indicated beam of a target cell. More specifically, the handover interruption time may include a duration for processing the cell switch command by the UE (Tcmd+ Tprocessing,2), a duration for downlink synchronization by the UE (Tsearch+ T?+ Tmargin), a duration for uplink synchronization by the UE (TIU+ TRAR), and a duration until the UE performs the first downlink reception or uplink transmission after reception of the RAR, where Tcmdrefers to time for processing L1 / L2 command, Tprocessing,2refers to time for UE processing after the cell switch command, Tsearchrefers to time required to search the target cell, T?refers to time for fine tracking and acquiring full timing information, Tmarginrefers to time for SSB or CSI-RS post-processing, TIUrefers to interruption uncertainty in acquiring the first available PRACH occasion in the target cell, and TRARrefers to time for RAR delay. Furthermore, a cell switch decision may depend on Layer 1 measurements and reporting, and therefore procedures and methods for Layer 1 measurement and reporting are of importance.

[0058] RRC pre-configuration

[0059] 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 and / or apply the received configuration for an LTM 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, and / or UL data channel specific configuration.

[0060] 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, RRC pre-configuration may be applied by an RRC reconfiguration procedure. In some implementations, RRC pre-configuration may include a reference configuration and a delta configuration.

[0061] Cell switch command

[0062] During an LTM 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 MAC-CE (e.g., 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 the target cell (e.g., PCI index of the 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), and / or 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. The cell switching may include a PCell Change (e.g., switching from the source PCell to the target PCell), an SCell change, and / or a 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.

[0063] DL synchronization

[0064] During the LTM procedure, a UE may execute 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. The received information may include logical cell ID (e.g., the IDs or PCIs of the candidate cells, and / or the ID 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, and / or TCI state configuration associated with the target cell.

[0065] UL synchronization

[0066] During the LTM procedure, a UE may execute 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, which may include a contention-based RA procedure, a contention-free RA procedure, a 2-step RA procedure, or a 4-step RA procedure for the candidate cells or the target cell. In some implementations, the UE may perform a 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. 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 (e.g., NUL or SUL) for the candidate cells or the target cell, SRS configuration associated with the candidate cells or the target cell, and / or TCI state configuration associated with the candidate cells or the target cell.

[0067] L1 measurement and report

[0068] 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 and 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).

[0069] 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, PCI of the serving cell, or PCI of the target cell). In some implementations, the L1 measurement report may include one or more RS IDs.

[0070] In some implementations, L1 measurement report as UCI transmitted on PUCCH or PUSCH may be considered as the result of measurement from the UE’s perspective. In some implementations, L1 measurement report type may include 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.

[0071] CSI report content

[0072] 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, and / or 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).

[0073] CSI acquisition

[0074] CSI acquisition relies on reference signals such as CSI-RS and CSI report containing CQI, PMI, LI, and RI to aid in beamforming, resource allocation, and modulation and coding schemes. Reporting may be configured periodically or triggered aperiodically, offering flexibility for diverse scenarios, including high-mobility and handover events. By enabling adaptive and efficient transmission strategies, CSI acquisition may enhance spectrum efficiency, reduce interference, and ensure reliable communication.

[0075] Cell switch command (CSC) MAC CE

[0076] In some implementations, a cell switch command MAC CE may include the information for instructing a UE to switch from a first cell / a source BS to a second cell / a target BS. The information may include reserved bits, target configuration ID, timing advance command, TCI state ID, UL TCI state ID, a field that indicates the presence of the contention-free random access resource fields, a field that indicates which UL carrier to transmit the PRACH of the contention-free random access resources, random access preamble index, SS / PBCH index, PRACH mask index, and / or repetition number.

[0077] Scenarios

[0078] 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, and / or inter-CU case. A network node (e.g., BS) may include a CU and several DUs. A CU is 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 is a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU. One DU may support one or multiple cells. The CU may connect to several DUs via F1 interfaces.

[0079] Intra-node mobility

[0080] 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, the intra-CU with intra-DU case and the intra-CU with inter-DU case.

[0081] 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.

[0082] Inter-node mobility

[0083] 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 entities 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 the special cell, PSCell, or SCell.

[0084] LTM procedure

[0085] FIG. 1A is a diagram illustrating a RACH-less LTM procedure 100A, according to an example implementation of the present disclosure. The LTM procedure 100A may include several stages, including LTM preparation 120, early synchronization 126, LTM cell switch execution 138, and LTM cell switch completion 142.

[0086] The UE 102 may be in the RRC_CONNECTED state 110. The UE 102 may send a measurement report message 112 to the source gNB 104. The source gNB 104 may determine to configure LTM and initiate LTM preparation, such as LTM candidate preparation 114. The source gNB 104 may transmit an RRC reconfiguration message to the UE including the LTM candidate configurations 116. The UE 102 may store the LTM candidate configurations and transmit an RRC reconfiguration complete message 118 to the source gNB 104.

[0087] In the action 122, the UE 102 may perform DL synchronization with the LTM candidate cell(s) before receiving the cell switch command 132. The UE may activate and deactivate Transmission Configuration Indicator (TCI) states of LTM candidate cell(s), as triggered by the source gNB 104. In the action 124, the UE 102 may perform UL synchronization with LTM candidate cell(s) before receiving the cell switch command 132, by using UE-based TA measurement, if configured, and / or by transmitting a preamble towards the candidate cell, as triggered by the source gNB 104. When UE-based TA measurement is configured, the UE 102 may acquire the TA value(s) of the candidate cell(s) by measurement. The UE 102 may perform early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command as specified in clause 9.2.6 of the 3GPP TS 38.300. This may be done via Contention Free Random Access (CFRA) triggered by a PDCCH order from the source cell, following which the UE 102 may send preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE 102 may not receive random access response from the network for the purpose of TA value acquisition, and the TA value of the candidate cell may be indicated in the cell switch command 132. The UE 102 may not maintain the TA timer for the candidate cell and may rely on network implementation to guarantee the TA validity.

[0088] The UE 102 may perform L1 measurements on the configured LTM candidate cell(s) and transmit L1 measurement reports 128 to the source gNB 104. The L1 measurement may be performed as long as RRC reconfiguration (e.g., the LTM candidate configuration 116) is applicable. In the action 130, the source gNB 104 may determine to execute cell switch to a target cell associated with the target gNB 106. The source gNB 104 may transmit an LTM cell switch command 132 (e.g., a cell switch command MAC CE) triggering cell switch by including a target configuration ID that indicates the index of the candidate configuration of the target cell, a beam indicated with a TCI state or beams indicated with DL and UL TCI states, and a timing advance command for the target cell, if available. In the action 134, the UE 102 may detach from the source cell, switch to the target cell, and apply the candidate configuration indicated by the target configuration ID.

[0089] In the action 140, the UE 102 may complete the LTM cell switch procedure by sending an RRC reconfiguration complete message to the target gNB 106. For RACH-less LTM, the UE 102 may consider that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0090] In some implementations, the stages including early synchronization 126, LTM cell switch execution 138, and LTM cell switch completion 142, may be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in the LTM candidate configuration 116.

[0091] FIG. 1B is a diagram illustrating a RACH-based LTM procedure 100B, according to an example implementation of the present disclosure. The RACH-based LTM procedure 100B is similar to the RACH-less LTM procedure 100A, except that the action for UL synchronization in the RACH-less LTM procedure 100A (e.g., the action 124) is omitted, and instead the RACH-based LTM procedure 100B includes a corresponding action for UL synchronization (e.g., the action 136).

[0092] In the action 136, the UE 102 may perform a random access procedure towards the target cell associated with the target gNB 106, if the UE 102 does not have valid TA of the target cell as specified in clause 5.18.35 of the 3GPP TS 38.321. The action 136 may be optionally omitted in the RACH-less LTM procedure 100A. If the UE 102 has performed a RA procedure in the action 136 the UE 102 may consider that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. In the RACH-based LTM procedure 100B, the action 136 for UL synchronization with the candidate cells may be performed after the reception of the cell switch command 132.

[0093] In some implementations, a method performed by a UE for performing an LTM operation may include: 　　　　receiving, from a first BS or cell, a Radio Resource Control (RRC) reconfiguration message including at least one LTM candidate configuration to configure CSI resource set and CSI report for a second BS or cell; 　　　　receiving, from the first BS or cell, a cell switch command (CSC) that indicates an LTM candidate configuration from the at least one LTM candidate configuration and a CSI report configuration ID for the second BS or cell; and 　　　　transmitting a CSI report on an UL resource to the second BS or cell, either prior to or together with an RRC reconfiguration complete message to the second BS or cell, 　　　　where the CSI report quantity type corresponds to at least one of cri-RI-PMI-CQI, cri-RI-i1, cri-RI-i1-CQI, cri-RI-CQI, and cri-RI-LI-PMI-CQI, and the UL resource is the first UL transmission after the reception of the CSC.

[0094] In some implementations, a UE may receive, from a first BS or cell, an RRC reconfiguration message including LTM configuration for CSI resource set and CSI report for CSI acquisition for LTM, and then the UE may receive, from the first BS or cell, a cell switch command that indicates the LTM configuration for a second BS or cell. Lastly, the UE may transmit the CSI report for CSI acquisition for LTM on an UL resource based on the RRC reconfiguration message to the second BS or cell after the cell switch command. In some implementations, the UE may transmit the CSI report before transmitting the cell switch completion message (e.g., the RRCReconfigurationComplete message to the target cell). Therefore, in some implementations, the first UL transmission may correspond to the UL transmission with the CSI report for CSI acquisition for LTM. In some implementations, the first UL transmission may correspond to the UL transmission with the RRCReconfigurationCompelete message and the CSI report for CSI acquisition for LTM.

[0095] In some implementations, a UE may receive, from a first BS or cell, an RRC reconfiguration message including LTM configuration for CSI resource set and CSI report for CSI acquisition for LTM, and then the UE may receive, from the first BS or cell, a cell switch command that indicates the LTM configuration for a second BS or cell. Lastly, the UE may transmit the CSI report for CSI acquisition for LTM on an UL resource based on the RRC reconfiguration message to the second BS or cell after the cell switch command. In some implementations, the UE may transmit the CSI report with the cell switch completion message (e.g., the RRCReconfigurationComplete message) to the target cell.

[0096] In some implementations, a CSI report configuration for CSI acquisition for LTM (e.g., the ltm-CSI-ReportConfig or ltm-CSI-AperiodicReport) may be configured in the LTM-Candidate and associated with a candidate cell (e.g., the cell indicated in the CSC). More specifically, the CSI report configuration for CSI acquisition may refer to the reportquantity indicating at least one of the following parameters: cri-RI-PMI-CQI, cri-RI-i1, cri-RI-i1-CQI, cri-RI-CQI, and cri-RI-LI-PMI-CQI.

[0097] In some implementations, a CSI report configuration for CSI acquisition for LTM (e.g., the ltm-CSI-ReportConfig or ltm-CSI-AperiodicReport) may be configured in the LTM-Config and associated with a candidate cell (e.g., the cell indicated in the CSC).

[0098] In some implementations, only one CSI report configuration for CSI acquisition for LTM may be included in a configuration to configure CSI report related information for an LTM candidate, to be used upon the reception of the LTM cell switch procedure.

[0099] In some implementations, a list of CSI report configurations, each identified by a corresponding reportconfigId, may be included in a triggering state list configuration (e.g., the ltm-CSI-AperiodicTriggeringState). Each CSI report configuration may correspond to different report quantities or report types. When a triggering state index in the triggering state list is indicated, the corresponding list of CSI report configurations may be indicated at the same time. Thus, a first CSI resource set associated with a first CSI report configuration and a second CSI resource set associated with a second CSI report configuration may be configured simultaneously, enabling the UE to measure CSI-RS based on the first CSI resource set and the second CSI resource set and to transmit CSI report based on the first CSI and second CSI report configurations.

[0100] In some implementations, the CSI report configuration for LTM may not have a corresponding reportConfigId, indicating that the CSI report configuration is dedicated specifically to CSI acquisition for LTM purposes.

[0101] In some implementations, the reportConfigType in the CSI report configuration for CSI acquisition for LTM may be indicated as aperiodic without using a CHOICE type. In some implementations, the CSI report for CSI acquisition for LTM may be triggered by a CSC. In other words, the CSI report triggered by the CSC may be dedicated to the CSI report for CSI acquisition for LTM. Therefore, the UE may not expect a reportConfigType to be present in the CSI report configuration for CSI acquisition for LTM.

[0102] In some implementations, the CSI report configuration for LTM may be associated with an UL transmission resource, where the UL transmission resource may include at least one of the following:

[0103] - CG PUSCH for LTM (e.g., the first UL transmission for RACH-less LTM);

[0104] - DG PUSCH for LTM (e.g., the first UL transmission);

[0105] - PUSCH Message 3 (e.g., the first UL transmission for RACH-based LTM); and

[0106] - An UL resource configured in LTM candidate configuration.

[0107] The PUSCH Message 3 may also be referred to as PUSCH Msg3, Message 3 PUSCH, Msg3 PUSCH, or PUSCH scheduled by an RAR UL grant in the present disclosure.

[0108] The first UL transmission for RACH-less LTM corresponding to a DG or CG may also be referred to as the first PUSCH corresponding to the DG or CG. In some implementations, the first PUSCH may correspond to the first PUSCH occurring subsequent to the RACH-less LTM cell switch corresponding to the DG or CG. The first PUSCH may also be referred to as the first valid PUSCH or the first available PUSCH after the RACH-less LTM cell switch. In some implementations, the CSI report may be transmitted on the first available PUSCH subsequent to the RACH-less LTM cell switch, where the first available PUSCH corresponds to a dynamic grant or a configured grant.

[0109] The association between the CSI report configuration and the UL resource may be configured in the CSI report configuration for CSI acquisition for LTM, where the resource for the first UL transmission may be configured as an INTEGER form (e.g., ULallocationId, CGConfigId, PUCCHResourceId). For example, the first UL transmission resource may correspond to an index of a UL time domain resource, a CG configuration index, or a PUCCH resource index.

[0110] In some implementations, the UE may transmit the CSI report for CSI acquisition for LTM on the first UL transmission, and the association between the CSI report configuration and the first UL transmission may not be needed in the CSI report configuration. In other words, the CSI report for CSI acquisition for LTM may be transmitted on the first UL transmission by default.

[0111] In some implementations, the UE may transmit the CSI report for CSI acquisition for LTM on the first UL transmission, and the information for the CSI report may be included in the CSC or an control message (e.g., a DCI format, a MAC CE), where the information may include a CSI request indication, a CSI report configuration index, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication for indicating whether to multiplex / transmit the CSI report and RRC reconfiguration complete message together in the first UL transmission. The UE may transmit the CSI report for CSI acquisition for LTM on the first UL transmission based on the information for the CSI report, where the UE may receive the information for the CSI report from the source cell.

[0112] In some implementations, the CSI request indication may correspond to a single bit, where a bit value of 0 may indicate no CSI report triggering, and a bit value of 1 may indicate CSI report triggering.

[0113] In some implementations, the CSI request indication may correspond to multiple bits, where the number of bits may be determined by a corresponding RRC parameter (e.g., the reportTriggerSize). The CSI request indication may indicate one of multiple triggering states, with each triggering state including the associated CSI report configuration information.

[0114] In some implementations, the CSI report configuration index may indicate a CSI report configuration from a list of CSI report configurations.

[0115] In some implementations, the triggering state indication may indicate one of the triggering states from the associated configuration (e.g., the aperiodicTriggerStateList).

[0116] In some implementations, the CSI-RS resource set triggering offset indication may indicate the offset between the CSC / control message and the CSI resource set, where the CSI resource set may be associated with the indicated CSI report configuration. The triggering offset indication may indicate an offset value N with a bit size of log2(N). The triggering offset indication may correspond to a mapping value of the offset. For example, a value of 1 may correspond to an offset of 0 slots, and a value of 6 may correspond to an offset of 64 slots. Thus, the bit size may be based on the mapping value (e.g., log2(64)). The offset may be indicated in units of slots, symbols, milliseconds, or subframes.

[0117] In some implementations, an indication for indicating whether a CSI report and an RRC reconfiguration complete message are multiplexed and transmitted together in a first UL transmission may correspond to a single bit. For example, a bit value of 0 may indicate that the CSI report and the RRC reconfiguration complete message are not multiplexed or transmitted together in the first UL transmission, and a bit value of 1 may indicate that the CSI report and the RRC reconfiguration complete message are multiplexed and transmitted together in the first UL transmission. The single-bit indication may be included in the CSC or control message.

[0118] In some implementations, an indication for indicating whether a CSI report and an RRC reconfiguration complete message are multiplexed and transmitted together in a first UL transmission may be expressed as an enumerated value {enable} or {disable}. For example, the enumerated value {enable} may indicate that the CSI report and the RRC reconfiguration complete message are multiplexed and transmitted together in the first UL transmission, and the enumerated value {disable} may indicate that the CSI report and the RRC reconfiguration complete message are not multiplexed or transmitted together in the first UL transmission.

[0119] In some implementations, an indication for indicating whether a CSI report and an RRC reconfiguration complete message are multiplexed and transmitted together in a first uplink transmission may correspond to an enumerated value {true}. For example, the enumerated value {true} may indicate that the CSI report and the RRC reconfiguration complete message are multiplexed and transmitted together in the first UL transmission. On the other hand, if the enumerated value {true} is not configured, or if the indication for indicating whether to multiplex and transmit the CSI report and the RRC reconfiguration complete message together in the first uplink transmission is absent, the CSI report may not be multiplexed or transmitted together with the RRC reconfiguration complete message in the first UL transmission.

[0120] In some implementations, the UE may determine whether to multiplex / transmit the CSI report and RRC reconfiguration complete message together in the first UL transmission according to a specific parameter or an RRC IE. In some implementations, when the specific parameter or the RRC IE is provided, the UE may multiplex and transmit the CSI report and the RRC reconfiguration complete message together in the first UL transmission, and when the specific parameter or the RRC IE is not provided, the UE may transmit the CSI report and the RRC reconfiguration complete message separately. In some implementations, when the specific parameter or the RRC IE is not provided, the UE may multiplex and transmit the CSI report and the RRC reconfiguration complete message together in the first UL transmission, and when the specific parameter or the RRC IE is provided, the UE may transmit the CSI report and the RRC reconfiguration complete message separately.

[0121] In some implementations, the UE may not expect to multiplex / transmit the CSI report and RRC reconfiguration complete message together in the first UL transmission.

[0122] In some implementations, the CSI report for CSI acquisition for LTM may be transmitted in uplink control information (UCI) form. If the CSI report is transmitted in the UCI form, the CSI report may be multiplexed with a bit sequence (e.g., the RRCReconfigurationComplete message or data) in the first UL transmission.

[0123] In some implementations, the CSI report for CSI acquisition for LTM may be transmitted in UL MAC CE form. If the CSI report is transmitted in the UL MAC CE form, the CSI report may be transmitted with the bit sequence (e.g., the RRCReconfigurationComplete message or data) in the first UL transmission. The CSI report may correspond to a first bit sequence and the other message may correspond to a second bit sequence. In the first UL transmission, the bit sequences may be allocated in an order in which the first bit sequence corresponding to the CSI report is allocated prior to the second bit sequence corresponding to the other message.

[0124] In some implementations, a priority of a CSI report (e.g., specific to a conditional LTM operation) may be higher than a priority of an RRC reconfiguration complete message during a multiplexing procedure. In some implementations, the priority of the RRC reconfiguration complete message may be higher than the priority of the CSI report (e.g., specific to the conditional LTM operation). In some implementations, a serving RAN may configure whether the priority of the CSI report (e.g., specific to the conditional LTM operation) is higher than or lower than the priority of the RRC reconfiguration complete message. In some implementations, the priority relationship may be predefined in a technical specification or implemented in a UE module. A processing, generation, or transmission mechanism for the CSI report specific to the conditional LTM operation may be different from a processing, generation, or transmission mechanism for other types of CSI reports.

[0125] In some implementations, the UE may multiplex / transmit the CSI report for CSI acquisition for LTM and the RRC reconfiguration complete message together without the indication.

[0126] In some implementations, if the UE transmits the CSI report for CSI acquisition for LTM on the CG PUSCH, the UE may expect that the first symbol of the CG PUSCH in the slot satisfies the timeline conditions. Therefore, the UE may expect to transmit the CSI report starting no earlier than symbol X after the end of the last symbol of the CSC / control message that triggers the CSI report, where X corresponds to the timeline conditions.

[0127] X may be defined as the next uplink symbol with its CP starting Tproc,CSI+ d or T’proc,CSI+ d, where Tproc,CSI=(Z)(2048+144)?TC+ Tswitch, T’proc,CSI= (Z’)(2048+144)?κ2-μ?TC. Z or Z’ may be related to CSI computation delay requirement. The value d may be based on whether the CSI report is multiplexed with other message(s) (e.g., the RRC reconfiguration complete message). In some implementations, if the CSI report is not multiplexed with other message(s), the value d may be equal to 0. In some implementations, if the CSI report is multiplexed with other message(s), the value d may be equal to a value larger than 0 and the value d may be based on the UE capability.

[0128] In some implementations, the UE may transmit the CSI report for CSI acquisition for LTM on PUSCH Message 3 during RA procedure, and the information in RAR for scheduling PUSCH Message 3 may include a CSI request indication, a CSI report configuration index, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication for indicating whether to multiplex the CSI report and the RRC reconfiguration complete message together in the PUSCH Message 3.

[0129] In some implementations, the UE may transmit the CSI report for CSI acquisition for LTM on an UL resource that is configured specific to CSI acquisition for LTM, and an UL grant for scheduling the UL resource may be included in the CSC. The UL grant may include a field corresponding to time domain allocation information for the scheduled UL resource to ensure that the CSI processing timeline is satisfied and / or a bit field to indicate the CSI request.

[0130] In some implementations, the UE may transmit the CSI report for CSI acquisition for LTM on an UL resource that is configured specific to CSI acquisition for LTM, and an UL grant for scheduling the UL resource may be scheduled after the CSC in time domain. The UL grant may include time domain allocation information for the scheduled UL resource to ensure that the CSI processing timeline is satisfied. Furthermore, the CSC may include the search space ID and the CORESET ID for the UE to detect the UL grant. The UL grant may be a DCI format or a MAC CE scheduling the UL resource for the CSI report for CSI acquisition for LTM.

[0131] In some implementations, the UE may indicate the condition that “a CSI report associated with the target cell is available” in the LTM complete message (e.g., in the RRC Reconfiguration Complete message or in the MAC CE transmitted associated with the RRCReconfigurationComplete message). After receiving the indication, the serving cell may configure a UL grant (e.g., a dynamic grant via DCI) to request the CSI report (e.g., specific for LTM) from the UE.

[0132] In some implementations, the CSI report (e.g., specific to LTM or conditional LTM operation) may be transmitted via PUSCH with or without further indication of “UCI-OnPUSCH”. In some implementations, a specific indication may be provided to indicate whether the CSI report specific to LTM or conditional LTM operation is to be transmitted on the PUSCH.

[0133] In some implementations, the CSI report specific to the LTM operation may be further configured with a CSI_DelayTimer. The UE may initiate counting of the CSI_DelayTimer (e.g., setting an initial value and counting down to zero) upon or after the CSI report triggered by the LTM operation is generated. The UE may drop the CSI report if the CSI report is still pending when the CSI_DelayTimer expires. In some implementations, the CSI report may be dropped because the serving RAN does not request or enquire the UE to transmit the CSI report. In some implementations, the UE may trigger the CSI_DelayTimer based on conditional LTM operations. For example, the CSI_DelayTimer may be triggered when the UE initiates a conditional LTM operation, transmits the LTM complete message or RRC Reconfiguration Complete message, or indicates to the serving RAN that the CSI report associated with the target cell is available. The CSI_DelayTimer may be released upon or after the CSI report is successfully transmitted to the serving RAN.

[0134] In some implementations, if a UE capability is reported indicating that CSI measurement may be performed after reception of the CSC, the CSI measurement type may be specific to an aperiodic CSI resource set and the associated CSI report type may be specific to an aperiodic CSI report.

[0135] In some implementations, if a UE capability is not reported, the CSI measurement may be performed after reception of the CSC, and the CSI measurement type may be specific to an aperiodic CSI resource set and the associated CSI report type may be specific to an aperiodic CSI report.

[0136] In some implementations, the CSI measurement information (e.g., CSI measurement resource) may be configured in a CSI report configuration, and the CSI report configuration may be configured in an LTM candidate or LTM-Config. The CSI measurement information may be dedicated to a candidate cell indicated in the CSC. Thus, the CSI report configuration may include an LTM candidate index.

[0137] In some implementations, the CSI measurement information (e.g., CSI measurement resource) may be configured in an LTM candidate or LTM-Config, and the CSI report configuration may include the CSI measurement information (e.g., a CSI resource configuration index) to associate the CSI report with the CSI measurement. In other words, the UE may measure the CSI-RS based on the received CSI measurement information. After CSI computation, the UE may transmit the CSI measurement results in the associated CSI report. The CSI measurement information may be dedicated to a candidate cell indicated in the CSC. Thus, the CSI measurement information may include an LTM candidate index to associate the CSI resource set with a candidate cell.

[0138] In some implementations, if a UE capability is reported indicating that the CSI measurement may be performed before reception of the CSC, the CSI measurement type may correspond to a periodic CSI resource set, a semi-persistent CSI resource set, or an aperiodic CSI resource set.

[0139] The CSI measurement information may be configured in the CSI report configuration, and the CSI measurement information may correspond to the CSI resource set associated with one or more candidate cells. Thus, the CSI measurement information may include a list of LTM candidate indexes.

[0140] FIG. 2 is a flowchart illustrating a method / process 200 performed by a UE for performing an LTM operation, according to an example implementation of the present disclosure. In the action 202, the process 200 may start by receiving, from a serving cell, at least one LTM candidate configuration. For example, the serving cell may correspond to the source gNB 104 illustrated in FIG. 1A and FIG. 1B. The LTM candidate configuration may correspond to the LTM candidate configuration 116 illustrated in FIG. 1A and FIG. 1B.

[0141] In the action 204, the process 200 may receive, from the serving cell, an LTM CSC that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration, the first LTM candidate configuration including an ID associated with an LTM candidate cell and an LTM CSI report configuration associated with the LTM candidate cell. For example, the LTM CSC may correspond to the cell switch command 132 illustrated in FIG. 1A and FIG. 1B.

[0142] In the action 206, the process 200 may transmit, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC. For example, the LTM candidate cell may correspond to the target gNB 106 illustrated in FIG. 1A and FIG. 1B. The process 200 may then end.

[0143] The steps / actions shown in FIG. 2 should not be construed as necessarily order dependent. The order in which the process is described is not intended to be construed as a limitation. Moreover, some of the actions shown in FIG. 2 may be omitted in some implementations and one or more actions shown in FIG. 2 may be combined.

[0144] The technical problem addressed by the method illustrated in FIG. 2 is efficiently acquiring CSI for a target cell during a conditional LTM operation. By directly associating the LTM candidate configuration with an LTM CSI report configuration in the CSC, the UE may immediately determine the appropriate CSI report parameters for the target cell. This reduces signaling overhead, minimizes latency for CSI reporting, improves accuracy and timeliness of channel quality measurements for the target cell, and enhances overall mobility performance during conditional LTM operations. The approach ensures that the UE may efficiently transmit the CSI report on an uplink resource based on the LTM CSI report configuration.

[0145] In some implementations, the UE may perform a RACH-less LTM cell switch to the LTM candidate cell. The uplink resource may include the first PUSCH corresponding to a dynamic grant or a configured grant. In some implementations, the first PUSCH may correspond to the first PUSCH (e.g., the first available PUSCH or the first valid PUSCH) occurring after the RACH-less LTM cell switch corresponding to the DG or CG. An example of the RACH-less LTM procedure is illustrated in FIG. 1A.

[0146] In some implementations, the UE may perform a RACH-based LTM cell switch to the LTM candidate cell. The uplink resource may include a Msg3 PUSCH, which may be also referred to as Message 3 PUSCH, PUSCH Message 3, PUSCH Msg3, or PUSCH scheduled by an RAR UL grant in the present disclosure. An example of the RACH-based LTM procedure is illustrated in FIG. 1B.

[0147] In some implementations, the at least one LTM candidate configuration may be received from the serving cell via an RRC reconfiguration message.

[0148] In some implementations, the LTM CSI report configuration may include CSI measurement information, such as a CSI resource. The UE may measure a corresponding CSI resource based on the CSI measurement information.

[0149] FIG. 3 is a flowchart illustrating a method / process 300 performed by a BS for configuring an LTM operation, according to an example implementation of the present disclosure. In the action 302, the process 300 may start by transmitting, to a UE, at least one LTM candidate configuration. In the action 304, the process 300 may transmit, to the UE, an LTM CSC that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration. The first LTM candidate configuration may include an ID associated with an LTM candidate cell and an LTM CSI report configuration associated with the LTM candidate cell. The UE may transmit, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC. The process 300 may then end. The method illustrated in FIG. 3 is similar to that in FIG. 2, except that it is described from the perspective of the BS (instead of the UE). For example, the process 300 may be performed by the source gNB 104 illustrated in FIG. 1A and FIG. 1B.

[0150] FIG. 4 is a block diagram illustrating a node 400 for wireless communication, according to an example implementation of the present disclosure. As illustrated in FIG. 4, a node 400 may include a transceiver 420, a processor 428, a memory 434, one or more presentation components 438, and at least one antenna 436. The node 400 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. 4).

[0151] Each of the components may directly or indirectly communicate with each other over one or more buses 440. The node 400 may be a UE or a BS that performs various functions disclosed with reference to FIGS. 1A through 3.

[0152] The transceiver 420 has a transmitter 422 (e.g., transmitting / transmission circuitry) and a receiver 424 (e.g., receiving / reception circuitry) and may be configured to transmit and / or receive time and / or frequency resource partitioning information. The transceiver 420 may be configured to transmit in different types of subframes and slots including, but not limited to, usable, non-usable, and flexibly usable subframes and slot formats. The transceiver 420 may be configured to receive data and control channels.

[0153] The node 400 may include a variety of computer-readable media. Computer-readable media may be any available media that may be accessed by the node 400 and include volatile (and / or non-volatile) media and removable (and / or non-removable) media.

[0154] The computer-readable media may include computer-storage media and communication media. Computer-storage media may include both volatile (and / or non-volatile media), and removable (and / or non-removable) media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, AI / ML module(s), or data.

[0155] Computer-storage media may include RAM, ROM, EPROM, EEPROM, flash memory (or other memory technology), CD-ROM, Digital Versatile Disks (DVD) (or other optical disk storage), magnetic cassettes, magnetic tape, magnetic disk storage (or other magnetic storage devices), etc. Computer-storage media may not include a propagated data signal. Communication media may typically embody computer-readable instructions (e.g., computer-readable instructions related to AI module(s) and / or the ML module(s)), data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transport mechanisms and include any information delivery media.

[0156] The term “modulated data signal” may mean a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. Communication media may include wired media, such as a wired network or direct-wired connection, and wireless media, such as acoustic, RF, infrared, and other wireless media. Combinations of any of the above listed components should also be included within the scope of computer-readable media.

[0157] The memory 434 may include computer-storage media in the form of volatile and / or non-volatile memory. The memory 434 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. 4, the memory 434 may store a computer-readable and / or computer-executable instructions 432 (e.g., software codes) that are configured to, when executed, cause the processor 428 to perform various functions disclosed herein, for example, with reference to FIGS. 1A through 3. Alternatively, the instructions 432 may not be directly executable by the processor 428 but may be configured to cause the node 400 (e.g., when compiled and executed) to perform various functions disclosed herein.

[0158] The processor 428 (e.g., having processing circuitry) may include an intelligent hardware device, e.g., a Central Processing Unit (CPU), a microcontroller, an ASIC, etc. The processor 428 may include memory. The processor 428 may process the data 430 and the instructions 432 received from the memory 434, and information transmitted and received via the transceiver 420, the baseband communications module, and / or the network communications module. The processor 428 may also process information to send to the transceiver 420 for transmission via the antenna 436 to the network communications module for transmission to a CN.

[0159] One or more presentation components 438 may present data indications to a person or another device. Examples of presentation components 438 may include a display device, a speaker, a printing component, a vibrating component, etc.

[0160] In view of the present disclosure, it is obvious that various techniques may be used for implementing the disclosed concepts without departing from the scope of those concepts. Moreover, while the concepts have been disclosed with specific reference to certain implementations, a person of ordinary skill in the art may recognize that changes may be made in form and detail without departing from the scope of those concepts. As such, the disclosed implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the present disclosure is not limited to the particular implementations disclosed and many rearrangements, modifications, and substitutions are possible without departing from the scope of the present disclosure.

Claims

1. A User Equipment (UE) for performing a Layer 1 / Layer 2 Triggered Mobility (LTM) operation, the UE comprising: 　　　　at least one processor; and 　　　　at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the UE to: 　　　　　　　　receive, from a serving cell, at least one LTM candidate configuration; 　　　　　　　　receive, from the serving cell, an LTM Cell Switch Command (CSC) that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration, the first LTM candidate configuration comprising an identifier (ID) associated with an LTM candidate cell and an LTM Channel State Information (CSI) report configuration associated with the LTM candidate cell; and 　　　　　　　　transmit, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC.

2. The UE of claim 1, wherein: 　　　　the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to perform a Random Access Channel (RACH)-less LTM cell switch to the LTM candidate cell, and 　　　　the uplink resource comprises a first Physical Uplink Shared Channel (PUSCH) corresponding to a dynamic grant or a configured grant.

3. The UE of claim 1, wherein: 　　　　the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to perform a Random Access Channel (RACH)-based LTM cell switch to the LTM candidate cell, and 　　　　the uplink resource comprises a Message 3 (Msg3) Physical Uplink Shared Channel (PUSCH).

4. The UE of claim 1, wherein: 　　　　the at least one LTM candidate configuration is received from the serving cell via a Radio Resource Control (RRC) reconfiguration message.

5. The UE of claim 1, wherein: 　　　　the LTM CSI report configuration comprises CSI measurement information, and 　　　　the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to measure a corresponding CSI resource based on the CSI measurement information.

6. A Base Station (BS) for configuring a Layer 1 / Layer 2 Triggered Mobility (LTM) operation, the BS comprising: 　　　　at least one processor; and 　　　　at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the BS to: 　　　　　　　　transmit, to a User Equipment (UE), at least one LTM candidate configuration; and 　　　　　　　　transmit, to the UE, an LTM Cell Switch Command (CSC) that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration, the first LTM candidate configuration comprising an identifier (ID) associated with an LTM candidate cell and an LTM Channel State Information (CSI) report configuration associated with the LTM candidate cell, wherein: 　　　　the UE transmits, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC.

7. The BS of claim 6, wherein: 　　　　the UE performs a Random Access Channel (RACH)-less LTM cell switch to the LTM candidate cell, and 　　　　the uplink resource comprises a first Physical Uplink Shared Channel (PUSCH) corresponding to a dynamic grant or a configured grant.

8. The BS of claim 6, wherein: 　　　　the UE performs a Random Access Channel (RACH)-based LTM cell switch to the LTM candidate cell, and 　　　　the uplink resource comprises a Message 3 (Msg3) Physical Uplink Shared Channel (PUSCH).

9. The BS of claim 6, wherein: 　　　　the at least one LTM candidate configuration is transmitted to the UE via a Radio Resource Control (RRC) reconfiguration message.

10. The BS of claim 6, wherein: 　　　　the LTM CSI report configuration comprises CSI measurement information, and 　　　　the UE measures a corresponding CSI resource based on the CSI measurement information.

11. A method performed by a User Equipment (UE) for performing a Layer 1 / Layer 2 Triggered Mobility (LTM) operation, the method comprising: 　　　　receiving, from a serving cell, at least one LTM candidate configuration; 　　　　receiving, from the serving cell, an LTM Cell Switch Command (CSC) that identifies a first LTM candidate configuration selected from the at least one LTM candidate configuration, the first LTM candidate configuration comprising an identifier (ID) associated with an LTM candidate cell and an LTM Channel State Information (CSI) report configuration associated with the LTM candidate cell; and 　　　　transmitting, to the LTM candidate cell, a CSI report on an uplink resource based on the LTM CSI report configuration in response to receiving the LTM CSC.

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