Apparatus, method, and computer program for cell handover

Abstract

This disclosure relates to a method comprising: receiving, by a user equipment, a command from a base station providing a source cell for triggering a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells; determining, by the user equipment, that the subset of candidate target cells includes a first candidate target cell; attempting a cell handover from the source cell to the first candidate target cell; determining, by the user equipment, that the cell handover from the source cell to the first candidate target cell is unsuccessful; determining, by the user equipment, that the subset of candidate target cells includes a second candidate target cell; and attempting a cell handover from the source cell to the second candidate target cell in the subset of candidate target cells.

Description

Technical Field

[0001] This disclosure relates to methods, apparatus, and computer programs for managing mobility in communication systems. Background Technology

[0002] A communication system can be viewed as a facility that enables communication sessions between two or more entities, such as communication devices, base stations, and / or other nodes, by providing carriers between various entities involved in the communication path.

[0003] Communication systems and associated entities typically operate according to given guidelines or specifications that outline what the associated entities are allowed to do and how they should be implemented. The communication protocols and / or parameters that should be used for the connection are also usually defined. An example of such guidelines is the so-called 5G guidelines. Summary of the Invention

[0004] According to one aspect, a method is provided, the method comprising: receiving, by a user equipment, a command from a base station providing a source cell for triggering a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells; determining, by the user equipment, that the subset of candidate target cells includes a first candidate target cell; attempting a cell handover from the source cell to the first candidate target cell; determining, by the user equipment, that the cell handover from the source cell to the first candidate target cell is unsuccessful; determining, by the user equipment, that the subset of candidate target cells includes a second candidate target cell; and attempting a cell handover from the source cell to the second candidate target cell in the subset of candidate target cells.

[0005] The terms "cell switch", "cell handover", or "mobility" can be used interchangeably.

[0006] The command received by the user equipment from the base station providing the source cell to trigger a cell handover from the source cell to the candidate target cell may include: the user equipment receiving the command from the source distributed unit of the base station providing the source cell to trigger a cell handover from the source cell to the candidate target cell.

[0007] A subset of candidate target cells may include multiple candidate target cells in priority order; a subset of candidate target cells may include preferred candidate target cells and multiple candidate target cells not in priority order; or a subset of candidate target cells may include preferred candidate target cells and multiple candidate target cells in priority order.

[0008] The first candidate target cell can have the first priority, and the second candidate target cell.

[0009] The first candidate target cell can be a preferred candidate target cell, and the second candidate target cell can be selected from multiple candidate target cells based on measurements of multiple candidate target cells.

[0010] Cell handover attempts by a user equipment from a source cell to a first candidate target cell or a second candidate target cell may include: cell handover attempts from a source cell to a first candidate target cell or a second candidate target cell without a random access channel.

[0011] The method may include: the user equipment determining that the cell handover from the source cell to the second target cell was successful.

[0012] The user equipment's determination of a successful cell handover from the source cell to the second candidate target cell may include: the user equipment determining the completion of the cell handover from the source cell to the second candidate target cell before the timer for the second candidate target cell expires.

[0013] The method may include: the user equipment determining that the cell handover from the source cell to the second candidate target cell was unsuccessful; the user equipment determining that the subset of candidate target cells includes a third candidate target cell; and the user equipment attempting a cell handover from the source cell to the third candidate target cell.

[0014] The method may include: the user equipment determining that the cell handover from the source cell to the second target cell was unsuccessful; the user equipment determining that the subset of candidate target cells does not include a third candidate target cell; and the user equipment attempting to restore the cell handover.

[0015] The user equipment's determination that the cell handover from the source cell to the first candidate target cell or the second candidate target cell was unsuccessful may include: the user equipment determining the expiration of a timer for the second candidate target cell before the cell handover from the source cell to the second candidate target cell is completed.

[0016] The process of a user equipment attempting cell handover recovery may include: the user equipment selecting a cell to recover; the user equipment determining that the cell to recover is in a configured set of candidate target cells; and the user equipment attempting a cell handover from the source cell to the cell to recover.

[0017] Cell handover attempts by user equipment from the source cell to the recovery cell may include attempts at random access channel-based cell handover from the source cell to the recovery cell.

[0018] The process of a user equipment attempting cell handover recovery may include: the user equipment selecting a cell to recover; the user equipment determining that the cell to recover is not in the configured set of candidate target cells; and the user equipment sending a radio resource control reconstruction request to the base station providing the cell to recover.

[0019] Selecting a cell to be restored by the user equipment may include: detecting at least one neighboring cell by the user equipment; and selecting a cell to be restored from at least one neighboring cell by the user equipment.

[0020] The restored cell may or may not be selected from the subset of candidate target cells.

[0021] A command used to trigger a cell handover from a source cell to a candidate target cell may include information indicating at least one of the following: a subset of timing advance values ​​for a subset of candidate target cells; a subset of timer values ​​for a subset of candidate target cells; or a subset of identifiers or timer identifiers or pointers for a subset of candidate target cells.

[0022] The timer value subset may include the T304 value subset.

[0023] The user equipment's determination that the cell handover from the source cell to the first candidate target cell or the second candidate target cell was unsuccessful may include: the user equipment detecting that the radio link with the first candidate target cell failed before the expiration of the timer for the first candidate target cell or the second candidate target cell; or detecting the expiration of the timer for the first candidate target cell or the second candidate target cell, or the radio link failure before the expiration of the timer for the first candidate target cell or the second candidate target cell.

[0024] Commands used to trigger cell handover from the source cell to the candidate target cell can be received in the Media Access Control control element.

[0025] The method may include: sending a measurement of a configured set of candidate target cells to a base station by a user equipment; and selecting a subset of candidate target cells from the configured set of candidate target cells based on the measurement of the configured set of candidate target cells and at least one selection criterion.

[0026] Measurements for the configured set of candidate target cells can include Layer 1 measurements.

[0027] The measurements of the configured candidate target cell set may include at least one of the following: synchronization signal block measurement or channel state information reference signal measurement.

[0028] The measurements of the configured candidate target cell set may include at least one of the following: intensity measurement or quality measurement.

[0029] The selection criteria may include at least one of the following: intensity threshold or quality threshold.

[0030] The method may include: receiving a radio resource control configuration set for a configured set of candidate target cells from a base station by a user equipment; and decoding the radio resource control configuration set for the configured set of candidate target cells by the user equipment.

[0031] Each radio resource control configuration for a configured candidate target cell may include at least one of the following: first configuration information for performing measurements for the configured candidate target cell, or second configuration information for attempting a cell handover from a source cell to a configured candidate target cell.

[0032] User equipment can perform downlink synchronization for a configured set of candidate target cells.

[0033] Performing downlink synchronization for a selected subset of candidate target cells may include decoding a subset of synchronization signal blocks for the configured set of candidate target cells.

[0034] User equipment can obtain a subset of timing advance values ​​for a configured set of candidate target cells.

[0035] Obtaining a subset of timing advance values ​​for a configured set of candidate target cells may include performing a random access procedure for the configured set of candidate target cells.

[0036] According to one aspect, a user equipment is provided, the user equipment comprising: components for receiving from a base station providing a source cell a command for triggering a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells; components for determining that the subset of candidate target cells includes a first candidate target cell; components for attempting a cell handover from the source cell to the first candidate target cell; components for determining that the cell handover from the source cell to the first candidate target cell is unsuccessful; components for determining that the subset of candidate target cells includes a second candidate target cell; and components for attempting a cell handover from the source cell to the second candidate target cell in the subset of candidate target cells.

[0037] The terms "cell switch", "cell handover", or "mobility" can be used interchangeably.

[0038] The component for receiving a command from the base station providing the source cell to trigger a cell handover from the source cell to the candidate target cell may include: a component for receiving a command from the source distributed unit of the base station providing the source cell to trigger a cell handover from the source cell to the candidate target cell.

[0039] A subset of candidate target cells may include multiple candidate target cells in priority order; a subset of candidate target cells may include preferred candidate target cells and multiple candidate target cells not in priority order; or a subset of candidate target cells may include preferred candidate target cells and multiple candidate target cells in priority order.

[0040] The first candidate target cell can have the first priority, and the second candidate target cell.

[0041] The first candidate target cell can be a preferred candidate target cell, and the second candidate target cell can be selected from multiple candidate target cells based on measurements of multiple candidate target cells.

[0042] The components for attempting a cell handover from the source cell to the first candidate target cell or the second candidate target cell may include: components for attempting a cell handover without a random access channel from the source cell to the first candidate target cell or the second candidate target cell.

[0043] User equipment may include components for determining the success of a cell handover from a source cell to a second target cell.

[0044] The components used to determine that a cell handover from the source cell to the second candidate target cell is successful may include: components for the user equipment to determine that a cell handover from the source cell to the second candidate target cell is complete before the expiration of a timer for the second candidate target cell.

[0045] The user equipment may include: components for determining that a cell handover from the source cell to the second candidate target cell was unsuccessful; components for determining that a subset of candidate target cells includes a third candidate target cell; and components for the user equipment to attempt a cell handover from the source cell to the third candidate target cell.

[0046] The user equipment may include: components for determining that a cell handover from the source cell to the second target cell was unsuccessful; components for determining that the subset of candidate target cells does not include a third candidate target cell; and components for the user equipment to attempt cell handover recovery.

[0047] The components used to determine that a cell handover from the source cell to the first candidate target cell or the second candidate target cell was unsuccessful may include: components used to determine the expiration of a timer for the second candidate target cell before the cell handover from the source cell to the second candidate target cell is completed.

[0048] Components for attempting cell handover recovery may include: components for selecting a cell to be recovered; components for determining whether the cell to be recovered is in a configured set of candidate target cells; and components for attempting a cell handover from the source cell to the recovered cell.

[0049] The components used to attempt a cell handover from the source cell to the recovery cell may include components for attempting a random access channel-based cell handover from the source cell to the recovery cell.

[0050] The components used to attempt cell handover recovery may include: components for selecting a cell to be recovered; components for determining that the cell to be recovered is not in the configured set of candidate target cells; and components for sending a radio resource control reconstruction request to the base station providing the cell to be recovered.

[0051] The components for selecting a cell to be restored may include: components for detecting at least one neighboring cell; and components for selecting a cell to be restored from at least one neighboring cell.

[0052] The restored cell may or may not be selected from the subset of candidate target cells.

[0053] A command used to trigger a cell handover from a source cell to a candidate target cell may include information indicating at least one of the following: a subset of timing advance values ​​for a subset of candidate target cells; a subset of timer values ​​for a subset of candidate target cells; or a subset of identifiers or timer identifiers or pointers for a subset of candidate target cells.

[0054] The timer value subset may include the T304 value subset.

[0055] The components used to determine that a cell handover from the source cell to the first candidate target cell or the second candidate target cell was unsuccessful may include: components for detecting the failure of the radio link with the first candidate target cell before the expiration of a timer for the first candidate target cell or the second candidate target cell; or components for detecting the expiration of a timer for the first candidate target cell or the second candidate target cell, or the failure of the radio link before the expiration of a timer for the first candidate target cell or the second candidate target cell.

[0056] Commands used to trigger cell handover from the source cell to the candidate target cell can be received in the Media Access Control control element.

[0057] User equipment may include: a component for transmitting measurements of a configured set of candidate target cells to a base station; and a subset of candidate target cells may be selected from the configured set of candidate target cells based on measurements of the configured set of candidate target cells and at least one selection criterion.

[0058] Measurements for the configured set of candidate target cells can include Layer 1 measurements.

[0059] The measurements of the configured candidate target cell set may include at least one of the following: synchronization signal block measurement or channel state information reference signal measurement.

[0060] The measurements of the configured candidate target cell set may include at least one of the following: intensity measurement or quality measurement.

[0061] The selection criteria may include at least one of the following: intensity threshold or quality threshold.

[0062] User equipment may include: a component for receiving from a base station a set of radio resource control configurations for a configured set of candidate target cells; and a component for decoding the set of radio resource control configurations for the configured set of candidate target cells.

[0063] Each radio resource control configuration for a configured candidate target cell may include at least one of the following: first configuration information for performing measurements for the configured candidate target cell, or second configuration information for attempting a cell handover from the source cell to the configured candidate target cell.

[0064] User equipment can perform downlink synchronization for a configured set of candidate target cells.

[0065] Performing downlink synchronization for a selected subset of candidate target cells may include decoding a subset of synchronization signal blocks for the configured set of candidate target cells.

[0066] User equipment can obtain a subset of timing advance values ​​for a configured set of candidate target cells.

[0067] Obtaining a subset of timing advance values ​​for a configured set of candidate target cells may include performing a random access procedure for the configured set of candidate target cells.

[0068] According to one aspect, a user equipment is provided, the user equipment including circuitry configured to perform the following: receiving from a base station providing a source cell a command for triggering a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells; determining that the subset of candidate target cells includes a first candidate target cell; attempting a cell handover from the source cell to the first candidate target cell; determining that the cell handover from the source cell to the first candidate target cell is unsuccessful; determining that the subset of candidate target cells includes a second candidate target cell; and attempting a cell handover from the source cell to the second candidate target cell in the subset of candidate target cells.

[0069] According to one aspect, a user equipment is provided, the user equipment including at least one processor and at least one memory, the at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to at least: receive from a base station providing a source cell a command for triggering a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells; determine that the subset of candidate target cells includes a first candidate target cell; attempt a cell handover from the source cell to the first candidate target cell; determine that the cell handover from the source cell to the first candidate target cell is unsuccessful; determine that the subset of candidate target cells includes a second candidate target cell; and attempt a cell handover from the source cell to the second candidate target cell in the subset of candidate target cells.

[0070] According to one aspect, a computer program including computer-executable code is provided, which, when run on at least one processor, is configured to perform: receiving from a base station providing a source cell a command for triggering a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells; determining that the subset of candidate target cells includes a first candidate target cell; attempting a cell handover from the source cell to the first candidate target cell; determining that the cell handover from the source cell to the first candidate target cell is unsuccessful; determining that the subset of candidate target cells includes a second candidate target cell; and attempting a cell handover from the source cell to the second candidate target cell in the subset of candidate target cells.

[0071] According to one aspect, a method is provided, the method comprising: providing a source cell by a base station; selecting a subset of candidate target cells from a configured set of candidate target cells by the base station; and sending a command by the base station to a user equipment for triggering a cell handover from the source cell to the candidate target cells, wherein the command includes information indicating the subset of candidate target cells.

[0072] The provision of the source cell by the base station may include: the source cell being provided by the source distributed unit of the base station; the selection of a subset of candidate target cells by the base station from a configured set of candidate target cells may include: the selection of a subset of candidate target cells by the source distributed unit of the base station from a configured set of candidate target cells; and the sending of a command by the base station to the user equipment to trigger a cell handover from the source cell to the candidate target cell may include: the sending of a command by the source distributed unit of the base station to the user equipment to trigger a cell handover from the source cell to the candidate target cell.

[0073] The method may include: receiving measurements of a configured set of candidate target cells from a user equipment by a base station; and selecting a subset of candidate target cells from the configured set of candidate target cells by the base station including: selecting a subset of candidate target cells from the configured set of candidate target cells based on measurements of the configured set of candidate target cells and at least one selection criterion.

[0074] The measurement of the configured set of candidate target cells received by the base station from the user equipment may include: the measurement of the configured set of candidate target cells received by the source distributed element of the base station from the user equipment; and the selection of a subset of candidate target cells from the configured set of candidate target cells by the base station based on the measurement of the configured set of candidate target cells and at least one selection criterion may include: the selection of a subset of candidate target cells from the configured set of candidate target cells by the source distributed element of the base station based on the measurement and at least one selection criterion.

[0075] The method may include: configuring data forwarding from the central unit of the base station to a subset of candidate target cells.

[0076] The method may include: receiving information from a target distributed unit of a base station that provides candidate target cells in a subset of candidate target cells, the information indicating that a cell handover from a source cell to a candidate target cell in the subset of candidate target cells was successful; maintaining data forwarding to the candidate target cells in the subset of candidate target cells by the central unit of the base station; and releasing data forwarding to other candidate target cells in the subset of candidate target cells by the central unit of the base station.

[0077] According to one aspect, a base station is provided, the base station comprising: components for providing a source cell; components for selecting a subset of candidate target cells from a configured set of candidate target cells; and components for sending a command to a user equipment for triggering a cell handover from the source cell to the candidate target cells, wherein the command includes information indicating the subset of candidate target cells.

[0078] The components for providing the source cell may include: components for providing the source cell by the source distributed unit of the base station; components for selecting a subset of candidate target cells from a configured set of candidate target cells may include: components for selecting a subset of candidate target cells from a configured set of candidate target cells by the source distributed unit of the base station; and components for sending a command to the user equipment to trigger a cell handover from the source cell to the candidate target cell may include: components for sending a command to the user equipment by the source distributed unit of the base station to trigger a cell handover from the source cell to the candidate target cell.

[0079] The base station may include: a component for receiving measurements of a configured set of candidate target cells from a user equipment; and a component for selecting a subset of candidate target cells from the configured set of candidate target cells, including: a component for selecting a subset of candidate target cells from the configured set of candidate target cells based on measurements of the configured set of candidate target cells and at least one selection criterion.

[0080] The component for receiving measurements of a configured set of candidate target cells from a user equipment may include: a component for receiving measurements of a configured set of candidate target cells from a user equipment by a source distributed element of a base station; and the component for selecting a subset of candidate target cells from the configured set of candidate target cells based on the measurements of the configured set of candidate target cells and at least one selection criterion may include: a component for selecting a subset of candidate target cells from the configured set of candidate target cells by a source distributed element of a base station based on the measurements and at least one selection criterion.

[0081] The base station may include components for forwarding data to a subset of candidate target cells, configured by the central unit of the base station.

[0082] The base station may include: a component for receiving information from a target distributed unit of the base station providing candidate target cells in a subset of candidate target cells, the information indicating a successful cell handover from a source cell to a candidate target cell in the subset of candidate target cells; a component for maintaining data forwarding to the candidate target cells in the subset of candidate target cells by the central unit of the base station; and a component for releasing data forwarding to other candidate target cells in the subset of candidate target cells by the central unit of the base station.

[0083] According to one aspect, a base station is provided, the base station including a circuit system configured to perform: receiving measurements of a configured set of candidate target cells from a user equipment; and selecting a subset of candidate target cells from the configured set of candidate target cells including: selecting a subset of candidate target cells from the configured set of candidate target cells based on the measurements of the configured set of candidate target cells and at least one selection criterion.

[0084] According to one aspect, a base station is provided, the base station including at least one processor and at least one memory, the at least one memory storing instructions that, when executed by the at least one processor, cause a user equipment to at least: receive measurements of a configured set of candidate target cells from the user equipment; and select a subset of candidate target cells from the configured set of candidate target cells including: selecting a subset of candidate target cells from the configured set of candidate target cells based on the measurements of the configured set of candidate target cells and at least one selection criterion.

[0085] According to one aspect, a computer program including computer-executable code is provided, which, when run on at least one processor, is configured to perform: receiving measurements of a configured set of candidate target cells from a user equipment; and selecting a subset of candidate target cells from the configured set of candidate target cells including: selecting a subset of candidate target cells from the configured set of candidate target cells based on the measurements of the configured set of candidate target cells and at least one selection criterion.

[0086] According to one aspect, a computer-readable medium is provided including program instructions stored thereon for performing at least one of the methods described above.

[0087] According to one aspect, a non-transitory computer-readable medium is provided including program instructions stored thereon for performing at least one of the methods described above.

[0088] According to one aspect, a non-volatile physical memory medium is provided comprising program instructions stored thereon for performing at least one of the methods described above.

[0089] Many different aspects have been described above. It should be understood that additional aspects can be provided through any combination of two or more of the aspects mentioned above.

[0090] Various other aspects are also described in the following detailed description and the appended claims. List of abbreviations AF: Application Functions AMF: Access and Mobility Management Functions AUSF: Authentication Server Function BS: Base Station CSI: Channel State Information CU: Centralized Unit DL: Downlink DN: Data Network DU: Distributed Unit gNB: gNodeB LTM: Low-level triggered mobility MAC CE: Media Access Control Element MS: Mobile Station NEF: Network Open Functionality NR: New Radio PDCCH: Physical Downlink Control Channel PDSCH: Physical Downlink Shared Channel RAM: Random Access Memory RAN: Radio Access Network ROM: Read-Only Memory RRC: Radio Resource Control RS: Reference signal RSRQ: Reference Signal Reception Quality RSRP: Reference Signal Received Power SMF: Session Management Function SSB: Synchronization Signal Block UDM: Unified Data Management UE: User Equipment UL: Uplink UPF: User-Face Functionality 5G: Fifth Generation 5GC: 5G Core Network 5GS: 5G system Attached Figure Description

[0091] Embodiments will now be described by way of example only with reference to the accompanying drawings, in which:

[0092] Figure 1 A schematic diagram of the communication system is shown;

[0093] Figure 2 A schematic diagram of the control device is shown;

[0094] Figure 3 A schematic diagram of the user equipment is shown;

[0095] Figure 4a , Figure 4b and Figure 4c A signaling diagram illustrating the process used to manage mobility in a communication system is shown.

[0096] Figure 5 A block diagram of a method for managing mobility in a communication system is shown;

[0097] Figure 6 A block diagram of another method for managing mobility in a communication system is shown; and

[0098] Figure 7 A schematic diagram is shown of a non-volatile memory medium for storing instructions, which, when executed by the processor, allow the processor to perform... Figure 5 and Figure 6 One or more steps of the method. Detailed Implementation

[0099] Before explaining the exemplary embodiments in detail, refer to Figure 1 , Figure 2 and Figure 3A brief explanation of some general principles of wireless communication systems, their access systems, and communication equipment is provided to aid in understanding the underlying technology of the described examples. In the following description, the terms communication equipment and user equipment are used interchangeably.

[0100] Figure 1 A schematic diagram of a communication system is shown. The communication system may include user equipment, a 5G system (5GS), application functions (AF), and a data network (DN).

[0101] 5GS can include multiple public terrestrial mobile networks. Each PLMN can include a 5G radio access network (5G RAN) and a 5G core network (5GC).

[0102] 5G RAN may include one or more base stations. A base station may be a gNodeB (gNB). A gNB may include gNB distributed units (gNB-DU) connected to one or more gNB centralized units (gNB-CU).

[0103] 5GC may include one or more of the following: Authentication Server Function (AUSF), User Data Management (UDM), Network Open Function (NEF), Access and Mobility Management Function (AMF), Session Management Function (SMF), and User Plane Function (UPF).

[0104] Figure 2 It shows the control Figure 1 An example of a control device 200 for the functions of the illustrated RAN. The control device 200 may include at least one random access memory (RAM) 211a, at least one read-only memory (ROM) 211b, at least one processor 212, 213, and an input / output interface 214. At least one processor 212, 213 may be coupled to RAM 211a and ROM 211b. At least one processor 212, 213 may be configured to execute appropriate software code 215. The software code 215 may, for example, allow the execution of one or more steps to perform one or more aspects of the invention. The software code 215 may be stored in ROM 211b. The control device 200 may interconnect with other control devices 200 that control other functions of the 5G RAN or 5GC. In some embodiments, each RAN includes a control device 200. In alternative embodiments, two or more RANs may share a control device.

[0105] Figure 3 The illustration shows UE 300 (such as...) Figure 1The above diagram illustrates an example of a UE. UE 300 is a communication device capable of (or configured to) transmit and receive wireless signals. Non-limiting examples include mobile stations (MS) or mobile devices, such as mobile phones or so-called 'smartphones', computers equipped with wireless interface cards or other wireless interface facilities (e.g., USB dongles), personal data assistants (PDAs) or tablets equipped with wireless communication capabilities, machine-type communication (MTC) devices, cellular Internet of Things (CIoT) devices, or any combination of these devices. UE 300 can provide, for example, communication for carrying data. Communication can be one or more of the following: voice, email, text messages, multimedia, data, machine data, etc.

[0106] UE 300 can receive signals via air or radio interface 307 through appropriate means for receiving, and can transmit signals via appropriate means for transmitting radio signals. Figure 3 In this diagram, the transceiver device is schematically designated by block 306. The transceiver device 306 may be provided, for example, by means of a wireless section and an associated antenna arrangement. The antenna arrangement may be located inside or outside the mobile device.

[0107] UE 300 may be provided with at least one processor 301, at least one memory ROM 302a, at least one RAM 302b, and other possible components 303 for software and hardware-assisted execution of tasks it is designed to perform, including controlling access to and communication with access systems and other communication devices. At least one processor 301 is coupled to RAM 302b and ROM 302a. At least one processor 301 may be configured to execute appropriate software code 308. The software code 308 may, for example, allow the execution of one or more aspects of the present invention. The software code 308 may be stored in ROM 302a.

[0108] The processor, memory, and other related control devices may be provided on a suitable circuit board and / or chipset. This feature is indicated by reference numeral 304. The device may optionally have a user interface, such as a keypad 305, a touch-sensitive screen or pad, or a combination thereof. Optionally, depending on the type of device, one or more of a display, speakers, and microphone may be provided.

[0109] One or more aspects of this disclosure relate to managing mobility in communication systems.

[0110] It should be understood that although one or more aspects of this disclosure relate to communication systems including 5GS, one or more aspects of this disclosure can be applied to communication systems including other cellular systems.

[0111] It should be understood that although one or more aspects of this disclosure relate to lower-level (e.g., layer 1 or layer 2) mobility triggering, one or more aspects of this disclosure may be applied to higher-level (e.g., layer 3) mobility triggering.

[0112] It should be understood that although one or more aspects of this disclosure relate to a split architecture (e.g., the distributed unit and central unit of a base station are split in different devices), one or more aspects of this disclosure can be applied to a non-split architecture (e.g., the distributed unit and central unit of a base station are co-located in the same device).

[0113] When a UE changes location within the communication system, the radio link between the UE and the serving cell provided by the gNB-DU may experience significant fluctuations. In low-layer (e.g., Layer 1 or Layer 2) triggered mobility (LTM), the gNB-CU can receive measurement reports, including Layer 1 measurements, from the UE via the gNB-DU. The gNB-CU can determine that the UE should perform a cell handover. The gNB-CU can send a command to the UE via the gNB-DU to trigger a cell handover from the source cell to a candidate target cell. This command can be sent in the Media Access Control Element (MAC CE). The command may include information indicating the candidate target cell. The UE can attempt a cell handover from the source cell to the candidate target cell using Radio Resource Control (RRC) configuration information of the candidate target cell, which was previously prepared by the gNB-CU and received from the gNB-CU via RRC signaling through the gNB-DU.

[0114] One or more aspects of this disclosure provide techniques for reducing delays in completing cell handover.

[0115] One or more aspects of this disclosure provide techniques for reducing service disruptions during cell handover.

[0116] One or more aspects of this disclosure provide techniques for reducing the occurrence of cell handover recovery.

[0117] It should be understood that in this disclosure, the terms "cell switch", "cellhandover" or "mobility" are used interchangeably.

[0118] Figure 4a , Figure 4b and Figure 4c A signaling diagram illustrating the process used to manage mobility in a communication system is shown.

[0119] At step 1, the UE may send a measurement report to the source gNB-DU (i.e., the gNB DU providing the source cell). The measurement report may include measurements of the source cell and neighboring cells. Measurements may include Layer 3 measurements. Layer 3 measurements can be obtained by filtering Layer 1 measurements. Layer 1 measurements may include at least one of the following: Synchronization Block (SSB) measurement or Channel State Information (CSI) Reference Signal (RS) measurement. Layer 1 measurements may include at least one of the following: Strength measurement or Quality measurement. Strength measurements may include Reference Signal Received Power (RSRP) measurement. Quality measurements may include Reference Signal Received Quality (RSRQ) measurement.

[0120] In step 2, the source gNB-DU can send a measurement report to the gNB-CU. The measurement report can be sent in an uplink (UL) RRC message transmission message.

[0121] At step 3, the gNB-CU can select a set of candidate target cells based on measurement and selection criteria. The selection criteria may include at least one of the following: an intensity threshold or a quality threshold.

[0122] In step 4, the gNB-CU can send a UE context establishment request to the target gNB-DU (i.e., the gNB-DU that provides the configuration of the candidate target cell).

[0123] At step 5, the gNB-CU can receive a UE context establishment response from the target gNB-DU.

[0124] In step 6, the gNB-CU can send a UE context modification request to the gNB-DU.

[0125] At step 7, gNB-CU can receive a UE context modification response from gNB-DU.

[0126] At step 8, the gNB-CU can generate an RRC configuration set for the configured candidate target cell set. Each radio resource control configuration for the configured candidate target cell may include at least one of the following: first configuration information for performing measurements for the configured candidate target cell, or second configuration information for attempting a cell handover from the source cell to the configured candidate target cell.

[0127] At step 9, the gNB-CU can send an RRC configuration set for the configured candidate target cell set to the source gNB-DU. The RRC configuration set for the configured candidate target cell set can be sent in a downlink (DL) RRC message transmission message.

[0128] In step 10, the source gNB-DU can send the RRC configuration set for the configured candidate target cell set to the UE.

[0129] In step 11, the UE can decode the RRC configuration set for the configured candidate target cell set. The UE can then send an RRC reconfiguration complete message to the source DU.

[0130] At step 12, the source DU can send a UL RRC message to the gNB-CU.

[0131] At step 13, the UE can perform DL synchronization for the configured set of candidate target cells. The UE can decode the SSB subset for the configured subset of candidate target cells and can perform DL synchronization for the configured set of candidate target cells based on the SSB subset for the configured subset of candidate target cells.

[0132] At step 14, the UE can obtain a subset of timing advance (TA) values ​​for the configured set of candidate target cells. The UE can then perform a random access (RACH) procedure for the configured set of candidate target cells.

[0133] At step 15, the UE may send a measurement report to the gNB-DU. The measurement report may include measurements of the configured candidate target cell set.

[0134] Measurements may include layer 1 measurements. Layer 1 measurements may include at least one of the following: SSB measurement or CSI RS measurement. Layer 1 measurements may include at least one of the following: strength measurement or mass measurement. Strength measurements may include RSRP measurements. Mass measurements may include RSRQ measurements.

[0135] At step 16, the source DU can select a subset of candidate target cells from the configured set of candidate target cells based on measurements and at least one selection criterion. The at least one criterion can include at least one of the following: an intensity threshold or a quality threshold.

[0136] Here, the source DU can be selected from cell 1, cell 2 and cell 3.

[0137] At step 17, the source DU may send a command to the UE to trigger a cell handover from the source cell to a candidate target cell. This command may include a subset of candidate target cells. This command may include a subset of TA values ​​for the subset of candidate target cells. This command may include an identifier for the subset of candidate target cells or a subset of timer identifiers pointing to a timer (e.g., T304 or a subset of protection timer identifiers).

[0138] In one implementation, the subset of candidate target cells may include multiple candidate target cells in priority order. The UE can select one of the multiple candidate target cells to perform cell handover based on the priority order. If cell handover fails, the UE can select another candidate target cell from the multiple candidate target cells to perform cell handover.

[0139] In another implementation, the subset of candidate target cells may include a preferred candidate target cell and multiple candidate target cells not in priority order. The UE may select the preferred candidate target cell to perform cell handover. If cell handover fails, the UE may select one of the multiple candidate target cells to perform cell handover based on measurements of the multiple candidate target cells.

[0140] In another implementation, the subset of candidate target cells may include a preferred candidate target cell and multiple candidate target cells in priority order. The UE can select the preferred candidate target cell to perform cell handover. If cell handover fails, the UE can select one of the multiple candidate target cells based on priority order to perform cell handover.

[0141] Here, the candidate target cell subset can include cell 1, cell 2, and cell 3. Cell 1 can have the highest priority, while cell 3 can have a lower priority.

[0142] In one implementation, the command may include a subset of TA values ​​for a subset of candidate target cells. The command may also include a subset of timer values ​​(e.g., T304 or a subset of protection timer values) for a subset of candidate target cells.

[0143] Here, the command may include subsets of TA values ​​TA1, TA2, and TA3 for cell 1, cell 2, and cell 3, as well as subsets of timer values ​​T304_1, T304_2, and T304_3.

[0144] In another implementation, the command may include a subset of TA values ​​for a subset of candidate target cells. The command may include an identifier for the subset of candidate target cells or a subset of timer identifiers or pointers to timers (e.g., T304 or a subset of protection timer values). As part of step 10, a set of timer values ​​(e.g., T304 or a set of protection timer values) for a configured set of candidate target cells, a set of timer values ​​(e.g., T304 or a set of protection timer values) for a configured set of candidate target cells, and a set of timer identifiers or pointers (e.g., T304 or a set of protection timer identifiers or pointers) for a configured set of candidate target cells may have already been received.

[0145] The UE can configure a subset of timers for a subset of candidate target cells based on a subset of timer values ​​for a subset of candidate target cells.

[0146] At step 18, the source DU may send a subset of candidate target cells to the gNB-CU. The source DU may send a subset of TA values ​​for the subset of candidate target cells to the gNB-CU. The source DU may send a subset of timer identifiers or pointers (e.g., T304 or a subset of protection timer identifiers or pointers) for the subset of candidate target cells to the gNB-CU.

[0147] In step 19, the gNB-CU can be configured to forward data to the source cell. The gNB-CU can also be configured to forward data to a subset of candidate target cells.

[0148] At step 20, the UE may determine that the subset of candidate target cells includes a first candidate target cell (e.g., cell 1). The UE may start a timer associated with the first candidate target cell. The UE may attempt a cell handover from the source cell to the first candidate target cell (i.e., the UE may attempt to access the first candidate target cell). The cell handover from the source cell to the first candidate target cell may include a RACH-free handover from the source cell to the first candidate target cell (i.e., a cell handover from the source cell to the first candidate target cell without a RACH procedure).

[0149] The UE can determine that the cell handover from the source cell to the first candidate target cell was unsuccessful. The UE can determine the expiration of a timer associated with the first candidate target cell before the handover is completed, or determine that the radio link has failed before the expiration of the timer associated with the first candidate target cell. The completion of the cell handover from the source cell to the first candidate target cell may include: the UE receiving DL communication from the first candidate target cell on the Physical Downlink Control Channel (PDCCH) or Physical Downlink Shared Channel (PDSCH). The DL communication cell may be a UL scheduling grant, DL allocation, or acknowledgment.

[0150] Cell handover from the source cell to the first candidate target cell may fail for various reasons, such as radio conditions, TA value usage failure, access failure, or expiration of configuration authorization. Access failure to the target candidate cell can refer to failure to receive DL data before T304 expires, failure to schedule authorization on the PDCCH before T304 expires, etc.

[0151] At step 21, the UE may determine that the subset of candidate target cells includes a second candidate target cell (e.g., cell 2). The UE may start a timer associated with the second candidate target cell. The UE may attempt a cell handover from the source cell to the second candidate target cell (i.e., the UE may attempt to access the second candidate target cell).

[0152] Cell handover from the source cell to the second candidate target cell can include RACH-free handover from the source cell to the second candidate target cell (i.e., cell handover from the source cell to the second candidate target cell without a RACH process).

[0153] The UE can determine that the cell handover from the source cell to the second candidate target cell was successful. The UE can determine the completion of the cell handover from the source cell to the second candidate target cell before the expiration of the timer associated with the second candidate target cell. The completion of the cell handover from the source cell to the second candidate target cell may include: the UE receiving DL communication from the second candidate target cell on the PDCCH or PDSCH. DL communication may be UL scheduling authorization, DL allocation, or acknowledgment.

[0154] At step 22, the UE can send an RRC reconfiguration complete message to the target DU.

[0155] At step 23, the target DU can send a UL RRC message to the gNB-CU.

[0156] At step 24, the gNB-CU can send a UE context release command message to the source DU.

[0157] At step 25, the gNB-CU can receive the UE context release complete message from the source DU.

[0158] At step 26, the gNB-CU can maintain data forwarding to the second candidate target cell in the candidate target cell subset. The gNB-CU can release data forwarding to other candidate target cells in the candidate target cell subset. The gNB-CU can release data forwarding to the source cell.

[0159] Alternatively, at step 21, the UE may determine that the subset of candidate target cells includes a second candidate target cell (e.g., cell 2). The UE may start a timer associated with the second candidate target cell. The UE may attempt a cell handover from the source cell to the second candidate target cell. The UE may determine that the cell handover from the source cell to the second candidate target cell is unsuccessful.

[0160] The UE can determine that the subset of candidate target cells includes a third candidate target cell (e.g., cell 3). The UE can start a timer associated with the third candidate target cell. The UE can attempt a cell handover from the source cell to the third candidate target cell. The UE can determine that the cell handover from the source cell to the third candidate target cell was successful. The method then proceeds to steps similar to steps 22 to 26.

[0161] The UE can determine that the subset of candidate target cells includes a third candidate target cell (e.g., cell 3). The UE can start a timer associated with the third candidate target cell. The UE can attempt a cell handover from the source cell to the third candidate target cell. The UE can determine that the cell handover from the source cell to the third candidate target cell is unsuccessful.

[0162] The UE can determine that the subset of candidate target cells does not include the fourth candidate target cell. The UE can attempt cell handover recovery.

[0163] The UE can select a cell to recover. For example, the UE can detect at least one neighboring cell. The UE can perform measurements on at least one neighboring cell. The UE can select a cell to recover from at least one neighboring cell based on the measurements and at least one selection criterion. Measurements can include Layer 1 measurements. Layer 1 measurements can include at least one of the following: SSB measurement or CSI RS measurement. Layer 1 measurements can include at least one of the following: intensity measurement or quality measurement. Intensity measurements can include RSRP measurements. Quality measurements can include RSRQ measurements. Selection criteria can include at least one of the following: highest intensity or highest quality.

[0164] The cell to be restored may or may not be a candidate cell in the configured set of candidate target cells.

[0165] The cell to be restored may or may not be a candidate target cell in a subset of candidate target cells.

[0166] The UE can determine whether the cell to be restored is in the configured set of candidate target cells.

[0167] If the UE determines that the recoverable cell is in the configured set of candidate target cells, the UE can attempt a cell handover from the source cell to the recoverable cell. The cell handover from the source cell to the recoverable cell can be a RACH-based cell handover from the source cell to the recoverable cell (i.e., the cell handover from the source cell to the recoverable cell includes the RACH procedure with the recoverable cell).

[0168] If the UE determines that the cell to be restored is not in the configured set of candidate target cells, the UE can send an RRC reconstruction request to the gNB-DU that provides the cell to be restored.

[0169] One or more aspects of this disclosure may be advantageous because they can reduce the latency of completing a cell handover. The UE may attempt multiple cell handovers from the source cell to multiple candidate target cells. When multiple cell handovers from the source cell to multiple candidate target cells are unsuccessful, the UE may attempt a cell handover recovery process from the source cell to a recoverable cell.

[0170] One or more aspects of this disclosure can be advantageous because they can reduce service interruptions during cell handover. The gNB-CU can forward data to candidate target cells before the UE attempts multiple cell handovers from the source cell to multiple candidate target cells.

[0171] One or more aspects of this disclosure may be advantageous because it can reduce the occurrence of cell handover recovery.

[0172] Figure 5 A block diagram of a method for managing mobility in a communication system is shown.

[0173] At 500, the UE can receive a command from the BS providing the source cell to trigger a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells.

[0174] At position 502, the UE can determine that the subset of candidate target cells includes the first candidate target cell.

[0175] At position 504, the UE can attempt a cell handover from the source cell to the first candidate target cell.

[0176] At point 506, the UE can determine that the cell handover from the source cell to the first candidate target cell was unsuccessful.

[0177] At point 508, the UE can determine that the subset of candidate target cells includes the second candidate target cell.

[0178] At point 510, the UE can attempt a cell handover from the source cell to the second candidate target cell in the candidate target cell subset.

[0179] Figure 6 A block diagram of a method for managing mobility in a communication system is shown.

[0180] At 600, BS can provide the source cell.

[0181] At position 602, the BS can select a subset of candidate target cells from the configured set of candidate target cells.

[0182] At 604, the BS can send a command to the UE to trigger a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells.

[0183] Figure 7 A schematic diagram of a non-volatile memory medium 1100 for storing instructions is shown. These instructions, when executed by the processor, allow the processor to perform... Figure 5 and Figure 6 One or more steps in the method.

[0184] It should be noted that although exemplary embodiments have been described above, several changes and modifications can be made to the disclosed solutions without departing from the scope of the invention.

[0185] Therefore, these embodiments can vary within the scope of the appended claims. Typically, some embodiments can be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while others may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device, but the embodiments are not limited thereto. While various embodiments may be illustrated and described as block diagrams, flowcharts, or using some other graphical representation, it is well understood that, by way of non-limiting example, the blocks, apparatuses, systems, techniques, or methods described herein can be implemented in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers, or other computing devices, or some combination thereof.

[0186] These embodiments can be implemented by computer software stored in memory and executable by at least one data processor of the entity involved, or by hardware, or by a combination of software and hardware. Furthermore, it should be noted in this regard that, for example, Figure 5 and Figure 6 Any process within the software can represent a program step, or an interconnected logic circuit, block, and function, or a combination of program steps and logic circuits, blocks, and functions. Software can be stored on physical media (such as memory chips or blocks of memory implemented within a processor), magnetic media (such as hard disks or floppy disks), and optical media (such as DVDs and their data variants, CDs).

[0187] The memory can be of any type suitable for the local technical environment and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The data processor can be of any type suitable for the local technical environment and can include one or more of the following as non-limiting examples: general-purpose computers, special-purpose computers, microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), gate-level circuits, and processors based on multi-core processor architectures.

[0188] Alternatively or additionally, some embodiments may be implemented using a circuit system. The circuit system may be configured to perform one or more of the previously described functions and / or method steps. The circuit system may be located in a base station and / or user equipment.

[0189] As used in this application, the term "circuit system" may refer to one or more or all of the following: (a) Hardware circuit implementation only (such as analog and / or digital circuit systems only); and (b) A combination of hardware circuits and software, such as: (i) A combination of (multiple) analog and / or digital hardware circuits having software / firmware, and (ii) Any part of the (multiple) hardware processors having software (including (multiple) digital signal processors), software, and (multiple) memories, which work together to enable the apparatus (such as a communication device or base station) to perform the various functions previously described); and (c) (Multiple) hardware circuits and / or (multiple) processors, such as (multiple) microprocessors or a portion thereof, which require software (e.g., firmware) to operate, but may be absent when operation does not require the software.

[0190] This definition of circuit system applies to all uses of the term in this application (including in any claim). As another example, as used in this application, the term circuit system also covers only hardware circuitry or a processor (or processors) or portions of hardware circuitry or a processor and its accompanying software and / or firmware implementation. The term circuit system also includes, for example, integrated devices.

[0191] The foregoing description provides a complete and informative description of some embodiments through exemplary and non-limiting examples. However, when read in conjunction with the accompanying drawings and appended claims, various modifications and adaptations will become apparent to those skilled in the art in light of the foregoing description. Nevertheless, all such and similar modifications to the teachings will still fall within the scope defined in the appended claims.

Claims

1. A method comprising: The user equipment receives a command from the base station providing the source cell to trigger a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells; The user equipment determines that the subset of candidate target cells includes a first candidate target cell; The user equipment attempts a cell handover from the source cell to the first candidate target cell; The user equipment determines that the cell handover from the source cell to the first candidate target cell was unsuccessful; The user equipment determines that the subset of candidate target cells includes a second candidate target cell; as well as The user equipment attempts a cell handover from the source cell to the second candidate target cell in the subset of candidate target cells.

2. The method of claim 1, wherein receiving a command from the base station providing the source cell to trigger a cell handover from the source cell to the candidate target cell by the user equipment comprises: The user equipment receives a command from the source distributed unit of the base station providing the source cell to trigger a cell handover from the source cell to the candidate target cell.

3. The method according to claim 1 or claim 2, wherein the subset of candidate target cells includes a plurality of candidate target cells in priority order; The subset of candidate target cells includes preferred candidate target cells and multiple candidate target cells not in priority order; or The subset of candidate target cells includes preferred candidate target cells and multiple candidate target cells in priority order.

4. The method according to any one of claims 1 to 3, wherein the cell handover attempt by the user equipment from the source cell to the first candidate target cell or the second candidate target cell comprises: An attempt is made to perform a cell handover without a random access channel from the source cell to the first candidate target cell or the second candidate target cell.

5. The method according to any one of claims 1 to 4, comprising: The user equipment determines that the cell handover from the source cell to the second target cell was successful.

6. The method according to any one of claims 1 to 4, comprising: The user equipment determines that the cell handover from the source cell to the second candidate target cell was unsuccessful; The user equipment determines that the subset of candidate target cells includes a third candidate target cell; as well as The user equipment attempts a cell handover from the source cell to the third candidate target cell.

7. The method according to any one of claims 1 to 4, comprising: The user equipment determines that the cell handover from the source cell to the second target cell was unsuccessful; The user equipment determines that the subset of candidate target cells does not include a third candidate target cell; as well as The user equipment attempts to restore the cell handover.

8. The method of claim 7, wherein the attempt by the user equipment to restore cell handover comprises: The user equipment selects the cell to be restored; The user equipment determines that the cell to be restored is among the configured set of candidate target cells; as well as The user equipment attempts a cell handover from the source cell to the recovered cell.

9. The method of claim 8, wherein the cell handover attempt by the user equipment from the source cell to the recovery cell includes an attempt at a random access channel-based cell handover from the source cell to the recovery cell.

10. The method of claim 7, wherein the attempt by the user equipment to restore cell handover comprises: The user equipment selects the cell to be restored; The user equipment determines that the cell to be restored is not in the configured set of candidate target cells; as well as The user equipment sends a radio resource control reconstruction request to the base station providing the restored cell.

11. The method according to any one of claims 8 to 10, wherein selecting the cell to be restored by the user equipment comprises: The user equipment detects at least one neighboring cell; as well as The user equipment selects the recovery cell from the at least one neighboring cell.

12. The method according to any one of claims 1 to 11, wherein the command for triggering a cell handover from the source cell to the candidate target cell includes information indicating at least one of the following: A subset of timing advance values ​​for the subset of candidate target cells; A subset of timer values ​​for the subset of candidate target cells; or The subset of candidate target cells is an identifier or a timer identifier or pointer subset pointing to a timer.

13. The method according to any one of claims 1 to 12, wherein determining by the user equipment that the cell handover from the source cell to the first candidate target cell or the second candidate target cell was unsuccessful includes: The user equipment detects that the radio link with the first candidate target cell has failed before the timer for the first candidate target cell or the second candidate target cell expires; or The system detects the expiration of a timer for the first or second candidate target cell, or a radio link failure prior to the expiration of a timer for the first or second candidate target cell.

14. The method according to any one of claims 1 to 13, wherein the command for triggering a cell handover from the source cell to the candidate target cell is received in a media access control control element.

15. The method according to any one of claims 1 to 14, comprising: The user equipment sends measurements of the configured candidate target cell set to the base station; and The subset of candidate target cells is selected from the configured set of candidate target cells based on the measurement and at least one selection criterion of the configured set of candidate target cells.

16. The method according to any one of claims 1 to 15, comprising: The user equipment receives from the base station a set of radio resource control configurations for the configured set of candidate target cells; as well as The user equipment decodes the radio resource control configuration set for the configured set of candidate target cells.

17. A method comprising: The source cell is provided by the base station; The base station selects a subset of candidate target cells from the configured set of candidate target cells; as well as The base station sends a command to the user equipment to trigger a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of the candidate target cells.

18. The method of claim 17, wherein the source cell provided by the base station comprises: The source cell is provided by the source distribution unit of the base station; The selection of the subset of candidate target cells by the base station from the configured set of candidate target cells includes: The source distributed unit of the base station selects a subset of candidate target cells from the configured set of candidate target cells; and The command sent by the base station to the user equipment to trigger the cell handover from the source cell to the candidate target cell includes: The source distributed unit of the base station sends a command to the user equipment to trigger a cell handover from the source cell to the candidate target cell.

19. The method according to claim 17 or claim 18, comprising: The base station receives measurements of the configured candidate target cell set from the user equipment. as well as The selection of a subset of candidate target cells by the base station from the configured set of candidate target cells includes: selecting a subset of candidate target cells from the configured set of candidate target cells based on the measurement of the configured set of candidate target cells and at least one selection criterion.

20. The method of claim 19, wherein receiving the configured set of candidate target cells from the user equipment by the base station comprises: The source distributed element of the base station receives measurements of the configured candidate target cell set from the user equipment; and The selection of a subset of candidate target cells from the configured candidate target cell set by the base station based on the measurements and at least one selection criterion of the configured candidate target cell set includes: The source distributed unit of the base station selects a subset of candidate target cells from the configured set of candidate target cells based on the measurement and at least one selection criterion.

21. The method according to any one of claims 18 to 20, comprising: Data forwarding is configured by the central unit of the base station to the subset of candidate target cells.

22. The method of claim 21, comprising: The central unit of the base station receives information from the target distributed unit of the base station that provides candidate target cells in the subset of candidate target cells, the information indicating that the cell handover from the source cell to the candidate target cell in the subset of candidate target cells was successful; The central unit of the base station maintains data forwarding to the candidate target cells in the subset of candidate target cells; as well as The central unit of the base station releases data forwarding to other candidate target cells in the candidate target cell subset.

23. A user equipment, comprising: A component for receiving from a base station providing a source cell a command to trigger a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of candidate target cells selected from a configured set of candidate target cells; Components used to determine that the subset of candidate target cells includes the first candidate target cell; Components used to attempt a cell handover from the source cell to the first candidate target cell; Components used to determine that the cell handover from the source cell to the first candidate target cell was unsuccessful; Components used to determine that the subset of candidate target cells includes a second candidate target cell; as well as A component for attempting a cell handover from the source cell to a second candidate target cell in the subset of candidate target cells.

24. A base station, comprising: Components used to provide the source cell; A component used to select a subset of candidate target cells from a configured set of candidate target cells; as well as A component for sending a command to a user equipment to trigger a cell handover from the source cell to a candidate target cell, wherein the command includes information indicating a subset of the candidate target cells.

25. A computer program comprising computer-executable instructions that, when run on one or more processors, perform the steps of the method according to any one of claims 1 to 22.

Images