Methods and apparatuses for performing layer 1 / layer 2 triggered mobility

Abstract

Embodiments described herein relate to methods and apparatuses for enabling a user equipment to determine whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell. A method performed by a user equipment comprises receiving at least an LTM candidate cell configuration for the target LTM candidate cell; obtaining a reset indication of whether an L2 reset procedure is to be performed for the first LTM cell switch procedure; obtaining an indication of an L2 reset group of the target LTM candidate cell; performing the first LTM cell switch procedure; and determining, based on the reset indication and the indication of the L2 reset group of the target LTM candidate cell, whether to perform an L2 reset.

Description

[0001] METHODS AND APPARATUSES FOR PERFORMING LAYER 1 / LAYER 2 TRIGGERED

[0002] MOBILITY

[0003] TECHNICAL FIELD

[0004] Embodiments described herein relate to methods and apparatuses for determining whether to perform a layer 2 (L2) reset for a first Layer 1 (L1) / L2 triggered mobility, LTM cell switch procedure from a source cell to a target LTM candidate cell.

[0005] BACKGROUND

[0006] L1 / L2 based inter-cell mobility in Rel-18

[0007] In 3GPP Release 18, a work item known as Further New Radio (NR) mobility enhancements is ongoing. This work item includes a technical area entitled Layer 1 / Layer 2 (L1 / L2) based inter-cell mobility. According to the Work Item Description, “when the UE moves from the coverage area of one cell to another cell, at some point a serving cell change needs to be performed. Currently serving cell change is triggered by L3 measurements and is done by RRC signaling triggered Reconfiguration with Synchronization for change of PCell and / or PSCell, as well as release add for SCells when applicable. All cases involve complete L2 (and L1) resets, leading to longer latency, larger overhead and longer interruption time compared to beam switch mobility (beam management procedures, TCI state activation). The goal of L1 / L2 based inter-cell mobility is to enable a serving cell change via L1 / L2 signaling, in order to reduce the latency, overhead and interruption time.”

[0008] In this work item, the following is included as one objective of the work:

[0009] 1. To specify mechanism and procedures of L1 / L2 based inter-cell mobility for mobility latency reduction: o Configuration and maintenance for multiple candidate cells to allow fast application of configurations for candidate cells [RAN2, RAN3] o Dynamic switch mechanism among candidate serving cells (including SpCell and SCell) for the potential applicable scenarios based on L1 / L2 signalling [RAN2, RAN1] o L1 enhancements for inter-cell beam management, including L1 measurement and reporting, and beam indication [RAN 1, RAN2]

[0010] Note 1: Early RAN2 involvement is necessary, including the possibility of further clarifying the interaction between this bullet with the previous bullet o Timing Advance management [RAN 1, RAN2] o CU-DU interface signaling to support L1 / L2 mobility, if needed [RAN 3] Note 2: FR2 specific enhancements are not precluded, if any.

[0011] Note 3: The procedure of L1 / L2 based inter-cell mobility are applicable to the following scenarios:

[0012] □ Standalone, CA and NR-DC case with serving cell change within one CG

[0013] □ Intra-DU case and intra-CU inter-DU case (applicable for Standalone and CA: no new RAN interfaces are expected)

[0014] □ Both intra-frequency and inter-frequency

[0015] □ Both FR1 and FR2

[0016] □ Source and target cells may be synchronized or non-synchronized

[0017] In 3GPP, discussions have started regarding solutions for L1 / L2 based inter-cell mobility (sometimes also referred to as LTM, L1 / L2-triggered mobility or lower layer-triggered mobility). A basic principle with L1 / L2-triggered mobility is that a user equipment (UE) may be preconfigured, by the network, with an RRC configuration per LTM candidate cell, sometimes also known as a LTM candidate cell configuration. Such a LTM candidate cell configuration may be comprised in an RRCReconfiguration message or one or more information elements (IEs) / fields / parameters such as CellGroupConfig. The UE may perform measurements on these LTM candidate cells and may transmit corresponding measurement reports to the network. The network then triggers the execution of a LTM cell switch procedure in the UE to one of these LTM candidate cells by transmitting lower layer signaling in a MAC CE, sometimes also referred to as an LTM cell switch command, to the UE, which then connects to the particular LTM candidate cell and switches to the LTM candidate cell configuration.

[0018] The interactions between UE, CU, S-DU and C-DU may be summarized as in the latest version of the running CR for TS 38.401 a section quoted from R3-23349 is provided below for reference.

[0019] Inter-qNB-DU LTM

[0020] This procedure is used for the case when the UE moves from one gNB-DU to another gNB- DU within the same gNB-CU during NR operation for LTM. Figure 1 illustrates the inter-gNB- DU LTM procedure for intra-NR.

[0021] Figure 1: inter gNB-DU LTM

[0022] 1. The UE sends a MeasurementReport message (L3 measurement result FFS) to the source gNB-DU containing measurements of neighboring cells. The source gNB-DU sends an UL RRC MESSAGE TRANSFER message conveying the received MeasurementReport message to the gNB-CU.

[0023] 2. The gNB-CU determines to initiate LTM configuration.

[0024] 3. The gNB-CU sends a UE CONTEXT SETUP REQUEST message to the candidate gNB-DU, containing one target candidate cell ID.

[0025] 4. If the candidate gNB-DU accepts the request of LTM configuration, it responds to the gNB-CU with a UE CONTEXT SETUP RESPONSE message including the generated lower layer RRC configuration for the accepted target candidate cell.

[0026] 5. The gNB-CU sends a DL RRC MESSAGE TRANSFER message to the source gNB- DU, which includes the generated RRCReconfiguration message with the LTM configuration.

[0027] FFS: whether it is DL RRC MESSAGE TRANSFER message or UE CONTEXT MODIFICATION REQUEST message.

[0028] 6. The source gNB-DU forwards the received RRCReconfiguration message to the UE.

[0029] 7. The UE responds to the source gNB-DU with an RRCReconfigurationComplete message."

[0030] 8. The source gNB-DU forwards the RRCReconfigurationComplete message to the gNB- CU via an UL RRC MESSAGE TRANSFER message.

[0031] FFS: whether it is UL RRC MESSAGE TRANSFER message or UE CONTEXT MODIFICATION RESPONSE message.

[0032] 9. The UE sends the lower layer measurement result to the source gNB-DU.

[0033] 10. The source gNB-DU decides to execute LTM to a candidate target cell.

[0034] FFS: Notifying the LTM triggering decision to the other nodes as well.

[0035] 11. The source gNB-DU sends LTM command to the UE.

[0036] Editor’s note: The LTM command needs to be updated according to RAN2’s discussion.

[0037] 12. W : The source gNB-DU sends the LTM CELL CHANGE NOTIFICATION message to the gNB-CU to indicate the initiation of the LTM command to the UE including the target cell ID.

[0038] 13. FFS: how the target gNB-DU detects the UE access. 14. The target gNB-DU sends the ACCESS SUCCESS message to the gNB-CU with the target cell ID.

[0039] 15. The gNB-CU may send the UE CONTEXT RELEASE COMMAND message to the source gNB-DU to release the resources of prepared cells.

[0040] 16. The source gNB-DU responds with a UE CONTEXT RELEASE COMPLETE message."

[0041] SUMMARY

[0042] There currently exist certain challenge(s).

[0043] During an LTM cell switch procedure, 3GPP RAN2 has agreed that whether the UE performs partial or full MAC reset (a partial reset may be, e.g. to avoid data loss), re-establishes RLC, or performs data recovery with Packet Data Convergence Protocol (PDCP), is explicitly controlled by the network and configured by RRC. When the UE performs an inter-DU LTM cell switch (that is, an LTM cell switch between a source cell and a target cell controlled by different distributed units, DUs), there is a need to perform L2 reset, but not necessarily for the intra-DU case. Thus, whether an L2 reset is needed or not depends on the source cell that the UE is leaving and the target cell to which the UE is entering.

[0044] Since performing an L2 reset during LTM cell switch (e.g. for intra-DU) results in more data loss it may be desirable to avoid L2 reset when it is not necessary, at least for those services that are sensitive to losses or delays, such as time-critical communication or real-time video streaming. Also, L2 reset may need to be performed by the UE for the inter-DU LTM cell switches. If this is not performed the protocol entities in the UE and network may become out of sync and that may cause more data lass and / or delays than if the L2 reset was performed.

[0045] Further, RAN2 has agreed to support subsequent LTM cell switch procedures between LTM candidates without the need for an RRC reconfiguration in between each LTM cell switch procedure. In other words, looking at the network architecture illustrated in Figure 2, when the UE is in a cell A and receives an LTM configuration with LTM candidate cells B, C (from a first C-DU) and LTM candidate cells D, E, F (from a second DU), the UE should be able to perform an LTM cell switch from A to one of these LTM candidate cells, and further LTM cell switch from that LTM candidate cells to one of the other LTM candidate cells.

[0046] In some examples, when the UE performs an LTM cell switch from a source cell A to an LTM candidate cell B (with both A and B) from the same DU, L2 reset may not be required. However, after a sub-sequent LTM, when an LTM cell switch is from a cell D to the LTM candidate cell B (with D being from a different DU than A and B), L2 reset may be required. Thus, it is may not be sufficient to configure the indication of a L2 reset (or the absence of a L2 reset) in the candidate cell configuration, as the need to perform L2 reset or not depends on the LTM candidate cell, but also the source cell.

[0047] In the RAN2#121 meeting, the following agreement has been taken about the L2 reset during an LTM cell switch procedure:

[0048] => To determine if to reset L2 or not is based on RRC configuration (e.g. set of cells. FFS if separate for RLC, MAC, PDCP).

[0049] One solution may be to provide the UE (by the network) with sets of cells (or groups) for which a L2 reset (or not) is needed when doing an LTM cell switch between cells that are part of the same set. Since whether a L2 reset is needed or not is determined by the source cell that the UE is leaving and by the target cell to which the UE is entering, this also means that the L2 reset for a given cell may be very much dependent on the source cell that has triggered the LTM cell switch procedure. Assuming the previous example with cells A, B, C from a first DU, and cells D, E, F from the second DU, a first group the UE is configured with for no L2 reset could contains cells (A, B, C) and a second group could contains (D, E, F) as, as long as the UE performs LTM cell switches within the same group or set, there would be no need to perform a L2 reset.

[0050] However, the way in which the cells are referred at the UE is by assigning an LTM candidate identifier (denoted in the latest running CR with the field ltm-Candidateld-r18 of IE LTM- Candidateld-r18).ln some scenarios, the source cell (e.g. cell A in this example) may not be configured as an LTM candidate cell and, consequently, that cell would not have an LTM candidate identifier assigned to it.

[0051] Thus, the problem that embodiments described herein address is the fact that in some scenarios the source cell in which the UE receives the LTM command, may not be configured as a LTM candidate, and therefore not included in the list of groups of cells indicating whether L2 reset is needed or not. In these cases, the UE may not be able to determine whether a L2 reset is needed or not. One scenario where this occurs is when the UE is first configured with LTM, where the current serving cell may not be configured as an LTM candidate cell for subsequent LTM. In other words, that first cell is a source cell for LTM, but may not be an LTM candidate cell for LTM. Another scenario is where the network uses legacy L3 handover (i.e. RRCReconfiguration) to move the UE to a serving cell, for which the UE does not have a LTM candidate configuration.

[0052] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges.

[0053] In order to address the above challenges, the embodiments described herein present methods and apparatuses for a User Equipment (UE), in order to determine whether a L2 reset is needed when executing a first LTM cell switch procedure. The first LTM cell switch procedure may be from a source cell, for which the UE does not have an LTM candidate cell configuration, towards a target LTM candidate cell. It will be appreciated that throughout this disclosure the first LTM cell switch procedure need not necessarily be an initial LTM cell switch procedure, and that the first LTM cell switch procedure may comprise any suitable LTM cell switch procedure from a source cell for which the UE does not have an LTM candidate cell configuration.

[0054] The method may comprise the UE receiving at least a LTM configuration which includes at least an LTM candidate cell configuration and an indication indicating whether a L2 reset is needed or not during an execution of a first LTM cell switch procedure (i.e. from the cell in which LTM has been configured or re-configured), and further receiving an LTM cell switch command and performing an LTM cell switch and based on the obtained indication determining whether to perform L2 reset or not during the first LTM cell switch procedure.

[0055] The method also comprises the UE in a first serving cell (e.g. a first source PCell) being configured with one or more LTM candidate cell(s), wherein the first serving cell is not configured as one of the LTM candidate cells, wherein the UE receives an indication of whether L2 reset is to be performed or not when the UE performs the LTM cell switch from the first serving cell to one of the LTM candidate cells. The first serving cell may be a cell in which the UE transitions to a CONNECTED state (e.g. RRC CONNECTED) or a cell the UE moves to in a reconfiguration with sync (L3 handover).

[0056] In one option, the UE receives an indication of which group the first serving cell belongs to (e.g. when the first serving cell is not an LTM candidate cell), wherein the UE is configured with one or more groups of LTM candidate cells, wherein a group indicates that i) the UE shall not perform a L2 reset when performing LTM cell switch between cells of the same group; and that ii) the UE shall perform a L2 reset when performing LTM cell switch between cells of different groups. For example, if the UE is in cell A and is configured with LTM candidates cells B, C; and D, E, F, the UE is indicated that (B, C) form a first group and (D, E, F) forms a second group, and, as cell A is not an LTM candidate, the UE is also indicated that A belong to the first group together with cells B and C, so that when the UE performs an LTM cell switch from A to B (or C), the UE does not perform a L2 reset; or when the UE performs an LTM cell switch from A to D (or E, or F), the UE performs a L2 reset. Below different alternatives are described illustrating how to indicate to the UE which group the first cell belongs to.

[0057] The invention also present methods for a third network node (or serving network node), such as a (serving) Central Unit (CU), (serving) gNB-CU, comprising transmitting to a source network node information to be transmitted to the UE indicating to the UE whether a L2 reset is to be performed or not upon an LTM cell switch procedure.

[0058] The invention also present methods for a source network node, such as a source gNB, a source Distributed Unit, DU, or serving network node such as a serving DU), for a UE to determine whether a L2 reset is needed when executing the first LTM cell switch procedure, comprising receiving information from a third network node to be transmitted to the UE indicating to the UE whether a L2 reset is needed upon an LTM cell switch procedure, transmitting to the UE at least an LTM configuration which include at least an LTM candidate cell configuration and an indication to the UE whether a L2 reset is to be performed or not during the execution of a LTM cell switch procedure, and further transmitting an LTM cell switch command to the UE in order to trigger the execution of an LTM cell switch procedure.

[0059] The method also comprises the third network node being associated to a first serving cell the UE is connected to (denoted e.g. first source PCell), wherein the third network node configures the UE with one or more LTM candidate cell(s), wherein the first serving cell is not configured as one of the LTM candidate cells, wherein the UE receives an indication of whether L2 reset is to be performed or not when the UE performs the LTM cell switch from the first serving cell to one of the LTM candidate cells. In one option, the third network node indicates to the UE a group in which the first serving cell belongs to (e.g. when the first serving cell is not an LTM candidate cell), wherein the UE is configured with one or more groups of LTM candidate cells, wherein a group indicates that i) the UE shall not perform a L2 reset when performing LTM cell switch between cells of the same group; and that ii) the UE shall perform a L2 reset when performing LTM cell switch between cells of different groups.

[0060] The invention also presents methods for a target network node, such as a target DU (or target gNB-Dll), to determine whether a L2 reset is needed when executing an LTM cell switch procedure for a UE to one or more LTM candidate cells belonging to that target network node, comprising receiving a request for configuration for one or more LTM candidate cell(s), e.g. from a serving third network node, and transmitting to the third network node information about between which cells (including at least one LTM candidate cell belonging to that target network node) the UE shall perform (or not perform) a L2 reset upon an LTM cell switch.

[0061] According to some embodiments there is provided a method, performed by a user equipment, for determining whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell. The method comprises receiving at least an LTM candidate cell configuration for the target LTM candidate cell; obtaining a reset indication of whether an L2 reset procedure is to be performed for the first LTM cell switch procedure; obtaining an indication of an L2 reset group of the target LTM candidate cell; performing the first LTM cell switch procedure; and determining, based on the reset indication and the indication of the L2 reset group of the target LTM candidate cell, whether to perform an L2 reset.

[0062] According to some embodiments there is provided a user equipment adapted to perform the method above.

[0063] According to some embodiments there is provided method in a source network node for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell. The method comprises transmitting, to the UE, at least an LTM candidate cell configuration for the target LTM candidate cell comprising an indication of an L2 reset group of the target LTM candidate cell; and transmitting, to the UE, a reset indication of whether a L2 reset is to be performed for the first LTM cell switch procedure.

[0064] According to some embodiments there is provided a source network node adapted to perform the method described above.

[0065] According to some embodiments there is provided a method, performed by a target network node, for enabling a UE to determine whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell to a target candidate LTM cell belonging to the target network node. The method comprises transmitting to a third network node an indication of a L2 reset group to which the target LTM candidate cell belongs. According to some embodiments there is provided a target network node adapted to perform the method described above.

[0066] According to some embodiments there is provided a user equipment for determining whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell. The user equipment comprises processing circuitry and memory, the memory containing instructions executable by the processing circuitry whereby the user equipment is operable to: receive at least an LTM candidate cell configuration for the target LTM candidate cell; obtain a reset indication of whether an L2 reset procedure is to be performed for the first LTM cell switch procedure; obtain an indication of an L2 reset group of the target LTM candidate cell; perform the first LTM cell switch procedure; and determine, based on the reset indication and the indication of the L2 reset group of the target LTM candidate cell, whether to perform an L2 reset.

[0067] According to some embodiments there is provided a source network node for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell. The source network node comprises processing circuitry and memory, the memory containing instructions executable by the processing circuitry whereby the source network node is operable to: transmit, to the UE, at least an LTM candidate cell configuration for the target LTM candidate cell comprising an indication of an L2 reset group of the target LTM candidate cell; and transmit, to the UE, a reset indication of whether a L2 reset is to be performed for the first LTM cell switch procedure.

[0068] According to some embodiments there is provided a target network node for enabling a UE to determine whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell to a target candidate LTM cell belonging to the target network node. The target network node comprises processing circuitry and memory, the memory containing instructions executable by the processing circuitry whereby the target network node is operable to: transmit to a third network node an indication of a L2 reset group to which the target LTM candidate cell belongs.

[0069] According to some embodiments there is provided a computer program, comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out any of the methods described above. According to some embodiments there is provided a carrier containing the computer program as described above, wherein the carrier comprises one of an electronic signal, optical signal, radio signal or computer readable storage medium.

[0070] According to some embodiments there is provided a computer-readable medium comprising instructions that, when executed on at least one processor, cause the at least one processor to perform any of the methods described above.

[0071] According to some embodiments there is provided a computer program product comprising non transitory computer readable media having stored thereon a computer program as described above.

[0072] Certain embodiments may provide one or more of the following technical advantage(s).

[0073] The embodiments described herein enable the network to control the UE L2 reset during an LTM cell switch procedure, but more importantly enable the UE to determine whether a L2 reset is needed when performing a LTM cell switch procedure from a source cell, that is not an LTM candidate cell itself, to a target network node (which is an LTM candidate cell).

[0074] BRIEF DESCRIPTION OF THE DRAWINGS

[0075] For a better understanding of the embodiments of the present disclosure, and to show how it may be put into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0076] Fig. 1 illustrates inter gNB-DU LTM

[0077] Fig. 2 illustrates grouping of cells;

[0078] Fig. 3 Illustrates an example of the overall architecture (with both NG-RAN and 5GC), with NG-RAN split in CU and DU connected via F1 interface;

[0079] Fig. 4 is a flow chart illustrating a method in accordance with some embodiments;

[0080] Fig. 5 is a flow chart illustrating a method in accordance with some embodiments;

[0081] Fig. 6 is a flow chart illustrating a method in accordance with some embodiments;

[0082] Fig. 7 is a flow chart illustrating a method in accordance with some embodiments;

[0083] Fig. 8 is a flow chart illustrating a method in accordance with some embodiments;

[0084] Fig. 9 is a flow chart illustrating a method in accordance with some embodiments;

[0085] Fig. 10 shows an example of a communication system in accordance with some embodiments;

[0086] Fig. 11 shows a UE in accordance with some embodiments; Fig. 12 shows a network node in accordance with some embodiments;

[0087] Fig. 13 is a block diagram illustrating a virtualization environment in which functions implemented by some embodiments may be virtualized.

[0088] DETAILED DESCRIPTION

[0089] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0090] Figure 3 illustrates an example of an overall architecture for implementing embodiments described herein. In this example, the overall architecture (with both NG-RAN and 5GC), with NG-RAN split in CU and DU connected via F1 interface. The architecture comprises a central unit (CU) and a distributed unit (DU) in a Radio Access Network (RAN). Embodiments described herein may use the following example: a Radio Access Network (RAN) corresponding to a Next-Generation RAN (NG-RAN), which may be referred as the 5G RAN. However, the embodiments described herein may be applicable to any RAN such as a Sixth Generation (6G) RAN architecture, which may follow a similar split or a different functional split.

[0091] The RAN (e.g. NG-RAN) comprises of a set of RAN nodes (e.g. gNBs, 6G gNodeBs) connected to a Core Network (e.g. a 5GC, 6G Core Network) through a RAN / CN interface (e.g. NG interface, S1 interface, 6G NG 1). In the case of NG-RAN, that may comprise one or more ng-eNBs, wherein an ng-eNB may consist of an ng-eNB-CU and one or more ng-eNB- DU(s). A gNB may consist of a gNB-CU and one or more gNB-DU(s). A gNB-CU and a gNB- DU is connected via F1 interface. A gNB-DU may be connected to multiple gNB-CUs by appropriate implementation.

[0092] NG, Xn and F1 are logical interfaces. And, in case of the NG-RAN, the NG and Xn-C interfaces for a gNB consisting of a gNB-CU and gNB-DUs, terminate in the gNB-CU. For EN-DC, the S1-U and X2-C interfaces for a gNB consisting of a gNB-CU and gNB-DUs, terminate in the gNB-CU. The gNB-CU and connected gNB-DUs are only visible to other gNBs and the 5GC as a gNB. A possible deployment scenario is shown below. The Protocol terminations of the NG and Xn interfaces are depicted as ellipses and, the terms "Central Entity" and "Distributed Entity" shown below refer to physical network nodes. Thus, when the method refers to the CU the method comprises the action(s) being performed by any entities comprised within the CU e.g. CU-CP, gNB-CU-CP.

[0093] In some cases, there may be an interface directly between different gNB-DUs. Signalling that is sent from one gNB-Dll to another gNB-Dll, e.g. from / to a source gNB-Dll to / from a target gNB-Dll, can then be sent directly between the gNB-DUs without going via the gNB-CU. In cases throughout this invention where it is written that there is signalling from one DU (e.g. a gNB-DU) to another DU (e.g. a gNB-DU) via the CU (e.g. a gNB-CU) it covers also the case where the signalling goes directly from one DU (e.g. a gNB-DU) to the other DU (e.g. a gNB- DU).

[0094] The text refers to the term “L1 / L2 based inter-cell mobility” as used in the Work Item Description in 3GPP, though it interchangeably also uses the terms L1 / L2 mobility, L1 -mobility, L1 based mobility, L1 / L2-centric inter-cell mobility, L1 / L2 inter-cell mobility L1 / L2-Triggered Mobility, Lower-layer triggered Mobility or LTM. The basic principle is that the UE receives a lower layer signaling from the network indicating to the UE a change (or switch or activation) of its serving cell (e.g. change of PCell, from a source to a target PCell), wherein a lower layer signaling is a message / signaling of a lower layer protocol, which may be referred as a L1 / L2 inter-cell mobility execution command or LTM cell switch command. The change of serving cell (e.g. change of PCell) may also lead to a change in Scell(s) for the same cell group e.g. in case the command triggers the UE to change to another cell group configuration of the same type (e.g. another MCG configuration). Before the UE receives the LTM cell switch command, the UE is configured by the network with one or more LTM candidate cell configurations (e.g. reception of an RRC Reconfiguration message, with at least one LTM candidate cell configuration) A LTM candidate cell configuration may include parameters in the IE CellGroupConfig for an LTM candidate cell and / or an embedded RRC Reconfiguration for an LTM candidate cell.

[0095] The term LTM cell switch procedure refers to the process of a UE switching (or changing) its cell from a source cell to a target cell (which may be called here an LTM candidate cell or a neighbour cell), using L1 / L2-triggered mobility (LTM). In the context of L1 / L2-triggered mobility (LTM), an LTM cell switch procedure may sometimes also be known as L1 / L2 based inter-cell mobility execution, LTM execution, dynamic switch, LTM switch, (LTM) cell switch, (LTM) serving cell change or (LTM) cell change. In the context of embodiments described herein, switching to the LTM candidate cell configuration comprises the UE considering that an LTM candidate cell becomes its new special cell (SpCell) e.g. PCell in case of LTM being configured for a Master Cell Group (MCG) and / or PSCell in case of LTM being configured for a Secondary Cell Group (SCG); or, changing its SpCell from the current PCell to an LTM candidate cell.

[0096] Even if the term switch or change of cells is used, that may comprise a switch or change of a whole cell group configuration, which includes a change in the SpCell (e.g. change of PCell, or change of PSCell), a change in SCells of the cell group (e.g., addition, modification and / or release of one or more SCells) or a swap between SpCell and SCell roles for two cells (e.g. as result of the switch or change, a first cell which was SpCell becomes an SCell and a second cell that was an SCell becomes the new SpCell).

[0097] The text refers to a LTM candidate cell, which is a cell the UE is configured with when configured with L1 / L2-triggered mobility. That is a cell the UE can move to in a LTM cell switch procedure, upon reception of a LTM cell switch command. Such cells may also be called candidate cell(s), candidates, mobility candidates, non-serving cells, additional cells, target candidate cell, target candidate, etc. A LTM candidate cell is a cell the UE may perform measurements on (e.g., CSI measurements) so that the UE reports these measurements and network may take educated decision on which beam (e.g. TCI state) and / or cell the UE is to be switched to. An LTM candidate cell may be a candidate to be a target PCell or PSCell, or an SCell of a cell group (e.g., MCG SCell or a SCG SCell).

[0098] The text refers to at least one LTM candidate cell configuration and that the UE has received at least one LTM candidate cell configuration. This is also sometimes referred to as a configuration of a LTM candidate cell, which may be an RRC configuration, such as encapsulated in an RRC Reconfiguration message, that the UE receives when being configured with L1 / L2-Triggered Mobility. A LTM candidate cell configuration comprises the configuration which the UE needs to start to operate accordingly when it performs an LTM cell switch procedure to that LTM candidate cell e.g., upon reception of the LTM cell switch command to that LTM candidate cell, which becomes the target cell and the current (new) SpCell, or an SCell in a serving frequency. The LTM candidate cell configuration comprises parameters of a serving cell (or multiple serving cells, such as a cell group), comprising one or more of the groups of parameters, such as an RRCReconfiguration message an IE CellGroupConfig or an IE SpCellConfig (or the IE SCellConfig, in the case of a Secondary Cell). A LTM candidate cell configuration may in one example comprise one or more of: i) the PCell configuration and one or more SCell configuration(s) of a Master Cell Group (MCG); i) the PSCell configuration and one or more SCell configuration(s) of a secondary Cell Group (SCG). The terms (LTM) candidate configuration, LTM configuration, (LTM) candidate target cell configuration, (LTM) target candidate (cell) configuration may be used interchangeably when referring to LTM candidate cell configuration.

[0099] The actual LTM candidate cell configuration and its exact content and / or structure of this IE and / or embedded message may be called an RRC model for the candidate configuration, or simply RRC model. An LTM candidate cell configuration comprises the configuration which the UE needs to operate accordingly when it performs (executes) L1 / L2 based inter-cell mobility execution to a LTM candidate cell, upon reception of the lower layer signaling (MAC CE) indicating a L1 / L2 based inter-cell mobility to a LTM candidate cell (which becomes the target cell and the current (new) PCell, or an SCell in a serving frequency), or upon reception of the lower layer signaling (MAC CE) indicating a L1 / L2 based inter-cell mobility to a LTM candidate cell configuration indicated with a candidate configuration identifier, identity or index (sometimes also denoted candidate configuration ID). The UE may be configured with multiple LTM candidate cell configurations, so a Candidate DU (C-DU) generates and sends to the CU multiple configuration(s). The actual LTM candidate cell configuration the UE receives during the LTM configuration may be a delta signaling to be applied on top of a reference configuration, so that the actual configuration the UE is to use in the LTM candidate cell upon LTM cell switch is the combination of the LTM candidate cell configuration and the reference configuration (e.g. separately signaled by the network to the UE). That combination of the LTM candidate cell configuration and the reference configuration the UE uses may also be called a complete LTM candidate cell configuration. For the context of the invention, unless stated otherwise, this complete LTM candidate cell configuration may also be considered as an LTM candidate cell configuration.

[0100] The text refers to serving cell. A serving cell is a cell configured for the UE for example an SpCell, PCell, PSCell or SCell.

[0101] The text refers to source cell and target cell. A source cell is a cell configured as a serving cell for the UE prior to the execution of the LTM cell switch procedure. A target cell is a cell configured as a serving cell, for example an SpCell, PCell, PSCell or SCell, for the UE after, or as a result of, the execution of the LTM cell switch procedure, which may include a cell indicated in the LTM cell switch command indicating to the UE the LTM cell switch procedure or a cell configured as result of the UE switching to the LTM candidate cell configuration provided by an indication of an LTM candidate cell configuration, also sometimes known as a candidate configuration index, an LTM configuration index or an LTM candidate cell index, in the LTM cell switch command .In the context of a LTM cell switch procedure executed by the UE, given cell may be either a source cell, a target cell, both a source cell and target cell or neither a source cell nor a target cell.

[0102] The text refers to source configuration, which may be the UE configuration when receiving the LTM cell switch command indicating to the UE the LTM cell switch procedure.

[0103] The text refers to “first serving cell”, sometimes also referred to as first PCell, first SpCell, first PSCell, first SCell, first cell group, first, MCG, first SCG. The first serving cell is a cell which is configured as a serving cell for the UE (e.g. as an SpCell, PCell, PSCell or a SCell) and in context of LTM cell switch it is a source cell from which the UE performs a first LTM cell switch procedure. The first serving cell may be a cell for which the UE does not have a LTM candidate configuration. In the context of a first LTM cell switch procedure the first serving cell may be the source cell.

[0104] The text refers to a “source cell for which the UE does not have an LTM candidate cell configuration”. This includes that the current serving SpCell (such as the PCell or PSCell), and being a source cell in the context of mobility, is not included as an SpCell in one of the LTM candidate configurations the UE has received and stored and has not yet deleted.

[0105] The text refers to L2 reset. An L2 reset may include one or more of the actions MAC reset, partial MAC reset, HARQ reset, RLC re-establishment, PDCP data recovery or PDCP reestablishment as also described in 3GPP specifications TS 38.321 v 17.4.0, 38.322 v 17.2.0 and 38.323 v 17.4.0.

[0106] The text also refer to a “L2 reset group” to which the serving cell and one or more LTM candidate cell may belong to. In this case, a “L2 reset group” is a group of cells from which a L2 reset may be needed (or not). This basically means that if the source cell and the target cell involved in a LTM cell switch procedure are within the same “L2 reset group”, then the UE will understand that it should do (or not do) a L2 reset.

[0107] Figure 4 illustrates a method in accordance with some embodiments. The method of Figure 4 may be performed by a UE or wireless device (e.g. the UE 1012 or UE 1100 as described later with reference to Figures 10 and 11 respectively). The method may be for determining whether to perform a layer 2, L2, reset for (e.g. when executing) a first layer 1 / layer 1 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell. In some examples, the source cell may be a cell for which the UE does not have an LTM candidate cell configuration. The method begins at step 402 with receiving at least an LTM candidate cell configuration for the target LTM candidate cell. In step 404 the method comprises obtaining a reset indication of whether an L2 reset procedure is to be performed for the first LTM cell switch procedure. In step 406 the method comprises performing the first LTM cell switch procedure. In step 408 the method comprises determining, based on the reset indication, whether to perform an L2 reset. In some examples, the method further comprises, responsive to determining to perform an L2 reset procedure, performing an L2 reset procedure.

[0108] In some examples, the method of Figure 4 further comprises obtaining an indication of an L2 reset group of the target LTM candidate cell (e.g. receiving an indication of at least one group (e.g. “L2 reset group”) of cells). Each L2 reset group is formed by LTM candidate cells or LTM candidate configuration IDs, indicating that a L2 reset is not needed for LTM execution within each group of cells. For example, the indication of at least one L2 reset group of LTM candidate cells may comprise a list of LTM candidate configuration identifications for the cells in the group. The step 408 may, in some examples, be based on the indication of the at least one group and the reset indication. For example, step 408 may comprise determining, based on the reset indication and the indication of the L2 reset group of the target LTM candidate cell, whether to perform an L2 reset.

[0109] In some examples the method of Figure 4 further comprises performing the first LTM cell switch procedure in response to receiving an LTM cell switch command. In some examples, step 404 comprises receiving the reset indication in the LTM cell switch command. In other words, the UE receives the indication of whether L2 reset is needed during the execution of LTM cell switch in the LTM cell switch command.

[0110] In some examples, step 404 comprises receiving the reset indication during execution of the first LTM cell switch procedure in an RRC reconfiguration message. In other words, the UE receives the indication of whether L2 reset is needed during the execution of LTM cell switch in an RRC reconfiguration message, including.

[0111] In some examples, Step 404 comprises receiving the reset indication in a first LTM configuration. In other words, the UE receives the indication of whether L2 reset is needed during the execution of LTM cell switch in the first LTM configuration. In some examples, step 404 comprises receiving the first LTM configuration before receiving the at least one LTM candidate cell configuration. This may be the case when the UE is already configured with a LTM candidate cell configuration and the network may decide to modify the indication on whether a L2 reset is needed or not. In such a case, there is no need to re-configure the entire LTM candidate cell configuration, but the UE may simply receive the updated indication with the new behavior (e.g., L2 reset or no L2 reset). In some examples, step 404 comprises receiving the first LTM configuration with the reset indication after receiving the at least one LTM candidate cell configuration. In other words, the UE receives the LTM configuration with the indication to determine whether a L2 reset is needed during the execution of a LTM cell switch procedure after receiving at least one LTM candidate cell configuration. In some examples, step 404 comprises receiving the first LTM configuration from the current serving cell to any LTM candidate cell, or the serving node to any LTM candidate cell. In other words, the UE receives the LTM configuration with the indication to determine whether a L2 reset is needed during the execution of a LTM cell switch procedure from the current serving cell to any LTM candidate cell.

[0112] In some examples, the method of Figure 4 further comprises receiving the at least one LTM candidate cell configuration in a second LTM configuration. In other words, the UE receives the LTM candidate cell configuration and the indication to determine whether a L2 reset is needed during the execution of a LTM cell switch procedure in separate LTM configuration.

[0113] The first LTM configuration may be received at the UE from a source network node (e.g. a DU) providing the source cell, or from a third network node (e.g. a CU) via the source network node.

[0114] In some examples, the reset indication of step 404 comprises an indication associating the source cell or a source network node providing the source cell with a first L2 reset group of LTM candidate cells. The reset indication may additionally or alternatively comprise the L2 group of the target LTM candidate cell. In this case, when the UE executes an LTM cell switch procedure towards one of the LTM candidate cells that belong to the same L2 reset group as the source cell (e.g. current serving cell) or the source network node it determines that L2 reset is not needed (or the vice versa that L2 reset is needed). In other words, the method of Figure 4 may further comprise response to the target LTM candidate cell belonging to the first L2 reset group of LTM candidate cells, determining not to perform an L2 reset and / or responsive to the target LTM candidate cell not belonging to the first L2 reset group of LTM candidate cells, determining to perform an L2 reset. For example, the step 408 may comprise responsive to the indication of the L2 reset group of the target LTM candidate cell indicating that the target LTM candidate cell belongs to the first L2 reset group of LTM candidate cells, determining not to perform an L2 reset. Step 408 may comprise responsive to the indication of the L2 reset group of the target LTM candidate cell indicating that the target LTM candidate cell does not belong to the first L2 reset group of LTM candidate cells, determining to perform an L2 reset.

[0115] In some examples, step 408 comprises, responsive to determining that the source cell, or the source network node serving the source cell does not belong to a L2 reset group, determining to perform an L2 reset or determining not to perform an L2 reset.

[0116] In some examples, step 408 comprises responsive to determining that the target LTM candidate cell belongs to a L2 reset group, determining to perform an L2 reset or determining not to perform an L2 reset.

[0117] In some examples, the method of Figure 4 further comprises using the indication of the L2 reset group in the target LTM candidate cell as an indication of a L2 reset group of a new serving cell (e.g. the previous target cell) after the execution of the first LTM cell switch procedure. In other words, the UE, when executing an LTM cell switch procedure, may use an indication of a L2 reset group in the LTM candidate configuration it switched to at the LTM cell switch procedure as the indication to which L2 reset group the target cell (new current serving cell) belongs to after the execution of the LTM cell switch.

[0118] In some examples, the method of Figure 4 further comprises using an indication of a L2 reset group the source cell belongs to determine the indication of a L2 reset group the target LTM candidate cell belongs to after the execution of the first LTM cell switch procedure. In other words, the UE, when executing an LTM cell switch procedure, may use the indication to which L2 reset group the current serving cell belongs to determine the indication to which L2 reset group the target cell (new current serving cell) belongs to after the execution of the LTM cell switch. In one example, the UE uses the indication of the L2 reset group for the new serving cell as the indication of the L2 reset group for the source cell.

[0119] In some examples, the method of Figure 4 further comprises further comprising setting the indication to of a L2 reset group the target LTM candidate cell belongs to after the performing the first LTM cell switch procedure. In other words, the method of Figure 4 may comprise setting the value of the reset indication to the value of the indication of the L2 reset group of the target LTM candidate cell after performing the first LTM cell switch procedure. In other words, the UE, when executing an LTM cell switch procedure, may set the indication to which L2 reset group the target cell (new current serving cell) belongs to after the execution of the LTM cell switch as it does not belong to any L2 reset group.

[0120] In some examples, the reset indication of step 404 comprises an indication of whether to perform L2 reset specifically for the first LTM cell switch procedure.

[0121] In some examples, the reset indication of step 404 comprises a list of candidate network nodes for which L2 reset is needed or not needed when an LTM cell switch procedure is executed towards on the candidate network nodes. In other words, the reset indication may comprise a list of (Candidate) network nodes for which L2 reset is needed (or not needed) for the LTM cell switch procedure.

[0122] In some examples, the reset indication comprises if the Source network node is also an LTM candidate cell, the LTM candidate cell configuration index that identify the Source network node. This may be needed as if the UE is configured with “X” LTM candidate cell configuration, it may not be able to distinguish which LTM candidate cell configuration correspond to the Source network node.

[0123] In some examples, the method of Figure 4 may comprise responsive to not obtaining a reset indication, either performing or not performing the L2 reset. It will be appreciated that whether or not L2 reset is performed in this scenario may be specified in a standard document.

[0124] Figure 5 depicts a method in accordance with particular embodiments. The method of Figure 5 may be performed by a UE or wireless device (e.g. the UE 1012 or UE 1100 as described later with reference to Figures 10 and 11 respectively). The method may be for executing a first layer 1 / layer 1 triggered mobility, LTM, cell switch procedure from a source cell (e.g. for which the UE does not have an LTM candidate cell configuration) towards a target LTM candidate cell. The method begins at step at step 502 with receiving at least an LTM candidate cell configuration for the target LTM candidate cell. In step 504 the method comprises performing the first LTM cell switch procedure; and in step 506 the method comprises performing or not performing an L2 reset. For example, a specification may state that the UE shall perform L2 reset when executing an LTM cell switch procedure from, a source cell for which the UE does not have an LTM candidate cell configuration or when there is no reset indication available. Or for example, a specification may state that the UE shall not perform L2 reset when executing an LTM cell switch procedure from, a source cell for which the UE does not have an LTM candidate cell configuration or when there is no reset indication available.

[0125] Figure 6 depicts a method in accordance with particular embodiments. The method of Figure 6 may be performed by a network node (e.g. the network node 1010 or network node 1200 as described later with reference to Figures 10 and 12 respectively). The source network node may comprise one of: a source gNB, a source DU, serving DU or a source CU. The method may be for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 1 triggered mobility, LTM, cell switch procedure from a source cell (e.g. for which the UE does not have an LTM candidate cell configuration) towards a target LTM candidate cell. The method begins at step 602 with transmitting, to the UE, at least an LTM candidate cell configuration for the target LTM candidate cell, for example, comprising an indication of an L2 reset group of the target LTM candidate cell. In step 604 the method comprises transmitting, to the UE, a reset indication of whether a L2 reset is to be performed for the first LTM cell switch procedure.

[0126] In some examples, the method further comprises transmitting an LTM cell switch command to the UE in order to trigger the execution of the first LTM cell switch procedure.

[0127] In some examples the method of Figure 6 comprises receiving from a third network node (e.g. a CU) a first LTM configuration comprising the reset indication. For example, the method may comprise receiving information from the third network node (CU) to be transmitted to the UE to determine whether a L2 reset is needed upon the LTM cell switch procedure.

[0128] Step 604 may comprise transmitting to the UE at least the first LTM configuration which may comprise at least an LTM candidate cell configuration and the reset indication.

[0129] In some examples, the method of Figure 6 comprises receiving from the third network node the first LTM configuration comprising the reset indication before receiving a request from the third network node to setup an LTM candidate cell configuration. In one example, this feature may occur when the third network node decides to configure LTM at the UE but the current Source network node of the UE is not one of the LTM candidate cell selected by the third network node.

[0130] In some examples, the method of Figure 6 comprises receiving the first LTM configuration in the same signaling that requests source network node to configure an LTM candidate cell configuration at the UE. In other words, the Source network node receives from the third network node the LTM configuration comprising the indication for the UE to determine whether a L2 reset is needed upon the LTM cell switch procedure in the same signaling that request the Source network node to configure an LTM candidate cell configuration at the UE.

[0131] In some examples, the method of Figure 6 comprises receiving the first LTM configuration responsive to transmitting a request for the first LTM configuration to the third network node. In other words, the Source network node may receive from the third network node the LTM configuration comprising the indication for the UE to determine whether a L2 reset is needed upon the LTM cell switch procedure upon an explicit request (i.e., from the Source network node to the third network node).

[0132] In some examples, signaling exchanges between the source network node and the third network node are performed over a F1AP interface. In other words, the signaling exchanges between the Source network node and the third network node may be done within a message over the F1AP interface.

[0133] Figure 7 depicts a method in accordance with particular embodiments. The method of Figure 7 may be performed by a third network node (e.g. the network node 1010 or network node 1200 as described later with reference to Figures 10 and 12 respectively). The third network node ay comprise one of: a (serving) Central Unit (CU), (serving) gNB-CU. The method may be for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 1 triggered mobility, LTM, cell switch procedure from a source cell, for which the UE does not have an LTM candidate cell configuration, towards a target LTM candidate cell. The method begins at step 702 with transmitting to a source network node a reset indication of whether a L2 reset is to be performed for the first LTM cell switch procedure.

[0134] In some examples, the step 702 may be worded as transmitting to a source network node LTM related information to be transmitted to the UE to determine whether a L2 reset is needed upon an LTM cell switch procedure.

[0135] In some examples, the method of Figure 7 further comprises transmitting to the source network node, a first LTM configuration comprising the reset indication before transmitting a request to the source network node to setup an LTM candidate cell configuration. In other words, the third network node may transmit to the Source network node the LTM configuration comprising the indication for the UE to determine whether a L2 reset is needed upon the LTM cell switch procedure before receiving a request from the third network node to setup an LTM candidate cell configuration. In one example, this would be the case when the third network node decides to configure LTM at the UE but the current Source network node of the UE is not one of the LTM candidate cell selected by the third network node. In one example, the LTM configuration is included in an RRCReconfiguration message to be transmitted to the UE.

[0136] In some examples, the first LTM configuration is comprised in a radio resource control, RRC, reconfiguration message to be transmitted to the UE.

[0137] In some examples, the method of Figure 7 further comprises transmitting the first TLM configuration in the same signaling that requests the source network node to configure an LTM candidate cell configuration at the UE. In other words, the third network node may transmit to the Source network node the LTM configuration comprising the indication for the UE to determine whether a L2 reset is needed upon the LTM cell switch procedure in the same signaling that request the Source network node to configure an LTM candidate cell configuration at the UE.

[0138] In some examples, the method of Figure 7 further comprises transmitting the first LTM configuration in response to explicit request received for the first LTM configuration from the source network node. In other words, the third network node may transmit to the Source network node the LTM configuration comprising the indication for the UE to determine whether a L2 reset is needed upon the LTM cell switch procedure upon an explicit request received from the Source network node.

[0139] In some examples the method of Figure 7 further comprises receiving, from a target network node, information relating to whether the UE shall perform an L2 reset procedure upon performing the first LTM cell switch procedure. For example, the third network node may receive, from a target network node, an indication of whether a L2 reset is needed upon cell switch to an LTM candidate cell. For example, the method 7 may comprise receiving the information from the target network node responsive to transmitting a request to the target network node to configure an LTM candidate cell. In other words, the indication may be a response to a request, transmitted to the target network node, to configure an LTM candidate cell. The indication may indicates a L2 reset group to which the LTM candidate cell belongs. The third network node may use the received indication to determine the information, transmitted to the source network node or to the UE, to determine whether a L2 reset is needed upon an LTM cell switch procedure.

[0140] Signaling exchanges between the Source network node and the third network node may be performed within a message over the F1AP interface.

[0141] Figure 8 depicts a method in accordance with particular embodiments. The method of Figure 8 may be performed by a target network node (e.g. the network node 1010 or network node 1200 as described later with reference to Figures 10 and 12 respectively). The target network node ay comprise one of: a target DU (or target gNB-DU). The method may be for enabling a user equipment, UE, to determine whether to perform a layer 2, L2, reset for a first layer 1 / layer 1 triggered mobility, LTM, cell switch procedure from a source cell (e.g. for which the UE does not have an LTM candidate cell configuration) towards a target LTM candidate cell. The method begins at step 802 with transmitting to a third network node information relating to whether the UE shall perform an L2 reset procedure for the first LTM cell switch procedure.

[0142] Step 802 may in some examples, be worded as transmitting to the third network node information about between which cells (including at least one LTM candidate cell belonging to that target network node) the UE shall perform (or not perform) a L2 reset upon an LTM cell switch.

[0143] The information of step 802 may comprise an indication of a L2 reset group to which the (one or more) LTM candidate cell belongs.

[0144] In some examples, the method further comprises receiving, from the third network node, a request for configuration for one or more LTM candidate cell(s).

[0145] In some examples, the method of Figure 8 further comprises indicating to the third network node that a L2 reset is or is not needed when executing an LTM cell switch to one or more LTM candidate cell belonging to the target network node. In other words, the target network node may (determine and) indicate to the third network node that a L2 reset is needed when executing an LTM cell switch to the LTM candidate target cell(s) belonging to that target network node and / or the target network node may (determine and) indicate to the third network node that L2 reset is not needed when executing an LTM cell switch to the LTM candidate target cell(s) belonging to that target network node

[0146] In some examples, the method of Figure 8 further comprises indicating to the third network node that an L2 reset is needed when executing an LTM cell switch to a subset of LTM candidate cell(s) belonging to the target network node and that an L2 reset is not needed when executing an LTM cell switch to another subset of the LTM candidate cell(s) belonging to the target network node. In other words, the target network node may (determine and) indicate to the third network node that L2 reset is needed when executing an LTM cell switch to a subset of the LTM candidate target cell(s) belonging to that target network node and that L2 reset is not needed when executing an LTM cell switch to another subset of the LTM candidate target cell(s) belonging to that target network node.

[0147] In some examples, the need to perform (or not perform) a L2 reset when executing an LTM cell switch to the LTM candidate target cell(s) belonging to that target network node, is valid for the case when the LTM cell switch is executed from the current serving cell of the UE.

[0148] In some examples, the method of Figure 8 further comprises indicating to the third network node that an L2 reset is needed when executing an LTM cell switch procedure to the LTM candidate cell(s) belonging to that target network node, when the source cell of the UE does not belong to the target network node. In other words, the target network node may (determine and) indicate to the third network node that L2 reset is needed when executing an LTM cell switch to the LTM candidate target cell(s) belonging to that target network node, when the serving cell of the UE does not belong to that candidate target node.

[0149] In some examples, the method of Figure 8 further comprises indicating to the third network node that L2 reset is not needed when executing an LTM cell switch to the LTM candidate cell(s) belonging to the target network node, when the source cell of the UE also belongs to the target network node. In other words, the target network node may (determine and) indicate to the third network node that L2 reset is not needed when executing an LTM cell switch to the LTM candidate target cell(s) belonging to that target network node, when the serving cell of the UE also belongs to that candidate target node.

[0150] In some examples, the target network node (determines and) indicates to the third network node that L2 reset is needed when executing an LTM cell switch from one or more LTM candidate cells belonging to that target network node to one or more LTM candidate cells belonging to that target network node. In some examples, the target network node (determines and) indicates to the third network node that L2 reset is not needed when executing an LTM cell switch from one or more LTM candidate cells belonging to that target network node to one or more LTM candidate cells belonging to that target network node.

[0151] Figure 9 illustrates steps performed by the UE according to some embodiments. In this example, the UE performed the main steps as follows. Step 901. The UE receives at least one LTM configuration which include at least an LTM candidate cell configuration and at least one L2 reset group of cells, wherein each L2 reset group is formed by LTM candidate cells or LTM candidate configuration IDs, indicating that a L2 reset is not needed for LTM execution within each L2 reset group of cells.

[0152] Step 902. The UE receives an indication to determine whether a L2 reset is needed during the execution of an LTM cell switch procedure.

[0153] Step 903. The UE performs execution of an LTM cell switch procedure from a source cell for which it does not have an LTM candidate cell configuration.

[0154] Step 904. The UE determines, based on the L2 reset group(s) and the indication, whether to perform L2 reset or not during the LTM cell switch.

[0155] The following depicts a possible implementation of the embodiment for the standard document TS 38.331. The baseline text taken for this example is from the 3GPP tdoc in R2- 2306015. New parts are bold and underlined.

[0156] — LTM-Config

[0157] The IE LTM-Config is used to provide LTM candidate cell configuration.

[0158] LTM-Config information element

[0159] — ASNl START

[0160] — TAG-LTM-CONFIG-START

[0161] LTM-Conf ig-rl8 : := SEQUENCE {

[0162] Itm-Ref erenceConf iguration-rl8 OCTET STRING (CONTAINING RRCReconf iguration) , OPTIONAL, — Cond FirstLTM-Candidate ltm-CandidateToReleaseList-rl8 LTM-

[0163] CandidateToReleaseList-rl8 OPTIONAL, — Need N ltm-CandidateToAddModList-rl8 LTM-CandidateToAddModList- rl8 OPTIONAL, — Need N

[0164] _ Itm-ServingCellNoResetID-rlS INTEGER (1. . maxNrof CellsLTM-r 18 ) OPTIONAL,

[0165] Cond FirstLTM-Only

[0166] Itm-CSI-ResourceConf igToAddModList-rl8 SEQUENCE (SIZE

[0167] (1. .maxNrofCSI-ResourceConf igurations ) ) OF LTM-CSI-ResourceConf ig

[0168] OPTIONAL, — Need N

[0169] Itm-CSI-ResourceConf igToReleaseList-rl8 SEQUENCE (SIZE

[0170] (1. .maxNrofCSI-ResourceConf igurations ) ) OF LTM-CSI-ResourceConf igld

[0171] OPTIONAL, — Need N Editor' s Note: FFS on whether the LTM-CandidateNoResetL2-List field should include separate reset flags for RLC, and PDCP recovery.

[0172] LTM-CandidateToReleaseList-rl8 : := SEQUENCE (SIZE ( 1. .maxNrofCellsLTM-rl8 ) ) OF LTM-Candidateld-rl 8 OPTIONAL -- Need N

[0173] — TAG-LTM-CONFIG-STOP

[0174] — ASN1STOP

[0175] — LTM-CandidateToAddModList

[0176] The IE LTM-CandidateToAddModList concerns a list of LTM candidate cell configurations to add or modify.

[0177] LTM-CandidateToAddModList information element

[0178] — ASNl START

[0179] — TAG-LTM-CANDIDATETOADDMODLIST-START

[0180] LTM-CandidateToAddModList-rl8 : := SEQUENCE (SIZE

[0181] ( 1. .maxNrofCellsLTM-r!8 ) ) OF LTM-Candidate-rl 8

[0182] LTM-Candidate-rl8 SEQUENCE { ltm-Candidate!d-rl8 LTM-Candidateld- rl8 ,

[0183] Itm-CandidateConf ig-rl8 OCTET STRING

[0184] (CONTAINING RRCReconfiguration) , itm-Conf igComplete-rl8 ENUMERATED {true}

[0185] OPTIONAL, — Need R

[0186] Itm-EarlyUlSyncConf ig-rl8 SetupRelease {

[0187] EarlyUlSyncConf ig-rl8 } OPTIONAL, -- Need M

[0188] Itm-NoResetID-rlS _ INTEGER (1. . maxNrof CellsLTM-r 18 ) _ OPTIONAL, — Need M ltm-Candidate-Tci-States-ToAddModList-rl8 Candidate-Tci-

[0189] States-rl8 OPTIONAL, — Need N ltm-Candidate-Tci-States-ToReleaseList-rl8 Candidate-Tci-

[0190] Statesld-rl8 OPTIONAL, — Need N

[0191] }

[0192] Editors' s Note: FES how to indicate to the UE that RACH should be skipped when doing an LTM cell switch.

[0193] — TAG-LTM-CANDIDATETOADDMODLIST-STOP

[0194] — ASN1STOP

[0195] Figure 10 shows an example of a communication system 1000 in accordance with some embodiments.

[0196] In the example, the communication system 1000 includes a telecommunication network 1002 that includes an access network 1004, such as a radio access network (RAN), and a core network 1006, which includes one or more core network nodes 1008. The access network 1004 includes one or more access network nodes, such as network nodes 1010a and 1010b (one or more of which may be generally referred to as network nodes 1010), or any other similar 3rdGeneration Partnership Project (3GPP) access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network 1002 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network 1002 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network 1002, including one or more network nodes 1010 and / or core network nodes 1008.

[0197] Examples of an ORAN network node include an open radio unit (0-Rll), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU-CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an A1 , F1 , W1 , E1 , E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. The network nodes 1010 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 1012a, 1012b, 1012c, and 1012d (one or more of which may be generally referred to as UEs 1012) to the core network 1006 over one or more wireless connections.

[0198] Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 1000 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. The communication system 1000 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0199] The UEs 1012 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with the network nodes 1010 and other communication devices. Similarly, the network nodes 1010 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs 1012 and / or with other network nodes or equipment in the telecommunication network 1002 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in the telecommunication network 1002.

[0200] In the depicted example, the core network 1006 connects the network nodes 1010 to one or more hosts, such as host 1016. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 1006 includes one more core network nodes (e.g., core network node 1008) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 1008. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0201] The host 1016 may be under the ownership or control of a service provider other than an operator or provider of the access network 1004 and / or the telecommunication network 1002, and may be operated by the service provider or on behalf of the service provider. The host 1016 may host a variety of applications to provide one or more services. Examples of such applications include the provision of live and / or pre-recorded audio / video content, data collection services, for example, retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server. As a whole, the communication system 1000 of Figure 10 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low- power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0202] In some examples, the telecommunication network 1002 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 1002 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 1002. For example, the telecommunications network 1002 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive loT services to yet further UEs.

[0203] In some examples, the UEs 1012 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 1004 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 1004. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[0204] In the example illustrated in Figure 10, the hub 1014 communicates with the access network 1004 to facilitate indirect communication between one or more UEs (e.g., UE 1012c and / or 1012d) and network nodes (e.g., network node 1010b). In some examples, the hub 1014 may be a controller, router, a content source and analytics node, or any of the other communication devices described herein regarding UEs. For example, the hub 1014 may be a broadband router enabling access to the core network 1006 for the UEs. As another example, the hub 1014 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1010, or by executable code, script, process, or other instructions in the hub 1014. As another example, the hub 1014 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 1014 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 1014 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 1014 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 1014 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0205] The hub 1014 may have a constant / persistent or intermittent connection to the network node 1010b. The hub 1014 may also allow for a different communication scheme and / or schedule between the hub 1014 and UEs (e.g., UE 1012c and / or 1012d), and between the hub 1014 and the core network 1006. In other examples, the hub 1014 is connected to the core network 1006 and / or one or more UEs via a wired connection. Moreover, the hub 1014 may be configured to connect to an M2M service provider over the access network 1004 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 1010 while still connected via the hub 1014 via a wired or wireless connection. In some embodiments, the hub 1014 may be a dedicated hub - that is, a hub whose primary function is to route communications to / from the UEs from / to the network node 1010b. In other embodiments, the hub 1014 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 1010b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0206] Figure 11 shows a UE 1100 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless camera, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-loT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0207] A UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0208] The UE 1100 includes processing circuitry 1102 that is operatively coupled via a bus 1104 to an input / output interface 1106, a power source 1108, a memory 1110, a communication interface 1112, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 11. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0209] The processing circuitry 1102 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 1110. The processing circuitry 1102 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 1102 may include multiple central processing units (CPUs). The processing circuitry 1102 may be operable to provide, either alone or in conjunction with other UE 1100 components, such as the memory 1110, UE 1100 functionality. For example, the processing circuitry 1102 may be configured to cause the UE 1102 to perform the methods as described with reference to Figure 4, 5 or 9. In the example, the input / output interface 1106 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 1100. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[0210] In some embodiments, the power source 1108 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 1108 may further include power circuitry for delivering power from the power source 1108 itself, and / or an external power source, to the various parts of the UE 1100 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 1108. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 1108 to make the power suitable for the respective components of the UE 1100 to which power is supplied.

[0211] The memory 1110 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 1110 includes one or more application programs 1114, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1116. The memory 1110 may store, for use by the UE 1100, any of a variety of various operating systems or combinations of operating systems. The memory 1110 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or I SI M , other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUlCC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ The memory 1110 may allow the UE 1100 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 1110, which may be or comprise a device-readable storage medium.

[0212] The processing circuitry 1102 may be configured to communicate with an access network or other network using the communication interface 1112. The communication interface 1112 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1122. The communication interface 1112 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 1118 and / or a receiver 1120 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 1118 and receiver 1120 may be coupled to one or more antennas (e.g., antenna 1122) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0213] In some embodiments, communication functions of the communication interface 1112 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and / or standards, such as IEEE 802.11 , Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0214] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1112, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0215] As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or controls a robotic arm performing a medical procedure according to the received input.

[0216] A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are devices which are or which are embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), awearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and / or software in dependence on the intended application of the loT device in addition to other components as described in relation to the UE 1100 shown in Figure 11.

[0217] As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another UE and / or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-loT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0218] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and / or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

[0219] Figure 12 shows a network node 1200 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with a UE and / or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)), O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU).

[0220] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0221] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0222] The network node 1200 includes processing circuitry 1202, a memory 1204, a communication interface 1206, and a power source 1208, and / or any other component, or any combination thereof. The network node 1200 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 1200 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 1200 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1204 for different RATs) and some components may be reused (e.g., a same antenna 1210 may be shared by different RATs). The network node 1200 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1200, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1200.

[0223] The processing circuitry 1202 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other network node 1200 components, such as the memory 1204, network node 1200 functionality. For example, the processing circuitry 1202 may be configured to cause the network node to perform the methods as described with reference to Figure 6, 7 and / or 8.

[0224] In some embodiments, the processing circuitry 1202 includes a system on a chip (SOC). In some embodiments, the processing circuitry 1202 includes one or more of radio frequency (RF) transceiver circuitry 1212 and baseband processing circuitry 1214. In some embodiments, the radio frequency (RF) transceiver circuitry 1212 and the baseband processing circuitry 1214 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1212 and baseband processing circuitry 1214 may be on the same chip or set of chips, boards, or units.

[0225] The memory 1204 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processing circuitry 1202. The memory 1204 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions capable of being executed by the processing circuitry 1202 and utilized by the network node 1200. The memory 1204 may be used to store any calculations made by the processing circuitry 1202 and / or any data received via the communication interface 1206. In some embodiments, the processing circuitry 1202 and memory 1204 is integrated.

[0226] The communication interface 1206 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, the communication interface 1206 comprises port(s) / terminal(s) 1216 to send and receive data, for example to and from a network over a wired connection. The communication interface 1206 also includes radio front-end circuitry 1218 that may be coupled to, or in certain embodiments a part of, the antenna 1210. Radio front-end circuitry 1218 comprises filters 1220 and amplifiers 1222. The radio front-end circuitry 1218 may be connected to an antenna 1210 and processing circuitry 1202. The radio front-end circuitry may be configured to condition signals communicated between antenna 1210 and processing circuitry 1202. The radio front-end circuitry 1218 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 1218 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1220 and / or amplifiers 1222. The radio signal may then be transmitted via the antenna 1210. Similarly, when receiving data, the antenna 1210 may collect radio signals which are then converted into digital data by the radio front-end circuitry 1218. The digital data may be passed to the processing circuitry 1202. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0227] In certain alternative embodiments, the network node 1200 does not include separate radio front-end circuitry 1218, instead, the processing circuitry 1202 includes radio front-end circuitry and is connected to the antenna 1210. Similarly, in some embodiments, all or some of the RF transceiver circuitry 1212 is part of the communication interface 1206. In still other embodiments, the communication interface 1206 includes one or more ports or terminals 1216, the radio front-end circuitry 1218, and the RF transceiver circuitry 1212, as part of a radio unit (not shown), and the communication interface 1206 communicates with the baseband processing circuitry 1214, which is part of a digital unit (not shown).

[0228] The antenna 1210 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 1210 may be coupled to the radio front-end circuitry 1218 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 1210 is separate from the network node 1200 and connectable to the network node 1200 through an interface or port.

[0229] The antenna 1210, communication interface 1206, and / or the processing circuitry 1202 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, the antenna 1210, the communication interface 1206, and / or the processing circuitry 1202 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment. The power source 1208 provides power to the various components of network node 1200 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 1208 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 1200 with power for performing the functionality described herein. For example, the network node 1200 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 1208. As a further example, the power source 1208 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0230] Embodiments of the network node 1200 may include additional components beyond those shown in Figure 12 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, the network node 1200 may include user interface equipment to allow input of information into the network node 1200 and to allow output of information from the network node 1200. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 1200.

[0231] Figure 13 is a block diagram illustrating a virtualization environment 1300 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1300 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 1300 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface. Applications 1302 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment Q400 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0232] Hardware 1304 includes processing circuitry, memory that stores software and / or instructions executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1306 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1308a and 1308b (one or more of which may be generally referred to as VMs 1308), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. The virtualization layer 1306 may present a virtual operating platform that appears like networking hardware to the VMs 1308.

[0233] The VMs 1308 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1306. Different embodiments of the instance of a virtual appliance 1302 may be implemented on one or more of VMs 1308, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0234] In the context of NFV, a VM 1308 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs 1308, and that part of hardware 1304 that executes thatVM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1308 on top of the hardware 1304 and corresponds to the application 1302.

[0235] Hardware 1304 may be implemented in a standalone network node with generic or specific components. Hardware 1304 may implement some functions via virtualization. Alternatively, hardware 1304 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 1310, which, among others, oversees lifecycle management of applications 1302. In some embodiments, hardware 1304 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1312 which may alternatively be used for communication between hardware nodes and radio units.

[0236] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0237] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device- readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.

[0238] EMBODIMENTS

[0239] Group A Embodiments

[0240] 1 . A method, performed by a user equipment, for determining whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell, for which the UE does not have an LTM candidate cell configuration, towards a target LTM candidate cell, the method comprising: receiving at least an LTM candidate cell configuration for the target LTM candidate cell; obtaining a reset indication of whether an L2 reset procedure is to be performed for of the first LTM cell switch procedure; performing the first LTM cell switch procedure; and determining, based on the reset indication, whether to perform an L2 reset.

[0241] 2. The method of embodiment 1 further comprising, responsive to determining to perform an L2 reset procedure, performing an L2 reset procedure.

[0242] 3. The method of embodiment 1 or 2 further comprising receiving an indication of at least one group of LTM candidate cells.

[0243] 4. The method of embodiment 3 wherein the indication of at least one L2 reset group of LTM candidate cells, comprises a list of LTM candidate configuration identifications for the cells in the L2 reset group.

[0244] 5. The method of any previous embodiment further comprising performing the first LTM cell switch procedure response to receiving an LTM cell switch command.

[0245] 6. The method of any one of embodiments 5 wherein obtaining the reset indication comprises receiving the reset indication in the LTM cell switch command.

[0246] 7. The method of any one of embodiments 1 to 5 wherein obtaining the reset indication comprises receiving the reset indication during execution of the first LTM cell switch procedure in an RRC reconfiguration message.

[0247] 8. The method of any one of embodiment 1 to 5 wherein obtaining the reset indication comprises receiving the reset indication in a first LTM configuration. The method of embodiment 8 wherein receiving the first LTM configuration before receiving the at least one LTM candidate cell configuration. The method of embodiment 8 further comprising receiving the first LTM configuration with the reset indication after receiving the at least one LTM candidate cell configuration. The method of embodiment 8 further comprising receiving the first LTM configuration from the current serving cell to any LTM candidate cell, or a serving node to any LTM candidate cell. The method of any one of embodiments 8 to 11 further comprising receiving the at least one LTM candidate cell configuration in a second LTM configuration. The method of any one of embodiments 8 to 12, further comprising receiving the first LTM configuration from a source network node providing the source cell or from a third network node via the source network node. The method of any one of embodiments 1 to 13 wherein the reset indication comprises: an indication associating the source cell or a source network node providing the source cell with a first L2 reset group of LTM candidate cells. The method of embodiment 14 wherein the step of determining whether to perform an L2 reset comprises:

[0248] Response to the target LTM candidate cell belonging to the first L2 reset group of LTM candidate cells, determining not to perform an L2 reset. The method of embodiment 14 or 15 wherein the step of determining whether to perform an L2 reset comprises: responsive to the target LTM candidate cell not belonging to the first L2 reset group of LTM candidate cells, determining to perform an L2 reset. The method any one of embodiments 1 to 16 wherein the step of determining whether to perform an L2 reset comprises: responsive to determining that the source cell, or the source network node serving the source cell does not belong to a L2 reset group, determining to perform an L2 reset or determining not to perform an L2 reset. The method in any one of embodiments 1 to 17, wherein the step of determining whether to perform an L2 reset comprises: responsive to determining that the target LTM candidate cell belongs to a L2 reset group, determining to perform an L2 reset or determining not to perform an L2 reset. The method as in embodiment 17 or 18 wherein the reset indication comprises the L2 group of the target LTM candidate cell. The method as in any one of embodiments 1 to 19 further comprising using an indication of a L2 reset group in the LTM candidate configuration of the target LTM candidate cell as an indication of a L2 reset group the target cell belongs to after the execution of the first LTM cell switch procedure. The method as in any one of embodiments 1 to 20, further comprising using an indication of a L2 reset group the source cell belongs to determine the indication of a L2 reset group the target LTM candidate cell belongs to after the execution of the first LTM cell switch procedure. The method as in any one of embodiments 1 to 21 , further comprising setting the indication to of a L2 reset group the target LTM candidate cell belongs to after the performing the first LTM cell switch procedure. The method of any one of embodiments 1 to 22 wherein the reset indication comprises an indication of whether to perform L2 reset specifically for the first LTM cell switch procedure. The method of any one of embodiments 1 to 23 wherein the reset indication comprises a list of candidate network nodes for which L2 reset is needed or not needed when an LTM cell switch procedure is executed towards on the candidate network nodes. 25. The method of any one embodiments 1 to 24 wherein the reset indication comprises, if the source network node is also an LTM candidate cell, the LTM candidate cell configuration index that identify the Source network node.

[0249] 26. A method, performed by a user equipment, for executing a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell, forwhich the UE does not have an LTM candidate cell configuration, towards a target LTM candidate cell, the method comprising: receiving at least an LTM candidate cell configuration for the target LTM candidate cell; performing the first LTM cell switch procedure; and performing or not performing an L2 reset.

[0250] 27. The method of any of the previous embodiments, further comprising: providing user data; and forwarding the user data to a host via the transmission to the network node.

[0251] Group B Embodiments

[0252] 28. A method in a source network node for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell, forwhich the UE does not have an LTM candidate cell configuration, towards a target LTM candidate cell, comprising: transmitting, to the UE, at least an LTM candidate cell configuration for the target LTM candidate cell; and transmitting, to the UE, a reset indication of whether a L2 reset is to be performed for the first LTM cell switch procedure.

[0253] 29. The method as in embodiment 28 further comprising transmitting an LTM cell switch command to the UE in order to trigger the execution of the first LTM cell switch procedure.

[0254] 30. The method as in embodiment 28 or 29 further comprising receiving from a third network node a first LTM configuration comprising the reset indication. The method as in embodiment 30 further comprising receiving a request from the third network node to setup an LTM candidate cell configuration. The method as in embodiment 30, further comprising receiving the first LTM configuration in the same signaling that requests source network node to configure an LTM candidate cell configuration at the UE. The method as in embodiment 30 further comprising receiving the first LTM configuration responsive to transmitting a request for the first LTM configuration to the third network node. The method as in any one of embodiments 30 to 33 wherein signaling exchanges between the source network node and the third network node are performed over a F1AP interface. A method, performed by a third network node for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell, for which the UE does not have an LTM candidate cell configuration, towards a target LTM candidate cell, the method comprising: transmitting to a source network node a reset indication of whether a L2 reset is to be performed for of the first LTM cell switch procedure. The method as in embodiment 35, further comprising transmitting to the source network node, a first LTM configuration comprising the reset indication before transmitting a request to the source network node to setup an LTM candidate cell configuration. The method of embodiment 36, wherein the first LTM configuration is comprised in a radio resource control, RRC, reconfiguration message to be transmitted to the UE. The method of embodiment 36, further comprising transmitting the first TLM configuration in the same signaling that requests the source network node to configure an LTM candidate cell configuration at the UE. 39. The method of embodiment 36, further comprising transmitting the first LTM configuration in response to explicit request received for the first LTM configuration from the source network node.

[0255] 40. The method of any one of embodiments 35 to 39, further comprising receiving, from a target network node, information relating to whether the UE shall perform an L2 reset procedure upon performing the first LTM cell switch procedure.

[0256] 41. The method of embodiment 40 further comprising receiving the information from the target network node responsive to transmitting a request to the target network node to configure an LTM candidate cell.

[0257] 42. The method of embodiment 41 wherein the reset indication indicates a L2 reset group to which the target LTM candidate cell belongs.

[0258] 43. A method, performed by a target network node, to enabling a UE to determine whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell, for which the UE does not have an LTM candidate cell configuration, to a target candidate LTM cell belonging to the target network node, the method comprising: transmitting to a third network node information relating to whether the UE shall perform an L2 reset procedure for the first LTM cell switch procedure.

[0259] 44. The method as in embodiment 43, wherein the information comprises an indication of a L2 reset group to which the target LTM candidate cell belongs.

[0260] 45. The method as in embodiments 43 or 44, further comprising receiving, from the third network node, a request for configuration for one or more LTM candidate cell(s).

[0261] 46. The method as in any one of embodiments 43 to 45 further comprising indicating to the third network node that a L2 reset is or is not needed when executing an LTM cell switch to one or more LTM candidate cell belonging to the target network node.

[0262] 47. The method as in any one of embodiments 43 to 45, further comprising indicating to the third network node that an L2 reset is needed when executing an LTM cell switch to a subset of LTM candidate cell(s) belonging to the target network node and that an L2 reset is not needed when executing an LTM cell switch to another subset of the LTM candidate cell(s) belonging to the target network node.

[0263] 48. The method as in any one of embodiments 43 to 47 further comprising indicating to the third network node that an L2 reset is needed when executing an LTM cell switch procedure to the LTM candidate cell(s) belonging to that target network node, when the source cell of the UE does not belong to the target network node.

[0264] 49. The method as in any one of embodiments 43 to 48 further comprising indicating to the third network node that L2 reset is not needed when executing an LTM cell switch to the LTM candidate cell(s) belonging to the target network node, when the source cell of the UE also belongs to the target network node.

[0265] 50. The method of any of the previous embodiments, further comprising: obtaining user data; and forwarding the user data to a host or a user equipment.

[0266] Group C Embodiments

[0267] 51 . A user equipment for enabling a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell, when the UE does not have an LTM candidate cell configuration for the source cell, the user equipment comprising: processing circuitry configured to cause the user equipment to perform any of the steps of any of the Group A embodiments; and power supply circuitry configured to supply power to the processing circuitry.

[0268] 52. A network node for enabling a user equipment, UE, to perform a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell, forwhich the UE does not have an LTM candidate cell configuration, towards a target LTM candidate cell, the network node comprising: processing circuitry configured to cause the network node to perform any of the steps of any of the Group B embodiments; power supply circuitry configured to supply power to the processing circuitry. 53. A user equipment (UE) for enabling a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell, when the UE does not have an LTM candidate cell configuration for the source cell, the UE comprising: an antenna configured to send and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of the Group A embodiments; an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the

[0269] UE.

Claims

CLAIMS1 . A method, performed by a user equipment, for determining whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell, the method comprising: receiving (402) at least an LTM candidate cell configuration for the target LTM candidate cell; obtaining (404) a reset indication of whether an L2 reset procedure is to be performed for the first LTM cell switch procedure; obtaining an indication of an L2 reset group of the target LTM candidate cell; performing (406) the first LTM cell switch procedure; and determining (408), based on the reset indication and the indication of the L2 reset group of the target LTM candidate cell, whether to perform an L2 reset.

2. The method of claim 1 further comprising, responsive to determining to perform an L2 reset procedure, performing an L2 reset procedure.

3. The method of any previous claim further comprising performing the first LTM cell switch procedure in response to receiving an LTM cell switch command.

4. The method of any one of claims 1 to 3 wherein the reset indication comprises: an indication associating the source cell with a first L2 reset group of LTM candidate cells.

5. The method of claim 4 wherein the step of determining whether to perform an L2 reset comprises: responsive to the indication of the L2 reset group of the target LTM candidate cell indicating that the target LTM candidate cell belongs to the first L2 reset group of LTM candidate cells, determining not to perform an L2 reset.

6. The method of claim 4 or 5 wherein the step of determining whether to perform an L2 reset comprises: responsive to the indication of the L2 reset group of the target LTM candidate cell indicating that the target LTM candidate cell does not belong to the first L2 reset group of LTM candidate cells, determining to perform an L2 reset.

7. The method of any one of claim 1 to 6 wherein obtaining the reset indication comprises receiving the reset indication in a first LTM configuration.

8. The method of claim 7 wherein receiving the first LTM configuration before receiving the at least one LTM candidate cell configuration.

9. The method of any one of claims 7 to 8, further comprising receiving the first LTM configuration from a source network node providing the source cell or from a third network node via the source network node.

10. The method as in any one of claims 1 to 9 further comprising using the indication of the L2 reset group of the target LTM candidate cell as an indication of a L2 reset group of a new serving cell after the execution of the first LTM cell switch procedure.11 . The method as in any one of claims 1 to 10, further comprising setting the value of the reset indication to the value of the indication of the L2 reset group of the target LTM candidate cell after performing the first LTM cell switch procedure.

12. The method as claimed in any one of claims 1 to 11 wherein the reset indication comprises a Itm-ServingCellNoResetID.

13. The method as claimed in any one of claim 1 to 12 wherein the L2 reset group of the target LTM candidate cell comprises an Itm-NoResetID.

14. A method in a source network node for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell, comprising: transmitting (602), to the UE, at least an LTM candidate cell configuration for the target LTM candidate cell comprising an indication of an L2 reset group of the target LTM candidate cell; and transmitting (604), to the UE, a reset indication of whether a L2 reset is to be performed for the first LTM cell switch procedure.

15. The method as in claim 14 further comprising transmitting an LTM cell switch command to the UE in order to trigger the execution of the first LTM cell switch procedure.

16. The method as in claim 14 or 15 further comprising receiving from a third network node a first LTM configuration comprising the reset indication.

17. The method as in claim 14, further comprising receiving a request from the third network node to setup an LTM candidate cell configuration.

18. The method as in claim 14, further comprising receiving the first LTM configuration in the same signaling that requests source network node to configure an LTM candidate cell configuration at the UE.

19. The method as in claim 14 further comprising receiving the first LTM configuration responsive to transmitting a request for the first LTM configuration to the third network node.

20. The method as claimed in any one of claims 14 to 19 wherein the reset indication comprises a Itm-ServingCellNoResetID.21 . The method as claimed in any one of claim 14 to 20 wherein the L2 reset group of the target LTM candidate cell comprises an Itm-NoResetID.

22. A method, performed by a target network node, for enabling a UE to determine whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell to a target candidate LTM cell belonging to the target network node, the method comprising: transmitting (802) to a third network node an indication of a L2 reset group to which the target LTM candidate cell belongs.

23. The method as in claims 22, further comprising receiving, from the third network node, a request for configuration for one or more LTM candidate cell(s).

24. The method as in any one of claims 22 to 23, further comprising indicating to the third network node that a L2 reset is or is not needed when executing an LTM cell switch to one or more LTM candidate cell belonging to the target network node.

25. The method as in any one of claims 22 to 24, further comprising indicating to the third network node that an L2 reset is needed when executing an LTM cell switch to a subset of LTM candidate cell(s) belonging to the target network node and that an L2 reset is not needed when executing an LTM cell switch to another subset of the LTM candidate cell(s) belonging to the target network node.

26. The method as in any one of claims 22 to 25, further comprising indicating to the third network node that an L2 reset is needed when executing an LTM cell switch procedure to the LTM candidate cell(s) belonging to that target network node, when the source cell of the UE does not belong to the target network node.

27. The method as in any one of claims 22 to 26, further comprising indicating to the third network node that L2 reset is not needed when executing an LTM cell switch to the LTM candidate cell(s) belonging to the target network node, when the source cell of the UE also belongs to the target network node.

28. The method as claimed in any one of claim 22 to 27 wherein the L2 reset group of the target LTM candidate cell comprises an Itm-NoResetID.

29. A user equipment (1100) for determining whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell, the user equipment comprising processing circuitry (1102) and memory (1110), the memory containing instructions executable by the processing circuitry whereby the user equipment is operable to: receive (402) at least an LTM candidate cell configuration for the target LTM candidate cell; obtain (404) a reset indication of whether an L2 reset procedure is to be performed for the first LTM cell switch procedure; obtain an indication of an L2 reset group of the target LTM candidate cell; perform (406) the first LTM cell switch procedure; and determine (408), based on the reset indication and the indication of the L2 reset group of the target LTM candidate cell, whether to perform an L2 reset.

30. The user equipment as claimed in claim 29 wherein the memory comprises furtherinstructions executable by the processing circuitry whereby the user equipment is operable to perform the method as claimed in any one of claims 2 to 13.

31. A source network node (1200) for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell, the source network node comprising processing circuitry (1202) and memory (1204), the memory containing instructions executable by the processing circuitry whereby the source network node is operable to: transmit (602), to the UE, at least an LTM candidate cell configuration for the target LTM candidate cell comprising an indication of an L2 reset group of the target LTM candidate cell; and transmit (604), to the UE, a reset indication of whether a L2 reset is to be performed for the first LTM cell switch procedure.

32. The source network node as claimed in claim 31 wherein the memory comprises further instructions executable by the processing circuitry whereby the source network node is operable to perform the method as claimed in any one of claims 15 to 21.

33. A target network node (1200) for enabling a UE to determine whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell to a target candidate LTM cell belonging to the target network node, the target network node comprising processing circuitry (1202) and memory (1204), the memory containing instructions executable by the processing circuitry whereby the target network node is operable to: transmit (802) to a third network node an indication of a L2 reset group to which the target LTM candidate cell belongs.

34. The target network node as claimed in claim 33 wherein the memory comprises further instructions executable by the processing circuitry whereby the target network node is operable to perform the method as claimed in any one of claims 23 to 28.

35. A user equipment for determining whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell, wherein the user equipment is adapted to perform the method as claimed in any one of claims 1 to 13.

36. A source network node for enabling a user equipment, UE, to determine to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell towards a target LTM candidate cell, wherein the source network is adapted to perform the method as claimed in any one of claims 14 to 21 .

37. A target network node for enabling a UE to determine whether to perform a layer 2, L2, reset for a first layer 1 / layer 2 triggered mobility, LTM, cell switch procedure from a source cell to a target candidate LTM cell belonging to the target network node, wherein the target network node is adapted to perform the method as claimed in any one of claims 22 to 28.

38. A computer program, comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out a method according to any of claims 1 to 28.

39. A carrier containing the computer program according to claim 38, wherein the carrier comprises one of an electronic signal, optical signal, radio signal or computer readable storage medium.

40. A computer-readable medium comprising instructions that, when executed on at least one processor, cause the at least one processor to perform the method according to any of claims 1 to 28.

41. A computer program product comprising non transitory computer readable media having stored thereon a computer program according to claim 38.

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