Method, apparatus and computer program

Abstract

There is provided an apparatus comprising means for: receiving, at a target cell, information indicating a current serving cell of a user equipment; and performing, by the target cell, a handover of the user equipment from the current serving cell to the target cell, wherein the handover is based on the information indicating the current serving cell.

Description

Technical Field

[0001] The present application relates to a method, an apparatus and a computer program, in particular but not limited to informing a target cell of a current serving cell of a user equipment to perform a handover. Background Art

[0002] A communication system may be viewed as a facility that enables a communication session between two or more entities (such as user terminals, base stations and / or other nodes) by providing a bearer between the various entities involved in the communication path. A communication system may be provided, for example, by a communication network and one or more compatible communication devices. A communication session may include, for example, data communications for carrying communications, such as voice, video, electronic mail (email), text messages, multimedia and / or content data, etc. Non-limiting examples of the services provided include two-way or multi-way calls, data communications or multimedia services, and access to a data network system (such as the Internet).

[0003] In a wireless communication system, at least a portion of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems include public land mobile networks (PLMNs), satellite-based communication systems, and different wireless local networks, such as wireless local area networks (WLANs). Some wireless systems can be divided into cells and are therefore often referred to as cellular systems.

[0004] A user can access the communication system through an appropriate communication device or terminal. The user's communication device may be referred to as a user equipment (UE) or user device. The communication device is provided with appropriate signal receiving and sending devices for implementing communication, for example, implementing access to a communication network or direct communication with other users. The communication device can access a carrier provided by a station (e.g., a base station of a cell) and send and / or receive communications on the carrier.

[0005] Communication systems and associated equipment typically operate according to a given standard or specification that specifies what the various entities associated with the system are allowed to do and how it should be implemented. The communication protocols and / or parameters used for the connection are also typically defined. An example of a communication system is UTRAN (3G radio). Other examples of communication systems are the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology and the so-called 5G or New Radio (NR) networks. NR is being standardized by the Third Generation Partnership Project (3GPP). Summary of the invention

[0006] According to one aspect, an apparatus is provided, comprising means for: receiving, at a target cell, information indicating a current serving cell of a user equipment; and performing, by the target cell, handover of the user equipment from the current serving cell to the target cell, wherein the handover is based on the information indicating the current serving cell.

[0007] The component may be configured to: receive, at a target cell, a conditional handover configuration for the user equipment from an initial source cell serving the user equipment; wherein performing the handover is further based on the conditional handover configuration.

[0008] The component may be configured to: after the handover is completed, send information indicating that the target cell is a new current serving cell of the user equipment to one or more other cells.

[0009] Performing the handover may include: receiving a message including a physical random access channel preamble from the user equipment, the physical random access channel preamble being configured based on the conditional handover; sending a message including a random access channel response to the user equipment in response to the physical random access channel preamble; and receiving a radio resource control reconfiguration completion message from the user equipment.

[0010] Information indicating a current serving cell of a user equipment may be received from one of: the user equipment during a handover of the user equipment from a current serving cell to a target cell; the current serving cell during a handover of the user equipment from a current serving cell to a target cell; and an initial source cell during a handover of the user equipment from a current serving cell to a target cell.

[0011] Performing the handover based on the information indicating the current serving cell may include receiving state information associated with the user equipment and / or data buffered in the current serving cell from the current serving cell for transmission to the user equipment based on the information indicating the current serving cell.

[0012] According to one aspect, an apparatus is provided, comprising components for: when a user equipment performs a handover from a current serving cell to a target cell, sending information indicating the current serving cell of the user equipment from the user equipment to the target cell; and performing a handover of the user equipment from the current serving cell to the target cell at the user equipment, wherein the handover is based on the information indicating the current serving cell.

[0013] The component may be configured to: receive, at the user equipment, at least one conditional handover configuration for the user equipment from an initial source cell serving the user equipment; wherein performing the handover is further based on the conditional handover configuration.

[0014] Performing a handover may include: determining at a user equipment that at least one condition associated with a target cell is satisfied based on a conditional handover configuration; in response to the determination, sending a message including a physical random access channel preamble to the target cell, the physical random access channel preamble being based on the conditional handover configuration; receiving a message including a random access channel response from the target cell; and in response to receiving the message including the random access channel response, sending a radio resource control reconfiguration completion message to the target cell.

[0015] The information indicating the current serving cell of the user equipment may be included in a radio resource control reconfiguration complete message sent to a target cell when performing handover.

[0016] The component may be configured to: store the radio resource control configuration of the initial source cell; and apply a change in the radio resource control configuration on top of the radio resource control configuration of the initial source cell when a handover of the user equipment is performed.

[0017] The component may be configured to: receive a message from a current serving cell including an indication that one or more additional target cells are no longer available for conditional handover of the user equipment; and update a conditional handover configuration of the user equipment based on the received message.

[0018] According to one aspect, an apparatus is provided, comprising means for sending information indicating a current serving cell of the user equipment to a target cell when the user equipment switches from the current serving cell to the target cell.

[0019] The apparatus may include a current serving cell, and wherein the component may also be configured to: receive an indication from a target cell that a handover has been performed for the user equipment to the target cell; and in response to receiving the indication, send state information associated with the user equipment and / or data buffered in the current serving cell to the target cell for transmission to the user equipment.

[0020] The component may be configured to: receive information from an initial source cell indicating that one or more further target cells are no longer available for conditional handover of the user equipment; and send a message to the user equipment including an indication that one or more further target cells are no longer available for conditional handover of the user equipment.

[0021] The apparatus may include an initial source cell; and wherein the component may also be configured to: send a conditional handover configuration for the user equipment to a target cell.

[0022] The component can be used to: receive information indicating that the user equipment has been switched to the current serving cell from the current serving cell; store information identifying the current serving cell of the user equipment at the initial source cell based on the received information; and send information indicating the current serving cell of the user equipment to the target cell.

[0023] The component can be used to: receive information from one or more additional target cells indicating that the one or more additional target cells are no longer available for conditional switching of the user equipment; and send a message to the current serving cell including an indication that the one or more additional target cells are no longer available for conditional switching of the user equipment.

[0024] The information indicating the current serving cell of the user equipment may include a physical cell identity of the current serving cell or a global cell identity of the current serving cell.

[0025] According to one aspect, an apparatus is provided, comprising at least one processor and at least one memory, the at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: receive information indicating a current serving cell of a user equipment; and perform handover of the user equipment from the current serving cell to a target cell, wherein the handover is based on the information indicating the current serving cell.

[0026] At least one memory and at least one processor may be configured to cause the apparatus to: receive a conditional switching configuration for the user equipment from an initial source cell serving the user equipment; wherein the at least one memory and at least one processor may be configured to cause the apparatus to perform switching based on the conditional switching configuration.

[0027] The at least one memory and the at least one processor may be configured to cause the apparatus to: after completion of the handover, send information indicating that the target cell is a new current serving cell of the user equipment to one or more additional cells.

[0028] At least one memory and at least one processor may be configured to cause the apparatus to perform switching by causing the apparatus to at least: receive a message including a physical random access channel preamble from a user equipment, the physical random access channel preamble being configured based on a conditional switching; send a message including a random access channel response to the user equipment in response to the physical random access channel preamble; and receive a radio resource control reconfiguration completion message from the user equipment.

[0029] Information indicating a current serving cell of a user equipment may be received from one of: the user equipment during a handover of the user equipment from a current serving cell to a target cell; the current serving cell during a handover of the user equipment from a current serving cell to a target cell; and an initial source cell during a handover of the user equipment from a current serving cell to a target cell.

[0030] The at least one memory and the at least one processor may be configured to cause the apparatus to: receive state information associated with the user equipment and / or data buffered in the current serving cell from the current serving cell based on the information indicating the current serving cell for transmission to the user equipment.

[0031] According to one aspect, an apparatus is provided, comprising at least one processor and at least one memory, the at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: when a user equipment performs a handover from a current serving cell to a target cell, send information indicating the current serving cell of the user equipment from the user equipment to the target cell; and perform, at the user equipment, the handover of the user equipment from the current serving cell to the target cell, wherein the handover is based on the information indicating the current serving cell.

[0032] At least one memory and at least one processor may be configured to cause the apparatus to: receive, at the user equipment, at least one conditional handover configuration for the user equipment from an initial source cell serving the user equipment; wherein performing the handover is further based on the conditional handover configuration.

[0033] At least one memory and at least one processor may be configured to cause the apparatus to perform a handover by causing the apparatus to at least: determine, based on a conditional handover configuration, that at least one condition associated with a target cell is satisfied; in response to the determination, send a message including a physical random access channel preamble to the target cell, the physical random access channel preamble being based on the conditional handover configuration; receive a message including a random access channel response from the target cell; and in response to receiving the message including the random access channel response, send a radio resource control reconfiguration completion message to the target cell.

[0034] The information indicating the current serving cell of the user equipment may be included in a radio resource control reconfiguration complete message sent to a target cell when performing handover.

[0035] The at least one memory and the at least one processor may be configured to cause the apparatus to: store the radio resource control configuration of the initial source cell; and apply a change in the radio resource control configuration over the radio resource control configuration of the initial source cell when handover of the user equipment is performed.

[0036] At least one memory and at least one processor may be configured to cause the apparatus to: receive a message from a current serving cell including an indication that one or more additional target cells are no longer available for conditional switching of the user equipment; and update a conditional switching configuration of the user equipment based on the received message.

[0037] According to one aspect, an apparatus is provided, comprising at least one processor and at least one memory, the at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: when a user equipment switches from a current serving cell to a target cell, send information indicating the current serving cell of the user equipment to the target cell.

[0038] The apparatus may include a current serving cell, and wherein the at least one memory and the at least one processor may be configured to cause the apparatus to: receive an indication from a target cell that a handover has been performed for a user equipment to the target cell; and in response to receiving the indication, send to the target cell state information associated with the user equipment and / or data buffered in the current serving cell for transmission to the user equipment.

[0039] At least one memory and at least one processor may be configured to cause the apparatus to: receive information from an initial source cell indicating that one or more additional target cells are no longer available for conditional switching of a user equipment; and send a message to the user equipment including an indication that one or more additional target cells are no longer available for conditional switching of the user equipment.

[0040] The apparatus may include an initial source cell; and the at least one memory and the at least one processor may be configured to cause the apparatus to: send a conditional handover configuration for a user equipment to a target cell.

[0041] At least one memory and at least one processor may be configured to cause the apparatus to: receive information indicating that the user equipment has been switched to the current serving cell from a current serving cell; store information identifying the current serving cell of the user equipment at an initial source cell based on the received information; and send information indicating the current serving cell of the user equipment to a target cell.

[0042] At least one memory and at least one processor may be configured to cause the apparatus to: receive information from one or more additional target cells indicating that the one or more additional target cells are no longer available for conditional switching of the user equipment; and send a message to the current serving cell including an indication that the one or more additional target cells are no longer available for conditional switching of the user equipment.

[0043] The information indicating the current serving cell of the user equipment may include a physical cell identity of the current serving cell or a global cell identity of the current serving cell.

[0044] According to one aspect, a method is provided, comprising: receiving information indicating a current serving cell of a user equipment; and performing handover of the user equipment from the current serving cell to a target cell, wherein the handover is based on the information indicating the current serving cell.

[0045] The method may include: receiving a conditional handover configuration for the user equipment from an initial source cell serving the user equipment; wherein performing the handover is further based on the conditional handover configuration.

[0046] The method may include, after completion of the handover, sending information to one or more further cells indicating that the target cell is a new current serving cell for the user equipment.

[0047] Performing the handover may include: receiving a message including a physical random access channel preamble from the user equipment, the physical random access channel preamble being configured based on the conditional handover; sending a message including a random access channel response to the user equipment in response to the physical random access channel preamble; and receiving a radio resource control reconfiguration completion message from the user equipment.

[0048] Information indicating a current serving cell of a user equipment may be received from one of: the user equipment during a handover of the user equipment from a current serving cell to a target cell; the current serving cell during a handover of the user equipment from a current serving cell to a target cell; and an initial source cell during a handover of the user equipment from a current serving cell to a target cell.

[0049] Performing the handover based on the information indicating the current serving cell may include receiving state information associated with the user equipment and / or data buffered in the current serving cell from the current serving cell for transmission to the user equipment based on the information indicating the current serving cell.

[0050] According to one aspect, a method is provided, comprising: when a user equipment performs a handover from a current serving cell to a target cell, sending information indicating the current serving cell of the user equipment from the user equipment to the target cell; and performing a handover of the user equipment from the current serving cell to the target cell at the user equipment, wherein the handover is based on the information indicating the current serving cell.

[0051] The method may include: receiving, at the user equipment, at least one conditional handover configuration for the user equipment from an initial source cell serving the user equipment; wherein performing the handover is further based on the conditional handover configuration.

[0052] Performing a handover may include: determining at a user equipment that at least one condition associated with a target cell is satisfied based on a conditional handover configuration; in response to the determination, sending a message including a physical random access channel preamble to the target cell, the physical random access channel preamble being based on the conditional handover configuration; receiving a message including a random access channel response from the target cell; and in response to receiving the message including the random access channel response, sending a radio resource control reconfiguration completion message to the target cell.

[0053] The information indicating the current serving cell of the user equipment may be included in a radio resource control reconfiguration complete message sent to a target cell when performing handover.

[0054] The method may include: storing a radio resource control configuration of an initial source cell; and applying a change of the radio resource control configuration over the radio resource control configuration of the initial source cell when handover of the user equipment is performed.

[0055] The method may include: receiving a message including an indication that one or more additional target cells are no longer available for conditional handover of the user equipment from a current serving cell; and updating a conditional handover configuration of the user equipment based on the received message.

[0056] According to one aspect, a method is provided, comprising: when user equipment switches from a current serving cell to a target cell, sending information indicating a current serving cell of the user equipment to the target cell.

[0057] The method may be performed at a current serving cell, and the method may include: receiving an indication from a target cell that a handover has been performed for a user equipment to the target cell; and in response to receiving the indication, sending status information associated with the user equipment and / or data buffered in the current serving cell to the target cell for transmission to the user equipment.

[0058] The method may include: receiving information from an initial source cell indicating that one or more further target cells are no longer available for conditional handover of the user equipment; and sending a message to the user equipment including an indication that the one or more further target cells are no longer available for conditional handover of the user equipment.

[0059] The method may be performed at an initial source cell; and the method may include: sending a conditional handover configuration for the user equipment to a target cell.

[0060] The method may include: receiving information indicating that the user equipment has been switched to the current serving cell from the current serving cell; storing information identifying the current serving cell of the user equipment at the initial source cell based on the received information; and sending information indicating the current serving cell of the user equipment to the target cell.

[0061] The method may include: receiving information from one or more additional target cells indicating that the one or more additional target cells are no longer available for conditional switching of the user equipment; and sending a message to the current serving cell including an indication that the one or more additional target cells are no longer available for conditional switching of the user equipment.

[0062] The information indicating the current serving cell of the user equipment may include a physical cell identity of the current serving cell or a global cell identity of the current serving cell.

[0063] According to one aspect, a computer-readable medium is provided, comprising program instructions for causing an apparatus to perform at least the following: receiving information indicating a current serving cell of a user equipment at a target cell; and performing a handover of the user equipment from the current serving cell to the target cell, wherein the handover is based on the information indicating the current serving cell.

[0064] A computer-readable medium including program instructions may be used to cause the apparatus to execute: receiving, at a target cell, a conditional handover configuration for a user equipment from an initial source cell serving the user equipment; wherein performing the handover is further based on the conditional handover configuration.

[0065] The computer-readable medium including program instructions may be used to cause the apparatus to execute: after the handover is completed, sending information indicating that the target cell is a new current serving cell of the user equipment to one or more other cells.

[0066] Performing the handover may include: receiving a message including a physical random access channel preamble from the user equipment, the physical random access channel preamble being configured based on the conditional handover; sending a message including a random access channel response to the user equipment in response to the physical random access channel preamble; and receiving a radio resource control reconfiguration completion message from the user equipment.

[0067] Information indicating a current serving cell of a user equipment may be received from one of: the user equipment during a handover of the user equipment from a current serving cell to a target cell; the current serving cell during a handover of the user equipment from a current serving cell to a target cell; and an initial source cell during a handover of the user equipment from a current serving cell to a target cell.

[0068] Performing the handover based on the information indicating the current serving cell may include receiving state information associated with the user equipment and / or data buffered in the current serving cell from the current serving cell based on the information indicating the current serving cell to transmit to the user equipment.

[0069] According to one aspect, a computer-readable medium is provided, comprising program instructions for causing an apparatus to perform at least the following: when a user equipment performs a handover from a current serving cell to a target cell, sending information indicating the current serving cell of the user equipment from the user equipment to the target cell; and performing a handover of the user equipment from the current serving cell to the target cell at the user equipment, wherein the handover is based on the information indicating the current serving cell.

[0070] A computer-readable medium including program instructions may be used to cause the apparatus to execute: receiving at a user equipment at least one conditional handover configuration for the user equipment from an initial source cell serving the user equipment; wherein performing the handover is further based on the conditional handover configuration.

[0071] Performing a handover may include: determining at a user equipment that at least one condition associated with a target cell is satisfied based on a conditional handover configuration; in response to the determination, sending a message including a physical random access channel preamble to the target cell, the physical random access channel preamble being based on the conditional handover configuration; receiving a message including a random access channel response from the target cell; and in response to receiving the message including the random access channel response, sending a radio resource control reconfiguration completion message to the target cell.

[0072] The information indicating the current serving cell of the user equipment may be included in a radio resource control reconfiguration complete message sent to a target cell when performing handover.

[0073] A computer readable medium including program instructions may be used to cause the apparatus to execute: storing a radio resource control configuration of an initial source cell; and applying a change in the radio resource control configuration over the radio resource control configuration of the initial source cell when handover of the user equipment is performed.

[0074] A computer-readable medium including program instructions can be used to cause the apparatus to execute: receiving a message including an indication that one or more additional target cells are no longer available for conditional switching of the user equipment from a current serving cell; and updating a conditional switching configuration of the user equipment based on the received message.

[0075] According to one aspect, a computer-readable medium is provided, comprising program instructions for causing an apparatus to perform at least the following: when a user equipment switches from a current serving cell to a target cell, sending information indicating a current serving cell of the user equipment to the target cell.

[0076] The apparatus may include a current serving cell, and a computer-readable medium including program instructions may be used to cause the apparatus to perform: receiving an indication from a target cell that a handover has been performed for a user equipment to the target cell; and in response to receiving the indication, sending to the target cell state information associated with the user equipment and / or data buffered in the current serving cell for transmission to the user equipment.

[0077] A computer-readable medium including program instructions can be used to cause the apparatus to execute: receiving information from an initial source cell indicating that one or more additional target cells are no longer available for conditional switching of a user equipment; and sending a message to the user equipment including an indication that one or more additional target cells are no longer available for conditional switching of the user equipment.

[0078] The apparatus may include an initial source cell; and a computer-readable medium including program instructions may be used to cause the apparatus to execute: sending a conditional handover configuration for a user equipment to a target cell.

[0079] A computer-readable medium including program instructions can be used to cause the apparatus to execute: receiving information indicating that a user equipment has been switched to the current serving cell from a current serving cell; storing information identifying the current serving cell of the user equipment at an initial source cell based on the received information; and sending information indicating the current serving cell of the user equipment to a target cell.

[0080] A computer-readable medium including program instructions can be used to cause the apparatus to execute: receiving information from one or more additional target cells indicating that the one or more additional target cells are no longer available for conditional switching of a user equipment; and sending a message to a current serving cell including an indication that the one or more additional target cells are no longer available for conditional switching of the user equipment.

[0081] The information indicating the current serving cell of the user equipment may include a physical cell identity of the current serving cell or a global cell identity of the current serving cell.

[0082] According to one aspect, a non-transitory computer-readable medium is provided, comprising program instructions for causing an apparatus to execute at least a method according to any of the preceding aspects.

[0083] In the above, many different embodiments have been described. It should be understood that further embodiments can be provided by combining any two or more of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0085] Figure 1 shows a representation of a network system according to some example embodiments;

[0086] Figure 2 shows a representation of a control device according to some example embodiments;

[0087] Figure 3 shows representations of apparatus according to some example embodiments;

[0088] Figure 4 shows a signaling exchange according to some examples;

[0089] Figure 5 Methods according to some examples are shown; and

[0090] Figures 6 to 9 Various signaling exchanges are shown according to some examples. DETAILED DESCRIPTION

[0091] In the following, certain embodiments will be explained with reference to a mobile communication device capable of communicating via a wireless cellular system and a mobile communication system serving such a mobile communication device. Before explaining the exemplary embodiments in detail, certain general principles of a wireless communication system, its access system and a mobile communication device will be explained with reference to Figure 1 , 2 and 3 are briefly explained to help understand the technology on which the examples are based.

[0092] Figure 1 A schematic diagram of a 5G system (5GS) is shown. The 5GS may include a terminal or user equipment (UE), a 5G radio access network (5GRAN) or a next generation radio access network (NG-RAN), a 5G core network (5GC), one or more application functions (AFs), and one or more data networks (DNs).

[0093] 5G-RAN may include one or more gNodeBs (GNBs) or one or more gNodeB (GNB) distributed unit functions connected to one or more gNodeB (GNB) centralized unit functions. 5GC may include the following entities: Network Slice Selection Function (NSSF); Network Exposure Function; Network Repository Function (NRF); Policy Control Function (PCF); Unified Data Management (UDM); Application Function (AF); Authentication Server Function (AUSF); Access and Mobility Management Function (AMF); and Session Management Function (SMF).

[0094] Figure 2 Shows the control Figure 1 An example of a control device 200 for a 5GRAN or 5GC function shown. The control device 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 the RAM 211a and the 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 one or more steps to be executed to perform one or more of the present aspects. The software code 215 may be stored in the ROM 211b. The control device 200 may be interconnected with another control device 200 that controls another function of the 5GRAN or 5GC. In some embodiments, each function of the 5GRAN or 5GC includes a control device 200. In an alternative embodiment, two or more functions of the 5GRAN or 5GC may share a control device.

[0095] Figure 3 An example of a terminal 300 is shown, such as Figure 1The terminal shown. The terminal 300 can be provided by any device capable of sending and receiving radio signals. Non-limiting examples include user equipment, a mobile station (MS) or a mobile device (such as a mobile phone or a so-called "smartphone"), a computer provided with a wireless interface card or other wireless interface facilities (such as a USB dongle), a personal data assistant (PDA) or a tablet computer provided with wireless communication capabilities, a machine type communication (MTC) device, an Internet of Things (IoT) type communication device, or any combination of these devices or similar devices. The terminal 300 can provide, for example, communication for carrying data for communication. The communication can be one or more of voice, electronic mail (email), text message, multimedia, data, machine data, etc.

[0096] The terminal 300 may receive signals over the air or radio interface 307 via appropriate means for receiving, and may transmit signals via appropriate means for transmitting radio signals. Figure 3 In the mobile device, the transceiver arrangement is schematically designated by block 306. The transceiver arrangement 306 may be provided, for example, by a radio part and an associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

[0097] The terminal 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 use in software and hardware assisted execution of the tasks it is designed to perform, including controlling access to and communication with access systems and other communication devices. The at least one processor 301 is coupled to the RAM 302b and the ROM 302a. The at least one processor 301 may be configured to execute appropriate software code 308. The software code 308 may, for example, allow execution of one or more of the present aspects. The software code 308 may be stored in the ROM 302a.

[0098] The processor, storage and other related control means may be provided in an appropriate circuit board and / or chipset. This feature is represented by reference 304. The device may optionally have a user interface, such as a keyboard 305, a touch screen or touch pad, a combination thereof, etc. Depending on the type of device, one or more displays, speakers and microphones may optionally be provided.

[0099] Conditional Handover (CHO) has been introduced in 3GPP Rel.16 to ensure the robustness of the handover process.

[0100] In CHO, the serving cell prepares multiple target cells and provides the relevant conditional reconfiguration to the UE along with the CHO execution conditions. This is done to ensure that the radio conditions are still sufficient for the UE to receive the reconfiguration. After receiving the CHO configuration, the UE evaluates the CHO execution conditions and initiates a handover to a specific target cell once its corresponding CHO execution condition is met.

[0101] refer to Figure 4 , where an example CHO process is shown.

[0102] In step 400, the configured event condition is established and this triggers the UE to send a measurement report to the serving cell. For example, the UE may determine that the signal strength received from the source node is below a threshold for a certain amount of time, or that the received signal strength of a neighboring cell is above a threshold for a certain amount of time.

[0103] Based on the report, the source node may prepare one or more target cells for handover, as shown in steps 402 to 408 .

[0104] At step 402, the source node determines whether CHO is to be performed. If the source node determines that CHO is to be performed, the source node sends a CHO request to one or more target nodes at steps 403 and 404. At steps 405 and 406, the one or more target nodes perform admission control and send a CHO request confirmation back to the source node at steps 407 and 408.

[0105] At step 409, the source node sends an RRC reconfiguration (CHO command) to the UE. At step 410, the UE evaluates the CHO execution conditions, and once one of the conditions is met, it accesses the target node and exchanges user data.

[0106] Switch to Figure 4 411 to 414 of . At step 411, the UE determines that the conditional handover condition for the target node 1 is satisfied. At step 412, the UE sends a PRACH preamble to the target node, and the target node sends a RACH response at step 413. At step 14, the UE completes the handover execution to the target node, for example, by sending an RRC reconfiguration complete to the target node.

[0107] When the target node receives the RRC reconfiguration complete message, at step 15, the target node sends a "successful handover" indication to the source node. Receipt of the "successful handover" indication triggers:

[0108] The source node stops transmission to the UE and starts forwarding user plane packet data to the target node (steps 416 to 418); and

[0109] The source node initiates the release of the CHO preparation in other target nodes / cells (which are no longer needed) (step 419).

[0110] After the SN status transmission and data forwarding have been sent and the CHO preparation is released, the path switch for the UE is completed in step 420 .

[0111] In some cases, such as at higher frequencies, a cell change (often referred to as a "handover" in connected mode) may not always be the result of a UE moving linearly along a trajectory. A UE that is not moving at all (or only moving slowly) may also experience a handover, such as caused by:

[0112] Moving a larger obstacle (e.g. a car) towards or away from the UE may temporarily block radio propagation from / to a serving cell with a smaller wavelength and thus require a handover;

[0113] Similarly, a smaller obstacle near the UE may also block transmission in any direction (e.g., a person's hand holding the UE); or

[0114] • When narrow beams are also used for transmission on the UE side, rotating the UE may also cause a sudden drop in directional gain and cause a handover (especially when the spherical coverage is not 100%).

[0115] This may also be a problem in the case of Reduced Capability (RedCap) UEs which are expected to be static (or have limited mobility).

[0116] According to the 3GPP Rel.16 CHO procedure, when the UE switches to a target cell for which the CHO execution conditions are met, it releases all stored CHO configurations (corresponding to the prepared candidate target cells).

[0117] Therefore, after performing CHO, the preparation of the (new) target needs to happen again, thus requiring:

[0118] 1. When handover is performed to the target cell, the candidate target cell prepared by the source node is released;

[0119] 2. Preparation of new candidate target cells of the new serving / source cell (i.e. the cell that served as the candidate target cell in the previous CHO); and

[0120] 3. Transmission of a new RRC configuration message containing the CHO configuration of the newly prepared candidate target cell by the new serving / source cell to the UE.

[0121] Re-initiating CHO preparation from scratch may cause unnecessary signaling and may delay the execution of subsequent handover.

[0122] To address this issue, some solutions have been proposed where the UE can keep the CHO configuration after handover so that the UE can trigger another subsequent HO to another cell without restarting the CHO preparation. However, such solutions may have disadvantages.

[0123] In one example, cell 1 (serving cell) prepares candidate target cells 2, 3 and cell 4. All candidate cells 2, 3 and 4 know that cell 1 is currently the serving cell. Once the corresponding CHO execution condition is met, the UE can perform CHO to the candidate target cell 2. Cell 2 notifies cell 1 of the cell change through a handover success message. The UE maintains the CHO configuration for cells 3 and 4.

[0124] However, if the CHO execution condition for cell 3 holds while the UE is connected to cell 2, the UE may perform CHO to cell 3. Cell 3 may not know which cell (e.g., 1, 2, or 4) to notify of the cell change so that it can start data forwarding of packets or trigger path switching when needed. Cell 3 may blindly notify the handover to cell 1 or 2 or 4, but this approach may not work because the wrong target cell will be contacted in most cases (67% of the cases in this example).

[0125] Therefore, in some examples, the target cell may not know to which serving cell the HO success message should be sent ( Figure 4 415 in step 416), because the target cell may not have been prepared by the last source cell. This may cause the source cell to continue transmitting to the UE while the UE is waiting to be served by the new cell. In addition, the target cell may not be aware of the previous cell to which the UE has been connected to receive the SN status transmission ( Figure 4 Step 417 in ) and data forwarding ( Figure 4 418 in step 418).

[0126] Another problem that may arise with the proposed solution is that in case the candidate target cell wants to trigger a cancellation or modification of the CHO preparation, the candidate target cell may not know which serving cell to contact.

[0127] For example, if a candidate target (e.g., cell 4) wants to release the UE context (CHO preparation), cell 4 may not know which serving cell (e.g., cell 1, 3, or 4) to contact in order for the serving cell to release the CHO preparation of cell 4 from the UE side - for example, by sending an RRC reconfiguration message to the UE to release the CHO preparation of cell 4.

[0128] Some examples of the present disclosure aim to address one or more of these issues.

[0129] refer to Figure 5, which shows a method according to some examples.

[0130] In step 500, the method includes receiving, at a target cell, information indicating a current serving cell of a user equipment.

[0131] In step 502, the method includes performing, by the target cell, handover of the user equipment from a current serving cell to the target cell, wherein the handover is based on information indicating the current serving cell.

[0132] In step 504, the method includes sending information indicating a current serving cell of the user equipment from the user equipment to the target cell when the user equipment performs a handover from the current serving cell to the target cell.

[0133] In step 506, the method includes performing, at the user equipment, a handover of the user equipment from a current serving cell to a target cell, wherein the handover is based on information indicating the current serving cell.

[0134] In step 508, the method includes sending information indicating the current serving cell of the user equipment to the target cell when the user equipment switches from the current serving cell to the target cell.

[0135] As used herein, the initial source cell is defined as a serving cell that has initiated CHO preparation for the UE. That is, the initial source cell is the cell that sends a CHO request to other cells.

[0136] In some examples, the UE may notify the target cell for which the CHO execution condition is satisfied of the previous serving cell (the handover source cell). For example, the UE may notify the target cell through lower layer (MAC) or higher layer signaling (RRC) during CHO execution, such as a random access procedure, or the UE may notify the target cell through lower layer or higher layer signaling after the CHO execution is completed.

[0137] refer to Figure 6 , which shows the CHO process according to some examples.

[0138] Figure 6 The process starts from steps 601 to 608, which correspond to the steps previously described in Figure 4 In short, the source node prepares multiple target nodes, such as target node 1 (controlling target cell 1) and target node 2 (controlling target cell 2), based on UE measurements.

[0139] In steps 609 and 610, the source node sends a message to the target node, the message including information about other prepared cells configured by the UE for CHO.

[0140] In some examples, the message may cause the target node to infer that the CHO configuration will be maintained after the switch, either implicitly (received via the message) or explicitly (eg, the content of the message indicates this).

[0141] In step 611, the source node sends an RRC reconfiguration for CHO to the UE.

[0142] In step 612, the UE evaluates the CHO condition while being served by the source node and exchanging user data with the source node.

[0143] In steps 613 to 615, once the conditions for the CHO target cell are met, the UE performs RACH signaling to the target cell for which the CHO conditions are met.

[0144] Once the RACH is completed, the UE sends a message, such as an RRC Reconfiguration Complete (HO Complete) message, to the target node in step 616. The message includes information about the current serving (ie source) cell.

[0145] Therefore, the new serving cell is informed of which cell to send the HO success message to initiate the data forwarding process.

[0146] In step 617, the target node 1 sends a message indicating a successful handover (eg, HO success) to the source node. The target node may know the source node because the CHO request (ie, message 603) has been sent by the source node.

[0147] Steps 618 to 620 follow Figure 4 Steps 416 to 418.

[0148] After the SN status transmission and data forwarding have been sent and the CHO is ready to release, the path switch for the UE is completed in step 621.

[0149] Some examples may provide the complete RRC configuration to the UE in step 611. In other examples, the UE may store the RRC configuration of the initial source cell and apply the prepared incremental configuration of the candidate cell based on this.

[0150] It should be noted that in case the cells involved are handled by the same central unit, the security keys may not be changed.

[0151] In some examples, the new serving cell (the target cell for which the CHO execution condition is met) or the source cell of the CHO may notify other prepared candidate target cells of the serving cell change. In some examples, this may include notifying other prepared candidate target cells of the cell identity (physical cell identity (PCI) or NR global cell identity (NCGI)) of the new serving cell.

[0152] refer to Figure 7 , which shows the CHO process according to some examples. In this example, the UE target cell can be notified of the cell change via interaction with the source cell.

[0153] Figure 7 The process starts from steps 701 to 715, which corresponds to Figure 6 Steps 601 to 615.

[0154] In step 716, the UE provides an RRC Reconfiguration Complete (HO Complete) to the target node.

[0155] In step 717, the target node sends a message indicating successful handover (eg, HO success) to the source node. Since the CHO request (ie, message 703) has been sent by the source node, the target node may know the source node.

[0156] In step 718, the source node stops transmitting to or receiving from the UE.

[0157] In step 719a, the source node may inform all other target candidate cells of the serving cell change except the cell to which the UE has been handed over. Thus, the target cells will know the cell identity (PCI or NGCI) of the new serving node.

[0158] Alternatively, in step 719b, the target node may inform all other potential target cells of the UE's serving cell change. Thus, the target cells will know the cell identity of the new serving node.

[0159] Steps 720 to 722 follow Figure 6 Steps 619 to 621.

[0160] Some examples may provide the complete RRC configuration to the UE in step 711. In other examples, the UE may store the RRC configuration of the initial source cell and apply the prepared incremental configuration of the candidate cell based on this.

[0161] It should be noted that in case the cells involved are handled by the same central unit, the security keys may not be changed.

[0162] In some examples, the initial source cell may notify the prepared cell of the serving cell change each time a HO success message is received. In these examples, the target cell for which the CHO execution condition is satisfied may send a HO success message to the initial source cell. Thus, the initial source cell may act as an anchor point to relay the HO success to the prepared cell and also relay the HO cancellation request from the candidate target cell to the correct serving cell.

[0163] refer to Figure 8, which shows a CHO procedure according to some examples. In this example, the initial source cell acts as an anchor point for successfully relaying the HO to the serving cell during each handover process by maintaining the latest serving cell table of the UE.

[0164] Figure 8 The process starts from steps 801 to 817, which correspond to Figure 7 Steps 701 to 717.

[0165] In step 818, the source node that is ready for CHO determines whether the source node needs to relay an indication of handover success to other target nodes. For example, the source node may maintain a table of the latest serving cells of the UE and use the table in the determination at step 818. In this example, the latest serving cell is the source node, so no HO success relay message is required.

[0166] The UE then connects to target node 1 and may decide to perform a CHO to target node 2, for example using steps 819 to 823.

[0167] In step 820 , the UE evaluates the CHO condition while being served by the target node 1 and exchanging user data with the target node 1 .

[0168] In steps 821 to 822 , once the conditions for the CHO target cell are met, the UE performs RACH signaling to the target cell for which the CHO conditions are met, which is the target node 2 in this example.

[0169] Once the RACH is completed, the UE sends a message, such as an RRC Reconfiguration Complete (HO Complete) message, to the target node in step 823 .

[0170] In step 824, the target node 2 provides a HO success message to the prepared source node requesting the CHO configuration.

[0171] In step 825, the source node that prepares the CHO and maintains the latest serving cell table of the UE (from the latest received HO success) identifies that the latest serving cell is cell 1 controlled by target node 1, and therefore determines that an indication of the current serving cell needs to be sent to target node 1, for example in a handover success relay message.

[0172] In step 826 , in response to the identification and determination in step 825 , the source node sends a HO success relay message to the target node 1 .

[0173] The HO success relay message may include information about the UE's new serving cell (ie, the target cell to which the UE has performed random access in steps 821 to 824), so that SN status transmission and data forwarding can be initiated from the current serving cell to the target cell.

[0174] At step 827, target node 1 stops transmitting to and receiving from the UE.

[0175] Steps 828 to 830 follow Figure 7 Steps 720 to 722.

[0176] Some examples may provide the complete RRC configuration to the UE in step 811. In other alternative implementations, the UE may store the RRC configuration of the initial source cell and apply the incremental configuration based on this.

[0177] It should be noted that in case the cells involved are handled by the same central unit, the security keys are not changed, which simplifies the procedure.

[0178] In some examples, one of the target cells may decide to cancel the HO preparation for CHO. The initial source cell may act as an anchor point to relay this message to other target nodes. An example process for relaying the cancellation of HO preparation is described in Fig. 9 is displayed.

[0179] exist Fig. 9 In the example of , there are an initial source node, target node 1 (which is the current source node) and target cell 2 (which is a candidate target node for the UE). Initially, as shown at 900, the UE exchanges user data with target node 1.

[0180] At step 901, the target node 2 sends a HO cancellation message to the original source node.

[0181] At step 902, the initial source node checks whether the network node controlling the current serving cell must be notified of the cancellation of HO in target node 2. In this case, the initial source node determines that target node 1 is the current source node and the cancellation of HO in target node 2 needs to be notified.

[0182] In step 903, the initial source node sends information about HO cancellation in the target node 2 to the target node 1. The information may include information about the PCI ID of the target node 2.

[0183] In some examples, if the target node has information about other prepared cells, the target node may additionally or alternatively send a HO cancellation message to the other prepared cells.

[0184] At step 904, in response to receiving the information about the HO cancellation in the target node 2, the target node 1 sends an RRC reconfiguration message to the UE. The RRC reconfiguration may enable the UE to remove the target node 2 as a possible option for conditional handover.

[0185] Therefore, in some examples, after the handover operation, the target node may be informed of which cell is currently serving the UE (ie, the current serving node). The target node may be informed by the initial source node, the new serving node, or the UE.

[0186] Thus, in some examples, when the UE performs a handover to a target cell, the target cell knows to which serving cell it should send a HO success message, thereby facilitating the handover and allowing SN state transfer and data forwarding to be performed correctly. In addition, examples may enable the target cell to identify which serving cell to contact in the event that the target cell wants to trigger a cancellation or modification of a CHO preparation.

[0187] In some examples, an apparatus is provided, comprising components for: receiving information indicating a current serving cell of a user equipment at a target cell; and performing, by the target cell, a handover of the user equipment from the current serving cell to the target cell, wherein the handover is based on the information indicating the current serving cell.

[0188] In some examples, the apparatus includes at least one processor and at least one memory, the at least one memory including computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: receive information indicating a current serving cell of a user equipment; and perform a handover of the user equipment from the current serving cell to a target cell, wherein the handover is based on the information indicating the current serving cell.

[0189] In some examples, an apparatus is provided, comprising components for: sending information indicating the current serving cell of the user equipment from the user equipment to the target cell when the user equipment performs a handover from the current serving cell to the target cell; and performing a handover of the user equipment from the current serving cell to the target cell at the user equipment, wherein the handover is based on the information indicating the current serving cell.

[0190] In some examples, the apparatus includes at least one processor and at least one memory, the at least one memory including computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: send information indicating the current serving cell of the user equipment to the target cell when the user equipment performs a handover from the current serving cell to the target cell; and perform a handover of the user equipment from the current serving cell to the target cell, wherein the handover is based on the information indicating the current serving cell.

[0191] In some examples, an apparatus is provided that includes components for sending information indicating a current serving cell of the user equipment to the target cell when the user equipment performs a handover from the current serving cell to the target cell.

[0192] In some examples, the apparatus includes at least one processor and at least one memory, the at least one memory including computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: send information indicating the current serving cell of the user equipment to the target cell when the user equipment switches from the current serving cell to the target cell.

[0193] It should be understood that the apparatus may include or be coupled to other units or modules for transmission and / or reception, such as a radio component or a radio head, etc. Although the apparatus has been described as one entity, the different modules and memories may be implemented in one or more physical or logical entities.

[0194] It should be noted that although some embodiments have been described in relation to embodiments of 5G networks, similar principles may be applied with respect to other networks and communication systems. Thus, although certain embodiments are described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, the embodiments may be applied to any other suitable form of communication system in addition to the communication system shown and described herein.

[0195] It is also noted herein that while the above describes example embodiments, there are numerous variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

[0196] In general, various embodiments may be implemented in hardware or dedicated circuit systems, software, logic, or any combination thereof. Certain aspects of the present disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device, but the present disclosure is not limited thereto. Although various aspects of the present disclosure may be illustrated and described in block diagrams, flow charts, or using other graphical representations, it is fully understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or combinations thereof.

[0197] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0198] (a) implemented solely in hardware circuitry (e.g., implemented solely in analog and / or digital circuitry) and

[0199] (b) a combination of hardware circuitry and software such as (where applicable):

[0200] (i) a combination of analog and / or digital hardware circuits and software / firmware and

[0201] (ii) any portion of hardware processor(s) with software (including digital signal processor(s), software and memory(s) that work together to enable a device (such as a mobile phone or server) to perform various functions and

[0202] (c) Hardware circuits and / or processor(s), such as microprocessor(s) or portion(s) of microprocessor(s), require software (e.g., firmware) to operate, but the software may not be present when the software is not required for operation.

[0203] This definition of circuitry applies to all uses of the term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term "circuitry" also covers, for example, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or network device, if applicable to the particular claim element.

[0204] The embodiments of the present disclosure may be implemented by computer software executable by a data processor of a mobile device (such as a processor entity), or by hardware, or by a combination of software and hardware. Computer software or programs (also referred to as program products) include software routines, applets and / or macros, which can be stored in a data storage medium readable by any device, and they include program instructions for performing specific tasks. A computer program product may include one or more computer executable components that are configured to perform an embodiment when the program is run. One or more computer executable components may be at least one software code or a portion thereof.

[0205] Furthermore, it should be noted in this regard that any block of the logic flow in the figure may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on physical media such as memory chips or memory blocks implemented within a processor, magnetic media such as hard disks or floppy disks, and optical media such as, for example, DVDs and their data variants CDs. Physical media are non-transient media.

[0206] The memory may be of any type suitable for the local technical environment and may 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 may be of any type suitable for the local technical environment and may include, as non-limiting examples, one or more of the following: a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an FPGA, a gate-level circuit, and a processor based on a multi-core processor architecture.

[0207] Embodiments of the present disclosure may be practiced in various components, such as integrated circuit modules. The design of integrated circuits is generally a highly automated process. Complex and powerful software tools are available to convert a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0208] The scope of protection sought by various embodiments of the present disclosure is defined by the independent claims. Embodiments and features described in this specification that do not belong to the scope of the independent claims (if any) should be interpreted as examples that help understand the various embodiments of the present disclosure.

[0209] The foregoing description has provided by way of non-limiting examples a complete and informative description of exemplary embodiments of the present disclosure. However, various modifications and adaptations may become apparent to those skilled in the relevant art in view of the foregoing description when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of the present disclosure will still fall within the scope of the present invention as defined in the appended claims. Indeed, there are additional embodiments that include a combination of one or more embodiments with any other embodiments previously discussed.

Claims

1. A device comprising components for: receiving, at the target cell, information indicating a current serving cell of the user equipment; and A handover of the user equipment from the current serving cell to the target cell is performed by the target cell, wherein the handover is based on the information indicating the current serving cell.

2. The device according to claim 1, wherein the component is used to: receiving, at the target cell, a conditional handover configuration for the user equipment from an initial source cell serving the user equipment; The performing of the switching is also based on the conditional switching configuration.

3. The device according to claim 2, wherein the component is used to: After the handover is completed, information indicating that the target cell is a new current serving cell of the user equipment is sent to one or more other cells.

4. The apparatus of any preceding claim, wherein the information indicative of the current serving cell of the user equipment is received from one of: the user equipment during the handover of the user equipment from the current serving cell to the target cell; the current serving cell during the handover of the user equipment from the current serving cell to the target cell; as well as The initial source cell during the handover of the user equipment from the current serving cell to the target cell.

5. The apparatus of any preceding claim, wherein performing the handover based on the information indicative of the current serving cell comprises: Based on the information indicating the current serving cell, state information associated with the user equipment and / or data buffered in the current serving cell are received from the current serving cell to be transmitted to the user equipment.

6. An apparatus comprising components for: When the user equipment performs a handover from the current serving cell to the target cell, sending information indicating the current serving cell of the user equipment from the user equipment to the target cell; and A handover of the user equipment from the current serving cell to the target cell is performed at the user equipment, wherein the handover is based on the information indicating the current serving cell.

7. The device according to claim 6, wherein the component is used to: receiving, at the user equipment, at least one conditional handover configuration for the user equipment from an initial source cell serving the user equipment; The performing of the switching is also based on the conditional switching configuration.

8. The apparatus according to claim 7, wherein the information indicating the current serving cell of the user equipment is included in a radio resource control reconfiguration complete message sent to the target cell when the handover is performed.

9. The device according to any one of claims 6 to 8, wherein the component is used to: storing a radio resource control configuration of the initial source cell; and When handover of the user equipment is performed, the change in the radio resource control configuration is applied over the radio resource control configuration of the initial source cell.

10. The apparatus of claim 7 or any claim dependent thereon, wherein the component is for: receiving a message from the current serving cell including an indication that one or more further target cells are no longer available for conditional handover of the user equipment; and The conditional handover configuration of the user equipment is updated based on the received message.

11. An apparatus comprising components for: When the user equipment switches from the current serving cell to the target cell, information indicating the current serving cell of the user equipment is sent to the target cell.

12. The apparatus of claim 11, wherein the apparatus comprises the current serving cell, and wherein the component is further configured to: receiving an indication from the target cell that a handover has been performed for the user equipment to the target cell; and In response to receiving the indication, state information associated with the user equipment and / or data buffered in the current serving cell are sent to the target cell for transmission to the user equipment.

13. The device according to claim 12, wherein the component is used to: receiving information from the initial source cell indicating that the one or more further target cells are no longer available for conditional handover of the user equipment; and A message is sent to the user equipment including an indication that the one or more further target cells are no longer available for conditional handover of the user equipment.

14. The apparatus of claim 12, wherein the apparatus comprises an initial source cell; and wherein the means is further configured to: A conditional handover configuration for the user equipment is sent to the target cell.

15. The device according to claim 14, wherein the component is used to: receiving, from the current serving cell, information indicating that the user equipment has been handed over to the current serving cell; storing, at the initial source cell, information identifying the current serving cell of the user equipment based on the received information; and The information indicating the current serving cell of the user equipment is sent to the target cell.

16. The device according to claim 14 or 15, wherein the component is used to: receiving, from one or more further target cells, information indicating that the one or more further target cells are no longer available for conditional handover of the user equipment; and A message is sent to the current serving cell including an indication that one or more additional target cells are no longer available for conditional handover of the user equipment.

Images