Handling of SCG at inter-MN ltm

Abstract

A method, performed by a wireless communications device configured with Dual- Connectivity, DC, for handling a Secondary Cell Group, SCG, at an L1 / L2-Triggered Mobility, LTM, procedure of the wireless communications device between a source network node and a target network node. The method comprises receiving (8001) an LTM configuration for a Master Cell Group, MCG. The method further comprises receiving (8002) an indication about SCG handling. The method further comprises executing (8003) the LTM procedure for the MCG according to the received LTM configuration for the MCG. While executing the LTM procedure the method further comprises handling (8004) the SCG according to the received indication about SCG handling.

Description

[0001] HANDLING OF SCG AT INTER-MN LTM

[0002] TECHNICAL FIELD

[0003] The embodiments herein relate to a UE and network nodes for handling of SCG at inter-MN LTM and methods for the same. A corresponding computer program and a computer program carrier are also disclosed.

[0004] BACKGROUND

[0005] In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (ST A) and / or User Equipments (UE), communicate via a Local Area Network such as a Wi-Fi network or a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio access node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in 5G. A service area or cell area is a geographical area where radio coverage is provided by the radio access node. The radio access node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio access node.

[0006] Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network also referred to as 5G New Radio (NR). The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E- UTRAN / LTE is a variant of a 3GPP radio access network wherein the radio access nodes are directly connected to the EPC core network rather than to RNCs used in 3G networks. In general, in E-UTRAN / LTE the functions of a 3G RNC are distributed between the radio access nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio access nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio access nodes, this interface being denoted the X2 interface.

[0007] Wireless communication systems in 3GPP

[0008] Figure 1a illustrates a simplified wireless communication system with a UE 12, which communicates with one or multiple access nodes 103-104, which in turn is connected to a network node 106. The access nodes 103-104 are part of a radio access network 10.

[0009] For wireless communication systems pursuant to 3GPP Evolved Packet System, (EPS), also referred to as Long Term Evolution, LTE, or 4G, standard specifications, such as specified in 3GPP TS 36.300 and related specifications, the access nodes 103-104 corresponds typically to a Evolved NodeBs (eNBs) and the network node 106 corresponds typically to either a Mobility Management Entity (MME) and / or a Serving Gateway (SGW). The eNB is part of the radio access network 10, which in this case is the E-UTRAN (Evolved Universal Terrestrial Radio Access Network), while the MME and SGW are both part of the EPC (Evolved Packet Core network). The eNBs are interconnected via the X2 interface, and connected to EPC via the S1 interface, more specifically via S1-C to the MME and S1-U to the SGW.

[0010] For wireless communication systems pursuant to 3GPP 5G System, 5GS (also referred to as New Radio, NR, or 5G) standard specifications, such as specified in 3GPP TS 38.300 and related specifications, on the other hand, the access nodes 103-104 corresponds typically to an 5G NodeB (gNB) and the network node 106 corresponds typically to either a Access and Mobility Management Function (AMF) and / or a User Plane Function (UPF). The gNB is part of the radio access network 10, which in this case is the NG-RAN (Next Generation Radio Access Network), while the AMF and UPF are both part of the 5G Core Network (5GC). The gNBs are inter-connected via the Xn interface, and connected to 5GC via the NG interface, more specifically via NG-C to the AMF and NG-U to the UPF.

[0011] To support fast mobility between NR and LTE and avoid change of core network, LTE eNBs may also be connected to the 5G-CN via NG-U / NG-C and support the Xn interface. An eNB connected to 5GC is called a next generation eNB (ng-eNB) and is considered part of the NG-RAN. LTE connected to 5GC will not be discussed further in this document; however, it should be noted that most of the solutions / features described for LTE and NR in this document also apply to LTE connected to 5GC. In this document, when the term LTE is used without further specification it refers to LTE-EPC. L1 / L2 Triggered Mobility (LTM) in 3GPP Rel-18 and Rel-19

[0012] In 3GPP Release 18, as part of a work item known as Further NR mobility enhancements, a technical area entitled L1 / L2 based inter-cell mobility is included. According to a 3gpp Work Item Description (WID) RP-233970 the goal of L1 / L2 based inter-cell mobility (also known as L1 / L2 Triggered Mobility) is to enable a serving cell change, sometimes also known as an LTM cell switch or an LTM cell switch procedure, via L1 / L2 signalling, in order to reduce the latency, overhead and interruption time.

[0013] A basic principle with L1 / L2 triggered mobility is that the UE is pre-configured, by the network, with an LTM configuration which includes information such as measurement configuration and an RRC configuration per LTM candidate cell, sometimes also known as an LTM candidate cell configuration. Such an LTM candidate cell configuration may be an RRCReconfiguration message or one or more IEs / fields / parameters such as CellGroupConfig. The UE performs measurements on LTM candidate cells and beams in those cells, according to the measurement configuration included in the LTM configuration received from the network. The UE transmits L1 measurement reports for LTM including L1-RSRP measurements for up to four LTM candidate cells and up to four beams in in each cell. When the network (e.g. a gNB or a gNB-DU), receives the L1 measurement report for LTM, it may use the content of this report to trigger an LTM cell switch towards one of the LTM candidate cells.

[0014] The network triggers the execution of a LTM cell switch procedure in the UE to one of these LTM candidate cells by transmitting an LTM cell switch command MAC Control Element, MAC CE, to the UE. The LTM cell switch command includes information such as a reference to an LTM candidate cell configuration and an indication of a target beam in the LTM candidate cell. The UE then connects to the beam and switches to the LTM candidate cell configuration.

[0015] The overall procedures for LTM in Rel-18 are described in 3GPP TS 38.300 V18.0.0, subclause 9.2.3.5, and for the gNB-CU / gNB-DU Architecture in 3GPP TS 38.401 V18.0.0, subclauses 8.2.1.4-8.2.1.6.

[0016] LTM in Rel-18 is limited to intra-gNB (including intra-CU intra-DU and intra-CU inter- DU) mobility.

[0017] In 3GPP Rel-19, a WID RP-240299 on NR Mobility enhancements Phase 4 has started, which aims to enhance mobility features, including introducing support for inter- CU LTM according to the objective below.

[0018] • Specify support for inter-CU Layerl / Layer 2 Triggered Mobility (LTM) [RAN2, RAN3] o Prioritize the case when CU is acting as Master Node (MN) when DC is not configured o As secondary priority, support the case when NR-DC is configured and CU is acting as SN and MCG is unchanged o As secondary priority, support the case when NR-DC is configured, CU is acting as MN and SCG is unchanged or SCG is released

[0019] ■ Note: The case that LTM is configured in both MCG and SCG is excluded o Specify support for subsequent LTM mobility procedures aiming to avoid RRC configuration between cell switches as per Rel-18 LTM

[0020] ■ Coordination with SA3 needed with respect to security key handling Note: Rel. 18 intra-CU LTM procedure is considered as baseline for adding inter-CU support.

[0021] 3GPP Dual Connectivity

[0022] In 3GPP Rel-12, the LTE feature Dual Connectivity (DC) was introduced, to enable the UE to be connected in two cell groups, each controlled by an LTE access node, eNBs, labelled as the Master eNB, MeNB and the Secondary eNB, SeNB. The UE still only has one RRC connection with the network. In 3GPP, the Dual Connectivity (DC) solution has since then been evolved and is now also specified for NR as well as between LTE and NR. With introduction of 5G, the term MR-DC (Multi-Radio Dual Connectivity, see also 3GPP TS 37.340 v. 18.0.0) was defined as a generic term for all dual connectivity options which includes at least one NR access node. Using the MR-DC generalized terminology, the UE is connected in a Master Cell Group (MCG), controlled by the MN, and in a Secondary Cell Group (SCG) controlled by a Secondary Node (SN).

[0023] Further, in MR-DC, when dual connectivity is configured for the UE, within each of the two cell groups, MCG and SCG, carrier aggregation may be used as well. In this case, within the Master Cell Group, MCG, controlled by the MN, the UE may use one PCell and one or more SCell(s). And within the Secondary Cell Group, SCG, controlled by the secondary node (SN), the UE may use one Primary SCell (PSCell, also known as the primary SCG cell in NR) and one or more SCell(s). This combined case is illustrated in Figure 1 b. In NR, the primary cell of a master or secondary cell group is sometimes also referred to as the Special Cell (SpCell). Hence, the SpCell in the MCG is the PCell and the SpCell in the SCG is the PSCell. In NR dual connectivity, NR-DC, both the MN, controlling the MCG, and the SN, controlling the SCG, use NR as the radio access technology.

[0024] In 3GPP Rel-18, the L1 / L2 triggered mobility (LTM) is limited to intra-CU mobility use cases (for both intra-DU and inter-DU). In other words, when the UE is in a serving cell of a serving CU, the UE can only be configured with LTM candidate cell(s) also from that serving CU, which are either cells of the same serving DU, or a candidate DU, but not cells of a different CU. LTM in Rel-18 supports NR dual connectivity, NR-DC and intra-CU LTM can be configured and used for the master cell group, MCG, and / or for the secondary cell group, SCG. For the support of NR-DC in Rel-18 LTM, RAN2 has agreed the following:

[0025] 2b) The case of SCG LTM, without MN involvement is supported as a working assumption (can be revisited e.g. at the last meeting), it is assumed that other MCG / SCG cases are not supported.

[0026] UE only releases SCG configuration at MCG LTM execution if configured by the network (revert prior agreement). No intention to optimize further bearer handling for this case.

[0027] No restriction of configuring MCG LTM and SCG LTM. No intention to further work in R2 on network interaction to better enable this.

[0028] Based on the above agreements, in Rel-18, LTM may be used for either MCG mobility (handover, PCell change) or SCG (PSCell change). However, during LTM in NR- DC, either the MCG or the SCG can be reconfigured, not both. During LTM for the MCG, the SCG can be kept or released, as configured by the network. No inter-node signalling in the network, such as Xn signalling between MN and SN, has been specified in Rel-18 to better support the NR-DC cases.

[0029] In 3GPP Rel-19, the WID RP-240299 on NR Mobility enhancements Phase 4 is planned to introduce support for inter-CU LTM in the specifications. Thus, this expects to enable LTM for the mobility use cases requiring mobility between NR base stations, gNBs. For example, the UE may be configured with LTM candidate cells of a different serving CU. These gNBs (e.g. gNB-CU(s)) are connected to each other over the Xn interface, which is a direct interface that is needed to perform mobility within the radio access network, RAN. It is also expected that inter-CU LTM will support scenarios when NR dual connectivity is configured for the UE. According to the WID RP-240299, the following scenario is to be supported for inter-CU LTM: o As secondary priority, support the case when NR-DC is configured, CU is acting as MN and SCG is unchanged or SCG is released

[0030] ■ Note: The case that LTM is configured in both MCG and SCG is excluded

[0031] Thus, there is a need for a solution to perform inter-CU LTM in NR-DC when the CU is configured as MN and SCG is either unchanged or released. It is not clear how the network and the UE determines whether to either keep or release SCG during the inter- MN mobility in NR-DC, especially if keeping SCG does not allow the SCG to be changed (reconfigured).

[0032] The scope of the work in Rel-19 also includes to specify support for subsequent LTM mobility procedures, i.e. so that RRC configuration may be avoided between different cell switches. This is supported for LTM in Rel-18. It is then however also unclear how the network and the UE determines the handling of configurations if the SCG is released in one LTM cell switch (for the MCG), where the LTM candidate configuration includes that the SCG is released, and then performs a subsequent LTM cell switch (for the MCG) to a candidate cell for which the SCG was to be kept. A problem caused by the subsequent procedures is that the order of execution is typically not known in advance (i.e. at the time of configuration). Depending on the order of execution, the SCG may then either be still present, or already released, when a (subsequent) LTM cell switch is to be performed. For example, the LTM candidate cell configuration may have become outdated and cannot be used. This leads to UE reconfiguration after an LTM cell switch which may make subsequent LTM not possible to perform.

[0033] SUMMARY

[0034] There is thus a need for a more efficient approach for LTM.

[0035] An object of embodiments herein may be to obviate some of the problems mentioned above.

[0036] In order to address the above challenges, the embodiments herein presents solutions in cases when a wireless communications device is configured with dual connectivity, NR-DC, with a source master cell group, source MCG, including a source cell, controlled by a source network node, a target MCG including a target cell, controlled by a target network node, and a secondary cell group, SCG, controlled by a third network node. In the embodiments herein, solutions are presented for the wireless communications device and network node to handle a secondary cell group at mobility of the MCG for the wireless communications device. In embodiments herein, the secondary cell group, SCG, is handled, for example kept or released, during configuration or execution of inter-MN LTM for the wireless communications device. In embodiments herein, an indication about SCG handling is used by the wireless communications device and one or more network nodes to determine the handling of the SCG.

[0037] According to a first aspect, the object is achieved by method, performed by a wireless communications device, such as a UE, for handling an SCG at an LTM procedure of the wireless communications device. The wireless communications device is configured with Dual-Connectivity, DC. The LTM procedure is between a source network node and a target network node. The method comprises receiving an LTM configuration for an MCG. The method further comprises receiving an indication about SCG handling. The method further comprises executing the LTM procedure for the MCG according to the received LTM configuration for the MCG. While executing the LTM procedure the method further comprises handling the SCG according to the received indication about SCG handling.

[0038] The LTM configuration may be received from a network node, such as a source or target master network node. The indication about SCG handling may be received from a further network node, such as a secondary node.

[0039] The further network node may be the same network node as the network node that sent the LTM configuration. However, the mobility configuration may have been received some time ago when the wireless communications device was served with a completely different network node compared to the network node that serves the wireless communications device when it executes the LTM procedure performs the switch. Thus, the indication about SCG handling may have been received from the same network node or a different network node that sent the mobility configuration.

[0040] In some embodiments herein, the mobility configuration includes at least one LTM candidate cell configuration.

[0041] In some other embodiments herein, the wireless communications device executes the LTM procedure by executing an LTM cell switch procedure including applying an LTM candidate cell configuration. In some embodiments herein, the wireless communications device, such as the UE, keeps or releases the SCG. In some examples, the wireless communications device receives, from a source network node, an LTM cell switch command triggering the LTM cell switch procedure. The indication about SCG handling may be received from the source network node, a target network node or a third network node. The indication about SCG handling may be included in the received mobility configuration, such as in the at least one LTM candidate cell configuration, or in the LTM cell switch command.

[0042] According to a second aspect, the object is achieved by a wireless communications device, such as a UE, for handling an SCG at a mobility procedure of the wireless communications device. The wireless communications device is adapted to perform the method according to the first aspect above.

[0043] Embodiments herein also present methods for a source network node, such as a source gNB, source Master Node, MN or source gNB-CU, to handle an SCG at a mobility procedure for a wireless communications device configured with NR-DC. The mobility procedure is an LTM procedure for an MCG between a source network node and a target network node.

[0044] According to a third aspect, the object is achieved by a method, performed by the source network node.

[0045] The method comprises transmitting, to the wireless communications device, an indication about SCG handling to be applied during the LTM procedure for the MCG.

[0046] In some examples, the source network node transmits, to the wireless communications device, a mobility configuration. In examples, the mobility configuration includes at least one LTM candidate cell configuration. In some examples, the source network node transmits, to the wireless communications device, a message triggering the mobility procedure, such as a handover command or an LTM cell switch command. In some examples, the mobility procedure is triggered by a condition, such as at a conditional LTM or conditional handover procedure.

[0047] The indication about SCG handling may be included in the transmitted mobility configuration, such as in the at least one LTM candidate cell configuration, or in the message triggering the mobility procedure, such as in the LTM cell switch command.

[0048] In some examples, the source network node transmits, to the target network node, an indication about mobility procedure for the wireless communications device. The transmitted indication about a mobility procedure may be a request to configure a mobility procedure, such as a request to configure inter-MN LTM, or an indication about execution of a mobility procedure, such as an indication about execution of an inter-MN LTM cell switch procedure. In one example, the transmitted indication about an LTM procedure includes an indication about SCG handling.

[0049] In some examples, the source network node receives, from the target network node, an indication about mobility procedure for the wireless communications device. The received indication about mobility procedure may be an indication that the mobility procedure, such as inter-MN LTM, for the wireless communications device has been configured (e.g. as a response to a transmitted request) or an indication about execution of a mobility procedure, such as an indication of execution of an inter-MN LTM cell switch procedure. In one example, the received indication about a mobility procedure includes an indication about SCG handling.

[0050] In some examples, the source network node handles the SCG during the mobility procedure, such as keeping or releasing the SCG at execution of the mobility procedure. In one example the target network node uses the received indication about SCG handling to determine how to handle the SCG.

[0051] According to a fourth aspect, the object is achieved by a source network node for handling an SCG at a mobility procedure of a wireless communications device, such as a wireless communications device, configured with NR-DC. The source network node is adapted to perform the method according to the third aspect above.

[0052] Embodiments herein also disclose methods for a target network node, such as a target gNB, target Master Node, MN, or target gNB-CU, to handle an SCG at an LTM procedure between a source network node and the target network node for a wireless communications device configured with NR-DC.

[0053] According to a fifth aspect, the object is achieved by a method, performed by the target network node.

[0054] The method comprises receiving, from the source network node, an indication about the LTM procedure for the wireless communications device. The indication comprises an identity of at least one LTM candidate cell.

[0055] The method further comprises handling the SCG during the LTM procedure for the

[0056] MCG. The handling of the SCG during the mobility procedure may be based on the received indication about the mobility procedure for the wireless communications device. For example, the received indication about the mobility procedure for the wireless communications device may include an indication about SCG handling.

[0057] The received indication about the mobility procedure for the wireless communications device may be used by the target network node to prepare to receive UL data or signaling from the wireless communications device in the target cell (id of that cell is included in the indication). The received indication about the mobility procedure for the wireless communications device may be a request to configure a mobility procedure, such as inter-MN LTM, or an indication about execution of a mobility procedure, such as execution of an inter-MN LTM cell switch procedure. In one example, the received indication about an LTM procedure for the wireless communications device includes an indication about SCG handling and the target network node uses that indication to determine how to handle the SCG. The received indication about the mobility procedure for the wireless communications device may be a first indication about the mobility procedure for the wireless communications device.

[0058] In some examples, the target network node transmits, to the source network node, an indication about a mobility procedure for the wireless communications device. Thus, the target network node may transmit, to the source network node, a second indication about a mobility procedure for the wireless communications device. The mobility procedure for the wireless communications device of the second indication may be the same mobility procedure for the wireless communications device as of the first indication.

[0059] The transmitted indication about the mobility procedure may be an indication that the mobility procedure for the wireless communications device has been configured, such as inter-MN LTM has been configured, (e.g. as a response to a received request) or an indication about execution of a mobility procedure, such as an indication of execution of an inter-MN LTM cell switch procedure. In one example, the transmitted indication about a mobility procedure includes an indication about the SCG handling.

[0060] According to a sixth aspect, the object is achieved by a target network node for handling an SCG at an LTM procedure of a wireless communications device, such as a UE, configured with NR-DC, between a source network node and the target network node. The target network node is adapted to perform the method according to the fifth aspect above. Embodiments herein also present methods for a third network node, such as a gNB or a Secondary Node, SN, controlling a Secondary Cell Group, SCG, for a wireless communications device configured with Dual Connectivity, DC, to handle the SCG at an LTM procedure for the wireless communications device.

[0061] According to a seventh aspect, the object is achieved by a method, performed by the third network node.

[0062] The method comprises:

[0063] • receiving, from the source network node or the target network node, an indication about the LTM procedure for the wireless communications device; and

[0064] • in response to receiving the indication, handling the SCG during the mobility procedure.

[0065] The received indication about the mobility procedure for the wireless communications device may be a third indication about the mobility procedure for the wireless communications device. The received indication is used by the third network node to perform any actions resulting from the mobility procedure. An example of an action is to change the used security key for the wireless communications device.

[0066] The indication gives information on whether the SCG is to be reconfigured, setup, kept or released.

[0067] Handling the SCG during the mobility procedure may be based on the received indication.

[0068] The received indication about the mobility procedure may be a request to configure a mobility procedure, such as configuration of inter-MN LTM, or a request to configure, setup or release an SCG.

[0069] In some examples, the received indication about a mobility procedure includes an indication about SCG handling.

[0070] The third network node handles the SCG during the mobility procedure, such as keeping or releasing the SCG at configuration or execution of the mobility procedure. In one example the third network node uses the received indication about SCG handling to determine how to handle the SCG.

[0071] In some examples, the third network node transmits, to the target network node, a response message to a previously received request, from the target network node. The response message may include one or more of:

[0072] • an indication about SCG handling

[0073] • a configuration of a mobility procedure, such as a configuration of inter-MN LTM, an SCG configuration a result of the received request, such as accept or reject a cause for rejecting the request

[0074] According to an eighth aspect, the object is achieved by a third network node, such as a gNB or a Secondary Node, SN, controlling a Secondary Cell Group, SCG, for a wireless communications device configured with Dual Connectivity, DC, for handling the SCG at an LTM procedure of the wireless communications device, such as a UE, between a source network node and a target network node. The third network node is adapted to perform the method according to the seventh aspect above.

[0075] According to a further aspect, the object is achieved by a computer program comprising instructions, which when executed by a processor, causes the processor to perform actions according to any of the aspects above.

[0076] According to a further aspect, the object is achieved by a carrier comprising the computer program of the aspect above, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

[0077] BRIEF DESCRIPTION OF THE DRAWINGS

[0078] In the figures, features that appear in some embodiments are indicated by dashed lines.

[0079] The various aspects of embodiments disclosed herein, including particular features and advantages thereof, will be readily understood from the following detailed description and the accompanying drawings, in which:

[0080] Figure 1a is a block diagram illustrating a simplified wireless communication system, Figure 1 b is a block diagram illustrating dual connectivity and carrier aggregation, Figure 2 is a block diagram schematically illustrating a system structure according to embodiments herein,

[0081] Figure 3 is a signalling diagram illustrating methods according to embodiments herein,

[0082] Figure 4 is a signalling diagram illustrating methods according to embodiments herein, Figure 5 is a signalling diagram illustrating methods according to embodiments herein,

[0083] Figure 6 is a signalling diagram illustrating methods according to embodiments herein,

[0084] Figure 7 is a signalling diagram illustrating methods according to embodiments herein,

[0085] Figure 8 is a flow chart illustrating a method of a wireless communications device according to some embodiments herein,

[0086] Figure 9 is a block diagram schematically illustrating a wireless communications device according to some embodiments herein,

[0087] Figure 10 is a block diagram schematically illustrating a network node according to some embodiments herein,

[0088] DETAILED DESCRIPTION

[0089] The text refers to the term “L1 / L2 based inter-cell mobility” as used in the 3gpp WID RP-233970, though it interchangeably also uses the terms L1 / L2 mobility, L1 -mobility, L1 based mobility, L1 / L2-centric inter-cell mobility, L1 / L2 inter-cell mobility, L1 / L2 Triggered Mobility, Lower-layer triggered Mobility or LTM. The basic principle is that a wireless communications device receives a lower layer signaling, e.g. a MAC CE, from the network indicating to the wireless communications device a change or switch or activation of its serving cell, e.g. change of PCell, from a source to a target PCell. A lower layer signaling is a message or signaling of a lower layer protocol, which may be referred as a L1 / L2 inter-cell mobility execution command or LTM cell switch command. The change of serving cell (e.g. change of PCell) may also lead to a change in Scell(s) for the same cell group e.g. in case the command triggers the wireless communications device to change to another cell group configuration of the same type (e.g. another MCG configuration). Before the wireless communications device receives the LTM cell switch command, the wireless communications device is configured by the network with one or more LTM candidate cells (e.g. reception of an RRC Reconfiguration message, with at least one LTM candidate cell configuration). A candidate cell configuration may include parameters in the IE CellGroupConfig per candidate cell and / or an embedded RRC Reconfiguration per candidate cell.

[0090] The term LTM cell switch procedure refers to the process of a wireless communications device changing its cell from a source cell to a target cell (which may be called here a candidate cell or a neighbour cell), using L1 / L2 triggered mobility (LTM). In the context of L1 / L2 triggered mobility (LTM), an LTM cell switch procedure may sometimes also be known as dynamic switch, LTM switch, (LTM) cell switch, (LTM) serving cell change or (LTM) cell change. Even if the term change of cell is used, that may comprise a change of a whole cell group configuration, which includes a change in the SpCell (e.g. change of PCell, or change of PSCell) and a change in SCells of the cell group (e.g. addition, modification and / or release of one or more SCells). The LTM cell switch procedure may be triggered by the wireless communications device receiving an LTM cell switch command from the network. The source and target cells in a LTM cell switch procedure may be controlled by the same gNB, which sometimes is referred to as the intra-gNB case, or when the gNB uses a distributed CU / DU RAN architecture, the intra-CU inter-DU case or the intra-CU intra-DU case (depending on whether the cells are controlled by the same DU or different DUs). When the source and target cells in a LTM cell switch procedure are controlled by different gNBs, this is sometimes referred to as the inter-gNB case, or inter-CU case, or sometimes known as an inter-CU LTM cell switch procedure.

[0091] The text refers to at least one LTM candidate cell configuration. This is also sometimes referred to as a configuration of a LTM candidate cell, which may be an RRC configuration, such as encapsulated in an RRC Reconfiguration message, that the wireless communications device receives when being configured with L1 / L2 Triggered Mobility. A LTM candidate cell configuration comprises the configuration which the wireless communications device needs to start to operate accordingly when it performs an LTM cell switch procedure to that LTM candidate cell e.g. upon reception of the LTM cell switch command indicating the wireless communications device to perform a LTM cell switch procedure to that LTM candidate cell, which becomes the target cell and the current (new) SpCell, or an SCell in a serving frequency. The LTM candidate cell configuration comprises parameters of a serving cell (or multiple serving cells, such as a cell group), comprising one or more of the groups of parameters, such as an RRCReconfiguration message, an IE CellGroupConfig or an IE SpCellConfig (or the IE SCellConfig, in the case of a Secondary Cell).

[0092] An LTM candidate cell configuration is associated with an identifier which is used in the signaling when referring to a certain LTM candidate cell configuration, such as when the wireless communications device receives the LTM candidate cell configuration and when the wireless communications device receives an LTM cell switch command indicating to the wireless communications device to perform a LTM cell switch procedure to that LTM candidate cell. This identifier is sometimes known as the LTM candidate cell configuration identity or LTM candidate configuration index (or similar).

[0093] An inter-CU LTM cell switch procedure, sometimes also referred to as inter-CU LTM or inter-gNB LTM, is an LTM cell switch procedure resulting in a change of serving cell, e.g. change of SpCell, PCell, PSCell, to an LTM candidate cell controlled by a different gNB than the source gNB or serving gNB of the wireless communications device when the execution LTM cell switch procedure was triggered (e.g. upon reception of the LTM cell switch command). From a point of view of the wireless communications device, the actions performed during an inter-CU LTM cell switch procedure may be the same type of actions as of an LTM cell switch procedure, but may also include additional actions, such as change of security key(s).

[0094] The text refers to inter Master Node L1 / L2 Triggered Mobility, inter-MN LTM, configuration of inter-MN LTM, execution of inter-MN LTM and an inter-MN LTM cell switch procedure. In the context of this disclosure, inter-MN LTM refers to inter-CU LTM, sometimes also referred to as inter-gNB LTM, handover or MCG mobility, when the wireless communications device is configured with dual connectivity, such as NR-DC, and where the source cell and target cell are both part of the source and target MCG, respectively, and controlled by different CUs or different gNBs.

[0095] The term conditional LTM refers to L1 / L2 Triggered Mobility where the execution of the LTM cell switch is triggered by the wireless communications device when an execution condition, such as a layer 1 , layer 2 or a layer 3 event, criterion or condition related to, for example, a radio measurement, is fulfilled. Upon the cell switch the wireless communications device applies a stored LTM candidate cell configuration.

[0096] The text refers to an inter-CU LTM candidate cell configuration. An inter-CU LTM candidate cell configuration is a LTM candidate cell configuration which contains the configuration which the wireless communications device needs to start to operate accordingly when it performs an LTM cell switch procedure to an LTM candidate cell which is controlled by a different base station, e.g. gNB, from the current source base station e.g. serving gNB of the wireless communications device. In some cases, the wireless communications device may receive an inter-CU LTM candidate cell configuration during configuration of inter-MN LTM. In some cases, the wireless communications device may apply an inter-CU LTM candidate cell configuration during execution of inter-MN LTM.

[0097] An inter-CU LTM candidate cell configuration, sometimes referred to as inter-MN LTM configuration, may be the same as an LTM candidate cell configuration but it may also include additional information than what is included in the LTM candidate cell configuration used for inter-CU cell switch.. This additional information may be, for example:

[0098] • Information to perform security key refresh, e.g. the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes SecurityConfig with SecurityAlgorithmConfig

[0099] • Indication to perform PDCP re-establishment

[0100] • Indication to perform a full configuration, e.g. the RRC field fullConfig •

[0101] The text refers to a mobility procedure, configuration of a mobility procedure or execution of a mobility procedure. In the context of this disclosure, a mobility procedure may be L1 / L2 Triggered Mobility, LTM, inter-CU LTM, inter-MN LTM, L3 handover, PCell handover, conditional handover (CHO), conditional LTM, PSCell change or conditional PSCell Addition or Change (CPAC). Embodiments herein sometimes use the inter-MN LTM as an example mobility procedure. However, many of the examples may also be applied for other mobility procedures, for example, LTM, inter-CU LTM, conditional LTM or CHO.

[0102] The text refers to a mobility configuration. When the wireless communications device has been configured with a mobility configuration, it may use the mobility configuration during preparation of a mobility procedure, including measurements (such as RSRP measurements on neighbor or serving cells), triggering and transmission of measurement reports, synchronization towards neighbor cells, evaluation of conditions (for conditional mobility, e.g. CHO), and during the execution of a mobility procedure (e.g. execution of an LTM cell switch procedure, execution of an inter-MN LTM cell switch procedure or execution of handover).

[0103] A mobility configuration may include one or multiple of the following type of elements where each element contains a configuration of one aspect of LTM, for example as follows:

[0104] • LTM candidate cell configuration(s),

[0105] • inter-CU LTM candidate cell configuration(s),

[0106] • inter-MN LTM configuration(s)

[0107] • reference configuration(s) • lower layer information, such as physical layer configuration, MAC layer configuration or RLC layer configuration, Cell Group configuration, serving cell configuration

[0108] • higher layer information, such as RRC protocol parameters, such as timer values, PDCP layer configuration, radio bearer configuration or measurement configuration

[0109] • Configuration of measurements for LTM

[0110] • Configuration for measurement reports for LTM

[0111] • CSI resource configuration(s) for LTM

[0112] • CSI report configuration for LTM

[0113] • Configurations of early synchronization procedures, such as o Configurations for DL pre-sync for LTM, such as configurations for early TCI state activation o Configurations for UL pre-sync for LTM, such as configurations for reception of PDCCH ordered triggered preamble transmission and reception of TA

[0114] • Configurations for the execution of an LTM cell switch procedure for a given LTM candidate cell configuration or inter-CU LTM candidate cell configuration (e.g., whether to perform random access procedure, whether to perform RLC reestablishment, or MAC reset, or PDCP recovery), a timer value, configured UL grants, dedicated RA preambles .

[0115] • A configuration which the wireless communications device needs to start to operate accordingly when it performs an LTM cell switch procedure to an LTM candidate cell which is controlled by a different base station, e.g. gNB, from the current source base station e.g. serving gNB of the wireless communications device.

[0116] • Information to perform security key refresh, e.g. the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes SecurityConfig with SecurityAlgorithmConfig.

[0117] • Indication to perform a complete configuration

[0118] • Indication to perform a full configuration, e.g. the RRC field fullConfig.

[0119] • Indication to perform L2 reset or re-establishment, such as an indication to perform MAC reset, RLC re-establishment, PDCP recovery, PDCP re-establishment for one or multiple bearers. The term “subsequent LTM”, sometimes also referred to a “subsequent LTM cell switch (procedures)” refers to that the wireless communications device performs a first LTM cell switch procedure from a source cell to a first target cell, then performs a second LTM cell switch procedure from the first target cell (which is now the new source cell) to a second target cell, and between the first and second LTM cell switch procedures there is no RRC reconfiguration of the wireless communications device. This implies also that the network does not add / remove / modify the LTM candidate cell configuration(s) or inter-CU LTM candidate cell configuration(s) in the wireless communications device between the two LTM cell switch procedures.

[0120] The text refers to an indication about SCG handling. An indication about SCG handling indicates how the wireless communications device, or a network node, such as source MN, target MN or an SN, should handle the SCG at LTM when the wireless communications device is configured with dual connectivity, such as NR-DC, with a master cell group, MCG, and a secondary cell group, SCG. The indication about SCG handling may typically be used during configuration or execution of a mobility procedure for the MCG, such as an LTM cell switch procedure for the MCG, or may be used during any other mobility procedure, such as handover, inter-RAT handover, inter-system handover, PCell change, conditional handover, conditional LTM, PSCell change, conditional PSCell change.

[0121] An indication about SCG handling may be used by the wireless communications device or a network node to determine how to handle the SCG during mobility, e.g. whether to keep an SCG, release an SCG, reconfigure an SCG or part of an SCG, activate or deactivate an SCG, add an SCG or keep an SCG unchanged. An indication about SCG handling may be included in LTM configuration, LTM candidate cell configuration or inter-CU LTM candidate cell configuration, and / or as an RRC or XnAP field or information element (IE), for example an SCG configuration such as the RRC information field mrdc-SecondaryCellGroupConfig. An indication about SCG handling may alternatively be included in the LTM cell switch command, for example as a one bit indicating whether the wireless communications device should keep or release the SCG upon executing the LTM cell switch procedure.

[0122] The indication about SCG handling may also be implicit. In one example, the indication about SCG handling is implicit by using a message type, e.g. an SN ADDITION REQUEST XnAP message indicates the SCG is kept and an SN ADDITION REQUEST REJECT XnAP message indicates the SN is released. In another example, the indication about SCG handling is implicit by having two alternative configurations (such as LTM configuration, LTM candidate cell configuration or inter-CU LTM candidate cell configuration) where the LTM cell switch command indicates which of them to apply during the LTM cell switch procedure. Alternatively, the wireless communications device determines the handling of the SCG based on a criteria or a condition, e.g. whether it has an SCG configured or not at the execution of the LTM cell switch procedure.

[0123] The text uses the term “cell” to identify a location (or coverage) on which the wireless communications device is located. However, the term “cell” may also be exchanged without any loss of meaning with the terms “radio resources”, “beams”, “TCI state”, or “TRS”. This is just to clarify that embodiments herein do not target specifically a scenario where there is a cell, but rather when a wireless communications device uses a set of source radio resources and need to switch to a target set of radio resources. In such a case, radio resource may also identify a set of configurations, field, parameters, or ASN.1 structures or IBs.

[0124] The text further uses the term MCG to identify a first network node that provides a first connectivity link to the wireless communications device and SCG to identify a second network node that provides a second connectivity link to the wireless communications device. However, the terms “MCG” and “MN” may be exchanged without any loss of meaning as well as the terms “SCG” and “SN”.

[0125] System overview

[0126] Figure 2 illustrates a system structure including the entities involved in embodiments herein.

[0127] A wireless communications device 1001 , also sometimes referred to as User Equipment (UE) herein, may be a wireless terminal, such as a cellular smartphone, sometimes connected to a first network node 1002 over a wireless interface 1004 and sometimes connected to a second network node 1003, to which the wireless communications device 1001 is connected over a wireless interface 1005.

[0128] A source network node 1002, sometimes referred to as the first network node or serving network node, controls a source cell 1007 (sometimes called serving cell or Special Cell, SpCell, PCell or PSCell. A target network node 1003, sometimes referred to the second network node or candidate network node, controls a target cell 1008, sometimes referred to as neighbour cell, candidate cell, LTM candidate cell or inter-CU LTM candidate cell. Each of the source network node 1002 and the target network node 1003 may be a base station such as, when they e.g. are part of NG-RAN, e.g. a gNB. The source network node and the target network node are connected over an interface 1006, which may be an Xn or Xn-C type of interface, for example when the source network node and target network node are of type gNB and part of an NG-RAN.

[0129] In case of a distributed CU / DU RAN architecture, each of the source network node 1002 and / or the target network node 1003 may be divided into a distributed unit, sometimes known as gNB-DU or DU, and a central unit, CU, sometimes referred to as gNB-CU, CU, gNB-CU-CP or gNB-CU-UP. Thus, in such a case the source network node 1002 may be divided into a source central unit, CU 1009, sometimes referred to as serving CU, and a source distributed unit, DU, 1010, and target network node 1003 may be divided into a target central unit, CU 1012, sometimes referred to as target CU or candidate CU, and a target distributed unit, DU, 1013. Sometimes the source central unit, CU, is referred to as the source network node and the target central unit, CU, is referred to as the target network node.

[0130] The source CU 1009 and the source DU 1010 are connected over a source interface 1011 , which may be an F1 type of interface in case of NG-RAN. Correspondingly, the target CU 1012 and the target DU 1013 are connected over a target interface 1014, which may be an F1 type of interface in case of NG-RAN.

[0131] The source network node 1002 and the target network node 1003 may be connected to a third network node 1015 over second and third interfaces 1016 and 1017, respectively. The third network node 1015 may be a base station such as, when it is e.g. part of NG-RAN, a gNB. In the latter case the interfaces 1016 and 1017 may both be an Xn or Xn-C type of interface. The wireless communications device 1001 may sometimes be connected to the third network node over a wireless interface (not shown in the figure).

[0132] Sometimes the wireless communications device 1001 is configured with dual connectivity, such as NR-DC. In this case the wireless communications device 1001 may be configured with an MCG, and an SCG. The source network node controls an MCG, sometimes called source MCG or first MCG, which includes the source cell. In this case, the target network node controls also an MCG, sometimes known as candidate MCG, second MCG or target MCG, which includes the target cell. In this case, including in the context of mobility for the MCG, such as inter-MN LTM, when controlling an MCG, the source network node may be referred to as source Master Node, source MN, serving MN or first MN, and the target network node may be referred to as target Master Node, target MN, candidate MN or second MN.

[0133] When the wireless communications device 1001 is configured with dual connectivity, such as NR-DC, the third network node 1015 controls a secondary cell group, SCG, sometimes referred to as first SCG, including a third cell, which sometimes may be referred to as a PSCell (not illustrated in the figure). In this case the third network node may be referred to as a Secondary Node, SN.

[0134] Embodiments herein target a scenario where the wireless communications device 1001 is configured with dual connectivity, such as NR-DC and is configured with LTM for the MCG.

[0135] Embodiments contain a set of methods in the wireless communications device 1001 and the source and target network nodes for handling of a secondary cell group during the execution of a mobility procedure. In the detailed embodiments, inter-CU LTM is used as example of a mobility procedure, but the methods may also be applied to other mobility procedures in order to enable handling of secondary cell groups at handover, e.g., conditional handover, conditional LTM, LTM Cell switch, etc. etc.

[0136] Embodiments present methods for a wireless communications device 1001 , configured with dual connectivity, such as NR-DC, and network nodes to handle a secondary cell group during mobility (such as inter-CU LTM) of a master cell group.

[0137] In the context of the embodiments disclosed herein, inter-CU LTM may include performing LTM procedures, such as configuration (sometimes referred to as preparation) of LTM for a wireless communications device 1001 , or execution of LTM (sometimes referred to as performing an LTM cell switch procedure).

[0138] The wireless communications device 1001 is thus configured with both an MCG and an SCG, and is configured with one or more LTM candidate cell configurations for the MCG, i.e. for a possible change of the PCell. To perform the LTM cell switch to the candidate PCell the wireless communications device 1001 applies the corresponding LTM candidate configuration and executes the corresponding LTM cell switch procedure. Embodiments disclosed herein includes methods for, but is not limited to, inter-CU LTM cell switches, i.e. between cells (PCells) that belong to different CUs or gNBs, sometimes referred to as inter-MN LTM.

[0139] In methods of the embodiments disclosed herein the wireless communications device 1001 is in NR-DC, i.e. it is configured with both an MCG and an SCG, and receives one or more LTM candidate cell configurations from a network node, e.g. from the Master Node (MN), for LTM cell switch of the MCG (for the PCell). As part of performing the LTM cell switch for the MCG there is also a need to handle the SCG that the wireless communications device 1001 was configured with when the LTM cell switch was triggered.

[0140] In some embodiments the wireless communications device 1001 may either keep or release the SCG as part of the LTM cell switch for the MCG. The source and target cells of the LTM cell switch belong to different CUs or gNBs, such as at inter-MN LTM, and the wireless communications device 1001 receives an indication about SCG handling from the network about whether to e.g. keep or release the SCG as part of the LTM cell switch. The indications may be received from e.g. the source (serving) Master Node (MN), from the candidate target MN or from the Secondary Node (SN). In one option the indication about the SCG handling is included within the LTM candidate cell configuration, i.e. in the RRCReconfiguration message included in ltm-CandidateConfig-r18 within the LTM- Candidate-r18 for the LTM candidate cell (for the MCG) to which the triggered LTM cell switch is to be performed. In one example the indication consists of that the RRCReconfiguration message in the LTM candidate cell configuration includes the mrdc- SecondaryCellGroupConfig set to release, which indicates that the wireless communications device 1001 shall release the SCG as part of the inter-CU LTM cell switch procedure for the MCG. If the mrdc-SecondaryCellGroupConfig is not included in the LTM candidate cell configuration the wireless communications device 1001 instead keeps the SCG configuration as part of the inter-CU LTM cell switch.

[0141] In some embodiments an indication about the handling of the SCG (e.g. whether to release it or keep it) is included within LTM-Candidate-r18 for the LTM candidate cell configuration (for the MCG), but outside the ltm-CandidateConfig-r18. In some alternatives there are indications about the handling of the SCG both within the Itm- CandidateConfig-r18 and outside the ltm-CandidateConfig-r18, e.g. so that the two indications are used together to determine the handling of the SCG at the corresponding LTM cell switch(es) for the MCG.

[0142] In some embodiments there is an indication about the handling of the SCG configuration (e.g. whether to keep or release the SCG) at the LTM cell switch execution within the LTM Cell Switch Command MAC CE, which triggers the LTM cell switch execution for the MCG, or sent together with that MAC CE such as e.g. in another MAC CE.

[0143] In some embodiments, the indication about handling the SCG configuration is implicit. This means that how the wireless communications device 1001 should handle the SCG is decided in advance. An example of this option is that if the LTM cell switch procedure is executed towards an inter-CU LTM candidate cell, the wireless communications device 1001 always release the SCG, even if the network did not indicate anything to the wireless communications device 1001. In another example of this option, in case the wireless communications device 1001 performs an LTM cell switch procedure towards an intra-CU LTM candidate cell, the wireless communications device 1001 always keeps the SCG, unless instructed otherwise by the network. A further example of this option is that the wireless communications device 1001 always releases dual connectivity (i.e., release the SCG) before executing an LTM cell switch procedure, if this LTM cell switch procedure is executed towards an inter-CU LTM candidate cell. In yet another example of this option, the wireless communications device 1001 handles the SCG according to one or more pieces of information which is part of an LTM candidate cell configuration, such as whether L2 reset needs to be performed and whether security change needs to be performed.

[0144] To include the indication in the MAC CE that is sent at the trigger of the LTM cell switch (for the MCG) there may be different handling of the SCG, e.g. whether to keep or release the SCG, at an LTM cell switch to the same LTM candidate cell (for the MCG), at different occasions. This may be due to that the current traffic situation at the point in time of the LTM cell switch may differ so that if the amount of traffic is low it may e.g. be beneficial to release the SCG. Another reason may be due to that the coverage of the SCG (e.g. of the current PSCell) is not so good and that it therefore is better to release it as part of the LTM cell switch to a new PCell which then may belong to a different MN.

[0145] The LTM candidate configurations that the wireless communications device 1001 is configured with may be kept at mobility procedures, such as when the wireless communications device 1001 executes one of the corresponding LTM cell switch procedures. This is often referred to as subsequent LTM and means that a subsequent LTM cell switch procedure may be triggered / performed without any RRC reconfiguration. For the case of subsequent LTM for the MCG, i.e. between different PCells that may belong to the same or different MNs, the handling of the SCG configurations then however becomes unclear if it can only be indicated as being kept or released. A problem caused by the subsequent procedures is that the order of execution is typically not known in advance (i.e. at the time of configuration). Depending on the order of execution, the SCG may then either be still present, or already released, when a (subsequent) LTM cell switch is to be performed. For example, the wireless communications device 1001 in NR-DC is configured to release the SCG as part of MCG LTM cell switch to one LTM candidate cell (PCelh) and to keep the SCG as part of MCG LTM cell switch to another LTM candidate cell (PCelh), and the wireless communications device 1001 performs an LTM cell switch to PCelh according to the corresponding LTM candidate configuration. In that case, the wireless communications device 1001 would have released the SCG configuration and thus no longer be in NR-DC. In case of a subsequent LTM cell switch to PCelh that configuration would correspond to that the wireless communications device 1001 keeps the SCG, but that would then not be possible since the SCG is already released in that case. There may then be a mismatch in the configuration in the wireless communications device 1001 and the configuration in the network, such as in the MN that handles PCelh- Also the MCG configuration that is included in the LTM candidate cell configuration for PCelh may be set according to that the wireless communications device 1001 has an SCG configured, which then may be an incorrect (or not optimal) configuration in case the wireless communications device 1001 is not configured with an SCG.

[0146] In one method, even if the wireless communications device 1001 is configured to release the SCG during a first LTM cell switch procedure, this means that wireless communications device 1001 will release DC but will still keep the SCG configuration. In case the wireless communications device 1001 perform a second LTM cell switch procedure, if this LTM cell switch configures the wireless communications device 1001 to keep the SCG, since the wireless communications device 1001 does not have an SCG anymore this is an implicit indication that the wireless communications device 1001 should initiate a random access procedure towards the SCG which is associated to the SCG that was kept.

[0147] In one method, releasing the SCG does not mean that the SCG is released on both the network and the UE side. The instruction of “releasing the SCG” may mean that the SCG is “deactivated” or “dormant”. Thus, even if the SCG is released from the point of view of the wireless communications device 1001 , in the sense the wireless communications device 1001 will not perform any more transmission or reception toward that SCG, the wireless communications device 1001 is not released on the network side. Also, the wireless communications device 1001 will keep the SCG configuration, even if this SCG will be in a sort of “holding” state.

[0148] In some embodiments herein, the wireless communications device 1001 is configured with more than one LTM candidate cell configuration for the same LTM candidate cell, including a configuration that corresponds to that the SCG configuration is to be kept as present and a configuration that corresponds to that no SCG configuration is present. In one example, the LTM candidate cell configuration that corresponds to that the SCG configuration is to be kept does not include mrdc-SecondaryCellGroupConfig but includes an MCG configuration that is set according to that there is an SCG, i.e. thus corresponding to that the SCG that the wireless communications device 1001 had before the LTM cell switch execution is kept. The RRCReconfiguration message included in Itm- CandidateConfig-r18 (i.e. the MCG configuration) may e.g. include the sk-counter or the scg-State.

[0149] In one example, the LTM candidate cell configuration that corresponds to that no SCG configuration is present includes the mrdc-SecondaryCellGroupConfig set to release. In another example, it does not include the mrdc-SecondaryCellGroupConfig and it includes an MCG configuration that is set according to that there is no SCG configured.

[0150] In one alternative, the wireless communications device 1001 is configured with different LTM candidate cell configurations for the same LTM candidate cell (PCell): one that corresponds to that the SCG configuration is to be kept as present and a configuration that corresponds to that no SCG configuration is present. Then the wireless communications device 1001 receives an indication in (or together with) the LTM Cell Switch MAC CE triggering the LTM cell switch to that PCell about which of the configurations to use. In one option, each LTM candidate cell configuration includes an own candidate identity, e.g. that they correspond to separate LTM-Candidate-r18 with their own Itm-Candidateld. The MAC CE (e.g. the LTM Cell Switch MAC CE) then includes an indication about whether to keep or release the SCG as part of the LTM cell switch by indicating which LTM candidate cell configuration that the wireless communications device 1001 shall apply in order to perform the LTM cell switch to the PCell, e.g. the Itm-Candidateld of the LTM candidate cell configuration that corresponds to that the SCG configuration is to be kept as present or the Itm-Candidateld of the LTM candidate cell configuration that corresponds to that the SCG configuration is to be released, respectively.

[0151] In one option, there is an indication to the DU (gNB) that triggers the LTM cell switch about which configuration that corresponds to that there is an SCG kept and which that corresponds to that the SCG is released. E.g. an indication about SCG presence with each LTM candidate configuration also in the inter-node signaling.

[0152] In one option, the different LTM candidate cell configurations for the same LTM candidate cell (PCell), i.e. for configurations with SCG present or not, are included within the same LTM-Candidate-r18 and thus have the same Itm-Candidateld. The LTM- Candidate-r18 then includes different configurations (e.g. different RRCReconfiguration messages) to be applied at the LTM cell switch with an indication about which includes an SCG and which does not. In one example, the MAC CE (e.g. the LTM Cell Switch MAC CE) includes an indication about the LTM candidate cell configuration that the LTM cell switch (for the MCG) concerns (e.g. using Itm-Candidateld) and an indication whether the wireless communications device 1001 should keep or release the SCG as part of the LTM cell switch execution. The wireless communications device 1001 then applies the corresponding configuration (one of the RRCReconfiguration messages within the indicated LTM-Candidate-r18) that corresponds to whether the SCG is to be kept or released, i.e. with SCG present or not. In one example, the MAC CE (e.g. the LTM Cell Switch MAC CE) includes an indication about the LTM candidate cell configuration that the LTM cell switch (for the MCG) concerns (e.g. using Itm-Candidateld) and the wireless communications device 1001 applies one of the included configurations (one of the RRCReconfiguration messages within the indicated LTM-Candidate-r18). The selection of configuration depends on whether the wireless communications device 1001 has an SCG configured or not when the LTM cell switch is triggered, i.e. whether it has an SCG configured with the source PCell of the LTM cell switch procedure when it e.g. receives the LTM Cell Switch Command MAC CE in the source PCell. If the wireless communications device 1001 is configured with an SCG when it receives the LTM Cell Switch Command MAC CE it applies the configuration (in the LTM candidate cell configuration for the target PCell) that corresponds to that an SCG is present (and thus kept at the LTM cell switch execution). If the wireless communications device 1001 is not configured with an SCG when it receives the LTM Cell Switch Command MAC CE it applies the configuration (in the LTM candidate cell configuration for the target PCell) that corresponds to that no SCG is present.

[0153] In some embodiments, the LTM candidate cell configuration (for MCG LTM cell switches) includes an indication about whether it includes an SCG configuration or not, or one or more of the different configurations in the LTM candidate cell configuration for the MCG (e.g. within LTM-Candidate-r18) is / are associated with an indication (or separate indications) of whether it / they include an SCG configuration, or not.

[0154] At the execution of the LTM candidate cell switch for the MCG, i.e. to the corresponding candidate target PCell, the wireless communications device 1001 may thus use different configurations depending on whether it has been indicated to keep the SCG or to release it as part of the LTM cell switch execution for the MCG. In some methods, the wireless communications device 1001 then sends an indication to the network (to the candidate target MN) about whether the SCG is kept present or not as part of the LTM cell switch execution procedure for the MCG. In some alternatives, the wireless communications device 1001 includes the indication in the RRCReconfigurationComplete message that is sent to the target PCell (to the candidate target MN in case of inter-CU LTM cell switch) as part of the LTM cell switch execution procedure for the MCG. In some embodiments, the MN handling the target PCell of the LTM cell switch procedure determines whether the wireless communications device 1001 has applied an LTM cell candidate configuration with or without an SCG based on which MCG configuration that the wireless communications device 1001 used towards the target PCell at the LTM cell switch. In some alternatives, the source network node of the LTM cell switch procedure (e.g. the source DU and / or the source CU / gNB) sends an indication to the target network node (e.g. the target DU and / or the target CU / gNB) about which LTM candidate cell configuration that the wireless communications device 1001 will perform the LTM cell switch with towards the target PCell, e.g. whether it will use a configuration with or without an SCG configuration.

[0155] When the wireless communications device 1001 performs a mobility procedure to a different MN, e.g. an inter-CU LTM cell switch for the MCG, a security key change needs to be performed for the MCG as part of the procedure. In other words, the wireless communications device 1001 will need to apply and use a new security key configuration towards the network (i.e. towards the target MN) after the inter-CU LTM cell switch. This will then also impact the security key that is used towards the SCG since that is based on the security key that is used for the MCG. This means that even if the SCG is kept at the inter-CU LTM cell switch procedure, the security key towards the SCG may need to be changed. This, in turn, means that a random access procedure may need to be performed towards the SCG (the PSCell) when an inter-CU LTM cell switch procedure is executed for the MCG. This may e.g. be needed in order to align the wireless communications device 1001 and the network about when the new key is to be used.

[0156] In some embodiments, the wireless communications device 1001 therefore receives configuration related to how to perform random access towards the SCG when the same SCG is kept at the LTM cell switch execution procedure for the MCG, and the wireless communications device 1001 then performs a corresponding random access procedure towards the SCG associated to the LTM cell switch procedure for the MCG. In one example the wireless communications device 1001 has a random access configuration for the current SCG (PSCell), e.g. within ServingCellConfigCommon, which the wireless communications device 1001 uses when it performs a random access towards the SCG / PSCell at the LTM cell switch execution for the MCG. In one example the LTM candidate cell configuration for the MCG, which includes that the wireless communications device 1001 keeps the SCG as part of the LTM cell switch execution for the MCG, according to any of the embodiments above, includes a random access configuration for the SCG that the wireless communications device 1001 uses when performing a random access towards the SCG as part of the LTM cell switch execution procedure for the MCG. This may e.g. be included as a reconfigurationWithSync for the SCG. In one example, the wireless communications device 1001 receives a separate configuration associated to how to perform the random access procedure towards the SCG at the LTM cell switch execution procedure for the MCG.

[0157] In some embodiments it may also be considered that the wireless communications device 1001 may be configured to add or change the SCG configuration as part of the LTM cell switch procedure for the MCG, e.g. within the LTM candidate cell configuration. As an example, the wireless communications device 1001 is only configured with an MCG, i.e. it is not in NR-DC, when execution of an LTM cell switch procedure is triggered and it then performs an SCG / PSCell addition as part of the LTM cell switch procedure for the MCG, according to any of the above-disclosed embodiments.

[0158] In some embodiments, the wireless communications device 1001 performs the above methods for intra-CU LTM cell switches, i.e. between cells (PCells) that belong to the same CU or gNB.

[0159] As the wireless communications device 1001 has executed an LTM cell switch execution for the MCG to a PCell and then released its SCG configuration, it does not make sense for other candidate target MNs (that had MCG LTM candidate cell configuration for the same wireless communications device 1001 that included an SCG configuration) to keep their connection for that wireless communications device 1001 towards the network node that acts as an SN (i.e. that provided the SCG configuration). In some method embodiments, the network node acting as a candidate target MN MNcti) for the wireless communications device 1001 , by having provided an MCG LTM candidate cell configuration for the wireless communications device 1001 , therefore performs a release of its connection for the wireless communications device 1001 towards the SN due to that the wireless communications device 1001 has performed an MCG LTM cell switch execution to a PCell located in another MN. In one example the MNcti then sends an XnAP S-NODE RELEASE REQUEST message to the SN in order to trigger a release of its connection for the wireless communications device 1001 to that SN. In one alternative, the candidate target MN (MNcti) gets an indication from the current MN of the wireless communications device 1001 that the SCG has been released and it triggers the release of the connection to the SN (for the wireless communications device 1001) when it receives that indication. In one alternative, the candidate target MN MNcti) gets the indication from the network node that handled the source PCell of the executed LTM cell switch procedure (for the MCG) for the wireless communications device 1001.

[0160] In one example the wireless communications device 1001 is configured with NR-DC and during configuration of inter-MN LTM, the target MN determines that the SCG is to be released. In order to not move to single connectivity for the wireless communications device 1001 , the target MN initiates the change of SN as in CHO. So in the configuration phase of inter-MN LTM the target MN sends in one example an SN ADDITION REQUEST message to a candidate SN. This message will not be related to LTM.

[0161] In a method, when the source network node requests a target network node to configure a mobility procedure, such as LTM. In case the source network node is communicating with a third network node (because DC is configured), the source network node in the request to the target network node includes also restrictions and capability limitation that the source network node and the third network node had agreed when DC was configured. This means that the target network node may decide how to handle the SCG based on this restriction and capability agreed by the source network node and third network node. If the target network node is okay with such restriction and capabilities, then the target network node may decide to keep the SCG, otherwise it may decide to release the SCG. In a further example, if the target network node is not okay with such restrictions and capabilities, then the target network node may decide to release the SCG, or alternatively to re-configure the SCG (where the reconfiguration of the SCG imply that the mobility procedure requested by the source network node will not be configured after all).

[0162] Sequence diagrams

[0163] Figure 3 illustrates a message sequence chart for some first embodiments. In these first embodiments, the wireless communications device 1001 is configured with NR-DC and during configuration of inter-MN LTM, the target MN and the SN determines that the SCG is to be kept unchanged and keeps the context of the wireless communications device 1001 (UE context).

[0164] Referring to Figure 3, some actions in this example are as follows.

[0165] Action 301. The source MN receives, from the wireless communications device 1001 L3 measurement reports indicating measurements on neighboring cells.

[0166] Action 302. The source MN decides to configure LTM for the wireless communications device 1001 , where at least one of the LTM candidate cell(s) for MCG mobility is controlled by a different gNB. In this example, the source MN decides to configure inter-MN LTM where at least one LTM candidate cell is controlled by a target MN.

[0167] Action 303. In some embodiments disclosed herein the source network node 1002 transmits, to the target network node 1003, an indication about the LTM procedure for the MCG. The indication may comprise an identity of at least one LTM candidate cell for the MCG. The indication about the LTM procedure for the MCG transmitted to the target network node 1003 may further include an indication about SCG handling.

[0168] For example, the source MN transmits a message to request the target MN to perform configuration of inter-MN LTM for the wireless communications device 1001. In one example, the message is a new XnAP message, such as an LTM CONFIGURATION REQUEST message. In another example, the message is an existing XnAP message, such as a HANDOVER REQUEST XnAP message. The message includes an identity of at least one LTM candidate cell. The message may also include the current configuration of the wireless communications device 1001 (UE configuration) and / or an indication about SCG handling. The message may also include references to the current SN controlling the SCG configured for the wireless communications device 1001 , a context reference of the wireless communications device 1001 (UE context reference) at that SN and a list of capabilities of the wireless communications device 1001 (UE capabilities).

[0169] Action 304. The target network node 1003 handles the SCG during the LTM procedure for the MCG.

[0170] For example, upon reception of the request message, the target MN determines how to handle the SCG during the executionof inter-MN LTM to the target MN, e.g. whether it wants to keep or release the SCG. In this example, the target MN determines it should attempt to keep the SCG.

[0171] Action 305. The second network node 1003 transmits an indication about the LTM procedure to the third network node 1015. For example, the target MN transmits a message, for example an SN ADDITION REQUEST XnAP message to the SN that controls the SCG for the wireless communications device 1001. In the message, it may include a reference of the wireless communications device 1001 in this SN and an indication about SCG handling (e.g. indicating to keep the SCG). The message may also indicate that this is about LTM, such as an LTM indicator, a list of the UE capabilities and an indicator of new SN key.

[0172] Action 306. The SN determines how to handle the SCG during the configuration of inter-MN LTM. In this example, the SN determines to keep SCG, which in this example means the SCG is kept unchanged. For this determination, the SN may, for example, use the received indication about SCG handling and the UE capabilities.

[0173] Action 307. The third network node 1015 transmits an indication about the LTM procedure to the source network node 1002 or the target network node 1003 as a response to the received request to configure the inter-Master Node LTM procedure or the received request to configure, setup or release the SCG. For example, the SN may respond to the target MN in an SN ADDITION REQUEST ACKNOWLEDGE XnAP message as in Figure 3. The message includes an indication about SCG handling. In this example, it indicates the SCG is kept unchanged. In one example, the indication is an CG-Config RRC IE with the field scg-CellGroupConfig absent.

[0174] Action 308. The source network node may receive, from the target network node 1003, an indication about the LTM procedure, such as inter-MN LTM, for the wireless communications device 1001. Thus, the target network node 1003 transmits, to the source network node 1002, a second indication about the LTM procedure for the MCG. The second indication about the LTM procedure for the MCG is an indication that the LTM procedure for the MCG has been configured or that that the LTM procedure for the MCG has been executed.

[0175] For example, the target MN transmits, to the source MN, a response message including at least one LTM candidate cell configuration. In one example, the message is a new XnAP message, such as an LTM CONFIGURATION REQUEST ACKNOWLEDGE message. In another example, the message is an existing XnAP message, such as a HANDOVER REQUEST ACKNOWLEDGE XnAP message. In this example, the message includes an indication about SCG handling. In this example, it indicates the SCG is kept unchanged. In one example, the indication about SCG handling is included in the LTM candidate cell configuration by having the SCG configuration or mrdc- SecondaryCellGroupConfig IE absent (not present). In another example, the indication about SCG handling is included in the XnAP part of the message. In some cases, for the SN terminated bearers using MCG resources, the target MN provides Xn-U DL TNL address information in the Xn-U Address Indication message.

[0176] Action 309. The source network node 1002 transmits to the wireless communications device 1001 , an indication about SCG handling to be applied during the LTM procedure for the MCG. For example, the source MN transmits, to the wireless communications device 1001 , an LTM configuration, including the at least one LTM candidate cell configuration received from the target MN, for example in an RRCReconfiguration message. In this example, the message includes an indication about SCG handling. In this example, it indicates the SCG is kept unchanged. In one example, the indication about SCG handling is included in the LTM candidate cell configuration by having the SCG configuration or mrdc-SecondaryCellGroupConfig IE absent (not present). In one example the source MN uses a received indication about SCG handling to determine how the SCG is to be handled during later execution.

[0177] Action 310. The wireless communications device 1001 stores the received LTM configuration, and in this example it includes the indication about SCG handling, e.g. included in the LTM candidate cell configuration. In this example, it indicates the SCG is kept unchanged, e.g. by having the SCG configuration or mrdc- SecondaryCellGroupConfig IE absent (not present).

[0178] Action 311. The wireless communications device 1001 responds, to the source MN, for example in an RRCReconfigurationComplete message.

[0179] Figure 4 illustrates a message sequence chart for some second embodiments. In these second embodiments, the wireless communications device 1001 is configured with NR-DC and during configuration of inter-MN LTM, the SN determines that the SCG is to be released.

[0180] Referring to Figure 4, the actions in are as follows.

[0181] Actions 401-405. Same as the corresponding actions in Figure 3.

[0182] Action 406. The SN determines how to handle the SCG during the configuration of inter-MN LTM. In this example, the SN determines to release SCG. For this determination, the SN may, for example, use the received indication about SCG handling and the UE capabilities.

[0183] Action 407. The SN responds to the target MN to inform about releasing SCG, for example in an SN ADDITION REQUEST REJECT, SN ADDITION REQUEST ACKNOWLEDGE or SN RELEASE REQUIRED XnAP message. The message includes an indication about SCG handling. In this example, this indication is implicit by using the message type.

[0184] Action 408. The target MN transmits, to the source MN, a response message including at least one LTM candidate cell configuration. In one example, the message is a new XnAP message, such as an LTM CONFIGURATION REQUEST ACKNOWLEDGE message. In another example, the message is an existing XnAP message, such as a HANDOVER REQUEST ACKNOWLEDGE XnAP message. In this example, the message includes an indication about SCG handling. In this example, it indicates the SCG is released. In one example, the indication about SCG handling is included in the LTM candidate cell configuration by setting the mrdc-SecondaryCellGroupConfig to value “Release”.

[0185] Action 409. The source MN transmits, to the wireless communications device 1001 , an LTM configuration, including the at least one LTM candidate cell configuration received from the target MN, for example in an RRCReconfiguration message. In this example, the message includes an indication about SCG handling. In this example, it indicates the SCG is released. In one example, the indication about SCG handling is included in the LTM candidate cell configuration by setting the SCG configuration or the mrdc- SecondaryCellGroupConfig to value “Release”.

[0186] Actions 410. The wireless communications device 1001 stores the received LTM configuration, and in this example it includes the indication about SCG handling, e.g. included in the LTM candidate cell configuration. In this example, it indicates the SCG is released, e.g. by setting the SCG configuration or the mrdc-SecondaryCellGroupConfig to value “Release”.

[0187] Action 411. The wireless communications device 1001 responds, to the source MN, for example in an RRCReconfigurationComplete message.

[0188] Figure 5 illustrates a message sequence chart of some third embodiments. In these third embodiments, the wireless communications device 1001 is configured with NR-DC and during configuration of inter-MN LTM, the target MN determines that the SCG is to be released.

[0189] Referring to Figure 5, the actions of the method are as follows.

[0190] Actions 501-503. Same as the corresponding actions in Figure 3.

[0191] Action 504. Upon reception of the request message, the target MN determines how to handle the SCG during the configuration of inter-MN LTM, e.g. whether it wants to keep or release the SCG. In this example, the target MN determines to release the SCG. Actions 505-508. Same as actions 408-411 in Figure 4.

[0192] Figure 6 illustrates a message sequence chart of some fourth embodiments. In these fourth embodiments, the wireless communications device 1001 is configured with NR-DC and during execution of inter-MN LTM the SCG is kept unchanged. In this message chart, only the interaction between the wireless communications device 1001 and the RAN nodes and the interaction between RAN nodes is shown. Interaction with core network nodes, such as AMF and UPF is omitted.

[0193] Referring to Figure 6, the actions are as follows.

[0194] Action 601. The wireless communications device 1001 is configured for inter-MN LTM, for example by using the example illustrated in Figure 3.

[0195] Action 602. The wireless communications device 1001 transmits, to the source MN, lower-layer measurement reports with measurements on LTM candidate cells and serving cells.

[0196] Action 603. The source MN decides to trigger an inter-MN LTM cell switch procedure towards an LTM candidate cell controlled by the target MN.

[0197] Action 604. The source MN transmits, to the wireless communications device 1001 , an LTM cell switch command, indicating an LTM candidate cell configuration, to trigger the inter-MN LTM cell switch procedure towards the indicated LTM candidate cell. In one example, LTM cell switch command also includes an indication about SCG handling. In one example, the indication about SCG handling indicates to keep the SCG.

[0198] Action 605. The source MN transmits, to the target MN, a message indicating execution inter-MN LTM cell switch. The message may be a new message, such as an CELL CHANGE NOTIFICATION message or an existing XnAP message, such as HANDOVER REQUEST. The message may include a target cell ID, or an identity of the LTM candidate cell configuration. The message may also include an indication about SCG handling. In one example, the indication about SCG handling indicates to keep the SCG.

[0199] Action 606. The target MN determines how to handle the SCG during the execution inter-MN LTM cell switch. In one example, it uses the target cell ID or identity of the LTM candidate cell configuration in this determination. In one example, the target MN uses the received target cell ID or identity of the LTM candidate cell configuration to identify a LTM candidate cell configuration that was prepared during the LTM configuration and in this LTM candidate cell configuration it checks an indication about SCG handling, such as the value or presence of an IE or field. In one example, the SCG configuration or mrdc- SecondaryCellGroupConfig IE is absent (not present) which indicates that the SCG is to be kept. In another example, the target MN uses a received indication about SCG handling from the source MN in the determination.

[0200] Action 607. The target MN transmits, to the SN, a message indicating a mobility procedure for the MCG, such as an indication about the inter-MN LTM cell switch procedure. In one example, the message includes an indication about SCG handling. In one example, the message includes a new SN key.

[0201] Action 608. Upon receiving the indication, the SN is prepared for the inter-MN LTM cell switch procedure by the wireless communications device 1001 , for example the SN may switch the SN key.

[0202] Action 609. The wireless communications device 1001 executes the inter-MN LTM cell switch procedure and uses the received indication about SCG handling to determine how to handle the SCG. In this example, the wireless communications device 1001 keeps the SCG. The indication about SCG handling may be included in the LTM candidate cell configuration (explicitly or implicitly) the wireless communications device 1001 applies during execution or in the received LTM cell switch command.

[0203] Actions 610-611. The wireless communications device 1001 transmits the first UL data in the target cell and an RRCReconfigurationComplete message.

[0204] Actions 612-613. Upon detecting the wireless communications device 1001 accessing the target cell, the target MN transits an indication to the source MN, such as an HANDOVER ACCESS and / or an LTM CONFIGURATION RELEASE and / or a UE CONTEXT RELEASE message.

[0205] Action 614. The source MN determines how to handle the SCG during execution. In this case it determines to keep the SCG.

[0206] Figure 7 illustrates a message sequence chart of some fifth embodiments. In these fifth embodiments, the wireless communications device 1001 is configured with NR-DC and during execution of inter-MN LTM the SCG is released. In this message chart, only the interaction between the wireless communications device 1001 and the RAN nodes and the interaction between RAN nodes is shown. Interaction with core network nodes, such as AMF and UPF is omitted.

[0207] Referring to Figure 7, the actions are as follows.

[0208] Actions 701-703. Same as corresponding actions in Figure 6.

[0209] Action 704. The source MN transmits, to the wireless communications device 1001 , an LTM cell switch command, indicating an LTM candidate cell configuration, to trigger the inter-MN LTM cell switch procedure towards the indicated LTM candidate cell. In one example, LTM cell switch command also includes an indication about SCG handling. In one example, the indication about SCG handling indicates to release the SCG.

[0210] Action 705. The source MN transmits, to the target MN, a message indicating execution of inter-MN LTM cell switch. The message may be a new message, such as an CELL CHANGE NOTIFICATION message or an existing XnAP message, such as HANDOVER REQUEST. The message may include a target cell ID, or an identity of the LTM candidate cell configuration. The message may also include an indication about SCG handling. In one example, the indication about SCG handling indicates to release the SCG.

[0211] Action 706. The target MN determines how to handle the SCG during the execution inter-MN LTM cell switch. In one example, it uses the target cell ID or identity of the LTM candidate cell configuration in this determination. In one example, the target MN uses the received target cell ID or identity of the LTM candidate cell configuration to identify a LTM candidate cell configuration that was prepared during the LTM configuration and in this LTM candidate cell configuration it checks an indication about SCG handling, such as the value or presence of an IE or field. In one example, the SCG configuration or the mrdc- SecondaryCellGroupConfig is set to value “Release”. In another example, the target MN uses a received indication about SCG handling from the source MN in the determination. In this example, the target MN determines that the SCG is released during execution.

[0212] Action 707. The wireless communications device 1001 executes the inter-MN LTM cell switch procedure and uses the received indication about SCG handling to determine how to handle the SCG. In this example, the wireless communications device 1001 releases the SCG. The indication about SCG handling may be included in the LTM candidate cell configuration (explicitly or implicitly) the wireless communications device 1001 applies during execution or in the received LTM cell switch command.

[0213] Actions 708-711. Same as actions 610-613 in Figure 6.

[0214] Action 712. The source MN determines how to handle the SCG during execution. In this case it determines to release the SCG.

[0215] Actions 713-715. The source MN requests the SN to release the SCG by transmitting to the SN a message, such as SN RELEASE REQUEST. The SN releases the SCG resources for the wireless communications device 1001 and responds with e.g. SN RELEASE REQUEST ACKNOWLEDGE.

[0216] Flowcharts Figure 8 illustrates a flow chart with actions performed by the wireless communications device 1001 according to some embodiments disclosed herein. The flow chart is directed to a method, performed by the wireless communications device 1001. The wireless communications device 1001 is configured with DC. The method is for handling an SCG, at an LTM procedure of the wireless communications device 1001 between a source network node 1002 and a target network node 1003. In some embodiments herein the LTM procedure is inter-CU LTM or conditional LTM.

[0217] Referring to Figure 8, the actions performed by the wireless communications device 1001 in this example are as follows.

[0218] Action 8001. The wireless communications device 1001 receives an LTM configuration for an MCG. For example, the wireless communications device 1001 receives, from a network node, a reconfiguration message (such as RRCReconfiguration) including an LTM configuration. In one example the LTM configuration includes at least one LTM candidate cell configuration. In another example, the LTM configuration concerns inter-MN LTM.

[0219] The LTM configuration may include at least one of:

[0220] • LTM candidate cell configuration(s);

[0221] • inter-CU LTM candidate cell configuration(s);

[0222] • inter-Master Node LTM configuration(s);

[0223] • reference configuration(s);

[0224] • lower layer information;

[0225] • higher layer information;

[0226] • Configuration of measurements for LTM;

[0227] • Configuration for measurement reports for LTM;

[0228] • CSI resource configuration(s) for LTM;

[0229] • CSI report configuration for LTM;

[0230] • Configurations of early synchronization procedures;

[0231] • Configurations for the execution of an LTM cell switch procedure;

[0232] • A configuration which the wireless communications device 1001 needs to start to operate accordingly when it performs an LTM cell switch procedure to an LTM candidate cell;

[0233] • Information to perform security key refresh;

[0234] • Indication to perform a complete configuration;

[0235] • Indication to perform a full configuration, e.g. the RRC field fullConfig; or Indication to perform L2 reset or re-establishment, such as an indication to perform MAC reset, RLC re-establishment, PDCP recovery, PDCP re-establishment for one or multiple bearers.

[0236] Action 8002. The wireless communications device 1001 receives, e.g. from a network node, an indication about SCG handling, for example as part of the LTM configuration or in a received LTM cell switch command. In some embodiments herein the indication about SCG handling is included in an LTM candidate cell configuration applied during execution of the LTM procedure for the MCG.

[0237] The SCG handling may be performed during the LTM procedure, e.g. during an inter-MN mobility in NR-DC.

[0238] In some embodiments herein the indication about SCG handling consists of that the RRCReconfiguration message in the LTM candidate cell configuration includes the mrdc- SecondaryCellGroupConfig set to release. This is then an explicit indication that the UE shall release the SCG as part of the (inter-CU) LTM cell switch procedure.

[0239] The LTM candidate cell configuration for the MCG may indicate that the wireless communications device 1001 keeps the SCG as part of the LTM cell switch execution for the MCG. Then the indication about SCG handling may include a random access configuration for the SCG. The random access configuration for the SCG may e.g. be included as a reconfigurationWithSync for the SCG. In one example, the wireless communications device 1001 receives a separate configuration associated to how to perform the random access procedure towards the SCG at the LTM cell switch execution procedure for the MCG.

[0240] The indication about SCG handling may be included in a message triggering the LTM procedure, such as a handover command or an LTM cell switch command.

[0241] The received indication about SCG handling may indicate one of:

[0242] • Keeping the SCG;

[0243] • releasing the SCG;

[0244] • reconfiguring the SCG;

[0245] • adding an SCG;

[0246] • setting up an SCG;

[0247] • activating an SCG;

[0248] • deactivating an SCG; or

[0249] • keeping an SCG unchanged. Action 8003. The wireless communications device 1001 executes an LTM procedure for the MCG, such as an LTM cell switch procedure, according to the received LTM configuration for the MCG. In one example, the wireless communications device 1001 executes inter-MN LTM during this procedure.

[0250] Action 8004. While executing the LTM procedure, the wireless communications device 1001 handles the SCG according to the received indication about SCG handling, such as keeping or releasing the SCG during the LTM cell switch procedure.

[0251] The method may further comprise determining how to handle the SCG according to whether or not the indication about SCG handling indicates: a) that a security key is changed, or b) that an L2 reset is done.

[0252] Embodiments disclosed herein are also directed to a method, performed by the source network node 1002, to handle an SCG, at an LTM procedure for the MCG between the source network node 1002 and the target network node 1003. The MCG is of the wireless communications device 1001 which is configured with DC.

[0253] The method comprises transmitting, to the wireless communications device 1001 , an indication about SCG handling to be applied during the LTM procedure for the MCG.

[0254] As mentioned above, the indication about SCG handling may comprise one or more of:

[0255] • Keeping the SCG

[0256] • releasing the SCG

[0257] • reconfiguring the SCG

[0258] • adding an SCG

[0259] • setting up an SCG

[0260] • activating an SCG

[0261] • deactivating an SCG

[0262] • keeping an SCG unchanged.

[0263] In some embodiments herein the method further comprises transmitting, to the wireless communications device 1001 , an LTM configuration for configuring the LTM procedure for the MCG for the wireless communications device 1001. The indication about SCG handling may be included in the LTM configuration for the MCG.

[0264] The method may further comprise transmitting, to the target network node 1003, an indication about the LTM procedure for the MCG. The indication may comprise an identity of at least one LTM candidate cell for the MCG.

[0265] The indication about the LTM procedure for the MCG transmitted to the target network node 1003 may include an indication about SCG handling.

[0266] In some embodiments herein the transmitted indication about the LTM procedure for the MCG for the wireless communications device 1001 is a request to configure the LTM procedure, such as a request to configure inter-MN LTM, or about execution of the LTM procedure.

[0267] The source network node 1002 may further receive, from the target network node 1003, an indication about the LTM procedure for the wireless communications device 1001. The received indication about the LTM procedure for the wireless communications device 1001 may include an indication about SCG handling.

[0268] The received indication about the LTM procedure for the MCG for the wireless communications device 1001 may be an indication that the mobility procedure has been configured, e.g. as a response to a transmitted request, or about execution of the mobility procedure, such as an indication of execution of inter-MN LTM cell switch procedure.

[0269] Embodiments disclosed herein are further directed to a method performed by the target network node 1003 to handle the SCG at an LTM procedure for the MCG between the source network node 1002 and the target network node 1003 of a wireless communications device 1001 configured with DC.

[0270] The target network node 1003 receives, from the source network node 1002, an indication about the LTM procedure for the MCG of the wireless communications device 1001. The indication comprises an identity of at least one LTM candidate cell.

[0271] The target network node 1003 handles the SCG during the LTM procedure for the MCG.

[0272] In some embodiments herein the received indication about the LTM procedure for the wireless communications device 1001 includes an indication about SCG handling. The received indication about the LTM procedure for the MCG may be a request to configure the LTM procedure for the MCG or an indication about execution of the LTM procedure for the MCG. As an example, when the source network node 1002 triggers the execution of the LTM cell switch procedure, it also sends a message to the target network node 1003 about the execution of the LTM cell switch procedure (e.g. action 605 in Figure 6). The target node thus prepares itself for that the UE will execute the LTM cell switch to the target node.

[0273] The target network node 1003 may further transmit, to the source network node 1002, a second indication about the LTM procedure for the MCG. The second indication about the LTM procedure for the MCG is an indication that the LTM procedure for the MCG has been configured or that that the LTM procedure for the MCG has been executed. The transmitted second indication about the LTM procedure for the MCG may include a second indication about the SCG handling.

[0274] In some embodiments herein the target network node 1003 transmits, to the third network node 1015, a third indication about the LTM procedure for the wireless communications device 1001. The third indication may comprise information to the third network node 1015 (such as the SN) about the LTM cell switch for the MCG, which involves (or may lead to) an impact to the SCG configuration. For example, the third indication may comprise an indication about SCG handling, such as a request to configure, setup or release the SCG.

[0275] The target network node 1003 may handle the SCG according to the received indication about SCG handling or the transmitted second indication about the SCG handling.

[0276] The indication about the mobility procedure for the wireless communications device 1001 may be an indication about configuring a mobility procedure for the wireless communications device 1001.

[0277] In some embodiments herein the target network node 1003, in response to transmitting the third indication, further receives from the third network node 1015 an indication about SCG handling. For example, the received indication about SCG handling may comprise an indication that the SCG is kept unchanged or that an SN ADDITION REQUEST (addition of one or more SN cells) has been rejected. Embodiments disclosed herein are further directed to a method, performed by the third network node 1015 controlling the SCG for a wireless communications device 1001 configured with Dual Connectivity, DC, to handle the SCG at an LTM procedure for a Master Cell Group, MCG, of the wireless communications device 1001 between a source network node 1002 and a target network node 1003.

[0278] The third network node 1015 receives, from the source network node 1002 or the target network node 1003, an indication about the LTM procedure.

[0279] In response to receiving the indication about the LTM procedure the third network node 1015 handles the SCG during the LTM procedure.

[0280] The received indication about the LTM procedure may be a request to configure an inter-Master NodeLTM procedure.

[0281] The received indication about the LTM procedure may be a request to configure, setup or release the SCG during the LTM procedure.

[0282] In some embodiments herein the third network node 1015 transmits an indication about the LTM procedure to the source network node 1002 or the target network node 1003 as a response to the received request to configure the inter-Master Node LTM procedure or the received request to configure, setup or release the SCG.

[0283] The received indication about the LTM procedure or the transmitted indication about the LTM procedure may include an indication about SCG handling.

[0284] In some embodiments herein handling the SCG during the LTM procedure comprises handling the SCG according to the received indication or the transmitted indication about SCG handling.

[0285] The transmitted indication about the LTM procedure for the wireless communications device 1001 may include one or more of:

[0286] • a configuration of the LTM procedure;

[0287] • an SCG configuration;

[0288] • a result, such as accept or reject of the received request; or

[0289] • a cause for rejecting the request. Figure 9 and Figure 10 illustrate further optional details of the wireless communications device 1001 / UE 1001 and the network nodes 1002, 1003, 1015 respectively. The UE 1001 is configured to perform the method actions of Figure 8 and some of the method actions of Figures 3-7 above. The network nodes 1002, 1003, 1015 are each configured to perform actions described above, for example in relation to Figures 3-7.

[0290] Specifically, the wireless communications device 1001 is adapted for handling the SCG at the LTM procedure of the wireless communications device 1001. The wireless communications device 1001 is further adapted to receive the LTM configuration for the MCG.

[0291] The wireless communications device 1001 is further adapted to receive the indication about SCG handling during the LTM procedure of the wireless communications device 1001.

[0292] The wireless communications device 1001 is further adapted to execute the LTM procedure for the MCG according to the LTM configuration for the MCG.

[0293] The wireless communications device 1001 is further adapted to handle the SCG according to the received indication about SCG handling during execution of the LTM procedure for the MCG.

[0294] The source network node 1002 is adapted to handle the SCG at the LTM procedure for the MCG of the wireless communications device 1001. The source network node 1002 is further adapted to transmit the indication about SCG handling to the wireless communications device 1001 to be applied during the LTM procedure for the MCG.

[0295] The target network node 1003 is adapted to handle the SCG, at the LTM procedure for the MCG of the wireless communications device 1001. The target network node 1003 is further adapted to receive, from the source network node 1002, an indication about the LTM procedure for the MCG. The indication comprises an identity of at least one LTM candidate cell. The target network node 1003 is adapted to handle the SCG during the LTM procedure for the MCG.

[0296] The third network node 1015 is adapted to handle the SCG at the LTM procedure of the wireless communications device 1001. The third network node 1015 is further adapted to receive, from the source network node 1002 or the target network node 1003, an indication about the LTM. The third network node 1015 is adapted to handle the SCG during the LTM procedure in response to the received indication about the LTM procedure.

[0297] The embodiments herein may be implemented through a processor or one or more processors, such as the processor 904, 1104 of a processing circuitry in the UE 1001 and each of the network nodes 1002, 1003, 1015, and depicted in Figures 9 and 10 together with computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the UE 1001 and each of the network nodes 1002, 1003, 1015. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the UE 1001 and each of the network nodes 1002, 1003, 1015.

[0298] The UE 1001 and each of the network nodes 1002, 1003, 1015 may further comprise a memory 902, 1102 comprising one or more memory units. The memory comprises instructions executable by the processor in the UE 1001 and each of the network nodes 1002, 1003, 1015.

[0299] The respective memory 902, 1102 is arranged to be used to store e.g. information, data, configurations, and applications to perform the methods herein when being executed in the UE 1001 and each of the network nodes 1002, 1003, 1015.

[0300] In some embodiments, a computer program 903, 1103 comprises instructions, which when executed by the at least one processor, cause the at least one processor of the UE 1001 and each of the network nodes 1002, 1003, 1015 to perform the actions above.

[0301] In some embodiments, a carrier 905, 1105 comprises the computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. The UE 1001 and each of the network nodes 1002, 1003, 1015 may further comprise an input and output interface, I / O, 906, 1106 configured to communicate with other devices. The input and output interface 906, 1106 may comprise a wireless transceiver.

[0302] Those skilled in the art will also appreciate that the units described above may refer to a combination of analog and digital circuits, and / or one or more processors configured with software and / or firmware, e.g. stored in the UE 1001 and each of the network nodes 1002, 1003, 1015, that when executed by the respective one or more processors such as the processors described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system- on-a-chip (SoC).

[0303] Example embodiments will now be described with respect to the 3GPP TS 38.423, v18.0.0 (2023-12), Xn application protocol (XnAP) (new text is underlined and bold).

[0304] 8.2.1 Handover Preparation

[0305] 8.2.1.1 General

[0306] This procedure is used to establish necessary resources in an NG-RAN node for an incoming handover. If the procedure concerns a conditional handover, parallel transactions are allowed. Possible parallel requests are identified by the target cell ID when the source UE AP IDs are the same.

[0307] The procedure uses UE-associated signalling.

[0308] Existing specification text omitted here for saving space.

[0309] If the SCG Indicator \E is included in the HANDOVER REQUEST message, the target NG-RAN node shall use this information as specified in TS 37.340 f81.

[0310] If the SCG Indicator \E is included in the HANDOVER REQUEST ACKNOWLEDGE message, the source NG-RAN node shall use this information as specified in TS 37.340 f81.

[0311] 8.3.1 S-NG-RAN node Addition Preparation

[0312] 8.3.1.1 General

[0313] The purpose of the S-NG-RAN node Addition Preparation procedure is to request the S- NG-RAN node to allocate resources for dual connectivity operation for a specific UE. Possible parallel requests are identified by the PCell ID when the source UE AP IDs are the same.

[0314] The procedure uses UE-associated signalling.

[0315] Existing specification text omitted here for saving space. If the SCG Indicator \E is contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, store this information and use it as defined in TS 37.340 [8],

[0316] If the SCG Indicator \E is contained in the S-NODE ADDITION REQUEST ACKNOWLEDGE message, the S-NG-RAN node shall, if supported, store this information and use it as defined in TS 37.340 f81.

[0317] 9.1.1.1 HANDOVER REQUEST

[0318] This message is sent by the source NG-RAN node to the target NG-RAN node to request the preparation of resources for a handover.

[0319] Direction: source NG-RAN node -^ target NG-RAN node.

[0320] Existing specification text omitted here for saving space.

[0321] 9.1.1.2 HANDOVER REQUEST ACKNOWLEDGE

[0322] This message is sent by the target NG-RAN node to inform the source NG-RAN node about the prepared resources at the target.

[0323] Direction: target NG-RAN node source NG-RAN node.

[0324] Existing specification text omitted here for saving space.

[0325] 9.1.2.1 S-NODE ADDITION REQUEST

[0326] This message is sent by the M-NG-RAN node to the S-NG-RAN node to request the preparation of resources for dual connectivity operation for a specific UE.

[0327] Direction: M-NG-RAN node node.

[0328] Existing specification text omitted here for saving space. 9.1.2.2 S-NODE ADDITION REQUEST ACKNOWLEDGE

[0329] This message is sent by the S-NG-RAN node to confirm the M-NG-RAN node about the S-NG-RAN node addition preparation.

[0330] Direction: S-NG-RAN node M-NG-RAN node. Existing specification text omitted here for saving space.

[0331] 9.2.3. xx SCG Indicator

[0332] This IE indicates whether the SCG is kept or released or modified at the S-NG-RAN node in case of an M-NG-RAN node handover with or without S-NG-RAN node change.

[0333] When using the word "comprise" or “comprising” it shall be interpreted as non- limiting, i.e. meaning "consist at least of'.

[0334] The embodiments herein are not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used.

[0335]

[0336] NUMBERED EMBODIMENTS

[0337] 1 . A method, performed by a wireless communications device, such as a UE, for handling an SCG at a mobility procedure of the wireless communications device, the method comprises: receiving, from a network node, a mobility configuration; receiving, from a further network node, an indication about SCG handling; executing a mobility procedure according to the mobility configuration; and handling the SCG according to the received indication about SCG handling.

[0338] 2. The method according to embodiment 1 , wherein handling the SCG comprises one of: Keeping the SCG; releasing the SCG; reconfiguring the SCG; adding an SCG; setting up an SCG; activating an SCG; deactivating an SCG; or keeping an SCG unchanged.

[0339] 3. The method according to any of the embodiments 1-2, wherein the indication about SCG handling indicates one of:

[0340] • Keeping the SCG;

[0341] • releasing the SCG;

[0342] • reconfiguring the SCG;

[0343] • adding an SCG;

[0344] • setting up an SCG;

[0345] • activating an SCG;

[0346] • deactivating an SCG; or

[0347] • keeping an SCG unchanged.

[0348] 4. The method according to embodiment 3, wherein the indication about SCG handling is implicit. The method according to embodiment 2, wherein the handling of the SCG is done implicit by the UE.

[0349] Here implicit means that the handling of the SCG is determined based on some other action or indication which is not about the SCG itself (e.g as given in the options below). In that case the "indication about SCG handling" is also implicit because the indication does not relate to the SCG itself.

[0350] In one option, the UE determines how to handle the SCG according to whether a security key is changed or not.

[0351] In one option, the UE determines how to handle the SCG according to whether an L2 reset is done or not. The method according to any of the embodiments 1-5, wherein the mobility procedure is LTM, inter-CU LTM or conditional LTM. The method according to any of the embodiments 1-6, wherein the mobility configuration includes at least one of:

[0352] • LTM candidate cell configuration(s);

[0353] • inter-CU LTM candidate cell configuration(s);

[0354] • inter-MN LTM configuration(s);

[0355] • reference configuration(s);

[0356] • lower layer information;

[0357] • higher layer information;

[0358] • Configuration of measurements for LTM;

[0359] • Configuration for measurement reports for LTM;

[0360] • CSI resource configuration(s) for LTM;

[0361] • CSI report configuration for LTM;

[0362] • Configurations of early synchronization procedures;

[0363] • Configurations for the execution of an LTM cell switch procedure;

[0364] • A configuration which the UE needs to start to operate accordingly when it performs an LTM cell switch procedure to an LTM candidate cell;

[0365] • Information to perform security key refresh;

[0366] • Indication to perform a complete configuration;

[0367] • Indication to perform a full configuration, e.g. the RRC field fullConfig; or Indication to perform L2 reset or re-establishment, such as an indication to perform MAC reset, RLC re-establishment, PDCP recovery, PDCP re-establishment for one or multiple bearers.

[0368] 8. The method according to any of the embodiments 1-7, wherein the indication about SCG handling is included in the mobility configuration.

[0369] 9. The method according to any of the embodiments 1-8, wherein the indication about SCG handling is included in an LTM candidate cell configuration applied during execution of a mobility procedure.

[0370] 10. The method according to embodiment 9, wherein the indication about SCG handling consists of that the RRCReconfiguration message in the LTM candidate cell configuration includes the mrdc-SecondaryCellGroupConfig set to release.

[0371] 11. The method according to any of the embodiments 1-10, wherein the indication about SCG handling is included in a message triggering the mobility procedure, such as a handover command or an LTM cell switch command.

[0372] 12. A wireless communications device, such as a UE, adapted for handling an SCG at a mobility procedure of the wireless communications device. The wireless communications device is adapted to perform the method of any of the embodiments 1-12.

[0373] 13. A method, performed by a source network node, such as a source gNB, source Master Node, MN or source gNB-CU, to handle an SCG at a mobility procedure for a UE configured with NR-DC, the method comprises: transmitting to the UE, an indication about SCG handling.

[0374] 14. The method according to embodiment 13, wherein the source network node handles the SCG according to one of:

[0375] • Keeping the SCG

[0376] • releasing the SCG

[0377] • reconfiguring the SCG

[0378] • adding an SCG • setting up an SCG

[0379] • activating an SCG

[0380] • deactivating an SCG

[0381] • keeping an SCG unchanged.

[0382] 15. The method according to any of the embodiments 13-14, wherein the source network node transmits, to the UE, a mobility configuration for configuring the mobility procedure for the UE. For example, the indication about SCG handling may be included in the mobility configuration. The UE may also need the mobility configuration in order to perform a mobility procedure during which SCG is handled.

[0383] 16. The method according to embodiment 15, wherein the indication about SCG handling is included in the mobility configuration.

[0384] 17. The method according to embodiment 15 or 16, wherein the mobility configuration includes at least one of:

[0385] LTM candidate cell configuration(s), inter-CU LTM candidate cell configuration(s), inter-MN LTM configuration(s) reference configuration(s) lower layer information higher layer information

[0386] Configuration of measurements for LTM

[0387] Configuration for measurement reports for LTM

[0388] CSI resource configuration(s) for LTM

[0389] CSI report configuration for LTM

[0390] Configurations of early synchronization procedures

[0391] Configurations for the execution of an LTM cell switch procedure.

[0392] A configuration which the UE needs to start to operate accordingly when it performs an LTM cell switch procedure to an LTM candidate cell.

[0393] Information to perform security key refresh.

[0394] Indication to perform a complete configuration

[0395] Indication to perform a full configuration, e.g. the RRC field fullConfig. Indication to perform L2 reset or re-establishment, such as an indication to perform MAC reset, RLC re-establishment, PDCP recovery, PDCP re-establishment for one or multiple bearers.

[0396] 18. The method according to any of the embodiments 13-17, wherein the source network node transmits, to the UE, a message triggering the mobility procedure, such as a handover command or an LTM cell switch command.

[0397] 19. The method according to embodiment 18, wherein the indication about SCG handling is included in the message triggering the mobility procedure.

[0398] 20. The method according to any of the embodiments 13-19 wherein the source network node transmits, to the target network node, an indication about mobility procedure for the UE.

[0399] 21 . The method according to embodiment 20, wherein the transmitted indication about the mobility procedure for the UE includes an indication about SCG handling.

[0400] 22. The method according to embodiment 20 or 21 , wherein the transmitted indication about the mobility procedure for the UE is a request to configure a mobility procedure, such as a request to configure inter-MN LTM.

[0401] 23. The method according to embodiment 20 or 21 , wherein the transmitted indication about mobility procedure for the UE is an indication about execution of a mobility procedure, such as indication about execution of an inter-MN LTM cell switch procedure.

[0402] 24. The method according to any of the embodiments 13-23, wherein the source network node receives, from the target network node, an indication about mobility procedure for the UE.

[0403] 25. The method according to embodiment 24, wherein the received indication about the mobility procedure for the UE includes an indication about SCG handling. 26. The method according to embodiment 24 or 25, wherein the received indication about mobility procedure for the UE is an indication that the mobility procedure, such as inter-MN LTM, for the UE has been configured (e.g. as a response to a transmitted request).

[0404] 27. The method according to embodiment 24 or 25, wherein the received indication about mobility procedure for the UE is an indication about execution of a mobility procedure, such as an indication of execution inter-MN LTM cell switch procedure.

[0405] 28. The method according to any of the embodiments 13-27, wherein the source network node handles the SCG according to the transmitted or received indication about SCG handling.

[0406] 29. The method according to any of the embodiments 13-28, wherein the indication about SCG handling indicates one of:

[0407] Keeping the SCG releasing the SCG reconfiguring the SCG adding an SCG setup an SCG activating an SCG deactivating an SCG keeping an SCG unchanged

[0408] 30. The method according to any of the embodiments 13-29, wherein the indication about SCG handling is implicit.

[0409] 31. The method according to any of the embodiments 13-30, wherein the source network node receives from the target network node an indication that the request for a mobility configuration, which include an indication about SCG handling, has been rejected.

[0410] 32. A source network node, adapted to handle an SCG at a mobility procedure for a UE configured with NR-DC. The source network node is further adapted to perform the method of any of the embodiments 13-. 33. Method for a target network node, such as a target gNB, target Master Node, MN, or target gNB-CU, to handle an SCG at a mobility procedure for a UE configured with NR-DC, the method comprising: receiving, from a source network node, an indication about mobility procedure for the UE; and handling the SCG during the mobility procedure.

[0411] 34. The method according to embodiment 33, wherein the received indication about a mobility procedure for the UE includes an indication about SCG handling.

[0412] 35. The method according to any of the embodiments 33-34, wherein the received indication about a mobility procedure for the UE is a request to configure a mobility procedure, such as inter-MN LTM.

[0413] 36. The method according to any of the embodiments 33-34, wherein the received indication about a mobility procedure for the UE is an indication about execution of a mobility procedure, such as an indication of execution of an inter-MN LTM cell switch procedure.

[0414] 37. The method according to any of the embodiments 33-36, wherein the target network node transmits, to the source network node, an indication about a mobility procedure for the UE.

[0415] 38. The method according to any of the embodiments 33-37, wherein the transmitted indication about the mobility procedure for the UE includes an indication about SCG handling.

[0416] 39. The method according to any of the embodiments 37-38, wherein the transmitted indication about mobility procedure for the UE is an indication that the mobility procedure for the UE has been configured, such as inter-MN LTM has been configured, (e.g. as a response to a received request).

[0417] 40. The method according to any of the embodiments 37-38, wherein the transmitted indication about mobility procedure for the UE is an indication about execution of a mobility procedure, such as an indication of execution of an inter-MN LTM cell switch procedure. The method according to any of the embodiments 33-40, wherein the target network node transmits, to a third network node, an indication about a mobility procedure for the UE. The method according to any of the embodiments 34-41 , wherein the indication about SCG handling indicates one of:

[0418] Keeping the SCG releasing the SCG reconfiguring the SCG adding an SCG setting up an SCG activating an SCG deactivating an SCG keeping an SCG unchanged The method according to any of the embodiments 34-42, wherein the indication about SCG handling is implicit. The method according to any of the embodiments 33-43, wherein the target network node handles the SCG according to a received or transmitted indication about SCG handling. The method according to any of the embodiments 33-44, wherein the target network node handles the SCG according to one of:

[0419] Keeping the SCG releasing the SCG reconfiguring the SCG adding an SCG setting up an SCG activating an SCG deactivating an SCG; or keeping an SCG unchanged. 46. The method according to any of the embodiments 33-45, wherein the target network node transmits, to a third network node, an indication about configuring a mobility procedure for the UE.

[0420] 47. The method according to any of the embodiments 33-46, wherein the target network node transmits to the source network node an indication that a request for a mobility configuration, which include an indication about SCG handling, has been rejected.

[0421] 48. A method for a third network node, such as a gNB or a Secondary Node, SN, to handle an SCG at a mobility procedure for a UE configured with NR-DC, the method comprising: receiving, from a source network node or a target network node, an indication about a mobility procedure for the UE; and handling the SCG during the mobility procedure

[0422] 49. The method according to embodiment 48, wherein the received indication about a mobility procedure for the UE is a request to configure a mobility procedure, such as configuration of inter-MN LTM.

[0423] 50. The method according to embodiment 48 or 49, wherein the received indication about a mobility procedure for the UE is a request to configure, setup or release an SCG.

[0424] 51. The method according to any of the embodiments 48-50, wherein the third network node, transmits, to the source network node or the target network node, indication about a mobility procedure for the UE.

[0425] 52. The method according to embodiment 51 dependent on embodiment 50 or 49, wherein the transmitted indication about a mobility procedure for the UE is a response to the received indication of the request to configure a mobility procedure or to configure, setup or release an SCG.

[0426] 53. The method according to any of the embodiments 48-52, wherein the received or transmitted indication about a mobility procedure for the UE includes an indication about SCG handling. 54. The method according to embodiment 53 wherein the target network node handles the SCG according to a received or transmitted indication about SCG handling.

[0427] 55. The method according to embodiment 53 or 54, wherein the indication about SCG handling indicates one of:

[0428] Keeping the SCG releasing the SCG reconfiguring the SCG adding an SCG setting up an SCG activating an SCG deactivating an SCG; or keeping an SCG unchanged.

[0429] 56. The method according to any of the embodiments 53-55, wherein the indication about SCG handling is implicit.

[0430] 57. The method according to any of the embodiments 53-55, wherein the target network node handles the SCG according to one of:

[0431] Keeping the SCG releasing the SCG reconfiguring the SCG adding an SCG setup an SCG activating an SCG deactivating an SCG; or keeping an SCG unchanged.

[0432] 58. The method according to any of the embodiments 51-57, wherein the transmitted indication about a mobility procedure for the UE includes one of:

[0433] • a configuration of a mobility procedure, such as a configuration of inter-MN LTM,

[0434] • an SCG configuration

[0435] • a result (accept / reject) of the received request; or

[0436] • a cause for rejecting the request. A computer program, comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any any of the embodiments 1-58. A carrier comprising the computer program according to the preceding claim, wherein the carrier is one of an electronic signal, an optical signal, a radio signal and a computer readable medium.

Claims

CLAIMS1 . A method, performed by a wireless communications device (1001) configured with Dual-Connectivity, DC, for handling a Secondary Cell Group, SCG, at an L1 / L2- Triggered Mobility, LTM procedure of the wireless communications device (1001) between a source network node (1002) and a target network node (1003), the method comprises: receiving (8001), from the source network node (1002) or the target network node (1003), an LTM configuration for a Master Cell Group, MCG; receiving (8002), from a further network node (1015), an indication about SCG handling; executing (8003) the LTM procedure for the MCG according to the received LTM configuration for the MCG; and while executing the LTM procedure, handling (8004) the SCG according to the received indication about SCG handling.

2. The method according to claim 1 , wherein the received indication about SCG handling indicates one of:• Keeping the SCG;• releasing the SCG;• reconfiguring the SCG;• adding an SCG;• setting up an SCG;• activating an SCG;• deactivating an SCG; or• keeping an SCG unchanged.

3. The method according to claim 1 or 2, further comprising determining how to handle the SCG according to whether or not the indication about SCG handling indicates: a) that a security key is changed, or b) that an L2 reset is done.

4. The method according to any of the claims 1-3, wherein the LTM procedure is inter- CU LTM or conditional LTM.

5. The method according to any of the claims 1-4, wherein the LTM configuration includes at least one of:• LTM candidate cell configuration(s);• inter-CU LTM candidate cell configuration(s);• inter-Master Node LTM configuration(s);• reference configuration(s);• lower layer information;• higher layer information;• Configuration of measurements for LTM;• Configuration for measurement reports for LTM;• CSI resource configuration(s) for LTM;• CSI report configuration for LTM;• Configurations of early synchronization procedures;• Configurations for the execution of an LTM cell switch procedure;• A configuration which the wireless communications device (1001) needs to start to operate accordingly when it performs an LTM cell switch procedure to an LTM candidate cell;• Information to perform security key refresh;• Indication to perform a complete configuration;• Indication to perform a full configuration; or• Indication to perform L2 reset or re-establishment, such as an indication to perform MAC reset, RLC re-establishment, PDCP recovery, PDCP re-establishment for one or multiple bearers.

6. The method according to any of the claims 1-5, wherein the indication about SCG handling is included in the LTM configuration.

7. The method according to any of the claims 1-6, wherein the indication about SCG handling is included in an LTM candidate cell configuration applied during execution of the LTM procedure for the MCG.

8. The method according to claim 7, wherein the indication about SCG handling consists of that the RRCReconfiguration message in the LTM candidate cell configuration includes the mrdc-SecondaryCellGroupConfig set to release.

9. The method according to any of the claims 1-8, wherein the indication about SCG handling is included in a message triggering the LTM procedure.

10. The method according to any of the claims 1-9, wherein an LTM candidate cell configuration for the MCG indicates that the wireless communications device (1001) keeps the SCG as part of the LTM cell switch execution for the MCG and wherein the indication about SCG handling includes a random access configuration for the SCG.

11. A wireless communications device (1001) configured with Dual Connectivity, DC, and adapted for handling a Secondary Cell Group, SCG, at an L1 / L2-Triggered Mobility, LTM procedure of the wireless communications device between a source network node (1002) and a target network node (1003), and further adapted to: receive an LTM configuration for a Master Cell Group, MCG; receive an indication about SCG handling during the LTM procedure of the wireless communications device (1001); execute the LTM procedure for the MCG according to the LTM configuration for the MCG; and during execution of the LTM procedure for the MCG, handle the SCG according to the received indication about SCG handling.

12. The wireless communications device (1001) according to claim 11 , further adapted to perform the method of any of the claims 2-10.

13. A method, performed by a source network node (1002), to handle a Secondary Cell Group, SCG, at an L1 / L2-Triggered Mobility, LTM, procedure for a Master Cell Group, MCG between a source network node (1002) and a target network node (1003) of a wireless communications device (1001) configured with Dual Connectivity, DC, the method comprises: transmitting (309) to the wireless communications device (1001), an indication about SCG handling to be applied during the LTM procedure for the MCG.

14. The method according to claim 13, wherein the indication about SCG handling comprises one or more of:• Keeping the SCG• releasing the SCG• reconfiguring the SCG• adding an SCG• setting up an SCGactivating an SCG deactivating an SCG keeping an SCG unchanged.

15. The method according to any of the claims 13-14, further comprising transmitting (309), to the wireless communications device (1001), an LTM configuration for configuring the LTM procedure for the MCG for the wireless communications device (1001).

16. The method according to claim 15, wherein the indication about SCG handling is included in the LTM configuration for the MCG.

17. The method according to any of the claims 13-16, further comprising transmitting (303), to the target network node (1003), an indication about the LTM procedure for the MCG, wherein the indication comprises an identity of at least one LTM candidate cell for the MCG.

18. The method according to claim 17, wherein the indication about the LTM procedure for the MCG transmitted to the target network node (1003) includes an indication about SCG handling.

19. The method according to claim 17 or 18, wherein the transmitted indication about the LTM procedure for the MCG for the wireless communications device (1001) is a request to configure the LTM procedure, or about execution of the LTM procedure.

20. The method according to any of the claims 17-19, wherein the transmitted indication about the LTM procedure for the MCG is transmitted in a HANDOVER REQUEST XnAP message.

21. The method according to any of the claims 13-20, further comprising receiving (308), from the target network node (1003), an indication about the LTM procedure for the wireless communications device (1001).

22. The method according to claim 21 , wherein the received indication about the mobility procedure for the wireless communications device (1001) includes an indication about SCG handling.

23. The method according to claim 21 or 22, wherein the received indication about the LTM procedure for the MCG for the wireless communications device (1001) is an indication that the mobility procedure has been configured, or about execution of the mobility procedure.

24. A source network node (1002), adapted to handle a Secondary Cell Group, SCG, at an L1 / L2-Triggered Mobility, LTM procedure for a Master Cell Group between the source network node (1002) and a target network node (1003) of a wireless communications device (1001) configured with Dual Connectivity, DC, and further adapted to: transmit an indication about SCG handling to the wireless communications device (1001) to be applied during the LTM procedure for the MCG.

25. The source network node (1002) according to claim 24, further adapted to perform the method of any of the claims 14-23.

26. Method performed by a target network node (1003) to handle a Secondary Cell Group, SCG, at an L1 / L2-Triggered Mobility, LTM procedure for a Master Cell Group between a source network node (1002) and the target network node (1003) of a wireless communications device (1001) configured with Dual Connectivity, DC, the method comprising: receiving (303), from the source network node (1002), an indication about the LTM procedure for the MCG of the wireless communications device (1001), wherein the indication comprises an identity of at least one LTM candidate cell; and handling (304) the SCG during the LTM procedure for the MCG.

27. The method according to claim 26, wherein the received indication about the LTM procedure for the wireless communications device (1001) includes an indication about SCG handling.

28. The method according to any of the claims 26-27, wherein the received indication about the LTM procedure for the MCG is a request to configure the LTM procedure for the MCG or an indication about execution of the LTM procedure for the MCG.

29. The method according to any of the embodiments 26-28, further comprising transmitting (308, 612, 710), to the source network node (1002), a second indication about the LTM procedure for the MCG, wherein the second indication about the LTM procedure for the MCG is an indication that the LTM procedure for the MCG has been configured or that that the LTM procedure for the MCG has been executed.

30. The method according to embodiment 29, wherein the transmitted second indication about the LTM procedure for the MCG includes a second indication about the SCG handling.

31. The method according to any of the embodiments 26-30, wherein the target network node (1003) handles the SCG according to the received indication about SCG handling or the transmitted second indication about the SCG handling.

32. The method according to claim 31 , wherein the indication about the mobility procedure for the wireless communications device (1001) is an indication about configuring a mobility procedure for the wireless communications device (1001).

33. The method according to any of the claims 26-32, further comprising transmitting (405), to a third network node (1015), a third indication about an LTM procedure for the wireless communications device (1001).

34. The method according to claim 33, further comprising in response to transmitting the third indication, receiving (407) from the third network node (1015) an indication about SCG handling.

35. A target network node (1003), adapted to handle a Secondary Cell Group, SCG, at an L1 / L2-Triggered Mobility, LTM procedure for a Master Cell Group, MCG, between a source network node (1002) and a target network node (1003) of a wireless communications device (1001) configured with Dual Connectivity, DC, and further adapted to:receive, from a source network node (1002), an indication about the LTM procedure for the MCG, wherein the indication comprises an identity of at least one LTM candidate cell; and handle the SCG during the LTM procedure for the MCG.

36. The target network node (1003) according to claim 35, further adapted to perform the method of any of the claims 26-33.

37. A method performed by a third network node (1015) controlling a Secondary Cell Group, SCG, for a wireless communications device (1001) configured with Dual Connectivity, DC, to handle the SCG at an L1 / L2-Triggered Mobility, LTM, procedure for a Master Cell Group, MCG, of the wireless communications device (1001) between a source network node (1002) and a target network node (1003), the method comprising: receiving (305), from the source network node (1002) or the target network node (1003), an indication about the LTM procedure ; and in response to receiving the indication about the LTM procedure handling (306) the SCG during the LTM procedure.

38. The method according to claim 37, wherein the received indication about the LTM procedure is a request to configure an inter-Master Node LTM procedure.

39. The method according to claim 37, wherein the received indication about the LTM procedure is a request to configure, setup or release the SCG during the LTM procedure.

40. The method according to claim 38 or 39, further comprising transmitting (307) an indication about the LTM procedure to the source network node (1002) or the target network node (1003) as a response to the received request to configure the interMaster Node LTM procedure or the received request to configure, setup or release the SCG.

41. The method according to any of the claims 36-40, wherein the received indication about the LTM procedure or the transmitted indication about the LTM procedure includes an indication about SCG handling.

42. The method according to claim 41 , wherein handling the SCG during the LTM procedure comprises handling the SCG according to the received indication or the transmitted indication about SCG handling.

43. The method according to any of the claims 40-42, wherein the transmitted indication about the LTM procedure for the wireless communications device (1001) includes one or more of:• a configuration of the LTM procedure;• an SCG configuration;• a result of the received request; or• a cause for rejecting the request.

44. A third network node (1015), adapted to handle a Secondary Cell Group, SCG, at an LTM procedure between a source network node (1002) and a target network node (1003) of a wireless communications device (1001) configured with Dual Connectivity, DC, and further adapted to: receive, from the source network node (1002) or the target network node (1003), an indication about the LTM; and handle the SCG during the LTM procedure in response to the received indication about the LTM procedure.

45. The third network node (1015) according to claim 44, further adapted to perform the method of any of the claims 38-43.

46. A computer program, comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any of the claims 1-10.

47. A computer program, comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any of the claims 13-23.

48. A computer program, comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any of the claims 26-34.

49. A computer program, comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any of the claims 37-43.

50. A carrier comprising the computer program according to any of the claims 46-49, wherein the carrier is one of an electronic signal, an optical signal, a radio signal and a computer readable medium.

Images