Method and apparatus for handling handover procedures

Abstract

A method performed by a UE for handling handover (HO) procedures is provided. The method performs a first HO procedure. The method receives information associated with a second HO procedure during the first HO procedure. The method in response to receiving the information, determines whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure.

Description

METHOD AND APPARATUS FOR HANDLING HANDOVER PROCEDURES

[0001] The present disclosure is related to wireless communication and, more specifically, to a User Equipment (UE), Base Station (BS), and method for handling handover (HO) procedures 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 handling handover (HO) procedures in the wireless communication networks.

[0004] In a first aspect of the present disclosure, a UE for handling handover (HO) procedures 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: perform a first HO procedure; receive information associated with a second HO procedure during the first HO procedure; and in response to receiving the information, determine whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure.

[0005] In some implementations of the first aspect, the first HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure includes a layer 3 (L3) HO procedure, and the information includes a L3 HO command received from a source base station (BS).

[0006] In some implementations of the first aspect, the first HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure includes a layer 3 (L3) HO procedure, and the information includes a L3 HO command received from a source base station (BS). In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: after determining that the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure, ignoring the L3 HO command and continuing performing the inter-CU LTM cell switch procedure.

[0007] In some implementations of the first aspect, the first HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure includes a layer 3 (L3) HO procedure, and the information includes a L3 HO command received from a source base station (BS). In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: stopping the LTM cell switch procedure, and performing the L3 HO procedure.

[0008] In some implementations of the first aspect, the first HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure includes a layer 3 (L3) HO procedure, and the information includes a L3 HO command received from a source base station (BS). In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: determining whether a first target BS indicated by the L3 HO command is the same as a second target BS indicated by an LTM cell switch command associated with the LTM cell switch procedure; after determining that the first target BS is the same as the second target BS, ignoring the L3 HO command and continuing performing the LTM cell switch procedure; and after determining that the first target BS is different from the second target BS, stopping the LTM cell switch procedure and performing the L3 HO procedure.

[0009] In some implementations of the first aspect, the first HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure includes a layer 3 (L3) HO procedure, and the information includes a L3 HO command received from a source base station (BS). In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: starting a timer upon receiving the L3 HO command; determining whether an LTM cell switch command associated with the LTM cell switch procedure is received from a lower layer of the UE before the timer expires; after determining that the LTM cell switch command associated with the LTM cell switch procedure is received from the lower layer of the UE before the timer expires, continuing performing the LTM cell switch procedure; and after determining that the LTM cell switch command associated with the LTM cell switch procedure is not received from the lower layer of the UE before the timer expires, stopping the LTM cell switch procedure and performing the L3 HO procedure.

[0010] In some implementations of the first aspect, the first HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure includes a layer 3 (L3) HO procedure, and the information includes a L3 HO command received from a source base station (BS). The LTM cell switch procedure includes an intra-central unit (CU) LTM cell switch procedure or an inter-CU LTM cell switch procedure, and in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: starting a timer upon receiving the L3 HO command; determining whether an LTM cell switch command associated with the LTM cell switch procedure is received from a lower layer of the UE before the timer expires; after determining that the LTM cell switch command associated with the LTM cell switch procedure is received from the lower layer of the UE before the timer expires, determining that the LTM cell switch command indicates the intra-CU LTM cell switch procedure or the inter-CU LTM cell switch procedure; after determining that the LTM cell switch command indicates the intra-CU LTM cell switch procedure, stopping the intra-CU LTM cell switch procedure and performing the L3 HO procedure; and after determining that the LTM cell switch command indicates the inter-CU LTM cell switch procedure, ignoring the L3 HO command and continuing performing the inter-CU LTM cell switch procedure.

[0011] In some implementations of the first aspect, the first HO procedure includes a layer 3 (L3) HO procedure, the second HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information includes an LTM cell switch command received from a lower layer of the UE.

[0012] In some implementations of the first aspect, the first HO procedure includes a layer 3 (L3) HO procedure, the second HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information includes an LTM cell switch command received from a lower layer of the UE. In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: ignoring the LTM cell switch command, and continuing performing the L3 HO procedure.

[0013] In some implementations of the first aspect, the first HO procedure includes a layer 3 (L3) HO procedure, the second HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information includes an LTM cell switch command received from a lower layer of the UE. In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: stopping the L3 HO procedure, and performing the LTM cell switch procedure.

[0014] In some implementations of the first aspect, the first HO procedure includes a layer 3 (L3) HO procedure, the second HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information includes an LTM cell switch command received from a lower layer of the UE. In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: determining whether a first target BS indicated by the LTM cell switch command is the same as a second target BS indicated by a L3 HO command associated with the L3 HO procedure; after determining that the first target BS is the same as the second target BS, ignoring the LTM cell switch command and continuing performing the L3 HO procedure; and after determining that the first target BS is different from the second target BS, stopping the L3 HO procedure and performing the LTM cell switch procedure.

[0015] In some implementations of the first aspect, the first HO procedure includes a layer 3 (L3) HO procedure, the second HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information includes an LTM cell switch command received from a lower layer of the UE. In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: after determining that the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure, ignoring the LTM cell switch command and continuing performing the L3 HO procedure.

[0016] In some implementations of the first aspect, the first HO procedure includes a layer 3 (L3) HO procedure, the second HO procedure includes a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information includes an LTM cell switch command received from a lower layer of the UE. In response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure includes: after determining the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure and the LTM cell switch command from the lower layer of the UE is received after receiving a L3 HO command associated with the L3 HO procedure, stopping the L3 HO procedure and performing the inter-CU LTM cell switch procedure; and after determining that the LTM cell switch procedure is an intra-CU LTM cell switch procedure and the LTM cell switch command from the lower layer of the UE is received after receiving the L3 HO command associated with the L3 HO procedure, ignoring the LTM cell switch command and continuing performing the L3 HO procedure.

[0017] In a second aspect of the present disclosure, a method performed by a user equipment (UE) for handling handover (HO) procedures is provided. The method includes: performing a first HO procedure; receiving information associated with a second HO procedure during the first HO procedure; and in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure.

[0018] In a third aspect of the present application, a BS for handling handover (HO) procedures 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: during a first HO procedure, transmit information associated with a second HO procedure, where the information causes a user equipment (UE) to: in response to receiving the information, determine whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure.

[0019] Aspects of the present disclosure are best understood from the following detailed disclosure when read with the accompanying drawings. Various features are not drawn to scale. Dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

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

[0021] FIG. 2 is a diagram illustrating protocol stacks and architecture, according to an example implementation of the present disclosure.

[0022] FIG. 3 is a diagram illustrating an intra-AMF / UPF handover procedure, according to an example implementation of the present disclosure.

[0023] FIG. 4 is a flowchart illustrating a method / process performed by a UE for handling handover (HO) procedures, according to an example implementation of the present disclosure.

[0024] FIG. 5 is a flowchart illustrating a method / process performed by a BS for handling handover (HO) procedures, according to an example implementation of the present disclosure.

[0025] FIG. 6 is a block diagram illustrating a node for wireless communication, according to an example implementation of the present disclosure.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] A software implementation may include computer executable instructions stored on a computer-readable medium, such as memory or other type of storage devices. One or more microprocessors or general-purpose computers with communication processing capability may be programmed with corresponding executable instructions and perform the disclosed network function(s) or algorithm(s).

[0034] The microprocessors or general-purpose computers may include Application-Specific Integrated Circuits (ASICs), programmable logic arrays, and / or one or more Digital Signal Processor (DSPs). Although some of the disclosed implementations are oriented to software installed and executing on computer hardware, alternative implementations implemented as firmware, as hardware, or as a combination of hardware and software are well within the scope of the present disclosure. The computer-readable medium includes but is not limited to Random Access Memory (RAM), Read Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), flash memory, Compact Disc Read-Only Memory (CD-ROM), magnetic cassettes, magnetic tape, magnetic disk storage, or any other equivalent medium capable of storing computer-readable instructions.

[0035] A radio communication network architecture such as a Long-Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Pro system, or a 5G NR Radio Access Network (RAN) typically includes at least one base station (BS), at least one UE, and one or more optional network elements that provide connection within a network. The UE communicates with the network such as a Core Network (CN), an Evolved Packet Core (EPC) network, an Evolved Universal Terrestrial RAN (E-UTRAN), a 5G Core (5GC), a 6G Core (6GC), or an internet via a RAN established by one or more BSs.

[0036] A UE may include, but is not limited to, a mobile station, a mobile terminal or device, or a user communication radio terminal. The UE may be a portable radio equipment that includes, but is not limited to, a mobile phone, a tablet, a wearable device, a sensor, a vehicle, or a Personal Digital Assistant (PDA) with wireless communication capability. The UE is configured to receive and transmit signals over an air interface to one or more cells in a RAN.

[0037] The BS may be configured to provide communication services according to at least a Radio Access Technology (RAT) such as Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM) that is often referred to as 2G, GSM Enhanced Data rates for GSM Evolution (EDGE) RAN (GERAN), General Packet Radio Service (GPRS), Universal Mobile Telecommunication System (UMTS) that is often referred to as 3G based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), LTE, LTE-A, evolved 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.

[0038] The BS may include, but is not limited to, a node B (NB) in the UMTS, an evolved node B (eNB) in LTE or LTE-A, a radio network controller (RNC) in UMTS, a BS controller (BSC) in the GSM / GERAN, 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.

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

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

[0041] A cell may allocate sidelink (SL) resources for supporting the Proximity Services (ProSe) or Vehicle to Everything (V2X) services. Each cell may have overlapped coverage areas with other cells.

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

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

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

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

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

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

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

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

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

[0051] Multiple public land mobile networks (PLMNs) may operate on the unlicensed spectrum. Multiple PLMNs may share the same unlicensed carrier. The PLMNs may be public or private. Public PLMNs may be, but are not limited to, the operators or virtual operators, which provide radio services to the public subscribers. Public PLMNs may own the licensed spectrum and support the radio access technology on the licensed spectrum as well. Private PLMNs may be, but are not limited to, the micro-operators, factories, or enterprises, which provide radio services to their private users (e.g., the employees or machines). In some implementations, public PLMNs may support more deployment scenarios (e.g., the carrier aggregation between the licensed band NR (PCell) and NR-U (SCell), the dual connectivity between the licensed band LTE (PCell) and NR-U (PSCell), the stand-alone NR-U, an NR cell with DL in the unlicensed band and UL in the licensed band, the dual connectivity between the licensed band NR (PCell) and NR-U (PSCell)). In some implementations, private PLMNs may mainly support, but are not limited to, the stand-alone unlicensed radio access technology (e.g., the stand-alone NR-U).

[0052] The terms “network (NW)”, “cell”, “camped cell”, “serving cell”, “base station”, “gNB”, “eNB”, and “ng-eNB” may be used interchangeably. In some implementations, some of these terms may refer to the same network entity.

[0053] The RAT may be, but is not limited to, NR, LTE, E-UTRA connected to 5GC, LTE connected to 5GC, E-UTRA connected to EPC, and LTE connected to EPC. The proposed mechanism in the present disclosure may be applied to UEs in public networks or in private networks (e.g., non-public network (NPN), standalone NPN (SNPN), public network integrated-NPN (PNI-NPN)).

[0054] The proposed mechanism in the present disclosure may be used for the licensed frequency and / or the unlicensed frequency.

[0055] The system information (SI) may refer to the MIB, SIB1, and other SI. The minimum SI may include the MIB and SIB1. Other SI may refer to SIB3, SIB4, SIB5, and other SIB(s).

[0056] The dedicated signaling may refer to, but is not limited to, the RRC message(s). For example, the RRC (Connection) Setup Request message, RRC (Connection) Setup message, RRC (Connection) Setup Complete message, RRC (Connection) Reconfiguration message, RRC Connection Reconfiguration message including the mobility control information, RRC Connection Reconfiguration message without the mobility control information inside, RRC Reconfiguration message including the configuration with sync, RRC Reconfiguration message without the configuration with sync inside, RRC (Connection) Reconfiguration Complete message, RRC (Connection) Resume Request message, RRC (Connection) Resume message, RRC (Connection) Resume Complete message, RRC (Connection) Reestablishment Request message, RRC (Connection) Reestablishment message, RRC (Connection) Reestablishment Complete message, RRC (Connection) Reject message, RRC (Connection) Release message, RRC System Information Request message, UE Assistance Information message, UE Capability Enquiry message, and UE Capability Information message.

[0057] The proposed implementations described in the present disclosure may be applied to the RRC_CONNECTED UE, RRC_INACTIVE UE, and RRC_IDLE UE.

[0058] The UE may be served by a cell (e.g., a serving cell). The serving cell may serve, but is not limited to, an RRC_CONNECTED UE. The serving cell may be, but is not limited to, a suitable cell.

[0059] Examples of some selected terms in the present disclosure are provided as follows.

[0060] Primary Cell (PCell): The MCG cell, operating on the primary frequency, in which the UE either performs the initial connection establishment procedure or initiates the connection re-establishment procedure.

[0061] Primary SCG Cell (PSCell): For dual connectivity operation, the SCG cell in which the UE performs the random access when performing the Reconfiguration with Sync procedure.

[0062] Serving Cell: For a UE in the RRC_CONNECTED not configured with CA / DC, there may be only one serving cell including the primary cell. For a UE in the RRC_CONNECTED configured with CA / DC, the term “serving cells” may be used to denote the set of cells including the Special Cell(s) and all secondary cells.

[0063] Secondary Cell (SCell): For a UE configured with CA, a cell that provides additional radio resources on top of the Special Cell.

[0064] Special Cell (SpCell): For Dual Connectivity operation, the term “Special Cell” may refer to the PCell of the MCG or the PSCell of the SCG, otherwise the term “Special Cell” may refer to the PCell.

[0065] Master Cell Group: In MR-DC, a group of serving cells associated with the Master Node, including the SpCell (or PCell) and optionally one or more SCells.

[0066] Master node: In MR-DC, the radio access node that provides the control plane connection to the core network. The master node may include a Master eNB (e.g., in EN-DC), a Master ng-eNB (e.g., in NGEN-DC) or a Master gNB (e.g., in NR-DC and NE-DC).

[0067] Secondary Cell Group: In MR-DC, a group of serving cells associated with the Secondary Node, including the SpCell (or PSCell) and optionally one or more SCells.

[0068] Secondary node: In MR-DC, the radio access node, with no control plane connection to the core network, providing additional resources to the UE. The secondary node may include an en-gNB (e.g., in EN-DC), a Secondary ng-eNB (e.g., in NE-DC) or a Secondary gNB (e.g., in NR-DC and NGEN-DC).

[0069] The terms “serving cell”, “TRP associated with the PCI of the serving cell”, “TRP associated with the serving cell”, “TRP of a serving cell”, and “TRP of the serving cell” may be used interchangeably.

[0070] The terms “target cell”, “target serving cell”, “TRP associated with a PCI different from the PCI of the serving cell”, and “TRP associated with the target cell” may be used interchangeably. A target serving cell may be identified by a PCI or a PCI index. A UE may be configured with at most 1, 4, 8, or 32 PCI indices. Each PCI index may identify a target serving cell of the UE. The terms “candidate cell”, “neighboring cell”, and “candidate target cell” may be used interchangeably.

[0071] The serving cell in the present disclosure may include a PCell, SCell or PSCell. The target cell in the present disclosure may include a PCell, SCell or PSCell. The terms “MAC layer” and “MAC entity” may be used interchangeably. The fact that the UE is configured with the unified TCI framework (e.g., the unified TCI configuration) may be equivalent to the fact that the UE is configured with the unified TCI state operation.

[0072] SpCellConfig IE: Serving cell specific MAC and physical (PHY) parameters for a SpCell. Parameters for the SpCell of this cell group (PCell of MCG or PSCell of SCG). SpCellConfig is included in CellGroupConfig. SpCellConfig may include ServingCellConfig.

[0073] SCellConfig IE: The SCellConfig IE may be included in the CellGroupConfig IE. The SCellConfig IE may include the ServingCellConfig IE.

[0074] ServingCellConfig IE: The ServingCellConfig IE may be used to configure (e.g., add or modify) the UE with a serving cell, which may be the SpCell or an SCell of an MCG or SCG. The parameters included in the ServingCellConfig IE may be mostly UE-specific but partly also cell-specific (e.g., in additionally configured bandwidth parts). The reconfiguration between a PUCCH and PUCCHless SCell may only be supported using an SCell release and add.

[0075] CellGroupConfig IE: The configuration of a Cell-Group. The CellGroupConfig IE may be used to configure a master cell group (MCG) or secondary cell group (SCG). A cell group may include a MAC entity, a set of logical channels with associated RLC entities, a primary cell (SpCell), and one or more secondary cells (SCells).

[0076] In some implementations, the fact that the UE determines that the L1 / L2 mobility enhancement fails may include the fact that the RRC pre-configuration step fails, the fact that the cell switch fails, the fact that the L1 measurement and reports fail, the fact that DL synchronization fails, the fact that the UL synchronization fails, and / or the fact that the subsequent cell switches fail.

[0077] In some implementations, the fact that the UE determines that the L1 / L2 mobility enhancement completes successfully may include the fact that the RRC pre-configuration step completes successfully, the fact that the cell switch completes successfully, the fact that the L1 measurement and reports completes successfully, the fact that DL synchronization completes successfully, the fact that the UL synchronization completes successfully, and the fact that the subsequent cell switches complete successfully.

[0078] In some implementations, the source gNB / cell may refer to the gNB / cell that serves the UE when the UE receives the RRC message during the RRC preconfiguration step. For example, the source gNB / cell in the cell switch and the subsequent cell switch may refer to the same source gNB / cell. In some implementations, the source gNB / cell may refer to the gNB / cell that serves the UE before the UE switches to a new cell. For example, the source gNB / cell in the cell switch step and the source gNB / cell in the subsequent cell switch step may refer to different source gNBs / cells.

[0079] In some implementations the previous selected target gNB / cell may refer to the selected target gNB / cell in the previous cell switch per RRC preconfiguration. For example, the UE may perform a first cell switch and a subsequent cell switch based on an RRC preconfiguration. The RRC preconfiguration may be provided to the UE by the source gNB / cell. The UE may select a target gNB / cell in the first cell switch. During the first cell switch, the UE may switch to the selected target gNB / cell from the source gNB / cell. During the subsequent cell switch, the selected target gNB / cell may become the UE’s previous selected target gNB / cell. During the subsequent cell switch, the UE may select another target gNB / cell and perform the subsequent cell switch from the previous selected target gNB / cell to the another selected target gNB / cell.

[0080] Layer 1 / Layer 2-Triggered mobility (LTM): A PCell (or PSCell) cell switch procedure that is triggered by the network via the MAC CE based on the L1 measurement.

[0081] Random Access Channel-less (RACH-less) LTM: An LTM cell switch procedure where the UE skips the RA procedure.

[0082] Subsequent LTM: Subsequent LTM cell switch procedures between candidate cells where the UE does not need to be reconfigured by the network in between.

[0083] The cell switch command may refer to, but is not limited to, the LTM cell switch command MAC CE. The reference signal may refer to, but is not limited to, the SSB, CSI-RS, TRS, PT-RS, SRS, and DM-RS.

[0084] In some implementations, the source gNB / cell / PCell may refer to the gNB / cell / PCell where the UE receives the RRC pre-configuration (e.g., RRC Reconfiguration message) and / or the cell switch command. When the subsequent cell switch is considered, the source gNB / cell / PCell may refer to the gNB / cell / PCell where the UE receives the RRC pre-configuration (e.g., RRC Reconfiguration message) and / or the cell switch command for the subsequent cell switch. It may be possible that during the subsequent cell switch, the target gNB / cell / PCell in the first cell switch may become the source gNB / cell / PCell in the second cell switch. Furthermore, it may be possible that during the subsequent cell switch, the target gNB / cell / PCell in the N-th cell switch may become the source gNB / cell / PCell in the (N+1)-th cell switch, where N is a positive integer.

[0085] A timer may be running once it is started, until it is stopped or until it expires; otherwise it is not running. A timer may be started if it is not running or restarted if it is running. A Timer may always be started or restarted from its initial value. The duration of a timer may not be updated until the timer is stopped or the timer expires (e.g. due to a BWP switching). When the MAC entity applies zero value for a timer, the timer may be started and immediately expires unless explicitly stated otherwise.

[0086] The terms “source CU”, “source gNB / cell”, and “source MN” may be used interchangeably. The terms “target CU”, “target gNB / cell”, and “target MN” may be used interchangeably. The terms “LTM”, “L1 / L2-triggered mobility”, and “L1 / L2 mobility enhancements” may be used interchangeably. The terms “RRC pre-configuration”, “RRC pre-configuration step”, “RRC preconfiguration”, “RRC preconfiguration step”, “RRC (pre)configuration”, “RRC (pre)configuration step”, and “LTM preparation” may be used interchangeably. The terms “L1 measurement and reports” and “L1 measurement and reports step” may be used interchangeably. The terms “DL synchronization” and “DL synchronization step” may be used interchangeably. The terms “UL synchronization” and “UL synchronization step” may be used interchangeably. The terms “Cell switch” and “cell switch step” may be used interchangeably. The terms “Subsequent cell switch” and “subsequent cell switch step” may be used interchangeably.

[0087] In the wireless cellular network, mobile devices (e.g., User Equipments (UEs)) may move from the coverage area of one cell to another cell. To avoid the connection interruption and ensure the service continuity, a handover procedure may be applied for the mobile devices when the handover procedure is triggered under certain conditions (e.g., when the signal quality of the source cell becomes poorer / lower than a threshold for a period).

[0088] The handover procedure may be triggered by Layer 3 (L3) measurements and may be completed by Radio Resource Control (RRC) signaling-triggered Reconfiguration with Synchronization for change of Primary Cell (PCell) and Primary Secondary Cell (PSCell) and for release and addition of Secondary Cells (SCells). In addition, the Conditional Handover (CHO) was proposed to enhance the robustness so that the mobile device can receive the configuration of the target cell in advance (e.g., when the signal quality between the mobile device and the source cell is stable). The Dual Active Protocol Stack (DAPS) handover was proposed to reduce the interruption time since the mobile device can maintain two protocol stacks (e.g., one is associated with the source cell and another one is associated with the target cell, for simultaneous connections with the source cell and the target cell during the handover).

[0089] The handover procedure, conditional handover, and DAPS handover may require a complete Layer 2 (L2) reset and Layer 1 (L1) reset. The L2 may refer to the Medium Access Control (MAC) layer, Radio Link Control (RLC) layer, and Packet Data Convergence Protocol (PDCP) layer. The L1 may refer to the Physical (PHY) layer. The complete L1 / L2 reset may result in longer latency, larger overhead, and longer interruption time than beam switch mobility. Thus, it may be desirable to investigate the L1 / L2 mobility enhancement (e.g., enabling a serving cell change via L1 / L2 signaling, to reduce the latency, overhead, and interruption time during the handover procedures).

[0090] The Layer 1 / Layer 2-Triggered mobility (LTM) was introduced to offer improvements in handover latency and interruption time compared to the Layer 3-based mobility (e.g., the legacy handover procedure, CHO, DAPS, Conditional PSCell Addition and Change (CPAC), and Conditional PSCell Change (CPC)). The LTM operation may be targeted at reducing the latency, overhead, and interruption time due to UE mobility (e.g., by enabling a serving cell change via L1 / L2 signaling, for the handover procedures). The LTM operation may involve the RRC pre-configuration of the information associated with the candidate target cells, L1 measurement and report, Downlink (DL) synchronization with the candidate target cells, Uplink (UL) synchronization with the candidate target cells, cell switch to the target cell, subsequent cell switch to the target cells, etc.

[0091] However, the current LTM may suffer from a number of limitations compared to the Layer 3-based mobility because the current LTM operation may only be supported for mobility between cells of the same gNB (e.g., cells of the same central unit (CU), intra-CU). Such limitations may have a great impact on the network deployments and the opportunities to use the LTM. Thus, it may be desired to enhance the LTM operation between cells of different gNBs (e.g., cells of different CUs, inter-CU) so that the network will gain the benefits of the LTM for a greater number of handovers.

[0092] Once the inter-CU LTM is introduced, it may be more likely that the complete LTM operation, including the intra-CU LTM and inter-CU LTM, may be adopted by the network to achieve lower handover latency and short interruption time. Depending on the network deployments, the complete LTM operation and Layer 3-based mobility schemes empower the network to handle mobility problems efficiently. However, the issues raised from the co-existence of different mobility schemes, especially the LTM and Layer 3-based mobility, should be further investigated.

[0093] The general guidance to deal with the co-existence of the intra-CU LTM and Layer 3-based mobility schemes was introduced. While the UE has stored LTM candidate configurations, the UE may also execute any L3 handover except for the DAPS handover. Upon reception of the LTM cell switch command MAC CE before any CHO execution condition is satisfied, the UE may perform the LTM cell switch procedure regardless of any previously received CHO configuration. However, the detailed design may be unclear. The co-existence of the inter-CU LTM and Layer 3-based mobility schemes should be further investigated. In the present disclosure, the network may apply both the LTM operation (e.g., the intra-CU LTM and inter-CU LTM) and the L3-based mobility scheme (e.g., the legacy L3 handover procedure). The detailed design on how to perform the handover or cell switch resulted from the co-existence of different mobility schemes in the network including at least a UE and at least two cells (or two gNBs) is proposed. The design may be expected to be efficient (e.g., signaling overhead reduction, energy-efficient), reliable, low latency, and robust.

[0094] L1 / L2-triggered Mobility

[0095] The L1 / L2 mobility enhancement may be referred to, but is not limited to, the L1 / L2-triggered Mobility (LTM). Generally, lots of mobility enhancements from different perspectives and from different protocol layers may be proposed to realize the LTM. The LTM may be a procedure involving, but is not limited to, the RRC pre-configuration step (e.g., the LTM preparation), early synchronization including DL synchronization step and UL synchronization step, LTM cell switch execution including L1 measurement and reports step and (subsequent) cell switch step, and LTM cell switch completion.

[0096] FIG. 1 is a diagram illustrating an LTM procedure, according to an example implementation of the present disclosure. During the LTM preparation, the UE may transmit, to the gNB, a measurement report while the UE is in the RRC_CONNECTED state (e.g., the action 1 of FIG. 1). When the gNB receives the measurement report, the gNB may perform the LTM candidate preparation. The gNB may then transmit, to the UE, an RRC reconfiguration message (e.g., including an LTM candidate configuration) (e.g., the action 2 of FIG. 1). When the RRC reconfiguration is completed, the UE may transmit, to the gNB, an RRC reconfiguration complete message (e.g., the action 3 of FIG. 1). During the early synchronization, the UE may perform the DL synchronization with the LTM candidate cells (e.g., the action 4a of FIG. 1) and the UL synchronization with the LTM candidate cells (e.g., the action 4b of FIG. 1). During the LTM cell switch execution, the UE may transmit, to the gNB, an L1 measurement report (e.g., the action 5 of FIG. 1). When the gNB receives the L1 measurement report, the gNB may perform the LTM decision and then transmit, to the UE, an LTM cell switch command (e.g., via the MAC CE) (e.g., the action 6 of FIG. 1). When the UE receives the LTM cell switch command, the UE may detach from the source cell and apply the target configurations. Then, the UE may perform the RACH procedure (e.g., the action 7 of FIG. 1). During the LTM cell switch completion, the UE may complete the LTM cell switch (e.g., the action 8 of FIG. 1).

[0097] LTM Scenarios

[0098] Several scenarios may be supported by the LTM, such as the intra-gNB-Distributed Unit (DU) (e.g., the intra-Central Unit (CU) intra-DU) mobility, inter-gNB-DU (e.g., the intra-CU inter-DU) mobility (e.g., the source cell and the target cell may belong to different DUs but the same CU), inter-CU mobility (e.g., the source cell and the target cell may belong to different CUs), inter-frequency mobility, PCell change in non-CA scenario, PCell change without SCell change in Carrier Aggregation (CA) scenario, PCell change with SCell changes in CA scenario, and dual connectivity scenario (e.g., at least for the PSCell change without MN involvement case, such as intra-Secondary Node (SN)). The PCell change with SCell changes in CA scenario may include the three cases: (1) the target PCell / target SCell(s) is not a current serving cell (e.g., CA-to-CA scenario with PCell change), (2) the target PCell is a current SCell, and (3) the target SCell is the current PCell. Each CU may belong to different gNBs.

[0099] FIG. 2 is a diagram illustrating protocol stacks and architecture, according to an example implementation of the present disclosure. In FIG. 2, the relationships among the access and mobility management function (AMF), user plane function (UPF), gNB, CU, DU, and remote radio head (RRH), and the corresponding interfaces are illustrated. From the perspectives of the protocol stacks, a DU may control and include the PHY layer, MAC layer, and RLC layer. A CU may control and include the PDCP layer and RRC layer. Specifically, a central unit-control plane (CU-CP) may control and include the control plane part of the PDCP layer and RRC layer. A central unit-user plane (CU-UP) may control and include the user plane part of the PDCP layer and service data adaptation protocol (SDAP) layer. Specifically, the higher part of the PHY layer may be controlled by and included in a DU, while the lower part of the PHY layer is controlled by and included in an RRH.

[0100] For intra-gNB-DU mobility, the UE may switch from the source cell to the selected target cell, where the source cell and the selected target cell may belong to the same CU and the same DU within a gNB. The UE may apply the same PHY layer of the UE for the source cell and for the selected target cell. The UE may apply the same MAC layer of the UE for the source cell and for the selected target cell. The UE may apply the same RLC layer of the UE for the source cell and for the selected target cell. The UE may apply the same PDCP layer of the UE for the source cell and for the selected target cell. The UE may apply the same RRC layer of the UE for the source cell and for the selected target cell.

[0101] For inter-CU LTM scenarios, whether the dual connectivity (DC) is supported may be further discussed. There may be at least three prioritized scenarios: (1) there is no DC, and the source CU and target CU act as a Master Node (MN), (2) New Radio-Dual Connectivity (NR-DC) is configured, and the source CU and target CU act as a SN while the master cell group (MCG) is unchanged, and (3) NR-DC is configured, and the source CU and target CU act as MN while secondary cell group (SCG) is unchanged or released. According to FIG. 1, if the UE performs the inter-CU LTM, the source CU and the target CU may belong to different gNBs, which is similar with the L3 handover, where the UE may perform the L3 handover from the source gNB to the target gNB. Thus, when both the L3 handover and inter-CU LTM are configured to the UE, the detailed UE behaviors for the inter-CU LTM and for the L3 handover may be further designed.

[0102] RRC Pre-configuration

[0103] During RRC pre-configuration step, the source gNB / cell may transmit the information / configuration associated with the candidate target cells to the UE via RRC signaling. The source gNB / cell may prepare one or more candidate target cells (e.g., for the LTM procedure and / or handover), generate the RRC message (e.g., RRC Reconfiguration message) and / or the information element (IE) (e.g., the CellGroupConfig IE, LTM-specific IE, and / or LTM-Config IE) including the information / configuration associated with the candidate target cells, and / or transmit the generated RRC message and / or IE to the UE. Upon receiving the information / configuration associated with the candidate target cells, the UE may store and / or apply the received information / configuration for the handover procedures (e.g., the L1 / L2-triggered mobility). The RRC message (e.g., RRC Reconfiguration message) may include the information (IE) (e.g., the CellGroupConfig IE, LTM-specific IE, and / or LTM-Config IE) to provide the LTM candidate configuration.

[0104] The UE may receive two independent LTM candidate configurations (e.g., CellGroupConfig IE, LTM-specific IE, and / or LTM-Config IE) in the RRC Reconfiguration message transmitted from the source SpCell, where one LTM candidate configuration may be associated with the MCG and the other LTM candidate configuration may be associated with the SCG. The LTM candidate configuration may include, but is not limited to, the following listed IEs (A)-(H).

[0105] (A) the ltm-Reference Configuration IE

[0106] (B) the ltm-CandidateToAddModList IE: This IE may include a list of LTM candidate cell configurations to add or modify. An LTM candidate cell configuration may be represented as the LTM-Candidate IE. The LTM candidate cell configuration may include, but is not limited to, the following listed IEs (a-i). (a) the ltm-CandidateId IE, (b) the ltm-CandidatePCI IE, (c) the ltm-SSB-Config IE, (d) the ltm-CandidateConfig IE, (e) the ltm-ConfigComplete IE, (f) the ltm-EarlyUL-SyncConfig IE, (g) the ltm-TCI-Info IE, (h) the ltm-NoResetID IE, and (i) the ltm-UE-MeasuredTA-ID IE.

[0107] (C) ltm-CandidateToReleaseList IE

[0108] (D) ltmServingCellNoResetID IE

[0109] (E) ltm-CSI-ResourceConfigToAddModList IE

[0110] (F) ltm-CSI-ResourceConfigToReleaseList IE

[0111] (G) attemptLTM-Switch IE

[0112] (H) ltm-ServingCellUE-MeasureTA-ID IE

[0113] In response to the reception of the RRC Reconfiguration message for the LTM candidate configuration from the source cell, the UE may store the LTM candidate configurations and transmit an RRC Reconfiguration Complete message to the source cell.

[0114] DL Synchronization

[0115] The UE may perform the DL synchronization to the selected target cell or to the candidate target cells during the LTM operation. Generally, the UE may perform the DL synchronization after the cell switch to the selected target cell in order to acquire the DL time and / or frequency synchronization, the DL system information, and the DL data from the selected target cell. In some implementations, the UE may perform the DL synchronization after the cell switch to the selected target cell and after the subsequent cell switch(es) to the selected target cells. In some implementations, the UE may perform the DL synchronization before receiving the cell switch command in order to reduce the interruption time, but at the sacrifice of complexity and overhead. In one cell switch, the UE may switch to a target cell. In some implementations, the UE may perform the DL synchronization before receiving the cell switch command from the source cell and / or before receiving the cell switch command corresponding to the subsequent cell switch. The UE may activate and deactivate TCI states of LTM candidate cell(s), as triggered by the gNB.

[0116] The UE may receive and / or be configured with the information required for the DL synchronization to the selected target cell or to the candidate target cells from the source gNB / cell via RRC signaling and / or lower layer signaling (e.g., the L1 signaling or L2 signaling). For example, the UE may receive, from the source gNB / cell, the RRC message including the information required for the DL synchronization during the RRC pre-configuration. For example, the UE may receive, from the source gNB / cell, the Medium Access Control (MAC) Control Element (CE) (or cell switch command or candidate cell TCI states activation / deactivation MAC CE) including the information required for the DL synchronization. For example, the UE may receive Downlink Control Information (DCI) including the information required for the DL synchronization. The information required for the DL synchronization may include, but is not limited to, the Identities (IDs) or indices of the candidate target cells, the ID or index of the selected target cell, the indices of reference signals (e.g., SSB) associated with the candidate target cells, the indices of the resource blocks associated with the selected target cell, the time / frequency information associated with the candidate target cells, the time / frequency information associated with the selected target cell, the TCI state ID associated with the candidate target cells or the selected target cell, etc.

[0117] The cell switch command or candidate cell TCI states activation / deactivation MAC CE may be a MAC CE including the required information (e.g., the beam information, PCI, logical ID (e.g., additionalPCIIndex), DL / UL synchronization information corresponding to the selected candidate target cell) for the UE to switch to the selected target cell and / or activate (or deactivate) the TCI states associated with the selected target cell. The selected target cell may be one of candidate target cells that the source gNB / cell indicates to a UE to perform the cell switch.

[0118] UL Synchronization

[0119] The UE may perform the UL synchronization (e.g., including the (early) Timing Advance (TA) acquisition, RACH-less LTM mechanism, PDCCH-ordered RA procedure with Random Access Response (RAR), PDCCH-ordered RA procedure without RAR and UE-based TA measurement) to the selected target cell or to the candidate target cells during the LTM operation. Generally, the UE may perform the UL synchronization after the DL synchronization completes, but not limited to. In some implementations, the UE may perform the UL synchronization to the selected target cell after the cell switch. In some implementations, to reduce the interruption time, the UE may perform the UL synchronization to the candidate target cells before the cell switch, at the sacrifice of overhead and complexity. In some implementations, the UE may perform the UL synchronization after the cell switch. In some implementations, the UE may perform the DL synchronization before the cell switch and UL synchronization after the cell switch. In some implementations, the UE may not perform the UL synchronization to the selected target cell after the UE receives the TA information of the selected target cell (e.g., in the cell switch command or in the MAC CE) from the source cell.

[0120] In the UE-based TA measurement, the UE may derive the TA(s) for the candidate (or target) cells based on Rx timing difference between the current serving cell (e.g., the source cell) and the candidate cells as well as TA value for the current serving cell. The UE-based TA measurement may be supported without performing the PDCCH-ordered RACH for candidate cells.

[0121] In the RACH-less LTM mechanism, the UE may acquire the TA for the candidate (or target) cells by receiving the cell switch command from the source serving cell, where the cell switch command may indicate TA value of target cell as TA=0, indicate to keep the same TA value as that for the source serving cell, or indicate any TA values. In some implementations, the UE may perform the RACH-less LTM when the UE switches to the target cell and / or if the UE does not need to acquire TA during the cell switch (e.g., when the target cell is the (source) SCell or when the target cell is the (source) PSCell). The target cell may refer to the target PCell.

[0122] During UL synchronization step, the UE may perform a Random Access (RA) procedure (e.g., the contention-based random access procedure, contention-free random access procedure, 2-step RA procedure, or 4-step RA procedure) with the selected target cell or with the candidate target cells in order to acquire the UL timing and / or Timing Advance information, and / or transmit the UL data to the selected target cell or to the candidate target cells. In some implementations, during UL synchronization, the UE may perform a Random Access Channel-less (RACH-less) procedure (e.g., without performing an RA procedure) with the selected target cell or with the candidate target cells in order to acquire the UL timing and / or Timing Advance information, and / or transmit the UL data to the selected target cell or to the candidate target cells.

[0123] The UE may receive the information required for the UL synchronization via RRC signaling or lower layer signaling (e.g., the MAC CE or Downlink Control Information (DCI)) from the source gNB / cell. Upon receiving the information required for the UL synchronization, the UE may configure the information. For example, during RRC pre-configuration step, the UE may receive the RRC message including the information required for the UL synchronization from the source gNB / cell. For example, the UE may receive the MAC CE including the information required for the UL synchronization from the source gNB / cell.

[0124] The information required for the UL synchronization may include, but is not limited to, the Physical Random Access Channel (PRACH) resource configuration associated with the selected target cell, PRACH resource configurations associated with the candidate target cells, preamble sequence configuration associated with the selected target cell, preamble sequence configurations associated with the candidate target cells, indication for performing a RACH-less procedure, indication for performing an RA procedure, indication for indicating to perform 2-step RACH or 4-step RACH, Timing Advance Group Index (TAG ID) associated with the selected target cell, TAG IDs associated with the candidate target cells, UL carrier types (e.g., Normal UL (NUL), Supplementary UL (SUL)) associated with the selected target cell, UL carrier types associated with the candidate target cells, Sounding Reference Signal (SRS) configuration associated with the selected target cell, SRS configurations associated with the candidate target cells, etc.

[0125] L1 Measurement and Reports

[0126] The UE may perform the L1 measurement and transmit the L1 measurement reports during the LTM operation. The UE may perform the L1 measurement on the configured LTM candidate cells and transmit the L1 measurement reports to the source gNB / cell. The L1 measurement may be performed as long as RRC reconfiguration is applicable.

[0127] Based on the measurement configuration, the UE may perform the L1 measurement on the neighboring cells and / or on the candidate target cells. The UE may receive the measurement configuration from the source gNB / cell via RRC signaling (e.g., during, before and / or after the RRC pre-configuration step). That is, the UE may perform the L1 measurement and transmit the L1 measurement reports before or after the RRC pre-configuration step during the LTM operation. The measurement configuration may include information / configuration that the UE requires to perform the L1 measurement. The information / configuration that the UE requires to perform the L1 measurement may include, but is not limited to, the reference resource configuration associated with the neighboring cells and / or the candidate target cells to be measured. For example, the UE may measure the received signal quality and / or the received signal strength on at least one of reference resources (or Reference Signal (RS)) (e.g., Synchronization Signal Block (SSB), Channel State Information-RS (CSI-RS), and / or Tracking RS (TRS)) associated with the neighboring cells and / or the candidate target cells. In some implementations, the reference resource configuration may include the association among the at least one of the reference resources and the neighboring cells and / or the candidate target cells. In some implementations, the measurement configuration may include the association among the at least one of reference resources and the neighboring cells and / or the candidate target cells.

[0128] The UE may report the L1 measurement results to the source gNB / cell, periodically or based on an event. Specifically, after performing the L1 measurements, the UE may report the L1 measurement results to the source gNB / cell, periodically or after an event is triggered. In some implementations, the UE may report the L1 measurement results to the source gNB / cell periodically based on an event. Specifically, the UE may report the L1 measurement results to the source gNB / cell periodically after an event is triggered. The UE may receive the report configuration from the source gNB / cell via RRC signaling (e.g., before, during and / or after the RRC pre-configuration step). The UE may report the L1 measurement results to the source gNB / cell via the RRC message and / or the lower layer signaling (e.g., the Uplink Control Information (UCI)). The UE may report the L1 measurement results to the source gNB / cell via PUCCH, PUSCH, and / or MAC CE. The L1 measurement results may include, but are not limited to, the RS index of the reference resources associated with the neighboring cells and / or candidate target cells to be measured, the Reference Signal Received Power (RSRP) values of the reference resources associated with the neighboring cells and / or candidate target cells to be measured, and / or the Reference Signal Received Quality (RSRQ) values of the reference resources associated with the neighboring cells and / or candidate target cells to be measured. The UE may report the RSRP values of the reference resources associated with the neighboring cells and / or candidate target cells to be measured, and / or the RSRQ values of the reference resources associated with the neighboring cells and / or candidate target cells to be measured. The measurement results may be reported to the source gNB / cell, one or more candidate target cell(s) configured to the UE for channel quality / strength measurement and report, and / or at least one of candidate target cells provided in the RRC pre-configuration step. The report configuration may include the information of when the UE reports the L1 measurement results, a timer value (e.g., how long the UE reports the measurement results once, the periodicity to report the measurement results), the information of resources on which the UE reports the L1 measurement results, the information of reference resources based on which the UE reports the L1 measurement results, etc.

[0129] The report configuration may include one or more thresholds for a UE to determine whether to transmit the L1 measurement report(s) corresponding to the measurement results of the reference resources associated with the neighboring cells and / or candidate target cells to be measured, where the one or more thresholds may include one or more RSRP threshold values or one or more RSRQ threshold values.

[0130] (Subsequent) Cell Switch

[0131] During the LTM operation, the source gNB / cell may change the UE’s serving cell(s) (e.g., UE’s PCell, UE’s SCells, and / or UE’s PSCell) via the MAC CE. The source gNB / cell may determine (or select) a target cell among candidate target cells and then transmit the cell switch command (e.g., a MAC CE or an LTM cell switch command MAC CE), to the UE, where the cell switch command may include the required information for the UE to switch to the selected target cell. The selected target cell may include, but is not limited to, neighboring cells, candidate target cells, UE’s SCells, and UE’s PSCell. The source gNB / cell may determine (or select) the target cell based on, but is not limited to, the candidate target cell configurations provided to the UE during the RRC pre-configuration, the received L1 measurement reports from the UE, the information (e.g., the TA related information) transmitted by the candidate target cell, the network topology, the resource availability, etc.

[0132] The cell switch command (e.g., a MAC CE or an LTM cell switch command MAC CE) may include, but is not limited to, the index (e.g., the PCI value, addition PCI index, and / or serving cell index) of the selected target cell, the (unified) TCI state (e.g., the joint TCI state, DL TCI state, and / or UL TCI state) associated with the selected target cell, TA information (e.g., the TAG ID, TA value, and / or Timing Advance Command) associated with the selected target cell, the index of the candidate target cell configuration associated with the selected target cell, the index of the BWP (e.g., the initial BWP, the DL BWP, the UL BWP, the first active downlink BWP, the first active uplink BWP, and / or the BWP the UE may switch to) associated with the selected target cell, the cell type to be switched (e.g., the PCell, SCell, and / or PSCell), the index of the MAC CE as a cell switch command for a RRC pre-configuration, the total number of cell switches per RRC pre-configuration, a dedicated DCI format for informing the cell switch, a DCI field including information for the cell switch etc. The index of the MAC CE as a cell switch command for a RRC pre-configuration, and the total number of cell switches per RRC pre-configuration may be useful for the subsequent cell switch during the (subsequent) LTM procedure.

[0133] Upon the UE receives the cell switch command (e.g., a MAC CE) from the source gNB / cell, the UE may perform the cell switch to the target cell indicated in the cell switch command and based on the information in the cell switch command. Depending on the content of the cell switch command, the cell switch may be the PCell change (e.g., switch from the source PCell to a target PCell), SCell change (e.g., switch from the source SCell to a target SCell), and / or PSCell change (e.g., switch from the source PSCell to a target PSCell).

[0134] In some implementations, if the UE does not release the stored candidate target cell configurations upon performing the cell switch, and if the UE receives a subsequent cell switch command (e.g., a MAC CE or an LTM cell switch command MAC CE) and / or Candidate Cell TCI States Activation / Deactivation MAC CE, the UE may perform the subsequent cell switch. That is, the subsequent LTM between the candidate target cells may be performed by the UE and the gNB / cell without a new RRC (pre)configuration after the first cell switch and before one or more subsequent cell switches. That is, the RRC pre-configuration for the first cell switch may be applied by the UE for the subsequent cell switches.

[0135] A subsequent LTM may be completed by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidate configurations after each LTM cell switch completion. In some implementations, during the subsequent cell switches, the UE may not need to perform the UL synchronization to acquire the TA values of the target cell(s). The UE may (by default) perform the RACH-less LTM mechanism.

[0136] If the UE does not have a valid TA of the target cell, the UE may perform the random access (RA) procedure towards the target cell. The UE may complete the LTM cell switch procedure by transmitting an RRC Reconfiguration Complete message to the target cell. If the UE performs an RA procedure to the target cell, the UE may determine that LTM cell switch execution is successfully completed when the RA procedure is successfully completed. For RACH-less LTM, the UE may determine that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0137] L3-based Mobility

[0138] Generally, in L3-based mobility, based on the measurement configuration and report configuration received from the source gNB / cell, the UE may perform the L3 measurement and / or RRM measurement to the neighboring cells. The UE may report the L3 measurement results to the source gNB / cell, periodically or in aperiodic (e.g., based on a triggered event). The source gNB / cell may determine to perform the L3 handover based on the L3 measurement reports. After the source gNB / cell negotiates with the target gNB / cell and acquires the required information from the target gNB / cell, the source gNB / cell may transmit an RRC Reconfiguration message including Reconfiguration with Sync IE (e.g., the reconfigurationWithSync IE) to the UE. The required information may include the configurations for the UE to access the target gNB / cell. The Reconfiguration with Sync IE may include the configurations for the UE to access the target gNB / cell. Upon reception of the RRC Reconfiguration message including the Reconfiguration with Sync IE (e.g., the L3 HO command), the UE may perform the RA procedure with the target cell to synchronize and access to the target cell. The UE may complete the RRC handover procedure by transmitting the RRC Reconfiguration Complete message to the target gNB / cell. The L3-based mobility may include an intra-AMF / UPF handover.

[0139] FIG. 3 is a diagram illustrating an intra-AMF / UPF handover procedure, according to an example implementation of the present disclosure. During the handover preparation, the mobility control information may be provided by the AMF to the source gNB (e.g., the action 0 of FIG. 3). The UE may perform the measurements and transmit the measurement reports to the source gNB (e.g., the action 1 of FIG. 3). When the source gNB receives the measurement reports, the source gNB may perform the handover decision (e.g., the action 2 of FIG. 3). The source gNB may then transmit, to the target gNB, a handover request message (e.g., the action 3 of FIG. 3). When the target gNB receives the handover request message, the target gNB may perform an admission control (e.g., the action 4 of FIG. 3) and then transmit, to the source gNB, a handover request acknowledge (e.g., the action 5 of FIG. 3). During the handover execution, the source gNB and the UE may perform an RAN handover initiation (e.g., the action 6 of FIG. 3). The source gNB may deliver, to the target gNB, the buffered data and new data from UPF(s). The source gNB may then transfer the early status and SN status to the target gNB (e.g., the actions 7a and 7 of FIG. 3). The UE may detach from the source gNB and synchronize to the target gNB. During the handover completion, the target gNB may transmit a handover success confirmation to the source gNB after the UE successfully switches to the target gNB (e.g., the action 8a of FIG. 3). The source gNB may transmit the SN status to the target gNB (e.g., the action 8b of FIG. 3). The target gNB may send a path switch request to the AMF (e.g., the action 9 of FIG. 3). The AMF and UPF(s) may perform a path switch (e.g., the action 10 of FIG. 3). The AMF may send a path switch request acknowledge to the target gNB to confirm the path switch (e.g., the action 11 of FIG. 3). The target gNB may initiate a UE context release to the source gNB to release the UE context (e.g., the action 12 of FIG. 3).

[0140] The Co-existence Scenarios

[0141] When the UE is configured with the L3 measurement configuration and report configuration, the UE (e.g., the RRC layer of the UE) may receive the L3 HO command (e.g., an RRC Reconfiguration message including the CellGroupConfig IE, where the CellGroupConfig IE may include the spCellConfig IE with the reconfigurationWithSync IE) from the source gNB / cell. Upon the reception of the reconfigurationWithSync IE, the UE may perform the L3 handover to the target gNB / cell. Specifically, according to the information in the reconfigurationWithSync IE, the UE may perform the RA procedure to get UL synchronization to the target cell. The UE may perform the MAC reset and the refresh of security and re-establishment of the RLC and PDCP triggered by explicit indicators. The UE may determine the target SpCell to be one on the SSB frequency of the source SpCell with a physical cell identity indicated by the physCellID IE. The UE may start DL synchronizing to the target SpCell. The UE may apply the specified BCCH configuration for the target SpCell. The UE may acquire the MIB of the target SpCell.

[0142] The reconfiguration with the sync IE may include parameters for the synchronous reconfiguration to the target SpCell. The parameters may include, but are not limited to, the serving cell configuration common IE for the target SpCell, new UE identity (e.g., RNTI value) used in the target SpCell, t304 value used for the timer T304, RA configuration used to access to and synchronize with the target SpCell. The reconfiguration with the sync IE may be included in a special cell configuration (e.g., the SpCellConfig IE) and may be associated with a serving cell index (e.g., the ServCellIndex IE) included in the SpCellConfig IE. The special cell configuration may include serving cell-specific MAC and PHY parameters for an SpCell.

[0143] When the UE is configured to perform the LTM operation, upon the UE (e.g., the RRC layer of the UE) receives an indication and the target configuration ID from the lower layers of the UE, the UE may perform the LTM cell switch execution. The indication from the lower layers may indicate that an LTM cell switch procedure is triggered. The detailed procedure for the LTM cell switch execution may be referred to the 3GPP TS 38.331.

[0144] In the present disclosure, the co-existence scenarios where the UE is configured, by the source gNB / cell, to perform both L3 handover procedure and LTM operation may be discussed. The UE may be configured with the L3 measurement configuration and report configuration by the source gNB / cell. Thus, the UE may report the L3 measurement results to the source gNB / cell so that the source gNB / cell may determine the L3 handover and instruct the UE to perform the L3 handover based on the L3 measurement results. In the meanwhile, the UE may be configured with the LTM candidate configuration by the source gNB / cell so that the UE may perform the (subsequent) intra-CU cell switch or the (subsequent) inter-CU cell switch to the target cell.

[0145] Although the source gNB / cell may perform the LTM decision (e.g., as shown in FIG. 1) and the handover decision (e.g., as shown in FIG. 3), it may be possible that the source gNB / cell may override its previous decision. For example, since the source gNB / cell may receive the L1 measurement reports and the L3 measurement reports at different timings, it may be possible that the target cell determined by the LTM decision and the target cell determined by the handover decision are different. For another reason, from the aspects of the UE’s RRC layer and the UE’s internal processing delay, the RRC layer of the UE may receive the L3 HO command after the RRC layer of the UE receives the indication from lower layers that an LTM cell switch procedure is triggered. Whether the UE should continue performing the LTM operation or change to L3 handover may not be clear. For another example, the RRC layer of the UE may receive the indication from lower layers that an LTM cell switch procedure is triggered after the RRC layer of the UE receives the L3 HO command. Whether the UE should continue performing the L3 handover or change to LTM operation may not be clear. Thus, the designs on the UE behaviors to handle the co-existence scenarios may be proposed in the present disclosure. Furthermore, the network design to avoid the UE’s confusion raised by the co-existence scenarios may also be proposed in the present disclosure.

[0146] The proposed designs and implementations may be applicable in several situations, for example, but not limited to, the following situations (a) and (b).

[0147] (a) When the L3 handover is triggered during the (subsequent) intra-CU / inter-CU LTM operation.

[0148] In some implementations, the situation (a) may include when the UE (e.g., the RRC layer of the UE) receives the L3 HO command after the UE (e.g., the MAC layer of the UE) receives an LTM cell switch command MAC CE from the source gNB / cell, where the UE may not yet perform the RA procedure to the target cell or the UE may not yet receive the ACK and / or RAR from the target cell during the RA procedure.

[0149] In some implementations, the situation (a) may include when the source gNB / cell transmits the L3 HO command to the UE after the source gNB / cell transmits an LTM cell switch command MAC CE to the UE.

[0150] In some implementations, the situation (a) may include when the UE (e.g., the RRC layer of the UE) receives the L3 HO command after the UE (e.g., the RRC layer of the UE) receives the indication from lower layers that an LTM cell switch procedure is triggered, where the UE may not yet perform the RA procedure to the target cell or the UE may not yet receive the ACK and / or RAR from the target cell during the RA procedure.

[0151] In some implementations, the situation (a) may include when the UE (e.g., the RRC layer of the UE) receives the L3 HO command after the UE performs the early synchronization to the candidate gNBs / cells, where the UE may not yet transmit the L1 measurement reports to the source gNB / cell, the UE (e.g., the MAC layer of the UE) may not yet receive an LTM cell switch command MAC CE from the source gNB / cell or the UE (e.g., the RRC layer of the UE) may not yet receive the indication from lower layers that an LTM cell switch procedure is triggered.

[0152] In some implementations, the situation (a) may include when the UE (e.g., the RRC layer of the UE) receives the L3 HO command after the UE transmits the L1 measurement reports to the source gNB / cell, where the UE (e.g., the MAC layer of the UE) may not yet receive an LTM cell switch command MAC CE from the source gNB / cell or the UE (e.g., the RRC layer of the UE) may not yet receive the indication from lower layers that an LTM cell switch procedure is triggered.

[0153] (b)　　　　When the (subsequent) intra-CU / inter-CU LTM is triggered during the L3 handover or when the (subsequent) intra-CU / inter-CU LTM is triggered after the L3 handover is triggered.

[0154] In some implementations, the situation (b) may include when the UE (e.g., the MAC layer of the UE) receives an LTM cell switch command MAC CE from the source gNB / cell after the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, where the UE may not yet transmit the RRC Reconfiguration Complete message to the target cell.

[0155] In some implementations, the situation (b) may include when the source gNB / cell transmits an LTM cell switch command MAC CE to the UE after the source gNB / cell transmits the L3 HO command to the UE.

[0156] In some implementations, the situation (b) may include when the UE (e.g., the RRC layer of the UE) receives the indication from lower layers that an LTM cell switch procedure is triggered after the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, where the UE may not yet transmit the RRC Reconfiguration Complete message to the target cell.

[0157] Proposed Design and Implementations

[0158] When the UE is configured to perform both L3 handover and LTM operation in the co-existence scenarios, several implementations may be proposed to address, but are not limited to, the UE behaviors, especially in the above-mentioned situations. When the above-mentioned situations occur, the UE may behave based on the proposed implementations.

[0159] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may determine whether the UE is configured with LTM candidate configurations. If the UE is configured with LTM candidate configurations, the UE may ignore the received L3 HO command. The UE may further discard the received L3 HO command. The UE may not store the received L3 HO command. The UE may continue performing the LTM operation based on the configured LTM candidate configurations. The UE may further determine that the L3 handover fails. If the UE is not configured with LTM candidate configurations, the UE may perform the legacy L3 handover based on the configurations in the received L3 HO command. For example, the UE may perform the RA procedure to the target cell indicated in the L3 HO command, where the L3 HO command may provide the RACH configuration for the RA procedure.

[0160] The fact that the UE determines whether the UE is configured with LTM candidate configurations (e.g., the LTM-Config IE) may include the fact that the UE determines whether the UE is performing the LTM operation (e.g., the LTM preparation, early synchronization, LTM cell switch execution, and LTM cell switch completion). The fact that the UE determines that the UE is configured with LTM candidate configurations may include the fact that the UE determines that the UE is performing the LTM operation (e.g., the LTM preparation, early synchronization, L1 measurement and reports, LTM cell switch execution and LTM cell switch completion). The fact that the UE determines that the UE is configured with the LTM candidate configuration may include the fact that the UE determines that the UE is configured with the LTM candidate configuration specific for the inter-CU LTM. The UE may determine that the UE is configured with LTM candidate configuration when the UE is configured with the LTM-Config IE, LTM-Candidate IE, LTM-CSI-ReportConfig IE, and / or LTM-CSI-ResourceConfig IE. The UE may determine that the UE is configured with the LTM candidate configuration when the UE is configured with the ltm-ServingCellUE-MeasuredTA-ID-r18 IE, and / or ltm-EarlyUL-SyncConfig-r18 IE. The UE may determine that the UE is configured with the LTM candidate configuration when the UE is configured with the LTM-TCI-Info IE.

[0161] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may determine whether the UE is configured with LTM candidate configurations. If the UE is configured with LTM candidate configurations, the UE may stop the ongoing LTM operation and perform the L3 handover based on the received L3 HO command. In some implementations, when the UE determines to perform the L3 handover and / or stop the ongoing LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing yjr ltm-Config IE). In some implementations, once the UE determines to perform the L3 handover and / or stop the ongoing LTM operation, the UE may release part of the stored LTM candidate configurations (e.g., the inter-CU LTM candidate configurations may be released while intra-CU LTM candidate configurations are maintained). The inter-CU LTM candidate configurations may include the LTM configurations associated with the inter-CU LTM candidates. The intra-CU LTM candidate configurations may include the LTM configurations associated with the intra-CU LTM candidates. In some implementations, the UE may further declare and / or trigger the LTM failure. In some implementations, when the UE receives the L3 HO command from the source gNB / cell after receiving the LTM cell switch command MAC CE or after the UE (e.g., the RRC layer of the UE) receives the indication from lower layers that triggers the LTM cell switch procedure, the UE may stop the LTM operation and / or send an LTM failure notification (or an LTM termination notification) to the source gNB / cell. The LTM failure notification (or an LTM termination notification) may be an indication in an RRC message, a MAC CE, or UCI.

[0162] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may determine whether the UE is configured with LTM candidate configurations. If the UE is configured with LTM candidate configurations, the UE may suspend the ongoing LTM operation and perform the L3 handover based on the received L3 HO command. The UE may further determine whether to release the LTM candidate configurations or to stop the LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports). In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release).

[0163] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may not determine whether the UE is configured with LTM candidate configurations. The UE may just perform the L3 handover directly based on the received L3 HO command without checking whether there are ongoing L1 / L2 / L3 mobility schemes (e.g., the LTM operation). The UE may suspend and / or abort the ongoing L1 / L2 / L3 mobility schemes (e.g., the LTM operation), if any. For example, the UE may release and / or discard any configuration related to the ongoing L1 / L2 / L3 mobility schemes when the L3 handover is successfully completed. In some implementations, the UE may release and / or discard any configuration related to the ongoing L1 / L2 / L3 mobility schemes once the UE receives the L3 HO command and / or once the UE starts to perform the L3 handover based on the received L3 HO command.

[0164] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE (e.g., the RRC layer of the UE) may not expect to receive the indication from the lower layers that an LTM cell switch procedure is triggered. In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE (e.g., the MAC layer of the UE) may not expect to receive the LTM cell switch command MAC CE from the source gNB / cell.

[0165] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the indication from the lower layers that an LTM cell switch procedure is triggered, the UE (e.g., the RRC layer of the UE) may not expect to receive the L3 HO command from the source gNB / cell. In some implementations, when the UE (e.g., the MAC layer of the UE) receives the LTM cell switch command MAC CE from the source gNB / cell, the UE (e.g., the RRC layer of the UE) may not expect to receive the L3 HO command from the source gNB / cell. In some implementations, when the UE (e.g., the MAC layer of the UE) receives the LTM TCI activation / deactivation MAC CE from the source gNB / cell, the UE (e.g., the RRC layer of the UE) may not expect to receive the L3 HO command from the source gNB / cell.

[0166] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE (e.g., the RRC layer of the UE) may determine whether the UE (e.g., the RRC layer of the UE) has received the indication from the lower layers that an LTM cell switch procedure is triggered. In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE (e.g., the RRC layer of the UE) may transmit a first indication to the lower layers (e.g., the MAC layer of the UE) that requests whether the lower layers has received an LTM cell switch command MAC CE from the source gNB / cell. In response to the first indication, the UE (e.g., the RRC layer of the UE) may expect to receive a second indication from the lower layer (e.g., the MAC layer of the UE) that indicates an LTM cell switch procedure is triggered or indicates that an LTM cell switch command MAC CE is received from the source gNB / cell. In response to the first indication, the UE (e.g., the RRC layer of the UE) may expect to receive a third indication from the lower layer (e.g., the MAC layer of the UE) that indicates an LTM cell switch procedure is not triggered or indicates that an LTM cell switch command MAC CE is not received from the source gNB / cell. In some implementations, the UE (e.g., the RRC layer of the UE) may expect to receive a fourth indication from the lower layer (e.g., the MAC layer of the UE) that indicates an LTM cell switch procedure is triggered or indicates that an LTM cell switch command MAC CE is received from the source gNB / cell, within a duration. If the UE does not receive the fourth indication after the duration, the UE may determine that the LTM cell switch procedure is not triggered or the LTM cell switch command MAC CE is not received from the source gNB / cell. The duration may start from when the UE transmits the first indication. The duration length (or the initial value of the duration) may be a fixed value or configured by the source gNB / cell.

[0167] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell and determines that (1) the UE (e.g., the RRC layer of the UE) has received the indication from the lower layers that an LTM cell switch procedure is triggered, (2) the UE has received the second indication from the lower layer that indicates the LTM cell switch procedure is triggered or indicates that the LTM cell switch command MAC CE is received from the source gNB / cell, (3) the UE has received the fourth indication from the lower layer that indicates the LTM cell switch procedure is triggered or indicates that the LTM cell switch command MAC CE is received from the source gNB / cell, and / or (4) the LTM cell switch procedure is triggered or the LTM cell switch command MAC CE is received, the UE may ignore the received L3 HO command. The UE may further discard the received L3 HO command. The UE may not store the received L3 HO command. The UE may continue performing the LTM operation based on the configured LTM candidate configurations. The UE may further determine that the L3 handover fails. In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell and determines that (1) the UE (e.g., the RRC layer of the UE) has not received the indication by the lower layers that an LTM cell switch procedure is triggered, (2) the UE has not received the second indication from the lower layer that indicates the LTM cell switch procedure is triggered or indicates that the LTM cell switch command MAC CE is received from the source gNB / cell, (3) the UE has not received the fourth indication from the lower layer that indicates the LTM cell switch procedure is triggered or indicates that the LTM cell switch command MAC CE is received from the source gNB / cell, and / or (4) the LTM cell switch procedure is not triggered or the LTM cell switch command MAC CE is not received, the UE may perform the legacy L3 handover based on the configurations in the received L3 HO command. For example, the UE may perform the RA procedure to the target cell indicated in the L3 HO command, where the L3 HO command may provide the RACH configuration for the RA procedure.

[0168] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell and determines that (1) the UE (e.g., the RRC layer of the UE) has received the indication by the lower layers that an LTM cell switch procedure is triggered, (2) the UE has received the second indication from the lower layer that indicates the LTM cell switch procedure is triggered or indicates that the LTM cell switch command MAC CE is received from the source gNB / cell, (3) the UE has received the fourth indication from the lower layer that indicates the LTM cell switch procedure is triggered or indicates that the LTM cell switch command MAC CE is received from the source gNB / cell, and / or (4) the LTM cell switch procedure is triggered or the LTM cell switch command MAC CE is received, the UE may stop the ongoing LTM operation and perform the L3 handover based on the received L3 HO command. In some implementations, when the UE determines to perform the L3 handover and / or stop the ongoing LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing the ltm-Config IE). In some implementations, the UE may further declare and / or trigger the LTM failure.

[0169] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell and determines that (1) the UE (e.g., the RRC layer of the UE) has received the indication by the lower layers that an LTM cell switch procedure is triggered, (2) the UE has received the second indication from the lower layer that indicates the LTM cell switch procedure is triggered or indicates that the LTM cell switch command MAC CE is received from the source gNB / cell, (3) the UE has received the fourth indication from the lower layer that indicates the LTM cell switch procedure is triggered or indicates that the LTM cell switch command MAC CE is received from the source gNB / cell, and / or (4) the LTM cell switch procedure is triggered or the LTM cell switch command MAC CE is received, the UE may suspend the ongoing LTM operation and perform the L3 handover based on the received L3 HO command. The UE may further determine whether to release the LTM candidate configurations or to stop the LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports). In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release).

[0170] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may not determine whether the UE (e.g., the RRC layer of the UE) has received the indication by the lower layers that an LTM cell switch procedure is triggered, or the UE may not transmit a first indication to the lower layers (e.g., the MAC layer of the UE) that requests whether the lower layers has received an LTM cell switch command MAC CE from the source gNB / cell, or the UE may not expect to receive a fourth indication from the lower layer (e.g., the MAC layer of the UE) that indicates an LTM cell switch procedure is triggered or indicates that an LTM cell switch command MAC CE is received from the source gNB / cell within a duration. The UE may just perform the L3 handover directly based on the received L3 HO command without checking whether there is ongoing L1 / L2 / L3 mobility schemes (e.g., the LTM operation). The UE may suspend and / or abort the ongoing L1 / L2 / L3 mobility schemes (e.g., the LTM operation), if any. For example, the UE may release and / or discard any configuration related to the ongoing L1 / L2 / L3 mobility schemes when the L3 handover is successfully completed. In some implementations, the UE may release and / or discard any configuration related to the ongoing L1 / L2 / L3 mobility schemes once the UE receives the L3 HO command and / or once the UE starts to perform the L3 handover based on the received L3 HO command.

[0171] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may determine whether the UE is performing L1 measurements and reports. In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE (e.g., the RRC layer of the UE) may determine whether the UE (e.g., the PHY layer of the UE) has transmitted the L1 measurement reports to the source gNB / cell. In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE (e.g., the RRC layer of the UE) may determine whether the UE (e.g., the PHY layer of the UE) needs / is going to transmit the L1 measurement reports. In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may transmit a fifth indication to the lower layers (e.g., the MAC layer of the UE, the PHY layer of the UE) to request whether the UE has transmitted the L1 measurement reports to the source gNB / cell and / or whether the UE needs / is going to transmit the L1 measurement reports and / or whether the UE is performing the L1 measurements. In response to the fifth indication, the UE (e.g., the RRC layer of the UE) may expect to receive a sixth indication from the lower layer (e.g., the MAC layer of the UE, the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE needs / is going to transmit the L1 measurement reports and / or the UE is performing the L1 measurements. In response to the fifth indication, the UE (e.g., the RRC layer of the UE) may expect to receive a seventh indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were not transmitted to the source gNB / cell and / or the UE does not need (or is not going) to transmit the L1 measurement reports and / or the UE is not performing the L1 measurements. In some implementations, the UE (e.g., the RRC layer of the UE) may expect to receive an eighth indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE needs / is going to transmit the L1 measurement reports and / or the UE is performing the L1 measurements, within a duration. If the UE does not receive the eighth indication after the duration, the UE may determine that the UE is not performing L1 measurements and / or the UE does not need (or is not going) to transmit the L1 measurement reports and / or the L1 measurement reports were not yet transmitted. The duration may begin when the UE transmits the fifth indication to the lower layers. The initial value of the duration (or the duration length) may be predefined to be a fixed value or be configured by the source gNB / cell.

[0172] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell and determines that (1) the UE is performing L1 measurements and reports, (2) the UE has transmitted the L1 measurement reports to the source gNB / cell, (3) the UE has received the sixth indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE is performing the L1 measurements, and / or (4) the UE has received the eighth indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE is performing the L1 measurements, within a duration, the UE may ignore the received L3 HO command. The UE may further discard the received L3 HO command. The UE may not store the received L3 HO command. The UE may continue performing the LTM operation based on the configured LTM candidate configurations. The UE may further determine that the L3 handover fails. In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell and determines that (1) the UE is not performing the L1 measurements and reports, (2) the UE has not transmitted the L1 measurement reports to the source gNB / cell, (3) the UE has received the seventh indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were not transmitted to the source gNB / cell and / or the UE is not performing the L1 measurements, and / or (4) the UE has not received the eighth indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE is performing the L1 measurements, within a duration, the UE may perform the legacy L3 handover based on the configurations in the received L3 HO command. For example, the UE may perform the RA procedure to the target cell indicated in the L3 HO command, where the L3 HO command may provide the RACH configuration for the RA procedure.

[0173] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell and determines that (1) the UE is performing the L1 measurements and reports, (2) the UE has transmitted the L1 measurement reports to the source gNB / cell, (3) the UE has received the sixth indication from the lower layer (e.g., the MAC layer of the UE, the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE is performing the L1 measurements, and / or (4) the UE has received the eighth indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE is performing the L1 measurements, within a duration, the UE may stop the ongoing LTM operation (e.g., including the L1 measurement and reports) and perform the L3 handover based on the received L3 HO command. In some implementations, when the UE determines to perform the L3 handover and / or stop the ongoing LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing the ltm-Config IE). In some implementations, the UE may further declare and / or trigger the LTM failure.

[0174] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell and determines that (1) the UE is performing L1 measurements and reports, (2) the UE has transmitted the L1 measurement reports to the source gNB / cell, (3) the UE has received the sixth indication from the lower layer (e.g., the MAC layer of the UE, the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE is performing the L1 measurements, and / or (4) the UE has received the eighth indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE is performing the L1 measurements, within a duration, the UE may suspend the ongoing LTM operation (e.g., including the L1 measurement and reports) and perform the L3 handover based on the received L3 HO command. The UE may further determine whether to release the LTM candidate configurations or to stop the LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports). In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release).

[0175] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may not determine whether the UE is performing L1 measurements and reports, or the UE may not determine whether the UE has transmitted the L1 measurement reports to the source gNB / cell, or the UE may not transmit a fifth indication to the lower layers (e.g., the MAC layer of the UE or the PHY layer of the UE) that requests whether the UE has transmitted the L1 measurement reports to the source gNB / cell and / or whether the UE is performing the L1 measurements, or the UE may not expect to receive an eighth indication from the lower layer (e.g., the MAC layer of the UE or the PHY layer of the UE) that indicates L1 measurement reports were transmitted to the source gNB / cell and / or the UE is performing the L1 measurements, within a duration. The UE may just perform the L3 handover directly based on the received L3 HO command without checking whether there is ongoing L1 / L2 / L3 mobility schemes (e.g., the LTM operation). The UE may suspend and / or abort the ongoing L1 / L2 / L3 mobility schemes (e.g., the LTM operation), if any. For example, the UE may release and / or discard any configuration related to the ongoing L1 / L2 / L3 mobility schemes when the L3 handover is successfully completed. In some implementations, the UE may release and / or discard any configuration related to the ongoing L1 / L2 / L3 mobility schemes once the UE receives the L3 HO command and / or once the UE starts to perform the L3 handover based on the received L3 HO command.

[0176] In some implementations, when the UE receives a notification of the LTM suspension from the source gNB / cell, the UE may not perform the L1 measurements or may not send the L1 measurement reports. The UE may stop performing the L1 measurement and / or stop transmitting the L1 measurement report. The notification of the LTM suspension may be an indication in an RRC message, a MAC CE, or DCI. In some implementations, the UE may receive a notification of the LTM resumption from the source gNB / cell, which indicates the UE to resume to perform the L1 measurements and / or transmit the L1 measurement reports if required or if triggered.

[0177] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may determine the content of the L3 HO command and / or determine whether the UE receives an L3-HO-first indication associated with the L3 HO command.

[0178] In some implementations, the content of the L3 HO command may include a (Boolean) indication in the ENUMERATED format {‘L3 HO’}, or {‘L3 HO’, ‘LTM’}.

[0179] In some implementations, if the (Boolean) indication is ‘L3 HO’, the UE may perform the L3 handover based on the L3 HO command and suspend the ongoing LTM operation, if any. The UE may further determine whether to release the LTM candidate configurations or to stop the LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports). In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release).

[0180] In some implementations, if the (Boolean) indication is ‘L3 HO’, the UE may perform the L3 handover based on the L3 HO command and stop the ongoing LTM operation, if any. In some implementations, when the UE determines to perform the L3 handover and / or stop the ongoing LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing the ltm-Config IE). In some implementations, the UE may further declare and / or trigger the LTM failure.

[0181] In some implementations, if the (Boolean) indication is ‘LTM’ or absent, the UE may perform the ongoing LTM operation, if any, and ignore the L3 HO command. However, if there is no ongoing LTM operation, the UE may perform the L3 handover based on the L3 HO command.

[0182] In some implementations, if the UE receives an L3-HO-first indication associated with the received L3 HO command, the UE may perform the L3 handover based on the L3 HO command and stop the ongoing LTM operation, if any. In some implementations, when the UE determines to perform the L3 handover and / or stops the ongoing LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing the ltm-Config IE). In some implementations, the UE may further declare and / or trigger the LTM failure.

[0183] In some implementations, if the UE receives an L3-HO-first indication associated with the received L3 HO command, the UE may perform the L3 handover based on the L3 HO command and suspend the ongoing LTM operation, if any. The UE may further determine whether to release the LTM candidate configurations or to stop the LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports). In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release).

[0184] In some implementations, if the UE does not receive an L3-HO-first indication associated with the received L3 HO command, the UE may perform the ongoing LTM operation, if any, and ignore the L3 HO command. However, if there is no ongoing LTM operation, the UE may perform the L3 handover based on the L3 HO command.

[0185] In some implementations, if the UE receives an L3-HO-first indication associated with the received L3 HO command, the UE may perform the ongoing LTM operation, if any, and ignore the L3 HO command. However, if there is no ongoing LTM operation, the UE may perform the L3 handover based on the L3 HO command.

[0186] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, and if the UE (e.g., the RRC layer of the UE) has received the target configuration ID from the lower layers, the UE may further compare whether the first target cell identity (e.g., the PhysCellID in the ServingCellConfigCommon IE in the ReconfigurationWithSync IE) in the L3 HO command is the same as or different from the second target cell identity (e.g., the ltm-CandidatePCI IE in the LTM-Candidate IE, where the target configuration ID may be associated with the ltm-CandidateId IE in the LTM-Candidate IE and may be associated with the Target Config ID in the received LTM cell switch command MAC CE) associated with the target configuration ID. In some implementations, if they are the same, the UE may ignore the L3 HO command. The UE may further discard the received L3 HO command. The UE may not store the received L3 HO command. The UE may continue performing the LTM operation based on the configured LTM candidate configurations. The UE may further determine that the L3 handover fails. In some implementations, if they are different, the UE may stop the ongoing LTM operation and perform the L3 handover based on the received L3 HO command. In some implementations, when the UE determines to perform the L3 handover and / or stop the ongoing LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing the ltm-Config IE). In some implementations, the UE may further declare and / or trigger the LTM failure. In some implementations, if they are different, the UE may suspend the ongoing LTM operation and perform the L3 handover based on the received L3 HO command. The UE may further determine whether to release the LTM candidate configurations or to stop the LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports). In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release).

[0187] In some implementations, the UE may not expect to receive the configuration that configures the same first target cell identity and the second target cell identity. For example, the UE may not expect that the target gNB / cell identity in the received L3 HO command is the same as the target gNB / cell identity associated with the target configuration ID in the received LTM cell switch MAC CE.

[0188] In implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, and if the UE (e.g., the RRC layer of the UE) has been configured with LTM operations, the UE may further compare whether the first target cell identity (e.g., the PhysCellID IE in the ServingCellConfigCommon IE in the ReconfigurationWithSync IE) in the L3 HO command is one of candidate target cell identities (e.g., the ltm-CandidatePCI IE in the LTM-Candidate IE) received in RRC reconfiguration message to configure the UE with the LTM operations. In some implementations, if the first target cell identity is not one of candidate target cell identities, the UE may stop the ongoing LTM operation (e.g., including the L1 measurement and reports) and perform the L3 handover based on the received L3 HO command. In some implementations, when the UE determines to perform the L3 handover and / or stop the ongoing LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing the ltm-Config IE). In some implementations, the UE may further declare and / or trigger the LTM failure.

[0189] In some implementations, if the first target cell identity is one of candidate target cell identities, the UE may suspend the ongoing LTM operation (e.g., including the L1 measurement and reports) and perform the L3 handover based on the received L3 HO command. The UE may further determine whether to release the LTM candidate configurations or to stop the LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports).

[0190] In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the first target cell identity is one of candidate target cell identities, the UE may ignore the received L3 HO command. The UE may further discard the received L3 HO command. The UE may not store the received L3 HO command. The UE may continue performing the LTM operation based on the configured LTM candidate configurations. The UE may further determine that the L3 handover fails.

[0191] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, the UE may determine whether the UE performs the ongoing inter-CU LTM operation and / or whether the UE is configured with the inter-CU LTM operation, based on the content of the received, if any, the LTM cell switch command MAC CE and / or based on the indication received from the lower layers that an inter-CU LTM procedure is triggered.

[0192] In some implementations, when the UE receives an LTM cell switch command MAC CE from the source gNB / cell, where the content of the LTM cell switch command MAC CE may include a bit ‘1’ indicating that it is an inter-CU LTM cell switch command MAC CE, the UE (e.g., the MAC layer of the UE) may notify the upper layer of the UE (e.g., the RRC layer of the UE) that an inter-CU LTM procedure is triggered.

[0193] In some implementations, when the UE receives an LTM cell switch command MAC CE from the source gNB / cell, where the content of the LTM cell switch command MAC CE may include a bit ‘0’ indicating that it is an intra-CU LTM cell switch command MAC CE, the UE (e.g., the MAC layer of the UE) may notify the upper layer of the UE (e.g., the RRC layer of the UE) that an intra-CU LTM procedure is triggered.

[0194] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, and the UE further determines that an inter-CU LTM operation is ongoing (e.g., based on the indication received from the lower layers that an inter-CU LTM procedure is triggered), the UE may stop the ongoing inter-CU LTM operation (e.g., including the L1 measurement and reports) and perform the L3 handover based on the received L3 HO command. In some implementations, when the UE determines to perform the L3 handover and / or stop the ongoing inter-CU LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing the ltm-Config IE). In some implementations, the UE may further declare and / or trigger the inter-CU LTM failure.

[0195] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, and the UE further determines that an inter-CU LTM operation is ongoing (e.g., based on the indication received from the lower layers that an inter-CU LTM procedure is triggered), the UE may suspend the ongoing inter-CU LTM operation (e.g., including the L1 measurement and reports) and perform the L3 handover based on the received L3 HO command. The UE may further determine whether to release the LTM candidate configurations or to stop the inter-CU LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing inter-CU LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports).

[0196] In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing inter-CU LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release).

[0197] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, and the UE further determines that an inter-CU LTM operation is ongoing (e.g., based on the indication received from the lower layers that an inter-CU LTM procedure is triggered), the UE may ignore the received L3 HO command. The UE may further discard the received L3 HO command. The UE may not store the received L3 HO command. The UE may continue performing the inter-CU LTM operation based on the configured LTM candidate configurations. The UE may further determine that the L3 handover fails.

[0198] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, and the UE further determines that an intra-CU LTM operation is ongoing (e.g., based on the indication received from the lower layers that an intra-CU LTM procedure is triggered), the UE may stop the ongoing intra-CU LTM operation (e.g., including the L1 measurement and reports) and perform the L3 handover based on the received L3 HO command. In some implementations, when the UE determines to perform the L3 handover and / or stop the ongoing intra-CU LTM operation, the UE may release the stored LTM candidate configurations (e.g., by performing the LTM configuration release, such as removing the entry in the VarLTM-ServingCellNoResetID IE, removing the entry in the VarLTM-ServingCell UE-MeasuredTA-ID IE, and / or releasing the ltm-Config IE). In some implementations, the UE may further declare and / or trigger the intra-CU LTM failure.

[0199] In some implementations, when the UE (e.g., the RRC layer of the UE) receives the L3 HO command from the source gNB / cell, and the UE further determines that an intra-CU LTM operation is ongoing (e.g., based on the indication received from the lower layers that an inter-CU LTM procedure is triggered), the UE may suspend the ongoing intra-CU LTM operation (e.g., including the L1 measurement and reports) and perform the L3 handover based on the received L3 HO command. The UE may further determine whether to release the LTM candidate configurations or to stop the intra-CU LTM operation based on the L3 handover results. If the L3 handover is successfully completed (e.g., when the UE transmits an RRC Reconfiguration Complete message to the target cell), the UE may release the stored LTM candidate configurations. If the L3 handover fails, the UE may resume the ongoing intra-CU LTM operation (e.g., by continuing the early synchronization, by continuing the L1 measurement and reports).

[0200] In some implementations, if the L3 handover fails and before the UE selects a cell during the RRC reestablishment procedure, the UE may resume the ongoing inter-CU LTM operation. If the L3 handover fails and after the UE selects a cell during the RRC reestablishment procedure, or if the L3 handover fails and after the RRC reestablishment procedure completes, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release). In some implementations, if the L3 handover fails and the UE determines that the selected cell during the RRC reestablishment procedure is the same as the source cell from which the UE receives the LTM candidate configurations, the UE may resume the ongoing LTM operation. If the L3 handover fails and the UE determines that the selected cell during RRC the reestablishment procedure is not the source cell from which the UE receives the LTM candidate configurations, the UE may release the stored LTM candidate configuration (e.g., by performing the LTM configuration release).

[0201] In some implementations, when the first target cell identity associated with the Target Configuration ID in the LTM cell switch MAC CE is the same as the second target cell identity indicated in the L3 HO command, no matter the LTM operation or L3 HO is determined by the UE (e.g., based on the criteria proposed in the present disclosure, UE implementation to determine), the RRC Reconfiguration Complete message that the UE transmits to the target gNB / cell identified by the first / second target cell identity may include an indication to notify the target gNB / cell that the UE performs either the LTM operation or the L3 HO to such target gNB / cell. The indication may be in a format of ENUMERATED{LTM} or ENUMERATED {LTM, L3 HO}. If the indication is ‘LTM’, the UE may inform the target gNB / cell that the UE completes the LTM operation successfully to handover to the target gNB / cell. If the indication is ‘LTM’ or is absent, the UE may inform the target gNB / cell that the UE completes the L3 handover successfully to handover to the target gNB / cell.

[0202] In some implementations, once the UE transmits the RRC Reconfiguration Complete message to notify the target gNB / cell that either the LTM or the L3 HO is used for handover, the UE may ignore or stop the failure handling of the other mobility schemes. In some implementations, when the UE completes the LTM cell switch to a target gNB / cell which is also the target gNB / cell indicated in L3 HO command and / or if the UE transmits the RRC Reconfiguration Complete message to notify the target gNB / cell that LTM is used for handover, the UE may not report the L3 HO failure to the source gNB / cell. The UE may not perform the legacy UE behaviors (e.g., the RRC reestablishment procedure) following the L3 HO failure or the termination of the L3 HO. The UE may stop the L3 HO related actions / procedures once the UE transmits the RRC Reconfiguration Complete message to the target gNB / cell. In some implementations, when the UE completes the L3 HO to a target gNB / cell which is also the target gNB / cell associated with the Target Configuration ID in the LTM cell switch MAC CE and / or if the UE transmits the RRC Reconfiguration Complete message to notify the target gNB / cell that the L3 HO is used for handover, the UE may not report the LTM failure to the source gNB / cell. The UE may not perform the legacy UE behaviors (e.g., the RRC reestablishment procedure) following the LTM failure or the LTM termination. The UE may stop the LTM related actions / procedures once the UE transmits the RRC Reconfiguration Complete message to the target gNB / cell.

[0203] In some implementations, once the target gNB / cell receives the RRC Reconfiguration Complete message for the notification of the target gNB / cell that either the LTM or the L3 HO is used for handover, the target gNB / cell may transmit an XnAP message to inform the source gNB / cell that which mobility scheme (e.g., the LTM, L3 HO) is applied. The source gNB / cell may perform the data forwarding corresponding to the selected mobility schemes.

[0204] In some implementations, when L3 HO failure is triggered due to the fact that the UE performs LTM operation to the target gNB / cell successfully, and / or due to the fact that the UE ignores the L3 HO command after the UE determines to perform the LTM operation, the UE may or may not follow the legacy procedure for the L3 HO failure. In some implementations, the UE may not report the L3 HO failure report, may not perform the RRC reestablishment procedure, and / or may not perform the cell reselection after such L3 HO failure is triggered.

[0205] In some implementations, when LTM failure is triggered due to the fact that the UE performs L3 HO to the target gNB / cell successfully, and / or due to the fact that the UE suspends / stop the LTM operation after the UE determines to perform the L3 HO, the UE may or may not follow the legacy procedure for the LTM failure. In some implementations, the UE may not perform the RRC reestablishment procedure and / or may not perform the cell reselection after such LTM failure is triggered.

[0206] In some implementations, if the MAC entity of the UE already performs the early synchronization and cell switch to a target cell, the MAC layer of the UE may ignore the request from the RRC layer of the UE to perform the RA to another target cell indicated in the L3 HO command.

[0207] FIG. 4 is a flowchart illustrating a method / process 400 performed by a UE for handling handover (HO) procedures, according to an example implementation of the present disclosure.

[0208] In the action 402, the process 400 may start by performing a first HO procedure. In the action 404, the process 400 may receive information associated with a second HO procedure during the first HO procedure. In the action 406, the process 400 may in response to receiving the information, determine whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure. The process 400 may then end.

[0209] In some implementations, the first HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure may include a layer 3 (L3) HO procedure, and the information may include a L3 HO command received from a source base station (BS).

[0210] In some implementations, the first HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure may include a layer 3 (L3) HO procedure, and the information may include a L3 HO command received from a source base station (BS), and in the action 406, the process 400 may after determining that the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure, ignore the L3 HO command and continue performing the inter-CU LTM cell switch procedure.

[0211] In some implementations, the first HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure may include a layer 3 (L3) HO procedure, and the information may include a L3 HO command received from a source base station (BS), and in the action 406, the process 400 may stop the LTM cell switch procedure and perform the L3 HO procedure.

[0212] In some implementations, the first HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure may include a layer 3 (L3) HO procedure, and the information may include a L3 HO command received from a source base station (BS), and in the action 406, the process 400 may determine whether a first target BS indicated by the L3 HO command is the same as a second target BS indicated by an LTM cell switch command associated with the LTM cell switch procedure; after determining that the first target BS is the same as the second target BS, ignore the L3 HO command and continue performing the LTM cell switch procedure; and after determining that the first target BS is different from the second target BS, stop the LTM cell switch procedure and perform the L3 HO procedure.

[0213] In some implementations, the first HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure may include a layer 3 (L3) HO procedure, and the information may include a L3 HO command received from a source base station (BS), and in the action 406, the process 400 may start a timer upon receiving the L3 HO command; determine whether an LTM cell switch command associated with the LTM cell switch procedure is received from a lower layer of the UE before the timer expires; after determining that the LTM cell switch command associated with the LTM cell switch procedure is received from the lower layer of the UE before the timer expires, continue performing the LTM cell switch procedure; and after determining that the LTM cell switch command associated with the LTM cell switch procedure is not received from the lower layer of the UE before the timer expires, stop the LTM cell switch procedure and perform the L3 HO procedure.

[0214] In some implementations, the first HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, the second HO procedure may include a layer 3 (L3) HO procedure, and the information may include a L3 HO command received from a source base station (BS), the LTM cell switch procedure may include an intra-central unit (CU) LTM cell switch procedure or an inter-CU LTM cell switch procedure, and in the action 406, the process 400 may start a timer upon receiving the L3 HO command; determine whether an LTM cell switch command associated with the LTM cell switch procedure is received from a lower layer of the UE before the timer expires; after determining that the LTM cell switch command associated with the LTM cell switch procedure is received from the lower layer of the UE before the timer expires, determine that the LTM cell switch command indicates the intra-CU LTM cell switch procedure or the inter-CU LTM cell switch procedure; after determining that the LTM cell switch command indicates the intra-CU LTM cell switch procedure, stop the intra-CU LTM cell switch procedure and perform the L3 HO procedure; and after determining that the LTM cell switch command indicates the inter-CU LTM cell switch procedure, ignore the L3 HO command and continue performing the inter-CU LTM cell switch procedure.

[0215] In some implementations, the first HO procedure may include a layer 3 (L3) HO procedure, the second HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information may include an LTM cell switch command received from a lower layer of the UE.

[0216] In some implementations, the first HO procedure may include a layer 3 (L3) HO procedure, the second HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information may include an LTM cell switch command received from a lower layer of the UE, and in the action 406, the process 400 may ignore the LTM cell switch command and continue performing the L3 HO procedure.

[0217] In some implementations, in the action 406, the first HO procedure may include a layer 3 (L3) HO procedure, the second HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information may include an LTM cell switch command received from a lower layer of the UE, and the process 400 may stop the L3 HO procedure and perform the LTM cell switch procedure.

[0218] In some implementations, the first HO procedure may include a layer 3 (L3) HO procedure, the second HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information may include an LTM cell switch command received from a lower layer of the UE, and in the action 406, the process 400 may determine whether a first target BS indicated by the LTM cell switch command is the same as a second target BS indicated by a L3 HO command associated with the L3 HO procedure; after determining that the first target BS is the same as the second target BS, ignore the LTM cell switch command and continue performing the L3 HO procedure; and after determining that the first target BS is different from the second target BS, stop the L3 HO procedure and perform the LTM cell switch procedure.

[0219] In some implementations, the first HO procedure may include a layer 3 (L3) HO procedure, the second HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information may include an LTM cell switch command received from a lower layer of the UE, and in the action 406, the process 400 may after determining that the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure, ignore the LTM cell switch command and continue performing the L3 HO procedure.

[0220] In some implementations, the first HO procedure may include a layer 3 (L3) HO procedure, the second HO procedure may include a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and the information may include an LTM cell switch command received from a lower layer of the UE, and in the action 406, the process 400 may after determining the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure and the LTM cell switch command from the lower layer of the UE is received after receiving a L3 HO command associated with the L3 HO procedure, stop the L3 HO procedure and perform the inter-CU LTM cell switch procedure; and after determining that the LTM cell switch procedure is an intra-CU LTM cell switch procedure and the LTM cell switch command from the lower layer of the UE is received after receiving the L3 HO command associated with the L3 HO procedure, ignore the LTM cell switch command and continue performing the L3 HO procedure.

[0221] The steps / actions shown in FIG. 4 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. 4 may be omitted in some implementations and one or more actions shown in FIG. 4 may be combined.

[0222] The technical problem addressed by the method illustrated in FIG. 4 is how to efficiently manage dual handover (HO) procedures in a user equipment (UE) to ensure seamless mobility and resource optimization, particularly when the UE receives information about a second HO procedure while already performing a first HO procedure, which can lead to conflicts or inefficiencies in traditional handover mechanisms. The advantageous technical effect achieved by the method illustrated in FIG. 4 is the improved flexibility and adaptability of the UE in handling multiple handover options, allowing it to dynamically decide whether to continue the first HO procedure or switch to the second HO procedure based on received information, thereby reducing service interruption and enhancing network performance in dynamic environments.

[0223] FIG. 5 is a flowchart illustrating a method / process 500 performed by a BS for handling handover (HO) procedures, according to an example implementation of the present disclosure.

[0224] In the action 502, the process 500 may start by during a first HO procedure, transmitting information associated with a second HO procedure. In the action 504, the information may cause a user equipment (UE) to in response to receiving the information, determine whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure. The process 500 may then end.

[0225] The steps / actions shown in FIG. 5 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. 5 may be omitted in some implementations and one or more actions shown in FIG. 5 may be combined.

[0226] The method illustrated in FIG. 5 is similar to that in FIG. 4, except that it is described from the perspective of the BS (instead of the UE).

[0227] FIG. 6 is a block diagram illustrating a node 600 for wireless communication in accordance with various aspects of the present disclosure. As illustrated in FIG. 6, a node 600 may include a transceiver 620, a processor 628, a memory 634, one or more presentation components 638, and at least one antenna 636. The node 600 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. 6).

[0228] Each of the components may directly or indirectly communicate with each other over one or more buses 640. The node 600 may be a UE or a BS that performs various functions disclosed with reference to FIGS. 1 through 5.

[0229] The transceiver 620 has a transmitter 622 (e.g., transmitting / transmission circuitry) and a receiver 624 (e.g., receiving / reception circuitry) and may be configured to transmit and / or receive time and / or frequency resource partitioning information. The transceiver 620 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 620 may be configured to receive data and control channels.

[0230] The node 600 may include a variety of computer-readable media. Computer-readable media may be any available media that may be accessed by the node 600 and include volatile (and / or non-volatile) media and removable (and / or non-removable) media.

[0231] 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.

[0232] Computer-storage media may include RAM, ROM, EPROM, EEPROM, flash memory (or other memory technology), CD-ROM, Digital Versatile Disks (DVD) (or other optical disk storage), magnetic cassettes, magnetic tape, magnetic disk storage (or other magnetic storage devices), etc. Computer-storage media may not include a propagated data signal. Communication media may typically embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transport mechanisms and include any information delivery media.

[0233] 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.

[0234] The memory 634 may include computer-storage media in the form of volatile and / or non-volatile memory. The memory 634 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. 6, the memory 634 may store a computer-readable and / or computer-executable instructions 632 (e.g., software codes) that are configured to, when executed, cause the processor 628 to perform various functions disclosed herein, for example, with reference to FIGS. 1 through 5. Alternatively, the instructions 632 may not be directly executable by the processor 628 but may be configured to cause the node 600 (e.g., when compiled and executed) to perform various functions disclosed herein.

[0235] The processor 628 (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 628 may include memory. The processor 628 may process the data 630 and the instructions 632 received from the memory 634, and information transmitted and received via the transceiver 620, the baseband communications module, and / or the network communications module. The processor 628 may also process information to send to the transceiver 620 for transmission via the antenna 636 to the network communications module for transmission to a CN.

[0236] One or more presentation components 638 may present data indications to a person or another device. Examples of presentation components 638 may include a display device, a speaker, a printing component, a vibrating component, etc.

[0237] In view of the present disclosure, it is obvious that various techniques may be used for implementing the disclosed concepts without departing from the scope of those concepts. Moreover, while the concepts have been disclosed with specific reference to certain implementations, a person of ordinary skill in the art may recognize that changes may be made in form and detail without departing from the scope of those concepts. As such, the disclosed implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the present disclosure is not limited to the particular implementations disclosed and many rearrangements, modifications, and substitutions are possible without departing from the scope of the present disclosure.

Claims

1. A user equipment (UE) for handing handover (HO) procedures, 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: 　　　　　　　　perform a first HO procedure; 　　　　　　　　receive information associated with a second HO procedure during the first HO procedure; and 　　　　　　　　in response to receiving the information, determine whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure.

2. The UE of claim 1, wherein: 　　　　the first HO procedure comprises a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, 　　　　the second HO procedure comprises a layer 3 (L3) HO procedure, and 　　　　the information includes a L3 HO command received from a source base station (BS).

3. The UE of claim 2, wherein in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　 after determining that the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure: 　　　　　　　　ignoring the L3 HO command, and 　　　　　　　　continuing performing the inter-CU LTM cell switch procedure.

4. The UE of claim 2, wherein in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　stopping the LTM cell switch procedure, and 　　　　performing the L3 HO procedure.

5. The UE of claim 2, wherein in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　determining whether a first target BS indicated by the L3 HO command is the same as a second target BS indicated by an LTM cell switch command associated with the LTM cell switch procedure; 　　　　after determining that the first target BS is the same as the second target BS: 　　　　　　　　ignoring the L3 HO command, and 　　　　　　　　continuing performing the LTM cell switch procedure; and 　　　　after determining that the first target BS is different from the second target BS: 　　　　　　　　stopping the LTM cell switch procedure, and 　　　　　　　　performing the L3 HO procedure.

6. The UE of claim 2, wherein in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　starting a timer upon receiving the L3 HO command; 　　　　determining whether an LTM cell switch command associated with the LTM cell switch procedure is received from a lower layer of the UE before the timer expires; 　　　　after determining that the LTM cell switch command associated with the LTM cell switch procedure is received from the lower layer of the UE before the timer expires, continuing performing the LTM cell switch procedure; and 　　　　after determining that the LTM cell switch command associated with the LTM cell switch procedure is not received from the lower layer of the UE before the timer expires: 　　　　　　　　stopping the LTM cell switch procedure, and 　　　　　　　　performing the L3 HO procedure.

7. The UE of claim 2, wherein: 　　　　the LTM cell switch procedure comprises an intra-central unit (CU) LTM cell switch procedure or an inter-CU LTM cell switch procedure, and 　　　　in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　　　　　starting a timer upon receiving the L3 HO command; 　　　　　　　　determining whether an LTM cell switch command associated with the LTM cell switch procedure is received from a lower layer of the UE before the timer expires; 　　　　　　　　after determining that the LTM cell switch command associated with the LTM cell switch procedure is received from the lower layer of the UE before the timer expires, determining that the LTM cell switch command indicates the intra-CU LTM cell switch procedure or the inter-CU LTM cell switch procedure; 　　　　　　　　after determining that the LTM cell switch command indicates the intra-CU LTM cell switch procedure: 　　　　　　　　　　　　stopping the intra-CU LTM cell switch procedure, and 　　　　　　　　　　　　performing the L3 HO procedure; and 　　　　　　　　after determining that the LTM cell switch command indicates the inter-CU LTM cell switch procedure: 　　　　　　　　　　　　ignoring the L3 HO command, and 　　　　　　　　　　　　continuing performing the inter-CU LTM cell switch procedure.

8. The UE of claim 1, wherein: 　　　　the first HO procedure comprises a layer 3 (L3) HO procedure, 　　　　the second HO procedure comprises a layer 1 / layer 2 triggered mobility (LTM) cell switch procedure, and 　　　　the information includes an LTM cell switch command received from a lower layer of the UE.

9. The UE of claim 8, wherein in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　ignoring the LTM cell switch command, and 　　　　continuing performing the L3 HO procedure.

10. The UE of claim 8, wherein in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　stopping the L3 HO procedure, and 　　　　performing the LTM cell switch procedure.

11. The UE of claim 8, wherein in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　determining whether a first target BS indicated by the LTM cell switch command is the same as a second target BS indicated by a L3 HO command associated with the L3 HO procedure; 　　　　after determining that the first target BS is the same as the second target BS: 　　　　　　　　ignoring the LTM cell switch command, and 　　　　　　　　continuing performing the L3 HO procedure; and 　　　　after determining that the first target BS is different from the second target BS: 　　　　　　　　stopping the L3 HO procedure, and 　　　　　　　　performing the LTM cell switch procedure.

12. The UE of claim 8, wherein in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　after determining that the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure: 　　　　　　　　ignoring the LTM cell switch command, and 　　　　　　　　continuing performing the L3 HO procedure.

13. The UE of claim 8, wherein 　　　　in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure comprises: 　　　　　　　　after determining the LTM cell switch procedure is an inter-central unit (CU) LTM cell switch procedure and the LTM cell switch command from the lower layer of the UE is received after receiving a L3 HO command associated with the L3 HO procedure: 　　　　　　　　　　　　stopping the L3 HO procedure, and 　　　　　　　　　　　　performing the inter-CU LTM cell switch procedure; and 　　　　　　　　after determining that the LTM cell switch procedure is an intra-CU LTM cell switch procedure and the LTM cell switch command from the lower layer of the UE is received after receiving the L3 HO command associated with the L3 HO procedure: 　　　　　　　　　　　　ignoring the LTM cell switch command, and 　　　　　　　　　　　　continuing performing the L3 HO procedure.

14. A method performed by a user equipment (UE) for handling handover (HO) procedures, the method comprising: 　　　　performing a first HO procedure; 　　　　receiving information associated with a second HO procedure during the first HO procedure; and 　　　　in response to receiving the information, determining whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure.

15. A base station (BS) for handling handover (HO) procedures, 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: 　　　　　　　　during a first HO procedure, transmit information associated with a second HO procedure, wherein the information causes a user equipment (UE) to: 　　　　　　　　　　　　in response to receiving the information, determine whether to (i) continue performing the first HO procedure or (ii) stop the first HO procedure and perform the second HO procedure.

Images