KR20240030905A - Method and device for peforming communication by a first distributed unit in a wireless communication system - Google Patents

Abstract

The present disclosure relates to a method and apparatus for a first distributed unit (DU) to perform communication in a wireless communication system. In a wireless communication system according to an embodiment of the present disclosure, a method of performing communication by a first distributed unit (DU) includes obtaining inter-DU interface configuration information for connection with a second DU, and Connection with a second DU is performed based on inter-DU interface configuration information, and information about the throughput of each RU is performed based on information about at least one radio unit (RU) connected to the first DU. Information may be obtained, at least one target RU may be selected based on information about the throughput of each RU, and migration of the target RU to the second DU may be performed.

Description

Method and device for a distributed unit to perform communication in a wireless communication system {METHOD AND DEVICE FOR PEFORMING COMMUNICATION BY A FIRST DISTRIBUTED UNIT IN A WIRELESS COMMUNICATION SYSTEM}

The present disclosure relates to a wireless communication system, and more specifically, to a method and device for efficiently performing a wireless network function through dynamic scaling in/out.

Looking back at the development of wireless communication through successive generations, technologies have been developed mainly for human services, such as voice, multimedia, and data. After the commercialization of 5G (5th-generation) communication systems, an explosive increase in connected devices is expected to be connected to communication networks. Examples of objects connected to the network may include vehicles, robots, drones, home appliances, displays, smart sensors installed in various infrastructures, construction machinery, and factory equipment. Mobile devices are expected to evolve into various form factors such as augmented reality glasses, virtual reality headsets, and hologram devices. In the 6G (6th-generation) era, efforts are being made to develop an improved 6G communication system to provide a variety of services by connecting hundreds of billions of devices and objects. For this reason, the 6G communication system is called a beyond 5G system.

In the 6G communication system, which is expected to be realized around 2030, the maximum transmission speed is tera (i.e. 1,000 gigabit) bps and the wireless delay time is 100 microseconds (μsec). In other words, compared to the 5G communication system, the transmission speed in the 6G communication system is 50 times faster and the wireless delay time is reduced by one-tenth.

To achieve these high data rates and ultra-low latency, 6G communication systems will operate in terahertz bands (e.g., 95 GHz to 3 THz). Implementation is being considered. In the terahertz band, the importance of technology that can guarantee signal reach, or coverage, is expected to increase due to more serious path loss and atmospheric absorption compared to the mmWave band introduced in 5G. The main technologies to ensure coverage are RF (radio frequency) elements, antennas, new waveforms that are better in terms of coverage than OFDM (orthogonal frequency division multiplexing), beamforming, and massive multiple input/output (Massive multiple input/output). Multi-antenna transmission technologies such as input and multiple-output (massive MIMO), full dimensional MIMO (FD-MIMO), array antenna, and large scale antenna must be developed. In addition, to improve the coverage of terahertz band signals, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing technology using OAM (orbital angular momentum), and RIS (reconfigurable intelligent surface) are being discussed.

In addition, in order to improve frequency efficiency and system network, the 6G communication system uses full duplex technology where uplink and downlink simultaneously utilize the same frequency resources at the same time, satellite and Network technology that integrates HAPS (high-altitude platform stations), network structure innovation technology that supports mobile base stations and enables network operation optimization and automation, and dynamic frequency sharing through collision avoidance based on spectrum usage prediction. (dynamic spectrum sharing) technology, AI-based communication technology that utilizes AI (artificial intelligence) from the design stage and internalizes end-to-end AI support functions to realize system optimization, and overcomes the limits of terminal computing capabilities. Next-generation distributed computing technologies that realize complex services using ultra-high-performance communication and computing resources (mobile edge computing (MEC), cloud, etc.) are being developed. In addition, through the design of new protocols to be used in the 6G communication system, the implementation of a hardware-based security environment, the development of mechanisms for safe use of data, and the development of technologies for maintaining privacy, the connectivity between devices is further strengthened and the network is further improved. Attempts are continuing to optimize, promote softwareization of network entities, and increase the openness of wireless communications.

Due to the research and development of these 6G communication systems, a new level of hyper-connected experience (the next hyper-connected) is possible through the hyper-connectivity of the 6G communication system, which includes not only connections between objects but also connections between people and objects. experience) is expected to become possible. Specifically, it is expected that the 6G communication system will be able to provide services such as truly immersive extended reality (truly immersive XR), high-fidelity mobile hologram, and digital replica. In addition, services such as remote surgery, industrial automation, and emergency response through improved security and reliability are provided through the 6G communication system, enabling application in various fields such as industry, medicine, automobiles, and home appliances. It will be.

According to an embodiment of the present disclosure, a method for a first distributed unit (DU) to perform communication in a wireless communication system may be provided. The method includes obtaining inter-DU interface configuration information for connection to a second DU; Performing connection with a second DU based on the inter-DU interface configuration information; Throughput of each RU based on information about at least one radio unit (RU) connected to the first DU Obtaining information about; selecting at least one target RU based on information about the throughput of each RU; And it may include performing migration of the target RU to the second DU.

According to an embodiment of the present disclosure, a first DU that performs communication in a wireless communication system may be provided. The first DU performing communication in a wireless communication system includes: a transceiver; And it may include at least one processor connected to the transceiver. The at least one processor acquires inter-DU interface configuration information for connection with the second DU, performs connection with the second DU based on the inter-DU interface configuration information, and at least connects to the first DU. Obtain information about the throughput of each RU based on information about one RU, select at least one target RU based on the information about the throughput of each RU, and select the at least one target RU with the second DU. RU transfer can be performed.

FIG. 1A is a diagram for explaining the structure of a radio access network (RAN).
Figure 1b is a diagram for explaining the structure of a wireless protocol of NR (new radio).
FIG. 2 is a diagram for explaining the structure of RAN after dynamic scaling according to an embodiment.
FIG. 3 is a diagram illustrating a scaling in/out scenario of a DU according to a change in traffic of the DU, according to an embodiment.
FIG. 4 is a diagram for explaining the structure and interface of RAN after dynamic scaling, according to one embodiment.
Figure 5a is a diagram for explaining the initial access procedure of the UE.
Figure 5b is a diagram to explain the transition procedure from the RRC inactive state to the RRC connected state.
Figure 6 is a diagram for explaining a paging procedure according to an embodiment of the present disclosure.
FIGS. 7A and 7B are diagrams for explaining a method of performing RU transfer, according to one embodiment.
FIG. 8 is a diagram for explaining a method of performing UE transfer, according to an embodiment of the present disclosure.
FIG. 9 is a flowchart of a method for a first DU to transfer a RU to a second DU, according to an embodiment of the present disclosure.
Figure 10 is a schematic block diagram of DU 20 according to one embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings.

Since the present disclosure can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail through detailed description. However, this is not intended to limit the embodiments of the present disclosure, and the present disclosure should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the various embodiments.

In describing the embodiments, if it is determined that detailed descriptions of related known technologies may unnecessarily obscure the gist of the present disclosure, the detailed descriptions will be omitted. In addition, numbers (eg, first, second, etc.) used in the description of the specification are merely identifiers to distinguish one component from another component.

The terms used in the embodiments of the present specification are general terms that are currently widely used as much as possible while considering the function of the present disclosure, but this may vary depending on the intention or precedent of a person working in the art, the emergence of new technology, etc. . In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the relevant embodiment. Therefore, the terms used in this disclosure should be defined based on the meaning of the term and the overall content of this disclosure, rather than simply the name of the term.

The scope of the present disclosure may be indicated by the claims described below rather than the detailed description above. Various features mentioned in one claim category of the present disclosure (e.g., method claims) may also be claimed in other claim categories (e.g., system claims). Additionally, 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 construed as including the meaning and scope of the patent claims and all changes or modified forms derived from the equivalent concept thereof.

In addition, in the present disclosure, when a component is referred to as "connected" or "connected" to another component, the component may be directly connected or directly connected to the other component, but specifically Unless there is a contrary description, it should be understood that it may be connected or connected through another component in the middle. In addition, it includes not only cases of being “directly connected” or “physically connected,” but also cases of being “electrically connected” with another element in between. In this disclosure, the terms “transmit,” “receive,” and “communicate” include both direct and indirect communication. Throughout the present disclosure, when a part “includes” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

In addition, in the present disclosure, components expressed as '~unit (unit)', 'module', etc. are two or more components combined into one component, or one component is divided into two or more components for each more detailed function. It may be differentiated into These functions may be implemented as hardware or software, or as a combination of hardware and software. In addition, each of the components described below may additionally perform some or all of the functions of other components in addition to the main functions that each component is responsible for, and some of the main functions of each component may be different from other components. Of course, it can also be performed exclusively by a component.

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

Throughout this disclosure, unless specifically stated to the contrary, “or” is inclusive and not exclusive. Accordingly, unless clearly indicated otherwise or context dictates otherwise, “A or B” may refer to “A, B, or both.” In the present disclosure, the phrase “at least one of” or “one or more of” means that different combinations of one or more of the listed items may be used, and that only any one of the listed items is required. It may also mean a case. 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.

It will be understood that each block of the processing flow diagrams and combinations of the flow diagram diagrams may be performed by computer program instructions. These computer program instructions may be mounted on a processor of a general-purpose computer, special-purpose computer, or other programmable data processing equipment, so that the instructions performed through the processor of a computer or other programmable data processing equipment may be as described in the flow chart block(s). It creates the means to perform functions. These computer program instructions may also be stored in computer-usable or computer-readable memory that can be directed to a computer or other programmable data processing equipment to implement a function in a particular manner, so that the computer-usable or computer-readable memory The instructions stored in may also produce manufactured items containing instruction means that perform the functions described in the flow diagram block(s). Computer program instructions can also be mounted on a computer or other programmable data processing equipment, so that a series of operational steps are performed on the computer or other programmable data processing equipment to create a process that is executed by the computer, thereby generating a process that is executed by the computer or other programmable data processing equipment. Instructions that perform processing equipment may also provide steps for executing the functions described in the flow diagram block(s).

Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for executing specified logical function(s). Additionally, it should be noted that in some alternative execution examples it is possible for the functions mentioned in the blocks to occur out of order. For example, it is possible for two blocks shown in succession to be performed substantially at the same time, or it is possible for the blocks to be performed in reverse order depending on the corresponding function.

Below, with reference to the attached drawings, embodiments of the present disclosure will be described in detail so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present disclosure in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

In addition, although LTE, LTE-A, or 5G systems may be described below as examples, embodiments of the present disclosure can also be applied to other communication systems with similar technical background or channel types. For example, it may include 5G-Advance, which is developed after 5G mobile communication technology (NR), or 6G (beyond 5G), and the term 5G hereinafter may include existing LTE, LTE-A, and other similar services. there is. In addition, the present disclosure may be applied to other communication systems through some modifications without significantly departing from the scope of the present disclosure at the discretion of a person with skilled technical knowledge.

Terms used in the present disclosure will be briefly described, and an embodiment of the present invention will be described in detail.

The terms described below are terms defined in consideration of functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, the definition should be made based on the contents throughout this specification.

In the present disclosure, the base station is an entity that performs resource allocation for the terminal, such as gNode B, eNode B, Node B (or x Node B (x is the alphabet including g and e)), BS (Base Station), and wireless It may be, but is not limited to, at least one of an access unit, a base station controller, a satellite, an airborn, or a node on a network. The base station in this disclosure may mean the base station itself, a cell, or a RU, depending on the interpretation, and the object exchanging messages with the UE may be a DU or CU depending on the structure.

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 communication functions. there is.

Additionally, in the present disclosure, a cell may represent an area covered by one base station in wireless communication. Cells can be classified into mega cells, macro cells, micro cells, and pico cells depending on their size, but this is only an example and the types of cells are as described above. It is not limited to bars.

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

Additionally, in the present disclosure, the centralized unit (CU) is a central device and may include RRC, SDAP, and PDCP call layers. One CU can manage one or more DUs and is connected to the DUs through the F1 interface. In one embodiment of the present disclosure, a virtualized CU (virtualized CU) may be included.

Additionally, in the present disclosure, a radio unit (RU) serves to convert radio signals into digital signals for transmission through a packet network.

Additionally, in the present disclosure, 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 may employ an orthogonal frequency division multiplexing (OFDM) method.

Additionally, in this disclosure, uplink (upink) 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 may adopt the SC-FDMA (single carrier frequency division multiplexing access) method.

Additionally, in the present disclosure, a packet refers to a unit that transmits signals related to data or control. A packet may include both downlink or uplink data or signals related to control.

In the present disclosure, scale-in may mean increasing the amount of resources, such as increasing the number of DUs or servers connected to a DU, and scale-out may mean increasing the amount of resources, such as increasing the number of DUs or servers connected to a DU. This may mean reducing the amount of resources, such as reducing .

Terms referring to broadcast information, terms referring to control information, terms related to communication coverage, terms referring to state changes (e.g., events), and network entities used in the following description. Terms referring to ), terms referring to messages, terms referring to components of the device, etc. are exemplified for convenience of explanation. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meaning may be used.

For convenience of description below, the present disclosure uses terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP) standard, or terms and names modified based thereon. However, the present disclosure is not limited by the above-described terms and names, and can be equally applied to wireless communication systems complying with other standards. For example, an embodiment of the present disclosure is described using a 5th generation wireless communication technology (5G, new radio, NR) system as an example, but the present disclosure can also be applied to other wireless communication systems with similar technical background or channel type. Examples may be applied. According to another example, embodiments of the present disclosure may be applied to LTE or LTE-A, which are wireless communication systems before NR, and further, embodiments of the present disclosure may be applied to wireless communication systems developed after NR. Furthermore, at the discretion of a person with skilled technical knowledge, the embodiments of the present disclosure may be applied to other wireless communication systems through some modifications without significantly departing from the scope of the present disclosure.

Embodiments of the present disclosure may also be applied to other wireless communication systems through modification.

FIG. 1A is a diagram for explaining the structure of a radio access network (RAN).

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

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

The DU 20 may process the signal received from the RU 30 and transmit the processed signal to the CU 10 through the F1 interface. Additionally, a signal can be received and processed from the CU 10 through the F1 interface, or the signal can be transmitted to the RU 30. DU 20 can perform various wireless access network functions for signal processing. The wireless access network function may include a radio link control (RLC) layer function, a medium access control (MAC) layer function, or a higher physical (H-PHY) layer function, but this is only an example, and the wireless access network function This is not limited to the above-described example.

Figure 1b is a diagram for explaining the structure of a wireless protocol of NR (new radio).

The wireless protocol consists of SDAP (service data association protocol), PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), and MAC (Medium Access Control) in the terminal and base station.

Below, the functions of the SDAP layer, PDCP layer, RLC layer, MAC layer, and PHY layer will be described.

The main functions of SDAP may include some of the following functions:

- Transfer of user data (transfer of user plane data)

- Mapping function of QoS flow and data bearer for uplink and downlink (mapping between a QoS flow and a DRB for both DL and UL)

- Marking QoS flow ID in both DL and UL packets for uplink and downlink

- A function to map the relective QoS flow to the data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

For the SDAP layer device, the terminal can use an RRC message to configure whether to use the header of the SDAP layer device or use the function of the SDAP layer device for each PDCP layer device, each bearer, or each logical channel. When the SDAP header is set, the 1-bit indicator (NAS reflective QoS) and the AS QoS reflection setting 1-bit indicator (AS reflective QoS) of the SDAP header indicate the UE's NAS QoS flow and data bearer information. You can instruct to update or reset the mapping information. The SDAP header may include QoS flow ID information indicating QoS. QoS information can be used as data processing priority, scheduling information, etc. to support smooth service.

The main functions of PDCP may include some of the following functions:

- Header compression and decompression: ROHC only

- Transfer of user data

- In-sequence delivery of upper layer PDUs

- Out-of-sequence delivery of upper layer PDUs

- Order reordering function (PDCP PDU reordering for reception)

- Duplicate detection of lower layer SDUs

- Retransmission of PDCP SDUs

- Encryption and decryption function (Ciphering and deciphering)

- Timer-based SDU discard in uplink.

The reordering function of the PDCP device refers to the function of rearranging the PDCP PDUs received from the lower layer in order based on the PDCP SN (sequence number), and may include the function of delivering data to the upper layer in the reordered order. Alternatively, it may include a function to transmit immediately without considering the order, it may include a function to rearrange the order and record lost PDCP PDUs, and it may include a function to record lost PDCP PDUs, and it may include a function to report the status of the lost PDCP PDUs to the transmitting side. It may include a function to request retransmission of lost PDCP PDUs.

The RLC layer function may include at least some of the following functions.

- Transfer of upper layer PDUs

- In-sequence delivery of upper layer PDUs

- Out-of-sequence delivery of upper layer PDUs

- Error Correction through ARQ

- Concatenation, segmentation and reassembly of RLC SDUs

- Re-segmentation of RLC data

- Reordering of RLC data

- Duplicate detection

- Protocol error detection

- RLC SDU deletion function (RLC SDU discard)

- RLC re-establishment function

The in-sequence delivery function of the RLC layer refers to the function of delivering RLC SDUs (service data units) received from the lower layer to the upper layer in order, and one RLC SDU is divided into several RLC SDUs. When received, it may include a function to reassemble and deliver it. In addition, the sequential delivery function includes a function to rearrange received RLC PDUs based on RLC SN (sequence number) or PDCP SN (sequence number), a function to rearrange the order and record lost RLC PDUs, and a function to record lost RLC PDUs. It may include at least one of the functions of reporting status to the sending side. Additionally, the sequential delivery function may include a function to request retransmission of lost RLC PDUs, and if there is a lost RLC SDU, only the RLC SDUs up to the lost RLC SDU are delivered to the upper layer in order. Functions may be included. Additionally, the sequential delivery function may include a function of delivering all RLC SDUs received before the timer starts to the upper layer in order if a predetermined timer expires even if there are lost RLC SDUs, or even if there are lost RLC SDUs. If a predetermined timer expires, a function may be included to deliver all RLC SDUs received to date to the upper layer in order.

The RLC layer can process RLC PDUs in the order they are received and deliver 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 single RLC PDU, and then transmit the RLC PDU to the PDCP layer. Meanwhile, in new radio (NR), 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.

The functions of the MAC layer may include at least some of the following functions.

- Mapping between logical channels and transport channels

- Multiplexing and demultiplexing of MAC SDUs (Multiplexing/demultiplexing of MAC SDUs)

- Scheduling information reporting function

- Error correction through HARQ

- Priority handling between logical channels of one UE

- Priority handling between UEs by means of dynamic scheduling

- MBMS service identification function

- Transport format selection function

- Padding function

The PHY layer can perform at least some of the following functions.

- Data transmission and reception using electrical signals

- Channel coding/decoding function

- Modulation/demodulation function

- Power control

- Cell search

The PHY layer performs channel coding and modulation on the data of the upper layer, converts it into an OFDM symbol, and transmits it through a wireless channel. Additionally, the PHY layer can perform demodulation and channel decoding on OFDM symbols received through a wireless channel, and transmit the resulting data to a higher layer.

RU 30 can transmit signals to DU 20 through a fronthaul interface. Additionally, the RU (30) can receive a signal from the DU (20) through the fronthaul interface. The fronthaul is a network part that connects the RU (30) of the cell site to the DU (20) and can perform digital signal processing (DSP), power amplification, and filtering functions.

In order to efficiently use the resources of DUs 20, the present disclosure seeks to provide a method for dynamically managing the number of DUs 20 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 on a single device by integrating and managing multiple physical resources.

FIG. 2 is a diagram for explaining the structure of RAN after dynamic scaling according to an embodiment.

Referring to FIG. 2, RAN is a network that supports wireless access to UE (user equipment) and can be viewed as a set of base stations. In one embodiment, the RAN may be divided into a centralized unit (CU), 10, a distributed unit (DU), 20, and a radio unit (RU).

In the present disclosure, in order to efficiently use the resources of the DU 20, scaling in/out can be performed to dynamically allocate DUs as needed. With the CU 10 and N DUs 20 connected, if scaling out of the DU is required based on traffic information or resource information, the N+1th DU 20b can be added. In one embodiment of the present disclosure, whether scaling out or scaling in of the DU is necessary may be identified by OAM (Operation Administration Maintenance, 50). OAM 50 may mean, but is not limited to, O&M, OAM&P, OAMP, scaling agent, or scaling controller (SC).

In one embodiment of the present disclosure, the OAM 50 may determine whether to scale in/out by comparing traffic information and resource information of the DU 20. For example, if the resource throughput of the DU 20 is greater than a preset value, scaling out may be performed. Alternatively, scaling in/out can be determined by comparing the difference between the resource throughput of the DU and the traffic amount with a preset value. Hereinafter, for convenience of explanation, the existing DU will be referred to as the first DU (20a), and the DU added through scaling out will be referred to as the second DU (20b).

In one embodiment of the present disclosure, the first DU may be expressed as a source DU, a master DU, or a DU N, and may include a virtualized DU (vDU). In one embodiment of the present disclosure, the second DU may be expressed as a target DU, a slave DU, or DU N+1, and may include a virtualized DU (vDU). In one embodiment of the present disclosure, OAM 50 may periodically acquire resource information of the first DU 20a. Based on the resource information of the first DU 20a, the OAM 50 may activate the second DU 20b for scaling out.

The first DU (20a) is at least one RU to be connected to the second DU (20b) among the at least one RU (30a, b) that was connected to the first DU (20a) according to the scaling out of the second DU (20b) (30b) can be determined. The determined RU (30b) can transmit and receive packets with the second DU (20b) through the fronthaul interface. In one embodiment of the present disclosure, RU 30b may disconnect from the first DU 20a. Additionally, when scaling in, the fronthaul interface can be reconfigured between the RU (30b) and the first DU (20a).

In one embodiment of the present disclosure, an inter-DU interface may be established between the first DU (20a) and the second DU (20b). In this disclosure, the inter-DU interface refers to an interface for transmitting and receiving packets between DUs. The inter-DU interface can be expressed in various ways, such as an Xd interface and a DU-DU interface, and is not limited to the examples mentioned. Since the CU 10 can transmit and receive packets using the IP of the already connected DU based on the F1 interface setting, it cannot obtain information including the IP address of the dynamically added second DU 20b. Therefore, the CU 10 recognizes up to N already connected DUs, but does not recognize the dynamically added second DU 20b. The second DU 20b can transmit and receive packets through the inter-DU interface using the first DU 20a and the F1 splitter inside the DU.

DU (20, 20a, 20b) may include at least one of cell context information or UE context information. One RU may correspond to one cell context, and if a DU is connected to one or more RUs, the DU may have one or more cell contexts. For example, if the DU has 1 RU, it may include 1 cell context, and if the DU has 3 RUs, it may include 3 cell contexts.

Cell context information includes cell-related information such as the ID of the cell used by the base station, frequency-related information used, sub-carrier spacing (SCS)-related information, random access (RA)-related information, and radio resource information. Alternatively, it may include at least one of UE information related to the cell.

The UE context information may include at least one of UE state-related information, RLC entity-related information including buffers, information to be used by the MAC when scheduling the UE, or cell information related to the UE. The UE context may include at least one of UE-specific context and buffer data of the RLC layer or UE-specific context and buffer data of the MAC layer.

FIG. 3 is a diagram illustrating a scaling in/out scenario of a distributed unit (DU) according to a change in traffic of the distributed unit (DU), according to an embodiment.

Figure 3 shows information about traffic generated from a plurality of base stations or CUs. Hereinafter, traffic is the flow of packets or data passing through a communication network within a certain period of time.

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, data transmission/reception amount per unit time, etc. Additionally, the traffic processing information may include traffic information about a plurality of base stations from which traffic is generated and resource information used to process traffic generated from the plurality of base stations. For example, traffic information may include traffic processing speed per cell (eg, bps), number of UEs connected to the RU, generated frequency band, etc. Additionally, in one embodiment of the present disclosure, resource information may mean 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 only examples, and traffic information or resource information is not limited to the above-described examples. The resource usage of the DU may be determined or calculated based on at least one of central processing unit (CPU) usage, memory usage, or Ethernet link usage related to the network of the DU server.

In the case of existing RAN systems, the total amount of DU resources is determined by the maximum amount of traffic that can enter a cell site connected 1:1 to the DU. However, as shown in Figure 3, as the traffic amount per hour is not constant and changes, the efficiency of the DU's resources decreases. For example, the maximum traffic volume per hour is observed in the section from 18:00 to 21:00 (320a), and in the case of 3:00 to 5:00 (310a, 330a), the traffic volume is only about 20% of the maximum traffic volume per hour (320a). appear. The total amount of DU resources that is excessive compared to the amount of traffic may be allocated.

As the amount of traffic is not constant, a method for efficiently using DU resources is designed in this disclosure. Specifically, the present disclosure proposes a method that can dynamically and efficiently allocate required resources to DUs based on traffic information or resource information without violating the F1 interface. A method for efficiently transferring RUs and UEs while reducing the occurrence of communication disconnection of UEs connected to RUs is proposed.

In one embodiment of the present disclosure, the OAM 50 may obtain traffic information or resource information and, based on the obtained information, identify whether the DU 20 is additionally connected. In one embodiment of the present disclosure, OAM 50 may be a separate entity from the CU or DU and may be an entity that exists externally. In addition, the OAM (50) identifies the RU (30) connected to the DU (20) when scaling in/out of the DU (20) and provides information about the identified RU (30) to the DU (20). You can.

For example, in a section (310a) where the amount of traffic per hour is small, traffic is processed with one DU (310b). In the section 320a where the traffic amount per hour increases according to the change in the traffic amount, the number of DUs is increased, that is, the total amount of DU resources is increased through scaling out of the DUs (320b). The OAM 50 may determine the number of DUs to be scaled out based on the acquired traffic information or resource information. 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 and the CU through the inter-DU interface. Performance can be improved by sharing the load of the DU server.

In one embodiment, in the section 330a where the amount of traffic per hour decreases again, the OAM 50 reduces the number of DUs, that is, reduces the total amount of resources of the DU through scaling in of the DU (330b). . According to dynamic allocation of DU resources, DU resources can be prevented from being wasted. In one embodiment, OAM 50 may determine the number of DUs to be scaled in based on acquired traffic information or resource information. Additionally, at least one RU connected to a DU to be scaled in may be connected to a DU that was previously connected or a DU that has not been scaled in. Scaling in can save DU resources and reduce power consumption.

FIG. 4 is a diagram for explaining the structure and interface of RAN after dynamic scaling, according to one embodiment.

Referring to FIG. 4, the CU 10 and the first DU 20a are connected through the F1 interface. DU (20) and RU (30) are connected through a front haul interface. DU (20) has an F1 handler to control the F1 interface and RLC/MAC/H-PHY to perform wireless network communication functions.

DU 20 may include at least one of cell context information, UE context information, and RLC buffer. The DU may include a context synchronizer (Context Synchronizer, 420) that performs RU migration or UE migration. Cell context information may be expressed as cell information.

The context synchronization device 420 may determine which RU to migrate and the order based on cell information and UE context information within the DU. Additionally, it is possible to determine which UE within the RU for which transfer has been determined will be transferred from the first DU to the second DU and the transfer order.

The migration of a RU can be understood as the transmission of information about the RU from the first DU to the second DU. In one embodiment, information about a RU may be understood as information about a cell and may include at least one of cell context information 401 or UE context information 402.

In one embodiment, the CU and DU synchronize and manage the cell context and UE context through the F1 interface. In one embodiment, the cell context and UE context may include the cell context and UE context of the RLC or the cell context and UE context of the MAC. In one embodiment, data can be processed continuously as the second DU has cell context information and UE context information.

RAN supports connection with one CU (10) for one DU (20) based on the F1 interface. The F1 handler of the DU (20) connected to the CU (10) is activated and can perform a connection based on the F1 interface. The F1 interface consists of F1-C for control data and F1-U for user data. The structure of the F1 interface protocol is described in 3GPP TS38.470.

In the structure of F1-C, the Transport Network Layer is based on IP transport consisting of SCTP over 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 consisting of UDP and GTP-U over IP.

On the F1 interface, the CU 10 obtains information about the DU 20 and manages the DU 20 based on the acquired IP information of the DU 20. Therefore, when a DU is dynamically scaled out, as in an embodiment of the present disclosure, the new DU may be assigned a new IP that is different from the existing DU.

In RAN, DU 20 can perform various radio access network functions for signal processing. The wireless access network function may include, for example, at least one of a radio link control (RLC) layer function, a medium access controller (MAC) layer function, or a high-physical (H-PHY) layer function, but this is one example. However, the wireless access network function is not limited to the examples described above. Refer to Figure 1 for specific network functions.

According to scaling out of the DU, the first DU 20a and at least one second DU 20b are connected through an inter-DU interface. The Inter-DU interface is an interface for packet transmission and reception between DUs (20a, 20b) and is controlled by the F1 splitter and inter-DU handler. In one embodiment of the present disclosure, there may be one or more second DUs 20b. When there are a plurality of second DUs 20b, the first DU 20a can establish an inter-DU interface with each of the plurality of second DUs 20b. The OAM 50 may determine the RU 30 to be connected to each of the plurality of second DUs 20b.

The CU 10 can set up an F1 interface with the first DU 20a and transmit and receive packets through the F1 interface. The first DU 20a transmits IP information along with an F1 interface configuration request to the CU 10, and the CU 10 can configure the F1 interface with the first DU 20a based on the received IP information. The CU 10 can transmit and receive packets with the second DU 20b through the first DU 20a.

For example, a downlink packet to be transmitted to the second DU 20b is transmitted from the CU 10 to the first DU 20a and is transmitted to the second DU 20b through the inter-DU interface by the F1 splitter. ) can be transmitted. Alternatively, in the case of an uplink packet, it may be transmitted from the second DU 20b to the first DU 20a through an inter-DU interface and then transmitted and/or forwarded to the CU 10. In one embodiment of the present disclosure, the uplink packet from the second DU 20b may be merged with the uplink packet of the first DU 20a and transmitted to the CU 10.

The first DU 20a may be connected to the CU 10 through an F1 interface, the second DU 20b through an inter-DU interface, and the RU 30 through a fronthaul interface. In one embodiment of the present disclosure, based on the F1 interface, a connection is activated between the CU 10 and the first DU 20a, and no direct connection is made between the CU 10 and the second DU 20b. For example, the F1 handler of the first DU 20a may be activated and connect to the CU 10 based on the F1 interface. The F1 handler of the second DU may remain disabled.

In one embodiment of the present disclosure, the F1 splitter of the first DU may transmit the packet to the destination according to the contents of the packet. For example, in the case of a downlink packet received from the CU 10 through the F1 interface, the first DU 20a may directly process the packet or transmit the packet to the second DU 20b depending on the content of the data. When transmitting a downlink packet to the second DU 20b, the packet can be transmitted using an F1 splitter and an inter-DU handler through the inter-DU interface. Additionally, the F1 splitter can control the DU 20 to directly process the packet or transmit the packet to the RU 30 depending on the contents of the packet.

In one embodiment of the present disclosure, the inter-DU handler may configure an inter-DU interface between DUs 20a and 20b based on the obtained inter-DU interface configuration information. Inter-DU interface configuration information may include F1 interface configuration information between the first DU (20a) and CU (10). Additionally, the inter-DU handler can transmit and receive packets transmitted from the F1 splitter through the inter-DU interface.

The first DU (20a) and the RU (30) may be connected through a fronthaul interface. The fronthaul interface is a network part that connects DUs and RUs and can perform digital signal processing (DSP), power amplification, and filtering functions. The first DU 20a and the RU 30 can transmit and receive uplink and/or downlink packets through the fronthaul interface. In one embodiment of the present disclosure, OAM 50 may determine at least one RU to be connected to the DU according to scaling out. According to scaling out, the RU can set up a new DU and fronthaul interface and transmit and receive packets.

The second DU 20b may be connected to the first DU 20a through an inter-DU interface and to the RU 30 through a fronthaul interface. RU 30 may disconnect from the first DU 20a according to scaling out. Additionally, the RU 30 may disconnect from the second DU 20b and reconnect with the first DU 20a according to scaling in.

In one embodiment of the present disclosure, the F1 splitter of the second DU 20b determines whether to directly process the packet from the second DU 20b or the RU 30 according to the contents of the downlink packet received from the first DU 20a. You can identify whether to transmit the packet or not. Packet transmission and reception from the second DU 20b to the RU 30 may be performed based on the fronthaul interface. The uplink packet generated in the second DU 20b or received from the RU 30 may be transmitted to the first DU 20a through an inter-DU interface using an F1 splitter.

In one embodiment of the present disclosure, OAM 50 may identify whether connection with at least one second DU 20b is necessary based on traffic information or resource information. For example, when the traffic volume is greater than the processing capacity of the first DU (20a), the OAM 50 may determine that a connection with the second DU (20b) is necessary. In one embodiment of the present disclosure, the second DU 20b may request inter-DU interface configuration information from the first DU 20a. The second DU 20b may configure an inter-DU interface with the first DU 20a based on inter-DU interface configuration information obtained in response to the request. Inter-DU interface configuration information may include F1 interface configuration information between the first DU (20a) and CU (10).

When transferring an RU, overhead may occur at least among the F1 splitter and Xd tasks (Xd-C Task, Xd-U task) of the first and second DUs. Therefore, as the throughput of the transferred RU increases, the overhead occurring in the corresponding component may increase. An embodiment of the present disclosure proposes a method in which overhead is reduced compared to the case of randomly performing RU transfer. For specific details, refer to FIGS. 7A and 7B.

Figure 5a is a diagram for explaining the initial access procedure of the UE.

In step 5a -1, the UE transmits an RRCSetupRequest message to the gNB-DU.

In step 5a-2, the gNB-DU may transmit the RRC message and, if the UE is approved, an INITIAL UL RRC MESSAGE TRANSFER message containing the corresponding lower layer configuration information for the UE to the gNB-CU. In one embodiment, the INITIAL UL RRC MESSAGE TRANSFER message may include the C-RTI allocated by the gNB-DU. If the gNB-DU identifies the UE as a RedCapability UE during the random access procedure, the NR RedCap UE indication is provided in the initial UL RRC MESSAGE TRANSFER message.

In step 5a -3, the gNB-CU may allocate a gNB-CU UE F1AP ID for the UE and generate an RRC configuration message toward the UE. In one embodiment, the RRC message may be encapsulated in a DL RRC MESSAGE TRANSFER message.

In step 5a -4, the gNB-DU transmits an RRC configuration message to the UE.

In step 5a-5, the UE transmits an RRC CONNECTION SETUP COMPLETE message to the gNB-DU.

In step 5a-6, the gNB-DU encapsulates the RRC message in a URLRC MESSAGE TRANSFER message and transmits it to the gNB-CU.

In step 5a-7, the gNB-CU transmits an INITIAL UE MESSAGE message to the AMF.

In step 5a-8, AMF transmits an INITIAL CONTENT SETUP REQUEST message to the gNB-CU.

In step 5a -9, the gNB-CU sets the UE context of the gNB-DU by sending a UE CONTEX SETUP REQUEST message. In one embodiment, a SecurityModeCommand message may be encapsulated in the UE CONTEX SETUP REQUEST message. For NG-RAN sharing, the gNB-CU contains the serving PLMN ID (for SNPN, serving SNPN ID).

In step 5a-10, the gNB-DU transmits a security mode command message to the UE.

In step 5a -11, the gNB-DU transmits a UE CONTECT SETUP RESPONSE message to the gNB-CU.

In steps 5a-12, the UE responds with a Security Mode Complete message.

In step 5a-13, the gNB-DU encapsulates the RRC message in a URLRC MESSAGE TRANSFER message and transmits it to the gNB-CU.

In step 5a-14, the gNB-CU generates an RRC Configuration message and encapsulates it in the DLRRC MESSAGE TRANSFER message.

In step 5a-15, the gNB-DU sends an RRC configuration message to the UE.

In step 5a-16, the UE transmits an RRC configuration complete message to the gNB-DU.

In step 5a-17, the gNB-DU encapsulates the RRC message in a URLRC MESSAGE TRANSFER message and transmits it to the gNB-CU.

In step 5a-18, the gNB-CU transmits an INITIAL CONTEXT SETUP RESPONSE message to the AMF.

Figure 5b is a diagram to explain the transition procedure from the RRC inactive state to the RRC connected state.

In step 5b -0, gNB-CU-UP receives DL data on the NG-U interface.

In step 5b -1, gNB-CU-UP transmits a DL DATA NOTIFY message to gNB-CU-CP.

In step 5b -2, the gNB-CU-CP transmits a paging message to the gNB-DU.

In step 5b-3, the gNB-DU transmits a paging message to the terminal. Steps 0-3 may be necessary only for DL data. For UL data, steps 0-3 can be omitted.

In step 5b-4, the UE transmits an RRRCesumeRequest message upon RAN paging or UL data arrival.

In step 5b-5, the gNB-DU transmits the INITIAL URLRC MESSAGE TRANSFER message to the gNB-CU-CP.

In step 5b-6, the gNB-CU-CP creates a UE context in the gNB-DU by sending a UE CONTENCE SETUP REQUEST message including the stored F1 ULTEID.

In step 5b-7, the gNB-DU responds with a UE CONTEXT SETUP RESPONSE message including the F1 DL TEIDs assigned to the DRB.

In step 5b -8, the gNB-CU-CP and UE perform the RRC-Resume procedure through the gNB-DU.

In step 5b -9, the gNB-CU-CP sends a Bearer Context Modification Request message with an RRC Resumption Indication indicating that the UE is resuming from the RRC inactive state. The gNB-CU-CP also includes the F1 DL TEID received from the gNB-DU in step 7. NOTE Steps 8 and 9 can be performed in parallel.

In step 5b-10, gNB-CU-UP responds with a bearer context modification response message.

FIG. 6 is a diagram for explaining a paging procedure according to an embodiment of the present disclosure.

The network may initiate the paging procedure by sending a paging message to the UE's paging occasion (600) (610, 620). The network can address multiple UEs within a paging message by including one paging record for each UE. The network may include one or more Temporary Mobile Group Identity (TMGI) in the paging message. At least one of IMSI (International Mobile Subscriber Identity) or TMSI (Temporary Mobile Subscriber Identity) may be included in the paging message. The terminal may receive a paging message 610 or receive a paging record.

FIGS. 7A and 7B are diagrams for explaining a method of transferring a RU, according to one embodiment.

The first DU can determine whether RU migration needs to be performed based on information about the resource usage of the first DU. If the resource usage of the first DU is greater than or equal to the configured value for the resource usage of the first DU, it may be determined that RU transfer is necessary. Resource usage may be determined or calculated based on at least one of CPU (central processing unit) usage, memory usage, or Ethernet link usage related to the network of the DU server.

The first DU may select at least one target RU based on information about the throughput of the RU connected to the first DU. The first DU may transfer the target RU to the second DU. The RU determined to perform the transfer may be referred to as the target RU. At least one target RU may be expressed in the form of a RU list or RU set including a RU ID (identifier). For example, the RU set can be expressed as the previous RU (Migration RU) set Set 1={R1}, Set 2={R1, R2} Set 3={R2, R3}.

The first DU may obtain information about the throughput of some RUs or information about the throughput of all RUs for at least one RU connected to the first DU based on information about the RU. The throughput of the RU may be determined or calculated based on the amount of data transmitted and received by the UE connected to the RU. The amount of data transmitted and received by the UE measured by the MAC may be included in the information about the RU. Meanwhile, the throughput of the Inter-DU interface is determined based on the throughput of the target RU transferred to the second DU.

For example, if the first DU is connected to RU 1 and RU 2, UE 1, UE 2, and UE 3 belong to RU 1, and UE 4 belongs to RU 2, then the context sync of the first DU Using the MAC module of the first DU, Niger can obtain or measure the data transmission/reception amount of UE 1, the data transmission/reception amount of UE 2, and the data transmission/reception amount of UE 3 over a certain period of time, and can measure the data transmission/reception amount of all UEs. You can calculate the throughput of RU 1 by dividing it by a certain amount of time. The throughput of RU 2 can be obtained by dividing the data transmission and reception amount of UE 4 by a certain amount of time.

When a RU is transferred from the first DU to the second DU, the transferred RU processes data through the second DU. In order to comply with the F1 interface standard, the data can be transmitted to the first DU through the inter-DU interface in order for the RU to transmit and receive data with the CU or CN (Core Network).

The RU transferred from the first DU to the second DU may be referred to as the target RU. The resource usage of the first DU may be reduced by the resource usage of the first DU of the target RU. Meanwhile, as the target RU transmits and receives data through the first DU through the inter-DU interface, the throughput of the inter-DU interface may increase in proportion to the throughput of the target RU. Resource usage for inter-DU interface communication may increase in proportion to the throughput of the inter-DU interface.

Resource usage for the first DU of a target RU may be determined, identified, or calculated based on the throughput of the target RU. For example, the resource resource usage for the first DU of the target RU ( ) can be calculated according to the following equation (1):

Equation (1)

Total resources of the 1st DU ( ), throughput of target RU ( ), the total throughput of the first DU ( ) Based on, the first DU determines the resource resource usage for the first DU of the target RU ( ) can be calculated. Total throughput of the 1st DU ( ) can be understood as the total throughput of at least one RU connected to the DU.

For example, referring to Figures 5A and 5B, the sum of the throughput of each RU belonging to the set {RU 1, ..., RU N} is the total throughput of the first DU ( ) corresponds to When the transferred {RU M+1, ..., RU N} is called a target RU, the total sum of the throughput of RUs belonging to the {RU M+1, ..., RU N} set is the throughput of the target RU ( ) corresponds to

When transferring the target RU, the resource usage of the first DU decreases in proportion to the throughput of the target RU, but the throughput of the inter-DU interface may increase in proportion to the throughput of the target RU. As the throughput of the inter-DU interface increases, resource usage for inter-DU interface communication may increase. The greater the throughput of the transferred RU, the greater the resource use for inter-DU interface communication, and the resource saving effect due to scaling out and RU transfer may be deteriorated in relation to the resources of the first DU.

An embodiment of the present disclosure can reduce required server resources and reduce power consumption through DU Scaling. Additionally, by streamlining the migration operation, the resource usage of CPU, memory, or Ethernet link required for migration that occurs during scaling can be reduced.

The first DU may determine the target RU such that the throughput of at least one target RU is less than or equal to the threshold throughput of the inter-DU interface. The throughput of at least one target RU can be understood as the sum of the throughput of RUs belonging to the target RU set, and the sum of throughput of RUs belonging to the target RU set may be less than or equal to the threshold throughput of the inter-DU interface. For example, if the target RU is RU 1, the throughput of RU 1 is less than or equal to the threshold throughput of the inter-DU interface, and if the target RU is {RU 2, RU 3}, the sum of the throughput of RU 2 and the throughput of RU 3 is inter-DU interface. -The critical throughput of the DU interface is below.

The threshold throughput of the inter-DU interface can be set based on the network capacity between inter-DUs. For example, the larger the network capacity, the larger the threshold throughput of the inter-DU interface may be set by a base station operator such as a telecommunication company.

The target RU may be determined such that the resource usage for the first DU of the at least one target RU is greater than or equal to a resource usage threshold. The resource usage threshold may be set by an operator such as a telecommunication company or a base station based on resource usage by which the first DU operates stably in the server.

For example, it may be set by the operator or the base station as the total resource usage of the first DU minus the resource usage of the first DU operating stably in the server. The first DU may select, identify, or determine at least one target RU based on information about the resource usage of the first DU and information about the throughput of the RU.

In the first DU, the throughput of at least one target RU is less than or equal to the threshold throughput of the inter-DU interface, and the resource usage of the first DU of at least one target RU is greater than or equal to the resource usage threshold. A target RU can be selected.

FIG. 8 is a diagram for explaining a method of performing UE transfer, according to an embodiment of the present disclosure.

While transferring the UE from the first DU to the second DU, the UE may not receive a schedule from the MAC. If the schedule is not received for more than a certain period of time, RLF (radio link failure) may occur in the UE. The UE where RLF occurs can perform RA (random access). If multiple UEs perform RA simultaneously, signaling overhead of the base station system may increase and quality of service (QoS) may decrease. The present disclosure determines the transfer order of UEs, such as grouping and transferring UEs one by one or in certain groups, so that the transfer time can be reduced when multiple UEs are transferred together, and the occurrence of RLF can be reduced, A rapid decrease in QoS can be prevented. Additionally, the present disclosure can increase resource efficiency and reduce users' experience of communication disconnection.

Referring to FIG. 8, the first DU is based on at least one of information about the previous time spent, RRC state (Radio Resource Control state), or QoS (Quality of Service) of the UE connected to the target RU, and the second DU Transfer can be performed for at least one target UE. The target UE may be understood as a UE that has decided to perform UE transfer. In this disclosure, for convenience of explanation, it is referred to as a target UE, but it can be expressed in various ways, such as a first UE, a previous target UE, and a previous UE, and is not limited to the examples mentioned. The transfer of a UE can be understood as an operation to transmit UE-related information. Transfer can be performed together for one or multiple UEs. UE-related information may include at least one of UE context information or RLC buffer.

The previous time spent by the UE connected to the target RU is based on at least one of the size information of the UE context, the size information of the RLC buffer (Radio Link Control buffer), or information about the inter-DU network capacity (Inter DU Network Capacity) Can be determined or calculated. The UE's transfer time may include the time it takes to transmit UE-related information from the first DU to the second DU.

The larger the UE context, the longer the UE transfer time may be. The larger the size of the RLC buffer, the longer the UE's transfer time may be. The larger the network capacity between DUs, the shorter the time required for UE transfer. For example, when the size of the UE Context is 100Kbytes, the size of the RLC Buffer is 3000Kbytes, and the Network Capacity between Inter DUs is 10Gbps, the time taken to move 1000 UEs from the first DU to the second DU is calculated by the following equation ( 2) It can be calculated as follows.

Equation (2)

3100Kbytes/unit * 1000 units / 10Gbps= 3100*1024*1000*8 bit / 10*1024*1024*1024 bit/s= 2.36 seconds

The first DU determines whether to perform transfer of the UE connected to the target RU based on at least one of information about the transfer time of the UE connected to the target RU, RRC state (Radio Resource Control state), or QoS (Quality of Service). can be determined, and the transfer order of the target UE can be determined.

The first DU may determine whether to perform transfer of the UE connected to the RU and the transfer order based on the transfer time. For example, if the transfer time required for UE 1 connected to the target RU is longer than the threshold time related to radio link failure (RLF), the first DU decides to perform transfer of UEs excluding UE 1. You can. The first DU can perform transfer for a UE whose transfer time is shorter than the RLF-related threshold time.

The RLF-related threshold time can be determined based on the maximum number of times that RLC can request retransmission and the retransmission waiting time per time. For example, if the maximum number of times to request retransmission (maxRetxThreshold) set for UE 1 is 8 and the waiting time for retransmission per time (t-pollRetransmit) is 45ms, the RLF-related threshold time is calculated as 8*45=360ms. You can. If the previous time taken is shorter than 360ms, the UE's RLF may not occur.

The maximum number of times a retransmission can be requested (maxRetxThreshold) and the waiting time for each retransmission (t-pollRetransmit) can be set by base station operators such as telecommunication companies among the values set in the NR specifications as shown in Table 1. For example, by default, it can be set to request retransmission 8 times at 45ms each.

* maxRetxThreshold - default: t8
ENUMERATED { t1, t2, t3, t4, t6, t8, t16, t32 }
Parameter for RLC AM in TS 38.322 [4].
Value t1 corresponds to 1 retransmission, value t2 corresponds to 2 retransmissions and so on.
* t-pollRetransmit - default: ms45
ENUMERATED {
ms5, ms10, ms15, ms20, ms25, ms30, ms35,
ms40, ms45, ms50, ms55, ms60, ms65, ms70,
ms75, ms90, ms95, ms90, ms95, ms100, ms105,
ms110, ms115, ms120, ms125, ms130, ms135,
ms140, ms145, ms150, ms155, ms160, ms165,
ms170, ms175, ms180, ms185, ms190, ms195,
ms200, ms205, ms210, ms215, ms220, ms225,
ms230, ms235, ms240, ms245, ms250, ms300,
ms350, ms400, ms450, ms500, ms900, ms1000,
ms2000, ms4000, ms1-v1610, ms2-v1610, ms3-v1610,
ms4-v1610,spare1}

1 DU can determine whether to perform UE transfer and the UE transfer order based on the RRC status of the UE connected to the target RU. The first DU may transfer at least one of the UE in the idle state or the UE in the inactive state before the UE in the active state. A UE in an idle state or a UE in an inactive state may be converted to an active state without a re-registration process. When transferring a UE in an idle state or a UE in an inactive state, the transfer time may be shorter than when transferring a UE in an active state by transmitting only UE context information. The UE in an idle state and a UE in an inactive state are combined into one. By grouping, it is possible to determine whether to perform transfer of UEs belonging to the group, the transfer order of UEs, and perform transfer. When transferring UEs in an idle state and UEs in an inactive state, the UE in an idle state may be transferred before the UE in an inactive state. A UE in an idle state may have a smaller UE context information size and a smaller type of paging procedure than a UE in an inactive state, so after performing a UE transfer in an idle state, a UE transfer in an inactive state may be performed. You can.

When the RRC state of the UE connected to the target RU corresponds to an idle state or an inactive state, the first DU is a UE corresponding to an idle state or an inactive state based on at least one of the paging signal period or the previous time spent. Transfer of at least one UE among the corresponding UEs may be performed. For example, if the time until the next paging signal processing is longer than the previous time, the UE may be transferred. If the time until the next paging signal is processed is shorter than the previous time, the UE context can be transferred after waiting until the next paging signal arrives. When performing UE transfer according to an embodiment of the present disclosure, the occurrence of RLF of the UE can be reduced.

If the RRC state of the UE connected to the target RU is active state, transfer can be performed for UEs whose transfer time is shorter than or equal to the threshold time. If the RRC state of the UE is active and the transfer time is greater than the threshold time, after the set time has passed, it may be determined whether to perform the UE transfer based on the second transfer time, and based on the determination result Transfer can be performed.

The second transfer time can be determined based on information about the size of the UE context after the set time has elapsed, information about the size of the RLC buffer (Radio Link Control buffer), or information about the inter-DU network capacity (Inter DU Network Capacity). there is. The transfer may be performed for the UE if the time required for the second transfer is longer than the threshold time. Even after the set time has passed, transfer may not be performed for UEs whose second transfer time is longer than the threshold time. According to an embodiment of the present disclosure, a UE whose second transfer time is longer than the threshold time may perform RA or transfer to another DU including the second DU.

FIG. 9 is a diagram of a method for transferring a RU from a first DU to a second DU, according to an embodiment of the present disclosure.

In step S910, the first DU obtains inter-DU interface configuration information for connection with the second DU.

In one embodiment, the first DU may receive inter-DU interface configuration information from the OAM 50. The inter-DU interface configuration information may include configuration information for connection between the first DU and the second DU, F1 interface configuration information between the first DU and CU, and may be transmitted through higher layer signaling or physical layer signaling. . In one embodiment, inter-DU interface configuration information may be transmitted from the OAM 50 to the first DU based on the first DU's request for inter-DU interface configuration information.

In step S920, the first DU establishes a connection with the second DU based on inter-DU interface configuration information. In one embodiment, the first DU may connect to one or more DUs. In one embodiment, the inter-DU interface between the first DU and the second DU may be configured based on inter-DU interface configuration information. In one embodiment, the first DU may transmit and receive packets with the second DU through an inter-DU interface.

The context synchronizer of the first DU may obtain information about resource usage of the first DU. Resource usage of the first DU may be determined or calculated based on at least one of central processing unit (CPU) usage, memory usage, or Ethernet link usage related to the network of the DU server.

The first DU may determine whether RU transfer is necessary based on information about the resource usage of the first DU. If the resource usage of the first DU is greater than or equal to the configured value for the resource usage of the first DU, it may be determined that RU transfer is necessary. If it is determined to perform RU migration, the first DU may perform RU migration to at least one target RU based on the throughput of each RU connected to the first DU. The method for performing RU transfer may correspond to the description of FIGS. 7A and 7B, and some overlapping parts may be omitted.

In step S930, the first DU obtains information about the throughput of the RU connected to the first DU based on information about at least one radio unit (RU) connected to the first DU. In one embodiment, information about the RU may include at least one of cell context information or UE context information. The UE's data transmission and reception amount may be included in UE context information.

The throughput of the RU is determined based on the data transmission and reception amount of the UE connected to the RU. The first DU may obtain information about the throughput of some RUs or information about the throughput of all RUs for at least one RU connected to the first DU.

In step S940, the first DU selects, identifies, or determines at least one target RU based on information about the throughput of each RU.

The target RU may be understood as a RU that the first DU has decided to transfer to the second DU. At least one target RU may be expressed in the form of a RU list or RU set including a RU ID (identifier). The first DU may determine the target RU such that the throughput of at least one target RU is less than or equal to the threshold throughput of the inter-DU interface. For example, the sum of throughput of RUs belonging to the target RU set may be less than or equal to the threshold throughput of the inter-DU interface.

The threshold throughput of the inter-DU interface can be set based on the network capacity between inter-DUs. For example, the larger the network capacity, the larger the threshold throughput of the inter-DU interface may be set by a base station operator such as a telecommunication company.

The target RU may be determined such that the resource usage for the first DU of at least one target RU is greater than or equal to the resource usage threshold. The resource usage threshold may be set by an operator such as a telecommunication company or a base station based on resource usage by which the first DU operates stably in the server. For example, it may be set by the operator or the base station as the total resource usage of the first DU minus the resource usage of the first DU operating stably on the server.

Resource usage for the first DU of a target RU may be determined, identified, or calculated based on the throughput of the target RU. For example, the resource resource usage for the first DU of the target RU ( ) can be calculated according to equation (1).

Equation (1)

The first DU may select, identify, or determine at least one target RU based on information about the resource usage of the first DU and information about the throughput of the RU.

In step S950, the first DU performs migration of the target RU to the second DU.

In one embodiment, the first DU may transmit information about the RU from the first DU to the second DU. Information about the RU may include at least one of cell context information or UE context information.

The first DU connects at least one target UE to the second DU based on at least one of information about the previous time spent, RRC state (Radio Resource Control state), or QoS (Quality of Service) of the UE connected to the target RU. Transfer can be performed for . The target UE may be understood as a UE that has decided to perform UE transfer. In this disclosure, for convenience of explanation, it is referred to as a target UE, but it can be expressed in various ways, such as a first UE, a previous target UE, and a previous UE, and is not limited to the examples mentioned.

The transfer of a UE can be understood as an operation to transmit UE-related information. UE-related information may include at least one of UE context information or RLC buffer. The first DU may perform transfer together for one or multiple UEs. The method of performing the transfer may correspond to the description of FIG. 8, and some overlapping parts may be omitted.

The previous time spent by the UE connected to the target RU is based on at least one of the size information of the UE context, the size information of the RLC buffer (Radio Link Control buffer), or information about the inter-DU network capacity (Inter DU Network Capacity) Can be determined or calculated. The UE's transfer time may include the time it takes to transmit UE-related information from the first DU to the second DU.

The larger the UE context, the longer the UE transfer time may be. The larger the size of the RLC buffer, the longer the UE's transfer time may be. The larger the network capacity between DUs, the shorter the time required for UE transfer.

For example, when the size of the UE Context is 100Kbytes, the size of the RLC Buffer is 3000Kbytes, and the Network Capacity between Inter DUs is 10Gbps, the time taken to move 1000 UEs from the first DU to the second DU is Equation (2) It can be calculated as follows.

The first DU determines whether to perform transfer of the UE connected to the target RU based on at least one of information about the transfer time of the UE connected to the target RU, RRC state (Radio Resource Control state), or QoS (Quality of Service). can be determined, and the transfer order of the target UE can be determined.

The first DU may determine whether to perform transfer of the UE connected to the RU and the transfer order based on the transfer time. For example, if the transfer time required for UE 1 connected to the target RU is longer than the threshold time related to radio link failure (RLF), it may be decided to perform transfer of UEs excluding UE 1. Transfer can be performed for UEs whose transfer time is shorter than the RLF-related threshold time. The RLF-related threshold time can be determined based on the maximum number of times that RLC can request retransmission and the retransmission waiting time per time.

The first DU may determine whether to perform transfer of the UE and the transfer order of the UE based on the RRC status of the UE connected to the target RU. The first DU may transfer at least one of the UE in the idle state or the UE in the inactive state before the UE in the active state. A UE in an idle state or a UE in an inactive state may be converted to an active state without a re-registration process. When transferring a UE in an idle state or a UE in an inactive state, the transfer time may be shorter than when transferring a UE in an active state by transmitting only UE context information.

By grouping UEs in an idle state and UEs in an inactive state into one group, it is possible to determine whether to perform a transfer of UEs belonging to the group, the transfer order of the UEs, and perform the transfer. When transferring UEs in an idle state and UEs in an inactive state, the UE in an idle state may be transferred before the UE in an inactive state. A UE in an idle state may have a smaller UE context information size and a smaller type of paging procedure than a UE in an inactive state, so after performing a UE transfer in an idle state, a UE transfer in an inactive state may be performed. You can.

When the RRC state of the UE connected to the target RU corresponds to an idle state or an inactive state, the first DU is a UE corresponding to an idle state or an inactive state based on at least one of the paging signal period or the previous time spent. Transfer of at least one UE among the corresponding UEs may be performed. For example, if the time until the next paging signal processing is longer than the previous time, the UE may be transferred. If the time until the next paging signal is processed is shorter than the previous time, the UE context can be transferred after waiting until the next paging signal arrives. When performing UE transfer according to an embodiment of the present disclosure, the occurrence of RLF of the UE can be reduced.

If the RRC state of the UE connected to the target RU is active state, transfer can be performed for UEs whose transfer time is shorter than or equal to the threshold time. If the RRC state of the UE is active and the transfer time is greater than the threshold time, after the set time has passed, it may be determined whether to perform the UE transfer based on the second transfer time, and based on the determination result Transfer can be performed.

The second transfer time can be determined based on information about the size of the UE context after the set time has elapsed, information about the size of the RLC buffer (Radio Link Control buffer), or information about the inter-DU network capacity (Inter DU Network Capacity). there is. The transfer may be performed for the UE if the time required for the second transfer is longer than the threshold time. Even after the set time has passed, transfer may not be performed for UEs whose second transfer time is longer than the threshold time. According to an embodiment of the present disclosure, a UE whose second transfer time is longer than the threshold time may perform RA or transfer to another DU including the second DU.

According to an embodiment of the present disclosure, the overhead of the first DU can be reduced and communication disconnection with the UE can be reduced. Additionally, it can increase the DU's resource use efficiency and reduce the UE's QoS degradation. By making the transfer operation efficient, the resource use required during transfer can be reduced.

Figure 10 is a schematic block diagram of DU 20 according to one embodiment.

Referring to FIG. 10, the DU 20 according to the present disclosure may be composed of a processor 1010, a transceiver 1020, and a memory (not shown). However, the components of DU 20 are not limited to the examples described above. For example, DU 20 may include more or fewer components than those described above. In one embodiment of the present disclosure, the processor 1010, the memory, and the transceiver 1020 may be implemented in the form of a single chip.

Processor 1010 may be comprised of one or multiple processors. At this time, one or more processors may be CPU, AP, DSP (Digital Signal Processor), etc.

The processor 1010 can control a series of processes to enable the DU 20 to operate according to the above-described embodiment of the present disclosure. For example, the processor 1010 may receive control signals and data signals through the transceiver 1020 and process the received control signals and data signals. The processor 1010 can transmit the processed control signal and data signal through the transceiver 1020 and detect an event. Additionally, the processor 1010 can control processing of input data derived from the received control signal and data signal according to predefined operation rules or artificial intelligence models stored in memory. The processor 1010 can write and read data to memory. Additionally, the processor 1010 can perform protocol stack functions required by communication standards. According to one embodiment, the processor 1010 may include at least one processor. In one embodiment of the present disclosure, a part of the transceiver 1020 or the processor 1010 may be referred to as a communication processor (CP). The processor 1010 can activate or deactivate the F1 handler, F1 splitter, and inter-DU handler of the DU 20 according to the above-described embodiment of the present disclosure, and set the inter-DU interface.

The memory can store programs and data necessary for the operation of the DU 20. Additionally, the memory may store control information or data included in the signal obtained from the DU 20. Additionally, the memory may store predefined operation rules or artificial intelligence models used in the DU 20. Memory may be composed of storage media such as ROM, RAM, hard disk, CD-ROM, and DVD, or a combination of storage media. Additionally, the memory may not exist separately but may be included in the processor 1010. Memory may be comprised of volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. The memory may provide stored data upon request from the processor 1010.

The transceiving unit 1020 is a general term for the transmitting unit and the receiving unit. The transceiving unit 1020 of the DU 20 can transmit and receive signals with a base station or a network entity. Signals being transmitted and received may include control information and data. To this end, the transceiver 1020 may be composed of an RF transmitter that up-converts and amplifies the frequency of the transmitted signal, and an RF receiver that amplifies the received signal with low noise and down-converts the frequency. However, this is one embodiment of the transceiver 1020, and the components of the transceiver 1020 are not limited to the RF transmitter and RF receiver. Additionally, the transceiver 1020 may receive a signal through a wireless channel and output it to the processor 1010, and transmit the signal output from the processor 1010 through a wireless channel. The transmitting and receiving unit 1020 can transmit and receive data between DUs through an inter-DU interface.

The first DU can obtain inter-DU interface configuration information for connection with the second DU. The first DU may perform a connection with the second DU based on the inter-DU interface configuration information. The first DU may obtain information about the throughput of each RU based on information about at least one radio unit (RU) connected to the first DU. The first DU may select at least one target RU based on information about the throughput of each RU. Migration of the target RU can be performed to the second DU.

According to an embodiment of the present disclosure, the first DU may determine whether to perform migration of the RU connected to the first DU based on information related to resource usage of the first DU. Resource usage of the first DU may be determined based on at least one of CPU (central processing unit) usage, memory usage, or Ethernet link usage.

The throughput of each RU may be determined based on the data transmission/reception size of UE (User Equipment) connected to each RU. The throughput of the at least one target RU may be less than or equal to the threshold throughput of the inter-DU interface.

Resource usage for the first DU of the at least one target RU may be greater than or equal to a resource usage threshold. Resource usage for the first DU of the target RU may be determined based on the throughput of the target RU.

At least one target to the second DU based on at least one of the Radio Resource Control state (RRC state) of the UE (User Equipment) connected to the target RU, the previous time spent, or information about Quality of Service (QoS) Transfer can be performed for the UE.

The previous time taken by the UE connected to the target RU is based on at least one of UE context size information, RLC buffer (Radio Link Control buffer) size information, or information about inter DU network capacity (Inter DU Network Capacity). It can be decided.

If the RRC state of the UE connected to the target RU is in an idle state, the UE in the idle state can be transferred. If the RRC state of the UE connected to the target RU corresponds to the inactive state, the UE in the inactive state can be transferred based on the paging signal period and the transfer time. If the RRC state of the UE connected to the target RU corresponds to the active state, transfer can be performed for the UE whose transfer time is less than the threshold time. The threshold time may be determined based on the maximum number of times the RLC can request retransmission and the waiting time for retransmission per time. After the configured time has passed, UE transfer can be performed among UEs connected to the target RU. If the transfer time of the first UE connected to the target RU is greater than the threshold time, transfer may be performed for UEs other than the first UE among the plurality of UEs.

According to an embodiment of the present disclosure, the first DU may include a transceiver and at least one processor. The at least one processor may obtain inter-DU interface configuration information for connection to the second DU. The at least one processor may perform connection with the second DU based on the inter-DU interface configuration information. The at least one processor may obtain information about the throughput of each RU based on information about at least one RU connected to the first DU. The at least one processor may select at least one target RU based on information about the throughput of each RU. The at least one processor may perform transfer of the at least one target RU to the second DU.

A storage medium that can be read by a device may be provided in the form of a non-transitory storage medium. Here, 'non-transitory storage medium' simply means that it is a tangible device and does not contain signals (e.g. electromagnetic waves). This term refers to cases where data is semi-permanently stored in a storage medium and temporary storage media. It does not distinguish between cases where it is stored as . For example, a 'non-transitory storage medium' may include a buffer where data is temporarily stored.

According to one embodiment, methods according to various embodiments disclosed in this document may be provided and included in a computer program product. Computer program products are commodities and can be traded between sellers and buyers. A 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 through an application store or between two user devices (e.g. smartphones). It can be distributed in person or online (e.g. downloaded or uploaded). In the case of online distribution, at least a portion of the computer program product (e.g., a downloadable app) is stored on a machine-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or a relay server. It can be temporarily stored or created temporarily.

Claims (20)

In a method for a first distributed unit (DU) to perform communication in a wireless communication system,
Obtaining inter-DU interface configuration information for connection to a second DU;
performing connection with a second DU based on the inter-DU interface configuration information;
Obtaining information about the throughput of each RU based on information about at least one radio unit (RU) connected to the first DU;
selecting at least one target RU based on information about the throughput of each RU; and
A method comprising performing migration of the target RU to the second DU. According to claim 1,
Further comprising determining whether to perform migration of the RU connected to the first DU based on information related to resource usage of the first DU,
The method wherein the resource usage of the first DU is determined based on at least one of CPU (central processing unit) usage, memory (Memory) usage, or Ethernet Link (Ethernet Link) usage. According to claim 1,
The method wherein the throughput of each RU is determined based on the data transmission and reception size of UE (User Equipment) connected to each RU. According to clause 1,
The method wherein the throughput of the at least one target RU is less than or equal to the threshold throughput of the inter-DU interface. According to claim 1,
The resource usage for the first DU of the at least one target RU is greater than or equal to a resource usage threshold,
The method wherein the resource usage for the first DU of the target RU is determined based on the throughput of the target RU. According to claim 1,
At least one target to the second DU based on at least one of the Radio Resource Control state (RRC state) of the UE (User Equipment) connected to the target RU, the previous time spent, or information about Quality of Service (QoS) The method further comprising performing a transfer for the UE. According to claim 6,
The previous time taken by the UE connected to the target RU is based on at least one of UE context size information, RLC buffer (Radio Link Control buffer) size information, or information on inter-DU network capacity (Inter DU Network Capacity). determined by the method. According to claim 6,
The step of performing a transfer for the at least one target UE includes:
When the RRC state of the UE connected to the target RU corresponds to an idle state, the method includes performing a transfer of the UE corresponding to the idle state. According to claim 6,
The step of performing a transfer for the at least one target UE includes:
When the RRC state of the UE connected to the target RU corresponds to the inactive state, performing transfer of the UE corresponding to the inactive state based on the paging signal period and the time required for the transfer. How to. According to claim 6,
The step of performing a transfer for the at least one target UE includes:
When the RRC state of the UE connected to the target RU corresponds to the active state, performing transfer for the UE whose transfer time is less than or equal to a threshold time,
The threshold time is determined based on the maximum number of times the RLC can request retransmission and the retransmission waiting time per time. According to claim 10,
The method further includes re-performing transfer of a UE among UEs connected to the target RU after a configured time has elapsed. According to claim 1,
If the transfer time of the first UE connected to the target RU is greater than the threshold time, the method further includes performing transfer for UEs other than the first UE among the plurality of UEs. The first DU performing communication in the wireless communication system is:
Transmitter and receiver; and
Includes at least one processor connected to the transceiver,
The at least one processor,
Obtain inter-DU interface configuration information for connection to the second DU,
Perform connection with a second DU based on the inter-DU interface configuration information,
Obtaining information about the throughput of each RU based on information about at least one RU connected to the first DU,
Select at least one target RU based on information about the throughput of each RU,
A first DU performing transfer of the at least one target RU to the second DU. According to claim 13,
The at least one processor,
Determine whether to perform migration of the RU connected to the first DU based on information related to resource usage of the first DU,
The resource usage of the first DU is determined based on at least one of CPU (central processing unit) usage, memory (Memory) usage, or Ethernet Link (Ethernet Link) usage. According to claim 13,
A first DU where the throughput of each RU is determined based on the data transmission/reception size of the UE (User Equipment) connected to each RU. According to claim 13,
A first DU wherein the throughput of the at least one target RU is less than or equal to the threshold throughput of the inter-DU interface. According to claim 13,
The resource usage for the first DU of the at least one target RU is greater than or equal to a resource usage threshold,
The resource usage for the first DU of the target RU is determined based on the throughput of the target RU. According to claim 13,
The at least one processor,
Transfer of at least one target UE to the second DU based on at least one of information about the RRC state (Radio Resource Control state), transfer time required, or QoS (Quality of Service) of the UE connected to the target RU. Performing, 1st DU. According to claim 13,
The previous time taken by the UE connected to the target RU is based on at least one of UE context size information, RLC buffer (Radio Link Control buffer) size information, or information about inter DU network capacity. 1st DU, as determined. According to claim 13,
When the RRC state of the UE connected to the target RU corresponds to an idle state or an inactive state, a first DU comprising first performing transfer of the UE corresponding to the idle state.

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