Signaling for UE-based ta management in ltm

Abstract

Systems and methods related to User Equipment (UE)-based Timing Advance (TA) management in Layer (L1) / Layer 2 (L2) Triggered Mobility (LTM) are disclosed In one embodiment, a method performed by a UE comprises receiving, from a serving network node, information that configures the UE with one TA estimation group for each of two or more configured cells of the UE, the configured cells comprising a serving cell of the UE and one or more LTM candidate cells. The method further comprises, in association with performing a LTM cell switch procedure from a source cell to a target cell where the source cell is the serving cell of the UE and the target cell is one of the LTM candidate cells, either performing UE-based TA estimation for the target cell or not, based on whether the TA estimation groups configured for the source and target cells are the same.

Description

[0001] SIGNALING FOR UE-BASED TA MANAGEMENT IN LTM

[0002] Related Applications

[0003] This application claims the benefit of provisional patent application serial number 63 / 586,742, filed September 29, 2023, the disclosure of which is hereby incorporated herein by reference in its entirety.

[0004] Technical Field

[0005] The present disclosure relates to a cellular communications system and, more specifically, to Timing Advance (TA) and uplink synchronization in a cellular communications system during a Layer 1 (LI) / Layer (2) Triggered Mobility (LTM) cell switch procedure.

[0006] Background

[0007] In 3rd Generation Partnership Project (3GPP) cellular communications network (e.g., New Radio (NR) network), different User Equipments (UEs) in the same cell may typically be located at different positions within the cell and then with different distances to the base station (e.g., NR gNodeB (gNB)). The transmissions from different UEs thus suffer from different delays until they reach the base station. In order to make sure that the Uplink (UL) transmissions from a UE reaches the base station within the corresponding receive window for the base station, an uplink timing control procedure is used. This avoids intracell interference from occurring, both between UEs assigned to transmit in consecutive subframes and between UEs transmitting on adjacent subcarriers. Time alignment of the uplink transmissions is achieved by applying a timing advance at the UE transmitter, relative to the received downlink timing. The main role of this is to counteract differing propagation delays between different UEs.

[0008] In order to achieve the time alignment, to obtain UL synchronization, the base station (e.g. gNB in the case of NR, eNodeB (eNB) in the case of Long Term Evolution (LTE)) derives the Timing Advance (TA) value that the UE needs to use for UL transmissions in order for the UL transmissions to reach the base station within the receive window and indicates the derived TA value to the UE. When the UE first accesses a cell, it uses the random-access procedure where the received Msgl (i.e., the Physical Random Access Channel (PRACH) preamble) is used by the base station to determine the UE’s initial TA to use for UL transmissions in the cell. During the connection, the base station then continuously monitors whether the UE needs to advance / delay the UL transmissions, in order to compensate for changes in propagation delay, and indicates to the UE if there is a need to change the TA value. The TA value may either be an actual timing adjustment value to be applied and / or an index (e.g., TA) pointing a timing adjustment value to be applied.

[0009] In 3GPP Release 18, a work item known as further NR mobility enhancements has been agreed. This work item includes a technical area entitled Layer 1 (Ll) / Layer 2 (L2) based intercell mobility. According to the Work Item Description (WID) (RP -223520, 3GPP work item description: Further NR mobility enhancements, MediaTek Inc, Apple, 3GPP TSG RAN Meeting #98-e, Electronic Meeting, December 12-16, 2022), 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 layer 3 (L3) measurements and is done by Radio Resource Control (RRC) signaling triggered Reconfiguration with Synchronization for change of Primary Cell (PCell) and Primary Secondary Cell (PSCell), as well as release / add for Secondary Cells (SCells) when applicable. All cases involve complete L2 (and LI) resets, leading to longer latency, larger overhead, and longer interruption time than beam switch mobility. 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.

[0010] The work items include the following objectives. One objective is to specify a mechanism and procedures of L1 / L2 based inter-cell mobility for mobility latency reduction. This includes configuration and maintenance for multiple candidate cells to allow fast application of configurations for candidate cells; dynamic switch mechanism among candidate serving cells (including Special Cell (SpCell) and SCell) for the potential applicable scenarios based on L1 / L2 signaling; LI enhancements for inter-cell beam management, including LI measurement and reporting, and beam indication; Timing Advance management; and Central Unit (CU) - Distributed Unit (DU) interface signaling to support L1 / L2 mobility.

[0011] The procedure of L1 / L2 based inter-cell mobility are applicable to the following scenarios: standalone, carrier aggregation (CA) and NR dual connectivity (NR-DC) case with serving cell change within one cell group (CG); intra-DU case and intra-CU inter-DU case (applicable for standalone and CA); both intra-frequency and inter-frequency; both FR1 and FR2; and source and target cells may be synchronized or non-synchronized.

[0012] In 3GPP, discussions have started on solutions for L1 / L2 based inter-cell mobility (sometimes also referred to as L1 / L2 -triggered mobility (LTM) or lower layer-triggered mobility). A basic principle with L1 / L2 -triggered mobility (LTM) is that the UE is preconfigured, by the network, with an RRC configuration per LTM candidate cell, sometimes also known as an LTM candidate cell configuration. Such an LTM candidate cell configuration may be an RRCReconfiguration message (e.g., delta signaling associated to a reference configuration or the UE’s current configuration) or one or more Information Elements (IEs) / fields / parameters such as CellGroupConfig. The UE performs LI measurements (e.g., Channel State Information (CSI) measurements, such as Synchronization Signal Reference Signal Received Power (SS- RSRP), LI Reference Signal Received Power (RSRP) per Synchronization Signal Block (SSB)) on these LTM candidate cells and transmits corresponding LI measurement reports to the network (e.g., on Physical Uplink Control Channel (PUCCH) and / or Physical Uplink Shared Channel (PUSCH)). The network then triggers the execution of a LTM cell switch in the UE to one of these LTM candidate cells by transmitting an LTM cell switch command (such as a Medium Access Control (MAC) Control Element (CE)), to the UE, which then connects to the particular LTM candidate cell and switches to an RRC configuration of this LTM candidate cell.

[0013] In the area of TA management to reduce latency for LI / L2 -triggered mobility, 3GPP RANI has made, among others, these agreements:

[0014] For Physical Downlink Control Channel (PDCCH) ordered-Random Access Channel (RACH) for candidate cell(s), Random Access Response (RAR) reception can be configured / indicated o If reception of RAR is not configured / indicated (without RAR)

[0015] ■ TA value of candidate cell is indicated in cell switch command

[0016] ■ For Future Study (FFS): whether UE should re-transmit PRACH when reception of RAR is not configured / indicated

[0017] ■ FFS: how UE determine the transmit power of subsequent PRACH triggered by PDCCH order o If reception of RAR is configured / indicated (with RAR), FFS

[0018] ■ whether RAR is received from serving cell or candidate cell

[0019] • if RAR is received from candidate cell, whether Typel-PDCCH Common Search Space (CSS) of the candidate cell is configured to the UE

[0020] ■ content of RAR o FFS: signaling for configuration / indication of whether RAR needs to be received o UE can report the support combination of with RAR only and without RAR only, where support of one default scheme is the baseline UE approach for LTM o Send Liaison Statement (LS) to RAN2 and RAN3 to check the feasibility about this agreement o Note: Definition of candidate cells is up to RAN2

[0021] If reception of RAR is configured / indicated, RAR contains at least TA of candidate cell. o The maximum number of TA values memorized by UE is a UE capability o FFS: whether other parameters such as UE Identity (ID), candidate cell ID etc. is contained in RAR

[0022] Confirm the following Working Assumption, and sent LS to RAN4 to clarify the feasibility of supporting this mechanism o Working Assumption

[0023] From RAN 1 perspective, UE-based TA measurement (UE derives TA based on Receive (Rx) timing difference between current serving cell and candidate cell as well as TA value for the current serving cell) is supported.

[0024] • Corresponding UE capability is to be introduced to support UE-based TA measurement

[0025] • For a UE that reports support of this capability, configuration of UE-based TA measurement is supported

[0026] • FFS: other impacts on RANI specification

[0027] Summary

[0028] Systems and methods related to User Equipment (UE)-based Timing Advance (TA) management in Layer (Ll) / Layer 2 (L2) Triggered Mobility (LTM) are disclosed. In one embodiment, a method performed by a UE for LTM comprises receiving, from a serving network node, information that configures the UE with one TA estimation group for each of two or more configured cells of the UE, the two or more configured cells comprising a serving cell of the UE and one or more LTM candidate cells. The method further comprises, in association with performing a LTM cell switch procedure from a source cell to a target cell where the source cell is the serving cell of the UE and the target cell is one of the one or more LTM candidate cells, either performing UE-based TA estimation for the target cell or not, based, at least in part, on whether the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell. In this manner, the UE may be configured with UE-based TA estimation for cell pairs in LTM cell-switch, without requiring any reconfiguration after the execution of an LTM cell-switch.

[0029] In one embodiment, the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell, and either performing UE-based TA estimation or not comprises performing UE-based TA estimation for the target cell responsive to the TA estimation group configured for the source cell being the same as the TA estimation group configured for the target cell. In one embodiment, the TA estimation group configured for the source cell is not the same as the TA estimation group configured for the target cell, and either performing UE-based TA estimation or not comprises applying a TA value comprised in an associated LTM cell switch command received by the UE responsive to the TA estimation group configured for the source cell not being the same as the TA estimation group configured for the target cell.

[0030] In one embodiment, either performing UE-based TA estimation or not comprises performing UE-based TA estimation for the target cell if the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell. In one embodiment, either performing UE-based TA estimation for the target cell or not further comprises applying a TA value comprised in an associated LTM cell switch command received by the UE if the TA estimation group configured for the source cell is not the same as the TA estimation group configured for the target cell.

[0031] In one embodiment, the method further comprises receiving an LTM cell switch command from the serving network node, the LTM cell switch command being a command to perform the LTM cell switch procedure from the source cell to the target cell.

[0032] In one embodiment, the method further comprises receiving, from the serving network node, an indication regarding whether or not the UE is allowed to perform UE-based TA estimation for the target cell. In one embodiment, the indication received from the serving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell, the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell, and either performing UE-based TA estimation or not comprises performing UE-based TA estimation for the target cell responsive to (a) the indication received from the serving network node indicating that the UE is allowed to perform UE-based TA estimation for the target cell and (b) the TA estimation group configured for the source cell being the same as the TA estimation group configured for the target cell.

[0033] In another embodiment, the indication received from the serving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell, the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell, and either performing UE-based TA estimation or not comprises applying a TA value comprised in an associated LTM cell switch command received by the UE responsive to the TA estimation group configured for the source cell not being the same as the TA estimation group configured for the target cell even though the indication received from the serving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell. In another embodiment, either performing UE-based TA estimation for the target cell or not comprises performing UE-based TA estimation for the target cell if: (a) the indication received from the serving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell and (b) the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell. In one embodiment, either performing UE-based TA estimation for the target cell or not further comprises applying a TA value comprised in an associated LTM cell switch command received by the UE (102) if either: (a) the indication received from the serving network node indicates that the UE is not allowed to perform UE-based TA estimation for the target cell or (b) the TA estimation group configured for the source cell is not the same as the TA estimation group configured for the target cell.

[0034] In one embodiment, the method further comprises receiving an LTM cell switch command from the serving network node (104), the LTM cell switch command being a command to perform the LTM cell switch procedure from the source cell to the target cell.

[0035] In one embodiment, the indication regarding whether or not the UE is allowed to perform UE-based TA estimation is specific to the LTM candidate cell that is the target cell. In one embodiment, receiving the indication regarding whether or not the UE is allowed to perform UE- based TA estimation for the target cell comprises receiving the indication via an RRCReconfiguration message that configures the LTM candidate cell that is the target cell.

[0036] In one embodiment, the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell is common to all of the one or more LTM candidate cells configured for the UE. In one embodiment, receiving the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving the indication via an RRCReconfiguration message that configures a reference configuration for LTM.

[0037] In one embodiment, receiving the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving the indication via the associated LTM cell switch command.

[0038] In one embodiment, receiving the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving the indication via system information broadcasted on the serving cell.

[0039] In one embodiment, receiving the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving the indication via a Physical Downlink Control Channel (PDCCH) order. In one embodiment, receiving the information that configures the UE with the one TA estimation group for each of the two or more configured cells of the UE comprises, for each configured cell, receiving information that configures the one TA estimation group for the configured cell as part of a configuration of the configured cell.

[0040] Corresponding embodiments of a UE are also disclosed. In one embodiment, a UE for LTM is adapted to receive, from a serving network node, information that configures the UE with one TA estimation group for each of two or more configured cells of the UE, the two or more configured cells comprising a serving cell of the UE and one or more LTM candidate cells. The UE is further adapted to, in association with performing a LTM cell switch procedure from a source cell to a target cell where the source cell is the serving cell of the UE and the target cell is one of the one or more LTM candidate cells, either perform UE-based TA estimation for the target cell or not, based, at least in part, on whether the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

[0041] In one embodiment, a UE for LTM comprises a communication interface comprising a transmitter and a receiver, and processing circuitry associated with the communication interface. The processing circuitry is configured to cause the UE to receive, from a serving network node, information that configures the UE with one TA estimation group for each of two or more configured cells of the UE, the two or more configured cells comprising a serving cell of the UE and one or more LTM candidate cells. The UE is further adapted to, in association with performing a LTM cell switch procedure from a source cell to a target cell where the source cell is the serving cell of the UE and the target cell is one of the one or more LTM candidate cells, either perform UE-based TA estimation for the target cell or not, based, at least in part, on whether the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

[0042] Embodiments of a method performed by a network node for LTM are also disclosed. In one embodiment, a method performed by a network node for LTM comprises sending, to a UE, information that configures the UE with one TA estimation group for each of two or more configured cells of the UE, the two or more configured cells comprising a serving cell of the UE and one or more LTM candidate cells. The method further comprises sending an LTM cell switch command to the UE, the LTM cell switch command being a command to perform an LTM cell switch procedure from a source cell to a target cell.

[0043] In one embodiment, the method further comprises sending, to the UE, an indication regarding whether or not the UE is allowed to perform UE-based TA estimation. In one embodiment, the indication regarding whether or not the UE is allowed to perform UE-based TA estimation is specific to the LTM candidate cell that is the target cell. In one embodiment, sending the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending the indication via an RRCReconfiguration message that configures the LTM candidate cell that is the target cell.

[0044] In one embodiment, the indication regarding whether or not the UE is allowed to perform UE-based TA estimation is common to all of the one or more LTM candidate cells configured for the UE. In one embodiment, sending the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending the indication via an RRCReconfiguration message that configures a reference configuration for LTM.

[0045] In one embodiment, sending the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending the indication via the associated LTM cell switch command.

[0046] In one embodiment, sending the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending the indication via system information broadcasted on the serving cell.

[0047] In one embodiment, sending the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending the indication via a PDCCH order.

[0048] In one embodiment, sending the information that configures the UE with the one TA estimation group for each of the two or more configured cells of the UE comprises, for each configured cell, sending information that configures the one TA estimation group for the configured cell as part of a configuration of the configured cell.

[0049] Corresponding embodiments of a network node are also disclosed. In one embodiment, a network node for LTM is adapted to send, to a UE, information that configures the UE with one TA estimation group for each of two or more configured cells of the UE, the two or more configured cells comprising a serving cell of the UE and one or more LTM candidate cells. The network node is further adapted to send an LTM cell switch command to the UE, the LTM cell switch command being a command to perform an LTM cell switch procedure from a source cell to a target cell.

[0050] In one embodiment, a network node for LTM comprises processing circuitry configured to cause the network node to send, to a UE, information that configures the UE with one TA estimation group for each of two or more configured cells of the UE, the two or more configured cells comprising a serving cell of the UE and one or more LTM candidate cells. The processing circuitry is further configured to cause the network node to send an LTM cell switch command to the UE, the LTM cell switch command being a command to perform an LTM cell switch procedure from a source cell to a target cell.

[0051] Brief Description of the Drawings

[0052] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0053] Figure 1 illustrates a system including entities involved in embodiments of the present disclosure;

[0054] Figure 2 illustrates an example embodiment in which a Timing Advance (TA) estimation group is provided as part of the Radio Resource Control (RRC) Information Element (IE) LTM- Candidateld-rl8;

[0055] Figure 3 illustrates another example embodiment in which a TA estimation group for a serving cell is provided as part of the RRC IE LTM-Config-rl8;

[0056] Figure 4 illustrates a procedure performed by a User Equipment (UE) and a serving network node for Layer 1 (LI) / Layer (2) Triggered Mobility (LTM) cell switch from a source cell operated by the serving network node to a target cell operated by, e.g., a target network node, in accordance with an example embodiment of the present disclosure;

[0057] Figure 5 shows an example of a communication system in accordance with some embodiments;

[0058] Figure 6 shows a UE in accordance with some embodiments;

[0059] Figure 7 shows a network node in accordance with some embodiments;

[0060] Figure 8 is a block diagram of a host, which may be an embodiment of the host of Figure 5, in accordance with various aspects described herein; and

[0061] Figure 9 is a block diagram illustrating a virtualization environment in which functions implemented by some embodiments may be virtualized.

[0062] Detailed Description

[0063] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure. 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.

[0064] There currently exist certain challenge(s). As described in the Background, in 3rd Generation Partnership Project (3GPP), Radio Access Network (RAN) Working Group (WG) 1 (RANI) has agreed to support a User Equipment (UE)-based Timing Advance (TA) measurement, where the UE estimates the TA of a candidate cell (a target cell) using the TA of the current serving cell (the source cell) and the receive (Rx) timing difference between current serving cell (the source cell) and candidate cell (the target cell). This procedure will only work if the transmissions from source and target cell are synchronized. In other words, this UE-based TA adjustment will only work for certain pairs of cells.

[0065] Since the configuration is provided per candidate cell, it is unclear how the UE would be provided with the information that UE-based TA estimation would be performed for a certain pair of cells. It is then not possible to configure UE-based TA estimation as part of the configuration for a candidate cell since it also depends on the current serving cell. If UE-based TA estimation is included in the candidate cell configuration, the configuration would have to be updated when the serving cell changes.

[0066] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. Systems and methods are disclosed herein for configuring a UE to perform UE-based TA adjustment among a current serving cell of the UE and all candidate cells without requiring intermediate Radio Resource Control (RRC) reconfiguration.

[0067] Certain embodiments may provide one or more of the following technical advantage(s). Embodiments of the systems and methods disclosed herein may enable the network to configure the UE with UE-based TA estimation for all cell pairs in an Ll / L2-Triggered Mobility (LTM) cell-switch, without requiring any RRC reconfiguration after the execution of an LTM cellswitch. In other words, UE-based TA estimation is made possible also for subsequent LTM execution.

[0068] Before further describing embodiments of the present disclosure, the following notes regarding terminology used herein is beneficial. The description herein 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, Ll-mobility, LI based mobility, L1 / L2- centric inter-cell mobility, L1 / L2 inter-cell mobility Ll / 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 Primary Cell (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 Secondary Cell(s) (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 Master Cell Group (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 Information Element (IE) CellGroupConfig for an LTM candidate cell and / or an embedded RRC Reconfiguration for an LTM candidate cell.

[0069] As used herein, 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 referred to herein as an “LTM candidate cell” or a “neighbor cell”), using LTM. In the context of 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 the present disclosure, 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 MCG and / or Primary Secondary Cell (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.

[0070] The term “subsequent 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 referred to herein as an “LTM candidate cell” or a “neighbor cell”), using LTM, without the need of a further reconfiguration.

[0071] Even if the term “switch of cells” 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).

[0072] The description herein refers to a “LTM candidate cell”, which is a cell the UE is configured with when configured with Ll / L2-triggered mobility, i.e., a cell the UE can move to in an LTM cell switch procedure, upon reception of an 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. An LTM candidate cell is a cell the UE may perform measurements on (e.g., Channel State Information (CSI) measurements) so that the UE reports these measurements and network may take educated decision on which beam (e.g., Transmission Configuration Indication (TCI) state) and / or cell to which the UE is to be switched. 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).

[0073] The description herein 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 Ll / L2-Triggered Mobility. An 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). An 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 an MCG); (ii) the PSCell configuration and one or more SCell configuration(s) of a 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.

[0074] The actual LTM candidate cell configuration and its exact content and / or structure of this Information Element (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 (Medium Access Control (MAC) Control Element (GE)) 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 Distributed Unit (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 present disclosure, unless stated otherwise, this complete LTM candidate cell configuration may also be considered as an LTM candidate cell configuration.

[0075] The description herein refers to “serving cell”. A serving cell is a cell configured for the UE for example an SpCell, PCell, PSCell or SCell.

[0076] The description herein 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.

[0077] The description herein 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.

[0078] The description herein refers to a “TA value”, which may refer to a Timing Advance (TA) value. In the description herein, a “TA value” may correspond to an actual TA value to be applied or an indication of a TA value, such as an integer value the UE receives which maps to an actual TA value or shift to be applied for UL transmissions. One example of a TA value is a Timing Advance Command, which comprises a number of bits indicating an index value TA used to control the amount of timing adjustment that the MAC entity has to apply for a candidate for an UL transmission on, e.g., Sounding Reference Signal (SRS), Physical Uplink Control Channel (PUCCH), Physical Uplink Shared Channel (PUSCH), etc. The TA value may be delivered to the UE in the LTM cell switch command.

[0079] Embodiments of the solution(s) described herein are applicable for the case in which the UE transmit an uplink (UL) signal for TA establishment or update at a first point in time (e.g. timing for UL preamble transmission) and receives at a second point in time the LTM cell switch command, which is the timing in which the UE starts to operate in the LTM candidate cell indicated in the LTM cell switch command.

[0080] The description herein also refers to “UE-based TA estimation”, which refers to a procedure where the UE estimates the TA of a target cell using quantities the UE knows or can measure. For example, the UE may estimate the TA of a target cell from the TA of the source cell, and the difference between the propagation delays of the target and the source. The UE may, e.g., estimate the difference between the propagation delays from the difference between the receive timing of the DL transmissions received from the target and the source.

[0081] The description herein also refers to “TA estimation group” which refers to the case on where a certain LTM candidate cell (and / or the serving cell) belongs to a group where all the other cells within the same group are synchronized to each other. For example, if Cell A and Cell B both belong to the TA estimation group with ID 1, this means that Cell A and Cell B are synchronized and UE is able to perform the UE-based TA estimation procedure in case an LTM cell switch procedure is executed from Cell A to Cell B and vice versa.

[0082] Figure 1 illustrates a system 100 including entities involved in embodiments of the present disclosure. As illustrated, the system 100 includes a User Equipment (UE) 102, a source network node 104, a target network node 106, and optionally a third network node 108. The UE 102 is a wireless terminal, such as a cellular smartphone, sometimes connected to the source network node 104 over a wireless interface 110 and sometimes connected to the target network node 106, to which the UE 102 is connected over a wireless interface 112.

[0083] In the context of a mobility procedure, such as an LTM cell switch procedure, for the UE, the source network node 104, sometimes also referred to as the serving network node, controls a source cell 114 (sometimes called serving cell or Special Cell (SpCell)). The target network node 106 controls a target cell 116 (sometimes called neighbor cell, candidate cell or LTM candidate cell). Each of source network node 104 and the target network node 106 may be a base station such as, e.g., gNB, or, e.g., in case of a distributed Central Unit (CU) / Distributed Unit (DU) Radio Access Network (RAN) architecture, a distributed unit, sometimes known as either gNB- DU or DU. Hence the source network node 104 corresponds to a source DU (S-DU), sometimes also known as serving DU, and the target network node 106 corresponds to a target DU (T-DU), sometimes called neighbor DU or candidate DU (C-DU). Both the source network node 104 and the target network node 106 are connected to a third network node 108, sometimes also referred to as serving network node, via respective interfaces 118 and 120. The source network node 104 and the target network node 106 may be the same network node. In some scenarios, the source network node 104 and the target network node 106 may be connected to different third network nodes 108.

[0084] Further, the third network node 108 may, e.g. in case of a distributed CU / DU RAN architecture, be a central unit (CU), sometimes referred to as the serving CU, known as either a gNB-CU, CU, gNB-CU-Control Plane (CP) or gNB-CU-User Plane (UP), or a core network node such as a User Plane Function (UPF) or an Access and Mobility management Function (AMF).

[0085] In one embodiment of the present disclosure, the UE (e.g., UE 102) is configured with one TA estimation group for each cell configuration. The TA estimation group could be, e.g., an integer. TA estimation groups are configured for the serving cell, as well as for each candidate cell. When the UE executes an LTM cell switch procedure from a source cell to a target cell, and if the TA estimation group for the source and target cell are equal, the UE performs UE-based TA estimation. The UE would then ignore any TA command that is provided in the LTM cell switch command. If the TA estimation group for the source and target cell are not equal, the UE would not perform UE-based TA estimation. The UE would instead apply the TA value included in the LTM cell switch command.

[0086] In a related embodiment, even if the UE is provided with a TA estimation group for the serving cell and for each LTM candidate cell, the network may still indicate to the UE on whether the UE is allowed to perform the UE-based TA estimation procedure or not. This indication can be a simple 1 -bit where 1 means the UE is allowed to perform the UE-based TA estimation procedure and 0 that is not allowed (or vice versa). In case the network indicates to the UE that is not allowed to perform the UE-based TA estimation procedure, the UE ignores any TA estimation group received and instead applies the TA value received in the LTM cell switch command, if received. In this case, the indication may be included according to one or more of the following option:

[0087] • Within an RRCReconfiguration message that is used to configure an LTM candidate cell; o In such a case, the indication would be specific for a certain LTM candidate cell.

[0088] • Within an RRCReconfiguration message that is used to configure a reference configuration for LTM; o In such a case, the indication is common for all the LTM candidate cells • Within the LTM cell switch command; o In this case, the indication is only related to the LTM cell switch from a source cell to a target cell.

[0089] • Within a system information message broadcasted by the serving cell; or

[0090] • Within a Physical Downlink Control Channel (PDCCH) order.

[0091] In a related embodiment, the UE is provided the TA estimation group as part of the RRC configuration for the serving cell and each candidate cell. For example, in one embodiment, the TA estimation group is provided as part of the RRC IE LTM-CandidateId-rl8, as depicted in Figure 2 (additions are underlined).

[0092] As another example, in one embodiment, the TA estimation group for the serving cell is provided as part of the RRC IE LTM-Config-rl8, as depicted in Figure 3 (additions are underlined):

[0093] In one dependent embodiment, the TA estimation group may alternatively be referred to as any one or more of the following:

[0094] • TA estimation key

[0095] • UE-based TA group ID

[0096] • UE-based TA key

[0097] • TA estimation ID

[0098] • UE-based TA group ID

[0099] • UE-based TA key ID

[0100] • UE-based TA key

[0101] Figure 4 illustrates a procedure performed by a UE (e.g., UE 102) and a serving network node (e.g., source network node 104) for LTM cell switch from a source cell (operated by the serving network node) to a target cell (e.g., operated by the target network node 106), in accordance with an example embodiment of the present disclosure. Note that optional steps are represented in Figure 4 by dashed lines / boxes. Further, while the actions performed by the various nodes are referred to as “steps” and illustrated in Figure 4 as occurring in a particular order, these steps may be performed in any suitable order and / or some of these steps may be performed in parallel.

[0102] As illustrated in Figure 4, the serving network node transmits, and the UE receives, information that configures the UE with one TA estimation group for each of two or more cells configured for the UE (i.e., for each cell configuration) (step 400). In other words, the information received from the network in step 400 configures one TA estimation group for each configured cell of the UE, where the configured cells of the UE include the serving cell of the UE and one or more LTM candidate cells. Details regarding example embodiments of the particular information and the messages used to send this information to the UE are described above and are equally applicable here.

[0103] Optionally, the network transmits, and the UE receives, an indication regarding whether the UE is allowed to perform UE-based TA estimation (step 402). As discussed above, this indication may be specific for each LTM candidate cell (e.g., included in the RRCReconfiguration message used to configure the LTM candidate cell) or common for all LTM candidate cells (e.g., included in an RRCReconfiguration message used to configure a reference configuration for LTM). As another alternative, the indication may be included in the LTM switch command (see below), in system information broadcasted by the serving network node on the serving cell, or in a PDCCH order (e.g., a PDCCH order associated with L1 / L2 mobility such as, e.g., a PDCCH order to perform a RACH procedure for a candidate cell(s). Other details regarding this indication described above are equally applicable here to step 402.

[0104] In order to enable LTM, in this example, the UE performs measurements (e.g., LI measurements) on the LTM candidate cells configured for the UE (step 404). These measurements may include, for example, CSI measurements such as, e.g., SS-RSRP measurements, Ll-RSRP measurements per SSB, or the like. The UE reports measurements for one or more of the LTM candidate cells (e.g., for LTM cells for which the corresponding measurements satisfy one or more predefined criteria for reporting to the network) to the serving network node (step 406). Based on the measurements, the serving network node decides to trigger LTM cell switch from a source cell (e.g., the serving cell operated by the serving network node) to a target cell, which in this example is a LTM candidate cell operated by the target network node (e.g., target network node 106), and sends a corresponding LTM cell switch command to the UE (step 408). In some embodiments, the LTM cell switch command may include a TA value for the target cell (i.e., for the candidate LTM cell that is the target cell for the LTM cell switch).

[0105] Responsive to the LTM cell switch command, the UE performs, or executes, an LTM cell switch procedure from the source cell to the target cell (step 410). In one embodiment (e.g., an embodiment in which there is no indication received from the network regarding whether the UE is allowed to perform UE-based TA estimation, i.e., there is no step 402), in association with the LTM cell switch from the source cell to the target cell, the UE performs UE-based TA estimation for the target cell (and ignores any TA value that is provided in the LTM cell switch command) if the TA estimation group configured for the target cell is the same as the TA estimation group configured for the source cell (step 410A-1). Otherwise, the UE applies the TA value (for TA for the target cell) included in the LTM cell switch command (step 410A-2).

[0106] In another embodiment in which the UE receives the indication from the serving network node in step 402, the UE performs UE-based TA estimation for the target cell if (e.g., only if) both: (a) the indication received in step 402 indicates that the UE is allowed to perform UE-based TA estimation and (b) the TA estimation group configured for the target cell is the same as the TA estimation group configured for the source cell (step 410B-1). Otherwise, if the indication of step 402 indicates that the UE is not allowed to perform UE-based TA estimation or if the indication of step 402 indicates that the UE is allowed to perform UE-based TA estimation but the source and target cells have different TA estimation groups, the UE applies the TA value (for TA for the target cell) included in the LTM cell switch command (step 41 OB-2).

[0107] Figure 5 shows an example of a communication system 500 in accordance with some embodiments.

[0108] In the example, the communication system 500 includes a telecommunication network 502 that includes an access network 504, such as a Radio Access Network (RAN), and a core network 506, which includes one or more core network nodes 508. The access network 504 includes one or more access network nodes, such as network nodes 510A and 510B (one or more of which may be generally referred to as network nodes 510), or any other similar Third Generation Partnership Project (3GPP) access nodes or non-3GPP Access Points (APs). 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 502 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network 502 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 502, including one or more network nodes 510 and / or core network nodes 508.

[0109] Examples of an ORAN network node include an Open Radio Unit (O-RU), 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 Al, Fl, Wl, El, 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 0-2 interface defined by the 0-RAN Alliance or comparable technologies. The network nodes 510 facilitate direct or indirect connection of User Equipment (UE), such as by connecting UEs 512A, 512B, 512C, and 512D (one or more of which may be generally referred to as UEs 512) to the core network 506 over one or more wireless connections.

[0110] 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 500 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 500 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0111] The UEs 512 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 510 and other communication devices. Similarly, the network nodes 510 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs 512 and / or with other network nodes or equipment in the telecommunication network 502 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 502.

[0112] In the depicted example, the core network 506 connects the network nodes 510 to one or more hosts, such as host 516. 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 506 includes one more core network nodes (e.g., core network node 508) 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 508. 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).

[0113] The host 516 may be under the ownership or control of a service provider other than an operator or provider of the access network 504 and / or the telecommunication network 502, and may be operated by the service provider or on behalf of the service provider. The host 516 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as 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.

[0114] As a whole, the communication system 500 of Figure 5 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system 500 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 Second, Third, Fourth, or Fifth Generation (2G, 3G, 4G, or 5G) standards, or any applicable future generation standard (e.g., Sixth Generation (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.

[0115] In some examples, the telecommunication network 502 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunication network 502 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 502. For example, the telecommunication network 502 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 Internet of Things (loT) services to yet further UEs.

[0116] In some examples, the UEs 512 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 504 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 504. Additionally, a UE may be configured for operating in single- or multi -Radio Access Technology (RAT) or multi-standard mode. For example, a UE may operate with any one or combination of WiFi, New Radio (NR), and LTE, i.e. being configured for Multi -Radio Dual Connectivity (MR-DC), such as Evolved UMTS Terrestrial RAN (E-UTRAN) NR - Dual Connectivity (EN-DC).

[0117] In the example, a hub 514 communicates with the access network 504 to facilitate indirect communication between one or more UEs (e.g., UE 512C and / or 512D) and network nodes (e.g., network node 510B). In some examples, the hub 514 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 514 may be a broadband router enabling access to the core network 506 for the UEs. As another example, the hub 514 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 510, or by executable code, script, process, or other instructions in the hub 514. As another example, the hub 514 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 514 may be a content source. For example, for a UE that is a Virtual Reality (VR) headset, display, loudspeaker or other media delivery device, the hub 514 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 514 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 514 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0118] The hub 514 may have a constant / persistent or intermittent connection to the network node 510B. The hub 514 may also allow for a different communication scheme and / or schedule between the hub 514 and UEs (e.g., UE 512C and / or 512D), and between the hub 514 and the core network 506. In other examples, the hub 514 is connected to the core network 506 and / or one or more UEs via a wired connection. Moreover, the hub 514 may be configured to connect to a Machine-to-Machine (M2M) service provider over the access network 504 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 510 while still connected via the hub 514 via a wired or wireless connection. In some embodiments, the hub 514 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 510B. In other embodiments, the hub 514 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and the network node 51 OB, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0119] Figure 6 shows a UE 600 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 Internet Protocol (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 3GPP, including a Narrowband Internet of Things (NB-IoT) UE, a Machine Type Communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0120] A UE may support Device-to-Device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), Vehi cl e-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).

[0121] The UE 600 includes processing circuitry 602 that is operatively coupled via a bus 604 to an input / output interface 606, a power source 608, memory 610, a communication interface 612, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 6. 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. The processing circuitry 602 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 610. The processing circuitry 602 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 602 may include multiple Central Processing Units (CPUs).

[0122] In the example, the input / output interface 606 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 600. 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.

[0123] In some embodiments, the power source 608 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 608 may further include power circuitry for delivering power from the power source 608 itself, and / or an external power source, to the various parts of the UE 600 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 608. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 608 to make the power suitable for the respective components of the UE 600 to which power is supplied.

[0124] The memory 610 may be or be configured to include memory such as Random Access Memory (RAM), Read Only Memory (ROM), Programmable ROM (PROM), Erasable PROM (EPROM), Electrically EPROM (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 610 includes one or more application programs 614, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 616. The memory 610 may store, for use by the UE 600, any of a variety of various operating systems or combinations of operating systems.

[0125] The memory 610 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 RAM (SDRAM), external micro-DIMM SDRAM, smartcard memory such as a tamper resistant module in the form of a Universal Integrated Circuit Card (UICC) including one or more Subscriber Identity Modules (SIMs), such as a Universal SIM (USIM) and / or Internet Protocol Multimedia Services Identity Module (ISIM), other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as a ‘SIM card.’ The memory 610 may allow the UE 600 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 610, which may be or comprise a device-readable storage medium.

[0126] The processing circuitry 602 may be configured to communicate with an access network or other network using the communication interface 612. The communication interface 612 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 622. The communication interface 612 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 618 and / or a receiver 620 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 618 and receiver 620 may be coupled to one or more antennas (e.g., the antenna 622) and may share circuit components, software, or firmware, or alternatively be implemented separately.

[0127] In the illustrated embodiment, communication functions of the communication interface 612 may include cellular communication, WiFi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, NFC, 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 according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband CDMA (WCDMA), GSM, LTE, NR, UMTS, WiMax, Ethernet, Transmission Control Protocol / Internet Protocol (TCP / IP), Synchronous Optical Networking (SONET), Asynchronous Transfer Mode (ATM), Quick User Datagram Protocol Internet Connection (QUIC), Hypertext Transfer Protocol (HTTP), and so forth.

[0128] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 612, 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).

[0129] 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 to a robotic arm performing a medical procedure according to the received input.

[0130] A UE, when in the form of an 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 a device which is or which is embedded in: a connected refrigerator or freezer, a television, 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 VR, a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or itemtracking 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 of the intended application of the loT device in addition to other components as described in relation to the UE 600 shown in Figure 6.

[0131] 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 3 GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship, an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0132] 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.

[0133] Figure 7 shows a network node 700 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, APs (e.g., radio APs), Base Stations (BSs) (e.g., radio BSs, Node Bs, evolved Node Bs (eNBs), NR. Node Bs (gNBs)), and 0-RAN nodes or components of an 0-RAN node (e.g., 0-RU, 0-DU, O- CU).

[0134] 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 0-RAN access node), and / or Remote Radio Units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such RRUs 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).

[0135] 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 BS 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).

[0136] The network node 700 includes processing circuitry 702, memory 704, a communication interface 706, and a power source 708. The network node 700 may be composed of multiple physically separate components (e.g., a NodeB component and an 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 700 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 700 may be configured to support multiple RATs. In such embodiments, some components may be duplicated (e.g., separate memory 704 for different RATs) and some components may be reused (e.g., a same antenna 710 may be shared by different RATs). The network node 700 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 700, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, Long Range Wide Area Network (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 the network node 700.

[0137] The processing circuitry 702 may comprise a combination of one or more of a microprocessor, controller, microcontroller, CPU, DSP, ASIC, FPGA, 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 700 components, such as the memory 704, to provide network node 700 functionality.

[0138] In some embodiments, the processing circuitry 702 includes a System on a Chip (SOC). In some embodiments, the processing circuitry 702 includes one or more of Radio Frequency (RF) transceiver circuitry 712 and baseband processing circuitry 714. In some embodiments, the RF transceiver circuitry 712 and the baseband processing circuitry 714 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 the RF transceiver circuitry 712 and the baseband processing circuitry 714 may be on the same chip or set of chips, boards, or units.

[0139] The memory 704 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, RAM, 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 702. The memory 704 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 702 and utilized by the network node 700. The memory 704 may be used to store any calculations made by the processing circuitry 702 and / or any data received via the communication interface 706. In some embodiments, the processing circuitry 702 and the memory 704 are integrated.

[0140] The communication interface 706 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 706 comprises port(s) / terminal(s) 716 to send and receive data, for example to and from a network over a wired connection. The communication interface 706 also includes radio front-end circuitry 718 that may be coupled to, or in certain embodiments a part of, the antenna 710. The radio front-end circuitry 718 comprises filters 720 and amplifiers 722. The radio front-end circuitry 718 may be connected to the antenna 710 and the processing circuitry 702. The radio front-end circuitry 718 may be configured to condition signals communicated between the antenna 710 and the processing circuitry 702. The radio front-end circuitry 718 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 718 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of the filters 720 and / or the amplifiers 722. The radio signal may then be transmitted via the antenna 710. Similarly, when receiving data, the antenna 710 may collect radio signals which are then converted into digital data by the radio front-end circuitry 718. The digital data may be passed to the processing circuitry 702. In other embodiments, the communication interface 706 may comprise different components and / or different combinations of components.

[0141] In certain alternative embodiments, the network node 700 does not include separate radio front-end circuitry 718; instead, the processing circuitry 702 includes radio front-end circuitry and is connected to the antenna 710. Similarly, in some embodiments, all or some of the RF transceiver circuitry 712 is part of the communication interface 706. In still other embodiments, the communication interface 706 includes the one or more ports or terminals 716, the radio frontend circuitry 718, and the RF transceiver circuitry 712 as part of a radio unit (not shown), and the communication interface 706 communicates with the baseband processing circuitry 714, which is part of a digital unit (not shown).

[0142] The antenna 710 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 710 may be coupled to the radio front-end circuitry 718 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 710 is separate from the network node 700 and connectable to the network node 700 through an interface or port.

[0143] The antenna 710, the communication interface 706, and / or the processing circuitry 702 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node 700. Any information, data, and / or signals may be received from a UE, another network node, and / or any other network equipment. Similarly, the antenna 710, the communication interface 706, and / or the processing circuitry 702 may be configured to perform any transmitting operations described herein as being performed by the network node 700. Any information, data, and / or signals may be transmitted to a UE, another network node, and / or any other network equipment.

[0144] The power source 708 provides power to the various components of the network node 700 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 708 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 700 with power for performing the functionality described herein. For example, the network node 700 may be connectable to an external power source (e.g., the power grid or an electricity outlet) via input circuitry or an interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 708. As a further example, the power source 708 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. Embodiments of the network node 700 may include additional components beyond those shown in Figure 7 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 700 may include user interface equipment to allow input of information into the network node 700 and to allow output of information from the network node 700. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 700.

[0145] Figure 8 is a block diagram of a host 800, which may be an embodiment of the host 516 of Figure 5, in accordance with various aspects described herein. As used herein, the host 800 may be or comprise various combinations of hardware and / or software including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host 800 may provide one or more services to one or more UEs.

[0146] The host 800 includes processing circuitry 802 that is operatively coupled via a bus 804 to an input / output interface 806, a network interface 808, a power source 810, and memory 812. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figures 6 and 7, such that the descriptions thereof are generally applicable to the corresponding components of the host 800.

[0147] The memory 812 may include one or more computer programs including one or more host application programs 814 and data 816, which may include user data, e.g. data generated by a UE for the host 800 or data generated by the host 800 for a UE. Embodiments of the host 800 may utilize only a subset or all of the components shown. The host application programs 814 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), Moving Picture Experts Group (MPEG), VP9) and audio codecs (e.g., Free Lossless Audio Codec (FL AC), Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, and heads-up display systems). The host application programs 814 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host 800 may select and / or indicate a different host for Over-The-Top (OTT) services for a UE. The host application programs 814 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (DASH or MPEG-DASH), etc.

[0148] Figure 9 is a block diagram illustrating a virtualization environment 900 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 900 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 900 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.

[0149] Applications 902 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 900 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0150] Hardware 904 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 906 (also referred to as hypervisors or VM Monitors (VMMs)), provide VMs 908A and 908B (one or more of which may be generally referred to as VMs 908), and / or perform any of the functions, features, and / or benefits described in relation with some embodiments described herein. The virtualization layer 906 may present a virtual operating platform that appears like networking hardware to the VMs 908.

[0151] The VMs 908 comprise virtual processing, virtual memory, virtual networking, or interface and virtual storage, and may be run by a corresponding virtualization layer 906. Different embodiments of the instance of a virtual appliance 902 may be implemented on one or more of the VMs 908, 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.

[0152] In the context of NFV, a VM 908 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 908, and that part of the hardware 904 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs 908, 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 908 on top of the hardware 904 and corresponds to the application 902.

[0153] The hardware 904 may be implemented in a standalone network node with generic or specific components. The hardware 904 may implement some functions via virtualization. Alternatively, the hardware 904 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 910, which, among others, oversees lifecycle management of the applications 902. In some embodiments, the hardware 904 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 RAN or a base station. In some embodiments, some signaling can be provided with the use of a control system 912 which may alternatively be used for communication between hardware nodes and radio units.

[0154] 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.

[0155] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored 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 hardwired 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.

[0156] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

[0157] Some example embodiments of the present disclosure are as follows:

[0158] Group A Embodiments

[0159] Embodiment 1 : A method performed by a User Equipment, UE, (102) for Layer 1, LI, / Layer 2, L2, Triggered Mobility, LTM, the method comprising: receiving (400), from a serving network node (104), information that configures the UE (102) with one Timing Advance, TA, estimation group for each of two or more configured cells of the UE (102), the two or more configured cells comprising a serving cell of the UE (102) and one or more LTM candidate cells; performing (410) a LTM cell switch procedure from a source cell to a target cell, wherein the source cell is the serving cell of the UE (102) and the target cell is one of the one or more LTM candidate cells; in association with performing (410) the LTM cell switch procedure from the source cell to the target cell, either performing (410A-1 or 410B-1) UE-based TA estimation for the target cell or not, based, at least in part, on whether the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

[0160] Embodiment 2: The method of embodiment 1, wherein either performing (410A-1) UE- based TA estimation or not comprises: performing (410A-1) UE-based TA estimation for the target cell if the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

[0161] Embodiment 3: The method of embodiment 2, wherein either performing (410A-1) UE- based TA estimation for the target cell or not further comprises applying (410A-2) a TA value comprised in an associated LTM cell switch command received by the UE (102) if the TA estimation group configured for the source cell is not the same as the TA estimation group configured for the target cell.

[0162] Embodiment 4: The method of embodiment 3, further comprising receiving (408) the LTM cell switch command from the serving network node (104), the LTM cell switch command being a command to perform the LTM cell switch procedure from the source cell to the target cell.

[0163] Embodiment 5: The method of embodiment 1, further comprising receiving (402), from the serving network node (104), an indication regarding whether or not the UE is allowed to perform UE-based TA estimation for the target cell.

[0164] Embodiment 6: The method of embodiment 5, wherein either performing (410B-1) UE- based TA estimation for the target cell or not comprises: performing (410B-1) UE-based TA estimation for the target cell if: (a) the indication received from the serving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell and (b) the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

[0165] Embodiment 7: The method of embodiment 6, wherein either performing (410B-1) UE- based TA estimation for the target cell or not further comprises: applying (41 OB-2) a TA value comprised in an associated LTM cell switch command received by the UE (102) if either: (a) the indication received from the serving network node indicates that the UE is not allowed to perform UE-based TA estimation for the target cell or (b) the TA estimation group configured for the source cell is not the same as the TA estimation group configured for the target cell.

[0166] Embodiment 8: The method of embodiment 7, further comprising receiving (408) the LTM cell switch command from the serving network node (104), the LTM cell switch command being a command to perform the LTM cell switch procedure from the source cell to the target cell. Embodiment 9: The method of any of embodiments 5 to 8, wherein the indication regarding whether or not the UE is allowed to perform UE-based TA estimation is specific to the LTM candidate cell that is the target cell.

[0167] Embodiment 10: The method of embodiment 9, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for the target cell comprises receiving (402) the indication via an RRCReconfiguration message that configures the LTM candidate cell that is the target cell.

[0168] Embodiment 11 : The method of any of embodiments 5 to 8, wherein the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell is common to all of the one or more LTM candidate cells configured for the UE.

[0169] Embodiment 12: The method of embodiment 11, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving (402) the indication via an RRCReconfiguration message that configures a reference configuration for LTM.

[0170] Embodiment 13 : The method of any of embodiments 5 to 8, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving (402) the indication via the associated LTM cell switch command.

[0171] Embodiment 14: The method of any of embodiments 5 to 8, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving (402) the indication via system information broadcasted on the serving cell.

[0172] Embodiment 15: The method of any of embodiments 5 to 8, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving (402) the indication via a PDCCH order.

[0173] Embodiment 16: The method of any of embodiments 1 to 15, wherein receiving (400) the information that configures the UE (102) with the one TA estimation group for each of the two or more configured cells of the UE (102) comprises, for each configured cell, receiving information that configures the one TA estimation group for the configured cell as part of a configuration of the configured cell.

[0174] Group B Embodiments

[0175] Embodiment 17: A method performed by a network node for Layer 1, LI, / Layer 2, L2, Triggered Mobility, LTM, the method comprising: sending (400), to a User Equipment, UE, (102), information that configures the UE (102) with one Timing Advance, TA, estimation group for each of two or more configured cells of the UE (102), the two or more configured cells comprising a serving cell of the UE (102) and one or more LTM candidate cells.

[0176] Embodiment 18: The method of embodiment 17, further comprising sending (408) an LTM cell switch command to the UE (102), the LTM cell switch command being a command to perform an LTM cell switch procedure from a source cell to a target cell.

[0177] Embodiment 19: The method of embodiment 17 or 18, further comprising sending (402), to the UE (102), an indication regarding whether or not the UE is allowed to perform UE-based TA estimation.

[0178] Embodiment 20: The method of embodiment 19, wherein the indication regarding whether or not the UE is allowed to perform UE-based TA estimation is specific to the LTM candidate cell that is the target cell.

[0179] Embodiment 21 : The method of embodiment 20, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via an RRCReconfiguration message that configures the LTM candidate cell that is the target cell.

[0180] Embodiment 22: The method of embodiment 19, wherein the indication regarding whether or not the UE is allowed to perform UE-based TA estimation common to all of the one or more LTM candidate cells configured for the UE.

[0181] Embodiment 23 : The method of embodiment 22, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via an RRCReconfiguration message that configures a reference configuration for LTM.

[0182] Embodiment 24: The method of embodiment 19, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via the associated LTM cell switch command.

[0183] Embodiment 25: The method of embodiment 19, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via system information broadcasted on the serving cell.

[0184] Embodiment 26: The method of embodiment 19, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via a PDCCH order.

[0185] Embodiment 27: The method of any of embodiments 17 to 26, wherein sending (400) the information that configures the UE (102) with the one TA estimation group for each of the two or more configured cells of the UE (102) comprises, for each configured cell, sending information that configures the one TA estimation group for the configured cell as part of a configuration of the configured cell.

[0186] Group C Embodiments

[0187] Embodiment 28: A user equipment comprising: processing circuitry configured 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.

[0188] Embodiment 29: A network node comprising: processing circuitry configured to perform any of the steps of any of the Group B embodiments; and power supply circuitry configured to supply power to the processing circuitry.

[0189] Embodiment 30: A user equipment (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 UE.

[0190] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

Claims1. A method performed by a User Equipment, UE, (102) for Layer 1, LI, / Layer 2, L2, Triggered Mobility, LTM, the method comprising: receiving (400), from a serving network node (104), information that configures the UE (102) with one Timing Advance, TA, estimation group for each of two or more configured cells of the UE (102), the two or more configured cells comprising a serving cell of the UE (102) and one or more LTM candidate cells; and in association with performing (410) a LTM cell switch procedure from a source cell to a target cell where the source cell is the serving cell of the UE (1001) and the target cell is one of the one or more LTM candidate cells, either performing (410A-1 or 410B-1) UE-based TA estimation for the target cell or not, based, at least in part, on whether the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

2. The method of claim 1, wherein: the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell; and either performing (410A-1) UE-based TA estimation or not comprises performing (410A- 1) UE-based TA estimation for the target cell responsive to the TA estimation group configured for the source cell being the same as the TA estimation group configured for the target cell.

3. The method of claim 1, wherein: the TA estimation group configured for the source cell is not the same as the TA estimation group configured for the target cell; and either performing (410A-1) UE-based TA estimation or not comprises applying (410A-2) a TA value comprised in an associated LTM cell switch command received by the UE (102) responsive to the TA estimation group configured for the source cell not being the same as the TA estimation group configured for the target cell.

4. The method of claim 1, wherein either performing (410A-1) UE-based TA estimation or not comprises performing (410A-1) UE-based TA estimation for the target cell if the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

5. The method of claim 4, wherein either performing (410A-1) UE-based TA estimation for the target cell or not further comprises applying (410A-2) a TA value comprised in an associated LTM cell switch command received by the UE (102) if the TA estimation group configured for the source cell is not the same as the TA estimation group configured for the target cell.

6. The method of any of claims 1 to 5, further comprising receiving (408) an LTM cell switch command from the serving network node (104), the LTM cell switch command being a command to perform the LTM cell switch procedure from the source cell to the target cell.

7. The method of claim 1, further comprising receiving (402), from the serving network node (104), an indication regarding whether or not the UE is allowed to perform UE-based TA estimation for the target cell.

8. The method of claim 7, wherein: the indication received from the serving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell; the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell; and either performing (410A-1) UE-based TA estimation or not comprises performing (410A- 1) UE-based TA estimation for the target cell responsive to (a) the indication received from the serving network node indicating that the UE is allowed to perform UE-based TA estimation for the target cell and (b) the TA estimation group configured for the source cell being the same as the TA estimation group configured for the target cell.

9. The method of claim 7, wherein: the indication received from the serving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell; the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell; and either performing (410A-1) UE-based TA estimation or not comprises applying (410A-2) a TA value comprised in an associated LTM cell switch command received by the UE (102) responsive to the TA estimation group configured for the source cell not being the same as the TA estimation group configured for the target cell even though the indication received from theserving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell.

10. The method of claim 7, wherein either performing (410B-1) UE-based TA estimation for the target cell or not comprises: performing (410B-1) UE-based TA estimation for the target cell if: (a) the indication received from the serving network node indicates that the UE is allowed to perform UE-based TA estimation for the target cell and (b) the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

11. The method of claim 10, wherein either performing (410B-1) UE-based TA estimation for the target cell or not further comprises: applying (41 OB-2) a TA value comprised in an associated LTM cell switch command received by the UE (102) if either: (a) the indication received from the serving network node indicates that the UE is not allowed to perform UE-based TA estimation for the target cell or (b) the TA estimation group configured for the source cell is not the same as the TA estimation group configured for the target cell.

12. The method of any of claims 7 to 11, further comprising receiving (408) an LTM cell switch command from the serving network node (104), the LTM cell switch command being a command to perform the LTM cell switch procedure from the source cell to the target cell.

13. The method of any of claims 7 to 12, wherein the indication regarding whether or not the UE is allowed to perform UE-based TA estimation is specific to the LTM candidate cell that is the target cell.

14. The method of claim 13, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for the target cell comprises receiving (402) the indication via an RRCReconfiguration message that configures the LTM candidate cell that is the target cell.

15. The method of any of claims 7 to 12, wherein the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell is common to all of the one or more LTM candidate cells configured for the UE.

16. The method of claim 15, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving (402) the indication via an RRCReconfiguration message that configures a reference configuration for LTM.

17. The method of any of claims 7 to 12, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving (402) the indication via the associated LTM cell switch command.

18. The method of any of claims 7 to 12, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving (402) the indication via system information broadcasted on the serving cell.

19. The method of any of claims 7 to 12, wherein receiving (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation for a target cell comprises receiving (402) the indication via a Physical Downlink Control Channel, PDCCH, order.

20. The method of any of claims 1 to 19, wherein receiving (400) the information that configures the UE (102) with the one TA estimation group for each of the two or more configured cells of the UE (102) comprises, for each configured cell, receiving information that configures the one TA estimation group for the configured cell as part of a configuration of the configured cell.

21. A User Equipment, UE, (102) for Layer 1, LI, / Layer 2, L2, Triggered Mobility, LTM, the UE (102) adapted to: receive (400), from a serving network node (104), information that configures the UE (102) with one Timing Advance, TA, estimation group for each of two or more configured cells of the UE (102), the two or more configured cells comprising a serving cell of the UE (102) and one or more LTM candidate cells; and in association with performing (410) a LTM cell switch procedure from a source cell to a target cell where the source cell is the serving cell of the UE (1001) and the target cell is one of the one or more LTM candidate cells, either perform (410A-1 or 410B-1) UE-based TA estimation for the target cell or not, based, at least in part, on whether the TA estimation groupconfigured for the source cell is the same as the TA estimation group configured for the target cell.

22. The UE (102) of claim 21, further adapted to perform the method of any of claims 2 to 20.

23. A User Equipment, UE, (102; 600) for Layer 1, LI, / Layer 2, L2, Triggered Mobility, LTM, the UE (102; 600) comprising: a communication interface (612) comprising a transmitter (618) and a receiver (620); and processing circuitry (602) associated with the communication interface (612), the processing circuitry (602) configured to cause the UE (102; 600) to: receive (400), from a serving network node (104), information that configures the UE (102) with one Timing Advance, TA, estimation group for each of two or more configured cells of the UE (102), the two or more configured cells comprising a serving cell of the UE (102) and one or more LTM candidate cells; and in association with performing (410) a LTM cell switch procedure from a source cell to a target cell where the source cell is the serving cell of the UE (1001) and the target cell is one of the one or more LTM candidate cells, either perform (410A-1 or 410B-1) UE-based TA estimation for the target cell or not, based, at least in part, on whether the TA estimation group configured for the source cell is the same as the TA estimation group configured for the target cell.

24. The UE (102; 600) of claim 23, wherein the processing circuitry (602) is further configured to cause the UE (102; 600) to perform the method of any of claims 2 to 20.

25. A method performed by a network node for Layer 1, LI, / Layer 2, L2, Triggered Mobility, LTM, the method comprising: sending (400), to a User Equipment, UE, (102), information that configures the UE (102) with one Timing Advance, TA, estimation group for each of two or more configured cells of the UE (102), the two or more configured cells comprising a serving cell of the UE (102) and one or more LTM candidate cells; and sending (408) an LTM cell switch command to the UE (102), the LTM cell switch command being a command to perform an LTM cell switch procedure from a source cell to a target cell.

26. The method of claim 25, further comprising sending (402), to the UE (102), an indication regarding whether or not the UE is allowed to perform UE-based TA estimation.

27. The method of claim 26, wherein the indication regarding whether or not the UE is allowed to perform UE-based TA estimation is specific to the LTM candidate cell that is the target cell.

28. The method of claim 27, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via an RRCReconfiguration message that configures the LTM candidate cell that is the target cell.

29. The method of claim 26, wherein the indication regarding whether or not the UE is allowed to perform UE-based TA estimation is common to all of the one or more LTM candidate cells configured for the UE.

30. The method of claim 29, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via an RRCReconfiguration message that configures a reference configuration for LTM.

31. The method of claim 26, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via the associated LTM cell switch command.

32. The method of claim 26, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via system information broadcasted on the serving cell.

33. The method of claim 26, wherein sending (402) the indication regarding whether or not the UE is allowed to perform UE-based TA estimation comprises sending (402) the indication via a Physical Downlink Control Channel, PDCCH, order.

34. The method of any of claims 25 to 33, wherein sending (400) the information that configures the UE (102) with the one TA estimation group for each of the two or moreconfigured cells of the UE (102) comprises, for each configured cell, sending information that configures the one TA estimation group for the configured cell as part of a configuration of the configured cell.

35. A network node for Layer 1, LI, / Layer 2, L2, Triggered Mobility, LTM, the network node adapted to: send (400), to a User Equipment, UE, (102), information that configures the UE (102) with one Timing Advance, TA, estimation group for each of two or more configured cells of the UE (102), the two or more configured cells comprising a serving cell of the UE (102) and one or more LTM candidate cells; and send (408) an LTM cell switch command to the UE (102), the LTM cell switch command being a command to perform an LTM cell switch procedure from a source cell to a target cell.

36. The network node of claim 35, further adapted to perform the method of any of claims 26 to 34.

37. A network node (700) for Layer 1, LI, / Layer 2, L2, Triggered Mobility, LTM, the network node (700) comprising: a communication interface (706); and processing circuitry (702) associated with the communication interface (706), the processing circuitry (702) configured to cause the network node (700) to: send (400), to a User Equipment, UE, (102), information that configures the UE(102) with one Timing Advance, TA, estimation group for each of two or more configured cells of the UE (102), the two or more configured cells comprising a serving cell of the UE (102) and one or more LTM candidate cells; and send (408) an LTM cell switch command to the UE (102), the LTM cell switch command being a command to perform an LTM cell switch procedure from a source cell to a target cell.

38. The network node (700) of claim 37, wherein the processing circuitry (702) is further configured to cause the network node (700) to perform the method of any of claims 26 to 34.

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