Scheduling first uplink transmission in random access channel less conditional layer1 / layer 2 triggered mobility

Abstract

Embodiments disclosed herein provide a method and system for receiving, from a serving gNB-DU, a configuration message comprising information, pertaining to one or more Layer 1 / Layer 2 triggered mobility (LTM) candidate cells of a target / candidate gNB-DU, for performing a conditional LTM (C-LTM). Further, based on the configuration message, at least one LTM candidate cell is selected from the one or more LTM candidate cells, and an associated candidate cell beam. Furthermore, the method comprises transmitting information of the at least one selected LTM candidate cell and the associated candidate cell beam to the serving gNB DU. The method also involves performing, based on the received configuration message associated with the at least one selected LTM candidate cell, Random-Access Channel (RACH)-less C-LTM cell switch with the target / candidate gNB DU.

Description

Attorney Docket No. RAKU-12900WOSCHEDULING FIRST UPLINK TRANSMISSION IN RANDOM ACCESS CHANNEL LESS CONDITIONAL LAYER1 / LAYER 2 TRIGGERED MOBILITYCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to Indian patent application no. 202441085846, filed April 30, 2025, which claims the benefit of Indian provisional patent application no. 202441085846, filed on November 08, 2024; the entire contents of which are incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to scheduling first Uplink (UL) transmission in Random Access Channel (RACH)-less conditional Layerl / Layer 2 triggered mobility (LTM).BACKGROUND

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

[0004] The mobile telecommunications industry is experiencing tremendous growth in recent decades, driven by ever-increasing demand for connectivity and data services. To cater to the ever-increasing demand of connectivity and data services, the technology is being constantly advanced and the advances in the technology have resulted in rapid growth in the field of wireless communication technology. The latest advancement in wireless communication technology is the development of next generation wireless communication systems (e.g., 5G / 6G wireless communication systems) which aim to provide high reliability and throughput, lower latency, and support for a large number of devices compared to earlier wireless communication system.

[0005] In a typical next generation wireless communication system, a user equipment (UE) may be provided communication services using a Radio Access Network (RAN) and a Core Network (CN). The RAN may comprise at least one base station (also referred to as a “gNodeB” or a “gNB”). In a disaggregated architecture as defined in 3GPP, the gNB may be partitioned into multiple logical entities, as shown in the architecture 100 of Figure 1. The logical network entities may include one or more centralized units (CUs) and one or more distributed unit (DUs) which may be interconnected with each other via the interfaces F l-C and Fl-U (as shown in Figure 1).Atorney Docket No. RAKU-12900WO Each CU may be further partitioned into one or more control-plane entities (CU-CP) and one or more user-plane entities (CU-UPs) that handle the control-plane and user-plane processing of the CU, respectively. The CU-CP(s) and CU-Ups may be communicatively coupled with each other and with the one or more DUs via the interfaces as shown in Figure 1.

[0006] A single DU may host multiple cells (e.g., a max of 512 in current 3GPP specifications). The gNB-CU-CP hosts the PDCP and RRC layers, while the gNB-DU hosts the RLC, MAC, and PHY layers. The scheduling operation takes place at the gNB-DU.

[0007] Layer 1 / Layer 2 triggered mobility (LTM) was introduced in Release-18 and may offer improvements in handover latency and interruption time compared to Layer 3 based mobility. However, LTM, as introduced in Rel-18 also has some limitations, e.g., inter-CU LTM is not supported. Future releases (e.g., the Rel-19 work item) aim to remove a number of these limitations. Therefore, further enhancements are needed for the communication systems.SUMMARY

[0008] In modern 5G networks, user equipment (UE) connects via a disaggregated gNodeB (gNB) architecture comprising centralized units (CUs) and distributed units (DUs). While recent advancements like Layerl / Layer 2 triggered mobility (LTM) introduced in 3GPP Release-18 offer reduced handover latency and interruption time. The LTM lacks support for inter-CU. These limitations hinder seamless mobility across distributed network elements. Thus, there is a need to improve the LTM method to support broader mobility scenarios, such as inter-CU handovers, and to improve overall performance in disaggregated RAN architectures. The present disclosure relates to a method comprising the steps of receiving, from a serving gNodeB (gNB), a configuration message comprising configuration information and at least one execution condition, pertaining to one or more conditional-Layer 1 / Layer 2 triggered mobility (C-LTM) candidate cells of a target / candidate gNB, for performing a conditional-LTM (C-LTM) cell switch. Further, the method comprises monitoring and determining that the at least one execution condition, pertaining to the one or more C-LTM candidate cells, is satisfied. Further, in response to the at least one execution condition being satisfied, the method comprises selecting, based on the configuration information, an associated target / candidate cell beam. Furthermore, information of the at least one selected C-LTM candidate cell and an identifier (ID) of the associated target / candidate cell beam is transmitted to the serving gNB. The method further comprises, receiving commands from the serving gNB-DU for executing UL and DL syncAtorney Docket No. RAKU-12900WO functions and performing, based on the configuration information pertaining to the at least one selected C-LTM candidate cell, Random-Access Channel (RACH)-less C-LTM cell switch to the target / candidate gNB.

[0009] The present disclosure also relates to an apparatus configured to receive, from a serving gNodeB (gNB), a configuration message comprising configuration information and at least one execution condition, pertaining to one or more conditional-Layer 1 / Layer 2 triggered mobility (C-LTM) candidate cells of a target / candidate Distributed Unit (DU) cell, for performing a conditional-LTM (C-LTM) cell switch. Further, the apparatus is configured to determine that the at least one execution condition, pertaining to the one or more C-LTM candidate cells, is satisfied. Furthermore, in response to the at least one execution condition being satisfied, the apparatus is further configured to select, based on the configuration information, an associated target / candidate cell beam. The apparatus is also configured to transmit, to the serving gNB, information of the at least one selected C-LTM candidate cell and the associated target / candidate cell beam. The apparatus is also configured to receive commands from the serving gNB for executing UL and DL sync functions and perform, based on the configuration information pertaining to the at least one selected C-LTM candidate cell, Random-Access Channel (RACH)- less C-LTM cell switch to the target / candidate gNB.

[0010] The present disclosure also relates to an apparatus configured to receive, at a target / candidate gNodeB (gNB) from a serving gNB associated with a User Equipment (UE), information comprising a selected conditional C-LTM target / candidate cell, by the UE, and an identifier (ID) of an associated candidate cell beam. Further, the apparatus configured to transmit, from the target / candidate gNB and to the UE, dynamic scheduling information on the associated candidate cell beam of the at least one selected C-LTM candidate cell. The apparatus is also configured to receive, at the target / candidate gNB and from the UE, based on the dynamic scheduling information, uplink data from the UE.

[0011] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.BRIEF DESCRIPTION OF THE DRAWINGSAtorney Docket No. RAKU-12900WO

[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:

[0013] FIG. 1 illustrates an existing disaggregated gNB architecture.

[0014] FIG. 2 illustrates conditional Layer 1 / Layer 2 triggered mobility (LTM) in the disaggregated gNB architecture.

[0015] FIG. 3 illustrates a target / candidate distributed unit (DU) operation for performing a Random-Access Channel (RACH)-less C-LTM cell switch, in accordance with some embodiments of the present disclosure.

[0016] FIG. 4 is a signaling diagram illustrating methods for performing Random-Access Channel (RACH)-less C-LTM cell switch with the target / candidate DU.

[0017] FIG. 5 illustrates a flowchart of a method for Random-Access Channel (RACH)-less C- LTM cell switch with the target / candidate DU, in accordance with some embodiments of the present disclosure an aspect of the subject matter in accordance with one embodiment.

[0018] FIG. 6 illustrates a flowchart of a method for performing early synchronization with the at least one selected C-LTM, according to the embodiments as disclosed herein.

[0019] FIG. 7 illustrates an embodiment of a device wherein the method for performing Random-Access Channel (RACH)-less C-LTM cell switch with the target / candidate DU, is implemented, according to the embodiments as disclosed herein.

[0020] It should be appreciated by those skilled in the art that any block diagram herein represents conceptual views of illustrative systems embodying the principles of the present subject matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and executed by a computer or processor, whether or not such computer or processor is explicitly shown.DETAILED DESCRIPTON

[0021] 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 theAtorney Docket No. RAKU-12900WO 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 flow chart 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).

[0022] 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.

[0023] Even though particular combinations of features are recited in the claims and / or disclosed in the specification, the particular 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 claims and / or disclosed in the specification. Even if a dependent claim directly depends on only one claim, the present disclosure may indicate that the dependent claim is dependent on other claims in the claim set.

[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, 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.

[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 andAtorney Docket No. RAKU-12900WO variations are possible in light of the above disclosure or may be acquired from practice of the implementations.

[0026] FIG. 1 illustrates an existing disaggregated gNB architecture. In an existing (or conventional) disaggregated gNB architecture, a conventional gNB 100 may be decomposed into multiple logical entities, as defined in 3 GPP. For example, the conventional gNB 100 may include a gNB-Control Unit-Control Plane (CU-CP) 101 (gNB-Control Unit-Control Plane (CU- CP) and a gNB-Control Unit-User Plane (CU-UP) 103 (gNB-Control Unit-User Plane (CU-UP). CU-CP and CU-UP is also referred hereinafter as gNB-Centralized Unit (CU) for the sake of brevity) and the gNB DU 102. Likewise, a single DU 102 may be responsible to host multiple cells (not shown). As an example, a single DU 102 may be responsible to host a maximum of 512 cells in current 3GPP specifications. The gNB-CU-CP 101 may host a Packet Data Convergence Protocol (PDCP-c) and a Radio Resource Control (RRC) layer, while the gNB -DU 102 hosts a Radio Link Control (RLC), a Medium Access Control (MAC), and a Physical (PHY) layer. The scheduling operation takes place at the gNB-DU 102. In order to support L1 / L2 triggered mobility (LTM) cell switch, related to the changing of serving cell (not shown), in the disaggregated gNB architecture, a mechanism is implemented in which the handover preparation would be performed by the gNB-CU-CP 101, but the cell switch is executed autonomously by the gNB-DU 102 without any further interaction with the upper layers. For example, the mechanism involves performing the handover preparation by the gNB-CU-CP 101, but autonomously executing the handover by the gNB-DU 102 without further interaction with upper layers, such as PDCP and the RRC layer.

[0027] Conventionally, the disaggregated gNB architecture may also include a logical node, such as a gNB-CU-User Plane (gNB-CU-UP) 103 to host user plane part of the PDCP-u protocol of the gNB-CU 101 and / or the Service Data Adaptation Protocol (SDAP) protocol. The gNB- CU-UP 103 terminates El interface connected with the gNB-CU-CP 101 and the Fl-U interface connected with the gNB-DU 102.

[0028] Layerl / Layer 2 triggered mobility (LTM) was introduced in Rel-18 and can offer improvements in handover latency and interruption time compared to Layer 3 based mobility. However, LTM as introduced in Rel-18 also has some scope limitations, eg: inter-CU LTM is not supported. The present subject matter (Rel-19 work item) describes techniques to remove a number of these limitations.Atorney Docket No. RAKU-12900WO

[0029] The disaggregated architecture is defined in 3GPP decomposing the gNB into multiple logical entities. Likewise, a single DU may host multiple cells (max of 512 in current specifications). The gNB-CU-CP hosts the PDCP and RRC layers, while the gNB-DU hosts the RLC / , MAC and PHY layers. The scheduling operation takes place at the gNB-DU.

[0030] In order to support L1 / L2 triggered mobility (i.e. change of serving cell) in the disaggregated gNB architecture, a new mechanism is needed in which handover (HO) preparation would take place at the gNB-CU-CP, but be executed autonomously by the gNB-DU, without further interaction with the upper layers.

[0031] The target of this invention is Rel 19 WI on L1 / L2 Triggered mobility. The work item description can be found in RP-234036 : R19-Mobility-Enhancements.

[0032] Below is one of the primary objectives of the present subject matter.

[0033] Specify support of conditional LTM [RAN2, RAN3, RANI]• Specify UE evaluated conditions for triggering LTM• Aim to support conditional LTM including subsequent LTM• Prioritise intra-CU LTM• Checkpoint to review objective at RAN#105. RAN WG work to not start before this checkpoint.

[0034] As per the present subject matter, Layer 3 mobility has evolved over several releases. Conditional handover (CHO) and other conditional mobility procedures (CPAC, SCPAC) were developed to achieve high robustness by enabling the procedure to be executed without necessitating a signalling exchange with source cell beforehand. LTM as introduced in Rel- 18 offers short interruption time but not with the same level of robustness as the conditional L3 mobility procedures. The present subject matter (Rel-19), provides enhancements to the system to benefit from both the high robustness and short interruption.

[0035] Conditional LTM is a combination of techniques used for Conditional HO and LTM. In C-LTM, Source cell sends the conditional LTM configuration of a candidate cell via RRCReconfiguration message to UE, which includes the LTM candidate configurations, and the corresponding execution conditions. Each candidate cell provides its own execution condition for conditional LTM.Atorney Docket No. RAKU-12900WO

[0036] So, in C-LTM, the UE is configured with one or more LTM candidate cell(s) and C- LTM execution condition(s) and when the execution condition is satisfied, the UE executes C- LTM cell switch by detaching from the source cell, applies the stored corresponding C-LTM candidate cell configuration for that selected candidate cell, performs RACH-less C-LTM HO to that candidate cell and completes the RACH-less C-LTM HO procedure by sending RRCReconfigurationComplete message to the target gNB-DU

[0037] Conditional LTM is triggered by UE and the target beam selection is also performed by UE. Hence, the candidate cell is not aware of the beam the UE will select during conditional LTM execution.

[0038] Unlike Rel. 18 LTM, there is no notification from source gNB-DU to the target gNB- DU (via gNB-CU) about the LTM cell switch execution where the selected beam is indicated. Therefore, in the existing techniques, there is no possibility of allocating a dynamic grant to the UE at the target cell.

[0039] During conditional RACH-less LTM, if the NW is not aware of the candidate cell selected as target cell and the beam of this candidate cell selected by UE, there is no possibility for the candidate cell to know when and on which beam to perform dynamic scheduling for the first PUSCH transmission.

[0040] A solution provided by the existing techniques, could be that each candidate cell keeps sending the dynamic scheduling information on each candidate beam or keeps monitoring the UL transmission among all CG occasions after the preparation phase. However, such technique is very inefficient and sub-optimal.

[0041] The present subject matter describes that when C-LTM is configured for a UE:Approach 1-

[0042] Whenever the LI execution condition of a C-LTM candidate cell is satisfied and the target cell beam selection is performed, if the UE’s radio link with the source cell is intact, the UE shall indicate the selected target cell and beam information to the source cell. In such a case, the Rel 18 mechanism can be re-used to inform the cell and beam ID to the target gNB-DU.

[0043] The UE periodically sends an LI measurement report to the source cell, which indicates the potential target cells / beams. The source cell can inform all the corresponding potential targetAtorney Docket No. RAKU-12900WO gNB-DUs to send dynamic scheduling information on each candidate beam and / or monitor the UL transmission among all CG occasions in those beams.

[0044] Alternatively, L3 measurement report could also be used instead of LI, but it causes overhead when the candidate cells belong to the same gNB-DU.Approach 2:

[0045] A dedicated scheduling request (SR) could be used by the UE in UL to request dynamic scheduling grants from the target cell (new serving cell), once the CLTM cell switch is executed..

[0046] In this case, the dedicated SR is proposed to be a common SR for all the beams of the target cell. The dynamic scheduling success relies on the target gNB-DU identifying the beam ID on which the dedicated scheduling request was sent by the UE.

[0047] The present subject matter provides following advantages:• Dynamic grant and configured grant are possible to be scheduled during C-LTM.

[0048] FIG. 2 illustrates conditional Layer 1 / Layer 2 triggered mobility (LTM) in the disaggregated gNB architecture 200.

[0049] FIG. 2 shows a serving (gNodeB (gNB)) Distributed Unit (DU) 202 (also referred hereinafter as serving DU 202) and a target / candidate gNB DU 206 (also referred hereinafter as target / candidate gNB DU 206) in a disaggregated gNB architecture 200. The serving gNB DU 202 is configured to provide a configuration message that includes configuration information related to conditional-LTM (C-LTM) candidate cells 204A-N and an associated target / candidate cell beam 208. For example, the serving gNB DU 202 is configured to provide the configuration message that includes configuration information related to C-LTM candidate cells 204A-N and an identifier (ID) of the associated target / candidate cell beam 208. The C-LTM candidate cells 204A-N are associated with the target / candidate gNB DU 206. The target / candidate cell beam 208 is linked to the C-LTM candidate cells 204A-N and used for performing C-LTM operations. The configuration message may include identifiers of candidate cells, corresponding beam information, and mobility trigger conditions associated with each candidate cell. In an embodiment, a user equipment (UE) (not shown in Fig. 2) is associated with the serving gNB and the UE is in an intact connection with the serving gNB.

[0050] In some embodiments, the configuration message comprises C-LTM configurations for the one or more C-LTM candidate cells 204 A-N and one or more corresponding executionAtorney Docket No. RAKU-12900WO conditions for performing the C-LTM. For example, the configuration message may include all the L1 / L2 / L3 configuration parameters and specify via an execution condition that the cell switch is triggered when the received signal strength from a candidate cell 204A exceeds a threshold.

[0051] In an embodiment, upon receiving the configuration message from the serving gNB DU 202, it is monitored that the at least one execution condition, pertaining to the one or more C- LTM candidate cells 204A-N, is satisfied.

[0052] Further, in response to the at least one execution condition being satisfied, an associated target / candidate cell beam is selected based on the configuration information.

[0053] In some embodiments, at least one C-LTM candidate cell is selected from the one or more C-LTM candidate cells 204A-N and an associated target / candidate cell beam 208 based on the configuration message. In some embodiments, an early synchronization is performed between the at least one selected C-LTM candidate cell 204A and the serving gNB 202The early synchronization may include performing a Downlink (DL) synchronization with the at least one selected C-LTM candidate cell 204A and an Uplink (UL) synchronization with the at least one selected C-LTM candidate cell 204A.

[0054] The information of the at least one selected C-LTM candidate cell 204A and the associated target / candidate cell beam 208 is transmitted to the serving gNB DU 202. The selection information is transmitted back to the serving gNB DU 202. Based on the configuration and the selection, a Random-Access Channel (RACH)-less C-LTM cell switch is performed to the target / candidate gNB DU 206, without requiring a new random access procedure. The selected target / candidate cell beam 208 ensures that the switch is performed along the specific beam direction associated with the C-LTM Candidate Cell 204A.

[0055] In an embodiment, the information of the at least one selected C-LTM candidate cell and an identifier (ID) of the associated target / candidate cell beam is transmitted to the serving gNB DU 202 using a Layer-1 (LI) measurement report. This information is relayed by the source / serving gNB-DU to the target / candidate gNB-DU.

[0056] In an embodiment, the one or more C-LTM candidate cells 204 A-N of the target / candidate gNB DU 206include one of intra-CU candidate cells or inter-CU candidate cells. In an embodiment, if the one or more C-LTM candidate cells of the target / candidate gNB includes the intra-CU candidate cells, then the configuration message includes a pre-determined weight for the intra-CU candidate cells.Atorney Docket No. RAKU-12900WO

[0057] In an embodiment, upon transmitting the information, a C-LTM cell switch is performed to the target / candidate DU cell, based on the configuration information pertaining to the at least one selected C-LTM candidate cell. The C-LTM cell switch may include Random-Access Channel (RACH)-less.

[0058] FIG. 3 illustrates a target / candidate distributed unit (DU) 206B operation for performing a Random-Access Channel (RACH)-less Conditional Layer 1 / Layer 2 Triggered Mobility (C- LTM) cell switch, in accordance with some embodiments of the present disclosure. The serving Distributed Unit (DU) 202B is associated with User Equipment (UE) 212. The UE 212 selects at least one C-LTM candidate cell and its corresponding beam, and this selection is provided to the serving gNB-DU 202B, which is related to the Target / candidate gNB DU 206B, via the gNB-CU. Based on the selection, the Target / candidate gNB DU 206B transmits dynamic scheduling information on an associated target / candidate cell beam 208B of the at least one selected C-LTM candidate cell to the UE 212.

[0059] FIG. 4 is a signaling diagram illustrating methods for performing Random-Access Channel (RACH)-less C-LTM cell switch with the target / candidate DU.

[0060] One or more steps have been described below with the help of a target / candidate cell for ease of description. However, it may be appreciated that the one or more steps may also be performed with multiple target / candidate cells.

[0061] At step 404, the UE 400 is in RRC_CONNECTED state with the serving gNB 402.

[0062] At step 406, the UE 400 transmits a Measurement Report to the gNB 402 to assist in identifying potential target cells for conditional mobility.

[0063] At step 408, the gNB 402 performs Conditional LTM Candidate Preparation, determining potential target cells and configurations based on the measurement report.

[0064] At step 410, the gNB 402 sends an RRC Reconfiguration message (Conditional LTM Configuration) to the UE 400, including details of candidate cells and associated configurations.

[0065] At step 412, the UE 400 completes the reconfiguration and sends an RRC Reconfiguration Complete message back to the gNB 402.

[0066] At step 414, the UE 400 performs downlink synchronization with the candidate cells based on the configuration received.

[0067] At step 416, the UE 400 performs uplink synchronization with the candidate cells.Atorney Docket No. RAKU-12900WO

[0068] At step 418, the UE 400 sends a Measurement Report containing updated information on the candidate cells to the gNB 402.

[0069] At step 420, the gNB 402 determines the potential target cells for first uplink transmission scheduling, considering the latest measurement report and synchronization status.

[0070] At step 422, the UE 400 evaluates the execution conditions to check if conditional mobility towards any target cell is triggered.

[0071] At step 424, if the conditions are satisfied, the UE 400 detaches from the source cell and applies the target configuration to establish communication with the target cell.

[0072] At step 426, the UE 400 initiates the RACH Procedure with the target cell to finalize the cell switch.

[0073] At step 428, the Conditional LTM Procedure is completed, ensuring that the UE is now connected to the new target cell without requiring a complete handover process.

[0074] FIG. 5 illustrates a flowchart of a method for Random-Access Channel (RACH)-less C- LTM cell switch with the target / candidate gNB DU 206, in accordance with some embodiments of the present disclosure an aspect of the subject matter in accordance with one embodiment.

[0075] As illustrated in FIG. 5, the method 500 may comprise one or more steps. The method 500 may be described in the general context of computer executable instructions. Generally, computer executable instructions can include routines, programs, objects, components, data structures, procedures, modules, and functions, which perform particular functions or implement particular abstract data types.

[0076] The order in which the method 500 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0077] At step 502, a configuration message is received at a User Equipment (UE) 212, from a serving gNodeB (gNB)-Distributed Unit (DU) 202. The configuration message includes configuration information and at least one execution condition, pertaining to one or more conditional Layer 1 / Layer 2 triggered mobility (C-LTM) candidate cells of a target / candidate gNB Distributed Unit (DU) cell, for performing a conditional Layer 1 / Layer 2 TriggeredAtorney Docket No. RAKU-12900WO Mobility (C-LTM) cell switch. For example, the configuration message may include identifiers of candidate cells, corresponding beam information, and mobility trigger conditions associated with each candidate cell.

[0078] At step 504, the method comprises determining that the at least one execution condition, pertaining to the one or more C-LTM candidate cells 204A-N, is satisfied.

[0079] In response to the at least one execution condition being satisfied, at step 506, an associated target / candidate cell beam is selected, based on the configuration information. For example, the UE 212 may select a candidate cell having the strongest signal quality or the lowest latency path and determine beam ID (identifier) corresponding to that cell for optimized connectivity.

[0080] At step 508, information of the at least one selected C-LTM candidate cell and an identifier (ID) of the associated target / candidate cell beam is transmitted to the serving gNB DU 202A, 202B. For example, the UE 212 may send a report containing the selected cell ID and beam index to the serving gNB DU 202A, 202B to enable further mobility preparation.

[0081] At step 510, Random -Access Channel (RACH)-less C-LTM cell switch to the target / candidate gNB DU cell is performed based on the configuration information pertaining to the at least one selected C-LTM candidate cell. For example, the UE 212 may synchronize and switch to the target / candidate gNB DU 206 directly on the selected beam without executing a random-access procedure, thereby reducing mobility latency.

[0082] In an embodiment, the information of the at least one selected C-LTM candidate cell and the associated candidate cell beam is transmitted to the serving gNB DU 202using a Layer- 1 (LI) measurement report or another L1 / L2 message. In an embodiment, the one or more C- LTM candidate cells of the target / candidate gNB DU 206include one of intra-CU candidate cells or inter-CU candidate cells.

[0083] FIG. 6 illustrates a flowchart of a method 600 for performing early synchronization with the at least one selected C-LTM 210A, in accordance with some embodiments of the present disclosure an aspect of the subject matter in accordance with one embodiment.

[0084] As illustrated in FIG. 6, the method 600 may comprise one or more steps. The method 600 may be described in the general context of computer executable instructions. Generally, computer executable instructions can include routines, programs, objects, components, dataAtorney Docket No. RAKU-12900WO structures, procedures, modules, and functions, which perform particular functions or implement particular abstract data types.

[0085] The order in which the method 600 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0086] At step 602, an early synchronization is performed with the at least one selected C-LTM candidate cell to enable RACH-less CLTM cell switch.

[0087] To perform the early synchronization, at step 604, a Downlink (DL) synchronization is performed with the at least one selected C-LTM candidate cell. For example, the UE 212 may perform DL synchronization by detecting the Synchronization Signal Block (SSB) or reference signals transmitted by the candidate cell to align with its timing and frequency.

[0088] At step 606, an Uplink (UL) synchronization is performed with the at least one selected C-LTM candidate cell. For example, the UE 212 may transmit a Sounding Reference Signal (SRS) or a predefined UL reference signal towards the selected candidate cell to enable timing alignment and UL beam management for the upcoming transmission.

[0089] FIG. 7 illustrates an embodiment of a device 700 wherein the method for performing dynamic resource optimization in a distributed unit node of a wireless communication network may be implemented, according to the embodiments as disclosed herein. It will be appreciated that the device 700 is associated with the UE 212. As shown in FIG. 7, the device 700 comprises 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.

[0090] 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.Atorney Docket No. RAKU-12900WO

[0091] Memory 720 includes a non-transitory computer readable medium. 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.

[0092] 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.

[0093] 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).

[0094] 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, instructions to an external device, and / or one or more light-emitting diodes (LEDs).

[0095] 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 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.

[0096] 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.Atorney Docket No. RAKU-12900WO

[0097] 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 device 700 may perform one or more functions described as being performed by another set of components of 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.

[0098] In an embodiment [1], a method comprising: receiving, from a serving gNodeB (gNB), a configuration message comprising configuration information and at least one execution condition, pertaining to one or more conditional-Layer 1 / Layer 2 triggered mobility (C-LTM) candidate cells of a target / candidate gNB, for performing a conditional-LTM (C-LTM) cell switch; determining that the at least one execution condition, pertaining to the one or more C- LTM candidate cells, is satisfied; and in response to the at least one execution condition being satisfied, the method comprises: selecting, based on the configuration information, an associated target / candidate cell beam; transmitting, to the serving gNB, information of the at least one selected C-LTM candidate cell and an identifier (ID) of the associated target / candidate cell beam; and performing, based on the configuration information pertaining to the at least one selected C- LTM candidate cell, a C-LTM cell switch to the target / candidate gNB.

[0099] In an embodiment [2], the method, described in the embodiment [1], further comprises: performing an early synchronization with the at least one selected C-LTM candidate cell to enable the Random Access Channel (RACH)-less C-LTM cell switch by: performing a Downlink (DL) synchronization with the at least one selected C-LTM candidate cell; and performing an Uplink (UL) synchronization with the at least one selected C-LTM candidate cell.

[0100] In an embodiment [3], in the method, described in the embodiments [1] to [2], wherein the information of the at least one selected C-LTM candidate cell and the associated target / candidate cell beam is transmitted to the serving gNB using a Layer-1 (LI) measurement report or another L1 / L2 message.

[0101] In an embodiment [4], in the method, described in the embodiments [1] to [3], wherein the one or more C-LTM candidate cells of the target / candidate gNB comprises one of intra- Centralized Unit (CU) candidate cells or inter-CU candidate cells.Atorney Docket No. RAKU-12900WO

[0102] In an embodiment [5], in the method, described in the embodiments [1] to [4], wherein, if the one or more C-LTM candidate cells of the target / candidate gNB comprises the intra-CU candidate cells, the configuration message comprises a pre-determined weight for the intra-CU candidate cells.

[0103] In an embodiment [6], in the method, described in the embodiments [1] to [5], wherein determining that the at least one execution condition is satisfied, further comprises: determining that a received signal strength from the at least one selected C-LTM candidate cell exceeds a threshold.

[0104] In an embodiment [7], in the method, described in the embodiments [1] to [6], wherein the C-LTM cell switch comprises a Random-Access Channel (RACH)-less C-LTM cell switch.

[0105] In an embodiment [8], in the method, described in the embodiments

[0001] to [7], wherein a user equipment (UE) is associated with the serving gNB and the UE is in an intact connection with the serving gNB.

[0106] In an embodiment [9], an apparatus is configured to: receive, from a serving gNodeB (gNB), a configuration message comprising configuration information and at least one execution condition, pertaining to one or more conditional-Layer 1 / Layer 2 triggered mobility (C-LTM) candidate cells of a target / candidate gNB, for performing a conditional-LTM (C-LTM) cell switch; determine that the at least one execution condition, pertaining to the one or more C-LTM candidate cells, is satisfied; and in response to the at least one execution condition being satisfied, the method comprises: select, based on the configuration information, an associated target / candidate cell beam; transmit, to the serving gNB, information of the at least one selected C-LTM candidate cell and an identifier (ID) of the associated target / candidate cell beam; and perform, based on the configuration information pertaining to the at least one selected C-LTM candidate cell, a C-LTM cell switch to the target / candidate gNB.

[0107] In an embodiment

[0010] , the apparatus, described in the embodiment [9], is further configured to: perform an early synchronization with the at least one selected C-LTM candidate cell to enable a Random Access Channel (RACH)-less C-LTM cell switch, wherein, to perform the early synchronization, the apparatus is configured to: perform a Downlink (DL) synchronization with the at least one selected C-LTM candidate cell; and perform an Uplink (UL) synchronization with the at least one selected C-LTM candidate cell.Atorney Docket No. RAKU-12900WO

[0108] In an embodiment

[0011] , in the apparatus, described in the embodiments [9] to

[0010] , wherein the information of the at least one selected C-LTM candidate cell and the associated target / candidate cell beam is transmitted to the serving gNB using a Layer-1 (LI) measurement report or another L1 / L2 message.

[0109] In an embodiment

[0012] , in the apparatus, described in the embodiments [9] to

[0011] , wherein the one or more C-LTM candidate cells of the target / candidate gNB comprises one of intra-Centralized Unit (CU) candidate cells or inter-CU candidate cells.

[0110] In an embodiment

[0013] , in the apparatus, described in the embodiments [9] to

[0012] , wherein, if the one or more C-LTM candidate cells of the target / candidate gNB comprises the intra-CU candidate cells, the configuration message comprises a pre-determined weight for the intra-CU candidate cells.[OHl] In an embodiment

[0014] , in the apparatus, described in the embodiments [9] to

[0013] , wherein, to determine that the at least one execution condition is satisfied, the apparatus is further configured to: determine that a received signal strength from the at least one selected C-LTM candidate cell exceeds a threshold.

[0112] In an embodiment

[0015] , in the apparatus, described in the embodiments [9] to

[0014] , wherein the C-LTM cell switch comprises a Random-Access Channel (RACH)-less C-LTM cell switch.

[0113] In an embodiment

[0016] , in the apparatus, described in the embodiments [9] to

[0015] , wherein a user equipment (UE) is associated with the serving gNB and the UE is in intact connection with the serving gNB.

[0114] In an embodiment

[0017] , an apparatus is configured to: receive, at a target / candidate gNodeB (gNB) from a serving gNB associated with a User Equipment (UE), information comprising a selected conditional CLTM target / candidate cell, by the UE, and an identifier (ID) of an associated target / candidate cell beam; transmit, from the target / candidate gNB to the UE, dynamic scheduling information on the associated target / candidate cell beam of the at least one selected C-LTM target / candidate cell; and receive, at the target / candidate gNB and from the UE, based on the dynamic scheduling information, uplink data from the UE.

[0115] In an embodiment

[0018] , the apparatus, described in the embodiment

[0017] , wherein the apparatus is further configured to: monitor, at the target / candidate gNB and on the at least one selected C-LTM target / candidate cell, an Uplink (UL) transmission from the UE.Atorney Docket No. RAKU-12900WO

[0116] In an embodiment

[0019] , the apparatus, described in the embodiment

[0017] to

[0018] , wherein, if the UE is disconnected from the serving gNB, the uplink data comprises a dedicated scheduling request (SR) to request the dynamic scheduling information from the target / candidate gNB on the associated target / candidate cell beam.

[0117] Conditional LTM is triggered by UE and the target beam selection is also performed by UE. Hence, the candidate cell is not aware of the beam the UE will select during conditional LTM execution. Unlike Rel 18 LTM, there is no notification from source gNB-DU to the target gNB-DU (via gNB-CU) about the LTM cell switch execution where the selected beam is indicated. Therefore, there is no possibility of allocating dynamic grant to the UE at the target cell. During conditional RACH-less LTM, if the NW is not aware of the candidate cell selected as target cell and the beam of this candidate cell selected by UE, there is no possibility for the candidate cell to know when and on which beam to perform dynamic scheduling for the first PUSCH transmission. An obvious solution could be that each candidate cell keeps sending the dynamic scheduling information on each candidate beam or keeps monitoring the UL transmission among all CG occasions after the preparation phase. This is very inefficient and sub-optimal. We propose that when C-LTM is configured for a UE.Method 1

[0118] Whenever the LI execution condition of a C-LTM candidate cell is satisfied and the target cell beam selection is performed, if the UE’s radio link with the source cell is intact, the UE shall indicate the selected target cell and beam information to the source cell. In such a case, the Rel 18 mechanism can be re-used to inform the cell and beam Id to the target gNB-DU.

[0119] The UE periodically sends an LI measurement report to the source cell, which indicates the potential target cells / beams. The source cell can inform the all the corresponding potential target gNB-DUs to send dynamic scheduling information on each candidate beam and / or monitor the UL transmission among all CG occasions in those beams.

[0120] Alternatively, L3 measurement report could also be used instead of LI, but it causes overhead when the candidate cells belong to the same gNB-DU.Method 2

[0121] A dedicated scheduling request could be used by the UE in UL to request dynamic scheduling grants from the target cell (new serving cell), once the CLTM cell switch is executed.Atorney Docket No. RAKU-12900WO

[0122] In this case, the dedicated SR is assumed to be a common one for all the beams of the target cell. The dynamic scheduling success relies on the target gNB-DU identifying the beam ID on which the dedicated scheduling request was sent by the UE.

[0123] Advantages: Dynamic grant and configured grant are possible to be scheduled during C- LTM. This is a SEP and has impacts to MAC / RRC specifications. This is planned to be proposed in 3GPP as a new proposal to Rel 19 WI on Mobility enhancements.

[0124] In a non-limiting embodiment of the present disclosure, one or more non-transitory computer-readable media may be utilized for implementing the embodiments consistent with the present disclosure. A computer-readable medium refers to any type of physical memory (such as memory 720) on which information or data readable by a processor may be stored. Thus, a computer-readable media may store one or more instructions for execution by the at least one processor 710, including instructions for causing the at least one processor 710 to perform steps or stages consistent with the embodiments described herein. The term “computer-readable media” should be understood to include tangible items and exclude carrier waves and transient signals. By way of example, and not limitation, such computer-readable media can comprise Random Access Memory (RAM), Read-Only Memory (ROM), volatile memory, non-volatile memory, hard drives, Compact Disc (CD) ROMs, Digital Video Disc (DVDs), flash drives, disks, and any other known physical storage media.

[0125] Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer readable media having instructions stored (and / or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein. For certain aspects, the computer program product may include packaging material.

[0126] The various illustrative logical blocks, units, and operations described in connection with the present disclosure may be implemented or performed with a general-purpose processor, discrete gate or transistor logic, discrete hardware components or any combination thereof designed to perform the functions described herein. A general-purpose processor may include a microprocessor, but in the alternative, the processor may include any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a plurality of microprocessors, or any other such configuration.Atorney Docket No. RAKU-12900WO

[0127] 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 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 preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein.

Claims

Attorney Docket No. RAKU-12900WOClaimsWe Claim:1 . A method comprising: receiving, from a serving gNodeB (gNB), a configuration message comprising configuration information and at least one execution condition, pertaining to one or more conditional-Layer 1 / Layer 2 triggered mobility (C-LTM) candidate cells of a target / candidate gNB, for performing a conditional-LTM (C-LTM) cell switch; determining that the at least one execution condition, pertaining to the one or more C-LTM candidate cells, is satisfied; and in response to the at least one execution condition being satisfied, the method comprises: selecting, based on the configuration information, an associated target / candidate cell beam; transmitting, to the serving gNB, information of the at least one selected C-LTM candidate cell and an identifier (ID) of the associated target / candidate cell beam; and performing, based on the configuration information pertaining to the at least one selected C-LTM candidate cell, a C-LTM cell switch to the target / candidate gNB.

2. The method as claimed in claim 1, further comprising: performing an early synchronization with the at least one selected C-LTM candidate cell to enable a Random Access Channel (RACH)-less C-LTM cell switch by: performing a Downlink (DL) synchronization with the at least one selected C-LTM candidate cell; and performing an Uplink (UL) synchronization with the at least one selected C-LTM candidate cell.

3. The method as claimed in claim 1, wherein the information of the at least one selected C- LTM candidate cell and the associated target / candidate cell beam is transmitted to the serving gNB using a Layer-1 (LI) measurement report or another L1 / L2 message.

4. The method as claimed in claim 1, wherein the one or more C-LTM candidate cells of the target / candidate gNB comprises one of intra-Centralized Unit (CU) candidate cells or inter-CU candidate cells.Atorney Docket No. RAKU-12900WO5. The method as claimed in claim 4, wherein, if the one or more C-LTM candidate cells of the target / candidate gNB comprises the intra-CU candidate cells, the configuration message comprises a pre-determined weight for the intra-CU candidate cells.

6. The method as claimed in claim 1, wherein determining that the at least one execution condition is satisfied, further comprises: determining that a received signal strength from the at least one selected C-LTM candidate cell exceeds a threshold.

7. The method as claimed in claim 1, wherein the C-LTM cell switch comprises a Random- Access Channel (RACH)-less C-LTM cell switch.

8. The method as claimed in claim 1, wherein a user equipment (UE) is associated with the serving gNB and the UE is in an intact connection with the serving gNB.

9. An apparatus configured to: receive, from a serving gNodeB (gNB), a configuration message comprising configuration information and at least one execution condition, pertaining to one or more conditional-Layer 1 / Layer 2 triggered mobility (C-LTM) candidate cells of a target / candidate gNB, for performing a conditional-LTM (C-LTM) cell switch; determine that the at least one execution condition, pertaining to the one or more C-LTM candidate cells, is satisfied; and in response to the at least one execution condition being satisfied, the apparatus is configured to: select, based on the configuration information, an associated target / candidate cell beam; transmit, to the serving gNB, information of the at least one selected C-LTM candidate cell and an identifier (ID) of the associated target / candidate cell beam; and perform, based on the configuration information pertaining to the at least one selected C-LTM candidate cell, a C-LTM cell switch to the target / candidate gNB.

10. The apparatus as claimed in claim 9, further configured to:Atorney Docket No. RAKU-12900WO perform an early synchronization with the at least one selected C-LTM candidate cell to enable a Random Access Channel (RACH)-less C-LTM cell switch, wherein, to perform the early synchronization, the apparatus is configured to: perform a Downlink (DL) synchronization with the at least one selected C-LTM candidate cell; and perform an Uplink (UL) synchronization with the at least one selected C-LTM candidate cell.

11. The apparatus as claimed in claim 9, wherein the information of the at least one selected C-LTM candidate cell and the associated target / candidate cell beam is transmitted to the serving gNB using a Layer-1 (LI) measurement report or another L1 / L2 message.

12. The apparatus as claimed in claim 9, wherein the one or more C-LTM candidate cells of the target / candidate gNB comprises one of intra-Centralized Unit (CU) candidate cells or inter- CU candidate cells.

13. The apparatus as claimed in claim 12, wherein, if the one or more C-LTM candidate cells of the target / candidate gNB comprises the intra-CU candidate cells, the configuration message comprises a pre-determined weight for the intra-CU candidate cells.

14. The apparatus as claimed in claim 9, wherein, to determine that the at least one execution condition is satisfied, the apparatus is further configured to: determine that a received signal strength from the at least one selected C-LTM candidate cell exceeds a threshold.

15. The apparatus as claimed in claim 9, wherein the C-LTM cell switch comprises a Random- Access Channel (RACH)-less C-LTM cell switch.

16. The apparatus as claimed in claim 9, wherein a user equipment (UE) is associated with the serving gNB and the UE is in intact connection with the serving gNB17. An apparatus configured to:Atorney Docket No. RAKU-12900WO receive, at a target / candidate gNodeB (gNB) from a serving gNB associated with a User Equipment (UE), information comprising a selected conditional CLTM target / candidate cell, by the UE, and an identifier (ID) of an associated target / candidate cell beam; transmit, from the target / candidate gNB to the UE, dynamic scheduling information on the associated target / candidate cell beam of the at least one selected C-LTM target / candidate cell; and receive, at the target / candidate gNB and from the UE, based on the dynamic scheduling information, uplink data from the UE.

18. The apparatus as claimed in claim 17, wherein the apparatus is further configured to: monitor, at the target / candidate gNB and on the at least one selected C-LTM target / candidate cell, an Uplink (UL) transmission from the UE.

19. The apparatus as claimed in claim 17, wherein, if the UE is disconnected from the serving gNB, the uplink data comprises a dedicated scheduling request (SR) to request the dynamic scheduling information from the target / candidate gNB on the associated target / candidate cell beam.

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