Logging and reporting of timing-related information associated with UE mobility operation

Abstract

An example method, in a user equipment, UE, operating in a wireless network, comprises the step of receiving (510), from the wireless network, a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed. The method further comprises subsequently logging (520), in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between said receiving and said successful change or addition of cell or failed mobility procedure.

Description

[0001] LOGGING AND REPORTING OF TIMING-RELATED INFORMATION ASSOCIATED WITH UE MOBILITY OPERATION

[0002] TECHNICAL FIELD

[0003] The present application relates generally to the field of wireless networks, and more specifically to improving mobility of user equipment (UEs) across multiple cells in a wireless network, specifically mobility based on layer-1 (LI) and / or layer-2 (L2) procedures that incur less delay than conventional layer-3 mobility procedures.

[0004] BACKGROUND

[0005] Currently the fifth generation (5G) of cellular systems is being standardized within the Third- Generation Partnership Project (3GPP). NR is developed for maximum flexibility to support multiple and substantially different use cases. These include enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device-to- device (D2D), and several other use cases.

[0006] Figure 1 illustrates a high-level view of an exemplary 5G network architecture, consisting of a Next Generation Radio Access Network (NG-RAN, 199) and a 5G Core (5GC, 198). The NG-RAN can include one or more gNodeBs (gNBs) connected to the 5GC via one or more NG interfaces, such as gNBs (100, 150) connected via respective interfaces (102, 152). More specifically, the gNBs can be connected to one or more Access and Mobility Management Functions (AMFs) in the 5GC via respective NG-C interfaces and to one or more User Plane Functions (UPFs) in 5GC via respective NG- U interfaces. The 5GC can include various other network functions (NFs), such as Session Management Function(s) (SMF).

[0007] Figure 2 shows an exemplary configuration of NR user plane (UP) and control plane (CP) protocol stacks.

[0008] Although not shown in Figure 1, in some deployments the 5GC can be replaced by an Evolved Packet Core (EPC), which conventionally has been used together with a fourth generation (4G) Long-Term Evolution (LTE) Evolved UMTS RAN (E-UTRAN). In such deployments, gNBs (e.g., 100, 150) can connect to one or more Mobility Management Entities (MMEs) in EPC 198 via respective Sl-C interfaces. Similarly, gNBs can connect to one or more Serving Gateways (SGWs) in EPC via respective NG-U interfaces.

[0009] In addition, the gNBs can be connected to each other via one or more Xn interfaces, such as Xn interface (140) between gNBs (100, 150). The radio technology for the NG-RAN is often referred to as "New Radio" (NR). With respect to the NR interface to UEs, each of the gNBs can support frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. Each of the gNBs can serve a geographic coverage area including one or more cells and, in some cases, can also use various directional beams to provide coverage in the respective cells. In general, a DL "beam" is a coverage area of a network-transmitted reference signal (RS) that may be measured or monitored by a UE.

[0010] NG RAN logical nodes (e.g., gNB 100) include a Central Unit (CU or gNB-CU, e.g., 110) and one or more Distributed Units (DU or gNB-DU, e.g., 120, 130). CUs are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs. DUs are decentralized logical nodes that host lower layer protocols and can include, depending on the functional split option, various subsets of the gNB functions. Each CU and DU can include various circuitry needed to perform their respective functions, including processing circuitry, communication interface circuitry (e.g., transceivers), and power supply circuitry.

[0011] A gNB-CU connects to one or more gNB-DUs over respective Fl logical interfaces (e.g., 122 and 132 shown in Figure 1). However, a gNB-DU can be connected to only a single gNB-CU. The gNB-CU and its connected gNB-DU(s) are only visible to other gNBs and the 5GC as a gNB. In other words, the Fl interface is not visible beyond gNB-CU.

[0012] Seamless handovers are a key feature of 3GPP technologies. A UE is handed over from a source or serving cell, provided by a source node, to a target cell provided by a target node. Successful handovers ensure that the UE moves around in the coverage area of different cells without causing too many interruptions in the data transmission. However, handover can have various problems related to robustness. For example, a handover command (e.g., RRCReconfiguration message including a reconfigurationWithSync information element) is normally sent when the radio conditions for the UE are already quite bad and may not reach the UE before the UE's degraded connection with the source node / cell is dropped.

[0013] Upon receiving a handover command, a UE starts a timer T304 to monitor whether the handover is successful. Upon T304 expiry the UE considers the handover failed and performs recovery actions such as initiation of an RRC Re-establishment procedure including cell selection while another timer T311 is running. While T304 is running, the UE's radio resource control (RRC) layer triggers a randomaccess (RA) procedure with a target cell indicated in the reconfigurationWithSync IE. The handover is considered successful when the RA procedure is successfully completed before T304 expiry. The reconfiguration with sync procedure during handover is further defined in 3GPP TS 38.331 (vl7.2.0) section 5.3.5.5.2.

[0014] A RACH-less handover was specified for LTE in 3GPP Rel-14. If the UE receives a handover command with a rach-Skip field, the UE should perform the handover to the target cell without performing a RA procedure. The UE initiates T304 in a similar manner as described above, but the handover is considered successful if the UE successfully receives certain information from the network via the target cell indicated in the handover command.

[0015] When the UE moves between the coverage areas of two cells, a serving cell change needs to be performed at some point. Currently, serving cell change is triggered by layer 3 (L3, e.g., RRC) measurements and involves RRC signaling to change PCell and / or PSCell (e.g., when dual connectivity is configured), as well as release / add SCells (e.g., when CA is configured). Currently, L3 inter-cell mobility involves complete layer 2 (L2) and layer 1 (LI, i.e., PHY) resets, leading to longer latency, increased signaling overhead, and longer interruptions than for intra-cell beam switching.

[0016] Layer 1 / Layer 2 (Ll / L2)-Triggered Mobility (LTM) in 3GPP Rel-18

[0017] Layer 1 / Layer 2-Triggered Mobility (LTM) has been specified in Release 18 of the 3GPP specifications as part of the Mobility enhancements Work Item. According to a version of the running change request (CR) for 3GPP TS 38.300, LTM is a procedure in which a gNB receives LI measurement report(s) from a UE and, on their basis, changes a UE's serving cell using a cell switch command signalled via a MAC CE. The cell switch command indicates an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through RRC signalling. Upon receipt of the command, the UE switches to the target cell, according to the cell switch command. The LTM procedure can be used to reduce mobility latency.

[0018] LTM supports both intra-gNB-DU and intra-gNB-CU / inter-gNB-DU mobility. LTM supports both intrafrequency and inter-frequency mobility, including mobility to an inter-frequency cell that is not a current serving cell.

[0019] Figure 3 illustrates the signaling procedure for LTM.

[0020] The steps shown in the procedure illustrated in Figure 3 are as follows:

[0021] 1. The UE sends a MeasurementReport message to the gNB. The gNB decides to configure LTM and initiates candidate cell(s) preparation.

[0022] 2. The gNB transmits an RRCReconfiguration message to the UE including the LTM candidate cell configurations of one or multiple candidate cells. 3. The UE stores the LTM candidate cell configurations and transmits an RRCReconfigurationComplete message to the gNB.

[0023] 4a. The UE may perform DL synchronization with the candidate cell(s) before receiving the cell switch command. This step may be referred to as DL pre-sync (since it occurs before the LTM cell switch command is received) or early DL sync, or pre-activation of TCI states of LTM candidate cell(s).

[0024] 4b. When UE-based TA measurement is configured, the UE may acquire the TA value(s) of the candidate cell(s) by measurement. Otherwise, the UE may perform early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command. The present disclosure is more directly (but not exclusively) concerned with early DL sync, so further details of this step are not discussed here.

[0025] 5. The UE performs LI measurements on the configured candidate cell(s) and transmits LI measurement reports to the gNB. LI measurement should be performed as long as RRC reconfiguration(step 2) is applicable.

[0026] 6. The gNB decides to execute cell switch to a target cell and transmits a MAC CE triggering cell switch by including the candidate configuration index of the target cell. The UE switches to the target cell and applies the configuration indicated by candidate configuration index. The MAC CE for LTM cell switch may also include a beam indication (a TCI State ID) of the LTM candidate cell indicated by the the candidate configuration index. The network includes the beam indication based on the LI measurements reported by the UE.

[0027] 7. The UE performs a random access procedure towards the target cell, if UE does not have valid TA of the target cell. The UE performs CFRA if the LTM cell switch command MAC CE contains information for CFRA as specified in clause 6.1.3.xy of TS 38.321(6].

[0028] 8. The UE completes the LTM cell switch procedure by sending RRCReconfigurationComplete message to target cell. If the UE has performed a RA procedure in step 7, the UE considers that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE considers that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data. The UE determines successful reception of its first UL data by receiving a PDCCH addressing the UE's C-RNTI in the target cell, which schedules a new transmission following the first UL data. The PDCCH carries either a DL assignment or an UL grant addressing the same HARQ. process as the first UL data. According to the above procedures, it is noted that the LTM Cell Switch command from the network to the UE includes a beam indication and an indication of an LTM candidate cell, based on which the UE accesses the indicated LTM candidate cell, i.e., the UE performs the LTM cell switch and transmits an RRC complete message (e.g., RRC Reconfiguration Complete).

[0029] In NR, that "beam indication" is specified as a TCI State Identity (ID) associated to the LTM candidate cell, which is indicated as an LTM candidate configuration ID in the LTM cell switch command. When the UE receives the beam indication in the LTM cell switch command (e.g., a MAC Control Element) the UE monitors a Physical Downlink Control Channel (PDCCH) on that indicated beam of that indicated LTM candidate cell: in other words, the UE considers the TCI State for the indicated TCI state ID as an activated TCI State (or pre-activated) in the indicated LTM candidate cell, when performing the LTM cell switch. The TCI state is also associated to a Reference Signal (RS) and / or synchronization signal, such as a Synchronization Signal Block (SSB) or CSI-RS, which may also be called a Quasi-Co-Iocation (QCL) source. Thus, when a beam is indicated, one may say that an SSB and / or CSI-RS is being indicated.

[0030] Self-Organizing Networks (SON) in 3GPP

[0031] A Self-Organizing Network (SON) is an automation technology designed to make the planning, configuration, management, optimization and healing of mobile radio access networks simpler and faster. SON functionality and behavior has been defined and specified in generally accepted mobile industry recommendations produced by organizations such as 3GPP (3rd Generation Partnership Project) and the NGMN (Next Generation Mobile Networks).

[0032] In 3GPP, the processes within the SON area are classified into Self-configuration process and Selfoptimization process. Self-configuration process is the process where newly deployed nodes are configured by automatic installation procedures to get the necessary basic configuration for system operation.

[0033] This process works in pre-operational state. Pre-operational state is understood as the state from when the eNB is powered up and has backbone connectivity until the RF transmitter is switched on.

[0034] As illustrated in Figure 4, functions handled in the pre-operational state, such as basic setup and initial radio configuration, are covered by the Self Configuration process.

[0035] Self-optimization process is defined as the process where UE and access node measurements and performance measurements are used to auto-tune the network. This process works in operational state. Operational state is understood as the state where the RF interface is additionally switched on. As shown in Figure 4, functions handled in the operational state such as Optimization / Adaptation are covered by the Self Optimization process.

[0036] In LTE, support for Self-Configuration and Self-Optimization is specified, as described in 3GPP TS 36.300 section 22.2, including features such as Dynamic configuration, Automatic Neighbour Relation (ANR), Mobility load balancing, Mobility Robustness Optimization (MRO), RACH optimization and support for energy saving.

[0037] In NR, support for Self-Configuration and Self-Optimization is specified as well, starting with SelfConfiguration features such as Dynamic configuration, Automatic Neighbour Relation (ANR) in Rel-15, as described in 3GPP TS 38.300 section 15. In NR Rel-16, more SON features are being specified, including Self-Optimization features such as Mobility Robustness Optimization (MRO).

[0038] Mobility Robustness Optimization (MRO) in 3GPP

[0039] Seamless handovers are a key feature of 3GPP technologies. Successful handovers ensure that the UE moves around in the coverage area of different cells without causing excess interruptions in the data transmission. However, there will be scenarios when the network fails to handover the UE to the 'correct' neighbor cell in time and in such scenarios the UE will declare a radio link failure (RLF) or Handover Failure (HOF).

[0040] Upon HOF and RLF, the UE may take autonomous actions, i.e., trying to select a cell and initiate reestablishment procedure, so that it can be reachable again. An RLF will cause a poor user experience, as the RLF is declared by the UE only when it realizes that there is no reliable communication channel (radio link) available between itself and the network. Also, reestablishing the connection requires signaling with the newly selected cell (random access procedure, RRC Reestablishment Request, RRC Reestablishment RRC Reestablishment Complete, RRC Reconfiguration and RRC Reconfiguration Complete) and adds some latency, until the UE can exchange data with the network again.

[0041] According to the specifications (3GPP TS 36.331), possible causes for the radio link failure could be one of the following:

[0042] 1) Expiry of the radio link monitoring related timer T310;

[0043] 2) Expiry of the measurement reporting associated timer T312 (not receiving the handover command from the network within this timer's duration despite sending the measurement report when T310 was running);

[0044] 3) Upon reaching the maximum number of RLC retransmissions;

[0045] 4) Upon receiving random access problem indication from the MAC entity; As RLF leads to reestablishment, which degrades performance and user experience, it is in the interest of the network to understand the reasons for RLF and try to optimize mobility related parameters (e.g., trigger conditions of measurement reports) to avoid later RLFs. Before the standardization of MRO related report handling in the network, only the UE was aware of some information, such as how the radio quality looked at the time of RLF, the actual reason for declaring RLF, etc. For the network to identify the reason for the RLF, the network needs more information, both from the UE and also from the neighboring base stations.

[0046] As part of the MRO solution in LTE, the RLF reporting procedure was introduced in the RRC specification in Rel-9 RAN2 work. That has impacted the RRC specifications (especially 3GPP TS 36.331) in that it was standardized that the UE would log relevant information at the moment of an RLF and later report to a target cell to which the UE successfully connects (e.g., after reestablishment). That has also impacted the inter-gNodeB interface, i.e., X2AP specifications (3GPP TS 36.423), as an eNodeB receiving an RLF report could forward to the eNodeB where the failure has been originated.

[0047] For the RLF report generated by the UE, its contents have been enhanced with more details in the subsequent releases. The measurements included in the measurement report based on the latest LTE RRC specification are:

[0048] 1) Measurement quantities (RSRP, RSRQ) of the last serving cell (PCell).

[0049] 2) Measurement quantities of the neighbor cells in different frequencies of different RATs (EUTRA, UTRA, GERAN, CDMA2000).

[0050] 3) Measurement quantity (RSSI) associated to WLAN Aps.

[0051] 4) Measurement quantity (RSSI) associated to Bluetooth beacons.

[0052] 5) Location information, if available (including location coordinates and velocity)

[0053] 6) Globally unique identity of the last serving cell, if available, otherwise the PCI and the carrier frequency of the last serving cell.

[0054] 7) Tracking area code of the PCell.

[0055] 8) Time elapsed since the last reception of the 'Handover command' message.

[0056] 9) C-RNTI used in the previous serving cell.

[0057] 10) Whether or not the UE was configured with a DRB having QCI value of 1.

[0058] After an RLF is declared, the RLF report is logged and include in the VarRLF-Report and, once the UE selects a cell and succeeds with a reestablishment, it includes an indication that it has an RLF report available in the RRC Reestablishment Complete message, to make the target cell aware of that availability. Then, upon receiving an UElnformationRequest message with a flag "rlf-ReportReq-r9" the UE shall include the RLF report (stored in a UE variable VarRLF-Report, as described above) in an UElnformationResponse message and send it to the network.

[0059] Based on the RLF report from the UE and knowledge about which cell the UE reestablished itself with, the original source cell can deduce whether the RLF was caused due to a coverage hole or due to handover associated parameter configurations. If the RLF was deemed to be due to handover associated parameter configurations, the original serving cell can further classify the handover related failure among too-early, too-late, or handover to wrong cell classes. These handover failure classes are explained in brief below.

[0060] 1) Whether the handover failure occurred due to the 'too-late handover / mobility' cases a. The original serving cell can classify a handover failure to be 'too late handover / mobility' when the original serving cell fails to send the handover command to the UE associated to a handover towards a particular target cell and if the UE reestablishes itself in this target cell post RLF. b. An example corrective action from the original serving cell could be to initiate the handover procedure towards this target cell a bit earlier by decreasing the CIO (cell individual offset) towards the target cell that controls when the IE sends the event triggered measurement report that leads to taking the handover decision.

[0061] 2) Whether the handover failure occurred due to the 'too-early handover / mobility' cases a. The original serving cell can classify a handover failure to be 'too early handover / mobility' when the original serving cell is successful in sending the handover command to the UE associated to a handover however the UE fails to perform the random access towards this target cell or the UE declares RLF in the target cell soon afterwards. b. An example corrective action from the original serving cell could be to initiate the handover procedure towards this target cell a bit later by increasing the CIO (cell individual offset) towards the target cell that controls when the IE sends the event triggered measurement report that leads to taking the handover decision.

[0062] 3) Whether the handover failure occurred due to the 'handover / mobility-to-wrong-cell' cases a. The original serving cell can classify a handover failure to be 'handover / mobility-to- wrong-cell' when the original serving cell intends to perform the handover for this UE towards a particular target cell but the UE declares failure or declares failure shortly after successfully completing the handover and then reestablishes itself in a third cell. b. A corrective action from the original serving cell could be to initiate the measurement reporting procedure that leads to handover towards the target cell a bit later by decreasing the CIO (cell individual offset) towards the target cell or via initiating the handover towards the cell in which the UE reestablished a bit earlier by increasing the CIO towards the reestablishment cell.

[0063] SON and LTM

[0064] SON / MDT Enhancements remains a high priority item for standardization. There is interest in considering, for MRO:

[0065] RO enhancement for R18 mobility mechanisms, Lower layer triggered mobility (LTM), CHO with candidate SCGs, subsequent CPAC [RAN3, RAN2]: o Identify and specify necessary UE reporting to enhance the mobility parameter tuning [RAN2]

[0066] A goal of LTM cell switch is to reduce latency, overhead and interruption time. The decision to trigger an LTM cell switch procedure is taken by the source DU, while the legacy L3 mobility decisions are taken by the source CU-CP. The LTM candidate cells are expected to be configured in a UE-specific way. A UE might have limitations on how many inter-cell mobility candidates can it keep in the memory (e.g., 8 LTM candidate cells) and thus different UEs in the same DU might be configured with different LTM candidate cells depending on each UE's location, mobility characteristics and other parameters. Further, 3GPP has decided to call L1 / L2 inter-cell mobility with the name of L1 / L2 Triggered Mobility (LTM).

[0067] A SON / MDT work item in Release 19 will comprise data collection for the LTM cell switch procedure, and for the sake of troubleshooting and enhancements the existing SON reports e.g., RLF report or successful handover report, etc., might be enhanced to collect measurements and information for the LTM cell switch procedure.

[0068] Several issues remain.

[0069] SUMMARY

[0070] In an LTM cell switch, the step in which the UE activates the TCI state (upon reception of the command from the NW) and synchronizes with the LTM candidate cell, before it can monitor PDCCH and / or transmit a scheduling request for UL transmissions, takes time and consumes UE processing and battery resources. In LTM, to reduce the mobility interruption time in LTM Cell Switch, a downlink and uplink pre-synchronization mechanism has been introduced, as shown at steps 4a and 4b in Figure 3. According to this mechanism, the network, upon configuring one or more LTM candidate cells, can instruct the UE to perform synchronization towards one or more of the LTM candidate cells (that are different from the serving cell(s)).

[0071] Such pre-synchronization should not be ordered by the network too late, i.e., too close to the point in time in which the LTM switch command should be executed, because the UE may not have enough time to perform the requested synchronization. On the other hand, the pre-synchronization should not be ordered by the network too early, i.e., too far away from the point in time in which the LTM switch command should be executed, because that may imply that the UE may need to keep the synchronization towards the target cell for long time, thereby increasing the UE complexity and power consumption; or order to avoid this issue, the UE may need to resynchronize at the time of executing the cell switch, thereby erasing the gains of pre-synchronization. Thus, it is important for the network to know the best possible time for ordering the pre-synchronization operations at the UE.

[0072] Techniques, apparatuses, and systems described herein address this problem. According to at least some of these techniques, apparatuses, and systems, a UE records, or "logs," information relating the timing of pre-synchronization operations to subsequent LTM successes or failures, for later reporting to the network. This information can then be used by the network to optimize pre-synchronization orders.

[0073] An example method, according to some embodiments, is carried out by a user equipment (UE) operating in a wireless network and comprises the step of receiving, from the wireless network, a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed. This command may be, for example, a TCI state activation command or TCI state deactivation command, in the context of LTM. The method further comprises the step of subsequently logging, in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between the receiving of this command and the successful change or addition of cell or failed mobility procedure. This information may be included in a Radio Link Failure (RLF) report or a Successful Handover Report (SHR), for example, where the report is subsequently transmitted to the network, e.g., on request from the network.

[0074] Another example method, according to some embodiments, is carried out by a network node and comprises the step of receiving, from a user equipment (UE), a report of a successful or unsuccessful mobility event or of a radio link failure, the report comprising information indicative of a timing relationship between reception, by the UE, of a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed, and a subsequent successful change or addition of cell or failed mobility procedure. Again, this command may be, for example, a TCI state activation command or TCI state deactivation command, in the context of LTM. Likewise, the information may be received in a Radio Link Failure (RLF) report or a Successful Handover Report (SHR), for example, where the report is received by the network, e.g., in response to a request from the network.

[0075] Other embodiments include apparatuses and systems in which the methods described above and / or variants of such methods are implemented.

[0076] BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 shows a high-level view of an exemplary 5G network architecture.

[0078] Figure 2 shows an exemplary configuration of NR UP and CP protocol stacks.

[0079] Figure 3 illustrates the signaling procedure for LTM.

[0080] Figure 4 shows ramifications of Self-Configuration / Self-Optimization functionality (from 3GPP TS 36.300 figure 22.1-1).

[0081] Figure 5 shows an exemplary method (e.g., procedure) for a UE, according to various embodiments of the present disclosure.

[0082] Figure 6 shows an exemplary method (e.g., procedure) for a network node, according to various embodiments of the present disclosure.

[0083] Figure 7 shows a communication system according to various embodiments of the present disclosure.

[0084] Figure 8 shows a UE according to various embodiments of the present disclosure.

[0085] Figure 9 shows a network node according to various embodiments of the present disclosure.

[0086] Figure 10 is a block diagram of a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized. DETAILED DESCRIPTION

[0087] This disclosure may use 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, Ll / L2-centric inter-cell mobility, L1 / L2 inter-cell mobility Ll / L2-Triggered Mobility, Lower-layer Triggered Mobility or simply LTM. The basic principle of LTM is that the UE receives a lower layer signaling from the network indicating to the UE a change (or switch or activation) of its serving cell (e.g., change of PCell, from a source to a target Pcell) in accordance with configuration information previously received by the UE, wherein a lower layer signaling is a message / signaling of a lower layer protocol, which may be referred as a L1 / L2 inter-cell mobility execution command or LTM cell switch command. The change of serving cell (e.g., change of Pcell) may also lead to a change in Scell(s) for the same cell group, e.g., in case the command triggers the UE to change to another cell group configuration of the same type (e.g. another MCG configuration). Before the UE receives the LTM cell switch command, the UE is configured by the network with one or more LTM candidate cell configurations (e.g., reception of an RRC Reconfiguration message, with at least one LTM candidate cell configuration). An LTM candidate cell configuration may include parameters in the IE CellGroupConfig per candidate cell and / or an embedded RRC Reconfiguration per LTM candidate cell.

[0088] The term LTM cell switch procedure refers to the process of a UE switching (or changing) its cell from a source cell to a target cell (which may be called here an LTM candidate cell or a neighbour cell), using Ll / L2-triggered mobility (LTM). In the context of Ll / L2-triggered mobility (LTM), an LTM cell switch procedure may sometimes also be known as L1 / L2 based inter-cell mobility execution, LTM execution, dynamic switch, LTM switch, (LTM) cell switch, (LTM) serving cell change or (LTM) cell change. In the context of the invention, switching to the LTM candidate cell configuration comprises the UE considering that an LTM candidate cell becomes its new special cell (SpCell), e.g., Pcell in case of LTM being configured for a Master Cell Group (MCG) and / or PSCell in case of LTM being configured for a Secondary Cell Group (SCG); or, changing its SpCell from the current Pcell to an LTM candidate cell.

[0089] Where the term "change of cell" is used, the change of cell may comprise a change of a whole cell group configuration, which includes a change in the SpCell (e.g., change of Pcell, or change of PSCell) and a change in Scells of the cell group (e.g., addition, modification and / or release of one or more Seel Is).

[0090] An LTM cell switch procedure may be triggered in the UE by reception of a LTM cell switch command, e.g., a MAC CE. This document often refers to an LTM candidate cell, which is a cell the UE is configured with when configured with Ll / L2-triggered mobility. That is, a cell the UE can move to in a LTM cell switch procedure, upon reception of a LTM cell switch command. These cells may also be called candidate cell(s), candidates, mobility candidates, non-serving cells, additional cells, target candidate cell, target candidate, etc. A LTM candidate cell is a cell the UE performs measurements on (e.g., CSI measurements) so that the UE reports these measurements and the network may take educated decision on which beam (e.g. TCI state) and / or cell the UE is to be switched to. An LTM candidate cell may be a candidate to be a target Pcell or PSCell, or an Scell of a cell group (e.g. MCG Scell).

[0091] This disclosure also refers often to "at least one LTM candidate cell configuration" and may state 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. A LTM candidate cell configuration comprises the configuration 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 an LTM cell switch command indicating the UE to perform a LTM cell switch procedure to that LTM candidate cell, which becomes the target cell and the current (new) SpCell, or an SCell in a serving frequency. The LTM candidate cell configuration comprises parameters of a serving cell (or multiple serving cells, such as a cell group), comprising one or more of the groups of parameters, such as an RRCReconfiguration message an IE CellGroupConfig or an IE SpCellConfig (or the IE SCellConfig, in the case of a Secondary Cell). A LTM candidate cell configuration may in one example comprise one or more of: i) the PCell configuration and one or more SCell configuration (s) of a Master Cell Group (MCG); i) the PSCell configuration and one or more SCell configuration(s) of a secondary Cell Group (SCG). The terms (LTM) candidate configuration, LTM configuration, (LTM) candidate target cell configuration, (LTM) target candidate (cell) configuration may be used interchangeably when referring to LTM candidate cell configuration. An LTM candidate cell configuration is associated with an identifier which is used in the signaling when referring to a certain LTM candidate cell configuration, such as when the UE receives the LTM candidate cell configuration and when the UE receives an LTM cell switch command indicating the UE to perform a LTM cell switch procedure to that LTM candidate cell. This identifier is sometimes known as the LTM candidate cell configuration identity or LTM candidate configuration index (or similar).

[0092] The terms "triggering" the LTM cell switch or "executing" the LTM cell switch are used interchangeably in this disclosure. As discussed above, in an LTM cell switch, the step in which the UE activates the TCI state (upon reception of the command from the NW) and synchronizes with the LTM candidate cell, before it can monitor PDCCH and / or transmit a scheduling request for UL transmissions, takes time and consumes UE processing and battery resources. In LTM, to reduce the mobility interruption time in LTM Cell Switch, a downlink and uplink pre-synchronization mechanism has been introduced, as shown at steps 4a and 4b in Figure 3. According to this mechanism, the network, upon configuring one or more LTM candidate cells, can instruct the UE to perform synchronization towards one or more of the LTM candidate cells (that are different from the serving cell(s)).

[0093] Such pre-synchronization should not be ordered by the network too late, i.e., too close to the point in time in which the LTM switch command should be executed, because the UE may not have enough time to perform the requested synchronization. On the other hand, the pre-synchronization should not be ordered by the network too early, i.e., too far away from the point in time in which the LTM switch command should be executed, because that may imply that the UE may need to keep the synchronization towards the target cell for long time, thereby increasing the UE complexity and power consumption; or order to avoid this issue, the UE may need to resynchronize at the time of executing the cell switch, thereby erasing the gains of pre-synchronization. Thus, it is important for the network to know the best possible time for ordering the pre-synchronization operations at the UE.

[0094] Techniques described herein address this problem. According to at least some of these techniques, a UE records, or "logs," information relating the timing of pre-synchronization operations to subsequent LTM successes or failures, for later reporting to the network. This information can then be used by the network to optimize pre-synchronization orders. Note that the terms "log" and "logging" may be understood as referring to the saving of information to memory. In some embodiments or instances, this logging may comprise saving the relevant information directly into a data structure that forms all or part of a RLF report or SHR report that is subsequently transmitted to the network; in other embodiments or instances, this information may be saved in memory in a record that is later modified and / or duplicated to form such a report.

[0095] In the discussion herein, these techniques are described in the context of LTM cell switch procedures, and are more particularly described with respect to TCI state activation and deactivation commands (which are sent as Medium Access Control Control Elements, MAC CEs), where the TCI state activation command is a command to perform downlink pre-synchronization, with respect to a particular cell and / or beam, and where the TCI state deactivation command is a command that informs the UE that downlink synchronization for a particular cell and / or beam is no longer necessary, such that it can be released. Despite the discussion of the techniques specifically in the LTM context and using this terminology, it should be appreciated that the techniques are more generally applicable to mobility-related scenarios, where "mobility" refers to cell changes, cell additions and removals, handovers, conditional handovers, etc., and / or where the commands instructing a UE (or other wireless device) to perform downlink pre-synch or informing a UE (or other wireless device) that downlink synchronization is no longer necessary are commands other than TCI state activation / deactivation commands and / or are known by different names.

[0096] An advantage of the techniques described herein is to allow mobility-robust optimizations associated to the timing adopted to trigger the UL / DL synchronization to the UE and to the execution of the mobility procedure, such as the LTM cell switch. According to some methods described herein, the serving / source network node becomes aware whether the timing used to send the presynchronization commands, namely the TCI states activation / deactivation MAC CEs for the candidate target cells, is appropriate with the respect to the time needed by the UE to get synchronization and with the time the mobility procedure, such as the LTM cell switch, is executed. That is both to prevent for example that the UE gets the pre-synchronization commands too early with respect to the actual execution of the mobility procedure (which may affect the UE power consumption and success of the synchronization, i.e., a UE not in good coverage of the target cell and associated beams), or too late (which may affect the UE power consumption and success of the synchronization, i.e., the UE may not have time to acquire synchronization by the time the mobility procedure is executed).

[0097] According to some other methods, the serving / source network node becomes aware of how long the UE was able to keep using the TCI state, i.e. the beam, configured by the source cell and associated to the target cell after completing the mobility procedure. If the time is short, the serving / source network node may for example decide to provide the TCI state for another beam associated to the target cell.

[0098] According to some other methods, the serving / source network node becomes aware of how long it took for the UE to get synchronization for the various TCI states, i.e. beams, for one or more of the candidate target cells. This would allow the network to adjust the timing of the transmission of the TCI state activation commands for each of the TCI states of interest, in relationship with the time needed by the UE to get synchronization for the various TCI states.

[0099] The techniques described herein therefore include methods carried out by a wireless terminal, or a so-called user equipment (UE), where the UE: 1. Receives configurations indicating one or more candidate target cells for the mobility procedures (L3 reconfiguration with synch, so called handover, or LTM cell Switch operation), from the serving RAN node (e.g., from the gNB-CU).

[0100] 2. Receives configurations specifying the performing of pre-synchronization (e.g., configurations for TCI state activation / deactivation) toward one or more candidate cell(s), where each TCI state configuration for a given candidate cell indicates one or more RS(s), e.g., SSB index and / or a CSI resource identifier, associated to a beam (since different RSs may be transmitted in different spatial directions).

[0101] 3. Receives one or more TCI state activation (or pre-activation) / deactivation commands (e.g., Candidate Cell TCI States Activation / Deactivation), each command indicating a candidate cell (e.g., by including a candidate cell identifier) and one or more TCI state identifiers of the indicated candidate cell (e.g., one or more TCI State IDs), wherein the command is received before a command for a mobility procedure (e.g., before a MAC CE for LTM cell switch) and while the UE is connected to a source cell.

[0102] 4. Detects an event which is either a successful mobility procedure or a failure, after having performed the pre-synchronization, where the failure may be one of: i) a Radio Link Failure (RLF) in the source cell (e.g., Primary cell before a mobility procedure); ii) a mobility related failure when the UE is leaving the source cell (e.g. handover failure, reconfiguration with sync failure, LTM cell switch failure, conditional handover execution failure); ill) a RLF in a target cell after the mobility procedure is completed; iv) a successful completion of the mobility procedure (e.g. reconfiguration with sync, handover, PScell addition / change, LTM cell switch, conditional handover execution, conditional LTM execution).

[0103] 5. Logs in a SON report in response of step 4 (e.g., an RLF report or a successful handover report, or a successful LTM report, or a successful PSCell change or addition report) timing- related information related to the reception of the TCI state activation / deactivation command, in relationship with the successful mobility procedure or failed mobility procedure.

[0104] In more detail, variants of this approach may include, for example, a method at a User Equipment (UE) configured with a lower-layer triggered mobility configuration, where this method comprises: Logging and reporting timing-related information related to an activation / deactivation of a TCI state of a candidate cell and / or a DL synchronization of an candidate cell, where the logging and reporting is in response to an event associated to a mobility procedure, such as: An indication of time elapsed between the reception in the source cell of the TCI state activation / deactivation associated to a candidate cell, and the mobility procedure execution (e.g. reception of the LTM Cell switch command or indication of a successful mobility execution), wherein the cell can be the target cell to which the mobility procedure is executed, or candidate target cell of the mobility procedure. An indication of time elapsed between the reception in the source cell of a TCI state associated to the target cell, and the mobility procedure execution for the said TCI state of the said target cell. An indication of time elapsed between the reception in the source cell of the TCI state activation for a beam (TCI state) of a cell, and the point in time in which the UE is synchronized to the said beam. An indication of time elapsed between the point in time in which the UE receives the TCI state activation for a beam (TCI state) of a cell and the point in time in which the UE loses the synchronization to the said beam. An indication of time elapsed between the point in time in which the UE is synchronized to the beam (TCI state) of a cell (after the reception in the source cell of the corresponding TCI state activation) and the point in time in which the UE loses the synchronization to the said beam. An indication of time elapsed between the point in time in which the UE is synchronized to the beam of a cell (after the reception in the source cell of the corresponding TCI state activation for the said cell) and the mobility procedure execution, wherein the cell can be the target cell to which mobility procedure is executed, or candidate target cell of the mobility procedure An indication of time elapsed between the point in time in which the UE executes the mobility procedure towards a certain beam of the target cell, and the point in which the TCI state deactivation is received for the said beam in the target cell. An indication of time elapsed between the point in time in which the UE executes the mobility procedure towards a certain beam of the target cell, and the point in which a TCI state activation is received for one or more beams in the target cell. Indication indicating whether at the time of execution of mobility procedure, the UE had received in the source cell a TCI state activation command for the beam of the target cell to which the UE executes the mobility procedure, and it was synchronized with the said beam at the time of the said mobility procedure execution. o Indication indicating whether for the beam of the target cell to which the UE executes the mobility procedure, a TCI state activation command was received in the source cell prior the LTM cell switch execution. o Indication indicating whether for the beam of the target cell to which the UE executes the mobility procedure, a TCI state deactivation command was received in the source cell prior the mobility procedure execution. o Indication indicating whether a TCI state activation is received from the target cell for a beam for which a TCI state activation was received in the source cell prior to the mobility procedure execution. o An indication of time elapsed between the reception in the source cell of the TCI state activation / deactivation associated to a cell, and the failure in the source cell or during the mobility procedure. o An indication of the time elapsed between the reception of a command to activate a TCI state and the reception of a command to deactivate the TCI state e.g. associated to an LTM candidate cell and / or RS (SSB) of the LTM candidate cell. This may occur when the network determines to pre-activate a TCI state and later determines to deactivated it, before an LTM cell switch. o An indication that a change of status occurred i.e. that a given TCI state associated to a beam (e.g. SSB, RS) and / or LTM candidate cell has changed from activated to deactivated before an LTM cell switch. As the initial status is "deactivated", a change may not be logged for the first time it is changed from deactivated (initial status) to activated. So one may interpret that as an indication of activated to deactivated status. o An indication of how many times a change of status occurred i.e. how many times a given TCI state associated to a beam (e.g. SSB, RS) and / or LTM candidate cell has changed from activated to deactivated before an LTM cell switch. As the initial status is "deactivated", a change may not be logged for the first time it is changed from deactivated (initial status) to activated. So one may interpret that as an indication of activated to deactivated status.

[0105] In some embodiments or variants of the above, the timing-related information is logged when the mobility procedure is executed towards a beam of the target cell for which the TCI state activation was received while the UE was connected to the source cell. At least some of the timing-related information may be with respect to the last TCI state activation / deactivation received while the UE was connected to the source cell prior to the mobility procedure execution. Likewise, at least some of the timing-related information is with respect to the last TCI state activation associated to a beam of the target cell to which the mobility procedure is executed, wherein the said last TCI state activation was received while the UE was connected to the source cell prior to the mobility procedure execution.

[0106] In some embodiments or variants of the above, at least some of the timing-related information is with respect to the last TCI state deactivation associated to a beam of the target cell to which the mobility procedure is executed, where the said last TCI state deactivation was received while the UE was connected to the source cell prior to the mobility procedure execution.

[0107] In some embodiments or instances, the information is logged by the UE in a radio link failure report or so-called RLF report triggered upon failure during the mobility procedure execution. Similarly, in other embodiments or instances, the information is logged by the UE in a radio link failure report triggered upon a failure after a successful mobility procedure. In still other embodiments or instances, the information may be logged by the UE in a radio link failure report triggered upon a failure before any mobility procedure while being configured with the candidate cells for the LTM mobility operation.

[0108] In some embodiments or instances, the information referred to above is logged by the UE in a successful handover report, or so-called SHR, triggred upon a successful execution of mobility procedure.

[0109] In various embodiments or instances, any of the mobility procedures referred to above may be:

[0110] A L3 (RRC) based reconfiguration with synch procedure such as normal handover (reconfigurationWithSynch) or conditional handover (reconfigurationWithSynch) performed between source and target primary cell (so called PCell) or between source and target primary secondary cell (PSCell), or

[0111] A Layer 1 or Layer 2 based mobility procedure so called LTM cell switch procedure performed between source and target primary cell (so called PCell) or between source and target primary secondary cell (PSCell).

[0112] The event that triggers the logging of the information may be any of several different events, in various embodiments or instances. For example, the logging may be triggered by a failure of a mobility procedure, where the failure of the mobility procedure occurs while the UE is operating in a beam with a TCI state activated by the source cell. The logging may be in a successful handover report, where the te successful handover report is logged due to a specific cause occurred during successful execution of a mobility procedure.

[0113] Although much of the discussion herein has focused on TCI state activation or deactivation commands that pertain to downlink pre-synchronization, the techniques described herein are more generally applicable to commands instructing the UE to perform downlink and / or uplink presynchronization or informing the UE that this synchronization is no longer needed, for a given beam and / or cell. Thus, the command may be a TCI state activation / deactivation for a DL or UL, or for a a joint UL and DL TCI state.

[0114] In particular examples, the synchronization procedure according to the TCI state activation / deactivation indication or command is for acquiring DL synchronization to the corresponding beam of a cell.

[0115] In some embodiments, or instances, the TCI state activation / deactivation command may be represented by the Candidate Cell TCI States Activation / Deactivation MAC CE. The subsequent LTM cell switch command, in the context of Ll / L2-triggered mobility (LTM), may be represented by the LTM cell switch MAC CE.

[0116] As seen in the above examples, then, in various embodiments and instances of the presently disclosed techniques, a UE (a term that is used herein to refer generally to a wireless access terminal for operating in a wireless network, whether or not it is a 3GPP wireless access terminal) logs and reports to a network, e.g., to a cell served by a network node, timing-related information about presynchronization performed by the UE toward candidate cells of the mobility procedures. Presynchronization refers to any procedure (and / or steps in a procedure) in which a UE connected to a source cell is further configured with one or more candidate cell (s) for mobility, e.g., configured with LTM candidate cell(s) and, in that procedure (or in steps of that procedure) the UE synchronizes with one or of the candidate cells, e.g., based on a command from the network. This is called presynchronization because the UE synchronizes with one or more candidate cell(s) before the UE receives a mobility command. For example, in the case of LTM, the UE is configured with an LTM candidate, and before it receives an LTM cell switch command, while connected to the source cell, the UE synchronizes with the LTM candidate cell.

[0117] The term "beam" may be utilized to represent a TCI state. A TCI state may be associated to a Reference Signal (RS), e.g., Synchronization Signal Block (SSB), wherein the RS is configured as Quasi- co-located ( QCL) source of the TCI state, and the RS is transmitted in a spatial direction (beam). Thus, activating a TCI state may comprise synchronizing with the RS configured as a QCL source of the TCI state, where the RS is transmitted in a beam. Thus, when this document describes a beam of a target cell, that may directly correspond to a TCI state of the target (LTM candidate) cell and / or a RS configured as QCL source of the TCI state.

[0118] In some of the embodiments of the techniques described herein, the UE takes into account a point in time at which the UE receives a TCI state activation / deactivation command from the source cell of the mobility procedure, where the TCI state activation / deactivation command is, for example, the Candidate Cell TCI States Activation / Deactivation MAC CE.

[0119] In some embodiments, the UE takes into account a point in time at which the UE receives a command for the LTM cell switch to a target cell, where the LTM cell switch command is, for example, the LTM Cell Switch Command MAC CE, and the target cell is represented by the Target Configuration ID included in the LTM Cell Switch Command MAC CE. The LTM Cell Switch Command MAC CE for the said target cell may indicate the TCI state associated to the beam of the target cell to which the UE is to execute an LTM cell switch.

[0120] The timing-related information recorded, i.e., logged, by the UE may comprise any of following information elements, in various embodiments or instances:

[0121] • An indication of time elapsed between reception by the UE in the source cell of the TCI state activation / deactivation associated to a cell, and a subsequent mobility procedure execution, where the cell can be the target cell to which the mobility procedure is executed, or candidate target cell of the mobility procedure. o In one example, the source cell may transmit the TCI state activation / deactivation command associated to one or more candidate target cells of an LTM-related mobility procedure. The UE may then compute and log the time elapsed between the reception of the last TCI state activation / deactivation and the mobility procedure execution. o In another embodiment or instance, the UE may compute and log the time elapsed between the reception of the last TCI state activation / deactivation associated to the target cell, i.e. the reception of the last Candidate Cell TCI States Activation / Deactivation MAC CE including TCI states activation / deactivation for the said target cell, and the mobility procedure execution towards the said target cell. o In another embodiment or instance, the UE may compute and log, for each candidate target cell, the time elapsed between the reception of the last TCI state activation / deactivation associated to the corresponding target cell, i.e., the reception of the last Candidate Cell TCI States Activation / Deactivation MAC CE including TCI states activation / deactivation for the said candidate target cell, and the mobility procedure execution. o In some embodiments or instances, any of the above may be performed in relation to the reception of the Candidate Cell TCI States Activation / Deactivation MAC CE indicating the activation of the TCI state for a candidate cell. o In some embodiments or instances, any of the above may be performed in relationship to the reception of the Candidate Cell TCI States Activation / Deactivation MAC CE indicating the deactivation of the TCI state for a candidate cell.

[0122] • An indication of time elapsed between reception in the source cell of a specific TCI state activation / deactivation associated to the target cell, and the mobility procedure execution for the specific TCI state of the said target cell. o In some embodiments or instances, the UE may compute and log the time elapsed between the reception of the last TCI state activation / deactivation for a specific beam associated to the target cell, i.e., the reception of the last Candidate Cell TCI States Activation / Deactivation MAC CE including TCI state activation / deactivation of a specific beam for the said target cell, and the mobility procedure execution for the said beam of the said target cell, i.e., the reception of the LTM Cell Switch Command MAC CE including mobility indication for the said target cell and for the said TCI state for which the Candidate Cell TCI States Activation / Deactivation MAC CE was received in the source cell . o In some embodiments or instances, any of the above may be performed in relationship to the reception of the Candidate Cell TCI States Activation / Deactivation MAC CE indicating the activation of the specific TCI state for the target cell for which the mobility procedure command is executed, i.e., the LTM Cell Switch Command MAC CE included mobility indication for the said TCI state (for which Candidate Cell TCI States Activation / Deactivation MAC CE indicating the activation was previously received) of the said target cell. o In some embodiments or instances, any of the above may be performed in relation to the reception of the Candidate Cell TCI States Activation / Deactivation MAC CE indicating the deactivation of the specific TCI state for the target cell for which the mobility procedure command is executed, i.e., the LTM Cell Switch Command MAC CE included mobility indication for the said TCI state (for which Candidate Cell TCI States Activation / Deactivation MAC CE indicating the deactivation was previously received) of the said target cell. • An indication of time elapsed between reception in the source cell of the TCI state activation for a beam of a cell, and the point in time at which the UE becomes synchronized to the said beam. o The UE may log the time elapsed between the reception of the Candidate Cell TCI States Activation / Deactivation MAC CE from the source cell for a candidate target cell including a TCI state activation, and the time the UE until the acquisition of the synchronization with the beam for that TCI state activation.

[0123] • An indication of time elapsed between the point in time at which the UE receives the TCI state activation for a beam of a cell and the point in time at which the UE loses synchronization to that beam. o The UE may log the time elapsed between the reception of the Candidate Cell TCI States Activation / Deactivation MAC CE from the source cell for a candidate target cell including a TCI state activation and the time the UE loses the synchronization with the beam associated with that TCI state activation.

[0124] • An indication of time elapsed between the point in time at which the UE becomes synchronized to the beam of a cell (after the reception in the source cell of the corresponding TCI state activation) and the point in time at which the UE loses the synchronization to that beam. o The UE may log the time elapsed between the point in time at which the UE completes the acquisition of the synchronization according to the TCI state activation included in the Candidate Cell TCI States Activation / Deactivation MAC CE received from the source cell for a candidate target cell until the UE loses the synchronization with the beam associated with that TCI state activation.

[0125] • An indication of time elapsed between the point in time at which the UE becomes synchronized to the beam of a cell (after reception in the source cell of the corresponding TCI state activation for the said cell) and the mobility procedure execution, where the cell can be the target cell to which mobility procedure is executed, or candidate target cell of the mobility procedure. o The UE may log the time elapsed between the UE completes the acquisition of the synchronization according to the TCI state activation included in the Candidate Cell TCI States Activation / Deactivation MAC CE received from the source cell for a candidate target cell until the UE performs the mobility procedure execution o In some cases, the UE may only consider the time elapsed between the acquisition of the synchronization to a beam according to the TCI state activation included in the Candidate Cell TCI States Activation / Deactivation MAC CE received from the source cell for the target cell and the mobility procedure execution for the said target cell for that same beam, i.e., the mobility procedure execution is performed according to the LTM cell switch command indicating the said target cell and the TCI state for the the beam.

[0126] • An indication of time elapsed between the point in time at which the UE executes the mobility procedure towards a certain beam of the target cell, and the point at which the TCI state deactivation is received for the said beam in the target cell. o The UE may log the time elapsed between when the UE performs the mobility procedure, i.e., it receives the LTM cell switch command indicating the target cell and the TCI state, and the point in time at which the target cell deactivates the TCI state to which the mobility procedure was executed.

[0127] • An indication of time elapsed between the point in time at which the UE executes the mobility procedure towards a certain beam of the target cell, and the point at which a TCI state activation is received for one or more beams in the target cell. o The UE may log the time elapsed between when the UE performs the mobility procedure, i.e., it receives the LTM cell switch command indicating the target cell and the TCI state, and the point in time at which the target cell activates one or more TCI states different from the TCI state to which the mobility procedure was executed.

[0128] • An indication of whether, at the time of execution of mobility procedure, the UE had received in the source cell a TCI state activation command for the beam of the target cell to which the UE executes the mobility procedure, and it was synchronized with the said beam at the time of the said mobility procedure execution. o The UE may log an indication, e.g. a flag, indicating whether the TCI state activation command for a TCI state for a candidate target cell was received, i.e., the UE has received a Candidate Cell TCI States Activation / Deactivation MAC CE including activation for the target cell and the TCI state to which the mobility procedure is executed, i.e., the UE has received after the said Candidate Cell TCI States Activation / Deactivation MAC CE a LTM cell switch MAC CE for the same target cell and the same TCI state. o In some embodiments or instances, this indication is logged if the UE also manages to acquire the synchronization according to the said Candidate Cell TCI States Activation / Deactivation MAC CE for the said target cell and TCI state. • An indication of whether, for the beam of the target cell to which the UE executes the mobility procedure, a TCI state activation command was received in the source cell prior the LTM cell switch execution.

[0129] • An indication of whether, for the beam of the target cell to which the UE executes the mobility procedure, a TCI state deactivation command was received in the source cell prior the mobility procedure execution. o The UE may log whether the UE received a TCI state deactivation for the target cell and for a certain TCI state, i.e., the UE has received a Candidate Cell TCI States Activation / Deactivation MAC CE including TCI deactivation for the target cell and the TCI state to which the mobility procedure is executed.

[0130] • An indication of whether a TCI state activation is received from the target cell for a beam for which a TCI state activation was received in the source cell prior to the mobility procedure execution. o The UE may log whether the UE received from the target cell, after the completion of the mobility procedure, a TCI state activation for a certain TCI state, i.e., whether the UE has received a TCI States Activation / Deactivation MAC CE (e.g. TCI States Activation / Deactivation for UE-specific PDSCH MAC CE), and for which the TCI States Activation / Deactivation MAC CE was received in the source cell for the said TCI state and target cell, i.e.. the UE received before the mobility procedure execution the Candidate Cell TCI States Activation / Deactivation MAC CE including activation for the said TCI state and target cell.

[0131] • An indication of time elapsed between the reception in the source cell of the TCI state activation / deactivation associated to a cell, and the failure in the source cell or during the mobility procedure. o This applies when the UE fails to perform the mobility procedure, either before executing it or while executing it. o For the case in which the failure occurs before executing the mobility procedure, the UE may log the time elapsed since the reception of the last Candidate Cell TCI States Activation / Deactivation MAC CE and the failure. o For the case in which the failure occurs while executing the mobility procedure, the UE may log the time elapsed since the reception of the last Candidate Cell TCI States Activation / Deactivation MAC CE for the target cell and TCI state to which the failed mobility procedure was executing, i.e., the UE received the LTM cell switch MAC CE including the said target cell and the said TCI state. As per some of the above embodiments, the UE is required to compute and log the time elapsed between certain events. The time elapsed may be indicated to the network in relative time units, such as seconds, milliseconds, and / or in terms of radio related timing units, such as number of OFDM symbols, number of subframes, number of slots, number of radio frames, etc. The measuring of the time elapsed by the UE may be performed by starting a timer when the UE receives a first command for starting the measuring of the time elapsed, and stopping the timer when the UE receives a command which indicates the timing to stop measuring the time elapsed. It should be noted that precision in matching a logged point in time to the beginning, end, or some intermediate point of a particular event is of less importance than consistency, or repeatability, in such logging. Thus, for example, when this document refers to a point in time at which a UE executes a mobility procedure, that point in time may be referenced to any part of the mobility procedure, but preferably to the same part, in repeated instances.

[0132] In some embodiments or instances, the UE may be configured with a timer which starts when the UE receives a command to activate a TCI state. And, when the UE does not receive an LTM cell switch command and does not receive a command to deactivate the TCI state, and the timer expires, the UE does not count the change in status of a TCI state.

[0133] Any of various ones of the information elements described above may be logged by the UE, in response to any of the following events:

[0134] • Successful completion of the mobility procedure. In which case the information may be logged in the SHR (if the mobility procedure is for the change of the PCell, i.e., classical HO), or in the SPR (if the mobility procedure is for the addition or change of the PSCell).

[0135] • Radio link failure during the mobility procedure execution. In this case, the information may be logged in the RLF-Report.

[0136] • Radio link failure before the mobility procedure was executed and the UE was configured with LTM candidate cells. In this case, the information may be logged in the RLF-Report.

[0137] • Radio link failure after the mobility procedure was executed, i.e., the failure occurs in the target cell. In this case, the information may be logged in the RLF- Report.

[0138] The above information may be logged in response to any of the above events as long as certain conditions are met, in some embodiments or instances. For example, the information may be logged only in case the mobility procedure is executed towards a beam of the target cell for which the TCI state activation was received while the UE was connected to the source cell, i.e., the UE executes the cell switch according to the LTM cell switch MAC CE indicating the target cell and a corresponding TCI state for which the UE received previous in the source cell the Candidate Cell TCI States Activation / Deactivation MAC CE for the said target cell and TCI state, i.e., the UE was requested by the source cell to synchronize to the beam according the said TCI state for the target cell.

[0139] In another case, the above information are logged only in the case the failure after successfully completing the mobility procedure occurs while the UE was operating on the same TCI state configured by the source cell during the mobility procedure, i.e. failure while operating on the TCI state indicated in the LTM cell switch MAC CE for the target cell.

[0140] In view of the detailed examples given above, it should be understood that Figure 5 is a process flow illustrating an example method carried out by a UE or other wireless terminal operating in a wireless network. The illustrated method is intended to be a generalization of the UE-related techniques described above - hence, where terminology used to describe the method of Figure 5 differs in some respects from similar or related terminology used above, the former should be understood to at least encompass the latter, unless the context clearly indicates otherwise. Further, it should be appreciated that while the following discussion describes certain variations or specific examples of the illustrated method, the method in its broadest conception is not limited to these variations or specific examples.

[0141] As shown at block 510, the method includes the step of receiving, from the wireless network, a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed. As discussed above, this command may be a TCI state activation or deactivation command, in some embodiments. The method further comprises, as shown at block 520, the step of subsequently logging, in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between said receiving and said successful change or addition of cell or failed mobility procedure.

[0142] In some embodiments or instances, the method further comprises transmitting the logged information to the wireless network. This is shown at block 550. The method may comprise, prior to this transmitting, sending an indication of the availability of the logged information to the wireless network, as shown at block 530, where the transmitting is in response to receipt of a request for the logged information, e.g., as shown at block 540. As noted above, in some embodiments or instances, the command received by the UE is a TCI state activation command or a TCI state deactivation command. In some embodiments or instances, the successful change or addition of cell or failed mobility procedure that triggers the logging is triggered by a Layer 1 / Layer 2-triggered Mobility (LTM) cell switch command. In others, the successful change or addition of cell or failed mobility procedure may be triggered by a Layer 3-based reconfiguration or conditional handover.

[0143] In various embodiments or instances, the logged information may comprise any of the following: an indication of time elapsed between reception of the command by the UE and a subsequent mobility procedure execution; an indication of time elapsed between reception by the UE of a Transmission Configuration Indication (TCI) state for a target cell and mobility procedure execution for said TCI state of said target cell; an indication of time elapsed between reception by the UE of TCI state activation for a beam (TCI state) of a cell, and a point in time at which the UE is synchronized to said beam; an indication of time elapsed between a point in time at which the UE receives a TCI state activation for a beam (TCI state) of a cell and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam (TCI state) of a cell after reception of the command and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam of a cell after reception of the command and mobility procedure execution, wherein that cell can be a target cell to which mobility procedure is executed or a candidate target cell of the mobility procedure; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of a target cell and a point in which a TCI state deactivation is received for the certain beam in the target cell; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of the target cell and a point in time at which a TCI state activation is received for one or more beams in the target cell; an indication of whether, at a time of execution of a mobility procedure, the UE had received a TCI state activation command for the beam of the target cell to which the UE executes the mobility procedure and whether it was synchronized with said beam at the time of the said mobility procedure execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state activation command was received prior to the LTM cell switch execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state deactivation command was received prior to the mobility procedure execution; an indication of whether a TCI state activation is received from a target cell for a beam for which a TCI state activation was received in a source cell for the UE, prior to a mobility procedure execution; an indication of time elapsed between reception of the command by the UE and a failure in a source cell for the UE or a failure during a mobility procedure; an indication of time elapsed between reception of a command to activate a TCI state and reception of a command to deactivate the TCI state; an indication that a change of status of a TCI state associated to a beam and / or LTM candidate cell has changed from activated to deactivated before an LTM cell switch; an indication of how many times a change of status of a TCI state associated to a beam and / or LTM candidate cell occurred before an LTM cell switch. These are non-limiting examples - the discussion above provides additional examples as well as details and variations of these.

[0144] In some embodiments or instances, the logging is responsive to execution of a mobility procedure towards a beam of a target cell for which TCI state activation was received while the UE was connected to a source cell for the mobility procedure. In some embodiments or instances, at least some of the logged information is timing-related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution.

[0145] In some embodiments or instances, the method includes including the logged information in a radio link failure report. The radio link failure report may be one that that is triggered (by a radio link failure) sometime after a successful mobility procedure following reception of the command, in some embodiments or instances.

[0146] In some embodiments or instances, the method instead includes including the logged information in a successful handover report.

[0147] Figure 6 is a process flow diagram illustrating an example method performed in a network node, such as a gNB, operating in a wireless network. Again, the illustrated method, which complements the UE- based methods described above, is intended to be a generalization of the network node-related techniques described above - hence, where terminology used to describe the method of Figure 6 differs in some respects from similar or related terminology used above, the former should be understood to at least encompass the latter, unless the context clearly indicates otherwise.

[0148] As shown at block 630, the method comprises receiving, from a user equipment (UE), a report of a successful or unsuccessful mobility event or of a radio link failure, the report comprising information indicative of a timing relationship between reception, by the UE, of a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed, and a subsequent successful change or addition of cell or failed mobility procedure. In some embodiments or instances, the method comprises receiving the report in response to a request for the report sent to the UE, e.g., as shown at block 620. This sending of the request for the report may in turn be in response to receiving, from the UE, an indication that the report is available, as shown at block 610.

[0149] In some embodiments or instances, the command referred to above is a TCI state activation command or a TCI state deactivation command. In some embodiments or instances, the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility (LTM) cell switch command, which may be sent by the network node carrying out the method of Figure 6 or another network node. In others, it may be triggered by a Layer 3-based reconfiguration or conditional handover, which again may be sent by the network node carrying out the method of Figure 6 or another.

[0150] As was the case with the corresponding method shown in Figure 5, the "information" referred to above may comprise any of the following: an indication of time elapsed between reception of the command by the UE and a subsequent mobility procedure execution; an indication of time elapsed between reception by the UE of a Transmission Configuration Indication (TCI) state for a target cell and mobility procedure execution for said TCI state of said target cell; an indication of time elapsed between reception by the UE of TCI state activation for a beam (TCI state) of a cell, and a point in time at which the UE is synchronized to said beam; an indication of time elapsed between a point in time at which the UE receives a TCI state activation for a beam (TCI state) of a cell and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam (TCI state) of a cell after reception of the command and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam of a cell after reception of the command and mobility procedure execution, wherein that cell can be a target cell to which mobility procedure is executed or a candidate target cell of the mobility procedure; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of a target cell and a point in which a TCI state deactivation is received for the certain beam in the target cell; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of the target cell and a point in time at which a TCI state activation is received for one or more beams in the target cell; an indication of whether, at a time of execution of a mobility procedure, the UE had received a TCI state activation command for the beam of the target cell to which the UE executes the mobility procedure and whether it was synchronized with said beam at the time of the said mobility procedure execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state activation command was received prior to the LTM cell switch execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state deactivation command was received prior to the mobility procedure execution; an indication of whether a TCI state activation is received from a target cell for a beam for which a TCI state activation was received in a source cell for the UE, prior to a mobility procedure execution; an indication of time elapsed between reception of the command by the UE and a failure in a source cell for the UE or a failure during a mobility procedure; an indication of time elapsed between reception of a command to activate a TCI state and reception of a command to deactivate the TCI state; an indication that a change of status of a TCI state associated to a beam and / or LTM candidate cell has changed from activated to deactivated before an LTM cell switch; and an indication of how many times a change of status of a TCI state associated to a beam and / or LTM candidate cell occurred before an LTM cell switch.

[0151] In various embodiments or instances, at least some of the logged information may be timing-related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution. In some instances or embodiments, the information may be received in a radio link failure report. In some others, it may be received in a successful handover report.

[0152] Figure 7 shows an example of a communication system 700 in accordance with some embodiments. In this example, communication system 700 includes telecommunication network 702 that includes access network 704 (e.g., RAN) and a core network 706, which includes one or more core network nodes 708. Access network 704 includes one or more access network nodes, such as network nodes 710a-b (one or more of which may be generally referred to as network nodes 710), or any other similar 3GPP access node or non-3GPP access point. Network nodes 710 facilitate direct or indirect connection of UEs, such as by connecting UEs 712a-d (one or more of which may be generally referred to as UEs 712) to core network 706 over one or more wireless connections.

[0153] 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, communication system 700 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. Communication system 700 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0154] UEs 712 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with network nodes 710 and other communication devices. Similarly, network nodes 710 are arranged, capable, configured, and / or operable to communicate directly or indirectly with UEs 712 and / or with other network nodes or equipment in telecommunication network 702 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in telecommunication network 702.

[0155] In the depicted example, core network 706 connects network nodes 710 to one or more hosts, such as host 716. 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. Core network 706 includes one or more core network nodes (e.g., 708) 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 core network node 708. 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).

[0156] Host 716 may be under the ownership or control of a service provider other than an operator or provider of access network 704 and / or telecommunication network 702, and may be operated by the service provider or on behalf of the service provider. Host 716 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.

[0157] As a whole, communication system 700 of Figure 7 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution ( LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low- power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0158] In some examples, telecommunication network 702 is a cellular network that implements 3GPP standardized features. Accordingly, telecommunication network 702 may support network slicing to provide different logical networks to different devices that are connected to telecommunication network 702. For example, telecommunication network 702 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive loT services to yet further UEs.

[0159] In some examples, UEs 712 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to access network 704 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from access network 704. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e., being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN- DC).

[0160] In the example, hub 714 communicates with access network 704 to facilitate indirect communication between one or more UEs (e.g., UE 712c and / or 712d) and network nodes (e.g., network node 710b). In some examples, hub 714 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, hub 714 may be a broadband router enabling access to core network 706 for the UEs. As another example, hub 714 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 710, or by executable code, script, process, or other instructions in hub 714. As another example, hub 714 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, hub 714 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, hub 714 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which hub 714 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, hub 714 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy loT devices.

[0161] Hub 714 may have a constant / persistent or intermittent connection to network node 710b. Hub 714 may also allow for a different communication scheme and / or schedule between hub 714 and UEs (e.g., UE 712c and / or 712d), and between hub 714 and core network 706. In other examples, hub 714 is connected to core network 706 and / or one or more UEs via a wired connection. Moreover, hub 714 may be configured to connect to an M2M service provider over access network 704 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with network nodes 710 while still connected via hub 714 via a wired or wireless connection. In some embodiments, hub 714 may be a dedicated hub - that is, a hub whose primary function is to route communications to / from the UEs from / to network node 710b. In other embodiments, hub 714 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 710b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0162] Figure 8 shows a UE 800 in accordance with some embodiments. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, 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-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by 3GPP, including a narrow band internet of things (NB-loT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0163] A UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to- vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0164] UE 800 includes processing circuitry 802 that is operatively coupled via bus 804 to input / output interface 806, power source 808, memory 810, communication interface 812, and possibly other components not explicitly shown. Certain UEs may utilize all or a subset of the components shown in Figure 8. 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.

[0165] Processing circuitry 802 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 memory 810. Processing circuitry 802 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, processing circuitry 802 may include multiple central processing units (CPUs).

[0166] In the example, input / output interface 806 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 UE 800. 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.

[0167] In some embodiments, power source 808 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. Power source 808 may further include power circuitry for delivering power from power source 808 itself, and / or an external power source, to the various parts of UE 800 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging power source 808. Power circuitry may perform any formatting, converting, or other modification to the power from power source 808 to make the power suitable for the respective components of UE 800 to which power is supplied.

[0168] Memory 810 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable readonly memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, memory 810 includes one or more application programs 814, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 816. Memory 810 may store, for use by UE 800, any of a variety of various operating systems or combinations of operating systems.

[0169] Memory 810 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUlCC), integrated UICC (iUICC) or a removable UICC commonly known as 'SIM card.' Memory 810 may allow UE 800 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 memory 810, which may be or comprise a device-readable storage medium.

[0170] Processing circuitry 802 may be configured to communicate with an access network or other network using communication interface 812. Communication interface 812 may comprise one or more communication subsystems and may include or be communicatively coupled to antenna 822. Communication interface 812 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 transmitter 818 and / or receiver 820 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, transmitter 818 and receiver 820 may be coupled to one or more antennas (e.g., 822) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0171] In the illustrated embodiment, communication functions of communication interface 812 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0172] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 812, 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 12 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., an alert is sent when moisture is detected), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0173] 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.

[0174] A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and / or software in dependence of the intended application of the loT device in addition to other components as described in relation to UE 800 shown in Figure 8.

[0175] As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another UE and / or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-loT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0176] 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.

[0177] Figure 9 shows a network node 900 in accordance with some embodiments. Examples of network nodes include, but are not limited to, access points (e.g., radio access points) and base stations (e.g., radio base stations, Node Bs, eNBs, and gNBs).

[0178] 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 and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0179] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0180] Network node 900 includes processing circuitry 902, memory 904, communication interface 906, and power source 908. Network node 900 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which network node 900 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, network node 900 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 904 for different RATs) and some components may be reused (e.g., a same antenna 910 may be shared by different RATs). Network node 900 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 900, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z- wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 900.

[0181] Processing circuitry 902 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other network node 900 components, such as memory 904, to provide network node 900 functionality.

[0182] In some embodiments, processing circuitry 902 includes a system on a chip (SOC). In some embodiments, processing circuitry 902 includes one or more of radio frequency ( RF) transceiver circuitry 912 and baseband processing circuitry 914. In some embodiments, RF transceiver circuitry 912 and baseband processing circuitry 914 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 912 and baseband processing circuitry 914 may be on the same chip or set of chips, boards, or units.

[0183] Memory 904 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non- transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by processing circuitry 902. Memory 904 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 (collectively denoted computer program product 904a) capable of being executed by processing circuitry 902 and utilized by network node 900. Memory 904 may be used to store any calculations made by processing circuitry 902 and / or any data received via communication interface 906. In some embodiments, processing circuitry 902 and memory 904 is integrated.

[0184] Communication interface 906 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, communication interface 906 comprises port(s) / terminal(s) 916 to send and receive data, for example to and from a network over a wired connection. Communication interface 906 also includes radio front-end circuitry 918 that may be coupled to, or in certain embodiments a part of, antenna 910. Radio front-end circuitry 918 comprises filters 920 and amplifiers 922. Radio front-end circuitry 918 may be connected to antenna 910 and processing circuitry 902. The radio front-end circuitry may be configured to condition signals communicated between antenna 910 and processing circuitry 902. Radio front-end circuitry 918 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. Radio front-end circuitry 918 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 920 and / or amplifiers 922. The radio signal may then be transmitted via antenna 910. Similarly, when receiving data, antenna 910 may collect radio signals which are then converted into digital data by radio front-end circuitry 918. The digital data may be passed to processing circuitry 902. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0185] In certain alternative embodiments, network node 900 does not include separate radio front-end circuitry 918, instead, processing circuitry 902 includes radio front-end circuitry and is connected to antenna 910. Similarly, in some embodiments, all or some of RF transceiver circuitry 912 is part of communication interface 906. In still other embodiments, communication interface 906 includes one or more ports or terminals 916, radio front-end circuitry 918, and RF transceiver circuitry 912, as part of a radio unit (not shown), and communication interface 906 communicates with the baseband processing circuitry 914, which is part of a digital unit (not shown).

[0186] Antenna 910 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. Antenna 910 may be coupled to radio front-end circuitry 918 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, antenna 910 is separate from network node 900 and connectable to network node 900 through an interface or port.

[0187] Antenna 910, communication interface 906, and / or processing circuitry 902 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, antenna 910, communication interface 906, and / or processing circuitry 902 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment.

[0188] Power source 908 provides power to the various components of network node 900 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 908 may further comprise, or be coupled to, power management circuitry to supply the components of network node 900 with power for performing the functionality described herein. For example, network node 900 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of power source 908. As a further example, power source 908 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.

[0189] Embodiments of network node 900 may include additional components beyond those shown in Figure 9 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, network node 900 may include user interface equipment to allow input of information into network node 900 and to allow output of information from network node 900. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 900.

[0190] Figure 10 is a block diagram illustrating a virtualization environment 1000 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 1000 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.

[0191] Applications 1002 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1000 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0192] Hardware 1004 includes processing circuitry, memory that stores software and / or instructions (collectively denoted computer program product 1004a) 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 1006 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1008a-b (one or more of which may be generally referred to as VMs 1008), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. The virtualization layer 1006 may present a virtual operating platform that appears like networking hardware to VMs 1008.

[0193] VMs 1008 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1006. Different embodiments of the instance of a virtual appliance 1002 may be implemented on one or more of VMs 1008, and the implementations may differ. 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.

[0194] In the context of NFV, each VM 1008 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 VMs 1008, and that part of hardware 1004 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1008 on top of hardware 1004 and corresponds to application 1002.

[0195] Hardware 1004 may be implemented in a standalone network node with generic or specific components. Hardware 1004 may implement some functions via virtualization. Alternatively, hardware 1004 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 1010, which, among others, oversees lifecycle management of applications 1002. In some embodiments, hardware 1004 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of control system 1012 which may alternatively be used for communication between hardware nodes and radio units.

[0196] The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art.

[0197] The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and / or electronic devices and can include, for example, electrical and / or electronic circuitry, devices, modules, processors, memories, logic solid state and / or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and / or displaying functions, and so on, as such as those that are described herein.

[0198] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure.

[0199] As described herein, device and / or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and / or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person. Furthermore, functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and / or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices.

[0200] In addition, certain terms used in the present disclosure, including the specification, drawings and embodiments thereof, can be used synonymously in certain instances, including, but not limited to, e.g., data and information. It should be understood that, while these words and / or other words that can be synonymous to one another, can be used synonymously herein, that there can be instances when such words can be intended to not be used synonymously. Further, to the extent that the prior art knowledge has not been explicitly incorporated by reference herein above, it is explicitly incorporated herein in its entirety. All publications referenced are incorporated herein by reference in their entireties.

[0201] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0202] In addition, certain terms used in the present disclosure, including the specification and drawings, can be used synonymously in certain instances (e.g., "data" and "information"). It should be understood, that although these terms (and / or other terms that can be synonymous to one another) can be used synonymously herein, there can be instances when such words can be intended to not be used synonymously.

[0203] The techniques and apparatus described herein include, but are not limited to, the following enumerated examples:

[0204] Al. A method, in a user equipment (UE) operating in a wireless network, the method comprising: receiving, from the wireless network, a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed; and subsequently logging, in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between said receiving and said successful change or addition of cell or failed mobility procedure.

[0205] A2. The method of example embodiment Al, wherein the method further comprises transmitting the logged information to the wireless network.

[0206] A3. The method of example embodiment A2, wherein the method comprises, prior to said transmitting, sending an indication of the availability of the logged information to the wireless network, wherein said transmitting is in response to receipt of a request for the logged information.

[0207] A4. The method of any one of example embodiments A1-A3, wherein the command is a TCI state activation command or a TCI state deactivation command.

[0208] A5. The method of any one of example embodiments A1-A4, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility (LTM) cell switch command.

[0209] A6. The method of any of example embodiments A1-A4, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 3-based reconfiguration or conditional handover.

[0210] A7. The method of any one of example embodiments A1-A6, wherein the logged information comprises any one or more of: an indication of time elapsed between reception of the command by the UE and a subsequent mobility procedure execution; an indication of time elapsed between reception by the UE of a Transmission Configuration Indication (TCI) state for a target cell and mobility procedure execution for said TCI state of said target cell; an indication of time elapsed between reception by the UE of TCI state activation for a beam (TCI state) of a cell, and a point in time at which the UE is synchronized to said beam; an indication of time elapsed between a point in time at which the UE receives a TCI state activation for a beam (TCI state) of a cell and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam (TCI state) of a cell after reception of the command and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam of a cell after reception of the command and mobility procedure execution, wherein that cell can be a target cell to which mobility procedure is executed or a candidate target cell of the mobility procedure; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of a target cell and a point in which a TCI state deactivation is received for the certain beam in the target cell; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of the target cell and a point in time at which a TCI state activation is received for one or more beams in the target cell; an indication of whether, at a time of execution of a mobility procedure, the UE had received a TCI state activation command for the beam of the target cell to which the UE executes the mobility procedure and whether it was synchronized with said beam at the time of the said mobility procedure execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state activation command was received prior to the LTM cell switch execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state deactivation command was received prior to the mobility procedure execution; an indication of whether a TCI state activation is received from a target cell for a beam for which a TCI state activation was received in a source cell for the UE, prior to a mobility procedure execution; an indication of time elapsed between reception of the command by the UE and a failure in a source cell for the UE or a failure during a mobility procedure; an indication of time elapsed between reception of a command to activate a TCI state and reception of a command to deactivate the TCI state; an indication that a change of status of a TCI state associated to a beam and / or LTM candidate cell has changed from activated to deactivated before an LTM cell switch; an indication of how many times a change of status of a TCI state associated to a beam and / or LTM candidate cell occurred before an LTM cell switch.

[0211] A8. The method of any of example embodiments A1-A7, wherein said logging is responsive to execution of a mobility procedure towards a beam of a target cell for which TCI state activation was received while the UE was connected to a source cell for the mobility procedure.

[0212] A9. The method of any of example embodiments A1-A8, wherein at least some of the logged information is timing-related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution.

[0213] AID. The method of any of example embodiments A1-A9, wherein the method includes including the logged information in a radio link failure report.

[0214] All. The method of example embodiment AID, wherein the radio link failure report is triggered after a successful mobility procedure following reception of the command.

[0215] A12. The method of any of example embodiments A1-A8, wherein the method includes including the logged information in a successful handover report.

[0216] Bl. A method, in a network node operating in a wireless network, the method comprising: receiving, from a user equipment (UE), a report of a successful or unsuccessful mobility event or of a radio link failure, the report comprising information indicative of a timing relationship between reception, by the UE, of a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed, and a subsequent successful change or addition of cell or failed mobility procedure.

[0217] B2. The method of any one of example embodiments B1-B3, wherein the method comprises receiving the report in response to a request for the report sent to the UE. B3. The method of example embodiment B2, wherein the method comprises receiving, from the UE, an indication that the report is available and sending the request for the report in response to said indication.

[0218] B4. The method of any one of example embodiments B1-B3, wherein the command is a TCI state activation command or a TCI state deactivation command.

[0219] B5. The method of any one of example embodiments B1-B4, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility (LTM) cell switch command.

[0220] B6. The method of any of example embodiments B1-B4, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 3-based reconfiguration or conditional handover.

[0221] B7. The method of any one of example embodiments B1-B6, wherein the information comprises any one or more of: an indication of time elapsed between reception of the command by the UE and a subsequent mobility procedure execution; an indication of time elapsed between reception by the UE of a Transmission Configuration Indication (TCI) state for a target cell and mobility procedure execution for said TCI state of said target cell; an indication of time elapsed between reception by the UE of TCI state activation for a beam (TCI state) of a cell, and a point in time at which the UE is synchronized to said beam; an indication of time elapsed between a point in time at which the UE receives a TCI state activation for a beam (TCI state) of a cell and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam (TCI state) of a cell after reception of the command and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam of a cell after reception of the command and mobility procedure execution, wherein that cell can be a target cell to which mobility procedure is executed or a candidate target cell of the mobility procedure; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of a target cell and a point in which a TCI state deactivation is received for the certain beam in the target cell; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of the target cell and a point in time at which a TCI state activation is received for one or more beams in the target cell; an indication of whether, at a time of execution of a mobility procedure, the UE had received a TCI state activation command for the beam of the target cell to which the UE executes the mobility procedure and whether it was synchronized with said beam at the time of the said mobility procedure execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state activation command was received prior to the LTM cell switch execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state deactivation command was received prior to the mobility procedure execution; an indication of whether a TCI state activation is received from a target cell for a beam for which a TCI state activation was received in a source cell for the UE, prior to a mobility procedure execution; an indication of time elapsed between reception of the command by the UE and a failure in a source cell for the UE or a failure during a mobility procedure; an indication of time elapsed between reception of a command to activate a TCI state and reception of a command to deactivate the TCI state; an indication that a change of status of a TCI state associated to a beam and / or LTM candidate cell has changed from activated to deactivated before an LTM cell switch; an indication of how many times a change of status of a TCI state associated to a beam and / or LTM candidate cell occurred before an LTM cell switch.

[0222] B8. The method of any of example embodiments B1-B7, wherein at least some of the logged information is timing-related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution. B9. The method of any of example embodiments B1-B8, wherein the information is received in a radio link failure report.

[0223] BIO. The method of any of example embodiments B1-B8, wherein the information is received in a successful handover report.

[0224] Cl. A user equipment, UE, comprising: communication interface circuitry configured to communicate with a RAN node via at least one serving cell; and processing circuitry operably coupled to the communication interface circuitry, wherein the processing circuitry and communication interface circuitry are configured to: receive, from the wireless network, a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed; and subsequently log, in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between said receiving and said successful change or addition of cell or failed mobility procedure.

[0225] C2. The UE of example embodiment Cl, wherein the processing circuitry and communication interface circuitry are further configured to transmit the logged information to the wireless network.

[0226] C3. The UE of example embodiment C2, wherein the processing circuitry and communication interface circuitry are configured to, prior to said transmitting, send an indication of the availability of the logged information to the wireless network, wherein said transmitting is in response to receipt of a request for the logged information.

[0227] C4. The UE of any one of example embodiments C1-C3, wherein the command is a TCI state activation command or a TCI state deactivation command. C5. The UE of any one of example embodiments C1-C4, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility (LTM) cell switch command.

[0228] C6. The UE of any of example embodiments C1-C4, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 3-based reconfiguration or conditional handover.

[0229] C7. The UE of any one of example embodiments C1-C6, wherein the logged information comprises any one or more of: an indication of time elapsed between reception of the command by the UE and a subsequent mobility procedure execution; an indication of time elapsed between reception by the UE of a Transmission Configuration Indication (TCI) state for a target cell and mobility procedure execution for said TCI state of said target cell; an indication of time elapsed between reception by the UE of TCI state activation for a beam (TCI state) of a cell, and a point in time at which the UE is synchronized to said beam; an indication of time elapsed between a point in time at which the UE receives a TCI state activation for a beam (TCI state) of a cell and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam (TCI state) of a cell after reception of the command and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam of a cell after reception of the command and mobility procedure execution, wherein that cell can be a target cell to which mobility procedure is executed or a candidate target cell of the mobility procedure; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of a target cell and a point in which a TCI state deactivation is received for the certain beam in the target cell; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of the target cell and a point in time at which a TCI state activation is received for one or more beams in the target cell; an indication of whether, at a time of execution of a mobility procedure, the UE had received a TCI state activation command for the beam of the target cell to which the UE executes the mobility procedure and whether it was synchronized with said beam at the time of the said mobility procedure execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state activation command was received prior to the LTM cell switch execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state deactivation command was received prior to the mobility procedure execution; an indication of whether a TCI state activation is received from a target cell for a beam for which a TCI state activation was received in a source cell for the UE, prior to a mobility procedure execution; an indication of time elapsed between reception of the command by the UE and a failure in a source cell for the UE or a failure during a mobility procedure; an indication of time elapsed between reception of a command to activate a TCI state and reception of a command to deactivate the TCI state; an indication that a change of status of a TCI state associated to a beam and / or LTM candidate cell has changed from activated to deactivated before an LTM cell switch; an indication of how many times a change of status of a TCI state associated to a beam and / or LTM candidate cell occurred before an LTM cell switch.

[0230] C8. The UE of any of example embodiments C1-C7, wherein the processing circuitry and communication interface circuitry are configured to perform said logging responsive to execution of a mobility procedure towards a beam of a target cell for which TCI state activation was received while the UE was connected to a source cell for the mobility procedure.

[0231] C9. The UE of any of example embodiments C1-C8, wherein at least some of the logged information is timing-related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution.

[0232] CIO. The UE of any of example embodiments C1-C9, wherein the processing circuitry and communication interface circuitry are configured to include the logged information in a radio link failure report. Cll. The UE of example embodiment CIO, wherein the radio link failure report is triggered after a successful mobility procedure following reception of the command.

[0233] C12. The UE of any of example embodiments C1-C8, wherein the processing circuitry and communication interface circuitry are configured to include the logged information in a successful handover report.

[0234] C13. A user equipment, UE, being adapted to: receive, from the wireless network, a command instructing the UE to perform downlink presynchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed; and subsequently log, in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between said receiving and said successful change or addition of cell or failed mobility procedure.

[0235] C14. The UE of example embodiment C13, being further adapted to perform operations corresponding to any of the methods of example embodiments A2-A12.

[0236] C15. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a user equipment, UE, configure the UE to perform operations corresponding to any of the methods of example embodiments A1-A12.

[0237] C16. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a user equipment, UE, configure the UE to perform operations corresponding to any of the methods of example embodiments A1-A12.

[0238] DI. A network node, RAN, the network node comprising: communication interface circuitry configured to communicate with one or more user equipments, UEs, via at least one serving cell; and processing circuitry operably coupled to the communication interface circuitry, wherein the processing circuitry and communication interface circuitry are configured to: receive, from a user equipment (UE), a report of a successful or unsuccessful mobility event or of a radio link failure, the report comprising information indicative of a timing relationship between reception, by the UE, of a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed, and a subsequent successful change or addition of cell or failed mobility procedure.

[0239] D2. The network node of any one of example embodiments D1-D3, wherein the processing circuitry and communication interface circuitry are configured to receive the report in response to a request for the report sent to the UE.

[0240] D3. The network node of example embodiment D2, wherein the processing circuitry and communication interface circuitry are configured to receive, from the UE, an indication that the report is available, and send the request for the report in response to said indication.

[0241] D4. The network node of any one of example embodiments D1-D3, wherein the command is a TCI state activation command or a TCI state deactivation command.

[0242] D5. The network node of any one of example embodiments D1-D4, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility (LTM) cell switch command.

[0243] D6. The network node of any of example embodiments D1-D4, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 3-based reconfiguration or conditional handover.

[0244] D7. The network node of any one of example embodiments D1-D6, wherein the information comprises any one or more of: an indication of time elapsed between reception of the command by the UE and a subsequent mobility procedure execution; an indication of time elapsed between reception by the UE of a Transmission Configuration Indication (TCI) state for a target cell and mobility procedure execution for said TCI state of said target cell; an indication of time elapsed between reception by the UE of TCI state activation for a beam (TCI state) of a cell, and a point in time at which the UE is synchronized to said beam; an indication of time elapsed between a point in time at which the UE receives a TCI state activation for a beam (TCI state) of a cell and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam (TCI state) of a cell after reception of the command and a point in time at which the UE loses synchronization to that beam; an indication of time elapsed between a point in time at which the UE is synchronized to a beam of a cell after reception of the command and mobility procedure execution, wherein that cell can be a target cell to which mobility procedure is executed or a candidate target cell of the mobility procedure; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of a target cell and a point in which a TCI state deactivation is received for the certain beam in the target cell; an indication of time elapsed between a point in time at which the UE executes a mobility procedure towards a certain beam of the target cell and a point in time at which a TCI state activation is received for one or more beams in the target cell; an indication of whether, at a time of execution of a mobility procedure, the UE had received a TCI state activation command for the beam of the target cell to which the UE executes the mobility procedure and whether it was synchronized with said beam at the time of the said mobility procedure execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state activation command was received prior to the LTM cell switch execution; an indication of whether, for a beam of a target cell to which the UE executes a mobility procedure, a TCI state deactivation command was received prior to the mobility procedure execution; an indication of whether a TCI state activation is received from a target cell for a beam for which a TCI state activation was received in a source cell for the UE, prior to a mobility procedure execution; an indication of time elapsed between reception of the command by the UE and a failure in a source cell for the UE or a failure during a mobility procedure; an indication of time elapsed between reception of a command to activate a TCI state and reception of a command to deactivate the TCI state; an indication that a change of status of a TCI state associated to a beam and / or LTM candidate cell has changed from activated to deactivated before an LTM cell switch; an indication of how many times a change of status of a TCI state associated to a beam and / or LTM candidate cell occurred before an LTM cell switch.

[0245] D8. The network node of any of example embodiments D1-D7, wherein at least some of the logged information is timing-related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution.

[0246] D9. The network node of any of example embodiments D1-D8, wherein the information is received in a radio link failure report.

[0247] DIO. The network node of any of example embodiments D1-D8, wherein the information is received in a successful handover report.

[0248] Dll. A network node, the network node being adapted to: receive, from a user equipment (UE), a report of a successful or unsuccessful mobility event or of a radio link failure, the report comprising information indicative of a timing relationship between reception, by the UE, of a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed, and a subsequent successful change or addition of cell or failed mobility procedure.

[0249] D12. The network node of example embodiment Dll, wherein the network node is adapted to carry out a method according to any one of example embodiments B2-10. D13. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a network node, configure the network node to perform operations corresponding to any of the methods of example embodiments B1-B10.

[0250] Some abbreviations:

[0251] BFD Beam Failure Detection

[0252] BFI Beam Failure Indication

[0253] BFR Beam Failure Recovery

[0254] BWP Bandwidth Part

[0255] CE Control Element

[0256] CBRA Contention Based Random Access

[0257] CFRA Contention Free Random Access

[0258] CHO Conditional Handover

[0259] CP Control Plane

[0260] C-RNTI Cell- Radio Network Temporary Identifier.

[0261] CSI Channel State Information

[0262] CSI-RS Channel State Information - Reference Signal

[0263] CU Central unit

[0264] CU-gNB gNB-CU

[0265] DCI Downlink Control Information

[0266] DL Downlink

[0267] DRB Data Radio Bearer

[0268] DU Distributed unit eNB Base station supporting the LTE air interface gNB Base station supporting the NR air interface gNB-CU gNB Central Unit gNB-DU gNB Distributed Unit

[0269] HARQ Hybrid Automatic Repeat Request

[0270] HOF Handover Failure

[0271] IE Information Element

[0272] LI Layer-1

[0273] L2 La yer- 2

[0274] L3 Layer-3

[0275] LTE Long Term Evolution LTM Layer 1 / Layer 2 (Ll / L2)-Triggered Mobility, or Lower-Layer Triggered Mobility

[0276] MAC Medium Access Control

[0277] MDT Minimization of Drive Test

[0278] MHI Mobility History Report

[0279] MCG Master Cell Group

[0280] MN Master Node

[0281] NR New Radio

[0282] PCell Primary Cell

[0283] PCI Physical cell identifier

[0284] PDCCH Physical Downlink Control Channel

[0285] PSCell Primary Secondary Cell

[0286] PRACH Physical Random Access Channel

[0287] QCI Quality of Service Class Indicator

[0288] RA Random Access

[0289] RACH Random Access Channel

[0290] RACH based Random Access Channel based

[0291] RACH-less Random Access Channel Less (i.e., without RA procedure)

[0292] RAN Radio Access Network

[0293] RAT Radio Access Technology

[0294] RLF Radio Link Failure

[0295] RRC Radio Resource Control

[0296] RS Reference Signal

[0297] RSRP Received Signal Received Power

[0298] RSRQ Received Signal Received Quality

[0299] RSSI Received Signal Strength Indicator

[0300] SCell Secondary Cell

[0301] S / U supplementary uplink / uplink

[0302] SCG Secondary Cell Group

[0303] S-DU Source Distributed Unit

[0304] S-gNB-DU Source-gNB-Distributed Unit

[0305] SHR Successful Handover Report

[0306] SINR Signal to Interference Noise ratio

[0307] SN Secondary Node

[0308] SpCell Special Cell SSB Synchronization Signal / PBCH block (SSB)

[0309] SS / PBCH Synchronization Signal / Physical Broadcast Channel

[0310] SS-RSRP Synchronization Signal-Received Signal Received Power

[0311] SS-RSRQ Synchronization Signal-Received Signal Received Quality

[0312] SS-SINR Synchronization Signal-Signal To Interference Noise Ratio

[0313] TA Time Advance

[0314] TCI Transmission Configuration Indicator

[0315] UE User Equipment

[0316] UL Uplink WLAN AP wireless local-area network Access Point

Claims

CLAIMS1. A method, in a user equipment, UE, operating in a wireless network, the method comprising: receiving (510), from the wireless network, a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed; and subsequently logging (520), in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between said receiving and said successful change or addition of cell or failed mobility procedure.

2. The method of claim 1, wherein the method further comprises transmitting (550) the logged information to the wireless network.

3. The method of claim 1 or 2, wherein the command is a Transmission Configuration Indication, TCI, state activation command or a TCI state deactivation command.

4. The method of any one of claims 1-3, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility, LTM, cell switch command.

5. The method of any one of claims 1-4, wherein the logged information comprises an indication of time elapsed between reception by the UE of a TCI state for a target cell and mobility procedure execution for said TCI state of said target cell.

6. The method of any one of claims 1-5, wherein said logging is responsive to execution of a mobility procedure towards a beam of a target cell for which TCI state activation was received while the UE was connected to a source cell for the mobility procedure.

7. The method of any one of claims 1-6, wherein at least some of the logged information is timing- related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution.

8. A method, in a network node operating in a wireless network, the method comprising:receiving (630), from a user equipment, UE, a report of a successful or unsuccessful mobility event or of a radio link failure, the report comprising information indicative of a timing relationship between reception, by the UE, of a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed, and a subsequent successful change or addition of cell or failed mobility procedure.

9. The method of claim 8, wherein the method comprises receiving the report in response to a request for the report sent (620) to the UE.

10. The method of claim 8 or 9, wherein the command is a Transmission Configuration Indication, TCI, state activation command or a TCI state deactivation command.

11. The method of any one of claims 8-10, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility, LTM, cell switch command.

12. The method of any one of claims 8-11, wherein the information comprises an indication of time elapsed between reception by the UE of a TCI state for a target cell and mobility procedure execution for said TCI state of said target cell.

13. The method of any one of claims 8-12, wherein at least some of the logged information is timing- related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution.

14. A user equipment, UE (800), comprising: communication interface circuitry (812) configured to communicate with a wireless network via at least one serving cell; and processing circuitry (802) operably coupled to the communication interface circuitry (812), wherein the processing circuitry (802) and communication interface circuitry (812) are configured to: receive, from the wireless network, a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility orinforming the UE that downlink synchronization for the candidate target cell for mobility is no longer needed; and subsequently log, in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between said receiving and said successful change or addition of cell or failed mobility procedure.

15. The UE (800) of claim 14, wherein the processing circuitry (802) and communication interface circuitry (812) are further configured to transmit the logged information to the wireless network.

16. The UE (800) of claim 14 or 15, wherein the command is a Transmission Configuration Indication, TCI, state activation command or a TCI state deactivation command.

17. The UE (800) of any one of claims 14-16, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility, LTM, cell switch command.

18. The UE (800) of any one of claims 14-17, wherein the logged information comprises an indication of time elapsed between reception by the UE of a TCI state for a target cell and mobility procedure execution for said TCI state of said target cell.

19. The UE (800) of any one of claims 14-18, wherein the processing circuitry (802) and communication interface circuitry (812) are configured to perform said logging responsive to execution of a mobility procedure towards a beam of a target cell for which TCI state activation was received while the UE was connected to a source cell for the mobility procedure.

20. The UE (800) of any one of claims 14-19, wherein at least some of the logged information is timing-related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution.

21. A network node (900), comprising: communication interface circuitry (906) configured to communicate with one or more user equipments, UEs, via at least one serving cell; andprocessing circuitry (902) operably coupled to the communication interface circuitry, wherein the processing circuitry (902) and communication interface circuitry (906) are configured to: receive, from a UE, a report of a successful or unsuccessful mobility event or of a radio link failure, the report comprising information indicative of a timing relationship between reception, by the UE, of a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed, and a subsequent successful change or addition of cell or failed mobility procedure.

22. The network node (900) of claim 21, wherein the processing circuitry (902) and communication interface circuitry (906) are configured to receive the report in response to a request for the report sent to the UE.

23. The network node (900) of claim 21 or 22, wherein the command is a Transmission Configuration Indication, TCI, state activation command or a TCI state deactivation command.

24. The network node (900) of any one of claims 21-23, wherein the successful change or addition of cell or failed mobility procedure is triggered by a Layer 1 / Layer 2-triggered Mobility, LTM, cell switch command.

25. The network node (900) of any one of claims 21-24, wherein the information comprises an indication of time elapsed between reception by the UE of a TCI state for a target cell and mobility procedure execution for said TCI state of said target cell.

26. The network node (900) of any one of claims 21-25, wherein at least some of the logged information is timing-related information related to a last TCI state activation command or last TCI state deactivation received by the UE while the UE was connected to a source cell prior to a mobility procedure execution.

27. A user equipment, UE (800), adapted to: receive, from the wireless network, a command instructing the UE to perform downlink presynchronization for a candidate target cell for mobility or informing the UE thatdownlink synchronization for the candidate target cell for mobility is no longer needed; and subsequently log, in response to a successful change or addition of cell or in response to a failed mobility procedure, information indicative of a timing relationship between said receiving and said successful change or addition of cell or failed mobility procedure.

28. The UE (800) of claim 27, being further adapted to carry out a method according to any one of claims 2-7.

29. A network node (900), adapted to: receive, from a user equipment, UE, a report of a successful or unsuccessful mobility event or of a radio link failure, the report comprising information indicative of a timing relationship between reception, by the UE, of a command instructing the UE to perform downlink pre-synchronization for a candidate target cell for mobility or informing the UE that downlink synchronization for the candidate target cell for mobility is no longer needed, and a subsequent successful change or addition of cell or failed mobility procedure.

30. The network node (900) of claim 29, being further adapted to carry out a method according to any one of claims 9-13.

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