WO2025235014A1 - Ltm recovery procedure in dual connectivity systems - Google Patents

Abstract

A method includes detecting a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) with a target cell hosted by a first distributed unit; receiving measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE, from a centralised unit via a second distributed unit, wherein the centralised unit is connected to the first distributed unit and the second distributed unit; identifying a new target cell, wherein the new target cell is present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report; and transmitting information of the new target cell to the UE, via the centralised unit and the second distributed unit, for performing the LTM cell switch.

Description

LTM RECOVERY PROCEDURE IN DUAL CONNECTIVITY SYSTEMS

RELATED APPLICATIONS

[01] This application claims priority to Indian Patent Application IN 2024-41036176, filed May 7, 2024, the entire contents of which are hereby incorporated by reference.

FIELD

[02] The present disclosure relates to Lower-layer Triggered Mobility (LTM) recovery procedure in dual-connectivity systems.

BACKGROUND

[03] A handover mechanism is a process in mobile communication in which cellular transmission is transferred from one cell to another neighbouring cell of a network without losing connectivity to the cellular transmission. In other words, the handover (mobility) is a process of transferring an ongoing communication session of a User Equipment (UE) from one cell (i.e., base station or gNodeB (gNB)) to another cell. A Lower-layer Triggered mobility (LTM) or L1/L2 based mobility was introduced in Release 18 of Third Generation Partnership Project (3GPP). LTM enables a serving cell change via L1/L2 signaling, while maintaining configuration of upper layers and/or minimizing changes of configuration of the lower layers. The LTM provides improvements in handover latency and interruption time compared to Layer 3 based mobility. However, LTM as introduced in Release 18 has several limitations compared to Layer 3 mobility. [04] In 3GPP, a disaggregated architecture of gNodeB (gNB) is defined as decomposing the gNB into multiple logical entities. The gNB is split into three logical nodes i.e., Centralised unit (CU), Distributed Unit (DU), and Radio Unit (RU). A single DU may host multiple cells. For instance, the 3GPP defines that a DU can host up to 512 cells. The CU (also referred as gNB-CU) hosts upper layers such as Packet Data Convergence Protocol (PDCP) and Radio Resource Control (RRC) layers, while the DU (also referred as gNB-DU) hosts lower layers such as Radio Link Control (RLC), Media Access Control (MAC), and Physical (PHY) layers. The scheduling operation takes place at the gNB-DU.

[05] 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.

SUMMARY

[06] In an embodiment, the present disclosure discloses a method. The method comprises detecting a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) configured with dual connectivity, with a target cell. The target cell is hosted by a first distributed unit. Further, the method comprises receiving measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE, via a centralised unit and a second distributed unit. The centralised unit is connected to the first distributed unit and the second distributed unit. Furthermore, the method comprises identifying a new target cell present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report. Thereafter, the method comprises transmitting information of the new target cell to the UE, via the centralised unit and the second distributed unit. The information of the new target cell is transmitted for performing the LTM cell switch.

[07] In an embodiment, the present disclosure discloses a first distributed unit. The first distributed unit is configured to detect an LTM execution failure of an LTM cell switch of a UE configured with dual connectivity, with a target cell. The target cell is hosted by a first distributed unit. Further, the first distributed unit is configured to receive measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE, via a centralised unit and a second distributed unit. The centralised unit is connected to the first distributed unit and the second distributed unit. Furthermore, the first distributed unit is configured to identify a new target cell present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report. Thereafter, the first distributed unit is configured to transmit information of the new target cell to the UE, via the centralised unit and the second distributed unit. The information of the new target cell is transmitted for performing the LTM cell switch.

[08] In an embodiment, the present disclosure discloses a non-transitory computer readable medium including instructions for performing operations. The operations comprise detecting a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) configured with dual connectivity, with a target cell. The target cell is hosted by a first distributed unit. Further, the operations comprise receiving measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE, via a centralised unit and a second distributed unit. The centralised unit is connected to the first distributed unit and the second distributed unit. Furthermore, the operations comprise identifying a new target cell present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report. Thereafter, the operations comprise transmitting information of the new target cell to the UE, via the centralised unit and the second distributed unit. The information of the new target cell is transmitted for performing the LTM cell switch.

BRIEF DESCRIPTION OF THE DRAWINGS

[09] 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:

[010] Figure 1A illustrates a conventional disaggregated gNodeB (gNB) architecture;

[Oil] Figures IB and 1C illustrate an exemplary environment for performing Lower-layer Triggered Mobility (LTM) recovery procedure, in accordance with some embodiments of the present disclosure;

[012] Figure 2 illustrates a detailed diagram of a first distributed unit, in accordance with some embodiments of the present disclosure;

[013] Figures 3A and 3B illustrate exemplary flow diagrams for performing LTM recovery procedure, in accordance with some embodiments of the present disclosure;

[014] Figures 4 and 5 show exemplary flow charts illustrating method steps for performing LTM recovery procedure, in accordance with some embodiments of the present disclosure; and [015] Figure 6 shows a diagram of example components of a first distributed unit for performing LTM recovery procedure, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

[016] 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 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).

[017] 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.

[018] 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 claims and/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.

[019] 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.

[020] The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the implementations. [021] Lower-layer Triggered mobility (LTM) introduced in Release 18 of Third Generation Partnership (3GPP) project enables a serving cell change via L1/L2 signaling, while maintaining configuration of upper layers and/or minimizing changes of configuration of the lower layers. However, LTM as introduced in Release 18 has several limitations compared to Layer 3 mobility.

[022] In 3GPP, a disaggregated architecture of gNodeB (gNB) is defined as decomposing the gNB into multiple logical entities, as shown in Figure 1A. The gNB is split into three logical nodes i.e., Centralised Unit (CU) (also referred as gNB-CU), Distributed Unit (DU) (also referred as gNB-DU), and Radio Unit (RU). In order to support L1/L2 centric inter-cell change (i.e. change of serving cell)/LTM in the disaggregated gNB architecture, a new mechanism is needed in which configuration takes place at the gNB-CU, but is executed autonomously by the gNB-DU without further interaction with upper layers.

[023] In Release 18, LTM is limited to intra-CU and single connectivity. In Release 19, LTM support for New Radio- Dual Connectivity (NR-DC) is included as stated below:

Specify support for inter-CU Layer 2 Mobility (LTM) [RAN2, RAN3] o Prioritize the case when CU is acting as MN when DC is not configured o As secondary priority, support the case when NR-DC is configured and CU is acting as SN and MCG is unchanged o As secondary priority, support the case when NR-DC is configured, CU is acting as MN and SCG is unchanged or SCG is released

■ Note: The case that LTM is configured in both MCG and SCG is excluded o Specify support for subsequent LTM mobility procedures aiming to avoid RRC configuration between cell switches as per Rel-18 LTM ■ Coordination with SA3 needed with respect to security key handling o Note: Rel. 18 intra-CU LTM procedure is considered as baseline for adding inter- CU support

Measurements related enhancements for purpose of supporting LTM: [RAN2, RANI ] o Measurement related enhancements are applicable to Intra-CU MCG/SCG LTM and Inter-CU MCG/SCG LTM o Specify necessary components to support event triggered LI measurement reporting [RAN2, RANI ]

■ RANI and RAN2 to progress independently on the event triggered measurements objectives of their respective MIMO and Mobility enhancement WIs. Review progress at RAN#105 to see if any modification of objectives is required to avoid/manage any overlap in the work o Specify support for CSI-RS measurements for LTM procedures and enable CSI-RS based beam management, and/or other necessary physical layer operations on candidate cells before LTM [RANI ]

Specify support of conditional LTM [RAN2, RAN 3, RANI ] o Prioritize intra-CU LTM o Checkpoint to review objective at RAN#! 05. RAN WG work to not start before this checkpoint

Specify RRM requirements related to the above objectives as necessary [RAN4] [024] The LTM for NR-DC can be depicted in two variants as shown in Figures IB and 1C. As shown, in a first variant, the gNB comprises multiple distributed units hosting Master Cell Group (MCG) and Secondary Cell Group (SCG) separately. A centralised unit hosts both Master Node (MN) and Secondary Node (SN). In a second variant, the gNB is divided into multiple distributed units and centralised units. The distributed units host MCG and SCG separately. Also, the centralised units host MN and SN separately.

[025] In LTM, the gNB receives LI measurement report(s) from a UE, and the gNB changes a serving cell of the UE based on the measurement report, by signaling a cell switch command. A LTM failure is caused when the cell switch command is not received by the UE, or the UE fails to connect to a target cell identified by the gNB. In such case, the UE performs a LTM failure recovery. The Release 18 of 3GPP defines the following in TS 38.300:

Timer based handover failure procedure is supported in NR. RRC connection re-establishment procedure is used for recovering from handover failure except in certain CHO, DAPS handover or LTM cell switch scenarios:

- When DAPS handover fails, the UE falls back to the source cell configuration, resumes the connection with the source cell, and reports DAPS handover failure via the source without triggering RRC connection re-establishment if the source link has not been released.

- When initial CHO execution attempt fails or HO fails, the UE performs cell selection, and if the selected cell is a CHO candidate and if network configured the UE to try CHO after handover/CHO failure, then the UE attempts CHO execution once, otherwise reestablishment is performed. - When initial LTM execution attempt fails or HO fails, the UE performs cell selection and if the selected cell is an LTM candidate cell and if network configured the UE to try LTM after LTM execution failure, then the UE attempts LTM execution once, otherwise reestablishment is performed.

[026] The above-mentioned statements implies that whenever there is an LTM cell switch failure, the UE performs a cell selection based on prevalent radio conditions. When the selected cell happens to be a cell with LTM candidate cell configuration, the UE performs another LTM execution, post failure (only if the network has configured). This is attempted only once and if failure occurs again, RRC re-establishment is initiated. During RRC re-establishment, both MCG and SCG bearers need to be released. The LTM failure recovery is autonomous in nature and does not require an LTM switch command (Downlink MAC Control Element (DL MAC CE) from the gNB. However, the whole objective of a failure recovery is to avoid RRC reestablishment. Further, in the context of NR-DC i.e. when there is a SCG and an MCG, the LTM failure recovery needs to be addressed differently.

[027] The present disclosure provides methods and apparatuses to perform LTM recovery procedure. When initial LTM execution attempt or handover fails, the UE performs cell selection and when the selected cell is an LTM candidate SCG cell and when network has configured the UE to try LTM after LTM execution failure, then the UE attempts LTM execution once. This is termed as LTM recovery attempt or autonomous LTM execution. The present disclosure enables the UE configured with dual connectivity to transmit measurement report(s) to a distributed unit (or a gNB-DU), via a centralised unit (gNB-CU). The distributed unit checks whether radio condition of any cell indicated in the measurement report is suitable for LTM cell switch. When the radio condition is satisfactory and the cell is already prepared for LTM, the distributed unit transmits a DL MAC CE to perform LTM cell switch. In this way, the present disclosure enables performing LTM cell switch without RRC re-establishment. Also, the present disclosure describes such methods and apparatuses for both variant 1 and variant 2 of NR-DC as stated above. Hence, the present disclosure defines LTM recovery procedure for DC scenario.

[028] Figure 1A illustrates a conventional disaggregated gNodeB (gNB) architecture. In Fifth Generation (5G) networks, a base station or a gNB is split into three distinct components i.e., a Centralized Unit (CU) (also referred as the gNB-CU in the description), a Distributed Unit (DU) (also referred as the gNB-DU in the description), and a Remote Radio Unit (RU) (not illustrated in figures). The gNB-CU serves as central intelligence, adeptly handling complex and centralized network functions. These functions include, but are not limited to, proficient radio resource management, effective network control, and seamless coordination with the 5GC. The gNB-DU is responsible for managing data plane processing, encompassing vital tasks such as data transmission and reception with a User Equipment (UE) (not illustrated in Figure 1). The gNB-DU interfaces seamlessly with the gNB-CU over Fl interface. Figure 1 A further illustrates a separation of control-plane and user-plane for the gNB-CU (i.e., gNB- CU-CP and gNB-CU-UP). The gNB-CU-CP is connected to the gNB-DU through Fl-C interface. The gNB-CU-UP is connected to the gNB-DU through Fl-U interface. The gNB- CU-CP is connected to gNB-CU-CP(s) over El interface. The RU deals with physical layer functions, housing antennas and radio transceivers that facilitate the actual transmission and reception of radio signals. The description of the present disclosure is explained considering Fifth Generation (5G) networks only. However, the present disclosure is applicable to any type of networks such as Fourth Generation (4G) networks, 6G networks, and the like. [029] Figures IB and 1C illustrate an exemplary environment for performing LTM recovery procedure, in accordance with embodiments of the present disclosure. Figure IB shows implementation of the present disclosure according to a first variant 102 of NR-DC. In the first variant 102, the gNB comprises distributed units i.e. gNB-DUl 106i and gNB-DU2 IO62 connected to a single centralised unit gNB-CU 104. In one embodiment, the gNB-DUl IO61 hosts a SCG and the gNB-DU2 IO62 hosts an MCG (as illustrated in Figure IB). In another embodiment, the gNB-DUl IO61 hosts the MCG and the gNB-DUl IO61 hosts the SCG (not shown in Figures). The centralised unit gNB-CU 104 hosts both MN and SN. Figure IB illustrates a UE 108. The UE 108 represents end-user devices that access services and applications through a wireless network. The UE 108 is configured to connect to the centralised units and the distributed units over the wireless network. Examples of the UE 108 include, but not limited to, any device used by a user to communicate over the wireless network, such as, but not limited to, mobile phones, smartphones, laptops, wearables, Internet of Things (loTs), and the like. The UE 108 communicates to the centralised unit gNB-CU 104 via the gNB-DUl IO61 and the gNB-DU2 IO62, over Fl interface.

[030] In the second variant 110, the gNB comprises distributed units i.e. gNB-DUl IO61 and gNB-DU2 IO62. The gNB-DUl IO61 is connected to gNB-CUl 104i, and gNB-DU2 IO62 is connected to gNB-CU2 104₂. The gNB-DUl IO61 and gNB-DU2 IO62 host SCG and MCG separately. Also, the gNB-CUl 104i and gNB-CU2 1042 host MN and SN separately. In one embodiment, the gNB-DUl IO61 hosts a SCG and the gNB-DUl IO61 hosts an MCG. The gNB-CUl 104i hosts the SN and the gNB-CU2 1042 hosts the MN (as illustrated in Figure 1C). In another embodiment, the gNB-DUl IO61 hosts the MCG and the gNB-DUl IO61 hosts the SCG. The gNB-CUl 1041 hosts the MN and the gNB-CU2 1042 hosts the SN (not illustrated in Figures). The UE 108 communicates with the gNB-CUl 104i and gNB-CU2 1042 via the gNB-DUl 106i and the gNB-DU2 IO62, over the Fl interface. The gNB-CUl 104i and gNB- CU2 1042 communicate over Xn interface. The present disclosure is explained with respect to NR-DC. However, this should not be considered as limiting. The present disclosure is applicable to any other dual connectivity system. Hereafter, the gNB-DUl IO61 is referred as a first distributed unit IO61. The gNB-DU2 IO62 is referred as a second distributed unit IO62. The gNB-CU2 104 is referred as a centralised unit 104. The gNB-CUl 104i is referred as a first centralised unit 104i and the gNB-CU2 1042 is referred as a second centralised unit 1042.

[031] In the present disclosure, the first distributed unit IO61 is configured to perform the LTM recovery procedure in dual connectivity systems. Herein, the first distributed unit IO61 detects a failure in execution of a LTM cell switch of the UE 108 configured with dual connectivity, with a target cell hosted by the first distributed unit 106i . In such case, the present disclosure enables the UE 108 to transmit measurement report to the first distributed unit IO61, upon such failure. According to the first variant 102, the first distributed unit 1061 receives the measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE 108, via the centralised unit 104 and the second distributed unit IO62. The first distributed unit IO61 identifies an availability of a new target cell in already configured LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report. Then, the first distributed unit IO61 transmits information of such target cell to the UE 108 for performing the LTM cell switch in the dual connectivity system. According to the first variant 102, the information is transmitted to the UE 108 via the centralised unit 104 and the second distributed unit IO62. [032] The present disclosure also enables the first distributed unit 106i to perform the LTM recovery procedure in dual connectivity systems, according to the second variant 110. According to the second variant 110, the first distributed unit 106i receives the measurement report of the UE 108 from the first centralised unit 104i via the second centralised unit 1042 and the second distributed unit IO62. According to the second variant 110, the information is transmitted to the UE 108 from the first centralised unit 104i, via the second centralised unit 1042 and the second distributed unit IO62.

[033] Figure 2 illustrates a detailed diagram of the first distributed unit IO61 , in accordance with some embodiments of the present disclosure. The first distributed unit IO61 may include Input/ Output (I/O) interface 202, a memory 204, and a Central Processing Unit (also referred as “CPU” or “a processor 206”). In some embodiments, the memory 204 may be communicatively coupled to the processor 206. The memory 204 stores instructions executable by the processor 206. The processor 206 may comprise at least one data processor for executing program components for executing user or system-generated requests. The memory 204 may be communicatively coupled to the processor 206. The memory 204 stores instructions, executable by the processor 206, which, on execution, may cause the processor 206 to perform the LTM recovery procedure. The I/O interface 202 is coupled with the processor 206 through which an input signal or/and an output signal is communicated. For example, the first distributed unit 1061 may receive the measurement report from the UE 108, via the I/O interface 202. In an embodiment, the first distributed unit IO61 may be implemented in a variety of computing systems, such as a server, a network server, a cloud-based server, and the like. [034] In an embodiment, the memory 204 may include one or more modules 210 and data 208. The one or more modules 210 may be configured to perform the steps of the present disclosure using the data 208. In an embodiment, each of the one or more modules 210 may be a hardware unit which may be outside the memory 204 and coupled with the first distributed unit 106i. As used herein, the term modules 210 refer to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a Field-Programmable Gate Arrays (FPGA), Programmable System-on-Chip (PSoC), a combinational logic circuit, and/or other suitable components that provide described functionality. The one or more modules 210 when configured with the described functionality defined in the present disclosure will result in a novel hardware.

[035] In one implementation, the modules 210 may include, for example, a detection module 222, a reception module 224, an identification module 226, a transmission module 228, and other modules 230. It will be appreciated that such aforementioned modules may be represented as a single module or a combination of different modules. In one implementation, the data 208 may include, for example, detection data 212, measurement data 214, identification data 216, transmission data 218, and other data 220.

[036] Firstly, the modules 210 and the data 208 are explained with respect to the first variant 102 of the NR-DC.

[037] In an embodiment, the detection module 222 may be configured to detect a LTM execution failure of an LTM cell switch of the UE 108 configured with dual connectivity, with a target cell. The target cell may be hosted by the first distributed unit 1061. The first distributed unit 106i may host multiple cells. For instance, the first distributed unit 106i may host a maximum of 512 cells. The UE 108 may be currently camped on a serving cell of the first distributed unit 106i. The UE 108 may try connecting to the target cell hosted by the first distributed unit 106i by performing the LTM cell switch. Herein, the first distributed unit 106i may transmit an LTM serving cell switch command to the UE 108 for switching from the serving cell to the target cell. The LTM cell switch may fail due to several reasons. In one example, consider the UE 108 does not receive the LTM serving cell switch command indicating the target cell from the first distributed unit 106i due to radio link failure at source or handover failure at the target. In such case, the LTM cell switch fails. In another example, consider the UE 108 receives the LTM serving cell switch command from the first distributed unit 106i, however the UE 108 is unable to connect to the target cell. In such case, the LTM cell switch fails. Then, the UE 108 may perform an LTM recovery attempt according to conventional procedure i.e., the UE 108 may perform cell re-selection and when the selected cell is an LTM candidate cell, then the UE 108 attempts LTM execution once. The detection module 222 may detect a failure in LTM recovery attempt.

[038] Figure 2 along with Figure 3A is explained considering the LTM execution failure of the LTM cell switch at SCG. The gNB-DUl 106i hosts the SCG and the gNB-DU2 IO62 hosts the MCG. The gNB-CU hosts both MN and SN (represented as MN/SN). Referring to Figure 3A, the UE 108 performs SCG LTM cell switch as shown in steps 1-3. The SCG LTM cell switch fails as shown in steps 4 and 5. The UE 108 performs the cell re-selection and performs the LTM recovery attempt as shown in step 6. The LTM recovery attempt fails as shown in step 7. Referring back to Figure 2, data related to detection of the LTM execution failure of the SCG LTM cell switch of the UE 108 may be stored as the detection data 212 in the memory 204.

In an embodiment, the reception module 224 may be configured to receive the detection data 212 from the detection module 222. Further, the reception module 224 may be configured to receive measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE 108. The UE 108 may perform measurements based on LTM configurations received from the first distributed unit 106i.The UE 108 may generate Layer 1 (LI) and Layer 3 (L3) measurement reports based on the measurements. The measurement reports may comprise information regarding SCG LTM candidate cells. The UE 108 may transmit the measurement report comprising the LI and L3 measurement reports to the first distributed unit 106i . According to the first variant 102, the first distributed unit 1061 may receive the measurement report from the UE 108, via the centralised unit 104 and the second distributed unit IO62. Herein, the second distributed unit IO62 may receive the measurement report from the UE 108, as there is no link established between the UE 108 and the first distributed unit IO61, due to the LTM execution failure. The second distributed unit IO62 may transmit the measurement report to the centralised unit 104. The centralised unit 104 may receive the measurement report including the L3 measurement report and the LI measurement report. In an example, the LI measurement report may be received as a container. The centralised unit 104 may transmit the LI measurement report (received as pay load) to the reception module 224 of the first distributed unit IO61 via the Fl interface.

[039] Referring again to Figure 3A, the centralised unit 104 (MN+SN) may receive the measurement report i.e., RRC measurement report from the UE 108 via the second distributed unit IO62 (MCG), as shown in step 8. The centralised unit 104 (MN+SN) checks the measurement report for LTM cell preparation as shown in step 9, which is explained in detail in subsequent paragraphs of the description. The reception module 224 of the first distributed unit 106i (SCG) may receive the LI measurement report from the centralised unit 104 (MN+SN) as shown in step 11. Referring back to Figure 2, the received measurement report of the UE 108 may be stored as the measurement data 214 in the memory 204. The present disclosure enables the UE 108 to transmit the measurement report to the network (the centralised unit 104 and the first distributed unit 106i (SCG)), in case of a failure in the LTM recovery attempt. The network performs the LTM cell switch based on the measurement report. Hence, the LTM cell switch is performed and RRC re-establishment upon failure is avoided.

[040] In an embodiment, the identification module 226 may be configured to receive the measurement data 214 from the reception module 224. Further, the identification module 226 may be configured to identify a new target cell present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report The measurement report received by the identification module 226 may comprise the plurality of LTM candidate cells. The plurality of LTM candidate cells may be cells already configured by network (i.e., the first distributed unit 106i). The identification module 226 may determine availability of new target cell from the plurality of LTM candidate cells. Herein, the identification module 226 may determine whether a radio condition of any cell indicated in the measurement report is suitable/satisfactory for LTM cell switch.

[041] In an embodiment illustrated in Figure 3A, the first distributed unit 1061 hosts the SCG, and the second distributed unit IO62 hosts the MCG. The centralised unit 104 hosts both MN and SN. In such case, the measurement report received from the UE 108 may comprise configuration of SCG LTM candidate cells. In another embodiment (not illustrated in Figures), the first distributed unit 106i hosts the MCG, and the second distributed unit IO62 hosts the SCG. In such case, the measurement report received from the UE 108 may comprise configuration of MCG LTM candidate cells. Referring again to Figure 3A, the identification module 226 may determine whether the LTM cell switch can be performed to a different cell/the at least one candidate/target cell at step 12.

[042] Referring back to Figure 2, in an embodiment, the identification module 226 may determine that the new target cell is not present in the plurality of configured LTM candidate cells. In such case, the identification module 226 may receive information of at least one new candidate/target cell from the centralised unit 104 for performing the LTM candidate/target cell preparation and cell switch. Herein, the centralised unit 104 identifies the at least one new candidate/target cell for the LTM cell switch based on the L3 measurement report received from the UE 108. Referring again to Figure 3 A, the centralised unit 104 (MN+SN) prepares the new candidate cell for the SCG LTM cell switch based on the L3 measurement report, as shown in step 9. The centralised unit 104 (MN+SN) may transmit the information of the new candidate/target cell to the identification module 226 in UE context modification request via the Fl interface. Referring back to Figure 2, the information of the identified at least one new candidate/target cell may be stored as the identification data 216 in the memory 204. The present disclosure enables the network to perform the LTM cell switch based on the measurement report of the UE 108. Hence, the LTM cell switch is performed and RRC reestablishment upon failure is avoided. [043] In an embodiment, the transmission module 228 may be configured to receive the identification data 216 from the identification module 226. Further, the transmission module 228 may be configured to transmit the information of the new target cell to the UE 108. Herein, the transmission module 228 may be configured to transmit the information of the new target cell when the radio condition of the new target cell is satisfactory and the new target cell is already prepared for LTM. In an embodiment, the transmission module 228 may transmit the information of the new target cell in a LTM serving cell switch command or a DL MAC CE to perform the LTM cell switch. The DL MAC CE may be sent as a payload. A target cell beam, Random Access Channel (RACH) preamble (if required for Contention Free random Access (CFRA)) and corresponding Timing Advance (TA) may also be included in the DL MAC CE.

[044] The transmission module 228 may transmit the information of the new target cell via the centralised unit 104 and the second distributed unit IO62 to the UE 108, over the Fl interface. The information of the at least one new candidate/target cell may be transmitted via the centralised unit 104 and the second distributed unit IO62 to the UE 108, over the Fl interface, when the new target cell is not available. Referring again to Figure 3A, the information of the at least one new candidate/target cell may be transmitted to the UE 108, as shown in steps 13- 16. The SCG LTM cell switch may be performed as shown in steps 17-21. Referring back to Figure 2, the information transmitted to the UE 108 may be stored as the transmission data 218 in the memory 204.

[045] Figure 2 is explained along with Figure 3A, considering the LTM execution failure of the LTM cell switch at SCG. Herein, the gNB-DUl IO61 hosts the SCG and the gNB-DU2 IO62 hosts the MCG. The similar steps are applicable when the LTM execution failure of the LTM cell switch occurs at MCG, the gNB-DUl IO61 hosts the MCG and the gNB-DU2 IO62 hosts the SCG. The explanation for the LTM execution failure at MCG is not provided for the sake of brevity.

[046] The present disclosure enables the UE 108 and the network to perform the LTM cell switch upon the failure in LTM recovery attempt, without RRC re-establishment. After the LTM cell switch failure and the LTM recovery attempt failure at the first distributed unit 106i, since the second distributed unit IO62 is still active, the UE 108 need not initiate RRC reestablishment. The centralised unit 104 configures the UE 108 to perform the LTM recovery procedure using a new RRC parameter (RRC measurement reports). This saves network resources as release of MCG/SCG bearers is avoided. The present disclosure enables providing the information of the new target cell to the UE 108. In a case where LTM cell switch is failed due to UE 108 not receiving the LTM serving cell switch command, the UE 108 can perform the LTM cell switch using the information of the new target cell. In another case, where the UE 108 is unable to connect to a target cell, the UE 108 can perform the LTM cell switch using the information of the new target cell without performing RRC re-establishment.

[047] The other data 220 may store data, including temporary data and temporary files, generated by the one or more modules 210 for performing the various functions of the first distributed unit 106] . The other data 220 may be stored in the memory 204. The one or more modules 210 may also include the other modules 230 to perform various miscellaneous functionalities of the first distributed unit 1061.

[048] Now, the modules 210 and the data 208 are explained with respect to the second variant 110 of the NR-DC. [049] The detection module 222 configured to perform the LTM recovery procedure for the second variant 110 is similarly configured as the first variant 102, and is thus not explained again for the sake of brevity.

[050] In an embodiment, the reception module 224 may be configured to receive the detection data 212 from the detection module 222. Further, the reception module 224 may be configured to receive measurement report of the UE 108. The UE 108 may transmit the measurement report comprising the LI and L3 measurement reports to the first distributed unit 106i. According to the second variant 110, the reception module 224 of the first distributed unit 1061 may receive the measurement report from the UE 108, via the first centralised unit 104i, the second centralised unit 1042, and the second distributed unit IO62. Herein, the second distributed unit IO62 may receive the measurement report from the UE 108, as there is no link established between the UE and the first distributed unit IO61, due to the LTM execution failure. The second distributed unit IO62 may transmit the measurement report to the second centralised unit 1042. The second centralised unit 1042 may receive the measurement report including the L3 measurement report and the LI measurement report. The second centralised unit 1042 may transmit the LI measurement report (received as payload) to the first centralised unit 104] via the Xn interface, which is then forwarded to the reception module 224 of the first distributed unit IO61 via the Fl interface.

[051] Figure 3B is explained considering the LTM execution failure of the LTM cell switch at SCG. Referring to Figure 3B, the steps 1-7 illustrate the LTM execution failure and the failure in LTM recovery attempt. The reception module 224 of the first distributed unit IO61 (SCG) may receive the measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE 108 from the from the first centralised unit 104i (SN) via the second centralised unit 1042 (MN) and the second distributed unit IO62 (MCG), over Xn + Fl interfaces, as shown in steps 8, 11, and 12. The second centralised unit 1042 (MN) checks the measurement report for LTM cell preparation as shown in step 9. Referring back to Figure 2, the received measurement report of the UE 108 may be stored as the measurement data 214 in the memory 204.

[052] The identification module 226 configured to perform the LTM recovery procedure for the second variant 110 is similarly configured as the first variant 102, and is thus not explained again for the sake of brevity.

[053] In an embodiment, the transmission module 228 may be configured to receive the identification data 216 from the identification module 226. Further, the transmission module 228 may be configured to transmit the information of the new target cell to the UE 108. Herein, the transmission module 228 may be configured to transmit the information of the new target cell when the radio condition of the new target cell is satisfactory and the new target cell is already prepared for LTM. In an embodiment, the transmission module 228 may transmit the information of the new target cell in a LTM serving cell switch command or a DL MAC CE to perform the LTM cell switch.

[054] The transmission module 228 may transmit the information of the new target cell from the first centralised unit 104i, via the second centralised unit 1042 and the second distributed unit IO62, over the Xn + Fl interfaces. The information of the at least one new candidate/target cell may be transmitted from the first centralised unit 1041 , via the second centralised unit 1042 and the second distributed unit IO62, over the Xn + Fl interfaces, when the new target cell is not available. Referring again to Figure 3B, the information of the new target cell may be transmitted to the UE 108 from the first centralised unit 1041 (SN), via the second centralised unit 1042 (MN) and the second distributed unit 1062(MCG), as shown in steps 14-17. The SCG LTM cell switch may be performed as shown in steps 18-22. Referring back to Figure 2, the information transmitted to the UE 108 may be stored as the transmission data 218 in the memory 204.

[055] Figure 2 is explained along with Figure 3B, considering the LTM execution failure of the LTM cell switch at SCG. Herein, the gNB-DU 1 1061 hosts the SCG and the gNB-DU2 IO62 hosts the MCG, the gNB-CUl 104i hosts the SN, the gNB-CU2 1042 hosts the MN. The similar steps are applicable when the LTM execution failure of the LTM cell switch occurs at MCG, the gNB-DUl hosts the SCG and the gNB-DU2 hosts the MCG, the gNB-CUl 104i hosts the MN, the gNB-CU2 1042 hosts the SN. The explanation for the LTM execution failure at MCG is not provided for the sake of brevity.

[056] The other data 220 may store data, including temporary data and temporary files, generated by the one or more modules 210 for performing the various functions of the first distributed unit IO61. The other data 220 may be stored in the memory 204. The one or more modules 210 may also include the other modules 230 to perform various miscellaneous functionalities of the first distributed unit 1061.

[057] Figure 4 shows an exemplary flow chart illustrating method steps for performing LTM recovery procedure, in accordance with some embodiments of the present disclosure. As illustrated in Figure 4, the method 400 may comprise one or more steps. The method 400 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.

[058] The order in which the method 400 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.

[059] At step 402, the LTM execution failure of the LTM cell switch of the UE 108 configured with dual connectivity, with a target cell may be detected. The target cell may be hosted by the first distributed unit 106i . The first distributed unit 106i may host multiple cells. The UE 108 may perform an LTM recovery attempt when the LTM cell switch fails i.e., the UE 108 may perform cell re-selection and when the selected cell is an LTM candidate cell, then the UE 108 attempts LTM execution once. The first distributed unit 106i may detect a failure in LTM recovery attempt.

[060] At step 404, the measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure may be received, from the UE 108. The UE 108 may transmit the measurement report comprising the LI and L3 measurement reports to the first distributed unit 106i. According to the first variant 102, the first distributed unit 106i may receive the measurement report from the UE 108, via the centralised unit 104 and the second distributed unit IO62.

[061] At step 406, a new target cell present in the plurality of LTM candidate cells belonging to a cell group associated with failure may be identified for the LTM cell switch, based on the measurement report. The plurality of LTM candidate cells may be cells already configured by network (i.e., the first distributed unit 106])- Herein, the first distributed unit IO61 may determine whether a radio condition of any cell indicated in the measurement report is suitable/satisfactory for LTM cell switch.

[062] At step 408, the information of the new target cell may be transmitted to the UE 108. Herein, the first distributed unit 106] may be configured to transmit the information of the new target cell when the radio condition of the new target cell is satisfactory and the new target cell is already prepared for LTM. In an embodiment, the first distributed unit IO61 may transmit the information of the new target cell in an LTM serving cell switch command or a DL MAC CE to perform the LTM cell switch. The first distributed unit 1061 may transmit the information of the new target cell via the centralised unit 104 and the second distributed unit IO62 to the UE 108, over the Fl interface. The information of at least one new candidate/target cell may be transmitted via the centralised unit 104 and the second distributed unit IO62 to the UE 108, over the Fl interface, when the new target cell is not available.

[063] Figure 5 shows an exemplary flow chart illustrating method steps for performing LTM recovery procedure, in accordance with some embodiments of the present disclosure. As illustrated in Figure 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.

[064] 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.

[065] The step 502 is similar to the step 402, and thus not explained for the sake of brevity.

[066] At step 504, the measurement report of the UE 108 may be received. The UE 108 may transmit the measurement report comprising the El and L3 measurement reports to the first distributed unit 106i . According to the second variant 110, the first distributed unit 106i may receive the measurement report from the UE 108 , via the first centralised unit 104i,the second centralised unit 1042, and the second distributed unit IO62. Herein, the second distributed unit IO62 may receive the measurement report from the UE 108, as there is no link established between the UE and the first distributed unit 106], due to the LTM execution failure. The second distributed unit IO62 may transmit the measurement report to the second centralised unit 1042. The second centralised unit 1042 may receive the measurement report including the L3 measurement report and the LI measurement report. The second centralised unit 1042 may transmit the LI measurement report (received as payload) to the first centralised unit 104i via the Xn interface, which is then forwarded to the first distributed unit 106i via the Fl interface.

[067] The step 506 is similar to the step 406, and thus not explained for the sake of brevity.

[068] At step 508, the information of the new target cell may be transmitted to the UE 108. Herein, the first distributed unit 106i may be configured to transmit the information of the new target cell when the radio condition of the new target cell is satisfactory and the new cell is already prepared for LTM. In an embodiment, the first distributed unit 1061 may transmit the information of the new target cell in an LTM serving cell switch command or a DL MAC CE to perform the LTM cell switch. The first distributed unit 106] may transmit the information of the new target cell from the first centralised unit 104i, via the second centralised unit 1042 and the second distributed unit IO62, over the Xn + Fl interfaces. The information of at least one candidate/new target cell may be transmitted from the first centralised unit 104i, via the second centralised unit 1042 and the second distributed unit IO62, over the Xn + Fl interfaces, when the new target cell is not available.

[069] FIGURE 6 illustrates an embodiment of a first distributed unit 600. As shown in FIGURE 6, the first distributed unit 600 comprises a processor 602, a memory 604, a storage component 606, an input component 608, an output component 610, a communication interface 612, and a bus 614. The first distributed unit 600 may be used to realize the first distributed unit IO61 of Figure 2. Hence, the first distributed unit 600 may be used to perform the LTM recovery procedure, in accordance with embodiments of the present disclosure. [070] The processor 602, as used herein, means any type of computational circuit that may comprise hardware elements and software elements. The processor 602 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 602 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. The processor 602 may be used to realize the processor 206 described in Figure 2.

[071] The memory 604 includes a non-transitory computer readable medium. Memory 604 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 602. The memory 604 comprises machine-readable instructions which are executable by the processor 602. These machine-readable instructions when executed by the processor 602 cause the processor 602 to perform one or more method steps of an embodiment described above. The memory 604 may be used to realize the memory 204 described in Figure 2. The memory 604 is communicatively coupled to the processor 602. The memory 604 stores instructions, executable by the one or more processors 602, which, on execution, may cause the processor 602 to perform LTM recovery procedure, in accordance with embodiments of the present disclosure.

[072] The storage component 606 stores information and/or software related to the operation and use of the first distributed unit 600. For example, the storage component 606 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.

[073] The input component 608 is configured to receive information, such as user input. For example, the input component 608 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 608 may include a sensor for sensing information (e.g., a global positioning system (GPS), an accelerometer, a gyroscope, and/or an actuator).

[074] The output component 610 is configured to provide output information from the first distributed unit 600. For example, the output component 610 may be, but not limited to, a display, a speaker, instructions to an external device, and/or one or more light-emitting diodes (LEDs).

[075] The communication interface 612 is an interface that provides a communication connection to other devices, such as external devices and internal devices. The connection by the communication interface 612 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 first distributed unit 600 and other devices. In other words, the standard of the communication interface 612 is not limited. The computer system 600 may communicate with the second distributed unit IO62, the centralised unit 104, and the UE, over a communication network 609. [076] The bus 614 acts as an interconnect between the processor 602, the memory 604, the storage component 606, the input component 608, the output component 610, and the communication interface 612 of the first distributed unit 600. The bus 614 may include a wired interconnection or a wireless interconnection.

[077] The number and arrangement of components shown in FIGURE 6 are provided as an example. In practice, the first distributed unit 600 may include additional components, fewer components, different components, or differently arranged components than those shown in FIGURE 6. Additionally, or alternatively, a set of components (e.g., one or more components) of the first distributed unit 600 may perform one or more functions described as being performed by another set of components of the first distributed unit 600. Further, one or more method steps described in any of the embodiments may be performed utilizing a plurality of the first distributed units 600 in communication with one another.

[078] In an embodiment, the present disclosure, discloses a method comprising detecting a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) (108) configured with dual connectivity, with a target cell hosted by the first distributed unit ( 1061 ). The method comprises receiving a measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE (108), via a centralised unit (104) and a second distributed unit (IO62). The centralised unit (104) is connected to the first distributed unit (IO61) and the second distributed unit (IO62). Further, the method comprises identifying a new target cell present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report. Thereafter, the method comprises transmitting, by the first distributed unit (1061), information of the new target cell to the UE (108), via the centralised unit (104) and the second distributed unit (IO62), for performing the LTM cell switch.

[079] In an embodiment, the measurement report received from the UE (108) is LI measurement report.

[080] In an embodiment, the method further comprises determining that the new target cell is not present in the plurality of LTM candidate cells belonging to the cell group associated with the failure; and receiving information of the at least one new candidate/ target cell from the centralised unit (104) for performing the LTM candidate/target cell preparation and cell switch. The centralised unit (104) prepares the at least one new candidate/target cell for the LTM cell switch based on a L3 measurement report received from the UE (108). The information of the at least one new candidate/target cell is communicated to the UE (108) via the centralised unit (104) and the second distributed unit (IO62).

[081] In an embodiment, the method comprises detecting a failure in LTM recovery attempt, upon the LTM execution failure.

[082] In an embodiment, the first distributed unit (IO61) hosts a Master Cell Group (MCG), and the second distributed unit (IO62) hosts a Secondary Cell Group (SCG). In another embodiment, the first distributed unit (1061) hosts a SCG, and the second distributed unit (IO62) hosts an MCG.

[083] In an embodiment, the information of the new target cell is communicated to the UE (108) via the centralised unit (104) and the second distributed unit (IO62) over Fl interface. [084] In an embodiment, the present dislcosure discloses a first distributed unit (1061). The first distributed unit (106i) detects a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) (108) configured with dual connectivity with a target cell hosted by the first distributed unit (106i). Further, the first distributed unit (106i) receives measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE (108), via a centralised unit (104) and a second distributed unit (IO62). The centralised unit (104) is connected to the first distributed unit (IO61) and the second distributed unit (IO62). Furthermore, the first distributed unit (IO61) identifies a new target cell present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report. The first distributed unit (IO61) transmits information of the new target cell to the UE (108), via the centralised unit (104) and the second distributed unit (IO62), for performing the LTM cell switch.

[085] In an embodiment, the first distributed unit (IO61) is configured to determine that the new target cell is not present in the plurality of LTM candidate cells belonging to the cell group associated with the failure. The first distributed unit (IO61) receives information of the at least one new candidate/ target cell from the centralised unit (104) for performing the LTM candidate/target cell preparation and cell switch. The centralised unit (104) prepares the at least one new candidate/target cell for the LTM cell switch based on a L3 measurement report received from the UE (108). The information of the at least one new candidate/target cell is communicated to the UE (108) via the centralised unit (104) and the second distributed unit (IO62). [086] In an embodiment, the first distributed unit (106i) detects the LTM execution failure of the UE (108) with the target cell by detecting a failure in LTM recovery attempt, upon the LTM execution failure.

[087] In an embodiment, the first distributed unit (1061) communicates the information of the new target cell to the UE (108) via the centralised unit (104) and the second distributed unit (IO62) over Fl interface.

[088] In an embodiment, the present disclosure discloses a non-transitory computer readable medium including instructions for performing operations comprising detecting a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) (108) configured with dual connectivity, with a target cell hosted by the first distributed unit (IO61). Further, the operations comprise receiving a measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE (108), via a centralised unit (104) and a second distributed unit (IO62), wherein the centralised unit (104) is connected to the first distributed unit (IO61) and the second distributed unit (IO62). Furthermore, the operations comprise identifying a new target cell, wherein the new target cell is present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report. Thereafter, the operations comprise transmit information of the new target cell to the UE (108), via the centralised unit (104) and the second distributed unit (IO62), for performing the LTM cell switch.

Claims

We claim:

1. A method comprising: detecting, by a first distributed unit, a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) configured with dual connectivity, with a target cell hosted by the first distributed unit; receiving, by the first distributed unit, a measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE, via a centralised unit and a second distributed unit, wherein the centralised unit is connected to the first distributed unit and the second distributed unit; identifying, by the first distributed unit, a new target cell, wherein the new target cell is present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report; and transmitting, by the first distributed unit, information of the new target cell to the UE, via the centralised unit and the second distributed unit, for performing the LTM cell switch.

2. The method as claimed in claim 1 , wherein the measurement report received from the UE is LI measurement report.

3. The method as claimed in claim 1 , further comprising: determining that the new target cell is not present in the plurality of LTM candidate cells belonging to the cell group associated with the failure; and receiving information of the at least one new candidate/ target cell from the centralised unit for performing the LTM candidate/target cell preparation and cell switch, wherein the centralised unit prepares the at least one new candidate/target cell for the LTM cell switch based on a L3 measurement report received from the UE, wherein the information of the at least one new candidate/target cell is communicated to the UE via the centralised unit and the second distributed unit.

4. The method as claimed in claim 1 , wherein detecting the LTM execution failure of the UE with the target cell comprising: detecting a failure in LTM recovery attempt, upon the LTM execution failure.

5. The method as claimed in claim 1, wherein the first distributed unit hosts a Master Cell Group (MCG), and the second distributed unit hosts a Secondary Cell Group (SCG).

6. The method as claimed in claim 1, wherein the first distributed unit hosts a SCG, and the second distributed unit hosts an MCG.

7. The method as claimed in claims 1 and claim 3, wherein the information of the new target cell is communicated to the UE via the centralised unit and the second distributed unit over Fl interface.

8. A first distributed unit configured to: detect a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) configured with dual connectivity with a target cell hosted by the first distributed unit; receive measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE, via a centralised unit and a second distributed unit, wherein the centralised unit is connected to the first distributed unit and the second distributed unit; identifying a new target cell, wherein the new target cell is present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report; and transmit information of the new target cell to the UE, via the centralised unit and the second distributed unit, for performing the LTM cell switch.

9. The first distributed unit as claimed in claim 8, wherein the measurement report received from the UE is LI measurement report.

10. The first distributed unit as claimed in claim 8, further configured to: determining that the new target cell is not present in the plurality of LTM candidate cells belonging to the cell group associated with the failure; and receiving information of the at least one new candidate/ target cell from the centralised unit for performing the LTM candidate/target cell preparation and cell switch, wherein the centralised unit prepares the at least one new candidate/target cell for the LTM cell switch based on a L3 measurement report received from the UE, wherein the information of the at least one new candidate/target cell is communicated to the UE via the centralised unit and the second distributed unit.

11. The first distributed unit as claimed in claim 8, detects the LTM execution failure of the UE with the target cell by: detecting a failure in LTM recovery attempt, upon the LTM execution failure.

12. The first distributed unit as claimed in claim 8 hosts a Master Cell Group (MCG), and the second distributed unit hosts a Secondary Cell Group (SCG).

13. The first distributed unit as claimed in claim 8 hosts a SCG, and the second distributed unit hosts an MCG.

14. The first distributed unit as claimed in claims 8 and claim 10 communicates the information of the new target cell to the UE via the centralised unit and the second distributed unit over Fl interface.

15. A non-transitory computer readable medium including instructions for performing operations comprising: detecting a Lower-layer Triggered Mobility (LTM) execution failure of an LTM cell switch of a User Equipment (UE) configured with dual connectivity, with a target cell hosted by the first distributed unit; receiving a measurement report of a plurality of LTM candidate cells belonging to a cell group associated with the failure, from the UE, via a centralised unit and a second distributed unit, wherein the centralised unit is connected to the first distributed unit and the second distributed unit; identifying a new target cell, wherein the new target cell is present in the plurality of LTM candidate cells belonging to a cell group associated with failure, for the LTM cell switch, based on the measurement report; and transmit information of the new target cell to the UE, via the centralised unit and the second distributed unit, for performing the LTM cell switch.