Restricting LTM configuration at MN or sn

Abstract

A method, performed by a wireless communications device configured for Dual- Connectivity, DC, for handling a configuration for L1 / L2-Triggered Mobility, LTM, which is associated to a Master Cell Group, MCG, or a Secondary Cell Group, SCG, serving the wireless communications device The method comprises receiving (8001), from a first network node, a first LTM configuration for MCG mobility or SCG mobility. The method further comprises determining (8002) whether or not the wireless communications device (1001) has stored a second LTM configuration associated with a further network node (1015). The method further comprises executing a mobility procedure based on determining whether or not the wireless communications device (1001) has stored the second LTM configuration.

Description

[0001] RESTRICTING LTM CONFIGURATION AT MN OR SN

[0002] TECHNICAL FIELD

[0003] The embodiments herein relate to a wireless communications device and network nodes for restricting an LTM configuration at an MN or an SN, 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 ( N) 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] SUMMARY

[0029] However, in Rel-19 the configuration of LTM on the MCG and SCG will be different. In fact, according to a note which is in the WID, LTM may be configured either at the MCG or SCG but not in both at the same time:

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

[0031] However, in order to achieve this, new signalling is required between the MN, controlling the MCG, and the SN, controlling the SCG, which was not discussed or addressed during Rel-18. This is because in Rel-18 the configuration and execution of LTM at the MCG and SCG is done independently.

[0032] There is thus a need for a more efficient approach for LTM.

[0033] An object of embodiments herein may be to obviate some of the problems mentioned above. In order to address the above challenges, the embodiments herein presents solutions in cases when a UE 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.

[0034] In order to address the above challenges, embodiments herein restrict the configuration of LTM for a UE configured with dual connectivity, such as NR-DC, to only one of the cell groups i.e., either the MCG or the SCG, but not both.

[0035] According to a first aspect the object is achieved by a method for a User Equipment (UE), configured with dual connectivity, such as NR-DC, which receives a configuration for LTM which is associated to the MCG or SCG which serves the wireless communications device. The method comprises receiving, from a first network node a first mobility configuration. The first mobility configuration is a first LTM configuration for MCG mobility or SCG mobility.

[0036] The method further comprises determining whether or not the wireless communications device has stored a second mobility configuration associated with a further network node.

[0037] The method further comprises executing a mobility procedure. The mobility procedure may be based on determining whether or not the wireless communications device has stored the second LTM configuration. The mobility procedure may be further based on determining how to handle the second mobility configuration.

[0038] The method may further comprises determining how to handle the second mobility configuration based on the received first mobility configuration, e.g., based on the content of the first and / or second mobility configuration.

[0039] According to a second aspect the object is achieved by a User Equipment (UE), configured to perform the method according to the first aspect above.

[0040] The embodiments herein also include a method for a first network node, to configure LTM for a UE configured with dual connectivity, such as NR-DC, either at the MCG or SCG. The method comprises:

[0041] • Determining whether a mobility configuration needs to be sent to the UE; • Transmitting to a second network node an indication about how to handle the configuration of the mobility procedure; and

[0042] • Transmitting to the UE the mobility configuration based on determining that the mobility configuration needs to be sent to the UE.

[0043] The embodiments herein also include a method for a second network node, to configure LTM for a UE configured with dual connectivity, such as NR-DC, either at the MCG or SCG. The method comprises:

[0044] • Receiving from a first network node an indication about handling of the configuration of a mobility procedure;

[0045] • Determining whether a mobility configuration needs to be sent to the UE;

[0046] • Transmitting to the UE a mobility configuration (either directly or via the first network node).

[0047] The method may further comprise transmitting to the first network node a second indication about the handling of the configuration of the mobility procedure.

[0048] The received indication is what the first network node proposes to do (e.g. keep or release a configuration). The transmitted second indication indicates what the second network node intends to do, e.g., whether the second network node intends to do the received proposal (e.g. whether it agrees or rejects the received proposal from the first network node, e.g. keep or release a configuration).

[0049] 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.

[0050] 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.

[0051] The proposed solution enables the network to configure LTM either at the MCG or the SCG. This avoids an increased signaling overhead on the network side to coordinate the configuration and execution of LTM between the MCG and the SCG. Also, the risk of race condition and misalignments in what the network triggers and what the UE executes is minimized and this brings benefits in terms of lower radio link failure and lower connectivity interruptions due to the RRC re-establishment procedure. For example, if mobility (such as execution of LTM) is executed for both the MCG and the SCG in an uncoordinated manner the configuration of the UE would depend on the order in which these were executed by the UE. Sometimes the order would depend on network delays and radio conditions and may therefore not be predicted.

[0052] BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In the figures, features that appear in some embodiments are indicated by dashed lines.

[0054] 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:

[0055] Figure 1a is a block diagram illustrating a simplified wireless communication system, Figure 1b 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,

[0056] Figure 3 is a signalling diagram illustrating methods according to some embodiments herein,

[0057] Figure 4 is a signalling diagram illustrating methods according to some further embodiments herein,

[0058] Figure 5 is a signalling diagram illustrating methods according to some further embodiments herein,

[0059] Figure 6 is a signalling diagram illustrating methods according to some further embodiments herein,

[0060] Figure 7 is a signalling diagram illustrating methods according to embodiments herein,

[0061] Figure 8 is a flow chart illustrating a method of a UE according to some embodiments herein,

[0062] Figure 9 is a block diagram schematically illustrating a UE according to some embodiments herein,

[0063] Figure 10 is a block diagram schematically illustrating a network node according to some embodiments herein, DETAILED DESCRIPTION

[0064] 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 the UE receives a lower layer signaling, e.g. a MAC CE, from the network indicating to the UE 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 UE to change to another cell group configuration of the same type (e.g. another MCG configuration). Before the UE receives the LTM cell switch command, the UE 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.

[0065] The term LTM cell switch procedure refers to the process of a UE 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 UE 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. 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 UE receives when being configured with L1 / L2 Triggered Mobility. A LTM candidate cell configuration comprises the configuration which the UE 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 UE 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).

[0066] 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 UE receives the LTM candidate cell configuration and when the UE receives an LTM cell switch command indicating to the UE 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).

[0067] 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 UE when the execution LTM cell switch procedure was triggered (e.g. upon reception of the LTM cell switch command). From a UE point of view, 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).

[0068] 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 UE 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. The term conditional LTM refers to L1 / L2 Triggered Mobility where the execution of the LTM cell switch is triggered by the UE 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 UE applies a stored LTM candidate cell configuration.

[0069] 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 UE 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 UE. In some cases, the UE may receive an inter-CU LTM candidate cell configuration during configuration of inter-MN LTM. In some cases, the UE may apply an inter-CU LTM candidate cell configuration during execution of inter-MN LTM.

[0070] 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:

[0071] • Information to perform security key refresh, e.g. the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes Security Config with SecurityAlgorithmConfig

[0072] • Indication to perform PDCP re-establishment

[0073] • Indication to perform a full configuration, e.g. the RRC field fullConfig

[0074] •

[0075] 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. The text refers to a mobility configuration. When the UE 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).

[0076] 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:

[0077] • LTM candidate cell configuration(s),

[0078] • inter-CU LTM candidate cell configuration(s),

[0079] • inter-MN LTM configuration(s)

[0080] • reference configuration(s)

[0081] • lower layer information, such as physical layer configuration, MAC layer configuration or RLC layer configuration, Cell Group configuration, serving cell configuration

[0082] • higher layer information, such as RRC protocol parameters, such as timer values, PDCP layer configuration, radio bearer configuration or measurement configuration

[0083] • Configuration of measurements for LTM

[0084] • Configuration for measurement reports for LTM

[0085] • CSI resource configuration(s) for LTM

[0086] • CSI report configuration for LTM

[0087] • 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

[0088] • 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 . • A configuration which the UE 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 UE.

[0089] • Information to perform security key refresh, e.g. the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes Security Config with SecurityAlgorithmConfig.

[0090] • Indication to perform a complete configuration

[0091] • Indication to perform a full configuration, e.g. the RRC field fullConfig.

[0092] • 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.

[0093] The term “subsequent LTM”, sometimes also referred to a “subsequent LTM cell switch (procedures)” refers to that the UE 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 UE. 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 UE between the two LTM cell switch procedures.

[0094] The text refers to an indication about SCG handling. An indication about SCG handling indicates how the UE, or a network node, such as source MN, target MN or an SN, should handle the SCG at LTM when the UE 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.

[0095] An indication about SCG handling may be used by the UE 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 UE should keep or release the SCG upon executing the LTM cell switch procedure.

[0096] 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 UE 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.

[0097] The text uses the term “cell” to identify a location (or coverage) on which the UE 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 UE 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 lEs.

[0098] The text further uses the term MCG to identify a first network node that provides a first connectivity link to the UE and SCG to identify a second network node that provides a second connectivity link to the UE. However, the terms “MCG” and “MN” may be exchanged without any loss of meaning as well as the terms “SCG” and “SN”.

[0099] System overview

[0100] Figure 2 illustrates a system structure including the entities involved in embodiments herein.

[0101] A User Equipment (UE) 1001 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 UE 1001 is connected over a wireless interface 1005.

[0102] A source network node 1002, sometimes referred to as 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 as a 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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 UE may sometimes be connected to the third network node over a wireless interface (not shown in the figure). Sometimes the UE 1001 is configured with dual connectivity, such as NR-DC. In this case the UE may be configured with a master cell group (MCG), and a secondary cell group (SCG).

[0107] The first network node 1002 may control either the MCG or SCG. In this case, the second network node 1002 may control an MCG or an SCG, sometimes known as candidate MCG or target MCG, candidate SCG or target SCG, respectively. In this case, the first network node 1002 or second network node 1003 may be referred to as Master Node, MN (when controlling an MCG) or Secondary Node, SN (when controlling an SCG).

[0108] Each of first network node 1002 and the second network node 1003 may be a base station such as, when they e.g. are part of NG-RAN, e.g. a gNB. The first network node and the second network node are connected over the interface 1006.

[0109] In the context of mobility, such as LTM, the first network node 1002 may sometimes be referred to as either source network node, source gNB, source MN, source SN, serving network node or serving gNB.

[0110] Figure 3 illustrates a message sequence chart for some embodiments disclosed herein. In these embodiments the UE is configured with NR-DC and the source MN decides to configure the UE with LTM for the MCG and the SN accepts.

[0111] Referring to Figure 3, the actions are as follows:

[0112] Action 1. The source MN receives, from the UE L3 measurement reports indicating measurements on neighbouring cells.

[0113] Action 2. The source MN decides to configure LTM for the UE, 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.

[0114] Action 3. The source MN transmits, to the SN, a request for configuration of LTM. The message includes an indication about the handling of the configuration of the mobility procedure.

[0115] Action 4. The SN determines to accept the LTM configuration for the MCG.

[0116] Action 5. The SN responds to the source MN and includes an indication about the handling of the configuration of the mobility procedure.

[0117] Action 6. The source MN transmits, to the target MN, a request to configure LTM. Action 7. The target MN generates an LTM configuration and responds to the source MN including the generated LTM candidate configuration for the MCG, for example an inter-CU LTM configuration.

[0118] Action 8. The source MN transmits, to the UE, the LTM candidate configuration for the MCG.

[0119] Action 9. The UE stores the received configuration.

[0120] Action 10. The UE transmits a response to the source MN that the configuration has been received.

[0121] Action 11. The source MN decides to trigger an LTM cell switch procedure for the MCG.

[0122] Action 12. The source MN transmits, to the UE an LTM cell switch command indicating an LTM candidate cell configuration for the MCG.

[0123] Action 13. The UE executes the LTM cell switch for the MCG.

[0124] Actions 14-15. The UE transmits, to the target MN, first UL data or signalling using the applied LTM candidate cell configuration for the MCG.

[0125] Figure 4 illustrates a message sequence chart for some embodiments disclosed herein. In these embodiments the UE is configured with NR-DC and the source MN decides to configure the UE with LTM for the MCG and the SN rejects.

[0126] Referring to Figure 4, the actions in this example are as follows:

[0127] Action 1. The source MN receives, from the UE L3 measurement reports indicating measurements on neighbouring cells.

[0128] Action 2. The source MN decides to configure LTM for the UE, 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.

[0129] Action 3. The source MN transmits, to the SN, a request for configuration of LTM, for example with an SN MODIFICATION REQUEST message. The message includes an indication about the handling of the configuration of the mobility procedure.

[0130] Action 4. The SN determines to reject the LTM configuration for the MCG.

[0131] Action 5. The SN responds with the reject to the source MN, for example with an SN MODIFICATION REQUEST REJECT message and may include an indication about the handling of the configuration of the mobility procedure and / or a cause for the reject. Figure 5 illustrates a message sequence chart for some embodiments disclosed herein. In these embodiments the UE is configured with NR-DC and the source MN decides to configure the UE with LTM for the MCG and the UE accepts. The target MN also accepts the configuration.

[0132] Referring to Figure 5, the actions in this example are as follows:

[0133] Action 1. The source MN receives, from the UE L3 measurement reports indicating measurements on neighbouring cells.

[0134] Action 2. The source MN decides to configure LTM for the UE, 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.

[0135] Action 3. The source MN transmits, to the target MN, a request to configure LTM.

[0136] Action 4. The target MN generates an LTM configuration and responds to the source MN including the generated LTM candidate configuration for the MCG, for example an inter-CU LTM configuration.

[0137] Action 5. The source MN transmits, to the UE, the LTM candidate configuration for the MCG.

[0138] Action 6. The UE determines to accept the LTM candidate cell configuration for the MCG and stores the received LTM configuration.

[0139] Action 7. The UE transmits a response to the source MN that the configuration has been received and the transmission of this message indicates that the UE has accepted the LTM candidate cell configuration for the MCG.

[0140] Action 8. The source MN decides to trigger an LTM cell switch procedure for the MCG.

[0141] Action 9. The source MN transmits, to the UE an LTM cell switch command indicating an LTM candidate cell configuration for the MCG.

[0142] Action 10. The UE executes the LTM cell switch for the MCG.

[0143] Actions 11-12. The UE transmits, to the target MN, first UL data or signalling using the applied LTM candidate cell configuration for the MCG.

[0144] Figure 6 illustrates a message sequence chart for some embodiments disclosed herein. In these embodiments the UE is configured with NR-DC and the source SN decides to configure the UE with LTM for the SCG and the MN accepts.

[0145] Referring to Figure 6, the actions in this example are as follows: Action 1. The source SN receives, from the UE L3 measurement reports indicating measurements on neighbouring cells.

[0146] Action 2. The source SN decides to configure LTM for the UE, where at least one of the LTM candidate cell(s) for SCG mobility is controlled by a different gNB. In this example, the source SN decides to configure inter-SN LTM where at least one LTM candidate cell is controlled by a target SN.

[0147] Action 3. The source SN transmits, to the MN, a request for configuration of LTM, for example an SN MODIFICATION REQUIRED message. The message includes an indication about the handling of the configuration of the mobility procedure.

[0148] Action 4. The MN determines to accept the LTM configuration for the SCG.

[0149] Action 5. The MN transmits, to the target SN, a request to configure LTM.

[0150] Action 6. The target SN generates an LTM configuration and responds to the MN, including the generated LTM candidate configuration for the SCG, for example an inter- CU LTM configuration.

[0151] Actions 7-8. The MN responds to the source SN, such as with a SN MODIFICATION REQUEST message, and includes an indication about the handling of the configuration of the mobility procedure and the LTM candidate configuration for the SCG. The source SN responds to the MN, such as with a SN MODIFICATION REQUEST ACK message.

[0152] Action 9. The source SN transmits, to the UE, the LTM candidate configuration for the SCG.

[0153] Action 10. The UE stores the received configuration.

[0154] Action 11. The UE transmits a response to the source SN that the configuration has been received.

[0155] Action 12. The source SN decides to trigger an LTM cell switch procedure for the SCG.

[0156] Action 13. The source SN transmits, to the UE an LTM cell switch command indicating an LTM candidate cell configuration for the SCG.

[0157] Action 14. The UE executes the LTM cell switch for the SCG.

[0158] Actions 15-16. The UE transmits, to the target SN, first UL data or signalling using the applied LTM candidate cell configuration for the SCG.

[0159] Figure 7 illustrates a message sequence chart for some embodiments disclosed herein. In these embodiments the UE is configured with NR-DC and the source SN decides to configure the UE with LTM for the SCG and the MN rejects. Action 1. The source SN receives, from the UE L3 measurement reports indicating measurements on neighbouring cells.

[0160] Action 2. The source SN decides to configure LTM for the UE, where at least one of the LTM candidate cell(s) for SCG mobility is controlled by a different gNB. In this example, the source SN decides to configure inter-SN LTM where at least one LTM candidate cell is controlled by a target SN.

[0161] Action 3. The source SN transmits, to the MN, a request for configuration of LTM, for example an SN MODIFICATION REQUIRED message. The message includes an indication about the handling of the configuration of the mobility procedure.

[0162] Action 4. The MN determines to reject the LTM configuration for the SCG.

[0163] Action 5. The MN responds to the source SN, such as with a SN MODIFICATION REFUSE message, and may include an indication about the handling of the configuration of the mobility procedure.

[0164] Figure 8 illustrates a flow chart with the actions performed by a wireless communications device, such as the UE 1001 according to some embodiments disclosed herein. In the following, the UE 1001 will be referred to as the wireless communications device 1001.

[0165] Action 8001. The wireless communications device 1001 receives, from a first network node 1002, a first mobility configuration, such as a first LTM configuration for MCG mobility or SCG mobility. In some embodiments disclosed herein the first LTM configuration is received via Signaling Radio Bearerl , SRB1 , or split SRB1.

[0166] The first LTM configuration may be associated to any of the MCG, SCG, PCell, PSCell, or SCell.

[0167] The first LTM configuration may comprise one or more of the following information:

[0168] • an indication of a network node to which the first LTM configuration is associated;

[0169] • an indication about the handling of another mobility configuration associated to another network node which is different from the network node with which the first LTM configuration is associated;

[0170] • an identifier of the first LTM configuration to be configured or modified at the wireless communications device 1001 ; and

[0171] • an identifier of an LTM configuration to be released at the wireless communications device 1001. Action 8002. The wireless communications device 1001 determines if there is already a second mobility configuration associated with a further network node, such as the third network node 1015. Thus, the wireless communications device 1001 determines whether or not the wireless communications device 1001 has stored a second LTM configuration associated with the further network node. The second LTM configuration may be received via SRB3.

[0172] In some embodiments disclosed herein the wireless communications device 1001 determines that it already has stored a mobility configuration associated with the further network node 1015 by comparing an identity of the network node to which the stored mobility configuration is associated and an identity of the network node to which the received mobility configuration is associated.

[0173] The first LTM configuration and the second LTM configuration may both be inter-CU LTM configurations.

[0174] The second LTM configuration may comprise one or more of the following information:

[0175] • an indication of a network node to which the second LTM configuration is associated;

[0176] • an indication about the handling of another mobility configuration associated to another network node which is different from the network node with which the second LTM configuration is associated;

[0177] • An identifier of the second LTM configuration to be configured or modified at the wireless communications device 1001 ; and

[0178] • An identifier of an LTM configuration to be released at the wireless communications device 1001.

[0179] In some embodiments disclosed herein the first LTM configuration is for MCG mobility only and the second LTM configuration is for SCG only. In some other embodiments disclosed herein the first LTM configuration is for SCG mobility only and the second LTM configuration is for MCG only.

[0180] Action 8003. The wireless communications device 1001 may handle the second mobility configuration. If it was determined that the wireless communications device 1001 has stored the second LTM configuration, then the wireless communications device 1001 may determine how to handle the second mobility configuration based on a content of the received first LTM configuration. For example, if there is not already a second mobility configuration associated with a second network node the wireless communications device 1001 keeps the first configuration. Or for example, if there is already a second mobility configuration associated with the further network node the wireless communications device 1001 releases one or more of the mobility configurations associated with the further network node. Or for example, if there is already a second mobility configuration associated with the further network node which does not interfere with the first mobility configuration it keeps the second mobility configuration.

[0181] In some embodiments disclosed herein the wireless communications device 1001 upon receiving the first LTM configuration releases autonomously the second LTM configuration associated with the further network node 1015.

[0182] In some other embodiments disclosed herein the wireless communications device 1001 upon receiving the first LTM configuration releases the second LTM configuration according to the received first LTM configuration.

[0183] Action 8004. The wireless communications device 1001 executes a mobility procedure, for example an LTM cell switch procedure. Action 8004 may be triggered by receiving a message from the network or triggered by a condition being fulfilled.

[0184] The wireless communications device 1001 executes the mobility procedure based on determining whether or not the wireless communications device 1001 has stored the second LTM configuration. In some embodiments disclosed herein executing the mobility procedure is further based on determining how to handle the second mobility configuration.

[0185] Actions performed by the first network node 1002 will now be described according to some embodiments disclosed herein. The actions may be for a method for configuring LTM for either an MCG, or an SCG.

[0186] The method comprises determining whether or not a first LTM configuration for either an MCG or an SCG needs to be sent to a wireless communications device 1001 served by the MCG or SCG.

[0187] The first LTM configuration may be associated to any of the MCG, SCG, PCell, PSCell, or SCell.

[0188] The first LTM configuration may comprise one or more of the following information:

[0189] • an indication of a network node to which the first LTM configuration is associated; • an indication about the handling of another mobility configuration associated to another network node which is different from the network node with which the first LTM configuration is associated;

[0190] • an identifier of the first LTM configuration to be configured or modified at the wireless communications device 1001 ; and

[0191] • an identifier of an LTM configuration to be released at the wireless communications device 1001.

[0192] Determining whether the first LTM configuration needs to be sent to the wireless communications device 1001 may be triggered based on one or more of the following:

[0193] • A reception of a measurement report from the wireless communications device 1001 ;

[0194] • An indication from the wireless communications device 1001 which indicate that an LTM configuration is required; and

[0195] • An indication from the further network node 1015 that an LTM configuration can be configured at the wireless communications device 1001.

[0196] The method further comprises transmitting, to a further network node 1015 controlling an SCG serving the wireless communications device 1001 if the first network node 1002 controls an MCG or controlling an MCG serving the wireless communications device 1001 if the first network node 1002 controls an SCG, an indication about a handling of a first LTM configuration.

[0197] The indication to the further network node 1015 may be any of:

[0198] • a suggestion for the further network node 1015 to configure or to not configure any mobility procedure at the wireless communications device 1001 ; or

[0199] • a request for the further network node 1015 to configure or not configure any mobility procedure at the wireless communications device 1001 ; and

[0200] • a restriction for the further network node 1015 that it is allowed or not allowed to configure any mobility procedure at the wireless communications device 1001.

[0201] The first network node may, in the indication transmitted to the further network node 1015 to indicate how to handle the first LTM configuration, include an indication that the first network node 1002 will perform another mobility procedure to another further network node. As an example the MN may inform the SN that it will perform SN change based on L3 HO to another network node. In some embodiments disclosed herein the first network node to prevent the configuration of a mobility procedure by the further network node 1015 further sends to the further network node 1015, e.g., together with the above indication, one or more of the following:

[0202] • A timer to indicate how long the further network node should configure or not configure the mobility procedure at the wireless communications device 1001 ;

[0203] • What type of mobility procedure the further network node is allowed or not allowed to configure at the wireless communications device 1001 ;

[0204] • An indication on which frequency the further network node should or should not configure the mobility procedure at the wireless communications device 1001 ;

[0205] • One or more cell identifiers for which the further network node should or should not configure the mobility procedure at the wireless communications device 1001.

[0206] The method may further comprise after transmitting the indication to the further network node 1015 to indicate how to handle the first LTM configuration, receiving a response from the further network node 1015 which rejects the indication from the first network node 1002 and proposes a different handling.

[0207] In some embodiments disclosed herein the method further comprises, after transmitting the indication about the handling of the first LTM configuration to the further network node 1015, receiving a response from the further network node 1015 which rejects the indicated handling transmitted from the first network node 1002 and

[0208] • initiating a release procedure of the further network node 1015; or

[0209] • initiating a change of the further network node 1015; or

[0210] • initiating a release of a mobility procedure associated to the first network node 1002 at the wireless communications device 1001.

[0211] In some other embodiments disclosed herein the method further comprises comprising after transmitting the indication to the further network node 1015 to indicate how to handle the first LTM configuration, receiving a response from the further network node 1015 which indicates acceptance of the indication from the first network node, and wherein the first LTM configuration to the wireless communications device 1001 comprises also indications for the wireless communications device 1001 on how to handle a second LTM configuration associated to the further network node 1015, or wherein the method further comprises initiating a release of the first LTM configuration at the wireless communications device 1001.

[0212] The method further comprises transmitting, to the wireless communications device 1001 , the first LTM configuration or a second LTM configuration based on a received response from the further network node 1015 to the transmitted indication.

[0213] In some embodiments herein determining which one of the first network node 1002 or the second network node that determines how to handle the mobility configuration is based on a configuration received from an operation and maintenance, OAM system.

[0214] The embodiments and actions described herein for the first network node are applicable to the second network node.

[0215] The embodiments and actions described herein for the second network node are applicable to the first network node.

[0216] The signalling exchange between the first network node 1002 and the further network node 1015 may be done via a message over the Xn interface or with inter-node RRC messages.

[0217] Embodiments disclosed herein are also directed to a wireless communications device 1001 adapted for receiving a configuration for LTM which is associated to an MCG or an SCG. The wireless communications device 1001 is further adapted to receive, from a first network node 1002, a first LTM configuration for MCG mobility or SCG mobility.

[0218] The wireless communications device 1001 is further adapted to determine whether or not the wireless communications device 1001 has stored a second LTM configuration associated with a further network node 1015.

[0219] The wireless communications device 1001 is further adapted to execute a mobility procedure based on determining whether or not the wireless communications device 1001 has stored the second LTM configuration.

[0220] Embodiments disclosed herein are also directed to a first network node 1002 adapted for configuring LTM either at an MCG or SCG and further adapted to determine whether or not a first LTM configuration for either an MCG or an SCG needs to be sent to a wireless communications device 1001 served by the MCG or SCG. The first network node 1002 is further adapted to transmit, to a further network node 1015 controlling an SCG serving the wireless communications device 1001 if the first network node 1002 controls an MCG or controlling an MCG serving the wireless communications device 1001 if the first network node 1002 controls an SCG, an indication about a handling of a first LTM configuration.

[0221] The first network node 1002 is further adapted to transmit, to the wireless communications device 1001, the first LTM configuration or a second LTM configuration based on a received response from the further network node 1015 to the transmitted indication.

[0222] Figure 9 and Figure 10 illustrate further optional details of the UE 1001 and the network nodes 1002, 1003, 1015 respectively. The UE 1001 is configured to perform the method actions of Figure 8 above. The network nodes 1002, 1003, 1015 are each configured to perform actions described above, for example in relation Figures 3-7.

[0223] 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.

[0224] 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.

[0225] 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. 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.

[0226] 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.

[0227] 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.

[0228] 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).

[0229] When using the word "comprise" or “comprising" it shall be interpreted as nonlimiting, i.e. meaning "consist at least of".

[0230] The embodiments herein are not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used.

[0231] NUMBERED EMBODIMENTS

[0232] 1. A method, performed by a wireless communications device, such as a UE, for receiving a configuration for LTM which is associated only to an MCG or an SCG, the method comprises: receiving, from a first network node, a first mobility configuration; determining if there is a second mobility configuration associated with a second network node and handling the second configuration according to the received first mobility configuration; and

[0233] Executing a mobility procedure.

[0234] 2. The method according to embodiment 1, wherein the mobility configuration is associated to the MCG, SCG, PCell, PSCell, or SCell.

[0235] 3. The method according to embodiment 1 or 2, wherein the mobility configuration comprises one or more of the following information:

[0236] • An indication of a network node to which the mobility indication is associated

[0237] • An indication about the handling of other mobility configurations associated to the second network node which is different from the first network node from which the mobility configuration is associated to.

[0238] • A mobility configuration to be configured or modified at the UE

[0239] • A mobility configuration to be released at the UE (an identifier of the mobility configuration).

[0240] 4. The method according to any of the embodiments 1-3, wherein the UE determines that it already has a mobility configuration associated with a second network node by comparing the network node to which the mobility configuration stored in its memory is associated to and the network node to which the mobility configuration received is associated to.

[0241] 5. The method according to any of the embodiments 1-4, wherein the UE upon receiving a mobility configuration associated with the first network node releases autonomously all the one or more mobility configurations associated with a second network node.

[0242] 6. The method according to any of the embodiments 1-5, wherein the UE upon receiving a mobility configuration associated with the first network node releases the other mobility configurations according to the received mobility configuration from the first network node.

[0243] 7. The method according to any of the embodiments 1-6, wherein the first network node controls an MCG, and SCG, a PCell, a PSCell, or an SCell.

[0244] 8. The method according to any of the embodiments 1-7, wherein the second network node controls an MCG, and SCG, a PCell, a PSCell, or an SCell.

[0245] 9. The method according to any of the embodiments 1-8, wherein the mobility configuration associated to the first network node is received via SRB1 , or split SRB1 .

[0246] 10. The method according to any of the embodiments 1-9, wherein the mobility configuration associated to the second network node is received via SRB3.

[0247] 11. The method according to any of the embodiments 1-10, wherein the embodiment and actions described for the first network node are applicable to the second network node.

[0248] 12. The method according to any of the embodiments 1-11 , wherein the embodiments and actions described for the second network node are applicable to the first network node.

[0249] 13. A wireless communications device, such as a UE, adapted for receiving a configuration for LTM which is associated only to an MCG or an SCG. The wireless communications device is adapted to perform the method of any of the claims 1-12.

[0250] 14. A method, performed by a network node, such as a first network node or a second network node, for configuring LTM either at the MCG or SCG, the method comprises:

[0251] • Determining whether a mobility configuration needs to be sent at the UE

[0252] • Transmitting to a further network node an indication about the handling of the configuration of the mobility procedure

[0253] • Transmitting to the UE a mobility configuration.

[0254] 15. The method according to embodiment 14, wherein the mobility configuration is associated to the MCG, SCG, PCell, PSCell, or SCell. The method according to embodiment 14 or 15, wherein the mobility configuration comprises one or more of the following information:

[0255] • An indication of a network node to which the mobility indication is associated

[0256] • An indication about the handling of other mobility configurations associated to second network node which is different from the first network node from which the mobility configuration is associated to.

[0257] • A mobility configuration to be configured or modified at the UE

[0258] • A mobility configuration to be released at the UE (an identifier of the mobility configuration). The method according to any of the embodiments 14-16, wherein the first network node determines whether a mobility configuration needs to be sent to the UE according to one or more of the following:

[0259] • A reception of a measurement report from the UE

[0260] • In one option the measurement report is a L1 measurement report

[0261] • In one option the measurement report is a L3 measurement report

[0262] • An indication from the UE which indicate that a mobility configuration is required

[0263] • An indication from a second network node that a mobility configuration can be configured at the UE. The method according to any of the embodiments 14-17, wherein the first network node after determining whether a mobility procedure needs to be configured at the UE transmits an indication to a second network node to indicate how to handle the configuration of a mobility procedure by the second network node.

[0264] • In one option, the indication is a suggestion for the second network node to configure or to not configure any mobility procedure at the UE

[0265] • In one option, the indication is a request for the second network node to configure or not configure any mobility procedure at the UE

[0266] • In one option, the indication is a restriction for the second network node that it is allowed or not allowed to configure any mobility procedure at the UE. The method according to any of the embodiments 14-18, wherein the first network node to prevent the configuration of a mobility procedure by the second network node further sends to the second network node, e.g., together with the indication, one or more of the following: • A timer “T” to indicate for how long the second network should configure or not configure a mobility procedure at the UE

[0267] • What type of mobility procedure the second network node can or cannot configure at the UE

[0268] • For example, LTM, CHO, Conditional LTM, DAPS, CPC, CPA, subsequent CPAC

[0269] • A frequency “F” to indicate on which frequency the second network should or should not configure a mobility procedure at the UE

[0270] • One or more cell identifiers for which the second network should or should not configure a mobility procedure at the UE

[0271] 20. The method according to any of the embodiments 14-19, wherein the first network node after transmitting an indication to a second network node to indicate how to handle the configuration of a mobility procedure by the second network node, receive a response from the second network node which reject the indication from the first network node.

[0272] • In one option, if the indication from the first network node is rejected, the first network node initiates a release procedure of the second network node (i.e., it means that DC is released at the UE);

[0273] • In one option, if the indication from the first network node is rejected, the first network node initiates a change of the second network node;

[0274] • In one option, if the indication from the first network node is rejected, the first network node initiates the release of the mobility procedure (associated to the first network node) to the UE.

[0275] 21. The method according to any of the embodiments 14-20, wherein the first network node after transmitting an indication to a second network node to indicate how to handle the configuration of a mobility procedure by the second network node, receive a response from the second network node which accept the indication from the first network node.

[0276] • In one option, if the indication from the first network node is accepted, the first network node sends a mobility configuration at the UE associated to the first network node a. In one option, the mobility configuration associated with the first network node contains also indications for the UE on how to handle the mobility configuration associated to the second network node b. In one option, the second network node send an indication to the UE on how to handle the mobility configuration associated to the second network node directly to the UE. c. In one option, the second network node sends an indication to the UE on how to handle the mobility configuration associated to the second network node via the first network node.

[0277] • In one option, if the indication from the first network node is accepted, the first network node initiates the release of the mobility procedure (associated to the first network node) to the UE. The method according to any of the embodiments 14-20, wherein the first network node after transmitting an indication to a second network node to indicate how to handle the configuration of a mobility procedure by the second network node, receive a response from the second network node which reject the indication from the first network node and propose a different handling.

[0278] • In one option, the second network node indicates that another mobility procedure to another network node should be performed (as an example SN suggests to MN to instead perform SN change based on the L3 HO procedures).

[0279] • In one option, the second network node initiates on its own another mobility procedure to another network node (as an example the SN initiates an SN initiated SN change). The method according to any of the embodiments 14-22, wherein the first network node in the indication transmitted to a second network node to indicate how to handle the configuration of a mobility procedure by the second network node, includes an indication that the first network node will instead perform another mobility procedure to a third network node (as an example the MN informs the SN that it will perform SN change based on L3 HO to another network node). The method according to any of the embodiments 14-23, wherein the first network node is an MCG, and SCG, a PCell, a PSCell, or an SCell. The method according to any of the embodiments 14-24, wherein the second network node is an MCG, and SCG, a PCell, a PSCell, or an SCell. 26. The method according to any of the embodiments 14-25, wherein the mobility configuration associated to the first network node is transmitted via SRB1 , or split SRB1.

[0280] 27. The method according to any of the embodiments 14-26, wherein the mobility configuration associated to the second network node is transmitted via SRB3.

[0281] 28. The method according to any of the embodiments 14-27, wherein the embodiment and actions described for the first network node are applicable to the second network node.

[0282] 29. The method according to any of the embodiments 14-28, wherein the embodiments and actions described for the second network node are applicable to the first network node.

[0283] 30. The method according to any of the embodiments 14-29, wherein the signalling exchange between the first network node and the second network node (and vice versa) is done via a message over the Xn interface.

[0284] 31. The method according to any of the embodiments 14-29, wherein the signalling exchange between the first network node and second network node (and vice versa) is done with inter-node RRC messages.

[0285] 32. The method according to any of the embodiments 14-31 , wherein the signalling exchange between the first network node and second network node (and vice versa) is decided by OAM, e.g., which network node can be configured with LTM to the UE.

[0286] For example, which on of the first network node or the second network node that determines how to handle the mobility configuration may be based on a configuration received by an operation and maintenance (OAM) system.

[0287] 33. A network node, such as a first network node or a second network node, adapted for configuring LTM either at the MCG or SCG. The network node is adapted to perform the method of any of the claims 14-32. 34. A computer program, comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any one of claims 1-32. 35. 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 for Dual-Connectivity, DC, for handling a configuration for L1 / L2-Triggered Mobility, LTM, which is associated to a Master Cell Group, MCG, or a Secondary Cell Group, SCG, serving the wireless communications device (1001), the method comprises: receiving (8001), from a first network node (1002), a first LTM configuration for MCG mobility or SCG mobility; determining (8002) whether or not the wireless communications device (1001) has stored a second LTM configuration associated with a further network node (1015); and executing a mobility procedure based on determining whether or not the wireless communications device (1001) has stored the second LTM configuration.

2. The method according to claim 1 , further comprising, if it was determined that the wireless communications device (1001) has stored the second LTM configuration, determining how to handle the second mobility configuration based on a content of the received first LTM configuration.

3. The method according to claim 2, wherein executing the mobility procedure is further based on determining how to handle the second mobility configuration.

4. The method according to any of the claims 1-3, wherein the first LTM configuration is associated to any of the MCG, SCG, PCell, PSCell, or SCell.

5. The method according to any of the claims 1-4, wherein the first LTM configuration is for MCG mobility only and the second LTM configuration is for SCG only or wherein the first LTM configuration is for SCG mobility only and the second LTM configuration is for MCG only.

6. The method according to any of the claims 1-5, wherein the first LTM configuration comprises one or more of the following information:• an indication of a network node to which the first LTM configuration is associated;• an indication about the handling of another mobility configuration associated to another network node which is different from the network node with which the first LTM configuration is associated;• An identifier of the first LTM configuration to be configured or modified at the wireless communications device (1001); and• An identifier of an LTM configuration to be released at the wireless communications device (1001).

7. The method according to any of the claims 1-6, wherein the second LTM configuration comprises one or more of the following information:• an indication of a network node to which the second LTM configuration is associated;• an indication about the handling of another mobility configuration associated to another network node which is different from the network node with which the second LTM configuration is associated;• An identifier of the second LTM configuration to be configured or modified at the wireless communications device (1001); and• An identifier of an LTM configuration to be released at the wireless communications device (1001).

8. The method according to any of the claims 1-7, wherein the wireless communications device (1001) determines that it already has stored a mobility configuration associated with the further network node (1015) by comparing an identity of the network node to which the stored mobility configuration is associated and an identity of the network node to which the received mobility configuration is associated.

9. The method according to any of the claims 1-8, wherein the wireless communications device (1001) upon receiving the first LTM configuration releases autonomously the second LTM configuration associated with the further network node (1015).

10. The method according to any of the claims 1-9, wherein the wireless communications device (1001) upon receiving the first LTM configuration releases the second LTM configuration according to the received first LTM configuration.

11. The method according to any of the claims 1-10, wherein the first LTM configuration and the second LTM configuration both are inter-CU LTM configurations.

12. The method according to any of the claims 1-11 , wherein the first LTM configuration is received via Signaling Radio Bearerl , SRB1 , or split SRB1.

13. The method according to any of the claims 1-12, wherein the second LTM configuration is received via SRB3.

14. A wireless communications device (1001) adapted for receiving a configuration for LTM which is associated to an MCG or an SCG. The wireless communications device is further adapted to: receive, from a first network node (1002), a first LTM configuration for MCG mobility or SCG mobility; determine whether or not the wireless communications device (1001) has stored a second LTM configuration associated with a further network node (1015); and execute a mobility procedure based on determining whether or not the wireless communications device (1001) has stored the second LTM configuration.

15. The wireless communications device (1001) according to claim 14, wherein the wireless communications device (1001) is further adapted to perform the method of any of the claims 2-13.

16. A method, performed by a first network node (1002), for configuring L1 / L2-Triggered Mobility, LTM, for either a Master Cell Group, MCG, or a Secondary Cell Group, SCG, the method comprises: determining whether or not a first LTM configuration for either an MCG or an SCG needs to be sent to a wireless communications device (1001) served by the MCG or SCG;transmitting, to a further network node (1015) controlling an SCG serving the wireless communications device (1001) if the first network node (1002) controls an MCG or controlling an MCG serving the wireless communications device (1001) if the first network node (1002) controls an SCG, an indication about a handling of a first LTM configuration; and transmitting, to the wireless communications device (1001), the first LTM configuration or a second LTM configuration based on a received response from the further network node (1015) to the transmitted indication.

17. The method according to claim 16, wherein the first LTM configuration is associated to the MCG, SCG, PCell, PSCell, or SCell.

18. The method according to claim 16 or 17, wherein the first LTM configuration further comprises one or more of the following information:• an indication of a network node to which the mobility indication is associated;• an indication about a handling of a second LTM configuration associated to the further network node (1015) which is different from the network node with which the first mobility configuration is associated to;• an identifier of the second LTM configuration to be configured or modified at the wireless communications device (1001); and• an identifier of an LTM configuration to be released at the wireless communications device (1001).

19. The method according to any of the claims 16-18, wherein determining whether the first LTM configuration needs to be sent to the wireless communications device (1001) is triggered based on one or more of the following:• A reception of a measurement report from the wireless communications device (1001);• An indication from the wireless communications device (1001) which indicate that an LTM configuration is required; and• An indication from the further network node (1015) that an LTM configuration can be configured at the wireless communications device (1001).

20. The method according to any of the claims 16-19, wherein the indication to the further network node (1015) is any of:• a suggestion for the further network node (1015) to configure or to not configure any mobility procedure at the wireless communications device (1001); or• a request for the further network node (1015) to configure or not configure any mobility procedure at the wireless communications device (1001); and• a restriction for the further network node (1015) that it is allowed or not allowed to configure any mobility procedure at the wireless communications device (1001).

21. The method according to any of the claims 16-20, wherein the first network node to prevent the configuration of a mobility procedure by the further network node (1015) further sends to the further network node (1015) one or more of the following:• A timer to indicate how long the further network node should configure or not configure the mobility procedure at the wireless communications device (1001);• What type of mobility procedure the further network node is allowed or not allowed to configure at the wireless communications device (1001);• An indication on which frequency the further network node should or should not configure the mobility procedure at the wireless communications device (1001);• One or more cell identifiers for which the further network node should or should not configure the mobility procedure at the wireless communications device (1001).

22. The method according to any of the claims 16-21 , further comprising, after transmitting the indication about the handling of the first LTM configuration to the further network node (1015), receiving a response from the further network node (1015) which rejects the indicated handling transmitted from the first network node (1002); and• initiating a release procedure of the further network node (1015); or• initiating a change of the further network node (1015); or• initiating a release of a mobility procedure associated to the first network node (1002) at the wireless communications device (1001).

23. The method according to any of the claims 16-21 , further comprising after transmitting the indication to the further network node (1015) to indicate how to handle the first LTM configuration, receiving a response from the further network node (1015) which indicates acceptance of the indication from the first network node, and wherein the first LTM configuration to the wireless communications device (1001) comprises also indications for the wireless communications device (1001) on how to handle a second LTM configuration associated to the further network node (1015), or wherein the method further comprises initiating a release of the first LTM configuration at the wireless communications device (1001).

24. The method according to any of the claims 16-22, further comprising after transmitting the indication to the further network node (1015) to indicate how to handle the first LTM configuration, receiving a response from the further network node (1015) which rejects the indication from the first network node (1002) and proposes a different handling.

25. The method according to any of the claims 16-24, wherein the first network node (1002) in the indication transmitted to the further network node (1015) to indicate how to handle the first LTM configuration, includes an indication that the first network node (1002) will perform another mobility procedure to another further network node.

26. The method according to any of the claims 16-25, wherein the signalling exchange between the first network node (1002) and the further network node (1015) is done via a message over the Xn interface or with inter-node RRC messages.

27. A first network node (1002) adapted for configuring LTM either at an MCG or SCG and further adapted to: determine whether or not a first LTM configuration for either an MCG or an SCG needs to be sent to a wireless communications device (1001) served by the MCG or SCG; transmit, to a further network node (1015) controlling an SCG serving the wireless communications device (1001) if the first network node (1002) controls an MCG or controlling an MCG serving the wireless communications device (1001) if the first network node (1002) controls an SCG, an indication about a handling of a first LTM configuration; and transmit, to the wireless communications device (1001), the first LTM configuration or a second LTM configuration based on a received response from the further network node (1015) to the transmitted indication.

28. A computer program, comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any one of claims 1-13.

29. A computer program, comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any one of claims 16-26.

30. A carrier comprising the computer program according to any of claims 28-29, wherein the carrier is one of an electronic signal, an optical signal, a radio signal and a computer readable medium.

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