Method and apparatus for scaling distributed unit in system supporting merging of plurality of cells

Abstract

Disclosed are a method and an apparatus for scaling a distributed unit in a system supporting merging of a plurality of cells. The method may comprise the steps of: switching a path between an RU of a first cell and a PHY entity of a first DU to a path between the RU and a PHY entity of a second DU; identifying whether the first cell is configured as a PCell or an SCell for a terminal; on the basis that the first cell is configured as the PCell for the terminal, switching a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between the RLC entity of the first DU and a MAC entity of the second DU; and transferring context information of the terminal related to the RLC entity of the first DU to an RLC entity of the second DU.

Description

Method and device for scaling a distributed unit in a system supporting merging of multiple cells

[0001] The present disclosure relates to a method and apparatus for scaling a distributed unit in a system supporting merging of multiple cells.

[0002] In the communications industry, technology for virtualized radio access networks (RANs), or vRANs, is rapidly growing. Conventional hardware-based RANs require specialized hardware to perform each communication function. Due to hardware compatibility issues, mobile carriers have had to build RANs using hardware configurations from the same manufacturer. However, vRANs are software-based, not hardware-based. Their communication functions can be performed by software. In other words, vRANs do not require specialized hardware to perform communication functions, and their software configurations can be run on general-purpose servers to perform communication functions. Consequently, mobile carriers can build vRANs using products from various manufacturers, rather than being tied to a single manufacturer's product.

[0003] 4G(4 th Generation) LTE (Long-Term Evolution) or 5G (5G) thA wireless communication system based on NR (New Radio) can support CA (Carrier Aggregation) using multiple carriers (or carrier waves). CA is a technology that combines multiple carriers and utilizes them as a single carrier to address the lack of frequency bands. Through CA, multiple component carriers, each with a narrow band, can be aggregated to establish a wide band. For example, in a wireless communication system using CA, a UE can communicate with a core network simultaneously using multiple aggregated carriers, thereby providing a high data transmission rate and low transmission delay to the UE.

[0004] The present disclosure can be implemented in various ways, including as a method, system, device, or computer program stored on a computer-readable storage medium.

[0005] In one embodiment of the present disclosure, a method of scaling at least one Distributed Unit (DU), performed by a network device supporting carrier aggregation, may include: switching a path between a Radio Unit (RU) of a first cell and a Physical (PHY) entity of the first DU to a path between the RU and a PHY entity of a second DU. In one embodiment of the present disclosure, the method may include identifying whether the first cell is configured as a Primary Cell (PCell) or a Secondary Cell (SCell) for the terminal. In one embodiment of the present disclosure, the method may include: switching a path between a Radio Link Control (RLC) entity of the first DU and a Medium Access Control (MAC) entity of the first DU to a path between the RLC entity of the first DU and the MAC entity of the second DU, based on the first cell being configured as the PCell for the terminal. In one embodiment of the present disclosure, the method may include a step of transferring context information of the terminal related to the RLC entity of the first DU to the RLC entity of the second DU. In one embodiment of the present disclosure, the method may include a step of switching a path between a Central Unit (CU) and the RLC entity of the first DU to a path between the CU and the RLC entity of the second DU. In one embodiment of the present disclosure, the method may include a step of switching a path between the RLC entity of the first DU and a MAC entity of the second DU to a path between the RLC entity of the second DU and the MAC entity of the second DU.

[0006] In one embodiment of the present disclosure, a program for performing the method on a computer can be recorded on a computer-readable recording medium.

[0007] In one embodiment of the present disclosure, a network device supporting carrier aggregation may include a memory storing one or more instructions. In one embodiment of the present disclosure, the network device may include at least one processor that executes the one or more instructions stored in the memory. In one embodiment of the present disclosure, in order to scale at least one Distributed Unit (DU), the at least one processor may cause the network device to switch a path between a Radio Unit (RU) of a first cell and a Physical (PHY) entity of the first DU to a path between the RU and a PHY entity of a second DU by executing the one or more instructions. In one embodiment of the present disclosure, the at least one processor may cause the network device to identify whether the first cell is configured as a Primary Cell (PCell) or a Secondary Cell (SCell) for a terminal by executing the one or more instructions. In one embodiment of the present disclosure, the at least one processor may cause the network device to switch a path between a Radio Link Control (RLC) entity of the first DU and a Medium Access Control (MAC) entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU based on the first cell being configured as a PCell for the terminal by executing the one or more commands. In one embodiment of the present disclosure, the at least one processor may cause the network device to transfer context information of the terminal related to the RLC entity of the first DU to the RLC entity of the second DU by executing the one or more commands.In one embodiment of the present disclosure, the at least one processor may cause the network device to switch a path between a Central Unit (CU) and an RLC entity of the first DU to a path between the CU and an RLC entity of the second DU by executing the one or more instructions. In one embodiment of the present disclosure, the at least one processor may cause the network device to switch a path between an RLC entity of the first DU and a MAC entity of the second DU to a path between an RLC entity of the second DU and a MAC entity of the second DU by executing the one or more instructions.

[0008] FIG. 1 illustrates an example of a wireless communication system according to one embodiment of the present disclosure.

[0009] FIG. 2 illustrates an example of cell transfer from a first DU to a second DU within a RAN system according to one embodiment of the present disclosure.

[0010] FIG. 3 illustrates carrier aggregation (CA) according to one embodiment of the present disclosure.

[0011] FIG. 4A illustrates carrier-merged first and second cells according to one embodiment of the present disclosure.

[0012] FIG. 4b illustrates an exemplary carrier-merged first cell and second cell according to one embodiment of the present disclosure.

[0013] FIG. 5 illustrates an exemplary method of scaling at least one Distributed Unit (DU) by a network device that supports aggregation of multiple cells, including a first cell and a second cell, according to one embodiment of the present disclosure.

[0014] FIG. 6 illustrates an exemplary flowchart of a method for scaling out a first DU to a second DU by a network device according to one embodiment of the present disclosure.

[0015] FIGS. 7A to 7C illustrate data flow in a user plane due to scaling out a first DU to a second DU by a network device according to one embodiment of the present disclosure.

[0016] FIGS. 8A to 8C illustrate data flow in a user plane due to scaling out a first DU to a second DU by a network device according to one embodiment of the present disclosure.

[0017] FIG. 9 illustrates an exemplary flowchart of a method for scaling a first DU into a second DU by a network device according to one embodiment of the present disclosure.

[0018] FIGS. 10A to 10C illustrate data flow in a user plane due to scaling of a first DU to a second DU by a network device according to one embodiment of the present disclosure.

[0019] FIG. 11 illustrates an example of an electronic device according to one embodiment of the present disclosure.

[0020] This disclosure may be subject to various modifications and various embodiments. Specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the disclosure.

[0021] When describing embodiments, detailed descriptions of related known technologies are omitted if they are deemed to unnecessarily obscure the main point. Furthermore, numbers (e.g., "first," "second," etc.) used in the description of embodiments are merely identifiers used to distinguish one component from another.

[0022] Below, with reference to the attached drawings, embodiments of the present disclosure are described in detail to facilitate implementation by those skilled in the art. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein. Before proceeding with a detailed description of the invention, the terms used herein are defined or understood as follows.

[0023] When a component is referred to herein as being "connected" or "connected" to another component, it should be understood that the component may be directly connected to or connected to the other component, but may also be connected or connected via another component in between, unless otherwise specifically stated. Furthermore, "connection" may include a wireless connection or a wired connection.

[0024] In addition, in this specification, components expressed as 'unit', 'module', etc. may be two or more components combined into one component, or one component may be divided into two or more components with more detailed functions. In addition, each component described below may additionally perform some or all of the functions performed by other components in addition to its own main function, and of course, some of the main functions performed by each component may be performed exclusively by other components.

[0025] In this disclosure, the expression "at least one of a, b, and / or c" can refer to "a", "b", "c", "a and b", "a and c", "b and c", "all of a, b, and c", or variations thereof. In this disclosure, the expression "a or b" can refer to "a", "b", "a and b", or variations thereof. In this disclosure, the expression "a (or, b, c)" or the expression "a, b, or c" can refer to "a", "b", "c", "a and b", "a and c", "b and c", "all of a, b, and c", or variations thereof.

[0026] In one embodiment of the present disclosure, the term "transfer" may include moving, copying, duplicating, or synchronizing previous target information contained in any logical or physical space to any other space. In one embodiment of the present disclosure, the term "transfer" may include causing previous target information (e.g., context information) contained, stored, configured, or set in space A (or device A, module A) to be contained, stored, configured, or set in space B (or device B, module B). In one embodiment of the present disclosure, "transfer" may include causing previous target information contained, stored, configured, or set in space A (or device A, module A) to be contained, stored, configured, or set in space B (device B or module B), and removing, deleting, releasing, or deactivating the previous target information in space A (device A or module A).

[0027] In one embodiment of the present disclosure, a "cell transfer" may include the transfer of at least one of information, context, or interface associated with a cell. For example, a "cell transfer" may include the transfer of cell configuration information. For example, a "cell transfer" may be a cell-by-cell transfer, and may include the transfer of cell configuration information and the UE context of a User Equipment (UE) associated with the cell. For example, a "cell transfer" may be a UE-by-UE transfer, and may include the transfer of an interface for user data (e.g., an F1-U interface).

[0028] In one embodiment of the present disclosure, a “MAC (Medium Access Control) context” may include cell configuration information or UE context included in a MAC layer (or an entity performing the function of the MAC layer).

[0029] In one embodiment of the present disclosure, "cell configuration information" may include information about basic settings, operation methods, configurations, or parameters of each cell in a wireless communication system. For example, "cell configuration information" may include information about frequency bands, channel bands, frequency allocation information, transmission output power settings, cell identifiers, settings in the time and frequency domains, interference management with other cells and base stations, scheduling information (e.g., DL (Downlink) / UL (Uplink) Max Resource Block, PDSCH (Physical Downlink Shared Channel), PUSCH (Physical Uplink Shared Channel), SSB (Synchronization Signal Block), etc.), or timing information (e.g., number of slots per flame, etc.). All UEs connected to (or attached to) a cell and the cell may be connected and managed based on the "cell configuration information."

[0030] In one embodiment of the present disclosure, the "UE context" may include information for wireless communication of each UE in a wireless communication system. For example, the "UE context" may include location information of the terminal, a terminal identifier, a status of the terminal, service requirements, information on the network and cell currently in use, performance information of the terminal, function information, security information, or authentication information. For example, the UE context may include a unique number for each situation of UEs connected to a base station (e.g., a Radio Network Temporary Identifier (RNTI)), information on DL Data Volume per UE (e.g., a Buffer Occupancy (BO)), information on UL Data Volume per UE (e.g., a Buffer Status Report (BSR)), a PDCCH (Physical Downlink Control Channel) monitoring period for the UE to transmit and receive new DL / UL traffic (e.g., a DRX (Discontinuous Reception)), and retransmission information per UE (e.g., HARQ (Hybrid Automatic Repeat Request) information).

[0031] In one embodiment of the present disclosure, "connection relationship" may include the meaning of "connection relationship," "inclusion relationship," "attachment relationship," or "matching relationship." For example, "connected" may include the meaning of "connected," "inclusion," "attached," or "matched." In one embodiment of the present disclosure, "connection" may include the meaning of data communication being possible, either wired or wireless. For example, "A and B are connected" may include the meaning that A and B are capable of data communication, i.e., can transmit and receive data to and from each other.

[0032] In one embodiment of the present disclosure, “A performing action B” may include “A directly performing action B” or “A controlling C to perform action B.” In one embodiment of the present disclosure, “A controlling action B” may include “A directly performing action B” or “A controlling C to perform action B.”

[0033] In one embodiment of the present disclosure, a “UE associated with a cell” may include a UE associated with a cell, a UE attached to a cell, a UE communicating with (i.e., transmitting and receiving data) a Radio Unit (RU) including a cell, a UE receiving a communication service via a cell, a UE transmitting and receiving data via a cell, a UE accessing a network via a cell, a UE included in the range (e.g., effective range, communication range) of a cell, a UE requesting a radio resource of a cell, or a UE allocated a radio resource of a cell, etc. For example, one or more UEs associated with a target cell may have a connection established and managed based on cell configuration information for the target cell.

[0034] In one embodiment of the present disclosure, "path" or "interface" may include the meaning of a module (e.g., a software module, a hardware module) that enables data transmission and reception. In one embodiment of the present disclosure, "path" or "interface" may include the meaning of a logical or physical connection relationship. In one embodiment of the present disclosure, "path" or "interface" may include the meaning of a data transmission and reception path. In one embodiment of the present disclosure, "establishing an interface (or path) between A and B" may include the meaning of establishing a configuration that enables A and B to transmit and receive data with each other and process the received data.

[0035] In one embodiment of the present disclosure, "scale-out for a DU (Distribution Unit)" and "scaling-out for a DU" may include adding a new DU to a DU pool containing DUs. In one embodiment of the present disclosure, "scale-out for a DU" and "scaling-out for a DU" may include moving cells contained in the DU to another DU (e.g., a newly added DU).

[0036] In one embodiment of the present disclosure, “scale-in for a DU” and “scaling-in for a DU” may include removing the DU from the DU pool. In one embodiment of the present disclosure, “scale-in for a DU” and “scaling-in for a DU” may include transferring cells included in the DU to another DU (e.g., an existing DU).

[0037] In one embodiment of the present disclosure, a "target cell" may refer to a cell to which a DU is to be migrated through scale-in or scale-out for a DU. A "source DU" may refer to a DU that was processing the target cell before migration of the target cell. Depending on the configuration of the RAN system, a target cell may be processed by one or more source DUs, and thus, multiple source DUs may exist for the target cell. When scale-in for a DU is performed, the source DU (or any one of the multiple source DUs) may refer to a DU to be removed from the DU pool. A "target DU" may refer to a DU that is changed to process the target cell through migration of the target cell. When scale-out for a DU is performed, the target DU may be a DU to be added to the DU pool.

[0038] FIG. 1 exemplarily illustrates a wireless communication system according to one embodiment of the present disclosure. In one embodiment of the present disclosure, the wireless communication system (100) may include a core network (110) and a radio access network (RAN) system (120). The core network (110) may include user authentication information for each telecommunications company, etc., and may be a platform network that is wired and connected to servers and systems of various service providers via optical cables. In one embodiment of the present disclosure, the RAN system (120) may include at least one RU (128_1, 128_2, 128_3, 128_4, 128_5, 128_6), at least one DU (124_1, 124_2, 124_3, 124_4), and a centralized unit (CU) (122). In one embodiment of the present disclosure, the RAN system (120) may include, but is not limited to, a vRAN (virtualized Radio Access Network) system. For example, the RAN system (120) may include a 5GS (5G System), 4GS, or other wireless communication system, and may also refer to a wireless communication system to be developed in the future.

[0039] In one embodiment of the present disclosure, the CU (122) may be an entity that performs functions of some of the protocol layers of a network. For example, the CU (122) may be an entity that performs network functions of the RRC (Radio Resource Control) layer and the PDCP (Packet Data Convergence Protocol) layer, but is not limited thereto. For example, the CU (122) may perform functions such as QoS (Quality of Service) settings, packet reordering, and security settings or processing. For example, the CU (122) may be implemented as a vCU (virtualized-CU) of a vRAN system, but is not limited thereto.

[0040] One CU (122) can be connected to N DUs, where N can be any integer greater than 1. The CU (122) and the DUs (124_1, 124_2, 124_3, 124_4) can be connected by an interface (or path). For example, the interface between the CU (122) and the DUs (124_1, 124_2, 124_3, 124_4) can be an F1 interface (or midhaul interface). For example, the F1 interface can include F1-C, which is an F1 interface of a control plane, and F1-U, which is an F1 interface of a user plane.

[0041] The RAN system (120) may include DUs (124_1), DUs (124_2), and DUs (124_3). DUs (124_1), DUs (124_2), and DUs (124_3) may be implemented in substantially the same manner and may perform substantially the same functions. DUs (124_3) will be described below as an example.

[0042] In one embodiment of the present disclosure, the DU (124_3) may be an entity that performs functions of some layers among the protocol layers of the network except for some layers performed by the CU (122). For example, the DU (124_3) may be an entity that performs network functions (e.g., baseband functions) of the RLC (Radio Link Control) layer, the MAC (Medium Access Control) layer, or the PHY (Physical) layer, but the functions that the DU (124_3) can process are not limited to the functions of the RLC layer, the MAC layer, and the PHY layer described above. For example, the DU (124_3) may perform a buffer function, a radio resource scheduling function, a data reprocessing function, etc. For example, the DU (124_3) may be a vDU (virtualized-DU) of a vRAN system, but is not limited thereto. For example, DU (124_3) may correspond to a processing pod, a component module, an arbitrary processing operation unit, a deployment unit performing arbitrary processing, software, etc. For example, DU (124_3) may correspond to a single server.

[0043] A DU can be connected to one or more RUs. Referring to FIG. 1, DU (124_1) can be connected to RU (128_1) and RU (128_2), DU (124_2) can be connected to RU (128_3) and RU (128_4), and DU (124_3) can be connected to RU (128_5) and RU (128_6). In one embodiment of the present disclosure, DU (124_3) and RUs (128_5, 128_6) can be connected by an interface (or path). For example, the interface between DU (124_3) and RUs (128_5, 128_6) can be a fronthaul interface.

[0044] RU(128_1), RU(128_2), RU(128_3), RU(128_4), RU(128_5), and RU(128_6) can communicate with one or more UEs. For example, RU(128_1), RU(128_2), RU(128_3), RU(128_4), RU(128_5), and RU(128_6) can communicate with one or more UEs(130_1, 130_2, 130_3, 130_4, 130_5, 130_6), respectively. RU(128_1), RU(128_2), RU(128_3), RU(128_4), RU(128_5), and RU(128_6) can be implemented in substantially the same manner and can perform substantially the same functions. RU(128_6) is described below as an example.

[0045] In one embodiment of the present disclosure, the RU (128_6) may be an entity that performs some functions of the PHY layer other than those handled by the DU (124_3). For example, the DU (124_3) may perform a function of the upper physical (high-PHY) layer. The RU (128_6) may perform a function of the lower physical (low-PHY) layer. For example, the RU (128_6) may perform a data transmission and reception function via an RF (radio frequency) antenna. For example, the RU (128_6) may be, but is not limited to, a vRU (virtualized-RU) of a vRAN system. One of one or more UEs (130_6) may communicate with the core network (110) via the RU (128_6), the DU (124_3), and the CU (122).

[0046] In a RAN system, a DU can be connected 1:1 to a cell site containing one or more RUs, and the processing capacity of the DU can be determined based on the maximum traffic that can enter the corresponding cell site. Depending on the change in traffic trends over time, the time when peak traffic occurs may be limited. For example, traffic may increase during daytime hours when the number of users increases, and decrease during nighttime hours when the number of users decreases. Typically, peak traffic may occur between 5 PM and 8 PM. Therefore, in a RAN system with a fixed number of DUs, unused DU resources, i.e., available remaining resources, may exist during times when peak traffic does not occur.

[0047] According to one embodiment of the present disclosure, a vRAN system may be applied with a virtualized DU (vDU) pooling technology that breaks the existing 1:1 relationship between a DU and a cell site (a set of RUs) and virtualizes the DUs by pooling them. For example, one DU may process at least a portion of the traffic from a first cell site and at least a portion of the traffic from a second cell site. Accordingly, the number of physical servers required to build a RAN system may be reduced, thereby reducing capital expenditures (CAPEX). In addition, power consumption may be reduced compared to existing RAN systems, and operating expenditures (OPEX) may also be reduced.

[0048] A vRAN system according to one embodiment of the present disclosure may employ vCU pooling technology, which pools and virtualizes CUs. This can reduce the number of physical servers and power consumption required to build a RAN system, resulting in savings in CAPEX and OPEX.

[0049] In one embodiment of the present disclosure, a vDU scaling method may be used in the RAN system (120) to efficiently use server resources by dynamically scaling out or scaling in DUs according to current traffic conditions. In the case of scaling out, a DU (124_4) may be newly created in the RAN system (120), but is not limited thereto. For example, the DU (124_4) may have previously existed in the RAN system (120) but may not have been associated with the RU (128_6), and may be associated with the RU (128_6) through scaling out. In the case of scaling in, the DU (124_4) may have previously existed in the RAN system (120).

[0050] Through vDU scaling, a first cell (or first cell site) whose data was being processed by a source DU can be migrated from the source DU to a target DU, and the first cell can be referred to as a target cell. For example, before vDU scaling, traffic from the first cell can be processed by the source DU, and after vDU scaling, traffic from the first cell can be processed by the target DU.

[0051] In one embodiment of the present disclosure, scale-out may mean that a new DU (e.g., target DU or DU (124_4)) is added to the DU pool for CU (122). For example, when the amount of traffic that a source DU (e.g., DU (124_3)) included in the DU pool must process increases, a target DU (e.g., DU (124_4)) may be added to the DU pool. For example, adding DU (124_4) to the DU pool may mean adding a processing pod corresponding to DU (124_4) to the DU pool. For example, adding DU (124_4) to the DU pool may mean starting an additional server capable of processing data. When the capacity or performance of DU (124_3) (e.g., an existing server) to process data reaches its limit, DU (124_4) (a non-limiting example, a server with similar specifications) may be added to the RAN system (120) through scale-out. In this case, a cell whose data was being processed by DU (124_3) may be transferred from DU (124_3) to DU (124_4), so that the data of the cell may be processed by DU (124_4).

[0052] In the embodiment illustrated in FIG. 1, as traffic increases, the load of DU (124_3) may need to be shared with DU (124_4). Accordingly, scale-out may be performed. In this case, DU (124_3) may correspond to the source DU, and DU (124_4) may correspond to the target DU. Before scale-out, traffic from the first cell attached to RU (128_6) may be processed by DU (124_3), and after scale-out, traffic from the first cell attached to RU (128_6) may be processed by DU (124_4). By scale-out, the performance of the RAN system (120) may be improved.

[0053] In an embodiment of the present disclosure, scale-in may mean that a DU included in the DU pool for a CU (122) is removed. For example, when the amount of traffic that the DUs included in the DU pool must process decreases, a target DU (e.g., DU (124_4)) may be removed from the DU pool. For example, the removal of DU (124_4) from the DU pool may mean that the processing pod corresponding to DU (124_4) is removed. For example, the removal of DU (124_4) from the DU pool may mean that a server that was processing data stops operating. By using scale-in, the number of servers that are no longer needed to operate can be reduced, and resources can be saved. Through scale-in, a target cell whose data was being processed by the target DU can be transferred to the source DU. For example, through scale-in, a cell whose data is processed by DU (124_4) can be transferred from DU (124_4) to DU (124_3), and thus the data of the cell can be processed by DU (124_3).

[0054] In the embodiment illustrated in FIG. 1, as traffic decreases, the amount of traffic processed by the DU (124_4) may decrease, so that there may be no need to operate the DU (124_4). Accordingly, scale-in may be performed. In this case, the DU (124_3) may correspond to the target DU, and the DU (124_4) may correspond to the source DU. Before scale-in, traffic from the second cell attached to the RU (128_6) may be processed by the DU (124_4), and after scale-in, traffic from the second cell attached to the RU (128_6) may be processed by the DU (124_3). By scale-in, resources of the RAN system (120) may be saved.

[0055] In one embodiment of the present disclosure, DU (124_3) and DU (124_4) may be connected by an inter DU interface (Xd interface) (126).

[0056] In one embodiment of the present disclosure, in addition to scaling by adding or removing a DU (124_4) to or from a DU pool, a target cell may be moved from another DU to the DU (124_4), or a target cell may be moved from the DU (124_4) to another DU. For example, a cell whose data is processed by the DU (124_4) may be moved from the DU (124_4) to the DU (124_3), so that the data of the cell is processed by the DU (124_3), or a cell whose data is processed by the DU (124_3) may be moved from the DU (124_3) to the DU (124_4), so that the data of the cell is processed by the DU (124_4). For example, by moving a cell from a DU (124_3) with a large amount of traffic to a DU (124_4) with a relatively small amount of traffic, the data of the cell can be processed by the DU (124_4), thereby improving the efficiency of the RAN system (200).

[0057] FIG. 2 exemplarily illustrates a cell transfer from a first DU to a second DU within a RAN system according to one embodiment of the present disclosure. Referring to FIG. 2 , a RAN system (200) may include a CU (210), an Operations, Administration, and Maintenance (OAM) module (220), a scale agent (230), DUs (240, 250), and an RU (260). In one embodiment of the present disclosure, the RAN system (200) may include a vRAN system, in which the CU (210) may be implemented as a vCU and the DUs (240, 250) may be implemented as vDUs.

[0058] The CU (210) may be an entity including a PDCP layer. The PDCP layer of the CU (210) may include at least one PDCP entity (211). The CU (210) may transmit data from DUs (240, 250) to a core network (not shown).

[0059] The OAM module (220) can determine a scaling situation for the DU (240). The scaling situation can include scale-out and scale-in. The OAM module (220) can determine whether to perform scale-out or scale-in for the DU (240). Based on the determination, the OAM module (220) can determine a scaling situation. The OAM module (220) can notify the scale agent (230) of the determined scaling situation.

[0060] The OAM module (220) may determine whether to migrate a target cell associated with the DU (240) to the DU (250). Based on the determination to migrate the target cell to the DU (250), the OAM module (220) may request the scale agent (230) to migrate the target cell from the DU (240) to the DU (250).

[0061] In one embodiment of the present disclosure, the OAM module (220) may determine to perform scale-out on the DU (240) in order to add a new DU (e.g., DU (250)) to the DU pool including the DU (240). Based on this determination, the OAM module (220) may determine the scaling situation to be scale-out. In one embodiment of the present disclosure, the OAM module (220) may determine to perform scale-in on the DU (240) in order to remove the DU (240) from the DU pool including the DU (240). Based on this determination, the OAM module (220) may determine the scaling situation to be scale-in.

[0062] Based on the decision to perform scale-out on the DU (240), the OAM module (220) can create a DU. For example, the OAM module (220) can set (or configure) a new DU (250) in the DU pool that includes the DU (240). For example, the OAM module (220) can set the DU (250) on an existing operating server device. For example, the OAM module (220) can initiate operation of an additional server device and set a second DU (250) on the additional server device. Based on the decision to perform scale-out on the DU (240), the OAM module (220) can activate a DU (250) that was inactive prior to the scale-out.

[0063] The OAM module (220) can establish a connection between the DU (250) and the CU (210). In one embodiment of the present disclosure, the OAM module (220) can register the DU (250) with a mid-haul splitter (not shown) for the CU (210). For example, the OAM module (220) can establish (or create) a mid-haul path (interface) connecting the DU (250) and the CU (210). The mid-haul splitter for the CU (210) may be an entity external to the CU (210) or an entity internal to the CU (210).

[0064] The OAM module (220) can establish a connection between the DU (250) and the RU (270). In one embodiment of the present disclosure, the OAM module (220) can register the DU (250) with a fronthaul splitter (not shown) for the RU (270). For example, the OAM module (220) can establish (or create) a fronthaul path (interface) for connecting the DU (250) and the RU (270). The fronthaul splitter for the RU (260) may be an entity external to the RU (260) or an entity internal to the RU (260).

[0065] The scale agent (230) can transfer a target cell associated with the DU (240) to the DU (250). For example, the scale agent (230) can be requested by the OAM module (220) to transfer a target cell from the DU (240) to the DU (250), and in response to the request, can perform operations to transfer the target cell from the DU (240) to the DU (250). Before transferring to the DU (250), the data of the target cell can be processed by the DU (240), and after transferring to the DU (250), the data of the target cell can be processed by the DU (250).

[0066] In one embodiment of the present disclosure, the scale agent (230) can identify a target cell to be transferred from the DU (240) to the DU (250). The target cell may be selected from one or more cells associated with the DU (240) by the scale agent (230) or the OAM module (220), but is not limited thereto. For example, the target cell may be selected based on information about the DU (240) (e.g., processing capacity, remaining resources, or traffic of the DU (240)), information about the DU (250), information about each cell associated with the DU (240) (e.g., traffic of the cell), etc. For example, the target cell may be randomly selected from one or more cells associated with the DU (240). The scale agent (230) may select any one cell from among the one or more cells associated with the DU (240) and identify the selected cell as the target cell. The scale agent (230) may be requested by the OAM module (220) to transfer a target cell from a DU (240) to a DU (250), and may identify the target cell based on the request.

[0067] In one embodiment of the present disclosure, the scale agent (230) may receive (or acquire) information about a scaling situation from the OAM module (220). Based on the information about the scaling situation, the scale agent (230) may identify the scaling situation as either scale-out or scale-in. Based on the identified scaling situation, the scale agent (230) may transfer the target cell associated with the DU (240) to the DU (250).

[0068] The scale agent (230) can transfer contexts included in the DU (240) to the DU (250). The context included in the DU can include at least one of system information, scheduling context, control information, frequency resource information, spatial resource information, UE context, or RU context. In one embodiment of the present disclosure, the scale agent (230) can transfer the context of a target cell included in the RLC entity (241), the MAC entity (242), or the PHY entity (243) of the DU (240) to the RLC entity (241), the MAC entity (252), or the PHY entity (253) of the second DU (250). For example, the scale agent (230) can synchronize the cell context and the UE context for the target cell of the DU (240) to the DU (250).

[0069] The scale agent (230) can control the path (or interface) between the CU (210), the DU (240), the DU (250), and the RU (260). For example, the scale agent (230) can switch the fronthaul path (interface) between the RU (260) and the DU (240) for the target cell to the fronthaul path between the RU (260) and the DU (250). The scale agent (230) can switch the path between the PHY entity (243) of the RU (260) and the DU (240) for the target cell to the path between the RU (260) and the PHY entity (253) of the DU (250). Accordingly, the target cell can communicate with the DU (250) instead of the DU (240) via the RU (260).

[0070] In one embodiment of the present disclosure, the scale agent (230) can release the fronthaul path between the DU (240) and the RU (260) for the target cell and establish a fronthaul path between the DU (250) and the RU (260). Accordingly, the RU (260) can be connected to the target cell through one DU and the fronthaul path.

[0071] In one embodiment of the present disclosure, an RU associated with multiple cells may be connected to a first DU for a first cell, and to a second DU for a second cell. In this embodiment, an RU may be connected to multiple DUs via multiple fronthaul paths on a cell-by-cell basis. For example, different fronthaul paths may be configured for each cell. In one embodiment of the present disclosure, a single DU may also be connected to multiple RUs via multiple fronthaul paths.

[0072] The scale agent (230) can switch the midhaul path (interface) between the CU (210) and the DU (240) for the target cell to the path between the CU (210) and the DU (250). The scale agent (230) can switch the path between the CU (210) and the RLC entity (241) of the DU (240) for the target cell to the path between the CU (210) and the RLC entity (251) of the DU (250). For example, the scale agent (230) can switch the F1-U path between the CU (210) and the RLC entity (241) of the DU (240) for the target cell to the path between the CU (210) and the RLC entity (251) of the DU (250).

[0073] In one embodiment of the present disclosure, the scale agent (230) can release the mid-haul path between the DU (240) and the CU (210) for the target cell, and establish a mid-haul path between the DU (250) and the CU (210). Accordingly, the CU (210) can be connected to one DU and the mid-haul path for the target cell.

[0074] In one embodiment of the present disclosure, a CU associated with multiple cells may be connected to a first DU for a first cell and to a second DU for a second cell. In this embodiment, the CU may be connected to multiple DUs via multiple midhaul paths on a cell-by-cell basis. For example, different midhaul paths may be configured for each cell. For example, the midhaul paths may be independently configured for each UE attached to the target cell. In one embodiment of the present disclosure, a single DU may also be connected to multiple CUs via multiple midhaul paths.

[0075] In one embodiment of the present disclosure, the DU (240) may include an RLC entity (241), a MAC entity (242), and a PHY entity (243). The RLC entity (241) may be included in the RLC layer of the DU (240). The RLC entity (241) may include (store) a UE context for one or more UEs communicating with the RU (260) or a cell context for one or more cells communicating with the RU (260). The RLC entity (241) may function as an RLC layer of the DU (240). The RLC entity (241) may be connected to the CU (210) via a midhaul path between the CU (210) and the DU (240). The MAC entity (242) may be included in the MAC layer of the DU (240). The MAC entity (242) may include a cell context for one or more cells communicating with the RU (260). The MAC entity (242) may function as a MAC layer of the DU (240). The PHY entity (243) may be included in the PHY layer of the DU (240). The PHY entity (243) may function as a PHY layer of the DU (240). The PHY entity (243) may include a cell context for one or more cells communicating with the RU (260). The PHY entity (243) may be connected to the RU (260) via a fronthaul path between the PHY entity (243) and the RU (260). The DU (240) may include a plurality of RLC entities, a plurality of MAC entities, or a plurality of PHY entities.

[0076] In one embodiment of the present disclosure, the DU (250) may include an RLC entity (251), a MAC entity (252), and a PHY entity (253). The RLC entity (251) may be included in the RLC layer of the DU (250). The RLC entity (251) may function as an RLC layer of the DU (250). By path switching of the scale agent (230), the RLC entity (251) may be connected to the CU (210) through a midhaul path between the CU (210) and the DU (250). By the scale agent (230), a cell context or UE context included in the RLC entity (241) of the DU (240) may be transferred to the RLC entity (251) of the DU (250). The MAC entity (252) may be included in the MAC layer of the DU (250). The MAC entity (252) may function as a MAC layer of the DU (250). By the scale agent (230), a cell context included in the MAC entity (242) of the DU (240) may be transferred to the MAC entity (252) of the DU (250). The PHY entity (243) may be included in the PHY layer of the DU (240). The PHY entity (253) may function as a PHY layer of the DU (250). By the scale agent (230), a cell context included in the PHY entity (243) of the DU (240) may be transferred to the PHY entity (253) of the DU (250). By path switching of the scale agent (230), the PHY entity (253) can be connected to the RU (260) through the fronthaul path between the PHY entity (253) and the RU (260). The DU (250) may include multiple RLC entities, multiple MAC entities, or multiple PHY entities.

[0077] FIG. 3 illustrates carrier aggregation (CA) according to an embodiment of the present disclosure. Referring to FIG. 3 , a RAN system (300) may include a CU (310), a DU (320), a PCell (Primary Cell) (341), and a SCell (Secondary Cell) (342). The RAN system (300) may support the aggregation of multiple component carriers.

[0078] The UE can communicate with the core network via the PCell (341) and the SCell (342). The PCell (341) and the SCell (342) may be cells for data transmission / reception between entities within the RAN system (300). The PCell (341) and the SCell (342) may use different frequency bands. For example, the PCell (341) and the SCell (342) may correspond to different component carriers. The SCell (342) may share the traffic of the PCell (341) or provide coverage in areas where the coverage of the PCell (341) is limited. For example, the PCell (341) may provide connectivity (e.g., connectivity with other entities, such as the core network, within the RAN system (300)) and traffic forwarding to the UE. On the other hand, SCell (342) can only forward traffic from the UE to other entities within the RAN system (300). For example, PCell can correspond to a serving cell where the UE has established an RRC (Radio Resource Control) connection with the core network.

[0079] To support communication with PCell (341) and SCell (342), DU (320) may include modems (331, 332). Modem (331) may serve PCell (341), and modem (332) may serve SCell (342). Modem (331) may include an RLC entity (331_1) included in an RLC layer of modem (331), a MAC entity (331_2) included in a MAC layer of modem (331), and a PHY entity (331_3) included in a PHY layer of modem (331). The modem (332) may include an RLC entity (332_1) included in the RLC layer of the modem (332), a MAC entity (332_2) included in the MAC layer of the modem (332), and a PHY entity (332_3) included in the PHY layer of the modem (332). The modems (331, 332) may be modems implemented in software on the DU (320), but are not limited thereto. In the embodiment of FIG. 3, the modems (331, 332) are implemented on a single DU (320), but the modems (331, 332) may be implemented on different DUs.

[0080] To support CA, the RAN system (300) can distribute IP (Internet Protocol) traffic to the PCell (341) and the SCell (342) in one of various split methods (31, 32, 33). In method (31), the IP traffic can be distributed in the PCDP layer of the CU (310). For example, IP traffic from the core network can be distributed based on the PDCP layer of the CU (310), and accordingly, IP traffic for the PCell (341) can be delivered to the modem (331) and IP traffic for the SCell (341) can be delivered to the modem (332).

[0081] In method (32), IP traffic can be distributed at the RLC layer. For example, IP traffic from the core network can be distributed at the RLC layer of the modem (331) for the PCell (341) of the DU (320) (e.g., the RLC entity (331_1) included in the RLC layer). Accordingly, IP traffic for the PCell (341) can be delivered to the MAC layer of the modem (331) (e.g., the MAC entity (331_2) included in the MAC layer), and IP traffic for the SCell (341) can be delivered to the MAC layer of the modem (332) (e.g., the MAC entity (332_2)).

[0082] In method (33), IP traffic can be distributed at the MAC layer. For example, IP traffic from the core network can be distributed at the MAC layer (e.g., MAC entity (331_2)) of the modem (331) for the PCell (341) of the DU (320). Accordingly, IP traffic for the PCell (341) can be delivered to the PHY layer (e.g., PHY entity (331_3)) of the modem (331), and IP traffic for the SCell (341) can be delivered to the PHY layer (e.g., PHY entity (332_2)) of the modem (332).

[0083] In one embodiment of the present disclosure, a RAN system supporting CA can distribute traffic for PCell and SCell according to method (32). Accordingly, the efficiency of control information exchange between protocol entities can be improved, and communication overhead can be reduced. Below, implementation scenarios of a RAN system supporting CA based on method (32) will be described with reference to FIGS. 4A and 4B.

[0084] FIG. 4A illustrates carrier-aggregated cells according to an embodiment of the present disclosure. Referring to FIG. 4A, in a RAN system (400a) supporting CA, cell (431) and cell (432) may be carrier-aggregated cells. For example, UE (441) and UE (442) may communicate with DU (420a) and CU (410) via cells (431, 432). The PCell of UE (441) may be cell (431) corresponding to component carrier 'CC 1', and the SCell of UE (441) may be cell (432) corresponding to component carrier 'CC2'. To support communication between UE (441) and the core network, component carrier 'CC1' and component carrier 'CC2' may be aggregated and provided to UE (441) (CA1). The PCell of the UE (442) may be a cell (432) corresponding to component carrier 'CC2', and the SCell of the UE (442) may be a cell (431) corresponding to component carrier 'CC1'. To support communication between the UE (442) and the core network, the component carrier 'CC2' and the component carrier 'CC1' may be merged and provided to the UE (442) (CA2).

[0085] For convenience of illustration, only two cells (431, 432) are shown in FIG. 4a, but the number of carrier-aggregated cells is not limited thereto. The RAN system (400a) may process three or more cells, and these cells may be processed by the DU (420a).

[0086] In the embodiment illustrated in FIG. 4a, a modem processing traffic from a PCell and a modem processing traffic from a SCell can be implemented within a single DU (420a). The configuration illustrated in FIG. 4a can be understood as an intra-DU CA scenario.

[0087] The DU (420a) may include an RLC entity (421a) and a MAC / PHY entity (422a). The RLC entity (421a) may perform functions of the RLC layer of the DU (420a). The MAC / PHY entity (422a) may perform functions of the MAC layer and the PHY layer of the DU (420a). The MAC / PHY entity (422a) may include an entity performing a MAC function and an entity performing a PHY function.

[0088] The 'UE 1 PCell path' may be understood as a data path for 'UE 1' (i.e., UE (441)) to communicate with the core network via the PCell (i.e., cell (431)) using the component carrier 'CC1'. For example, data transmitted from the UE (441) to the cell (431) via the component carrier 'CC1' may be transmitted to the CU (410) via the 'UE 1 PCell path' between the UE (441) and the cell (431), the 'UE 1 PCell path' between the cell (431) and the MAC / PHY entity (422a), the 'UE 1 PCell path' between the MAC / PHY entity (422a) and the RLC entity (421a), and the midhaul path (P1) for the cell (431) between the RLC entity (421a) and the CU (410). Data from UE (441) transmitted to CU (410) can be transmitted to the core network via CU (410).

[0089] In a similar manner, the 'UE 1 SCell path' can be understood as a data path for 'UE 1' (i.e., UE (441)) to communicate with the core network via the SCell (i.e., cell (432)). The 'UE 2 PCell path' can be understood as a data path for 'UE 2' (i.e., UE (442)) to communicate with the core network via the PCell (i.e., cell (432)) using component carrier 'CC2'. The 'UE 1 PCell path' can be understood as a data path for 'UE 1' (i.e., UE (441)) to communicate with the core network via the PCell (i.e., cell (431)) using component carrier 'CC1'. The 'UE 2 SCell path' can be understood as a data path for 'UE 2' (i.e., UE (442)) to communicate with the core network via the SCell (i.e., cell (431)).

[0090] As described above, the RAN system (400a) may be implemented according to the method (32) of FIG. 3. For example, the CU (410) may transmit IP traffic for the UE (441) from the core network to the RLC entity (421a) of the DU (420a) via the path (P1). The path (P1) may correspond to a midhaul path (or interface) for the UE (441) between the CU (410) and the DU (420a). The RLC entity (421a) may distribute the IP traffic for the UE (441) from the CU (410). For example, the RLC entity (421a) may transmit data to be processed by the PCell among IP traffic for the UE (441) to the MAC / PHY entity (422a) via the 'UE 1 PCell path' between the RLC entity (421a) and the MAC / PHY entity (422a). The RLC entity (421a) may transmit data to be processed by the SCell among IP traffic for the UE (441) to the MAC / PHY entity (422a) via the 'UE 1 SCell path' between the RLC entity (421a) and the MAC / PHY entity (422a). In a similar manner, the CU (410) may transmit IP traffic for the UE (442) from the core network to the RLC entity (421a) of the DU (420a) via the path (P2). Path (P2) may correspond to a midhaul path (or interface) for UE (442) between CU (410) and DU (420a). RLC entity (421a) may distribute IP traffic from CU (410) to UE (442).

[0091] Cell (431) can process data from UE (441) and data from UE (442) transmitted via component carrier 'CC1'. Cell (431) can process data received from DU (420a) and transmit the processed data to UE (441) or UE (442) via carrier 'CC1'. Cell (432) can process data from UE (441) and data from UE (442) transmitted via component carrier 'CC2'. Cell (432) can process data received from DU (420a) and transmit the processed data to UE (441) or UE (442) via carrier 'CC2'.

[0092] FIG. 4B illustrates an example of a carrier-aggregated first cell and a second cell according to an embodiment of the present disclosure. Referring to FIG. 4B, in a RAN system (400b) supporting CA, a modem for processing traffic from a PCell and a modem for processing traffic from a SCell may be implemented within different DUs. For example, traffic from a PCell (i.e., cell 431) of a UE (441) may be processed by a DU (421b), and traffic from a SCell (i.e., cell 432) of a UE (441) may be processed by a DU (422b). The configuration illustrated in FIG. 4B may be understood as an intra-DU CA scenario.

[0093] For convenience of illustration, only two cells (431, 432) and two DUs (721, 722) are illustrated in FIG. 4b, but the number of carrier-aggregated cells and DUs is not limited thereto. The RAN system (400b) may process three or more cells, and the DU pool of the RAN system (400b) may contain three or more DUs for processing cells together.

[0094] In the embodiment illustrated in FIG. 4b, the RAN system (400b) may include a DU (421b) for a cell (431) and a DU (422b) for a cell (432). The DU (421b) may include an RLC entity (421b_1) and a MAC / PHY entity (421b_2). The RLC entity (421b_1) may perform the functions of the RLC layer of the DU (421b). The MAC / PHY entity (421b_2) may perform the functions of the MAC layer and the PHY layer of the DU (421b). The MAC / PHY entity (421b_2) may include an entity performing a MAC function and an entity performing a PHY function.

[0095] As described above, the RAN system (400b) may be implemented according to the method (32) of FIG. 3. For example, the CU (410) may transmit IP traffic for the UE (441) from the core network to the RLC entity (421b_1) of the DU (421b) via the path (P1). The path (P1) may correspond to a midhaul path (or interface) for the UE (441) between the CU (410) and the DU (421b). The RLC entity (421b_1) may distribute the IP traffic for the UE (441) from the CU (410). For example, the RLC entity (421b_1) can transmit data to be processed by the PCell among IP traffic for the UE (441) to the MAC / PHY entity (421b_2) via the 'UE 1 PCell path' between the RLC entity (421b_1) and the MAC / PHY entity (421b_2). The RLC entity (421b_1) can transmit data to be processed by the SCell among IP traffic for the UE (441) to the MAC / PHY entity (421b_2) via the 'UE 1 SCell path' between the RLC entity (421b_1) and the MAC / PHY entity (421b_2). In a similar manner, the CU (410) may transmit IP traffic for the UE (442) from the core network to the RLC entity (422b_1) of the DU (422b) via path (P2). Path (P2) may correspond to a midhaul path for the UE (442) between the CU (410) and the DU (422b). The RLC entity (422b_1) may distribute the IP traffic for the UE (442) from the CU (410) and then transmit the distributed traffic to the MAC / PHY entity (422b_2) and the MAC / PHY entity (421b_2), respectively.

[0096] In a RAN system that does not support CA, a scale agent can transfer service for a specific cell served by an RU from a target DU to a source DU without considering communication with other cells. However, in a RAN system that supports CA (e.g., RAN system (400a) of FIG. 4a and RAN system (400b) of FIG. 4b), when transferring service for a specific cell from a target DU to a source DU, since multiple cells are carrier-aggregated, flow control of user plane traffic between the cell transferred to the target DU and the remaining cells in the source DU needs to be considered.

[0097] For convenience of illustration, in FIGS. 4a, 4b, 7a to 7c, 8a to 8c, and 10a to 10c, the MAC entity and the PHY entity are illustrated as integrated as a 'MAC / PHY entity'; however, it will be appreciated that the MAC entity and the PHY entity may be configured independently as separate entities. For example, in the embodiment of FIG. 4a, the MAC / PHY entity (422a) may exist independently as a separate MAC entity and PHY entity. For example, in the embodiment of FIG. 4b, the MAC / PHY entity (422b_2) and the MAC / PHY entity (421b_2) may exist independently as separate MAC entities and PHY entities, respectively.

[0098] FIG. 5 illustrates an exemplary method for scaling at least one Distributed Unit (DU), performed by a network device that supports aggregation of a plurality of cells, including a first cell and a second cell, according to an embodiment of the present disclosure. Referring to FIGS. 2 and 5 , a method (500) for scaling at least one DU according to an embodiment of the present disclosure may include steps (501 to 506). In an embodiment of the present disclosure, the method (500) may be performed by a network device of a RAN system. For example, the method (500) may be performed by a network device that manages scaling of DUs, such as the scale agent (230) of FIG. 2 . For example, the method (500) may be performed by the network device (1100) of FIG. 11 . In an embodiment of the present disclosure, steps (501 to 506) of the method (500) may be executed by at least one processor included in an electronic device. The method (500) is not limited to that illustrated in FIG. 5, and in one or more embodiments, the method (500) may further include steps not illustrated in FIG. 5, or some of the steps in FIG. 5 may be omitted from the method (500).

[0099] In the embodiment of FIG. 2, when the scale agent (230) performs the method (500), the first cell in the RU (260) can communicate with the DU (250) instead of the DU (240). For example, the first cell that was communicating with the CU (210) via the DU (240) can communicate with the CU (210) via the DU (240) instead of the DU (240) as the scale agent (230) performs the method (500). In this example, the DU (240) can be understood as a source DU, the DU (250) can be understood as a target DU, and the first cell can be understood as a target cell.

[0100] A network device according to one embodiment of the present disclosure may switch a path between an RU of a first cell and a PHY entity of a first DU to a path between the RU and a PHY entity of a second DU (501). For example, in the embodiment of FIG. 2, the scale agent (230) may switch a fronthaul path between an RU of a first cell and a first DU to be connected between the RU of the first cell and a second DU. For example, the scale agent (230) may switch (or change) a fronthaul path connected between a DU (240) and a RU (260) to be connected between a DU (250) and a RU (260). For example, the scale agent (230) may release a fronthaul path connected between a DU (240) and a RU (260), and establish a fronthaul path between a second DU (250) and a RU (260). Thereafter, the scale agent (230) may perform step (502).

[0101] In one embodiment of the present disclosure, if the first cell did not communicate with the second DU prior to step (501) (e.g., if the RU (260) did not communicate with the DU (250) prior to step (501), the second DU (e.g., the DU (250)) may be configured prior to step (501) or subsequent to step (501). The configuration of the second DU may be performed by a network device that performs functions for managing and maintaining the RAN system. For example, in the embodiment of FIG. 2, the OAM module (220) may initiate the DU (250). The OAM module (220) may initiate the DU (250) by creating (or configuring, establishing, setting up, activating) the DU (250). The OAM module (220) can establish an F1 interface (or midhaul path, midhaul interface) between the DU (250) and the CU (210). The OAM module (220) can create a connection between the PDCP entity (211) of the CU (210) and the RLC entity (251) of the DU (250). Thereafter, the scale agent (230) can establish a cell context of the first cell for the DU (250). The cell context can include information for establishing or managing connections with UEs connected (or attached) to the first cell. For example, the cell context of the first cell can include information for data communication of UEs attached to the first cell, such as a frequency band of the first cell, a radio resource scheduling method of the first cell, or a common signal transmitted to UEs attached to the first cell.

[0102] In one embodiment of the present disclosure, the RAN system (200) may further include a mid-haul splitter (not shown). The CU (210) and the DU (240) may communicate with each other through the mid-haul splitter. For example, the CU (210) and the DU (240) may each include an F1 message handler, and the F1 message handler of the CU (210) and the F1 message handler of the DU (240) may be connected through the mid-haul splitter. Similarly, the DU (250) may also include an F1 message handler. By registering the F1 message handler of the DU (250) with the mid-haul splitter, the OAM module (220) may establish a mid-haul path between the DU (250) and the CU (210).

[0103] A network device according to one embodiment of the present disclosure can identify whether a first cell is configured as a PCell or an SCell for a terminal (e.g., a first UE) (502). For example, in the embodiment of FIG. 2, a scale agent (230) can obtain information from a DU (240) indicating whether the first cell is a PCell or an SCell for each of the UEs communicating with the DU (240). Based on the obtained information, the scale agent (230) can identify (or determine) whether the first cell is configured as a PCell or an SCell for the first UE. For example, based on the obtained information, the scale agent (230) can identify at least one of a PCell or an SCell for the first UE.

[0104] In one embodiment of the present disclosure, information indicating whether the first cell is the PCell of the first UE or the SCell of the first UE may be stored in a MAC Scheduler (not shown). The MAC Scheduler may be located within the DU (240) (e.g., the MAC entity (242)) or may be located outside the DU (240). The MAC Scheduler may store information indicating which cells are configured as the PCell and which cells are configured as the SCell for each of the UEs communicating with the DU (240), information indicating whether the first cell is configured as the PCell or the SCell for each of the UEs communicating with the DU (240), or information indicating whether each of the cells communicating with the DU (240) is configured as the PCell or the SCell for each of the UEs communicating with the DU (240). The scale agent (230) can obtain information from the MAC scheduler indicating whether the first cell is the PCell of the first UE or the SCell of the first UE. Based on the obtained information, the scale agent (230) can identify whether the first cell is configured as the PCell of the first UE or as the SCell of the first UE.

[0105] In one embodiment of the present disclosure, before performing step (503), the network device may transfer a cell context corresponding to the first cell, which is included in at least one of the RLC entity, the MAC entity, and the PHY entity of the first DU communicating with the terminal, to a corresponding entity among the RLC entity, the MAC entity, and the PHY entity of the second DU. For example, in the embodiment of FIG. 2, the scale agent (230) may store at least one parameter that was used to set the cell context of the first cell for at least one of the RLC entity (241), the MAC entity (242), and the PHY entity (243) of the DU (240). The scale agent (230) may generate a cell context of the first cell for at least one of the RLC entity (241), the MAC entity (242), and the PHY entity (243) based on at least one stored parameter, and may set the generated cell context to a corresponding entity among the RLC entity (251), the MAC entity (252), and the PHY entity (253) of the DU (250). For example, the scale agent (230) may copy the cell context corresponding to the first cell, which is included in at least one of the RLC entity (241), the MAC entity (242), and the PHY entity (243) of the DU (240), to the corresponding entity (251 / 252 / 253) of the DU (250).

[0106] In one embodiment of the present disclosure, before performing step (503), the network device may transfer the MAC context for the first cell, which is included in at least one of the MAC entity and the PHY entity of the first DU, to a corresponding entity of the second DU. For example, in the embodiment of FIG. 2, the scale agent (230) may transfer the MAC context for the first cell, which is included in at least one of the MAC entity (242) and the PHY entity (243) of the DU (240), to a corresponding entity of the DU (250). The scale agent (230) may copy the MAC context for all UEs attached to the first cell to the DU (250).

[0107] In one embodiment of the present disclosure, the network device may switch the path between the RLC entity of the first DU and the MAC entity of the first DU to the path between the RLC entity of the first DU and the MAC entity of the second DU based on the fact that the first cell is configured as the PCell for the terminal (503). For example, in the embodiment of FIG. 2, the scale agent (230) may identify in step (503) that the first cell is configured as the PCell for the first UE, and based on the identification, may switch (or change) the path between the RLC entity (241) of the DU (240) and the MAC entity (242) of the DU (240). The scale agent (230) can switch the path for the first UE between the RLC entity (241) of the DU (240) and the MAC entity (242) of the DU (240) to be connected between the RLC entity (241) of the DU (240) and the MAC entity (252) of the DU (250).

[0108] The switched path in step (503) may be a data path for the terminal to communicate with the CU (210) via the first cell. For example, the first UE may communicate with the core network via the CU (210) via the first cell and the switched path. In this embodiment, the switched path may be understood as a data path for the PCell (i.e., the first cell) of the terminal. For example, a message, data, or traffic from the terminal may be transmitted to the core network via the PCell (i.e., the first cell), the RU (260), the fronthaul path, the switched path, the midhaul path, and the CU (210). After step (503), data from the terminal may be transmitted to the CU (210) via the switched path from the MAC entity of the second DU to the RLC entity of the first DU.

[0109] In one embodiment of the present disclosure, the network device may transfer context information of a terminal associated with an RLC entity of a first DU to an RLC entity of a second DU based on the fact that the first cell is configured as a PCell for the terminal (504). For example, in the embodiment of FIG. 2, if the first cell is a PCell of the first UE, the scale agent (230) may transfer the UE context of the first UE included in the RLC entity (241) of the DU (240) to the RLC entity (251) of the DU (250).

[0110] In one embodiment of the present disclosure, the network device may switch the path between the CU and the RLC entity of the first DU to the path between the CU and the RLC entity of the second DU based on the first cell being configured as the PCell for the terminal (505). For example, if the first cell is the PCell for the first UE, in the embodiment of FIG. 2, the scale agent (230) may release the midhaul path (or F1-U interface, F1-U path) between the PDCP entity (211) of the CU (210) and the RLC entity (241) of the DU (240), and may set (or establish, create) the midhaul path (or F1-U interface, F1-U path) between the PDCP entity (211) and the RLC entity (251) of the DU (250).

[0111] In one embodiment of the present disclosure, the network device may switch a path between an RLC entity of a first DU and a MAC entity of a second DU to a path between an RLC entity of the second DU and a MAC entity of the second DU based on the fact that the first cell is configured as a PCell for the terminal (506). For example, in the embodiment of FIG. 2, if the first cell is a PCell for the first UE, the scale agent (230) may switch a path that was switched to be connected between an RLC entity (241) of a DU (240) and a MAC entity (252) of a DU (250) in step (503) to be connected between an RLC entity (251) of a DU (250) and a MAC entity (252) of a DU (250). After step (506), data from the terminal can be transmitted from the MAC entity (252) of the DU (250) to the RLC entity (251) of the DU (250) through the switched path to the CU (210).

[0112] The network device can, by performing the method (500), at least partially transfer the first cell, which is a target cell, from the first DU to the second DU. For example, in the embodiment of FIG. 2, after the scale agent (230) performs the method (500), data transmitted from a terminal attached to the first cell to the PCell (i.e., the first cell) can be transmitted to the CU (210) via the DU (250), instead of the DU (240). The scale agent (230) can identify whether the first cell is configured as a PCell or an SCell for the terminal, and based on the identification, can switch at least some of the paths for the terminal between the RLC entity and the MAC entity. For example, whether the scale agent (230) switches the PCell data path for the terminal can be determined based on whether the first cell is configured as a PCell for the terminal. Therefore, the endpoints of the RLC entity and the MAC entity of the PCell data path for the terminal may depend on whether the first cell is configured as the PCell for the terminal.

[0113] In one embodiment of the present disclosure, the OAM module (220) can quickly switch over the first cell from the DU (240) to the DU (250) within a predetermined time (e.g., a reference time). For example, the OAM module (220) can simultaneously transfer all of the midhaul path, the fronthaul path, the cell context and the UE context included in each entity of the DU (240) from the DU (240) to the second DU (250) within a predetermined time.

[0114] In one embodiment of the present disclosure, the OAM module (220) can notify the scale agent (230) of a scaling situation. The OAM module (220) can determine (or identify) whether scaling in or scaling out is required for the source DU, and based on the determination (or identification), determine (or identify) the scaling situation as scale in or scale out. The scale agent (230) can identify the scaling situation notified from the OAM module (220), and based on the identified scaling situation, perform either the method (600) of FIG. 6 or the method (900) of FIG. 9. For example, based on identifying the scaling situation as scale out, the scale agent (230) can perform the method (600) of FIG. 6. Based on identifying the scaling situation as scale in, the scale agent (230) can perform the method (900) of FIG. 9. The method (600) of FIG. 6 and the method (900) of FIG. 9 are described in detail below.

[0115] FIG. 6 exemplarily illustrates a flowchart of a method for scaling out a first DU to a second DU, performed by a network device according to an embodiment of the present disclosure. Referring to FIG. 6 , the method (600) may include steps (601 to 617). The method (600) may be performed by a network device of a RAN system. For example, the method (600) may be performed by the scale agent (230) of FIG. 2 . For example, the scale agent (230) may perform the method (600) based on identifying a scaling situation as a scale out. Before the method (600) is performed, the first cell may be able to communicate with the CU (210) via a corresponding RU (e.g., RU (260)) and a first DU (e.g., DU (240)). Method (600) may be a method for transferring a first cell from a first DU to a second DU (which did not previously communicate with the first cell). In one embodiment of the present disclosure, steps (601 to 617) of method (600) may be executed by at least one processor included in an electronic device. Method (600) is not limited to that illustrated in FIG. 6, and in one or more embodiments, method (600) may further include steps not illustrated in FIG. 6, or some of the steps in FIG. 6 may be omitted from method (600).

[0116] In one embodiment of the present disclosure, before the method (600) is performed, the number of DUs capable of communicating with the first cell may be one or more. For example, before the method (600) is performed, there may be multiple source DUs capable of communicating with the first cell. The scale agent (230) may transfer the first cell (i.e., the target cell) from a first DU (i.e., the first source DU) among the multiple source DUs to a second DU (i.e., the target DU) by performing the method (600). For example, after the scale agent (230) performs the method (600), the first cell may be capable of communicating with the CU through the second DU, instead of the first DU.

[0117] In one embodiment of the present disclosure, before the method (600) is performed, the second DU may not exist in the DU pool of the RAN system (200), or may exist but be deactivated. In such a case, the second DU may be configured before the method (600) is performed. The configuration of the second DU may be performed by a network device that performs functions for managing and maintaining the RAN system. For example, in the embodiment of FIG. 2, the OAM module (220) may initiate the second DU. For example, the OAM module (220) may create a second DU that did not exist or activate a deactivated second DU. The OAM module (220) may establish a mid-haul path between the second DU and the CU (210). For example, the OAM module (220) may create (or configure, establish) a path between the PHY entity of the second DU and the CU (210).

[0118] In one embodiment of the present disclosure, a network device can transfer a cell context of a first cell included in a first DU to a second DU (601). For example, the network device can copy a cell context of a first cell included in the first DU (or at least one of multiple source DUs) to the second DU. For example, the scale agent (230) can generate a cell context of the first cell based on pre-stored parameters and set the generated cell context to the second DU.

[0119] In one embodiment of the present disclosure, the network device may transfer a MAC context of a first cell associated with a MAC entity of a first DU to a MAC entity of a second DU (602). For example, the network device may transfer or copy a MAC context for a first cell, which is included in at least one of a MAC entity and a PHY entity of the first DU (or at least one of multiple source DUs), to a corresponding entity of the second DU.

[0120] In one embodiment of the present disclosure, the network device may suspend MAC scheduling of the first cell (603). For example, the network device may control the MAC scheduler in the first DU to suspend MAC scheduling for the first cell of the first DU. The network device may at least partially suspend MAC scheduling of the first DU. For example, the network device may suspend MAC scheduling of the first DU for at least some or all of the cells communicating with the first DU, including the first cell. The network device may perform steps (604 to 610) while MAC scaling for the first cell of the first DU is suspended.

[0121] In one embodiment of the present disclosure, a network device may switch a fronthaul path for a first cell (604). For example, the network device may switch (or change) a fronthaul path connected between a first DU and an RU including the first cell to be connected between a second DU and the RU. Accordingly, a path between an RU of the first cell and a PHY entity of the first DU may be switched to a path between the RU and a PHY entity of the second DU.

[0122] In one embodiment of the present disclosure, a network device may select a terminal to be transferred to a second DU from among the terminals of the first cell connected to the MAC entity of the first DU (605). For example, the network device may randomly select one terminal to be transferred to the MAC entity of the second DU from among the terminals (e.g., UEs) attached to the first cell connected to the MAC entity of the first DU.

[0123] In one embodiment of the present disclosure, a network device can determine a transfer order for terminals attached to a first cell. The network device can sequentially select terminals based on the determined transfer order. For example, in step (605), the network device can select the first terminal among the terminals attached to the first cell based on the determined transfer order. Thereafter, when step (605) is performed again, the network device can select the next terminal based on the determined transfer order.

[0124] In one embodiment of the present disclosure, each terminal attached to the first cell may be assigned an identifier for selection. For example, the network device may assign a unique identifier for selection to each terminal attached to the first cell. For example, the network device may use an identifier already assigned to the terminal (e.g., a Cell Radio Network Temporary Identifier (C-RNTI) or a terminal identifier stored in the UE context) as an identifier for selection. The scale agent may select one of the terminals and store the identifier of the selected terminal. For example, the network device may manage a data structure for recording the identifier of the selected terminal. The data structure may be stored in a storage device (or memory) within the network device or a storage device external to the network device and may be managed by the network device. Thereafter, when step (605) is performed again, the network device may select a terminal that has not yet been selected based on the stored identifier.

[0125] In one embodiment of the present disclosure, the network device can identify (606) whether the first cell is configured as a PCell or an SCell for the selected terminal in step (605). For example, the network device can obtain information indicating whether the first cell is the PCell or the SCell of the selected terminal from the MAC scheduler, and based on the obtained information, identify whether the PCell of the selected terminal is the first cell.

[0126] In one embodiment of the present disclosure, the network device may switch a path for the PCell between the RLC entity and the MAC entity of the selected terminal based on the first cell being set as the PCell for the selected terminal in step (605) (607). For example, the network device may switch a path for the PCell between the RLC entity and the MAC entity of the selected terminal (e.g., an 'RLC-MAC PCell path') to a path between the RLC entity and the MAC entity of the second DU. When the PCell of a terminal is the first cell, the PCell data path between the RLC entity and the MAC entity of the terminal may be a path for communication between the RLC entity of the first DU and the MAC entity of the first DU via the PCell of the terminal, as illustrated in FIGS. 4A and 4B . Accordingly, the network device can switch the path between the RLC entity (241) of the first DU of the corresponding terminal and the MAC entity (242) of the first DU. For example, the network device can switch the path for the PCell between the RLC entity of the first DU of the selected terminal and the MAC entity of the first DU so as to be connected between the RLC entity of the first DU and the MAC entity of the second DU. Accordingly, the MAC endpoint of the PCell path between the RLC entity and the MAC entity of the selected terminal can be switched from the first DU to the second DU.

[0127] In one embodiment of the present disclosure, the network device may switch a path for an SCell between an RLC entity and a MAC entity of a selected terminal (608) based on the fact that the first cell is set as a PCell for the selected terminal in step (605). As illustrated in FIGS. 4A and 4B , when an SCell of a terminal is a first cell, an SCell data path between an RLC entity and a MAC entity of the terminal may be a path for communication via the SCell of the terminal between the RLC entity of the first DU and the MAC entity of the first DU (or a path for communication via the SCell of the terminal between the RLC entity of one source DU and the MAC entity of another source DU). For example, in the embodiment of FIG. 4a, when a cell (431) is transferred from a source DU (i.e., DU (420a)) to a separate DU (target DU), the SCell path between the RLC entity and the MAC entity of the UE (442) whose SCell the cell (431) is, may be the SCell path (i.e., the dotted line path) between the RLC entity (421a) and the MAC entity (422a) of the DU (420a). For example, in the embodiment of FIG. 4b, when a cell (441) is transferred from source DUs (i.e., DUs (421b, 422b)) to a separate DU (target DU), the SCell data path between the RLC entity and the MAC entity of the UE (442) whose SCell the cell (441) is, may be the SCell path (i.e., the dotted line path) between the RLC entity (421b_1) of the second source DU (421b) and the MAC entity (422b_1) of the first source DU (422b).

[0128] In step (608), therefore, the network device may switch the SCell data path (e.g., 'RLC-MAC SCell path') between the RLC entity of the first DU of the selected terminal and the MAC entity of the first DU (or another source DU). For example, the network device may switch the path for communication via the SCell between the RLC entity of the first DU and the MAC entity of the first DU to be connected between the RLC entity of the first DU and the MAC entity of the second DU. Accordingly, the MAC endpoint of the SCell path between the RLC entity and the MAC entity of the selected terminal may be switched from the first DU to the second DU.

[0129] In one embodiment of the present disclosure, the network device can identify whether there is a terminal to be transferred to a second DU among the terminals of the first cell connected to the MAC entity of the first DU (609). In one embodiment of the present disclosure, the network device can identify whether the terminal selected in step (606) is the last terminal based on the determined transfer order. Based on the fact that the terminal selected in step (606) is not the last terminal, the network device can identify whether there is a terminal to be transferred to a second DU among the terminals of the first cell connected to the MAC entity of the first DU, and can perform step (606) again to select the next terminal among the terminals attached to the first cell. Based on the determined transfer order, steps (606 to 608) can be iterated. Based on the determined transfer order, in step (609), the network device can identify whether the iteration of the terminals has ended. For example, the network device can identify that the repetition of terminals has ended based on the terminal selected in the previous step (606) being the last terminal.

[0130] In one embodiment of the present disclosure, identifiers may be assigned to terminals. The network device may assign a unique identifier to the terminals for selection, or may use an identifier already assigned to the terminals as an identifier for selection. The network device may identify whether there is a UE that has not yet been selected based on the identifiers of the terminals. Based on the remaining UEs that have not yet been selected, the network device may identify whether there is a terminal among the terminals of the first cell connected to the MAC entity of the first DU that is to be transferred to the second DU, and may perform step (606) again to select one of the one or more terminals that have not yet been selected. Based on the fact that there are no UEs that have not yet been selected, the network device may identify whether there is no terminal among the terminals of the first cell connected to the MAC entity of the first DU that is to be transferred to the second DU, and may perform step (610).

[0131] In one embodiment of the present disclosure, the network device can identify whether there is a terminal among the terminals of the first cell that does not have a connected path between an RLC entity of any activated DU in the DU pool (e.g., an RLC entity of the first DU, or an RLC entity of another activated DU) and a MAC entity of a second DU. Based on whether there remains a terminal among the terminals of the first cell connected to the MAC entity of the first DU that does not have a connected path between the RLC entity of any activated DU in the DU pool and the MAC entity of the second DU, or based on whether at least one terminal attached to the first cell is not capable of communicating with the CU via the first cell through at least one path between an RLC entity of any one of the DUs capable of communicating with the CU and the MAC entity of the second DU, the network device can identify whether there is a terminal among the terminals of the first cell that is to migrate to the second DU, and perform network device steps (605 to 609) again. Based on the fact that no terminal remains in the first cell without a path connected between the RLC entity of any activated DU in the DU pool and the MAC entity of the second DU, or based on the fact that all terminals attached to the first cell can communicate with the CU via the first cell through at least one path between the RLC entity of any one of the DUs capable of communicating with the CU and the MAC entity of the second DU, the network device can identify that no terminal exists among the terminals of the first cell connected to the MAC entity of the first DU to move to the second DU, and perform step (610).

[0132] Through steps (605 to 608), for all terminals attached to the first cell, it is identified whether the PCell of each terminal is set to the first cell, and based on the identification, either the PCell path or the SCell path of each terminal can be switched. Thereafter, in one embodiment of the present disclosure, the network device can resume MAC scheduling of the first cell (610). For example, based on the fact that no terminal remains among the terminals of the first cell that has a path connected between the RLC entity of any activated DU in the DU pool and the MAC entity of the second DU, the network device can resume MAC scheduling of the second DU for the first cell. For example, based on the fact that all terminals attached to the first cell can communicate with the CU via the first cell through at least one data path connected between an RLC entity of an activated DU in the DU pool and a MAC entity of the second DU, the network device can control the MAC scheduler of the second DU to resume MAC scheduling for the first cell of the second DU. If identifiers for selection are assigned to UEs, the network device can reset or erase memory for the selected identifiers.

[0133] According to steps (602 to 610), paths for the PCells of UEs whose target cells are configured as PCells between the RLC entity of the source DU (or any DU among the source DUs) and the MAC entity of the source DU may be switched to paths between the RLC entity of the source DU and the MAC entity of the target DU. For example, paths for the PCells of UEs whose target cells are configured as PCells may be switched from the 'RLC of the source DU - MAC of the source DU' path to the 'RLC of the source DU - MAC of the target DU' path. According to steps (602 to 610), paths for the SCells of UEs whose target cells are configured as SCells between the RLC entity of the source DU and the MAC entity of the source DU may be switched to paths between the RLC entity of the source DU and the MAC entity of the target DU. For example, the paths for SCells of UEs whose target cell is set as SCell can be switched from the 'RLC of source DU - MAC of source DU' path to the 'RLC of source DU - MAC of target DU' path.

[0134] In one embodiment of the present disclosure, the network device may set an RLC context of the first DU for the second DU (611). The RLC context may include cell configuration information included in an RLC entity. The network device may transfer the RLC context included in the RLC entity of the first DU (or at least one of the multiple source DUs) to the RLC entity of the second DU.

[0135] In one embodiment of the present disclosure, the network device may select a terminal to be transferred to a second DU from among the terminals of the first cell connected to the RLC entity of the first DU (612). For example, the network device may select one terminal to be transferred to the RLC entity of the second DU from among the terminals attached to the first cell connected to the RLC entity of the first DU. For example, the network device may perform step (612) in a manner similar to performing step (606). In one embodiment of the present disclosure, the order for transferring the terminals attached to the first cell may be predetermined, but the transfer order of the terminals for performing step (606) and the transfer order of the terminals for performing step (612) may be the same as or different from each other. In one embodiment of the present disclosure, unique identifiers of terminals may be used for terminal selection, but the identifiers of terminals used in step (606) and the identifiers of terminals used in step (612) may be the same or different from each other.

[0136] In one embodiment of the present disclosure, the network device can identify whether the first cell is configured as a PCell or an SCell for the terminal selected in step (612) (613). The network device can obtain information indicating whether the first cell is the PCell or SCell of the selected terminal from the MAC scheduler in a similar manner as in step (606), and can identify whether the PCell of the selected terminal is the first cell based on the obtained information. Based on whether the first cell is configured as the PCell of the selected terminal, the network device can perform steps (614 to 616). Based on whether the first cell is configured as the PCell of the selected terminal, the network device can perform step (617) without switching (changing) the path for the selected terminal any further.

[0137] In one embodiment of the present disclosure, the network device may perform steps (614 to 616) based on the first cell being set as the PCell of the terminal selected in step (613). The network device may set an RLC UE context for the selected terminal in the second DU (614). For example, the network device may transfer context information of the selected terminal associated with the RLC entity of the first DU to the RLC entity of the second DU.

[0138] In one embodiment of the present disclosure, based on the first cell being set as the PCell of the terminal selected in step (613), the network device may switch the midhaul path of the second DU (615). For example, the network device may switch the midhaul path between the first DU and the CU for the selected terminal to be connected between the second DU and the CU. Accordingly, the path between the CU and the RLC entity of the first DU may be switched to the path between the CU and the RLC entity of the second DU.

[0139] In one embodiment of the present disclosure, based on the first cell being set as the PCell of the selected terminal in step (613), the network device may switch the PCell path and the SCell path between the RLC entity and the MAC entity for the selected terminal (616). For example, the network device may switch the PCell data path of the selected terminal, which is connected between the RLC entity of the first DU and the MAC entity of the second DU, which is switched in step (607), to be connected between the RLC entity of the second DU and the MAC entity of the second DU. The network device may switch the SCell data path of the selected terminal, which is connected between the RLC entity of the first DU and the MAC entity of the first DU (or another source DU), to be connected between the RLC entity of the second DU and the MAC entity of the first DU.

[0140] In one embodiment of the present disclosure, the network device can identify whether there is a terminal to be transferred to the second DU among the terminals of the first cell connected to the RLC entity of the first DU (617). For example, the network device can identify whether the terminal selected in step (612) is the last terminal in the determined transfer order. For example, the network device can identify whether there are any terminals that have not been selected yet, based on the identifiers of the terminals. For example, the network device can identify whether there are any terminals connected to the RLC entity of the first DU among the terminals for which the first cell is configured as the PCell. For example, the network device can identify whether there are any terminals for which the first cell is configured as the PCell, the midhaul path of which is connected between the RLC entity and the CU of the first DU.

[0141] Based on whether there is a terminal to be transferred to the second DU among the terminals of the first cell connected to the RLC entity of the first DU, the network device may perform steps (612 to 617) again. For example, based on whether the terminal selected in step (612) is not the last terminal in the determined previous order or whether there are any unselected terminals remaining, the network device may identify whether there is (or is not) a terminal connected to the RLC entity of the first DU and perform steps (612 to 617) again. For example, based on whether the terminal selected in step (612) is the last terminal in the determined previous order or whether there are no unselected terminals remaining, the network device may identify whether there is (or is not) a terminal to be transferred to the second DU among the terminals connected to the RLC entity of the first DU and terminate the method (600).

[0142] According to steps (611 to 617), paths for the PCells of UEs whose target cells are configured as PCells between the RLC entity of the source DU and the MAC entity of the target DU may be switched to paths between the RLC entity of the target DU and the MAC entity of the target DU. For example, paths for the PCells of UEs whose target cells are configured as PCells may be switched from the 'RLC of the source DU - MAC of the target DU' path to the 'RLC of the target DU - MAC of the target DU' path. According to steps (611 to 617), paths for the SCells of UEs whose target cells are configured as SCells between the RLC entity of the source DU and the MAC entity of the source DU may be switched to paths between the RLC entity of the target DU and the MAC entity of the source DU. For example, paths for SCells of UEs whose target cell is set as PCell can be switched from the 'RLC of source DU - MAC of source DU' path to the 'RLC of target DU - MAC of source DU' path.

[0143] FIGS. 7A to 7C illustrate data flow in a user plane due to scaling out a first DU to a second DU by a network device according to an embodiment of the present disclosure. FIGS. 7A to 7C illustrate time-dependent changes in data flow due to migration of a cell (731) from a DU (721) to a DU (722) in a RAN system (700) implemented based on the intra-DU CA scenario illustrated in FIG. 4A. In the embodiment of FIGS. 7A to 7C, the DU (721) may be understood as a source DU or a first DU, the DU (722) may be understood as a target DU or a second DU, and the cell (731) may be understood as a target cell or a first cell. In the embodiment illustrated in FIG. 7a, the RAN system (700) can support carrier aggregation of cells (731) and (732), in a similar manner to the RAN system (400a) of FIG. 4a. For convenience of illustration, only two cells (731, 732) are illustrated in FIG. 7a, but the number of carrier-aggregated cells is not limited thereto.

[0144] A network device (e.g., an OAM module) that manages and maintains the RAN system (700) may determine whether to migrate a cell (731) from a DU (721) to a DU (722). For example, the network device may determine to scale out the DU (721) to a previously non-existent or inactive DU (722). The determination to scale out may include determining to migrate a cell (731) associated with the DU (721) to the DU (722). Based on the determination to scale out, the network device may determine a scaling situation for the scale out and may notify the network device (e.g., a scale agent) that manages scaling of the DU of the RAN system (700) of the determined scaling situation and a request for scale-out. The network device that manages and maintains the RAN system may initiate the DU (722).

[0145] A network device managing scaling of a DU of a RAN system (700) may identify a scaling situation as scale-out. Based on identifying the scaling situation as scale-out, the network device may transfer the cell context of a cell (731) included in a DU (721) from the DU (721) to the DU (722). For example, the network device may transfer the cell context of a cell (731) from the DU (721) to the DU (722) in a manner similar to step (601). Through the transfer of the cell context, the configuration of the cell (731) or the cell configuration information of the cell (731) may be set in the DU (722). FIG. 7A may illustrate a data flow of a RAN system (700) after a network device of the RAN system (700) performs step (601) of the method (600) of FIG.

[0146] The network device may transfer the MAC context of the cell (731) associated with the MAC / PHY entity (721_2) of the DU (721) to the MAC / PHY entity (722_2) of the DU (722) in a manner similar to step (602). The network device may stop MAC scheduling for the cell (731) of the DU (721) in a manner similar to step (603). The network device may switch the fronthaul path for the cell (731) in a manner similar to step (604). For example, the network device may switch the fronthaul path connected between the RU to which the cell (731) is connected and the MAC / PHY entity (721_2) of the DU (721) to the path between the RU to which the cell (731) is connected and the MAC / PHY entity (722_2) of the DU (722_2). Accordingly, the 'UE 1 PCell path' between the cell (731) and the MAC / PHY entity (721_2) of FIG. 7a can be switched to the 'UE 1 PCell path' between the cell (731) and the MAC / PHY entity (722_2) of FIG. 7b. Similarly, the 'UE 2 SCell path' between the cell (731) and the MAC / PHY entity (721_2) of FIG. 7a can be switched to the 'UE 2 SCell path' between the cell (731) and the MAC / PHY entity (722_2) of FIG. 7b.

[0147] The network device may select one of the UEs (741, 742) attached to the cell (731) in a manner similar to step (605). For example, the network device may select the UE (741) based on a predetermined previous order or randomly. The network device may identify whether the cell (731) is configured as a PCell or an SCell for the UE (741) in a manner similar to step (606). Based on the fact that the PCell of the UE (741) is configured as the cell (731) corresponding to the component carrier 'CC1', the network device may switch a path for the PCell between the RLC entity and the MAC entity of the UE (741) in a manner similar to step (607). In the embodiment of FIG. 7a, the path for the PCell between the RLC entity and the MAC entity of the UE (741) may be a 'UE 1 PCell path' between the RLC entity (721_1) and the MAC / PHY entity (721_2). The network device may switch the 'UE 1 PCell path' between the RLC entity (721_1) and the MAC / PHY entity (721_2) to a path between the RLC entity (721_2) and the MAC / PHY entity (722_2). Accordingly, the 'UE 1 PCell path' between the RLC entity (721_1) and the MAC / PHY entity (721_2) of FIG. 7a may be switched to the 'UE 1 PCell path' between the RLC entity (721_1) and the MAC / PHY entity (722_2) of the DU (722) of FIG. 7b.

[0148] The network device can identify whether there is a UE among the UEs (741, 742) of the cell (731) that needs to be migrated to the DU (722). For example, the network device can identify whether there is a UE among the UEs (741, 742) of the cell (731) that needs to be migrated to the DU (722) in a manner similar to step (609). The network device can identify that the UE (742) needs to be migrated to the DU (722), and therefore, can reselect the UE (742) to be migrated to the DU (722) of the cell (731) in a manner similar to step (605).

[0149] The network device can identify whether the cell (731) is configured as a PCell or an SCell for the selected UE (742), in a manner similar to step (606). Based on the SCell of the UE (742) being configured as the cell (731) corresponding to the component carrier 'CC1', the network device can switch the path for the SCell between the RLC entity and the MAC entity of the UE (742), in a manner similar to step (608). In the embodiment of FIG. 7A, the path for the SCell between the RLC entity and the MAC entity of the UE (742) may be the 'UE 2 SCell path' between the RLC entity (721_1) and the MAC / PHY entity (721_2). The network device can switch the 'UE 2 SCell path' between the RLC entity (721_1) and the MAC / PHY entity (721_2) to the path between the RLC entity (721_2) and the MAC / PHY entity (722_2). Accordingly, the 'UE 2 SCell path' between the RLC entity (721_1) and the MAC / PHY entity (721_2) of FIG. 7a can be switched to the 'UE 2 SCell path' between the RLC entity (722_1) and the MAC / PHY entity (722_2) of the DU (722) of FIG. 7b.

[0150] The network device can identify whether there is a UE among the UEs (741, 742) of the cell (731) that needs to be transferred to the DU (722) in a manner similar to step (609). For example, the network device can identify whether there is a UE among the UEs (741, 742) of the cell (731) that needs to be transferred to the DU (722) based on the manner described above in step (609).

[0151] In the embodiment of FIG. 7B, all of the UEs (741, 742) of the cell (731) may have been selected once to identify whether the cell (731) is configured as the PCell for the selected UE. Alternatively, since the path between the RLC entity and the MAC entity of each of the UEs (741, 742) of the cell (731) has been switched, all of the UEs (741, 742) of the cell (731) may have a path connected between the RLC entity (721_1) of the DU (721) and the MAC / PHY entity (722_2) of the DU (722). Alternatively, all of the UEs (741, 742) of the cell (731) can communicate with the CU via the cell (731) via a path between the RLC entity of any DU in the DU pool (in the embodiment of FIG. 7B, the RLC entity (722_1) of the DU (721)) and the MAC / PHY entity (722_2) of the DU (722). Accordingly, the network device can identify that there is no UE among the UEs (741, 742) of the cell (731) to be transferred to the DU (722). Based on identifying that there is no UE to be transferred to the DU (722), the network device can resume MAC scheduling for the cell (731) in a manner similar to step (610). For example, the network device may control (or command) the MAC / PHY entity (722_2) of the DU (722) to initiate MAC scheduling for the cell (731).

[0152] FIG. 7B may illustrate the data flow of the RAN system (700) after the network device of the RAN system (700) of FIG. 7A performs steps (602 to 610) of the method (600) of FIG. 6. Comparing FIG. 7A and FIG. 7B, the 'UE 1 PCell path' between the RLC entity (721_1) of the DU (721) and the MAC entity (721_2) of the DU (721) of FIG. 7A may be switched to the 'UE 1 PCell path' between the RLC entity (721_1) of the DU (721) and the MAC entity (722_2) of the DU (722) of FIG. 7B. The 'UE 2 SCell path' between the RLC entity (721_1) of the DU (721) and the MAC entity (721_2) of the DU (721) in FIG. 7a can be switched to the 'UE 2 SCell path' between the RLC entity (721_1) of the DU (721) and the MAC entity (722_2) of the DU (722) in FIG. 7b.

[0153] The network device may set an RLC context of the DU (721) for the DU (722) in a manner similar to step (611). The network device may select a UE to be transferred to the DU (722) from among the UEs (741, 742) of the cell (731) connected to the RLC entity (721_1) of the DU (721) in a manner similar to step (612). For example, the network device may select the UE (741) as the UE to be transferred. The network device may identify whether the cell (731) is configured as a PCell or an SCell for the UE (741) in a manner similar to step (613). Based on the fact that the PCell of the UE (741) is set to the cell (731) corresponding to the component carrier 'CC1', the network device may set an RLC UE context for the UE (741) in the RLC entity (722_2) of the DU (722) in a manner similar to step (614). The network device may switch the midhaul path (P1) for the UE (741) between the DU (721) and the CU (710) to a path between the RLC entity (722_1) of the DU (722) and the CU (710) in a manner similar to step (615).

[0154] The network device may switch the path for the PCell and the path for the SCell between the RLC entity and the MAC entity of the UE (741) in a similar manner to step (616). For example, the network device may switch the 'UE 1 PCell path' between the RLC entity (721_1) of the DU (721) and the MAC / PHY entity (722_2) of the DU (722), as shown in FIG. 7b, to between the RLC entity (722_1) of the DU (722) and the MAC / PHY entity (722_2) of the DU (722). The network device can switch the 'UE 1 SCell path' between the RLC entity (721_1) of the DU (721) and the MAC / PHY entity (721_2) of the DU (721), as shown in FIG. 7b, to between the RLC entity (722_1) of the DU (722) and the MAC / PHY entity (721_2) of the DU (721). Accordingly, the 'UE 1 PCell path' between the RLC entity (721_1) and the MAC / PHY entity (722_2) of FIG. 7b can be switched to the 'UE 1 PCell path' between the RLC entity (722_1) and the MAC / PHY entity (722_2) of the DU (722) as shown in FIG. 7c. The 'UE 1 SCell path' between the RLC entity (721_1) and the MAC / PHY entity (721_2) of FIG. 7b can be switched to the 'UE 1 SCell path' between the RLC entity (722_1) of the DU (722) and the MAC / PHY entity (721_2) of the DU (721) of FIG. 7c.

[0155] The network device can identify whether there is (or remains) a UE to be migrated to the RLC entity (722_1) of the DU (722) among the UEs (741, 742) of the cell (731) in a manner similar to step (617). The network device can identify that the UE (742) among the UEs (741, 742) of the cell (731) should be migrated to the RLC entity (722_1) of the DU (722), and select the UE (742) as the UE to be migrated to the DU (722) of the cell (731) in a manner similar to step (612).

[0156] The network device can identify whether the cell (731) is configured as a PCell or an SCell for the selected UE (742), in a manner similar to step (613). Based on the SCell of the UE (742) being configured as the cell (731) corresponding to the component carrier 'CC1', the network device can, without switching the path for the UE (742), identify again whether there is (or remains) a UE to be migrated to the RLC entity (722_1) of the DU (722) among the UEs (741, 742) of the cell (731), in a manner similar to step (617). Based on the fact that all the UEs (741, 742) of the cell (731) have been selected once, the network device can identify that there is no UE to be migrated to the RLC entity (722_1) of the DU (722), and terminate scaling.

[0157] FIG. 7c may illustrate the data flow of the RAN system (700) after the network device of the RAN system (700) of FIG. 7b performs steps (611 to 617) of the method (600) of FIG. 6. Comparing FIG. 7b and FIG. 7c, the 'UE 1 PCell path' between the RLC entity (721_1) of the DU (721) of FIG. 7b and the MAC entity (722_2) of the DU (722) may be switched to the 'UE 1 PCell path' between the RLC entity (722_1) of the DU (722) of FIG. 7c and the MAC entity (722_2) of the DU (722). The 'UE 1 SCell path' between the RLC entity (721_1) of the DU (721) in FIG. 7b and the MAC entity (721_2) of the DU (721) can be switched to the 'UE 1 SCell path' between the RLC entity (722_1) of the DU (722) in FIG. 7c and the MAC entity (721_2) of the DU (721).

[0158] Comparing FIGS. 7A and 7C, the cells (731) and (732) in FIG. 7A were processed by a single DU (721), but through scaling out, the cells (731) and (732) in FIG. 7C can be processed together by multiple DUs (721, 722). Therefore, in one embodiment of the present disclosure, the RAN system (700) in FIG. 7A according to the intra-DU CA scenario can be changed to follow the inter-DU CA scenario, as illustrated in FIG. 7C, after scaling out by adding a second DU.

[0159] FIGS. 8A to 8C illustrate data flow in a user plane due to scaling out a first DU to a second DU by a network device according to an embodiment of the present disclosure. FIGS. 8A to 8C illustrate time-dependent changes in data flow due to migration of a cell (831) from a DU (821) to a DU (822) in a RAN system (800) implemented based on the inter-DU CA scenario illustrated in FIG. 4B. In the embodiment of FIGS. 8A to 8C, the DU (821) may be understood as a source DU or a first source DU or a first DU, the DU (822) may be understood as a target DU or a second DU, the DU (823) may be understood as another source DU or a second source DU or a third DU, and the cell (831) may be understood as a target cell or a first cell. In the embodiment illustrated in FIG. 8a, the RAN system (800) can support carrier aggregation of cells (831) and (832), in a similar manner to the RAN system (400b) of FIG. 4b. For convenience of illustration, only two cells (731, 732) and two source DUs (821, 823) are illustrated in FIG. 8a, but the number of carrier-aggregated cells and the number of source DUs are not limited thereto.

[0160] A network device (e.g., an OAM module) that manages and maintains the RAN system (800) may determine whether to migrate a cell (831) from a DU (821) to a DU (822). For example, the network device may determine to scale out the DU (821) to a previously non-existent or inactive DU (822). The determination to scale out may include determining to migrate a cell (831) associated with the DU (821) to the DU (822). Based on the determination to scale out, the network device may determine a scaling situation for the scale out and may notify the network device (e.g., a scale agent) that manages scaling of the DU of the RAN system (800) of the determined scaling situation and a request for scale-out. The network device that manages and maintains the RAN system may initiate the DU (822).

[0161] A network device managing scaling of a DU of a RAN system (800) may identify a scaling situation as scale-out. Based on identifying the scaling situation as scale-out, the network device may transfer a cell context of a cell (831) included in at least one of a DU (821) or a DU (823) from at least one of the DU (821) or the DU (823) to a DU (822). For example, the network device may transfer the cell context of a cell (831) included in a DU (821) from the DU (821) to the DU (822), and / or transfer the cell context of a cell (831) included in a DU (821) from the DU (821) to the DU (822), in a manner similar to step (601). Through the transfer of the cell context, the configuration of the cell (831) or the cell configuration information of the cell (831) may be set in the DU (822). FIG. 8a may illustrate the data flow of the RAN system (800) after the network device of the RAN system (800) performs step (601) of the method (600) of FIG. 6.

[0162] The network device may transfer at least one of the MAC context of the cell (831) associated with the MAC / PHY entity (821_2) of the DU (821) or the MAC context of the cell (831) associated with the MAC / PHY entity (831_2) of the DU (821) to the MAC / PHY entity (822_2) of the DU (822), in a manner similar to step (602). The network device may stop MAC scheduling for the cell (831) of the DU (821), in a manner similar to step (603). The network device may switch the fronthaul path for the cell (831), in a manner similar to step (604). For example, the network device can switch the fronthaul path connected between the RU to which the cell (831) is connected and the MAC / PHY entity (821_2) of the DU (821) to the path between the RU to which the cell (831) is connected and the MAC / PHY entity (822_2) of the DU (822). Accordingly, the 'UE 1 PCell path' between the cell (831) and the MAC / PHY entity (821_2) of FIG. 8A can be switched to the 'UE 1 PCell path' between the cell (831) and the MAC / PHY entity (822_2) of FIG. 8B. Similarly, the 'UE 2 SCell path' between the cell (831) and the MAC / PHY entity (821_2) of FIG. 8A can be switched to the 'UE 2 SCell path' between the cell (831) and the MAC / PHY entity (822_2) of FIG. 8B.

[0163] The network device may select one of the UEs (841, 842) attached to the cell (831) in a manner similar to step (605). For example, the network device may select the UE (841) based on a predetermined previous order or randomly. The network device may identify whether the cell (831) is configured as a PCell or an SCell for the UE (841) in a manner similar to step (606). Based on the fact that the PCell of the UE (841) is configured as the cell (831) corresponding to the component carrier 'CC1', the network device may switch a path for the PCell between the RLC entity and the MAC entity of the UE (841) in a manner similar to step (607). In the embodiment of FIG. 8A, the path for the PCell between the RLC entity and the MAC entity of the UE (841) may be a 'UE 1 PCell path' between the RLC entity (821_1) of the DU (823) and the MAC / PHY entity (821_2) of the DU (821). The network device may switch the 'UE 1 PCell path' between the RLC entity (821_1) and the MAC / PHY entity (821_2) to a path between the RLC entity (821_1) and the MAC / PHY entity (822_2). Accordingly, the 'UE 1 PCell path' between the RLC entity (821_1) and the MAC / PHY entity (821_2) of FIG. 8a can be switched to the 'UE 1 PCell path' between the RLC entity (821_1) and the MAC / PHY entity (822_2) of the DU (822) of FIG. 8b.

[0164] The network device can identify whether there is a UE among the UEs (841, 842) of the cell (831) that needs to be migrated to the DU (822). For example, the network device can identify whether there is a UE among the UEs (841, 842) of the cell (831) that needs to be migrated to the DU (822) in a manner similar to step (609). The network device can identify that the UE (842) needs to be migrated to the DU (822), and therefore, can reselect the UE (842) to be migrated to the DU (822) of the cell (831) in a manner similar to step (605).

[0165] The network device can identify whether the cell (831) is configured as a PCell or an SCell for the selected UE (842), in a manner similar to step (606). Based on the SCell of the UE (842) being configured as the cell (831) corresponding to the component carrier 'CC1', the network device can switch the path for the SCell between the RLC entity and the MAC entity of the UE (842), in a manner similar to step (608). In the embodiment of FIG. 8A, the path for the SCell between the RLC entity and the MAC entity of the UE (842) may be a 'UE 2 SCell path' between the RLC entity (823_1) of the DU (823) and the MAC / PHY entity (821_2) of the DU (821). The network device can switch the 'UE 2 SCell path' between the RLC entity (823_1) and the MAC / PHY entity (821_2) to the path between the RLC entity (823_2) and the MAC / PHY entity (822_2). Accordingly, the 'UE 2 SCell path' between the RLC entity (823_1) and the MAC / PHY entity (821_2) of the DU (821) of FIG. 8a can be switched to the 'UE 2 SCell path' between the RLC entity (823_1) of the DU (823) and the MAC / PHY entity (821_2) of the DU (821) of FIG. 8ㅠ.

[0166] The network device can identify whether there is a UE among the UEs (841, 842) of the cell (831) that is to be transferred to the DU (822) in a manner similar to step (609). For example, the network device can identify whether there is a UE among the UEs (841, 842) of the cell (831) that is to be transferred to the DU (822) based on the manner described above in step (609). Based on identifying that there is no UE that is to be transferred to the DU (822), the network device can resume MAC scheduling for the cell (831) in a manner similar to step (610). For example, the network device can control (or command) the MAC / PHY entity (822_2) of the DU (822) to start MAC scheduling for the cell (831).

[0167] FIG. 8B may illustrate the data flow of the RAN system (800) after the network device of the RAN system (800) of FIG. 8A performs steps (602 to 610) of the method (600) of FIG. 6. Comparing FIG. 8A and FIG. 8B, the 'UE 1 PCell path' between the RLC entity (821_1) of the DU (821) and the MAC / PHY entity (821_2) of the DU (821) of FIG. 8A may be switched to the 'UE 1 PCell path' between the RLC entity (821_1) of the DU (821) and the MAC entity (822_2) of the DU (822) of FIG. 8B. The 'UE 2 SCell path' between the RLC entity (823_1) of the DU (823) and the MAC / PHY entity (821_2) of the DU (821) in FIG. 8a can be switched to the 'UE 2 SCell path' between the RLC entity (821_3) of the DU (823) and the MAC entity (822_2) of the DU (822) in FIG. 8b.

[0168] The network device may set an RLC context for the DU (822) in at least one RLC entity of the DU (821) or the DU (832), in a manner similar to step (611). The network device may select a UE to be transferred to the DU (822) from among the UEs (841, 842) of the cell (831) connected to the RLC entity (821_1) of the DU (821), in a manner similar to step (612). For example, the network device may select the UE (841) as the UE to be transferred. The network device may identify, in a manner similar to step (613), whether the cell (831) is configured as a PCell or an SCell for the UE (841). Based on the fact that the PCell of the UE (841) is set to the cell (831) corresponding to the component carrier 'CC1', the network device may set an RLC UE context for the UE (841) in the RLC entity (822_2) of the DU (822) in a manner similar to step (614). The network device may switch the midhaul path (P1) for the UE (841) between the DU (821) and the CU (810) to a path between the RLC entity (822_1) of the DU (822) and the CU (810) in a manner similar to step (615).

[0169] The network device may switch the path for the PCell and the path for the SCell between the RLC entity and the MAC entity of the UE (841) in a similar manner to step (616). For example, the network device may switch the 'UE 1 PCell path' between the RLC entity (821_1) of the DU (821) and the MAC / PHY entity (822_2) of the DU (822), as shown in FIG. 8b, to between the RLC entity (822_1) of the DU (822) and the MAC / PHY entity (822_2) of the DU (822). The network device can switch the 'UE 1 SCell path' between the RLC entity (821_1) of the DU (821) and the MAC / PHY entity (823_2) of the DU (823), as shown in FIG. 8b, to between the RLC entity (822_1) of the DU (822) and the MAC / PHY entity (823_2) of the DU (823). Accordingly, the 'UE 1 PCell path' between the RLC entity (821_1) and the MAC / PHY entity (822_2) of FIG. 8b can be switched to the 'UE 1 PCell path' between the RLC entity (822_1) and the MAC / PHY entity (822_2) of the DU (822) as shown in FIG. 8c. The 'UE 1 SCell path' between the RLC entity (821_1) and the MAC / PHY entity (823_2) of FIG. 8b can be switched to the 'UE 1 SCell path' between the RLC entity (822_1) of the DU (822) and the MAC / PHY entity (823_2) of the DU (823) of FIG. 8c.

[0170] The network device can identify whether there is (or remains) a UE to be migrated to the RLC entity (822_1) of the DU (822) among the UEs (841, 842) of the cell (831) in a manner similar to step (617). The network device can identify which UE (842) among the UEs (841, 842) of the cell (831) should be migrated to the RLC entity (822_1) of the DU (822), and select the UE (842) as the UE to be migrated to the DU (822) of the cell (831) in a manner similar to step (612).

[0171] The network device can identify whether the cell (831) is configured as a PCell or an SCell for the selected UE (842), in a manner similar to step (613). Based on the SCell of the UE (842) being configured as the cell (831) corresponding to the component carrier 'CC1', the network device can, without switching the path for the UE (842), identify again whether there is (or remains) a UE to be migrated to the RLC entity (822_1) of the DU (822) among the UEs (841, 842) of the cell (831), in a manner similar to step (617). Based on the fact that all the UEs (841, 842) of the cell (831) have been selected once, the network device can identify that there is no UE to be migrated to the RLC entity (822_1) of the DU (822), and terminate scaling.

[0172] FIG. 8C may illustrate the data flow of the RAN system (800) after the network device of the RAN system (800) of FIG. 8B performs steps (611 to 617) of the method (600) of FIG. 6. Comparing FIG. 8B and FIG. 8C, the 'UE 1 PCell path' between the RLC entity (821_1) of the DU (821) of FIG. 8B and the MAC entity (822_2) of the DU (822) may be switched to the 'UE 1 PCell path' between the RLC entity (822_1) of the DU (822) of FIG. 8C and the MAC entity (822_2) of the DU (822). The 'UE 1 SCell path' between the RLC entity (821_1) of the DU (821) in FIG. 8b and the MAC entity (823_2) of the DU (823) can be switched to the 'UE 1 SCell path' between the RLC entity (822_1) of the DU (822) in FIG. 8c and the MAC entity (823_2) of the DU (823).

[0173] Comparing FIGS. 8A and 8C, the cell (831) and the cell (832) of FIG. 8A were processed together by multiple DUs (821, 823), but through scaling out, the cell (831) and the cell (832) of FIG. 8A can be processed together by multiple DUs (822, 823). Therefore, in one embodiment of the present disclosure, the RAN system (800) of FIG. 8A according to the inter-DU CA scenario can still follow the inter-DU CA scenario, as illustrated in FIG. 8C, even after scaling out by adding a second DU.

[0174] FIG. 9 is an exemplary flowchart illustrating a method for scaling in a first DU to a second DU by a network device according to an embodiment of the present disclosure. Referring to FIG. 9 , the method (900) may include steps (901 to 916). The method (900) may be performed by the network device of FIG. 2 . For example, the network device may perform the method (900) based on identifying a scaling situation as a scale-in. The method (900) may be a method for transferring a first cell from a first DU to a second DU (which was previously communicating with the first cell). The method (900) may be a method for transferring a first cell being processed by a first DU to a second DU in order to use the second DU instead of the first DU or to remove the first DU from a DU pool. In one embodiment of the present disclosure, steps (901 to 916) of the method (900) may be executed by at least one processor included in an electronic device. The method (900) is not limited to that illustrated in FIG. 9 , and in one or more embodiments, the method (900) may further include steps not illustrated in FIG. 9 , or some of the steps in FIG. 9 may be omitted from the method (900).

[0175] In one embodiment of the present disclosure, the second DU may be a DU that was previously communicating with the first cell. Therefore, the second DU may already include the cell context of the first cell. In this embodiment, in method (900), unlike method (600) of FIG. 6, transferring the cell context of the first cell included in the first DU to the second DU may be omitted.

[0176] In one embodiment of the present disclosure, the network device may transfer a MAC context of a first cell associated with a MAC entity of a first DU to a MAC entity of a second DU (901). For example, the network device may transfer or copy a MAC context for a first cell, included in at least one of a MAC entity and a PHY entity of the first DU (or at least one of multiple source DUs), to a corresponding entity of the second DU, in a manner similar to step (602) of FIG. 6 .

[0177] In one embodiment of the present disclosure, the network device may suspend MAC scheduling of the first cell (902). For example, the network device may at least partially suspend MAC scheduling of the first DU in a manner similar to step (603) of FIG. 6 .

[0178] In one embodiment of the present disclosure, the network device may switch the fronthaul path for the first cell (903). For example, the network device may switch (or change) the fronthaul path connected between the first DU and the RU including the first cell to be connected between the second DU and the RU, in a manner similar to step (604) of FIG. 6 . Accordingly, the path between the RU of the first cell and the PHY entity of the first DU may be switched to the path between the RU and the PHY entity of the second DU.

[0179] In one embodiment of the present disclosure, the network device may select a terminal to be transferred to a second DU from among the terminals of the first cell connected to the MAC entity of the first DU (904). For example, the network device may randomly select one terminal to be transferred to the MAC entity of the second DU from among the terminals (e.g., UEs) attached to the first cell connected to the MAC entity of the first DU in a manner similar to step (605) of FIG. 6 .

[0180] In one embodiment of the present disclosure, the network device can identify (905) whether the first cell for the selected terminal is configured as a PCell or an SCell in step (904). For example, the network device can identify whether the PCell of the selected terminal is the first cell in a manner similar to step (606) of FIG. 6 .

[0181] In one embodiment of the present disclosure, the network device may switch a path for the PCell between the RLC entity and the MAC entity of the selected terminal (906) based on the fact that the first cell is set as the PCell for the selected terminal in step (904). For example, the network device may switch a path for the PCell between the RLC entity and the MAC entity of the selected terminal (e.g., an 'RLC-MAC PCell path') to a path between the RLC entity and the MAC entity of the second DU, in a manner similar to step (607) of FIG. 6 .

[0182] In one embodiment of the present disclosure, the network device may switch a path for an SCell between an RLC entity and a MAC entity of the selected terminal (907) based on the fact that the first cell is set as a PCell for the selected terminal in step (904). For example, the network device may switch an SCell data path (e.g., an 'RLC-MAC SCell path') between an RLC entity of a first DU of the selected terminal and a MAC entity of the first DU. For example, the network device may switch a path for communication via an SCell between an RLC entity of the first DU and a MAC entity of the first DU to be connected between an RLC entity of a second DU and a MAC entity of the second DU. Accordingly, both a MAC endpoint and an RLC endpoint of the SCell path between the RLC entity and the MAC entity of the selected terminal may be switched from the first DU to the second DU.

[0183] In one embodiment of the present disclosure, the network device can identify whether any terminals in the first cell connected to the MAC entity of the first DU are to be transferred to the second DU (908). For example, the network device can identify whether any terminals remain to be transferred to the second DU in a manner similar to step (609) of FIG. 6 .

[0184] Through steps (904 to 908), for all terminals attached to the first cell, it is identified whether the PCell of each terminal is set to the first cell, and based on the identification, either the PCell path or the SCell path of each terminal can be switched. Thereafter, in one embodiment of the present disclosure, the network device can resume MAC scheduling of the first cell (909). For example, the network device can resume MAC scheduling of the first cell in a manner similar to step (610).

[0185] According to steps (901 to 909), paths for the PCells of UEs for which the target cell is configured as the PCell between the RLC entity of the source DU (or any DU among the source DUs) and the MAC entity of the source DU may be switched to paths between the RLC entity of the source DU and the MAC entity of the target DU. For example, paths for the PCells of UEs for which the target cell is configured as the PCell may be switched from the 'RLC of the source DU - MAC of the source DU' path to the 'RLC of the source DU - MAC of the target DU' path. According to steps (901 to 909), paths for the SCells of UEs for which the target cell is configured as the SCell between the RLC entity of the source DU and the MAC entity of the source DU may be switched to paths between the RLC entity of the target DU and the MAC entity of the target DU. For example, the paths for SCells of UEs whose target cell is set as SCell can be switched from the 'RLC of source DU - MAC of source DU' path to the 'RLC of target DU - MAC of target DU' path.

[0186] In one embodiment of the present disclosure, the network device may set the RLC context of the first DU for the second DU (910). For example, the network device may set the RLC context of the first DU for the second DU in a manner similar to step (611).

[0187] In one embodiment of the present disclosure, the network device may select a terminal to be transferred to a second DU from among the terminals of the first cell connected to the RLC entity of the first DU (911). For example, the network device may select one terminal to be transferred to the RLC entity of the second DU from among the terminals attached to the first cell connected to the RLC entity of the first DU in a manner similar to step (612).

[0188] In one embodiment of the present disclosure, the network device can identify whether the first cell is configured as a PCell or an SCell for the terminal selected in step (911) (912). The network device can obtain information indicating whether the first cell is the PCell or SCell of the selected terminal from the MAC scheduler in a similar manner as in step (905), and can identify whether the PCell of the selected terminal is the first cell based on the obtained information. Based on whether the first cell is configured as the PCell of the selected terminal, the network device can perform steps (913 to 915). Based on whether the first cell is configured as the PCell of the selected terminal, the network device can perform step (916) without switching (changing) the path for the selected terminal any further.

[0189] In one embodiment of the present disclosure, the network device may perform steps (913 to 915) based on the first cell being set as the PCell of the terminal selected in step (912). The network device may set an RLC UE context for the selected terminal in the second DU (913). For example, the network device may transfer context information of the selected terminal associated with the RLC entity of the first DU to the RLC entity of the second DU.

[0190] In one embodiment of the present disclosure, based on the first cell being set as the PCell of the terminal selected in step (912), the network device may switch the midhaul path of the second DU (914). For example, the network device may switch the midhaul path between the first DU and the CU for the selected terminal to be connected between the second DU and the CU. Accordingly, the path between the CU and the RLC entity of the first DU may be switched to the path between the CU and the RLC entity of the second DU.

[0191] In one embodiment of the present disclosure, based on the first cell being set as the PCell of the selected terminal in step (912), the network device may switch the PCell path and the SCell path between the RLC entity and the MAC entity for the selected terminal (915). For example, the network device may switch the PCell data path of the selected terminal, which is connected between the RLC entity of the first DU and the MAC entity of the second DU, switched in step (906), to be connected between the RLC entity of the second DU and the MAC entity of the second DU. The network device may switch the SCell data path of the selected terminal, which is connected between the RLC entity of the first DU and the MAC entity of the first DU, to be connected between the RLC entity of the second DU and the MAC entity of the second DU.

[0192] In one embodiment of the present disclosure, a network device can identify whether, among the terminals of the first cell connected to the RLC entity of the first DU, there are any terminals that need to be transferred to the second DU (916). For example, the network device can identify whether there are any remaining terminals that need to be transferred to the second DU in a manner similar to step (617).

[0193] Based on whether there is a terminal to be transferred to the second DU among the terminals of the first cell connected to the RLC entity of the first DU, the network device may perform steps (911 to 916) again. For example, based on whether the terminal selected in step (911) is not the last terminal in the determined previous order or whether there are any unselected terminals remaining, the network device may identify whether there is (or is not) a terminal connected to the RLC entity of the first DU and perform steps (911 to 916) again. For example, based on whether the terminal selected in step (911) is the last terminal in the determined previous order or whether there are any unselected terminals remaining, the network device may identify whether there is (or is not) a terminal to be transferred to the second DU among the terminals connected to the RLC entity of the first DU and terminate the method (900).

[0194] According to steps (911 to 917), paths for the PCells of UEs whose target cells are configured as PCells between the RLC entity of the source DU and the MAC entity of the target DU may be switched to paths between the RLC entity of the target DU and the MAC entity of the target DU. For example, paths for the PCells of UEs whose target cells are configured as PCells may be switched from the 'RLC of the source DU - MAC of the target DU' path to the 'RLC of the target DU - MAC of the target DU' path. According to steps (910 to 916), paths for the SCells of UEs whose target cells are configured as SCells between the RLC entity of the source DU and the MAC entity of the target DU may be switched to paths between the RLC entity of the target DU and the MAC entity of the target DU. For example, paths for SCells of UEs whose target cell is set to PCell can be switched from the 'RLC of source DU - MAC of target DU' path to the 'RLC of target DU - MAC of target DU' path.

[0195] FIGS. 10A to 10C illustrate data flow in a user plane due to scaling of a first DU to a second DU by a network device according to an embodiment of the present disclosure. FIGS. 10A to 10C illustrate time-dependent changes in data flow due to transfer of a cell (1031) from a DU (1021) to a DU (1022) in a RAN system (1000) implemented based on the inter-DU CA scenario illustrated in FIG. 4B. In the embodiment of FIGS. 10A to 10C, the DU (1021) may be understood as a source DU or a first DU, the DU (1022) may be understood as a target DU or a second DU, and the cell (1031) may be understood as a target cell or a first cell. In the embodiment illustrated in FIG. 10a, the RAN system (1000) can support carrier aggregation of cells (1031) and (1032), in a similar manner to the RAN system (400a) of FIG. 4a. For convenience of illustration, only two cells (1031, 1032) are illustrated in FIG. 10a, but the number of carrier-aggregated cells is not limited thereto.

[0196] A network device (e.g., an OAM module) that manages and maintains a RAN system of a RAN system (1000) may determine whether to migrate a cell (1031) from a DU (1021) to a DU (1022). For example, the network device may determine to perform a scale-in for the DU (1021) to the DU (1022). The determination to perform the scale-in may include determining to migrate a cell (1031) associated with the DU (1021) to the DU (1022). Based on the determination to perform the scale-in, the network device may determine a scaling situation for the scale-in and notify a network device (e.g., a scale agent) that manages scaling of the DU of the determined scaling situation and a request for the scale-in.

[0197] A network device managing scaling of a DU of a RAN system (1000) can identify a scaling situation known by an OAM module as a scale-in. Based on identifying the scaling situation as a scale-in, the network device can omit transferring the cell context of a cell (1031) included in a DU (1021) from the DU (1021) to the DU (1022) and perform the method (900) of FIG. 9. FIG. 10A can illustrate the data flow of a RAN system (1000) before a network device of the RAN system (1000) performs the method (900) of FIG. 6.

[0198] The network device may transfer the MAC context of the cell (1031) associated with the MAC / PHY entity (1021_2) of the DU (1021) to the MAC / PHY entity (1022_2) of the DU (1022), in a manner similar to step (901). The network device may stop MAC scheduling for the cell (1031) of the DU (1021), in a manner similar to step (902). The network device may switch the fronthaul path for the cell (1031), in a manner similar to step (903). For example, the network device may switch the fronthaul path connected between the RU to which the cell (1031) is connected and the MAC / PHY entity (1021_2) of the DU (1021), to the path between the RU to which the cell (1031) is connected and the MAC / PHY entity (1022_2) of the DU (1022). Accordingly, the 'UE 1 PCell path' between the cell (1031) and the MAC / PHY entity (1021_2) of FIG. 10a can be switched to the 'UE 1 PCell path' between the cell (1031) and the MAC / PHY entity (1022_2) of FIG. 10b. Similarly, the 'UE 2 SCell path' between the cell (1031) and the MAC / PHY entity (1021_2) of FIG. 10a can be switched to the 'UE 2 SCell path' between the cell (1031) and the MAC / PHY entity (1022_2) of FIG. 10b.

[0199] The network device may select one of the UEs (1041, 1042) attached to the cell (1031) in a manner similar to step (904). For example, the network device may select the UE (1041) based on a predetermined previous order or randomly. The network device may identify whether the cell (1031) is configured as a PCell or an SCell for the UE (1041) in a manner similar to step (905). Based on the fact that the PCell of the UE (1041) is configured as the cell (1031) corresponding to the component carrier 'CC1', the network device may switch a path for the PCell between the RLC entity and the MAC entity of the UE (1041) in a manner similar to step (906). In the embodiment of FIG. 10A, the path for the PCell between the RLC entity and the MAC entity of the UE (1041) may be a 'UE 1 PCell path' between the RLC entity (1021_1) and the MAC / PHY entity (1021_2). The network device may switch the 'UE 1 PCell path' between the RLC entity (1021_1) and the MAC / PHY entity (1021_2) to a path between the RLC entity (1021_1) and the MAC / PHY entity (1022_2). Accordingly, the 'UE 1 PCell path' between the RLC entity (1021_1) and the MAC / PHY entity (1021_2) of FIG. 10a can be switched to the 'UE 1 PCell path' between the RLC entity (1021_1) and the MAC / PHY entity (1022_2) of the DU (1022) of FIG. 10b.

[0200] The network device can identify whether there is a UE among the UEs (1041, 1042) of the cell (1031) that needs to be migrated to the DU (1022). For example, the network device can identify whether there is a UE among the UEs (1041, 1042) of the cell (1031) that needs to be migrated to the DU (1022) in a manner similar to step (908). The network device can identify that the UE (1042) needs to be migrated to the DU (1022), and therefore, can reselect the UE (1042) to be migrated to the DU (1022) of the cell (1031) in a manner similar to step (904).

[0201] The network device can identify whether the cell (1031) is configured as a PCell or an SCell for the selected UE (1042), in a manner similar to step (905). Based on the SCell of the UE (1042) being configured as the cell (1031) corresponding to the component carrier 'CC1', the network device can switch the path for the SCell between the RLC entity and the MAC entity of the UE (1042), in a manner similar to step (907). In the embodiment of FIG. 10A, the path for the SCell between the RLC entity and the MAC entity of the UE (1042) may be a 'UE 2 SCell path' between the RLC entity (1022_1) and the MAC / PHY entity (1021_2). The network device can switch the 'UE 2 SCell path' between the RLC entity (1022_1) and the MAC / PHY entity (1021_2) to the path between the RLC entity (1022_2) and the MAC / PHY entity (1022_2). Accordingly, the 'UE 2 SCell path' between the RLC entity (1022_1) and the MAC / PHY entity (1021_2) of FIG. 10a can be switched to the 'UE 2 SCell path' between the RLC entity (1022_1) and the MAC / PHY entity (1022_2) of the DU (1022) of FIG. 10b.

[0202] The network device may identify whether there is a UE among the UEs (1041, 1042) of the cell (1031) that needs to be transferred to the DU (1022) in a manner similar to step (908). For example, the network device may identify whether there is a UE among the UEs (1041, 1042) of the cell (1031) that needs to be transferred to the DU (1022) based on the manner described above in step (908).

[0203] In the embodiment of FIG. 10b, all of the UEs (1041, 1042) of the cell (1031) may have been selected once to identify whether the cell (1031) is configured as the PCell for the selected UE. Alternatively, since the path between the RLC entity and the MAC entity of each of the UEs (1041, 1042) of the cell (1031) has been switched, all of the UEs (1041, 1042) of the cell (1031) may have a path connected between the RLC entity (1021_1) of the DU (1021) and the MAC / PHY entity (1022_2) of the DU (1022). Alternatively, all of the UEs (1041, 1042) of the cell (1031) can communicate with the CU via the cell (1031) via a path between the RLC entity of any DU in the DU pool (in the embodiment of FIG. 10b, the RLC entity (1022_1) of the DU (1021)) and the MAC / PHY entity (1022_2) of the DU (1022). Accordingly, the network device can identify that there is no UE among the UEs (1041, 1042) of the cell (1031) to migrate to the DU (1022). Based on identifying that there is no UE to migrate to the DU (1022), the network device can resume MAC scheduling for the cell (1031) in a manner similar to step (909). For example, the network device may control (or command) the MAC / PHY entity (1022_2) of the DU (1022) to initiate MAC scheduling for the cell (1031).

[0204] FIG. 10B may illustrate the data flow of the RAN system (1000) after the network device of the RAN system (1000) of FIG. 10A performs steps (901 to 909) of the method (900) of FIG. 9. Comparing FIG. 10A and FIG. 10B, the 'UE 1 PCell path' between the RLC entity (1021_1) of the DU (1021) of FIG. 10A and the MAC / PHY entity (1021_2) of the DU (1021) may be switched to the 'UE 1 PCell path' between the RLC entity (1021_1) of the DU (1021) of FIG. 10B and the MAC entity (1022_2) of the DU (1022). The 'UE 2 SCell path' between the RLC entity (1021_1) of the DU (1021) and the MAC entity (1022_2) of the DU (1022) in FIG. 10a can be switched to the 'UE 2 SCell path' between the RLC entity (1022_1) of the DU (1022) and the MAC entity (1022_2) of the DU (1022) in FIG. 10b.

[0205] The network device may set an RLC context of the DU (1021) for the DU (1022) in a manner similar to step (910). The network device may select a UE to be transferred to the DU (1022) from among the UEs (1041, 1042) of the cell (1031) connected to the RLC entity (1021_1) of the DU (1021) in a manner similar to step (911). For example, the network device may select the UE (1041) as the UE to be transferred. The network device may identify whether the cell (1031) is configured as a PCell or an SCell for the UE (1041) in a manner similar to step (912). Based on the fact that the PCell of the UE (1041) is set to the cell (1031) corresponding to the component carrier 'CC1', the network device may set an RLC UE context for the UE (1041) in the RLC entity (1022_2) of the DU (1022) in a manner similar to step (913). The network device may switch the midhaul path (P1) for the UE (1041) between the DU (1021) and the CU (1010) to a path between the RLC entity (1022_1) of the DU (1022) and the CU (1010) in a manner similar to step (914).

[0206] The network device may switch the path for the PCell and the path for the SCell between the RLC entity and the MAC entity of the UE (1041) in a similar manner to step (915). For example, the network device may switch the 'UE 1 PCell path' between the RLC entity (1021_1) of the DU (1021) and the MAC / PHY entity (1022_2) of the DU (1022), as shown in FIG. 10b, to between the RLC entity (1022_1) of the DU (1022) and the MAC / PHY entity (1022_2) of the DU (1022). The network device can switch the 'UE 1 SCell path' between the RLC entity (1021_1) of the DU (1021) and the MAC / PHY entity (1022_2) of the DU (1022), as shown in FIG. 10b, to between the RLC entity (1022_1) of the DU (1022) and the MAC / PHY entity (1022_2) of the DU (1022). Accordingly, the 'UE 1 PCell path' between the RLC entity (1021_1) and the MAC / PHY entity (1022_2) of FIG. 10b can be switched to the 'UE 1 PCell path' between the RLC entity (1022_1) and the MAC / PHY entity (1022_2) of the DU (1022) as shown in FIG. 10c. The 'UE 1 SCell path' between the RLC entity (1021_1) and the MAC / PHY entity (1022_2) of FIG. 10b can be switched to the 'UE 1 SCell path' between the RLC entity (1022_1) of the DU (1022) and the MAC / PHY entity (1022_2) of the DU (1022) of FIG. 10c.

[0207] The network device can identify whether there is (or remains) a UE among the UEs (1041, 1042) of the cell (1031) to be migrated to the RLC entity (1022_1) of the DU (1022), in a manner similar to step (916). The network device can identify that the UE (1042) among the UEs (1041, 1042) of the cell (1031) should be migrated to the RLC entity (1022_1) of the DU (1022), and select the UE (1042) as the UE to be migrated to the DU (1022) of the cell (1031), in a manner similar to step (911).

[0208] The network device can identify whether the cell (1031) is configured as a PCell or an SCell for the selected UE (1042), in a manner similar to step (912). Based on the SCell of the UE (1042) being configured as the cell (1031) corresponding to the component carrier 'CC1', the network device can, without switching the path for the UE (1042), identify again whether there is (or remains) a UE to be migrated to the RLC entity (1022_1) of the DU (1022) among the UEs (1041, 1042) of the cell (1031), in a manner similar to step (916). Based on the fact that all the UEs (1041, 1042) of the cell (1031) have been selected once, the network device can identify that there is no UE to be migrated to the RLC entity (1022_1) of the DU (1022), and terminate scaling.

[0209] FIG. 10C may illustrate the data flow of the RAN system (1000) after the network device of the RAN system (1000) of FIG. 10B performs steps (910 to 916) of the method (900) of FIG. 9. Comparing FIG. 10B and FIG. 10C, the 'UE 1 PCell path' between the RLC entity (1021_1) of the DU (1021) of FIG. 10B and the MAC entity (1022_2) of the DU (1022) may be switched to the 'UE 1 PCell path' between the RLC entity (1022_1) of the DU (1022) of FIG. 10C and the MAC entity (1022_2) of the DU (1022). The 'UE 1 SCell path' between the RLC entity (1021_1) of the DU (1021) in FIG. 10b and the MAC / PHY entity (1021_2) of the DU (1021) can be switched to the 'UE 1 SCell path' between the RLC entity (1022_1) of the DU (1022) in FIG. 10c and the MAC entity (1022_2) of the DU (1022).

[0210] Comparing FIGS. 10A and 10C, the cells (1031) and (1032) of FIG. 10A were processed together by multiple DUs (1021, 1022), but through scaling in, the cells (1031) and (1032) of FIG. 10C can be processed by a single DU (1021). Therefore, in one embodiment of the present disclosure, the RAN system (1000) of FIG. 10A according to the inter-DU CA scenario can be modified to follow the intra-DU CA scenario, as shown in FIG. 10C, after scaling in to deactivate the first DU. According to one embodiment of the present disclosure, scaling in can also be performed for the RAN system (400a) of FIG. 4A. For example, the OAM module of the RAN system (400a) may decide to migrate the cell (431) from the DU (420a) to another DU (target DU) in order to remove the DU (420a) from the DU pool of the RAN system (400a) or to reduce the load on the DU (420a). This migration may be performed in a manner similar to intra-DU scaling out, except that no initiation of the target DU is required because the target DU already exists in the DU pool. Accordingly, scaling in the DU (420a) of FIG. 4a to the target DU may be performed in a manner similar to the intra-DU scaling out method described with reference to the method (600) of FIG. 6 and FIGS. 7a to 7c.

[0211] FIG. 11 illustrates an example of a network device according to an embodiment of the present disclosure. The network device (1100) illustrated in FIG. 11 may be an electronic device that performs a cell transfer operation for a DU. For example, the network device (1100) may be a server device. For example, the network device (1100) may be a communication device constituting a RAN. The network device (1100) may be a network device or server device constituting an existing RAN, such as a network device or server device that performs an RU function, a network device or server device that performs a DU function, a network device or server device that performs a CU function, or a network device or server device that performs an OAM function. The network device (1100) may be a separate network device or server device (e.g., a scale agent device) that controls cell transfer.

[0212] In one embodiment of the present disclosure, the network device (1100) may include, but is not limited to, at least one processor (1110) and a memory (1120). The processor (1110) may be electrically connected to components included in the network device (1100) and may execute operations or data processing related to control and / or communication of the components included in the network device (1100). In one embodiment of the present disclosure, the processor (1110) may load and process a request, command, or data received from at least one of the other components into the memory (1120), and store the processing result data in the memory (1120). According to various embodiments, the processor (1110) may include at least one of a general-purpose processor such as a central processing unit (CPU), an application processor (AP), a digital signal processor (DSP), a graphics-only processor such as a graphics processing unit (GPU), a vision processing unit (VPU), or an artificial intelligence-only processor such as a neural processing unit (NPU).

[0213] The processor (1110) may be controlled to process input data according to predefined operation rules, algorithms, methods, or models stored in the memory (1120). The processor (1110) may be controlled to process input data based on data stored in the memory (1120). The processor (1110) may perform operations of predefined operation rules, algorithms, methods, or models stored in the memory (1120) using the input data. In one embodiment, the processor (1110) may include at least one processing circuit, such as a System-on-Chip (SoC) or an Integrated Circuit (IC).

[0214] The memory (1120) is electrically connected to the processor (1110) and can store one or more modules, algorithms, operation rules, models, programs, commands, or data related to the operation of the components included in the network device (1100). For example, the memory (1120) can store one or more modules, algorithms, operation rules, models, programs, commands, or data for processing and controlling the processor (1110). The memory (1120) can include at least one type of storage medium among a flash memory type, a hard disk type, a multimedia card micro type, a card type memory (e.g., SD or XD memory, etc.), a RAM (Random Access Memory), a SRAM (Static Random Access Memory), a ROM (Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), a PROM (Programmable Read-Only Memory), a magnetic memory, a magnetic disk, and an optical disk, but is not limited thereto.

[0215] In one embodiment, the memory (1120) may store data or information identified, acquired, generated, or determined by the network device (1100). The memory (1120) may store data or information identified, acquired, generated, or determined by the network device (1100) in a compressed form. In one embodiment, the memory (1120) may include one or more storage media storing one or more instructions executable by the processor (1110). The one or more instructions, when individually or collectively executed by the processor (1110), may cause the network device (1100) to perform at least some of the operations described with reference to FIGS. 1 to 10.

[0216] Some modules that perform at least one operation of the network device (1100) may be implemented as hardware modules, software modules, and / or a combination thereof. The memory (1120) may include software modules that perform at least some of the operations of the network device (1100) described above. In one embodiment of the present disclosure, the modules included in the memory (1120) may perform operations by being executed by the processor (1110). For example, the modules (i.e., software modules) included in the memory (1120) may include programs, models, or algorithms that are executed according to the control or command of the processor (1110) and are configured to perform operations that derive output data for input data. Some modules that perform at least one operation of the network device (1100) may be composed of a plurality of sub-modules or may constitute a single module.

[0217] The network device (1100) may include more components than those illustrated in FIG. 11. In one embodiment of the present disclosure, the network device (1100) may further include a communication interface (or communication module) for communicating with an external device. In one embodiment of the present disclosure, the network device (1100) may further include an input / output device and / or an input / output interface.

[0218] In the present disclosure, overlapping descriptions in FIGS. 1 to 11 may be omitted, and one or more of the above-described embodiments may be applied / implemented in combination with each other. In the present disclosure, an operation described as being performed by a module may be executed / performed by an electronic device in which the module is included or stored, or may be executed / performed by the control of at least one processor of the electronic device in which the module is included. An operation described as being performed by an electronic device may be executed / performed by a module included or stored in the electronic device, or may be performed by the control of at least one processor of the electronic device using a module included or stored in the electronic device.

[0219] A method for scaling at least one DU, performed by a network device supporting merging of a plurality of cells according to one embodiment of the present disclosure, comprises: switching a path between an RU of a first cell and a PHY entity of a first DU to a path between the RU and a PHY entity of a second DU; identifying whether the first cell is configured as a PCell or an SCell for a terminal; based on the first cell being configured as a PCell for the terminal: switching a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU; transferring context information of the terminal related to the RLC entity of the first DU to an RLC entity of the second DU; switching a path between a CU and an RLC entity of the first DU to a path between the CU and an RLC entity of the second DU; and a step of switching a path between the RLC entity of the first DU and the MAC entity of the second DU to a path between the RLC entity of the second DU and the MAC entity of the second DU.

[0220] Supporting CA may be common in 5G NR RAN systems. According to one embodiment of the present disclosure, target cells can be efficiently scaled from a source DU to a target DU even in a RAN system that supports CA. Therefore, by supporting both CA and DU scaling, the RAN system can secure a wider communication spectrum, increasing cell capacity while efficiently utilizing system resources.

[0221] According to one embodiment of the present disclosure, a method of scaling at least one DU may further include the steps of: transferring a MAC context of the terminal associated with a MAC entity of the first DU to a MAC entity of the second DU; and stopping MAC scheduling for the first cell.

[0222] According to one embodiment of the present disclosure, the method may further include a step of resuming MAC scheduling for the first cell when all terminals attached to the first cell are capable of communicating with the CU via the first cell through at least one path between an RLC entity of any one of the DUs capable of communicating with the CU and a MAC entity of the second DU.

[0223] According to one embodiment of the present disclosure, the method may further include a step of switching a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU, based on the first cell being set as an SCell for the terminal.

[0224] According to one embodiment of the present disclosure, the method may further include a step of switching a path between an RLC entity of a third DU and a MAC entity of the first DU to a path between an RLC entity of the third DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal. According to one embodiment of the present disclosure, the method may further include a step of switching a path between an RLC entity of the second DU and a MAC entity of the first DU to a path between an RLC entity of the second DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal.

[0225] According to one embodiment of the present disclosure, the method may further include a step of transferring a cell context of the first cell included in the first DU from the first DU to the second DU based on the scaling being scale-out.

[0226] According to one embodiment of the present disclosure, the method may include switching a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the second DU and a MAC entity of the first DU.

[0227] According to one embodiment of the present disclosure, the method may include switching a path between an RLC entity of a first DU and a MAC entity of the third DU to a path between an RLC entity of the second DU and a MAC entity of the third DU.

[0228] According to one embodiment of the present disclosure, the method may further include a step of switching a path between an RLC entity of the first DU and a MAC entity of the second DU to a path between an RLC entity of the second DU and a MAC entity of the second DU based on the scaling being scale-in.

[0229] According to one embodiment of the present disclosure, the method may further include a step of terminating the scaling based on no terminal of the first cell remaining connected to the RLC entity of the first DU.

[0230] A computer-readable non-transitory recording medium according to one embodiment of the present disclosure may be a computer-readable non-transitory recording medium having recorded thereon a program for performing a method of scaling at least one DU performed by a network device supporting merging of a plurality of cells according to one embodiment of the present disclosure.

[0231] A network device supporting merging of multiple cells according to one embodiment of the present disclosure may include: a memory storing one or more commands; and at least one processor executing the one or more commands stored in the memory. To scale at least one DU, the at least one processor executes the one or more commands to cause the network device to: switch a path between an RU of a first cell and a PHY entity of a first DU to a path between the RU and a PHY entity of a second DU; identify whether the first cell is configured as a PCell or an SCell for a terminal; and based on the first cell being configured as a PCell for the terminal: switch a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU; transfer context information of the terminal related to the RLC entity of the first DU to an RLC entity of the second DU; Switching a path between a CU and an RLC entity of the first DU to a path between the CU and an RLC entity of the second DU; and causing a path between an RLC entity of the first DU and a MAC entity of the second DU to be switched to a path between an RLC entity of the second DU and a MAC entity of the second DU.

[0232] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: transfer a MAC context of the terminal associated with a MAC entity of the first DU to a MAC entity of the second DU by executing the one or more instructions; and suspend MAC scheduling for the first cell, and resume MAC scheduling for the first cell if all terminals attached to the first cell are capable of communicating with the CU via the first cell through at least one path between an RLC entity of any one of the DUs capable of communicating with the CU and the MAC entity of the second DU.

[0233] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: switch a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0234] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to switch a path between an RLC entity of a third DU and a MAC entity of the first DU to a path between an RLC entity of the third DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0235] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: transfer a MAC context of the terminal associated with a MAC entity of the first DU to a MAC entity of the second DU by executing the one or more instructions; and suspend MAC scheduling for the first cell, and resume MAC scheduling for the first cell if all terminals attached to the first cell are capable of communicating with the CU via the first cell through at least one path between an RLC entity of any one of the DUs capable of communicating with the CU and the MAC entity of the second DU.

[0236] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: switch a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0237] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to switch a path between an RLC entity of a third DU and a MAC entity of the first DU to a path between an RLC entity of the third DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0238] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: switch a path between an RLC entity of the second DU and a MAC entity of the first DU to a path between an RLC entity of the second DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0239] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: switch a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0240] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to switch a path between an RLC entity of a third DU and a MAC entity of the first DU to a path between an RLC entity of the third DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0241] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: switch a path between an RLC entity of the second DU and a MAC entity of the first DU to a path between an RLC entity of the second DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0242] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: switch a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0243] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to switch a path between an RLC entity of a third DU and a MAC entity of the first DU to a path between an RLC entity of the third DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0244] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: switch a path between an RLC entity of the second DU and a MAC entity of the first DU to a path between an RLC entity of the second DU and a MAC entity of the second DU, based on the first cell being configured as an SCell for the terminal, by executing the one or more instructions.

[0245] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: transfer a cell context of the first cell included in the first DU from the first DU to the second DU based on the scaling being scale-out; and switch a path between an RLC entity of the first DU and a MAC entity of the first DU to a path between an RLC entity of the second DU and a MAC entity of the first DU.

[0246] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: transfer a cell context of the first cell included in the first DU from the first DU to the second DU based on the scaling being scale-out; and switch a path between an RLC entity of the first DU and a MAC entity of the third DU to a path between an RLC entity of the second DU and a MAC entity of the third DU.

[0247] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to: switch a path between an RLC entity of the first DU and a MAC entity of the second DU to a path between an RLC entity of the second DU and a MAC entity of the second DU, based on the scaling being scale-in, by executing the one or more instructions.

[0248] According to one embodiment of the present disclosure, the at least one processor may further cause the network device to terminate the scaling based on the fact that no terminal of the first cell remains connected to the RLC entity of the first DU by executing the one or more instructions.

[0249] A device-readable storage medium may be provided in the form of a non-transitory storage medium. Here, the term "non-transitory storage medium" simply means a tangible device that does not contain signals (e.g., electromagnetic waves). This term does not distinguish between cases where data is permanently stored in the storage medium and cases where data is temporarily stored. For example, a "non-transitory storage medium" may include a buffer in which data is temporarily stored.

[0250] According to one embodiment, the method according to various embodiments disclosed in the present document may be provided as included in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read-only memory (CD-ROM)), or may be distributed online (e.g., downloaded or uploaded) through an application store or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product (e.g., a downloadable app) may be temporarily stored or temporarily generated in a machine-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or an intermediary server.

[0251] Although the embodiments described above have been described by way of limited examples and drawings, those skilled in the art will appreciate that various changes and modifications may be made based on the above description. For example, appropriate results may still be achieved if the described techniques are performed in a different order than described, and / or if components such as the described computer system or modules are combined or combined in a different manner than described, or if they are replaced or substituted with other components or equivalents.

Claims

1. A method for scaling at least one DU (Distributed Unit), performed by a network device supporting carrier aggregation, A step (501) of switching a path between a RU (Radio Unit) of a first cell and a PHY (Physical) entity of a first DU to a path between the RU and a PHY entity of a second DU; A step (502) of identifying whether the first cell is set as a PCell (Primary Cell) or an SCell (Secondary Cell) in the terminal; Based on the above first cell being set as PCell in the terminal: A step (503) of switching a path between an RLC (Radio Link Control) entity of the first DU and a MAC (Medium Access Control) entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU; A step (504) of transferring context information of the terminal related to the RLC entity of the first DU to the RLC entity of the second DU; Step (505) of switching the path between the CU (Central Unit) and the RLC entity of the first DU to the path between the CU and the RLC entity of the second DU; and A method comprising the step (506) of switching a path between an RLC entity of the first DU and a MAC entity of the second DU to a path between an RLC entity of the second DU and a MAC entity of the second DU.

2. In paragraph 1, A step (602, 901) of transferring the MAC context of the terminal related to the MAC entity of the first DU to the MAC entity of the second DU; and A method further comprising a step (603, 902) of stopping MAC scheduling for the first cell.

3. In paragraph 1 or 2, A method further comprising a step (609, 908) of resuming MAC scheduling for the first cell, if all terminals attached to the first cell can communicate with the CU via the first cell through at least one path between an RLC entity of any one of the DUs capable of communicating with the CU and a MAC entity of the second DU.

4. In any one of paragraphs 1 to 3, A method further comprising the step of switching a path between an RLC entity (721_1) of the first DU and a MAC entity (721_2) of the first DU to a path between an RLC entity (721_1) of the first DU and a MAC entity (722_2) of the second DU based on the first cell (731) being set as an SCell to the terminal (742).

5. In any one of paragraphs 1 to 4, A method further comprising the step of switching a path between an RLC entity (823_1) of the third DU and a MAC / PHY entity (821_2) of the first DU to a path between an RLC entity (823_1) of the third DU and a MAC entity (822_2) of the second DU based on the first cell (831) being set as an SCell to the terminal (842).

6. In any one of paragraphs 1 to 5, A method further comprising the step of switching a path between an RLC entity (1022_1) of the second DU and a MAC / PHY entity (1021_2) of the first DU to a path between an RLC entity (1022_1) of the second DU and a MAC entity (1022_2) of the second DU based on the first cell (1031) being set as an SCell to the terminal (1042).

7. In any one of paragraphs 1 to 6, A method further comprising a step (601) of transferring a cell context of the first cell included in the first DU from the first DU to the second DU based on the scaling being scale-out.

8. In any one of paragraphs 1 to 7, A method comprising the step of switching a path between an RLC entity (721_1) of the first DU and a MAC entity (721_2) of the first DU to a path between an RLC entity (722_1) of the second DU and a MAC entity (721_2) of the first DU.

9. In any one of paragraphs 1 to 8, A method comprising the step of switching a path between an RLC entity (821_1) of the first DU and a MAC / PHY entity (823_2) of the third DU to a path between an RLC entity (822_1) of the second DU and a MAC / PHY entity (823_2) of the third DU.

10. In any one of paragraphs 1 to 9, A method comprising: switching a path between an RLC entity (1021_1) of the first DU and a MAC / PHY entity (1022_2) of the second DU based on the scaling being scale-in to a path between an RLC entity (1022_1) of the second DU and a MAC entity (1022_2) of the second DU.

11. A non-transitory computer-readable storage medium having recorded thereon a program for performing the method of any one of clauses 1 to 10 on a computer.

12. In a network device (1100) supporting carrier aggregation, A memory (1120) storing one or more instructions; and At least one processor (1110) for executing one or more instructions stored in the memory, To scale at least one Distributed Unit (DU), the at least one processor causes the network device to: Switching the path between the RU (Radio Unit) of the first cell and the PHY (Physical) entity of the first DU to the path between the RU and the PHY entity of the second DU; Identify whether the above first cell is set as a PCell (Primary Cell) or a SCell (Secondary Cell) in the terminal; Based on the above first cell being set as PCell in the terminal: Switching a path between an RLC (Radio Link Control) entity of the first DU and a MAC (Medium Access Control) entity of the first DU to a path between an RLC entity of the first DU and a MAC entity of the second DU; Transferring context information of the terminal related to the RLC entity of the first DU to the RLC entity of the second DU; Switching the path between the CU (Central Unit) and the RLC entity of the first DU to the path between the CU and the RLC entity of the second DU; and A network device that causes a path between an RLC entity of the first DU and a MAC entity of the second DU to be switched to a path between an RLC entity of the second DU and a MAC entity of the second DU.

13. In paragraph 12, The at least one processor causes the network device to: Transferring the MAC context of the terminal related to the MAC entity of the first DU to the MAC entity of the second DU; Stop MAC scheduling for the above first cell, A network device further causing MAC scheduling for the first cell to be resumed when all terminals attached to the first cell can communicate with the CU via the first cell through at least one path between an RLC entity of any one of the DUs capable of communicating with the CU and a MAC entity of the second DU.

14. In paragraph 12 or 13, The at least one processor causes the network device to: Based on the above scaling being scale-out, transferring the cell context of the first cell included in the first DU from the first DU to the second DU; and A network device further causing a path between the RLC entity of the first DU and the MAC entity of the first DU to be switched to a path between the RLC entity of the second DU and the MAC entity of the first DU.

15. In any one of paragraphs 12 to 14, The at least one processor causes the network device to: A network device further causing a path between the RLC entity of the second DU and the MAC entity of the first DU to be switched to a path between the RLC entity of the second DU and the MAC entity of the second DU based on the scaling being scale-in.

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