Method for performing UE unit transfer in wireless network system, and electronic device performing method

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate than a 4G communication system such as LTE. A method for performing UE unit transfer, according to an embodiment of the present disclosure, may identify information regarding a UE to be transferred from RLC of a first DU to RLC of a second DU. The method may change an F1-U interface from the RLC of a CU and the first DU to the RLC of the CU and the second DU. The method may reset information included in the RLC of the second DU. The method may change a connection between the RLC of the first DU and media access control (MAC) of the second DU to a connection between the RLC of the second DU and the MAC of the second DU.

Description

Method for performing terminal unit transfer in a wireless network system and electronic device for performing the method

[0001] Embodiments disclosed in this document relate to a method for performing terminal unit transfer in a wireless network system and an electronic device for performing the method.

[0002] Looking back at the evolution of wireless communication over successive generations, technologies have primarily been developed for human-facing services such as voice, multimedia, and data. With the commercialization of 5G (5th-generation) communication systems, an explosive increase in connected devices is expected to be connected to communication networks. Examples of networked objects include vehicles, robots, drones, home appliances, displays, smart sensors installed in various infrastructures, construction equipment, and factory equipment. Mobile devices are expected to evolve into diverse form factors, including augmented reality glasses, virtual reality headsets, and holographic devices. In the 6th-generation (6G) era, efforts are being made to develop improved 6G communication systems to connect hundreds of billions of devices and objects and provide diverse services. For this reason, 6G communication systems are often referred to as "beyond 5G."

[0003] The 6G communication system, expected to be realized around 2030, will have a maximum transmission speed of terabytes per second (i.e., 1,000 gigabits per second) and a wireless latency of 100 microseconds (μsec). In other words, compared to 5G, the transmission speed in a 6G communication system will be 50 times faster, while the wireless latency will be reduced to one-tenth.

[0004] To achieve these high data rates and ultra-low latency, 6G communication systems are being considered for implementation in the terahertz band (e.g., from 95 gigahertz (GHz) to 3 terahertz (THz)). Compared to the millimeter wave (mmWave) band introduced in 5G, the terahertz band is expected to experience more severe path loss and atmospheric absorption, making it more crucial to ensure signal reach, or coverage, in this band. Key technologies to ensure coverage include radio frequency (RF) components, antennas, new waveforms that offer better coverage than OFDM (orthogonal frequency division multiplexing), beamforming, and multiple antenna transmission technologies such as massive multiple-input and multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas. In addition, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing using orbital angular momentum (OAM), and reconfigurable intelligent surfaces (RIS) are being discussed to improve the coverage of terahertz band signals.

[0005] In addition, in order to improve frequency efficiency and system network, 6G communication systems are developing full duplex technology that utilizes the same frequency resources at the same time for uplink and downlink; network technology that integrates satellites and high-altitude platform stations (HAPS); network structure innovation technology that supports mobile base stations and enables optimization and automation of network operation; dynamic spectrum sharing technology through collision avoidance based on spectrum usage prediction; AI-based communication technology that utilizes artificial intelligence (AI) from the design stage and internalizes end-to-end AI support functions to realize system optimization; and next-generation distributed computing technology that realizes services with complexity that exceeds the limits of terminal computing capabilities by utilizing ultra-high-performance communication and computing resources (mobile edge computing (MEC), cloud, etc.). In addition, efforts are being made to further strengthen connectivity between devices, further optimize networks, promote softwareization of network entities, and increase the openness of wireless communications through the design of new protocols to be used in 6G communication systems, the implementation of hardware-based security environments, the development of mechanisms for the safe use of data, and the development of technologies for maintaining privacy.

[0006] Research and development of these 6G communication systems are expected to enable a new level of hyper-connected experience through the hyper-connectivity of 6G communication systems, which encompass not only connections between things but also connections between people and things. Specifically, 6G communication systems are expected to enable services such as truly immersive extended reality (Truly Immersive XR), high-fidelity mobile holograms, and digital replicas. Furthermore, services such as remote surgery, industrial automation, and emergency response, which are provided through enhanced security and reliability, will find application in diverse fields such as industry, healthcare, automotive, and home appliances.

[0007] In a radio access network (RAN) system, cell sites are connected to distributed units (DUs), and the processing (or conversion) capacity of a distributed unit is determined by the maximum traffic that can enter the cell site. This leaves the DU's resources unused outside of peak traffic times.

[0008] A virtualized RAN (vRAN) system can perform the functions of a radio access network by virtualizing a DU or CU (centralized unit) into a vDU (virtualized DU) and vCU (virtualized CU) based on software rather than hardware and running them through a general server device.

[0009] DUs and cell sites (e.g., a set of RUs) in a wireless access network can form a 1:1 connection relationship with each other. In a virtual wireless access network, vDU pooling breaks this 1:1 connection relationship, and by virtualizing through DU pooling, resources can be used efficiently and the number of servers can be reduced.

[0010] 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.

[0011] A method for performing terminal unit migration of a wireless network system according to one embodiment of the present disclosure may include a step of identifying information about a terminal to be migrated from a radio link control (RLC) of a first distributed unit (DU) to an RLC of a second DU. The method may include a step of changing an F1-U interface of a centralized unit (CU) from an RLC of the CU and the first DU to an RLC of the CU and the second DU. The method may include a step of resetting information included in the RLC of the second DU. The method may include a step of changing a connection between an RLC of the first DU and a media access control (MAC) of the second DU to a connection between an RLC of the second DU and a MAC of the second DU.

[0012] An electronic device for performing terminal unit transfer of a wireless network system according to one embodiment of the present disclosure may include a memory storing one or more instructions and at least one processor executing one or more instructions stored in the memory. The at least one processor may identify information about a terminal to be transferred from a radio link control (RLC) of a first distributed unit (DU) to an RLC of a second DU. The at least one processor may change an F1-U interface of a centralized unit (CU) from an RLC of the CU and the first DU to an RLC of the CU and the second DU. The at least one processor may reset information included in the RLC of the second DU. The at least one processor may change a connection between an RLC of the first DU and a media access control (MAC) of the second DU to a connection between an RLC of the second DU and a MAC of the second DU.

[0013] 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.

[0014] Figure 1 is a drawing for explaining the structure of RAN.

[0015] Figure 2 is a diagram for explaining the structure of RAN according to dynamic scaling.

[0016] FIG. 3 is a diagram for explaining a method of scaling in / out of a distributed unit (DU) according to a change in traffic of the DU, according to one embodiment.

[0017] Figure 4 is a diagram showing an example of packet loss during the scaling process of DU.

[0018] FIG. 5 is a diagram illustrating a method for performing terminal unit transfer according to one embodiment of the present disclosure.

[0019] FIG. 6 is a flowchart of a method for performing terminal unit transfer according to one embodiment of the present disclosure.

[0020] FIG. 7 is a diagram illustrating a method for performing cell unit transfer and terminal unit transfer according to one embodiment of the present disclosure.

[0021] FIG. 8 is a specific drawing of a method for performing terminal unit transfer according to one embodiment of the present disclosure.

[0022] FIG. 9 is a diagram illustrating a sequence for changing an F1-U interface according to one embodiment of the present disclosure.

[0023] FIG. 10 is a diagram of an RLC reset sequence according to one embodiment of the present disclosure.

[0024] FIG. 11A is a diagram illustrating a method of performing buffering in a CU as an example of controlling a downlink packet according to one embodiment of the present disclosure.

[0025] FIG. 11b is a diagram illustrating a method for performing buffering in an RLC of a source DU as an example of controlling a downlink packet according to an embodiment of the present disclosure.

[0026] FIG. 11c is a diagram illustrating a method for performing buffering in an RLC of a target DU as an example of controlling a downlink packet according to an embodiment of the present disclosure.

[0027] FIG. 12A is a diagram illustrating a method for limiting a schedule of an uplink packet, as an example of controlling an uplink packet according to one embodiment of the present disclosure.

[0028] FIG. 12b is a diagram illustrating a method for switching a path of an uplink packet as an example of controlling an uplink packet according to one embodiment of the present disclosure.

[0029] FIG. 13 is a schematic block diagram of an electronic device according to one embodiment of the present disclosure.

[0030] Hereinafter, embodiments of the present disclosure are described in detail with reference to the attached drawings.

[0031] The present disclosure may be subject to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments of the present disclosure, and it should be understood that the present disclosure encompasses all modifications, equivalents, and alternatives falling within the spirit and technical scope of the various embodiments.

[0032] In describing the embodiments, detailed descriptions of related known technologies are omitted if they are deemed to unnecessarily obscure the gist of the present disclosure. Furthermore, numbers (e.g., "first," "second," etc.) used throughout the description of the specification are merely identifiers used to distinguish one component from another.

[0033] The terms used in the embodiments of this specification have been selected from widely used, current terms, taking into account the functions of the present disclosure. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, the applicant may arbitrarily select terms, and in such cases, their meanings will be described in detail in the description of the relevant embodiments. Therefore, the terms used in this disclosure should not be defined simply as names of terms, but rather based on the meanings of the terms and the overall content of the present disclosure.

[0034] The scope of the present disclosure may be indicated by the claims that follow rather than the detailed description above. Various features mentioned in one claim category of the present disclosure (e.g., in a method claim) may also be claimed in another claim category (e.g., in a system claim). Furthermore, an embodiment of the present disclosure may include not only combinations of features specified in the appended claims, but also various combinations of individual features within the claims. The scope of the present disclosure should be interpreted to include all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts.

[0035] Also, in this disclosure, when a component is referred to as being "connected" or "connected" to another component, it should be understood that the component may be directly connected or directly connected to the other component, but may also be connected or connected via another component in between, unless specifically stated otherwise. Furthermore, it includes not only cases where it is "directly connected" or "physically connected," but also cases where it is "electrically connected" with another element in between. In this disclosure, the terms "transmit," "receive," and "communicate" include both direct and indirect communication. When a part throughout this disclosure is said to "include" a component, this does not exclude other components, but rather may include other components, unless specifically stated otherwise.

[0036] In addition, components expressed as 'unit', 'module', etc. in the present disclosure 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. These functions may be implemented by hardware or software, or a combination of hardware and software. 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 dedicated and performed by other components.

[0037] Singular expressions may include plural expressions unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art described herein.

[0038] Throughout this disclosure, unless specifically stated otherwise, "or" is inclusive and not exclusive. Thus, unless explicitly stated otherwise or the context dictates otherwise, "A or B" can mean "A, B, or both." As used herein, the phrases "at least one of" or "one or more of" can mean that different combinations of one or more of the listed items can be used, or that only any one of the listed items is required. For example, "at least one of A, B, and C" can include any of the following combinations: A, B, C, A and B, A and C, B and C, or A and B and C.

[0039] It will be appreciated that each block of the flowchart drawings and combinations of the flowchart drawings can be performed by computer program instructions. These computer program instructions can be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, such that the instructions, when executed by the processor of the computer or other programmable data processing equipment, create a means for performing the functions described in the flowchart block(s). These computer program instructions can also be stored in a computer-available or computer-readable memory that can direct a computer or other programmable data processing equipment to perform the functions in a specific manner, such that the instructions stored in the computer-available or computer-readable memory can produce an article of manufacture that includes instruction means for performing the functions described in the flowchart block(s). Since the computer program instructions may be installed on a computer or other programmable data processing device, a series of operational steps may be performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for performing the functions described in the flowchart block(s) may also provide steps for performing the functions described in the flowchart block(s).

[0040] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0041] Below, embodiments of the present disclosure are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein. In addition, for the purpose of clearly explaining the present disclosure in the drawings, parts irrelevant to the description are omitted, and similar parts are designated with similar reference numerals throughout the specification.

[0042] Furthermore, while LTE, LTE-A, or 5G systems may be used as examples in the following description, embodiments of the present disclosure may also be applied to other communication systems with similar technical backgrounds or channel types. For example, this may include 5G-Advance, or 6G (beyond 5G), which are developed after 5G mobile communication technology (NR), and the term "5G" below may encompass existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications, as determined by a person skilled in the art, without significantly departing from the scope of the present disclosure.

[0043] The terms used in this disclosure will be briefly explained, and an embodiment of the present invention will be specifically described.

[0044] The terms described below are defined based on their functions within the present invention, and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the contents of this specification.

[0045] In the present disclosure, a base station is an entity that performs resource allocation of a terminal, and may be at least one of a gNode B, an eNode B, a Node B (or, x Node B (where x is an alphabet including g and e)), a BS (Base Station), a wireless access unit, a base station controller, a satellite, an airborne vehicle, or a node on a network, but is not limited thereto. The base station in the present disclosure may mean the base station itself, a Cell, or an RU depending on the interpretation, and the target that exchanges messages with the UE may be a DU or a CU depending on the structure.

[0046] Additionally, in the present disclosure, user equipment (UE) may include a mobile station (MS), a cellular phone, a smartphone, a computer, a vehicle, a satellite, or a multimedia system capable of performing a communication function.

[0047] Additionally, in the present disclosure, a cell may represent an area covered by a single base station in wireless communications. Cells may be classified into mega cells, macro cells, micro cells, and pico cells based on their size, but these are merely examples, and the types of cells are not limited to the above.

[0048] Additionally, in the present disclosure, a distributed unit (DU) is connected to an RU and a CU and executes a portion of the RLC, MAC, and PHY layers. In one embodiment of the present disclosure, a virtualized DU (DU) may be included.

[0049] Additionally, in the present disclosure, a centralized unit (CU) may include RRC, SDAP, and PDCP layers as a central device. A single CU may manage one or more DUs and be connected to the DUs via an F1 interface. In one embodiment of the present disclosure, a virtualized CU may be included.

[0050] Additionally, in the present disclosure, the radio unit (RU) performs the role of converting a wireless signal into a digital signal for transmission over a packet network.

[0051] Additionally, in the present disclosure, the downlink is a wireless transmission path through which a base station transmits data or control signals to a terminal. Specifically, in the LTE system, the downlink employs the orthogonal frequency division multiplexing (OFDM) method.

[0052] In this disclosure, uplink refers to a wireless transmission path through which a terminal transmits data or control signals to a base station. Specifically, in the LTE system, the uplink employs the single carrier frequency division multiplexing access (SC-FDMA) method.

[0053] In this disclosure, the F1 interface consists of F1-C for control data and F1-U for user data. In the structure of F1-C, the Transport Network Layer is based on IP transport configured with SCTP on top of IP, and the application layer signaling protocol is called F1AP. In the structure of F1-U, the Transport Network Layer is based on IP transport configured with UDP and GTP-U on top of IP.

[0054] In the following description, terms referring to broadcast information, terms referring to control information, terms related to communication coverage, terms referring to state changes (e.g., events), terms referring to network entities, terms referring to messages, terms referring to device components, etc. are examples for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0055] For the convenience of the following description, the present disclosure uses terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP) standards, or terms and names modified therefrom. However, the present disclosure is not limited to the above-described terms and names, and can be equally applied to wireless communication systems conforming to other standards. For example, although the embodiments of the present disclosure are described using a 5th generation wireless communication technology (5G, new radio, NR) system as an example, an embodiment of the present disclosure may be applied to other wireless communication systems having a similar technical background or channel type. As another example, the embodiments of the present disclosure may be applied to LTE or LTE-A, which are wireless communication systems prior to NR, and further, the embodiments of the present disclosure may be applied to wireless communication systems developed after NR. Furthermore, the embodiments of the present disclosure may be applied to other wireless communication systems with some modifications, as determined by a person having skilled technical knowledge, without significantly departing from the scope of the present disclosure.

[0056] Figure 1 is a drawing for explaining the structure of RAN.

[0057] Referring to Figure 1, RAN is a network that supports wireless access to UE (user equipment) and can be viewed as a collection of base stations. RAN can be broadly divided into CU (centralized unit, 10), DU (distributed unit, 20), and RU (radio unit, 30). The topology of a conventional RAN consists of RU, DU, and CU in an N:M:1 (N>>M>>1) configuration. A cell corresponds to the area covered by a base station in a wireless communication system, and there can be at least one cell per base station.

[0058] CU (10) can receive signals from DU (20) or transmit signals to DU (20) via F1 interface. One CU (10) can be connected to multiple DU (20), but if the number of DU (20) is dynamically changed, the F1 interface may be violated.

[0059] DU (20) can process a signal received from RU (30) and transmit the processed signal to CU (10) through F1 interface. In addition, it can receive and process a signal from CU (10) through F1 interface or transmit the signal to RU (30). DU (20) can perform various wireless access network functions to process the signal. The wireless access network function can include RLC (radio link control) layer function, MAC (medium access control) function, or H-PHY (higher physical) layer function, but this is only an example, and the wireless access network function is not limited to the above-described examples.

[0060] Below, the functions of the RLC layer, MAC layer, and PHY layer are explained.

[0061] The RLC layer functionality may include at least some of the following functions:

[0062] - Transfer of upper layer PDUs

[0063] - In-sequence delivery of upper layer PDUs

[0064] - Out-of-sequence delivery of upper layer PDUs

[0065] - Error Correction through ARQ

[0066] - Concatenation, segmentation and reassembly of RLC SDUs

[0067] - Re-segmentation of RLC data

[0068] - Reordering of RLC data

[0069] - Duplicate detection function

[0070] - Protocol error detection

[0071] - RLC SDU discard function

[0072] - RLC re-establishment function

[0073] The in-sequence delivery function of the RLC layer refers to the function of sequentially delivering RLC SDUs (service data units) received from a lower layer to an upper layer, and may include a function of reassembling and delivering multiple RLC SDUs when one RLC SDU is received divided into multiple RLC SDUs. In addition, the in-sequence delivery function may include at least one of a function of reordering received RLC PDUs based on an RLC SN (sequence number) or a PDCP SN (sequence number), a function of recording lost RLC PDUs by reordering the sequence, and a function of reporting the status of lost RLC PDUs to the transmitting side. In addition, the in-sequence delivery function may include a function of requesting retransmission of lost RLC PDUs, and, when there is a lost RLC SDU, a function of sequentially delivering only the RLC SDUs up to the lost RLC SDU to an upper layer. Additionally, the in-order delivery function may include a function to sequentially deliver to the upper layer all RLC SDUs received before the timer starts if a predetermined timer has expired even if there are lost RLC SDUs, or a function to sequentially deliver to the upper layer all RLC SDUs received up to the present if a predetermined timer has expired even if there are lost RLC SDUs.

[0074] The RLC layer can process RLC PDUs in the order they are received and forward them to the PDCP layer, regardless of the sequence order. When a segment is received, the RLC layer can combine it with segments stored in the buffer or segments to be received later, reconstruct it into a complete RLC PDU, and then forward the RLC PDU to the PDCP layer. Meanwhile, in NR (new radio), the RLC layer may not include a concatenation function, and the concatenation function may be performed in the MAC layer or replaced by the multiplexing function of the MAC layer.

[0075] The functionality of the MAC layer may include at least some of the following functions:

[0076] - Mapping between logical channels and transport channels

[0077] - Multiplexing / demultiplexing of MAC SDUs

[0078] - Scheduling information reporting function

[0079] - Error correction through HARQ

[0080] - Priority handling between logical channels of one UE

[0081] - Priority handling between UEs by means of dynamic scheduling

[0082] - MBMS service identification function

[0083] - Transport format selection function

[0084] - Padding function

[0085] The PHY layer can perform at least some of the following functions:

[0086] - Data transmission and reception using electrical signals

[0087] - Channel coding / decoding function

[0088] - Modulation / demodulation function

[0089] - Power control

[0090] - Cell search

[0091] The PHY layer performs channel coding and modulation on data from higher layers, converting them into OFDM symbols for transmission over a wireless channel. Furthermore, the PHY layer performs demodulation and channel decoding on OFDM symbols received over a wireless channel, and can pass the resulting data to higher layers.

[0092] The RU (30) can transmit signals to the DU (20) through a fronthaul interface. In addition, it can receive signals from the DU (20) through the fronthaul interface. The fronthaul is a network portion that connects the RU (30) of a cell site to the DU (20), and can perform functions such as DSP (digital signal processing), power amplification, and filtering.

[0093] In order to efficiently utilize the resources of DU (20), the present disclosure aims to provide a packet processing method in DU (20) that is dynamically managed without violating the F1 interface. The CU (10), DU (20), and RU (30) described below can operate in a virtualized RAN. Virtualization refers to a technology that can expand the resources available in a single device by integrating and managing multiple physical resources.

[0094] Figure 2 is a diagram for explaining the structure of RAN after dynamic scaling.

[0095] Referring to Fig. 2, the RAN is a network that supports wireless access to user equipment (UE) and can be viewed as a collection of base stations. The RAN can be broadly divided into a centralized unit (CU, 10), a distributed unit (DU, 20), and a radio unit (RU, 30). In order to efficiently use the resources of the DU (20), an operation for dynamically scaling out or in the DU is disclosed.

[0096] In order to efficiently utilize the resources of a DU (20), the present disclosure proposes a packet processing method for dynamic allocation of DUs. When a CU (10) and N DUs (20) are connected, if scaling out of a DU is required based on traffic information or resource information, the N'th DU (20b) can be added. In one embodiment, if scaling in of a DU is required based on traffic information or resource information, the N'th DU (20b) can be removed.

[0097] In one embodiment of the present disclosure, traffic information and e-resource information of DU (20) can be compared to determine whether scaling in / out is performed. For example, if the resource processing capacity of DU (20) is greater than a preset value, scaling out can be performed. If the resource processing capacity of DU (20) is less than a preset value, scaling in can be performed. Alternatively, the difference between the resource processing capacity and traffic volume of DU can be compared with a preset value to determine whether scaling in / out is performed.

[0098] FIG. 3 is a diagram for explaining a method of scaling in / out of a distributed unit (DU) according to a change in traffic of the DU, according to one embodiment.

[0099] Figure 3 illustrates information regarding traffic generated from multiple base stations or CUs. Hereinafter, traffic refers to a flow of packets or data passing through a communication network within a certain period of time.

[0100] In one embodiment of the present disclosure, traffic may include data flow between a terminal and a base station, and may be expressed as a data transmission rate per unit time, etc. In addition, traffic processing information may include traffic information regarding a plurality of base stations where traffic is generated, and resource information used to process traffic generated by the plurality of base stations. For example, traffic information may include a traffic processing rate per cell (e.g., bps), the number of UEs connected to an RU, the generated frequency band, etc. In addition, in one embodiment of the present disclosure, resource information may refer to the ratio of DUs used for traffic processing, and the amount of resources of DUs used for traffic processing. However, the above-described examples are merely examples, and the traffic information or resource information is not limited to the above-described examples.

[0101] In existing RAN systems, the processing capacity of a DU is determined by the maximum amount of traffic that can enter a cell site directly connected to the DU. However, as shown in Figure 3, the hourly traffic volume is not constant and fluctuates, reducing the efficiency of the DU's resources. For example, the maximum hourly traffic volume is observed between 6:00 PM and 9:00 PM (320a), while between 3:00 PM and 5:00 PM (310a, 330a), the traffic volume is only about 20% of the maximum hourly traffic volume (320a).

[0102] Given the unstable nature of traffic volumes, a method is developed to efficiently utilize DU resources. Specifically, a method is provided to dynamically allocate DUs the required amount of resources based on traffic or resource information without violating the F1 interface.

[0103] For example, in a section (310a) with low traffic volume per hour, traffic is processed with one DU (310b). In a section (320a) where the maximum traffic volume per hour occurs depending on changes in traffic volume, the number of DUs is increased, that is, the total processing capacity of the DUs is increased through scaling out of the DUs (320b). When scaling out, the CU recognizes both the existing DU and the scaled-out DU as one, so the scaled-out DU can transmit and receive packets with the existing DU through the inter-DU interface. In addition, the CU can determine which RU among at least one RU connected to the existing DU will be connected to the scaled-out DU, and provide information about the determined RU to the DU.

[0104] In the section (330a) where the amount of traffic per hour decreases again, the number of DUs is reduced, i.e., the total processing capacity of the DUs is reduced through scaling in the DUs (330b). By dynamically allocating DU resources, waste of DU resources can be prevented. In addition, at least one RU connected to the DU to be scaled in can be connected to a previously connected DU or a DU that has not been scaled in.

[0105] Figure 4 is a diagram showing an example of packet loss during the scaling process of DU.

[0106] Referring to FIG. 4, a procedure for processing packets between a base station and a terminal is disclosed. FIG. 4 illustrates a process in which a downlink packet is transmitted from a CU (10) to a UE (40) via a DU (20) and an RU (30), and this can be similarly applied in the reverse direction to an uplink packet. FIG. 4 illustrates a state after the RLC entity of a source DU (20a) is connected to the MAC entity of a target DU (20b) according to cell migration. For convenience of explanation, the source DU (20a) is hereinafter referred to as the first DU, and the target DU (20b) is hereinafter referred to as the second DU.

[0107] In one embodiment of the present disclosure, when a CU (10) transmits a downlink packet having a specific sequence number to a UE (40), a problem may occur in the synchronization of packet information between the RLC of the DU and the RLC of the terminal due to dynamic scaling of the DU, and thus a radio link failure (RLF) may occur, in which the connection with the terminal is disconnected. Since the packet information between the RLCs of the UE (40) and the DU (20) is different, it is considered that an error has occurred, and thus the connection with the UE (40) is determined to be disconnected, and a problem may occur in which communication is disconnected as reconnection is performed through a random access procedure.

[0108] In one embodiment of the present disclosure, in order to perform a dynamic scaling operation from a source DU (20a) to a target DU (20b), a migration in PHY / MAC / Fronthaul is performed on a cell-by-cell basis and a migration in Midhaul / RLC is performed on a UE-by-UE basis. The MAC-RLC path can be changed through the cell-by-cell migration, and the present disclosure specifically discloses a terminal-by-terminal migration procedure following the cell-by-cell migration.

[0109] In one embodiment, the CU (10) may perform a unit-by-unit migration from a source DU (20a) to a target DU (20b). The F1-U path between the CU (10) and the DU (20) may change according to the unit-by-unit migration. In one embodiment, the F1-U path, i.e., the user packet path, may change (410) from the source DU (20a) to the target DU (20b). The connection between the RLC of the source DU (20a) and the MAC layer of the target DU (20b) connected through cell-by-cell migration may cause a MAC-RLC path change (440) according to the unit-by-unit migration. The connection between the RLC of the target DU (20b) and the MAC of the target DU (20b) may change according to the unit-by-unit migration. Hereinafter, a specific unit-by-unit migration procedure will be described in FIG. 5 and below.

[0110] In one embodiment, the CU (10) can transmit a downlink packet having a sequence number of 1 to 4 to the source DU (20a). In one embodiment, the source DU (20a) can buffer the received downlink packet. The RLC of the source DU (20a) can transmit the downlink packet to the MAC of the connected target DU (20b) according to cell-by-cell migration. The MAC / PHY layer of the target DU (20b) can transmit the downlink packet to the UE (40) through the RU (30). The CU (10) can transmit a downlink packet having a sequence number of 5 or 6 to the target DU (20b) as the user packet path changes (410). In one embodiment, the target DU (20b) can buffer the downlink packet received from the CU (10). The target DU (20b) can transmit the corresponding downlink packet to the UE (40) via the RU (30). The UE (40) can transmit (420) an "ACK" indicating packet reception confirmation depending on whether the downlink packet has been received or a "NACK" requesting retransmission of the corresponding packet depending on packet reception failure.

[0111] In one embodiment, a DU (20a, 20b) that receives a downlink packet from a CU (10) may store information about the downlink packet including the corresponding downlink packet in a packet buffer. For example, the information about the downlink packet may include, but is not limited to, the packet itself, status information indicating the processing status of the packet, various timer-related information, information about the user identifier that is the transmission target, information about the storage size, etc.

[0112] In one embodiment, when the DU (20a, 20b) receives an "ACK" signal, it may delete information about a packet having the corresponding sequence number. In one embodiment, when the DU (20a, 20b) receives a "NACK" signal, it may retransmit the downlink packet for the corresponding sequence to the UE (40) within a preset time. For example, the time limit for retransmission may be set to 1 ms to 2 s depending on the setting, and the default value may be set to 320 ms. In one embodiment, when the downlink packet corresponding to the "NACK" signal is not retransmitted within the preset time, the base station may determine / identify / decide that the connection with the UE (40) is broken.

[0113] In one embodiment, the CU (10) may transmit downlink packets having sequence numbers 1 to 4 to the source DU (20a) and downlink packets having sequence numbers 5 and 6 to the target DU (20b) according to user packet path change (440) in order to transmit downlink packets having sequence numbers 1 to 6 to the UE (40). In one embodiment, the source DU (20a) or the target DU (20b) may buffer downlink packets in a packet buffer. The downlink packets having sequence numbers 1 and 2 that the source DU (20a) was buffering may be transmitted to the UE (40) through the MAC / PHY layer of the target DU (20b) according to the MAC RLC path change (410). When the UE (40) successfully receives the packets, the UE (40) may transmit (420) an "ACK" for the packets. For example, a source DU (20a) that receives an "ACK" signal indicating that transmission of a downlink packet having sequence numbers 1 and 2 was successful can remove information about the downlink packet.

[0114] In one embodiment, when the UE (40) does not receive a downlink packet having a sequence number of '3' during transmission of a downlink packet, i.e., when a downlink packet having a sequence number of '3' is lost during communication (430), the UE (40) may transmit a "NACK" signal (420). At this time, as dynamic scaling is performed to the target DU (20b), the MAC-RLC path (410) and the user packet path are changed (440), so that the target DU (20b) that received the "NACK" signal may not store information about the downlink packet having the sequence number of '3'. Since the target DU (20b) does not store information about the downlink packet having the sequence number of '3', the target DU (20b) cannot perform retransmission of the corresponding downlink packet. If retransmission of the packet according to the "NACK" is not performed within a preset time, an RLF may occur, which may cause a delay in communication between the base station and the terminal. Below, we disclose a method for performing an RLC reset to synchronize RLCs to prevent such RLFs from occurring.

[0115] FIG. 5 is a diagram illustrating a method for performing terminal unit transfer according to one embodiment of the present disclosure.

[0116] Referring to FIG. 5, a method for preventing packet loss through RLC reset while performing terminal unit migration is illustrated. For convenience of explanation, the source DU (20a) is referred to as the first DU, and the target DU (20b) is referred to as the second DU.

[0117] In one embodiment of the present disclosure, a state after an RLC entity of a source DU (20a) is connected to a MAC entity of a target DU (20b) according to cell-by-cell migration is illustrated. In one embodiment, in order to perform a dynamic scaling operation from the source DU (20a) to the target DU (20b), migration in PHY / MAC / Fronthaul is performed on a cell-by-cell basis and migration in Midhaul / RLC is performed on a UE-by-UE basis. Through the cell-by-cell migration, a MAC-RLC path can be changed to a connection between the RLC entity of the source DU (20a) and the MAC entity of the target DU (20b), and the present disclosure specifically discloses a terminal-by-terminal migration procedure after the cell-by-cell migration.

[0118] In one embodiment, information about a UE (40) to be transferred from a source DU (20a) to a target DU (20b) may be identified to perform a terminal-by-terminal transfer. Information about the UE (40) may include, but is not limited to, an identifier of the UE (40), information about a packet to be transmitted or received, information about a timer, information about the storage size of the packet, information about the status of the packet, etc.

[0119] In one embodiment, when a UE to be transferred from a source DU (20a) to a target DU (20b) is identified according to a terminal unit transfer, the CU (10) or the DU (20a, 20b) can control downlink packets received from the data network. If downlink packets are continuously transmitted to the UE (40) during the terminal unit transfer procedure, an RLF may occur due to a missync between the RLC entity of the UE (40) and the information according to a sequence number update in the RLC entity of the DU (20a, 20b). Therefore, the CU (10) or the DU (20a, 20b) can perform control of the downlink packets.

[0120] In one embodiment, the CU (10) may buffer a downlink packet in the PDCP buffer of the CU (10) based on receiving a message requesting buffering of a downlink packet from the DU (20a, 20b). In one embodiment, the source DU (20a) may buffer a downlink packet received from the CU (10) via the F1-U interface in the buffer. In one embodiment, the target DU (20b) may buffer a downlink packet received from the CU (10) via the F1-U interface in the buffer. Hereinafter, for a specific method of controlling the downlink packet, refer to FIGS. 11a to 11c.

[0121] In one embodiment, the CU (10) can transmit downlink packets to the source DU (20a) and receive uplink packets via the F1-U interface. The F1 interface is composed of F1-C for control data and F1-U for user data. In the structure of F1-C, the Transport Network Layer is based on IP transport configured as SCTP on top of IP, and the application layer signaling protocol is called F1AP. In the structure of F1-U, the Transport Network Layer is based on IP transport configured as UDP and GTP-U on top of IP. Depending on the terminal unit transfer, the F1-U interface may be changed from a connection between the CU (10) and the source DU (20a) to a connection between the CU (10) and the target DU (20b). In other words, the user packet path may be changed from the source DU (20a) to the target DU (20b). In one embodiment, when a downlink packet is stored in the CU (10) according to downlink packet control, transmission of the downlink packet to the source DU (20a) or the target DU (20b) may not be performed.

[0122] For example, a downlink packet having a sequence number of 1 to 5 can be transmitted from a CU (10) to a source DU (20a). A downlink packet having a sequence number of 7 can be transmitted from a CU (10) to a target DU (20b) according to a change in the F1-U path.

[0123] In one embodiment, a DU (20a, 20b) that receives a downlink packet from a CU (10) may store information about a downlink packet including the corresponding downlink packet in a packet buffer. For example, information about a downlink packet may include, but is not limited to, the packet itself, status information indicating the processing status of the packet, various timer-related information, information about a user identifier that is a transmission target, information about a storage size, etc. In one embodiment, according to downlink packet control, a source DU (20a) or a target DU (20b) may buffer a downlink packet in a buffer and not transmit it to the entity thereafter.

[0124] In one embodiment, DUs (20a, 20b) can transmit downlink packets to UEs (40) via RUs (30). Since the RLC entity of the source DU (20a) is connected to the MAC entity of the target DU (20b) according to cell-by-cell transfer, the source DU (20b) can transmit downlink packets to RUs (30) via the MAC entity of the target DU (20b). For example, downlink packets corresponding to sequence numbers 1 to 6 received by the source DU (20b) can be transmitted from the RLC entity of the source DU (20a) to the MAC entity of the target DU (20b). The MAC entity of the target DU (20b) can transmit downlink packets to UEs (40) via RUs (30).

[0125] In one embodiment, the UE (40) may transmit an "ACK" indicating packet reception confirmation depending on whether a downlink packet has been received, or a "NACK" requesting retransmission of the packet depending on packet reception failure. In one embodiment, when the DU (20a, 20b) receives an "ACK" signal, it may delete information about the packet having the corresponding sequence number. In one embodiment, when the DU (20) receives a "NACK" signal, it may retransmit the downlink packet for the corresponding sequence to the UE (40) within a preset time. For example, the time limit for retransmission may be set to 1 ms to 2 s depending on the setting, and the default value may be set to 320 ms. In one embodiment, when the downlink packet corresponding to the "NACK" signal is not retransmitted within the preset time, it may be determined / identified / determined that the connection with the base station UE (40) is broken. For example, if a UE (40) successfully receives a downlink packet having a sequence number of 1 to 4, it may transmit an "ACK" indicating confirmation of receipt of the downlink packet. A source DU (20a) that receives an "ACK" for a downlink packet having a sequence number of 1 to 4 may delete information about the corresponding downlink packet.

[0126] In one embodiment, packet loss may occur and RLF may occur as a terminal-by-terminal transfer is performed during a downlink packet transmission process of a DU (20a, 20b) or an uplink packet transmission process of a terminal. For example, a source DU (20a) may transmit a downlink packet having a sequence number of 5 or 6 to a UE (40). The UE (40) may be in a state of receiving processing (520) for a downlink packet having a sequence number of '5' or transmitting (530) a downlink packet having a sequence number of '6'. The source DU (20a), which has not received an "ACK" indicating reception of a downlink packet from the UE (40), may wait (540) for a transmission completion signal. The target DU (20b) may wait (550) for transmission in order to transmit a downlink packet having a sequence number of '7' received from the CU (10) in accordance with the sequence number order. When the UE (40) transmits a "NACK" requesting retransmission for a downlink packet with a sequence number of '5' or '6' to the target DU (20b) according to the terminal unit transfer, a problem may occur in which the target DU (20b) that does not store information about the packet cannot perform retransmission. Before describing the RLC reset (560) procedure to prevent such RLF, a method for controlling an uplink packet will be described below.

[0127] In one embodiment, since uplink packets transmitted from the UE (40) may be lost during the terminal-by-terminal transfer procedure, the DUs (20a, 20b) may perform control on the uplink packets. In one embodiment, since the F1-U interface changes from the CU and the source DU to the CU and the target DU as the terminal-by-terminal transfer is performed, a problem occurs in which the source DU cannot transmit the uplink packets transmitted from the UE (40) to the CU. Since the first DU cannot transmit the uplink packets to the CU via the RLC layer after the F1-U interface changes, it is required to control this to prevent loss of the uplink packets. In one embodiment, the MAC scheduler of the target DU (20b) may stop allocating resources for the uplink packets transmitted by the UE (40). In one embodiment, the uplink packets may be buffered in the buffer of the source DU (20a). In one embodiment, before the RLC reset is completed due to the change of the F1-U path and the MAC-RLC path, the uplink packet can be transmitted to the CU (10) via the PHY and MAC entities of the target DU (20b) and the RLC entity of the source DU (20a). After the RLC reset is completed due to the change of the F1-U path and the MAC-RLC path, the uplink packet can be transmitted to the CU (10) via the PHY and MAC entities of the target DU (20b) and the RLC entity of the target DU (20a). Hereinafter, for a specific method of controlling the uplink packet, reference will be made to FIGS. 12a and 12b.

[0128] In one embodiment, an RLC reset may be performed to prevent information between the RLC entity of the target DU (20b) and the RLC entity of the UE (40) from becoming different due to a terminal unit transfer. If the information between the RLC entity of the target DU (20b) and the RLC entity of the UE (40) becomes different, the UE (40) may request retransmission of the packet. If the target DU (20b) that has received a signal requesting retransmission of the packet does not store information about the packet, an RLF may occur, and thus information included in the RLC entity of the target DU (20b) and the RLC entity of the UE (40) may be reset. In one embodiment, information to be subject to an RLC reset may include, but is not limited to, at least one of the packet itself, status information of the packet, a UE identifier, various timer-related information, or information about the storage size of the packet. For example, information about downlink packets having sequence numbers 5 to 7, excluding downlink packets having sequence numbers 1 to 4 for which successful reception of downlink packets has been achieved, can be removed / deleted from the RLC entity of the target DU (20b) and the RLC entity of the UE (40). Hereinafter, a specific procedure for RLC reset is described in detail in FIG. 11.

[0129] In one embodiment, the connection between the RLC entity of the source DU (20a) and the MAC entity of the target DU (20b) may be changed to the connection between the RLC entity of the target DU (20a) and the MAC entity of the target DU (20b) due to the terminal unit transfer. The source DU (20a) may not intervene with respect to the UE (40) that has become the target of the terminal unit transfer due to the MAC-RLC path change. In one embodiment, the downlink packet received from the CU (10) due to the MAC-RLC path change may be transmitted to the UE (40) through the RU (30) via only the target DU (20b). For example, a downlink packet having a sequence number of 5 may be transmitted from the CU (10) to the target DU (20b) through the F1-U interface due to an RLC reset. The target DU (20b) can transmit to the UE (40) through the RU (30) starting from the downlink packet having the sequence number 5. The CU (10), the target DU (20b), the RU (30), and the UE (40) can operate in the same manner as the CU (10), the source DU (20a), the RU (30), and the UE (40) before the DU dynamic scaling is performed for subsequent procedures.

[0130] In one embodiment, when the MAC-RLC path change is completed, the CU (10) or DU (20a, 20b) can release control over the downlink packet and normalize. When the CU (10) or DU (20a, 20b) determines that the RLC reset is completed, it can perform processing on the buffered downlink packet. In one embodiment, the CU (10) can sequentially transmit the downlink packet buffered in the PDCP buffer to the target DU (20b). In one embodiment, the buffer of the source DU (20a) itself can be transferred to the target DU (20b), so that the target DU (20b) can sequentially process the downlink packet buffered in the buffer transferred to the target DU (20b). In one embodiment, the target DU (20b) can sequentially process the downlink packet buffered in the buffer of the target DU (20b). Hereinafter, specific processing of downlink packets is described with reference to FIGS. 11a to 11c.

[0131] In one embodiment, the target DU (20b) can stop controlling the uplink packet and return to normal. In one embodiment, when the target DU (20b) determines that the RLC reset is complete, the MAC scheduler of the target DU (20b) can resume resource allocation for the uplink packet that the terminal wants to transmit. In one embodiment, when the RLC reset is determined to be complete, the buffer of the source DU (20a) can be transferred to the target DU (20b) to process the buffered uplink packet. Hereinafter, specific processing of the uplink packet will be described with reference to FIGS. 12a and 12b.

[0132] In one embodiment, the source DU (20a) may identify whether there is a UE to be transferred to the target DU (20b), and the CU and DU (20a, 20b) may repeat the above procedures. If it is determined that there is no UE to be transferred to the terminal unit, the source DU (20a) may delete information about the terminal transferred to the target DU (20b).

[0133] FIG. 6 is a flowchart of a method for performing terminal unit transfer according to one embodiment of the present disclosure.

[0134] In the present disclosure, a DU connected to a CU before dynamic scaling of a DU is referred to as a source DU or first DU, and a DU connected to a CU after dynamic scaling is referred to as a target DU or second DU.

[0135] In step S610, the electronic device (1300) can identify information about a terminal to be migrated from the RLC of the first DU to the RLC of the second DU. The electronic device (1300) can obtain information about the terminals included in the migrated cell according to a cell-by-cell migration operation. In the present disclosure, the cell-by-cell migration operation is for migrating cells from the first DU to the second DU according to dynamic scaling of the DU, and may include an operation in which the RLC entity of the first DU connects with the MAC entity of the second DU.

[0136] In one embodiment, the electronic device (1300) may obtain information about cells to be transferred to the target DU (or second DU) according to dynamic scaling of the DU, and may obtain information about terminals included in the cells. After completing the cell-by-cell transfer operation, the electronic device (1300) may identify information about terminals to be transferred from the first DU to the second DU.

[0137] In one embodiment, if the electronic device (1300) determines that there is no terminal to be transferred from the first DU to the second DU after the cell-by-cell transfer is completed, the electronic device (1300) may delete information about the terminal that has completed transfer to the second DU within the RLC of the first DU. In one embodiment, if the electronic device (1300) completes deleting information about the terminal that has completed transfer to the second DU within the RLC of the first DU, the electronic device (1300) may determine that the dynamic scaling of the DU is completed.

[0138] In one embodiment, if the electronic device (1300) identifies that there is a terminal to be transferred from the first DU to the second DU, it may control downlink packets to perform terminal-by-terminal transfer. The electronic device (1300) may control downlink packets to prevent RLFs that occur due to sequence number updates resulting from the processing of downlink packets. In one embodiment, the electronic device (1300) may buffer downlink packets received from a data network in a PDCP buffer of a CU. In one embodiment, the electronic device (1300) may buffer downlink packets received from a data network in a buffer of the first DU. In one embodiment, the electronic device (1300) may buffer downlink packets received from a data network in a buffer of the second DU. Hereinafter, for a specific method of controlling downlink, refer to FIGS. 11A to 11C.

[0139] In step S620, the electronic device can change the F1-U interface of the CU from the RLC of the CU and the first DU to the RLC of the CU and the second DU. The CU can transmit and receive user packets with the DU through the F1-U interface. The F1 interface protocol can operate according to the contents disclosed in 3GPP TS 38.470.

[0140] In one embodiment, the electronic device (1300) may switch a connection with a first DU to a connection with a second DU to perform a terminal-level migration. After completing the cell-level migration, the electronic device (1300) may change the F1-U interface from the first DU to the second DU to transmit and receive user packets with the second DU.

[0141] In one embodiment, the electronic device (1300) can control uplink packets because the first DU cannot transmit uplink packets transmitted from the terminal to the CU as the F1-U interface changes from the CU and the first DU to the CU and the second DU. For example, before the change of the F1-U interface, uplink packets can be transmitted from the terminal to the CU via the RU, the PHY / MAC layer of the second DU, and the RLC layer of the first DU. After the F1-U interface changes, the electronic device (1300) can control this to prevent loss of uplink packets because the first DU cannot transmit uplink packets to the CU via the RLC layer.

[0142] In one embodiment, to prevent loss of uplink packets, the MAC scheduler of the second DU may stop allocating resources for uplink packets. In one embodiment, the uplink packets may be buffered in the buffer of the first DU. In one embodiment, to prevent loss of uplink packets, the uplink packets may be processed through the first DU before an RLC reset and processed through the second DU after an RLC reset according to the synchronization of the RLC entity. Hereinafter, for a specific method of controlling the uplink, refer to FIGS. 12A and 12B.

[0143] In step S630, the electronic device may reset information contained in the RLC of the second DU and the RLC of the terminal. The electronic device (1300) may reset information contained in the RLC of the DU to synchronize the RLC entity and prevent the occurrence of RLF.

[0144] In one embodiment, the electronic device (1300) may determine whether to retransmit a packet by comparing information included in an RLC entity of a DU and an RLC entity of a terminal. If the information included in the RLC entity of the DU and the information included in the RLC entity of the terminal are different, for example, if the status information of a packet included in the RLC entity of the DU and the status information of a packet included in the RLC entity of the terminal are different, retransmission of the packet may be requested. In one embodiment, if a packet for which retransmission has been requested is not retransmitted within a preset time, an RLF occurs, and thus a delay time may occur through the reconnection procedure.

[0145] In one embodiment, the electronic device (1300) may reset information contained in an RLC entity of a second DU to perform terminal-level migration. The electronic device (1300) may reset information contained in an RLC entity of a UE that is a target of migration from the first DU to the second DU. In one embodiment, information subject to RLC reset may include, but is not limited to, at least one of the packet itself, packet status information, a UE identifier, various timer-related information, or information regarding the storage size of the packet. Hereinafter, the RLC reset will be described in detail with reference to FIG. 11.

[0146] Since a message cannot be directly transmitted to the UE to reset the RLC entity of the UE, a message may be transmitted in the order of DU->CU->DU->UE to convert it into an RRC message. The electronic device (1300) may determine that the information included in the RLC entity of the second DU and the information included in the RLC entity of the terminal to be transferred are the same when comparing the sync between the second DU and the RLC entity of the terminal. The electronic device (1300) may not request retransmission of the packet based on determining that the sync is correct between the second DU and the RLC entity of the terminal.

[0147] In step S640, the electronic device can change the connection between the RLC of the first DU and the MAC of the second DU to the connection between the RLC of the second DU and the MAC of the second DU. The electronic device (1300) can change the connection between the RLC of the first DU and the MAC of the second DU to the connection between the RLC of the second DU and the MAC of the second DU in order to transmit and receive packets through the terminal and the second DU.

[0148] In one embodiment, the electronic device (1300) may establish a connection between the RLC of the first DU and the MAC of the second DU according to cell migration. The electronic device (1300) may change and / or switch the connection between the RLC of the first DU and the MAC of the second DU to a connection between the RLC of the second DU and the MAC of the second DU in order to perform communication without using the first DU for a terminal that is migrated from the first DU to the second DU according to terminal-by-terminal migration.

[0149] In one embodiment, when the RLC reset and the connection between the MAC and RLC entities of the second DU are completed, the electronic device (1300) can normalize downlink packets and uplink packets to activate packet transmission and reception with the terminal.

[0150] In one embodiment, the electronic device (1300) may stop control of downlink packets and normalize them. When the electronic device (1300) determines that the RLC reset is complete, the electronic device (1300) may process buffered downlink packets. In one embodiment, the electronic device (1300) may sequentially transmit downlink packets buffered in the PDCP buffer of the CU to the second DU. In one embodiment, the electronic device (1300) may transfer the buffer of the first DU to the second DU. The electronic device (1300) may sequentially process downlink packets buffered in the buffer transferred to the second DU. In one embodiment, the electronic device (1300) may sequentially process downlink packets buffered in the buffer of the second DU. Hereinafter, specific processing of downlink packets will be described with reference to FIGS. 11A to 11C.

[0151] In one embodiment, the electronic device (1300) can stop control of uplink packets and return to normal operation. In one embodiment, when the electronic device (1300) determines that the RLC reset is complete, the MAC scheduler of the second DU can resume resource allocation for uplink packets that the terminal wishes to transmit. In one embodiment, when the electronic device (1300) determines that the RLC reset is complete, the electronic device (1300) can transfer the buffer of the first DU to the second DU to process the uplink packets. Hereinafter, specific processing of uplink packets will be described with reference to FIGS. 12A and 12B .

[0152] In one embodiment, the electronic device (1300) may return to step S610 and determine whether there is information regarding a terminal to be transferred from the first DU to the second DU. If the electronic device (1300) determines that there is no information regarding a terminal to be transferred from the first DU to the second DU, the electronic device (1300) may delete the information regarding the terminal transferred from the first DU and determine that dynamic scaling of the DU is complete.

[0153] FIG. 7 is a diagram illustrating a method for performing cell-by-cell transfer and terminal-by-terminal transfer according to one embodiment of the present disclosure.

[0154] Referring to Fig. 7, the overall scenario for dynamic scaling of DU can be examined. To perform dynamic scaling of DU, the electronic device (1300) can perform cell migration (700) and then perform terminal migration (UE migration) (750).

[0155] Briefly explain the cell unit transfer (700).

[0156] In step S705, the electronic device (1300) may determine whether dynamic scaling of the DU is necessary. The electronic device (1300) may dynamically scale out or scale in the DU to efficiently use the resources of the DU.

[0157] In one embodiment, the electronic device (1300) can perform scaling out or scaling in of the DU by comparing traffic information with resource information of the DU.

[0158] In step S710, the electronic device (1300) can generate a target DU and perform an F1AP connection. In the structure of F1-C, the transport network layer is based on IP transport configured with SCTP on top of IP, and the application layer signaling protocol is called F1AP.

[0159] In one embodiment, the electronic device (1300) can perform an F1AP connection between the generated target DU and the CU.

[0160] In step S715, the electronic device (1300) can transfer the cell context of the RLC / MAC / PHY to the target DU. The electronic device (1300) can transfer the cell context of the source DU to the target DU.

[0161] In one embodiment, the electronic device (1300) may transfer cell contexts of cells to be transferred from a source DU to a target DU on an RLC / MAC / PHY entity basis to perform cell-by-cell transfer. The context of the UE included in the transferred cell is also transferred together.

[0162] In step S720, the electronic device (1300) can switch the fronthaul to the target DU. The fronthaul refers to an interface for transmitting and receiving signals between the DU and the RU. The fronthaul is a network portion that connects the RU (30) of the cell site to the DU (20), and can perform functions such as DSP (digital signal processing), power amplification, and filtering.

[0163] In one embodiment, the electronic device (1300) can switch the fronthaul interface between the RU and the source DU between the RU and the target DU as the target DU is generated.

[0164] In step S725, the electronic device (1300) can change the MAC-RLC path. The electronic device (1300) can change the MAC-RLC path to transmit and receive packets with the UE using the target DU.

[0165] In one embodiment, the electronic device (1300) can connect the RLC of the source DU and the MAC of the target DU. As the fronthaul interface is connected between the added target DU and the RU by performing cell-by-cell transfer, the electronic device (1300) can transmit and receive packets with the UE using the MAC of the target DU. Accordingly, the electronic device (1300) can connect the RLC entity of the source DU and the MAC entity of the target DU.

[0166] In step S730, the electronic device (1300) can determine whether the previous cell communication service was successful. The electronic device (1300) can determine whether the communication service in the transferred cell was successful through cell-by-cell transfer.

[0167] In one embodiment, if the electronic device (1300) determines that the cell communication service is not successful, it may return to step S715 and re-perform the steps below.

[0168] In one embodiment, if the electronic device (1300) determines that the cell communication service is successful, the electronic device (1300) may remove the transferred cell and the included UE context from the MAC / PHY of the source DU according to step S735. Since the MAC / PHY layer of the source DU is not involved in the previously successful cell according to the cell-by-cell transfer, the electronic device (1300) may remove / delete the context of the cell and the UE included in the cell from the MAC and PHY entities.

[0169] In one embodiment, the electronic device (1300) can perform a terminal unit transfer (750) when the cell unit transfer (700) is completed.

[0170] Below, the terminal unit transfer procedure (750) is briefly described. For specific steps of the terminal unit transfer procedure, refer to FIGS. 6 and 8.

[0171] In S755, the electronic device (1300) can select a UE to be sent to the target DU among the UEs in the migration cell in the RLC of the source DU. The electronic device (1300) can select a UE to be transferred from the source DU to the target DU.

[0172] In one embodiment, the electronic device (1300) may obtain information about cells to be transferred to a target DU according to dynamic scaling of DUs in accordance with cell-by-cell transfer, and may obtain information about terminals included in the cells. Based on the obtained information about cells and / or information about terminals, the electronic device (1300) may select a UE to be transferred from a source DU to a target DU.

[0173] In S760, the electronic device (1300) may perform step S765 if a previous target UE exists, and may perform step S780 if it is determined that there is no UE to be transferred to the target DU.

[0174] In step S765, the electronic device (1300) can transfer the context of the UE to the target DU RLC. The electronic device (1300) can transfer the context of the UE to be transferred from the RLC of the source DU to the RLC of the target DU.

[0175] In one embodiment, the electronic device (1300) may transfer the context of the selected UE to the target DU so that the selected UE and the target DU can transmit and receive packets and transmit and receive multiple control messages to perform terminal unit transfer.

[0176] In one embodiment, the electronic device (1300) may control downlink packets to perform terminal-level transfer. The electronic device (1300) may control downlink packets to prevent RLFs that occur when updating sequence numbers within the RLC of a DU while processing downlink packets during terminal-level transfer. For specific methods of controlling downlink, refer to FIGS. 11A to 11C .

[0177] In step S770, the electronic device (1300) can change the F1-U path from the source DU to the target DU. The CU and DU can change the F1-U path to perform terminal-level transfer to the target DU as they transmit and receive packets through the F1-U interface.

[0178] In one embodiment, the F1-U interface between the CU and the source DU can be changed to between the CU and the target DU. By changing the F1-U interface, the CU can transmit and receive packets with the target DU.

[0179] In one embodiment, the electronic device (1300) can control uplink packets transmitted from the UE. The electronic device (1300) can control uplink packets because the first DU cannot transmit uplink packets transmitted from the UE to the CU as the F1-U interface changes from the CU and the first DU to the CU and the second DU. Hereinafter, for a specific method of controlling the uplink, refer to FIGS. 12A and 12B .

[0180] In one embodiment, the electronic device (1300) can perform an RLC reset. The electronic device (1300) can reset information contained in the RLC of the target DU and the RLC entity of the terminal. The electronic device (1300) can reset to synchronize information contained in both RLC entities by comparing information contained in the RLC entity of the DU and the RLC entity of the terminal to determine whether to retransmit a packet.

[0181] In step S775, the electronic device (1300) can change the MAC-RLC path. The electronic device (1300) can change the MAC-RLC path to transmit and receive packets through the target DU without intervention of the source DU through the terminal unit transfer procedure.

[0182] In one embodiment, after the MAC-RLC path change, the electronic device (1300) can normalize control over downlink packets and uplink packets and initiate packet transmission to the target DU. If the transfer for a specific UE is completed, the electronic device (1300) can return to step S755 and re-perform the terminal transfer procedure.

[0183] If it is determined that there is no UE to be transferred from the source DU to the target DU, the electronic device (1300) may delete previous UE information in the RLC of the source DU according to step S780. UE information that has completed transfer from the source DU to the target DU is unnecessary for the source DU, and thus may be deleted in the RLC of the source DU.

[0184] In step S785, the electronic device (1300) can identify / determine / judge that dynamic scaling of the DU is completed.

[0185] FIG. 8 is a diagram illustrating a method for performing terminal unit transfer according to one embodiment of the present disclosure.

[0186] Referring to FIG. 8, the UE migration procedure (750) of FIG. 7 is described in detail. For the sake of brevity of the description, any overlapping content with FIG. 6 and FIG. 7 is omitted.

[0187] In step S805, the electronic device (1300) selects a transfer target UE. The electronic device (1300) can select a UE to be transferred from a source DU to a target DU.

[0188] In one embodiment, the electronic device (1300) may obtain information about cells to be transferred to a target DU according to dynamic scaling of DUs in accordance with cell-by-cell transfer, and may obtain information about terminals included in the cells. Based on the obtained information about cells and / or information about terminals, the electronic device (1300) may select a UE to be transferred from a source DU to a target DU.

[0189] In step S810, the electronic device (1300) may perform step S815 if a previous target UE exists, and may perform step S845 if it is determined that there is no UE to be transferred to the target DU.

[0190] In step S815, the electronic device (1300) can control downlink packets. If the electronic device (1300) identifies that there is a terminal to be transferred from the source DU to the target DU, the electronic device (1300) can control downlink packets to perform terminal-level transfer.

[0191] In one embodiment, the electronic device (1300) may control downlink packets to prevent RLF caused by updating a sequence number in the RLC of a DU while processing downlink packets during terminal unit transfer. In one embodiment, the electronic device (1300) may buffer downlink packets received from a data network in a PDCP buffer of a CU. In one embodiment, the electronic device (1300) may buffer downlink packets received from a data network in a buffer of a first DU. In one embodiment, the electronic device (1300) may buffer downlink packets received from a data network in a buffer of a second DU. Hereinafter, for specific methods of controlling downlink, refer to FIGS. 11A to 11C.

[0192] In step S820, the electronic device (1300) can change the F1-U path from the source DU to the target DU. The CU and DU can change the F1-U path to perform terminal-level transfer to the target DU as they transmit and receive packets through the F1-U interface.

[0193] In one embodiment, the F1-U interface between the CU and the source DU can be changed to between the CU and the target DU. By changing the F1-U interface, the CU can transmit and receive packets with the target DU.

[0194] In step S825, the electronic device (1300) can control uplink packets. The electronic device (1300) can control uplink packets because the first DU cannot transmit uplink packets transmitted from the terminal to the CU as the F1-U interface changes from the CU and the first DU to the CU and the second DU.

[0195] In one embodiment, since the first DU cannot transmit uplink packets to the CU via the RLC layer after the F1-U interface is changed, the electronic device (1300) may control this to prevent loss of uplink packets. In one embodiment, to prevent loss of uplink packets, the MAC scheduler of the second DU may stop allocating resources for uplink packets. In one embodiment, the uplink packets may be buffered in the buffer of the first DU. In one embodiment, to prevent loss of uplink packets, the uplink packets may be processed through the first DU before an RLC reset according to the sync of the RLC entity, and the uplink packets may be processed through the second DU after an RLC reset. Hereinafter, for a specific method of controlling the uplink, refer to FIGS. 12A and 12B.

[0196] In step S830, the electronic device (1300) may perform an RLC reset. The electronic device (1300) may reset information included in the RLC of the target DU and the RLC entity of the terminal.

[0197] In one embodiment, the electronic device (1300) may reset to synchronize the information contained in both RLC entities by comparing information contained in the RLC entity of the DU and the RLC entity of the terminal to determine whether to retransmit the packet. If the electronic device (1300) determines that the RLC entity of the second DU and the terminal are in sync, the electronic device (1300) may not request retransmission of the packet.

[0198] In step S835, the electronic device (1300) can change the MAC-RLC path. The electronic device (1300) can change the MAC-RLC path to transmit and receive packets through the target DU without intervention of the source DU through the terminal unit transfer procedure.

[0199] In one embodiment, the connection between the RLC of the source DU and the MAC of the target DU established according to the cell-by-cell transfer procedure can be changed to the connection between the RLC of the target DU and the MAC of the target DU. The electronic device (1300) can change and / or switch the connection between the RLC of the source DU and the MAC of the target DU to the connection between the RLC of the target DU and the MAC of the target DU in order to perform communication without using the source DU for a terminal transferred from the source DU to the target DU according to the terminal-by-terminal transfer.

[0200] In step S840, the electronic device (1300) can normalize control over downlink packets and uplink packets and start transmitting packets to the target DU. The electronic device (1300) can normalize control over downlink packets and uplink packets in steps S815 and S825.

[0201] In one embodiment, when the electronic device (1300) determines that the RLC reset is completed, it may perform processing on the buffered downlink packets. In one embodiment, the electronic device (1300) may sequentially transmit the downlink packets buffered in the PDCP buffer of the CU to the second DU. In one embodiment, the electronic device (1300) may transfer the buffer of the first DU to the second DU. The electronic device (1300) may sequentially process the downlink packets buffered in the buffer transferred to the second DU. In one embodiment, the electronic device (1300) may sequentially process the downlink packets buffered in the buffer of the second DU. Hereinafter, specific processing of the downlink packets will be described with reference to FIGS. 11A to 11C. In one embodiment, the electronic device (1300) may stop controlling the uplink packets and return to normal. In one embodiment, when the electronic device (1300) determines that the RLC reset is complete, the MAC scheduler of the second DU may resume resource allocation for uplink packets to be transmitted by the terminal. Hereinafter, specific processing of uplink packets will be described with reference to FIGS. 12A and 12B .

[0202] In one embodiment, the electronic device (1300) may start transmitting and receiving packets through the target DU as the transfer from the source DU to the target DU for a specific terminal is completed.

[0203] In one embodiment, after performing step S840, the electronic device (1300) may return to step S810 to re-identify whether there is a UE to be transferred from the source DU to the target DU. If it is determined that there is a UE to be transferred to the target DU, the process may be repeated from step S815.

[0204] In one embodiment, if the electronic device (1300) determines that there is no UE to be transferred to the target DU, it may delete previous UE information in the RLC of the source DU according to step S845. UE information that has completed transfer from the source DU to the target DU is unnecessary for the source DU, and thus may be deleted in the RLC of the source DU.

[0205] At step S850, the electronic device (1300) can identify / determine / judge that dynamic scaling of the DU is completed.

[0206] FIG. 9 is a diagram illustrating a sequence for changing an F1-U interface according to one embodiment of the present disclosure.

[0207] Referring to Fig. 9, a method for changing the F1-U path and buffering downlink packets according to 3GPP TS 38.473 and TS 38.463 is illustrated. Although Fig. 9 only discloses a method for buffering downlink packets in CU (10), this is only an example of buffering downlink packets. CU (10) can be configured with CU-CP, which is a control plane, and CU-UP, which is a user plane, by the CUPS structure, and CU-CP and CU-CP can be connected by an E1 interface.

[0208] In one embodiment, the source DU (20a) may receive (910) a signal triggering an F1-U path switch. Before the F1-U path switch for the terminal unit transfer procedure is performed, the source DU (20a) may receive a signal triggering an F1-U path switch as the F1-U interface is connected between the source DU (20a) and the CU (10).

[0209] In one embodiment, the source DU (20a) may send a message to the CU (10) to switch the F1-U interface from a connection between the source DU (20a) and the CU (10) to a connection between the target DU (20b) and the CU (10).

[0210] In one embodiment, the source DU (20a) may transmit a message to the CU (10) to control downlink packets in order to switch the F1-U interface. Controlling the downlink packets is required to prevent RLFs caused by sequence number updates as the DU's RLC entity processes the downlink packets. In one embodiment, the CU (10) or the DU may control the downlink packets. Hereinafter, specific downlink packet control methods will be described with reference to FIGS. 11a to 11. FIG. 9 describes a method for buffering downlink packets in the CU (10).

[0211] In one embodiment, the source DU (20a) may request buffering of downlink packets from the CU-CP of the CU (10) using a control message of F1AP. For example, the source DU (20a) may request buffering of downlink packets from the CU-CP using an F1 UE Context Modification Required Message (920), but is not limited thereto.

[0212] In one embodiment, the CU-CP of the CU (10) may transmit a message to the CU-UP via the E1 interface upon receiving the F1 UE Context Modification Required Message (920). For example, the CU-CP may transmit a message requesting buffering of downlink packets and F1-U path update to the CU-UP using the E1 BearerContext Modification Request Message (930), but is not limited thereto.

[0213] In one embodiment, the CU-UP may buffer (940) downlink packets received from the data network upon receiving an E1 BearerContext Modification Request Message (930). The CU-UP may sequentially buffer downlink packets in the PDCP buffer according to sequence numbers.

[0214] In one embodiment, upon receiving an E1 BearerContext Modification Request Message (930), the CU-UP may update (950) the F1-U interface, which is an interface for transmitting and receiving user data with the DU. Following the terminal unit transfer, the CU-UP may convert the connection with the source DU (20a) to the connection with the target DU (20b), thereby establishing the F1-U interface between the CU (10) and the target DU (20b).

[0215] In one embodiment, the CU-UP may transmit (970) a completion message to the source DU (20a) via the CU-CP (960) upon completing the buffering (940) of the downlink packet and the F1-U interface update (950).

[0216] FIG. 10 is a diagram of an RLC reset sequence according to one embodiment of the present disclosure.

[0217] Referring to Fig. 10, a method for performing an RLC reset of a target DU and an RLC reset of a UE is illustrated according to 3GPP TS 38.471 and TS 38.331. In order to prevent RLF that occurs when determining whether to retransmit a packet by comparing the sync of information included in the RLC entity of the target DU and information included in the RLC entity of the UE, a reset of the RLC entity of the target DU and the RLC entity of the UE can be performed.

[0218] Reset of the RLC entity of the target DU (20b) can be done by sending a command directly to the target DU (20b), but reset of the RLC entity of the UE (40) can be done by changing an RLC message into an RRC message and sending it to the UE (40) through the CU (10).

[0219] In one embodiment, the source DU (20a) may perform an RLC reset before changing the MAC-RLC path from a connection between the RLC of the source DU (20a) and the MAC of the target DU (20b) to a connection between the RLC of the target DU (20b) and the MAC of the target DU (20b). The target DU (20b) may receive (1010) a signal that triggers an RLC reset. Based on the RLC reset trigger signal (1010), the target DU (20b) may reset (1015) information included in an RLC entity. For example, the information that is a target of an RLC reset may include, but is not limited to, at least one of the packet itself, status information of the packet, a UE identifier, various timer-related information, or information regarding the storage size of the packet. In one embodiment, the target DU (20b) may transmit a completion response (1020) upon completing the RLC reset.

[0220] In one embodiment, the source DU (20a) may receive (1025) a message that triggers an RLC reset of the UE. Since the RLC reset message cannot be transmitted directly to the UE (40), a message that commands an RLC reset of the UE may be transmitted along a path of DU->CU->DU->UE to change it to an RRC message. The source DU (20a) may transmit a message that triggers the CU (10) to transmit the RLC reset message of the UE. For example, the source DU (20a) may transmit (1030) a UE Context Modification Required Message to trigger the RLC reset message to the UE, but the type of the message is not limited thereto. Upon receiving the Context Modification Required Message (1030), the CU (10) may transmit the RLC reset message of the UE to the source DU (20a) as an RRC message through a UE Context Modification Confirm Message (1035), but the type of the message is not limited thereto. The source DU (20a) can transmit an RLC reset message of the UE to the UE (40). For example, the source DU (20a) can transmit a message commanding the RLC reset of the UE through a DL DCCH Message (1040), but the type of message is not limited thereto.

[0221] In one embodiment, the UE (40) may perform an RLC reset (1045) of the UE upon receiving a message to reset the RLC entity. For example, the information to be subject to the RLC reset may include, but is not limited to, at least one of the packet itself, packet status information, a UE identifier, various timer-related information, or information regarding the storage size of the packet.

[0222] In one embodiment, the UE (40) may transmit a message indicating that the RLC reset of the UE has been completed by performing an RLC reset. Since the UE (40) cannot transmit the message directly, the message may be transmitted in the order of UE->DU->CU->DU. In one embodiment, the UE (40) may transmit a message indicating that the RLC reset of the UE has been completed to the source DU (20a) via a UL DCCH Message (1050), but the type of message is not limited thereto.

[0223] In one embodiment, the source DU (20a) may transmit a message received from the UE (40) to the CU (10) via the F1 interface. For example, the source DU (20a) may transmit a response message of the UE to the CU (10) via the F1 UL RRC Message Transfer (1055), but the type of the message is not limited thereto. The CU (10) may convert the received message and transmit a completion response to the source DU (20a). The CU (10) may include the completion response in the F1 UE Context Modification Request Message (1060) and transmit it to the source DU (20a), but the type of the message is not limited thereto. The source DU (20a) may transmit a completion response (1065) according to the completion response received from the CU (10).

[0224] FIGS. 11A to 11C are diagrams illustrating a method for controlling a downlink packet according to one embodiment of the present disclosure.

[0225] FIGS. 11A to 11C illustrate a method for controlling downlink packets to prevent RLFs that occur due to sequence number updates resulting from the processing of downlink packets. FIGS. 11A to 11C illustrate an example of a method for buffering corresponding packets in a CU or DU to control downlink packets; however, the method for controlling downlink packets is not limited thereto.

[0226] FIG. 11A is a diagram illustrating a method of performing buffering in a CU as an example of controlling a downlink packet according to one embodiment of the present disclosure.

[0227] Referring to Fig. 11a, the CU (10) can receive downlink packets transmitted from a data network to a target terminal. The CU (10) can buffer downlink packets in a PDCP buffer to prevent RLF caused by processing of downlink packets during the terminal unit transfer process.

[0228] In one embodiment, the CU (10) may receive a message requesting buffering of a downlink packet from the source DU (20a). Before the terminal unit transfer is performed, since the CU (10) and the source DU (20a) are connected based on the F1-U interface, the source DU (20a) may transmit a message requesting buffering of a downlink packet to the CU (10) upon initiation of the terminal unit transfer. For example, the source DU (20a) may request buffering of a downlink packet using the F1 UE Context Modification Required Message, which is a control message of the F1AP, but is not limited thereto.

[0229] In one embodiment, the CU (10) may buffer downlink packets in a PDCP buffer upon receiving a message requesting buffering of downlink packets. In one embodiment, when a CU-CP among CUs receives a message from a source DU (20a), it may transmit a message instructing the CU-UP to buffer downlink packets, thereby buffering the downlink packets in the PDCP buffer. For example, when the CU-CP receives an F1 UE Context Modification Required Message from the source DU (20a), it may transmit an E1 BearerContext Modification Request Message to the CU-UP. The CU-UP that receives the message may temporarily buffer the downlink packets in the PDCP layer.

[0230] In one embodiment, when the RLC reset is completed, the CU (10) can sequentially transmit downlink packets to the target DU (20b) in the buffered order.

[0231] FIG. 11b is a diagram illustrating a method for performing buffering in an RLC of a source DU as an example of controlling a downlink packet according to an embodiment of the present disclosure.

[0232] Referring to FIG. 11b, the CU (10) can receive a downlink packet transmitted from a data network to a target terminal. The CU (10) can transmit the downlink packet to the source DU (20a) before the F1-U path is changed. The source DU (20a) can buffer the downlink packet received from the CU (10) in a buffer.

[0233] In one embodiment, the CU (10) may perform a procedure to change the connection between the CU (10) and the source DU (20a) to the connection between the CU (10) and the target DU (20b) by changing the F1-U path during the terminal unit migration procedure. Before performing the procedure, the CU (10) may transmit and receive downlink packets and / or uplink packets with the source DU (20a). The CU (10) may transmit downlink packets to the source DU (20a) through the F1 interface, and the source DU (20a) may buffer the downlink packets in a buffer to prevent RLF from occurring due to processing of the downlink packets.

[0234] In one embodiment, when the RLC reset is completed, the buffer of the source DU (20a) can be transferred to the target DU (20b). By transferring the buffer of the source DU (20a) to the target DU (20a), all downlink packets contained in the buffer and information about the downlink packets can be transferred to the target DU (20b). The target DU (20b) can sequentially process the downlink packets buffered in the buffer transferred to the target DU (20b).

[0235] FIG. 11c is a diagram illustrating a method for performing buffering in an RLC of a target DU as an example of controlling a downlink packet according to an embodiment of the present disclosure.

[0236] Referring to Fig. 11c, the CU (10) can receive a downlink packet transmitted from a data network to a target terminal. The CU (10) can transmit the downlink packet to the target DU (20b) after the F1-U path is changed. The target DU (20b) can buffer the downlink packet received from the CU (10) in a buffer.

[0237] In one embodiment, the CU (10) may perform a procedure to change the connection between the CU (10) and the source DU (20a) to the connection between the CU (10) and the target DU (20b) by changing the F1-U path during the terminal unit migration procedure. After performing the procedure, the CU (10) may transmit and receive downlink packets and / or uplink packets with the target DU (20b). The CU (10) may transmit downlink packets to the target DU (20b) through the F1 interface, and the target DU (20b) may buffer the downlink packets in a buffer to prevent RLF from occurring due to processing of the downlink packets.

[0238] In one embodiment, when the RLC reset is completed, the target DU (20b) can sequentially process downlink packets buffered in the buffer.

[0239] FIG. 12a and FIG. 12b are diagrams illustrating a method for controlling an uplink packet according to one embodiment of the present disclosure.

[0240] Although FIGS. 12a and 12b illustrate a method of adjusting scheduling for the uplink itself or switching the uplink path based on the RLC reset timing to control uplink packets, the method of controlling uplink packets is not limited thereto.

[0241] In one embodiment, as the terminal unit transfer occurs and the F1-U interface changes from CU and source DU to CU and target DU, a problem occurs in which the source DU cannot transmit uplink packets transmitted from the terminal to the CU. Before the change of the F1-U interface, the uplink packets can be transmitted from the terminal to the CU through the RU, the PHY / MAC layer of the second DU, and the RLC layer of the first DU. However, after the F1-U interface is changed, the first DU cannot transmit uplink packets to the CU through the RLC layer, and thus it is required to control this to prevent loss of uplink packets.

[0242] In one embodiment, a source DU, which receives an uplink packet from a UE through the PHY / MAC layer of the target DU, may buffer the uplink packet in a buffer. After the RLC reset is completed, the buffer of the source DU may be transferred to the target DU.

[0243] FIG. 12A is a diagram illustrating a method for limiting a schedule of an uplink packet, as an example of controlling an uplink packet according to one embodiment of the present disclosure.

[0244] Referring to Fig. 12a, the UE (40) can transmit an uplink packet to the DU (20) via the RU (30). In order for the UE (40) to transmit an uplink packet, the MAC scheduler of the DU (20) must perform resource allocation for the uplink packet.

[0245] In one embodiment, after cell migration is completed, resource allocation for uplink packets may be performed by the MAC scheduler of the target DU (20b) as the RLC of the source DU (20a) is connected to the MAC end of the target DU (20b). In order to prevent uplink packets from being lost due to terminal-level migration, the MAC scheduler of the target DU (20b) may stop resource allocation for uplink packets transmitted by the UE (40).

[0246] In one embodiment, before cell-by-cell transfer is completed, the MAC scheduler of the source DU (20a) may stop allocating resources to uplink packets of the UE (40) until both cell-by-cell transfer and terminal-by-terminal transfer are completed.

[0247] In one embodiment, when the RLC reset is completed, the MAC scheduler of the DU (20) can resume resource allocation for the uplink packet that the UE (40) wishes to transmit. In one embodiment, as the terminal unit transfer is completed, the target DU (20b) connected to the UE (40) through the RU (30) can resume resource allocation for the uplink packet.

[0248] FIG. 12b is a diagram illustrating a method for switching a path of an uplink packet as an example of controlling an uplink packet according to one embodiment of the present disclosure.

[0249] Referring to Figure 12b, the data packet's path may differ before and after the terminal unit transfer including the RLC reset is completed. Looking at the path of the uplink packet transmitted from the UE (40), the path of the uplink packet may change as the connection between the F1-U path and the MAC-RLC changes.

[0250] In one embodiment, before the RLC reset is completed, the RLC of the source DU (20a) is connected to the MAC layer of the target DU (20b) as the cell-by-cell transfer is completed, and the CU (10) can transmit and receive data with the source DU (20a) via the F1 interface. In the case of an uplink packet transmitted from the UE (40), it can be transmitted to the CU (10) via the PHY and MAC layers of the target DU (20b) via the RU (30) and then via the RLC layer of the source DU (20a).

[0251] In one embodiment, after the RLC reset is completed, the CU (10) can transmit and receive data with the target DU (20b) via the F1 interface, and the connection between the RLC of the source DU (20a) and the MAC of the target DU (20b) is changed to the connection between the RCL of the target DU (20b) and the MAC of the target DU (20b). In the case of an uplink packet transmitted from the UE (40), it can be transmitted to the CU (10) via the PHY and MAC layers of the target DU (20b) via the RU (30) and the RLC layer of the target DU (20b).

[0252] In one embodiment, uplink packets are processed in the source DU (20a) before the RLC reset is completed, and after the RLC reset is completed and synchronization is achieved between the RLC entities of the target DU (20b) and the UE (40), uplink packets can be processed in the target DU (20b).

[0253] FIG. 13 is a schematic block diagram of an electronic device according to one embodiment of the present disclosure.

[0254] Referring to FIG. 13, an electronic device (1300) according to an embodiment of the present disclosure may include at least one processor (1310) that performs at least one instruction, a memory (1320) that stores at least one instruction, and a communication unit (1330) that performs communication with an external device (e.g., another terminal, a base station, etc.). However, not all of the illustrated components are essential components, and the electronic device (1300) may be implemented with more or fewer components than the illustrated components.

[0255] The processor (1310) controls the overall operation of the electronic device (1300). For example, the processor (1310) may perform the functions of the electronic device (1300) described in the present disclosure by executing one or more instructions stored in the memory (1320). In this case, the memory (1320) may store one or more instructions executable by the processor (1310). In addition, the processor (1310) may store one or more instructions in an internally provided memory, and execute one or more instructions stored in the internally provided memory to control the performance of the aforementioned operations. That is, the processor (1310) may perform a predetermined operation by executing at least one instruction or program stored in the internal memory provided within the processor (1310) or the memory (1320).

[0256] The processor (1310) may include one or more processors. At this time, one or more processors may be a general-purpose processor, such as a CPU, an AP, or a Digital Signal Processor (DSP), a graphics-only processor, such as a GPU or a Vision Processing Unit (VPU), or an artificial intelligence-only processor, such as an NPU. If one or more processors are artificial intelligence-only processors, the artificial intelligence-only processors may be designed with a hardware structure specialized for processing a specific artificial intelligence model.

[0257] In one embodiment of the present disclosure, the processor (1310) can identify terminal information to be transferred for terminal unit transfer. The processor (1310) can control downlink packets to prevent RLF. In one embodiment, the processor (1310) can buffer downlink packets in the PDCP buffer of the CU. In one embodiment, the processor (1310) can buffer downlink packets in the buffer of the source DU or the buffer of the target DU.

[0258] In one embodiment of the present disclosure, the processor (1310) may update / change the F1-U interface, which is an interface between the CU and the DU, according to the transfer of the terminal unit. The processor (1310) may control uplink packets transmitted from the terminal. In one embodiment, the processor (1310) may stop resource allocation for uplink packets through the MAC scheduler of the DU. In one embodiment, the processor (1310) may process uplink packets using the source DU according to the RLC reset timing and then process uplink packets using the target DU.

[0259] In one embodiment of the present disclosure, the processor (1310) can reset information included in the RLC of the target DU and reset information included in the RLC of the UE. Through the RLC reset, the processor (1310) can synchronize the information included in the RLC of the target DU and the information included in the RLC of the UE.

[0260] In one embodiment of the present disclosure, the processor (1310) can change the connection between the RLC of the source DU and the MAC of the target DU to the connection between the RLC of the target DU and the MAC of the target DU. The processor (1310) can change the MAC-RLC path in order to transmit and receive signals with the UE through the target DU according to the terminal unit transfer. In one embodiment, the processor (1310) can normalize the control for downlink packets and uplink packets. The processor (1310) can transmit the downlink packets stored in the PDCP buffer of the CU to the target DU. The processor (1310) can transfer the buffer of the source DU to the target DU and process the downlink packets contained in the buffer. The processor (1310) can sequentially process the downlink packets buffered in the buffer of the target DU. The processor (1310) can resume resource allocation for uplink packets through the MAC scheduler of the target DU.

[0261] In one embodiment of the present disclosure, if the processor (1310) identifies that there is no UE that is a target for transfer from the source DU to the target DU, the processor (1310) may remove / delete the context of the transferred UEs from the RLC of the source DU.

[0262] The memory (1320) can store a program for processing and controlling the processor (1310), and can store data input to or output from the electronic device (1300). The memory (1320) 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.

[0263] The communication unit (1330) may include one or more modules that enable wireless communication between the electronic device (1300) and a network where another device is located. The communication unit (1330) may transmit and receive data or signals to and from a base station or a terminal via a wired or wireless network. The communication unit (1330) according to one embodiment of the present disclosure includes at least one communication module, such as a short-range communication module, a wired communication module, a mobile communication module, a broadcast reception module, etc. Here, at least one communication module refers to a communication module that can transmit and receive data via a network that follows a communication standard, such as a tuner that performs broadcast reception, Bluetooth, WLAN (Wireless LAN) (Wi-Fi), Wibro (Wireless broadband), Wimax (World Interoperability for Microwave Access), CDMA, WCDMA, etc.

[0264] For example, the communication unit (1330) may include a Wi-Fi module, a Bluetooth module, an infrared communication module, a wireless communication module, a LAN module, an Ethernet module, a wired communication module, etc. At this time, each communication module may be implemented in the form of at least one hardware chip. The Wi-Fi module and the Bluetooth module perform communication in the Wi-Fi method and the Bluetooth method, respectively. When using the Wi-Fi module or the Bluetooth module, various connection information such as the SSID and the session key may be first transmitted and received, and then communication may be established using this, and then various information may be transmitted and received. The wireless communication module may include at least one communication chip that performs communication according to various wireless communication standards such as Zigbee, 3G (3rd Generation), 3GPP (3rd Generation Partnership Project), LTE (Long Term Evolution), LTE-A (LTE Advanced), 4G (4th Generation), 5G (5th Generation), etc. The communication unit (930) may include a communication unit that performs communication with an electronic device and Bluetooth, and an interface unit that connects with an external device.

[0265] A method for performing terminal unit migration of a wireless network system according to one embodiment of the present disclosure may include a step of identifying information about a terminal to be migrated from a radio link control (RLC) of a first distributed unit (DU) to an RLC of a second DU. The method may include a step of changing an F1-U interface of a centralized unit (CU) from an RLC of the CU and the first DU to an RLC of the CU and the second DU. The method may include a step of resetting information included in the RLC of the second DU. The method may include a step of changing a connection between an RLC of the first DU and a media access control (MAC) of the second DU to a connection between an RLC of the second DU and a MAC of the second DU.

[0266] In one embodiment of the present disclosure, the method may further include a step of buffering downlink packets.

[0267] In one embodiment of the present disclosure, the method may include a step of buffering a downlink packet on a PDCH of the CU based on an F1 UE Context Modification Required Message received by the CU. The method may include a step of transmitting the buffered downlink packet to a second DU when the terminal unit transfer is completed.

[0268] In one embodiment of the present disclosure, the method may include a step of buffering a downlink packet in a buffer of a first DU. The method may include a step of transferring the buffer of the first DU to a second DU when terminal unit transfer is completed.

[0269] In one embodiment of the present disclosure, the method may include a step of buffering a downlink packet in a buffer of a second DU. The method may include a step of processing the buffered downlink packet in the second DU when the terminal unit transfer is completed.

[0270] In one embodiment of the present disclosure, the method may further include a step of controlling an uplink packet transmitted from a terminal.

[0271] In one embodiment of the present disclosure, the method may include a step of stopping resource allocation for uplink packets in the MAC of the second DU. The method may include a step of resuming resource allocation for uplink packets in the AMC of the second DU when the terminal unit transfer is completed.

[0272] In one embodiment of the present disclosure, the method may include a step of buffering an uplink packet in a buffer of a first DU. The method may include a step of transferring the buffer of the first DU to a second DU when terminal unit transfer is completed.

[0273] In one embodiment of the present disclosure, the method may include a step of processing an uplink packet by the RLC of the first DU. The method may also include a step of processing the uplink packet by the RLC of the second DU based on a change in the path of the uplink packet when the terminal unit transfer is completed.

[0274] In one embodiment of the present disclosure, the method may further include a step of deleting information about a terminal that has completed transfer to the second DU in the RLC of the first DU, if it is determined that there is no information about a terminal to be transferred from the RLC of the first DU to the RLC of the second DU.

[0275] An electronic device for performing terminal unit transfer of a wireless network system according to one embodiment of the present disclosure may include a memory storing one or more instructions and at least one processor for executing one or more instructions stored in the memory. The at least one processor may identify information about a terminal to be transferred from a radio link control (RLC) of a first distributed unit (DU) to an RLC of a second DU. The at least one processor may change an F1-U interface of a centralized unit (CU) from an RLC of the CU and the first DU to an RLC of the CU and the second DU. The at least one processor may reset information included in the RLC of the second DU. The at least one processor may change a connection between an RLC of the first DU and a media access control (MAC) of the second DU to a connection between an RLC of the second DU and a MAC of the second DU.

[0276] 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.

[0277] 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.

[0278] 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.

Claims

1. A method for performing terminal unit migration in a wireless network system, Step (S610) of identifying information about a terminal to be transferred from the RLC (radio link control) of the 1st DU (distributed unit) to the RLC of the 2nd DU; Step (S620) of changing the F1-U interface of the CU (centralized unit) from the RLC of the CU and the first DU to the RLC of the CU and the second DU; Step (S630) of resetting the information included in the RLC of the above 2nd DU; and A method comprising: a step (S640) of changing a connection between an RLC of the first DU and a MAC (media access control) of the second DU to a connection between an RLC of the second DU and a MAC of the second DU; 2. In paragraph 1, A method further comprising: buffering a downlink packet; 3. In paragraph 2, A step of buffering a downlink packet in the PDCP (packet data convergence protocol) of the CU based on the F1 UE Context Modification Required Message received by the CU; and A method comprising: a step of transmitting the buffered downlink packet to the second DU when the terminal unit transfer is completed; 4. In paragraph 2, a step of buffering the downlink packet in the buffer of the first DU; and A method comprising: a step of transferring the buffer of the first DU to the second DU when the transfer of the terminal unit is completed; 5. In paragraph 2, a step of buffering the downlink packet in the buffer of the second DU; and A method comprising: a step of processing a downlink packet buffered in the second DU when the above terminal unit transfer is completed; 6. In any one of paragraphs 1 to 5, A method further comprising: a step of controlling an uplink packet transmitted from the terminal; 7. In paragraph 6, A step of stopping resource allocation for the uplink packet in the MAC of the second DU; and A method comprising: a step of resuming resource allocation for the uplink packet in the MAC of the second DU when the terminal unit transfer is completed; 8. In paragraph 6, a step of buffering the above uplink packet in the buffer of the first DU; and A method comprising: a step of transferring the buffer of the first DU to the second DU when the transfer of the terminal unit is completed; 9. In paragraph 6, A step in which the RLC of the first DU processes the uplink packet; and A method comprising: a step of processing the uplink packet in the RLC of the second DU based on a change in the path of the uplink packet when the terminal unit transfer is completed; 10. In an electronic device (1300) that performs terminal migration in a wireless network system, a memory (1320) storing one or more instructions; and At least one processor (1310) for executing said one or more instructions stored in said memory, said at least one processor (1310), Identify information about the terminal to be transferred from the RLC of the 1st DU (distributed unit) to the RLC of the 2nd DU, Change the F1-U interface of the CU (centralized unit) from the RLC of the CU and the first DU to the RLC of the CU and the second DU, Reset the information included in the RLC of the above 2nd DU, An electronic device that changes a connection between an RLC of the first DU and a MAC (media access control) of the second DU to a connection between an RLC of the second DU and a MAC of the second DU.

11. In the 10th paragraph, at least one processor (1310) Buffering a downlink packet in at least one of the PDCP (packet data convergence protocol) of the CU, the buffer of the first DU, or the buffer of the second DU, An electronic device that processes the buffered downlink packet as the second DU when the above terminal transfer is completed.

12. In any one of paragraphs 10 and 11, the at least one processor (1310) Stop allocating resources for uplink packets in the MAC of the above 2nd DU, An electronic device that resumes resource allocation for the uplink packet in the MAC of the second DU when the above terminal transfer is completed.

13. In any one of clauses 10 to 12, the at least one processor (1310) Buffering the uplink packet in the buffer of the first DU, An electronic device that transfers the buffer of the first DU to the second DU when the terminal transfer is completed.

14. In any one of clauses 10 to 13, the at least one processor (1310) The RLC of the above first DU processes the uplink packet, An electronic device, wherein when the terminal transfer is completed, the uplink packet is processed in the RLC of the second DU based on the change in the path of the uplink packet.

15. A non-transitory computer-readable storage medium having recorded thereon a program for performing the method of any one of clauses 1 to 9 on a computer.

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