SYSTEM AND METHOD FOR ENABLED MULTIPLE BASE REFERENCE CONFIGURATIONS FOR LAYER 1 / LAYER 2 TRIGGERED MOBILITY IN TELECOMMUNICATIONS NETWORKS - Patent application

Abstract

A system and method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility in a telecommunications network includes receiving a first base reference configuration and an indicator indicating an association between the first base reference configuration and a type / characteristics of a first cell from a serving distribution unit (gNB-DU), where the serving gNB-DU supports a first cell serving a user equipment (UE), sending the first base reference configuration or an instruction to provide a new reference configuration to a target distribution unit (target gNB-DU) during candidate cell configuration preparation, where the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover, determining whether the first base reference configuration is usable with a delta configuration to obtain a complete second cell configuration for the second cell, and sending the second base reference configuration corresponding to the second cell configuration.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Indian Provisional Patent Application No. 202321013153, filed with the Indian Patent Office on February 27, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0002] Systems and methods consistent with example embodiments of the present disclosure relate to implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility in telecommunications networks. [Background technology]

[0003] The Radio Access Network (RAN) is a key component in telecommunications systems because it connects end-user devices (or user equipment) to the rest of the network. The RAN includes a combination of various network elements (NEs) that connect end-user devices to the core network. Traditionally, the hardware and / or software of a particular RAN is vendor-specific.

[0004] Open RAN (O-RAN) technology has emerged to allow multiple vendors to provide hardware and / or software for telecommunications systems. To this end, O-RAN decomposes the RAN functions into a Centralized Unit (CU), a Distributed Unit (DU), and a Radio Unit (RU).

[0005] The CU is a logical node for hosting the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and / or Packet Data Convergence Protocol (PDCP) sublayers of the RAN. The DU is a logical node for hosting the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) sublayers of the RAN. The RU is a physical node that converts radio signals from the antenna into digital signals that can be transmitted to the DU via the fronthaul. These entities have open protocols and interfaces between them, so they can be developed by different vendors.

[0006] Figure 1A shows the O-RAN architecture of the related art. Referring to Figure 1A, RAN functions in the O-RAN architecture are controlled and optimized by a RAN Intelligent Controller (RIC). The RIC is a software-defined component that implements modular applications to facilitate multi-vendor operability required in an O-RAN system and to automate and optimize RAN operations. RICs are divided into two types: non-real-time RIC (NRT RIC) and near-real-time RIC (nRT RIC).

[0007] The NRT RIC is the control point for non-real-time control loops and operates on timescales greater than one second within a Service Management and Orchestration (SMO) framework. Its functions are implemented through modular applications called rApps (rApp1, ..., rAppN in Figure 1A) and include providing policy-based guidance and enrichment over the A1 interface, which is the interface enabling communication between the NRT RIC and the nRT RIC, performing data analytics, artificial intelligence / machine learning (AI / ML) training and inference for RAN optimization, and / or recommending configuration management actions via the O1 interface, which is the interface connecting the SMO to RAN managed elements (e.g., nRT RIC, O-RA Centralized Unit (O-CU), O-RAN Distributed Unit (O-DU), etc.).

[0008] The nRT RIC operates on a timescale between 10 milliseconds and 1 second and connects to the O-DU, O-CU (decomposed into the O-CU control plane (O-CU-CP) and the O-CU user plane (O-CU-UP)), and the open evolved Node B (O-eNB) via the E2 interface. The O-CU communicates with the O-DU via the F1 interface (e.g., the O-CU-CP can communicate with the O-DU via the F1-C interface, and the O-CU-UP can communicate with the O-DU via the F1-U interface).

[0009] The nRT RIC controls the underlying RAN elements (E2 nodes / Network Functions (NFs)) through a near-real-time control loop using the E2 interface. The nRT RIC monitors, suspends / stops, overrides, and controls E2 nodes (O-CU, O-DU, and O-eNB) through policies. For example, the nRT sets policy parameters for activated functions of the E2 nodes. Additionally, the nRT RIC hosts xApps to implement functions such as quality of service (QoS) optimization, mobility optimization, slicing optimization, interference mitigation, load balancing, and security. The two types of RICs work together to optimize the O-RAN. For example, the NRT RIC provides policies, data, and AI / ML models that are enforced and used by the nRT RIC for RAN optimization via the A1 interface, and the nRT returns policy feedback (i.e., how the policies set by the NRT RIC are performing).

[0010] The SMO framework, in which the NRT RIC is located, manages and orchestrates RAN elements. Specifically, the SMO manages and orchestrates what is called the O-Ran Cloud (O-Cloud). The O-Cloud is a collection of physical RAN nodes that host the RIC, O-CU, and O-DU, supporting software components (e.g., operating systems and runtime environments), and the SMO itself. In other words, the SMO manages the O-Cloud from within. The O2 interface is the interface between the SMO and the O-Cloud in which it resides. Through the O2 interface, the SMO provides infrastructure management services (IMS) and deployment management services (DMS).

[0011] According to the related art O-RAN architecture, FIG. 1B shows a distributed architecture for separating gNB-CU-CP, gNB-CU-UP, and gNB-DU defined in the 3rd Generation Partnership Project (3GPP) (i.e., 3GPP TS 38.401 Version 16.3.0 Release 16), in which a next generation Node B (gNB) is decomposed into multiple logical entities.

[0012] Referring to Figure 1B, a gNB may include a gNB-CU-CP, multiple gNB-CU-UPs, and multiple gNB-DUs.

[0013] With regard to communications within the distributed architecture, the gNB-CU-CP is connected to the gNB-DU through an F1-C interface, the gNB-CU-UP is connected to the gNB-DU through an F1-U interface, and the gNB-CU-UP is connected to the gNB-CU-CP through an E1 interface, where one gNB-DU is connected to only one gNB-CU-CP and one gNB-CU-UP is connected to only one gNB-CU-CP. Furthermore, a single gNB-DU can host multiple cells (e.g., up to 512 cells as defined in the 3GPP specifications).

[0014] The gNB-DU hosts the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers, and information scheduling operations are performed in the gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU. The gNB-DU is therefore a logical node whose operation is partially controlled by the gNB-CU (i.e., 3GPP TS 38.401 Version 16.3.0 Release 16).

[0015] The gNB-CU-CP hosts the Packet Data Convergence Protocol (PDCP) layer and the Radio Resource Control (RRC) layer.

[0016] In particular, the gNB-CU-CP refers to the logical node that hosts the control plane portion of the Radio Resource Control (RRC) and PDCP protocols of the gNB-CU for an en-gNB or gNB. The gNB-CU-CP terminates the E1 interface connected to the gNB-CU-UP and the F1-C interface connected to the gNB-DU (i.e., 3GPP TS 38.401 Version 16.3.0 Release 16).

[0017] In the related art, scheduling operations do not support L1 / L2 inter-center cell changes (i.e., serving cell changes). To this end, in the related art, both configuration preparation and handover execution are performed by the gNB-CU-CP via RRC.

[0018] As a result, scheduling operations for both configuration preparation and handover execution according to the related art involve the exchange of extensive configuration data between network entities of the RAN (i.e., UE, O-RU, O-DU, and O-CU), which is time-consuming and requires high latency. Summary of the Invention

[0019] According to embodiments, systems and methods are provided that relate to the implementation of multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) in telecommunications networks, where scheduling operations optimize sequential L1 / L2 cell changes between source and candidate cells without additional RRC reconfiguration by implementing multiple base reference configurations to optimize inter-cell mobility and enabling New Radio (NR) mobility extensions that optimize LTM cell switching.

[0020] To this end, the system and method optimize the exchange of base reference configurations between logical nodes (i.e., gNB-CU, serving gNB-DU, candidate gNB-DU) and user entities (UEs). In particular, the system and method enable a gNB-CU to receive a base reference configuration for a source cell (i.e., serving cell) from a serving gNB-DU and a base reference configuration for at least one candidate cell from a candidate gNB-DU.

[0021] If the configuration of a candidate cell (i.e., a target cell) is substantially different from the configuration of the source cell (i.e., determining the candidate cell configuration using the base reference configuration of the serving cell is not simple, but rather complex and expensive), the gNB-CU maintains multiple base reference configurations according to the type and characteristics of the candidate cell (i.e., the base reference configuration of the serving cell from the serving gNB-DU and the base reference configuration from at least one candidate cell (i.e., a target cell) from the candidate gNB-DU).

[0022] Based on the information exchanged during gNB-DU setup, i.e., F1 interface setup, the gNB-CU is aware of the types of cells served by one or more gNB-DUs (i.e., the type and / or characteristics of the LTM candidate cells). Thus, the gNB-CU can easily determine which base reference configuration needs to be used when sending an LTM handover preparation request to the target gNB-DU (i.e., target gNB-DU), thereby effectively avoiding a subsequent long-term serving cell change (LTM SCC) with additional RRC reconfiguration due to the UE's inability to prepare the complete cell configuration of the candidate cells.

[0023] Thus, the systems and methods according to the example embodiments advantageously address the shortcomings of using a delta configuration over a reference configuration in LTM cell switching according to the related art, which significantly improves New Radio (NR) inter-cell mobility.

[0024] According to one embodiment, a system for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) in a telecommunications network includes at least one memory that stores instructions, and the instructions are executed to receive, by a central unit (gNB-CU) from a serving distributed unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between a type and / or characteristic of the first cell and the first base reference configuration, where the serving gNB-DU supports a first cell having a first LTM cell configuration corresponding to the first base reference configuration, the first cell being a serving cell for a user equipment (UE); and candidate cell configuration preparation. The method includes at least one processor configured to: send, by the gNB-CU, a first base reference configuration or an instruction to provide a new reference configuration to a target distributed unit (target gNB-DU), where the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover; determine, by the target gNB-DU, whether the first base reference configuration is usable together with a delta configuration to obtain a complete second cell configuration for the second cell; and send, by the target gNB-DU to the gNB-CU based on determining that the first base reference configuration is not usable to obtain the second cell configuration.

[0025] According to one embodiment, a method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) in a telecommunications network includes receiving, by a central unit (gNB-CU) from a serving distributed unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between the first base reference configuration and a type and / or characteristics of the first cell, where the serving gNB-DU supports a first cell having a first LTM cell configuration corresponding to the first base reference configuration, the first cell being a serving cell for a user equipment (UE); and receiving, by the gNB-CU during candidate cell configuration preparation, the first base reference configuration and an indicator indicating an association between the first base reference configuration and a type and / or characteristics of the first cell. The method includes sending a base reference configuration or an instruction to provide a new reference configuration to a target distributed unit (target gNB-DU), where the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover; determining, by the target gNB-DU, whether the first base reference configuration is usable together with the delta configuration to obtain a complete second cell configuration for the second cell; and, based on determining that the first base reference configuration is not usable to obtain the second cell configuration, sending, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration.

[0026] According to one embodiment, a non-transitory computer-readable storage medium having stored thereon instructions executable by at least one processor to cause at least one processor to execute a method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) in a telecommunications network, the method comprising: receiving, by a central unit (gNB-CU) from a serving distribution unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between the first base reference configuration and a type and / or characteristics of the first cell, the serving gNB-DU supporting a first cell having a first LTM cell configuration corresponding to the first base reference configuration, the first cell being a serving cell for a user equipment (UE); and, during candidate cell configuration preparation, sending, by the gNB-CU, the first base reference configuration or a new LTM cell configuration to a target distribution unit (target gNB-DU). The method includes sending an instruction to provide a new reference configuration, wherein the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for the LTM handover; determining, by the target gNB-DU, whether the first base reference configuration is usable together with the delta configuration to obtain a complete second cell configuration for the second cell; and sending, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration based on determining that the first base reference configuration is not usable to obtain the second cell configuration.

[0027] Additional aspects will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of presented embodiments of the present disclosure.

[0028] Features, aspects, and advantages of certain exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings, in which like reference numerals refer to like elements. [Brief explanation of the drawings]

[0029] [Figure 1A]FIG. 1 illustrates an O-RAN architecture according to the prior art.

[0030] [Figure 1B] Figure 1B is a diagram showing a distributed architecture for separating gNB-CU-CP, gNB-CU-UP, and gNB-DU according to the related art.

[0031] [Figure 2] FIG. 1 is a diagram showing an operational flowchart of a method for Layer 1 / Layer 2 triggered mobility (LTM) according to the related art.

[0032] [Figure 3A] FIG. 10 illustrates a delta configuration on top of a base reference configuration according to one embodiment.

[0033] [Figure 3B] FIG. 10 illustrates a delta configuration on top of a base reference configuration according to another embodiment.

[0034] [Figure 4] 1 is a flowchart of a method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM), according to one embodiment.

[0035] [Figure 5] 1 is a flowchart of a method for signaling a first base reference configuration between a serving gNB-DU, a gNB-CU, and a candidate gNB-DU via an F1 interface according to one embodiment.

[0036] [Figure 6] 1 is a flowchart of a method for signaling a second base reference configuration between a candidate gNB-DU, a gNB-CU, a serving gNB-DU, and a UE according to one embodiment.

[0037] [Figure 7]1 is a flowchart of a method for preparing a candidate cell configuration based on a base reference configuration index and delta configuration data of a selected candidate cell, according to one embodiment.

[0038] [Figure 8] 10 is a flowchart of a method for storing a base reference configuration as one base reference configuration type for multiple base reference configuration types, according to another embodiment.

[0039] [Figure 9] 10 is a flowchart of a method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) according to another embodiment.

[0040] [Figure 10] FIG. 1 is a diagram of an example environment in which the systems and / or methods described herein may be implemented.

[0041] [Figure 11] FIG. 2 is a diagram of exemplary components of a device according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0042] In the following detailed description of the exemplary embodiments, reference will be made to the accompanying drawings, in which the same reference numbers in different drawings may identify the same or similar elements.

[0043] The foregoing disclosure provides illustrations and descriptions, but is not intended to be exhaustive or to limit implementations to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of implementations. Furthermore, one or more features or components of one embodiment may be incorporated into or combined with another embodiment (or one or more features of another embodiment). Additionally, in the flowcharts and descriptions of operations provided below, it should be understood that one or more operations may be omitted, one or more operations may be added, one or more operations may occur (at least partially) concurrently, and the order of one or more operations may be rearranged.

[0044] It will be apparent that the systems and / or methods described herein may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and / or methods is not limiting of the implementation. Thus, the operation and behavior of the systems and / or methods are described herein without reference to specific software code. It will be understood that software and hardware can be designed to implement the systems and / or methods based on the description herein.

[0045] Although particular combinations of features are recited in the claims and / or disclosed herein, these combinations are not intended to limit the disclosure of possible implementations. Indeed, many of these features can be combined in ways not specifically recited in the claims and / or disclosed herein. Although each dependent claim listed below may depend directly on only one claim, the disclosure of possible implementations includes each dependent claim in combination with every other claim in the claim set.

[0046] No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles "a" and "an" are intended to include one or more items and may be used interchangeably with "one or more." Where only one item is intended, the term "one" or similar language is used. Also, as used herein, terms such as "has," "have," "having," "include," and "including" are intended to be open-ended terms. Furthermore, the phrase "based on" is intended to mean "based at least in part on," unless specifically stated otherwise. Furthermore, phrases such as "at least one of [A] and [B]" or "at least one of [A] or [B]" should be understood to include A only, B only, or both A and B.

[0047] 2 shows an operational flowchart of a method for Layer 1 / Layer 2 triggered mobility (LTM) according to the related art. Referring to FIG. 2, a serving cell change is triggered by Layer 3 (L3) measurements and is performed by RRC signaling (i.e., reconfiguration using synchronization information elements) for the serving cell change by a candidate cell (i.e., a target cell).

[0048] In this specification, target cell and candidate cell may be used interchangeably, and a target cell or selected candidate cell is a candidate cell selected for an LTM handover (ie, an LTM cell switch).

[0049] In operation 1, the UE sends a measurement report message to a gNodeB (gNB). In operation 2, based on the measurement report message, the gNB can decide to use LTM and start preparing an LTM candidate (i.e., preparing a candidate cell).

[0050] In operation 3, the gNB sends an RRC reconfiguration message to the UE including the configuration of at least one LTM candidate cell (i.e., target cell).

[0051] In operation 4, the UE stores the configuration of at least one LTM candidate cell (i.e., target cell) and sends an RRC reconfiguration complete message to the gNB.

[0052] In operation 5, the UE may perform downlink (DL) synchronization and timing advance (TA) acquisition with at least one LTM candidate cell (ie, target cell) before receiving the LTM cell switch command.

[0053] In operation 6, the UE performs Layer 1 (L1) measurements on at least one configured (i.e., selected) LTM candidate cell (i.e., target cell) from one or more LTM candidate target cells and sends a lower layer measurement report to the gNB.

[0054] In operation 7, the gNB decides to perform an LTM cell switch to the target cell based on predefined internal radio resource management (RRM) criteria.

[0055] In operation 8, the gNB sends a Medium Access Control (MAC) Control Element (MAC-CE) to the UE, triggering an LTM cell switch.

[0056] In operation 9, when the UE receives a Medium Access Control (MAC) control element containing an LTM cell switch command, the UE switches to the configuration of the candidate cell (ie, the target cell).

[0057] In operation 10, after switching to the configuration of the candidate cell (ie, the target cell), the UE can perform a random access procedure towards the target cell.

[0058] In operation 11, the UE indicates successful completion of the LTM cell switch to the target cell, for example, by sending an RRC Reconfiguration Acknowledge message to the gNB.

[0059] 3A illustrates a delta configuration over a base reference configuration according to one embodiment. Referring to FIG. 3A, a UE starts with cell A and is configured with LTM candidates B and C, where cells A, B, and C share the same base reference configuration.

[0060] The base reference configuration may refer, for example, to the configuration of a radio cell, i.e., the basic configuration of a radio cell type in the RAN. The cell configuration may be separated into common aspects (i.e., common information for all cells of the same gNB-DU or cells of neighboring gNB-DUs that have similar characteristics and cell-specific aspects, such as, for example, information specific to a given cell). The common aspects may be grouped together to form a reference configuration that can be used by all applicable cells.

[0061] For this purpose, for example, a base reference configuration may refer to a basic configuration of one of the major types of radio cells, such as a macrocell, a microcell, a picocell, a femtocell, etc.

[0062] For example, a macrocell's base reference configuration provides wide-area coverage, typically spanning several kilometers and covering outdoor areas such as urban, suburban, and rural areas where many users can be accommodated. It may be demonstrated that a macrocell's base reference configuration differs from that of a microcell, which provides coverage over a smaller area, typically ranging from a few hundred meters to a kilometer. Thus, a microcell's base reference configuration differs from that of a picocell, which ranges from tens to a few hundred meters, and a picocell's base reference configuration differs from that of a femtocell, which is designed to cover a small indoor space such as a home or office.

[0063] Furthermore, delta configurations such as Delta-A, Delta-B, and Delta-C refer to individual configurations of radio cells A, B, and C, respectively. Delta configurations extend beyond the base reference configuration to individualize cell configurations based on strategic topological placement to optimize user experience across different coverage areas and improve overall network performance.

[0064] In an LTM cell switch according to the related art, candidate cell configurations in the LTM cell switch are provided in the form of delta configurations (e.g., Delta-A, Delta-B, and Delta-C) on top of a base reference configuration (e.g., that of cells A, B, and C).

[0065] Furthermore, in an LTM cell switch according to one of the aspects, in addition to the base reference configuration (e.g., the current RRC configuration of cell A, B, or C), the UE maintains a separate reference configuration index (R) (i.e., a base reference configuration index that includes multiple base reference configuration types) as indicated by the network. This index can later be used by both the UE and the network to indicate which reference configuration is being referenced.

[0066] Upon an LTM cell switch (i.e., a cell switch command from the gNB), a target configuration (i.e., candidate cell configuration) based on the base split reference configuration (R) and the delta configuration is applied, thereby enabling the UE to prepare the complete configuration of the desired (selected) target cell (i.e., candidate cell) and subsequent LTM modifications, respectively.

[0067] As a result, the complete configuration of a candidate cell can be prepared by applying the delta configuration of that cell on top of the base configuration.

[0068] 3B illustrates a delta configuration on a base reference configuration according to another embodiment. Referring to FIG. 3B, LTM target cells (i.e., candidate cells for LTM cell switching) A and B have a first base reference configuration (e.g., Base Ref Conf1).

[0069] For example, the first base reference configuration may be a base reference configuration of a macrocell in the sub-6 GHz spectrum.

[0070] Meanwhile, LTM target cells (i.e., candidate cells for LTM cell switching) C and D have a second base reference configuration. For example, the first base reference configuration may be a femtocell base reference configuration in the mmWave band. Based on the different first and second base reference configurations, cells A, B, C, and D have individual delta configurations Delta-A, Delta-B, Delta-C, and Delta-D, respectively.

[0071] In the above scenarios, or in general, if the candidate cell configuration differs substantially from the source cell configuration, it may not be useful to provide the LTM candidate cell configuration as a delta configuration on top of the base reference configuration provided by the serving gNB-DU, as the delta is very likely to be huge. In such cases, the candidate cell configuration may need to be provided as a full configuration.

[0072] With respect to the operation in Figure 2 and the delta configuration over the base reference configuration according to Figures 3A and 3B, it may be impossible for the UE to determine which base reference configuration to use when determining the complete configuration of the target cell. For example, if LTM target cells A and B are prepared using Base Ref Conf1 and LTM target cells C and D are prepared using Base Ref Conf2, the UE will not be able to determine which base reference configuration to use to prepare the target cell configuration.

[0073] FIG. 4 illustrates a flowchart of a method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM), according to one embodiment.

[0074] Referring to FIG. 4, in step 401, a central unit (gNB-CU) receives a first base reference configuration and an indicator indicating an association between the type and / or characteristics of the first cell and the first base reference configuration from a serving distribution unit (i.e., a serving gNB-DU), where the serving gNB-DU supports a first LTM cell having a first cell configuration corresponding to the first base reference configuration, and the first cell is a serving cell for a user equipment (UE).

[0075] In step 402, during candidate cell configuration preparation, the gNB-CU sends a first base reference configuration or an instruction to provide a new reference configuration to the target distributed unit (i.e., the target gNB-DU), which supports a second cell to be prepared as an LTM candidate cell for LTM handover.

[0076] In step 403, the target gNB-DU determines whether the first base reference configuration can be used together with the delta configuration to obtain a complete second cell configuration for the second cell.

[0077] In step 404, based on determining that the first base reference configuration cannot be used to obtain the second cell configuration, the target gNB-DU sends a second base reference configuration corresponding to the second cell configuration to the gNB-CU.

[0078] In another embodiment, based on determining in step 404 that the first base reference configuration is not usable to obtain the second cell configuration, the target gNB-DU sends an indicator to the gNB-CU indicating an association between the type and / or characteristics of the target gNB-DU's LTM candidate cell and the second base reference configuration.

[0079] Furthermore, cells A and B and cells C and D may be hosted on different types of gNB-DUs, with cells A and B hosted on gNB-DU FR1 and cells C and D hosted on gNB-DU FR2. In this case, multiple base reference configurations may also be used to prepare LTM candidate cells.

[0080] Based on the method shown in Figure 4, the gNB-CU maintains multiple base reference configurations depending on the type and characteristics (i.e., indexed multiple base reference configuration types) of the candidate cell (i.e., target cell) from which the candidate cell (i.e., target cell) comes and / or the gNB-DU that hosts it.

[0081] As a result, based on the base multiple base reference configurations, the gNB-CU knows the type of cell served by the gNB-DU (i.e., the type and / or characteristics of the LTM candidate cell), and the gNB-CU can easily determine which base reference configuration it needs to use when sending an LTM handover preparation request to the target gNB-DU (i.e., the target gNB-DU), thereby effectively avoiding a subsequent long-term serving cell change (LTM SCC) using additional RRC reconfiguration due to the UE's inability to prepare a complete confirmation of the candidate cell.

[0082] Thus, unlike the related art, the method of FIG. 4 allows for the use of multiple base reference configurations for different LTM candidate cells, which allows for solving the dilemma described above and improving New Radio (NR) mobility by optimizing LTM cell switching according to the state of the art as shown in FIGS. 2, 3A, and 3B.

[0083] Therefore, the embodiment of FIG. 4 has the advantage of overcoming the shortcomings of the delta configuration in LTM cell switching according to the related art, which significantly improves New Radio (NR) inter-cell mobility.

[0084] FIG. 5 shows a flowchart of a method for signaling a first base reference configuration between a serving gNB-DU, a gNB-CU, and a candidate gNB-DU via an F1 interface according to one embodiment.

[0085] Referring to Figure 5, in step 501, based on a decision to prepare an inter-gNB-DU LTM candidate cell, the gNB-CU sends a user equipment (UE) context setup or modification request to the serving gNB-DU via the F1 interface.

[0086] In step 502, based on the request, the gNB-CU receives a UE context modification response from the serving gNB-DU via the F1 interface, where the UE context modification response includes a first base reference configuration.

[0087] In step 503, based on the UE context setup or modification response, the gNB-CU sends a UE context setup request to the target gNB-DU via the F1 interface, where the UE context setup request includes the first base reference configuration.

[0088] According to Figure 5, steps 501 to 503 are mandatory parts of the initial sequence sent in either case when setting up the serving gNB-DU or when the UE's serving gNB-DU is changed. However, in the case of preparation of a subsequent candidate cell for the serving gNB-DU, steps 501 to 503 may not be performed, e.g., where the UE's serving DU has not changed. As a result, the gNB-CU always knows the base reference configuration of the serving cell for the UE within the serving gNB-DU.

[0089] The method according to Figure 5 has the advantage that the gNB-CU is aware of the type of cell served by the gNB-DU (i.e., the type and / or characteristics of the LTM candidate cell) at initialization or when the UE's serving DU is changed. Thus, the gNB-CU can easily determine at any time which base reference configuration it needs to use when sending an LTM handover preparation request to the target gNB-DU (i.e., target gNB-DU), thereby effectively avoiding subsequent long-term serving cell changes (LTM SCCs) with additional RRC reconfigurations due to the UE's inability to prepare a complete confirmation of the candidate cell.

[0090] FIG. 6 shows a flowchart of a method for signaling a second base reference configuration between a candidate gNB-DU, a gNB-CU, a serving gNB-DU, and a UE according to one embodiment.

[0091] Referring to Figure 6, in step 601, the target gNB-DU, UE, sends a context setup response to the gNB-CU via the F1 interface, and the UE context setup response includes a second base reference configuration.

[0092] In step 602, the gNB-CU assigns a mapping between base reference configurations and types and / or characteristics of LTM candidate cells, the mapping including a mapping between a first base reference configuration and a first cell and a mapping between a second base reference configuration and a second cell.

[0093] In step 603, the gNB-CU sends a radio resource control (RRC) reconfiguration message indicating the mapping to the UE via the serving gNB-DU.

[0094] According to FIG. 6, based on the mapping between the base reference configuration and the type and / or characteristics of the LTM candidate cell, the method has the advantage that the gNB-CU can easily determine which base reference configuration it needs to use when sending an LTM handover preparation request to the target gNB-DU (i.e., target gNB-DU), thereby effectively avoiding a subsequent long-term serving cell change (LTM SCC) using additional RRC reconfiguration due to the UE being unable to prepare a complete confirmation of the candidate cell.

[0095] FIG. 7 illustrates a flowchart of a method for preparing a candidate cell configuration based on a base reference configuration index and delta configuration data of a selected candidate cell for one embodiment.

[0096] Referring to Figure 7, in step 701, the serving gNB-DU receives an intra-frequency or inter-frequency Layer 1 (L1) measurement report from the UE.

[0097] In step 702, based on the intra-frequency or inter-frequency L1 measurement report, the serving gNB-DU decides to perform a serving cell change.

[0098] In step 703, the serving gNB-DU sends a medium access control (MAC) control element (CE) to the UE including a serving cell change command indicating a change to one of the LTM candidate cells (i.e., one oTM candidate cell out of multiple LTM candidate cells).

[0099] In step 704, the UE obtains a complete LTM candidate cell configuration based on the base reference configuration and a delta configuration of one of the LTM candidate cells, where the base reference configuration is determined from a mapping included in the RRC reconfiguration message.

[0100] The method of Figure 7 has the advantage that the UE obtains a complete LTM candidate cell configuration based on the base reference configuration and delta configuration of one of the LTM candidate cells, and the cell configuration that needs to be used when sending an LTM handover preparation request to the target gNB-DU (i.e., target gNB-DU) is dynamically managed by the gNB-CU, thereby effectively avoiding a subsequent long-term serving cell change (LTM SCC) with additional RRC reconfiguration due to the UE being unable to prepare a complete confirmation of the candidate cell.

[0101] 8 shows a flowchart of a method for storing a base reference configuration as one base reference configuration type for multiple base reference configuration types according to another embodiment. Referring to FIG. 8, in step 801, the gNB-CU determines an association between each base reference configuration and the corresponding type of target cell and / or target gNB-DU.

[0102] In step 802, based on the association, the gNB-CU determines an appropriate base reference configuration to send to the candidate / target gNB-DU according to the type and / or characteristics of the candidate / target gNB-DU to prepare an inter-gNB-DU LTM candidate cell hosted by the candidate / target gNB-DU.

[0103] The method according to Figure 8 has the advantage that the gNB-CU determines the association between each base reference configuration and the corresponding type of target cell and / or target gNB-DU. As a result, the gNB-CU can easily determine which base reference configuration it needs to use when sending an LTM handover preparation request to the target gNB-DU (i.e., the target gNB-DU), thereby effectively avoiding a subsequent long-term serving cell change (LTM SCC) with additional RRC reconfiguration due to the UE's inability to prepare the complete cell configuration of the candidate cell.

[0104] 9 illustrates an operational flowchart of a method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) according to one embodiment. Referring to FIG. 9, in Operation 1, a UE sends a Layer 3 (L3) RRC measurement report message to a gNodeB (gNB).

[0105] In operation 2, based on the Layer 3 (L3) RRC measurement report message, the gNB-CU can decide to use LTM for the UE and starts preparing an inter-gNB-DU LTM candidate (i.e., preparing an inter-gNB-DU LTM candidate cell).

[0106] In operation 3, the gNB-CU sends a user entity (UE) context modification request to the serving gNB-DU via the F1 interface.

[0107] In operation 4, based on the request, the gNB-CU receives a UE context modification response from the serving gNB-DU via the F1 interface, where the UE context modification response includes the first base reference configuration.

[0108] In operation 5, based on the UE context modification response, the gNB-CU sends a UE context setup request to the candidate gNB-DU via the F1 interface, where the UE context setup request includes an instruction to prepare the first base reference configuration and / or a new second reference configuration. For example, the gNB-CU sends the first base reference configuration to the candidate gNB-DU, and the candidate gNB-DU may host at least one candidate cell having the second base reference configuration.

[0109] In operation 6, the candidate gNB-DU compares the second base reference configuration with the first base reference configuration. Further, the candidate gNB-DU determines that the first base reference configuration data and the second base reference configuration data are different, and based on the determination, the candidate gNB-DU prepares a candidate cell configuration including the second base reference configuration data and the delta configuration data.

[0110] In operation 7, the candidate gNB-DU sends a UE context setup response to the gNB-CU via the F1 interface, where the UE context setup response includes the candidate cell configuration (i.e., the candidate cell configuration including the second base reference configuration data and the delta configuration data).

[0111] In Operation 8, for each cell candidate having a second base reference configuration different from the first base reference configuration based on the candidate cell configuration, the gNB-CU maps the second base reference configuration to a base reference configuration type from the plurality of base reference configuration types. Further, based on the mapping to base reference configuration types maintained in the gNB-CU, the gNB-CU assigns a base reference configuration index to the base reference configuration type equal to the second base reference configuration. According to one embodiment, in Operation 8, for each cell candidate having a second base reference configuration different from the first base reference configuration based on the candidate cell configuration, the gNB-CU may determine that the second base reference configuration does not match any base reference configuration type from the plurality of base reference configuration types. In this case, the gNB-CU stores the second base reference configuration as a base reference configuration type for the plurality of base reference configuration types to maintain the second base reference configuration within the gNB-CU.

[0112] In operation 9, the gNB-CU sends a radio resource control (RRC) reconfiguration message to the serving gNB-DU via the F1 interface, where the RRC reconfiguration message includes a base reference configuration index and delta configuration data of the candidate cell.

[0113] In operation 10, upon receiving the RRC reconfiguration message, the serving gNB-DU sends an RRC reconfiguration message to the UE including a base reference configuration index and delta configuration data of the selected candidate cell.

[0114] In operation 11, the serving gNB-DU receives an inter-frequency Layer 1 (L1) measurement report from the UE.

[0115] In operation 12, based on the inter-frequency Layer 1 (L1) measurement report, the serving gNB-DU determines that the radio conditions of the candidate cell meet the conditions for changing the serving cell to the candidate cell.

[0116] In operation 13, the serving gNB-DU sends a medium access control (MAC) control element (CE) containing a serving cell change command to the UE.

[0117] In operation 14, the serving gNB-DU sends an LTM serving cell change (SCC) notification over the F1 interface.

[0118] In operation 15, the UE prepares a candidate cell configuration based on the base reference configuration index and the delta configuration data of the selected candidate cell.

[0119] According to an embodiment, upon receiving the RRC reconfiguration message, the UE may determine that the base reference configuration index does not match any base reference configuration index from the plurality of base reference configuration indices, in which case the UE stores the base reference configuration index as referring to a second base reference configuration type.

[0120] In operation 16, after switching to the configuration of the candidate cell (i.e., the target cell), the UE may perform a random access procedure towards the target cell hosted by the candidate gNB-DU.

[0121] In operation 17, the UE indicates successful completion of the LTM cell switch to the target cell, for example, by sending an RRC Reconfiguration Acknowledge message to the gNB.

[0122] Referring to Figure 9, Layer 1 (L1) / Layer 2 (L2)-based mobility (i.e., Lower Layer Triggered Mobility (LTM)) enables serving cell change via L1 / L2 signaling while maintaining higher layer configurations and / or minimizing lower layer configuration changes. This helps reduce latency, overhead, and disruption time during handover. LTM supports both intra-Distributed Unit (DU) mobility and intra-Central Unit (CU) inter-DU mobility. During LTM, the user plane continues with the target cell, possibly without resets (e.g., within the DU), to avoid data loss and additional delays in data recovery.

[0123] Further, according to the method of Figure 9, the gNB-CU maps the second base reference configuration to a base reference configuration type from the plurality of base reference configuration types for each cell candidate having a second base reference configuration different from the first base reference configuration. Further, based on the mapping to base reference configuration types maintained in the gNB-CU, the gNB-CU assigns a base reference configuration index to the second base reference configuration (or a base reference configuration type corresponding to the second base reference configuration).

[0124] As a result, based on the multiple base reference configurations, the gNB-CU knows the type of cell served by the gNB-DU, and the gNB-CU can easily determine which base reference configuration it needs to use when sending an LTM handover preparation request to the target gNB-DU (i.e., target gNB-DU), thereby effectively avoiding a subsequent long-term serving cell change (LTM SCC) using additional RRC reconfiguration due to the UE's inability to prepare a complete confirmation of the candidate cell.

[0125] Thus, unlike the related art, the method of FIG. 9 allows for the use of multiple base reference configurations for different LTM candidate cells, which allows for optimizing LTM cell switching according to the state of the art as shown in FIGS. 2, 3A, and 3B, thereby resolving the dilemma described above and improving New Radio (NR) mobility.

[0126] According to the embodiments of Figures 4 to 9, the type and / or characteristics of the LTM candidate cell may include at least one of cell frequency, gNB-DU capability, supported feature set, and cell size.

[0127] 10 is a diagram of an example environment 1000 in which the systems and / or methods described herein may be implemented. As shown in FIG. 10, environment 1000 may include a user device 1010, a platform 1020, and a network 1030. The devices in environment 1000 may be interconnected via wired connections, wireless connections, or a combination of wired and wireless connections. In embodiments, any of the functions and operations described with reference to FIGS. 1A-9 above may be performed by any combination of elements shown in FIG. 10.

[0128] The user device 1010 includes one or more devices capable of receiving, generating, storing, processing, and / or providing information related to the platform 1020. For example, the user device 1010 may include a computing device (e.g., a desktop computer, a laptop computer, a tablet computer, a handheld computer, a smart speaker, a server, etc.), a mobile phone (e.g., a smartphone, a wireless phone, etc.), a wearable device (e.g., smart glasses or a smart watch), or similar device. In some implementations, the user device 1010 may receive information from and / or transmit information to the platform 1020.

[0129] The platform 1020 includes one or more devices capable of receiving, generating, storing, processing, and / or providing information. In some implementations, the platform 1020 may include a cloud server or a group of cloud servers. In some implementations, the platform 1020 may be designed to be modular, such that particular software components can be swapped in or out according to particular needs. Thus, the platform 1020 may be easily and / or quickly reconfigured for different uses.

[0130] In some implementations, as shown, platform 1020 may be hosted in a cloud computing environment 1022. In particular, although the implementations described herein describe platform 1020 as being hosted within cloud computing environment 1022, in some implementations platform 1020 may not be cloud-based (i.e., may be implemented outside of a cloud computing environment) or may be partially cloud-based.

[0131] Cloud computing environment 1022 includes an environment that hosts platform 1020. Cloud computing environment 1022 can provide services such as computation, software, data access, storage, etc. that do not require end-user (e.g., user device 1010) knowledge of the physical location and configuration of the systems and / or devices that host platform 1020. As shown, cloud computing environment 1022 can include a group of computing resources 1024 (collectively referred to as “computing resources 1024” and individually referred to as “computing resource 1024”).

[0132] The computing resources 1024 include one or more personal computers, clusters of computing devices, workstation computers, server devices, or other types of computing and / or communication devices. In some implementations, the computing resources 1024 may host the platform 1020. Cloud resources may include compute instances running within the computing resources 1024, storage devices provided within the computing resources 1024, data transfer devices provided by the computing resources 1024, etc. In some implementations, the computing resources 1024 may communicate with other computing resources 1024 via wired connections, wireless connections, or a combination of wired and wireless connections.

[0133] As further shown in FIG. 10, computing resources 1024 include a group of cloud resources such as one or more applications (“APP”) 1024-1, one or more virtual machines (“VM”) 1024-2, virtualized storage (“VS”) 1024-3, and one or more hypervisors (“HYP”) 1024-4.

[0134] Applications 1024-1 include one or more software applications that may be provided to or accessed by user device 1010. Applications 1024-1 may obviate the need to install and run software applications on user device 1010. For example, applications 1024-1 may include software associated with platform 1020 and / or any other software that may be provided via cloud computing environment 1022. In some implementations, one application 1024-1 may send information to or receive information from one or more other applications 1024-1 via virtual machine 1024-2.

[0135] Virtual machine 1024-2 includes a software-implemented machine (e.g., a computer) that executes programs like a physical machine. Virtual machine 1024-2 can be either a system virtual machine or a process virtual machine, depending on the application and the degree to which virtual machine 1024-2 represents an actual machine. A system virtual machine can provide a complete system platform that supports the execution of a complete operating system (“OS”). A process virtual machine can execute a single program and support a single process. In some implementations, virtual machine 1024-2 may run on behalf of a user (e.g., user device 1010) and manage the infrastructure of cloud computing environment 1022, such as data management, synchronization, or long-term data transfer.

[0136] Virtualized storage 1024-3 includes one or more storage systems and / or one or more devices that use virtualization technology within the storage systems or devices of computing resources 1024. In one implementation, in the context of a storage system, types of virtualization may include block virtualization and file virtualization. Block virtualization may refer to the abstraction (or separation) of logical storage from physical storage so that the storage system can be accessed regardless of the physical storage or heterogeneous structure. The separation may provide storage system administrators with flexibility in how they manage storage for end users. File virtualization may eliminate the dependency between data accessed at the file level and where the file is physically stored. This may enable performance optimization of storage usage, server consolidation, and / or non-disruptive file migration.

[0137] The hypervisor 1024-4 may provide hardware virtualization technology that allows multiple operating systems (e.g., "guest operating systems") to run simultaneously on a host computer, such as computing resource 1024. The hypervisor 1024-4 may present a virtual operating platform to the guest operating systems and may manage the execution of the guest operating systems. Multiple instances of various operating systems may share virtualized hardware resources.

[0138] The network 1030 may include one or more wired and / or wireless networks. For example, the network 1030 may include a cellular network (e.g., a fifth-generation (5G) network, a long-term evolution (LTE) network, a third-generation (3G) network, a code division multiple access (CDMA) network, etc.), a public land mobile network (PLMN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), a telephone network (e.g., a public switched telephone network (PSTN)), a private network, an ad hoc network, an intranet, the Internet, an optical fiber-based network, etc., and / or a combination of these or other types of networks.

[0139] The number and arrangement of devices and networks shown in Figure 10 are provided as an example. In practice, there may be additional, fewer, different, or differently arranged devices and / or networks than those shown in Figure 10. Furthermore, two or more devices shown in Figure 10 may be implemented within a single device, or a single device shown in Figure 10 may be implemented as multiple distributed devices. Additionally, or instead, a set of devices (e.g., one or more devices) of environment 1000 may perform one or more functions that are described as being performed by another set of devices of environment 1000.

[0140] 11 is a diagram of example components of a device 1100. The device 1100 may correspond to a user device 1110 and / or a platform 1120. As shown in FIG. 11 , the device 1100 may include a bus 1110, a processor 1120, a memory 1130, a storage component 1140, an input component 1150, an output component 1160, and a communication interface 1170.

[0141] The bus 1110 includes components that enable communication between the components of the device 1100. The processor 1120 may be implemented in hardware, firmware, or a combination of hardware and software. The processor 1120 may be a central processing unit (CPU), a graphics processing unit (GPU), an accelerated processing unit (APU), a microprocessor, a microcontroller, a digital signal processor (DSP), a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or another type of processing component. In some implementations, the processor 1120 includes one or more processors that can be programmed to perform functions. The memory 1130 includes random access memory (RAM), read-only memory (ROM), and / or another type of dynamic or static storage device (e.g., flash memory, magnetic memory, and / or optical memory) that stores information and / or instructions used by the processor 1120.

[0142] Storage component 1140 stores information and / or software related to the operation and use of device 1100. For example, storage component 1140 may include a hard disk (e.g., a magnetic disk, optical disk, magneto-optical disk, and / or solid-state disk), a compact disk (CD), a digital versatile disk (DVD), a floppy disk, a cartridge, magnetic tape, and / or another type of non-transitory computer-readable medium, along with a corresponding drive. Input component 1150 includes components that enable device 1100 to receive information, such as via user input (e.g., a touchscreen display, a keyboard, a keypad, a mouse, buttons, switches, and / or a microphone). Additionally or alternatively, input component 1150 may include sensors for sensing information (e.g., a global positioning system (GPS) component, an accelerometer, a gyroscope, and / or an actuator). Output component 1160 includes components that provide output information from device 1100 (e.g., a display, a speaker, and / or one or more light-emitting diodes (LEDs)).

[0143] Communication interface 1170 includes transceiver-like components (e.g., a transceiver and / or a separate receiver and transmitter) that enable device 1100 to communicate with other devices via wired connections, wireless connections, or a combination of wired and wireless connections, etc. Communication interface 1170 may enable device 1100 to receive information from and / or provide information to another device. For example, communication interface 1170 may include an Ethernet interface, an optical interface, a coaxial interface, an infrared interface, a radio frequency (RF) interface, a universal serial bus (USB) interface, a Wi-Fi interface, a cellular network interface, etc.

[0144] Device 1100 may perform one or more processes described herein. Device 1100 may perform these processes in response to processor 1120 executing software instructions stored by a non-transitory computer-readable medium, such as memory 1130 and / or storage component 1140. A computer-readable medium is defined herein as a non-transitory memory device. A memory device includes memory space within a single physical storage device or memory space spread across multiple physical storage devices.

[0145] The software instructions may be loaded into memory 1130 and / or storage component 1140 from another computer-readable medium or from another device via communication interface 1170. When executed, the software instructions stored in memory 1130 and / or storage component 1140 may cause processor 1120 to perform one or more processes described herein.

[0146] Additionally, or alternatively, hardwired circuitry may be used in place of or in combination with software instructions to implement one or more processes described herein. Thus, implementations described herein are not limited to any specific combination of hardware circuitry and software.

[0147] The number and arrangement of components shown in Figure 11 are provided as an example. In practice, device 1100 may include additional, fewer, different, or differently arranged components than those shown in Figure 11. Additionally or alternatively, a set of components (e.g., one or more components) of device 1100 may perform one or more functions that are described as being performed by another set of components of device 1100.

[0148] In an embodiment, any one of the operations or processes of FIGS. 1A-9 may be implemented by or using any one of the elements shown in FIGS.

[0149] It is understood that other embodiments may be implemented in a variety of different architectures, including, but not limited to, bare metal architectures, or any cloud-based or deployment architecture such as Kubernetes, Docker, OpenStack, etc.

[0150] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit implementations to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the implementations.

[0151] An embodiment may relate to a system, method, and / or computer-readable medium at any possible level of technical detail integration. Furthermore, one or more of the above components described above may be implemented as instructions stored on a computer-readable medium and executable by at least one processor (and / or may include at least one processor). The computer-readable medium may include a computer-readable non-transitory storage medium (or media) having computer-readable program instructions for causing a processor to perform operations.

[0152] A computer-readable storage medium may be a tangible device capable of retaining and storing instructions for use by an instruction execution device. A computer-readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of computer-readable storage media includes portable computer diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disks (DVD), memory sticks, floppy disks, mechanically encoded devices such as punch cards or ridge-in-groove structures having instructions recorded thereon, and any suitable combination of the foregoing. Computer-readable storage medium, as used herein, should not be construed as being a transitory signal per se, such as an electric wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse passing through a fiber optic cable), or an electrical signal transmitted through a wire.

[0153] The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to each computing / processing device or to an external computer or storage device over a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include copper transmission cables, fiber optic transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface within each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage on a computer-readable storage medium within the respective computing / processing device.

[0154] The computer-readable program code / instructions for carrying out operations may be either source code or object code written in any combination of one or more programming languages, including assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, integrated circuit configuration data, or object-oriented programming languages ​​such as Smalltalk, C++, and procedural programming languages ​​such as the "C" programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA) may execute computer-readable program instructions to personalize the electronic circuitry by utilizing state information in the computer-readable program instructions to perform aspects or operations.

[0155] These computer-readable program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, executed by the processor of the computer or other programmable data processing apparatus, form means for implementing the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams. These computer-readable program instructions may also be stored on a computer-readable storage medium that can instruct a computer, programmable data processing apparatus, and / or other device to function in a particular way, such that the computer-readable storage medium on which the instructions are stored comprises an article of manufacture containing instructions that implement aspects of the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams.

[0156] The computer-readable program instructions may also be loaded into a computer, other programmable data processing apparatus, or other device to cause the computer, other programmable apparatus, or other device to perform a series of operational steps to create a computer-implemented process, such that the instructions, executing on the computer, other programmable apparatus, or other device, perform the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams.

[0157] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer-readable media according to various embodiments. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, or portion of instructions, including one or more executable instructions for implementing a particular logical function. The methods, computer systems, and computer-readable media may include additional, fewer, different, or differently arranged blocks than those shown in the figures. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may actually be executed concurrently or substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality involved. It should also be noted that each block in the block diagrams and / or flowchart diagrams, and combinations of blocks in the block diagrams and / or flowchart diagrams, may be implemented by a dedicated hardware-based system that performs the specified functions or operations or executes a combination of dedicated hardware and computer instructions.

[0158] It will be apparent that the systems and / or methods described herein may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and / or methods is not limiting of the implementation. Thus, the operation and behavior of the systems and / or methods are described herein without reference to specific software code. It will be understood that software and hardware can be designed to implement the systems and / or methods based on the description herein.

[0159] Various further respective aspects and features of embodiments of the present disclosure can be defined by the following clauses. Item [1] A system for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) in a telecommunications network, the system including at least one memory for storing instructions, and executing the instructions to receive, by a central unit (gNB-CU) from a serving distributed unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between the type and / or characteristics of the first cell and the first base reference, wherein the serving gNB-DU supports a first cell having a first LTM cell configuration corresponding to the first base reference configuration, and the first cell is a serving cell for a user equipment (UE); and receiving, by the gNB-CU during candidate cell configuration preparation, The system includes at least one processor configured to: send a first base reference configuration or an instruction to provide a new reference configuration to a target distributed unit (target gNB-DU), where the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover; determine, by the target gNB-DU, whether the first base reference configuration is usable together with a delta configuration to obtain a complete second cell configuration for the second cell; and, based on determining that the first base reference configuration is not usable to obtain the second cell configuration, send, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration. Item [2] The system described in Item [1], wherein at least one processor may be further configured to execute instructions to send, based on determining that the first base reference configuration is not usable for obtaining the second cell configuration, an indicator by the target gNB-DU to the gNB-CU indicating an association between the type and / or characteristics of the target gNB-DU's LTM candidate cell and the second base reference configuration. Item [3] The system described in any one of items [1 to 2], wherein at least one processor may be further configured to execute instructions to send a user equipment (UE) context setup or modification request by the gNB-CU to a serving gNB-DU via an F1 interface based on a decision to prepare an inter-gNB-DU LTM candidate cell, receive a UE context modification response by the gNB-CU from the serving gNB-DU via the F1 interface based on the request, where the UE context modification response may include a first base reference configuration, and send a UE context setup request by the gNB-CU to a target gNB-DU via the F1 interface based on the UE context setup or modification response, where the UE context setup request may include the first base reference configuration. Item [4] The system described in any one of items [1 to 3], wherein at least one processor may be further configured to execute instructions to: send, by the target gNB-DU, a UE context setup response to the gNB-CU via the F1 interface, where the UE context setup response may include a second base reference configuration; assign, by the gNB-CU, a mapping between the base reference configuration and the type and / or characteristics of the LTM candidate cell, where the mapping includes a mapping between the first base reference configuration and the first cell and a mapping between the second base reference configuration and the second cell; and send, by the gNB-CU, a radio resource control (RRC) reconfiguration message to the UE via the serving gNB-DU, indicating the mapping. Item [5] The system described in any one of items [1 to 4] may be further configured to: execute instructions such that at least one processor receives, by a serving gNB-DU, an intra-frequency or inter-frequency Layer 1 (L1) measurement report from the UE; decides, by the serving gNB-DU, to perform a serving cell change based on the intra-frequency or inter-frequency L1 measurement report; and sends, by the serving gNB-DU, a medium access control (MAC) control element (CE) to the UE, the medium access control (MAC) control element (CE) including a serving cell change command indicating a change to one of the LTM candidate cells; wherein a complete LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of one of the LTM candidate cells, and the base reference configuration is determined from a mapping included in the RRC reconfiguration message. Item [6] The system described in any one of items [1 to 5], wherein at least one processor may be further configured to execute instructions to determine, by the gNB-CU, an association between each base reference configuration and the type of corresponding target cell and / or target gNB-DU, and to determine, by the gNB-CU, based on the association, an appropriate base reference configuration to send to the candidate / target gNB-DU according to the type and / or characteristics of the candidate / target gNB-DU to prepare an inter-gNB-DU LTM candidate cell hosted by the candidate / target gNB-DU. Item [7] A system described in any one of items [1 to 6], wherein the type and / or characteristics of the LTM candidate cell may include at least one of cell frequency, gNB-DU capability, supported feature set, and cell size. Item [8] A method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) in a telecommunications network, comprising: receiving, by a central unit (gNB-CU) from a serving distributed unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between the first base reference configuration and a type and / or characteristics of the first cell, wherein the serving gNB-DU supports a first cell having a first LTM cell configuration corresponding to the first base reference configuration, and the first cell is a serving cell for a user equipment (UE); and receiving, by the gNB-CU during candidate cell configuration preparation, the first base reference configuration and an indicator indicating an association between the first base reference configuration and a type and / or characteristics of the first cell. a first base reference configuration or an instruction to provide a new reference configuration to a target distributed unit (target gNB-DU), where the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover; determining, by the target gNB-DU, whether the first base reference configuration is usable together with a delta configuration to obtain a complete second cell configuration for the second cell; and, based on determining that the first base reference configuration is not usable to obtain the second cell configuration, sending, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration. Item [9] The method of Item [8] may further include, based on determining that the first base reference configuration is not usable for obtaining the second cell configuration, sending an indicator by the target gNB-DU to the gNB-CU indicating an association between the type and / or characteristics of the LTM candidate cell of the target gNB-DU and the second base reference configuration. Item

[10] The method of any one of items [8 to 9] may further include: sending a user equipment (UE) context setup or modification request by the gNB-CU to the serving gNB-DU via the F1 interface based on a decision to prepare an inter-gNB-DU LTM candidate cell; receiving a UE context modification response by the gNB-CU from the serving gNB-DU via the F1 interface based on the request, where the UE context modification response may include a first base reference configuration; and sending a UE context setup request by the gNB-CU to the target gNB-DU via the F1 interface based on the UE context setup or modification response, where the UE context setup request may include the first base reference configuration. Item

[11] The method of any one of items [8 to 10] may further include: sending, by the target gNB-DU, a UE context setup response to the gNB-CU via the F1 interface, where the UE context setup response may include a second base reference configuration; assigning, by the gNB-CU, a mapping between the base reference configuration and the type and / or characteristics of the LTM candidate cell, where the mapping includes a mapping between the first base reference configuration and the first cell and a mapping between the second base reference configuration and the second cell; and sending, by the gNB-CU, a radio resource control (RRC) reconfiguration message to the UE via the serving gNB-DU, indicating the mapping. Item

[12] The method may further include receiving, by the serving gNB-DU, an intra-frequency or inter-frequency Layer 1 (L1) measurement report from the UE; determining, by the serving gNB-DU, to perform a serving cell change based on the intra-frequency or inter-frequency L1 measurement report; and sending, by the serving gNB-DU, a medium access control (MAC) control element (CE) to the UE, the medium access control (MAC) control element (CE) including a serving cell change command indicating a change to one of the LTM candidate cells, wherein a complete LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of one of the LTM candidate cells, and the base reference configuration is determined from a mapping included in the RRC reconfiguration message. Item

[13] The method of any one of items [8 to 12] may further include determining, by the gNB-CU, an association between each base reference configuration and the type of corresponding target cell and / or target gNB-DU, and determining, by the gNB-CU, based on the association, an appropriate base reference configuration to send to the candidate / target gNB-DU according to the type and / or characteristics of the candidate / target gNB-DU to prepare an inter-gNB-DU LTM candidate cell hosted by the candidate / target gNB-DU. Item

[14] A method according to any one of items [8 to 13], wherein the type and / or characteristics of the LTM candidate cell may include at least one of cell frequency, gNB-DU capability, supported feature set, and cell size. Item

[15] A non-transitory computer-readable storage medium having stored thereon instructions executable by at least one processor to cause at least one processor to execute a method for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) in a telecommunications network, the method comprising: receiving, by a central unit (gNB-CU) from a serving distributed unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between the first base reference configuration and a type and / or characteristics of the first cell, wherein the serving gNB-DU supports a first cell having a first LTM cell configuration corresponding to the first base reference configuration, and the first cell is a serving cell for a user equipment (UE). and sending, by the gNB-CU during candidate cell configuration preparation, a first base reference configuration or an instruction to provide a new reference configuration to a target distributed unit (target gNB-DU), wherein the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover; determining, by the target gNB-DU, whether the first base reference configuration is usable together with a delta configuration to obtain a complete second cell configuration for the second cell; and sending, by the target gNB-DU to the gNB-CU based on determining that the first base reference configuration is not usable to obtain the second cell configuration. Item

[16] A non-transitory computer-readable recording medium as described in Item

[15] , wherein the method may further include, based on determining that the first base reference configuration is not usable for obtaining the second cell configuration, sending an indicator by the target gNB-DU to the gNB-CU indicating an association between the type and / or characteristics of the LTM candidate cell of the target gNB-DU and the second base reference configuration. Item

[17] A non-transitory computer-readable storage medium described in any one of items [15 to 16], wherein the method may further include: sending a user equipment (UE) context setup or modification request by the gNB-CU to the serving gNB-DU via the F1 interface based on a decision to prepare an inter-gNB-DU LTM candidate cell; receiving a UE context modification response by the gNB-CU from the serving gNB-DU via the F1 interface based on the request, where the UE context modification response may include a first base reference configuration; and sending a UE context setup request by the gNB-CU to the target gNB-DU via the F1 interface based on the UE context setup or modification response, where the UE context setup request may include the first base reference configuration. Item

[18] The method may further include: sending, by the target gNB-DU, a UE context setup response to the gNB-CU via the F1 interface, where the UE context setup response may include a second base reference configuration; assigning, by the gNB-CU, a mapping between the base reference configuration and the type and / or characteristics of the LTM candidate cell, where the mapping includes a mapping between the first base reference configuration and the first cell and a mapping between the second base reference configuration and the second cell; and sending, by the gNB-CU, a radio resource control (RRC) reconfiguration message to the UE via the serving gNB-DU, indicating the mapping. Item

[19] The method may further include receiving, by the serving gNB-DU, an intra-frequency or inter-frequency Layer 1 (L1) measurement report from the UE; determining, by the serving gNB-DU, to perform a serving cell change based on the intra-frequency or inter-frequency L1 measurement report; and sending, by the serving gNB-DU, a medium access control (MAC) control element (CE) to the UE, the medium access control (CE) including a serving cell change command indicating a change to one of the LTM candidate cells, wherein a complete LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of one of the LTM candidate cells, and the base reference configuration is determined from a mapping included in the RRC reconfiguration message. A non-transitory computer-readable storage medium described in any one of items [15 to 18]. Item

[20] A non-transitory computer-readable recording medium described in any one of items [15 to 19], wherein the method may further include determining, by the gNB-CU, an association between each base reference configuration and the type of corresponding target cell and / or target gNB-DU, and determining, by the gNB-CU, based on the association, an appropriate base reference configuration to send to the candidate / target gNB-DU according to the type and / or characteristics of the candidate / target gNB-DU to prepare an inter-gNB-DU LTM candidate cell hosted by the candidate / target gNB-DU.

Claims

1. 1. A system for implementing multiple base reference configurations for Layer 1 / Layer 2 triggered mobility (LTM) in a telecommunications network, comprising: at least one memory for storing instructions; and Execute the instructions, Receiving, by a central unit (gNB-CU) from a serving distribution unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between a type and / or characteristics of a first cell and the first base reference configuration, wherein the serving gNB-DU supports the first cell having a first LTM cell configuration corresponding to the first base reference configuration, and the first cell is a serving cell for a user equipment (UE); Sending, by the gNB-CU during candidate cell configuration preparation, the first base reference configuration or an instruction to provide a new reference configuration to a target distribution unit (target gNB-DU), wherein the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover; Determining whether the first base reference configuration can be used together with the delta configuration to obtain a complete second cell configuration of the second cell by the target gNB-DU; sending, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration based on determining that the first base reference configuration cannot be used to obtain the second cell configuration; at least one processor configured to perform A system comprising:

2. The at least one processor executes the instructions to Based on determining that the first base reference configuration cannot be used to obtain the second cell configuration, an indicator is sent by the target gNB-DU to the gNB-CU indicating an association between the type and / or characteristics of the target gNB-DU's LTM candidate cell and the second base reference configuration. The system of claim 1 further configured to:

3. The at least one processor executes the instructions to Based on a decision to prepare an inter-gNB-DU LTM candidate cell, sending a user equipment (UE) context setup or modification request by the gNB-CU to the serving gNB-DU via an F1 interface; receiving, by the gNB-CU, a UE context modification response from the serving gNB-DU via the F1 interface based on the request, wherein the UE context modification response includes the first base reference configuration; sending, by the gNB-CU, a UE context setup request to the target gNB-DU via the F1 interface based on the UE context setup or modification response, wherein the UE context setup request includes the first base reference configuration; The system of claim 1 , further configured to:

4. The at least one processor executes the instructions to Sending a UE context setup response by the target gNB-DU to the gNB-CU via an F1 interface, wherein the UE context setup response includes the second base reference configuration; Allocating, by the gNB-CU, a mapping between base reference configurations and types and / or characteristics of LTM candidate cells, the mapping including a mapping between the first base reference configuration and the first cell, and a mapping between the second base reference configuration and the second cell; sending, by the gNB-CU, a radio resource control (RRC) reconfiguration message to the UE via the serving gNB-DU, indicating the mapping; The system of claim 1 , further configured to:

5. The at least one processor executes the instructions to receiving, by the serving gNB-DU, an intra-frequency or inter-frequency Layer 1 (L1) measurement report from the UE; Deciding to perform a serving cell change by the serving gNB-DU based on the intra-frequency or inter-frequency L1 measurement report; Sending a medium access control (MAC) control element (CE) to the UE by the serving gNB-DU, the CE including a serving cell change command indicating a change to one of the LTM candidate cells; and further configured to:

5. The system of claim 4, wherein a complete LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of the one of the LTM candidate cells, the base reference configuration being determined from the mapping included in the RRC reconfiguration message.

6. The at least one processor executes the instructions to Determining, by the gNB-CU, an association between each base reference configuration and the corresponding target cell and / or target gNB-DU type; and determining, by the gNB-CU, based on the association, an appropriate base reference configuration to send to the candidate / target gNB-DU according to the type and / or characteristics of the candidate / target gNB-DU to prepare an inter-gNB-DU LTM candidate cell hosted by the candidate / target gNB-DU; The system of claim 5 , further configured to:

7. The system of claim 6, wherein the type and / or characteristics of an LTM candidate cell include at least one of cell frequency, gNB-DU capability, supported feature set, and cell size.

8. 1. A method for implementing multiple base reference configurations for Layer 1 / Layer 2 Triggered Mobility (LTM) in a telecommunications network, comprising: Receiving, by a central unit (gNB-CU) from a serving distribution unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between a type and / or characteristics of a first cell and the first base reference configuration, wherein the serving gNB-DU supports the first cell having a first LTM cell configuration corresponding to the first base reference configuration, and the first cell is a serving cell for a user equipment (UE); Sending, by the gNB-CU during candidate cell configuration preparation, the first base reference configuration or an instruction to provide a new reference configuration to a target distribution unit (target gNB-DU), wherein the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover; Determining whether the first base reference configuration can be used together with the delta configuration to obtain a complete second cell configuration of the second cell by the target gNB-DU; sending, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration based on determining that the first base reference configuration cannot be used to obtain the second cell configuration; A method comprising:

9. The method comprises: sending, by the target gNB-DU to the gNB-CU, an indicator indicating an association between the type and / or characteristics of the target gNB-DU's LTM candidate cell and the second base reference configuration, based on determining that the first base reference configuration is not usable for obtaining the second cell configuration; The method of claim 8 further comprising:

10. The method comprises: Based on a decision to prepare an inter-gNB-DU LTM candidate cell, sending a user equipment (UE) context setup or modification request by the gNB-CU to the serving gNB-DU via an F1 interface; receiving, by the gNB-CU, a UE context modification response from the serving gNB-DU via the F1 interface based on the request, wherein the UE context modification response includes the first base reference configuration; sending, by the gNB-CU, a UE context setup request to the target gNB-DU via the F1 interface based on the UE context setup or modification response, wherein the UE context setup request includes the first base reference configuration; The method of claim 8 further comprising:

11. The method comprises: Sending a UE context setup response by the target gNB-DU to the gNB-CU via the F1 interface, wherein the UE context setup response includes the second base reference configuration; Allocating, by the gNB-CU, a mapping between base reference configurations and types and / or characteristics of LTM candidate cells, the mapping including a mapping between the first base reference configuration and the first cell, and a mapping between the second base reference configuration and the second cell; sending, by the gNB-CU, a radio resource control (RRC) reconfiguration message to the UE via the serving gNB-DU, indicating the mapping; The method of claim 10 further comprising:

12. The method comprises: receiving, by the serving gNB-DU, an intra-frequency or inter-frequency Layer 1 (L1) measurement report from the UE; Deciding to perform a serving cell change by the serving gNB-DU based on the intra-frequency or inter-frequency L1 measurement report; Sending a medium access control (MAC) control element (CE) to the UE by the serving gNB-DU, the CE including a serving cell change command indicating a change to one of the LTM candidate cells; further comprising 12. The method of claim 11, wherein a complete LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of the one of the LTM candidate cells, the base reference configuration being determined from the mapping included in the RRC reconfiguration message.

13. The method comprises: Determining, by the gNB-CU, an association between each base reference configuration and the corresponding target cell and / or target gNB-DU type; and determining, by the gNB-CU, based on the association, an appropriate base reference configuration to send to the candidate / target gNB-DU according to the type and / or characteristics of the candidate / target gNB-DU to prepare an inter-gNB-DU LTM candidate cell hosted by the candidate / target gNB-DU; The method of claim 12 further comprising:

14. The method of claim 13, wherein the type and / or characteristics of an LTM candidate cell include at least one of a cell frequency, a gNB-DU capability, a supported feature set, and a cell size.

15. 1. A non-transitory computer-readable storage medium having stored thereon instructions executable by at least one processor to cause the at least one processor to perform a method for implementing multiple base reference configurations for Layer 1 / Layer 2 Triggered Mobility (LTM) in a telecommunications network, the method comprising: Receiving, by a central unit (gNB-CU) from a serving distribution unit (serving gNB-DU), a first base reference configuration and an indicator indicating an association between a type and / or characteristics of a first cell and the first base reference configuration, wherein the serving gNB-DU supports the first cell having a first LTM cell configuration corresponding to the first base reference configuration, and the first cell is a serving cell for a user equipment (UE); Sending, by the gNB-CU during candidate cell configuration preparation, the first base reference configuration or an instruction to provide a new reference configuration to a target distribution unit (target gNB-DU), wherein the target gNB-DU supports a second cell to be prepared as an LTM candidate cell for LTM handover; Determining whether the first base reference configuration can be used together with the delta configuration to obtain a complete second cell configuration of the second cell by the target gNB-DU; sending, by the target gNB-DU to the gNB-CU, a second base reference configuration corresponding to the second cell configuration based on determining that the first base reference configuration cannot be used to obtain the second cell configuration; A non-transitory computer-readable recording medium comprising:

16. The method comprises: sending, by the target gNB-DU to the gNB-CU, an indicator indicating an association between the type and / or characteristics of the target gNB-DU's LTM candidate cell and the second base reference configuration, based on determining that the first base reference configuration is not usable for obtaining the second cell configuration; 16. The non-transitory computer-readable storage medium of claim 15, further comprising:

17. The method comprises: Based on a decision to prepare an inter-gNB-DU LTM candidate cell, sending a user equipment (UE) context setup or modification request by the gNB-CU to the serving gNB-DU via an F1 interface; receiving, by the gNB-CU, a UE context modification response from the serving gNB-DU via the F1 interface based on the request, wherein the UE context modification response includes the first base reference configuration; sending, by the gNB-CU, a UE context setup request to the target gNB-DU via the F1 interface based on the UE context setup or modification response, wherein the UE context setup request includes the first base reference configuration; 16. The non-transitory computer-readable storage medium of claim 15, further comprising:

18. The method comprises: Sending a UE context setup response by the target gNB-DU to the gNB-CU via the F1 interface, wherein the UE context setup response includes the second base reference configuration; Allocating, by the gNB-CU, a mapping between base reference configurations and types and / or characteristics of LTM candidate cells, the mapping including a mapping between the first base reference configuration and the first cell, and a mapping between the second base reference configuration and the second cell; sending, by the gNB-CU, a radio resource control (RRC) reconfiguration message to the UE via the serving gNB-DU, indicating the mapping; 20. The non-transitory computer-readable storage medium of claim 17, further comprising:

19. The method comprises: receiving, by the serving gNB-DU, an intra-frequency or inter-frequency Layer 1 (L1) measurement report from the UE; Deciding to perform a serving cell change by the serving gNB-DU based on the intra-frequency or inter-frequency L1 measurement report; Sending a medium access control (MAC) control element (CE) to the UE by the serving gNB-DU, the CE including a serving cell change command indicating a change to one of the LTM candidate cells; further comprising 20. The non-transitory computer-readable storage medium of claim 18, wherein a complete LTM candidate cell configuration is obtained by the UE based on a base reference configuration and a delta configuration of the one of the LTM candidate cells, the base reference configuration being determined from the mapping included in the RRC reconfiguration message.

20. The method comprises: Determining, by the gNB-CU, an association between each base reference configuration and the corresponding target cell and / or target gNB-DU type; and determining, by the gNB-CU, based on the association, an appropriate base reference configuration to send to the candidate / target gNB-DU according to the type and / or characteristics of the candidate / target gNB-DU to prepare an inter-gNB-DU LTM candidate cell hosted by the candidate / target gNB-DU; 20. The non-transitory computer-readable storage medium of claim 19, further comprising:

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