Conditional layer 1 / layer 2 triggered mobility for multiple transmit / receive points user equipment

Abstract

An apparatus is disclosed. The apparatus performs one of: a RACH-less C-LTM cell switch of one of at least two TRPs to a candidate TRP of a C-LTM candidate cell for which at least one C-LTM cell switch execution condition is met, a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell, based on the determination that one of the at least two TRPs is a master TRP, a RACH-less C-LTM cell switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells, based on determination that the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs.

Description

CONDITIONAL LAYER 1 / LAYER 2 TRIGGERED MOBILITY FOR MULTIPLETRANSMIT / RECEIVE POINTS USER EQUIPMENTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to India Provisional Application No. 202411084610, filed on November 5, 2024, and India Non-Provisional Application No. 202411084610, filed on March 27, 2025, the entire contents of which are incorporated herein by reference.FIELD

[0002] The present disclosure relates to Conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM) for multiple Transmit / Receive Points (m-TRP) User Equipment (UE).BACKGROUND

[0003] The information disclosed in this background section is only for the 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., base station or gNodeB (gNB) to another cell in a connected state while the user is on the move.

[0005] According to the concluded Third Generation Partnership Project (3GPP) Release 15, a handover or 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 Layer 1 / 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 the Release- 18 is reduced in scope and also includes a number of limitations compared to the L3-based mobility.

[0006] Currently, the ongoing 3 GPP Release- 19 work item (WI) on mobility enhancements aims to remove a number of these limitations. While Release-18 LTM is supported between cells served by the same gNB, the LTM framework in Release 19, has been 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 disclosure nor is it intended to determine the scope of the disclosure.

[0008] According to one embodiment of the present disclosure, an apparatus is disclosed. The apparatus is configured to receive one or more Conditional-Layer 1 / Layer 2 Triggered Mobility (C-LTM) candidate cell configurations corresponding to each of at least two Transmit / Receive Points (TRPs). The apparatus is configured to receive the one or more C-LTM candidate cell configurations at a User Equipment (UE) configured with the at least two TRPs. The apparatus is configured to receive the one or more C-LTM candidate cell configurations from a gNodeB (gNB). The one or more C-LTM candidate cell configurations comprise one or more C-LTM cell switchexecution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs. The apparatus is configured to monitor one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs. The apparatus is configured to monitor the one or more parameters based on the received one or more C-LTM candidate cell configurations. The apparatus is configured to monitor the one or more parameters to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP. The C-LTM candidate cell or the corresponding candidate TRP is among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs. Further, in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, the apparatus is configured to perform a Random Access Channel (RACH)-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met. Alternatively, in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, the apparatus is configured to perform: determine whether the one of the at least two TRPs is a master TRP. In response to determining that the one of the at least two TRPs is the master TRP and the at least one C-LTM cell switch execution condition is met, the apparatus is configured to perform a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C- LTM candidate cell. Alternatively, in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidateTRP, the apparatus is configured to perform: determine whether the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs. In response to determining that the at least one C-LTM cell switch execution condition is met for the other C-LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs, the apparatus is configured to perform a RACH-less C-LTM cell switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.

[0009] According to another embodiment of the present disclosure, a method is disclosed. The method includes receiving one or more Conditional-Layer 1 / Layer 2 Triggered Mobility (C-LTM) candidate cell configurations corresponding to each of at least two Transmit / Receive Points (TRPs). The method includes receiving the one or more C-LTM candidate cell configurations at a User Equipment (UE) configured with the at least two TRPs. The method includes receiving the one or more C-LTM candidate cell configurations from a gNodeB (gNB). The one or more C- LTM candidate cell configurations comprise one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs. The method includes monitoring one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs. The method includes monitoring the one or more parameters based on the received one or more C-LTM candidate cell configurations. The method includes monitoring the one or more parameters to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP. The C-LTM candidate cell or the corresponding candidate TRP isamong the one or more C-LTM candidate cells corresponding to one of the at least two TRPs.Further, in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, the method includes performing a Random Access Channel (RACH)-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met. Alternatively, in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, the method includes performing: determining whether the one of the at least two TRPs is a master TRP. In response to determining that the one of the at least two TRPs is the master TRP and the at least one C-LTM cell switch execution condition is met, the method includes performing a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell. Alternatively, in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, the method includes performing: determining whether the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs. In response to determining that the at least one C-LTM cell switch execution condition is met for the other C-LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs, the method includes performing a RACH-less C-LTM cell switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.

[0010] According to another embodiment of the present disclosure, a non-transitory computer- readable medium is disclosed. The non-transitory computer-readable medium stores instructions.The instructions comprise one or more instructions that are executed at a User Equipment (UE).The UE comprises one or more processors. The one or more instructions cause the one or more processors to receive one or more Conditional-Layer 1 / Layer 2 Triggered Mobility (C-LTM) candidate cell configurations corresponding to each of at least two Transmit / Receive Points (TRPs). The one or more processors are configured to receive the one or more C-LTM candidate cell configurations at a User Equipment (UE) configured with the at least two TRPs. The one or more processors are configured to receive the one or more C-LTM candidate cell configurations from a gNodeB (gNB). The one or more C-LTM candidate cell configurations comprise one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C- LTM candidate cells and corresponding one or more candidate TRPs. The one or more processors are configured to monitor one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs. The one or more processors are configured to monitor the one or more parameters based on the received one or more C-LTM candidate cell configurations. The one or more processors are configured to monitor the one or more parameters to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP. The C-LTM candidate cell or the corresponding candidate TRP is among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs. Further, in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, the one or more processors are configured to perform a Random Access Channel (RACH)-less C- LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidatecell for which the at least one C-LTM cell switch execution condition is met. Alternatively, in response to determining that the at least one C-LTM cell switch execution condition is met for theC-LTM candidate cell or the corresponding candidate TRP, the one or more processors are configured to perform: determine whether the one of the at least two TRPs is a master TRP. In response to determining that the one of the at least two TRPs is the master TRP and the at least one C-LTM cell switch execution condition is met, the one or more processors are configured to perform a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell. Alternatively, in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, the one or more processors are configured to perform: determine whether the at least one C- LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs. In response to determining that the at least one C-LTM cell switch execution condition is met for the other C- LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs, the one or more processors are configured to perform a RACH-less C-LTM cell switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.

[0011] 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 are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the disclosure and are therefore not to be considered limiting of its scope. Thedisclosure will be described and explained with additional specificity and detail in the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] 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:FIG. 1 illustrates a disaggregated architecture of a gNodeB (gNB), in accordance with the state of the art;FIG. 2 illustrates a sequence flow diagram of a Layerl / Layer 2 triggered mobility (LTM) procedure, in accordance with one or more conventional techniques;FIGS. 3A-3C illustrate various scenarios associated with Multiple Transmit / Receive Points (m- TRP) User Equipment (UE), in accordance with one or more conventional techniques;FIGS. 4A-4D illustrate methods to perform a Conditional -Layer 1 / Layer 2 Triggered Mobility (C- LTM) for the m-TRP UE, in accordance with an embodiment of the present disclosure;FIGS. 5A-5B illustrate a flow chart of an example method for performing the C-LTM for the m- TRP UE, in accordance with an embodiment of the present disclosure;FIG. 6 illustrates a flow chart of an example method for discarding other TRPs without performing a Radio Resource Control (RRC) re-establishment, in accordance with an embodiment of the present disclosure; andFIG. 7 illustrates an embodiment of an example device, in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION

[0013] The following detailed description of example embodiments refers to the accompanying drawings. 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 the 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 one of the various embodiments. 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).

[0014] 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 is not limiting of the 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.

[0015] Even though particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of implementations. In fact, many of these features may be combined in ways not specifically recited in the claimsand / or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of implementations includes each dependent claim in combination with every other claim in the claim set.

[0016] 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” 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, the 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.

[0017] 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 the practice of the implementations.

[0018] The present disclosure relates to Third Generation Partnership Project (3GPP) Rel 19 Work Item (WI) on Layer 1 / Layer 2 Triggered Mobility (LTM). The WI specifies support of conditional- LTM (C-LTM) in Radio Access Network 1 (RAN 1), RAN 2, and RAN 3. The WI specifies User Equipment (UE)-evaluated conditions for triggering LTM. The WI defines support for the C-LTM including subsequent LTM. The WI also prioritizes intra-Central Unit (CU) LTM.

[0019] Layer 3 (L3) mobility has evolved over several 3GPP releases. Further, conditional handover (CHO) and other conditional mobility procedures (Conditional PSCell Addition orChange (CP AC), Subsequent Conditional PSCell Addition or Change (SCPAC)) were developed to achieve high robustness by enabling the procedure to be executed without necessitating a signaling exchange with a source cell beforehand. The LTM as introduced in Rel-18 offers short interruption time, but not with the same level of robustness as conditional L3 mobility procedures. However, the LTM is required to have a system that can benefit from both the high robustness and short interruption.

[0020] Specifically, the C-LTM is a combination of techniques used for the CHO and the LTM. In the C-LTM, the source cell sends a conditional LTM configuration of a candidate cell via a Radio Resource Control (RRC)Reconfiguration message to a User Equipment (UE), which includes LTM candidate configurations, and corresponding execution conditions. Each candidate cell provides a corresponding execution condition for the conditional LTM.

[0021] Accordingly, in the C-LTM, the UE is configured with one or more LTM candidate cell(s) and their corresponding C-LTM execution condition(s), and when the execution condition is met, the UE executes a C-LTM cell switch towards a candidate cell. For example, when the execution condition is met, the UE detaches from the source cell, applies the stored corresponding C-LTM candidate cell configuration for a selected candidate cell, and performs a Random Access Channel (RACH)-less C-LTM HO to that candidate cell, if the UE has a valid Timing Advance (TA) of the candidate cell. The UE completes the RACH-less C-LTM HO procedure by sending an RRCReconfigurationComplete message to a target gNodeB-Distributed Unit (gNB-DU).

[0022] Moreover, the Rel-18 LTM procedure has been defined in Technical Specification (TS) 38.300. Specifically, the LTM is a procedure in which a gNB receives LI measurement report(s) from a UE, and the gNB may change the UE’s serving cell, based on the received LI measurementreport(s). The gNB may change the UE’s serving cell by a cell switch command signaled via aMedium Access Control-Control Element (MAC CE). The cell switch command indicates theLTM candidate configuration that the gNB previously prepared and provided to the UE through Radio Resource Control (RRC) signaling. Thereafter, the UE switches to the target configuration according to the cell switch command. The LTM procedure can be used to reduce the mobility latency.

[0023] In Rel-18 LTM, it is possible to activate Transmission Configuration Indicator (TCI) states of one or multiple cells that are different from the current serving cell, when configured by a network. For instance, the TCI states of the LTM candidate cells can be activated in advance before any of those cells become the serving cells. 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 the LTM cell switch execution.

[0024] Moreover, when configured by the network, it is possible to initiate Uplink (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 Network Timing Advance (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 the early TA acquisition of a candidate cell before a cell switch. The early TA acquisition procedure is triggered by a Physical Downlink Control Channel (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 gNB / gNB-DU to which the candidate cell belongs calculates the TA value and sends the calculated TA value to the gNB / gNB-DU to which the serving cell belongsvia the gNB-Centralized Unit (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, i.e., the UE- based TA measurement, 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 measured TA value and performs a RACH-less LTM upon receiving the cell switch command if the cell switch command does not include any valid TA value. The network may also send the TA value in the LTM cell switch command MAC CE without the early TA acquisition.

[0025] Therefore, depending on the availability of the valid TA value, the UE performs 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 an available valid TA value. The UE performs the RACH-less LTM cell switch upon receiving the cell switch command whenever the valid TA value is available. If no valid TA value is available, the UE performs the RACH-based LTM cell switch.

[0026] Furthermore, regardless of whether the UE is configured for the UE-based TA measurement for a certain candidate cell, the UE may follow the PDCCH order, which includes performing a random access procedure towards one or more candidate cells. This also applies to the candidate cells for which the UE is capable of deriving the TA values by itself. Additionally, regardless of whether the UE has already performed the random access procedure toward the candidate cells, the UE may follow the UE-based measurement configuration if configured by the network.

[0027] 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 theUE selects the configured grant occasion associated with a beam indicated in the cell switch command. Upon initiation of the LTM cell switch to the target cell, the UE starts to monitor the PDCCH on the target cell for dynamic scheduling. Before RACH-less LTM procedure completion, the UE may not trigger random access procedures if the UE does not have a valid PUCCH resource for triggered Scheduling Requests (SRs).

[0028] Furthermore, in the LTM, security keys are maintained upon the LTM cell switch, and the subsequent LTM is supported.

[0029] The LTM supports both an intra-gNB- Distributed Unit (DU) and an inter-gNB-DU mobility within the same gNB-Centralized Unit (CU). Also, the LTM supports both an intrafrequency and an inter-frequency mobility, including mobility to an inter-frequency cell that is not a current serving cell. However, the LTM is supported only for licensed spectrum. For example, the following scenarios are supported in the LTM:• Primary Cell (PCell) change in a non-Carrier Aggregation (C A) scenario and a nonDual Connectivity (DC) scenario;• PCell and Secondary Cell (SCell(s)) change in the CA scenario;• DC scenario including PCell and Master Cell Ground (MCG) SCell(s) change and an intra-Secondary Node (SN) Primary and Secondary cells (PSCell) and Secondary Cell Ground (SCG) SCell(s) change without Master Node (MN) involvement. However, the LTM for simultaneous PCell and PSCell change is not supported.

[0030] While the UE has stored the LTM candidate configurations, the UE can also execute any L3 handover except for a Dual Active Protocol Stack (DAPS) handover. In the RRC message that the UE uses to request any Layer 3 handover (excluding DAPS), the target cell has the ability to add, modify, or release the LTM candidate configurations.

[0031] In general, the cell switch command is conveyed in the MAC CE, which contains the required information to perform the LTM cell switch.

[0032] FIG. 1 illustrates a disaggregated architecture of a gNB 100, in accordance with the state of the art. The multiple logical entities may include one or more first units 102 represented by at least one distributed unit (referred to as 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 CULT 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.

[0033] 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, anda Physical (PHY) layer. The gNB-DU may also perform scheduling operations. Multiple gNB- RUs can be connected to a single gNB-DU, allowing for centralized 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.

[0034] 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 (SDAP). More specifically, 3GPP RAN3 cardinality for the 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-UP. 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 interface 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-CP entity with the gNB-CU-UP.

[0035] In Rel-18, the LTM is limited to intra-CU mobility. 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 100, the 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 the gNB-CU-CP.

[0036] However, there is a need for Handover (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.

[0037] FIG. 2 illustrates a sequence flow diagram of an LTM procedure 200, in accordance with one or more conventional techniques. The sequence flow diagram includes a sequence of operations between a UE 201 and a gNB 203. The gNB 203 may have a similar architecture as explained in reference to the gNB 100 (shown in FIG. 1). The UE 201 may be in an RRC-connected state with the gNB 203.

[0038] At operation 202, the UE 201 transmits an L3 measurement report to the gNB 203. At operation 204, the gNB 203 determines to configure the LTM and initiates preparation of LTM candidate configurations, based on the received L3 measurement report message.

[0039] At operation 206, the gNB 203 transmits an RRCReconfiguration to the UE 201. TheRRCReconfiguration message includes the LTM candidate configurations.

[0040] At operation 208, the UE 201 stores the LTM candidate configurations and transmits anRRCReconfigurationComplete to the gNB 203. Therefore, the operations 202-208 may correspond to LTM preparation.

[0041] At operation 210, the UE 201 performs DL synchronization with the LTM candidate cell(s) before receiving the cell switch command from the gNB 203. The UE 201 may activate the TCI states of the LTM candidate cell(s), as triggered by the gNB 203.

[0042] At operation 212, the UE 201 may perform UL synchronization with the LTM candidate cell(s) indicated by the network in the PDCCH order, 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 RACH 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 Based Random Access (CFRA) triggered by the PDCCH order from the source cell, following which the UE 201 sends a preamble towards the indicated candidate cell in the RACH Request message. 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. Further, the TA value of the candidate cell is sent to the serving DU via the gNB-CU which is indicated in the cell switch command to the UE 201. Moreover, the UE 201 may not maintain a TA timer for the LTM candidate cell and relies onnetwork implementation to guarantee the TA validity. Specifically, the operations 210 and 212 correspond to early synchronization with the LTM candidate cell(s).

[0043] At operation 214, 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 206) is applicable.

[0044] At operation 216, the gNB 203 may determine to execute a cell switch to a target cell. At operation 218, the gNB 203 transmits an LTM cell switch command Medium Access Control- Control Element (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 220, the UE 201 switches to the target cell and applies the candidate configuration indicated by the target configuration ID.

[0045] At operation 222, 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.

[0046] The operations 214 to 222 may correspond to LTM cell switch execution.

[0047] At operation 224, the UE 201 completes the LTM cell switch procedure by sending an RRCReconfigurationComplete message to the target cell. If the UE 201 has performed a Random Access (RA) procedure at operation 222, the UE 201 considers that LTM cell switch execution is completed when the RACH procedure is 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 corresponding first UL data.

[0048] Subsequent LTM is done by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidate configurations after each LTM cell switch completion. For example, the operations 210-224 may be performed multiple times for the subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in step 206. The general procedure over the air interface applies to SCG LTM. Further details of SCG LTM may be found in TS 37.340. The operations 210 to 224 may be performed multiple times for subsequent LTM cell switch executions using LTM candidate configuration(s) provided in the operation 206. The procedure over the air interface described in FIG.2 is applicable to both an intra-gNB-DU LTM and an inter-gNB-DU LTM. The overall LTM procedures over the Fl -C interface are captured in TS 38.401.

[0049] However, in a multi-Transmission and Reception Point (m-TRP) operation, a serving cell may schedule the UE 201 from two TRPs (belonging to the same or different cell), providing better coverage, reliability and / or data rates for a Physical Downlink Shared Channel (PDSCH), a Physical Downlink Control Channel (PDCCH), a Physical Uplink Shared Channel (PUSCH), and a Physical Uplink Control Channel (PUCCH). Specifically, there are two different operation modes to schedule multi-TRP PDSCH transmissions, i.e., a single- Downlink Control Information (DCI) mode and a multi -DCI mode. In the single-DCI mode, the UE 201 may be scheduled by the same DCI for both TRPs, and in the multi-DCI mode, the UE 201 may be scheduled by independent DCIs from each TRP.

[0050] Furthermore, the UE 201 may receive two PDCCH transmissions, one from each TRP, carrying the same DCI. For multi-TRP PUSCH repetition, according to indications in the singleDCI or in a semi-static configured grant provided over the RRC, the UE 201 may perform PUSCHtransmission of the same contents toward two TRPs with corresponding beam directions associated with different spatial relations. For multi-TRP PUCCH repetition, the UE 201 may performPUCCH transmission of the same contents toward two TRPs with corresponding beam directions associated with different spatial relations.

[0051] For an inter-cell multi-TRP operation and the multi -DCI PDSCH transmission, one or more TCI states may be associated with a Synchronization Signal Block (SSB) with a Physical Cell Identity (PCI) different from a serving cell PCI. The activated TCI states can be associated with at most one PCI different from the serving cell PCI at a time.

[0052] FIGS. 3A-3C illustrates various scenarios associated with Multiple Transmit / Receive Points (m-TRP) User Equipment (UE) 301 (hereinafter referred to as the UE 301), in accordance with one or more conventional techniques. The UE 301 may correspond to the UE 201, as shown in FIG. 2. FIG. 3 A illustrates a scenario where a TRP 1 and a TRP 2 transmit two different PDSCH (i.e., PDSCH 1 and PDSCH 2) to theUE 301. However, a single control channel (i.e., PDCCH / DCI) is transmitted by the TRP 1. Therefore, in case there is a problem in a radio link associated with the TRP 1 and the PDCCH reception fails, the communication via the TRP 2 is also impacted. FIG. 3B illustrates a scenario where the TRP 1 and the TRP 2 transmit two different PDSCH (i.e., PDSCH 1 and PDSCH 2) to the UE 301. Further, each of the TRP 1 and the TRP 2 transmits a corresponding control channel (i.e., PDCCH 1 / DCI and PDCCH 2 / DCI, respectively). In such a case, if there is any problem in the radio link with one of the TRPs (i.e., the TRP 1 or TRP 2), the communication via the other TRP can be intact. FIG. 3C illustrates a scenario wherein the TRP 1 and the TRP 2 are used to jointly process the DL and UL signals.

[0053] When the UE, configured with multiple TRPs (mTRP), is also configured with the C-LTM, the following conditions may occur:• There are at least two TRPs configured for the UE.• The TRPs may belong to different cells, which could belong to a same or a different gNB-DU, but the same gNB.• The UE may be configured with one or more C-LTM candidate cells coupled with an L1 / L3 execution condition.• The C-LTM candidate cells and the L1 / L3 execution condition may be TRP specific i.e., the candidate cells and execution condition of one TRP may not be applicable to the other.

[0054] The present disclosure provides a solution for performing the C-LTM when only one of the TRPs satisfies the LI execution condition for the C-LTM mobility and the other TRP(s) does not satisfy the LI execution condition.

[0055] FIGS. 4A-4D illustrate methods to perform the C-LTM for the m-TRP UE 301, in accordance with an embodiment of the present disclosure. Referring to FIG. 4A, at step 402a, the UE 301 may determine that only one TRP satisfies the execution condition(s). In one or more embodiments, the execution condition(s) may include an L1 / L3 execution condition, and a TA acquisition condition. Further, in response to determining that only one TRP (for example, the TRP 1) satisfies the execution condition(s), at step 404a, the UE 301 may perform the RACH-less C-LTM cell switch for only that TRP (for example, the TRP 1). The other TRPs may be retained by the UE 301 with the existing serving cell, as long as they can continue. In one embodiment, the UE 301 may retain the other TRPs in their current serving cell unless the TRP’s C-LTM executioncondition(s) is satisfied, and the C-LTM cell switch may be executed. In another embodiment, the UE 301 may retain the other TRPs unless the UE 301 detects a Radio Link Failure (RLF) for a TRP, and / or the TRP is autonomously discarded by the UE 301. Moreover, the UE 301 may also ensure that no RRC re-establishment is performed after the RLF detection for said TRP. In one or more embodiments, the UE 301 may attempt for TRP recovery, if configured and feasible.

[0056] Referring to FIG. 4B, at step 402b, the one of the at least two TRPs may be designated / configured as a master TRP by the gNB. Thereafter, at step 404b, the UE 301 may perform the C-LTM cell switch only if the C-LTM cell switch execution condition(s) (referred to here as the execution condition(s)) of the master TRP is satisfied. Further, the role of the master TRP may be assigned dynamically to either of the at least two TRPs, based on mobility and a prevalent radio condition of the at least two TRPs.

[0057] Referring to FIG. 4C, at step 402c, the UE 301 may determine that one of the at least two TRPs satisfies the execution condition(s) for the C-LTM cell switch. Therefore, at step 404c, the UE 301 may perform the C-LTM cell switch for that TRP without waiting for the other TRP’s execution condition(s) that may be present in the target C-LTM candidate configuration. At step 406c, the UE 301 may autonomously discard the other TRPs before performing the RACH-less C- LTM cell switch, as no valid target TRP can be selected for the other TRPs. At step 408c, new TRPs may be configured again at the target gNB-DU, if multi TRP is required.

[0058] Referring to FIG. 4D, at step 402d, the UE 301 may determine whether the execution condition(s) is satisfied for each of the at least two TRPs (for example, the TRP 1 and the TRP 2). At step 404d, the UE 301 may perform the C-LTM cell switch. Thus, the UE 301 may perform theC-LTM cell switch only when both / all TRPs have the execution condition(s) satisfied.

[0059] In one embodiment, when the C-LTM candidates are not prepared with the mTRP (only prepared for single TRP) and if C-LTM execution condition(s) is satisfied for one TRP at the source, the UE 301 may perform the C-LTM cell switch. Thereafter, the network may configure the mTRP again after a successful C-LTM cell switch.

[0060] Thus, the present disclosure enables the C-LTM mobility with the mTRP UE 301 even when execution condition(s) is satisfied only for one TRP.

[0061] FIGS. 5A-5B illustrate a flow chart of an example method 500 for performing the C-LTM for the m-TRP UE 301, in accordance with an embodiment of the present disclosure. FIG. 6 illustrates a flow chart of an example method 600 for discarding other TRPs without performing a Radio Resource Control (RRC) re-establishment, in accordance with an embodiment of the present disclosure. The methods 500 and 600 may be performed by an apparatus 700 (as shown in Figure 7), where the apparatus 700 corresponds to the UE 301. Further, FIGS. 5A, 5B, and 6 are explained in conjunction for the sake of brevity.

[0062] At step 502, the apparatus 700 receives one or more Conditional-Layer 1 / Layer 2 Triggered Mobility (C-LTM) candidate cell configurations corresponding to each of the at least two Transmit / Receive Points (TRPs). The apparatus 700 receives the one or more C-LTM candidate cells at the UE 301 configured with the at least two TRPs. The apparatus 700 receives the one or more (C-LTM) candidate cell configurations from the gNodeB (gNB). In an embodiment, the one or more C-LTM candidate cell configurations include one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs. In an embodiment, the one or more C-LTM cell switch execution conditions include at least one of an LI execution condition or L3 execution condition.

[0063] At step 504, the apparatus 700 is configured to monitor one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs. The one or more parameters may include Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal To Noise Ratio(SINR). The apparatus 700 is configured to monitor the one or more parameters based on the received one or more C-LTM candidate cell configurations. The apparatus 700 is configured to monitor the one or more parameters to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP. The C-LTM candidate cell or the corresponding candidate TRP is among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs.

[0064] At operation 506, the apparatus 700 is configured to perform one of the following operations as mentioned in subsequent paragraphs. The apparatus 700 is configured to perform one of the following operations in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP.

[0065] At operation 506a, the apparatus 700 is configured to perform a Random Access Channel (RACH)-less C-LTM cell switch of the one of the at least two TRPSs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met. In an advantageous aspect, the configuration ensures the RACH-less C-LTM cell switch with the mTRP UE 301.

[0066] The apparatus 700 is configured to retain the remaining TRPs from the at least two TRPs along with the respective serving cell. The apparatus 700 is configured to retain the remaining TRPs upon performing the RACH-less C-LTM cell switch of the one of the at least two TRPs tothe candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met.

[0067] Further, as shown in Figure 6, upon performing the RACH-less C-LTM cell switch, at operation 602, the apparatus 700 is configured to determine the Radio Link Failure (RLF) associated with the other TRPs among the at least two TRPs. At operation 604, the apparatus 700 is configured to discard the other TRPs without performing the Radio Resource Control (RRC) reestablishment, in response to determining the RLF.

[0068] Thereafter, the apparatus 700 is configured to perform a recovery of the other TRPs. The apparatus 700 is configured to perform the recovery of the other TRPs, in response to discarding the other TRP.

[0069] Referring back to FIG. 5B, at operation 506b, the apparatus 700 is configured to determine whether the one of the at least two TRPs is the master TRP. Further, in response to determining that the one of the at least two TRPs is the master TRP, and the at least one C-LTM cell switch execution condition is met, the apparatus 700 is configured to perform a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell. This configuration reduces latency and improves overall network performance.

[0070] At operation 506c, the apparatus 700 is configured to determine whether the at least one C-LTM cell switch execution is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs. Further, in response to determining that the at least one C-LTM cell switch execution condition is met for the other C-LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs, the apparatus 700 is configured to perform a RACH-less C-LTM cell switch of each of theat least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells. In an advantageous aspect, thus the configuration reduces latency, and interruption time, and consequently improves overall network performance.

[0071] Herein, the apparatus 700 is configured to discard the other TRPs from the at least two TRPs. The apparatus 700 discards the other TRPs, prior to performing the RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell

[0072] FIG.7 illustrates an embodiment of a device / apparatus 700. The device / apparatus 700 may correspond to the UE 301. 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 one or more components of the device 700 may be configured to implement one or more operations / functionalities of the present disclosure as discussed above.

[0073] 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), or another type of processing component.

[0074] 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 opticalmemory) that stores information and / or instructions for use by the 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.

[0075] The storage component 730 stores information and / or software related to the operation and use of the device 700. For example, the 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.

[0076] 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).

[0077] The output component 750 is configured to provide output information from the device 700. For example, the output component 750 may be, but not be limited to, a display, a speaker, an instruction device to an external device, and / or one or more light-emitting diodes (LEDs).

[0078] 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 a combination of wired and wireless connections, and can be a direct connection or an indirect connection via acommunication network that exists between the device 700 and other devices. In other words, the standard of the communication interface 760 is not limited.

[0079] 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.

[0080] The number and arrangement of components 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.

[0081] Examples of the techniques and apparatus described herein include, but are not limited to, the following enumerated embodiments:[1] An apparatus configured to: receive, at a User Equipment (UE) configured with at least two Transmit / Receive Points (TRPs), from a gNodeB (gNB), one or more Conditional-Layerl / Layer 2 Triggered Mobility (C- LTM) candidate cell configurations corresponding to each of the at least two TRPs, wherein the one or more C-LTM candidate cell configurations comprises one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs;monitor, based on the received one or more C-LTM candidate cell configurations, one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs; in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, perform one of: a Random Access Channel (RACH)-less Conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM) cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met; determine whether the one of the at least two TRPs is a master TRP, and in response to determining that the one of the at least two TRPs is the master TRP and the at least one C-LTM cell switch execution condition is met, perform a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell; or determine whether the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs, and in response to determining that the at least one C- LTM cell switch execution condition is met for the other C-LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs,perform a RACH-less C-LTM cell switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.[2] The apparatus as described in [1], wherein upon performing the RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met, the apparatus is configured to retain remaining TRPs from the at least two TRPs along with respective serving cell.[3] The apparatus as described in any one of [1] to [2], wherein the apparatus is configured to: determine a Radio Link Failure (RLF) associated with the other TRPs among the at least two TRPs; and in response to determining the RLF, discard the other TRPs without performing a Radio Resource Control (RRC) re-establishment.[4] The apparatus as described in any one of [1] to [3], wherein the apparatus is configured to: perform recovery of the other TRPs, in response to discarding the other TRP.[5] The apparatus as described in any one of [1] to [4], wherein prior to perform the RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell, the apparatus is configured to: discard the other TRPs from the at least two TRPs.[6] The apparatus as described in any one of [1] to [5], wherein the one or more C-LTM cell switch execution conditions comprise at least one of an LI execution condition or L3 execution condition.[7] A method comprising:receiving, at a User Equipment (UE) configured with at least two Transmit / Receive Points (TRPs), from a gNodeB (gNB), one or more Conditional-Layerl / Layer 2 Triggered Mobility (C- LTM) candidate cell configurations corresponding to each of the at least two TRPs, wherein the one or more C-LTM candidate cell configurations comprises one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs; monitoring, based on the received one or more C-LTM candidate cell configurations, one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs; in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, performing one of a Random Access Channel (RACH)-less Conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM) cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met; determining whether the one of the at least two TRPs is a master TRP, and in response to determining that the one of the at least two TRPs is the master TRP and the at least one C-LTM cell switch execution condition is met, perform a RACH-less C-LTM cellswitch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell; or determining whether the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs, and in response to determining that the at least one C- LTM cell switch execution condition is met for the other C-LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs, perform a RACH-less C-LTM cell switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.[8] The method as described in [7], wherein upon performing the RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met, the method comprises: retaining remaining TRPs from the at least two TRPs along with respective serving cell.[9] The method as described in any one of [7] to [8], wherein the method comprises: determining a Radio link Failure (RLF) associated with the other TRPs among the at least two TRPs; and in response to determining the RLF, discarding the other TRPs without performing a Radio Resource Control (RRC) re-establishment.

[0010] The method as described in any one of [7] to [9], wherein the method comprises: performing recovery of the other TRPs, in response to discarding the other TRP.

[0011] The method as described in any one of [7] to

[0010] , wherein prior to performing the RACH- less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell, the method comprises: discarding the other TRPs from the at least two TRPs.

[0012] The method as described in any one of [7] to

[0011] , wherein the one or more C-LTM cell switch execution conditions comprise at least one of an LI execution condition or L3 execution condition.

[0013] A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions that, when executed at a User Equipment (UE), the UE comprising one or more processors, cause the one or more processors to: receive, from a gNodeB (gNB), one or more Conditional-Layerl / Layer 2 Triggered Mobility (C-LTM) candidate cell configurations corresponding to each of the at least two TRPs, wherein the one or more C-LTM candidate cell configurations comprises one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs; monitor, based on the received one or more C-LTM candidate cell configurations, one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for aC-LTM candidate cell or a corresponding candidate TRP among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs;in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, perform one of: a Random Access Channel (RACH)-less Conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM) C-LTM switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met; determine whether the one of the at least two TRPs is a master TRP, and in response to determining that the one of the at least two TRPs is the master TRP, and the at least one C-LTM cell switch execution condition is met, perform a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell; or determine whether the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs, and in response to determining that the at least one C- LTM cell switch execution condition is met for the other C-LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs, perform a RACH-less C-LTM switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.

[0082] The present disclosure thus allows C-LTM mobility with the mTRP UE 301 even when the C-LTM cell switch execution conditions(s) are satisfied / met only for the one TRP. This is a SEP and has impacts on MAC / RRC specifications. This is planned to be proposed in 3GPP as a new proposal to Rel 19 WI on Mobility enhancements. The embodiments disclosed herein can beimplemented 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.

[0087] 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 / or 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

We Claim:

1. An apparatus configured to: receive, at a User Equipment (UE) configured with at least two Transmit / Receive Points (TRPs), from a gNodeB (gNB), one or more Conditional-Layerl / Layer 2 Triggered Mobility (C- LTM) candidate cell configurations corresponding to each of the at least two TRPs, wherein the one or more C-LTM candidate cell configurations comprises one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs; monitor, based on the received one or more C-LTM candidate cell configurations, one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs; in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, perform one of: a Random Access Channel (RACH)-less Conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM) cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met;determine whether the one of the at least two TRPs is a master TRP, and in response to determining that the one of the at least two TRPs is the master TRP and the at least one C-LTM cell switch execution condition is met, perform a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell; or determine whether the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs, and in response to determining that the at least one C- LTM cell switch execution condition is met for the other C-LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs, perform a RACH-less C-LTM cell switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.

2. The apparatus as claimed in claim 1, wherein upon performing the RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met, the apparatus is configured to: retain remaining TRPs from the at least two TRPs along with respective serving cell.

3. The apparatus as claimed in claim 1, wherein the apparatus is configured to: determine a Radio Link Failure (RLF) associated with the other TRPs among the at least two TRPs; andin response to determining the RLF, discard the other TRPs without performing a RadioResource Control (RRC) re-establishment.

4. The apparatus as claimed in claim 3, wherein the apparatus is configured to: perform recovery of the other TRPs, in response to discarding the other TRP.

5. The apparatus as claimed in claim 1, wherein prior to perform the RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell, the apparatus is configured to: discard the other TRPs from the at least two TRPs.

6. The apparatus as claimed in claim 1, wherein the one or more C-LTM cell switch execution conditions comprise at least one of an LI execution condition or L3 execution condition.

7. A method comprising: receiving, at a User Equipment (UE) configured with at least two Transmit / Receive Points (TRPs), from a gNodeB (gNB), one or more Conditional-Layerl / Layer 2 Triggered Mobility (C- LTM) candidate cell configurations corresponding to each of the at least two TRPs, wherein the one or more C-LTM candidate cell configurations comprises one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs;monitoring, based on the received one or more C-LTM candidate cell configurations, one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs; in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, performing one of: a Random Access Channel (RACH)-less Conditional Layer 1 / Layer 2 Triggered Mobility (C-LTM) cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met; determining whether the one of the at least two TRPs is a master TRP, and in response to determining that the one of the at least two TRPs is the master TRP and the at least one C-LTM cell switch execution condition is met, perform a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell; or determining whether the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs, and in response to determining that the at least one C-LTM cell switch execution condition is met for the other C-LTM candidate cells orcorresponding candidate TRPs configured with the other TRPs among the at least two TRPs, perform a RACH-less C-LTM cell switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.

8. The method as claimed in claim 7, wherein upon performing the RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met, the method comprises: retaining remaining TRPs from the at least two TRPs along with respective serving cell.

9. The method as claimed in claim 7, wherein the method comprises: determining a Radio link Failure (RLF) associated with the other TRPs among the at least two TRPs; and in response to determining the RLF, discarding the other TRPs without performing a Radio Resource Control (RRC) re-establishment.

10. The method as claimed in claim 9, wherein the method comprises: performing recovery of the other TRPs, in response to discarding the other TRP.

11. The method as claimed in claim 7, wherein prior to performing the RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell, the method comprises:discarding the other TRPs from the at least two TRPs.

12. The method as claimed in claim 7, wherein the one or more C-LTM cell switch execution conditions comprise at least one of an LI execution condition or L3 execution condition.

13. A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions that, when executed at a User Equipment (UE), the UE comprising one or more processors, cause the one or more processors to: receive, from a gNodeB (gNB), one or more Conditional-Layerl / Layer 2 Triggered Mobility (C-LTM) candidate cell configurations corresponding to each of the at least two TRPs, wherein the one or more C-LTM candidate cell configurations comprises one or more C-LTM cell switch execution conditions corresponding to at least one of one or more C-LTM candidate cells and corresponding one or more candidate TRPs; monitor, based on the received one or more C-LTM candidate cell configurations, one or more parameters associated with at least one of the one or more C-LTM candidate cells, and the corresponding one or more candidate TRPs to determine whether at least one C-LTM cell switch execution condition among the one or more C-LTM cell switch execution conditions is met for a C-LTM candidate cell or a corresponding candidate TRP among the one or more C-LTM candidate cells corresponding to one of the at least two TRPs; in response to determining that the at least one C-LTM cell switch execution condition is met for the C-LTM candidate cell or the corresponding candidate TRP, perform one of:a Random Access Channel (RACH)-less Conditional Layer 1 / Layer 2 TriggeredMobility (C-LTM) C-LTM switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell for which the at least one C-LTM cell switch execution condition is met; determine whether the one of the at least two TRPs is a master TRP, and in response to determining that the one of the at least two TRPs is the master TRP, and the at least one C-LTM cell switch execution condition is met, perform a RACH-less C-LTM cell switch of the one of the at least two TRPs to the candidate TRP of the C-LTM candidate cell; or determine whether the at least one C-LTM cell switch execution condition is met for other C-LTM candidate cells or corresponding candidate TRPs configured with other TRPs among the at least two TRPs, and in response to determining that the at least one C- LTM cell switch execution condition is met for the other C-LTM candidate cells or corresponding candidate TRPs configured with the other TRPs among the at least two TRPs, perform a RACH-less C-LTM switch of each of the at least two TRPs to candidate TRPs of the corresponding C-LTM candidate cells.

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