A user equipment, a network node, and a method

Abstract

A user equipment, UE, comprising: at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform: determining whether a condition for master cell group, MCG, link failure has been met; determining whether a cell switch command, CSC, for a secondary cell group, SCG, has been received from a network node; in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery; determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer; in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer: performing fast MCG link recovery based at least on the received reconfiguration information; and in dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC; and in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer, performing LTM at the SCG based at least on the CSC.

Description

[0001] TITLE

[0002] A USER EQUIPMENT, A NETWORK NODE, AND A METHOD

[0003] TECHNOLOGICAL FIELD

[0004] Examples of the disclosure relate to fast master cell group link recovery.

[0005] BACKGROUND

[0006] A wireless network comprises a plurality of network nodes including terminal nodes and access nodes. Communication between the terminal nodes and the access nodes is wireless. In a user equipment configured for dual connectivity, fast master cell group link recovery may be performed following radio link failure in a master cell group.

[0007] BRIEF SUMMARY

[0008] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims

[0009] BRIEF DESCRIPTION

[0010] Some examples will now be described with reference to the accompanying drawings in which: FIG. 1 shows an example of the subject matter described herein;

[0011] FIG. 2 shows another example of the subject matter described herein;

[0012] FIG. 3 shows another example of the subject matter described herein;

[0013] FIG. 4 shows another example of the subject matter described herein;

[0014] FIG. 5 shows another example of the subject matter described herein;

[0015] FIG. 6 shows another example of the subject matter described herein;

[0016] FIG. 7 shows another example of the subject matter described herein;

[0017] FIG. 8 shows another example of the subject matter described herein;

[0018] FIG. 9 shows another example of the subject matter described herein;

[0019] FIG. 10 shows another example of the subject matter described herein;

[0020] FIG. 11 shows another example of the subject matter described herein;

[0021] FIG. 12 shows another example of the subject matter described herein;

[0022] FIG. 13 shows another example of the subject matter described herein;

[0023] FIG. 14 shows another example of the subject matter described herein;

[0024] FIG. 15 shows another example of the subject matter described herein;

[0025] FIGs 16A and 16B show another example of the subject matter described herein; and FIGs 17A and 17B show another example of the subject matter described herein.The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

[0026] DETAILED DESCRIPTION

[0027] The Figures illustrate a user equipment, UE, comprising: at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform: receiving, from a network node, configuration information associated with conditional L1 / L2 triggered mobility, CLTM at a secondary cell group, SCG; initiating, based on the received configuration information, evaluation of one or more CLTM conditions for the SCG; receiving, from the network node, an indicator associated with fast master cell group, MCG, link recovery; determining whether a condition for MCG link failure has been met; and in dependence upon a determination that a condition for MCG link failure has been met, and based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0028] The Figures also illustrate a user equipment, UE, comprising: at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform: determining whether a condition for master cell group, MCG, link failure has been met; determining whether a cell switch command, CSC, for a secondary cell group, SCG, has been received from a network node; in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery; determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer; in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer: performing fast MCG link recovery based at least on the received reconfiguration information; and in dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC; and in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer, performing LTM at the SCG based at least on the CSC.This provides the technical effect of preventing potential failure of fast MCG link recovery procedure due to interruptions in SCG RL during SCG C-LTM execution.

[0029] In examples, it may be possible for fast MCG link recovery and conditional LTM in the SCG to be performed simultaneously. In some such examples, performance of CLTM in the SCG interrupts fast MCG link recovery, causing failure of the fast MCG link recovery.

[0030] Fig. 1 illustrates an example of a network 100 comprising a plurality of network entities including terminal apparatus 110, node apparatus 120 and one or more network apparatus 130. The terminal apparatus 110 and node apparatus 120 communicate 124 with each other. The one or more network apparatus 130 communicate 128 with the node apparatus 120.

[0031] In some examples the one or more network apparatus 130 communicate with the terminal apparatus 110. The one or more network apparatus 130 can, in some examples, communicate with each other. The one or more node apparatus 120 can, in some examples, communicate 126 with each other.

[0032] The network 100 can be a cellular network comprising a plurality of cells 122 each served by a node apparatus 120. In this example, the interface between the terminal apparatus 110 and a node apparatus 120 defining a cell 122 is a wireless interface 124.

[0033] The node apparatus 120 comprises one or more cellular radio transceivers. The terminal apparatus 110 comprises one or more cellular radio transceivers.

[0034] In the example illustrated the cellular network 100 is a third generation Partnership Project (3GPP) network in which the terminal apparatus 110 are user equipment (UE) and the node apparatus 120 can be access nodes such as base stations.

[0035] A user equipment comprises a mobile equipment. Where reference is made to user equipment that reference includes and encompasses, wherever possible, a reference to mobile equipment.

[0036] In some examples, during operation, a user equipment 110 comprises a mobile equipment comprising a smart card for authentication / encryption etc. such as a Subscriber Identity Module (SIM). In some examples, during operation, a user equipment 110 comprises mobileequipment comprising circuitry embedded as part of the user equipment 110 for authentication / encryption such as software SIM.

[0037] The node apparatus 120 can be any suitable access node such as a base station or transmission reception point. The node apparatus 120 can be a network element responsible for radio transmission and reception in one or more cells 122, to or from the UE 110. The node apparatus 120 can be a network element in a Radio Access Network (RAN), an Open-Radio Access Network (O-RAN) or any other suitable type of network.

[0038] The network apparatus 130 can be part of a core network. The network apparatus 130 can be configured to manage functions relating to connectivity for the UEs 110. For example, the network apparatus 130 can be configured to manage functions such as connectivity, mobility, authentication, authorization and / or other suitable functions. In some examples the network apparatus 130 can comprise an Access and Mobility management Function (AMF) and / or a User Plane Function (UPF) or any other suitable entities.

[0039] In the example of Fig. 1 the network apparatus 130 is shown as a single entity. In some examples the network apparatus 130 could be distributed across a plurality of entities. For example, the network apparatus 130 could be cloud based or distributed in any other suitable manner. The network apparatus 130 can be a core network node.

[0040] The network 100 can be a 4G or 5G network, for example. It can for example be a New Radio (NR) network that uses gNB or eNB as access nodes 120. New Radio is the 3GPP name for 5G technology. In such cases the node apparatus 120 can comprise gNodeBs (gNBs) 120 configured to provide user plane and control plane protocol terminations towards the UE 110 and / or to perform any other suitable functions. The gNBs 120 are interconnected with each other by means of an X2 / Xn interface 126. The gNBs are also connected by means of the N2 interface 128 to the network apparatus 130. The gNBs can be connected to an AMF or any other suitable network apparatus 130. Other types of networks and interfaces could be used in other examples. Other types of network could comprise next generation mobile and communication network, for example, a 6G network.

[0041] Release 18 of 3GPP specifications has introduced layer 1 (L1) / L2 based mobility that is also called lower layer triggered mobility (LTM) in the literature. LTM enables a serving cell change via L1 / L2 signaling, while keeping configuration of upper layers. Advantages of the LTMcompared with L3 handover include reduced latency, overhead and interruption time during handover or cell switch.

[0042] A terminal node 110, such as a user equipment (UE), can be configured to perform LTM to perform a handover procedure. For example, a terminal node 110 can be connected to a first access node 120 and can be configured to perform LTM to instead be connected to a second, different access node 120.

[0043] In examples, a terminal node 110 can be connected to a first distributed unit (DU) of a central unit (CU) and can be configured to perform LTM to instead be connected to a different DU of the CU.

[0044] In examples, a terminal node 110 can be connected to a first cell of an access node 120, and can be configured to perform LTM to instead be connected to a second, different cell of the access node 120.

[0045] A terminal node 110 can be configured to perform conditional LTM (CLTM). A terminal node 110 configured to perform CLTM can be configured with at least one condition associated with at least one candidate access node 120, and can trigger the handover autonomously to a candidate access node 120 when the associated condition(s) for a candidate access node 120 are fulfilled. This differs from the conventional (network-triggered) LTM where the handover is triggered via a cell switch command received by the terminal node 110.

[0046] A candidate access node 120 can be the access node 120 with which the terminal node 110 is connected (source access node), as the CLTM can be configured in relation to a different cell of the source access node.

[0047] In examples, a terminal node 110 that is configured to perform LTM and / or CLTM can be instructed, for example using a physical downlink control channel (PDCCH) order, to perform early synchronization and acquire timing advance (TA) information for at least one candidate access node. This is referred to below as TA information estimated by the terminal node 110. The terminal node may measure a timing difference between a serving cell and a candidate cell via downlink signal measurements and the TA information of the serving cell.

[0048] In examples, information is provided to the terminal node 110 that is configured to perform LTM and / or CLTM, to control use of TA information by the terminal node 110 during CLTM. Insome examples, information is provided to the terminal node 110 that is configured to perform LTM and / or CLTM, to control use of the network provided TA information and terminal node estimated TA information at the terminal node during LTM and / or CLTM.

[0049] In some examples, information is provided to the terminal node 110 that is configured to perform LTM and / or CLTM, to control estimation of TA information by the terminal node 110.

[0050] FIG. 2 illustrates an example of a method 200.

[0051] In examples, FIG. 2 can be considered to illustrate a plurality of methods. For example, FIG.

[0052] 2 illustrates one or more actions at a plurality of actors / entities, and, in examples, FIG. 2 can be considered to illustrate a plurality of methods performed by the individual actors / entities.

[0053] One or more of the features discussed in relation to FIG. 2 can be found in one or more of the other FIGs.

[0054] In the example of FIG. 2, a plurality of apparatuses transmit and / or receive one or more signals and / or one or more messages across and / or via and / or using a network. In examples, any suitable form of communication in any suitable network can be used. For example, at least a portion of the network 100 of FIG. 1 can be used.

[0055] Accordingly, in examples, the plurality of apparatuses in FIG. 2 form at least a portion of network 100 as described in relation to FIG. 1.

[0056] In the illustrated example, a terminal node 110 and an access node 120 transmit and / or receive one or more signals and / or one or more messages. The access node can comprise a gNodeB (gNB) and the terminal node 110 can comprise a UE.

[0057] In examples, communications and / or transmissions between elements illustrated in FIG. 2 can proceed via any number of intervening elements, including no intervening elements.

[0058] Although one terminal node 110 is illustrated in the example of FIG. 2, in examples any suitable number of terminal nodes 110, for example UEs, can be included. Similarly, in examples, any suitable number of access nodes 120 can be included.As described herein, a description of a function and / or action should also be considered to disclose enabling, and / or causing, and / or controlling that function and / or action. For example, a description of transmitting information should also be considered to disclose enabling, and / or causing, and / or controlling transmitting / transmission of information.

[0059] For example, a description of an apparatus, such as a UE, transmitting information should also be considered to disclose at least one controller of the apparatus enabling, and / or causing, and / or controlling the apparatus to transmit the information.

[0060] In the illustrated example, the location of blocks indicates the entity performing the functions(s) and / or action(s).

[0061] Because FIG. 2 illustrates one or more actions / features of transmitting, FIG. 2 illustrates the corresponding receiving / enabling and / or causing receiving action(s) / feature(s).

[0062] The preceding statements should be understood to apply to other FIGs described herein, for example FIGs 5, 7, 9, 10, 11, 12 and 13.

[0063] For the further discussion of FIG. 2 it will be considered that the terminal node 110 is a UE and that the access node 120 is a serving secondary node control unit (SN-CU).

[0064] At commencement of method 200, the UE is served by a serving SN-CU and a serving secondary node distributed unit (SN-DU). LTM cell switch at the SCG may cause the UE to switch to a candidate SN-DU.

[0065] At commencement of method 200, the UE is further served by a serving master node control unit (MN-CU). Fast MCG link recovery may cause the UE to switch to a recovery PCell.

[0066] For clarity, method blocks performed by the serving SN-DU, candidate SN-CU, candidate SN-DU and MN-CU are not illustrated in FIG. 2. Said method blocks are described in detail with reference to later FIGs.

[0067] From the point of view of the UE, at block 202, the method comprises receiving, from a network node, configuration information associated with CLTM at a SCG (referred to as the “configuration information” below). In the example of FIG. 2, the network node is the serving SN-CU.The information associated with CLTM at a SCG can comprise any suitable information. For example, the information associated with CLTM at a SCG can comprise any suitable information to enable the UE to determine configuration information associated with CLTM at the SCG.

[0068] In some, but not necessarily all, examples, the configuration information associated with CLTM is received via at least one radio resource control, RRC, reconfiguration message. The RRC reconfiguration message may be received via the SRB3 interface.

[0069] In examples, the information associated with CLTM comprises at least one CLTM execution condition. Examples of such execution conditions are described in the 3GPP specifications, and execution conditions may be defined, for example, in terms of measured reference signal metrics of one or more serving cells and one or more candidate cells for the CLTM. In examples, the information associated with CLTM comprises at least one layer 1 (L1) measurement reporting configuration. The at least one L1 measurement reporting configuration can comprise at least one pruned L1 measurement reporting configuration.

[0070] At block 204, the method comprises receiving, from the network node, an indicator associated with fast MCG link recovery (referred to as the “MCG recovery indicator” below).

[0071] In some, but not necessarily all, examples, the configuration information and the MCG recovery indicator are received within a single message. Therefore, in some, but not necessarily all, examples, blocks 202 and 204 are performed as a single block.

[0072] In some, but not necessarily all, examples, the MCG recovery indicator is received within an RRC Reconfiguration message. The RRC reconfiguration message may be received via the SRB3 interface.

[0073] In some, but not necessarily all, examples, the MCG recovery indicator comprises an indication that CLTM should not be performed for the SCG in case of MCG link failure.

[0074] In some, but not necessarily all, examples, the MCG recovery indicator comprises an indication that SCG CLTM condition evaluation should be suspended in case of MCG link failure.In some, but not necessarily all, examples, the MCG recovery indicator comprises an indication that SCG CLTM condition evaluation may be performed in case of MCG link failure, but that, if it is determined that a condition for CLTM at the SCG has been met, execution of CLTM at the SCG should be suspended. In some, but not necessarily all, examples, the indication comprises an additional SCG CLTM condition.

[0075] In some, but not necessarily all, examples, the MCG recovery indicator is comprised within a MAC CE which also comprises timing advance (TA) and TA validity timer (TAT) information

[0076] In some, but not necessarily all, examples, the MCG recovery indicator is comprised within a medium access control (MAC) control element (CE) comprising information associated with early transmission configuration indicator (TCI) state activation.

[0077] At block 206, the method comprises initiating, based on the received configuration information, evaluation of one or more CLTM conditions for the SCG.

[0078] At block 208, the method comprises determining whether a condition for MCG radio link failure (RLF) has been met.

[0079] In some, but not necessarily all, examples, determining whether a condition for MCG link failure has been met comprises determining whether a timer associated with MCG link failure (referred to herein as the “failure detection timer”) has expired. In some, but not necessarily all, examples, the failure detection timer is T310.

[0080] In some, but not necessarily all, examples, determining whether a condition for MCG link failure has been met comprises determining whether a number of in-sync indications received from a network node is below a threshold number of in-sync indications. In some, but not necessarily all, examples, the threshold number of in-sync indications is provided by N311.

[0081] In some, but not necessarily all, examples, it is determined that a condition for MCG link failure has been met if, when the failure detection timer has expired, the number of in-sync indications received from a network node is below the threshold number of in-sync indications.

[0082] In some, but not necessarily all, examples, the method further comprises, in dependence upon a determination that a condition for MCG link failure has been met, starting a timer associated with fast MCG recovery (referred to herein as the “recovery timer”).In some, but not necessarily all, examples, the recovery timer provides a time period during which fast MCG recovery may be performed. If the recovery timer expires before fast MCG recovery is successfully completed, RRC re-establishment is performed. If fast MCG recovery is successfully completed before the recovery timer expires, the recovery timer is stopped and, optionally, reset. In some, but not necessarily all, examples, the recovery timer is a T316 timer.

[0083] In some, but not necessarily all, examples, the method further comprises, in dependence upon a determination that a condition for MCG link failure has been met, preparing MCG failure information and transmitting the MCG failure information to a network node. In some, but not necessarily all, examples, the network node is a SN-Dll.

[0084] In some, but not necessarily all, examples, the method further comprises, in dependence upon a determination that a condition for MCG link failure has been met, suspending data transmissions on all MCG data bearers.

[0085] At block 210, the method comprises, in dependence upon a determination that a condition for MCG link failure has been met, based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0086] In some, but not necessarily all, examples, CLTM at the SCG is prevented until MCG link recovery has been performed successfully.

[0087] In some, but not necessarily all, examples, preventing CLTM at the SCG comprises stopping evaluation of the one or more CLTM conditions for the SCG. In some such examples, the MCG recovery indicator comprises an indication that SCG CLTM condition evaluation should be suspended in case of MCG link failure.

[0088] In some, but not necessarily all, examples, preventing CLTM at the SCG comprises, in dependence upon a determination that a condition for CLTM at the SCG has been met, stopping execution of CLTM at the SCG. In some such examples, the MCG recovery indicator comprises an indication that SCG CLGM condition evaluation may be performed in case of MCG link failure, but that, if it is determined that a condition for CLTM at the SCG has been met, execution of CLTM at the SCG should be suspended.Thus, in some, but not necessarily all, examples, preventing CLTM at the SCG comprises two sub-steps: first, determining that a CLTM condition for the SCG is met; and second, stopping execution of CLTM at the SCG.

[0089] Consequently, FIG. 2 illustrates a method 200 comprising:

[0090] at block 202, receiving, from a network node, configuration information associated with CLTM at a SCG;

[0091] at block 204, receiving, from the network node, an indicator associated with fast MCG link recovery;

[0092] at block 206, initiating, based on the received configuration information, evaluation of one or more CLTM conditions for the SCG;

[0093] at block 208, determining whether a condition for MCG link failure has been met; and at block 210, in dependence upon a determination that a condition for MCG link failure has been met, based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0094] From the point of view of the SN-CU, the method comprises, at block 202, transmitting, to the UE, configuration information associated with CLTM at a SCG.

[0095] At block 204, the method comprises transmitting, to the UE, an indicator associated with fast MCG link recovery.

[0096] Consequently, FIG. 2 illustrates a method comprising:

[0097] at block 202, transmitting, to the UE, configuration information associated with CLTM at a SCG; and

[0098] at block 204, transmitting, to the UE, an indicator associated with fast MCG link recovery.

[0099] FIG. 3 illustrates an example of a method 300.

[0100] The method 300 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG. 14.

[0101] In examples, the method 300 can be performed by a terminal node 110, such as a UE.

[0102] At block 302, the method comprises receiving, from a network node, configuration information associated with CLTM at a SCG.At block 304, the method comprises receiving, from the network node, an indicator associated with fast MCG link recovery.

[0103] At block 306, the method comprises initiating, based on the received configuration information, evaluation of one or more CLTM conditions for the SCG.

[0104] At block 308, the method comprises determining whether a condition for MCG link failure has been met.

[0105] At block 310, the method comprises, in dependence upon a determination that a condition for MCG link failure has been met, based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0106] Consequently, FIG. 3 illustrates a method 300 comprising:

[0107] at block 302, receiving, from a network node, configuration information associated CLTM at a SCG;

[0108] at block 304, receiving, from the network node, an indicator associated with fast MCG link recovery;

[0109] at block 306, initiating, based on the received configuration information, evaluation of one or more CLTM conditions for the SCG;

[0110] at block 308, determining whether a condition for MCG link failure has been met; and at block 310, in dependence upon a determination that a condition for MCG link failure has been met, based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0111] FIG. 4 illustrates an example of a method 400.

[0112] The method 400 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG. 14.

[0113] In examples, the method 400 can be performed by an access node.

[0114] At block 402, the method comprises transmitting, to the UE, configuration information associated with CLTM at a SCG.At block 404, the method comprises transmitting, to the UE, an indicator associated with fast MCG link recovery.

[0115] Consequently, FIG. 4 illustrates a method comprising:

[0116] at block 402, transmitting, to the UE, configuration information associated with CLTM at a SCG; and

[0117] at block 404, transmitting, to the UE, an indicator associated with fast MCG link recovery.

[0118] FIG. 5 illustrates an example of a method 500.

[0119] In some, but not necessarily all, examples, method 200 is succeeded by method 500. Method 200 may proceed directly to method 500 with no intervening blocks, or with one or more intervening blocks.

[0120] From the point of view of the UE, at block 502, the method comprises determining whether fast MCG recovery has been completed.

[0121] In some, but not necessarily all, examples, determining whether fast MCG recovery has been completed comprises determining whether the recovery timer has been stopped. If the recovery timer has been stopped, it is determined that fast MCG recovery has been completed. If the recovery timer has expired, it is determined that fast MCG recovery has not been completed.

[0122] In some, but not necessarily all, examples, the UE is configured to stop the recovery timer. In some such examples, block 502 comprises sub-blocks 502A, 502B and 502C (not illustrated in FIG. 5).

[0123] At sub-block 502A, the method comprises determining whether reconfiguration information associated with fast MCG link recovery has been received.

[0124] In some, but not necessarily all, examples, the reconfiguration information comprises an RRC reconfiguration indication with a handover command for the PCell.

[0125] At sub-block 502B, the method comprises, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received, stopping the recovery timer.At sub-block 502C, the method comprises, in dependence upon stopping the recovery timer, determining that fast MCG recovery has been completed.

[0126] In some, but not necessarily all, examples, determining whether fast MCG recovery has been completed comprises determining whether data transmission on MCG data bearers has been resumed.

[0127] In some, but not necessarily all, examples, the UE is configured to cause resumption of data transmission on MCG data bearers. In some such examples, block 502 comprises sub-blocks 502D, 502E and 502F (not illustrated in FIG. 5). One or more of sub-blocks 502D, 502E and 502F may be performed in addition to, or instead of, sub-blocks 502A, 502B and 502C.

[0128] At sub-block 502D, the method comprises determining whether reconfiguration associated with fast MCG link recovery has been received.

[0129] At sub-block 502E, the method comprises, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received, resuming data transmission on at least some of the MCG data bearers.

[0130] At sub-block 502F, the method comprises, in dependence upon resuming data transmission on at least some of the MCG data bearers, determining that fast MCG recovery has been completed.

[0131] In dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received, resuming data transmission on at least some of the MCG data bearers.

[0132] In some, but not necessarily all, examples, determining whether fast MCG recovery has been completed comprises determining whether an indication to resume CLTM has been received from a network node.

[0133] In some, but not necessarily all, examples, the indication to resume CLTM is received from the recovery PCell. In some such examples, the indication to resume CLTM is received from the recovery PCell via the SN-CU and the SN-DU.In some, but not necessarily all, examples, the indication to resume CLTM is received via a MAC CE or through L1 signalling.

[0134] At block 504, the method comprises, in dependence upon a determination that fast MCG recovery has been completed, enabling CLTM at the SCG.

[0135] In some, but not necessarily all, examples, enabling CLTM at the SCG may be performed in dependence upon receiving an indication to resume CLTM from a network node. In some such examples, it may be determined that fast MCG recovery has been completed, but CLTM at the SCG is not enabled unless the indication to resume CLTM is received.

[0136] In other examples, enabling CLTM at the SCG is performed in dependence upon a determination that fast MCG recovery has been completed, whether said determination occurs in response to an external signal or in response to an internal determination.

[0137] In some, but not necessarily all, examples, enabling CLTM at the SCG comprises resuming evaluation of the one or more CLTM conditions for the SCG.

[0138] In some, but not necessarily all, examples, enabling CLTM at the SCG comprises resuming execution of CLTM at the SCG.

[0139] Consequently, FIG. 5 illustrates a method comprising:

[0140] at block 502, determining whether fast MCG recovery has been completed; and

[0141] at block 504, in dependence upon a determination that fast MCG recovery has been completed, enabling CLTM at the SCG.

[0142] FIG. 6 illustrates an example of a method 600.

[0143] The method 600 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG. 14.

[0144] In examples, the method 600 can be performed by a terminal node 110, such as a UE.

[0145] At block 602, the method comprises determining whether fast MCG recovery has been completed.At block 604, the method comprises enabling CLTM at the SCG.

[0146] Consequently, FIG. 6 illustrates a method 600 comprising:

[0147] at block 602, determining whether fast MCG recovery has been completed; and

[0148] at block 604, enabling CLTM at the SCG.

[0149] FIG. 7 illustrates an example of a method 700.

[0150] In some, but not necessarily all, examples, method 700 is performed as an alternative to method 200.

[0151] In some, but not necessarily all, examples, method 700 is performed in addition to method 200. In some such examples, blocks from method 200 that are duplicated in method 700 are performed only once. For example, only one of block 208 and block 702 are performed.

[0152] From the point of the UE, at block 702, the method comprises determining whether a condition for MCG link failure has been met.

[0153] In some, but not necessarily all, examples, block 702 is performed as set out in relation to block 208 above.

[0154] At block 704, the method comprises determining whether a CSC for a SCG has been received from a network node.

[0155] In some, but not necessarily all, examples, the CSC is received via a medium access control, MAC, control element, CE.

[0156] At block 706, the method comprises, in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery and with LTM (referred to below as the “LTM countdown timer”).

[0157] In some, but not necessarily all, examples, the LTM countdown timer provides a time period during which fast MCG recovery may be performed.In some, but not necessarily all, examples, the LTM countdown timer and the recovery timer run simultaneously; that is, the LTM countdown timer and the recovery timer may be started at the same time, or one of the LTM countdown timer and the recovery timer may be started and, before expiry of said timer, the other of the LTM countdown timer and the recovery timer may be started.

[0158] At block 708, the method comprises determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the LTM countdown timer. The reconfiguration information may be reconfiguration information as described above.

[0159] After completion of block 708, the method proceeds to either block 710 or block 714.

[0160] In some, but not necessarily all, examples, block 708 comprises receiving reconfiguration information associated with fast MCG link recovery and, in dependence upon the receiving, determining that reconfiguration information associated with fast MCG link recovery has been received.

[0161] In some, but not necessarily all, examples, block 708 comprises determining whether the LTM countdown timer has expired.

[0162] If it is determined that reconfiguration information associated with fast MCG link recovery has been received and that the LTM countdown timer has not expired, it is determined that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer. The method then proceeds to block 710.

[0163] At block 710, the method comprises performing fast MCG link recovery based at least on the received reconfiguration information.

[0164] At block 712, the method comprises, in dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC.

[0165] If it is determined that the LTM countdown timer has expired, and it has not been determined that reconfiguration information associated with fast MCG link recovery has been received, it is determined that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer. The method then proceeds to block 714.At block 714, the method comprises performing LTM at the SCG based at least on the CSC.

[0166] Optionally, at block 716, the method comprises determining whether reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer.

[0167] At block 718, the method comprises, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer, performing fast MCG link recovery based at least on the received configuration information.

[0168] Consequently, FIG. 7 illustrates a method comprising:

[0169] at block 702, determining whether a condition for MCG link failure has been met;

[0170] at block 704, determining whether a CSC for a SCG has been received from a network node; at block 706, in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery;

[0171] at block 708, determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer; and either:

[0172] at block 710, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer, performing fast MCG link recovery based at least on the received reconfiguration information; and

[0173] at block 712, in dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC; or

[0174] at block 714, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer, performing LTM at the SCG based at least on the CSC;

[0175] optionally, at block 716, determining whether reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer; and

[0176] optionally, at block 718, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer, performing fast MCG link recovery based at least on the received configuration information.

[0177] FIG. 8 illustrates an example of a method 800.

[0178] The method 800 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG. 14.In examples, the method 800 can be performed by a terminal node 110, such as a UE.

[0179] At block 802, the method comprises determining whether a condition for MCG link failure has been met.

[0180] At block 804, the method comprises determining whether a CSC for a SCG has been received from a network node.

[0181] At block 806, the method comprises, in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery.

[0182] At block 808, the method comprises determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer.

[0183] At block 810, the method comprises, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer, performing fast MCG link recovery based at least on the received reconfiguration information.

[0184] At block 812, the method comprises, in dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC.

[0185] Alternatively to blocks 810 and 812, at block 814, the method comprises, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer, performing LTM at the SCG based at least on the CSC.

[0186] Optionally, at block 816, the method comprises determining whether reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer.

[0187] Optionally, at block 818, the method comprises, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer, performing fast MCG link recovery based at least one the received configuration information.Consequently, FIG. 8 illustrates a method comprising:

[0188] at block 802, determining whether a condition for MCG link failure has been met;

[0189] at block 804, determining whether a CSC for a SCG has been received from a network node; at block 806, in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery;

[0190] at block 808, determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer; and either:

[0191] at block 810, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer, performing fast MCG link recovery based at least on the received reconfiguration information; and

[0192] at block 812, in dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC; or

[0193] at block 814, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer, performing LTM at the SCG based at least on the CSC;

[0194] optionally, at block 816, determining whether reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer; and

[0195] optionally, at block 818, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer, performing fast MCG link recovery based at least on the received reconfiguration information.

[0196] FIGs 9 - 13 illustrate examples of methods 900, 1000, 1100, 1200, 1300.

[0197] The methods of FIGs 9 - 13 are performed by a terminal node 110 and five access nodes 120A, 120B, 120C, 120D, 120E.

[0198] In some, but not necessarily all, examples, a single access node may perform the function of two or more of the access nodes 120A, 120B, 120C, 120D, 120E.

[0199] For the further discussion of FIGs 9 - 13 it will be considered that: the terminal node 110 is a UE; the first access node 120A is a serving SN-Dll; the second access node 120B is a candidate SN-Dll; the third access node 120C is a serving SN-Cll; the fourth access node 120D is a recovery PCell; and the fifth access node 120E is an MN-Dll.One or more of FIGs 2, 5, or 7 may be considered to be sub-methods or partial sub-methods of one or more of methods 900, 1000, 1100, 1200, 1300. Therefore, any one or more of the blocks of any one or more of methods 900, 1000, 1100, 1200, 1300 may be performed in combination with any of methods 200, 500, or 700.

[0200] Blocks and / or features discussed in any of FIGs 9 - 13 may be considered equivalent to corresponding blocks discussed in any of FIGs 2, 5 or 7.

[0201] From the point of view of the UE, at block 902, the method comprises performing configuration of the UE with dual connectivity (DC) and SRB3.

[0202] At block 904, the method comprises receiving, from the MN-CU, MCG data.

[0203] At block 908, the method comprises receiving, from the SN-CU, configuration information associated with CLTM at a SCG and an indicator associated with fast MCG link recovery.

[0204] In some, but not necessarily all, examples, the configuration information associated with CLTM at a SCG is configuration information as described above. In some, but not necessarily all, examples, the indicator associated with fast MCG link recovery is a MCG recovery indicator as described above.

[0205] In some, but not necessarily all, examples, the configuration information and the MCG recovery indicator are received over the SRB3 interface.

[0206] In some, but not necessarily all, examples, the configuration information and the MCG recovery indicator are comprised within an RRC message.

[0207] At block 910, the method comprises transmitting, to the SN-CU, an indication that RRC reconfiguration is complete.

[0208] At block 912, the method comprises initiating evaluation of one or more CLTM conditions.

[0209] At block 914, the method comprises determining that radio link failure has occurred at the MN-CU.In some, but not necessarily all, examples, determining that radio link failure has occurred is performed as set out above with reference to block 208.

[0210] At block 916, the method comprises preparing an indication of MCG link failure.

[0211] In some, but not necessarily all, examples, preparing an indication of MCG link failure is performed in response to a determination that radio link failure has occurred at the MN-CLI.

[0212] At block 918, the method comprises stopping data transmission on all MCG data bearers.

[0213] In some, but not necessarily all, examples, stopping data transmission on all MCG data bearers is performed in response to a determination that radio link failure has occurred at the MN-CU.

[0214] At block 920, the method comprises transmitting, to the SN-Dll, the indication of MCG link failure.

[0215] In some, but not necessarily all, examples, the indication is transmitted in dependence on the preparation of an indication of MCG link failure.

[0216] In some, but not necessarily all, examples, the indication of MCG link failure is transmitted on the SRB3 interface.

[0217] At block 922, the method comprises starting a timer associated with fast MCG link recovery.

[0218] In some, but not necessarily all, examples, the timer is a recovery timer as described above.

[0219] At block 928, the method comprises transmitting, to the serving SN-Dll, L1 measurement reports.

[0220] In some, but not necessarily all, examples, block 928 comprises periodically transmitting L1 measurement reports until a ceasing condition is met, for example, until a CSC is received from the serving SN-Dll.

[0221] Consequently, FIG. 9 illustrates a method comprising:

[0222] at block 902, performing configuration of the UE with DC and SRB3;at block 904, receiving, from the MN-Cll, MCG data;

[0223] at block 908, receiving, from the SN-Cll, configuration information and a MCG recovery indicator;

[0224] at block 910, initiating evaluation of one or more CLTM conditions;

[0225] at block 912, transmitting, to the SN-Cll, an indication that RRC reconfiguration is complete; at block 914, determining that radio link failure has occurred at the MN-Cll;

[0226] at block 916, preparing an indication of MCG link failure;

[0227] at block 918, stopping data transmission on all MCG data bearers;

[0228] at block 920, transmitting, to the serving SN-Dll, the indication of MCG link failure;

[0229] at block 922, starting a timer associated with fast MCG link recovery; and

[0230] at block 924, transmitting, to the serving SN-Dll, L1 measurement reports.

[0231] From the point of view of the serving SN-Dll, method 900 comprises, at block 920, receiving, from the UE, the indication of MCG link failure.

[0232] At block 924, the method comprises transmitting, to the SN-Cll, the indication of MCG link failure.

[0233] At block 930, the method comprises receiving, from the UE, L1 measurement reports.

[0234] Consequently, FIG. 9 illustrates a method comprising:

[0235] at block 920, receiving, from the UE, the indication of MCG link failure;

[0236] at block 924, transmitting, to the SN-CU, the indication of MCG link failure; and

[0237] at block 930, receiving, from the UE, L1 measurement reports.

[0238] From the point of view of the serving SN-CU, method 900 comprises, at block 906, preparing the configuration information and the MCG recovery indicator.

[0239] At block 908, the method comprises transmitting, to the UE, the configuration information and the MCG recovery indicator.

[0240] At block 912, the method comprises receiving, from the UE, an indication that RRC reconfiguration is complete.

[0241] At block 924, the method comprises receiving, from the serving SN-DU, the indication of MCG link failure.At block 926, the method comprises transmitting, to the MN-Cll, the indication of MCG link failure.

[0242] Consequently, FIG. 9 illustrates a method comprising:

[0243] at block 906, preparing the configuration information and the MCG recovery indicator; at block 908, transmitting, to the UE, the configuration information and the MCG recovery indicator;

[0244] at block 912, receiving, from the UE, an indication that RRC reconfiguration is complete; at block 924, receiving, from the serving SN-DU, the indication of MCG link failure; and at block 926, transmitting, to the MN-CU, the indication of MCG link failure.

[0245] From the point of view of the MN-CU, the method comprises, at block 926, receiving, from the SN-CU, the indication of MCG link failure.

[0246] At block 928, the method comprises preparing reconfiguration information associated with fast MCG link recovery.

[0247] Consequently, FIG. 9 illustrates a method comprising:

[0248] at block 926, receiving, from the SN-CU, the indication of MCG link failure; and

[0249] at block 928, preparing reconfiguration information associated with fast MCG link recovery.

[0250] In some, but not necessarily all, examples, method 900 precedes any one or more of method 1000, method 1100, method 1200, or method 1300. Method 900 may proceed directly to any one or more of methods 1000, 1100, 1200 or 1300 with no intervening blocks, or with one or more intervening blocks.

[0251] FIG. 10 illustrates method 1000. From the point of view of the UE, method 1000 comprises, at block 1002, based on the MCG recovery indicator, stopping evaluation of conditions for CLTM at the SCG.

[0252] At block 1008, the method comprises receiving, from the SN-DU, reconfiguration information associated with fast MCG link recovery.

[0253] At block 1010, the method comprises stopping a timer associated with fast MCG link recovery.In some, but not necessarily all, examples, stopping the timer is performed in dependence upon receiving the reconfiguration information.

[0254] In some, but not necessarily all, examples, the timer is a recovery timer as described above.

[0255] In some, but not necessarily all, examples blocks 1012 - 1018 comprise blocks of a method of performing fast MCG link recovery.

[0256] At block 1012, the method comprises triggering random access to the recovery PCell.

[0257] At block 1014, the method comprises transmitting, to the recovery PCell, an indication that RRC reconfiguration is complete.

[0258] At block 1018, the method comprises resuming data transmission on one or more MCG data bearers.

[0259] At block 1020, the method comprises receiving, from the recovery PCell, an indication to resume CLTM at the SCG.

[0260] At block 1022, the method comprises enabling evaluation of CLTM conditions for the SCG.

[0261] Consequently, FIG. 10 illustrates a method comprising:

[0262] at block 1002, based on the MCG recovery indicator, preventing evaluation of conditions for CLTM at the SCG;

[0263] at block 1008, receiving, from the SN-DU, reconfiguration information associated with fast MCG link recovery;

[0264] at block 1010, stopping a timer associated with fast MCG link recovery;

[0265] at block 1012, triggering random access to the recovery PCell;

[0266] at block 1014, transmitting, to the recovery PCell, an indication that RRC reconfiguration is complete;

[0267] at block 1018, resuming data transmission on one or more MCG data bearers;

[0268] at block 1020, receiving, from the recovery PCell, an indication to resume CLTM at the SCG; and

[0269] at block 1022, enabling evaluation of CLTM conditions for the SCG.From the point of view of the SN-Dll, the method comprises, at block 1006, receiving, from the SN-Cll, reconfiguration information associated with fast MCG link recovery.

[0270] At block 1008, the method comprises transmitting, to the UE, reconfiguration information associated with fast MCG link recovery.

[0271] Consequently, Fig. 10 illustrates a method comprising:

[0272] at block 1006, receiving, from the SN-Cll, reconfiguration information associated with fast MCG link recovery; and

[0273] at block 1008, transmitting, to the UE, reconfiguration information associated with fast MCG link recovery.

[0274] From the point of view of the SN-CU, the method comprises, at block 1004, receiving, from the MN-CU, reconfiguration information associated with fast MCG link recovery.

[0275] At block 1006, the method comprises transmitting, to the SN-DU, the reconfiguration information associated with fast MCG link recovery.

[0276] Consequently, FIG. 10 illustrates a method comprising:

[0277] at block 1004, receiving, from the MN-CU, reconfiguration information associated with fast MCG link recovery; and

[0278] at block 1006, transmitting, to the SN-DU, the reconfiguration information associated with fast MCG link recovery.

[0279] From the point of view of the recovery PCell, the method comprises, at block 1012, triggering random access with the UE.

[0280] At block 1014, the method comprises receiving, from the UE, an indication that RRC reconfiguration is complete.

[0281] At block 1016, the method comprises transmitting, to the MN-CU, an indication that RRC reconfiguration is complete.

[0282] In some, but not necessarily all, examples, the indication that RRC reconfiguration is complete comprises an uplink (UL) RRC message.At block 1020, the method comprises transmitting, to the UE, an indication to resume CLTM at the SCG.

[0283] Consequently, FIG. 10 illustrates a method comprising:

[0284] at block 1012, triggering random access with the UE;

[0285] at block 1014, receiving, from the UE, an indication that RRC reconfiguration is complete; at block 1016, transmitting, to the MN-CU, a UL RRC message; and

[0286] at block 1020, transmitting, to the UE, an indication to resume CLTM at the SCG.

[0287] From the point of view of the MN-CU, the method comprises, at block 1004, transmitting, to the SN-CU, reconfiguration information associated with fast MCG link recovery.

[0288] In some, but not necessarily all, examples, the reconfiguration information is reconfiguration information as determined at block 928 of method 900.

[0289] At block 1016, the method comprises receiving, from the recovery PCell, an indication that RRC reconfiguration is complete.

[0290] Consequently, FIG. 10 illustrates a method comprising:

[0291] at block 1004, transmitting, to the SN-CU, reconfiguration information associated with fast MCG link recovery; and

[0292] at block 1016, receiving, from the recovery PCell, a UL RRC message.

[0293] FIG. 11 illustrates method 1100. From the point of view of the UE, method 1100 comprises, at block 1102, determining that at least one condition for CLTM at the SCG is met, and that fast MCG link recovery has not been performed.

[0294] At block 1104, the method comprises, in dependence upon a determination that at least one condition for CLTM at the SCG is met, and that fast MCG link recovery has not been performed, stopping execution of CLTM at the SCG.

[0295] At block 1110, the method comprises receiving, from the SN-DU, reconfiguration information associated with fast MCG link recovery.

[0296] At block 1112, the method comprises stopping a timer.In some, but not necessarily all, examples, the timer is a recovery timer as described above.

[0297] In some, but not necessarily all, examples, blocks 1114 - 1120 comprise one or more blocks of a method of performing fast MCG link recovery.

[0298] At block 1114, the method comprises triggering random access to the recovery PCell.

[0299] At block 1116, the method comprises transmitting, to the recovery PCell, an indication that RRC reconfiguration is complete.

[0300] At block 1120, the method comprises resuming data transmission on one or more MCG data bearers.

[0301] At block 1122, the method comprises receiving, from the recovery PCell, an indication to resume CLTM at the SCG.

[0302] At block 1124, the method comprises enabling CLTM for the SCG.

[0303] Consequently, FIG. 11 illustrates a method comprising:

[0304] at block 1102, determining that at least one condition for CLTM at the SCG is met, and that fast MCG link recovery has not been performed;

[0305] at block 1104, in dependence upon a determination that at least one condition for CLTM at the SCG is met, and that fast MCG link recovery has not been performed, stopping execution of CLTM at the SCG;

[0306] at block 1110, receiving, from the SN-DU, reconfiguration information associated with fast MCG link recovery;

[0307] at block 1112, stopping a timer;

[0308] at block 1114, triggering random access to the recovery PCell;

[0309] at block 1116, transmitting, to the recovery PCell, an indication that RRC reconfiguration is complete;

[0310] at block 1120, resuming data transmission on one or more MCG data bearers;

[0311] at block 1122, receiving, from the recovery PCell, an indication to resume CLTM at the SCG; and

[0312] at block 1124, enabling CLTM for the SCG.From the point of view of the SN-Dll, the method comprises, at block 1108, receiving, from the SN-Cll, reconfiguration information associated with fast MCG link recovery.

[0313] At block 1110, the method comprises transmitting, to the UE, reconfiguration information associated with fast MCG link recovery.

[0314] Consequently, FIG. 11 illustrates a method comprising:

[0315] at block 1108, receiving, from the SN-Cll, reconfiguration information associated with fast MCG link recovery; and

[0316] at block 1110, transmitting, to the UE, reconfiguration information associated with fast MCG link recovery.

[0317] From the point of view of the SN-CU, the method comprises, at block 1106, receiving, from the MN-CU, reconfiguration information associated with fast MCG link recovery.

[0318] At block 1108, the method comprises transmitting, to the SN-DU, the reconfiguration information associated with fast MCG link recovery.

[0319] Consequently, FIG. 11 illustrates a method comprising:

[0320] at block 1106, receiving, from the MN-CU, reconfiguration information associated with fast MCG link recovery; and

[0321] at block 1108, transmitting, to the SN-DU, the reconfiguration information associated with fast MCG link recovery.

[0322] From the point of view of the recovery PCell, the method comprises, at block 1114, triggering random access with the UE.

[0323] At block 1116, the method comprises receiving, from the UE, an indication that RRC reconfiguration is complete.

[0324] At block 1118, the method comprises transmitting, to the MN-CU, a UL RRC message.

[0325] At block 1122, the method comprises transmitting, to the UE, an indication to resume CLTM at the SCG.

[0326] Consequently, FIG. 11 illustrates a method comprising:at block 1114, triggering random access with the UE;

[0327] at block 1116, receiving, from the UE, an indication that RRC reconfiguration is complete; at block 1118, transmitting, to the MN-CU, a UL RRC message; and

[0328] at block 1122, transmitting, to the UE, an indication to resume CLTM at the SCG.

[0329] From the point of view of the MN-CU, the method comprises, at block 1106, transmitting, to the SN-CU, reconfiguration information associated with fast MCG link recovery.

[0330] At block 1118, the method comprises receiving, from the recovery PCell, a UL RRC message.

[0331] Consequently, FIG. 11 illustrates a method comprising:

[0332] at block 1106, transmitting, to the SN-CU, reconfiguration information associated with fast MCG link recovery; and

[0333] at block 1118, receiving, from the recovery PCell, a UL RRC message.

[0334] FIG. 12 illustrates a method 1200. From the point of view of the UE, the method comprises, at block 1204, receiving, from the serving SN-DU, a CSC MAC CE.

[0335] At block 1206, the method comprises starting a timer.

[0336] In some, but not necessarily all, examples, the timer is an LTM countdown timer as described above.

[0337] At block 1212, the method comprises receiving, from the serving SN-DU, reconfiguration information associated with fast MCG link recovery.

[0338] At block 1214, the method comprises determining that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer.

[0339] At block 1216, the method comprises stopping the timer.

[0340] At block 1218, the method comprises performing fast MCG link recovery.

[0341] At block 1220, the method comprises executing SCG LTM towards the candidate SN-DU.

[0342] Consequently, FIG. 12 illustrates a method comprising:at block 1204, receiving, from the serving SN-Dll, a CSC MAC CE;

[0343] at block 1206, starting a timer;

[0344] at block 1212, receiving, from the serving SN-Dll, reconfiguration information associated with fast MCG link recovery;

[0345] at block 1214, determining that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer;

[0346] at block 1216, stopping the timer;

[0347] at block 1218, performing fast MCG link recovery; and

[0348] at block 1220, executing SCG LTM towards the candidate SN-Dll.

[0349] From the point of view of the serving SN-Dll, the method comprises, at block 1202, determining that an SCG LTM cell switch should be performed.

[0350] At block 1204, the method comprises transmitting, to the UE, a CSC MAC CE.

[0351] At block 1210, the method comprises receiving, from the SN-Cll, reconfiguration information associated with fast MCG link recovery.

[0352] At block 1212, the method comprises transmitting, to the UE, reconfiguration information associated with fast MCG link recovery.

[0353] Consequently, Fig. 12 illustrates a method comprising:

[0354] at block 1202, determining that an SCG LTM cell switch should be performed;

[0355] at block 1204, transmitting, to the UE, a CSC MAC CE;

[0356] at block 1210, receiving, from the SN-CU, reconfiguration information associated fast MCG link recovery; and

[0357] at block 1212, transmitting, to the UE, reconfiguration information associated with fast MCG link recovery.

[0358] From the point of view of the candidate SN-DU, the method comprises, at block 1220, executing network triggered SCG LTM to the candidate node.

[0359] Consequently, FIG. 12 illustrates a method comprising:

[0360] at block 1220, executing network triggered SCG LTM to the candidate node.From the point of view of the SN-Cll, the method comprises, at block 1208, receiving, from the MN-Cll, reconfiguration information associated with fast MCG link recovery.

[0361] At block 1210, the method comprises transmitting, to the MN-Dll, reconfiguration information associated with fast MCG link recovery.

[0362] Consequently, FIG. 12 illustrates a method comprising:

[0363] at block 1208, receiving, from the MN-Cll, reconfiguration information associated with fast MCG link recovery; and

[0364] at block 1210, transmitting, to the SN-Dll, reconfiguration information associated with fast MCG link recovery.

[0365] From the point of view of the MN-Dll, the method comprises, at block 1208, transmitting, to the SN-Cll, reconfiguration information associated with fast MCG link recovery.

[0366] Consequently, FIG. 12 illustrates a method comprising:

[0367] at block 1208, transmitting, to the SN-Cll, reconfiguration information associated with fast MCG link recovery.

[0368] FIG. 13 illustrates method 1300. From the point of view of the UE, method 1300 comprises, at block 1304, receiving, from the serving SN-Dll, a CSC MAC CE.

[0369] At block 1306, the method comprises starting a timer.

[0370] In some, but not necessarily all, examples, the timer is an LTM countdown timer as described above.

[0371] At block 1308, the method comprises determining that the reconfiguration information has not been received before expiry of the timer.

[0372] At block 1310, the method comprises performing SCG LTM.

[0373] At block 1316, the method comprises receiving, from the candidate SN-Dll, reconfiguration information.

[0374] At block 1318, the method comprises executing fast MCG link recovery.Consequently, FIG. 13 illustrates a method comprising:

[0375] at block 1304, receiving, from the serving SN-Dll, a CSC MAC CE;

[0376] at block 1306, starting a timer;

[0377] at block 1308, determining that the reconfiguration information has not been received before expiry of the timer;

[0378] at block 1310, performing SCG LTM;

[0379] at block 1316, receiving, from the candidate SN-Dll, reconfiguration information; and at block 1318, executing fast MCG link recovery.

[0380] From the point of view of the serving SN-Dll, the method comprises, at block 1302, determining that an SCG LTM cell switch should be performed.

[0381] At block 1304, the method comprises transmitting, to the UE, a CSC MAC CE.

[0382] Consequently, FIG. 13 illustrates a method comprising:

[0383] at block 1302, determining that an SCG LTM cell switch should be performed; and at block 1304, transmitting, to the UE, a CSC MAC CE.

[0384] From the point of view of the candidate SN-DU, the method comprises, at block 1310, executing SCG LTM to the candidate SN-DU.

[0385] At block 1314, the method comprises receiving, from the SN-CU, reconfiguration information associated with fast MCG link recovery.

[0386] At block 1316, the method comprises transmitting, to the UE, reconfiguration information associated with fast MCG link recovery.

[0387] Consequently, FIG. 13 illustrates a method comprising:

[0388] at block 1314, receiving, from the SN-CU, reconfiguration information associated with fast MCT link recovery; and

[0389] at block 1316, transmitting, to the UE, reconfiguration information associated with fast MCG link recovery.

[0390] From the point of view of the SN-Cll, the method comprises, at block 1312, receiving, from the MN-Dll, reconfiguration information associated with fast MCG link recovery.At block 1314, the method comprises transmitting, to the candidate SN-Dll, reconfiguration information associated with fast MCG link recovery.

[0391] Consequently, FIG. 13 illustrates a method comprising:

[0392] at block 1312, receiving, from the MN-Dll, reconfiguration information associated with fast MCG link recovery; and

[0393] at block 1314, transmitting, to the candidate SN-Dll, reconfiguration information associated with fast MCG link recovery.

[0394] From the point of view of the recovery PCell, the method comprises, at block 1318, executing fast MCG link recovery.

[0395] Consequently, FIG. 13 illustrates a method comprising:

[0396] at block 1318, executing fast MCG link recovery.

[0397] From the point of view of the MN-Dll, the method comprises, at block 1312, transmitting, to the SN-Cll, reconfiguration information associated with fast MCG link recovery.

[0398] Consequently, FIG. 13 illustrates a method comprising:

[0399] at block 1312, transmitting, to the SN-Cll, reconfiguration information associated with fast MCG link recovery.

[0400] For dual connectivity scenarios, fast MCG link recovery is introduced in 3GPP Rel. 16 as an effective and latency resilient procedure when radio link failure (RLF) is detected in master cell group (MCG). RLF can occur over the MCG link whenever there are some blockages between the gNB of the PCell and the UE receiver which for example occurs quite frequently in case of vehicular communication as the link between the gNB and the vehicular UE gets obstructed thus leading to outages. In case the legacy UEs detects radio link failure (RLF) on the serving cell, it initiates RRC re-establishment procedure. Alternatively, a CHO recovery procedure may be performed: when RLF occurs in the source gNB or initial CHO execution attempt fails or HO fails, the UE performs cell selection for re-establishment, and if the selected cell is a CHO candidate and if network configured the UE to try CHO Recovery after RLF / HO / CHO failure, then the UE attempts CHO execution once, otherwise re-establishment procedure is performed.if the selected cell is one of the candidate cells for which the reconfigurationWithSync is included in the masterCellGroup in the MCG VarConditional Reconfig:

[0401] if the UE supports RLF-Report for conditional handover, set the choCellld in the VarRLF-Report to the global cell identity, if available, otherwise to the physical cell identity and carrier frequency of the selected cell;

[0402] However, these procedures are based on L3 measurement reports leading to high latencies and processing complexities.

[0403] Moreover, UE is expected to repeat the cell re-selection measurements and do a setup like procedure with the MN and during re-establishment UE loses PSCell connection. However, it is also specified in the specification on dual connectivity that “If radio link failure is detected for MCG, fast MCG link recovery is configured and the SCG is not deactivated, the UE triggers fast MCG link recover / ’. The main reason is UE prepares and reports the failure with MCGFailurelnformation message to the MN via the SCG, using the SCG leg of split SRB1 or SRB3. However, it is also specified that SN can trigger PSCell change independently.

[0404] In case fast MCG link recovery and conditional LTM in the SCG (inter-CU or intra-CU) is configured simultaneously, there can be certain problems. Disclosures presented herein address the issues related to the inter-working of fast MCG Link Recovery and intra CU SCG CLTM.

[0405] When fast MCG link recovery is triggered simultaneously with C-LTM PSCell change (intra-SN or inter-SN), there may be potential issues that may lead to interruptions and even higher latencies.

[0406] Issue#1a: Interruption in SCG RL due to SCG C-LTM execution - resulting in MCG failure recovery configuration not reaching the UE

[0407] UE if configured with CLTM, triggers conditional LTM cell switch execution autonomously upon meeting the conditions for CLTM cell switch based on either L1 or L3 measurements. When the SCG LTM procedure is configured to co-exist with the fast MCG failure recovery procedure, if UE triggers the conditional PSCell switch, then MN may not be aware of the ongoing SCG LTM execution, and may respond to MCG Failure Information received via SCG link with the RRCReconfiguration message with fast MCG link recovery configuration for the PCell. However, due to ongoing SCG CLTM execution, there may be SCG radio link interruption between the source SN and the UE; which may potentially result in interruption in receiving the RRCReconfiguration message.

[0408] Issue#1b: Interruption in SCG RL due to NW triggered SCG LTM while UE is evaluating SCG C-LTM - resulting in MCG failure recovery configuration not reaching the UEUE if configured with CLTM, triggers conditional LTM cell switch execution autonomously upon meeting the conditions for CLTM cell switch based on either L1 or L3 measurements. When the SCG LTM procedure is configured to co-exists with the fast MCG failure recovery procedure, there may be a scenario where network or the serving SN-DU may trigger a cell switch by sending a MAC CE which is a cell switch command (CSC MAC CE) while the evaluation of conditions for the CLTM PSCell switch execution is still ongoing. In such a case, UE will have to initiate cell switch execution towards the candidate PSCell. The MN may route the RRCReconfiguration message for the PCell via the source-SN. But since the network has already triggered SCG LTM, the SCG RL may experience interruption; due to which the RRCReconfiguration message may not reach the UE.

[0409] Note: Fast MCG link recovery procedure assumes SRB3 to be configured.

[0410] Proposed signaling enhancements at the network side

[0411] If UE is configured with intra-CU SCG CLTM and fast MCG Link Recovery

[0412] During the preparation phase of SCG CLTM, if UE is configured with fast MCG link Failure Recovery, serving SN-CU (if SRB3 is configured) will include an additional “SCG C-LTM condition evaluation suspension indication" to the UE along with the RRCReconfiguration message. Alternatively, UE may include “SCG LTM execution prevention criteria" within the CLTM execution conditions encapsulated within RRCReconfiguration message the (for e.g. condition which explicitly indicates UE that it will prevent execution of SCG CLTM cell switch even if the execution conditions are met if T316 is still running)

[0413] In case if network configures early UL synchronization for the SCG CLTM, “SCG C-LTM condition evaluation suspension indication" can be send to the UE over the proposed new MAC CE which is meant to convey the early Timing Advance

[0414] MN-DU corresponding to the recovered PCell, upon reception of the RRC Reconfiguration Complete from the UE will send “Resume C-LTM conditions evaluation indication for SCG CLTM" over MAC CE or through L1 signaling)

[0415] As an optional method S-MN-CU can use the SCG leg to transmit the “Successful MCG Link Recovery Indication", to the S-SN-CU (over Xn interface) and “Resume C-LTM conditions evaluation indication" from S-SN-DU to the UE over MAC CE or through L1 signaling Alternatively, UE can re-start CLTM conditions evaluation autonomously once the data transmission on the MCG data bearers resumes after the recovery procedure without any explicit signaling or indications from the network.

[0416] Proposed UE behavior upon reception of the proposed signaling enhancements from the network sideUE upon reception of the “SCG C-LTM condition evaluation suspension indication" either via RRC Reconfiguration or via new MAC CE, triggers the following behavior when configured with fast MCG link Recovery:

[0417] If UE detects MCG RLF and triggers fast MCG Link Recovery, it shall prevent the CLTM conditions evaluation for the candidate PSCells till the MCG recovery is executed successfully and data transmission resumes on the MCG bearers.

[0418] However, based on the configured measurement reporting criteria for the candidate PSCells, if the UE has measurements for the candidate PSCells to report, then the UE shall report the measurements to allow the NW to trigger PSCell change if there is an imminent possibility of SCG RLF.

[0419] In this case, the handling at the UE shall be as follows:

[0420] Case 1: If the UE receives LTM Cell switch command for PSCell switch from the NW before it receives the RRCReconfiguration message for fast MCG link recovery via SCG link, then it shall start a configurable timer and wait for the completion of fast MCG link recovery and then trigger the PSCell switch.

[0421] If the configurable timer expires and the RRCReconfiguration message is not received via SCG link, it may be up to UE implementation to handle this scenario e.g. handling may be, to execute PSCell switch as per the received MAC CE cell switch command.

[0422] Case 2: IF the UE receives LTM Cell switch command for PSCell from the NW together with RRCReconfiguration message for fast MCG link recovery via SCG link, then it shall complete the fast MCG link recovery and then trigger PSCell switch.

[0423] UE may resume the evaluation of configured candidate PSCell execution conditions autonomously either after completion of fast MCG link recovery or after Cell switch execution or up on reception of an indication from the NW e.g. “Resume C-LTM conditions evaluation indication" or when the data transmission resumes on the MCG data bearers.

[0424] The Suspend or Resume indication from the NW to hold the evaluation of configured candidate PSCell conditions during fast MCG link recovery may be signaled to the UE via RRC signaling or via MAC signaling. Alternatively, the NW may configure the evaluation condition in a way that enables the UE not to trigger any SCG LTM cell switch when certain scenarios are met if for e.g. T316 is running, or data transmission not resumed on MCG bearers.

[0425] FIGs 16A and 16B illustrate example methods. The methods illustrated in FIG. 16B succeed the methods of FIG. 16A.

[0426] Block-1: UE is configured with dual connectivity (DC) and SRB3.

[0427] Block -2: UE receives MCG data from MN (serving PCell)

[0428] Block -3: SN-CU decides to configure intra-CU SCG LTM and prepares the configuration (RRC Reconfiguration) for the intra-CU candidate PSCell(s).Block -4: SN-Cll includes an additional SCG CLTM conditions evaluation suspension indication and encapsulates it within the RRC Reconfiguration message send over SRB3 directly to the UE or SN-Cll may include an additional criteria in the CLTM execution condition which is encapsulated within the RRC message that if T316 is running then UE will not trigger a CLTM cell switch even if the execution conditions are met.

[0429] Block -4 (Optional): The SCG CLTM conditions evaluation suspension indication can be included within the new MAC CE that has been agreed which is supposed to include the TA and TAT information to the UE in case if network decides to configure UE for early UL synchronization. The SCG CLTM conditions evaluation suspension indication can also be included in new MAC CE which may be used for early TCI state activation

[0430] Block -5: UE sends RRC Reconfiguration Complete to the SN-CU.

[0431] Block -6: UE detects Radio Link Failure at the MN leading to PCell failure as T310 expires and no N311 in-sync indications has been received.

[0432] Block -7: UE prepares the MCG Failure Indication message.

[0433] Block -8: UE stops data transmission on all MCG data bearers.

[0434] Block -9: UE forwards MCG failure indication to the SN-DU.

[0435] Block -10: UE starts the T316 timer.

[0436] Block -11 and Block -12: Serving SN-DU forwards the MCG failure Indication to the MN via SN-CU using F1 and XN interfaces.

[0437] Block -13: MN prepares the MN RRCReconfiguration with HO command for the PCell (intra-CU candidate cell selected for PCell recovery). Upon receiving the MCG failure Indication. Block and Block -15: UE periodically reports the L1 measurement reports to the serving SN. Option-1

[0438] Block -16: Based on the received SCG CLTM conditions evaluation suspension indication, UE prevents conditions evaluation for SCG CLTM till data transmission / reception resumes on the MCG data bearers or recovery procedure is executed successfully. Furthermore, while the recovery procedure is ongoing, if UE receives a network triggered cell switch command for the SCG, it will refrain form triggering any cell switch till recovery is successfully completed. Block -17, Block -18 and Block -19: MN forwards the MN RRCReconfiguration with HO command for the PCell to the UE via SN-CU and SN-DU

[0439] Option-2

[0440] Block -20: UE keeps on evaluating the CLTM execution conditions.

[0441] Block -21 : UE find CLTM execution conditions are met but t316 is still running

[0442] Block -22: Based on the CLTM execution conditions in Step-4, UE suspends triggering the CLTM cell switch execution.Block -23, Block -24 and Block -25: MN forwards the MN RRCReconfiguration with HO command for the PCell to the UE via SN-Cll and SN-Dll

[0443] Block -26: UE stops the T316 timer.

[0444] Block -27: UE triggers random access to the recovery PCell.

[0445] Block -28 and Block -29: UE forwards RRC Reconfiguration Complete to the Recovered PCell and its forwards the same to the MN over an UL RRC message,

[0446] Block -30: UE resumes transmission on MCG data bearers.

[0447] Block -31: The MN-DU of the recovered PCell upon receiving RRC Reconfiguration Complete from the UE, will now trigger and “Resume C-LTM conditions evaluation indication" over MAC CE.

[0448] Block -32: UE can now re-start conditions evaluation for SCG-CLTM

[0449] FIGs 17A and 17B illustrate example methods. The methods of FIG 17B succeed the methods of FIG 17A.

[0450] Block -1: UE is configured with dual connectivity (DC) and SRB3.

[0451] Block -2: UE receives MCG data from MN (serving PCell)

[0452] Block -3: SN-CU decides to configure intra-CU SCG LTM and prepares the configuration (RRC Reconfiguration) for the intra-CU candidate PSCell(s).

[0453] Block -4: SN-CU includes an additional SCG CLTM conditions evaluation suspension indication and encapsulates it within the RRC Reconfiguration message send over SRB3 directly to the UE or SN-CU may include an additional criteria in the CLTM execution condition which is encapsulated within the RRC message that if T316 is running then UE will not trigger a CLTM cell switch even if the execution conditions are met.

[0454] Block -4 (Optional): The SCG CLTM conditions evaluation suspension indication can be included within the new MAC CE that has been agreed which is supposed to include the TA and TAT information to the UE in case if network decides to configure UE for early UL synchronization. The SCG CLTM conditions evaluation suspension indication can also be included in new MAC CE which may be used for early TCI state activation

[0455] Block -5: UE sends RRC Reconfiguration Complete to the SN-CU.

[0456] Block -6: UE detects Radio Link Failure at the MN leading to PCell failure as T310 expires and no N311 in-sync indications has been received.

[0457] Block -7: UE prepares the MCG Failure Indication message.

[0458] Block -8: UE stops data transmission on all MCG data bearers.

[0459] Block -9: UE forwards MCG failure indication to the SN-DU.

[0460] Block -10: UE starts the T316 timer.

[0461] Block -11 and Block -12: Serving SN-DU forwards the MCG failure Indication to the MN via SN-CU using F1 and XN interfaces.Block -13: MN prepares the MN RRCReconfiguration with HO command for the PCell (intra-Cll candidate cell selected for PCell recovery). Upon receiving the MCG failure Indication. Block and Block 15: UE periodically reports the L1 measurement reports to the serving SN. Block -16: Based on the received SCG CLTM conditions evaluation suspension indication, UE prevents conditions evaluation for SCG CLTM till data transmission / reception resumes on the MCG data bearers or recovery procedure is executed successfully. Furthermore, while the recovery procedure is ongoing, if UE receives a network triggered cell switch command for the SCG, it will refrain from triggering any cell switch till recovery is successfully completed.

[0462] Block -17 and Block 18: Based on L1 measurements, serving SN-DU anticipates an imminent RLF and decide s to trigger a network triggered SCG LTM cell switch and sends a CSC MAC CE to the UE to trigger SCG LTM

[0463] Case-1: MN configuration is received at the UE after it has received the CSC MAC CE (while the proposed timer is still running)

[0464] Block -19: As per new UE behavior, UE starts the new configurable timer and waits for the MN configuration for MCG recovery and doesn’t immediately trigger SCG LTM.

[0465] Block -20, Block -21 and Block -22: MN forwards the MN RRCReconfiguration with HO command for the PCell to the UE via SN-CU and SN-DU

[0466] Block -23: UE finds the MN configuration is received while the new proposed timer is still running.

[0467] Block -24: UE stops the timer and successfully executed the fast MCG link recovery.

[0468] Block -25: Once the fast MCG link recovery procedure is completed and data transmission starts on the MCG bearers, the UE can now decide to trigger SCG LTM cell switch towards candidate cell indicated by the network.

[0469] Block -26: UE triggers random access to the candidate cell and successfully executes SCG LTM

[0470] Case-2: MN configuration is not received at the UE after it has received the CSC MAC CE (while the proposed timer has expired)

[0471] Block -27: As per new UE behavior, UE starts the new configurable timer and waits for the MN configuration for MCG recovery and doesn’t immediately trigger SCG LTM.

[0472] Block -28: UE finds the MN configuration is not received while the new proposed timer has expired.

[0473] Block -29: UE decides to trigger random access to the candidate PSCell.

[0474] Block -30: UE triggers Random Access and execute the SCG LTM successfully.

[0475] Block -31, Block -32 and Block -33: MN forwards the MN RRCReconfiguration with HO command for the PCell to the UE via SN-CU and candidate PSCell under target SN-DU whichhas now become the serving PSCell. UE now successfully completes the fast MCG Link recovery

[0476] Disclosures presented herein prevent potential failure of fast MCG link recovery procedure due to interruption in SCG RL during SCG C-LTM execution.

[0477] The FIGs illustrate methods performed by a system comprising interaction between different system entities. The FIGs also illustrate a collection of separate methods performed separately by the different system entities.

[0478] There are present different sets of numbered paragraphs A1.1 , A1.2; A2.1 , A2.2; B1.1 , B1.2; B2.1 , B2.2; C, .... The first paragraph in any of these sets of paragraphs could form the basis for an independent claim. Features present in one set of paragraphs can be combined with features present in other sets of paragraphs.

[0479] A1.1. A user equipment, UE, comprising:

[0480] at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform:

[0481] receiving, from a network node, configuration information associated with conditional L1 / L2 triggered mobility, CLTM at a secondary cell group, SCG;

[0482] initiating, based on the received configuration information, evaluation of one or more CLTM conditions for the SCG;

[0483] receiving, from the network node, an indicator associated with fast master cell group, MCG, link recovery;

[0484] determining whether a condition for MCG link failure has been met; and

[0485] in dependence upon a determination that a condition for MCG link failure has been met, and based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG. A1.2. A UE as defined in paragraph 1, wherein preventing CLTM at the SCG comprises stopping evaluation of the one or more CLTM conditions for the SCG.

[0486] A1.3. A UE as defined in paragraph 1 or paragraph 2, wherein the instructions, when executed by the at least one processor, further cause the UE to perform determining whether a CLTM condition for the SCG has been met, wherein preventing CLTM at the SCG comprises, in dependence upon a determination that a condition for CLTM at the SCG has been met, stopping execution of CLTM at the SCG.

[0487] A1.4. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform, in dependence upon thedetermination that a condition for MCG link failure has been met, starting a timer associated with fast MCG recovery.

[0488] A1.5. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform, in dependence upon the determination that a condition for MCG link failure has been met, suspending data transmissions on all MCG data bearers.

[0489] A1.6. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform:

[0490] determining whether fast MCG recovery has been completed; and

[0491] in dependence upon a determination that fast MCG recovery has been completed, enabling CLTM at the SCG.

[0492] A1.7. A UE as defined in paragraph 6, wherein determining whether fast MCG recovery has been completed comprises determining whether the timer associated with fast MCG recovery has been stopped.

[0493] A1.8. A UE as defined in paragraph 6 or paragraph 7 wherein determining whether fast MCG recovery has been completed comprises determining whether data transmission on MCG data bearers has been resumed.

[0494] A1.9. A UE as defined in any of paragraphs 6 - 8, wherein determining whether fast MCG recovery has been completed comprises determining whether an indication to resume CLTM has been received from a network node.

[0495] A1.10. A UE as defined in any of paragraphs 6- 9 when dependent on paragraph 2, wherein enabling CLTM at the SCG comprises resuming evaluation of the one or more CLTM conditions for the SCG.

[0496] A1.11. A UE as defined in any of paragraphs 6- 9 when dependent on paragraph 3, wherein enabling CLTM at the SCG comprises resuming execution of CLTM at the SCG

[0497] A1.12. A method comprising:

[0498] receiving, from a network node, configuration information associated with conditional L1 / L2 triggered mobility, CLTM;

[0499] initiating, based on the received configuration information, evaluation of one or more CLTM conditions for a secondary cell group, SCG;

[0500] receiving, from the network node, an indicator associated with fast master cell group, MCG, link recovery;

[0501] determining whether a condition for MCG link failure has been met; and

[0502] in dependence upon a determination that a condition for MCG link failure has been met, and based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG. A1.13. A network node comprising:at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the network node at least to perform:

[0503] transmitting, to a user equipment, UE, configuration information associated with conditional L1 / L2 triggered mobility, CLTM, at a secondary cell group, SCG; and

[0504] transmitting, to the UE, an indicator associated with fast master cell group, MCG, link recovery.

[0505] A1.14. A method comprising:

[0506] transmitting, to a user equipment, UE, configuration information associated with conditional L1 / L2 triggered mobility, CLTM, at a secondary cell group, SCG; and

[0507] transmitting, to the UE, an indicator associated with fast master cell group, MCG, link recovery.

[0508] A1.15. A network node comprising:

[0509] at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the network node at least to perform:

[0510] receiving, from a user equipment, UE, an indication that fast MCG recovery has been performed; and

[0511] transmitting, to the UE, an indication to resume conditional L1 / L2 triggered mobility, CLTM, at a secondary cell group, SCG.

[0512] A1.16. A method comprising:

[0513] transmitting, to a user equipment, UE, an indication that fast MCG recovery has been performed; and

[0514] transmitting, to the UE, an indication to resume conditional L1 / L2 triggered mobility, CLGTM, at a secondary cell group, SCG.

[0515] B1.1. A user equipment, UE, comprising:

[0516] at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform:

[0517] determining whether a condition for master cell group, MCG, link failure has been met; determining whether a cell switch command, CSC, for a secondary cell group, SCG, has been received from a network node;

[0518] in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery;

[0519] determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer;in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer:

[0520] performing fast MCG link recovery based at least on the received reconfiguration information; and

[0521] in dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC; and

[0522] in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer, performing LTM at the SCG based at least on the CSC.

[0523] B1.2.A UE as described in paragraph 1 wherein the instructions, when executed by the at least one processor, further cause the UE to perform, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer, stopping the timer.

[0524] B1.3. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform determining whether reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer; and

[0525] in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer, performing fast MCG link recovery based at least on the received configuration information.

[0526] B1.4. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform:

[0527] receiving, from a network node, configuration information associated with conditional LTM, CLTM, at the SCG;

[0528] initiating, based on the received configuration information, evaluation of one or more CLTM conditions for the SCG;

[0529] receiving, from the network node, an indicator associated with fast MCG link recovery; and in dependence upon a determination that a condition for MCG link failure has been met, based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0530] B1.5. A UE as defined in any preceding paragraph, wherein preventing CLTM at the SCG comprises stopping evaluation of the one or more CLTM conditions for the SCG.

[0531] B1.6. A UE as defined in any of paragraphs 1 — 4, wherein the instructions, when executed by the at least one processor, further cause the UE to perform determining whether a CLTM condition for the SCG has been met, wherein preventing CLTM at the SCG comprises, in dependence upon a determination that a condition for CLTM at the SCG has been met, stopping execution of CLTM at the SCG.B1.7. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform, in dependence upon the determination that a condition for MCG link failure has been met, starting a second timer associated with fast MCG recovery.

[0532] B1.8. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform, in dependence upon the determination that a condition for MCG link failure has been met, suspending data transmission on all MCG data bearers.

[0533] B1.9. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform: determining whether fast MCG recovery has been completed; and

[0534] in dependence upon a determination that fast MCG recovery has been completed, enabling CLTM at the SCG.

[0535] B1.10. A UE as defined in any preceding paragraph, wherein the instructions, when executed by the at least one processor, further cause the UE to perform determining whether fast MCG recovery has been completed comprises determining at least one of:

[0536] whether the timer associated with fast MCG recovery has been stopped;

[0537] whether data transmission on MCG data bearers has been resumed; or

[0538] whether an indication to resume CLTM has been received from a network node.

[0539] B1.11. A UE as defined in any of paragraphs 5 - 10 wherein enabling CLTM at the SCG comprises resuming evaluation of the one or more CLTM conditions for the SCG.

[0540] B1.12. A UE as defined in any of paragraphs 6 - 10 wherein enabling CLTM at the SCG comprises resuming execution of CLTM at the SCG.

[0541] B1.13. A method comprising:

[0542] determining whether a condition for master cell group, MCG, link failure has been met; determining whether a cell switch command, CSC, for a secondary cell group, SCG, has been received from a network node;

[0543] in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery;

[0544] determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer;

[0545] in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer:

[0546] performing fast MCG link recovery based at least on the received reconfiguration information; andin dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC; and

[0547] in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer, performing LTM at the SCG based at least on the CSC.

[0548] B1.14. A network node comprising:

[0549] at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the network node at least to perform:

[0550] transmitting, to a user equipment, UE, a cell switch command.

[0551] B1.15. A method comprising:

[0552] transmitting, to a user equipment, UE, a cell switch command.

[0553] Fig 14 illustrates an example of a controller 1400 suitable for use in an apparatus 1410. Implementation of a controller 1400 may be as controller circuitry. The controller 1400 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

[0554] As illustrated in Fig 14 the controller 1400 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions 1406 in a general-purpose or special-purpose processor 1402 that may be stored on a machine readable storage medium (disk, memory etc.) to be executed by such a processor 1402.

[0555] The processor 1402 is configured to read from and write to the memory 1404. The processor 1402 may also comprise an output interface via which data and / or commands are output by the processor 1402 and an input interface via which data and / or commands are input to the processor 1402.

[0556] The memory 1404 stores instructions, program, or code 1406 that controls the operation of the apparatus 1410 when loaded into the processor 1402. The instructions, program, or code 1406, provide the logic and routines that enables the apparatus 1410 to perform the methods illustrated in the accompanying FIGs. The processor 1402 by reading the memory 1404 is configured to load and execute the instructions, program, or code 1406.

[0557] The apparatus 1410 comprises:

[0558] at least one processor 1402; andat least one memory 1404 storing instructions that, when executed by the at least one processor 1402, cause the apparatus at least to:

[0559] receive, from a network node, configuration information associated with conditional L1 / L2 triggered mobility, CLTM;

[0560] initiate, based on the received configuration information, evaluation of one or more CLTM conditions for a secondary cell group, SCG;

[0561] receive, from the network node, an indicator associated with fast master cell group, MCG, link recovery;

[0562] determine whether a condition for MCG link failure has been met; and

[0563] in dependence upon a determination that a condition for MCG link failure has been met, and based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0564] In some examples, there is a (computer implemented) system comprising:

[0565] receive, from a network node, configuration information associated with conditional L1 / L2 triggered mobility, CLTM;

[0566] initiate, based on the received configuration information, evaluation of one or more CLTM conditions for a secondary cell group, SCG;

[0567] receive, from the network node, an indicator associated with fast master cell group, MCG, link recovery;

[0568] determine whether a condition for MCG link failure has been met; and

[0569] in dependence upon a determination that a condition for MCG link failure has been met, and based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0570] As illustrated in Fig 15, the instructions, program, or code 1406 may arrive at the apparatus 1410 via any suitable delivery mechanism 1408. The delivery mechanism 1408 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a solid-state memory, an article of manufacture that comprises or tangibly embodies the instructions 1406. The delivery mechanism may be a signal configured to reliably transfer the instructions 1406. The apparatus 1410 may propagate or transmit the instructions! 406 as a data signal.

[0571] The term “non-transitory” as used herein, is a limitation of the medium itself (i.e. , tangible, not a signal ) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0572] The instructions 1406 cause an apparatus to perform at least the following:causing reception, from a network node, configuration information associated with conditional L1 / L2 triggered mobility, CLTM;

[0573] causing initiation, based on the received configuration information, evaluation of one or more CLTM conditions for a secondary cell group, SCG;

[0574] causing reception, from the network node, an indicator associated with fast master cell group, MCG, link recovery;

[0575] causing determination whether a condition for MCG link failure has been met; and causing in dependence upon a determination that a condition for MCG link failure has been met, and based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

[0576] The instructions 1406 may be comprised in a computer program, a non-transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the instructions 1406 may be distributed over more than one computer program.

[0577] Although the memory 1404 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable and / or may provide permanent / semi-permanent / dynamic / cached storage.

[0578] Although the processor 1402 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable. The processor 1402 may be a single core or multi-core processor.

[0579] References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry including quantum processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.As used in this application, the term ‘circuitry’ may refer to one or more or all the following: (a) hardware-only circuitry implementations (such as implementations in analog, digital and / or quantum circuitry) and

[0580] (b) combinations of hardware circuit(s) and software, such as (as applicable):

[0581] i. a combination of analog, digital and / or quantum hardware circuit(s) with software / firmware and

[0582] ii. any or all portions of hardware processor(s) (including digital and / or quantum processor(s)) with software, and memory(ies) that work together to cause an apparatus, such as a mobile device, computing device or server, to perform various functions and

[0583] (c) any or all portions of hardware circuit(s), such as a microprocessor(s) and / or quantum processors , that requires software (for example, firmware) for operation, but the software may not be present when it is not needed for operation.

[0584] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0585] The blocks illustrated in the accompanying Figs may represent steps in a method and / or sections of code in the instructions 1406. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

[0586] As used here ‘module’ refers to a unit or apparatus that excludes certain parts / components that would be added by an end manufacturer or a user. The apparatus 1410 can, for example be a module. A controller 1400 of the apparatus 1410 can, for example be a module.

[0587] Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.The above-described examples find application as enabling components of:

[0588] automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and / or augmented reality; personal systems including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things; virtualized networks; and related software and services.

[0589] The apparatus can be provided in an electronic device, for example, a mobile terminal, according to an example of the present disclosure. It should be understood, however, that a mobile terminal is merely illustrative of an electronic device that would benefit from examples of implementations of the present disclosure and, therefore, should not be taken to limit the scope of the present disclosure to the same. While in certain implementation examples, the apparatus can be provided in a mobile terminal, other types of electronic devices, such as, but not limited to: mobile communication devices, hand portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of electronic systems, can readily employ examples of the present disclosure. Furthermore, devices can readily employ examples of the present disclosure regardless of their intent to provide mobility.

[0590] The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to ‘comprising only one...’ or by using ‘consisting.’

[0591] In this description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e. , to provide direct or indirect connection / coupling / communication. Any such intervening components can include hardware and / or software components.

[0592] As used herein, the term "determine / determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database, or another datastructure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also, " determine / determining" can include resolving, selecting, choosing, establishing, and the like.

[0593] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’, or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

[0594] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0595] Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

[0596] Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

[0597] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0598] The description of a feature, such as an apparatus or a component of an apparatus, configured to perform a function, or for performing a function, should additionally be considered to also disclose a method of performing that function. For example, description of an apparatus configured to perform one or more actions, or for performing one or more actions, shouldadditionally be considered to disclose a method of performing those one or more actions with or without the apparatus.

[0599] Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

[0600] The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

[0601] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

[0602] In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

[0603] As used herein, the terms “the at least one” and “the one or more” mean “any one of the at least one” and “any one of the one or mor” respectively.

[0604] The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provideequivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

[0605] Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon.

Claims

1. 54CLAIMS1. A user equipment, UE, comprising:at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform:determining whether a condition for master cell group, MCG, link failure has been met;determining whether a cell switch command, CSC, for a secondary cell group, SCG, has been received from a network node;in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery;determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer;in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer:performing fast MCG link recovery based at least on the received reconfiguration information; andin dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC; andin dependence upon a determination that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer, performing LTM at the SCG based at least on the CSC.

2. A UE as claimed in claim 1 wherein the instructions, when executed by the at least one processor, further cause the UE to perform, in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer, stopping the timer.

3. A UE as claimed in any preceding claim, wherein the instructions, when executed by the at least one processor, further cause the UE to perform determining whether reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer; andin dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received after expiry of the timer, performing fast MCG link recovery based at least on the received configuration information.

554. A UE as claimed in any preceding claim, wherein the instructions, when executed by the at least one processor, further cause the UE to perform:receiving, from a network node, configuration information associated with conditional LTM, CLTM, at the SCG;initiating, based on the received configuration information, evaluation of one or more CLTM conditions for the SCG;receiving, from the network node, an indicator associated with fast MCG link recovery; andin dependence upon a determination that a condition for MCG link failure has been met, based on the indicator associated with fast MCG link recovery, preventing CLTM at the SCG.

5. A UE as claimed in any preceding claim, wherein preventing CLTM at the SCG comprises stopping evaluation of the one or more CLTM conditions for the SCG.

6. A UE as claimed in any of claims 1 - 4, wherein the instructions, when executed by the at least one processor, further cause the UE to perform determining whether a CLTM condition for the SCG has been met, wherein preventing CLTM at the SCG comprises, in dependence upon a determination that a condition for CLTM at the SCG has been met, stopping execution of CLTM at the SCG.

7. A UE as claimed in any preceding claim, wherein the instructions, when executed by the at least one processor, further cause the UE to perform, in dependence upon the determination that a condition for MCG link failure has been met, starting a second timer associated with fast MCG recovery.

8. A UE as claimed in any preceding claim, wherein the instructions, when executed by the at least one processor, further cause the UE to perform, in dependence upon the determination that a condition for MCG link failure has been met, suspending data transmission on all MCG data bearers.

9. A UE as claimed in any preceding claim, wherein the instructions, when executed by the at least one processor, further cause the UE to perform: determining whether fast MCG recovery has been completed; andin dependence upon a determination that fast MCG recovery has been completed, enabling CLTM at the SCG.5610. A UE as claimed in any preceding claim, wherein the instructions, when executed by the at least one processor, further cause the UE to perform determining whether fast MCG recovery has been completed comprises determining at least one of:whether the timer associated with fast MCG recovery has been stopped;whether data transmission on MCG data bearers has been resumed; orwhether an indication to resume CLTM has been received from a network node.

11. A UE as claimed in any of claims 5 - 10 wherein enabling CLTM at the SCG comprises resuming evaluation of the one or more CLTM conditions for the SCG.

12. A UE as claimed in any of claims 6 - 10 wherein enabling CLTM at the SCG comprises resuming execution of CLTM at the SCG.

13. A method comprising:determining whether a condition for master cell group, MCG, link failure has been met; determining whether a cell switch command, CSC, for a secondary cell group, SCG, has been received from a network node;in dependence upon a determination that a condition for MCG link failure has been met and that a CSC for the SCG has been received from the network node, starting a timer associated with fast MCG link recovery;determining whether reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer;in dependence upon a determination that reconfiguration information associated with fast MCG link recovery has been received before expiry of the timer:performing fast MCG link recovery based at least on the received reconfiguration information; andin dependence upon performance of the fast MCG link recovery, performing LTM at the SCG based at least on the CSC; andin dependence upon a determination that reconfiguration information associated with fast MCG link recovery has not been received before expiry of the timer, performing LTM at the SCG based at least on the CSC.

14. A network node comprising:at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the network node at least to perform:57transmitting, to a user equipment, UE, a cell switch command.

15. A method comprising:transmitting, to a user equipment, UE, a cell switch command.

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