Method and apparatus for conditional layer 1 / layer 2 triggered mobility

Abstract

A method performed by a UE for conditional L1 / L2 Triggered Mobility (LTM) is provided. The method receives, from a source cell, an RRC configuration including a CSI report configuration and CSI measurement configuration for candidate cells. The method transmits, to the source cell, a first CSI report including an L1-RSRP value based on the CSI measurement configuration. The method receives, from the source cell, a MAC CE including information for a second CSI report. The method transmits, to a target cell, the second CSI report based on the MAC CE. The target cell is one of the candidate cells, the CSI report configuration includes a CSI report quantity including combinations of CSI-RS resource indicator (CRI), rank indicator (RI), precoding matrix indicator (PMI), channel quality indicator (CQI), first PMI (i1), and layer indicator (LI).

Description

METHOD AND APPARATUS FOR CONDITIONAL LAYER 1 / LAYER 2 TRIGGERED MOBILITY

[0001] The present disclosure is related to wireless communication and, more specifically, to a User Equipment (UE), Base Station (BS), and method for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM) in the wireless communication networks.

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

[0003] The present disclosure is related to a UE, a BS, and a method for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM) in the wireless communication networks.

[0004] In a first aspect of the present disclosure, a UE for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM) is provided. The UE includes at least one processor and at least one non-transitory computer-readable medium that is coupled to the at least one processor and that stores one or more computer-executable instructions. The computer-executable instructions, when executed by the at least one processor, cause the UE to: receive, from a source cell, a radio resource control (RRC) configuration that includes a channel state information (CSI) report configuration and CSI measurement configuration for one or more candidate cells; transmit, to the source cell, a first CSI report including an L1-reference signal received power (RSRP) value based on the CSI measurement configuration; receive, from the source cell, a medium access control (MAC) control element (CE) including information for a second CSI report; and transmit, to a target cell, the second CSI report based on the MAC CE, where the target cell is one of the one or more candidate cells, the CSI report configuration includes a CSI report quantity, and the CSI report quantity includes at least one of: a first combination that includes a channel state information (CSI)-reference signal (RS) resource indicator (CRI), a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI), a second combination that includes the CRI, the RI, a first precoding matrix indicator (i1), a third combination that includes the CRI, the RI, the i1, and the CQI, a fourth combination that includes the CRI, the RI, and the CQI, and a fifth combination that includes the CRI, the RI, a layer indicator (LI), the PMI, and the CQI.

[0005] In a second aspect of the present disclosure, a method performed by a user equipment (UE) for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM) is provided. The method includes: receiving, from a source cell, a radio resource control (RRC) configuration that includes a channel state information (CSI) report configuration and CSI measurement configuration for one or more candidate cells; transmitting, to the source cell, a first CSI report including an L1-reference signal received power (RSRP) value based on the CSI measurement configuration; receiving, from the source cell, a medium access control (MAC) control element (CE) including information for a second CSI report; and transmitting, to a target cell, the second CSI report based on the MAC CE, where the target cell is one of the one or more candidate cells, the CSI report configuration includes a CSI report quantity, and the CSI report quantity includes at least one of: a first combination that includes a channel state information (CSI)-reference signal (RS) resource indicator (CRI), a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI), a second combination that includes the CRI, the RI, a first precoding matrix indicator (i1), a third combination that includes the CRI, the RI, the i1, and the CQI, a fourth combination that includes the CRI, the RI, and the CQI, and a fifth combination that includes the CRI, the RI, a layer indicator (LI), the PMI, and the CQI.

[0006] In a third aspect of the present application, a BS for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM) is provided. The BS includes at least one processor and at least one non-transitory computer-readable medium that is coupled to the at least one processor and that stores one or more computer-executable instructions. The computer-executable instructions, when executed by the at least one processor, cause the BS to: transmit, to a user equipment (UE) via a source cell, a radio resource control (RRC) configuration that includes a channel state information (CSI) report configuration and CSI measurement configuration for one or more candidate cells; receive, from the UE via the source cell, a first CSI report including an L1-reference signal received power (RSRP) value based on the CSI measurement configuration; transmit, to the UE via the source cell, a medium access control (MAC) control element (CE) including information for a second CSI report; and receive, from the UE via a target cell, the second CSI report based on the MAC CE, where the target cell is one of the one or more candidate cells, the CSI report configuration includes a CSI report quantity, and the CSI report quantity includes at least one of: a first combination that includes a channel state information (CSI)-reference signal (RS) resource indicator (CRI), a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI), a second combination that includes the CRI, the RI, a first precoding matrix indicator (i1), a third combination that includes the CRI, the RI, the i1, and the CQI, a fourth combination that includes the CRI, the RI, and the CQI, and a fifth combination that includes the CRI, the RI, a layer indicator (LI), the PMI, and the CQI.

[0007] 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.

[0008] FIG. 1 is a diagram illustrating a NW-triggered LTM procedure, according to an example implementation of the present disclosure.

[0009] FIG. 2A is a diagram illustrating a RACH-less conditional LTM cell switch procedure, according to an example implementation of the present disclosure.

[0010] FIG. 2B is a diagram illustrating a RACH-less conditional LTM cell switch procedure, according to an example implementation of the present disclosure.

[0011] FIG. 2C is a diagram illustrating a RACH-based conditional LTM cell switch procedure, according to an example implementation of the present disclosure.

[0012] FIG. 2D is a diagram illustrating a RACH-based conditional LTM cell switch procedure, according to an example implementation of the present disclosure.

[0013] FIG. 2E is a diagram illustrating a RACH-based conditional LTM cell switch procedure, according to an example implementation of the present disclosure.

[0014] FIG. 2F is a diagram illustrating a RACH-less conditional LTM cell switch procedure, according to an example implementation of the present disclosure.

[0015] FIG. 2G is a diagram illustrating a RACH-based conditional LTM cell switch procedure, according to an example implementation of the present disclosure.

[0016] FIG. 3 is a flowchart illustrating a method / process performed by a UE for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM), according to an example implementation of the present disclosure.

[0017] FIG. 4 is a block diagram illustrating a node for wireless communication, according to an example implementation of the present disclosure.

[0018] Some of the abbreviations used in the present disclosure include: Abbreviation　　　　Full name 3GPP　　　　3rdGeneration Partnership Project 5G　　　　5thGeneration 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 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　　　　L1 / L2 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 ML　　　　Machine Learning NACK　　　　Negative Acknowledgment NDI　　　　New Data Indicator NR　　　　New RAT / Radio NW　　　　Network NUL　　　　Normal UL 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 UL 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

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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 computer-executable instructions and perform the disclosed network function(s) or algorithm(s).

[0027] The microprocessors or general-purpose computers may include Application-Specific Integrated Circuits (ASICs), programmable logic arrays, and / or 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 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. The computer-readable medium may include, 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 (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.

[0028] A radio communication network architecture such as a Long-Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Pro system, a 5G NR Radio Access Network (RAN), 5G-Advanced (5G-A) system, or an open radio access network (O-RAN) may typically include at least one base station (BS), at least one UE, and one or more optional network elements that provide connection within a network. The BS and one or more optional network elements enable the UE to access a radio network. Thus, the UE may communicate with the network, such as a Core Network (CN), an Evolved Packet Core (EPC) network, an Evolved Universal Terrestrial RAN (E-UTRAN), a Next-Generation Core (NGC), a 5G Core (5GC), or an internet via a RAN established by one or more BSs and the network elements / functions.

[0029] 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.

[0030] 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.

[0031] 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. 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.

[0032] 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.

[0033] Each cell (may often referred to as a serving cell) may provide services to one or more UEs within the cell’s radio coverage, such that each cell schedules the DL (and optionally UL resources) to at least one UE within its radio coverage for DL (and optionally UL packet transmissions from the UE). The BS may communicate with one or more UEs in the radio communication system via the cells.

[0034] A cell may allocate Sidelink (SL) resources for supporting Proximity Service (ProSe), LTE SL services, LTE / NR sidelink communication services, LTE / NR sidelink discovery services, and / or LTE / NR Vehicle-to-Everything (V2X) services. In addition, a cell may allocate DL and / or UL resources for supporting Multicast / Broadcast Service (MBS) services, Non-Terrestrial Networks (NTN) services, positioning services, power serving services and / or Network Energy Saving (NES) services.

[0035] 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.

[0036] The terms, definitions, and abbreviations as given in the present disclosure may be 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.

[0037] As discussed above, the frame structure for NR may support flexible configurations for accommodating various next generation (e.g., 5G) communication requirements, such as Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC), and Ultra-Reliable and Low-Latency Communication (URLLC), while fulfilling high reliability, high data rate, and low latency requirements. The Orthogonal Frequency-Division Multiplexing (OFDM) technology in the 3GPP may serve as a baseline for an NR waveform. The scalable OFDM numerology, such as adaptive sub-carrier spacing, channel bandwidth, and Cyclic Prefix (CP), may also be used.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The term “A and / or B” within the present disclosure means “A”, “B”, or “A and B”. The term “A and / or B and / or C” within the present disclosure means “A”, “B”, “C”, “A and B”, “A and C”, “B and C”, or “A and B and C”. The term “A / B” within the present disclosure means “A” or “B”.

[0045] In some implementations, the network (NW), cell, camped cell, serving cell, base station, gNB, eNB and ng-eNB may be used interchangeably in the present disclosure. In some implementations, some of these items may refer to the same network entity.

[0046] Examples of some selected terms in the present disclosure are provided as follows.

[0047] 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.

[0048] 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.

[0049] 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).

[0050] Beam: A beam may refer 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 EM wave is radiated.

[0051] 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 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 a PCell and a PSCell, as well as release and / or add SCells when applicable. All cases 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, overhead and interruption time. Furthermore, when UE can determine whether to switch the serving cell based on some defined conditions, the cell switch latency can be reduced dramatically. Hence, conditional LTM may be introduced to enhance the handover process.

[0052] In transitioning from LTM procedures to conditional LTM in New Radio (NR), several challenges emerge due to the differences in operational mechanisms. The 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.

[0053] 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 UE in varying conditions. In some implementations, during the conditional LTM procedure, acquiring Channel State Information (CSI) reports may be critical to ensuring optimal coding schemes and channel quality for the first transmission in the target cell. This challenge may become more pronounced in L1 / L2 Triggered Mobility (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 may impose significant overhead on the User Equipment (UE), which can degrade system efficiency. Thus, how to apply a simplified CSI acquisition during the conditional LTM procedure may be discussed in the present disclosure.

[0054] When the 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 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.

[0055] In detail, mobility latency may include the time from UE receiving the cell switch command to 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+ Tprocess,2), the time that the UE executes DL synchronization (Tsearch+ TΔ+ Tmargin), the time that the UE executes UL synchronization (TIU+ TRAR), and the time that the UE performs the first DL reception / transmission after the random access response (RAR) may be considered as handover interruption time. In some implementations, Tcmdmay refer to time for processing the L1 / L2 command, Tprocess,2may refer to time for UE processing after the 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 the 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 need to be specified.

[0056] RRC pre-configuration

[0057] A source cell / BS may transmit a configuration or information for candidate cells to a UE via RRC (pre-configuration) signaling. After receiving the RRC pre-configuration (e.g., an RRC reconfiguration message), the UE may store and / or apply the received configuration for the L1 / L2 triggered mobility procedure. In some implementations, the RRC pre-configuration may include the resource allocation configuration (e.g., either time domain or frequency domain), the DL synchronization specific configuration, the UL synchronization specific configuration, the BWP configuration, the cell group configuration, the measurement configuration, the report configuration, the beam management configuration (e.g., TCI state configuration), the mobility scenarios configuration, the DL control channel specific configuration, the DL data channel specific configuration, the UL control channel specific configuration, or / and the UL data channel specific configuration.

[0058] In some implementations, the UE may receive the RRC pre-configuration(s) of all candidate cells simultaneously. In some implementations, the UE may receive the RRC pre-configuration of each candidate cell at different timings. In some implementations, the RRC pre-configuration may be applied to an RRC reconfiguration procedure. In some implementations, the RRC pre-configuration may include a reference configuration and a delta configuration.

[0059] Cell switch command

[0060] During the L1 / L2 triggered mobility procedure, the source cell may inform a UE of cell switching related information via 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 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), the RRC pre-configuration index associated with the candidate cells or the target cell, the BWP information for the candidate cells or the target cell, the TA information, the associated reference signal information (e.g., SSB index or CSI-RS resource index), or / and the 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. In some implementations, 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 a 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.

[0061] DL synchronization

[0062] During the L1 / L2 triggered mobility procedure, a UE may execute a DL synchronization process to acquire the DL time / frequency synchronization, the DL system information, and the DL data from the target cell. In some implementations, the UE may perform the DL synchronization before processing the cell switch command to reduce the interruption time. In some implementations, the UE may perform the DL synchronization after processing the cell switch command when the target cell is specifically indicated. In some implementations, the UE may receive information for the DL synchronization via the RRC pre-configuration, the MAC CE, or the DCI from the source cell. In some implementations, the received information may include the logical cell ID (e.g., the IDs of the candidate cells (or PCIs of the candidate cells), the ID of the target cell (or PCI of the target cell)), the SSB index associated with the candidate cells, the SSB index associated with the target cell, the time / frequency domain information for the candidate cells, the time / frequency domain information for the target cell, the CSI resource index associated with the candidate cells, the CSI resource index associated with the target cell, the TCI state configuration associated with the candidate cells, and / or the TCI state configuration associated with the target cell.

[0063] UL synchronization

[0064] During the L1 / L2 triggered mobility procedure, a UE may execute an UL synchronization process to evaluate the exact timing to send the UL information / data to the target cell (e.g., timing advance acquisition). In some implementations, the UE may perform the UL synchronization after finishing the DL synchronization process. In some implementations, the UE may perform the UL synchronization before processing the cell switch command to reduce the interruption time. In some implementations, the UE may perform the 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 (e.g., the contention-based RA procedure, contention-free RA procedure, 2-step RA procedure, or 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 the UL synchronization via the RRC pre-configuration, the MAC-CE, or the DCI from the source cell. In some implementations, the received information may include the PRACH resource configuration associated with the candidate cells or the target cell, the preamble sequence configuration associated with the candidate cells or the target cell, the RACH procedure indication, the 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, the SRS configuration associated with the candidate cells or the target cell, or / and the TCI state configuration associated with the candidate cells or the target cell.

[0065] L1 measurement and report

[0066] A UE may perform measurements and report measurement results based on the received configuration or indication. The L1 measurements may be classified into the L1 intra-frequency measurements or the L1 inter-frequency measurements. In some implementations, the L1 intra-frequency measurement and L1 inter-frequency measurement may be based on the L1-RSRP through measuring the SSB (e.g., SS-RSRP) or the CSI-RS (e.g., CSI-RSRP). In some implementations, the L1 intra-frequency measurement and the L1 inter-frequency measurement may be based on the L1-SINR through measuring the SSB (e.g., SS-SINR) or CSI-RS (e.g., CSI-SINR). In some implementations, the L1 intra-frequency measurement and the L1 inter-frequency measurement may be based on the L1-RSRQ through measuring the SSB (e.g., SS-RSRQ) or CSI-RS (e.g., CSI-RSRQ).

[0067] In some implementations, the L1 measurement report may include one or more PCIs (e.g., PCIs of the candidate cells, the PCI of the source cell, the PCI of the serving cell, or the PCI of the target cell). In some implementations, the L1 measurement report may include one or more RS IDs.

[0068] In some implementations, the L1 measurement report as UCI transmitted on the PUCCH or the PUSCH may be considered as the result of measurement from the UE’s perspective. In some implementations, the L1 measurement report type may refer to the periodic report on the PUCCH, the semi-persistent report on the PUCCH or the PUSCH, and the aperiodic report on the PUSCH. In some implementations, the L1 measurement report may be transmitted via a MAC CE.

[0069] CSI report content

[0070] In some implementations, the CSI report may include the Channel Quality Indicator (CQI), the Precoding Matrix Indicator (PMI), the CSI-RS resource indicator (CRI), the SS / PBCH block resource indicator (SSBRI), the Layer Indicator (LI), the Rank Indicator (RI), the Capability Index, the L1-RSRP, the L1-SINR, or / and the 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).

[0071] In some implementations, a cell in the present disclosure may refer to a PCell, a PSCell, a SpCell, an SCell, a candidate cell, a target cell, a neighbour cell, a serving cell, and / or a source cell.

[0072] CSI acquisition

[0073] The CSI acquisition may rely on reference signals such as CSI-RS and CSI report containing the Channel Quality Indicator (CQI), the Precoding Matrix Indicator (PMI), the Layer Indicator (LI), and the Rank Indicator (RI) to aid in beamforming, resource allocation, and modulation and coding schemes. The 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, the CSI acquisition may enhance spectrum efficiency, reduce interference, and ensure reliable communication.

[0074] Potential scenarios

[0075] Inter-cell mobility scenarios may include, but are not limited to, the intra-node mobility and the inter-node mobility. Moreover, each scenario may correspond to the intra-DU case, the inter-DU case, the intra-CU case, and / or the 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 its operation may be partly controlled by gNB-CU. A DU may support one or more cells. The CU may connect to the several DUs via F1 interfaces.

[0076] Intra-node mobility

[0077] 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 classified into two cases, which include the intra-CU with intra-DU case and the intra-CU with inter-DU case.

[0078] 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.

[0079] Inter-node mobility

[0080] 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 the special cell, PSCell, or SCell.

[0081] FIG. 1 is a diagram illustrating a NW-triggered LTM procedure 100, according to an example implementation of the present disclosure. As illustrated in FIG. 1, the LTM procedure (e.g., the conditional LTM procedure) 100 may divided into different parts such as the LTM preparation 120, the early synchronization 126, the LTM cell switch execution 138, and the LTM cell switch completion 142. Each part in the conditional LTM procedure 100 may be revisited since the UE 102 can determine the timing of performing cell switch when some predefined conditions are met in the conditional LTM operation.

[0082] The UE 102 may be in the RRC_CONNECTED state / mode 110. The UE 102 may send a measurement report message 112 to the gNB 104. The gNB 104 may determine to configure LTM and initiate LTM preparation, such as LTM candidate preparation 114. The 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 gNB 104. In the action 122, the UE 102 may perform DL synchronization with the LTM candidate cell(s). In the action 124, the UE 102 may perform UL synchronization with LTM candidate cell(s)

[0083] The UE 102 may perform L1 measurements on the configured LTM candidate cell(s) and transmit L1 measurement reports 128 to the gNB 104. In the action 130, the gNB 104 may determine to execute cell switch to a target cell. The gNB 104 may transmit an LTM cell switch command 132 (e.g., a cell switch command MAC CE) triggering cell switch. In the action 134, the UE 102 may detach from the source cell, switch to the target cell. In the action 136, the UE 102 may perform a random access procedure towards the target cell associated with the gNB 106, if the UE 102 does not have valid TA of the target cell. If the UE 102 has performed a RA procedure in the action 136 the UE 102 may consider that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. The action 136 for UL synchronization with the candidate cells may be performed after the reception of the cell switch command 132. In the action 140, the UE 102 may complete the LTM cell switch procedure by sending an RRC reconfiguration complete message to the gNB 106.

[0084] In some implementations, the predefined conditions may include the following (a)-(c).

[0085] (a) When the L1-RSRP / L1-SINR of the candidate cell becomes better by an amount of offset than the L1-RSRP / L1-SINR of the PCell / PSCell.

[0086] (b) When the L1-RSRP / L1-SINR of the candidate cell becomes better than an absolute threshold.

[0087] (c) When the L1-RSRP / L1-SINR of the PCell / PSCell becomes worse than a first absolute threshold and the L1-RSRP / L1-SINR of the candidate cell becomes better than a second absolute threshold.

[0088] 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. 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. The L1-RSRP / L1-SINR of the PCell / PSCell may be derived from the beam currently indicated for the PDCCH / PDSCH reception in the PCell / PSCell. 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. In some implementations, the gNB may be replaced by the eNB, RAN, Network, or BS.

[0089] Cell switch and CSI acquisition notification / Cell switch notification or CSI acquisition notification

[0090] In some implementations, a UE may transmit a cell switch and CSI acquisition notification or a cell switch notification to source cell to notify which target cell that satisfies one or more predefined conditions. Also, the cell switch and CSI acquisition notification and / or the CSI acquisition notification may be used to acquire the configuration and / or the resource of CSI report for the target cell that satisfies one or more predefined conditions. The cell switch and CSI acquisition notification, the cell switch notification, and / or the CSI acquisition notification may include a target cell index, a TCI state ID, a RS index, a CSI acquisition request indication, 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 (e.g., periodic PUCCH, dynamic PUCCH). In some implementations, the cell switch notification may be multiplexed with a CSI report in a PUSCH or PUCCH. The cell switch notification and CSI acquisition notification may be transmitted together. In some implementations, the cell switch notification and CSI acquisition notification may be transmitted separately.

[0091] In some implementations, the UE may transmit a CSI acquisition notification to enable the CSI report quantity indicating at least one of following combinations (a)-(e): (a) cri-RI-PMI-CQI, (b) cri-RI-i1, (c) cri-RI-i1-CQI, (d) cri-RI-CQI, and (e) cri-RI-LI-PMI-CQI.

[0092] The CSI report quantity may be configured in the LTM candidate configuration or may be configure during the LTM candidate preparation phase.

[0093] In some implementations, the UE may transmit cell switch and CSI acquisition notification and / or the CSI acquisition notification with the L3 measurement result or after transmitting the L3 measurement result via RRC signaling during the LTM candidate preparation phase, so the UE may transmit the notification before receiving RRC reconfiguration message including the LTM candidate configuration. In other words, the UE may determine the target cell for performing the CSI acquisition based on L3 measurement results (or L3 / L1 beam / cell measurement results) and use one bit indication for notifying whether to acquire CSI acquisition related information in the PUSCH with L3 measurement results. In some implementations, the UE may transmit a one-bit indication using an UL resource (e.g., PUCCH or PUSCH) to the source cell (e.g., gNB) after the UE transmits L3 measurement results. After receiving the cell switch and CSI acquisition notification and / or the CSI acquisition notification, the NW may transmit a CSI report configuration for the CSI acquisition in the LTM-Config IE or the LTM-candidate to the UE, where the CSI report configuration may include the CSI report quantity with at least the following combinations (a)-(e): (a) cri-RI-PMI-CQI, (b) cri-RI-i1, (c) cri-RI-i1-CQI, (d) cri-RI-CQI, and (e) cri-RI-LI-PMI-CQI.

[0094] In some implementations, the UE may transmit the CSI acquisition notification with the L1 measurement report. More specifically, a one-bit indication may be carried in the CSI report for L1 measurement results to indicate the source cell (gNB) to transmit an additional configuration other than the LTM configuration including information that refers to the CSI report quantity indicating at least one of following combinations (a)-(e): (a) cri-RI-PMI-CQI, (b) cri-RI-i1, (c) cri-RI-i1-CQI, (d) cri-RI-CQI, and (e) cri-RI-LI-PMI-CQI.

[0095] In some implementations, for RACH-based LTM cell switch, the UE may transmit the CSI acquisition notification after the L1 measurement report and before or upon the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB).

[0096] In some implementations, for RACH-less LTM cell switch, the UE may transmit the CSI acquisition notification after the L1 measurement report.

[0097] In some implementations, the CSI acquisition notification may refer to the UEAssistanceInformation message.

[0098] In some implementations, the UE may set the contents of the UEAssistanceInformation message as follows. If transmission of the UEAssistanceInformation message is initiated to provide a CSI acquisition report for the conditional LTM, the UE may include the PCI index / LTM configuration index / enableCSIACQ in the CSI-ReportPreference IE. The information included in the UEAssistanceInformation message and the IE are exemplary illustrations, and the information and the IE name may be compatible.

[0099] UE performs early synchronization without cell switch notification

[0100] In some implementations, the UE may perform the L1 measurement without sending the cell switch notification after receiving the RRC reconfiguration message containing the LTM candidate configuration and after transmitting RRC reconfiguration complete message. Then, the UE may evaluate whether the measurement result of one or more candidate cells meet the one or more conditions.

[0101] In some implementations, whether to perform the early synchronization towards the candidate cell may be based on the predefined condition. If a cell satisfies the predefined condition, the UE may perform the early synchronization to the cell. In other words, the UE may determine one or more candidate cells to perform the DL synchronization and UL synchronization based on the one or more 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 candidate cells. For UL synchronization, the UE may perform the RACH procedure to the one or more candidate cells based on the determined TCI state / RS index. More specifically, the UE may transmit the PRACH to the one or more candidate cells based on the LTM candidate configuration (e.g., the ltm-EarlyUL-SyncConfig-r18 IE) and the one or more candidate cells may perform beam sweeping to select a correspondence beam for the UL synchronization (e.g., to receive the PRACH from the UE).

[0102] 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 the conditional LTM. In other words, a group of preamble indexes or a group of SSB indexes may be configured as conditional LTM purpose. For example, an RRC parameter (e.g., the prach-ConfigurationIndex-condLTM IE) may be configured in the RACH-ConfigGeneric IE to identify a random access procedure for the conditional LTM.

[0103] In some implementations, after the UE transmits the PRACH to the one or more candidate cells, the UE may receive random access response (RAR) with a TA value (or TA command) from the one or more candidate cells based on the transmitted PRACH.

[0104] In some implementations, a dedicated search space for configuring the RAR of the 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 the CRC scrambled by the RA-RNTI or the conditional LTM purpose RA-RNTI. The beams for monitoring the RAR may be the same as the TCI state ID / RS index which has been selected in the DL synchronization. In some implementations, the dedicated search space may be target cell-specific search space. Thus, the UE may monitor the RAR based on the selected / activated TCI state / RS.

[0105] In some implementations, a dedicated DCI format carrying the TA value only in a common search space may be monitored, and the dedicated DCI format may be different from the DCI format carrying the RAR. The dedicated DCI format may be with CRC scrambled by a dedicated RNTI (e.g., the condLTM-RNTI IE) or a C-RNTI. Furthermore, the dedicated DCI format may include candidate cell information to let the UE know that the TA value is derived from which candidate cell. The beams for monitoring the RAR may be the same as the TCI state ID / RS index which has been selected in the DL synchronization. Thus, the UE may monitor the RAR based on the selected / activated TCI state / RS.

[0106] In some implementations, when the UE receives the RAR or the DCI format carrying the TA value only, the UL synchronization may be considered as complete. In other words, the UE may not need to transmit the message 3 (e.g., the MSG3 during a 4-step RA procedure) to proceed in the UL synchronization process, and the UE may be synchronized with the candidate cell.

[0107] In some implementations, after the UE transmits the PRACH to the one or more candidate cells, the UE may receive a MAC CE including the TA value from the source cell. In other words, the candidate cells may inform the source cell via 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.

[0108] In some implementations, the MAC CE may be carried in a DG PDSCH or a SPS PDSCH. In some implementations, a DCI format for scheduling the DG PDSCH or activating the SPS PDSCH may be dedicated for conditional LTM.

[0109] 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.

[0110] In some implementations, the field in the MAC CE may include one or more candidate cell IDs and its corresponding TA value.

[0111] 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 the message 3 to proceed in the UL synchronization process, and the UE may be synchronized with the candidate cell.

[0112] 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.

[0113] In some implementations, after the synchronization is considered as complete, the UE may determine to switch to a target cell among the candidate cells that finish the UL and / or DL synchronization process.

[0114] In some implementations, after the synchronization is considered as complete, the UE may further evaluate the one or more candidate cells based on the predefined conditions again to determine the switching point. More specifically, if s target cell from the candidate cells finishing the synchronization process satisfies the predefined condition, the UE may determine to 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 cell satisfies the predefined condition, it is up to UE implementation to determine which candidate cell is to be switched to.

[0115] In some implementations, the UE may be mandated to apply UE-based TA measurement after the DL synchronization is completed when the conditional LTM is configured.

[0116] 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.

[0117] UE performs CSI acquisition for RACH-less conditional LTM cell switch without CSI acquisition notification

[0118] In some implementations, for RACH-less conditional LTM cell switch, the UE may receive CSI acquisition related information via a MAC CE or a DCI format, from the serving cell (e.g., source cell / gNB), including a CSI request indication, a CSI report configuration index, a LTM candidate configuration index, CSI report quantity, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication to indicate whether to multiplex / transmit the CSI report and the RRC reconfiguration complete message together in the first UL transmission based on L1 measurement results and the predefined conditions.

[0119] In some implementations, the CSI request indication may correspond to one bit, where bit value 0 may refer to no CSI report (e.g., for CSI acquisition) triggering and bit value 1 may refer to CSI report triggering. In other words, if the CSI request indication indicates the trigger of CSI report, the UE may transmit the CSI report (e.g., for CSI acquisition) based on the CSI request indication. If the CSI request indication indicates no trigger of CSI report, the UE may not expect to transmit the CSI report (e.g., for CSI acquisition).

[0120] In some implementations, the CSI request indication may correspond to a number of bits, where the size of bits may be determined by the corresponding RRC parameter (e.g., the reportTriggerSize IE). Moreover, the CSI request indication may indicate one of triggering states, and one triggering state may include the associated CSI report configuration information (e.g., CSI report index, CSI resource set index).

[0121] In some implementations, the triggering state indication may indicate one triggering state index for CSI report configuration, where the triggering state may include the CSI report information and the associated CSI resource set information. In some implementations, the CSI-RS resource set triggering offset indication may indicate the offset between the MAC CE / control message (e.g., DCI) for triggering CSI report for CSI acquisition and the triggered CSI resource set, and the CSI resource set may be associated with the indicated CSI report configuration. In some implementations, the UE may determine to perform the L1 (beam / cell) measurement before the execution of the conditional LTM cell switch based on a UE capability. In some implementations, the UE may determine to perform the L1 (beam / cell) measurement after the execution of the conditional LTM cell switch based on a UE capability.

[0122] The UE may transmit the CSI report for CSI acquisition to the candidate cell (e.g., target cell / gNB) based on the received information in the MAC CE or the DCI format.

[0123] 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.

[0124] In some implementations, the first UL transmission may be an UL transmission (e.g., PUCCH or PUSCH) on the target cell after receiving TA information. In some implementations, the first UL transmission may include the CSI report for CSI acquisition and complete message for conditional LTM cell switch.

[0125] In some implementations, for RACH-less conditional LTM cell switch, the serving cell (e.g., source cell / gNB / eNB / CU / DU) may send an indication (e.g., UEID) to notify that the one or more candidate cells associated with the LTM candidate configuration is to be connected to a specific UE, and the UE may receive CSI acquisition related information via a MAC CE or a DCI format, from the one or more candidate cells (e.g., target cell / gNB / eNB / CU / DU) based on the measurement result and the predefined (configured) conditions (e.g., the candidate cell may refer to the cell with the highest L1-RSRP). The CSI acquisition related information may include a CSI request indication, a CSI report configuration index, a LTM candidate configuration index, CSI report quantity, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication to indicate whether to multiplex / transmit the CSI report and RRC reconfiguration complete message together in the first UL transmission. In some implementations, the UE may receive CSI acquisition related information via a MAC CE or a DCI format, from the candidate cell (e.g., target cell / gNB / eNB / CU / DU) after the UE switches to the candidate cell (e.g., target cell / gNB / eNB / CU / DU). In some implementations, the UE may determine to perform the L1 (beam / cell) measurement before the execution of conditional LTM cell switch based on a UE capability / feature set. In some implementations, the UE may determine to perform the L1 (beam / cell) measurement after the execution of conditional LTM cell switch based on a UE capability. Then, the UE may transmit the CSI report for CSI acquisition to the candidate cell (e.g., target cell / gNB) based on the received information in the MAC CE or the DCI format. Lastly, 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. In some implementations, the first UL transmission is an UL transmission (e.g., the PUCCH or PUSCH) on the target cell after receiving TA information. In some implementations, the first UL transmission may include the CSI report for CSI acquisition and a complete message for conditional LTM cell switch.

[0126] In some implementations, the MAC CE including the CSI acquisition related information may refer to a MAC CE including the TA information and the CSI acquisition related information. In some implementations, the MAC CE including the CSI acquisition related information may refer to a MAC CE including the CSI report related information only. In some implementations, the MAC CE including the CSI acquisition related information may refer to a MAC CE including the TCI state activation / deactivation / indication information. In some implementations, the DCI format including the CSI acquisition related information may refer to a DCI format specific to scheduling the CSI report. In some implementations, the DCI format including the CSI acquisition related information may refer to a DCI format for random access procedure.

[0127] In some implementations, the UE may receive the CSI acquisition related information before the reception of the TA information. In some implementations, the UE may receive the CSI acquisition related information before the TCI state activation / deactivation / indication. In some implementations, the UE may receive the CSI acquisition related information before the reception of DCI format for random access procedure (e.g., the PDCCH order).

[0128] Some exemplary procedures for performing the CSI acquisition for conditional LTM cell switch without CSI acquisition notification are illustrated in FIG. 2A and FIG. 2B.

[0129] FIG. 2A is a diagram illustrating a RACH-less conditional LTM cell switch procedure 200A, according to an example implementation of the present disclosure. The UE may receive the MAC CE including CSI report information from the source gNB for RACH-less conditional LTM cell switch. As illustrated in FIG. 2A, the LTM procedure (e.g., the RACH-less conditional LTM switch procedure) 200 may divided into different parts such as the LTM preparation 220, the early synchronization 226, the LTM cell switch execution 238, and the LTM cell switch completion 242.

[0130] The UE 202 may be in the RRC_CONNECTED state / mode 210. The UE 202 may send a measurement report message 212 to the source gNB 204. The source gNB 204 may determine to configure LTM and initiate LTM preparation, such as LTM candidate preparation 214. The source gNB 204 may transmit an RRC reconfiguration message to the UE including the LTM candidate configurations 216. The UE 202 may store the LTM candidate configurations and transmit an RRC reconfiguration complete message 218 to the source gNB 204. In the action 222, the UE 202 may perform DL synchronization with the LTM candidate cell(s). In the action 224, the UE 202 may perform UL synchronization with LTM candidate cell(s).

[0131] The UE 202 may perform L1 measurements 228 on the configured LTM candidate cell(s). In the action 230, the UE 202 may evaluate the predefined conditions. The UE 202 may receive, from the source gNB 204, a MAC CE including CSI report information 232. In the action 234, the UE 202 may detach from the source cell. The UE may then perform cell switch 236 to the target cell associated with the target gNB 206. After performing the cell switch to 236 to the target cell associated with the target gNB 206, the UE 202 may transmit the CSI report for CSI acquisition 240. In the action 244, the UE 202 may complete the LTM cell switch procedure by sending a conditional LTM complete message to the gNB 206.

[0132] FIG. 2B is a diagram illustrating a RACH-less conditional LTM cell switch procedure 200B, according to an example implementation of the present disclosure. The UE may receive the MAC CE including CSI report information from the target gNB for RACH-less conditional LTM cell switch. The RACH-less conditional LTM cell switch procedure 200B is similar to the RACH-less conditional LTM switch procedure 200A, except that the UE 202 may receive, from the target gNB 206, a MAC CE including the CSI report information 246 rather than receiving, from the source gNB 204, the MAC CE including the CSI report information 232. The UE 202 may receive, from the target gNB 206, the MAC CE 246 including the CSI report information after detaching from the source cell (e.g., the action 234).

[0133] UE performs CBRA without cell switch notification

[0134] In some implementations, the UE may perform the L1 measurement without sending the cell switch notification after receiving the RRC reconfiguration message containing the LTM candidate configuration and after transmitting the RRC reconfiguration complete message. Then, the UE may evaluate whether the measurement result of one or more candidate cells meet the one or more conditions.

[0135] In some implementations, the UE may select a target cell when the target cell satisfies the predefined conditions, and then the UE may switch to the target cell. After switching to the target cell, the UE may perform contention-based random access (CBRA) to do the DL and / or UL synchronization.

[0136] 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.

[0137] UE performs CSI acquisition for RACH-based conditional LTM cell switch without CSI acquisition notification

[0138] In some implementations, for RACH-based LTM cell switch, after the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB) and before or upon the RRCReconfigurationComplete message, the UE may transmit the CSI report for CSI acquisition for conditional LTM cell switch, where the CSI report may be directly transmitted to the candidate cell (e.g., target cell / gNB / eNB / CU / DU). Since there is no CSI acquisition notification to notify the serving cell which target cell the UE determines to be switched to, the UE may receive the CSI acquisition related information from the serving cell (e.g., source cell / gNB) based on the L1 measurement result before the PRACH transmission on the candidate cell (e.g., target cell / gNB). More specifically, the UE may receive a MAC CE or a DCI format, from the serving cell (e.g., source cell / gNB), where the MAC CE or the DCI format may include a CSI request indication, a CSI report configuration index, a LTM candidate configuration index, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication to indicate whether to multiplex / transmit the CSI report and RRC reconfiguration complete message together / jointly in the first UL transmission before the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB).

[0139] In some implementations, the UE may determine to perform the L1 (beam / cell) measurement before the execution of conditional LTM cell switch based on a UE capability. In some implementations, the UE may determine to perform the L1 measurement after the execution of conditional LTM cell switch based on a UE capability.

[0140] In some implementations, for RACH-based LTM cell switch, after the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB) and before or upon the RRCReconfigurationComplete message, the UE may transmit the CSI report for CSI acquisition for conditional LTM cell switch, where the CSI report may be directly transmitted to the candidate cell (e.g., target cell / gNB). Since there is no CSI acquisition notification to notify the serving cell which target cell the UE determines to be switched to, the serving cell (e.g., source cell / gNB / eNB / CU / DU) may send an indication (e.g., UEID) to notify that the one or more candidate cells associated with the LTM candidate configuration are to be connected to a specific UE, and the UE may receive the CSI acquisition related information from the one or more candidate cell (e.g., target cell / gNB) before the PRACH transmission on the one or more candidate cell (e.g., target cell / gNB). More specifically, the UE may receive a MAC CE or a DCI format, from the candidate cell (e.g., target cell / gNB), where the MAC CE or the DCI format may include a CSI request indication, a CSI report configuration index, a LTM candidate configuration index, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication to indicate whether to multiplex / transmit the CSI report and RRC reconfiguration complete message together in the first UL transmission before the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB). Lastly, the UE may transmit the CSI report to the candidate cell (e.g., target cell / gNB) for CSI acquisition for LTM on the first UL transmission based on the information for the CSI report.

[0141] In some implementations, for RACH-based LTM cell switch, after the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB) and before or upon the RRCReconfigurationComplete message, the UE may transmit the CSI report for CSI acquisition for conditional LTM cell switch, where the CSI report may be directly transmitted to the candidate cell (e.g., target cell / gNB). Since there is no CSI acquisition notification to notify the serving cell which target cell the UE determines to be switched to, the serving cell (e.g., source cell / gNB / eNB / CU / DU) may send an indication (e.g., UEID) to notify that the one or more candidate cells associated with the LTM candidate configuration are to be connected to a specific UE, and the UE may receive the CSI acquisition related information from the one or more candidate cells (e.g., target cell / gNB) after the completion of (e.g., a 2-step / 4-step) random access procedure on the candidate cell (e.g., target cell / gNB). More specifically, the UE may receive a MAC CE or a DCI format, from the one or more candidate cells (e.g., target cell / gNB), where the MAC CE or the DCI format may include a CSI request indication, a CSI report configuration index, a LTM candidate configuration index, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication to indicate whether to multiplex / transmit the CSI report and RRC reconfiguration complete message together in the first UL transmission before the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB).

[0142] In some implementations, the first UL transmission may include an UL transmission (e.g., PUCCH or PUSCH) on the target cell after the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB) and before or upon the completion message for conditional LTM cell switch.

[0143] In some implementations, the first UL transmission may include the Msg3 PUSCH or MsgA PUSCH and CSI report for CSI acquisition. In some implementations, the MAC CE including CSI acquisition related information may refer to a MAC CE including CSI report related information only. In some implementations, the MAC CE including CSI acquisition related information may refer to a MAC CE including TCI state activation / deactivation / indication information. In some implementations, the DCI format including CSI acquisition related information may refer to a DCI format specific to scheduling the CSI report.

[0144] Some exemplary procedures for performing CSI acquisition for conditional LTM cell switch without CSI acquisition notification are shown in FIG. 2C, FIG. 2D, and FIG. 2E.

[0145] FIG. 2C is a diagram illustrating a RACH-based conditional LTM cell switch procedure 200C, according to an example implementation of the present disclosure. The UE may receive the MAC CE including CSI report information from the source gNB for RACH-based conditional LTM cell switch. The RACH-based conditional LTM cell switch procedure 200C is similar to the RACH-less conditional LTM switch procedure 200A, except that the action for UL synchronization in the RACH-less LTM procedure 200A (e.g., the action 224) is omitted, and instead the RACH-based conditional LTM cell switch procedure 200C includes a corresponding action for UL synchronization (e.g., the action 248). In the RACH-based conditional LTM cell switch procedure 200C, the action 248 for UL synchronization with the candidate cells may be performed after performing cell switch 236 to the target cell associated with the target gNB 206.

[0146] FIG. 2D is a diagram illustrating a RACH-based conditional LTM cell switch procedure 200D, according to an example implementation of the present disclosure. The UE may receive the MAC CE including CSI report information from the target gNB for RACH-based conditional LTM cell switch. The RACH-based conditional LTM cell switch procedure 200D is similar to the RACH-based conditional LTM cell switch procedure 200C, except that the UE 202 may receive, from the target gNB 206, a MAC CE including the CSI report information 250 rather than receiving, from the source gNB 204, the MAC CE including the CSI report information 232. The UE 202 may receive, from the target gNB 206, the MAC CE including the CSI report information 250 before performing the UL synchronization with the candidate cells (e.g., the action 248).

[0147] FIG. 2E is a diagram illustrating a RACH-based conditional LTM cell switch procedure 200E, according to an example implementation of the present disclosure. The UE may receive the MAC CE including CSI report information from the target gNB for RACH-based conditional LTM cell switch. The RACH-based conditional LTM cell switch procedure 200E is similar to the RACH-based conditional LTM cell switch procedure 200C, except that the UE 202 may receive, from the target gNB 206, a MAC CE including the CSI report information 252 rather than receiving, from the source gNB 204, the MAC CE including the CSI report information 232. The UE 202 may receive, from the target gNB 206, the MAC CE including the CSI report information 252 after performing the UL synchronization with the candidate cells (e.g., the action 248).

[0148] UE performs early synchronization with cell switch notification

[0149] In some implementations, the UE may perform the 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.

[0150] In some implementations, the source cell may transmit one or more PDCCH orders to instruct the UE to perform the RACH procedure towards the candidate cells in the cell switch notification, where the one or more PDCCH orders may include the random access preamble index, SS / PBCH index, and / or PRACH mask index.

[0151] In some implementations, after the UE receives the PDCCH order, the UE may transmit the PRACH to the one or more candidate cells based on one or more PDCCH orders.

[0152] In some implementations, the UE may receive the RAR or TA value from the source cell. In some implementations, the candidate cell(s) may inform 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. 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 TA information for one or more candidate cells.

[0153] In some implementations, the UE may receive the RAR from the candidate cell(s). In some implementations, a dedicated search space for configuring the 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 the DCI format 1_0 / DCI format 1_1 / DCI format 2_0 / DCI format 2_1 / dedicated DCI format for LTM with the CRC scrambled by the RA-RNTI or the conditional LTM purpose RA-RNTI. The beams for monitoring the RAR may be the same as the TCI state ID / RS index which has been indicated the cell switch notification. Thus, the UE may monitor the RAR based on the selected / activated TCI state / RS by the UE. In some implementations, a dedicated DCI format in a common search space to carry TA value only may be monitored, and the dedicated DCI format may be different from the DCI format carrying the RAR. The dedicated DCI format may be with CRC scrambled by a dedicated RNTI (e.g., the condLTM-RNTI) or a C-RNTI. Furthermore, the dedicated DCI format may include candidate cell information to let the UE know that the TA value is derived from which candidate cell. The beams for monitoring the 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 the RAR based on the selected / activated TCI state / RS by the UE.

[0154] 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 the message 3 in the RACH process.

[0155] In some implementations, 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.

[0156] More specifically, the candidate cell(s) may be indicated by the LTM candidate ID(s), where the UE may consider that a candidate cell is associated with an LTM candidate ID if the cell ID (e.g., the physCellId) of the candidate cell and the LTM candidate ID is included in the same LTM-Candidate IE.

[0157] 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.

[0158] In some implementations, 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.

[0159] In some implementations, the UE may be 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.

[0160] In some implementations, the UE may be 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 it is not allowed to use the preamble index for preamble transmission towards the candidate cell for early TA acquisition purpose.

[0161] In some implementations, 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 it is not allowed to use the preamble index for preamble transmission towards the candidate cell for early TA acquisition purpose.

[0162] In some implementations, after the synchronization is considered as complete, the UE may determine to switch to a target cell from the candidate cells that finish the synchronization process.

[0163] In some implementations, after the synchronization is considered as complete, the UE may evaluate the one or more candidate cells based on the predefined conditions again to determine the switching point. More specifically, if a target cell from the candidate cells finishing the synchronization process satisfies the predefined condition, the UE may determine to switch to the target cell immediately. If there are more than one candidate cell satisfies the predefined condition, it is up to UE implementation to determine which candidate cell is to be switched to.

[0164] In some implementations, the predefined conditions may be configured in different LTM configurations. For example, 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., the DL synchronization phase, UL synchronization phase, cell switch phase). In some implementations, the different sets of conditions corresponding to different phase may be same or different.

[0165] NW performs early synchronization with cell switch notification

[0166] In some implementations, the UE may perform the 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.

[0167] In some implementations, for DL synchronization, the UE may receive an TCI state indication MAC CE from the source cell based on the cell switch notification. In some implementations, the MAC CE may include a TCI state ID (e.g., DL / joint TCI state or UL TCI state) or two TCI state IDs (e.g., DL TCI state and UL TCI state), a field to indicate whether each TCI codepoint has multiple TCI states or a single TCI state, and / or a candidate cell index. In some implementations, the MAC CE may include a RS index (e.g., RS index for DL or RS index for UL) or two RS indexes (e.g., RS indexes for DL and UL), a field to indicate whether each RS codepoint has multiple RS indexes or a single RS index, and / or a candidate cell index. If there is more than one candidate cell, the UE may receive more than one MAC CE for each candidate cell.

[0168] In some implementations, for UL synchronization, the UE may receive one or more PDCCH orders from the source cell to perform the RACH procedure towards the candidate cell(s). The received information in the one or more PDCCH orders may be based on the cell switch notification, and the PDCCH order may include the random access preamble index, SS / PBCH index, and / or PRACH mask index.

[0169] In some implementations, after the UE receives the one or more PDCCH orders, the UE may transmit the PRACH to the one or more candidate cells based on one or more PDCCH orders.

[0170] In some implementations, the UE may receive the RAR or TA value from the source cell. In some implementations, the candidate cell(s) may inform the 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. 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 TA information for one or more candidate cells. For example, 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).

[0171] In some implementations, the UE may receive the RAR from the candidate cell(s). In some implementations, a dedicated search space for configuring the 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 the 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 the RA-RNTI or the conditional LTM purpose RA-RNTI. The beams for monitoring the RAR may be the same as the TCI state ID / RS index which has been indicated the cell switch notification. Thus, the UE may monitor the RAR based on the selected / activated TCI state / RS by the UE. In some implementations, a dedicated DCI format in a common search space to carry the TA value only may be monitored, and the dedicated DCI format may be different from the DCI format carrying the RAR. The dedicated DCI format may be with CRC scrambled by a dedicated RNTI (e.g., the condLTM-RNTI) or a C-RNTI. Furthermore, the dedicated DCI format may include candidate cell information to let the UE know that the TA value is derived from which candidate cell. The beams for monitoring the RAR may be the same as the TCI state ID / RS index which has been indicated in cell switch notification. Thus, the UE may monitor the RAR based on the selected / activated TCI state / RS by the UE.

[0172] 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 in the RACH process.

[0173] In some implementations, after the synchronization is considered as complete, the UE may determine to switch to a target cell from the candidate cells that finish the synchronization process.

[0174] In some implementations, after the synchronization is considered as complete, the UE may evaluate the one or more candidate cells based on the predefined conditions again to determine the switching point. More specifically, if a target cell from the candidate cells finishing the synchronization process satisfies the predefined condition, the UE may determine to switch to the target cell immediately. If there are more than one candidate cell satisfies the predefined condition, it is up to UE implementation to determine which candidate cell is to be switched to.

[0175] UE performs CSI acquisition for RACH-less conditional LTM cell switch with CSI acquisition notification

[0176] In some implementations, for RACH-less conditional LTM cell switch, the UE may transmit a CSI acquisition notification to the serving cell (e.g., source cell / gNB). Then, the UE may receive the CSI acquisition related information via a MAC CE or a DCI format, from the serving cell (e.g., source cell / gNB / CU / DU), where the MAC CE or the DCI format may include a CSI request indication, a CSI report configuration index, a LTM candidate configuration index, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication to indicate whether to multiplex / transmit the CSI report and RRC reconfiguration complete message together in the first UL transmission based on the CSI acquisition notification. Thus, the UE may transmit the CSI report for CSI acquisition to the candidate cell (e.g., target cell / gNB / CU / DU) indicated in the CSI acquisition notification based on the received information in the MAC CE or the DCI format. The first UL transmission is an UL transmission (e.g., the PUCCH or PUSCH) on the target cell after receiving TA information.

[0177] In some implementations, the MAC CE including the CSI acquisition related information may refer to a MAC CE including TA information and CSI acquisition related information. In some implementations, the MAC CE including the CSI acquisition related information may refer to a MAC CE including the CSI report related information only. In some implementations, the DCI format including the CSI acquisition related information may refer to a DCI format specific to scheduling the CSI report. In some implementations, the DCI format including the CSI acquisition related information may refer to a DCI format for the random access procedure. In some implementations, the UE may receive the CSI acquisition related information before the reception of the TA information. In some implementations, the UE may receive the CSI acquisition related information before the TCI state activation / deactivation / indication. In some implementations, the UE may receive the CSI acquisition related information before the reception of the DCI format for the random access procedure (e.g., PDCCH order).

[0178] UE performs CSI acquisition for RACH-based conditional LTM cell switch with CSI acquisition notification

[0179] In some implementations, the UE may transmit a CSI acquisition notification to the serving cell (e.g., source cell / gNB). For RACH-based LTM cell switch, after the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB / CU / DU) and before or upon the RRCReconfigurationComplete message, the UE may transmit the CSI report for CSI acquisition for conditional LTM cell switch, where the CSI report may be directly transmitted to the candidate cell (e.g., target cell / gNB), and the UE may receive the CSI report for CSI acquisition related information from the serving cell (e.g., source cell / gNB / CU / DU) based on the CSI acquisition notification before the PRACH transmission on the candidate cell (e.g., target cell / gNB / CU / DU). More specifically, the UE may receive a MAC CE or a DCI format including a CSI request indication, a CSI report configuration index, a LTM candidate configuration index, a triggering state indication, a CSI-RS resource set triggering offset indication, and / or an indication to indicate whether to multiplex / transmit the CSI report and RRC reconfiguration complete message together in the first UL transmission before the completion of the random access procedure associated with the (e.g., 2-step / 4-step) PRACH transmission on the candidate cell (e.g., target cell / gNB / CU / DU).

[0180] In some implementations, the first UL transmission may include a UL transmission (e.g., PUCCH or PUSCH) on the target cell after the completion of the random access procedure associated with the PRACH transmission on the candidate cell (e.g., target cell / gNB). In some implementations, the first UL transmission may include the Msg3 PUSCH or MsgA PUSCH. In some implementations, the MAC CE including the CSI acquisition related information may refer to a MAC CE including the CSI report related information only. In some implementations, the MAC CE including the CSI acquisition related information may refer to a MAC CE including the TCI state activation / deactivation / indication information. In some implementations, the DCI format including the CSI acquisition related information may refer to a DCI format specific to scheduling the CSI report.

[0181] Some exemplary procedures for performing the CSI acquisition for the conditional LTM cell switch without the CSI acquisition notification are shown in FIG. 2F and FIG. 2G.

[0182] FIG. 2F is a diagram illustrating a RACH-less conditional LTM cell switch procedure 200F, according to an example implementation of the present disclosure. The UE may receive the MAC CE including CSI report information with CSI acquisition notification for RACH-less conditional LTM cell switch. The RACH-less conditional LTM cell switch procedure 200F is similar to the RACH-less conditional LTM cell switch procedure 200A, except that the UE 202 may transmit, to the source gNB 204, a CSI acquisition notification 254. The UE 202 may transmit, to the source gNB 204, the CSI acquisition notification 254 before receiving the MAC CE including the CSI report information 232.

[0183] FIG. 2G is a diagram illustrating a RACH-based conditional LTM cell switch procedure 200G, according to an example implementation of the present disclosure. The UE may receive the MAC CE including CSI report information with CSI acquisition notification for RACH-based conditional LTM cell switch. The RACH-based conditional LTM cell switch procedure 200G is similar to the RACH-based conditional LTM cell switch procedure 200C, except that the UE 202 may transmit, to the source gNB 204, a CSI acquisition notification 256. The UE 202 may transmit, to the source gNB 204, the CSI acquisition notification 256 before receiving the MAC CE including the CSI report information 232.

[0184] FIG. 3 is a flowchart illustrating a method / process 300 performed by a UE for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM), according to an example implementation of the present disclosure.

[0185] In the action 302, the process 300 may start by receiving, from a source cell, a radio resource control (RRC) configuration that includes a channel state information (CSI) report configuration and CSI measurement configuration for one or more candidate cells.

[0186] In the action 304, the process 300 may transmit, to the source cell, a first CSI report including an L1-reference signal received power (RSRP) value based on the CSI measurement configuration.

[0187] In the action 306, the process 300 may receive, from the source cell, a medium access control (MAC) control element (CE) including information for a second CSI report.

[0188] In the action 308, the process 300 may transmit, to a target cell, the second CSI report based on the MAC CE. The target cell may be one of the one or more candidate cells. The CSI report configuration may include a CSI report quantity, and the CSI report quantity may include at least one of: a first combination that includes a channel state information (CSI)-reference signal (RS) resource indicator (CRI), a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI) (e.g., cri-RI-PMI-CQI), a second combination that includes the CRI, the RI, a first precoding matrix indicator (i1) (e.g., cri-RI-i1), a third combination that includes the CRI, the RI, the i1, and the CQI (e.g., cri-RI-i1-CQI), a fourth combination that includes the CRI, the RI, and the CQI (e.g., cri-RI-CQI), and a fifth combination that includes the CRI, the RI, a layer indicator (LI), the PMI, and the CQI (e.g., cri-RI-LI-PMI-CQI). The process 300 may then end.

[0189] The steps / actions shown in FIG. 3 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. 3 may be omitted in some implementations and one or more actions shown in FIG. 3 may be combined.

[0190] The technical problem addressed by the method illustrated in FIG. 3 is how to streamline the CSI acquisition process during conditional LTM operations to reduce UE overhead while maintaining effective channel quality assessment for target cell transitions. The advantageous technical effect achieved by the method illustrated in FIG. 3 is that by utilizing pre-configured CSI report quantities with specific parameter combinations and MAC CE-triggered reporting, the UE can efficiently provide necessary CSI information to the target cell for optimal first transmission performance without the burden of maintaining full CSI reports for all candidate cells.

[0191] FIG. 4 is a block diagram illustrating a node 400 for wireless communication in accordance with various aspects 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).

[0192] 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. 1 through 3.

[0193] 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.

[0194] 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.

[0195] The computer-readable media may include computer-storage media and communication media. Computer-storage media may include both volatile (and / or non-volatile media), and removable (and / or non-removable) media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, Artificial Intelligence (AI) / Machine Learning (ML) module(s), or data.

[0196] Computer-storage media may include RAM, DRAM, HBM, MRAM, FRAM, PRAM, 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.

[0197] 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.

[0198] 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. 1 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. The AI / ML module(s) may be implemented with a supervised learning approach or an unsupervised learning approach (e.g., Transductive approach and Inductive approach).

[0199] 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.

[0200] 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.

[0201] In view of the present disclosure, it is obvious that various techniques may be used for implementing the disclosed concepts without departing from the scope of those concepts. Moreover, while the concepts have been disclosed with specific reference to certain implementations, a person of ordinary skill in the art may recognize that changes may be made in form and detail without departing from the scope of those concepts. As such, the disclosed implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the present disclosure is not limited to the particular implementations disclosed and many rearrangements, modifications, and substitutions are possible without departing from the scope of the present disclosure.

Claims

A user equipment (UE) for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM), the UE comprising:　　　　at least one processor; and　　　　at least one non-transitory computer-readable medium coupled to 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 comprises a channel state information (CSI) report configuration and CSI measurement configuration for one or more candidate cells;　　　　　　　　transmit, to the source cell, a first CSI report comprising an L1-reference signal received power (RSRP) value based on the CSI measurement configuration;　　　　　　　　receive, from the source cell, a medium access control (MAC) control element (CE) comprising information for a second CSI report; and　　　　　　　　transmit, to a target cell, the second CSI report based on the MAC CE, wherein:　　　　　　　　　　　　the target cell is one of the one or more candidate cells,　　　　　　　　　　　　the CSI report configuration comprises a CSI report quantity, and　　　　　　　　　　　　the CSI report quantity comprises at least one of:　　　　　　　　　　　　　　　　a first combination that comprises a channel state information (CSI)-reference signal (RS) resource indicator (CRI), a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI),　　　　　　　　　　　　　　　　a second combination that comprises the CRI, the RI, a first precoding matrix indicator (i1),　　　　　　　　　　　　　　　　a third combination that comprises the CRI, the RI, the i1, and the CQI,　　　　　　　　　　　　　　　　a fourth combination that comprises the CRI, the RI, and the CQI, and　　　　　　　　　　　　　　　　a fifth combination that comprises the CRI, the RI, a layer indicator (LI), the PMI, and the CQI.A method performed by a user equipment (UE) for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM), the method comprising:　　　　receiving, from a source cell, a radio resource control (RRC) configuration that comprises a channel state information (CSI) report configuration and CSI measurement configuration for one or more candidate cells;　　　　transmitting, to the source cell, a first CSI report comprising an L1-reference signal received power (RSRP) value based on the CSI measurement configuration;　　　　receiving, from the source cell, a medium access control (MAC) control element (CE) comprising information for a second CSI report; and　　　　transmitting, to a target cell, the second CSI report based on the MAC CE, wherein:　　　　　　　　the target cell is one of the one or more candidate cells,　　　　　　　　the CSI report configuration comprises a CSI report quantity, and　　　　　　　　the CSI report quantity comprises at least one of:　　　　　　　　　　　　a first combination that comprises a channel state information (CSI)-reference signal (RS) resource indicator (CRI), a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI),　　　　　　　　　　　　a second combination that comprises the CRI, the RI, a first precoding matrix indicator (i1),　　　　　　　　　　　　a third combination that comprises the CRI, the RI, the i1, and the CQI,　　　　　　　　　　　　a fourth combination that comprises the CRI, the RI, and the CQI, and　　　　　　　　　　　　a fifth combination that comprises the CRI, the RI, a layer indicator (LI), the PMI, and the CQI.A base station (BS) for measurement reporting for conditional layer 1 (L1) / layer 2 (L2) Triggered Mobility (LTM), the BS comprising:　　　　at least one processor; and　　　　at least one non-transitory computer-readable medium coupled to at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the BS to:　　　　　　　　transmit, to a user equipment (UE) via a source cell, a radio resource control (RRC) configuration that comprises a channel state information (CSI) report configuration and CSI measurement configuration for one or more candidate cells;　　　　　　　　receive, from the UE via the source cell, a first CSI report comprising an L1-reference signal received power (RSRP) value based on the CSI measurement configuration;　　　　　　　　transmit, to the UE via the source cell, a medium access control (MAC) control element (CE) comprising information for a second CSI report; and　　　　　　　　receive, from the UE via a target cell, the second CSI report based on the MAC CE, wherein:　　　　　　　　　　　　the target cell is one of the one or more candidate cells,　　　　　　　　　　　　the CSI report configuration comprises a CSI report quantity, and　　　　　　　　　　　　the CSI report quantity comprises at least one of:　　　　　　　　　　　　　　　　a first combination that comprises a channel state information (CSI)-reference signal (RS) resource indicator (CRI), a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI),　　　　　　　　　　　　　　　　a second combination that comprises the CRI, the RI, a first precoding matrix indicator (i1),　　　　　　　　　　　　　　　　a third combination that comprises the CRI, the RI, the i1, and the CQI,　　　　　　　　　　　　　　　　a fourth combination that comprises the CRI, the RI, and the CQI, and　　　　　　　　　　　　　　　　a fifth combination that comprises the CRI, the RI, a layer indicator (LI), the PMI, and the CQI.

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