Distributed Unit (DU) and UE candidate cell reconfiguration due to status change from intra-DU to inter-DU

Abstract

An embodiment of the present disclosure discloses a process for candidate cell reconfiguration of a serving / candidate distribution unit (DU) and a user equipment (UE) due to a status change from intra-DU to inter-DU. In one embodiment, a centralized unit (CU) receives a notification indicating a serving cell change due to L1 / L2 triggered mobility (LTM) of the UE. Furthermore, the CU determines status changes of one or more cells of the serving DU among multiple candidate / target DUs and one or more candidate / target cells of the candidate / target DU when changing the UE's serving cell to a new serving cell. The CU then sends a message to the new serving DU containing status change information of all candidate / target cells, including corresponding cell identifiers. Finally, the CU receives a reconfiguration confirmation corresponding to the status change in the new serving DU and the UE. The UE applies the one or more configuration changes provided by the CU before the change in serving cell. The present disclosure provides the advantage of reducing latency during LTM of the UE.

Description

[Technical Field]

[0001] The present disclosure generally relates to handling candidate cell reconfiguration of candidate / serving Distributed Units (DUs) and User Equipment (UEs) due to a status change from intra-DU to inter-DU. [Background technology]

[0002] Generally, a disaggregated architecture is defined in the 3rd Generation Partnership Project (3GPP®) that decomposes the Next Generation Node B (gNB) into multiple logical entities. Similarly, a single Distributed Unit (DU) can host multiple cells (up to 512 in the current 3GPP specification). The gNB Control Unit-Control Plane (CU-CP) hosts the Packet Data Convergence Protocol (PDCP) and Radio Resource Control (RRC) layers, while the DU hosts the Radio Link Control (RLC), Medium Access Control (MAC), and PHY layers. Scheduling operations are performed in the DU. To support L1 / L2-centric inter-cell changes (i.e., serving cell changes) in a disaggregated gNB architecture, a new mechanism is needed that is configured by the Centralized Unit (CU) (or gNB CU-CP) but is autonomously executed by the DU without further interaction with higher layers.

[0003] Existing literature supports sequential or subsequent L1 / L2 serving cell changes (SCCs) between candidates without additional RRC reconfiguration. Therefore, if multiple LTM candidate cells are configured for a user equipment (UE), an L1 / L2 triggered mobility (LTM) serving cell change does not need to mandatorily indicate an RRC reconfiguration for the remaining LTM candidate cells (as in conditional HO). Subsequent sequential LTM SCCs can also be performed without RRC reconfiguration. Consider an exemplary scenario in which a gNB has two DUs controlled by a CU, each of which can contain four cells. For example, cells 1, 2, 3, and 4 belong to DU1, and cells 5, 6, 7, and 8 belong to DU2. The UE also has its serving cell in cell 2, which consists of LTM candidate cells from both DUs, e.g., 3, 4, 5, and 6. In this case, the cell status is: Cell 2 - Serving cell (DU1) Cells 3, 4, 5 - Intra-DU candidate cells Cells 5 and 6 - Inter-DU candidate cells, which may be

[0004] There are two main scenarios: i) Intra-DU LTM SCC, ii) Inter-DU LTM SCC. During Intra-DU LTM SCC: When the above UE undergoes Intra-DU LTM SCC. For example, the scenario from cell 2 to cell 3 is not much different except for losing one candidate cell (if serving cell 2 is not automatically configured as a candidate cell). The cell status is: Cell 3 - Serving cell (DU1) Cell 4 - Intra-DU candidate cell Cells 5 and 6 - Inter-DU candidate cells, which may be

[0005] If the above UE experiences an inter-DU LTM SCC from, for example, cell 2 to cell 5, the scenario changes significantly (if ex-serving cell 2 is not automatically configured as a candidate cell). The cell status is: Cell 5 - Serving Cell (DU5) Cells 3 and 4 - Inter-DU candidate cells Cell 6 may be an intra-DU candidate cell.

[0006] There is no impact on the intra-DU LTM SCC. However, with inter-DU LTM SCC, an intra-DU candidate cell becomes an inter-DU candidate cell, and vice versa. There are several aspects of LTM that differ between intra-DU and inter-DU candidate cells. When an intra-DU candidate cell is changed to an inter-DU candidate cell, and vice versa, a reconfiguration is required. Therefore, it is desirable to address the above-mentioned or other drawbacks, or at least provide a useful alternative to ensure subsequent LTM SCC without additional RRC reconfiguration.

[0007] The information disclosed in this Background section of the present disclosure is intended only to enhance understanding of the general background of the present invention and should not be construed as an admission or any form of suggestion that this information forms prior art already known to those skilled in the art. Summary of the Invention [Means for solving the problem]

[0008] In L1 / L2 triggered mobility (LTM), cell change between candidates without RRC reconfiguration should be supported. This means that, assuming multiple LTM candidate cells configured for a UE, an LTM serving cell change (SCC) should not mandatorily indicate RRC reconfiguration for the remaining LTM candidate cells. Subsequent sequential LTM SCCs can also be performed without RRC reconfiguration. In other words, in the case of inter-DU LTM SCC, LTM SCC without RRC reconfiguration of the remaining LTM candidate cells is difficult.

[0009] In one embodiment, a centralized unit (CU) in a Next Generation Radio Access Network (NG-RAN) for processing a candidate cell reconfiguration of a serving / candidate distributed unit (DU) and a user equipment (UE) due to a status change from an intra-DU to an inter-DU is disclosed. The CU includes a processor and a memory. The memory is communicatively coupled to the processor and stores processor-executable instructions that, when executed, cause the processor to receive a notification from a serving DU of a UE in the NG-RAN indicating a serving cell change due to L1 / L2 triggered mobility (LTM) of the UE. Further, the processor determines status changes of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among multiple candidate / target DUs when changing the serving cell of the UE to a new serving cell. The new serving cell is one of the one or more candidate / target cells of the candidate / target DU. The processor then sends a message to the new serving DU including status change information of all candidate / target cells, including corresponding cell identifiers. The contents of the message are further transmitted to the UE by the new serving DU. Finally, the processor receives a confirmation of the reconfiguration corresponding to the status change in the new serving DU and the UE. As part of the reconfiguration, the UE applies one or more configuration changes provided by the CU before the change in serving cell.

[0010] In another embodiment, a method for processing candidate cell reconfiguration of a serving / candidate distribution unit (DU) and a user equipment (UE) due to a status change from an intra-DU to an inter-DU is disclosed. The method includes receiving, by a centralized unit (CU) of a next-generation radio access network (NG-RAN node), a notification from a serving DU of the UE in an NG-RAN indicating a serving cell change due to L1 / L2 triggered mobility (LTM) of the UE. The method further includes determining status changes of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among multiple candidate / target DUs when changing the serving cell of the UE to the new serving cell. The new serving cell is one of the one or more candidate / target cells of the candidate / target DU. The method then includes transmitting a message to the new serving DU containing status change information of all candidate / target cells, including corresponding cell identifiers. The content of the message is further transmitted by the new serving DU to the UE. Finally, the method includes receiving confirmation of the reconfiguration corresponding to the status change at the new serving DU and the UE. As part of the reconfiguration, the UE applies one or more configuration changes provided by the CU before the change in serving cell.

[0011] In yet another embodiment, a non-transitory computer-readable medium having instructions stored thereon, when the instructions are processed by at least one processor, causes a centralized unit (CU) of a next-generation radio access network (NG-RAN) to perform operations including receiving a notification from a serving distribution unit (DU) of a UE in the NG-RAN indicating a change of serving cell due to L1 / L2 triggered mobility (LTM) of the UE. The instructions further cause the processor to determine status changes of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among a plurality of candidate / target DUs upon changing the serving cell of the UE to a new serving cell. The new serving cell is one of the one or more candidate / target cells of the candidate / target DU. The instructions then cause the processor to send a message to the new serving DU including status change information of all candidate / target cells including corresponding cell identifiers. The content of the message is further transmitted by the new serving DU to the UE. Finally, the instructions cause the processor to receive a reconfiguration confirmation corresponding to the status change at the new serving DU and the UE. As part of the reconfiguration, the UE applies one or more configuration changes provided by the CU before the change in serving cell.

[0012] In one embodiment, a user equipment (UE) for processing a serving / candidate distribution unit (DU) and candidate cell reconfiguration of a UE caused by a status change from an intra-DU to an inter-DU is disclosed. The UE includes a processor and a memory. The memory is communicatively coupled to the processor and stores processor-executable instructions that, when executed, cause the processor to receive a notification indicating a serving cell change from a serving distribution unit (DU) of a next-generation radio access network (NG-RAN). The processor then establishes a connection with the new serving cell of the new serving DU. Upon successfully establishing the connection with the new serving cell, the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the RAN. Thereafter, the processor receives a message from the CU via the new serving DU when the UE's serving cell has changed to the new serving cell of the new serving DU, the message including a status change of one or more candidate / target cells of the new serving DU and all candidate / target DUs. Finally, the processor makes one or more configuration changes corresponding to the status change as part of the reconfiguration and sends a confirmation of the reconfiguration to the CU. The one or more configuration changes are received from the CU prior to the change in the serving cell.

[0013] In another embodiment, a method is disclosed for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and a user equipment (UE) due to a status change from an intra-DU to an inter-DU. The method includes receiving, by the user equipment (UE), a notification indicating a serving cell change from a serving distribution unit (DU) of a next-generation radio access network (NG-RAN). The method further includes establishing a connection with the new serving cell of the new serving DU. Upon successfully establishing the connection with the new serving cell, the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the RAN. Thereafter, the method includes receiving, from the CU via the new serving DU, a message including status changes of one or more candidate / target cells for the new serving DU and all candidate / target DUs when the UE's serving cell has changed to the new serving cell of the new serving DU. Finally, the method includes making one or more configuration changes corresponding to the status change as part of the reconfiguration and sending a confirmation of the reconfiguration to the CU. The one or more configuration changes are received from the CU before the change in serving cell.

[0014] In yet another embodiment, a non-transitory computer-readable medium having instructions stored thereon, when processed by at least one processor, causes a user equipment (UE) to perform operations including receiving a notification from a serving distribution unit (DU) of a next-generation radio access network (NG-RAN) indicating a change in serving cell. The instructions further cause the processor to establish a connection with the new serving cell of the new serving DU. Upon successfully establishing the connection with the new serving cell, the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the RAN. Thereafter, when the UE's serving cell is changed to the new serving cell of the new serving DU, the instructions cause the processor to receive from the CU via the new serving DU a message including status changes of one or more candidate / target cells for the new serving DU and all candidate / target DUs. Finally, the instructions cause the processor to make one or more configuration changes corresponding to the status changes as part of the reconfiguration and send a confirmation of the reconfiguration to the CU. The one or more configuration changes are received from the CU before the change in serving cell.

[0015] In one embodiment, a new serving / candidate distribution unit (DU) for processing candidate cell reconfiguration of a serving / candidate distribution unit (DU) and a user equipment (UE) caused by a status change from an intra-DU to an inter-DU is disclosed. The new serving DU includes a processor and a memory. The memory is communicatively coupled to the processor and stores processor-executable instructions that, when executed, cause the processor to receive a connection establishment from the UE after changing the serving cell to a new serving cell belonging to the new serving DU. Furthermore, the processor receives a message from a CU when the serving cell of the UE is changed to the new serving cell, the message including a status change of one or more of the candidate / target DUs and the cell of the new serving DU, and transmits the content of the message from the CU to the UE using a Layer 1 or Layer 2 message. Finally, the processor reconfigures the new serving DU based on the status change and transmits a confirmation of the reconfiguration to the CU.

[0016] In another embodiment, a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and a user equipment (UE) due to a status change from an intra-DU to an inter-DU is disclosed. The method includes receiving a connection establishment from the UE by the new serving DU after changing the serving cell to a new serving cell belonging to the new serving DU. The method further includes receiving a message from a CU when the UE's serving cell is changed to the new serving cell, the message including a status change of one or more of the candidate / target DUs and the candidate / target cell of the new serving DU, and transmitting the content of the message from the CU to the UE using a Layer 1 or Layer 2 message. Finally, the method includes reconfiguring the new serving DU based on the status change and transmitting a confirmation of the reconfiguration to the CU.

[0017] In yet another embodiment, a non-transitory computer-readable medium having instructions stored thereon, when the instructions are processed by at least one processor, causes a new serving distribution unit (DU) to perform operations including receiving a connection establishment from a user equipment (UE) after changing a serving cell to a new serving cell belonging to the new serving DU. The instructions further cause the processor to receive a message from a CU when the UE's serving cell is changed to the new serving cell, the message including a status change of one or more of the candidate / target DUs and the new serving DU's cells, and to transmit the contents of the message from the CU to the UE using a Layer 1 message or a Layer 2 message. Finally, the instructions cause the processor to reconfigure the new serving DU based on the status change and to transmit a confirmation of the reconfiguration to the CU.

[0018] The foregoing summary of the invention is illustrative only and is not intended to be in any way limiting. In addition to the exemplary aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

[0019] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, explain the disclosed principles. In the drawings, the leftmost digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer to like features and components. Some embodiments of systems and / or methods according to embodiments of the present subject matter will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 illustrates an example disaggregated next generation Node B (gNB) architecture, in accordance with some embodiments of the present disclosure. [Figure 2A] FIG. 1 shows a detailed block diagram of a control system (CU) according to some embodiments of the present disclosure. [Figure 2B] FIG. 2 is a detailed block diagram of a user equipment (UE) in accordance with some embodiments of the present disclosure. [Figure 2C] FIG. 2 is a detailed block diagram of a distributed unit (DU) according to some embodiments of the present disclosure. [Figure 3A] FIG. 10 is an example call flow diagram illustrating the process of candidate cell reconfiguration of a serving / candidate distribution unit (DU) and user equipment (UE) due to a status change from intra-DU to inter-DU, in accordance with some embodiments of the present disclosure. [Figure 3B] FIG. 10 is an exemplary call flow diagram illustrating broadcasting a status change to one or more candidate distribution units (DUs) in accordance with some embodiments of the present disclosure. [Figure 3C] 1 is an example scenario illustrating a change of serving cell for a user equipment (UE), in accordance with some embodiments of the present disclosure. [Figure 3D] 1 is an example scenario illustrating a change of serving cell for a user equipment (UE), in accordance with some embodiments of the present disclosure. [Figure 4A] 1 is a flowchart illustrating a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and user equipment (UE) due to a status change from intra-DU to inter-DU, according to some embodiments of the present disclosure. [Figure 4B] 1 is a flowchart illustrating a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and user equipment (UE) due to a status change from intra-DU to inter-DU, according to some embodiments of the present disclosure. [Figure 4C] 1 is a flowchart illustrating a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and user equipment (UE) due to a status change from intra-DU to inter-DU, according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0021] Those skilled in the art should understand that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the present subject matter. Similarly, it will be understood that any flowcharts, flow diagrams, state transition diagrams, pseudocode, etc. represent various processes, which may be substantially represented on a computer-readable medium and executed by such a computer or processor, whether or not such a computer or processor is explicitly shown.

[0022] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0023] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are described in detail below. It is to be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but rather, the disclosure is intended to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure.

[0024] The terms "comprises," "comprising," "includes," or any other variation thereof, are intended to cover non-exclusive inclusion, so that a setup, device, or method that includes a list of components or steps does not include only those components or steps, but may include other components or steps that are not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus that begin with "comprises..." does not, absent further constraints, exclude the presence of other or additional elements in the system or method.

[0025] In the following detailed description of embodiments of the present disclosure, reference is made to the accompanying drawings which form a part hereof, and which show, by way of illustration, specific embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it being understood that other embodiments may be utilized and changes may be made without departing from the scope of the present disclosure. Accordingly, the following description is not to be construed in a limiting sense.

[0026] It should be noted that for ease of explanation, this disclosure uses terms and names defined in the 3rd Generation Partnership Project Radio Access Network (3GPP RAN) standards. More specifically, the terms "Centralized Unit (CU)," "Distributed Unit (DU)," "Core Network," "Packet Data Convergence Protocol (PDCP)," "Radio Resource Control (RRC)," "Radio Resource Control (RRC) Configuration Message," "L1 / L2 Triggered Mobility (LTM)," and "Serving Cell Change (SCC)" should be interpreted as specified by the 3GPP RAN standards.

[0027] FIG. 1 illustrates an example disaggregated next generation Node B (gNB) architecture, in accordance with some embodiments of the present disclosure.

[0028] The exemplary architecture 100 illustrates a disaggregated next-generation node B (gNB) 101 architecture. The disaggregated gNB 101 may be a base station supporting 5G New Radio (NR). The gNB 101 may also be a next-generation radio access network (NG-RAN). In one embodiment, each gNB 101 includes a centralized unit (CU) 103 and distributed units (DUs) 1071-1077. N (Multiple DU107 NThe CU 103 may include multiple logical entities such as a gNB-Control Unit-Control Plane (CU-CP) 105 and one or more gNB-Control Unit-User Planes (CU-UPs) 109. The CU-CP 105 may host a Packet Data Convergence Protocol (PDCP) layer and a Radio Resource Control (RRC) layer. Multiple DUs 107 N Each of the DUs 107 may host one or more cells. Each cell within the one or more cells may refer to a defined coverage area provided to a user equipment (UE) (not shown). N Each DU in the gNB 101 may host a radio link control (RLC), a medium access control (MAC), and a PHY layer. In one embodiment, when a UE is connected to the network, the UE may be served by the DU's cell. By way of example, the UE may include, without limitation, any device used by a user to at least one of transmit and access content, including, but not limited to, a mobile phone, a smartphone, a laptop, a wearable, and an Internet of Things (IoT). The UE may be connected to the gNB 101 using a communication network. By way of example, the communication network may be a fifth-generation (5G) network. The cell to which the UE is currently connected may be referred to as the serving cell, since the cell is currently serving the UE. In one embodiment, during the movement of the UE, the serving cell of the UE may change based on the UE's serving area. In other words, once the serving area of ​​each cell is defined, the serving cell may change if the UE is moving. The UE must connect to the next cell to ensure that the UE receives service continuously and without interruption. This is also known as UE post-mobility or UE handover.

[0029] In one embodiment, the CU 103 may be configured to receive a notification from a serving DU of a UE in the NG-RAN indicating a change of serving cell due to L1 / L2 triggered mobility (LTM) of the UE. The UE may be served by a cell in the DU, which may be referred to as a serving cell, and the DU hosting the serving cell may be the serving DU. The LTM of the UE relates to, but is not limited to, a handover of the UE to a new serving cell when the signal quality received by the UE deteriorates or when the mobility of the UE deteriorates. In one embodiment, before receiving the notification, the CU 103 may perform a handover of the UE to a new serving cell based on a first measurement report received from the UE. N The CU 103 may detect one or more candidate / target DUs among the plurality of DUs 107. Each of the one or more candidate / target DUs may host one or more candidate / target cells. In one embodiment, the target DU may be a new serving DU among the one or more candidate DUs. The first measurement report may be a Radio Resource Control (RRC) (L3) measurement report received by the CU 103 from the UE. As an example, the Layer 3 (L3) measurement report may include, but is not limited to, the UE signal strength, the UE signal quality, and the UE location. Based on the received first measurement report, the CU 103 may determine that the UE is moving (UE mobility) and therefore there is a need for handover. The CU 103 may detect one or more candidate / target DUs among the plurality of DUs 107. N Upon detecting one or more candidate / target DUs among the CU 103 and the plurality of DUs 107, a setup request or a modification request requesting preparation of an LTM target cell configuration may be sent to each of the one or more candidate / target DUs detected based on the first measurement report. As an example, the setup request may be a UE ContextSetupRequest() sent using the F1 interface. As an example, the modification request may be a UE ContextModificationRequest() sent using the F1 interface. The F1 interface is used by the CU 103 and the plurality of DUs 107. NIn some embodiments, the change request may be an interface between the CU 103 and multiple DUs 107. NThe modification request received from the CU 103 may indicate a request for a change of the UE's serving cell. Upon receiving the modification request, the serving DU may perform a predefined modification operation and send a confirmation to the CU 103 upon performing the modification. As an example, the confirmation may be a UE contextModificationResponse() sent using the F1 interface. The setup request may be sent to each of one or more candidate / target DUs to prepare one or more candidate cells in the respective DUs. The one or more candidate / target DUs set up the one or more cells in the respective DUs to establish a connection with the UE. Upon performing the context setup, the one or more candidate / target DUs may respond to the setup request by sending a response to the CU 103. The CU 103 then sends one or more configuration changes to the serving DU corresponding to status changes to be made by the UE as part of the reconfiguration. As an example, the one or more configuration changes may be changes related to, but not limited to, MAC reset, RLC re-establishment, and PDCP recovery. In one embodiment, the one or more configuration changes may be sent to the serving DU as a downlink (DL) RRC message transfer. As an example, the one or more configuration changes may be sent as "DL RRC Message transfer(RRC Reconfiguration(LTM target cell configuration, Recon if for intra-DS⇔inter-DS changes))" in a container using the F1 interface. The serving DU can send the one or more configurations to the UE. As an example, the one or more configurations to the UE may be sent as "RRC Reconfiguration(LTM target cell configuration, Recon if for intra-DS⇔inter-DS changes))".

[0030] In one embodiment, the UE stores one or more configurations and reconfigures itself based on the one or more configurations as needed. In one embodiment, the UE transmits a second measurement report to the serving DU periodically or based on the occurrence of one or more events. By way of example, and without limitation, the one or more events may be when the UE first connects to the network, during UE handover, and when the serving DU requests a measurement report from the UE. The serving DU can determine a new serving cell for the UE based on the second measurement report. By way of example, the second measurement report may be an intra-frequency Layer 1 (L1) measurement report or an inter-frequency L1 measurement report. The new serving cell may be a target cell among one or more candidate cells. Based on the second measurement report, the serving DU can determine a new serving cell for the UE's new serving DU. By way of example, the serving DU can determine whether the LTM HO radio condition is met by any candidate / target cell among one or more candidate / target DUs. The serving DU then transmits a notification to the UE indicating the change of serving cell. As an example, the notification may be sent to the UE as a "MAC Control Element (CE) Serving Cell Change (SCC)." To establish a connection with the new serving cell of the new serving DU, the UE may establish a connection with the new serving DU. As an example, the UE may send a connection establishment request, which may be a random access channel (RACH (preamble)) to the new serving DU to establish the connection. Once the connection is established, the UE indicates the change of serving cell to the CU 103 by sending an RRC Reconfiguration Acknowledgement(). The serving DU may also send a notification to the CU 103 indicating the change of the UE's serving cell. The notification may include the cell identity (ID) of the new serving cell.

[0031] In one embodiment, upon receiving the notification, CU103 may be configured to determine a status change of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among the multiple candidate / target DUs when changing the UE's serving cell to a new serving cell. In one embodiment, CU103 may determine a status change of each of one or more cells of the serving DU and each of one or more candidate / target cells of the candidate / target DU from intra DU to inter DU or from inter DU to intra DU based on the change of the UE's serving cell. In one embodiment, this may be a change from intra DU to inter DU because the DU changes when the new serving cell is in a different DU than the serving DU. In other words, the status of the serving DU's cell changes from inter DU to intra DU because the new serving cell is not hosted in the serving DU. Consider an exemplary scenario in which a gNB has two DUs (DU1 and DU2) controlled by CU103, each capable of hosting four cells. For example, cells 1, 2, 3, and 4 belong to DU1, and cells 5, 6, 7, and 8 belong to DU2. Also, the UE's current serving cell is cell 2, and one or more candidate cells are cells 3, 4, 5, and 6. The status of each cell is shown below. Cell 2 - Serving cell (DU1) Cells 3 and 4 - Intra-DS candidate cells Cells 5 and 6 - Inter-DS candidate cells

[0032] Consider a scenario in which a serving DU undergoes an inter-DS serving cell change, i.e., the serving DU determines a new serving cell in DU2. Assume that the new serving cell is cell 5 in DU2. The status of the serving DU and one or more cells in the new serving DU will change due to the inter-DS serving cell change. The status of each cell changed due to the serving cell change is shown below. Cell 5 - Serving cell (DU2) Cells 3 and 4 - Inter-DS candidate cells Cell 6 - Intra-DS candidate cell

[0033] The above change may be determined by the CU 103 upon receiving the cell ID of the new serving cell from the serving DU.

[0034] In one embodiment, upon determining the status change, the CU 103 may be configured to send a message to the new serving DU containing status change information of all candidate / target cells, including corresponding cell identifiers. As an example, the message may be sent to the new serving DU as a contextModificationRequest(updated intra-DU⇔inter-DU change list). The message may be sent to the new serving DU using the F1 interface. Upon receiving the message, the new serving DU may perform a reconfiguration of the new serving DU based on the status change. In one embodiment, the UE receives the content of a message from the CU 103 via the new serving DU when the UE's serving cell is changed to the new serving cell of the new serving DU, the message containing the status changes of the serving DU and one or more cells of the new serving DU. As an example, the message may be "DL MAC CE(intra-DS⇔inter-DS change list)". After receiving the message, the new serving DU may perform one or more configuration changes corresponding to the status change as part of the reconfiguration. The new serving DU may receive one or more configuration changes from the CU 103 before the change in serving cell. By way of example, the one or more configuration changes may be, but are not limited to, turning RLC re-establishment on / off, turning PDCP recovery on / off, and turning partial MAC reset on / off.

[0035] In some embodiments, the CU 103 may be configured to broadcast a serving cell change notification message to each of one or more candidate / target DUs detected by the CU 103 based on the first measurement report received from the UE. As an example, the message may be sent to one or more candidate / target DUs as a contextModificationRequest(updated intraDU⇔interDU change list). Upon receiving the message, the one or more candidate / target DUs may perform a reconfiguration. Upon the message being broadcast, each of the one or more candidate / target DUs performs a reconfiguration including the new serving DU. Upon completion of the reconfiguration, the CU 103 receives reconfiguration information corresponding to the status change for each candidate / target cell from each of the one or more candidate / target DUs.

[0036] In one embodiment, upon sending the message, CU 103 may be configured to receive a reconfiguration confirmation corresponding to the new serving DU and the status change at the UE. As previously described, the UE applies one or more configuration changes provided by CU 103 as part of the reconfiguration and before the change in serving cell. As an example, the confirmation received from the new serving DU may be a contextModificationResponse(). In one embodiment, the UE may apply one or more configuration changes provided by CU 103 as part of the reconfiguration and before the change in serving cell. Upon making the configuration change, CU 103 may receive a confirmation from the UE. As an example, the confirmation may be an RRC Reconfiguration Acknowledgement(). As an example, during an inter-DU serving cell change, the UE may turn on RLC reestablishment, turn on PDCP recovery, and turn on partial MAC reset. On the other hand, if there is an intra-DU serving cell change, the UE may turn off RLC reestablishment, turn off PDCP recovery, and turn off partial MAC reset. The partial MAC reset may be comprehensive enough to continue to use the timing advance (TA) already obtained and the running time alignment timer (TAT).

[0037] FIG. 2A shows a detailed block diagram of a centralized unit (CU103) according to some embodiments of the present disclosure.

[0038] In some implementations, the CU 103 may include an I / O interface 201, a processor 203, and a memory 205. In one embodiment, the memory 205 of the CU 103 may be communicatively coupled to the processor 203 of the CU 103. The processor 203 of the CU 103 may be configured to perform one or more functions of the CU 103 to process a reconfiguration of a serving / candidate distribution unit (DU) and a candidate cell of a user equipment (UE) due to a status change from intra-DS to inter-DS using the data 207 and one or more modules 209 of the CU 103. In one embodiment, the memory 205 of the CU 103 may store the data 207 of the CU 103. While FIG. 2A illustrates hardware components of the CU 103, it should be understood that other embodiments are not so limited. In other embodiments, the CU 103 may include fewer or more components. Furthermore, component labels or names are used for illustrative purposes only and are not limiting in scope. One or more components may be combined together to perform the same or substantially similar technical features for candidate cell reconfiguration of DUs and UEs due to a status change from intra-DU to inter-DU.

[0039] In one embodiment, the data 207 of CU 103 stored in the memory 205 of CU 103 may include, but is not limited to, cell data 211 of CU 103, configuration data 213 of CU 103, and other data 215 of CU 103. In some implementations, the data 207 of CU 103 may be stored in the memory 205 of CU 103 in the form of various data structures. Furthermore, the data 207 of CU 103 may be organized using a data model, such as a relational or hierarchical data model. The other data 215 of CU 103 may include various temporary data and files generated by one or more modules 209 of CU 103.

[0040] In one embodiment, the cell data 211 of the CU 103 may be data related to one or more cells hosted by each DU. In one embodiment, a cell may refer to a defined coverage area provided to a UE connected to a cell. The cell data 211 of the CU 103 may also include data related to the serving cell and a new serving cell. When the serving cell is changed to a new serving cell, the cell data 211 may be updated. In one embodiment, the cell data 211 of the CU 103 may also store the status of each of one or more cells hosted by each DU. As an example, the status of each of the one or more cells may be one of intra-DU or inter-DU. For example, when a DU hosts a serving cell, the status of one or more cells in the same DU may be intra-DU. Alternatively, the status of one or more cells of another DU (which does not have a serving cell) may be inter-DU. In one embodiment, when the serving cell of a UE is changed to a new serving cell, the CU 103 may send a message including status change information of all cells, including their corresponding cell identifiers, to the new serving DU, which may be sent to the UE.

[0041] In one embodiment, the configuration data 213 of the CU 103 may be one or more configuration changes provided by the CU 103 prior to a change in serving cell as part of a reconfiguration. By way of example, and without limitation, the one or more configuration changes may be changes related to a MAC reset, an RLC re-establishment, and a PDCP recovery. In one embodiment, the one or more configuration changes may be applied by the UE when the serving cell is changed to a new serving cell. The one or more configuration changes may be transmitted from the CU 103 to the UE via a new serving DU.

[0042] In one embodiment, the data 207 of the CU 103 may be processed by one or more modules 209 of the CU 103. In some implementations, one or more modules 209 may be communicatively coupled to the processor 203 of the CU 103 to perform one or more functions of the CU 103. In one implementation, the one or more modules 209 of the CU 103 may include, but are not limited to, a transceiver module 217 of the CU 103, a decision module 219 of the CU 103, and other modules 221.

[0043] As used herein, the term module may refer to an application-specific integrated circuit (ASIC), electronic circuitry, hardware processor(s) 203 (shared, dedicated, or group) of CU 103, memory executing one or more software or firmware programs, combinatorial logic circuitry, and / or other suitable components that provide the described functionality. In one implementation, each of one or more modules 209 of CU 103 may be configured as a standalone hardware computing unit. In one embodiment, other modules 221 of CU 103 may be used to perform various miscellaneous functions on CU 103. It will be understood that such one or more modules 209 of CU 103 may be represented as a single module or as a combination of different modules.

[0044] In one embodiment, the transceiver module 217 of the CU 103 may be configured to receive a notification from a serving distribution unit (DU) of a UE in the NG-RAN indicating a change of serving cell due to L1 / L2 triggered mobility (LTM) of the user equipment (UE). In one embodiment, before receiving the notification, the transceiver module 217 of the CU 103 may be configured to: NThe CU 103 may detect one or more candidate / target DUs among the one or more candidate / target DUs. Each of the one or more candidate / target DUs may host one or more candidate / target cells. Upon detecting the one or more candidate / target DUs, the transceiver module 217 of the CU 103 may transmit a setup request or a modification request to each of the one or more candidate / target DUs detected based on the first measurement report, requesting preparation of an LTM target cell configuration. Thereafter, upon receiving the LTM candidate cell configuration from each of the one or more candidate / target DUs, the transceiver module 217 of the CU 103 may transmit one or more configuration changes to the serving DU corresponding to status changes made by the UE as part of the reconfiguration.

[0045] In one embodiment, the determination module 219 of the CU 103 may be configured to determine a status change of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among the multiple candidate / target DUs when changing the serving cell of the UE to a new serving cell. The new serving cell is one of the one or more candidate / target cells of the candidate / target DU. In one embodiment, the determination module 219 of the CU 103 may determine a status change of each of the one or more cells of the serving DU and each of the one or more candidate / target cells of the candidate / target DU from intra-DU to inter-DU or from inter-DU to intra-DU based on the change of the serving cell of the UE.

[0046] In some embodiments, the transceiver module 217 of the CU 103 may be configured to transmit a message to the new serving DU including status change information of all candidate / target cells, including their corresponding cell identifiers. The contents of the message may be further transmitted by the new serving DU to the UE. In some other embodiments, the transceiver module 217 of the CU 103 may broadcast a serving cell change notification message to each of the one or more candidate / target DUs detected by the CU 103 based on the first measurement report received from the UE. Additionally, the transceiver module 217 of the CU 103 may receive reconfiguration information from each of the one or more candidate / target DUs, which may include an acknowledgement corresponding to the status change for each candidate / target.

[0047] In one embodiment, the transceiver module 217 of the CU 103 may be configured to receive a confirmation of a reconfiguration corresponding to a new serving DU and a status change in the UE. The transceiver module 217 of the CU 103 may receive the confirmation when, as part of the reconfiguration, the UE applies one or more configuration changes provided by the CU 103 before the serving cell change.

[0048] FIG. 2B illustrates a detailed block diagram of a user equipment (UE) in accordance with some embodiments of the present disclosure.

[0049] In some implementations, the UE 231 may include an I / O interface 233, a processor 235, and a memory 237. In one embodiment, the memory 237 of the UE 231 may be communicatively coupled to the processor 235 of the UE 231. The processor 235 of the UE 231 may be configured to perform one or more functions of the UE 231 to process a serving / candidate distribution unit (DS) and candidate cell reconfiguration of the user equipment (UE) 231 due to a status change from intra-DU to inter-DU using the data 239 and one or more modules 241 of the UE 231. In one embodiment, the memory 237 of the UE 231 may store the data 239 of the UE 231. While FIG. 2B illustrates hardware components of the UE 231, it should be understood that other embodiments are not so limited. In other embodiments, the UE 231 may include fewer or more components. Furthermore, component labels or names are used for illustrative purposes only and are not limiting in scope. One or more components may be combined together to perform the same or substantially similar technical features for candidate cell reconfiguration of a DU and UE 231 due to a status change from intra-DU to inter-DU.

[0050] In one embodiment, the UE 231 data 239 stored in the UE 231 memory 237 may include, but is not limited to, cell data 243, configuration data 245, and other data 247. In some implementations, the UE 231 data 239 may be stored in the memory 237 in the form of various data structures. Furthermore, the UE 231 data 239 may be organized using a data model, such as a relational or hierarchical data model. The UE 231 other data 247 may include various temporary data and files generated by one or more modules 241 of the UE 231.

[0051] In one embodiment, the cell data 243 of the UE 231 may be data related to the serving cell of the UE 231. In one embodiment, a cell may refer to a defined coverage area provided to the UE 231 connected to a cell. The cell data 243 of the UE 231 may be updated when the serving cell may be changed to a new serving cell. The data related to the new serving cell may be stored in the UE 231. In one embodiment, the cell data 211 of the UE 231 may also store the status of each of one or more candidate / target cells. As an example, the status of each of the one or more cells may be one of intra-DU or inter-DU. For example, if a DU hosts a serving cell, the status of one or more cells in the same DU may be intra-DU. Alternatively, the status of one or more cells of another DU (which does not have a serving cell) may be inter-DU. In one embodiment, when the serving cell of the UE is changed to a new serving cell, the UE 231 may receive a message from the CU 103 via the new serving DU, including status change information of all cells, including corresponding cell identifiers.

[0052] In one embodiment, the configuration data 245 of the UE 231 may be one or more configuration changes provided by the CU 103 prior to a change in serving cell as part of a radio resource control (RRC) reconfiguration for the UE 231. By way of example, the one or more configuration changes may be changes related to, but not limited to, a MAC reset, an RLC re-establishment, and a PDCP recovery. In one embodiment, the UE 231 may apply the one or more configuration changes when the serving cell of the UE 231 is changed to a new serving cell. The UE 231 receives the one or more configuration changes from the CU 103 via a new serving DU.

[0053] In one embodiment, the data 239 of the UE 231 may be processed by one or more modules 241 of the UE 231. In some implementations, the one or more modules 241 of the UE 231 may be communicatively coupled to the processor 235 of the UE 231 to perform one or more functions of the UE 231. In one implementation, the one or more modules 241 of the UE 231 may include, but are not limited to, a transceiver module 249, a configuration module 251, and other modules 253.

[0054] As used herein, the term module may refer to an application-specific integrated circuit (ASIC), electronic circuitry, hardware processor(s) 235 (shared, dedicated, or group) of the UE 231, memory executing one or more software or firmware programs, combinatorial logic circuitry, and / or other suitable components that provide the described functionality. In one implementation, each of the one or more modules 241 of the UE 231 may be configured as a standalone hardware computing unit. In one embodiment, other modules 253 of the UE 231 may be used to perform various other functions on the UE 231. It will be understood that such one or more modules 241 of the UE 231 may be represented as a single module or a combination of different modules.

[0055] In one embodiment, the transceiver module 249 of the UE 231 may be configured to receive a notification indicating a change in serving cell from a serving distribution unit (DU) of a next-generation radio access network (NG-RAN). In one embodiment, before receiving the notification, the UE 231 may send a second measurement report to the serving DU periodically or based on the occurrence of one or more events. By way of example, and without limitation, the one or more events may be when the UE first connects to a network, during a handover of the UE, and when the serving DU requests a measurement report from the UE. The serving DU determines a new serving cell for the UE 231 based on the second measurement report. By way of example, the second measurement report may be an intra-frequency L1 measurement report or an inter-frequency L1 measurement report.

[0056] In one embodiment, the transceiver module 249 of the UE 231 may be configured to establish a connection with a new serving cell of the new serving DU. In some embodiments, the transceiver module 249 may send a connection establishment request to the new serving cell to establish the connection. Upon successfully establishing the connection with the new serving cell, the UE 231 may confirm application of the new serving cell configuration to the CU 103 of the NG-RAN.

[0057] In one embodiment, when the serving cell of the UE 231 is changed to a new serving cell of a new serving DU, the transceiver module 249 of the UE 231 may be configured to receive a message from the CU 103 via the new serving DU, including a status change of one or more candidate / target cells of the new serving DU and all candidate / target DUs.

[0058] In one embodiment, the configuration module 251 of the UE 231 may be configured to make one or more configuration changes corresponding to the status change as part of the reconfiguration and send a confirmation of the reconfiguration to the CU 103. The configuration module 251 of the UE 231 receives the one or more configuration changes from the CU 103 prior to the change in serving cell.

[0059] FIG. 2C is a detailed block diagram of a distribution unit (DU) according to some embodiments of the present disclosure.

[0060] In some implementations, a distribution unit (DU) 107 N The DU 107 may include an I / O interface 261, a processor 263, and a memory 265. In one embodiment, the DU 107 N The memory 265 is DU107 N The DU 107 may be communicatively coupled to the processor 263 of the N The processor 263 is DU107 N and one or more modules 269 to process candidate cell reconfiguration of serving / candidate DUs and user equipment (UE) 231 due to a status change from intra-DU to inter-DU. N In one embodiment, the DU 107 may be configured to perform one or more of the following functions: N The memory 265 is DU107 N The data 267 can be stored in the DU107. N Although the hardware components of the DU107 are shown, it should be understood that other embodiments are not limited thereto. Nmay include fewer or more components. Furthermore, the labels or names of the components are used for illustrative purposes only and are not intended to limit the scope. One or more components may be combined together to perform the same or substantially similar technical features for DU and candidate cell reconfiguration of a DU due to a status change from intra-DU to inter-DU. In one embodiment, the DU may be at least one of a serving DU, a candidate / target DU, and a new serving DU.

[0061] In one embodiment, DU107 N DU107 stored in memory 265 N Data 267 is DU107 N The data may include, but is not limited to, cell data 271 and other data 273. In some implementations, the DU 107 N The data 267 is in the form of various data structures DU107 N The DU107 can be stored in the memory 265. N The data 267 may be organized using a data model, such as a relational or hierarchical data model. N This may include various temporary data and files generated by one or more modules 269 of the

[0062] In one embodiment, DU107 N The cell data 271 of the DU 107 may be data related to one or more cells hosted by each DU. In one embodiment, a cell may refer to a defined coverage area provided to a UE 231 connected to the cell. N The cell data 271 of the DU 107 may also include data related to the serving cell and the new serving cell. When the serving cell is changed to the new serving cell, the DU 107 N In one embodiment, the cell data 271 of the DU 107 may be updated. N Cell data 211 is also DU107N The UE may also store the status of each of one or more cells hosted by the DU. As an example, the status of each of the one or more cells may be one of intra-DU or inter-DU. For example, if a DU hosts a serving cell, the status of one or more cells in the same DU may be intra-DU. Alternatively, the status of one or more cells of another DU (which does not have a serving cell) may be inter-DU. In one embodiment, when the UE's serving cell is changed to a new serving cell, the serving DU and the new serving DU may update the status of one or more cells. Specifically, the status of one or more cells of the serving DU may be changed from intra-DU to inter-DU. Similarly, the status of one or more cells of the new serving DU may be changed from inter-DU to intra-DU.

[0063] In one embodiment, the data 267 is N In some implementations, the DU 107 may be processed by one or more modules 269. N One or more modules 269 may be communicatively coupled to the processor 263 to perform one or more functions of the N One or more modules 209 of the receiving module 275, DU107 N Configuration module 277, and DU107 N Other modules 279 may include, but are not limited to:

[0064] As used herein, the term module refers to an application specific integrated circuit (ASIC), electronic circuit, DU107 N The DU 107 may refer to a hardware processor 263 (shared, dedicated, or group), memory that executes one or more software or firmware programs, combinational logic circuitry, and / or other suitable components that provide the described functionality. NEach of the one or more modules 269 may be configured as a standalone hardware computing unit. N Other modules 279 may be used to perform various miscellaneous functions on the DU 107. N It will be appreciated that such one or more modules 269 may be represented as a single module or a combination of different modules.

[0065] In one embodiment, the receiving module 275 may be configured to receive a connection establishment from the user equipment (UE) 231 after changing the serving cell to a new serving cell belonging to a new serving DU. In one embodiment, the receiving module 275 may receive a message including a status change of one or more of the candidate / target DUs and the cell of the new serving DU from the CU 103 when the serving cell of the UE 231 is changed to the new serving cell, and may transmit the content of the message from the CU to the UE 231 using a Layer 1 message or a Layer 2 message. As an example, the Layer 1 message or the Layer 2 message may be used to communicate between the UE 231 and the serving DU.

[0066] In one embodiment, the configuration module 277 may be configured to reconfigure a new serving DU based on the status change and send a confirmation of the reconfiguration to the CU 103.

[0067] FIG. 3A shows an example call flow diagram illustrating the process of candidate cell reconfiguration of a serving / candidate distribution unit (DU) and user equipment (UE) 231 due to a status change from intra-DU to inter-DU, in accordance with some embodiments of the present disclosure.

[0068] Referring to FIG. 3A, in step 1, a user equipment (UE) 231 may be served by a serving distribution unit (DU) 1071. The UE 231 may be configured with L1 / L2 triggered mobility (LTM). LTM enables the network to trigger a handover of the UE 231. In step 2, the UE 231 may send RRC measurements (L3) to the CU 103. In step 3, the CU 103 may make a decision to prepare an inter-gNB DU LTM candidate cell based on the RRC measurements (L3) received from the UE 231. Referring to FIG. 4C, as shown in the figure, the CU 103 may include three DUs. The UE 231 may be configured with cells 3011 to 3012. N Specifically, the UE 231 may be served by the cell 3011. Based on RRC measurements (L3), the CU 103 may be configured to serve the cells 3031 to 3033. N and 3051-305 N However, the candidate / target cells detected by the candidate / target DUs 1072 and 1073 may be 3031-3033, 3051-3053, and 3036, respectively. Since the serving cells are hosted by the same DU, one or more cells 3011-3012 of the serving DU may be detected. N Alternatively, the status of one or more cells 3031-3033 of the candidate / target DU 1072 may be intra. N The status of one or more cells 3051-3055 of the candidate / target DU 1073 may be inter-cell because the serving cells are hosted in different DUs. N The status may be inter since the serving cells are hosted in different DUs.

[0069] In step 4, the CU103 may be configured to send an F1:UE231 context Modification Request() to the serving DU 1071, and in step 5, the serving DU may respond to the modification request by sending an F1:UE231 context Modification Response() to the CU103. In step 6, the CU103 may be configured to send an F1:UE context setup request message to the candidate / target DU 1072, and similarly, in step 7, the CU103 may be configured to send an F1:UE context setup request message to the candidate / target DU 1073. The setup request is sent to prepare a new candidate / target cell in the respective DU. In step 8, the CU103 receives an F1:UE231 Context Setup Response(CellGroupConfig) from the candidate / target DU 1072, and in step 9, the CU103 receives an F1:UE Context Setup Response(CellGroupConfig) from the candidate / target DU 1073. At this point, the target DU has provided the candidate LTM cell configuration to the candidate / target DUs 1072 and 1073. Referring again to Figure 3C, the CU 103 may send an F1:UE context setup request message to the candidate / target DUs 1072 and 1073. In addition, the CU 103 receives an F1:UE Context Setup Response(CellGroupConfig) from the candidate / target DUs 1072 and 1073.

[0070] In step 10, the CU 103 may be configured to send an F1:DL RRC Message transfer (RRC Reconfiguration (LTM target cell configuration, Reconfiguration for intra-DU⇔inter-DU changes)) to the serving DU 1071. In step 11, the serving DU 1071 may be configured to send an RRC Reconfiguration (LTM target cell configuration, Reconfiguration for intra-DU⇔inter-DU changes)) to the UE 231. Here, a list of reconfiguration actions that may be applicable to LTM candidate cells undergoing a status change from intra-DU to inter-DU and vice versa is present in the list of reconfiguration actions. The list of reconfiguration actions may be expected to be applied by the UE 231 whenever such status change information is delivered to the UE 231. In step 12, the UE 231 may be configured to send an intra-frequency L1 measurement report to the serving DU 1071. In step 13, the serving DU 1071 may be configured to determine whether the LTM HO radio conditions are met by any candidate / target cells. If so, the CU 103 may perform a serving cell change to one of the one or more prepared candidate / target cells. In step 14, the serving DU 1071 may be configured to send a MAC CE (Serving Cell Change Command) to the UE 231, and in step 15, the serving DU 1071 may be configured to send an F1: Serving Cell Change Notification (Cell Identification (ID)) to the CU 103. The cell ID of the new serving cell may be sent to the UE 231. Referring to Figure 3D, the CU 103 may perform a serving cell change to a new serving cell 3031 hosted on the new serving DU 1072.Since the new serving cell 3031 is hosted on the new serving DU 1072, the status of the cell hosted by the serving DU 1071 (the previous serving DU, and the UE 231 is connected to the new serving DU 1072) is changed from intra-DU to inter-DU. Similarly, since the new serving cell 3031 is hosted on the new serving DU 1072, the status of the cell hosted by the new serving DU 1072 may be changed from inter-DU to intra-DU. However, the status of the cell hosted by the candidate / target DU 1073 remains the same, and since the new serving cell 3031 is hosted on the new serving DU 1072, there is no need to update the status of the cell hosted by the candidate / target DU 1073.

[0071] Further, in step 16, the UE 231 may be configured to transmit a RACH (preamble) to the new serving cell 3031. The new serving cell 3031 may be a cell among one or more candidate / target cells. In step 17, the UE 231 may be configured to transmit an RRC Reconfiguration Acknowledgement() to the CU 103. In step 18, the CU 103 may be configured to determine intra-DU⇔inter-DU status changes in all candidate cell configurations based on the new serving cell 3031 of the new serving DU 1072 information received from the old serving DU, and send an updated list to the new serving DU 1072. In step 19, the CU 103 may send an F1:UE231 context Modification Request (updated intra-DU⇔inter DU change list) to the new serving DU 1072. In step 20, the new serving DU 1072 may initiate reconfiguration for intra-DU⇔inter-DU related changes toward the UE 231. Meanwhile, in step 21, the new serving DU 1072 sends an F1:UE231 context Modification Response() to the CU 103. Further, in step 22, the new serving DU may be configured to send a DL MAC CE (intra-DU ⇔ inter DU change list) to the UE 231 to indicate all intra-DU ⇔ inter DU status changes. In step 23, the UE 231 may be configured to initiate reconfiguration for the intra-DU ⇔ inter DU related changes (previously configured by the CU 103 in an RRC message in step 10). In step 24, the UE 231 is configured to send an acknowledgement to the CU 103, and the UE 231 may be configured to send an RRC Reconfiguration Acknowledgement() to the CU 103.In one embodiment, the CU 103 may contain a list of reconfigurations to be performed whenever an intra-DU candidate cell is reconfigured as an inter-DU candidate cell, and vice versa. This is sent to the UE 231 in an RRC reconfiguration message each time an inter-DU candidate cell is configured. As an example, if an intra-DU is changed to an inter-DU, turn on RLC reestablishment and PDCP recovery and turn off partial MAC reset. If an inter-DU is changed to an intra-DU, turn on partial MAC reset and turn off RLC reestablishment and PDCP recovery.

[0072] In one embodiment, upon performing an LTM serving cell change 231 (via MAC CE in the downlink to the UE), the serving DU sends a serving cell change notification to the CU 103 (step 15). This is required to ensure that the CU 103 is aware of the UE's 231's new serving cell (used for paging and other procedures). Upon receiving the LTM serving cell change notification from the serving DU 1071, the CU 103 may be configured to send an intra-DU⇔inter-DU reconfiguration list to the new serving DU. Note that reconfiguration information is required in both directions. The new serving DU delivers the intra-DU⇔inter-DU reconfiguration information to the UE 231 in DL MAC CE signaling. The UE 231 applies the reconfiguration list whenever an intra-DU candidate cell is reconfigured as an inter-DU candidate cell, and vice versa, based on the configuration sent by the CU 103 (via RRC). This step is performed to cover known reconfigurations due to a serving cell change causing an LTM candidate cell to become an intra-DU⇔inter-DU, and to not include normal RRC reconfigurations that the target DU has to initiate due to changes in resource conditions or other configuration aspects.

[0073] FIG. 3B is an example call flow diagram illustrating broadcasting a status change to one or more candidate distributed units (DUs) according to some embodiments of the present disclosure.

[0074] Referring to FIG. 3A, in step 1, a user equipment (UE) 231 may be served by a serving distribution unit (DU) 1071. The UE 231 may be configured with L1 / L2 triggered mobility (LTM). LTM enables the network to trigger a handover of the UE 231. In step 2, the UE 231 may send RRC measurements (L3) to the CU 103. In step 3, the CU 103 may make a decision to prepare an inter-gNB DU LTM candidate cell based on the RRC measurements (L3) received from the UE 231. Referring to FIG. 4C, as shown in the figure, the CU 103 may include three DUs. The UE 231 may be configured with cells 3011 to 3012. N Specifically, the UE 231 may be served by the cell 3011. Based on RRC measurements (L3), the CU 103 may be configured to serve the cells 3031 to 3033. N and 3051-305 N However, the candidate / target cells detected by the candidate / target DUs 1072 and 1073 may be 3031-3033, 3051-3053, and 3036, respectively. Since the serving cells are hosted by the same DU, one or more cells 3011-3012 of the serving DU may be detected. N Alternatively, the status of one or more cells 3031-3033 of the candidate / target DU 1072 may be intra. N The status of one or more cells 3051-3055 of the candidate / target DU 1073 may be inter-cell because the serving cells are hosted in different DUs. N The status may be inter since the serving cells are hosted in different DUs.

[0075] In step 4, the CU103 may be configured to send an F1:UE231 context Modification Request() to the serving DU 1071, and in step 5, the serving DU may respond to the modification request by sending an F1:UE231 context Modification Response() to the CU103. In step 6, the CU103 may be configured to send an F1:UE context setup request message to the candidate / target DU 1072, and similarly, in step 7, the CU103 may be configured to send an F1:UE context setup request message to the candidate / target DU 1073. The setup request is sent to prepare a new candidate / target cell in the respective DU. In step 8, the CU103 receives an F1:UE231 Context Setup Response(CellGroupConfig) from the candidate / target DU 1072, and in step 9, the CU103 receives an F1:UE Context Setup Response(CellGroupConfig) from the candidate / target DU 1073. At this point, the target DU has provided the candidate LTM cell configuration to the candidate / target DUs 1072 and 1073. Referring again to Figure 3C, the CU 103 may send an F1:UE context setup request message to the candidate / target DUs 1072 and 1073. In addition, the CU 103 receives an F1:UE Context Setup Response(CellGroupConfig) from the candidate / target DUs 1072 and 1073.

[0076] In step 10, the CU 103 may be configured to send an F1:DL RRC Message transfer (RRC Reconfiguration (LTM target cell configuration, Reconfiguration for intra-DU⇔inter-DU changes)) to the serving DU 1071. In step 11, the serving DU 1071 may be configured to send an RRC Reconfiguration (LTM target cell configuration, Reconfiguration for intra-DU⇔inter-DU changes)) to the UE 231. Here, a list of reconfiguration actions that may be applicable to LTM candidate cells undergoing a status change from intra-DU to inter-DU and vice versa is present in the list of reconfiguration actions. The list of reconfiguration actions may be expected to be applied by the UE 231 whenever such status change information is delivered to the UE 231. In step 12, the UE 231 may be configured to send an intra-frequency L1 measurement report to the serving DU 1071. In step 13, the serving DU 1071 may be configured to determine whether the LTM HO radio conditions are met by any candidate / target cells. If so, the CU 103 may perform a serving cell change to one of the one or more prepared candidate / target cells. In step 14, the serving DU 1071 may be configured to send a MAC CE (Serving Cell Change Command) to the UE 231, and in step 15, the serving DU 1071 may be configured to send an F1: Serving Cell Change Notification (Cell Identification (ID)) to the CU 103. The cell ID of the new serving cell may be sent to the UE 231. Referring to Figure 3D, the CU 103 may perform a serving cell change to a new serving cell 3031 hosted on the new serving DU 1072.Since the new serving cell 3031 is hosted on the new serving DU 1072, the status of the cell hosted by the serving DU 1071 (the previous serving DU, and the UE 231 is connected to the new serving DU 1072) is changed from intra-DU to inter-DU. Similarly, since the new serving cell 3031 is hosted on the new serving DU 1072, the status of the cell hosted by the new serving DU 1072 may be changed from inter-DU to intra-DU. However, the status of the cell hosted by the candidate / target DU 1073 remains the same, and since the new serving cell 3031 is hosted on the new serving DU 1072, there is no need to update the status of the cell hosted by the candidate / target DU 1073.

[0077] Further, in step 16, the UE 231 may be configured to transmit a RACH (preamble) to the new serving DU 1072. The new serving cell may be a cell among one or more candidate / target cells. In step 17, the CU 103 may broadcast an LTM serving cell change notification to all candidate / target DUs. Referring to FIG. 3B, the LTM serving cell change notification may be broadcast to the candidate / target DUs 1072 and 1073. In step 18, the UE 231 may send an RRC Reconfiguration Acknowledgement() to the CU 103. In step 19, as part of the broadcast, the CU 103 sends an F1:UE231 context Modification Request (updated intra-DU⇔inter DU change list) to the new serving DU 1072, and in step 20, as part of the broadcast, the CU 103 can send an F1:UE231 context Modification Request (updated intra-DU⇔inter DU change list) to the candidate / target DU 1073. In step 21, if there are other LTM candidate cells belonging to this DU, the new serving DU 1072 can initiate RRC Reconfig including intra-DU⇔inter DU related changes, and in step 22, the candidate DU 1073 can initiate RRC Reconfig including intra-DU⇔inter DU related changes. In step 23, the new serving DU 1072 can send an F1:UE231 context Modification Response(Updated CellGroupConfig) to the CU 103, and in step 24, the candidate DU 1073 can send an F1:UE231 context Modification Response(Updated CellGroupConfig) to the CU 103, which includes the updated candidate cell configuration.Further, in step 25, the CU 103 sends an F1:DL RRC Message transfer (RRC Reconfiguration (modified LTM target cell configurations)) to the new serving DU 1072. Here, the RRC message is a container insider F1 message. In step 26, the new serving DU 1072 can send an RRC Reconfiguration (modified LTM target cell configurations()) to the UE 231.

[0078] Therefore, in the proposed embodiment, after performing the LTM SCC 231 (via MAC CE in the downlink to the UE), the serving DU sends a serving cell change notification to the CU 103 (step 15). This step is done to ensure that the CU 103 is aware of the UE's 231's current serving cell, which may be used for paging, etc. The CU 103 can broadcast a notification message to all candidate / target DUs, including the new serving DU and the serving DU. Based on this, each target DU issues a reconfiguration (only if necessary) and delivers it to the UE 231 via the CU 103.

[0079] FIG. 4A illustrates a flowchart illustrating a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and user equipment (UE) 231 due to a status change from intra-DU to inter-DU, according to some embodiments of the present disclosure.

[0080] 4A, method 400 may include one or more blocks illustrating a method for handling a serving / candidate distribution unit (DU) and candidate cell reconfiguration of user equipment (UE) 231 due to a status change from intra-DU to inter-DU in accordance with some embodiments of the present disclosure illustrated in FIG. 2A. Method 400 may be described in the general context of computer-executable instructions. Generally, computer-executable instructions may include routines, programs, objects, components, data structures, procedures, modules, and functions that perform particular functions or implement particular abstract data types.

[0081] The order in which method 400 is described is not intended to be construed as a limitation, as any number of the described method blocks may be combined in any order to implement the method. Moreover, individual blocks may be omitted from the method without departing from the scope of the subject matter described herein. Furthermore, the method may be implemented in any suitable hardware, software, firmware, or combination thereof.

[0082] In block 401, the method 400 includes receiving, by a processor 203 of a centralized unit (CU 103), a notification from a serving DU of a UE in a next generation radio access network (NG-RAN) indicating a change of serving cell due to L1 / L2 triggered mobility (LTM) of the UE 231. The notification received from the serving DU includes an identification number of a new serving cell of the new serving DU among one or more candidate / target DUs determined to serve the UE 231. In one embodiment, before receiving the notification, the processor 203 determines a new serving cell of a plurality of DUs 107 based on a first measurement report received from the UE 231. NThe processor 203 detects one or more candidate / target DUs among the one or more candidate / target DUs, each of which includes one or more candidate / target cells. Further, the processor 203 transmits a setup request or a modification request to each of the one or more candidate / target DUs detected based on the first measurement report, requesting preparation of an LTM target cell configuration. Thereafter, upon receiving the LTM candidate cell configuration from each of the one or more candidate / target DUs, the processor 203 transmits one or more configuration changes to the serving DU corresponding to status changes to be made by the UE 231 as part of the reconfiguration.

[0083] At block 403, the method 400 includes, by the processor 203, determining a status change of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among the plurality of candidate / target DUs when changing the serving cell of the UE 231 to a new serving cell. The new serving cell is one of the one or more candidate / target cells of the candidate / target DU. In one embodiment, to determine the status change, the processor 203 determines a status change of each of the one or more cells of the serving DU and each of the one or more candidate / target cells of the candidate / target DU from intra-DU to inter-DU or from inter-DU to intra-DU based on the change of the serving cell of the UE 231.

[0084] At block 405, the method 400 includes transmitting, by the processor 203, a message to the new serving DU including status change information of all candidate / target cells including corresponding cell identifiers. The content of the message is further transmitted by the new serving DU to the UE 231. In some embodiments, the content of the message may include status change information of all candidate / target cells including corresponding cell identifiers. In one embodiment, the processor 203 may broadcast a serving cell change notification message to each of one or more candidate / target DUs detected by the CU 103 based on the first measurement report received from the UE 231. Further, the processor 203 may receive reconfiguration information corresponding to the status change for each candidate / target cell from each of the one or more candidate / target DUs.

[0085] At block 407, the method 400 includes receiving, by the processor 203, a confirmation of a reconfiguration corresponding to the new serving DU and the status change in the UE 231. As part of the reconfiguration, the UE 231 applies the one or more configuration changes provided by the CU 103 before the change in serving cell. The one or more configuration changes are provided to the UE 231 using a Radio Resource Control (RRC) configuration message.

[0086] FIG. 4B illustrates a flowchart illustrating a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and user equipment (UE) 231 due to a status change from intra-DU to inter-DU, in accordance with some embodiments of the present disclosure.

[0087] 4B, method 420 may include one or more blocks illustrating a method for handling a serving / candidate distribution unit (DU) and candidate cell reconfiguration of user equipment (UE) 231 due to a status change from intra-DU to inter-DU in accordance with some embodiments of the present disclosure illustrated in FIG. 2B. Method 420 may be described in the general context of computer-executable instructions. Generally, computer-executable instructions may include routines, programs, objects, components, data structures, procedures, modules, and functions that perform particular functions or implement particular abstract data types.

[0088] The order in which method 420 is described is not intended to be construed as a limitation, as any number of the described method blocks may be combined in any order to implement the method. Additionally, individual blocks may be deleted from the method without departing from the scope of the subject matter described herein. Additionally, the method may be implemented in any suitable hardware, software, firmware, or combination thereof.

[0089] At block 421, the method 420 includes receiving, by a processor 235 of a user equipment (UE) 231, a notification indicating a change in the serving cell from a serving distribution unit (DU) of a next-generation radio access network (NG-RAN). In one embodiment, before receiving the notification, the processor 235 sends a second measurement report to the serving DU periodically or based on the occurrence of one or more events. By way of example, and without limitation, the one or more events may be when the UE first connects to the network, during a handover of the UE, and when the serving DU requests a measurement report from the UE. The serving DU determines a new serving cell for the UE 231 based on the second measurement report.

[0090] At block 423, the method 420 includes establishing a connection with the new serving cell of the new serving DU by the processor 235 of the UE 231. In one embodiment, the UE 231 may send a connection establishment request to establish the connection. Upon successfully establishing the connection with the new serving cell, the UE 231 confirms application of the new serving cell configuration to the centralized unit (CU 103) of the NG-RAN.

[0091] In block 425, the method 420 includes receiving, by the processor 235 of the UE 231 from the CU 103 via the new serving DU, a message including a status change of one or more candidate / target cells of the new serving DU and all candidate / target DUs when the serving cell of the UE 231 is changed to a new serving cell of the new serving DU.

[0092] At block 427, the method 420 includes making, by the processor 235 of the UE 231, one or more configuration changes corresponding to the status change as part of the reconfiguration and sending a confirmation of the reconfiguration to the CU 103. The one or more configuration changes are received from the CU 103 before the serving cell change.

[0093] FIG. 4C illustrates a flowchart illustrating a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and user equipment (UE) 231 due to a status change from intra-DU to inter-DU, in accordance with some embodiments of the present disclosure.

[0094] 4C, method 440 may include one or more blocks illustrating a method for handling a serving / candidate distribution unit (DU) and candidate cell reconfiguration of user equipment (UE) 231 due to a status change from intra-DU to inter-DU in accordance with some embodiments of the present disclosure illustrated in FIG. 2C. Method 440 may be described in the general context of computer-executable instructions. Generally, computer-executable instructions may include routines, programs, objects, components, data structures, procedures, modules, and functions that perform particular functions or implement particular abstract data types.

[0095] The order in which method 440 is described is not intended to be construed as a limitation, as any number of the described method blocks may be combined in any order to implement the method. Additionally, individual blocks may be deleted from the method without departing from the scope of the subject matter described herein. Additionally, the method may be implemented in any suitable hardware, software, firmware, or combination thereof.

[0096] In block 441, the method 440 N and receiving, by the processor 263 of the UE 231, a connection establishment from the UE 231 after changing the serving cell to a new serving cell belonging to the new serving DU.

[0097] At block 443, the method 440 N The method includes receiving, by the processor 263 of the UE 231, a message including a status change of one or more of the cells of the candidate / target DU and the new serving DU from the CU 103 when the serving cell of the UE 231 is changed to a new serving cell, and transmitting the content of the message from the CU 103 to the UE 231 using a Layer 1 message or a Layer 2 message.

[0098] At block 445, the method 440N The method includes: reconfiguring the new serving DU based on the status change by the processor 263 of the CU 103; and sending a confirmation of the reconfiguration to the CU 103. Claimable aspects: 1. In one embodiment, a centralized unit (CU) of a next-generation radio access network (NG-RAN) for processing a serving / candidate distribution unit (DU) and candidate cell reconfiguration of a user equipment (UE) due to a status change from an intra-DU to an inter-DU is disclosed in one aspect. The CU includes a processor and a memory. The memory is communicatively coupled to the processor and stores processor-executable instructions that, when executed, cause the processor to receive a notification from a serving DU of a UE in the NG-RAN indicating a serving cell change due to L1 / L2 triggered mobility (LTM) of the UE. Furthermore, the processor determines status changes of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among multiple candidate / target DUs when changing the serving cell of the UE to a new serving cell. The new serving cell is one of the one or more candidate / target cells of the candidate / target DU. The processor then sends a message to the new serving DU containing status change information of all candidate / target cells, including corresponding cell identifiers. The content of the message is further transmitted by the new serving DU to the UE. Finally, the processor receives a confirmation of the reconfiguration corresponding to the new serving DU and the status change in the UE. As part of the reconfiguration, the UE applies one or more configuration changes provided by the CU before the change in serving cell. 2. In the CU described in aspect 1, to determine a status change, the processor is configured to determine a status change from intra-DU to inter-DU or from inter-DU to intra-DU for each of one or more cells of the serving DU and each of one or more candidate / target cells of the candidate / target DU based on a change in the serving cell of the UE. 3. In one embodiment, in the CU described in aspects 1 to 2, before receiving the notification, a processor is configured to detect one or more candidate / target DUs among the multiple DUs based on a first measurement report received from the UE, each of the one or more candidate / target DUs including one or more candidate / target cells. The processor is configured to send a setup request or a modification request to each of the one or more candidate / target DUs detected based on the first measurement report, requesting preparation of an LTM target cell configuration. Upon receiving the LTM candidate cell configuration from each of the one or more candidate / target DUs, the processor is configured to send one or more configuration changes to the serving DU corresponding to status changes made by the UE as part of the reconfiguration. 4. In one embodiment, in the CU described in aspects 1 to 3, the one or more configuration changes are provided to the UE using a radio resource control (RRC) configuration message. 5. In the CU described in aspects 1 to 4, to transmit the message including the status change, the processor is configured to broadcast a serving cell change notification message to each of one or more candidate / target DUs detected by the CU based on the first measurement report received from the UE. The processor is configured to receive reconfiguration information corresponding to the status change for each candidate / target cell from each of the one or more candidate / target DUs. 6. In one embodiment, in the CU described in aspects 1 to 5, the notification received from the serving DU includes an identification number of a new serving cell of the new serving DU among the one or more candidate / target DUs determined to serve the UE. 7. In one embodiment, a user equipment (UE) for processing a serving / candidate distribution unit (DU) and candidate cell reconfiguration of a UE caused by a status change from an intra-DU to an inter-DU is disclosed in one aspect. The UE includes a processor and a memory. The memory is communicatively coupled to the processor and stores processor-executable instructions that, when executed, cause the processor to receive a notification indicating a serving cell change from a serving distribution unit (DU) of a next-generation radio access network (NG-RAN). The processor then establishes a connection with the new serving cell of the new serving DU. Upon successfully establishing the connection with the new serving cell, the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the RAN. Thereafter, the processor receives a message from the CU via the new serving DU when the serving cell of the UE has changed to the new serving cell of the new serving DU, the message including a status change of one or more candidate / target cells of the new serving DU and all candidate / target DUs. Finally, the processor makes one or more configuration changes corresponding to the status change as part of the reconfiguration and sends a confirmation of the reconfiguration to the CU. The one or more configuration changes are received from the CU prior to the change in the serving cell. 8. In one embodiment, in the CU described in aspect 7, before receiving the notification, the processor is configured to send a second measurement report to the serving DU periodically or based on the occurrence of one or more events, and the serving DU determines a new serving cell for the UE based on the second measurement report, and the second measurement report is an intra-frequency L1 measurement report or an inter-frequency L1 measurement report. 9. In one embodiment, a distributed unit (DU) for processing a serving / candidate DU and candidate cell reconfiguration of a UE caused by a status change from an intra-DU to an inter-DU is disclosed in one aspect. The new serving DU includes a processor and a memory. The memory is communicatively coupled to the processor and stores processor-executable instructions that, when executed, cause the processor to receive a connection establishment from the UE after changing the serving cell to a new serving cell belonging to the new serving DU. Furthermore, the processor receives a message from the CU when the serving cell of the UE is changed to the new serving cell, the message including a status change of one or more of the candidate / target DU and the cell of the new serving DU, and transmits the content of the message from the CU to the UE using a Layer 1 message or a Layer 2 message. Finally, the processor reconfigures the new serving DU based on the status change and transmits a confirmation of the reconfiguration to the CU. 10. In another embodiment, an aspect discloses a method for processing candidate cell reconfiguration of a serving / candidate distribution unit (DU) and a user equipment (UE) due to a status change from an intra-DU to an inter-DU. The method includes receiving, by a centralized unit (CU) of a next-generation radio access network (NG-RAN node), a notification from a serving DU of the UE in an NG-RAN indicating a serving cell change due to L1 / L2 triggered mobility (LTM) of the UE. The method further includes determining a status change of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among multiple candidate / target DUs when changing the serving cell of the UE to the new serving cell. The new serving cell is one of the one or more candidate / target cells of the candidate / target DU. Thereafter, the method includes transmitting a message to the new serving DU including status change information of all candidate / target cells, including corresponding cell identifiers. The content of the message is further transmitted by the new serving DU to the UE. Finally, the method includes receiving a confirmation of the reconfiguration corresponding to the status change at the new serving DU and the UE. As part of the reconfiguration, the UE applies one or more configuration changes provided by the CU before the change in serving cell. 11. In one embodiment, in the method described in aspect 10, determining the status change comprises determining, by the CU, a change of status from intra-DU to inter-DU or from inter-DU to intra-DU for each of one or more cells of the serving DU and each of one or more candidate / target cells of the candidate / target DU based on a change of serving cell of the UE. 12. In one embodiment, the method described in aspects 10 to 11 includes, before receiving the notification, detecting, by a CU, one or more candidate / target DUs among the plurality of DUs based on a first measurement report received from the UE, where each of the one or more candidate / target DUs includes one or more candidate / target cells. The method includes transmitting, by the CU, a setup request or a modification request to each of the one or more candidate / target DUs detected based on the first measurement report, requesting preparation of an LTM target cell configuration. The method includes, upon receiving the LTM candidate cell configuration from each of the one or more candidate / target DUs, transmitting, by the CU, one or more configuration changes corresponding to status changes made by the UE as part of the reconfiguration. 13. In an embodiment, in the method of aspects 10 to 12, the one or more configuration changes are provided to the UE using a radio resource control (RRC) configuration message. 14. In an embodiment, in the method described in aspects 10 to 13, transmitting the message including the status change further includes: broadcasting, by the CU, a serving cell change notification message to each of one or more candidate / target DUs detected by the CU based on the first measurement report received from the UE; and receiving, by the CU, reconfiguration information corresponding to the status change for each candidate / target cell from each of the one or more candidate / target DUs. 15. In one embodiment, in the method described in aspects 10 to 14, the notification received from the serving DU includes an identification number of a new serving cell of a new serving DU among one or more candidate / target DUs determined to serve the UE. 16. In another embodiment, an aspect discloses a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and a user equipment (UE) due to a status change from an intra-DU to an inter-DU. The method includes receiving, by the user equipment (UE), a notification indicating a serving cell change from a serving distribution unit (DU) of a next-generation radio access network (NG-RAN). The method further includes establishing a connection with the new serving cell of the new serving DU. Upon successfully establishing the connection with the new serving cell, the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the RAN. Thereafter, the method includes receiving, from the CU via the new serving DU, a message including status changes of one or more candidate / target cells for the new serving DU and all candidate / target DUs when the UE's serving cell has changed to the new serving cell of the new serving DU. Finally, the method includes making one or more configuration changes corresponding to the status change as part of the reconfiguration and sending a confirmation of the reconfiguration to the CU. The one or more configuration changes are received from the CU before the change in serving cell. 17. In one embodiment, in the method described in aspect 16, before receiving the notification, the method includes the UE sending a second measurement report to the serving DU periodically or based on the occurrence of one or more events, and the serving DU determining a new serving cell for the UE based on the second measurement report. 18. In another embodiment, an aspect discloses a method for handling candidate cell reconfiguration of a serving / candidate distribution unit (DU) and a user equipment (UE) due to a status change from an intra-DU to an inter-DU. The method includes receiving a connection establishment from the UE by the new serving DU after changing the serving cell to a new serving cell belonging to the new serving DU. Further, the method includes receiving a message from a CU when the serving cell of the UE is changed to the new serving cell, the message including a status change of one or more of the candidate / target DU and the candidate / target cell of the new serving DU, and transmitting the contents of the message from the CU to the UE using a Layer 1 message or a Layer 2 message. Finally, the method includes reconfiguring the new serving DU based on the status change and transmitting a confirmation of the reconfiguration to the CU. 19. In yet another embodiment, a non-transitory computer-readable medium having instructions stored thereon, when processed by at least one processor, causes a centralized unit (CU) of a next-generation radio access network (NG-RAN) to perform operations including receiving a notification from a serving distribution unit (DU) of a UE in the NG-RAN indicating a change of serving cell due to L1 / L2 triggered mobility (LTM) of the UE. The instructions further cause the processor to determine a status change of one or more cells of the serving DU and one or more candidate / target cells of the candidate / target DU among a plurality of candidate / target DUs upon changing the serving cell of the UE to a new serving cell. The new serving cell is one of the one or more candidate / target cells of the candidate / target DU. The instructions then cause the processor to send a message to the new serving DU including status change information of all candidate / target cells including corresponding cell identifiers. The content of the message is further transmitted by the new serving DU to the UE. Finally, the instructions cause the processor to receive a reconfiguration confirmation corresponding to the status change at the new serving DU and the UE. As part of the reconfiguration, the UE applies one or more configuration changes provided by the CU before the change in serving cell. 20. In yet another embodiment, a non-transitory computer-readable medium having instructions stored thereon, when the instructions are processed by at least one processor, causes a user equipment (UE) to perform operations including receiving a notification from a serving distribution unit (DU) of a next generation radio access network (NG-RAN) indicating a change in serving cell. The instructions further cause the processor to establish a connection with a new serving cell of the new serving DU. Upon successfully establishing the connection with the new serving cell, the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the RAN. Thereafter, when the UE's serving cell is changed to the new serving cell of the new serving DU, the instructions cause the processor to receive from the CU via the new serving DU a message including status changes of one or more candidate / target cells for the new serving DU and all candidate / target DUs. Finally, the instructions cause the processor to make one or more configuration changes corresponding to the status changes as part of the reconfiguration and send a confirmation of the reconfiguration to the CU. The one or more configuration changes are received from the CU before the change in serving cell. 21. In yet another embodiment, a non-transitory computer-readable medium having instructions stored thereon, when the instructions are processed by at least one processor, causes a new serving distribution unit (DU) to perform operations including receiving a connection establishment from a user equipment (UE) after changing the serving cell to a new serving cell belonging to the new serving DU. The instructions further cause the processor to receive a message from a CU when the UE's serving cell is changed to the new serving cell, the message including a status change of one or more of the candidate / target DUs and the cell of the new serving DU, and to transmit the contents of the message from the CU to the UE using a Layer 1 message or a Layer 2 message. Finally, the instructions cause the processor to reconfigure the new serving DU based on the status change and to transmit a confirmation of the reconfiguration to the CU.

[0099] Advantages of embodiments of the present disclosure are presented herein. In one embodiment, the proposed method reduces latency. Specifically, the following aspects of the present disclosure help reduce latency: Unlike existing techniques that provide additional information that may not be necessary for reconfiguration, only an updated list of intra-DU to inter-DU changes (status change) is provided to the UE for reconfiguration when the serving cell is changed. This reduces the amount of data transmitted to the UE, thereby reducing network latency. Unlike existing techniques that transmit to all candidate DUs, transmissions from intra-DU to inter-DU are changed only to the new serving DU, and vice versa. This helps reduce unnecessary interactions between the CU and other candidate DUs and reduce network latency during handover.

[0100] In one embodiment, the proposed method reduces signaling consumption, specifically, according to the present disclosure, the UE only receives an updated list (status change) for the change from intra DU to inter DU when changing the serving cell. This reduces the signaling consumption of the UE. Similarly, the signaling consumption of the candidate DU is reduced because the status change is only sent to the new serving DU and not to the other candidate DU.

[0101] In one embodiment, the proposed method reduces additional processing. Specifically, according to the present disclosure, the CU sends changes only to the new serving DU when changing from intra-DU to inter-DU or vice versa. This avoids additional processing of the CU when creating an updated list for all candidate DUs, and also eliminates processing of other candidate DUs during the reconfiguration, since their status does not need to be updated.

[0102] In one embodiment, the proposed method reduces delay. Specifically, according to the present disclosure, as described in the previous section, the CU provides only status change information to the UE, and the UE updates only the changes indicated by the CU in the RRC message while performing a reconfiguration corresponding to the status change. Therefore, delays in data transmission and subsequent UE mobility are reduced. In addition, the other candidate DU, which is not involved in receiving the reconfiguration message or performing the reconfiguration, similarly reduces delays in subsequent UE mobility.

[0103] As mentioned above, it should be noted that the method of the present disclosure can be used to overcome various technical problems associated with handling serving / candidate candidate cell reconfiguration of distributed units (DUs) and user equipment (UEs) due to a status change from intra-DU to inter-DU. In other words, the disclosed method has practical applications and provides a technically advanced solution relative to existing approaches to handling serving / candidate candidate cell reconfiguration of distributed units (DUs) and user equipment (UEs) due to a status change from intra-DU to inter-DU.

[0104] In light of the technical advances provided by the disclosed method, the claimed steps as described above are not routine, conventional, or well-known in the art, because the claimed steps provide the aforementioned solutions to technical problems existing in the prior art. Furthermore, since the claimed steps provide technical solutions to technical problems, it is clear that the claimed steps result in an improvement in the functionality of the system itself.

[0105] The terms "an embodiment," "embodiment," "embodiments," "the embodiment," "the embodiment," "the embodiment," "one or more embodiments," "some embodiments," and "one embodiment" mean "one or more (but not all) embodiments of the present invention," unless expressly stated otherwise.

[0106] The terms "including," "comprising," and "having" and variations thereof mean "including, but not limited to," unless expressly stated otherwise.

[0107] Unless expressly stated otherwise, an enumerated list of items does not imply that any or all of the items are mutually exclusive. The terms "a," "an," and "the" mean "one or more" unless otherwise specified.

[0108] A description of an embodiment having several components in communication with each other does not imply that all such components are required. Rather, various optional components are described to illustrate the wide variety of possible embodiments of the present invention.

[0109] Where a single device or article is described herein, it will be apparent that two or more devices / articles (whether or not they cooperate) may be used in place of the single device / article. Similarly, where two or more devices / articles (whether or not they cooperate) are described herein, it will be apparent that a single device / article may be used in place of the two or more devices / articles, or that a different number of devices / articles may be used in place of the number of devices or programs shown. The functionality and / or features of a device may alternatively be embodied by one or more other devices not explicitly described as having such functionality / features. Thus, other embodiments of the present invention need not include the device itself.

[0110] Finally, the language used herein has been chosen primarily for ease of reading and instructional purposes, and may not be chosen to delineate or limit the subject matter of the present invention. Accordingly, it is intended that the scope of the invention be limited not by this detailed description, but by the claims filed hereunder. Accordingly, the embodiments of the present disclosure are intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

[0111] While various aspects and embodiments are disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. [Explanation of symbols] 100 Environment 101 Next Generation Node B (gNB) 103 Centralized Unit 105 Next Generation Node B Control Unit Control Plane (gNB-CU-CP) 1071~107 N Distributed Unit 109 Next Generation Node B Control Unit User Plane (gNB-CU-UP) 201 CU I / O interface 203 CU processor 205 CU of memory 207 CU data 209 CU module Cell data for 211 CU Configuration data for 213 CUs Other data for 215 CU 217 Transceiver Module 219 Decision Module 221 other modules 231 User Equipment (UE) 233 UE I / O interface 235 UE processors 237 UE memory 239 UE data 241 UE modules 243 UE cell data 245 UE configuration data Other data for 247 UE 249 UE Transceiver Module 251 UE Configuration Module 253 Other modules of UE 261 DU I / O interface 263 DU processor 265 DU of memory Data for 267 DU 269 ​​DU module Cell data for 271 DU Other data for 273 DU 275 DU receiving module 277 DU configuration module Other modules of 279 DU 3011~301 N One or more cells hosted by DU1071 3031~303 NOne or more cells hosted by DU1072 3051~305 N One or more cells hosted by DU1073

Claims

1. A centralization unit (CU) (103) of a next generation radio access network (NG-RAN node), a processor; a memory communicatively coupled to the processor, the memory storing processor-executable instructions that, when executed, cause the processor to: receiving a notification from a serving distribution unit (DU) of a user equipment (UE) in the NG-RAN indicating a change of serving cell due to L1 / L2 triggered mobility (LTM) of the UE; determining a status change of one or more cells of the serving DU and one or more candidate / target cells of a candidate / target DU among a plurality of candidate / target DUs when changing the serving cell of the UE to a new serving cell, wherein the new serving cell is one of the one or more candidate / target cells of the candidate / target DU; sending a message to the new serving DU including the status change information of all the candidate / target cells including corresponding cell identifiers, the content of the message being further transmitted by the new serving DU to the UE; a centralization unit (CU) (103) that causes the UE to receive a confirmation of the new serving DU and a reconfiguration corresponding to the status change in the UE, wherein the UE applies, as part of the reconfiguration, one or more configuration changes provided by the CU before the change in the serving cell.

2. To determine the status change, the processor: The CU of claim 1, configured to determine a status change from intra-DU to inter-DU or from inter-DU to intra-DU for each of the one or more cells of the serving DU and each of the one or more candidate / target cells of the candidate / target DU based on the change in the serving cell of the UE.

3. Prior to receiving the notification, the processor: Detecting one or more candidate / target DUs among a plurality of DUs based on a first measurement report received from the UE, wherein each of the one or more candidate / target DUs includes the one or more candidate / target cells; sending a setup request or a modification request to each of the one or more candidate / target DUs detected based on the first measurement report, requesting preparation of an LTM target cell configuration; 2. The CU of claim 1, configured to: upon receiving an LTM candidate cell configuration from each of the one or more candidate / target DUs, transmit to the serving DU the one or more configuration changes corresponding to the status change made by the UE as part of the reconfiguration.

4. The CU of claim 3 , wherein the one or more configuration changes are provided to the UE using a radio resource control (RRC) configuration message.

5. To send the message including the status change, the processor: broadcasting the serving cell change notification message to each of one or more candidate / target DUs detected by the CU based on a first measurement report received from the UE; 2. The CU of claim 1, further configured to: receive, from each of the one or more candidate / target DUs, reconfiguration information corresponding to the status change for each of the candidate / target cells.

6. The CU of claim 1, wherein the notification received from the serving DU includes an identification number of the new serving cell of the new serving DU among one or more candidate / target DUs determined to serve the UE.

7. A user equipment (UE), a processor; a memory communicatively coupled to the processor, the memory storing processor-executable instructions that, when executed, cause the processor to: receiving a notification from a serving distribution unit (DU) of a next generation radio access network (NG-RAN) indicating a change of serving cell; Establishing a connection with a new serving cell of a new serving DU, wherein the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the NG-RAN when the UE successfully establishes the connection with the new serving cell; and When the serving cell of the UE is changed to the new serving cell of the new serving DU, receiving a message from the CU via the new serving DU, the message including a status change of one or more candidate / target cells of the new serving DU and all the candidate / target DUs; A user equipment (UE) that performs one or more configuration changes corresponding to the status change as part of a reconfiguration and sends a confirmation of the reconfiguration to the CU, wherein the one or more configuration changes are received from the CU before the change in the serving cell.

8. Prior to receiving the notification, the processor:

8. The UE of claim 7, further configured to send a second measurement report to the serving DU periodically or based on the occurrence of one or more events, the serving DU determining the new serving cell for the UE based on the second measurement report, the second measurement report being an intra-frequency L1 measurement report or an inter-frequency L1 measurement report.

9. A new Serving Distribution Unit (DU), a processor; a memory communicatively coupled to the processor, the memory storing processor-executable instructions that, when executed, cause the processor to: receiving a connection establishment from a user equipment (UE) after changing the serving cell to a new serving cell belonging to a new serving DU; When the serving cell of the UE is changed to the new serving cell, receiving a message from the CU including a status change of one or more of the cells of the candidate / target DU and the new serving DU, and transmitting the content of the message from the CU to the UE using a Layer 1 message or a Layer 2 message; a new serving distribution unit (DU) that reconfigures the new serving DU based on the status change and sends a confirmation of the reconfiguration to the CU;

10. 1. A method comprising: receiving, by a centralized unit (CU) of a next generation radio access network (NG-RAN) node, a notification indicating a change of serving cell due to L1 / L2 triggered mobility (LTM) of a user equipment (UE) from a serving distribution unit (DU) of the UE in the NG-RAN; When changing the serving cell of the UE to a new serving cell, determining by the CU to change the status of one or more cells of the serving DU among a plurality of candidate / target DUs and one or more candidate / target cells of the candidate / target DU, wherein the new serving cell is one of the one or more candidate / target cells of the candidate / target DU; sending, by the CU to the new serving DU, a message including the status change information of all the candidate / target cells including corresponding cell identifiers, the message content being further transmitted by the new serving DU to the UE; receiving by the CU a confirmation of a reconfiguration corresponding to the new serving DU and the status change in the UE, wherein the UE applies, as part of the reconfiguration, one or more configuration changes provided by the CU prior to the change in the serving cell.

11. determining said status change; The method of claim 10, comprising: determining, by the CU, a status change from intra-DU to inter-DU or from inter-DU to intra-DU for each of the one or more cells of the serving DU and each of the one or more candidate / target cells of the candidate / target DU based on the change in the serving cell of the UE.

12. Prior to receiving said notification, Detecting, by the CU, one or more candidate / target DUs among a plurality of DUs based on a first measurement report received from the UE, wherein each of the one or more candidate / target DUs includes the one or more candidate / target cells; sending, by the CU, a setup request or a modification request to prepare an LTM target cell configuration to each of the one or more candidate / target DUs detected based on the first measurement report; and upon receiving an LTM candidate cell configuration from each of the one or more candidate / target DUs, transmitting by the CU to the serving DU the one or more configuration changes corresponding to the status changes made by the UE as part of the reconfiguration.

13. The method of claim 12 , wherein the one or more configuration changes are provided to the UE using a radio resource control (RRC) configuration message.

14. Sending the message including the status change comprises: broadcasting, by the CU, the serving cell change notification message to each of one or more candidate / target DUs detected by the CU based on a first measurement report received from the UE; The method of claim 10 , further comprising: receiving, by the CU, reconfiguration information corresponding to the status change for each of the candidate / target cells from each of the one or more candidate / target DUs.

15. 11. The method of claim 10, wherein the notification received from the serving DU includes an identification number of the new serving cell of the new serving DU among one or more candidate / target DUs determined to serve the UE.

16. 1. A method comprising: receiving, by a user equipment (UE), a notification indicating a change of serving cell from a serving distribution unit (DU) of a next generation radio access network (NG-RAN); Establishing a connection with a new serving cell of a new serving DU by the UE, wherein the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the NG-RAN upon successfully establishing the connection with the new serving cell; When the serving cell of the UE is changed to the new serving cell of the new serving DU, receiving a message by the UE from the CU via the new serving DU, the message including a status change of one or more candidate / target cells of the new serving DU and all the candidate / target DUs; making one or more configuration changes by the UE corresponding to the status change as part of a reconfiguration and sending a confirmation of the reconfiguration to the CU, wherein the one or more configuration changes are received from the CU before the change in the serving cell.

17. Before receiving said notice, 17. The method of claim 16, comprising transmitting a second measurement report by the UE to the serving DU periodically or based on the occurrence of one or more events, the serving DU determining the new serving cell for the UE based on the second measurement report, the second measurement report being an intra-frequency L1 measurement report or an inter-frequency L1 measurement report.

18. 1. A method comprising: receiving a connection establishment from a user equipment (UE) by a new serving distribution unit (DU) after changing the serving cell to a new serving cell belonging to a new serving DU; When the serving cell of the UE is changed to the new serving cell, receiving a message from the CU by the new serving DU, the message including a status change of one or more of the candidate / target DUs and the candidate / target cell of the new serving DU, and transmitting the content of the message from the CU to the UE using a Layer 1 message or a Layer 2 message; reconfiguring the new serving DU based on the status change by the new serving DU and sending a confirmation of the reconfiguration to the CU.

19. A non-transitory computer-readable medium having instructions stored therein, the instructions, when processed by at least one processor, causing a centralized unit (CU) to: receiving, by a centralization unit (CU) of a next generation radio access network (NG-RAN node), a notification from a serving distribution unit (DU) of the NG-RAN indicating a change of serving cell due to L1 / L2 triggered mobility (LTM) of a user equipment (UE); When changing the serving cell of the UE to a new serving cell, determining by the CU to change the status of one or more cells of the serving DU and one or more candidate / target cells of a candidate / target DU among a plurality of candidate / target DUs, wherein the new serving cell is one of the one or more candidate / target cells of the candidate / target DU; sending a message by the CU to the new serving DU, the message including the status change information of all the candidate / target cells including corresponding cell identifiers, the message content being further sent by the new serving DU to the UE; receiving, by the CU, a confirmation of a reconfiguration corresponding to the new serving DU and the status change in the UE, wherein the UE applies, as part of the reconfiguration, one or more configuration changes provided by the CU prior to the change in the serving cell;

20. A non-transitory computer-readable medium comprising instructions stored therein, the instructions, when processed by at least one processor, causing a user equipment (UE) to: receiving, by a user equipment (UE), a notification indicating a change of serving cell from a serving distribution unit (DU) of a next generation radio access network (NG-RAN); Establishing a connection with a new serving cell of a new serving DU by the UE, wherein the UE confirms application of the new serving cell configuration to a centralized unit (CU) of the NG-RAN upon successfully establishing the connection with the new serving cell; When the serving cell of the UE is changed to the new serving cell of the new serving DU, receiving a message by the UE from the CU via the new serving DU, the message including a status change of one or more candidate / target cells of the new serving DU and all the candidate / target DUs; and performing, by the UE, one or more configuration changes corresponding to the status change as part of a reconfiguration, and transmitting a confirmation of the reconfiguration to the CU, the one or more configuration changes being received from the CU before the change in the serving cell.

21. A non-transitory computer-readable medium having instructions stored therein, the instructions, when processed by at least one processor, causing a new serving distribution unit (DU) to: receiving, by a new serving distribution unit (DU), a connection establishment from a user equipment (UE) after changing the serving cell to a new serving cell belonging to a new serving DU; When the serving cell of the UE is changed to the new serving cell, receiving a message from the CU by the new serving DU, the message including a status change of one or more of the candidate / target DUs and the candidate / target cell of the new serving DU, and transmitting the content of the message from the CU to the UE using a Layer 1 message or a Layer 2 message; a non-transitory computer-readable medium configured to cause the new serving DU to perform operations including: reconfiguring the new serving DU based on the status change, and sending a confirmation of the reconfiguration to the CU.

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