Uplink / downlink synchronization during conditional layer1 / layer 2 triggered mobility

Abstract

An apparatus is disclosed. The apparatus is further configured to monitor parameter(s) associated with each candidate cell to determine whether a TA acquisition execution condition and / or a at least one early DL sync execution condition is met. In response to determining that the at least one TA acquisition execution condition is met for a candidate cell, the apparatus transmits a RACH request message. In response, the apparatus receives the TA. In response to determining that the early DL sync execution condition is met, the apparatus sends a LI measurement report and performs DL sync with an activated TCI state indicated by the gNB- DU. Further, the apparatus monitors the parameters to determine whether the cell switch execution condition is met. In response to determining that the cell switch execution condition is met for the candidate cell, the apparatus is configured to perform a RACH-less handover.

Description

Attorney Docket No. RAKU-12200WOUPLINK / DOWNLINK SYNCHRONIZATION DURING CONDITIONAL LAYER1 / LAYER 2 TRIGGERED MOBILITYCROSS-REFERENCE TO RELATED APPLICATION (S)

[0001] This application claims priority to IN Provisional Application No. 202411062195, filed on August 16, 2024; the entire contents of which are incorporated herein by reference.FIELD

[0002] The present disclosure relates to uplink / downlink synchronization during conditional layerl / layer 2 triggered mobility.BACKGROUND

[0003] The information disclosed in this background section is only for an enhancement of understanding of the general background of the disclosure and should not be taken as an acknowledgment or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

[0004] Mobility or handover ensures seamless connectivity of an ongoing communication session of a User Equipment (UE) by transferring a session from one cell, i.e., a base station or a gNodeB (gNB) to another cell in a connected state while the user is on the move.

[0005] According to the 3 GPP Release 17, a transfer of cell change may be triggered by Layer 3 (L3) measurements and may be performed by Radio Resource Control (RRC) signaling. Further, the concluded 3GPP Release- 18 introduced Layerl / Layer 2 (L1 / L2) triggered mobility (LTM) for improvements in handover latency and an interruption time compared to L3 -based mobility. However, the LTM, as introduced in Release- 18 is reduced in scope and also includes a number of limitations compared to the L3-based mobility.Attorney Docket No. RAKU-12200WO

[0006] Currently, the 3GPP Release-19 work item (WI) aims to remove a number of these limitations. While Release- 18 LTM may support mobility between cells served by the same gNB, the LTM framework in Release 19, has extended to support handover between cells served by different gNBs.SUMMARY

[0007] This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the disclosure. This summary is neither intended to identify key or essential inventive concepts of the present disclosure nor is it intended to determine the scope of the disclosure.

[0008] In one embodiment of the present disclosure, an apparatus is disclosed. The apparatus is configured to receive one or more candidate cell configurations corresponding to one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM). The one or more candidate cell configurations are received from a gNodeB-Control Unit (gNB-CU) of a serving cell. Each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition. The apparatus is further configured to monitor one or more parameters associated with each of the one or more candidate cells based on the received one or more candidate cell configurations. The apparatus monitors the one or more parameters to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met. In response to determining that the at least one TA acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, the apparatus is configured to transmit a Random Access Channel (RACH) request message to request TA associated with the at least one candidate cell. The apparatus transmits the RACH request message to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidateAttorney Docket No. RAKU-12200WO cell. In response to the transmitted RACH request message, the apparatus is configured to receive the TA associated with the at least one candidate cell. In response to determining that the early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, the apparatus is configured to send an Layer 1 (LI) measurement report to a gNB-DU of the serving cell. The apparatus is also configured to perform DL sync with an activated Transmission Configuration Indicator (TCI) state indicated by the gNB-DU. The apparatus is further configured to monitor the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell. In response to determining that the at least one cell switch execution condition is met for the candidate cell, the apparatus is configured to perform a RACH-less handover to the candidate cell. The apparatus performs the RACH-less handover to the candidate cell based on the received corresponding TA.

[0009] In one embodiment of the present disclosure, a method is disclosed. The method includes receiving one or more candidate cell configurations corresponding to one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM). The one or more candidate cell configurations corresponding to one or more candidate cells are received by a User Equipment (UE) from a gNodeB-Control Unit (gNB-CU) of a serving cell. Each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition. The method further includes monitoring one or more parameters associated with each of the one or more candidate cells, to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met. The one or more parameters associated with each of the one or more candidate cells are monitored by the UE, based on the received one or more candidate cell configurations. In response to determining that the at least one TAAttorney Docket No. RAKU-12200WO acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, the method includes transmitting, a Random Access Channel (RACH) request message to request TA associated with the at least one candidate cell. The RACH request message is transmitted by the UE to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidate cell. In response to the transmitted RACH request message, the method includes receiving, by the UE, the TA associated with the at least one candidate cell. In response to determining that the early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, the method includes sending, by the UE, a Layer 1 (LI) measurement report to a gNB-DU of the serving cell. The method also includes performing DL sync with an activated TCI state indicated by the gNB-DU. The method further includes monitoring, by the UE, the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell. In response to determining that the at least one cell switch execution condition is met for the candidate cell, the method includes, performing, by the UE, a RACH-less handover to the candidate cell. The RACH-less handover to the candidate cell is performed based on the received corresponding TA.

[0010] In one embodiment of the present disclosure, an apparatus is disclosed. The apparatus is configured to receive one or more measurement reports corresponding to one or more candidate cells from a User Equipment (UE). The apparatus is further configured to transmit one or more candidate cell configurations corresponding to the one or more candidate cells to the UE. The one or more candidate cell configurations corresponding to the one or more candidate cells are transmitted for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM). The one or more candidate cell configurations corresponding to the one or more candidate cells are transmitted based on the received one or more measurement reports. Each of the one orAttorney Docket No. RAKU-12200WO more candidate cell configurations comprises at least one Timing Advance (TA) acquisition condition and at least one cell switch execution condition.

[0011] In one embodiment of the present disclosure, a method is disclosed. The method includes receiving one or more measurement reports corresponding to one or more candidate cells. The one or more measurement reports corresponding to one or more candidate cells are received by a gNodeB (gNB) of a serving cell, from a User Equipment (UE). The method further includes transmitting one or more candidate cell configurations corresponding to the one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM). The one or more candidate cell configurations corresponding to the one or more candidate cells are transmitted by the gNB to the UE. The one or more candidate cell configurations corresponding to the one or more candidate cells are transmitted based on the received one or more measurement reports. Each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition condition and at least one cell switch execution condition.

[0012] In one embodiment of the present disclosure, a non-transitory computer-readable medium storing instructions are disclosed. The instructions include one or more instructions. The one or more instructions are executed by a User Equipment (UE). The UE comprises one or more processors. The instructions cause the one or more processors to receive one or more candidate cell configurations corresponding to one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM). The one or more candidate cell configurations are received from a gNodeB -Control Unit (gNB-CU) of a serving cell. Each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition. The instructions cause the one or more processors to monitor one or more parameters associated with each of the one or moreAttorney Docket No. RAKU-12200WO candidate cells based on the received one or more candidate cell configurations. The one or more processors monitor the one or more parameters to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met. In response to determining that the at least one TA acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, the instructions cause the one or more processors to transmit a Random Access Channel (RACH) request message to request TA associated with the at least one candidate cell. The one or more processors transmit the RACH request message to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidate cell. In response to the transmitted RACH request message, the instructions cause the one or more processors to receive the TA associated with the at least one candidate cell. In response to determining that the early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, the instructions cause the one or more processors to send an Layer 1 (LI) measurement report to a gNB-DU of the serving cell. Further, the one or more processors perform DL sync with an activated TCI state indicated by the gNB-DU. The instructions cause the one or more processors to monitor the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell. In response to determining that the at least one cell switch execution condition is met for the candidate cell, the one or more instructions cause the one or more processors to perform a RACH-less handover to the candidate cell based on the received corresponding TA.

[0013] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawing. It is appreciated that these drawings depict only typical embodiments of the disclosure and are therefore not to be consideredAttorney Docket No. RAKU-12200WO limiting its scope. The disclosure will be described and explained with additional specificity and detail with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Features, aspects, and advantages of embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like reference numerals denote like elements, and wherein:

[0015] FIG. 1 illustrates a disaggregated architecture of a gNodeB (gNB), in accordance with a conventional technique;

[0016] FIGS. 2A-2B illustrate a sequence flow diagram of an intra Access and Mobility Management Function (AMF) or an intra User Plane Function (UPF) conditional handover, in accordance with a conventional technique;

[0017] FIGS. 3A-3B illustrate a sequence flow diagram of a signalling procedure for a Layer 1 / Layer 2 Triggered Mobility (LTM), in accordance with the state of the art;

[0018] FIGS. 4A-4B illustrate a sequence flow diagram of a signalling procedure for a Conditional LTM (C-LTM), in accordance with an embodiment of the present disclosure;

[0019] FIGS. 5A-5B illustrate a flowchart depicting a method for performing Uplink / Downlink (UL / DL) synchronization during the C-LTM, in accordance with an embodiment of the present disclosure;

[0020] FIG. 6 illustrates a flowchart depicting a method for performing the UL / DL synchronization during the C-LTM, in accordance with an embodiment of the present disclosure; and

[0021] FIG. 7 illustrates a diagram of example components of a device, in accordance with an embodiment of the present disclosure.Attorney Docket No. RAKU-12200WODETAILED DESCRIPTION

[0022] The following detailed description of example embodiments refers to the accompanying drawings. The present disclosure provides illustrations and descriptions, but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations are possible in light of the present disclosure or may be acquired from practice of the implementations. Further, one or more features or components of one embodiment may be incorporated into or combined with another embodiment (or one or more features of another embodiment). Additionally, the flowchart and description of operations provided below relate to at least one of the embodiments in the present disclosure. It should be noted that it is possible to make other embodiments that do not exactly match the flowchart and its description. It is understood that in other embodiments one or more operations may be omitted, one or more operations may be added, one or more operations may be performed simultaneously (at least in part).

[0023] It will be apparent that systems and / or methods, described herein, may be implemented in different forms of hardware, software, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and / or methods should not limit their implementations. Thus, the operation and behavior of the systems and / or methods are described herein without reference to specific software code. It is understood that software and hardware may be designed to implement the systems and / or methods based on the description herein.

[0024] No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” (in other words, nouns not mentioned in the plural) are intended to include one or more items and may be used interchangeably with “one or more.” Also, as used herein, the terms “has,” “have,” “having,” “include,” “including,” or the like are intended to be open-ended terms. Further, theAttorney Docket No. RAKU-12200WO phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Furthermore, expressions such as “at least one of [A] and [B],” “[A] and / or [B],” or “at least one of [A] or [B]” are to be understood as including only A, only B, or both A and B.

[0025] The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the implementations.

[0026] FIG. 1 illustrates a disaggregated architecture of a gNodeB (gNB) 100, in accordance with a conventional technique. The multiple logical entities may include one or more first units 102 represented by at least one distributed unit (referred to as the gNB- DU) and the one or more second units 104 represented by a centralized unit (referred to as gNB-CU). The gNB- CU may be further split into a CU Control Plane (CP) part, also referred to as a gNB-CU-CP, and a CU User Plane (UP) part, also referred to as a gNB-CU-UP. Such a split enables the implementation of the CU-CP and CU-UP parts in different locations. For example, such a split of the gNB 100 into the plurality of logical entities enables flexibility, scalability, and efficiency in the deployment and operation of 5G networks. The disaggregated architecture of the gNB 100 may also include a Radio Unit (gNB-RU), not shown in FIG. 1.

[0027] The gNB-RU may be responsible for the radio transmission and reception of signals. The gNB-RU may include physical Radio Frequency (RF) components such as antennas, power amplifiers, and analog-to-digital converters. The gNB-RU may be located at a cell site or a radio tower, close to the antennas. Further, the gNB-DU may perform baseband processing functions such as physical layer processing, channel coding, and modulation / demodulation. For example, the gNB-DU may host a Radio Link Control (RLC), a Medium Access Control (MAC) layer, and a Physical (PHY) layer. The gNB-DU may also perform scheduling operations. Multiple gNB-RUs may be connected to a single gNB-DU, allowing for centralizedAttorney Docket No. RAKU-12200WO processing of multiple radio units. Multiple gNB-DUs may be connected to a single gNB-CU. The gNB-CU may be responsible for higher-layer processing functions such as radio resource management, mobility management, and connection management. The gNB-CU may provide a centralized control point for multiple gNB-DUs, enabling network-wide coordination and optimization.

[0028] According to one configuration, the gNB-DU may host multiple cells (for example, a maximum of 512 cells as per current specifications). The gNB-CU-CP may host one or more gNB-DUs and one or more gNB-CU-UPs. Also, the gNB-CU-UP may host the Packet Data Convergence Protocol-User Plane part (PDCP-U) and Service Data Adaptation Protocols (SDAPs). More specifically, 3GPP Radio Access Network 3 (RAN3) cardinality for a 5G gNB defines that the gNB 100 may only include one gNB-CU-CP. There may be an “n” number of gNB-DUs controlled by a gNB-CU-CP. Further, there may be “m” number of gNB-CU-UP controlled by the gNB-CU-CP in the gNB 100. Also, one gNB-DU may be served by multiple gNB-CU-UPs. The various entities and / or network functions within the gNB 100 may communicate via one or more interfaces including an Fl-C interface, an Fl-U interface, and an El interface. The Fl-C interface is a control plane interface between the gNB-CU and the gNB-DU within the gNB 100. The Fl-C interface is used for signaling and control messages related to radio resource management, mobility management, and configuration management. The Fl-C interface facilitates coordination between the gNB-CU and the gNB-DU for efficient network operation and service delivery. The Fl-U interface is a user plane interface between the gNB-CU and the gNB-DU in the gNB 100 architecture. The Fl-U is responsible for transporting user data packets between the gNB-CU and the gNB-DU. The Fl-U interface handles user plane data processing, including packet forwarding, Quality of Service (QoS) management, and encryption / decryption functions. The El interface in the gNB 100 connects the gNB-CU-UP entity with the gNB-CU-CP.Attorney Docket No. RAKU-12200WO

[0029] In Rel-18, a Layer 1 / Layer 2 Triggered Mobility (LTM) is limited to an intra-CU mobility. The data scheduling operations generally take place at the gNB-DU. However, in order to support L1 / L2 centric inter-cell change (i.e. change of serving cell) in the disaggregated gNB architecture, a Handover (HO) preparation phase i.e., providing the candidate / target cell configuration to the UE is performed by the gNB-CU-CP, that is autonomously executed by the gNB-DU without requiring further interaction with upper layers in gNB-CU-CP.

[0030] However, there is a need for HO preparation that takes place at the gNB-CU-CP, but is executed autonomously by the gNB-DU, without further interaction with the upper layers.

[0031] Layer 3 mobility has evolved over several releases. A Conditional HO (CHO) and other conditional mobility procedures (Conditional Packet Access Control (CPAC), Secure Conditional Packet Access Control (SCPAC)) were developed to achieve high robustness by enabling the procedure to be executed without necessitating a signaling exchange with the source cell beforehand. The LTM as introduced in Rel-18, offers a short interruption time but not with the same level of robustness as the conditional L3 mobility procedures. In Rel-19, enhancements should be specified so that the system can benefit from both high robustness and short interruption.

[0032] A conditional-LTM (C-LTM) may be a combination of techniques used for the CHO and the LTM.

[0033] During the C-LTM, there is a need for the UE to acquire Timing Advance (TA) of a C- LTM candidate cell by performing Uplink-Synchronization (UL-Sync) to the candidate cell based on a Physical Downlink Control Channel (PDCCH) order from a serving gNodeB- Distributed Unit (gNB-DU). But this is inefficient as such procedure would require the UE to report periodic or event-based LI measurements to the gNB-DU and requires the PDCCH order from the gNB-DU based on the LI measurements. The present disclosure aims to solve theseAttorney Docket No. RAKU-12200WO problems by providing new execution conditions associated with the TA acquisition. The conditions have been elaborated in the forthcoming paragraphs.

[0034] In the context of the concluded 3GPP Release-19 work item (RP-234036: R19- Mobility-Enhancements) on the L1 / L2 Triggered Mobility (LTM), one or more of the following objectives were made during the discussion:

[0035] Specify support of conditional Layer triggered mobility (LTM) [Radio access network (RAN)-2, RAN-3, RAN-1J. a. Specify user equipment (UE) evaluated conditions for triggering LTM. b. Aim to support conditional LTM including subsequent LTM. c. Prioritise intra-centralized unit (CU) LTM. d. Checkpoint to review objective at RAN# 105. RAN Work Groups (WG) work to not start before this checkpoint.

[0036] In the first aspect of the present disclosure, the C-LTM for the CHO is provided (with reference from Technical Specification (TS) 38.300)).

[0037] In one embodiment, the CHO is defined as a handover that is executed by the UE when one or more handover execution conditions are met. The UE starts evaluating the execution condition(s) upon receiving CHO configuration and stops evaluating the execution condition(s) once a handover is executed.

[0038] The following principles apply to the CHO:The CHO configuration contains the configuration of CHO candidate cell(s) generated by the candidate gNB(s) and execution condition(s) generated by the source gNB.An execution condition may consist of one or two trigger condition(s) (CHO events A3 / A5). Only a single Reference Signal (RS) type is supported and at most two different trigger quantities (e.g. Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ), RSRP and Signal-to-Interference-plus-Noise Ratio (SINR), etc.) can beAttorney Docket No. RAKU-12200WO configured simultaneously for the evaluation of CHO execution condition of a single candidate cell.Before any CHO execution condition is satisfied, upon reception of the HO command (without CHO configuration) or an LTM cell switch command Medium Access Control - Control Element (MAC CE), the UE executes the HO procedure as described in clause 9.2.3.2 or the LTM cell switch procedure as described in clause 9.2.3.5, regardless of any previously received CHO configuration.While executing the CHO, i.e. from the time when the UE starts synchronization with the target cell, the UE does not monitor the source cell.

[0039] FIGS. 2A-2B illustrates a sequence flow diagram of an intra Access and Mobility Management Function (AMF) or an intra User Plane Function (UPF) conditional handover, in accordance with a conventional technique. The sequence flow diagrams include several operations outlined as follows. The sequence of operations is performed between the UE 201, a source gNB 203, a target gNB 205, other potential target gNB(s) 207, an AMF 209, and one or more UPF(s) 211.

[0040] As shown in FIGS. 2A-2B, a control plane handling method of a network is disclosed, depicting a basic conditional handover scenario where neither the AMF 209 nor the UPF 211 changes. As in intra-New Radio (intra-NR) Radio Access Network (RAN) handover, in intra- NR RAN CHO, the preparation and execution phase of the conditional handover procedure may be performed without the involvement of a 5G core network; i.e. preparation messages are directly exchanged between gNBs 203 and 205. The release of the resources at the source gNB 203 during the conditional handover completion phase may be triggered by the target gNB 205.Attorney Docket No. RAKU-12200WO

[0041] In an embodiment, operations 202 to operation 216 relate to a handover preparation stage. In an embodiment, operations 218 to operation 226 relate to a handover execution stage. In an embodiment, operations 228 to operation 234 relate to a handover completion stage.

[0042] At operation 202, the AMF 209 provides mobility control information to the network, as specified in clause 9.2.3.2. L At operation 204, the UE 201 sends a measurement control and reports message to the source gNB 203, as specified in clause 9.2.3.2.L At operation 206, the source gNB 203 decides to use the CHO. At operations 208a and 208b, the source gNB 203 requests the CHO for one or more candidate cells belonging to one or more candidate gNBs (i.e., the target gNB 205 and the other target potential gNB(s) 207 respectively). In an embodiment, an individual CHO request message is sent for each candidate cell at the target gNB 205 and at the other target potential gNB(s) 207. At operations 210a and 210b, admission control is performed at the target gNB 205 and the other target potential gNB(s) 207 respectively, as specified in clause 9.2.3.2.1. At operations 212a and 212b, the candidate gNB(s) (the target gNB 205 and the other target potential gNB(s) 207 respectively) sends a CHO response (HO REQUEST ACKNOWLEDGE) including a configuration of the CHO candidate cell(s) to the source gNB 203. The CHO response message is sent for each candidate cell. At operation 214, the source gNB 203 sends an RRCReconfiguration message to the UE 201, containing the configuration of the CHO candidate cell(s) and the CHO execution condition(s). In an embodiment, the CHO configuration of candidate cells may be followed by another reconfiguration from the source gNB 203. In another embodiment, a configuration of a CHO candidate cell may not contain a Dual Active Protocol Stack (DAPS) handover configuration. At operation 216, the UE 201 sends an RRCReconfigurationComplete message to the source gNB 203.

[0043] At operation 218, if early data forwarding is applied, the source gNB 203 sends the EARLY STATUS TRANSFER message. At operation 220, the UE 201 maintains theAttorney Docket No. RAKU-12200WO connection with the source gNB 203 after receiving the CHO configuration and starts evaluating the CHO execution conditions for the candidate cell(s). If at least one CHO candidate cell satisfies the corresponding CHO execution condition, at step 222, the UE 201 detaches from the source gNB 203, applies the stored corresponding configuration for the selected candidate cell, synchronizes to the candidate cell, and completes the RRC handover procedure by sending an RRCReconfigurationComplete message to the target gNB 205. At step 224, user data may be exchanged between the UPF 211, the source gNB 203, and the other potential target gNB(s) 207. At step 226, the UE 201 releases stored CHO configurations after the successful completion of the RRC handover procedure.

[0044] At operation 228, the target gNB 205 sends the HANDOVER SUCCESS message to the source gNB 203 to inform that the UE 201 has successfully accessed the target cell. At operation 230, in response to the HANDOVER SUCCESS message, the source gNB 203 sends a SECONDARY NODE (SN) STATUS TRANSFER message following the principles described in step 216 of Intra-AMF / UPF Handover, as specified in clause 9.2.3.2.1. In an embodiment, late data forwarding may be initiated (i.e., step 232) as soon as the source gNB 203 receives the HANDOVER SUCCESS message. At operation 234, the source gNB 203 sends the HANDOVER CANCEL message towards the other signaling connections or other candidate target gNBs (i.e., the target gNB 205 and the other target potential gNB(s) 207), if any, to cancel the CHO for the UE 201.

[0045] In the second aspect of the present disclosure, the conditional LTM for L1 / L2 Triggered Mobility (LTM) is provided (with reference from TS 38.300).

[0046] The LTM is a procedure in which a gNB (i.e., the source gNB 203) receives the LI measurement report(s) from the UE 201. On the basis of the received LI measurement report(s), the gNB 203 may change UE’s 201 serving cell by a cell switch command signaled via the MAC CE. The cell switch command indicates an LTM candidate configuration that theAttorney Docket No. RAKU-12200WO gNB previously prepared and provided to the UE through RRC signaling. Subsequently, the UE may switch to the target configuration according to the cell switch command. The LTM procedure can be used to reduce the mobility latency.

[0047] In an embodiment, when the UE is configured by the network, it is possible to activate Transmission Configuration Indicator (TCI) states of one or multiple cells that are different from the current serving cell. For instance, the TCI states of the LTM candidate cells can be activated in advance before any of those cells become the serving cell. This allows the UE to be downlink (DL) synchronized with those cells, thereby facilitating a faster cell switch to one of those cells when the cell switch is triggered. All the activated TCI states, except those received in the cell switch command, are deactivated upon LTM cell switch execution.

[0048] In an embodiment, when the UE is configured by the network, it is possible to initiate UL Timing Advance (TA) acquisition (called early TA) procedure of one or multiple cells that are different from the current serving cells. If the cell has the same NTA as the current serving cells or NTA=0, an early TA acquisition procedure is not required. The network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition procedure is triggered by the PDCCH order as specified in clause 9.2.6 or realized through UE-based TA measurement as configured by the RRC. In the former case, the gNodeB / gNB-DU to which the candidate cell belongs, and calculates the TA value and sends it to the gNB / gNB-DU to which the serving cell belongs via the gNB-CU. The serving cell sends the TA value in the LTM cell switch command MAC CE when triggering the LTM cell switch. In the latter case, the UE performs TA measurement for the candidate cells after being configured by the RRC but the exact time the UE performs TA measurement is up to UE implementation. The UE applies the TA value measured by itself and performs random-access channel (RACH)-less LTM upon receiving the cell switch command if it does not include anyAttorney Docket No. RAKU-12200WO valid TA value. The network may also send a TA value in the LTM cell switch command MAC CE without the early TA acquisition.

[0049] In an embodiment, depending on an availability of a valid TA value, the UE may perform either the RACH-less LTM or a RACH-based LTM cell switch. If the valid TA value is provided in the cell switch command, the UE applies the TA value as instructed by the network. In the case where UE-based TA measurement is configured, but no valid TA value is provided in the cell switch command, the UE applies the valid TA value by itself if available. The UE performs the RACH-less LTM cell switch upon receiving the cell switch command whenever a valid TA value is available. If no valid TA value is available, the UE may perform the RACH-based LTM cell switch.

[0050] In an embodiment, regardless of whether the UE is configured for the UE-based TA measurement for a certain candidate cell, it will still follow the PDCCH order, which includes performing a random access procedure toward one or more candidate cells. This also applies to the candidate cells for which the UE is capable of deriving TA values by itself. Additionally, regardless of whether the UE has already performed the random access procedure toward the candidate cells, it will still follow the UE-based measurement configuration if configured by the network.

[0051] For the RACH-less LTM, the UE accesses the target cell using either a configured grant or a dynamic grant. The configured grant is provided in the LTM candidate configuration, and the UE selects the configured grant occasion associated with the beam indicated in the cell switch command. Upon initiation of the LTM cell switch to the target cell, the UE starts to monitor PDCCH on the target cell for dynamic scheduling. Before the RACH-less LTM procedure completion, the UE shall not trigger the random access procedure if it does not have a valid Physical Uplink Control Channel (PUCCH) resource for triggered Scheduling Requests (SRs).Attorney Docket No. RAKU-12200WO

[0052] The following principles apply to the LTM:Security keys are maintained upon the LTM cell switch;Subsequent LTM is supported.

[0053] The LTM may support both intra-gNB-DU and inter-gNB-DU mobility within the same gNB-CU. Also, the LTM may support both intra-frequency and inter-frequency mobility, including mobility to inter-frequency cells that are not a currently serving cell. The LTM is supported only for licensed spectrum. The following scenarios are supported:Primary Cell (PCell) change in non-Carrier Aggregation (non-CA) scenario and nonDual Connectivity (non-DC) scenario;PCell and Secondary Cell(s) (SCell(s)) change in CA scenario;Dual connectivity scenario: including PCell and Master Cell Group (MCG) SCell(s) change and intra- Secondary Node (intra-SN) Primary Secondary Cell (PSCell) and Secondary Cell Group (SCG) SCell(s) change without Master Node (MN) involvement. The LTM for simultaneous PCell and PSCell change is not supported.

[0054] While the UE has stored the LTM candidate configurations, the UE can also execute any L3 handover except for the DAPS handover. In the RRC message which the UE applies for any L3 handover (except the DAPS HO), the LTM candidate configurations may be added / modified / released by the target cell.

[0055] FIGS. 3A-3B illustrate a sequence flow diagram of a signalling procedure 300 for the LTM, in accordance with the state of the art. The sequence flow diagrams include several operations outlined as follows. The sequence of operations is performed between the UE 201 and the source gNB 203 (also referred to herein as “gNB 203”). The UE 201 may be in an RRC connected state with the gNB 203.

[0056] At operation 302, the UE 201 transmits a measurement report message to the gNB 203. At operation 304, the gNB 203 decides to configure the LTM and initiates LTM preparationAttorney Docket No. RAKU-12200WO i.e., preparation of LTM candidate configurations, based on the received measurement report message.

[0057] At operation 306, the gNB 203 transmits an RRCReconfiguration message to the UE 201. The RRCReconfiguration message includes the LTM candidate configurations.

[0058] At operation 308, the UE 201 stores the LTM candidate configurations and transmits an RRCReconfigurationComplete message to the gNB 203. Therefore, the operations 302-308 may correspond to the LTM preparation.

[0059] At operation 310, the UE 201 performs DL synchronization with the LTM candidate cell(s) before receiving a cell switch command from the gNB 203. The UE 201 may activate and deactivate TCI states of the LTM candidate cell(s), as triggered by the gNB 203.

[0060] At operation 312, the UE 201 may perform UL synchronization with the LTM candidate cell(s) before receiving the cell switch command. The UE 201 may perform the UL synchronization by using the UE-based TA measurement, if configured, and / or by transmitting a preamble towards the candidate cell, as triggered by the gNB 203. When the UE-based TA measurement is configured, the UE 201 acquires the TA value(s) of the candidate cell(s) by measurement. The UE 201 may perform the early TA acquisition with the LTM candidate cell(s) as requested by the network before receiving the cell switch command as specified in clause 9.2.6. The UE 201 may perform the early TA acquisition via Contention Free Random Access (CFRA) procedure triggered by the PDCCH order from the source cell, following which the UE 201 sends a preamble towards the indicated candidate cell. In order to minimize data interruption of the source cell due to the CFRA towards the LTM candidate cell(s), the UE 201 does not receive a random access response from the network for the purpose of TA value acquisition and the TA value of the candidate cell is indicated in the cell switch command. Moreover, the UE 201 may not maintain a TA timer for the LTM candidate cell andAttorney Docket No. RAKU-12200WO relies on network implementation to guarantee the TA validity. Specifically, the operations 310 and 312 correspond to early synchronization with the LTM candidate cell(s).

[0061] At operation 314, the UE 201 performs LI measurements on the configured LTM candidate cell(s) and transmits LI measurement reports to the gNB 203. The UE 201 may perform the LI measurements as long as the RRC reconfiguration (received at operation 306) is applicable.

[0062] At operation 316, the gNB 203 may determine to execute a cell switch to the target cell. At operation 318, the gNB 203 transmits an LTM cell switch command MAC CE triggering cell switch. The LTM cell switch command may include a target configuration ID which indicates an index of the candidate configuration of the target cell, a beam indicated with a TCI state, or beams indicated with DL and UL TCI states, and a timing advance command for the target cell, if available. At operation 320, the UE 201 switches to the target cell and applies the candidate configuration indicated by the target configuration ID.

[0063] At operation 322, the UE 201 performs the RACH procedure towards the target cell, if the UE 201 does not have a valid TA of the target cell as specified in clause 5.18.35 of TS 38.321[6],

[0064] The operations 314 to 322 may correspond to LTM cell switch execution.

[0065] At operation 324, the UE 201 completes the LTM cell switch procedure by sending RRCReconfigurationComplete message to the target cell. If the UE 201 has performed a Random Access (RA) procedure at operation 322, the UE 201 considers that LTM cell switch execution is successfully completed when the RACH procedure is successfully completed. For the RACH-less LTM, the UE 201 considers that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0066] Subsequent LTM is performed by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidateAttorney Docket No. RAKU-12200WO configurations after each LTM cell switch completion. For example, the operations 310-324 may be performed multiple times for the subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in step 306. The general procedure over the air interface applies to SCG LTM. Further details of the SCG LTM may be found in TS 37.340

[0021] .

[0067] FIGS. 4A-4B illustrate a sequence flow diagram of a signalling procedure 400 for the C-LTM, in accordance with an embodiment of the present disclosure. The sequence flow diagrams include several operations outlined as follows. The sequence of operations is performed between the UE 201 and the gNB 203. The UE 201 may be in an RRC connected state with the gNB 203.

[0068] In an embodiment, subsequent LTM is performed by repeating the early synchronization, the LTM cell switch execution, and the LTM cell switch completion steps without releasing other LTM candidate configurations after each LTM cell switch completion. For the understanding of the following description of FIGS. 4A-4B, the LTM may correspond to the C-LTM with early UL / DL synchronization.

[0069] At operation 402, the UE 201 sends a L3 MeasurementReport message to the gNB 203. In an embodiment, in response to the received MeasurementReport message, at operation 404, the gNB 203 may decide to configure the C-LTM and initiate C-LTM candidate cell preparation.

[0070] At operation 406, the gNB 203 transmits an RRCRe configuration message to the UE 201. The RRCReconfiguration message may include TA acquisition execution condition, DL synchronization execution condition and the C-LTM switch execution condition. Further, the RRCReconfiguration message may include the C-LTM candidate configurations.

[0071] At operation 408, the UE 201 stores the C-LTM candidate configurations and the respective execution conditions and transmits an RRCReconfigurationComplete message to theAttorney Docket No. RAKU-12200WO gNB 203. In an embodiment, the RRC Reconfiguration message may include a new “TA acquisition execution condition” for UL synchronization and / or a “Downlink Synchronization execution condition” for DL synchronization or a common “UL / DL synchronization condition” which is applicable to both the UL and DL. At operation 409, the UE 201 may monitor the TA acquisition execution condition and / or the Downlink Synchronization execution condition for all C-LTM candidate cells. In another embodiment, the UE 201 may monitor the C-LTM cell switch execution conditions after the UL / DL synchronization, i.e., after operations 410-412, as explained below.

[0072] At operation 410, the UE 210 may report a periodic or event-based LI measurement report (not shown in FIGS. 4A-4B) and based on the Downlink Synchronization execution condition configured for the UE 201, the gNB 203 may activate the TCI states of the C-LTM candidate cells. The UE 201 monitors the Downlink Synchronization execution condition and performs the DL synchronization with the C-LTM candidate cell(s). The UE 201 may also activate and deactivate the TCI states of the C-LTM candidate cell(s).

[0073] At operation 412, the UE 201 may perform the UL synchronization with the C-LTM candidate cell(s), by transmitting a preamble in the RACH Request towards the candidate cell. In an embodiment, the UE 201 performs the early TA acquisition with the C-LTM candidate cell(s) by monitoring the TA acquisition execution condition before executing the cell switch based on the C-LTM cell switch execution condition. This is done via the CFRA triggered by the TA acquisition execution condition getting satisfied, following which the UE 201 sends the preamble to the indicated candidate cell. The UE 201 receives the TA of the C-LTM candidate cell in the Random Access Response message from the gNB-DU. This is essential for the UE 201 to perform the RACH-less C-LTM switch to the selected target cell.

[0074] At operation 414, the UE 201 starts monitoring the C-LTM cell switch execution condition to perform cell switch. The UE 201 is supposed to have successfully executed theAttorney Docket No. RAKU-12200WODL and UL synchronization. This enables the UE 201 to execute the RACH-less C-LTM cell switch. The UE 201 performs the LI measurements on the configured C-LTM candidate cell(s) and optionally transmits the LI measurement reports to the gNB 203 (i.e., serving gNB-DU). The LI measurement should be performed as long as RRC reconfiguration (step 406) is applicable.

[0075] At operation 416, the UE 201 decides to execute the C-LTM cell switch to the target cell, if the C-LTM cell switch execution condition is satisfied. The C-LTM cell switch may be RACH-less, if the TA acquisition in operation 414 was successful. At operation 418, the UE 201 switches to the target cell and applies the candidate configuration indicated by the target configuration ID.

[0076] At operation 420, the UE 201 performs the random access procedure towards the target cell, if UE 201 does not have the valid TA of the target cell.

[0077] At operation 422, the UE 201 completes the LTM cell switch procedure by sending RRCReconfigurationComplete message to the target cell (i.e., the gNB 203). If the UE 201 has performed the RA procedure in step 420, the UE 201 considers that C-LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For the RACH-less C-LTM, the UE 201 considers that LTM cell switch execution is successfully completed when the UE 201 determines that the network has successfully received its first UL data.

[0078] In an embodiment, operations 410-422 can be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in step 406.

[0079] In an embodiment, the procedure over the air interface, as described in FIGS. 4A-4B may be applicable to both intra-gNB-DU C-LTM and inter-gNB-DU C-LTM.

[0080] In an embodiment, referring to the first and the second aspects of the present disclosure:Attorney Docket No. RAKU-12200WO

[0081] During the CHO, the source gNB 203 sends an RRCReconfiguration message to the UE 201, containing the configuration of the CHO candidate cell(s) and the CHO execution condition(s). a. The UE 201 maintains a connection with the source gNB 203 after receiving the CHO configuration and starts evaluating the CHO execution conditions for the candidate cell(s). If at least one CHO candidate cell satisfies the corresponding CHO execution condition, the UE 201 detaches from the source gNB 203, applies the stored corresponding configuration for the selected candidate cell, synchronizes to the candidate cell, and completes the RRC handover procedure by sending the RRCReconfigurationComplete message to the target gNB 205.

[0082] During the LTM, the network may request the UE 201 to perform the early TA acquisition of the candidate cell before the cell switch. The early TA acquisition procedure is triggered by the PDCCH order. The UE 201 performs the RACH and the gNB / gNB-DU to which the candidate cell belongs, calculates the TA value, and sends it to the gNB / gNB-DU to which the serving cell belongs via the gNB-CU. a. The serving cell sends the TA value in the LTM cell switch command MAC CE when triggering the LTM cell switch. The UE 201 applies the TA value and performs the RACH- less LTM upon receiving the cell switch command.

[0083] Therefore, in the C-LTM, the UE 201 is configured with one or more LTM candidate cell(s) and C-LTM execution condition(s). The UE 201 executes the C-LTM when the execution condition is met, by detaching from the source gNB 203. Further, the UE 201 applies the stored corresponding C-LTM candidate cell configuration for that selected candidate cell. Furthermore, the UE 201 performs RACH-less C-LTM HO to that candidate cell and completes the RACH-less C-LTM HO procedure by sending the RRCReconfigurationComplete message to the target gNB 205.Attorney Docket No. RAKU-12200WO

[0084] The UL / DL synchronization during the C-LTM, as disclosed herein may provide numerous advantages as follows:

[0085] Faster UL and DL synchronization.

[0086] Require Less signaling.

[0087] Less overhead on the UE and the network.

[0088] FIGS. 5A-5B illustrate a flowchart depicting a method 500 for performing the UL / DL synchronization during the C-LTM, in accordance with an embodiment of the present disclosure. The method 500 may be performed by the UE 201.

[0089] At step 502, the UE 201 may transmit, to the gNB-CU of a serving cell (i.e., the gNB- CU associated with the gNB 203), one or more layer 3 measurement reports corresponding to the one or more neighbouring cells. The one or more candidate cells may be selected among the one or more neighbouring cells.

[0090] At step 504, the UE 201 may receive one or more candidate cell configurations corresponding to the one or more candidate cells for the C-LTM. The one or more candidate cell configurations may be received from a gNodeB-Control Unit (gNB-CU) of a serving cell 203. Each of the one or more candidate cell configurations may include at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition.

[0091] At step 506, the UE 201 may monitor based on the received one or more candidate cell configurations, one or more parameters associated with each of the one or more candidate cells. The monitoring may be performed to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met.

[0092] At step 508, in response to determining that the at least one TA acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, the UE may transmit a Random Access Channel (RACH) request message to request TA associatedAttorney Docket No. RAKU-12200WO with the at least one candidate cell. The UE 201 may transmit the RACH request message to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidate cell. In an embodiment, the RACH request message includes a predefined preamble indicating that the RACH request message corresponds to TA acquisition. In an embodiment, in response to determining that the at least one TA acquisition execution condition is met for the at least one candidate cell, the UE 201 may transmit the LI measurement report associated with the at least one candidate cell. The UE 201 may transmit the LI measurement report to the gNB-DU of the serving cell. The UE 201 may transmit the LI measurement report to enable the gNB-DU of the serving cell to send a Physical Downlink Control Channel (PDCCH) order to acquire the TA of at least one candidate cell.

[0093] At step 510, in response to the transmitted RACH request message, the UE 201 may receive the TA associated with the at least one candidate cell. In an embodiment, for receiving the TA associated with the at least one candidate cell, the UE 201 may receive, from the target gNB-DU associated with the at least one candidate cell, a Random Access Response (RAR) message including the TA. In an embodiment, for receiving the TA associated with the at least one candidate cell, the UE 201 may receive the TA associated with the at least one candidate cell via the gNB-DU through the gNB-CU of the serving cell. This enables faster UL synchronization with the candidate cell.

[0094] At step 512, in response to determining that the at least one early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, the UE 201 may send an Layer 1 (LI) measurement report to a gNB-DU of the serving cell. Thereafter, the UE 201 may perform DL synchronization with an activated TCI state indicated by the gNB-DU. In one embodiment, the UE 201 sends the LI measurement report associated with the at least one candidate cell to enable the serving gNB-DU to activate one or more TCI states for the at least one candidate cell beams.Attorney Docket No. RAKU-12200WO

[0095] At step 514, the UE 201 may monitor the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell. In an embodiment, the one or more parameters comprises one of Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal to Interference and Noise Ratio (SINR).

[0096] At step 516, in response to determining that the at least one cell switch execution condition is met for the candidate cell, the UE 201 may perform a RACH-less handover to the candidate cell based on the received corresponding TA. Thus, the present disclosure reduces measurement overhead on the UE 201 and the network, and thereby enables the UE 201 to perform RACH-less handover effectively and efficiently.

[0097] In an embodiment, the TA acquisition execution condition, the DL synchronization execution condition and the at least one cell switch execution condition correspond to at least one of LTM3 and LTM5 measurement events.

[0098] FIG. 6 illustrates a flowchart depicting a method 600 for performing the UL / DL synchronization during the C-LTM, in accordance with an embodiment of the present disclosure. The method 600 may be performed by the gNB 203 of the serving cell.

[0099] At step 602, the gNB 203 may receive, from the UE 201, the one or more measurement reports corresponding to the one or more candidate cells.

[0100] At step 604, the gNB 203 may transmit, to the UE 201, the one or more candidate cell configurations corresponding to the one or more candidate cells for the C-LTM based on the received one or more measurement reports. Each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition condition and at least one cell switch execution condition.

[0101] At step 606, the gNB 203 may receive, from the UE 201, the one or more LI measurement reports associated with at least one candidate cell among the one or moreAttorney Docket No. RAKU-12200WO candidate cells. The one or more LI measurement reports may be received when the UE 201 determines that the DL synchronization execution condition is met for the at least one candidate cell.

[0102] At step 608, the gNB 203 may activate the one or more TCI states for at least one candidate cell beam corresponding to the at least one candidate cell based on the received one or more LI measurement reports. The one or more TCI states may be activated to enable the UE 201 to perform the DL synchronization with the at least one candidate cell.

[0103] At step 610, the gNB 203 may receive, from the UE, the RACH request message requesting TA corresponding to the at least one candidate cell among the one or more candidate cells. The RACH request message may be received when the UE 201 determines that the at least one TA acquisition condition is met for the at least one candidate cell.

[0104] At step 612, the gNB 203 may transmit, to the UE 201 and / or gNB-CU, the TA associated with the at least one candidate cell based on the received RACH request message.

[0105] FIG. 7 illustrates an embodiment of an example device 700 (may also be referred to as the apparatus 700), in accordance with an embodiment of the present disclosure. As shown in FIG. 7, the device 700 includes a processor 710, a memory 720, a storage component 730, an input component 740, an output component 750, a communication interface 760, and a bus 770. The device / apparatus 700 may be implement the one or more above-mentioned methods.

[0106] The processor 710, as used herein, means any type of computational circuit that may comprise hardware elements and software elements. The processor 710 may be embodied as a multi-core processor, a single core processor, or a combination of one or more multi-core processors and / or one or more single core processors, a distributed processing system, or the like. The processor 710 may be a Central Processing Unit (CPU), a graphics processing unit (GPU), an accelerated processing unit (APU), an application-specific integrated circuit (ASIC),Attorney Docket No. RAKU-12200WO or another type of processing component. In one non-limiting example, the processor 710 may be configured to perform one or more functionalities of the core network entity.

[0107] The memory 720 includes a non-transitory computer readable medium. The memory 720 includes a random-access memory (RAM), a read only memory (ROM), and / or another type of dynamic or static storage device (e.g., a flash memory, a magnetic memory, and / or an optical memory) that stores information and / or instructions for use by processor 710. The memory 720 comprises machine-readable instructions which are executable by the processor 710. These machine-readable instructions when executed by the processor 710 cause the processor 710 to perform one or more method steps of an embodiment described above.

[0108] The storage component 730 stores information and / or software related to the operation and use of the device 700. For example, storage component 730 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, and / or a solid-state disk), a compact disc (CD), a digital versatile disc (DVD), a floppy disk, a cartridge, a magnetic tape, and / or another type of non-transitory computer-readable medium, along with a corresponding drive.

[0109] The input component 740 is configured to receive information, such as user input. For example, the input component 740 may include, but not be limited to, a touch screen display, a keyboard, a keypad, a mouse, a button, a switch, and / or a microphone. Additionally, or alternatively, the input component 740 may include a sensor for sensing information (e.g., a global positioning system (GPS), an accelerometer, a gyroscope, and / or an actuator).

[0110] The output component 750 is configured to provide output information from the device 700. For example, the output component 750 may be, but not limited to, a display, a speaker, an instruction device to an external device, and / or one or more light-emitting diodes (LEDs).

[0111] The communication interface 760 is an interface that provides a communication connection to other devices, such as external devices and internal devices. The connection by the communication interface 760 can be a wired connection, a wireless connection, or aAttorney Docket No. RAKU-12200WO combination of wired and wireless connections, and can be a direct connection or an indirect connection via a communication network that exists between the device 700 and other devices. In other words, the standard of the communication interface 760 is not limited.

[0112] The bus 770 acts as an interconnect between the processor 710, the memory 720, the storage component 730, the input component 740, the output component 750, and the communication interface 760 of the device 700. The bus 770 may include a wired interconnection or a wireless interconnection.

[0113] The number and arrangement of components are shown in FIG. 7 are provided as an example. In practice, device 700 may include additional components, fewer components, different components, or differently arranged components than those shown in FIG. 7. Additionally, or alternatively, a set of components (e.g., one or more components) of the device 700 may perform one or more functions described as being performed by another set of components of the device 700. Further, one or more method steps described in any of the embodiments may be performed utilizing a plurality of devices 700 in communication with one another.

[0114] Examples of the techniques and apparatus described herein include, but are not limited to, the following enumerated embodiments:

[0115] [1] An apparatus configured to:

[0116] receive, from a gNodeB-Control Unit (gNB-CU), one or more candidate cell configurations corresponding to one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM), wherein each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition;Attorney Docket No. RAKU-12200WO

[0117] monitor, based on the received one or more candidate cell configurations, one or more parameters associated with each of the one or more candidate cells, to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met;

[0118] in response to determining that the at least one TA acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, transmit, to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidate cell, a Random Access Channel (RACH) request message to request TA associated with the at least one candidate cell;

[0119] in response to the transmitted RACH request message, receive the TA associated with the at least one candidate cell;

[0120] in response to determining that the at least one early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, send an Layer 1 (LI) measurement report to a gNB-DU of the serving cell and perform DL sync with an activated Transmission Configuration Indicator (TCI) state indicated by the gNB-DU;

[0121] monitor the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell; and

[0122] in response to determining that the at least one cell switch execution condition is met for the candidate cell, perform a RACH-less handover to the candidate cell based on the received corresponding TA.

[0123] [2] The apparatus as described in [1], further configured to: a. in response to determining that the DL sync execution condition is met for the at least one candidate cell, send, to a serving gNB-DU, the LI measurement report associated with theAttorney Docket No. RAKU-12200WO at least one candidate cell to enable the serving gNB-DU to activate one or more TCI states for the at least one candidate cell beams; and b. in response to determining that the at least one TA acquisition execution condition is met for the at least one candidate cell, transmit, to a serving gNB-DU, the LI measurement report associated with the at least one candidate cell to enable the serving gNB-DU to send a Physical Downlink Control Channel (PDCCH) order to acquire the TA of at least one candidate cell.

[0124] [3] The apparatus as described in any one of [1] to [2], wherein to receive the TA associated with the at least one candidate cell, the apparatus is configured to: a. receive, from the target gNB-DU associated with the at least one candidate cell, a Random Access Response (RAR) message including the TA.

[0125] [4] The apparatus as described in any one of [1] to [3], wherein the apparatus is configured to receive the TA associated with the at least one candidate cell via a serving gNB- DU through the gNB-CU.

[0126] [5] The apparatus as described in any one of [1] to [4], wherein prior to receiving the one or more candidate cell configurations corresponding to the one or more candidate cells, the apparatus is configured to: a. transmit, to the gNB-CU, one or more layer 3 measurement reports corresponding to the one or more neighbouring cells, wherein the one or more candidate cells is select among the one or more neighbouring cells.

[0127] [6] The apparatus as described in any one of [1] to [5], wherein the RACH request message comprises a predefined preamble indicating that the RACH request message corresponds to TA acquisition.

[0128] [7] The apparatus as described in any one of [1] to [6], wherein the at least one TA acquisition execution condition, the at least one early DL sync execution condition, and the atAttorney Docket No. RAKU-12200WO least one cell switch execution condition correspond to at least one of LTM3 and LTM5 measurement events.

[0129] [8] The apparatus as described in any one of [1] to [7], wherein the one or more parameters comprises one of Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal to Interference and Noise Ratio (SINR).

[0130] [9] The apparatus as described in any one of [1] to [8], wherein the apparatus corresponds to a User Equipment (UE).

[0131]

[0010] A method comprising:

[0132] receiving, by a User Equipment (UE) from a gNodeB-Control Unit (gNB-CU), one or more candidate cell configurations corresponding to one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM), wherein each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition;

[0133] monitor, by the UE, based on the received one or more candidate cell configurations, one or more parameters associated with each of the one or more candidate cells, to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met;

[0134] in response to determining that the at least one TA acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, transmitting, by the UE, to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidate cell, a Random Access Channel (RACH) request message to request TA associated with the at least one candidate cell;

[0135] in response to the transmitted RACH request message, receiving, by the UE, the TA associated with the at least one candidate cell;Attorney Docket No. RAKU-12200WO

[0136] in response to determining that the at least one early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, sending, by the UE, a Layer 1 (LI) measurement report to a gNB-DU of the serving cell and perform DL sync with an activated TCI state indicated by the gNB-DU;

[0137] monitoring, by the UE, the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell; and

[0138] in response to determining that the at least one cell switch execution condition is met for the candidate cell, performing, by the UE, a RACH-less handover to the candidate cell based on the received corresponding TA.

[0139]

[0011] The method as described in

[0010] , further comprising: a. in response to determining that the DL sync execution condition is met for the at least one candidate cell, sending, to a serving gNB-DU, the LI measurement report associated with the at least one candidate cell to enable the serving gNB-DU to activate one or more TCI states for the at least one candidate cell beams; and b. in response to determining that the at least one TA acquisition execution condition is met for the at least one candidate cell, transmitting, by the UE to a serving gNB-DU, the LI measurement report associated with the at least one candidate cell to enable the serving gNB- DU to send a Physical Downlink Control Channel (PDCCH) order to acquire the TA of at least one candidate cell.

[0140]

[0012] The method as described in any one of

[0010] to

[0011] , wherein receiving the TA associated with the at least one candidate cell comprises: a. receiving, by the UE from the target gNB-DU associated with the at least one candidate cell, a Random Access Response (RAR) message including the TA.Attorney Docket No. RAKU-12200WO

[0141]

[0013] The method as described in any one of

[0010] to

[0012] , wherein receiving the TA associated with the at least one candidate cell comprises: a. receiving, by the UE, the TA associated with the at least one candidate cell via a serving gNB-DU through the gNB-CU.

[0142]

[0014] The method as described in any one of

[0010] to

[0013] , wherein prior to receiving the one or more candidate cell configurations corresponding to the one or more candidate cells, the method comprises: a. transmitting, by the UE to the gNB-CU, one or more layer 3 measurement reports corresponding to the one or more neighbouring cells, wherein the one or more candidate cells is select among the one or more neighbouring cells.

[0143]

[0015] The method as described in any one of

[0010] to

[0014] , wherein the RACH request message comprises a predefined preamble indicating that the RACH request message corresponds to TA acquisition.

[0144]

[0016] The method as described in any one of

[0010] to

[0015] , wherein the at least one TA acquisition execution condition, the at least one early DL sync execution condition, and the at least one cell switch execution condition correspond to at least one of LTM3 and LTM5 measurement events.

[0145]

[0017] The method as described in any one of

[0010] to

[0016] , wherein the one or more parameters comprises one of Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal to Interference and Noise Ratio (SINR).

[0146]

[0018] An apparatus configured to: a. receive, from a User Equipment (UE), one or more measurement reports corresponding to one or more candidate cells; and b. transmit, to the UE, one or more candidate cell configurations corresponding to the one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM) basedAttorney Docket No. RAKU-12200WO on the received one or more measurement reports, wherein each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition condition and at least one cell switch execution condition.

[0147]

[0019] The apparatus as described in

[0018] , further configured to: a. receive, from the UE, one or more Layer 1 (LI) measurement reports associated with at least one candidate cell among the one or more candidate cells when the UE determines that the at least one early DL sync execution condition is met for the at least one candidate cell; and b. activate one or more Transmission Configuration Indicator (TCI) states for at least one candidate cell beam corresponding to the at least one candidate cell based on the received one or more LI measurement reports to enable the UE to perform Downlink (DL) synchronization with the at least one candidate cell.

[0148]

[0020] The apparatus as described in any one of

[0018] to

[0019] , further configured to: a. receive, from the UE, a Random Access Channel (RACH) request message requesting TA corresponding to the at least one candidate cell among the one or more candidate cells when the UE determines that the TA acquisition condition is met for the at least one candidate cell; and b. transmit, to the UE and / or gNB-CU, the TA associated with the at least one candidate cell based on the received RACH request message.

[0149]

[0021] The apparatus as described in any one of

[0018] to

[0020] , wherein the apparatus corresponds to a gNodeB (gNB).

[0150]

[0022] A method comprising: a. receiving, by a gNodeB (gNB) from a User Equipment (UE), one or more measurement reports corresponding to one or more candidate cells; and b. transmitting, by the gNB to the UE, one or more candidate cell configurations corresponding to the one or more candidate cells for a conditional Layer 1 / Layer 2 TriggeredAttorney Docket No. RAKU-12200WOMobility (C-LTM) based on the received one or more measurement reports, wherein each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition condition and at least one cell switch execution condition.

[0151]

[0023] The method as described in

[0022] , further comprising: a. receiving, by the gNB from the UE, one or more Layer 1 (LI) measurement reports associated with at least one candidate cell among the one or more candidate cells when the UE determines that the at least one early DL sync execution condition is met for the at least one candidate cell; and b. activating one or more Transmission Configuration Indicator (TCI) states for at least one candidate cell beam corresponding to the at least one candidate cell based on the received one or more LI measurement reports to enable the UE to perform Downlink (DL) synchronization with the at least one candidate cell.

[0152]

[0024] The method as described in any one of

[0022] to

[0023] , further comprising: a. receiving, by the gNB from the UE, a Random Access Channel (RACH) request message requesting TA corresponding to the at least one candidate cell among the one or more candidate cells when the UE determines that the at least one TA acquisition condition is met for the at least one candidate cell; and b. transmitting, by the gNB to the UE and / or gNB-CU, the TA associated with the at least one candidate cell based on the received RACH request message.

[0153]

[0025] A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions that, when executed by a User Equipment (UE) comprising one or more processors, cause the one or more processors to:

[0154] receive, from a gNodeB-Control Unit (gNB-CU), one or more candidate cell configurations corresponding to one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM), wherein each of the one or more candidate cell configurationsAttorney Docket No. RAKU-12200WO comprises at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition;

[0155] monitor, based on the received one or more candidate cell configurations, one or more parameters associated with each of the one or more candidate cells, to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met;

[0156] in response to determining that the at least one TA acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, transmit, to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidate cell, a Random Access Channel (RACH) request message to request TA associated with the at least one candidate cell;

[0157] in response to the transmitted RACH request message, receive the TA associated with the at least one candidate cell;

[0158] in response to determining that the at least one early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, send an Layer 1 (LI) measurement report to a gNB-DU of the serving cell and perform DL sync with an activated Transmission Configuration Indicator (TCI) state indicated by the gNB-DU;

[0159] monitor the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell; and

[0160] in response to determining that the at least one cell switch execution condition is met for the candidate cell, perform a RACH-less handover to the candidate cell based on the received corresponding TA.Attorney Docket No. RAKU-12200WO

[0161] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the elements. The elements can be at least one of a hardware device or a combination of hardware devices and software modules.

[0162] It is understood that terms including “unit” or “module” at the end may refer to the unit for processing at least one function or operation and may be implemented in hardware, software, or a combination of hardware and software.

[0163] While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.

[0164] The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein.

[0165] Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

[0166] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, andAttorney Docket No. RAKU-12200WO any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.

[0167] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of at least one embodiment, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Claims

Attorney Docket No. RAKU-12200WOWe Claim:

1. An apparatus configured to: receive, from a gNodeB-Control Unit (gNB-CU), one or more candidate cell configurations corresponding to one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM), wherein each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition; monitor, based on the received one or more candidate cell configurations, one or more parameters associated with each of the one or more candidate cells, to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met; in response to determining that the at least one TA acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, transmit, to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidate cell, a Random Access Channel (RACH) request message to request TA associated with the at least one candidate cell; in response to the transmitted RACH request message, receive the TA associated with the at least one candidate cell; in response to determining that the at least one early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, send a Layer 1 (LI) measurement report to a gNB-DU of the serving cell and perform DL sync with an activated Transmission Configuration Indicator (TCI) state indicated by the gNB-DU;Attorney Docket No. RAKU-12200WO monitor the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell; and in response to determining that the at least one cell switch execution condition is met for the candidate cell, perform a RACH-less handover to the candidate cell based on the received corresponding TA.

2. The apparatus as claimed in claim 1, further configured to: in response to determining that the DL sync execution condition is met for the at least one candidate cell, send, to a serving gNB-DU, the LI measurement report associated with the at least one candidate cell to enable the serving gNB-DU to activate one or more TCI states for the at least one candidate cell beams; and in response to determining that the at least one TA acquisition execution condition is met for the at least one candidate cell, transmit, to the serving gNB-DU, the LI measurement report associated with the at least one candidate cell to enable the serving gNB-DU to send a Physical Downlink Control Channel (PDCCH) order to acquire the TA of at least one candidate cell.

3. The apparatus as claimed in claim 1, wherein to receive the TA associated with the at least one candidate cell, the apparatus is configured to: receive, from the target gNB-DU associated with the at least one candidate cell, a Random Access Response (RAR) message including the TA.

4. The apparatus as claimed in claim 1, wherein the apparatus is configured to receive the TA associated with the at least one candidate cell via a serving gNB-DU through the gNB-CU.Attorney Docket No. RAKU-12200WO5. The apparatus as claimed in claim 1, wherein prior to receiving the one or more candidate cell configurations corresponding to the one or more candidate cells, the apparatus is configured to: transmit, to the gNB-CU, one or more layer 3 measurement reports corresponding to one or more neighbouring cells, wherein the one or more candidate cells are selected among the one or more neighbouring cells.

6. The apparatus as claimed in claim 1, wherein the RACH request message comprises a predefined preamble indicating that the RACH request message corresponds to TA acquisition.

7. The apparatus as claimed in claim 1, wherein the at least one TA acquisition execution condition, the at least one early DL sync execution condition, and the at least one cell switch execution condition correspond to at least one of LTM3 and LTM5 measurement events.

8. The apparatus as claimed in claim 1, wherein the one or more parameters comprises one of Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal to Interference and Noise Ratio (SINR).

9. The apparatus as claimed in claim 1, wherein the apparatus corresponds to a User Equipment (UE).

10. A method compri sing : receiving, by a User Equipment (UE) from a gNodeB-Control Unit (gNB-CU), one or more candidate cell configurations corresponding to one or more candidate cells for aAttorney Docket No. RAKU-12200WO conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM), wherein each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition execution condition, at least one early Downlink (DL) synchronization (sync) execution condition, and at least one cell switch execution condition; monitoring, by the UE, based on the received one or more candidate cell configurations, one or more parameters associated with each of the one or more candidate cells, to determine whether one of the at least one TA acquisition execution condition or the at least one early DL sync execution condition is met; in response to determining that the at least one TA acquisition execution condition is met for at least one candidate cell among the one or more candidate cells, transmitting, by the UE, to a target gNB -Distributed Unit (gNB-DU) associated with the at least one candidate cell, a Random Access Channel (RACH) request message to request TA associated with the at least one candidate cell; in response to the transmitted RACH request message, receiving, by the UE, the TA associated with the at least one candidate cell; in response to determining that the at least one early DL sync execution condition is met for the at least one candidate cell among the one or more candidate cells, sending, by the UE, a Layer 1 (LI) measurement report to a gNB-DU of the serving cell and perform DL sync with an activated TCI state indicated by the gNB-DU; monitoring, by the UE, the one or more parameters associated with the at least one candidate cell to determine whether the at least one cell switch execution condition is met for a candidate cell among the at least one cell; and in response to determining that the at least one cell switch execution condition is met for the candidate cell, performing, by the UE, a RACH-less handover to the candidate cell based on the received corresponding TA.Attorney Docket No. RAKU-12200WO11. The method as claimed in claim 10, further comprising: in response to determining that the DL sync execution condition is met for the at least one candidate cell, sending, to a serving gNB-DU, the LI measurement report associated with the at least one candidate cell to enable the serving gNB-DU to activate one or more TCI states for the at least one candidate cell beams; and in response to determining that the at least one TA acquisition execution condition is met for the at least one candidate cell, transmitting, by the UE to a serving gNB-DU, the LI measurement report associated with the at least one candidate cell to enable the serving gNB- DU to send a Physical Downlink Control Channel (PDCCH) order to acquire the TA of at least one candidate cell.

12. The method as claimed in claim 10, wherein receiving the TA associated with the at least one candidate cell comprises: receiving, by the UE from the target gNB-DU associated with the at least one candidate cell, a Random Access Response (RAR) message including the TA.

13. The method as claimed in claim 10, wherein receiving the TA associated with the at least one candidate cell comprises: receiving, by the UE, the TA associated with the at least one candidate cell via a serving gNB-DU through the gNB-CU.

14. The method as claimed in claim 10, wherein prior to receiving the one or more candidate cell configurations corresponding to the one or more candidate cells, the method comprises:Attorney Docket No. RAKU-12200WO transmitting, by the UE to the gNB-CU, one or more layer 3 measurement reports corresponding to one or more neighbouring cells, wherein the one or more candidate cells are selected among the one or more neighbouring cells.

15. The method as claimed in claim 10, wherein the RACH request message comprises a predefined preamble indicating that the RACH request message corresponds to TA acquisition.

16. The method as claimed in claim 10, wherein the at least one TA acquisition execution condition, the at least one early DL sync execution condition, and the at least one cell switch execution condition correspond to at least one of LTM3 and LTM5 measurement events.

17. The method as claimed in claim 10, wherein the one or more parameters comprises one of Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal to Interference and Noise Ratio (SINR).

18. An apparatus configured to: receive, from a User Equipment (UE), one or more measurement reports corresponding to one or more candidate cells; and transmit, to the UE, one or more candidate cell configurations corresponding to the one or more candidate cells for a conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM) based on the received one or more measurement reports, wherein each of the one or more candidate cell configurations comprises at least one Timing Advance (TA) acquisition condition and at least one cell switch execution condition.

19. The apparatus as claimed in claim 18, further configured to:Attorney Docket No. RAKU-12200WO receive, from the UE, one or more Layer 1 (LI) measurement reports associated with at least one candidate cell among the one or more candidate cells when the UE determines that the at least one early DL sync execution condition is met for the at least one candidate cell; and activate one or more Transmission Configuration Indicator (TCI) states for at least one candidate cell beam corresponding to the at least one candidate cell based on the received one or more LI measurement reports to enable the UE to perform Downlink (DL) synchronization with the at least one candidate cell.

20. The apparatus as claimed in claim 18, further configured to: receive, from the UE, a Random Access Channel (RACH) request message requesting TA corresponding to the at least one candidate cell among the one or more candidate cells when the UE determines that the TA acquisition condition is met for the at least one candidate cell; and transmit, to the UE and / or gNB-CU, the TA associated with the at least one candidate cell based on the received RACH request message.

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