Handling condition switching preparation in failure scenarios

Abstract

The present disclosure relates, inter alia, to a user equipment. The user device may include at least one processor. The user device may also include at least one memory storing instructions. The instructions, when executed by the at least one processor, may cause the user device to perform receiving conditional switch 5 information from the first network node. The instructions, when executed by the at least one processor, may also cause the user equipment to perform at least a portion of the reservation conditional switching information during a reestablishment procedure following a failure to affect a radio link of the user equipment.

Description

Technical Field

[0001] Various example embodiments relate to wireless communication networks, and in particular to conditional handoffs in such networks. Background Art

[0002] In various wireless communication networks, mobility of wireless terminals (or user equipment, UE) is desired. Handover can be used to provide enhanced connectivity to UEs moving within a wireless communication network. Examples of wireless communication networks include cellular networks, such as networks operating according to Long Term Evolution (LTE) or 5G radio access technology. 5G radio access technology may also be referred to as new radio (NR) access technology. The Third Generation Partnership Project 3GPP develops standards for LTE and 5G / NR. One of the topics discussed within 3GPP is how to improve various technologies related to handover. Summary of the invention

[0003] Conditional Handover (CHO) has been introduced in 3GPP Rel.16 to improve mobility robustness, i.e., to improve connectivity of UEs moving within a geographical area served by a wireless communication network. The wireless communication network may include a plurality of cells, each of which may cover at least a portion of a geographical area served by the wireless communication network. Thus, each cell may be served by at least one base station (e.g., gNB or eNB) of the wireless communication network. Now, in the case of CHO, the wireless communication network may prepare a plurality of target cells located within the service area of ​​the wireless communication network to switch the UE from a source cell serving the UE (also referred to as a serving cell of the UE) to one of the target cells. To this end, the wireless communication network may provide CHO information, such as, for example, a CHO configuration and a CHO condition, to the UE, and may reserve resources for the UE at the target cell. Each CHO configuration may be associated with a corresponding CHO condition to be evaluated by the UE. When the CHO condition is met, the corresponding CHO configuration may be selected, and a handover (HO) from the serving cell to the target cell may be performed.

[0004] In this way, enhanced connectivity, i.e. improved mobility robustness, of UEs moving within a geographical area served by a wireless communication network may be achieved. In particular, by providing a CHO command (or CHO preparation) to the UE relatively early, i.e. before radio quality deteriorates, a failure in transmission of a measurement report triggering HO preparation and / or a failure in receiving a HO command may be avoided.

[0005] However, in scenarios with highly frequent HOs, for example when the UE stays in one serving cell for only a relatively short time, it may happen that the target cell fails to receive the measurement report that triggers CHO preparation or fails to provide the CHO command to the UE in a timely manner. This in turn may lead to radio link failure (RLF) and / or handover failure (HOF). In order to reduce the possibility of such RLF and / or HOF in scenarios with highly frequent handovers, a single CHO command can be used for more than one CHO so as to allow at least two consecutive CHOs based on a single CHO command. In other words, by using a single CHO command that allows at least two consecutive CHOs, the UE to which the CHO command is provided can perform two or more CHOs in succession without waiting for the wireless communication network to provide (multiple) additional CHO configurations after each handover. In this context, CHO preparation can be performed in particular together with neighboring cells for fast CHO (FCHO) execution, where the UE can evaluate the corresponding (sub) set of CHO conditions after each cell change (i.e., after each HO).

[0006] In this way, fast cell switching (FCS) between cells that have been prepared for FCHO can be enabled for the UE. This method is also called continuous CHO.

[0007] However, in case of failure, such as RLF due to CHO being performed too late to the target cell or HOF due to CHO being performed too early towards the target cell, the UE releases all CHO configurations and initiates a re-establishment procedure to connect to a cell of the wireless communication network, which may be a cell prepared for FCHO or a non-prepared cell. After completing the re-establishment procedure, all FCHO preparations have to be repeated, which results in additional delay and signaling overhead for the FCHO preparation procedure. Furthermore, after completing the re-establishment procedure, the UE will be prone to failure, since repeating (fast) CHO preparations after a failure may in turn result in a late reception of the CHO configuration by the UE, especially in FCS scenarios.

[0008] In view of the above, certain embodiments of the present disclosure may have the effect of providing improved handling of CHO preparation in failure scenarios. More specifically, certain embodiments may have the effect of avoiding repeating FCHO preparation after a failure, thereby avoiding additional delays and signaling overhead due to repeating FCHO preparation. In addition, certain embodiments may have the effect of updating FCHO preparation after a failure in an efficient manner, in particular with minimal signaling overhead. In addition, certain embodiments may have the effect of providing (fast) CHO configuration to the UE in a faster manner after a failure, which in turn enables the UE to perform CHO in a timely manner, thereby preventing the UE from experiencing (additional) failures after completing the reconstruction process.

[0009] According to a first exemplary aspect, a user equipment is disclosed. The user equipment may include at least one processor. The user equipment may also include at least one memory storing instructions. The instructions, when executed by the at least one processor, may cause the user equipment to perform receiving conditional handover information from a first network node. The instructions, when executed by the at least one processor, may also cause the user equipment to perform, during a reestablishment process after a failure of a radio link affecting the user equipment, retaining at least a portion of the conditional handover information.

[0010] According to a second exemplary aspect, a first network node is disclosed. The first network node may include at least one processor. The first network node may also include at least one memory storing instructions. The instructions, when executed by the at least one processor, may cause the first network node to send conditional handover information to a user equipment. The instructions, when executed by the at least one processor, may also cause the first network node to indicate to the user equipment that at least a portion of the conditional handover information is retained during a reestablishment process after a failure of a radio link affecting the user equipment.

[0011] According to a third exemplary aspect, a second network node is disclosed. The second network node may include at least one processor. The second network node may also include at least one memory storing instructions. The instructions, when executed by the at least one processor, may cause the second network node to receive a request from a user device to perform a reconstruction process, wherein the request includes an indication for identifying that the first network node is associated with the user device. The instructions, when executed by the at least one processor, may also cause the second network node to request context information for the user device from the first network node. The instructions, when executed by the at least one processor, may also cause the second network node to receive context information for the user device from the first network node, wherein the context information includes conditional switching information associated with the user device. The instructions, when executed by the at least one processor, may also cause the second network node to indicate to the first network node that at least a portion of the conditional switching information and / or at least a portion of the conditional switching resources that have been reserved for the user device are reserved.

[0012] According to each of the exemplary aspects, a corresponding method is also disclosed.

[0013] Thus, according to a first exemplary aspect, a method performed by a user equipment is disclosed. The method may include receiving conditional handover information from a first network node. The method may also include retaining at least a portion of the conditional handover information during a reestablishment procedure following a failure of a radio link affecting the user equipment.

[0014] According to a second exemplary aspect, a method performed by a first network node is disclosed. The method may include sending conditional handover information to a user equipment. The method may also include indicating to the user equipment that at least a portion of the conditional handover information is retained during a reestablishment process after a failure of a radio link affecting the user equipment.

[0015] According to a third exemplary aspect, a method performed by a second network node is disclosed. The method may include receiving a request from a user equipment to perform a reestablishment procedure, wherein the request includes an indication for identifying that a first network node is associated with the user equipment. The method may also include requesting context information for the user equipment from the first network node. The method may also include receiving context information for the user equipment from the first network node, wherein the context information includes conditional handover information associated with the user equipment. The method may also include indicating to the first network node that at least a portion of the conditional handover information and / or at least a portion of the conditional handover resources that have been reserved for the user equipment are retained.

[0016] Any of the disclosed devices (user equipment, network nodes) may be a fixed device or a mobile device. A user equipment may in particular be a terminal device, for example a mobile device, such as a smart phone, a tablet, a wearable device, a smart watch, a low-power device, an IoT device, an IIoT device, a vehicle, a truck, a drone, an airplane, etc. A user equipment may in particular be capable of communicating (sending and / or receiving signals and / or data to / from) one or more other user equipment and / or one or more network nodes (such as a base station of a wireless communication network). In general, a user equipment may be any device that enables communication with a wireless communication network and / or another user equipment.

[0017] A network node (e.g., a first network node or a second network node) may be understood as a wireless communication station installed at a fixed or mobile location, and may be an entity of a radio access network of a wireless communication system or an entity of a radio access network including a wireless communication system. For example, a network node may be a base station (e.g., gNB, eNodeB, NodeB, BTS, etc.) of a wireless communication network of any generation of 3GPP standards, including it or a part thereof. In general, a network node may be or include a hardware or software component that implements a specific function. For example, in an example, a network node may be a location management function LMF. In an example, a network node may be an entity (also referred to as a gNB) as defined by a 3GPP 5G or NR standard. Therefore, although a network node may be understood as being implemented in a single device or module or being a single device or module, a network node may also be implemented across multiple devices or modules or include multiple devices or modules. Therefore, a network node may be implemented in a fixed device or be a fixed device in particular. Multiple network nodes of an exemplary aspect may particularly establish a wireless communication system or network, which may particularly be an NR or 5G system (5GS) or any other wireless communication system defined by a past or future standard (particularly a successor to the current 3GPP standard). The network node of the example aspects may be capable of communicating directly and / or indirectly with the user equipment of the example aspects.

[0018] The components or functions of any of the disclosed devices or apparatuses (i.e., any of the user equipment and the first network node and the second network node) may be implemented in hardware and / or software. They may include one or more modules or units that provide the corresponding functions. They may, for example, include at least one processor for executing a computer program code for performing the desired function, at least one memory for storing the program code, or both. They may include, for example, a circuit designed to implement the desired function, such as implemented in a chipset or chip (such as an integrated circuit). Typically, the component may include, for example, one or more processing components or processors.

[0019] Specific components may be used to implement specific functions / functionalities / features, such as receiving components for receiving conditional switching information from a first network node; and / or retaining components for retaining at least a portion of the conditional switching information during a reestablishment process after a failure of a radio link affecting a user equipment (the components may be, for example, included by the user equipment). Additional examples of specific components may include, for example, sending components for sending conditional switching information to a user equipment; and / or indicating components for indicating to the user equipment that at least a portion of the conditional switching information is retained during a reestablishment process after a failure of a radio link affecting the user equipment (the components may be, for example, included by the first network node). Further examples of specific components may include, for example, a receiving component for receiving a request for performing a reestablishment procedure from a user equipment, wherein the request includes an indication for identifying that the first network node is associated with the user equipment; a requesting component for requesting context information for the user equipment from the first network node; a receiving component for receiving context information for the user equipment from the first network node, wherein the context information includes conditional switching information associated with the user equipment; and / or an indicating component for indicating to the first network node that at least a portion of the conditional switching information and / or at least a portion of the conditional switching resources that have been reserved for the user equipment is retained (the components may be included, for example, by the second network node).

[0020] Therefore, according to respective exemplary aspects of the present disclosure, in each case also a respective apparatus (ie user equipment, first network node, second network node) is disclosed, which comprises means for performing a method according to the respective aspect of the present disclosure.

[0021] However, any of the exemplary aspects disclosed above may generally be performed by an apparatus, which may be a component of a module or device, such as a chip. The disclosed apparatus may include the disclosed components, such as a part, a processor, a memory, or may further include one or more additional components.

[0022] According to exemplary aspects of the present disclosure, a computer program is also disclosed in each case, the computer program comprising instructions which, when executed by an apparatus, cause the apparatus to perform the method of the corresponding aspect.

[0023] The computer program may in each case be stored on a computer-readable storage medium, in particular a tangible and / or non-transitory medium. The computer-readable storage medium may be, for example, a disk or a memory or the like. The computer program may be stored in a computer-readable storage medium in the form of instructions encoding the computer-readable storage medium. The computer-readable storage medium may be intended for use in the operation of a device, such as an internal or external memory, such as a read-only memory (ROM) or a hard disk of a computer, or intended for distribution of the program, such as an optical disk.

[0024] According to exemplary aspects of the present disclosure, therefore, there is also disclosed in each case a computer-readable storage medium having the computer program of the respective aspect stored thereon.

[0025] The user equipment may be connected or connectable to one or more network nodes, in particular via a wireless communication link (also referred to as an air interface), such as, for example, a 5G / NR Uu interface. Being connected or connectable to a network node may, for example, mean that the user equipment is able to send / receive information and / or signals to / from the network node. Similarly, (multiple) network nodes may be able to send / receive information and / or signals to / from the user equipment. Each network node may be connected or connectable to at least one other network node, in particular via a wireless communication link (or air interface), such as, for example, a 5G / NR Xn interface. Each network node may be able to send / receive information and / or signals to / from at least one other network node.

[0026] As used herein, a cell may, for example, cover at least a portion of a geographical area served by a wireless communication network, in particular provide radio services for at least a portion of the geographical area. A cell may, for example, be associated with (e.g., served by) at least one network node. A serving cell may, for example, be understood as providing a radio service within a cell. Thus, a network node serving a cell may, for example, provide a radio service within a cell. In an example, a network node may be associated with (e.g., serve at least one cell).

[0027] As used herein, a handover between cell A and cell B may refer to a handover between cell A and cell B. Alternatively or additionally, a handover between cell A and cell B may refer to a handover between two network nodes (e.g., gNBs) associated with cells A and B, respectively, in particular wherein the network nodes serve cells A and B, respectively. In other words, a handover between cell A and cell B may alternatively or additionally refer to a handover between network node A and network node B, in particular wherein network node A is associated with (e.g., serves) cell A and / or wherein network node B is associated with (e.g., serves) cell B. Similarly, a handover between network node A and network node B may refer to a handover between network node A and network node B. However, alternatively or additionally, a handover between network node A and network node B may refer to a handover between cell A and cell B, in particular wherein cell A is associated with (e.g., served by) network node A and / or wherein cell B is associated with (e.g., served by) network node B. Therefore, when a handover between two cells is described hereinafter, it may alternatively or additionally be understood as a handover between two corresponding network nodes, and vice versa.

[0028] In preparing and / or using (fast) CHO, in certain failure scenarios, the described aspects may be advantageous in terms of at least one of speed, efficiency or robustness, compared to a scenario in which a repetition of all FCHO preparations is performed after a reestablishment procedure initiated by a UE for (re)connecting to a wireless communication network after a failure of a radio link affecting the UE has occurred (completed). More specifically, by retaining at least a portion of conditional handover information (e.g. associated with the UE) and / or conditional handover resources (e.g. reserved for the UE by a network node) during the reestablishment procedure after a failure of the radio link affecting the UE, the time and / or signaling overhead required to (re)enable FCHO for the UE may be reduced, in particular compared to first releasing all said information / resources and then repeating all FCHO preparations (i.e. obtaining / providing CHO information and / or reserving CHO resources). By reducing the required time and / or signaling overhead, the described aspects may allow for (re)enabling FCHO for the UE and / or updating the FCHO preparations of the UE in a faster and more efficient manner. Furthermore, since the described aspects may allow FCHO configuration to be provided to the UE more quickly than first releasing and then repeating all FCHO preparations, the UE may be prevented from experiencing further failures once the reestablishment process has been successfully completed.Thus, the described aspects may additionally allow for more robust FCHO.

[0029] Receiving conditional switching information from the first network node may, for example, be part of preparing one or more conditional switchings of the user equipment. Preparing one or more conditional switchings of the user equipment may, for example, be referred to as conditional switching preparation of the user equipment. Preparing one or more conditional switchings of the user equipment, i.e., conditional switching preparation of the user equipment, may include receiving conditional switching information by the user equipment and / or reserving conditional switching resources for the user equipment by at least one network node. The conditional switching preparation may, for example, prepare one or more conditional switchings of the user equipment within one or more network nodes for the user equipment and / or one or more network nodes. Therefore, the conditional switching preparation of the user equipment may, for example, allow the execution of one or more conditional switchings of the user equipment, in particular based on the conditional switching preparation of the user equipment. For example, the conditional switching preparation may be performed before one or more conditional switchings of the user equipment.

[0030] The conditional switching information may, for example, include or correspond to information supporting one or more conditional switchings. Switching may, for example, be understood as a change in the serving cell of the user equipment. The serving cell of the user equipment may, for example, serve the user equipment. In other words, switching may, for example, be understood as a process in which the UE switches from a first cell (currently) serving the UE to a second cell (thereafter) serving the UE. The serving cell may, for example, correspond to a serving cell defined in 3GPP specification 36.331. However, in other words, switching may, for example, be understood as a process in which an ongoing call or data session is transferred from one channel of the core network connected to the wireless communication network to another channel of the core network.

[0031] Conditional switching may be understood as switching that is performed or performed based on or in response to one or more switching conditions (or switching execution conditions) being satisfied. In other words, in the example, performing or performing conditional switching may include determining that one or more conditional switching conditions are satisfied, and performing or performing conditional switching based on or in response to determining that one or more conditional switching conditions are satisfied. To this end, in the example, the conditional switching information may include one or more conditional switching conditions and / or one or more conditional switching configurations. In the example, one or more conditional switching conditions may be provided by a network node currently serving the user equipment (e.g., a source gNB of the user equipment).

[0032] The conditional switching condition may, for example, include one or more (particularly one or two) triggering conditions for triggering switching. The triggering condition may be associated with a reference signal type, wherein, in an example, the triggering condition may be associated with a single reference signal type. The reference signal (corresponding to the reference signal type) may, for example, include or correspond to a channel state information reference signal (CSI-RS), a physical data shared channel demodulation reference signal (PDSCH DMRS), a physical downlink control channel demodulation reference signal (PDCCH DMRS), a physical broadcast channel demodulation reference signal (PBCH DMRS), a phase tracking reference signal (PTRS), a tracking reference signal, etc. The triggering condition may, for example, include at least one triggering amount. The triggering condition may particularly include up to two different triggering amounts. The triggering amount may, for example, correspond to a reference signal received power (RSRP), a reference signal received quality (RSRQ), a signal to interference plus noise ratio (SINR), etc. The triggering condition may be based on at least one threshold, at least one hysteresis and / or at least one offset, in particular wherein the threshold, hysteresis or offset is associated with at least one triggering amount. In an example, the conditional switching condition includes one or more measurement events. A measurement event may be understood, for example, as a predefined measurement report type, such as, for example, an A1, A2, A3, A4, A5, A6, B1 or B2 event, for example, according to 3GPP specification 38.331. In an example, the conditional switching condition may refer to a measurement ID that associates a measurement object with a reporting configuration. The measurement object may include or correspond to an object on which the user equipment should perform measurements. The reporting configuration may define a measurement event that triggers the execution of the conditional switching, in particular an A3 or A5 measurement event.

[0033] The conditional handover configuration may, for example, include or correspond to a configuration associated with a network node that allows a handover to be performed toward the network node. In an example, one or more conditional handover configurations may be provided by one or more network nodes toward which a handover should be performed, i.e., a target network node (e.g., a target gNB). In an example, applying a conditional handover configuration provided by such a target network node may result in performing a conditional handover toward the target network node. In other words, the conditional handover configuration may be used to perform or execute a conditional handover toward the target network node.

[0034] In the example, the conditional switching information may include or correspond to the fast or continuous conditional switching information supporting fast or continuous conditional switching. In this article, the terms fast conditional switching (FCHO) and continuous conditional switching (continuous CHO) are used interchangeably. For example, fast or continuous conditional switching can be performed between one or more cells prepared for fast or continuous conditional switching. In the example, fast or continuous conditional switching can enable the user equipment to switch cells between cells prepared for fast or continuous conditional switching (FCS). For this reason, in the example, the fast or continuous conditional switching information provided to the user equipment as part of a single command by the network node may, for example, include or correspond to the information supporting at least two continuous conditional switching. In other words, in the example, the user equipment can perform two or more continuous conditional switching based on the fast or continuous conditional switching information. Therefore, the user equipment can perform two or more continuous conditional switching without waiting for the wireless communication network to provide additional conditional switching information after each switching. In the example, the conditional switching preparation for fast or continuous conditional switching can be performed together with one or more adjacent cells of the service cell of the user equipment. For example, the adjacent cells of the service cell can be located adjacent to the service cell or located near the service cell. Being located nearby may for example mean that the distance between the neighboring cell and the serving cell is less than a predetermined distance threshold.In an example, when performing one or more rapid or continuous conditional handovers, the user equipment may evaluate a corresponding (sub)set of conditional handover conditions after each cell change, i.e. after each handover.

[0035] In an example, the reestablishment procedure may include or correspond to a procedure for reestablishing a radio link between a user equipment and a wireless communication network, in particular wherein the wireless communication network includes a first network node. The reestablishment procedure after a failure may, for example, mean that the reestablishment procedure is performed based on, in response to, after, or as a result of a failure. The reestablishment procedure may, for example, include at least one of: sending, by the user equipment, a request to perform a reestablishment procedure to a second network node; receiving, by the user equipment, a reestablishment message from the second network node; or sending, by the user equipment, a reestablishment completion message to the second network node. In an example, the reestablishment procedure may include or correspond to a radio resource control (RRC) connection reestablishment procedure.

[0036] Preserving at least a portion of the conditional switching information during the reconstruction process may, for example, mean preserving at least a portion of the conditional switching information in the following manner

[0037] - based on, in response to or following a request sent by the user equipment to the second network node for performing a re-establishment procedure;

[0038] - as part of or during a reconstruction process;

[0039] - until a reestablishment message is received by the user equipment from the second network node;

[0040] -until the user equipment sends a reestablishment completion message to the second network node;

[0041] - until the rebuilding process has been completed; and / or

[0042] - until the time that has elapsed since the free user equipment sent a request to the second network node for performing a re-establishment procedure exceeds a predetermined expiration time, in particular if the user equipment has not received a re-establishment message from the second network node within the predetermined expiration time.

[0043] The predetermined expiration time may, for example, include or correspond to a threshold time period. Sending a request by the user equipment to the second network node for performing a reestablishment procedure may, for example, include resending the request for performing a reestablishment procedure to the second network node at least once. If the user equipment does not receive a reestablishment message from the second network node within the predetermined expiration time, in particular despite resending the request at least once, the retained conditional handover information may, for example, be released by the user equipment. In this way, (storage) resources of the user equipment may not be allocated unnecessarily.

[0044] A failure of a radio link affecting the user equipment may correspond, for example, to a radio link failure or a handover failure. A radio link failure may, for example, be understood as a disconnection of the user equipment from the wireless communication network, in particular from the wireless communication network comprising the first network node. A handover failure may, for example, be understood as a radio link failure occurring during the execution of a handover of the user equipment, in particular from the first network node and / or towards a target network node.

[0045] The radio link affected by the failure may for example be a radio link between the user equipment and a wireless communication network, in particular wherein the wireless communication network comprises a first network node. The radio link may in particular be a radio link between the user equipment and the first network node. Alternatively, the radio link may be a radio link between the user equipment and a network node comprised by the wireless communication network and different from the first network node. For example, the user equipment may have performed one or more conditional handovers before the failure occurred.

[0046] In an example, the instructions, when executed by at least one processor, may also cause the user equipment to (particularly temporarily) store at least a portion of the conditional switching information that has been received by the user equipment from the first network node, particularly wherein storing at least a portion of the conditional switching information is performed before retaining at least a portion of the conditional switching information.

[0047] Retaining at least a portion of the conditional switching information during the reconstruction process does not exclude that at least a portion of the conditional switching information can be retained, for example (also) after the reconstruction process has been completed. Therefore, in the example, the user equipment can (even) retain at least a portion of the conditional switching information that has been retained during the reconstruction process (for example, continue) after the reconstruction process has been completed. In the example, the instruction, when executed by at least one processor, can also enable the user equipment to use at least a portion of the conditional switching information that has been (continuously) retained by the user equipment for one or more conditional switches that can be performed after the reconstruction process has been completed. By (re)using at least a portion of the retained conditional switching information, for example after the reconstruction process, the time and / or signaling overhead required to (re)enable FCHO for the UE can be advantageously reduced.

[0048] In an example, the instructions, when executed by at least one processor, may also cause the user equipment to send a measurement report to the first network node, in particular before receiving the conditional switching information from the first network node. The measurement report may, for example, include measurement information about at least one measurement quantity (e.g., RSRP, RSRQ, SINR, etc.). Sending the measurement report to the first network node may initiate conditional switching preparation of the user equipment. Therefore, the user equipment may receive the conditional switching information, for example, based on or in response to sending the measurement report to the first network node.

[0049] In an example, the instructions, when executed by at least one processor, may also cause the user equipment to monitor one or more conditional switching conditions included by the conditional switching information that has been received from the first network node. The monitored conditional switching conditions may, for example, include or correspond to conditional switching conditions for conditional switching from the first network node and / or at least one other network node, in particular, at least one other network node serving one or more neighboring cells of the cell served by the first network node. The user equipment may, for example, monitor the one or more conditional switching conditions based on or after receiving the conditional switching information from the first network node. In addition, the user equipment may, for example, monitor the one or more conditional switching conditions before a failure of a radio link affecting the user equipment.

[0050] In an example, the instructions, when executed by at least one processor, may also cause the user equipment to detect a failure of a radio link affecting the user equipment. For example, the failure may be detected by the user equipment itself. For example, the user equipment itself may detect a radio link failure or a handover failure. Alternatively, detecting the failure may include receiving an indication that the failure has occurred by the user equipment. The indication may be provided, for example, by a wireless communication network, in particular by a wireless communication network including a first network node. In an example, the failure may be detected after the user equipment has received conditional handover information from the first network node and / or during monitoring of one or more conditional handover conditions.

[0051] Based on or in response to detecting the failure, the user equipment may, for example, initiate a reestablishment procedure for reestablishing a radio link between the user equipment and the wireless communication network, in particular wherein the wireless communication network comprises the first network node. To this end, the user equipment may, for example, select a network node with which the reestablishment procedure should be performed.

[0052] The instructions, when executed by at least one processor, may also cause the user device to perform:

[0053] - receiving from the first network node an indication to retain at least a part of the conditional handover information during a re-establishment procedure following a failure of the radio link affecting the user equipment, in particular wherein the indication is received together with the conditional handover information.

[0054] Receiving an indication of retaining at least a portion of the conditional switching information may, for example, be understood as being requested to retain at least a portion of the conditional switching information. Thus, in the example, the user equipment may retain at least a portion of the conditional switching information based on receiving the indication. However, alternatively or in addition, the user equipment (itself) may be (pre) configured and / or able to decide when to retain at least a portion of the conditional switching, in particular without receiving the corresponding indication. Receiving the indication may be advantageous because it allows retaining at least a portion of the conditional switching information, even if the user equipment (itself) may not be (pre) configured and / or unable to decide when to do so, such as it may be the case, for example, for older user equipment.

[0055] Receiving the indication together with the conditional switching information may, for example, be understood as receiving the indication together with, in conjunction with and / or simultaneously with the conditional switching information. Thus, for example, both the conditional switching information and the indication may be received as part of a single message received by the user equipment from the first network node. Receiving the indication together with the conditional switching information may be advantageous in terms of signaling time and signaling overhead. However, alternatively, the indication may be received separately from the conditional switching information, for example, the conditional switching information and the indication are received as part of at least two different messages received by the user equipment from the first network node.

[0056] The instructions, when executed by at least one processor, may also cause the user device to perform:

[0057] - detecting failure of a radio link affecting user equipment; and

[0058] - Based on the detected failure, retaining at least a portion of the conditional switching information.

[0059] In an example, the failure may be detected by the user equipment itself. For example, the user equipment itself may detect a radio link failure or a handover failure. Alternatively, detecting the failure may include receiving an indication that the failure has occurred. The indication may be provided, for example, by a wireless communication network, for example a wireless communication network including the first network node.

[0060] Retaining at least a portion of the conditional switching information based on detecting a failure can, for example, mean retaining at least a portion of the conditional switching information in response to detecting a failure or after detecting a failure. In other words, in the example, first a failure is detected, and then, in response to detecting a failure, retaining at least a portion of the conditional switching information.

[0061] As described above, retaining at least a portion of the conditional handover information after a failure advantageously reduces the time and signaling overhead required to (re)enable FCHO for a UE that has experienced a failure, compared to first releasing all information and then repeating all FCHO preparations after (completing) the re-establishment process after the failure.

[0062] The instructions, when executed by at least one processor, may also cause the user device to perform:

[0063] - determining that, for a network node that has been selected by the user equipment for the re-establishment procedure, no conditional handover information is included in the conditional handover information that has been received by the user equipment from the first network node; and

[0064] - Based on the determination, retaining at least a portion of the conditional switching information.

[0065] For the selected network node, no conditional switching information is included in the conditional switching information that has been received by the user equipment, which may, for example, mean that the selected network node is a network node that has not been previously prepared for conditional switching of the user equipment. In other words, determining that for the selected network node, no conditional switching information is included in the conditional switching information may include or correspond to determining that the selected network node is not yet ready for conditional switching of the user equipment. In contrast to releasing / deleting all conditional switching information, when a network node that is determined to be not yet ready for conditional switching of the user equipment is selected for the reestablishment process, as described above, retaining at least a portion of the conditional switching information after a failure is advantageous in terms of the time and signaling overhead required to (re)enable FCHO for the UE.

[0066] The instructions, when executed by at least one processor, may also cause the user device to perform:

[0067] - Receiving the replaced conditional switching information from the second network node, in particular wherein the replaced conditional switching information is received during a reestablishment process.

[0068] The replaced conditional switching information can be understood, for example, as the second conditional switching information, wherein the conditional switching information already received by the user equipment from the first network node can be understood as the first conditional switching information. As will be described in detail below, the replaced conditional switching can allow updating, supplementing and / or clearing the conditional switching information previously received by the user equipment. This method can be particularly faster and more efficient than first releasing all CHO information and then obtaining the CHO information again after (completing) the reconstruction process.

[0069] The replacement condition switching information may include:

[0070] - updated conditional handover information, used to update at least a part of the conditional handover information that has been received by the user equipment from the first network node;

[0071] - additional conditional handover information, wherein the additional conditional handover information is associated with at least one additional network node, for which at least one additional network node no conditional handover information is included in the conditional handover information already received by the user equipment from the first network node, in particular wherein the at least one additional network node includes or corresponds to the second network node; and / or - conditional handover release information, which indicates that at least a part of the conditional handover information already received by the user equipment from the first network node should be released.

[0072] The updated conditional switching information may specifically include or correspond to newer conditional switching information of at least one network node that has previously received the conditional switching information, in particular, the conditional switching information of at least one network node that has previously received the conditional switching information has expired or become invalid. At least a portion of the conditional switching information to be updated may specifically be a portion of the conditional switching information that has been retained by the user equipment or correspond to the conditional switching information (because information that has not yet been retained cannot be updated).

[0073] The additional conditional handover information may in particular not be part of or correspond to conditional handover information that has previously been received and / or retained by the user equipment. For at least one additional network node, no conditional handover information is included in the conditional handover information that has previously been received, which may, for example, mean that the at least one additional network node is a network node that has not previously been prepared for conditional handover of the user equipment. The additional conditional handover information being associated with the at least one additional network node may, for example, mean that the additional conditional handover information supports or enables one or more conditional handovers from and / or to the at least one additional network node.

[0074] The conditional handover release information may specifically identify one or more network nodes whose conditional handover information is to be released by the user equipment. At least a portion of the conditional handover information to be released may specifically be a portion of the conditional handover information already retained by the user equipment or correspond to the conditional handover information (because information that has not been retained cannot be released).

[0075] As part of the replaced conditional handover, receiving updated conditional handover information, additional conditional handover information and / or conditional handover release information may allow updating, supplementing and / or clearing conditional handover information that has previously been received by the user equipment. This approach may be faster and more efficient than first releasing all CHO information and then obtaining CHO information again after (completing) the reestablishment process.

[0076] The instructions, when executed by at least one processor, may also cause the user equipment, particularly during a reestablishment process, to execute based on the replaced conditional switching information:

[0077] - updating at least a part of the conditional handover information that has been received by the user equipment from the first network node;

[0078] - releasing at least part of the conditional handover information that has been received by the user equipment from the first network node; and / or

[0079] - storing additional conditional handover information associated with at least one additional network node for which no conditional handover information is included in the conditional handover information already received by the user equipment from the first network node, in particular wherein the at least one additional network node comprises or corresponds to the second network node.

[0080] At least a portion of the conditional switching information to be updated may be updated, for example, based on the updated conditional switching information. At least a portion of the conditional switching information to be released may be released, for example, based on the conditional switching release information. The additional conditional switching information to be stored may correspond to the additional conditional switching information included by the replaced conditional switching information.

[0081] By updating and / or releasing at least a portion of the conditional switching information and / or storing additional conditional switching information, in particular during a reestablishment process following a failure of a radio link affecting the user equipment, FCHO preparations of the user equipment may be performed and updated in a more efficient manner than repeating all FCHO preparations after the reestablishment process is complete, as described above.

[0082] In an example, the instructions, when executed by at least one processor, may further cause the user equipment to send a reestablishment completion message to the second network node, in particular wherein the reestablishment completion message confirms that the reestablishment process has been completed. The reestablishment completion message may be sent in particular based on or in response to receiving the replaced conditional switching information from the second network node.

[0083] In an example, the instruction, when executed by at least one processor, may also cause the user equipment to monitor one or more conditional switching conditions included by the conditional switching information that has been retained and / or updated by the user equipment and / or by the additional conditional switching information that has been (e.g., temporarily) stored by the user equipment. In an example, the user equipment may monitor one or more conditional switching conditions based on or in response to updating at least a portion of the conditional switching information and / or storing the additional conditional switching information. In addition, the user equipment may monitor one or more conditional switching conditions based on or after sending a reconstruction completion message to the second network node. As described above, in particular by (re)using at least a portion of the retained conditional switching information, the time and / or signaling overhead required to (re)enable FCHO for the UE may be advantageously reduced.

[0084] If during monitoring of one or more conditional switching conditions, the conditional switching condition is met, the user equipment may perform the corresponding switching. Therefore, the instructions, when executed by at least one processor, may also cause the user equipment to determine that one or more conditional switching conditions are met, and based on or in response to determining that one or more switching conditions are met, perform the corresponding conditional switching, for example, by applying the corresponding conditional switching configuration.

[0085] After performing a conditional switch based on or in which one or more conditional switching conditions have been determined by the user equipment to be satisfied, the user equipment may, for example, (again) monitor one or more conditional switching conditions included in the conditional switching information already retained and / or updated by the user equipment and / or included in the additional conditional switching information already (e.g., temporarily) stored by the user equipment.

[0086] Sending the conditional handover information by the first network node to the user equipment may for example be part of preparing one or more conditional handovers of the user equipment, as described above.

[0087] The first network node indicating to the user equipment to retain at least a part of the conditional handover information may, for example, mean that the first network node requests, requires or causes the user equipment to retain at least a part of the conditional handover information.

[0088] In an example, the instructions stored by at least one memory included by the first network node, when executed by at least one processor included by the first network node, may also cause the first network node to receive a measurement report from the user equipment, in particular before sending the conditional switching information to the user equipment. In an example, receiving the measurement report may cause the first network node to prepare one or more conditional switchings of the user equipment, i.e., perform conditional switching preparation of the user equipment. Therefore, the first network node may, for example, send the conditional switching information to the user equipment based on or in response to receiving the measurement report from the user equipment.

[0089] To this end, the first network node may, for example, send a request to at least one further network node for preparing one or more (fast) conditional handovers of the user equipment, in particular wherein the at least one further network node may be a neighboring network node of the first network node. As part of or in conjunction with the request for preparing one or more conditional handovers of the user equipment, the first network node may request the at least one further network node to provide conditional handover information and / or to reserve conditional handover resources for the user equipment.

[0090] The first network node may also receive conditional switching information from at least one further network node, in particular based on or in response to requesting the conditional switching information. The received conditional switching information may, for example, support one or more conditional switchings of the user equipment from any one of the first network node and the at least one further network node to any other of the first network node and the at least one further network node (e.g., from the first network node to one of the at least one further network node, from one of the at least one further network node to the first network node, and / or from one of the at least one further network node to another of the at least one further network node).

[0091] In an example, the first network node may also receive a request to retrieve information about the context of the user equipment from a second network node that has received a request from the user equipment to perform a reestablishment procedure. Based on or in response to receiving the request to retrieve information about the context of the user equipment, the first network node may also send the context information of the user equipment to the second network node.

[0092] The indication to retain at least a portion of the conditional handover information may be sent together with the conditional handover information or separately from the conditional handover information.

[0093] Sending the indication together with the conditional switching information may, for example, be understood as sending the indication together with the conditional switching information, in conjunction with and / or simultaneously. Therefore, the conditional switching information and the indication may, for example, both be sent as a part of a single message sent by the first network node. Sending the indication together with the conditional switching information may be advantageous in terms of signaling time and signaling overhead. Sending the indication separately from the conditional switching information may, for example, be understood as sending the conditional switching information and the indication as a part of at least two different messages. The latter may be advantageous in terms of complying with bandwidth or message size restrictions.

[0094] The instructions stored by at least one memory included by the first network node, when executed by at least one processor included by the first network node, may further cause the first network node to execute:

[0095] - indicating to the user equipment that if a network node is selected by the user equipment for the reestablishment procedure for which no conditional handover information is included in the conditional handover information already sent by the first network node to the user equipment, at least a part of the conditional handover information is retained.

[0096] Similar to the above, for the selected network node, no conditional switching information is included in the conditional switching information that has been sent by the first network node to the user equipment, which may, for example, mean that the selected network node is a network node that has not been previously prepared for conditional switching of the user equipment. In contrast to the scenario of releasing / deleting all conditional switching information, when a network node that is determined to be not yet ready for conditional switching of the user equipment is selected for the reestablishment process, retaining at least a portion of the conditional switching information after a failure is advantageous in terms of the time and signaling overhead required to (re)enable FCHO for the UE.

[0097] The instructions stored by at least one memory included by the first network node, when executed by at least one processor included by the first network node, may further cause the first network node to execute:

[0098] - retaining at least a portion of the conditional handover information associated with the user equipment and already stored by the first network node; and / or

[0099] - reserving at least a portion of the conditional handover resources that have been reserved by the first network node for the user equipment.

[0100] In addition to the conditional switching information that can be received, stored and / or retained by the user equipment, the first network node can also store the conditional switching information associated with the user equipment. In other words, in the example, the instructions can also cause the first network node to store the conditional switching information associated with the user equipment. Storing the conditional switching information associated with the user equipment can be performed in particular before retaining at least a portion of the conditional switching information.

[0101] In addition, the first network node may reserve conditional handover resources for the user equipment. In other words, in the example, the instructions may also cause the first network node to reserve conditional handover resources for the user equipment. Reserving conditional handover resources for the user equipment may be performed in particular before reserving at least a portion of the conditional handover resources.

[0102] Reserving the reserved conditional handover resources may, for example, be understood as continuously reserving the conditional handover resources.

[0103] In an example, the first network node may retain at least a portion (particularly all) of the conditional handover information associated with the user equipment and already stored by the first network node and / or at least a portion (particularly all) of the conditional handover resources already reserved by the first network node for the user equipment in the following manner:

[0104] - based on, in response to or following detection of a failure of a radio link affecting the user equipment;

[0105] - based on, in response to or following receipt of an indication that a re-establishment procedure following a failure of a radio link affecting the user equipment has been initiated by the user equipment;

[0106] - as part of or during the reconstruction process;

[0107] - until the rebuilding process has been completed; and / or

[0108] - until the time that has elapsed since the failure was detected exceeds a predetermined expiry time, in particular if the first network node has not received an indication to retain the conditional handover information and / or the conditional handover resources within the predetermined expiry time.

[0109] Similar to the above, for example, the first network node itself can detect the failure. For example, the first network node itself can detect a radio link or switching failure that affects the radio link of the user equipment. Alternatively, detecting the failure can include receiving an indication that the failure has occurred by the first network node. The indication can be provided, for example, by a wireless communication network, in particular by a wireless communication network including the first network node. In particular, the indication can be provided by a second network node that has been selected by the user equipment to perform the reconstruction process. In an example, the failure can be detected after the first network node has sent conditional switching information to the user equipment. Similar to the above, the predetermined expiration time can, for example, include or correspond to a threshold time period. Therefore, in an example, the first network node can specifically retain at least a portion (e.g., all) of the conditional switching information and / or at least a portion (e.g., all) of the conditional switching resources (at least) until the reconstruction process has been completed.

[0110] In addition, in an example, the first network node may, for example, during the reconstruction process, (even) after the reconstruction process has been completed, (e.g., continue to) retain at least a portion of the conditional switching information and / or the conditional switching resources that have been reserved. To this end, the first network node may, for example, receive an (e.g., implicit) indication of the corresponding portion of the conditional switching information and / or the conditional switching resources that have been selected to be retained (even) after the reconstruction process has been completed. Therefore, in an example, the first network node may, for example, during the reconstruction process, based on or in response to, for example, receiving the (e.g., implicit) indication from the second network node, (e.g., continue to) retain at least a portion of the conditional switching information and / or the conditional switching resources. In an example, the (continuously) retained conditional switching information and / or at least a portion of the (continuously) retained conditional switching resources may then be used for at least one conditional switching that may be performed after the reconstruction process has been completed.

[0111] By retaining, by the first network node, conditional handover information associated with the user equipment and / or at least a portion of conditional handover resources reserved by the first network node for the user equipment, rather than first releasing all of said information / resources and then repeating all FCHO preparations, the time and / or signaling overhead required to (re)enable FCHO for the user equipment may be reduced, in particular after a failure of a radio link affecting the user equipment has occurred.

[0112] The instructions stored by at least one memory included by the first network node, when executed by at least one processor included by the first network node, may further cause the first network node to execute:

[0113] - receiving an instruction to perform at least one of the steps of claim 11 from the second network node, in particular during a reconstruction process, in particular wherein the instructions, when executed by at least one processor, cause the first network node to perform one or more of the steps of claim 11 based on receiving one or more corresponding instructions from the second network node.

[0114] Similar to the above, receiving an indication to perform one or more steps may, for example, be understood as being requested to perform one or more steps. The indication may, for example, include an indication of at least one start time, at least one end time and / or at least one time period for retaining at least a portion of the conditional switching information and / or conditional switching resources, as described above (e.g., after detecting a failure of the radio link affecting the user equipment, during the reestablishment process and / or until the reestablishment process has been completed). In addition, the indication may include an indication to retain at least a portion of the conditional switching information and / or conditional switching resources (even) after the reestablishment process has been completed (e.g., continue), as described above. As an alternative or in addition to receiving an indication, the first network node (itself) may be (pre-)configured and / or able to decide when to perform one or more of the steps according to claim 11, in particular without receiving a corresponding indication. However, receiving the indication may be advantageous because it allows the steps to be performed even if the first network node (itself) may not be (pre-)configured and / or unable to decide when to perform the steps, which may be the case, for example, for older network nodes.

[0115] The instructions stored by at least one memory comprised by the first network node, when executed by at least one processor comprised by the first network node, may further cause the first network node to send, to the second network node, in particular during a reconstruction process:

[0116] - updated conditional switching information, used to update at least a part of the conditional switching information that has been sent by the first network node to the user equipment and / or for updating at least a part of the conditional switching information associated with the user equipment and already stored by the second network node, in particular wherein the updated conditional switching information is associated with the first network node; and / or - additional conditional switching information associated with at least one additional network node, for which no conditional switching information is included in the conditional switching information that has been sent by the first network node to the user equipment, in particular wherein the additional conditional switching information is associated with the first network node and with the second network node.

[0117] Similar to the above, the updated conditional switching information may specifically include or correspond to newer conditional switching information of at least one network node that has previously received the conditional switching information, in particular, the conditional switching information of at least one network node that has previously received the conditional switching information has expired or become invalid. At least a portion of the conditional switching information to be updated may specifically be a portion of the conditional switching information that has been retained by the user equipment or correspond to the conditional switching information (because information that has not yet been retained cannot be updated).

[0118] Also similar to the above, the additional conditional switching information may not be part of or correspond to the conditional switching information that has been previously received and / or retained by the user equipment. For at least one additional network node, no conditional switching information is included in the conditional switching information that has been previously received, which may, for example, mean that the at least one additional network node is a network node that has not been previously prepared for conditional switching of the user equipment. The additional conditional switching information is associated with at least one additional network node, which may, for example, mean that the additional conditional switching information supports or enables one or more conditional switchings from and / or to at least one additional network node. Therefore, the additional conditional switching information is associated with the first network node and with the second network node, which may, for example, mean that the additional conditional switching information supports or enables one or more conditional switchings between the first network node and the second network node.

[0119] Sending the updated and / or additional conditional switching information to the second network node may allow updating and / or supplementing the conditional switching information stored by the second network node for the user equipment. Alternatively or in addition, the second network node may communicate at least a portion of the updated and / or additional conditional switching information to the user equipment, for example as part of the replaced conditional switching information, thereby allowing updating of the conditional switching information that has previously been sent by the first network node to the user equipment.

[0120] The request for performing the reestablishment procedure that has been received by the second network node from the user equipment may, for example, include or correspond to an RRC connection reestablishment request. The request including an indication for identifying that the first network node is associated with the user equipment may, for example, mean that the request includes an indication for identifying the last serving node of the user equipment. The last serving node of the user equipment may, for example, correspond to a serving node that served the user equipment before and / or until a failure of the radio link affecting the user equipment occurred. In an example, the request for performing the reestablishment procedure may be sent by the user equipment to the second network node based on, in response to, after, or as a result of such a failure.

[0121] The context information of the user equipment may, for example, include or correspond to information about the context of the user equipment. The UE context may be an information block in a network node associated with the corresponding active UE. The information block may include necessary information required to maintain one or more services towards the active UE, such as UE status information, security information, UE capability information and / or an identification of a connection associated with the UE. Requesting context information for the user equipment from the first network node may, for example, include or correspond to sending a request to the first network node to retrieve information about the context of the user equipment. Receiving context information for the user equipment from the first network node may, for example, include or correspond to receiving information about the context of the user equipment, for example as part of a context retrieval response sent by the first network node to the second network node.

[0122] Based on the indication from the second network node to the first network node to retain at least a portion of the conditional handover information associated with the user equipment and / or at least a portion of the conditional handover resources that have been reserved for the user equipment, the first network node may retain at least a portion of the conditional handover information and / or at least a portion of the conditional handover resources. Thus, as described above, the time and / or signaling overhead required to (re)enable FCHO for the user equipment may be reduced, in particular after a failure of a radio link affecting the user equipment has occurred.

[0123] Indicating to the first network node that at least a portion of the conditional switching information and / or at least a portion of the conditional switching resources are retained may, for example, include indicating to the first network node at least one start time, at least one end time and / or at least one time period for retaining at least a portion of the conditional switching information and / or at least a portion of the conditional switching resources, as described above (e.g., after detecting a failure of the radio link affecting the user equipment, during the reconstruction process and / or until the reconstruction process has been completed). In addition, the indication may include an indication to retain at least a portion of the conditional switching information and / or the conditional switching resources (even) after the reconstruction process has been completed (e.g., continue), as described above. In the example, the (persistently) retained conditional switching information and / or at least a portion of the (persistently) retained conditional switching resources can then be used for at least one conditional switching that can be performed after the reconstruction process has been completed.

[0124] In an example, the second network node may also receive a request from the first network node for preparing one or more (fast) conditional handovers of the user equipment, in particular before receiving a request from the user equipment to perform a reestablishment procedure and / or before a failure of a radio link affecting the user equipment.

[0125] Based on or in response to receiving a request for preparing one or more (fast) conditional handovers, the second network node may, for example, send conditional handover information to the first network node and / or may reserve conditional handover resources for the user equipment. The sent conditional handover information may, for example, support one or more conditional handovers of the user equipment from any one of the first network node and at least one further network node to the second network node and / or from the second network node to any one of the first network node and at least one further network node (e.g., from the first network node to the second network node, from any one of the at least one further network node to the second network node, from the second network node to the first network node, and / or from the second network node to any one of the at least one further network node).

[0126] The conditional handover information received by the second network node as part of the context information may not include conditional handover information of the second network node.

[0127] In other words, in the example, the second network node may be a network node that was not previously ready for conditional handover of the user equipment. Compared to a scenario in which all conditional handover preparations (e.g., stored CHO information and / or resources reserved for CHO) are released, the described method is advantageous when it is determined that a network node that is not yet ready for conditional handover of the user equipment is selected for the reestablishment process (e.g., which may be the case for the second network node). By indicating to the first network node that at least a portion of the conditional handover information and / or at least a portion of the conditional handover resources are retained even if the network node that has been selected for the reestablishment process is a non-ready node, the time and / or signaling overhead required to (re)enable FCHO for the user equipment can be advantageously reduced, particularly after a failure of a radio link affecting the user equipment has occurred.

[0128] The instructions stored by at least one memory included by the second network node, when executed by at least one processor included by the second network node, may also cause the second network node to execute:

[0129] - Selecting the conditional handover information to be retained or to be released and / or the corresponding part of the conditional handover resources already reserved for the user equipment.

[0130] Therefore, the second network node can, for example, select a portion of the conditional handover information to be retained, a portion of the conditional handover information to be released, a portion of the conditional handover resources to be retained, and / or a portion of the conditional handover resources to be released. In other words, the second network node can decide which (which) parts of the conditional handover preparation of the user equipment are to be maintained and which parts are to be released. By letting the second network node (i.e., the network node to which the user equipment is reestablished) select (or decide) which (which) parts of the conditional handover preparation are to be retained and which parts are to be released, the selection / decision can be performed particularly during the reconstruction process, which is particularly beneficial for updating and / or (re)enabling FCHO during the reconstruction process.

[0131] The instructions stored by at least one memory included by the second network node, when executed by at least one processor included by the second network node, may also cause the second network node to execute:

[0132] - Indicating to the first network node the part of the conditional handover information and / or the conditional handover resources that has been selected to be released.

[0133] Indicating to the first network node the portion of the conditional handover information and / or conditional handover resources that have been selected to be released may in particular include implicitly indicating the portion of the conditional handover information and / or conditional handover resources that have been selected to be retained. For example, if the second network node indicates to the first network node that conditional handover information and / or resources associated with a network node different from the first network node have been selected to be released, this may be an implicit indication to the first network node that the conditional handover information associated with the user equipment and already stored by the first network node and / or the conditional handover resources that have been reserved by the first network node for the user equipment should be retained.

[0134] Therefore, based on receiving the indication from the second network node, the first network node may, for example, retain at least a portion of the conditional switching information associated with the user equipment that has been stored by the first network node and / or at least a portion of the conditional switching resources that have been reserved for the user equipment by the first network node. Alternatively or additionally, based on receiving the indication from the second network node, the first network node may, for example, indicate to at least one other network node associated with the portion of the conditional switching information and / or conditional switching resources that has been selected to be released, to release the conditional switching information associated with the user equipment and that has been stored by at least one other network node, and / or to release the conditional switching resources that have been reserved for the user equipment by at least one other network node. In other words, in the example, the first network node may pass the indication to at least one other network node, in particular, wherein the conditional switching information and / or conditional switching resources associated with at least one other network node have been selected to be released.

[0135] The instructions stored by at least one memory included by the second network node, when executed by at least one processor included by the second network node, may also cause the second network node to execute:

[0136] - Instruct at least one other network node associated with the conditional switching information and / or part of the conditional switching resources that have been selected to be released to release the conditional switching information associated with the user equipment and already stored by at least one other network node, and / or to release the conditional switching resources that have been reserved for the user equipment by at least one other network node.

[0137] Therefore, as an alternative or in addition to the first network node communicating an indication of the portion of the conditional switching information and / or resources that has been selected to be released to at least one further network node (as described above), in an example, the second network node (itself) may indicate to at least one further network node the portion to be released. Indicating to at least one further network node the portion to be released by the second network node itself (in particular directly) requires less signaling overhead and time than first providing a corresponding indication to the first network node and then communicating the indication to at least one further network node by the first network node.

[0138] The instructions stored by at least one memory included by the second network node, when executed by at least one processor included by the second network node, may also cause the second network node to receive from the first network node:

[0139] - updated conditional switching information for updating at least a portion of conditional switching information that has been sent by the first network node to the user equipment and / or for updating at least a portion of conditional switching information that has been received by the second network node as part of context information, in particular wherein the updated conditional switching information is associated with the first network node; and / or - additional conditional switching information associated with at least one additional network node, for which no conditional switching information is included in the conditional switching information that has been sent by the first network node to the user equipment, in particular wherein the additional conditional switching information is associated with the first network node and with the second network node.

[0140] The updated conditional switching information and / or additional conditional switching information received by the second network node from the first network node may specifically correspond to the updated conditional switching information and / or additional conditional switching information sent by the first network node to the second network node, as already described above.

[0141] Receiving such updated and / or additional conditional switching information may in particular allow updating and / or supplementing conditional switching information already received by the second network node as part of the context information. Alternatively or in addition, the second network node may communicate at least a portion of the updated and / or additional conditional switching information to the user equipment, for example as part of the replaced conditional switching information, thereby allowing updating of conditional switching information that has previously been sent by the first network node to the user equipment.

[0142] The instructions stored by at least one memory included by the second network node, when executed by at least one processor included by the second network node, may also cause the second network node to indicate to at least one further network node associated with the user equipment and / or with the first network node:

[0143] - The user equipment is now served by the second network node;

[0144] - retaining at least a portion of the conditional handover information associated with the user equipment and already stored by at least one further network node; and / or

[0145] - reserving at least a portion of conditional handover resources that have been reserved for the user equipment by at least one further network node.

[0146] At least one further network node being associated with the user equipment and / or with the first network node may, for example, mean that at least one further network node is already prepared for conditional handover of the user equipment, in particular handover from the first network node and / or handover to the first network node. In other words, in the example, at least one further network node has been included in the (fast) conditional handover preparation of the user equipment, the preparation having been performed, for example, before a failure of the radio link affecting the user equipment occurs. In the example, at least one further network node may therefore be a neighboring node of the serving node of the user equipment. In addition, at least one further network node may be particularly associated with a portion of the conditional handover information that has been selected by the second network node to be retained, as described above. In other words, at least one further network node may be a network node that the second network node has decided to retain in the (fast) conditional handover preparation of the user equipment.

[0147] Indicating that the user equipment is now served by the second network node may for example comprise or correspond to indicating that the second network node is a (new) serving node for the user equipment, for example as a result of a reestablishment procedure or after initiating a reestablishment procedure. In an example, the indication comprises or corresponds to sending an identifier of the (new) serving node.

[0148] Similar to the above, by retaining, by at least one further network node, at least a portion of the conditional switching information associated with the user equipment and already stored by the at least one further network node and / or at least a portion of the conditional switching resources already reserved for the user equipment by the at least one further network node, rather than first releasing all of the information / resources and then repeating all FCHO preparations, the time and / or signaling overhead required to (re)enable FCHO for the user equipment can be advantageously reduced, particularly after a failure.

[0149] The instructions stored by at least one memory included by the second network node, when executed by at least one processor included by the second network node, may also cause the second network node to execute:

[0150] - Requesting additional conditional handover information from at least one further network node associated with the user equipment and / or with the first network node, in particular wherein the additional conditional handover information is associated with the second network node and the at least one further network node.

[0151] Being associated with the second network node and at least one further network node may, for example, mean that the additional conditional handover information supports or enables one or more conditional handovers between the second network node and one or more of the at least one further network node. Based on or in response to the second network node requesting the additional conditional handover information from the at least one further network node, the at least one further network node may, for example, send the additional conditional handover information to the second network node. In this way, the FCHO preparation of the user equipment may be advantageously supplemented so as to efficiently include the (e.g., previously unprepared) second network node in the FCHO preparation of the user equipment.

[0152] The instructions stored by at least one memory included by the second network node, when executed by at least one processor included by the second network node, may also cause the second network node to execute:

[0153] -Send the changed conditional switching information to the user equipment.

[0154] The replaced conditional switching information sent by the second network node to the user equipment can specifically correspond to the replaced conditional switching information already received by the user equipment from the second network node, as described above. Similar to the above, sending the replaced conditional switching information to the user equipment allows avoiding repeating all FCHO preparations after completing the reestablishment process, which will cost additional delay and signaling overhead.

[0155] Based on or after sending the changed conditional switching information to the user equipment, the second network node may also receive a reestablishment completion message from the user equipment, in particular, wherein the reestablishment completion message confirms that the reestablishment process has been completed.

[0156] When the instructions stored by at least one memory included by the second network node are executed by at least one processor included by the second network node, the second network node may also instruct the user equipment to perform the switching information based on the replaced condition:

[0157] - updating at least a part of the conditional handover information that has been received by the user equipment from the first network node;

[0158] - releasing at least part of the conditional handover information that has been received by the user equipment from the first network node; and / or

[0159] - storing additional conditional handover information associated with at least one additional network node for which no conditional handover information is included in the conditional handover information already received by the user equipment from the first network node, in particular wherein the at least one additional network node comprises or corresponds to the second network node.

[0160] Based on the replaced conditional handover information, the steps of updating at least a portion of the conditional handover information, releasing at least a portion of the conditional handover information, and storing the additional conditional handover information have been described above for the user equipment. Therefore, it can be understood by analogy that the user equipment is instructed to perform these steps. Performing one or more of these steps allows the FCHO preparation of the user equipment to be performed and / or updated in a more efficient manner than repeating all FCHO preparations after completing the reconstruction process.

[0161] The instructions stored by at least one memory included in the second network node, when executed by at least one processor included in the second network node, may also cause the second network node to perform one or more of the steps of claims 14 to 23 under the following conditions:

[0162] - based on receiving a request for performing a reconstruction process;

[0163] - as part of, or during, a reconstruction process performed upon receipt of a request;

[0164] - before a re-establishment message sent based on the received request is received; and / or - before a re-establishment process performed based on the received request has been completed.

[0165] Performing a step based on receiving a request may, for example, mean first receiving a request and then performing the corresponding step. Performing a step as part of a reestablishment process or during a reestablishment process may, for example, mean that the reestablishment process includes the step. The reestablishment message may, for example, be an RRC connection reestablishment message. The reestablishment process has been completed may, for example, mean that a reestablishment complete message (e.g., an RRC connection reestablishment complete message) has been sent by the user equipment and / or has been received by the second network node.

[0166] As used herein, the conditional switching information associated with a specific network node may, for example, mean that the conditional switching information supports or enables one or more conditional switchings from and / or to the network node. In other words, the conditional switching information associated with a specific network node may include one or more conditional switching configurations of the network node and / or one or more conditional switching conditions of the network node.

[0167] As used herein, retaining information (e.g., retaining conditional switching information) may be understood as keeping or maintaining the information or continuing to store or save the information, particularly wherein the information may have been stored or saved (e.g., temporarily) before being retained. As further used herein, retaining resources (e.g., retaining conditional switching resources) may be understood as continuing to allocate resources, particularly wherein the resources may have been reserved or allocated, for example, by a network node, before being retained.

[0168] As used herein, updating information may be understood as modifying and / or replacing information based on newer information.

[0169] As used herein, releasing information may be understood as deleting information. As further used herein, releasing resources may be understood as de-allocating resources.

[0170] As used herein, an indication may, for example, include or correspond to a request, a message, or a query.

[0171] As used herein, executing a second step in response to a first step may, for example, mean that the second step may be executed directly in response to the first step, such as without any intermediate steps between the first and second steps. Alternatively, executing a second step in response to a first step may mean that the second step may be executed (only) after the first step, such as such that there may be at least one intermediate step between the first and second steps.

[0172] As used herein, at least a portion of a set or quantity, such as, for example, at least a portion of conditional switching information, can be understood as a portion of a set or quantity or the whole of a set or quantity. Therefore, at least a portion of the conditional switching information can, for example, be understood as a portion or all of the conditional switching information. Similarly, at least a portion of a conditional switching resource can, for example, be understood as a portion or all of a conditional switching resource.

[0173] It should be understood that the embodiments disclosed herein are presented by way of example only and not limitation.

[0174] In this article, the disclosure of a method step should also be regarded as the disclosure of a component for performing the corresponding method step. Similarly, the disclosure of a component for performing a method step should also be regarded as the disclosure of the method step itself.

[0175] Other features of the present disclosure will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It should be understood, however, that the drawings are designed for illustrative purposes only and not as a definition of the limitations of the present disclosure, for which reference should be made to the appended claims. It should also be understood that the drawings are not drawn to scale and that they are intended only to conceptually illustrate the structures and processes described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0176] Some example embodiments will now be described with reference to the accompanying drawings, in which

[0177] Figure 1 User equipment and various network nodes are exemplarily shown;

[0178] Figure 2 An example embodiment of a method according to the present disclosure is shown;

[0179] Figure 3 Another example embodiment of a method according to the present disclosure is shown;

[0180] Figure 4 Another example embodiment of a method according to the present disclosure is shown;

[0181] FIG. 5A to FIG. 5C An example of a signaling flow diagram related to an exemplary embodiment of the present disclosure is shown;

[0182] FIG. 6A to FIG. 6C Another example of a signaling flow diagram related to an exemplary embodiment of the present disclosure is shown;

[0183] Figure 7 A block diagram illustrating an example of a user device;

[0184] Figure 8 A block diagram illustrating an example of a network node; and

[0185] Fig. 9 A schematic diagram illustrating an example of a tangible and non-transitory computer-readable storage medium is shown. DETAILED DESCRIPTION

[0186] The following description is intended to deepen the understanding of the present disclosure, and should be understood to supplement and be read together with the description of example embodiments of the present disclosure as provided in the above Summary section of this specification.

[0187] In the following, an example wireless communication system is described, in which the present disclosure may be applied. Although the specific radio system in the following example is a 5G / NR system, this should only be regarded as a non-limiting example.

[0188] Figure 1 UE 100 (an example of a user equipment according to the first exemplary aspect), gNB 110 (an example of a first network node according to the second exemplary aspect), gNB 120 (an example of a second network node according to the third exemplary aspect) and gNBs 130, 140 (an example of further network nodes) are exemplarily shown. In summary, the gNBs establish a wireless communication system or network to serve the geographical area where UE 100 is located.

[0189] UE 100 may be connected to gNB 110 and / or gNB 120 via radio links 111 and 121, respectively (e.g., corresponding to 5G / NR Uu interfaces). Either of radio links 111, 121 may be considered as an example of a radio link that may be affected by a failure. Although not shown, UE 100 may also be connected to gNBs 130 and 140. gNB 110 is connected to each of gNBs 120, 130, 140 via corresponding radio links 112, 113, 114 (e.g., corresponding to 5G / NR Xn interfaces). Similarly, gNB 120 is connected to each of gNBs 110, 130, 140 via corresponding radio links 112, 123, 124. Each of radio links 111, 121, 112, 113, 114, 123, 124 is capable of sending / receiving information and / or signals between corresponding devices. gNBs 110, 120, 130, 140 may be regarded as neighboring gNBs serving neighboring cells, respectively.

[0190] At a certain point in time, as indicated by arrow 50, UE 100 moves from a first position (starting point of arrow 50) to a second position (end point of arrow 50). While at the first (left) position gNB 110 serves the serving cell of UE 100, at the second (right) position, the cell served by gNB 120 has become the serving cell of UE 100. Therefore, during the movement of UE 100 along arrow 50, for example, a handover of UE 100 from gNB 110 (or the corresponding cell) to gNB 120 (or the corresponding cell) may have been performed. Alternatively, during the movement of UE 100 along arrow 50, the radio link 111 between UE 100 and gNB 110 may have been affected by a failure. After the failure, UE 100 may have initiated a reestablishment procedure towards gNB 120 in order to reestablish a connection with the wireless communication network through radio link 121.

[0191] Figure 2 An example embodiment 200 of the method according to the first exemplary aspect is shown. The method 200 may be performed, for example, by a user equipment according to the first exemplary aspect. First, conditional handover information may be received from a first network node (action 210). Furthermore, at least a portion of the conditional handover information may be retained during a reestablishment procedure after a failure of a radio link affecting the user equipment (action 220).

[0192] Figure 3 An example embodiment 300 of a method according to the second exemplary aspect is shown. The method 300 may be performed, for example, by a first network node according to the second exemplary aspect. First, conditional handover information may be sent to a user equipment (action 310). Furthermore, the user equipment may be indicated to retain at least a portion of the conditional handover information during a reestablishment procedure after a failure of a radio link affecting the user equipment (action 320).

[0193] Figure 4 An example embodiment 400 of a method according to the third exemplary aspect is shown. The method 400 may be performed, for example, by a second network node according to the third exemplary aspect. First, a request for performing a reestablishment procedure may be received from a user equipment, wherein the request comprises an indication for identifying that a first network node is associated with the user equipment (action 410). Furthermore, context information for the user equipment may be requested from the first network node (action 420). Furthermore, context information for the user equipment may be received from the first network node, wherein the context information may comprise conditional switching information associated with the user equipment (action 430). Furthermore, the first network node may be indicated to retain at least a portion of the conditional switching information and / or at least a portion of the conditional switching resources that have been reserved for the user equipment (action 440).

[0194] In the following, in the description FIG. 5A to FIG. 5C and FIG. 6A to FIG. 6C Before describing two examples of signaling flow charts, the signaling process of CHO of UE from the first gNB / cell (gNB-1 / cell-1) to the second gNB / cell (gNB-2 / cell-2) is described below. It should be understood that this description is for illustrative purposes only and is not meant to be limiting in any way.

[0195] Prior to CHO, the UE may be served by cell-1 in gNB-1. First, the UE may send a measurement report to its serving cell (i.e., cell-1) to initiate CHO preparation of the target cell-2 in gNB-2. Cell-1 may then prepare the target cell-2 by sending a CHO request to cell-2 and by receiving a CHO request confirmation from cell-2. Cell-1 may then send the CHO preparation as well as the CHO execution conditions to the UE using an RRC reconfiguration message. After the RRC reconfiguration message has been sent, user data may still be exchanged between the UE and cell-1 in gNB-1.

[0196] Once the CHO execution conditions for the target cell-2 in the target gNB-2 are met (or achieved), the UE will disengage from its source cell-1, i.e. stop transmitting / receiving (TX / RX) to / from the source cell-1 in the source gNB-1.

[0197] The UE may then initiate a random access (or random access channel, RACH) procedure towards the target cell-2 by sending a PRACH preamble. In response to the PRACH preamble, the target cell-2 may send a RACH response to the UE. In response to the RACH response from the target cell-2, the UE may send an RRC reconfiguration complete to the target cell-2. Once the random access procedure is successfully completed, the target cell-2 may notify the source cell-1 of the successful completion of the handover procedure by sending a handover success indication.

[0198] After receiving the handover success indication from the target cell-2, the source cell-1 can initiate data forwarding (and path switching) to the target cell-2. Once the data forwarding (and path switching) process is completed, the UE can continue its data transmission / reception with the network, thereby completing the CHO of the UE from gNB-1 / cell-1 to gNB-2 / cell-2.

[0199] As already described above, a single CHO command can be used for more than one CHO in order to allow at least two consecutive CHOs based on a single CHO command. By using a single CHO command that allows at least two consecutive CHOs, the UE to which the CHO command is provided can perform two or more CHOs consecutively without waiting for the wireless communication network to provide additional (multiple) CHO configurations after each handover. Such continuous or fast CHO (FCHO) can enable fast cell switching (FCS) of the UE between cells that have been prepared for FCHO.

[0200] In the description FIG. 5A to FIG. 5C and FIG. 6A to FIG. 6CBefore describing two examples of signaling flow charts, the signaling process of FCHO of a UE that first switches from a first gNB / cell (gNB-1 / cell-1) to a second gNB / cell (gNB-2 / cell-2) and then switches to a third gNB / cell (gNB-3 / cell-3) is described below. It should be understood that this description is for illustrative purposes only and is not meant to be limiting in any way.

[0201] First, the UE may send a measurement report to its serving cell-1.

[0202] Then, cell-1 may initiate consecutive CHO (fast CHO) preparations: one preparation from cell-1 to cell-2, and another preparation from cell-3 to cell-2, which is a temporary CHO preparation, i.e., if the UE switches to cell-3, it may perform a subsequent handover from cell-3 to cell-2. To this end, cell-1 may send a FCHO request to cell-2.

[0203] Similarly, cell-1 may initiate CHO preparation for handover from cell-1 to cell-3 and from cell-2 to cell-3, wherein the latter is a temporary preparation. To this end, cell-1 may send a FCHO request to cell-3.

[0204] Cell-2 may then confirm the CHO preparation requested by Cell-1. To this end, Cell-2 may send an FCHO request confirmation to Cell-1, which includes the CHO configuration from Cell-1 to Cell-2 and from Cell-3 to Cell-2. Cell-2 may also provide Cell-1 with the CHO conditions of the temporary CHO preparation from Cell-2 to Cell-1 and from Cell-2 to Cell-3 (to be monitored by the UE if the UE switches to Cell-2).

[0205] Similarly, Cell-3 may confirm the CHO preparation requested by Cell-1 by providing Cell-1 with CHO conditions of CHO configurations from Cell-1 to Cell-3 and from Cell-2 to Cell-3 and temporary CHO preparations from Cell-3 to Cell-1 and from Cell-3 to Cell-2.

[0206] Then, Cell-1 may send an RRC reconfiguration message including the CHO preparation and CHO condition that have been previously obtained to the UE.

[0207] Once the UE receives the RRC reconfiguration, the UE can monitor the CHO execution conditions: cell-1 to cell-2 and cell-1 to cell-3, because the current serving cell is cell-1, and cell-2 and cell-3 are target cells. The remaining conditions and configurations will be suspended until the UE switches to another cell.

[0208] Now, if the CHO execution conditions from cell-1 to cell-2 are met, the UE may initiate a CHO towards the target cell-2.

[0209] The UE may then perform handover towards target cell-2 using the previously provided configuration and the handover procedure may be completed.

[0210] The UE can then start monitoring the CHO execution conditions: Cell-2 to Cell-1 and Cell-2 to Cell-3, since Cell-2 is the new serving cell and Cell-1 and Cell-3 are target cells (no additional RRC reconfiguration from the network is required, since the UE has already acquired all necessary CHO configurations).

[0211] Similar to before, if the CHO execution conditions towards target cell-3 are met, the UE may handover from cell-2 to cell-3 using the previously provided RRC reconfiguration.

[0212] Once the CHO towards the target cell-3 is completed, the UE may start monitoring the CHO execution conditions from cell-3 to cell-1 and from cell-3 to cell-2.

[0213] Now go to FIG. 5A to FIG. 5C (Exemplary embodiment of the present disclosure), in FIG. 5A to FIG. 5C In a scenario, UE 100 (an example of a user equipment according to the first exemplary aspect) is served by gNB-1 (an example of a first network node according to the second exemplary aspect), which communicates with gNB-2, gNB-3, and gNB-4 (examples of further network nodes). As part of the signaling, gNB-1, -2, -3, and -4 will be prepared for FCHO of UE 100, allowing UE 100 to perform fast CHO between these gNBs. In addition, gNB-1 communicates with gNB-X (an example of a second network node according to the third exemplary aspect), which gNB-X will not be prepared for FCHO of UE 100, and UE 100 re-establishes to this gNB-X after experiencing a failure. Each gNB serves a corresponding cell (gNB-1 serves cell-1, gNB-2 serves cell-2, etc.).

[0214] In the following, the signaling process will be described with reference to the corresponding cell. However, it should be understood that any message, signaling or action described with reference to a cell in the following can also be understood to refer to a message, signaling or action towards the gNB serving the cell:

[0215] Step 501: The UE sends a measurement report to its serving cell (ie, cell-1).

[0216] Steps 502, 503, 504: Serving cell-1 decides to initiate fast CHO preparation of neighboring cells (i.e., cell-2, cell-3, and cell-4). Then, cell-1 sends fast CHO requests to cell-2, cell-3, and cell-4. In each request, cell-1 requests temporary CHO preparation of the cell for fast CHO, i.e., when the fast CHO request is sent to cell-2 (see message 502), cell-1 requests HO preparation for switching from cell-1, cell-3, or cell-4 to cell-2.

[0217] Steps 505, 506, 507: The neighboring cell sends the CHO configuration and CHO condition requested in the fast CHO request message to Cell-1.

[0218] Step 508: Serving cell-1 sends an RRC reconfiguration to the UE, which includes the fast CHO configuration required for the FCS between the prepared cells (an example of sending conditional switching information to the user equipment). If the cell selected for reconstruction after the failure is not the prepared cell, the network instructs the UE to maintain the CHO configuration (particularly if a network node is selected by the user equipment for the reconstruction process, for which no conditional switching information is included in the conditional switching information sent by the first network node to the user equipment, an example of instructing the user equipment to retain at least a part of the conditional switching information).

[0219] Step 509: The UE monitors the CHO execution conditions from the serving cell-1 to the neighboring cells, ie, cell-2, cell-3 and cell-4.

[0220] Step 510: The UE detects RLF or HOF (an example of detecting a failure of a radio link affecting the user equipment) and initiates a re-establishment procedure on a cell suitable for connection.

[0221] Step 511: The UE selects cell-X for reestablishment, which cell-X is not one of the prepared cells in the fast CHO preparation.

[0222] Step 512: The UE identifies that the selected cell-X is not one of the prepared cells (determining that for the network node that has been selected by the user equipment for the reestablishment procedure, no conditional handover information is included in the conditional handover information that has been received by the user equipment from the first network node). The UE maintains the fast CHO RRC reconfiguration provided in step 508 (an example of retaining at least a portion of the conditional handover information, in particular based on determining that cell-X is not ready).

[0223] Step 513: The UE initiates a re-establishment procedure towards the selected cell-X (an example of the user equipment sending a request for performing a re-establishment procedure to the second network node).

[0224] Step 514: Cell-X requests the UE context from Cell-1 (an example of requesting context information for the user equipment from the first network node) and indicates that Cell-1 should not release any CHO preparation (if any) for the UE (an example of indicating to the first network node that at least a portion of the conditional handover information and / or at least a portion of the conditional handover resources already reserved for the user equipment should be retained).

[0225] Step 515: Cell-X receives UE context from previous serving cell-1, the UE context including the UE previous fast CHO preparation (an example of receiving context information for the user equipment from the first network node, wherein the context information includes conditional handover information associated with the user equipment).

[0226] Step 516: The reestablished cell-X decides which fast CHO preparations to keep and which fast CHO preparations to release for the UE (an example of selecting the conditional handover information to be kept or to be released and / or the corresponding part of the conditional handover resources already reserved for the user equipment). In this example, cell-X decides to keep the fast CHO preparations of cell-1, cell-2 and cell-3, and decides to release the fast CHO preparation of cell-4.

[0227] In option 1 (steps 517, 518, 519, 520), the source cell-1 that has initiated the fast CHO preparation cancels the fast CHO preparation of the cell-4 that the new cell X has decided to release:

[0228] Step 517: In this case, Cell-X sends a request to cancel fast CHO preparation of Cell-4 to Source Cell-1 (an example of indicating to the first network node the portion of conditional handover information and / or conditional handover resources that have been selected to be released).

[0229] Step 518: This is an implicit indication to cell-1 to maintain fast CHO preparation of cell-1 (an example of receiving an indication to reserve at least a portion of conditional handover information and / or resources from the second network node), and thus cell-1 reserves its own fast CHO preparation for the UE (an example of retaining at least a portion of conditional handover information associated with the user equipment and / or retaining at least a portion of conditional handover resources already reserved for the user equipment).

[0230] Step 519: Cell-1 sends the CHO configuration for handover from Cell-X to Cell-1 and the CHO condition from Cell-1 to Cell-X (an example of sending additional conditional handover information associated with the first network node and the second network node to the second network node). Cell-1 may also use this procedure to update the previously provided fast CHO preparation configuration given to the UE in step 508 (an example of sending updated conditional handover information to the second network node for updating at least a portion of the conditional handover information that has been sent by the first network node to the user equipment).

[0231] Step 520: Cell-1 cancels the fast CHO preparation of Cell-4, and thus Cell-4 will release the fast CHO preparation of the UE.

[0232] In option 2 (steps 521, 522, 523), the cell-X to which the UE re-establishes cancels the fast CHO preparation of cell-4:

[0233] Step 521: Cell-X directly sends a CHO cancel message to Cell-4 to exclude Cell-4 from the fast CHO preparation (e.g., to indicate to release the conditional handover information and / or release the conditional handover resources to at least one other network node associated with the part of the conditional handover information and / or conditional handover resources that have been selected to be released). Cell-4 releases the fast CHO preparation and relative resource reservation accordingly.

[0234] Step 522: Cell-X indicates to Cell-1 that it decides to maintain the fast CHO preparation of Cell-1.

[0235] Step 523: Cell-1 confirms the decision of Cell-X to maintain the fast CHO preparation of Cell-1. Cell-1 also sends the CHO configuration for the handover from Cell-X to Cell-1 and the CHO condition for the handover from Cell-1 to Cell-X (an example of sending additional conditional handover information associated with the first network node and the second network node to the second network node). Cell-1 may use this procedure to update the previous fast CHO preparation configuration provided to the UE in step 508 (an example of sending updated conditional handover information to the second network node for updating at least a portion of the conditional handover information that has been sent by the first network node to the user equipment).

[0236] Steps 524, 525: Cell-X notifies the neighboring cells included in the fast CHO preparation, and Cell-X has decided to maintain the identity of the new serving cell (cell X in this example) (an example of indicating to at least one other network node associated with the user equipment and the first network node that the user equipment is now served by the second network node). Through this process, cell-X also sends a request to maintain the fast CHO preparation of the UE (for example, indicating to at least one other network node associated with the user equipment and the first network node to retain the conditional handover information associated with the user equipment and / or at least a portion of the conditional handover resources already reserved for the user equipment). Cell-X also sends a fast CHO preparation request to be included in the fast CHO preparation previously processed from step 502 to step 507, that is, requesting the target node to provide the CHO configuration and the CHO conditions to be evaluated to cell-X to decide to perform a handover toward cell-X (an example of requesting additional conditional handover information from at least one other network node associated with the user equipment and the first network node, wherein the additional conditional handover information is associated with the second network node and at least one other network node).

[0237] Steps 526, 527: Cell-2 and Cell-3 confirm that they will maintain the previous fast CHO preparation. They will also provide the necessary CHO configuration and conditions required to include Cell-X in the previous fast CHO preparation. The previously prepared cells, i.e., Cell-2 and Cell-3, also use this process to update the conditions / configuration of the previous fast CHO preparation.

[0238] Step 528: The reestablished cell-X sends an RRC reestablishment message to the UE to update the conditional reconfiguration retained by the UE in step 512 (an example of sending replaced conditional handover information to the user equipment). This message is used to update the previous CHO configuration, i.e., to notify the UE of the cell's cancelled CHO preparation (which is to be released by the UE) (an example of conditional handover release information) and updated CHO configuration and conditions (an example of updated conditional handover information), where the cell-X decides to keep them in the fast CHO preparation. The cell-X also includes the CHO configuration and conditions required to include the cell-X in the previous fast CHO preparation (an example of additional conditional handover information).

[0239] Step 529: The UE discards the fast CHO preparation related to cell-4 (an example of releasing at least a portion of the conditional switching information that has been received by the user equipment from the first network node) and updates the fast CHO preparation condition / configuration indicated by cell-X (an example of updating at least a portion of the conditional switching information that has been received by the user equipment from the first network node and / or an example of storing additional conditional switching information associated with at least one additional network node).

[0240] Step 530 : The UE sends an RRC Reestablishment Complete message to Cell-X to confirm the message from step 528 .

[0241] Steps 531-533: After a successful reestablishment process, the UE starts monitoring the CHO execution conditions from Cell-X to neighboring cells (i.e., Cell-1, Cell-2, and Cell-3). Cell-3 satisfies the CHO execution conditions, and the UE switches from Cell-X to Cell-3.

[0242] Step 534: After successfully completing the handover from Cell-X to Cell-3, the UE starts monitoring the CHO execution conditions from Cell-3 to Cell-1, Cell-2 and Cell-X, where the UE does not need RRC reconfiguration to perform CHO from Cell-3 to Cell-1 or Cell-2 again (because it is given in message 508 and reused).

[0243] Now go to FIG. 6A to FIG. 6C (Exemplary embodiment of the present disclosure), in FIG. 6A to FIG. 6C In a scenario, UE 100 (an example of a user equipment according to the first exemplary aspect) is served by gNB-1 (an example of a first network node according to the second exemplary aspect), which is connected to gNB-2 (an example of a second network node according to the third exemplary aspect) and gNB-3 and -4 (examples of further network nodes). As part of the signaling, gNB-1, -2, -3 and -4 will be prepared for FCHO of UE 100, allowing UE 100 to perform fast CHO between these gNBs. After experiencing a failure, UE 100 re-establishes to gNB-2. Each gNB serves a corresponding cell (gNB-1 serves cell-1, gNB-2 serves cell-2, gNB-3 serves cell-3, and gNB-4 serves cell-4).

[0244] In the following, the signaling flow will be described with reference to the corresponding cell. However, it should be understood that any message, signaling or action described below with reference to a cell can also be understood to refer to a message, signaling or action towards the gNB serving the cell:

[0245] Steps 601 to 613: These steps are similar to those in FIG. 5A to FIG. 5C The steps 501 to 513 described in the scenario are the same.

[0246] Step 614: Since the re-established cell-2 knows about the fast CHO preparation, it requests the source cell-1 (which has previously initiated the fast CHO preparation) to retain the fast CHO preparation (indicating to the first network node that at least a portion of the conditional switching information and / or an example of at least a portion of the conditional switching resources that have been reserved for the user equipment) .

[0247] Step 615: Source cell-1 sends the UE context of the UE that has experienced the failure to cell-2 (an example of sending context information of the user equipment by the first network node to the second network node).

[0248] Step 616: Cell-2 decides to keep / release some of the fast CHO preparations for the UE that has experienced the failure (an example of selecting the conditional handover information to be retained or to be released and / or the corresponding part of the conditional handover resources that have been reserved for the user equipment).

[0249] In option 1 (steps 617, 618, 619, 620), the source cell processes the cancellation of the fast CHO preparation that Cell-2 decides to release:

[0250] Step 617: Cell-2 (the cell to which the UE is reestablished) indicates the cells whose fast CHO preparation should be canceled (an example of indicating to the first network node that part of the conditional handover information and / or conditional handover resources that have been selected to be released). In this example, Cell-2 wishes to cancel the fast CHO preparation of Cell-4 (excluding Cell-4 from the fast CHO preparation).

[0251] Step 618: Step 617 would be an implicit statement from cell-2 to cell-1 that cell-2 wishes to maintain fast CHO preparation for cell-1 (an example of receiving an indication from the second network node to retain at least a portion of the conditional handover information and / or resources). Therefore, cell-1 decides to maintain fast CHO preparation for cell-1 (an example of retaining at least a portion of the conditional handover information associated with the user equipment and already stored by the first network node and / or retaining at least a portion of the conditional handover resources already reserved by the first network node for the user equipment).

[0252] Step 619: If necessary, cell-1 uses this procedure to update cell-1 related fast CHO preparation configuration / conditions (an example of sending updated conditional switching information for updating at least a part of the conditional switching information to the second network node, where the updated conditional switching information is associated with the first network node).

[0253] Step 620: Cell-1 cancels the fast CHO preparation of Cell-4, and thus Cell-4 will release the fast CHO preparation of the UE.

[0254] In option 2 (steps 621, 622, 623), the re-established cell-2 cancels the fast CHO preparation of cell-4:

[0255] Step 621: The re-established cell-2 cancels the fast CHO preparation of cell-4 which cell-2 decided to exclude from the fast CHO preparation (an example of indicating the release of conditional switching information and / or the release of conditional switching resources to at least one other network node associated with the part of the conditional switching information and / or conditional switching resources that have been selected to be released).

[0256] Steps 622-623: The reestablished cell-2 notifies the source cell-1 of its decision to maintain the fast CHO preparation of cell-1, and cell-1 confirms the decision. Cell-1 also uses this procedure to update the fast CHO preparation of cell-1, i.e., the CHO configuration and conditions related to the fast CHO preparation of cell-1 (an example of sending updated conditional handover information for updating at least a part of the conditional handover information to the second network node, wherein the updated conditional handover information is associated with the first network node).

[0257] Step 624: The re-established cell-2 notifies the neighboring cell (i.e., cell-3 included in the fast CHO preparation in steps 602 to 608 and not cancelled after the failure) of the serving cell change, i.e., the identifier of the new serving cell (an example of indicating to at least one further network node associated with the user equipment and the first network node that the user equipment is now served by the second network node).

[0258] Step 625: The notified cell, i.e., cell-3, confirms to retain the fast CHO preparation (an example of retaining at least a portion of the conditional switching information associated with the user equipment and / or the conditional switching resources already reserved for the user equipment). In addition, the notified cell uses this process to update the fast CHO configuration and conditions configured from step 602 to step 608.

[0259] Steps 626 to 632: The rest of the process is the same as FIG. 5A to FIG. 5C The steps 528 to 534 are the same as described in the scenario.

[0260] Now go to Figure 7 , a block diagram of an example of a UE 100 is shown. For example, the UE 100 may be one or a part of a smart phone, a tablet computer, a notebook computer, a smart watch, a smart bracelet, an IoT device, or a vehicle.

[0261] UE 100 includes a processor 101. Processor 101 may represent a single processor or two or more processors, which are, for example, at least partially coupled, for example, via a bus. Processor 101 executes program code stored in program memory 102 (for example, when executed on processor 101, UE 100 connected to network node 150 performs one or more or parts of the example embodiments of the method according to the present disclosure, and interfaces with main memory 103. Program memory 102 may also include an operating system for processor 101. Some or all of memories 102 and 103 may also be included in processor 101.

[0262] One or both of the processor's main memory and program memory (e.g., program memory 102 and main memory 103) may be fixedly connected to the processor (e.g., processor 101) or at least partially removable from the processor, e.g. in the form of a memory card or stick.

[0263] The program memory (e.g., program memory 102) may, for example, be a non-volatile memory. For example, it may be any of a FLASH memory (or a portion thereof), a ROM, a PROM, an EPROM, an MRAM or a FeRAM (or a portion thereof), or a hard disk (or a portion thereof), to name a few examples. For example, the program memory may, for example, include a first memory portion that is fixedly mounted and a second memory portion that is removable, for example in the form of a removable SD memory card.

[0264] The main memory (e.g., main memory 103) may be, for example, a volatile memory. It may be, for example, a DRAM memory, which is just a non-limiting example. It may be used, for example, as a working memory for the processor 101 when executing an operating system, an application, a program, etc.

[0265] The processor 101 also controls a communication interface 104 (e.g., a radio interface) configured to receive and / or send data and / or information. For example, the communication interface 104 may be configured to send and / or receive radio signals from a network node, in particular as described herein. It should be understood that any computer program code-based processing required to receive and / or evaluate radio signals may be stored in the communication interface 104's own memory and executed by the communication interface 104's own processor, and / or it may be stored, for example, in the memory 103 and executed, for example, by the processor 101.

[0266] The communication interface 104 may in particular be configured to communicate according to a cellular communication system, such as a 2G / 3G / 4G / 5G or future generation cellular communication system.The user equipment 100 may communicate with a network node using the radio interface 104 .

[0267] For example, the communication interface 104 may also include a BLE and / or Bluetooth radio interface, including a BLE transmitter, receiver or transceiver. For example, the radio interface 104 may additionally or alternatively include a WLAN radio interface, including at least one WLAN transmitter, receiver or transceiver.

[0268] The components 102 to 104 of the user equipment 100 may be connected to the processor 101 , for example, via one or more serial and / or parallel buses.

[0269] It should be understood that the user device 100 may include various other components. For example, the user device 100 may optionally include a user interface (eg, a touch-sensitive display, a keyboard, a touchpad, a display, etc.).

[0270] Figure 8 A block diagram of an example of a network node, such as a base station or gNB, is shown. For example, the network node 150 may be configured to schedule and / or send signals to the UE 100, as described above.

[0271] The network node 150 includes a processor 151. The processor 151 may represent a single processor or two or more processors, which are at least partially coupled, for example, via a bus. The processor 151 executes program codes stored in a program memory 152 (for example, program codes that cause the network node 150 to execute an exemplary embodiment of the present disclosure or a portion thereof, either alone or together with the user equipment 100), and interfaces with a main memory 153.

[0272] Program memory 152 may also include an operating system for processor 151. Some or all of memories 152 and 153 may also be included in processor 151.

[0273] In addition, the processor 151 controls the communication interface 154, which is configured to communicate according to a cellular communication system (such as a 2G / 3G / 4G / 5G cellular communication system). The communication interface 154 of the device 150 can be implemented by a radio head, for example, and can be provided for communication between a network node and a user equipment.

[0274] The components 152 to 154 of the device 150 may be connected to the processor 151 , for example, via one or more serial and / or parallel buses.

[0275] It should be understood that the apparatus 100, 150 may include various other components.

[0276] Fig. 9 A schematic diagram showing an example of a tangible and non-transitory computer-readable storage medium according to the present disclosure, which can be used, for example, to implement Figure 7 Memory 102 or Figure 8 Memory 152. To this end, Fig. 9 Shown are a flash memory 1000 (which may, for example, be soldered or glued to a printed circuit board), a solid-state drive 1001 comprising a plurality of memory chips (e.g., flash memory chips), a magnetic hard disk drive 1002, a secure digital (SD) card 1003, a universal serial bus (USB) memory stick 1004, an optical storage medium 1005 (such as, for example, a CD-ROM or DVD), and a magnetic storage medium 1006.

[0277] Any connections presented in the described embodiments should be understood as the components involved being operationally coupled. Therefore, the connection may be direct or indirect, with any number or combination of intermediate elements, and there may only be a functional relationship between the components.

[0278] Furthermore, the term "circuitry" as used herein may refer to any of the following:

[0279] (a) Hardware circuit implementation only (such as implementation with analog and / or digital circuits only)

[0280] (b) a combination of circuitry and software (and / or firmware) such as:

[0281] (i) a combination of processors or

[0282] (ii) (multiple) processors / software (including (multiple) digital signal processors), software and portions of (multiple) memories, which work together to enable the device (such as a mobile phone) to perform various functions) and (c) circuitry, such as (multiple) microprocessors or portions of (multiple) microprocessors, which requires software or firmware to operate, even if the software or firmware is not physically present.

[0283] This definition of "circuitry" applies to all uses of this term in this document, including in any claims. As a further example, as used in this document, the term "circuitry" also covers an implementation of merely a processor (or multiple processors) or portion of a processor and its (their) accompanying software and / or firmware. The term "circuitry" also covers, for example, a baseband integrated circuit or an application processor integrated circuit of a mobile phone.

[0284] Any processor mentioned in this document, in particular but not limited to Figure 7 and Figure 8The processors 101 and 151 may be any suitable type of processor. Any processor may include, but is not limited to, one or more microprocessors, one or more processors with (multiple) attached digital signal processors, one or more processors without (multiple) attached digital signal processors, one or more dedicated computer chips, one or more field programmable gate arrays (FPGAs), one or more controllers, one or more application specific integrated circuits (ASICs), or one or more computers. The relevant structure / hardware has been programmed to perform the described functions.

[0285] In addition, any actions or steps described or illustrated herein may be implemented using executable instructions in a general or special purpose processor and stored on a computer-readable storage medium (e.g., disk, memory, etc.) for execution by such processor. References to "computer-readable storage medium" should be understood to cover special purpose circuits such as FPGAs, ASICs, signal processing devices, and other devices.

[0286] As used herein, “at least one of: ” and “at least one of ” and similar expressions, where a list of two or more elements is connected by “and” or “or” means at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0287] The phrase "A, or B, or C, or a combination thereof" or "at least one of A, B and C" or "at least one of A, B or C" or "A, B and / or C" may be understood as being non-exhaustive and including at least the following: (i) A, or (ii) B, or (iii) C, or (iv) A and B, or (v) A and C, or (vi) B and C, or (vii) A, B and C.

[0288] It will be understood that the embodiments disclosed herein are exemplary only, and any feature presented for a specific example embodiment may be used alone with any aspect of the present disclosure, or in combination with any feature presented for the same or another specific example embodiment and / or in combination with any other features not mentioned. It will also be understood that any feature presented for a particular class of example embodiments may also be used in a corresponding manner in any other class of example embodiments.

Claims

1. A user equipment, comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the user equipment to at least perform: - receiving conditional switching information from the first network node; as well as - retaining at least a part of said conditional handover information during a re-establishment procedure following a failure of a radio link affecting said user equipment.

2. The user equipment of claim 1, wherein the instructions, when executed by the at least one processor, further cause the user equipment to execute: - receiving, from the first network node, an indication to retain at least a part of the conditional handover information during a re-establishment procedure following a failure of a radio link affecting the user equipment, in particular wherein the indication is received together with the conditional handover information.

3. The user equipment according to any one of claims 1 or 2, wherein the instructions, when executed by the at least one processor, further cause the user equipment to execute: - detecting a failure of a radio link affecting said user equipment; and - based on detecting said failure, retaining said at least a portion of said conditional switching information.

4. The user equipment according to any one of claims 1 to 3, wherein the instructions, when executed by the at least one processor, further cause the user equipment to execute: - determining that, for a network node that has been selected by the user equipment for the reestablishment procedure, no conditional handover information is included in the conditional handover information that has been received by the user equipment from the first network node; and - Based on said determining, retaining said at least a portion of said conditional switching information.

5. The user equipment according to any one of claims 1 to 4, wherein the instructions, when executed by the at least one processor, further cause the user equipment to execute: - receiving replaced conditional switching information from a second network node, in particular wherein said replaced conditional switching information is received during said reestablishment process.

6. The user equipment according to claim 5, wherein the replaced conditional switching information comprises: - updated conditional handover information, used to update at least a part of the conditional handover information that has been received by the user equipment from the first network node; - additional conditional handover information, wherein the additional conditional handover information is associated with at least one additional network node for which no conditional handover information is included in the conditional handover information already received by the user equipment from the first network node, in particular wherein the at least one additional network node comprises or corresponds to the second network node; and / or - Conditional handover release information, indicating that at least a part of the conditional handover information that has been received by the user equipment from the first network node should be released.

7. The user equipment according to any one of claims 5 or 6, wherein the instructions, when executed by the at least one processor, further cause the user equipment, in particular during the reconstruction process, to perform, based on the replaced conditional switching information: - updating at least a part of the conditional handover information that has been received by the user equipment from the first network node; - releasing at least a portion of the conditional handover information that has been received by the user equipment from the first network node; and / or - storing additional conditional handover information associated with at least one additional network node for which no conditional handover information is included in the conditional handover information already received by the user equipment from the first network node, in particular wherein the at least one additional network node comprises or corresponds to the second network node.

8. A first network node, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to at least perform: - Sending conditional switching information to the user equipment; as well as - Instructing the user equipment to retain at least a part of the conditional handover information during a re-establishment procedure following a failure of a radio link affecting the user equipment.

9. The first network node according to claim 8, wherein the indication to retain at least a portion of the conditional handover information is sent together with the conditional handover information or is sent separately from the conditional handover information.

10. The first network node according to any one of claims 8 or 9, wherein the instructions, when executed by the at least one processor, further cause the first network node to execute: - indicating to the user equipment that, if a network node is selected by the user equipment for the reestablishment procedure and for which no conditional switching information is included in the conditional switching information already sent by the first network node to the user equipment, then retaining the at least part of the conditional switching information.

11. The first network node according to any one of claims 8 to 10, wherein the instructions, when executed by the at least one processor, further cause the first network node to execute: - retaining at least a portion of the conditional handover information associated with the user equipment and already stored by the first network node; and / or - reserving at least a portion of conditional handover resources that have been reserved by the first network node for the user equipment.

12. The first network node of claim 11, wherein the instructions, when executed by the at least one processor, further cause the first network node to execute: - receiving, in particular during said reconstruction process, an instruction to perform at least one of the steps of claim 11 from a second network node, in particular wherein said instruction, when executed by said at least one processor, causes said first network node to perform one or more of the steps of claim 11 based on receiving one or more corresponding instructions from said second network node.

13. The first network node according to any one of claims 8 to 12, wherein the instructions, when executed by the at least one processor, further cause the first network node to send to the second network node, in particular during the reestablishment process: - updated conditional handover information, used to update at least a part of the conditional handover information that has been sent by the first network node to the user equipment, and / or used to update at least a part of the conditional handover information associated with the user equipment and already stored by the second network node, in particular wherein the updated conditional handover information is associated with the first network node; and / or - additional conditional handover information associated with at least one additional network node, for which no conditional handover information is included in the conditional handover information already sent by the first network node to the user equipment, in particular wherein the additional conditional handover information is associated with the first network node and with the second network node.

14. A second network node, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to at least perform: - receiving a request from a user equipment for performing a reestablishment procedure, wherein the request comprises an indication for identifying that a first network node is associated with the user equipment; - requesting context information for the user equipment from the first network node; - receiving context information for the user equipment from the first network node, wherein the context information comprises conditional handover information associated with the user equipment; as well as - Instructing the first network node to retain at least a portion of the conditional handover information and / or at least a portion of the conditional handover resources that have been reserved for the user equipment.

15. The second network node of claim 14, wherein the conditional handover information received by the second network node as part of the context information does not include conditional handover information for the second network node.

16. The second network node according to any one of claims 14 or 15, wherein the instructions, when executed by the at least one processor, further cause the second network node to execute: - Selecting the conditional handover information to be retained or to be released and / or a corresponding part of the conditional handover resources already reserved for the user equipment.

17. The second network node of claim 16, wherein the instructions, when executed by the at least one processor, further cause the second network node to execute: - indicating to the first network node the part of the conditional handover information and / or the conditional handover resources that has been selected to be released.

18. The second network node according to any one of claims 16 or 17, wherein the instructions, when executed by the at least one processor, further cause the second network node to execute: - Instruct at least one other network node associated with the conditional switching information and / or the part of the conditional switching resources that have been selected to be released to release the conditional switching information associated with the user equipment and already stored by the at least one other network node, and / or to release the conditional switching resources that have been reserved for the user equipment by the at least one other network node.

19. The second network node according to any one of claims 14 to 18, wherein the instructions, when executed by the at least one processor, further cause the second network node to receive from the first network node: - updated conditional handover information, for updating at least a part of the conditional handover information that has been sent by the first network node to the user equipment, and / or for updating at least a part of the conditional handover information that has been received by the second network node as part of the context information, in particular wherein the updated conditional handover information is associated with the first network node; and / or - additional conditional handover information associated with at least one additional network node, for which no conditional handover information is included in the conditional handover information already sent by the first network node to the user equipment, in particular wherein the additional conditional handover information is associated with the first network node and with the second network node.

20. The second network node according to any one of claims 14 to 19, wherein the instructions, when executed by the at least one processor, further cause the second network node to indicate to at least one further network node associated with the user equipment and / or with the first network node: - the user equipment is now served by the second network node; - retaining at least a portion of the conditional handover information associated with the user equipment and already stored by the at least one further network node; and / or - reserving at least a portion of conditional handover resources that have been reserved for the user equipment by the at least one further network node.

21. The second network node according to any one of claims 14 to 20, wherein the instructions, when executed by the at least one processor, further cause the second network node to execute: - requesting additional conditional handover information from at least one further network node associated with the user equipment and / or with the first network node, in particular wherein the additional conditional handover information is associated with the second network node and the at least one further network node.

22. The second network node according to any one of claims 14 to 21, wherein the instructions, when executed by the at least one processor, further cause the second network node to execute: - Sending changed conditional switching information to the user equipment.

23. The second network node according to claim 22, wherein the instructions, when executed by the at least one processor, further cause the second network node to instruct the user equipment to perform, based on the replaced conditional switching information: - updating at least a part of the conditional handover information that has been received by the user equipment from the first network node; - releasing at least part of the conditional handover information that has been received by the user equipment from the first network node; and / or - storing additional conditional handover information associated with at least one additional network node for which no conditional handover information is included in the conditional handover information already received by the user equipment from the first network node, in particular wherein the at least one additional network node comprises or corresponds to the second network node.

24. The second network node according to any one of claims 14 to 23, wherein the instructions, when executed by the at least one processor, further cause the second network node to perform one or more of the steps of claims 14 to 23 in the case of - based on receiving said request for performing a reconstruction process; - as part of, or during, a reconstruction process performed based on receipt of said request; - before a re-establishment message sent upon receipt of said request is received; and / or - before a reconstruction process performed upon receipt of said request has been completed.

25. A method performed by a user equipment, the method comprising: - receiving conditional switching information from the first network node; as well as - retaining at least a part of said conditional handover information during a re-establishment procedure following a failure of a radio link affecting said user equipment.

26. A method performed by a first network node, the method comprising: - Sending conditional switching information to the user equipment; as well as - Instructing the user equipment to retain at least a part of the conditional handover information during a re-establishment procedure following a failure of a radio link affecting the user equipment.

27. A method performed by a second network node, the method comprising: - receiving a request from a user equipment for performing a reestablishment procedure, wherein the request comprises an indication for identifying that a first network node is associated with the user equipment; - requesting context information for the user equipment from the first network node; - receiving context information for the user equipment from the first network node, wherein the context information comprises conditional handover information associated with the user equipment; as well as - Instructing the first network node to retain at least a portion of the conditional handover information and / or at least a portion of the conditional handover resources that have been reserved for the user equipment.

28. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus to perform the method according to any one of claims 25 to 27.

29. A computer-readable storage medium having stored thereon the computer program according to claim 28.

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