Apparatus, method and computer program

Abstract

An apparatus, method and computer program are provided for handover in a communications network to enable handover of a user equipment from a source network node to a target network node with robust mobility.

Description

[0001] APPARATUS, METHOD AND COMPUTER PROGRAM

[0002] TECHNICAL FIELD

[0003] Various example embodiments relate to an apparatus, methods and computer program products, in particular, but not exclusively, for network apparatuses (network nodes, gNBs) and user equipments (UEs) as parts of communications systems for efficient handover in such systems.

[0004] BACKGROUND

[0005] A communication system enables communication between two or more entities such as communication devices, base stations and / or other nodes by providing carriers between the various entities involved in the communications path.

[0006] The communication system may be a wireless communication system. Examples of wireless communication systems include public land mobile networks (PLMN) operating based on radio standards, for example radio standards provided by 3GPP, satellite-based communication systems and different wireless local networks, for example wireless local area networks (WLAN). The wireless systems can be divided into cells and are often referred to as cellular systems or cellular networks.

[0007] The communication system and associated devices typically operate in accordance with a given standard or specification, which sets out how the various entities associated with system are permitted to perform, how they are allowed to interact with each other and how that should be achieved. Communication protocols and / or parameters that shall be used for the connection(s) within the network are also defined by the standard or specification. As mentioned above, some examples of standards are the radio standards provided by 3GPP, for example 2G, 3G, 4G and 5G. The communication system described herein is based on the 5G standard. However, the described embodiments are not limited to operating according to 5G and may also be applicable to future radio standards, for example 6G.

[0008] SUMMARY

[0009] Accordingly, a user equipment is provided. The user equipment includes at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code being configured, with the at least one processor, to cause the user equipment at least to identify a mismatch in a configuration of a source cell and a handover configuration of a target cell applied in the user equipment upon executing a handover from the source cell to the target cell, and inform the target cell about the mismatch.

[0010] The handover can be a conditional PCell change or a conditional handover. When the handover is a conditional handover, the handover configuration is a conditional handover configuration.

[0011] In the user equipment, identifying a mismatch can include decoding the handover configuration of the target cell upon executing the handover from the source cell to the target cell, and detecting a mismatch between the decoded handover configuration and the configuration of the source cell. The mismatch can be a difference in a SDAP configuration, a DRB configuration, an RLC configuration or a cellGroupConfig.

[0012] The user equipment may be further configured to receive an updated handover configuration of the target cell according to a current configuration in the source cell. Receiving an updated handover configuration of the target cell can include receiving a reconfiguration from a network node providing access to the target cell.

[0013] In some embodiments, the updated handover configuration is received after a path switch delay. The updated handover configuration can be handled by a core network component. Alternatively, as mentioned above, the network node providing access to the target cell can provide an updated handover configuration.

[0014] At the user equipment, receiving an updated handover configuration of the target cell can comprise undergoing a RRCReconfiguration procedure to trigger a DRB setup or release. Alternatively, the user equipment can undergo a RRCReconfiguration procedure to trigger a DRB to QoS flow remapping.

[0015] A network node is also provided, for a network configured for handover of a user equipment from a source cell to a target cell. The network node is configured to provide access to the target cell and includes at least one processor and at least one memory including computer code for one or more programs. The at least one memory and the computer code are configured, with the at least one processor, to cause the network node at least to receive a current configuration of the source cell, store the configuration of the source cell, determine that there is a mismatch between the configuration of the source cell and a handover configuration of the target cell applied in the user equipment, and update the handover configuration of the target cell according to the current configuration of the source cell.

[0016] In the network node, the current configuration of the source cell can be received when a new PDU session setup or a PDU session modification is triggered.

[0017] Alternatively, the current configuration of the source cell is received when a QoS flow setup or release is triggered.

[0018] The network node can be further configured to send an updated handover configuration of the target cell to the user equipment each time a current configuration of the source cell is received. Sending an updated handover configuration of the target cell to the user equipment can include retrieving a stored updated handover configuration of the target cell and initiating a RRCReconfiguration procedure to reconfigure the user equipment with the stored updated handover configuration. Alternatively, sending an updated handover configuration of the target cell to the user equipment can include retrieving a stored updated handover configuration of the target cell and initiating a RRCReconfiguration procedure to trigger a DRB setup or release. In a further alternative, sending an updated handover configuration of the target cell can include retrieving a stored updated handover configuration of the target cell and initiating a RRCReconfiguration procedure to trigger a DRB to QoS flow remapping.

[0019] The network node can be further configured to send an indication of the mismatch between the configuration of the source cell and the handover configuration applied in the target cell to a core network component, such as an access management function (AMF). The indication of the mismatch between the configuration of the source cell and the handover configuration applied in the target cell can be performed in a PATH SWITCH REQUEST message. The core network component can then handle the mismatch.

[0020] The updated handover configuration applied in the target cell can be triggered by the core network component.

[0021] The network node can be further configured to receive the updated handover configuration applied in the target cell according to the current configuration of the source cell from a source network node.

[0022] The network node may also be configured to update the handover configuration applied in the target cell to be in synchronization with the current configuration of the source cell. Alternatively, the network node can be configured to perform a path switch, which causes a path switch delay before the user equipment has received the updated handover configuration of the target cell. The path switch delay can then be a period of time between releasing a DRB to the source cell and setting up a DRB to the target cell. Alternatively, the path switch delay can be a period of time to trigger a DRB to QoS flow remapping. The updated handover configuration may then include new QoS information.

[0023] A user equipment is also provided, which includes means for identifying a mismatch in a configuration of a source cell and a handover configuration of a target cell applied in the user equipment upon executing a handover from the source cell to the target cell, and means for informing the target cell about the mismatch.

[0024] A network node for a network configured for handover of a user equipment from a source cell to a target cell is also provided. The network node is configured to provide access to the target cell, and comprises means for receiving a current configuration of the source cell, means for storing the configuration of the source cell, means for determining that there is a mismatch between the configuration of the source cell and a handover configuration of the target cell applied in the user equipment, and means for updating the handover configuration of the target cell according to the current configuration of the source cell.

[0025] In one aspect, a method for a user equipment includes identifying a mismatch in a configuration of a source cell and a handover configuration of a target cell applied in the user equipment upon executing a handover from the source cell to the target cell, and informing the target cell about the mismatch.

[0026] The above method for a user equipment can be performed by non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine. The above methods for a user equipment can also be performed by a computer program product computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the above method.

[0027] A computer program product may also comprise program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the above method.

[0028] In another aspect, there is a method for a network node configured for handover of a user equipment from a source cell to a target cell. The network node is configured to provide access to the target cell. The method includes receiving a current configuration of the source cell, storing the configuration of the source cell, determining that there is a mismatch between the configuration of the source cell and a handover configuration of the target cell applied in the user equipment, and updating the handover configuration of the target cell according to the current configuration of the source cell.

[0029] The updated handover configuration can be the RRC configuration.

[0030] The above methods for a network node can be performed by non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine.

[0031] The above methods for a network node can also be performed by a computer program product computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the above method. A computer program product may also comprise program instructions which, when the program is executed by an apparatus, cause the apparatus to carry out the above method.

[0032] Example embodiments will now be described with reference to the accompanying drawings, in which:

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 shows a signalling diagram schematically showing conditional handover;

[0035] Figure 2 shows a signalling diagram schematically showing conditional handover;

[0036] Figure 3 is a simplified schematic diagram of a communications network;

[0037] Figure 4 is a simplified schematic diagram of a user equipment;

[0038] Figure 5 is a simplified schematic diagram of some examples of memories and storage media;

[0039] Figure 6 is a simplified schematic diagram of network components;

[0040] Figure 7 is a signalling diagram schematically showing an embodiment;

[0041] Figure 8 is a signalling diagram schematically showing an embodiment;

[0042] Figure 9 a signalling diagram schematically showing an embodiment;

[0043] Figure 10 is a flow diagram illustrating a method according to an embodiment;

[0044] Figure 11 is a flow diagram illustrating a method according to an embodiment;

[0045] Figure 12 is a flow diagram illustrating a method according to an embodiment;

[0046] Figure 13 is a flow diagram illustrating a method according to an embodiment;

[0047] Figure 14 is a flow diagram illustrating a method according to an embodiment; and

[0048] Figure 15 is a flow diagram illustrating a method according to an embodiment. DETAILED DESCRIPTION

[0049] The following embodiments are exemplary. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. For the purposes of the present disclosure, the phrases “at least one of A or B”, “at least one of A and B”, “A and / or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrases “A or B” and “A and / or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and / or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0050] It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments.

[0051] Conditional handover (CHO) is described in 3GPP Rel. 16, with the CHO procedure being a way to improve the mobility robustness. CHO is further developed in Rel. 17 and will continue to evolve in future 3GPP releases. In the case of CHO, the RAN network may prepare multiple target cells, where each conditional handover reconfiguration is associated with a CHO execution condition that is evaluated by the UE. The CHO execution condition refers to a measurement ID (associating a measurement object with a reporting configuration) and is configured by a source gNB. The reporting configuration defines the measurement event (A3 orA5), which triggers the CHO execution. Whenever a CHO execution condition is met, the corresponding target configuration is selected, and handover is executed towards the selected target cell.

[0052] CHO may also take place with dual connectivity, in order to further increase mobility robustness and achieve a smooth handover. In reference to this, mention is made to Primary Secondary Cells (PSCells), Primary Cells (PCells), and Secondary Cells (SCells). The following will outline features of PSCells in relation to 5G New Radio, using terminology used therein. However, it is understood that the presently described principles are not limited to such terminology and may be applied to other systems having a similar architecture. For example, in multi-radio-dual connectivity (MR-DC), a Primary Cell (PCell) may be a Long Term Evolution (LTE) cell (e.g., Evolved-Universal Terrestrial Radio Access-New Radio-dual connectivity (EN-DC)).

[0053] PSCells are a type of cell currently defined in 5G New Radio, along with Primary Cells (PCells), Secondary Cells (SCells) and Special Cells (SpCells). A PCell may be used as part of an initial access between a UE and an access network and is considered to be a main cell in a master cell group (MCG). A PSCell may be comprised as part of a secondary cell group (SCG). The SpCells and SCells may be in at least one of the MCG and the SCG.

[0054] The cells may be controlled by network nodes. There are two different types of network nodes in 5G New Radio: Master nodes (which provide a control plane connection to a core network); and Secondary Nodes (which do not have control plane connections to the core network). The Master and Secondary nodes may both provide user plane (e.g., data) connections to the core network. The Master node may control the PCell. In addition to the PCell, the Master node may control at least one PSCell, although this is not always the case. The Secondary node may control at least one PSCell.

[0055] There may further comprise an interface between the different nodes, depending on the dual connectivity option. An X2 interface is an interface between eNBs in LTE that may be reused between Radio Access Network (RAN) nodes in non-standalone operation (e.g., between an eNB and an en-gNB). The Xn interface is an interface between RAN nodes in operating in a standalone operation (e.g., between an ng- eNB and an ng-eNB / gNB and between a gNB / ng-eNB and an gNB).

[0056] Example embodiments herein relate to enhancements of subsequent conditional handover (CHO), which is one of the objectives of the 3GPP Rel. 18 WID. The description of objective 2 in the mobility enhancements work item (RP-221799) is as follows: To specify mechanism and procedures of NR-DC with selective activation of the cell groups (at least for SCG) via L3 enhancements:

[0057] To allow subsequent cell group change after changing CG without reconfiguration and re-initiation of CPC / CPA [RAN2, RAN3, RAN4]

[0058] Note 4: A harmonized RRC modelling approach for objectives 1 and 2 could be considered to minimize the workload in RAN2.

[0059] Selective activation of the master cell group (MCG), to allow conditional PCell change by the UE without having to reconfigure the UE after each PCell change is expected to be part of Rel. 19 NR Mobility Enhancements Wl scope, as subsequent PSCell Change is prioritized in Rel. 18 and investigated.

[0060] The signalling procedure for CHO is shown in Figure 1 , with reference to the network schematically illustrated in Figure 3.

[0061] A UE 140-1 is served by Cell-1 with network node gNB-1 providing access to Cell- 1 . In step 1 , the UE 140-1 sends a measurement report to the serving network node gNB-1 to initiate the CHO preparation of target cell Cell-2 served by the network node gNB-2. In step 2, the source network node gNB-1 sends a CHO request to the target network node gNB-2. In step 3, target network node gNB-2 sends a CHO Acknowledge message to network node gNB-1 to acknowledge the CHO request from source Cell-1 to target Cell-2. Cell-1 prepares the target Cell-2 and sends to the UE 140-1 the CHO configuration, along with the CHO execution condition with RRCReconfiguration message in step 4.

[0062] In step 5, once the CHO execution condition against target cell Cell-2 is met, the UE detaches from source network node gNB-1 : i.e.; stops transmission / reception to / from source cell Cell-1 .

[0063] In step 6, the UE 140-1 initiates the random access procedure towards target cell Cell-2 by sending a PRACH Preamble message to the access node gNB-2 serving the target cell Cell-2. Network node gNB-2 responds in step 7 by sending a RACH Response message back to the network node gNB-1 serving the source cell Cell-1 . In step 8, the UE sends the RRC Reconfiguration Complete message to the network node gNB-2 in the target cell Cell-2. Once the random access procedure is completed successfully, target cell Cell-2 notifies source cell Cell-1 about successful completion of the handover procedure by sending a Handover Success message from source network node gNB-1 to target network node gNB-2 in step 9.

[0064] In step 10, upon receiving the handover success indication from target network node gNB-2, source network node gNB-1 initiates data forwarding to target network node gNB-2 serving target cell Cell-2. Once the data forwarding procedure is completed, the UE 140-1 will continue its data transmission / reception with the network.

[0065] Consecutive CHO has been proposed to enable fast cell switching (FCS) for a UE between prepared cells. CHO is targeted to improve mobility robustness, and the benefit is that it avoids transmission failure of a measurement report triggering the handover and / or the failure to receive HO command. This is because the network will provide an early CHO command (CHO preparation) to the UE 140-1 before the radio quality deteriorates. However, in the scenario with highly frequent HOs, due to short stay in one serving cell, there is a risk that the target cell cannot receive the measurement report triggering the handover preparation or cannot provide the CHO command timely to the UE, which will lead to radio link failure (RLF).

[0066] For the FR2 consecutive handover (HO) scenario, if one CHO command can be used for more than one CHO, then it could reduce the RLF / HOF probability. In addition, it can also reduce the signaling overhead. As shown in Figure 2, with the consecutive CHO enhancement, UE 140-1 can execute the CHO consecutively in cells Cell-2 and Cell-3 and therefore does not need to wait for the CHO configuration from the network after each handover. Herein, CHO preparations are carried with neighbour cells for fast CHO execution where the UE 140-1 evaluates the corresponding (sub-set) of CHO execution conditions after each cell change.

[0067] Figure 2 (with reference to the network of Figure 3) shows the signaling diagram for fast CHO for a UE 140-1 that is handed over first from cell Cell-1 to cell Cell-2 and then from cell Cell-2 to cell Cell-3, which is served by the access node gNB-3. The signaling diagram is explained as follows:

[0068] In step 1 , the UE 140-1 sends a measurement report to its serving cell Cell-1 via network node gNB-1 . In step 2, serving cell Cell-1 initiates the consecutive CHO (Fast CHO) preparation as follows: a. One preparation from cell Cell-1 to cell Cell-2 b. Another preparation from cell Cell-3 to cell Cell-2 which is provisional CHO preparation. This means that, in case the UE hands over to cell Cell-3, it can execute a subsequent handover from cell Cell-3 to cell Cell-2.

[0069] In step 3, similarly to step-2, cell Cell-1 initiates the CHO preparation for a handover from cell Cell-1 to cell Cell-3 and from cell Cell-2 to cell Cell-3, where the latter is the provisional preparation.

[0070] In step 4, cell Cell-2 acknowledges the CHO preparations that are requested by the cell Cell-1 . It also provides the CHO condition for the provisional CHO preparation from cell Cell-2 to cell Cell-1 and cell Cell-2 to cell Cell-3 (which is to be monitored by the UE 140-1 if the UE 140-1 hands over to cell Cell-2).

[0071] Similarly to step 4, in step 5, cell Cell-3 acknowledges the CHO preparations that are requested by the cell Cell-1 , as well as the CHO conditions for provisional CHO preparations from cell Cell-3 to cell Cell-1 and cell Cell-3 to cell Cell-2.

[0072] In step 6, cell Cell-1 sends the RRC Reconfiguration message to the UE that includes the CHO preparations and CHO conditions that are obtained from steps 2 to 5.

[0073] In step 7, once the UE 140-1 receives the RRC Reconfiguration, it will monitor the CHO execution conditions: cell Cell-1 to cell Cell-2 and cell Cell-1 to cell Cell-3, as the current serving cell is cell Cell-1 , whereas cell Cell-2 and cell Cell-3 are the target cells. The rest of the conditions and configurations will be suspended until UE handovers to another cell.

[0074] In step 8, the CHO execution condition from cell Cell-1 to cell Cell-2 is satisfied and the UE 140-1 initiates the CHO towards target cell Cell-2. The UE 140-1 executes the handover towards target cell Cell-2 in step 9 using the configurations provided in step 6 and completes the handover procedure. Note that the UE 140-1 decodes the candidate configuration and knows the content of the configuration only at the time of CHO execution.

[0075] In step 10, the UE 140-1 starts monitoring the CHO execution conditions: cell Cell- 2 to cell Cell-1 and cell Cell-2 to cell Cell-3. This is because cell Cell-2 is the new serving cell whereas Cell-1 and Cell-3 are the target cells (without further RRC Reconfiguration from the network as the UE 140-1 has already acquired all the necessary CHO configurations in step 6).

[0076] In steps 11 and 12, similarly to steps 8 and 9, the CHO execution condition towards target cell Cell-3 is satisfied and the UE 140-1 hands over from Cell-2 to Cell-3 using the RRC Reconfiguration provided in step 6.

[0077] In step 13, once the CHO towards target cell Cell-3 is completed, the UE starts monitoring the CHO execution condition from Cell-3 to Cell-1 and Cell-3 to Cell-2 The configuration of the source cell is expected to change after preparation of conditional configuration at the target cell during Conditional PCell preparation or CHO preparation. This is because, after target cell preparation and before Conditional PCell or PSCell change execution or CHO execution, new PDU sessions and / or new QoS flows may be setup at the source cell; or existing PDU sessions or existing QoS flows may be released at the source cell, which could result in configuration mismatch at the source and the target cells at the time of HO execution.

[0078] The target cell may be re-prepared each time there is a change in source cell’s configuration, which requires reconfiguring the UE every time the target is reprepared.

[0079] If we consider a CHO, it is likely that the HO to the target cell is executed by the UE before the UE is reconfigured with a re-prepared target cell CHO configuration. Furthermore, if there is selective activation of the PCell, PSCell or a conditional PCell change, the UE 140-1 is not expected to be reconfigured by the network after each PCell or PSCell change.

[0080] In either of the above scenarios, the problem is that a HO to the target cell may be executed with a configuration that is not consistent with the source cell configuration at the time of HO.

[0081] Example embodiments provide a way for the configurations of the source cell and the target cell to be consistent at the time of handover.

[0082] Figure 3 schematically shows a system 100, according to an exemplary aspect, and in which the embodiments described herein may operate. The system 100 is part of a mobile communications network and comprises a mobile device 140-1 , which may be a terminal device or user equipment (UE) or Internet of Things (loT) device.

[0083] The term “terminal device” or “UE” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0084] For the purposes of this discussion, the part of the network depicted in Figure 3 by the system 100 will be referred to as a 3GPP 5G network. However, this network could be any type of communication network, for example a 3G or 4G network, or it could be a 6G or other future network. Furthermore, the part of the 5G network shown by the system 100 could interact with another network of a different generation, for example a 4G or LTE network, or a 6G or other future network.

[0085] The system 100 further comprises network nodes gNB-1 , gNB-2 and gNB-3 providing access to corresponding cells Cell-1 , Cell-2 and Cell-3. The network nodes gNB-1 , gNB-2, gNB-3 are part of a mobile communication network, which may include additional network nodes serving corresponding cells.

[0086] Embodiments described herein may be implemented in any mobile communication network or radio system, such as one comprising at least one of the following radio access technologies (RATs): Worldwide Interoperability for Micro-wave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced, and enhanced LTE (eLTE). Term ‘eLTE’ here denotes the LTE evolution that connects to a 5G core. LTE is also known as evolved UMTS terrestrial radio access (EUTRA) or as evolved UMTS terrestrial radio access network (EUTRAN). A term “resource” may refer to radio resources, such as a physical resource block (PRB), a radio frame, a subframe, a time slot, a subband, a frequency region, a sub-carrier, a beam, etc. The term “transmission” and / or “reception” may refer to wirelessly transmitting and / or receiving via a wireless propagation channel on radio resources.

[0087] The embodiments are not, however, restricted to the systems / RATs given as an example but a person skilled in the art may apply the solution to other communication system s / networks provided with necessary properties. Some examples of a suitable communication networks include a 5G network and / or a 6G network. The 3GPP solution to 5G is referred to as New Radio (NR). 6G is envisaged to be a further development of 5G. NR has been envisaged to use multiple-input-multiple-output (MIMO) multi-antenna transmission techniques, more base stations or nodes than the current network deployments of LTE (a so- called small cell concept), including macro sites operating in co-operation with smaller local area access nodes and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates. 5G will likely be comprised of more than one radio access technology I radio access network (RAT / RAN), each optimized for certain use cases and / or spectrum. 5G mobile communications may have a wider range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications, including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cm Wave and mmWave, and being integrable with existing legacy radio access technologies, such as the LTE.

[0088] The current architecture in LTE networks is distributed in the radio and centralized in the core network. The low latency applications and services in 5G may require to bring the content close to the radio which leads to local break out and multiaccess edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud / fog computing and grid / mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and / or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time- critical control, healthcare applications). Edge cloud may be brought into RAN by utilizing network function virtualization (NVF) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. Network slicing allows multiple virtual networks to be created on top of a common shared physical infrastructure. The virtual networks are then customised to meet the specific needs of applications, services, devices, customers or operators.

[0089] The signals of network nodes gNB-1 , gNB-2, gNB-3 are observable by the mobile devices or user equipment (UE). The UE 140-1 is served by the network node gNB-1 within the cell Cell-1 . For the purposes of this discussion the cell Cell-1 is the serving cell (also called the source cell) for the UE 140-1. The UE 140-1 is capable of executing conditional handover from serving cell Cell-1 to target cell Cell-2 or cell Cell-3 with corresponding network nodes gNB-2 and gNB-3. However, the cells Cell-1 , Cell-2 and Cell-3 may all act as either serving or target cells for the UE 140-1 . There may also be other UEs served by the network shown in Figure 3, which may be UE / loT devices, for example a mobile phone or an autonomously driving vehicle.

[0090] Network nodes gNB-1 , gNB-2, gNB-3 are connected to each other by an Xn interface and are each connected to a core network (5GC) 150 by a NG interface. However, they may also be part of a service-based architecture, and the connections may be non-physical or wireless.

[0091] Network nodes gNB-1 , gNB-2, gNB-3 may either act as source network nodes or target network nodes, in which handover takes place from a source network node to a target network node. A plurality of different broadcast and / or multicast services (MBS) may be provided by the network nodes in cells Cell-1 , Cell-2 and Cell-3 over Multicast Traffic Channels (MTCH) which are the data channels where the multicast / broadcast services are provided.

[0092] Network nodes gNB-1 , gNB-2, gNB-3 may be used provide information about the Multicast Traffic Channels (MTCHs).

[0093] The UE 140-1 may be in RRCJDLE, RRCJNACTIVE or RRC_CONNECTED state.

[0094] An example of a UE 140-1 , which may be any wireless communication device will now be described in more detail with reference to Figure 4, showing a schematic, partially sectioned view of a communication device 140-1 . An appropriate UE or mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is referred to as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information. The UE 140-1 may be for example a mobile device, that is, a device not fixed to a particular location, or it may be a stationary device. The wireless device may need human interaction for communication or may not need human interaction for communication. As described herein, the terms UE or “user” are used to refer to any type of wireless communication device.

[0095] The UE 140-1 may receive signals over an air or radio interface 201 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 4, a transceiver apparatus is designated schematically by block 202. The transceiver apparatus 202 may be provided, for example, by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the wireless device.

[0096] The UE 140-1 is typically provided with at least one data processing entity or processor 203, at least one memory 204 and other possible components 205 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and / or in chipsets. This feature is denoted by reference 206. The user may control the operation of the wireless device by means of a suitable user interface such as keypad 207, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a wireless communication device may comprise appropriate connectors (either wired or wireless) to other devices and / or for connecting external accessories, for example hands-free equipment, thereto.

[0097] The components of the UE 140-1 shown in Figure 4 and / or their associated circuitry may also be known as “means for receiving...”, “means for transmitting...”, “means for determining...”, etc. Figure 5 shows a schematic representation of non-volatile memory media 300a (e.g. computer disc (CD) or digital versatile disc (DVD)) and 300b (e.g. universal serial bus (USB) memory stick) storing instructions and / or parameters 304 which when executed by a processor allow the processor to perform one or more of the steps of the methods described herein and shown in the drawings.

[0098] As provided herein, various aspects are described in the detailed description of examples and in the claims. In general, some examples may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although examples are not limited thereto. While various examples may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0099] The examples may be implemented by computer software stored in a memory and executable by at least one data processor of the involved entities or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that any procedures, for example as schematically shown in the accompanying drawings, and / or otherwise described previously, may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media (such as hard disk or floppy disks), and optical media (such as for example DVD and the data variants thereof, CD, and so forth).

[0100] The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits, gate level circuits and processors based on multicore processor architecture, as nonlimiting examples.

[0101] Additionally or alternatively, some examples may be implemented using circuitry. The circuitry may be configured to perform one or more of the functions and / or method steps previously described. That circuitry may be provided in the base station and / or in the communications device and / or in a core network entity.

[0102] As used in this application, the term “circuitry” may refer to one or more or all of the following:

[0103] (a) hardware-only circuit implementations (such as implementations in only analogue and / or digital circuitry);

[0104] (b) combinations of hardware circuits and software, such as:

[0105] (i) a combination of analogue and / or digital hardware circuit(s) with software / firmware and

[0106] (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as the communications device or base station to perform the various functions previously described; and

[0107] (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0108] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example integrated devices.

[0109] Herein, different examples are described using, as an example of an access architecture to which the described techniques may be applied, a radio access architecture based on long term evolution advanced (LTE Advanced, LTE-A) or new radio (NR, 5G), without restricting the examples to such an architecture, however. The examples may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad-hoc networks (MANETs) and Internet Protocol multimedia subsystems (IMS) or any combination thereof.

[0110] Figure 6 shows examples of simplified system architectures only showing some elements and functional entities, all being logical units, whose implementation may differ from what is shown. The connections shown in Figure 6 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in Figure 6.

[0111] The examples are not, however, restricted to the system given as an example but a person skilled in the art may apply the solution to other communication systems provided with necessary properties.

[0112] The example of Figure 6 shows a part of an exemplifying radio access network. For example, the radio access network may also support other services than those shown. For simplicity, only the network node gNB-1 is shown, which provides the UE 140-1 with access to the serving cell Cell-1 , before it executes a handover operation. However, the structure and connections shown in Figure 6 may also apply to the network nodes gNB-2 and gNB-3, which provide access to cells Cell-2 and Cell-3, respectively.

[0113] Figure 6 shows UE 140-1. The UE 140-1 is configured to be in a wireless connection on one or more communication channels with the network node gNB-1 . The network node gNB-1 is further connected to a core network (5GC) 150. For the purposes of this discussion, the network node gNB-1 is a gNB serving UE 140- 1 in a source cell Cell-1 . However, the network node gNB-1 may also be LTE eNB or even a non-3GPP access node. The physical link from a UE to a gNB is called uplink or reverse link and the physical link from the gNB to the UE is called downlink or forward link. It should be appreciated that gNBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage.

[0114] The network node structure and function of gNB-1 shown in Figure 6 may also apply to the network nodes gNB-2 and gNB-3 shown schematically in Figure 3 but only gNB-1 is shown here for simplicity.

[0115] A communications system 100 typically comprises more than one network node gNB-1 , gNB-2, gNB-3, as shown in Figure 3, in which case the network nodes may also be configured to communicate with one another over links, wired or wireless, designed for the purpose, for example a Xn interface. These links may be used for signalling purposes. Alternatively, the network nodes gNB-1 , gNB-2 and gNB-3 may be part of a network that utilises a service-based architecture. The network node gNB-1 is a computing device configured to control the radio resources of communication system it is coupled to. The network node gNB-1 may also be referred to as a base station, an access point or any other type of interfacing device including a relay station capable of operating in a wireless environment. The network node gNB-1 includes or is coupled to transceivers. From the transceivers of the gNB, a connection is provided to an antenna unit that establishes bi-directional radio links to devices. The antenna unit may comprise a plurality of antennas or antenna elements. The network node gNB-1 is further connected to the 5G core network 150 (CN or next generation core NGC). Depending on the deployed technology, the network node gNB-1 is connected to a serving and packet data network gateway (S-GW +P-GW) or user plane function (UPF), for routing and forwarding user data packets and for providing connectivity of devices to one or more external packet data networks, and to a mobile management entity (MME) or access mobility management function (AMF), for controlling access and mobility of the devices (UEs).

[0116] Examples of a UE device 140-1 are a subscriber unit, a user device, a user equipment (UE), a user terminal, a terminal device, a mobile station, a mobile device, etc.

[0117] The UE device 140-1 typically refers to a mobile or static device (e.g. a portable or non-portable computing device) that includes wireless mobile communication devices operating with or without an universal subscriber identification module (USIM), including, but not limited to, the following types of devices: mobile phone, smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and / or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction, e.g. to be used in smart power grids and connected vehicles. The device may also utilise cloud. In some applications, a device may comprise a user portable device with radio parts (such as a watch, earphones or eyeglasses) and the computation is carried out in the cloud.

[0118] The UE 140-1 illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a device may be implemented with a corresponding apparatus, such as a relay node. An example of such a relay node is a layer 3 relay (self-backhauling relay) towards the base station. The device (or, in some examples, a layer 3 relay node) is configured to perform one or more of user equipment functionalities.

[0119] Various techniques described herein may also be applied to a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected information and communications technology, ICT, devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyberphysical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

[0120] Additionally, although the apparatuses have been depicted as single entities, different units, processors and / or memory units (not all shown in Figure 6) may be implemented.

[0121] 5G enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and / or spectrum available. 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control). 5G is expected to have multiple radio interfaces, for example below 6GHz or above 24 GHz, cm Wave and mmWave, and also being integrable with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cm Wave, 6 or above 24 GHz - cm Wave and mmWave). One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0122] The LTE network architecture is fully distributed in the radio and fully centralized in the core network. The low latency applications and services in 5G require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud / fog computing and grid / mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and / or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications).

[0123] The communication system 100 via the network nodes gNB-1 , gNB-2, gNB-3 is also able to communicate with other networks 160, as shown in Figure 6, such as a public switched telephone network, or a VoIP network, or the Internet, or a private network, or utilize services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service. This may also be referred to as Edge computing when performed away from the core network. The communication system may also comprise a central control entity, or a like, 1 providing facilities for networks of different operators to cooperate for example in spectrum sharing.

[0124] The technology of Edge computing may be brought into a radio access network (RAN) by utilizing network function virtualization (NFV) and software defined networking (SDN). Using the technology of edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at or close to a remote antenna site (in a distributed unit, DU 121 of the network node gNB-1 ) and centralized functions (also functions involving the core network 150) being carried out in a centralized manner (in a centralized unit CU 122 of the network node gNB-1 ). The DU 121 and CU are connected via the F1 interface. The CU 122 is connected to the 5G Core Network (5GC) 150 via the NG interface. The CU 122 may be split into a user plane CU- UP and a control plane CU-CP. However, in some cases there is no such split in the CU 122. The centralized unit control plane CU CP 123 of the CU 122 provides control data for broadcast services. CU CP 123 is connected to 5GC 150 with the NG-C interface. It should also be understood that the distribution of labour between core network operations and base station operations may in future differ from that of the 5G standard or even be non-existent. Some other technology advancements probably to be used are Big Data and all-IP, which may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where Edge computing servers can be placed between the core and the base station or nodeB (gNB). One example of Edge computing is MEC, which is defined by the European Telecommunications Standards Institute. It should be appreciated that MEC (and other Edge computing protocols) can be applied in 4G networks as well.

[0125] 5G may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board of vehicles, Mobile Broadband, (MBB) or ensuring service availability for critical communications, and future railway / maritime / aeronautical communications. Satellite communication may utilise geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). Each satellite in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on- ground cells may be created through an on-ground relay node or by a gNB located on-ground or in a satellite.

[0126] The system shown in Figure 6 is only an example of a part of a radio access system and in practice, the system may comprise a plurality of network nodes, the UE 140-1 may have access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the network nodes may be a Home(e / g)nodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which are large cells, usually having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The network node gNB-1 of Figure 6 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells.

[0127] In the context of this discussion, with reference to the conditional handover (CHO) procedure described above, the cells Cell-1 , Cell-2, Cell-3 may act as primary cells (PCells) or primary secondary cells (PSCells). Handover from a source cell to a target cell (source network node to a target network node) may be a conditional PSCell change or a conditional handover. The UE 140-1 can be configured by the network for a conditional PSCell change or CHO with a conditional PSCell change configuration or a CHO configuration, respectively.

[0128] Similarly to the UE 140-1 shown schematically in Figure 4, the network nodes gNB-1 , gNB-2 and gNB-3 are also typically provided with at least one processor, at least one memory and other possible components for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices.

[0129] The components of the network node gNB-1 shown in Figure 6 (as well as network nodes gNB-2 and gNB-3) and / or associated circuitry may also be known as “means for transmitting...”, “means for receiving...”, “means for determining...”, “means for providing...”, etc.

[0130] Example embodiments are described with reference to the system 100 in Figure 3, which shows an exemplary RAN network.

[0131] An example embodiment is illustrated by the signalling diagram in Figure 7. At the time of Conditional PSCell change or CHO execution from source cell Cell-1 (served by network node gNB-1 ) to the target cell Cell-2 (served by network node gNB-2) described in Figures 1 and 2, the UE 140-1 in the source cell Cell-1 identifies a mismatch in the configuration of the source cell Cell-1 and the applied CHO configuration in the target cell Cell-2, and indicates the configuration mismatch to the network when the UE 140-1 connects to the target cell Cell-2 via the network node gNB-2. The target network node gNB-2 then handles the mismatch without any impact to NGAP procedures.

[0132] After a Conditional PSCell change or CHO preparation from the source cell Cell-1 to the target cell Cell-2, the UE 140-1 is reconfigured with Conditional PSCell / CHO configuration. When a new PDU session or QoS flow setup or release is triggered, the source network node gNB-1 initiates a re-preparation of the target network node gNB-2 with the updated latest (current) configuration of the source cell Cell-1. The target network node gNB-2 stores the updated Conditional PSCell change or CHO configuration after each re-preparation. Assuming a Conditional PSCell change or CHO execution happens before the UE 140-1 is reconfigured with the updated configuration, at the time of CHO execution, the UE 140-1 decodes the Conditional PSCell or CHO configuration and shall detect the configuration mismatch between the decoded configuration and the source cell configuration.

[0133] The UE 140-1 includes a ‘ConfigMismatchlndication’ in RRCReconfigurationComplete message when it connects to the target cell Cell-2.

[0134] The ‘ConfigMismatchlndication’ may be a binary flag or may have more details including, for example, a bit mask.

[0135] The target network node gNB-2 shall delay the PATH SWITCH procedure to enable it to handle the mismatch without involving AMF (or impacting NGAP procedures).

[0136] The target network node gNB-2 may handle the configuration mismatch via one of the following options:

[0137] In the first option, the target network node gNB-2 retrieves a stored Conditional PSCell or CHO configuration and initiates a RRCReconfiguration procedure to reconfigure the UE 140-1 with the stored configuration; i.e.; the network node gNB-2 reconfigures the UE 140-1 with a full configuration.

[0138] In the second option, the target network node gNB-2 retrieves the stored Conditional PSCell or CHO configuration and initiates a RRCReconfiguration procedure to trigger delta configuration changes, by triggering the DRB setup or release or DRB to QoS flow remapping.

[0139] In the message flow diagram in Figure 7, steps 1 to 15 are the existing CHO procedures shown in the signalling diagrams of Figures 1 and 2.

[0140] Step 16 of Figure 7 onwards describes in further detail the example embodiment described above. In step 16 and 17, the source network node gNB-1 receives a PDU SESSION RESOURCE SETUP / MODIFY REQUEST from the AMF in the core network (5GC) 150. Step 18 of Figure 7 successfully acknowledges the request of step 16 which includes an updated user plane between the core network 150 and the source network node gNB-1 (not shown). The QoS flows from core network 150 are mapped to DRBs on the air interface and result in corresponding source and target cell configurations of the source and target cells Cell-1 and Cell-2, respectively.

[0141] In steps 19 and 20 of Figure 7, the source node gNB-1 initiates HO REQUEST towards the target node(s) gNB-2, gNB-3 to update the prepared configuration of target cells Cell-2, Cell-3.

[0142] In steps 24-26 of Figure 7 the target nodes gNB-2, gNB-3 store the updated target cell configuration of target cells Cell-2, Cell-3.

[0143] At step 29 of Figure 7 a CHO (or Conditional PSCell change) execution condition is met before the UE 140-1 is reconfigured with an updated target configuration for the target cell (for example Cell-2) in step 31 .

[0144] At step 29 of Figure 7, the UE 140-1 detects the configuration mismatch between the source cell configuration and the decoded CHO or Conditional PSCell configuration.

[0145] At step 33 of Figure 7, the UE 140-1 includes “ConfigurationMismatchlndication" in RRCReconfigurationComplete message.

[0146] At step 35 of Figure 7, the target network node gNB-2 has been enabled at step 33 to delay initiating the PATH SWITCH REQUEST procedure to handle the configuration mismatch between the source and the target cells Cell-1 and Cell-2.

[0147] At step 36 of Figure 7, the target network node gNB-2 retrieves the stored CHO or Conditional PSCell configuration and may trigger either step 37 (set up QoS flow to DRB remapping) or step 38 (update CHO configuration in RRCReconfiguration Procedure).

[0148] In step 31 of Figure 7, the RRC Reconfiguration with an updated CHO configuration for the target cell Cell-2 is deliberately not sent to the UE 140-1 in selective activation MCG, because selection activation / conditional PSCell Change behaviour in Rel.19 scope does not allow any reconfiguration of the UE 140-1 (a RAN requirement). In this case a problem arises when CHO conditions apply and the UE 140-1 applies the target cell configuration for the target cell Cell-2 which has not been communicated to the UE 140-1 . This problem also arises if step 29 happens before step 21 .

[0149] Step 33 of Figure 7 adds the mismatch indication into RRCReconfigComplete message and thereby informs the network node gNB-2 in the target cell Cell-2 about the mismatch. A mismatch is detected because the configuration of the source cell Cell-1 and the configuration of the target cell Cell-2 do not correspond to each other (because they should map to the same QoS flow from the core network 150 and in this case they do not).

[0150] In steps 33 - 39 of Figure 7, the target node gNB-2, providing access to the cell Cell-2, receives an indication of configuration mismatch from UE 140-1 at the network node gNB-2 and instead of executing a path switch procedure (changing the user plane path from the core network 150 to the target cell Cell-2 instead of the previous source cell Cell-1) immediately, the target network node gNB-2 analyses or evaluates the configuration mismatch based on a received indication and its own UE context, as well as information on established services / user plane. The target node gNB-2 generates a configuration consistent with the source cell Cell-1 (for example, according to the acknowledged QoS flows from step 18). The target node gNB-2 then shares the configuration of the target cell Cell-2 consistent with the that of the source cell Cell-1 , which corresponds to the previous configuration of the source cell Cell-1 , with the UE 140-1 , by sending a RRCReconfiguration message, then executes a path switch procedure at the target network node gNB-2 to the core network 150. The path switch procedure may be based on the configuration of the source cell Cell-1 previously acknowledged in step 18. Alternatively, if that is not possible, the path switch procedure can be in line with the configuration of the target cell Cell-2. The path switch procedure is delayed until the configuration of the target cell Cell-2 is repaired and / or shared towards the UE 140-1 . User plane operation is thereby restored between the UE 140-1 and the core network 150 with the agreed QoS flows.

[0151] In another example embodiment, which is illustrated by the message flow diagram shown in Figure 8, at the time of Conditional PSCell change or CHO execution, the UE 140-1 identifies a mismatch in the configuration of the source cell Cell-1 and the applied CHO configuration, and indicates the configuration mismatch to the network when the UE 140-1 connects to the target cell Cell-2, the network node gNB-2 includes the mismatch indication in a PATH SWITCH REQUEST message to the AMF in the core network 150, allowing the AMF to handle the mismatch.

[0152] There may be two possibilities in this case. In a first example, after Conditional PSCell change preparation or CHO preparation, and the UE 140-1 is reconfigured, when a new PDU session or QoS flow setup or release is triggered, the source network node gNB-1 shall initiate re-preparation of the target network node gNB-2 with the updated latest configuration of the source cell Cell-1 . The target network node gNB-2 stores the updated Conditional PSCell change or CHO configuration after each re-preparation with the latest or currently used configuration of the source cell Cell-1 .

[0153] Alternatively, in a second example, after a Conditional PSCell change or CHO preparation and the UE 140-1 is reconfigured, a new PDU session or QoS flow setup or release trigger does not initiate a re-preparation of target. Assuming a Conditional PSCell change, or CHO execution from source cell Cell-1 to target cell Cell-2 happens before the UE 140-1 is reconfigured with the updated configuration, at the time of CHO execution the UE 140-1 decodes the Conditional PSCell or CHO configuration and shall detect the configuration mismatch between the decoded configuration and the configuration of the source cell Cell-1 .

[0154] The UE 140-1 then includes a ‘Config Mismatch Indication’ in RRCReconfigurationComplete message when it connects to the target cell Cell-2.

[0155] The network node gNB-2 in the target cell Cell-2 shall include a

[0156] ‘Config Mismatch Indication’ in PATH SWITCH REQUEST message to allow the AMF in the core network 150 to handle the configuration mismatch between the source and target cells Cell-1 and Cell-2.

[0157] The ‘Config Mismatch Indication’ may be a binary flag or may have more details including, for example, a bit mask, where each bit may be mapped to a specific DRB configuration, a QoS Flow configuration or a PDU session.

[0158] In the second embodiment, illustrated in figure 8, the AMF in the core network 150 may handle the configuration mismatch between the source cell Cell-1 and the target cell Cell-2 as follows:

[0159] Assuming the second example outlined above, the AMF may detect a configuration mismatch between the source cell Cell-1 and the target cell Cell-2 from the “PDUSessionResourceToBeSwitchedDLList’ and / or the ” QosFlowAcceptedList’ and / or the “PDUSessionResourceFailedToSetupListPSReq’’ in the PATH SWITCH REQUEST compared with the UE context at the AMF in the core network 150. The detected configuration mismatch may be handled by the AMF, for example by including an indication in the PATH SWITCH REQUEST ACKNOWLEDGE to either setup a new QoS flow or PDU session, or to release an existing QoS flow or a PDU session at the target network node gNB-2. The network node gNB-2 may accordingly handle the new indication in the PATH SWITCH REQUEST ACKNOWLEDGE by triggering an E1 bearer context modification and an F1 UE Context Modification to handle the added or released QoS flow. This may result in the setup of new DRB or update an existing DRB to perform DRB to QoS flow remapping, via one of the following options:

[0160] Option 1 : The target network node gNB-2 retrieves the stored Conditional PSCell or CHO configuration and initiates RRCReconfigu ration procedure to reconfigure the UE 140-1 with the stored configuration (that is, the UE 140-1 is reconfigured with a full configuration).

[0161] Option 2: The target network node gNB-2 retrieves the stored Conditional PSCell or CHO configuration and initiates a RRCReconfiguration procedure to trigger delta configuration changes, for example by triggering the DRB setup or release, or DRB to QoS flow remapping.

[0162] The example embodiment above will now be described with reference to the signal flow diagram in Figure 8.

[0163] In Figure 8, the steps not described below are the existing CHO procedures shown, for example, in the signalling diagrams of Figures 1 and 2.

[0164] In step 16 of Figure 8, the source network node gNB-1 receives a PDU SESSION RESOURCE SETUP / MODIFY REQUEST from the AMF in the core network 150. At step 21 of Figure 8, a CHO (or Conditional PSCell change) execution condition is met (for handover from the source cell Cell-1 to the target cell Cell-2) before the UE 140-1 is reconfigured with an updated configuration of the target cell Cell-2 (in step 23).

[0165] At step 21 , the UE 140-1 detects the configuration mismatch between the source cell Cell-1 configuration and the decoded CHO or Conditional PSCell configuration.

[0166] At step 25 of Figure 8 the UE 140-1 includes “ConfigurationMismatchlndication" in RRCReconfigurationComplete message.

[0167] At step 27 of Figure 8, step 25 enabled the target node to include “ConfigurationMismatchlndication” in PATH SWITCH REQUEST procedure to allow the AMF to handle the configuration mismatch between the source and the target cells Cell-1 and Cell-2.

[0168] At step 28 of Figure 8, step 27 enabled the AMF to identify the mismatch from “PDUSessionResourceToBeSwitchedDLList” and / or the ’’QosFlowAcceptedList” and / or the “PDUSessionResourceFailedToSetupListPSReq” in the PATH SWITCH REQUEST compared with UE context at AMF.

[0169] At step 29of Figure 8, step 28 enabled the AMF to handle the configuration mismatch by including an Indication in the PATH SWITCH REQUEST ACKNOWLEDGE to either setup a new QoS flow or PDU session or to release an existing QoS flow or a PDU session at the target network node gNB-2.

[0170] At step 30 of Figure 8, step 29 enabled the target network node gNB-2 to initiate

[0171] E1 bearer context modification and F1 UE Context Modification to handle the added or released QoS flow, which may result in the setup of a new DRB at the target cell Cell-2 or modify an existing DRB to perform DRB to QoS flow remapping or to release an existing DRB.

[0172] In steps 31 and 32 of Figure 8, as a result of step 30, the target network node gNB-2 may either trigger set up QoS flow to DRB remapping or update the CHO configuration in RRCReconfiguration Procedure.

[0173] In another example embodiment illustrated by the message flow diagram shown in Figure 9, after successful handover of the UE 140-1 from the source cell Cell-1 to the target cell Cell-2, the target network node gNB-2, upon receiving a configuration of the source cell Cell-1 from the source network node gNB-1 via an XnAP message, detects the mismatch between the source cell configuration and the target cell configuration, and handles the mismatch by updating the CHO configuration of the target cell Cell-2 to be in synchronization with the configuration of the source cell Cell-1 .

[0174] After the UE 140-1 connects to the target cell Cell-2 and the source network node gNB-1 receives “HO SUCCESS” message from the target network node gNB-2, the source network node gNB-1 forwards the configuration of the source cell Cell-1 used by the UE 140-1 via UE XnAP connection to the target network node gNB-2.

[0175] The target network node gNB-2 delays the triggering of the PATH SWITCH procedure to read the received configuration of the source cell Cell-1 and to identify if there is any mismatch with the configuration of the target cell Cell-2.

[0176] The network node gNB-2, upon detecting a configuration mismatch, updates the Conditional PSCell or CHO configuration to be in synchronization with the received configuration of the source cell Cell-1 . The network node gNB-2 may accordingly perform E1 bearer context modification and F1 UE Context Modification to handle the added or released QoS flow, which may result in the setup of new DRB at the target cell Cell-2 or modify an existing DRB to perform DRB to QoS flow re- mapping, or to release an existing DRB. The PATH SWITCH procedure shall be triggered after the above handling of configuration mismatch.

[0177] This embodiment will now be described with reference to the signalling diagram in Figure 9. The steps of Figure 9 not described below are the existing CHO procedures shown, for example, in the signalling diagrams of Figures 1 and 2.

[0178] In step 16 of Figure 9, the network node gNB-1 in the source cell Cell-1 receives a PDU SESSION RESOURCE SETUP / MODIFY REQUEST from the AMF.

[0179] In step 21 of Figure 9, a CHO (or Conditional PSCell change) execution condition is met before the UE 140-1 is reconfigured with updated target configuration (shown in step 23 of Figure 9).

[0180] In step 24 of Figure 9, the UE 140-1 connects to the target cell Cell-2.

[0181] In step 26 of Figure 9, the gNB-2 in the target cell Cell-2 sends a HO SUCCESS message to inform the network node gNB-1 that the UE 140-1 has successfully connected to the target cell Cell-2.

[0182] In step 27 of Figure 9, the network node gNB-1 forwards the configuration of the source cell Cell-1 currently used by the UE 140-1 (for example, in a transparent container) via a XnAP UE associated signaling connection.

[0183] In step 28 of Figure 9, the network node gNB-2 in the target cell Cell-2 delays the PATH SWITCH PROCEDURE to detect if there is a configuration mismatch between the configuration of the source cell Cell-1 and a stored CHO or Conditional PSCell configuration. In step 29 of Figure 9, if a mismatch is detected, the network node gNB-1 updates the CHO or Conditional PSCell configuration to be in synchronization with the received source cell configuration in step 27.

[0184] In step 30 of Figure 9, the network node gNB-2 in the target cell Cell-2 may trigger E1 bearer context modification and F1 UE Context Modification to handle the configuration mismatch.

[0185] In step 31 / 32 of Figure 9, following step 30, the target network node gNB-2 may either trigger set up QoS flow to DRB remapping or update the CHO configuration in the RRCReconfiguration Procedure.

[0186] In an alternative to the example embodiments above, in which there is a binary “ConfigurationMismatchlndication” flag in ‘RRCReconfigurationComplete’ message, the UE 140-1 may include more specifics of configuration mismatch between the source cell Cell-1 and the target cell Cell-2, instead of just the binary “ConfigurationMismatchlndication” flag in ‘RRCReconfigurationComplete’ message.

[0187] Figures 10 and 11 are flow diagrams showing a general overview of the methods performed by the UE 140-1 and the network node gNB-2, respectively.

[0188] In step 10-1 of Figure 10, when the UE 140-1 executes a handover from the source cell Cell-1 to the target cell Cell-2, it identifies a mismatch in the configuration of the source cell Cell-1 and a handover configuration of the target cell Cell-2 applied in the UE 140-1. In step 10-2 the UE 140-1 informs the network node gNB-2 about the mismatch. The network node gNB-2 provides access to the target cell Cell-2. The handover from the cell Cell-1 to the cell Cell-2 is a conditional PSCell change or a conditional handover. Then the handover configuration of the target cell Cell- 2 applied in the UE 140-1 is a conditional handover configuration or a conditional PSCell configuration.

[0189] The UE 140-1 identifies the mismatch by decoding the handover configuration of the target cell Cell-2 when it executes the handover from the source cell Cell-1 to the target cell Cell-2. The UE 140-1 then detects if there is a mismatch between the decoded handover configuration and the configuration of the source cell. The mismatch in configurations is a difference in a SDAP configuration, a DRB configuration or an RLC configuration.

[0190] The UE 140-1 can also receive an updated handover configuration of the target cell Cell-2 according to a current configuration in the source cell Cell-1 , for example by receiving a reconfiguration from the network node gNB-2 providing access to the target cell Cell-2. This updated handover configuration can be received after a path switch delay. Alternatively, the updated handover configuration can be provided by a core network component in the 5G Core 150, such as the Access Management Function (AMF).

[0191] The UE 140-1 may also receive an updated handover configuration of the target cell Cell-2 by undergoing a RRCReconfiguration procedure to trigger a DRB setup or release. Alternatively, the UE 140-1 may receive an updated handover configuration of the target cell Cell-2 by undergoing a RRCReconfiguration procedure to trigger a DRB to QoS flow remapping.

[0192] The flow diagram in Figure 11 schematically shows a method performed by the network node gNB-2 providing access to the target cell Cell-2 when the UE 140-1 executes a handover from the source cell Cell-1 to the target cell Cell-2. In step 11-1 , the network node gNB-2 receives a current configuration of the source cell Cell-1 and in step 11-2 it stores the configuration of the source cell Cell-1 . The current configuration of the source cell is received at the network node gNB-2 when a new PDU session is triggered or when a QoS flow setup or release is triggered.

[0193] In step 11-3, the network node gNB-2 determines that there is a mismatch between the configuration of the source cell Cell-1 and a handover configuration of the target cell Cell-2 applied in the user equipment UE 140-1 . The network node gNB-2 can determine that there is a mismatch between the configuration of the source cell Cell-1 and a handover configuration of the target cell Cell-2 by receiving an indication of the mismatch from the UE 140-1 when the UE 140-1 connects with the network node gNB-2. Alternatively, the gNB-2 can detect the mismatch between the source cell configuration and the target cell configuration at the network node itself.

[0194] The network node gNB-2 then updates the handover configuration of the target cell Cell-2 according to the current configuration of the source cell Cell-1 in step 11-4. The updated handover configuration can include new QoS information, for example.

[0195] The network node gNB-2 can also be configured to send an updated handover configuration of the target cell Cell-2 each time it receives a current configuration of the source cell Cell-1 . The network node gNB-2 can do this by retrieving a stored updated handover configuration of the target cell Cell-2 and initiating a RRCReconfiguration procedure to reconfigure the user equipment 140-1 with the stored updated handover configuration. Alternatively, the network node gNB-2 can send an updated handover configuration of the target cell Cell-2 to the user equipment 140-1 by retrieving a stored updated handover configuration of the target cell Cell-2 and initiating a RRCReconfiguration procedure to trigger a DRB setup or release. In another alternative, the network node gNB-2 can send an updated handover configuration of the target cell Cell-2 to the user equipment 140- 1 by retrieving a stored updated handover configuration of the target cell Cell-2 and initiating a RRCReconfiguration procedure to trigger a DRB to QoS flow remapping.

[0196] The network node gNB-2 may also send an indication of the mismatch between the configuration of the source cell Cell-1 and the handover configuration applied in the target cell Cell-2 to a component in the core network 150. This can be performed in a PATH SWITCH REQUEST message. The mismatch can then be handled by the core network component, for example an access management function (AMF), in the core network 150. This is shown in greater detail in Figure 8.

[0197] Alternatively, the network node gNB-2 can be configured to receive the updated handover configuration applied in the target cell Cell-2 according to the current configuration of the source cell Cell-1 from the source network node gNB-1.

[0198] In a further alternative, the network node gNB-2 can update the handover configuration applied in the target cell Cell-2 to be in synchronization with the current configuration of the source cell Cell-1 . In this case, after successful handover of the UE 140-1 to the target cell Cell-2, the network node gNB-2 receives the configuration of the source cell Cell-1 from the source network node gNB-1 . The target network node gNB-2 then detects the mismatch between the configuration of the source cell Cell-1 and the configuration of the target cell Cell-2 and updates the configuration of the target cell Cell-2 to match the configuration of the source cell Cell-1 . This is shown in greater detail in Figure 9.

[0199] Before the user equipment 140-1 has received the updated handover configuration of the target cell Cell-2, the network node gNB-2 can perform a path switch, that causes a path switch delay before the user equipment 140-1 has received the updated handover configuration of the target cell Cell-2. The path switch delay is a period of time between releasing a DRB to the source cell Cell-1 and setting up a DRB to the target cell Cell-2 or a period of time to trigger a DRB to QoS flow remapping.

[0200] Figure 12 is a flow diagram schematically showing the embodiment of Figure 7 at a higher level from the point of view of the user equipment 140-1 .

[0201] In step 12-1 , the user equipment 140-1 decodes the handover configuration of the target cell Cell-2 (which is applied in the user equipment UE 140-1 ) when it undergoes CHO or conditional PSCell change from the source cell Cell-1 to the target cell Cell-2.

[0202] In step 12-2, the UE 140-1 identifies a mismatch in a configuration of the source cell Cell-1 and the handover configuration of the target cell Cell-2 upon connecting with the network node gNB-2 providing access to the target cell Cell-2. This happens if it is detected that the decoded handover configuration of the target cell Cell-2 does not match the configuration of the source cell Cell-1 .

[0203] In step 12-3, the UE 140-1 informs the target cell Cell-2 about the mismatch, and after a path switch delay in step 12-4, the UE 140-1 receives a reconfiguration from the network node gNB-2 providing access to the target cell Cell-2. The reconfiguration is an updated handover configuration of the target cell Cell-2 according to a current configuration applied in the source cell Cell-1 .

[0204] Figure 13 is a flow diagram schematically showing the embodiment described with reference to Figure 7 from the point of view of the target network node gNB-2 providing access to the target cell Cell-2. In step 13-1 , the network node gNB-2 receives a current configuration of the source cell Cell-1 and it stores the configuration of the source cell Cell-1 in step 13-2.

[0205] In step 13-3, the target network node gNB-2 stores an updated handover configuration of the target cell Cell-2 each time it receives a current configuration of the source cell Cell-1 .

[0206] In step 13-4, the UE 140-1 executes a handover from the source cell Cell-1 to the target cell Cell-2. When the UE 140-1 connects with the network node gNB-2 at handover, the network node gNB-2 receives an indication from the user equipment 140-1 that there is a mismatch between the configuration of the source cell Cell-1 and a handover configuration applied in the target cell Cell-2.

[0207] In step 13-5, the target network node gNB-2 sends an updated handover configuration of the target cell Cell-2 to the user equipment 140-1 . The updated handover configuration of the target cell Cell-2 corresponds to the current configuration of the source cell Cell-1 . The target network node gNB-2 retrieves the stored updated handover configuration of the target cell Cell-2 and initiates a reconfiguration procedure to reconfigure the user equipment 140-1 with the stored updated handover configuration.

[0208] In step 13-6 there is a path switch delay until the user equipment 140-1 has received the updated handover configuration of the target cell Cell-2 from the network node gNB-2.

[0209] Figure 14 is a flow diagram showing the embodiment described in Figure 8 at a higher level from the point of view of the user equipment 140-1 . In step 14-1 , the UE 140-1 executes a handover from the source cell Cell-1 to the target cell Cell-2, for example CHO or conditional PSCell change.

[0210] Upon connecting with the target cell Cell-2, in step 14-2, if the UE 140-1 identifies a mismatch in a configuration of the source cell Cell-1 and a handover configuration of the target cell Cell-2 applied in the UE 140-1 , it informs the target cell Cell-2 about the mismatch via the network node gNB-2 providing access to the target cell Cell-2.

[0211] In step 14-3 the UE 140-1 receives an updated handover configuration of the target cell Cell-2 initiated by a component of the core network 150, for example the AMF. The updated target cell Cell-2 handover configuration is provided when the component of the core network 150 handles the mismatch between the configuration of the source cell Cell-1 and the handover configuration of the target cell Cell-2 applied in the UE 140-1. The AMF provides an indication to the target cell Cell-2 to trigger a reconfiguration procedure, described in more detail with reference to Figure 8. The updated handover configuration of the target Cell-2 corresponds to the current configuration in the source cell Cell-1 .

[0212] Figure 15 is a flow diagram schematically showing the embodiment described with reference to Figure 9 from the point of view of the target network node gNB-2 providing access to the target cell Cell-2, when the UE executes CHO or conditional PCell change from Cell-1 to Cell-2.

[0213] In step 15-1 , the network node gNB-2 receives a current configuration of the source cell Cell-1 .

[0214] In step 15-2, the network node gNB-2 delays a path switch procedure. This is to detect if there is a configuration mismatch between the received current configuration of the source cell Cell-1 and a stored handover configuration. If such a configuration mismatch is detected, in step 15-3, the network node gNB-2 updates the handover configuration to be in synchronization with the received current configuration of the source cell Cell-1. In this way, a configuration mismatch between the source and the target cells at the time of CHO execution (including Conditional PCell change and Conditional PSCell change) shall be handled effectively, while QoS flow to DRB mapping principles of the source are fully applied at the target cell after HO. This provides a generic solution for various mobility scenarios including CHO NR-DC and MCG selective activation.

[0215] The various example embodiments also provide for implementation with or without UE impact, and with or without NGAP signaling impact, resulting in ease of implementation.

[0216] Although the foregoing has been described with reference to specific example embodiments, it is not limited to these embodiments, and no doubt further examples will occur to the skilled person, which lie within the scope of the claims.

[0217] Furthermore, each one of the embodiments may be implemented in combination with any of the other embodiments.

[0218] LIST OF ABBREVIATIONS

[0219] AMF - Access and Mobility Management Function

[0220] CHO - Conditional Handover

[0221] DRB - Data Radio Bearer

[0222] HO - Handover

[0223] MCG - Master Cell Group

[0224] NGAP - Next Generation Application Part

[0225] NG RAN - Next Generation Radio Access Network

[0226] PDU - Packet Data Unit

[0227] QoS - Quality of Service

[0228] RACH - Random Access Channel

[0229] UE - User Equipment

Claims

CLAIMS1. A user equipment, comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code being configured, with the at least one processor, to cause the user equipment at least to: identify a mismatch in a configuration of a source cell and a handover configuration of a target cell applied in the user equipment upon executing a handover from the source cell to the target cell; and inform a network node providing access to the target cell about the mismatch.

2. A user equipment according to claim 1 , wherein the handover is a conditional PSCell change.

3. A user equipment according to claim 1 , wherein the handover is a conditional handover.

4. A user equipment according to claim 3, wherein the handover configuration is a conditional handover configuration.

5. A user equipment according to any preceding claim, wherein identifying a mismatch comprises decoding the handover configuration of the target cell upon executing the handover from the source cell to the target cell and detecting a mismatch between the decoded handover configuration and the configuration of the source cell.

6. A user equipment according to claim 5, wherein said mismatch comprises a difference in a SDAP configuration, a DRB configuration or an RLC configuration.

7. A user equipment according to any preceding claim, the user equipment being further configured to receive an updated handover configuration of the target cell according to a current configuration in the source cell.

8. A user equipment according to claim 7, wherein receiving an updated handover configuration of the target cell comprises receiving a reconfiguration from a network node providing access to the target cell.

9. A user equipment according to claim 8, wherein the updated handover configuration is received after a path switch delay.

10. A user equipment according to claim 7, wherein said mismatch is handled by a core network component.

11. A user equipment according to any of claims 7 to 10, wherein receiving an updated handover configuration of the target cell comprises undergoing a RRCReconfiguration procedure to trigger a DRB setup or release.

12. A user equipment according to any of claims 7 to 10, wherein receiving an updated handover configuration of the target cell comprises undergoing a RRCReconfiguration procedure to trigger a DRB to QoS flow remapping.

13. A network node for a network configured for handover of a user equipment from a source cell to a target cell, the network node being configured to provide access to the target cell, and comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause the network node at least to: receive a current configuration of the source cell; store the configuration of the source cell;determine that there is a mismatch between the configuration of the source cell and a handover configuration of the target cell applied in the user equipment; and update the handover configuration of the target cell according to the current configuration of the source cell.

14. A network node according to claim 13, wherein determining that there is a mismatch between the configuration of the source cell and a handover configuration of the target cell applied in the user equipment comprises receiving an indication of a mismatch from the UE upon the UE connecting with the network node.

15. A network node according to claim 13, wherein determining that there is a mismatch between the configuration of the source cell and a handover configuration of the target cell applied in the user equipment comprises detecting the mismatch between the source cell configuration and the target cell configuration at the network node.

16. A network node according to claim 13, wherein the current configuration of the source cell is received when a new PDU session is triggered.

17. A network node according to claim 13, wherein the current configuration of the source cell is received when a QoS flow setup or release is triggered.

18. A network node according to any of claims 13 to 17, the network node being further configured to send an updated handover configuration of the target cell to the user equipment each time a current configuration of the source cell is received.

19. A network node according to claim 18, wherein sending an updated handover configuration of the target cell to the user equipment comprises retrieving a stored updated handover configuration of the target cell and initiating a RRCReconfiguration procedure to reconfigure the user equipment with the stored updated handover configuration.

20. A network node according to claim 18, wherein sending an updated handover configuration of the target cell to the user equipment comprises retrieving a stored updated handover configuration of the target cell and initiating a RRCReconfiguration procedure to trigger a DRB setup or release.

21. A network node according to claim 18, wherein sending an updated handover configuration of the target cell comprises retrieving a stored updated handover configuration of the target cell and initiating a RRCReconfiguration procedure to trigger a DRB to QoS flow remapping.

22. A network node according to any of claims 13 to 17, the network node being further configured to send an indication of the mismatch between the configuration of the source cell and the handover configuration applied in the target cell to a core network component.

23. A network node according to claim 22, wherein sending an indication of the mismatch between the configuration of the source cell and the handover configuration applied in the target cell is performed in a PATH SWITCH REQUEST message.

24. A network node according to claim 22 or claim 23, wherein the updated handover configuration applied in the target cell is triggered by the core network component.

25. A network node according to any of claims 22 to 24, wherein the core network component is an access management function.

26. A network node according to any of claims 13 to 17, the network node being further configured to receive the updated handover configuration applied in the target cell according to the current configuration of the source cell from a source network node.

27. A network node according to any of claims 13 to 17, the network node being further configured to update the handover configuration applied in the target cell to be in synchronization with the current configuration of the source cell.

28. A network node according to claim 13, the network node being further configured to perform a path switch, that causes a path switch delay before the user equipment has received the updated handover configuration of the target cell.

29. A network node according to claim 28, wherein the updated handover configuration includes new QoS information.

30. A network node according to claim 28 or 29, wherein the path switch delay is a period of time between releasing a DRB to the source cell and setting up a DRB to the target cell.

31. A network node according to claim 28 or 29, wherein the path switch delay is a period of time to trigger a DRB to QoS flow remapping.

32. A user equipment, comprising: means for identifying a mismatch in a configuration of a source cell and a handover configuration of a target cell applied in the user equipment upon executing a handover from the source cell to the target cell; and means for informing the target cell about the mismatch.

33. A network node for a network configured for handover of a user equipment from a source cell to a target cell, the network node being configured to provide access to the target cell, and comprising: means for receiving a current configuration of the source cell; means for storing the configuration of the source cell; means for determining that there is a mismatch between the configuration of the source cell and a handover configuration of the target cell applied in the user equipment; and means for updating the handover configuration of the target cell according to the current configuration of the source cell.

34. A method for a user equipment, comprising: identifying a mismatch in a configuration of a source cell and a handover configuration of a target cell applied in the user equipment upon executing a handover from the source cell to the target cell; and informing the target cell about the mismatch.

35. A method for a network node configured for handover of a user equipment from a source cell to a target cell, the network node being configured to provide access to the target cell, the method comprising: receiving a current configuration of the source cell;storing the configuration of the source cell; determining that there is a mismatch between the configuration of the source cell and a handover configuration of the target cell applied in the user equipment; and updating the handover configuration of the target cell according to the current configuration of the source cell.

36. A non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing the method according to claim 32 or claim 33.

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