Electronic device and method for communication between distributed units in wireless communication system

Abstract

According to one embodiment, an electronic device performing a function of a first distributed unit (DU) may comprise: a communication circuit; at least one processor; and a memory storing instructions and including one or more storage media. The instructions, when executed individually or collectively by the at least one processor, may instruct the electronic device to: receive a reset message from a second DU used together with the first DU for carrier aggregation (CA); identify a terminal connected to the first DU and the second DU for the CA; determine, for the terminal, whether the first DU provides a primary cell (PCell) for the CA or whether the first DU provides a secondary cell (SCell) for the CA; refrain from providing data for the terminal to the second DU, in response to determining that the first DU provides the PCell; and release a resource for the terminal, in response to determining that the first DU provides the SCell.

Description

Electronic device and method for communication between distributed units in a wireless communication system

[0001] The present disclosure relates to an electronic device and method for communication between distributed units in a wireless communication system.

[0002] Efforts are being made to develop improved 5G (5th generation) communication systems or pre-5G communication systems to meet the increasing demand for wireless data traffic following the commercialization of 4G (4th generation) communication systems. For this reason, 5G communication systems or pre-5G communication systems are referred to as Beyond 4G Network communication systems or Post-LTE systems.

[0003] To achieve high data transmission rates, 5G communication systems are being considered for implementation in the mmWave band (e.g., the 60 GHz band). To mitigate path loss and increase the transmission distance of radio waves in the mmWave band, beamforming, massive MIMO, full Dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large-scale antenna technologies are being discussed for 5G communication systems.

[0004] In addition, to improve the network of the system, technologies such as advanced small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network, Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation are being developed in 5G communication systems.

[0005] In addition, advanced coding modulation (ACM) methods such as FQAM (Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation) and SWSC (Sliding Window Superposition Coding), as well as advanced access technologies such as FBMC (Filter Bank Multi Carrier), NOMA (Non Orthogonal Multiple Access), and SCMA (Sparse Code Multiple Access) are being developed in 5G systems.

[0006] With the commercialization of 5G systems and NR (new radio or next radio) to meet the demand for wireless data traffic, it is expected that high data transmission rate services will be provided to users through 5G systems, similar to 4G, and that wireless communication services for various purposes, such as the Internet of Things and services requiring high reliability for specific purposes, can be provided. The O-RAN (open radio access network), established by operators and equipment providers in a system currently mixed with 4th generation and 5th generation communication systems, defines the E2AP (E2 application protocol) specification in the application protocol of the E2 interface between E2 nodes and Near-RT (real time) RIC (RAN (radio access network) intelligent controller).

[0007] Looking back at the evolution of wireless communication through successive generations, technologies have been developed primarily for human-oriented services, such as voice, multimedia, and data. Following the commercialization of 5G (5th Generation) communication systems, connected devices, which have been increasing explosively, are expected to be connected to communication networks. Examples of networked objects include vehicles, robots, drones, home appliances, displays, smart sensors installed in various infrastructures, construction machinery, and factory equipment. Mobile devices are expected to evolve into various form factors, such as augmented reality glasses, virtual reality headsets, and holographic devices. In the 6G (6th Generation) era, efforts are underway to develop improved 6G communication systems to connect hundreds of billions of devices and objects to provide diverse services. For this reason, 6G communication systems are being referred to as "beyond 5G" systems.

[0008] In the 6G communication system predicted to be realized around 2030, the maximum transmission speed is tera (i.e., 1,000 gigabit) bps (bit per second), and the wireless latency 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 latency is reduced to one-tenth.

[0009] To achieve such high data transmission speeds and ultra-low latency, 6G communication systems are being considered for implementation in the terahertz (THz) band (e.g., the 95 gigahertz (GHz) to 3 terahertz (3THz) band). Due to more severe path loss and atmospheric absorption phenomena compared to the millimeter wave (mmWave) band introduced in 5G, the importance of technologies capable of guaranteeing signal reach, or coverage, is expected to increase in the terahertz band. As key technologies to ensure coverage, new waveforms, beamforming, and multi-antenna transmission technologies such as massive Multiple-Input and Multiple-Output (MIMO), Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas, which are superior in terms of coverage compared to RF (Radio Frequency) devices, antennas, and OFDM (Orthogonal Frequency Division Multiplexing), must be developed. In addition, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS) are being discussed to improve the coverage of terahertz band signals.

[0010] In addition, to improve frequency efficiency and system network, development is underway in 6G communication systems for full duplex technology, in which uplink and downlink simultaneously utilize the same frequency resources at the same time; network technology that integrates satellites and HAPS (High-Altitude Platform Stations); network structure innovation technology that supports mobile base stations and enables network operation optimization and automation; dynamic spectrum sharing technology through collision avoidance based on spectrum usage prediction; AI-based communication technology that utilizes AI from the design stage and internalizes end-to-end AI support functions to realize system optimization; and next-generation distributed computing technology that realizes services of complexity exceeding the limits of terminal computing capabilities by utilizing ultra-high performance communication and computing resources (Mobile Edge Computing (MEC), cloud, etc.). In addition, attempts are continuing to further strengthen connectivity between devices, further optimize networks, promote the softwareization of network entities, and increase the openness of wireless communication through the design of new protocols to be used in 6G communication systems, the implementation of hardware-based security environments, the development of mechanisms for the safe utilization of data, and the development of technologies regarding privacy maintenance methods.

[0011] Due to the research and development of such 6G communication systems, it is expected that a new dimension of hyper-connected experience will become possible through the hyper-connectivity of 6G communication systems, which encompasses not only connections between objects but also connections between people and objects. Specifically, it is projected that 6G communication systems will enable the provision of services such as truly immersive eXtended Reality (XR), high-fidelity mobile holograms, and digital replicas. Furthermore, services such as remote surgery, industrial automation, and emergency response, which are provided through 6G communication systems with enhanced security and reliability, will be applied in various fields including industry, healthcare, automotive, and home appliances.

[0012] In 6G communication systems, it is expected that RAN functions will be further subdivided and separated into service subscribers and service providers. In service-based networks, the process of verifying subscribed services regarding the status of service subscriptions will be applied across various functions.

[0013] The information described above may be provided as related art for the purpose of aiding understanding of the present disclosure. No claim or determination is made as to whether any of the foregoing may be applied as prior art related to the present disclosure.

[0014] According to one embodiment, an electronic device performing the function of a first DU (distributed unit) may include at least one processor including a communication circuitry and a processing circuitry, and a memory including one or more storage media for storing instructions. When the above instructions are executed individually or collectively by the at least one processor, the electronic device receives a reset message from a second DU used for carrier aggregation (CA) together with the first DU, and based on the reset message, identifies a terminal connected to the first DU and the second DU for CA, and determines for the terminal whether the first DU provides a primary cell (PCell) for CA or whether the first DU provides a secondary cell (SCell) for CA, and in accordance with the determination that the first DU provides the PCell, refrains from providing data for the terminal to the second DU, and in accordance with the determination that the first DU provides the SCell, causes resources for the terminal to be released.

[0015] According to one embodiment, a method performed by an electronic device that performs the function of a first distributed unit (DU) may include: receiving a reset message from a second DU used for carrier aggregation (CA) together with the first DU; identifying a terminal connected to the first DU and the second DU for CA based on the reset message; determining, for the terminal, whether the first DU provides a primary cell (PCell) for the CA or whether the first DU provides a secondary cell (SCell) for the CA; refraining from providing data for the terminal to the second DU based on the determination that the first DU provides the PCell; and releasing resources for the terminal based on the determination that the first DU provides the SCell.

[0016] The above and other aspects, features, and advantages of specific embodiments of the present disclosure will become more apparent from the following description taken together with the accompanying drawings:

[0017] FIGS. 1a and 1b show examples of wireless communication systems.

[0018] FIGS. 2a to 2c show examples of spectrum aggregation environments.

[0019] Figure 3 shows examples of resource structures in the time domain and frequency domain.

[0020] Figure 4a shows the protocol stack in the control plane.

[0021] Figure 4b shows the protocol stack in the user plane.

[0022] Figure 5 shows an example of spectrum aggregation between distributed units (DUs).

[0023] Figure 6 shows an example of a protocol for spectrum aggregation between DUs.

[0024] FIG. 7 illustrates an example of a system for transmitting traffic through multiple DUs.

[0025] FIG. 8 illustrates an example of the operation of the first DU and the second DU to perform a reset process in the first DU.

[0026] FIG. 9 illustrates a flowchart regarding the operation of the first DU for performing a reset process.

[0027] FIG. 10 illustrates a flowchart regarding the operation of the first DU.

[0028] FIG. 11 illustrates an example of the operation of the first DU after the deactivation of the second DU is performed.

[0029] FIG. 12 illustrates an example of a plurality of terminals receiving data through the first DU and the second DU and CA.

[0030] FIG. 13 illustrates an example of the operation of a first DU for distinguishing multiple terminals.

[0031] FIG. 14 illustrates an example of a state diagram of a system including a first DU and a second DU.

[0032] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit the scope of other embodiments. A singular expression may include a plural expression unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as generally understood by those skilled in the art described in this disclosure. Terms used in this disclosure that are defined in a general dictionary may be interpreted as having the same or similar meaning as they have in the context of the relevant technology, and are not to be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure. In some cases, even terms defined in this disclosure are not to be interpreted to exclude the embodiments of this disclosure.

[0033] In the various embodiments of the present disclosure described below, a hardware-based approach is described as an example. However, since the various embodiments of the present disclosure include techniques using both hardware and software, the various embodiments of the present disclosure do not exclude a software-based approach.

[0034] Terms used in the following description to refer to signals (e.g., signal, information, message, signaling), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, RE (resource element), RB (resource block), BWP (bandwidth part), occasion), terms for operation states (e.g., step, operation, procedure), terms referring to data (e.g., packet, user stream, information, bit, symbol, codeword), terms referring to channels, terms referring to network entities, terms referring to device components, etc., are examples provided for the convenience of explanation. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used. Additionally, terms such as '...part', '...device', '...object', '...body' used below may refer to at least one shape structure or a unit that processes a function.

[0035] Additionally, in this disclosure, expressions of "greater than" or "less than" may be used to determine whether a specific condition is satisfied or fulfilled; however, this is merely for the purpose of expressing an example and does not exclude descriptions of "greater than" or "less than." Conditions described as "greater than" may be replaced with "greater than," conditions described as "less than" may be replaced with "less than," and conditions described as "greater than and less than" may be replaced with "greater than and less than." Furthermore, "A" to "B" below refer to at least one of elements from A (including A) to B (including B). Below, "C" and / or "D" refers to including at least one of "C" or "D," i.e., {"C", "D", "C" and "D"}.

[0036] This disclosure describes various embodiments using terms used in some communication standards (e.g., 3GPP (3rd Generation Partnership Project), xRAN (extensible radio access network), O-RAN (open-radio access network), but these are merely illustrative examples. Various embodiments of this disclosure can be easily modified and applied to other communication systems.

[0037] Currently, discussions are underway to improve and enhance the performance of the initial 5G mobile communication technology, taking into account the services that the 5G mobile communication technology was intended to support. Additionally, standardization of the physical layer is in progress for technologies such as V2X (Vehicle-to-Everything), which helps autonomous vehicles make driving decisions and enhance user convenience based on their own location and status information transmitted by the vehicle; NR-U (New Radio Unlicensed), which aims for system operation in unlicensed bands to comply with various regulatory requirements; NR terminal low power consumption technology (UE Power Saving); Non-Terrestrial Network (NTN), which is direct terminal-satellite communication for securing coverage in areas where communication with the terrestrial network is impossible; and positioning.

[0038] In addition, standardization is underway in the field of wireless interface architecture / protocols for technologies such as the Industrial Internet of Things (IIoT) to support new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) which provides nodes to expand network service areas by integrating wireless backhaul links and access links, Mobility Enhancement including Conditional Handover and Dual Active Protocol Stack (DAPS) Handover, and 2-step Random Access for NR which simplifies random access procedures. Standardization is also underway in the field of system architecture / services for 5G baseline architectures (e.g., Service based Architecture, Service based Interface) to incorporate Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC), which provides services based on the location of the terminal.

[0039] When such 5G mobile communication systems are commercialized, connected devices, which are increasing explosively, will be connected to communication networks. Accordingly, it is expected that there will be a need to enhance the functionality and performance of 5G mobile communication systems and to integrate the operation of connected devices. To this end, new research is planned to be conducted on 5G performance improvement and complexity reduction, support for AI services, support for metaverse services, and drone communication using eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0040] Furthermore, the advancement of these 5G mobile communication systems encompasses multi-antenna transmission technologies such as new waveforms to guarantee coverage in the terahertz band of 6G mobile communication technology, Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas; metamaterial-based lenses and antennas to improve terahertz band signal coverage; high-dimensional spatial multiplexing technology using OAM (Orbital Angular Momentum); and Reconfigurable Intelligent Surface (RIS) technology; as well as Full Duplex technology for enhancing frequency efficiency and system networks in 6G mobile communication technology; AI-based communication technologies that realize system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions; and the realization of services of complexity exceeding the limits of terminal computing capabilities by utilizing ultra-high-performance communication and computing resources. It could serve as a foundation for the development of next-generation distributed computing technologies.

[0041] Hereinafter, 4G and / or 5G environments have been described as examples, but such description does not limit the scope of the communication environments of the embodiments of the present disclosure. The technical principles according to the embodiments of the present disclosure may also be applied to 6G and subsequent communication technologies and network environments.

[0042] FIGS. 1a and 1b illustrate examples of wireless communication systems.

[0043] Referring to FIG. 1a, FIG. 1a illustrates a base station (110) and a terminal (120) as part of nodes using a wireless channel in a wireless communication system. FIG. 1a illustrates only one base station, but the wireless communication system may include other base stations identical or similar to the base station (110).

[0044] A base station (110) is a network infrastructure that provides wireless access to a terminal (120). The base station (110) has coverage defined based on the distance over which it can transmit signals. In addition to being a base station, the base station (110) may be referred to as an 'access point (AP)', 'eNodeB (eNB)', '5G node (5th generation node)', 'next generation nodeB (gNB)', 'wireless point', 'transmission / reception point (TRP)', or other terms having an equivalent technical meaning.

[0045] A terminal (120) is a device used by a user and communicates with a base station (110) via a wireless channel. The link from the base station (110) to the terminal (120) is referred to as a downlink (DL), and the link from the terminal (120) to the base station (110) is referred to as an uplink (UL). Additionally, although not shown in FIG. 1a, the terminal (120) and another terminal can communicate with each other via a wireless channel. In this case, the link between the terminal (120) and another terminal (device-to-device link, D2D) is referred to as a sidelink, and the sidelink may be used interchangeably with the PC5 interface. In some other embodiments, the terminal (120) may be operated without user involvement. According to one embodiment, the terminal (120) is a device that performs machine type communication (MTC) and may not be carried by the user. Additionally, according to one embodiment, the terminal (120) may be a narrowband (NB)-Internet of Things (IoT) device.

[0046] The terminal (120) may be referred to as 'user equipment (UE)', 'customer premises equipment (CPE)', 'mobile station', 'subscriber station', 'remote terminal', 'wireless terminal', 'electronic device', or 'user device' or other terms having an equivalent technical meaning.

[0047] The base station (110) can perform beamforming with the terminal (120). The base station (110) and the terminal (120) can transmit and receive wireless signals in a relatively low frequency band (e.g., FR 1 (frequency range 1) of NR). Additionally, the base station (110) and the terminal (120) can transmit and receive wireless signals in a relatively high frequency band (e.g., FR 2 (or FR 2-1, FR 2-2, FR 2-3), FR 3) of NR) and a millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, 60 GHz)). To improve channel gain, the base station (110) and the terminal (120) can perform beamforming. Here, beamforming may include transmit beamforming and receive beamforming. The base station (110) and the terminal (120) can impart directivity to the transmitted signal or the received signal. To this end, the base station (110) and the terminal (120) can select serving beams through a beam search or beam management procedure. After the serving beams are selected, subsequent communication can be performed through a resource that has a QCL relationship with the resource that transmitted the serving beams.

[0048] The terminal (120) may be configured with the cells of the base station (110) and a carrier aggregation (CA). The CA technology is a technology that increases the frequency usage efficiency of the terminal (120) and the base station (110) by connecting the terminal to a group of homogeneous wireless communication cells having a common wireless resource control entity and simultaneously utilizing frequency resources on the component carriers of each cell located in different frequency bands for signal transmission and reception. The cells configured for the CA may include one primary cell (PCell) and one or more secondary cells (SCells).

[0049] Referring to FIG. 1b, the terminal (120) may be configured in dual connectivity (DC) using a first base station (110-1) and a second base station (110-2). DC technology is a technology that increases frequency usage efficiency by simultaneously connecting the terminal to two independent heterogeneous or homogeneous radio communication cell groups having separate radio resource control entities, and utilizing frequency resources on component carriers of cells within each cell group located in different frequency bands for signal transmission and reception. The terminal (120) is connected to two different radio resource entities (e.g., a first base station (110-1), a second base station (110-2)) and is a technology for utilizing radio resources allocated by each radio resource entity. In MR-DC, a UE (e.g., terminal (120)) in a radio resource control (RRC) connected state (i.e., RRC_CONNCETED) can be configured to use radio resources provided by two independent schedulers. Each scheduler can be located at an NG-RAN node (e.g., first base station (110-1), second base station (110-2)). Here, one node is a master node (MN) and the other node is a secondary node (SN). The MN and the SN are connected via a network interface, and the MN can be connected to the core network. The SN may or may not be connected to the core network.

[0050] An MN may provide a master cell group (MCG). In addition to being an MN, the MN may be referred to as an M-NODE or an M-NG-RAN node. The MCG may include one or more cells. The MCG may include a PCell (primary cell). The MCG may include multiple aggregated cells. The MCG may include a PCell and one or more SCells (secondary cells). An SN may provide a secondary cell group (SCG). In addition to being an SN, the SN may be referred to as an S-NODE or an S-NG-RAN node. The SCG may include one or more cells. The SCG may include multiple aggregated cells. Like the MCG, the SCG may include a PCell and / or SCell. A cell functioning as a PCell within the SCG may be referred to as a PSCell (primary secondary cell). A sub-cell group may include a PSCell and one or more SCells. Hereinafter, the term SpCell (special cell) may be used to include PCell and PSCell. SpCell refers to the primary cell of an MCG or SCG. In other words, SpCell in an MCG refers to a PCell, and SpCell in an SCG refers to a SCell.

[0051] The possible types of DCs can be defined as follows.

[0052] 1) EN-DC: A dual connection in which an eNB is connected to an EPC (evolved packet core) and a terminal is connected to an eNB acting as an MN and a gNB acting as an SN (act as). Here, the gNB may be referred to as an en-gNB, and the en-gNB may or may not be connected to an EPC.

[0053] 2) NGEN-DC: A dual connection in which an eNB is connected to the 5GC (5G core) and a terminal is connected to an eNB operating as an MN and a gNB operating as an SN. Here, the eNB may be referred to as ng-eNB.

[0054] 3) NE-DC: A dual connection in which a gNB is connected to a 5GC, and a terminal is connected to a gNB operating as an MN and an eNB operating as an SN. Here, the eNB may be referred to as ng-eNB.

[0055] 4) NR-DC: A dual connection in which gNBs are connected to the 5GC, and terminals are connected to a gNB operating as an MN and a gNB operating as an SN. NR-DC can also be used when a UE is connected to a single gNB to perform both the roles of MN and SN and to configure both the MCG and SCG.

[0056] The terminal (120) can support MR (multi-radio)-DC. The terminal (120) can be connected to a first base station (110-1) and a second base station (110-2). The first base station (110-1) can be connected to the terminal as an MN and the second base station (110-2) can be connected as an SN. Along with carrier aggregation (CA) provided by each base station, DC technology can provide a higher data rate. The first base station (110-1) and the second base station (110-2) can transmit downlink traffic to the terminal (120) or receive uplink traffic from the terminal (120), as an MN and an SN, respectively.

[0057] FIGS. 2a to 2c illustrate examples of spectrum aggregation environments. Spectrum aggregation refers to a wireless communication technology that uses a specific frequency interval and another frequency interval together in the frequency domain. Depending on the technology used, the frequency interval may correspond to at least one of a resource block (RB), a bandwidth part (BWP), a bandwidth, a cell, a cell group, a frequency band, and / or a frequency range. For example, spectrum aggregation may include CA. The bandwidth of a primary cell (PCell) and the bandwidth of a primary cell (SCell) may be used together for data communication. For example, spectrum aggregation may include DC. The frequency domain occupied by the cells of the MCG of the MN and the frequency domain occupied by the cells of the SCG of the SN may be used together for communication. For example, spectrum aggregation may include CoMPs. Base stations with different frequency spectra may be used for data communication. For example, spectrum aggregation may include M(multi)-TRPs (transmission reception points). Resources allocated in different frequency ranges may be used for data transmission.

[0058] A cell may refer to an area (or coverage) that can be covered by a single base station (e.g., gNB) (or a single DU). A cell may represent a geographical area as well as an area occupying a specific spectrum in the frequency domain. A DU may cover one cell or multiple cells. Here, multiple cells may be distinguished by the supported frequency and the area of ​​the sector covered. A serving cell is a cell that provides upper-layer signaling (e.g., RRC (radio resource control) signaling) to a terminal, and may refer to one cell or multiple cells. If the terminal (120) is not configured to support CA (carrier aggregation) and DC (dual connectivity), the serving cell may be a single cell corresponding to a PCell. If the terminal (120) is configured to support CA or DC, the serving cell may be a set of cells including a PCell and one or more SCells.

[0059] Referring to FIG. 2a, a base station may be separated into a CU and a DU. For example, if the base station corresponds to a gNB, the CU is a logical node that hosts the base station's RRC, SDAP (service data adaptation protocol), and PDCP (packet data convergence protocol) protocols. The CU and the DU may be connected via an F1 interface. The DU is a logical node that hosts the RLC (radio link control), MAC (medium access control), and PHY (physical) layers. The DU may support one or more cells, and a cell may be supported by only one DU. The first base station (110-1) may include CU #1 (205-1) and DU #1 (210-1). DU #1 (210-1) may provide one or more cells. The second base station (110-2) may include CU #2 (205-2) and DU #2 (210-2). DU #2 (210-2) may provide one or more cells. For example, for DC operation, MgNB-DU may represent a gNB-DU of an en-gNB or gNB acting as a master node (e.g., DU #1 (210-1)), and SgNB-DU may represent a gNB-DU of an en-gNB or gNB acting as a secondary node (e.g., DU #2 (210-2)).

[0060] Referring to FIG. 2b, the base station may be separated into a CU and a DU. Unlike multiple independent base stations (e.g., a first base station (110-1), a second base station (110-2)) serving the terminal (120), one CU and multiple DUs may serve the terminal (120). For example, CU #1 (215) may be connected to DU #1 (231) and DU #2 (232). CU #1 (215) may be connected to DU #1 (231) and DU #2 (232), respectively, via an F1 interface. DU #1 (231) may provide one or more cells. DU #2 (232) may provide one or more cells. For example, for CA operation, DU #1 (231) may provide a cell corresponding to a PCell. DU #2 (232) may provide a cell corresponding to a SCell. Two cells can be configured for the terminal (120).

[0061] Referring to FIG. 2c, the base station may be separated into a CU and a DU. In addition to the distributed deployment separated into a CU and a DU, a base station (242) for a small cell may be deployed. For example, CU #1 (215) may be connected to DU #1 (231) via an F1 interface. The base station (242) may communicate with CU #1 (215) as an independent base station. DU #1 (231) may provide one or more cells. The base station (242) may provide one or more small cells. For example, for CA operation, DU #1 (231) may provide a cell corresponding to a PCell. DU #2 (232) may provide a cell corresponding to a SCell. Two cells may be configured for the terminal (120).

[0062] The vendors of the DUs (or the DU and the base station of the small cell) may differ from one another. The frequency bands used by multiple vendors may not be compatible with each other. For example, the vendor of the first DU and the vendor of the second DU may have purchased different frequency bands. The frequency range occupied by the cell provided by the first DU may differ from the frequency range occupied by the cell provided by the second DU. Since the second DU cannot accurately know the information regarding the cell of the first DU, it may be difficult to configure CA between the two cells. If CA between the two cells is configured, signaling through a CU or a higher-level entity is required because there is no interface between the first DU and the second DU. However, increased signaling causes delay, making effective resource management difficult.

[0063] Hereinafter, embodiments of the present disclosure describe a new interface, procedures for configuring said interface, and messages for spectrum aggregation, such as the CA or DC described above. First, resources at the physical layer are described through FIG. 3.

[0064] FIG. 3 illustrates examples of resource structures in the time domain and frequency domain. FIG. 3 illustrates a basic structure in the time-frequency domain, which is a wireless resource domain where data or control channels are transmitted in the downlink or uplink.

[0065] Referring to FIG. 3, the horizontal axis represents the time domain, and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDM (orthogonal frequency division multiplexing) symbol, where N-symb OFDM symbols (302) are combined to form a slot (306). The length of a subframe is defined as 1.0 ms, and the length of a radio frame (314) is defined as 10 ms. The minimum transmission unit in the frequency domain is a subcarrier, and the carrier bandwidth constituting the resource grid is composed of NBW subcarriers (304).

[0066] In the time-frequency domain, the basic unit of a resource is a resource element (hereinafter 'RE') (312), which can be represented by an OFDM symbol index and a subcarrier index. A resource block may include multiple resource elements. In an LTE system, a resource block (RB) (or physical resource block (hereinafter 'PRB')) is defined as N symb consecutive OFDM symbols in the time domain and NSCRB consecutive subcarriers in the frequency domain. In an NR system, a resource block (RB) (308) may be defined as NSCRB consecutive subcarriers (310) in the frequency domain. One RB (308) includes NSCRB REs (312) in the frequency axis. Generally, the minimum transmission unit of data is an RB, and the number of subcarriers NSCRB = 12. The frequency domain may include common resource blocks (CRBs). Physical resource blocks (PRBs) can be defined in the bandwidth part (BWP) in the frequency domain. CRB and PRB numbers can be determined according to subcarrier spacing. The data rate can be increased in proportion to the number of RBs scheduled to the terminal.

[0067] In NR systems, for frequency division duplex (FDD) systems that operate downlink and uplink by separating frequencies, the downlink transmission bandwidth and uplink transmission bandwidth may differ. Channel bandwidth represents the radio frequency (RF) bandwidth corresponding to the system transmission bandwidth. [Table 1] shows part of the correspondence between the system transmission bandwidth, subcarrier spacing (SCS), and channel bandwidth defined in NR systems in frequency bands lower than x GHz (e.g., frequency range 1 (310 MHz ~ 7125 MHz)). And [Table 2] shows part of the correspondence between the transmission bandwidth, subcarrier spacing, and channel bandwidth defined in NR systems in frequency bands higher than y GHz (e.g., FR2 (24250 MHz - 52600 MHz) or FR2-2 (52600 MHz ~ 71000 MHz)). For example, an NR system with a 100 MHz channel bandwidth and a 30 kHz subcarrier spacing has a transmission bandwidth consisting of 273 RBs. In [Table 1] and [Table 2], N / A may be a bandwidth-subcarrier combination that is not supported by the NR system.

[0068]

[0069]

[0070]

[0071] Referring to FIG. 4a, in an NR communication system, the wireless protocol of the control plane of a terminal (120) (e.g., UE) may include PHY (411), MAC (412), RLC (413), PDCP (414), and RRC (415). In an NR communication system, the wireless protocol of the control plane of a base station (110) (e.g., gNB) may include PHY (421), MAC (422), RLC (423), PDCP (424), and RRC (425).

[0072] The main functions of RRC(415, 425) may include some of the following functions.

[0073] - Broadcast system information related to AS (Access Stratum) and NAS (Non Access Stratum)

[0074] - Paging initiated by 5GC or NG-RAN

[0075] - Establish, maintain, and release the RRC connection between the UE and NG-RAN, including the following:

[0076] 1) Adding, modifying, and removing carrier aggregation

[0077] 2) Add, modify, and disable Dual Connectivity within NR or between E-UTRA and NR.

[0078] - Security functions including key management

[0079] - Setup, configuration, maintenance, and release of SRB (Signaling Radio Bearer) and DRB (Data Radio Bearer)

[0080] - Mobility features including the following:

[0081] 1) Handover and context transfer

[0082] 2) UE cell selection and reselection and control of cell selection and reselection

[0083] 3) Inter-RAT mobility

[0084] - QoS (Quality of Service) management function

[0085] - UE measurement reporting and reporting control;

[0086] - Detection of and recovery from radio link failure

[0087] - Send messages from / to / from the UE to / from the NAS.

[0088] The main functions of PDCP (414, 424) may include some of the following functions.

[0089] - Header compression and decompression features (ROHC only)

[0090] - User data transfer function (Transfer of user data)

[0091] - Sequential delivery function (In-sequence delivery of upper layer PDUs (protocol data units))

[0092] - Out-of-sequence delivery of upper layer PDUs

[0093] - Reordering function (PDCP PDU reordering for reception)

[0094] - Duplicate detection function (Duplicate detection of lower layer SDUs (service data units))

[0095] - Retransmission of PDCP SDUs

[0096] - Encryption and decryption functions (Ciphering and deciphering)

[0097] - Timer-based SDU discard in uplink.

[0098] In the above description, the reordering function of the PDCP layer may refer to a function that reorders PDCP PDUs received from lower layers in order based on PDCP SN (sequence number). The reordering function of the PDCP layer may include a function to transmit data to upper layers in the reordered order, a function to transmit immediately without considering the order, a function to record lost PDCP PDUs by reordering, a function to report the status of lost PDCP PDUs to the transmitting side, and a function to request retransmission of lost PDCP PDUs.

[0099] The main functions of RLC(413, 423) may include some of the following functions.

[0100] - Data transfer function (Transfer of upper layer PDUs)

[0101] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0102] - Out-of-sequence delivery of upper layer PDUs

[0103] - ARQ function (Error Correction through ARQ)

[0104] - Concatenation, segmentation, and reassembly functions of RLC SDUs

[0105] - Re-segmentation function (Re-segmentation of RLC data PDUs)

[0106] - Reordering function (Reordering of RLC data PDUs)

[0107] - Duplicate detection

[0108] - Error detection function (Protocol error detection)

[0109] - RLC SDU discard function

[0110] - RLC re-establishment function

[0111] In the above description, the in-sequence delivery function of the RLC layer may refer to the function of delivering RLC SDUs received from lower layers to upper layers in sequence. If a single RLC SDU is received divided into multiple RLC SDUs, the in-sequence delivery function of the RLC layer may include the function of reassembling and delivering them.

[0112] The in-sequence delivery function of the RLC layer may include a function to rearrange received RLC PDUs based on an RLC SN (sequence number) or PDCP SN (sequence number), a function to record lost RLC PDUs by rearranging the order, a function to report the status of lost RLC PDUs to the transmitting side, and a function to request retransmission of lost RLC PDUs.

[0113] The in-sequence delivery function of the RLC layer may include a function that, in the event of a lost RLC SDU, delivers only the RLC SDUs prior to the lost RLC SDU in order to the upper layer. Additionally, the in-sequence delivery function of the RLC layer may include a function that, even if there is a lost RLC SDU, if a predetermined timer has expired, delivers all RLC SDUs received before the timer started in order to the upper layer. Furthermore, the in-sequence delivery function of the RLC layer may include a function that, even if there is a lost RLC SDU, if a predetermined timer has expired, delivers all RLC SDUs received up to that point in order to the upper layer.

[0114] The RLC layer can process RLC PDUs in the order they are received, regardless of the sequence number (out-of-sequence delivery), and deliver them to the PDCP (405, 440) device.

[0115] When the RLC layer receives a segment, it can receive segments stored in a buffer or to be received later, reconstruct them into a single complete RLC PDU, and then transmit it to the PDCP device.

[0116] The RLC layer may not include concatenation functionality and can perform this function in the MAC layer or replace it with the multiplexing function of the MAC layer.

[0117] In the above description, the out-of-sequence delivery function of the RLC layer may refer to the function of delivering RLC SDUs received from a lower layer directly to an upper layer regardless of order. The out-of-sequence delivery function of the RLC layer may include the function of reassembling and delivering RLC SDUs when a single RLC SDU is received divided into multiple RLC SDUs. The out-of-sequence delivery function of the RLC layer may include the function of storing the RLC SN or PDCP SN of the received RLC PDUs, sorting the order, and recording lost RLC PDUs.

[0118] MAC (412, 422) can be connected to multiple RLC layers configured in a terminal, and the main functions of the MAC may include some of the following functions.

[0119] - Mapping function (Mapping between logical channels and transport channels)

[0120] - Multiplexing and demultiplexing functions (Multiplexing / demultiplexing of MAC SDUs)

[0121] - Scheduling information reporting function

[0122] - HARQ function (Error correction through HARQ)

[0123] - Priority handling between logical channels of one UE

[0124] - Priority handling between UEs by means of dynamic scheduling

[0125] - MBMS service identification

[0126] - Transport format selection function

[0127] - Padding

[0128] The PHY layer (411, 421) can perform the operation of channel coding and modulating upper layer data, creating OFDM symbols and transmitting them to the wireless channel, or demodulating OFDM symbols received through the wireless channel and channel decoding them to transmit them to the upper layer.

[0129] FIG. 4b illustrates a protocol stack (450) in the user plane.

[0130] Referring to FIG. 4b, the wireless protocol of the user plane of a terminal (120) (e.g., UE) may include PHY (461), MAC (462), RLC (463), PDCP (464), and SDAP (465). In an NR communication system, the wireless protocol of the user plane of a base station (110) (e.g., gNB) may include PHY (471), MAC (472), RLC (473), PDCP (474), and SDAP (475).

[0131] The main functions of SDAP (465, 475) may include some of the following functions.

[0132] - User data transfer function (transfer of user plane data)

[0133] - Mapping function between a QoS flow and a DRB for both DL and UL for uplink and downlink

[0134] - Marking QoS flow ID in both DL and UL packets for uplink and downlink

[0135] - Function to map reflective QoS flow to data bearers for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0136] Regarding the SDAP layer, the terminal (120) may receive a Radio Resource Control (RRC) message indicating whether to use the SDAP layer header or the SDAP layer function for each PDCP layer, for each bearer, or for each logical channel. If the SDAP header is set, the terminal (120) may be instructed to update or reset the mapping information for the uplink and downlink QoS flows and data bearers using the 1-bit indicator for the Non-Access Stratum (NAS) Quality of Service (QoS) reflection setting (NAS reflective QoS) and the 1-bit indicator for the Access Stratum (AS) QoS reflection setting (AS reflective QoS) of the SDAP header. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used for data processing priority, scheduling information, etc., to support smooth service.

[0137] For PDCP (464, 474) in the user plane, the description of PDCP (414, 424) in the control plane may be referenced. For RLC (463, 473) in the user plane, the description of RLC (413, 423) in the control plane may be referenced. For MAC (462, 472) in the user plane, the description of MAC (412, 422) in the control plane may be referenced. For PHY (461, 471) in the user plane, the description of PHY (411, 421) in the control plane may be referenced.

[0138] Although the radio protocol of an NR communication system in a radio access network has been described as an example, the embodiments of the present disclosure are not limited thereto. For example, in an LTE communication system, a DU may be defined (e.g., eNB-DU), in which case SDAP (465, 475) may be omitted. The embodiments of the present disclosure provide procedures for an interface between DUs or an interface between a DU and a base station (e.g., eNB / gNB) for spectrum aggregation applicable in 4G, 5G, and / or 6G systems, and various types of layers or protocols may be used in addition to the communication protocol of FIG. 4b.

[0139] As communication technology advances, the number of network entities increases, and since communicating with external nodes (e.g., base stations, other DUs) through CUs causes delays, it is necessary to define interfaces between DUs or between DUs and base stations. Below, for spectrum aggregation such as the CA described above, new interfaces and procedures and messages for configuring said interfaces are proposed. Although procedures and messages related to interfaces between DUs are described below, it is understood that such descriptions can be applied in the same or similar manner to interfaces between DUs and independent base stations (e.g., small cell base stations). In describing interfaces between DUs in this disclosure, the DUs may be from the same vendor or different vendors. That is, information exchange may occur between DUs of different vendors through the interfaces and messages described below.

[0140] FIG. 5 illustrates an example of spectrum aggregation between distributed units (DUs). The same reference numbers may be used to refer to the same descriptions.

[0141] Referring to FIG. 5, a communication network may include a wireless access network (500) and a core network (560). A node providing the wireless access network (500) (e.g., base station (110)) may provide communication services to a user device (e.g., terminal (120)) through one or more cells. The core network (560) may include various entities to ensure that the communication services are performed smoothly. For example, the core network (560) may include an entity responsible for an access management function (AMF). For example, the core network (560) may include an entity responsible for a user plane function (UPF). The core network (560) may be implemented through an NG interface with the wireless access network (500). The NG interface may include an NG-C interface for the control plane and an NG-U interface for the user plane. The NG-C interface may be defined between the node providing the wireless access network (500) and the AMF. The above NG-U interface can be defined between the node providing the wireless access network (500) and the above UPF.

[0142] A node providing a wireless access network (500) may be implemented with a central unit (CU) (505) configured to perform the functions of the upper layers (e.g., PDCP, RRC) of the access network and a distributed deployment based on a distributed unit (DU) configured to perform the functions of the lower layers (e.g., RLC, MAC, PHY). The interface between the CU (505) and the DU may be referred to as an F1 interface. The F1 interface may include an F1-C interface for the control plane and an F1-U interface for the user plane. The CU (505) may be connected to one or more DUs. For example, the CU (505) may be connected to DU #1 (510), DU #2 (520), …, DU #n (550). Each DU may provide one or more cells. For example, DU #1 (510) may provide cell #1 (511) and Cell #2 (512) can be provided. DU #2 (520) can provide Cell #1 (521) and Cell #2 (522). DU #n (550) can provide Cell #1 (551) and Cell #2 (552).

[0143] Carrier Aggregation (CA) can be formed by aggregating two or more cells. A cell may have a component carrier (CC). Depending on its capability, the terminal (120) (or terminal (130)) may simultaneously receive or transmit signals through one or more CCs. When CA is configured, the terminal (120) (or terminal (130)) may have only one RRC connection with the network. During RRC connection setup / re-establishment / handover, one serving cell may provide NAS mobility information, and during RRC connection re-establishment / handover, one serving cell may provide security input. The serving cell may be referred to as a Primary Cell (PCell). Depending on the UE capability of the terminal (120) (or terminal (130)), a Secondary Cell (SCell) may be configured to form a set of serving cells together with the PCell. A set of serving cells configured for a terminal (120) (or terminal (130)) can always be composed of one PCell and one or more SCells.

[0144] For example, cell #1 (511) of DU #1 (510) and cell #1 (521) of DU #2 (520) may be configured as a serving cell set for the terminal (120). Additionally, for example, cell #1 (511) of DU #1 (510), cell #1 (521) of DU #2 (520), and cell #1 (551) of DU #n (550) may be configured as a serving cell set for the terminal (120). Additionally, for example, cell #2 (512) of DU #1 (510) and cell #1 (551) of DU #n (550) may be configured as a serving cell set for the terminal (120).

[0145] For example, cell #2 (512) of DU #1 (510) and cell #2 (522) of DU #2 (520) may be configured as a serving cell set for the terminal (130). Additionally, for example, cell #2 (512) of DU #1 (510), cell #2 (522) of DU #2 (520), and cell #2 (552) of DU #n (550) may be configured as a serving cell set for the terminal (130). Additionally, for example, cell #1 (511) of DU #1 (510) and cell #2 (552) of DU #n (550) may be configured as a serving cell set for the terminal (130).

[0146] Setup, reconfiguration, addition, and removal of SCells can be performed by RRC. During handover within NR and while resuming the connection from RRC_INACTIVE, the network may also add, remove, retain, or reconfigure SCells to be used with the target PCell. When adding a new SCell, dedicated RRC signaling may be used to transmit all necessary system information for the SCell.

[0147] In the embodiments of the present disclosure, CA for a terminal (120) (or terminal (130)) may be configured through a plurality of DUs. Depending on the network environment and the status of carriers, the operator may deploy DUs across multiple sites or DUs for multiple vendors. An interface between DUs may be defined to support inter-DU CA even if they are not from the same vendor or are not in the same region. For example, if a product (or server) configured to perform the functions of a DU is difficult to upgrade to support a new bandwidth or function, inter-DU CA may be provided through the installation of additional DUs. Data throughput performance may be improved through such inter-DU CA. Hereinafter, the interface between DUs is referred to as the X1 interface, but the interface may be referred to by other terms having the same technical meaning (e.g., D2, M1, F3, MV, XD). In the control plane, the interface between DUs may be referred to as the X1-C interface (581). In the user plane, the interface between DUs may be referred to as the X1-U interface (582). The X1-C interface (581) can be used to share call control information between DUs and for setup procedures. The X1-U interface (582) can be used for CA bearer transfer between DUs, signaling between MAC layers, and information sharing.

[0148] According to one embodiment, each of the DUs may provide either a PCell or a SCell to each terminal. For example, DU #1 (510) may provide a PCell to the terminal (120) through cell #1 (511). DU #2 (520) may provide a SCell to the terminal (120) through cell #1 (521). DU #n (550) may provide a SCell to the terminal (120) through cell #1 (551). For example, DU #1 (510) may provide a SCell to the terminal (130) through cell #2 (512). DU #2 (520) may provide a PCell to the terminal (130) through cell #2 (522). DU #n (550) may provide a SCell to the terminal (130) through cell #2 (552). For example, DU #1 (510) can provide PCell to terminal (120) and SCell to terminal (130). DU #2 (520) can provide SCell to terminal (120) and PCell to terminal (130).

[0149] According to an embodiment, DU #1 (510) can provide PCell to the terminal (120) through cell #1 (511). DU #2 (520) can provide SCell to the terminal (120) through cell #1 (521). DU #n (550) can provide SCell to the terminal (120) through cell #1 (551). DU #1 (510) can provide SCell to the terminal (130) through cell #1 (511). DU #2 (520) can provide PCell to the terminal (130) through cell #1 (521). DU #n (550) can provide SCell to the terminal (130) through cell #1 (551).

[0150] In the present disclosure, a network architecture, protocols, and procedures between nodes are described, comprising a plurality of DUs (e.g., DU #1 (510) and DU #2 (520)) and CUs (e.g., CU (505)) that form a network for carrier aggregation (CA) of a terminal (120) (or terminal (130)). For CA between DUs, all traffic may be transmitted from the CU (505) to the DU providing the PCell (primary cell). Subsequently, the DU that receives the traffic may provide (or transmit) the traffic to the DU providing the SCell (secondary cell).

[0151] For example, CU (505) can transmit all traffic for terminal (120) to DU #1 (510) which provides PCell. DU #1 (510) can provide some of all traffic for terminal (120) to DU #2 (520) which provides SCell. DU #1 (510) provides the remaining portion of all traffic for terminal (120) to terminal (120), and DU #2 (520) can provide some of all traffic for terminal (120) received from DU #1 (510) to terminal (120).

[0152] For example, CU (505) can transmit all traffic for terminal (130) to DU #2 (520) which provides PCell. DU #2 (520) can provide some of all traffic for terminal (130) to DU #1 (510) which provides SCell. DU #2 (520) can provide the remaining portion of all traffic for terminal (130) to terminal (130), and DU #1 (510) can provide some of all traffic for terminal (130) to terminal (130).

[0153] FIG. 6 illustrates an example of a control plane for spectrum aggregation between DUs. Spectrum aggregation between DUs may be referred to as CA using the DUs. A network (e.g., an access network of a base station (110)) may be provided through a structure in which one CU (e.g., CU (505)) and a plurality of DUs (e.g., DU #1 (510), DU #2 (520))) are connected to the CU. Cells provided by the DUs may be used for CA. For inter-DU CA, an interface between DUs may be defined. Identical reference numbers may be used to refer to identical descriptions.

[0154] Referring to FIG. 6, the CU (505) can perform the functions of the RRC (615) and the PDCP (614). Cells provided by the DUs can be used for CA. For inter-DU CA, an interface between the DUs can be defined. The CU (505) can be connected to DU #1 (510) via an F1 interface. The F1 interface may include an F1-C interface (681) for the control plane and an F1-U interface (682) for the user plane. The CU (505) can be connected to DU #2 (520) via an F1 interface. The F1 interface may include an F1-U interface (683) for the user plane.

[0155] DU #1 (510) and DU #2 (520) can be connected via an X1 interface. The X1 interface may include an X1-C interface (581) for the control plane and an X1-U interface (582) for the user plane. DU #1 (510) may be a node providing a PCell of CA. DU #1 (510) may be referred to as a PCell DU or a PCell-gNB-DU. DU #1 (510) may include a MAC processing module (612), an RLC-H processing module (613a), an RLC-L processing module (613b), and a call processing block (671). The RLC-H processing module (613a) and the RLC-L processing module (613b) may be referred to as RLC entities (613). The MAC processing module (612) may be configured to process the functions of MAC (422) and MAC (472). The MAC processing module (612) may be referred to as the MAC entity (612). The RLC-H processing module (613a) and the RLC-L processing module (613b) may be configured to process the functions of RLC (423) and RLC (473). Among the functions of RLC (423) and RLC (473), functions requiring real-time processing (e.g., TTI-based functions) are processed in the RLC-L processing module (613b), and other functions requiring non-real-time processing are processed in the RLC-H processing module (613a). The call processing block (671) may be configured to process parameters received from the CU (505) (e.g., RRC IEs) or parameters received from DU #2 (520).

[0156] DU #2 (520) may be a node providing SCell for CA. DU #1 (510) may be referred to as SCell DU or SCell-gNB-DU. DU #2 (520) may include a MAC processing module (622), an RLC-H processing module (623a), an RLC-L processing module (623b), and a call processing block (672). The RLC-H processing module (623a) and the RLC-L processing module (623b) may be referred to as RLC entities (623). The MAC processing module (622) may be configured to process the functions of MAC (422) and MAC (472). The MAC processing module (622) may be referred to as MAC entities (622). The RLC-H processing module (623a) and the RLC-L processing module (623b) may be configured to process at least some of the functions of the RLC (423) and the RLC (473). The call processing block (672) may be configured to process parameters received from the CU (505) (e.g., RRC IEs) or parameters received from DU #1 (510).

[0157] According to one embodiment, a plurality of DUs can transmit data to a terminal through CA (carrier aggregation) (or inter-DU CA). One of the plurality of DUs can provide a PCell. The remaining DUs among the plurality of DUs can provide a SCell. For example, the first DU and the second DU can transmit data to the terminal through CA.

[0158] An abnormality (e.g., system down) may occur in the second DU among the first DU and the second DU. The second DU may perform a recovery process to resolve the abnormality. The second DU may be unable to transmit data to the terminal. Accordingly, the second DU may transmit a reset message to the first DU based on the recovery process. Based on the reset message, the first DU may perform a reset process to change the settings for the connection for CA with the terminal. In the specification below, technical features for performing a reset process to change the settings for the connection for CA with the terminal in the first DU, in which no abnormality has occurred, will be described.

[0159] FIG. 7 illustrates an example of a system for transmitting traffic through multiple DUs.

[0160] Referring to FIG. 7, the CU (750) can transmit traffic (or data) to the terminal (120) (or terminal (130)) using the first DU (710) and the second DU (720). For example, the CU (750) may be an example of the CU (505) of FIG. 5 and FIG. 6. The first DU (710) may be an example of DU #1 (510) of FIG. 5 and FIG. 6. The second DU (720) may be an example of DU #2 (520) of FIG. 5 and FIG. 6.

[0161] According to one embodiment, the first DU (710) and the second DU (720) may form a DU group to ensure service continuity and support CA. The first DU (710) and the second DU (720) may be included in the DU group.

[0162] For example, messages (or signals) may be exchanged through the X1 interface between the first DU (710) and the second DU (720). For example, messages (or signals) exchanged between the first DU (710) and the second DU (720) may be transmitted (or received) based on UDP (User Datagram Protocol) communication. For example, an IP (Internet Protocol) address based on UDP communication may be used for message exchange between the first DU (710) and the second DU (720). As an example, a first IP address may be assigned for the first DU (710). A second IP address may be assigned for the second DU (720).

[0163] For example, an IP (internet protocol) address based on UDP communication may be set based on at least one of an I-node ID (index-node identifier), a site ID, and / or a CPU (central processing unit) ID. The I-node ID may be an ID value (or unique ID value) set for each DU within the same site. The site ID may be an ID value (or unique ID value) set on a site-by-site basis. The CPU ID may indicate the CPU where the call processing block (e.g., the call processing block (671) or the call processing block (672) of FIG. 6) is located.

[0164] According to one embodiment, DUs included in a DU group (e.g., a first DU (710) and a second DU (720)) may support CA for a terminal (e.g., terminal (120) or terminal (130)). For example, the first DU (710) and the second DU (720) may organize (or form, create, establish, assemble) a DU group to transmit data to the terminal (120) (or terminal (130)) via CA. The first DU (710) and the second DU (720) may organize a DU group for the terminal (120) based on a DU group setup process. For example, the first DU (710) and the second DU (720) can form a DU group for the terminal (120) (or terminal (130)) based on the exchange of a DU group setup request message and a DU group setup response message. The first DU (710) and the second DU (720) included in the DU group can transmit data to the terminal (120) (or terminal (130)) through CA.

[0165] According to one embodiment, the first DU (710) may be configured to provide a PCell to the terminal (130) and a SCell to the terminal (120). The second DU (720) may be configured to provide a SCell to the terminal (130) and a PCell to the terminal (120).

[0166] For example, a first DU (710) providing a PCell for a terminal (130) may receive traffic for the terminal (130) from a CU (750). The first DU (710) may provide data to be transmitted to the second DU (720). The data provided to the second DU (720) may be part of the traffic for the terminal (130). The second DU (720) may receive part of the traffic for the terminal (130) from the first DU (710) and provide part of the traffic for the terminal (130) to the terminal (130). The first DU (710) may provide the remaining part of the traffic for the terminal (130) to the terminal (130). For example, the second DU (720) can transmit some of the traffic for the terminal (130) to the terminal (130) through an RU connected to the second DU (720). The first DU (710) can transmit the remaining portion of the traffic for the terminal (130) to the terminal (130) through an RU connected to the first DU (710).

[0167] For example, a second DU (720) that provides a PCell for a terminal (120) may receive traffic for the terminal (120) from a CU (750). The second DU (720) may provide data to the first DU (710) to be transmitted to the terminal (120). The data provided to the first DU (710) may be part of the traffic for the terminal (120). The first DU (710) may receive part of the traffic for the terminal (120) from the second DU (720) and provide part of the traffic for the terminal (120) to the terminal (120). The second DU (720) may provide the remaining part of the traffic for the terminal (120) to the terminal (120). For example, the first DU (710) can transmit some of the traffic for the terminal (120) to the terminal (120) through an RU connected to the first DU (710). The second DU (720) can transmit the remaining portion of the traffic for the terminal (120) to the terminal (120) through an RU connected to the second DU (720).

[0168] According to one embodiment, an abnormality may occur in the second DU (720), including at least one of a system down and / or reset of the second DU (720). If an abnormality occurs in the second DU (720), the second DU (720) may not be able to provide PCell for the terminal (120). The second DU (720) may not be able to provide SCell for the terminal (130). Consequently, CA may not be performed through the first DU (710) and the second DU (720). The first DU (710) may perform a reset process based on the abnormality of the second DU (720). Based on the reset process, the first DU (710) may refrain from providing data for the terminal (130) to the second DU (720) or release resources for the terminal (120). In the specification below, specific operations of the first DU (710) and the second DU (720) will be described in the event that an abnormality occurs in the first DU (710).

[0169] FIG. 8 illustrates an example of the operation of the first DU and the second DU to perform a reset process in the first DU.

[0170] Referring to FIG. 8, in operation 810, the second DU (720) can perform a recovery process. The above process can be performed in response to an abnormality of the second DU (720). For example, a system down (or system failure, system crash, reset) of the second DU (720) may occur. Through the recovery process, the system down of the second DU (720) can be resolved.

[0171] In operation 820, the second DU (720) may transmit a reset message to the first DU (710). For example, the second DU (720) may transmit a reset message to the first DU (710) via the X1 interface. The reset message may be transmitted to the first DU (710) based on the second DU (720) performing a recovery process. The first DU (710) may receive the reset message from the second DU (720). For example, the reset message may be referred to as an X1 reset message. The reset message may be used to notify other DUs in a group that includes the second DU (720) (e.g., the first DU (710)) of a failure. The reset message may be transmitted to cause another DU (e.g., the first DU (710)) to start a reset process for recovery from the failure.

[0172] In operation 830, the first DU (710) can perform a reset process based on a reset message. The first DU (710) can identify that an abnormality has occurred in the second DU (720) based on the reset message. The first DU (710) can perform a reset process to optimize internal system resources and release resources for terminals that support CA.

[0173] Depending on whether the first DU (710) functions to provide a PCell of a CA (e.g., inter-DU CA, Spectrum aggregation for multi-vendor) or a SCell of said CA for the terminal, the reset process performed in the first DU (710) may differ. Specific examples of the reset process in the first DU (710) for said terminal will be described later in FIG. 9.

[0174] In operation 840, the first DU (710) may send a reset acknowledgment message to the second DU (720) based on performing a reset process. For example, the reset acknowledgment message may be referred to as an X1 reset ACK (acknowledgement) message. The reset acknowledgment message allows the first DU (710) to identify a failure situation of the second DU (720). The reset acknowledgment message may be sent to inform the second DU (720) of the status regarding the reset process.

[0175] The second DU (720) may start a timer to receive a reset response message based on sending a reset message. The second DU (720) may identify whether a reset response message is received from the first DU (710) until the timer expires. If the second DU (720) does not receive a reset response message until the timer expires, it may send a reset message again to the first DU (710). While the timer is running, the second DU (720) may not be able to support CA between the second DU (720) and other DUs included in the DU group (e.g., the first DU (710)).

[0176] According to one embodiment, the reset message and the reset response message may include information according to the table below.

[0177]

[0178] Referring to [Table 3], in the reset message, 'Source DU ID', 'Source G-NodeB ID', and 'Source Site Id' may be associated with the second DU (720). In the reset message, 'Target DU ID', 'Target G-NodeB ID', and 'Target Site Id' may be associated with the first DU (710). In the reset message, 'Cause' may be set to 'Request'. In other words, the reset message may include at least one of an ID for the first DU (710) (e.g., 'Target DU ID', 'Target G-NodeB ID'), an ID for the second DU (720) (e.g., 'Source DU ID', 'Source G-NodeB ID'), an ID for the location of the first DU (710) (e.g., 'Target Site Id'), an ID for the location of the second DU (720) (e.g., and 'Source Site Id'), or information directing a request for a reset process.

[0179] Referring to [Table 3], in the reset response message, 'Source DU ID', 'Source G-NodeB ID', and 'Source Site Id' may be associated with the first DU (710). In the reset response message, 'Target DU ID', 'Target G-NodeB ID', and 'Target Site Id' may be associated with the second DU (720). In the reset response message, 'Cause' may be set to either 'complete' or 'retry'. For example, the first DU (710) may set 'Cause' of the reset response message to 'retry' to indicate a retry of the reset process. For example, the first DU (710) may set 'Cause' of the reset response message to 'complete' to indicate the completion of the reset process. In other words, the reset message may include at least one of an ID for the second DU (720) (e.g., 'Target DU ID', 'Target G-NodeB ID'), an ID for the first DU (710) (e.g., 'Source DU ID', 'Source G-NodeB ID'), an ID for the location of the first DU (710) (e.g., 'Source Site Id'), an ID for the location of the second DU (720) (e.g., and 'Target Site Id'), or information indicating the completion or retry of the reset process.

[0180] According to one embodiment, upon completion of the reset process, the second DU (720) may be removed from the DU group for CA (e.g., inter-DU CA, Spectrum aggregation for multi-vendor). According to one embodiment, the DU group containing the first DU (710) and the second DU (720) may be released. The first DU (710) and / or the second DU (720) may perform a DU group setup process to reconfigure the DU group. For example, the first DU (710) and the second DU (720) may reconfigure the DU group for the terminal (120) (or terminal (130)) based on the exchange of a DU group setup request message and a DU group setup response message. The first DU (710) and the second DU (720) included in the DU group can transmit data to the terminal (120) (or terminal (130)) through the CA (or inter-DU CA).

[0181] FIG. 9 illustrates a flowchart regarding the operation of the first DU for performing a reset process. In the following embodiments, each operation may be performed sequentially, but is not necessarily performed sequentially. For example, the order of each operation may be changed, and at least two operations may be performed in parallel.

[0182] Referring to FIG. 9, in operation 910, the first DU (710) can receive a reset message from the second DU (720) used for CA together with the first DU (710). For example, operation 910 may correspond to operation 820 of FIG. 8.

[0183] According to one embodiment, a reset message may be transmitted based on a recovery process following an anomaly in the first DU (710). Based on the occurrence of an anomaly in the first DU (710), a recovery process may be performed. Based on the performance of the recovery process, the first DU (710) may transmit a reset message to other DUs (e.g., the first DU (710)) within a DU group that includes the first DU (710). For example, the reset message may include at least one of an ID for the first DU (710), an ID for the second DU (720), an ID for the location of the first DU (710), an ID for the location of the second DU (720), or information indicating a request for a reset process.

[0184] The first DU (710) can receive a reset message from the second DU (720). The first DU (710) can identify the target information of the reset message (e.g., 'Target DU ID', 'Target G-NodeB ID', and 'Target Site Id'). The first DU (710) can identify whether the target information of the reset message is related to the first DU (710). If the target information of the reset message is not related to the first DU (710), the first DU (710) can identify the received reset message as an abnormal reset message. According to an embodiment, if the target information of the reset message is not related to the first DU (710), the first DU (710) can send a reset response message to the second DU (720) with 'cause' set to 'fail'.

[0185] The first DU (710) can identify source information of the reset message (e.g., 'Source DU ID', 'Source G-NodeB ID', and 'Source Site Id'). The first DU (710) can identify whether the second DU (720) according to the source information is included in at least one DU group (or at least one DU group containing the first DU (710)) regarding the first DU (710). If the second DU (720) according to the source information of the reset message is not included in at least one DU group regarding the first DU (710), the first DU (710) can identify the received reset message as an abnormal reset message. According to an embodiment, if the second DU (720) according to the source information of the reset message is not included in at least one DU group regarding the first DU (710), the first DU (710) may send a reset response message to the second DU (720) with 'cause' set to 'fail'.

[0186] The first DU (710) can perform operation 920 if the target information of the reset message is associated with the first DU (710) and the second DU (720) according to the source information of the reset message is included in at least one DU group related to the first DU (710).

[0187] In operation 920, the first DU (710) can identify a terminal (e.g., terminal (120) or terminal (130)) connected for CA with the first DU (710) and the second DU (720). For example, the first DU (710) can identify a terminal connected via call through the first DU (710) and the second DU (720). For example, the first DU (710) can identify a terminal connected via at least one of a PCell or a SCell. For example, the first DU (710) can identify a terminal (130) connected via a PCell. For example, the first DU (710) can identify a terminal (120) connected via a SCell.

[0188] In operation 930, the first DU (710) can determine whether the first DU (710) provides a PCell or whether the first DU (710) provides a SCell for the identified terminal. For example, the first DU (710) can identify whether the first DU (710) provides a PCell for the identified terminal. The first DU (710) can perform operation 940 based on the determination that the first DU (710) provides a PCell for the identified terminal. The first DU (710) can identify whether the first DU (710) provides a SCell for the identified terminal. The first DU (710) can perform operation 950 based on the determination that the first DU (710) provides a SCell for the identified terminal.

[0189] In operation 940, the first DU (710) may refrain from providing data for the terminal to the second DU (720). In operation 940, for the terminal, the first DU (710) may function to provide a PCell of a CA (e.g., inter-DU CA, Spectrum aggregation for multi-vendor), and the second DU (720) may function to provide a SCell of the CA. Depending on the decision that the first DU (710) provides a PCell for the identified terminal, it may refrain from providing data for the identified terminal to the second DU (720). For example, the first DU (710) may identify the terminal (130). The first DU (710) may identify that the first DU (710) provides a PCell for the terminal (130). The first DU (710) may refrain from providing data for the terminal (130) to the second DU (720) based on identifying that the first DU (710) provides a PCell to the terminal (130). For example, the first DU (710) may not be able to perform release for the SCell without a request from the CU (750). Therefore, the first DU (710) may refrain from providing data for the terminal (130) to the second DU (720) until release for the SCell is performed by the CU (750). For example, the first DU (710) may perform deactivation for the second DU (720). The first DU (710) may perform deactivation for the SCell of the second DU (720). Based on the above deactivation of the second DU (720), the first DU (710) may refrain from providing data for the terminal (130) to the second DU (720).

[0190] For example, the first DU (710) operating as a PCell for the terminal (130) cannot perform SCell release for the second DU (720) operating as a SCell for the terminal (130) without instructions from the CU (750). Deactivation of the SCell of the second DU (720) can be performed by not providing data for the terminal (130) to the second DU (720). As the SCell of the second DU (720) is deactivated, the terminal (130) may not receive data through the second DU (720) while the recovery process is being performed. According to an embodiment, the terminal (130) may receive data through the first DU (710).

[0191] In operation 950, the first DU (710) may release resources for the terminal. In operation 950, for the terminal, the first DU (710) may function to provide SCell of CA (e.g., inter-DU CA, Spectrum aggregation for multi-vendor), and the second DU (720) may function to provide PCell of CA. For example, the first DU (710) may release resources for the terminal based on the decision that the first DU (710) provides SCell for the terminal. For example, the first DU (710) may release resources for the terminal and exclude the terminal from a pool of terminals managed by the first DU (710). For example, the first DU (710) may identify the terminal (120). The first DU (710) can identify that the first DU (710) provides SCell to the terminal (120). Based on identifying that the first DU (710) provides SCell to the terminal (120), the first DU (710) can release resources for the terminal (120). For example, the second DU (720) can provide PCell to the terminal (120). Depending on the recovery process of the second DU (720) providing PCell to the terminal (120), data for the terminal (120) may not be provided to the first DU (710) from the second DU (720). Therefore, since the first DU (710) can no longer provide (or transmit) data to the terminal (120), resources for the terminal (120) can be released. Subsequently, the SCell provided by the second DU (720) may be released through an RRC reconfiguration message provided to the terminal (120). According to an embodiment, the first DU (710) may perform release of the SCell based on identifying that the first DU (710) provides the SCell to the terminal (120).

[0192] According to operations 910 to 950, the first DU (710) provides SCell for the terminal (120), so resources for the terminal (120) can be released. The first DU (710) provides PCell for the terminal (130), so data for the terminal (130) can be refrained from being provided to the second DU (720). Accordingly, the first DU (710) can perform a reset process for each terminal based on the abnormality (or recovery process) of the second DU (720).

[0193] FIG. 10 illustrates a flowchart regarding the operation of the first DU. In the following embodiments, each operation may be performed sequentially, but is not necessarily performed sequentially. For example, the order of each operation may be changed, and at least two operations may be performed in parallel.

[0194] Referring to FIG. 10, operation 1010 can be performed after operation 920 of FIG. 9 is performed. In operation 1010, the first DU (710) can identify whether the terminal is in an idle state. For example, the idle state may include an RRC idle state. The first DU (710) can identify whether the terminal is in an idle state in order to perform a reset process on the terminal.

[0195] In operation 1020, if the terminal is idle, the first DU (710) may perform a reset process. The first DU (710) may perform a reset process based on identifying that the terminal is idle. The reset process may correspond to operations 930 through 950 of FIG. 9. Based on identifying that the terminal is idle, the first DU (710) may perform a reset process by refraining from providing data for the terminal to the second DU (720) or by releasing resources for the terminal.

[0196] In operation 1030, the first DU (710) may send a reset response message to the second DU (720) indicating the completion of the reset process based on performing the reset process. For example, operation 1030 may correspond to operation 840 of FIG. 8.

[0197] For example, the first DU (710) may perform a reset process and then send a reset response message to the second DU (720) indicating the completion of the reset process. For example, the first DU (710) may send a reset response message to the second DU (720) with 'Cause' set to 'complete'. Based on the reset response message, the second DU (720) may identify that the reset process has been completed in the first DU (710). The second DU (720) may then send a DU group setup request message to the first DU (710) to form a DU group with the first DU (710). The second DU (720) may receive a DU group setup response message from the first DU (710) in response to the DU group setup request message. The first DU (710) and the second DU (720) can organize (or form, create, establish, assemble) the DU group based on the DU group setup request message and the DU group setup response message.

[0198] In operation 1030, if the terminal is not idle, the first DU (710) may send a reset response message to the second DU (720) instructing it to retry the reset process. For example, operation 1030 may correspond to operation 840 of FIG. 8.

[0199] For example, the first DU (710) may suspend processing for the terminal when the terminal is not in an idle state. Accordingly, the first DU (710) may send a reset response message to the second DU (720) instructing a retry of the reset process to perform the reset process again in order to wait until the terminal changes to an idle state. For example, the first DU (710) may send a reset response message to the second DU (720) with 'Cause' set to 'retry'.

[0200] The second DU (720) may receive a reset response message from the first DU (710) instructing a retry of the reset process. Based on the reset response message instructing a retry of the reset process, the second DU (720) may resend the reset message to the first DU (710). The above-described procedure for resending the reset message may be performed repeatedly during a specified time interval (e.g., a time interval according to a timer). According to an embodiment, the procedure for resending the reset message may be repeated indefinitely, but if the DU group setting is released by an operator, the procedure for resending the reset message (or the reset process of the first DU (710)) may be interrupted.

[0201] According to one embodiment, the first DU (710) can identify a plurality of terminals (e.g., terminal (120) and terminal (130)) connected to the second DU (720) for CA. For each of the plurality of terminals, the first DU (710) can determine whether the first DU (710) provides a PCell or whether the first DU (710) provides a SCell. Based on the determination of whether the first DU (710) provides a PCell or whether the first DU (710) provides a SCell for each of the plurality of terminals, the first DU (710) may refrain from providing data for each of the plurality of terminals to the second DU (720) or perform a reset process to release resources for each of the plurality of terminals. Based on the completion of the reset process, the first DU (710) may transmit a reset response message to the second DU (720) indicating the completion of the reset process. According to one embodiment, the first DU (710) may determine a reset process for each of the plurality of terminals to minimize processing delay time and may perform the reset process substantially simultaneously for each of the plurality of terminals. For example, the first DU (710) may perform the reset process substantially simultaneously for each of the plurality of terminals in response to transmitting a reset response message to the second DU (720) indicating the completion of the reset process.

[0202] According to one embodiment, if a terminal that is not idle is included among the plurality of terminals, the first DU (710) may send a reset response message to the second DU (720) instructing a retry of the reset process.

[0203] FIG. 11 illustrates an example of the operation of the first DU after the deactivation of the second DU is performed.

[0204] Referring to FIG. 11, the first DU (710) can provide PCell to the terminal (130). The second DU (720) can provide SCell to the terminal (130). If a malfunction occurs in the second DU (720), the first DU (710) cannot perform SCell release for the second DU (720) operating as SCell. Therefore, the first DU (710) can perform deactivation of the second DU (720).

[0205] For example, the first DU (710) may refrain from providing data for the terminal (130) to the second DU (720) so that data is not provided to the terminal (130) through the path (1110). By refraining from providing data for the terminal (130) to the second DU (720), the first DU (710) may perform deactivation of the second DU (720). According to an embodiment, the first DU (710) may provide data to the terminal (130) through the path (1120). The first DU (710) may provide data to the terminal (130) through a PCell. The first DU (710) may maintain the PCell and perform deactivation of the first DU (710) that provides the SCell. For example, the first DU (710) may disable the second DU (720) so that it does not distribute data to the SCell carrier.

[0206] In operation 1101, after the first DU (710) is deactivated, the CU (750) may send a UE context modification request message to the first DU (710). For example, the CU (750) may send a UE context modification request message to the first DU (710) based on a specified time interval. For example, the UE context modification request message may include list information regarding SCell. The list information regarding SCell may be referenced as 'SCellAddModList'.

[0207] For example, a UE context modification request message may include an F1 UE context modification request message. The F1 UE context modification request message may include information according to the table below.

[0208]

[0209]

[0210] Referring to [Table 4], [Table 4] may indicate some of the information included in the F1 UE context modification request message. For example, 'SCell To Be Setup List' in [Table 4] may be an example of list information regarding SCells. 'SCell To Be Setup List' may be a list of candidate SCells. If a SCell is already configured, the first DU (710) may replace the previously configured configuration information through 'SCell To Be Setup List'. For other information elements (IE) in [Table 4], descriptions of the 3GPP TS 38.473 specification may be referenced.

[0211] In operation 1102, the first DU (710) may send a UE context modification response message to the CU (750). The first DU (710) may send a UE context modification response message to the CU (750) in response to a UE context modification request message.

[0212] According to one embodiment, the first DU (710) can identify whether the list information regarding the SCell includes the SCell provided by the second DU (720) based on a UE context modification request message. Unlike what is illustrated, if the list information regarding the SCell includes the SCell provided by the second DU (720) and no deactivation of the second DU (720) is performed, the state in which the SCell is provided by the second DU (720) may be maintained.

[0213] For example, the first DU (710) can identify that the list information regarding the SCell includes the SCell provided by the second DU (720). Since the first DU (710) has disabled the second DU (720), it can transmit the SCell setup failure list information through the UE context modification response message. The SCell setup failure list information may include information about the SCell provided by the second DU (720).

[0214] For example, the UE context modification response message may include at least one of the F1 UE context modification response message or the F1 UE context modification failure message.

[0215] For example, an F1 UE context modification response message may be sent to confirm the UE context modification. For example, the F1 UE context modification response message may include information according to the table below.

[0216]

[0217]

[0218] Referring to [Table 5], [Table 5] may indicate some of the information included in the F1 UE context modification response message. For example, 'SCell Failed To Setup List' may be an example of the SCell setup failure list information described above. For example, if 'SCell Failed To Setup List' is included in the F1 UE context modification response message, the CU (750) can identify the cause information for each SCell that failed to set up and identify the SCell setup failure. For other information elements (IE) in [Table 5], descriptions of the 3GPP TS 38.473 specification may be referenced.

[0219] For example, an F1 UE context modification failure message may be transmitted to indicate a failure of UE context modification. For example, an F1 UE context modification failure message may include information according to the table below.

[0220]

[0221] Referring to [Table 6], [Table 6] may indicate some of the information included in the F1 UE context modification failure message. According to one embodiment, some of the information according to [Table 6] (e.g., 'Requested Target Cell ID') may be an example of SCell configuration failure list information. According to one embodiment, SCell configuration failure list information may be additionally included in the F1 UE context modification failure message along with the information according to [Table 6]. For other information elements (IE) in [Table 6], descriptions of the 3GPP TS 38.473 specification may be referenced.

[0222] In operation 1103, the CU (750) can identify SCell configuration failure list information included in the UE context modification response message. The CU (750) can identify that the SCell configuration failure list information includes the SCell provided by the second DU (720). The CU (750) can send an RRC reconfiguration message to the terminal (130) via the first DU (710). The RRC reconfiguration message can be sent to the terminal (130) to instruct the release of the SCell provided by the second DU (720). Based on the RRC reconfiguration message, the terminal (130) can release the connection with the SCell provided by the second DU (720).

[0223] FIG. 12 illustrates an example of a plurality of terminals receiving data through the first DU and the second DU and CA.

[0224] FIG. 13 illustrates an example of the operation of a first DU for distinguishing multiple terminals.

[0225] Referring to FIGS. 12 and 13, the first DU (710) and the second DU (720) can provide CA to a plurality of terminals (1210). Although not illustrated, the terminal (120) or terminal (130) according to the embodiments described above may be one of the plurality of terminals (1210).

[0226] According to one embodiment, the first DU (710) may provide one of PCell and SCell to each of the plurality of terminals (1210). The second DU (720) may provide one of PCell and SCell to each of the plurality of terminals (1210). For example, the first DU (710) may provide PCell to terminal (1210-1), and the second DU (720) may provide SCell to terminal (1210-1). For example, the first DU (710) may provide SCell to terminal (1210-2), and the first DU (720) may provide PCell to terminal (1210-1).

[0227] For example, if an abnormality occurs in the second DU (720), the second DU (720) may send a reset message to the first DU (710). Based on the reset message, the first DU (710) may perform a reset process for each of the plurality of terminals (1210). For example, the first DU (710) may determine for each of the plurality of terminals (1210) whether the first DU (710) provides a PCell or whether the first DU (710) provides a SCell.

[0228] For each of the plurality of terminals, the first DU (710) may refrain from providing data for each of the plurality of terminals to the second DU (720) or perform a reset process to release resources for each of the plurality of terminals based on determining whether the first DU (710) provides a PCell or whether the first DU (710) provides a SCell. For example, the first DU (710) may refrain from providing data for terminal (1210-1) to the second DU (720). For example, the first DU (710) may release resources for terminal (1210-2) for terminal (1210-2).

[0229] According to one embodiment, the first DU (710) may determine a reset process for each of the plurality of terminals (1210) to minimize processing delay time. For example, an operation to refrain from providing data for a terminal to the second DU (720) may be referred to as the first reset process. An operation to release resources for a terminal may be referred to as the second reset process.

[0230] In order for the first DU (710) to perform a reset process substantially simultaneously for each of the multiple terminals, it may store the IDs of the terminals for which the first reset process is performed in the first buffer (1310) and store the IDs of the terminals for which the second reset process is performed in the second buffer (1320). According to an embodiment, the number of IDs stored in each of the first buffer (1310) and the second buffer (1320) may be limited. For example, since the resources (e.g., processing resources) for the first DU (710) to perform the reset process simultaneously are limited, the number of IDs stored in each of the first buffer (1310) and the second buffer (1320) may be limited. As an example, the number of IDs stored in each of the first buffer (1310) and the second buffer (1320) may be set to 48. However, it is not limited thereto. Although not illustrated, according to an embodiment, since a reset process is not performed for terminals that are not in an idle state, the IDs of terminals whose processing is suspended may be stored in a third buffer (not illustrated).

[0231] For example, when the IDs of multiple terminals (1210) are all stored in the first buffer (1310) and the second buffer (1320), the first DU (710) can perform a reset process for the multiple terminals (1210). When the IDs of multiple terminals (1210) are all stored in the first buffer (1310) and the second buffer (1320), the first DU (710) can send a reset response message to the second DU (720) indicating the completion of the reset process. The first DU (710) can perform a reset process for the multiple terminals (1210) based on sending a reset response message to the second DU (720) indicating the completion of the reset process. According to an embodiment, after the first DU (710) performs a reset process for a plurality of terminals (1210), the first DU (710) may send a reset response message to the second DU (720) indicating the completion of the reset process.

[0232] According to an embodiment, among the plurality of terminals (1210), there may be a terminal that is not in an idle state. The first DU (710) may suspend processing for the terminal that is not in an idle state. In this case, the IDs of the plurality of terminals (1210) may not all be stored in the first buffer (1310) and the second buffer (1320). If the IDs of the plurality of terminals (1210) are not all stored in the first buffer (1310) and the second buffer (1320), the first DU (710) may send a reset response message to the second DU (720) instructing a retry of the reset process. For example, the first DU (710) may receive a reset message again from the second DU (720) during a specified time interval (e.g., a time interval according to a timer) and perform the above-described operation until the IDs of the plurality of terminals (1210) are all stored in the first buffer (1310) and the second buffer (1320).

[0233] FIG. 14 illustrates an example of a state diagram of a system including a first DU and a second DU.

[0234] Referring to FIG. 14, the state of the system including the first DU (710) and the second DU (720) may include three states. The state of the system may include a normal state (1410), an abnormal state (1420), and a reset state (1430).

[0235] According to one embodiment, in a normal state (1410), the first DU (710) and the second DU (720) can provide traffic (or data) to a terminal (or a plurality of terminals) through CA.

[0236] For example, as an abnormality occurs in at least one of the first DU (710) and the second DU (720), the state of the system may change according to the path (1412). For example, based on the occurrence of an abnormality in at least one of the first DU (710) and the second DU (720), the state of the system may change from a normal state (1410) to an abnormal state (1420).

[0237] According to one embodiment, in an abnormal state (1420), the first DU (710) and the second DU (720) may not be able to provide traffic (or data) to the terminal (or a plurality of terminals) through the CA.

[0238] For example, if an abnormality occurs in the second DU (720), a recovery process may be performed in the second DU (720). Based on performing the recovery process, the second DU (720) may send a reset message to the first DU (710). Based on the first DU (710) receiving the reset message, the state of the system may be changed along path (1423). Based on the first DU (710) receiving the reset message, the state of the system may be changed from an abnormal state (1420) to a reset state (1430).

[0239] According to one embodiment, if an abnormality occurs in the second DU (720), the first DU (710) can perform a reset process in the reset state (1430).

[0240] For example, the first DU (710) may send a reset response message to the second DU (720) instructing a retry of the reset process based on the fact that the terminal (or at least one of the plurality of terminals) is in an idle state. Based on the first DU (710) sending a reset response message to the second DU (720) instructing a retry of the reset process, the state of the system along path (1433) may be maintained in a reset state (1430). Based on receiving a reset response message from the first DU (710) instructing a retry of the reset process, the second DU (720) may send a reset message again to the first DU (710). For example, the procedure for retransmitting the reset message may be performed repeatedly during a time interval according to a timer (e.g., the timer in FIG. 8). According to an embodiment, the procedure for retransmitting the reset message may be interrupted when the DU group setting is released by the operator.

[0241] For example, the first DU (710) may send a reset response message to the second DU (720) indicating the completion of the reset process. Based on the first DU (710) sending a reset response message to the second DU (720) indicating the completion of the reset process, the state of the system may change along path (1431). The first DU (710) may send a reset response message to the second DU (720) indicating the completion of the reset process. The first DU (710) and the second DU (720) may perform a DU group setup process. After the DU group setup process is performed, the state of the system may change from the reset state (1430) to the normal state (1410). For example, the DU group setup process may be a process for grouping DUs. Resources required for CA may be exchanged between DUs according to the DU group setup process.

[0242] According to one embodiment, an electronic device performing the function of a first DU (distributed unit) may include at least one processor including a communication circuitry and a processing circuitry, and a memory including one or more storage media for storing instructions. When the above instructions are executed individually or collectively by the at least one processor, the electronic device receives a reset message from a second DU used for carrier aggregation (CA) together with the first DU, and based on the reset message, identifies a terminal connected to the first DU and the second DU for CA, and determines for the terminal whether the first DU provides a primary cell (PCell) for CA or whether the first DU provides a secondary cell (SCell) for CA, and in accordance with the determination that the first DU provides the PCell, refrains from providing data for the terminal to the second DU, and in accordance with the determination that the first DU provides the SCell, causes resources for the terminal to be released.

[0243] For example, when the above instructions are executed individually or collectively by the at least one processor, the electronic device may be caused to identify, based on the reset message, that the terminal is idle, and based on identifying that the terminal is idle, to determine whether the first DU provides the PCell or whether the first DU provides the SCell to the terminal.

[0244] For example, when the above instructions are executed individually or collectively by the at least one processor, the electronic device may cause the second DU to send a reset response message instructing a retry of the reset process based on identifying that the terminal is not in the idle state.

[0245] For example, when the above instructions are executed individually or collectively by the at least one processor, the electronic device may cause the second DU to transmit a reset response message indicating the completion of the reset process based on refraining from providing the data for the terminal to the second DU or releasing the resources for the terminal.

[0246] For example, when the above instructions are executed individually or collectively by the at least one processor, the electronic device may cause the DU group setup process to be performed with the second DU based on transmitting the reset response message to the second DU.

[0247] For example, when the above instructions are executed individually or collectively by the at least one processor, the electronic device may refrain from providing the data for the terminal to the second DU, receive a UE (user equipment) context modification request message from a CU (central unit) regarding the first DU and the second DU, and, based on identifying that the terminal is included in the SCell list included in the UE context modification request message, cause the device to send a UE context modification response message to the CU.

[0248] For example, the above UE context modification response message can be used in the above CU to cause the release of the above SCell provided in the above second DU.

[0249] For example, when the above instructions are executed individually or collectively by the at least one processor, the electronic device may, based on the reset message, identify a plurality of terminals including the terminal and connected to the first DU and the second DU and the CA, and for each of the plurality of terminals, determine whether the first DU provides a PCell or whether the first DU provides a SCell.

[0250] For example, when the above instructions are executed individually or collectively by the at least one processor, the electronic device may perform a reset process that refrains from providing data for each of the plurality of terminals to the second DU or releases resources for each of the plurality of terminals based on determining whether the first DU provides a PCell or whether the first DU provides a SCell for each of the plurality of terminals, and, based on the completion of the reset process, cause a reset response message to be transmitted to the second DU.

[0251] For example, the reset message may be transmitted based on a recovery process following an anomaly in the second DU. The reset message may include at least one of an identifier for the first DU, an identifier for the second DU, an identifier for the location of the first DU, an identifier for the location of the second DU, or information indicating a request for a reset process.

[0252] According to one embodiment, a method performed by an electronic device that performs the function of a first distributed unit (DU) may include: receiving a reset message from a second DU used for carrier aggregation (CA) together with the first DU; identifying a terminal connected to the first DU and the second DU for CA based on the reset message; determining, for the terminal, whether the first DU provides a primary cell (PCell) for the CA or whether the first DU provides a secondary cell (SCell) for the CA; refraining from providing data for the terminal to the second DU based on the determination that the first DU provides the PCell; and releasing resources for the terminal based on the determination that the first DU provides the SCell.

[0253] For example, the above method may include an operation of identifying that the terminal is in an idle state based on the reset message, and an operation of determining whether the first DU provides the PCell or the first DU provides the SCell to the terminal based on identifying that the terminal is in an idle state.

[0254] For example, the above method may include the operation of sending a reset response message to the second DU instructing a retry of the reset process based on identifying that the terminal is not in the idle state.

[0255] For example, the above method may include the operation of sending a reset response message to the second DU indicating the completion of a reset process based on refraining from providing the data for the terminal to the second DU or releasing the resources for the terminal.

[0256] For example, the above method may include an operation to perform a DU group setup process with the second DU based on transmitting the reset response message to the second DU.

[0257] For example, the above method may include the operation of receiving a UE (user equipment) context modification request message from a CU (central unit) regarding the first DU and the second DU after refraining from providing the data for the terminal to the second DU, and the operation of sending a UE context modification response message to the CU based on identifying that the terminal is included in the SCell list included in the UE context modification request message.

[0258] For example, the above UE context modification response message can be used in the above CU to cause the release of the above SCell provided in the above second DU.

[0259] For example, the above method may include, based on the reset message, an operation of identifying a plurality of terminals including the terminal and connected to the first DU and the second DU and the CA, and for each of the plurality of terminals, an operation of determining whether the first DU provides a PCell or whether the first DU provides a SCell.

[0260] For example, the above method may include an operation to perform a reset process of refraining from providing data for each of the plurality of terminals to the second DU or releasing resources for each of the plurality of terminals based on determining whether the first DU provides a PCell or whether the first DU provides a SCell for each of the plurality of terminals, and an operation to transmit a reset response message to the second DU based on the completion of the reset process.

[0261] For example, the reset message may be transmitted based on a recovery process following an anomaly in the second DU. The reset message may include at least one of an identifier for the first DU, an identifier for the second DU, an identifier for the location of the first DU, an identifier for the location of the second DU, or information indicating a request for a reset process.

[0262] According to the embodiments described above, in a 5G communication system, while multiple DUs are interconnected with network resources to perform communication, if an abnormality occurs in at least one of the multiple DUs, the other DUs within the group can perform a reset process. For example, when inter-DU CA is performed, frequency resources provided by different DUs may be utilized. Accordingly, wider bandwidth and faster services can be provided. However, in an inter-DU system, if an abnormality occurs in one of the DUs, the overall CA performance may be reduced. Therefore, according to the embodiments described above, inter-DU CA is operated efficiently, and in the event of an abnormality, effects such as reduced network recovery time, enhanced stability, and maximized service availability can be provided. According to the embodiments described above, the reliability of network operations is improved, and the quality of 5G services can be enhanced.

[0263] According to the above-described embodiment, when an individual DU becomes abnormal, such as going down, other DUs in the group can identify this and automatically perform a reset process. Therefore, the service stability of the terminal is guaranteed and system resources can be used efficiently.

[0264] Methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0265] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of this disclosure. The one or more programs may be provided as a computer program product. The computer program product may be traded between a seller and a buyer as a product. The computer program product may be distributed in the form of a device-readable storage medium (e.g., compact disc read-only memory (CD-ROM)), or distributed online (e.g., download or upload) through an application store (e.g., Play Store™) or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product may be temporarily stored or temporarily created on a device-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or a relay server.

[0266] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic disc storage devices, compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0267] Additionally, the program may be stored on an attachable storage device that can be accessed via a communication network such as the Internet, Intranet, LAN (local area network), WAN (wide area network), or SAN (storage area network), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present disclosure through an external port. Additionally, a separate storage device on a communication network may be connected to a device performing an embodiment of the present disclosure.

[0268] In the specific embodiments of the present disclosure described above, the components included in the disclosure are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present disclosure is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed of a singular form, and even if a component is expressed in the singular form, it may be composed of a plural form.

[0269] According to embodiments, one or more of the aforementioned components or operations may be omitted, or one or more other components or operations may be added. Generally or additionally, a plurality of components (e.g., modules or programs) may be integrated into a single component. In this case, the integrated component may perform one or more functions of each of the plurality of components in the same or similar manner as those performed by the corresponding component among the plurality of components prior to integration. According to embodiments, operations performed by a module, program, or other component may be executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be executed in a different order, omitted, or one or more other operations may be added.

[0270] Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, it is understood that various modifications are possible within the scope of the present disclosure.

Claims

1. In an electronic device that performs the function of a first DU (distributed unit), communication circuitry; At least one processor including a processing circuit and Memory that stores instructions and includes one or more storage media, When the above instructions are executed individually or collectively by the at least one processor, the electronic device: Receive a reset message from a second DU used for CA (carrier aggregation) together with the first DU, and Based on the above reset message, identify the terminal connected to the first DU and the second DU for CA, and With respect to the above terminal, determining whether the first DU provides a PCell (primary cell) for the CA or whether the first DU provides a SCell (secondary cell) for the CA, and Based on the decision that the first DU provides the PCell, refrain from providing data for the terminal to the second DU, Causing to release resources for the terminal in accordance with the decision that the first DU provides the SCell, Electronic device.

2. In claim 1, when the instructions are executed individually or collectively by the at least one processor, the electronic device: Based on the above reset message, identify that the terminal is in an idle state, and Based on identifying that the terminal is in the idle state, causing the terminal to determine whether the first DU provides the PCell or whether the first DU provides the SCell. Electronic device.

3. In claim 2, when the instructions are executed individually or collectively by the at least one processor, the electronic device: Causing the second DU to send a reset response message instructing a retry of the reset process based on identifying that the terminal is not in the idle state. Electronic device.

4. In claim 1, when the instructions are executed individually or collectively by the at least one processor, the electronic device: Causing to transmit a reset response message to the second DU indicating the completion of the reset process based on refraining from providing the data for the terminal to the second DU or releasing the resources for the terminal, Electronic device.

5. In claim 4, when the instructions are executed individually or collectively by the at least one processor, the electronic device: Based on transmitting the above reset response message to the second DU, causing the DU group setup process to be performed with the second DU, Electronic device.

6. In claim 1, when the instructions are executed individually or collectively by the at least one processor, the electronic device: After refraining from providing the data for the above terminal to the second DU, receiving a UE (user equipment) context modification request message from a CU (central unit) regarding the first DU and the second DU, and Based on identifying that the terminal is included in the SCell list included in the above UE context modification request message, causing the CU to send a UE context modification response message, Electronic device.

7. In claim 6, the UE context modification response message is, In the above CU, used to cause the release of the SCell provided in the above 2 DU, Electronic device.

8. In claim 1, when the instructions are executed individually or collectively by the at least one processor, the electronic device: Based on the above reset message, identify a plurality of terminals including the terminal and connected to the first DU and the second DU and the CA, and For each of the plurality of terminals above, causing to determine whether the first DU provides a PCell or whether the first DU provides a SCell, Electronic device.

9. In claim 8, when the instructions are executed individually or collectively by the at least one processor, the electronic device: Based on determining whether the first DU provides a PCell or whether the first DU provides a SCell for each of the plurality of terminals, a reset process is performed to refrain from providing data for each of the plurality of terminals to the second DU or to release resources for each of the plurality of terminals. Causing to transmit a reset response message to the second DU based on the completion of the above reset process, Electronic device.

10. In claim 1, the reset message is, Transmitted based on a recovery process following an anomaly in the above-mentioned second DU, and The above reset message is, at least one of an ID (identifier) ​​for the first DU, an ID for the second DU, an ID for the location of the first DU, an ID for the location of the second DU, or information indicating a request for a reset process, Electronic device.

11. A method performed by an electronic device that performs the function of a first DU (distributed unit), The operation of receiving a reset message from a second DU used for CA (carrier aggregation) together with the first DU; An operation to identify a terminal connected to the first DU and the second DU for CA based on the above reset message; With respect to the above terminal, an operation of determining whether the first DU provides a PCell (primary cell) for the CA or whether the first DU provides a SCell (secondary cell) for the CA; An operation to refrain from providing data for the terminal to the second DU in accordance with the decision that the first DU provides the PCell; and Based on the decision that the first DU provides the SCell, the operation of releasing resources for the terminal is included. method.

12. In claim 11, the above method is, An operation to identify that the terminal is in an idle state based on the above reset message; and Based on identifying that the terminal is in the idle state, the operation of determining, for the terminal, whether the first DU provides the PCell or whether the first DU provides the SCell, method.

13. In claim 12, the above method is, Based on identifying that the terminal is not in the idle state, the operation of transmitting a reset response message to the second DU instructing a retry of the reset process method.

14. In claim 11, the above method is, The operation of sending a reset response message to the second DU indicating the completion of a reset process based on refraining from providing the data for the terminal to the second DU or releasing the resources for the terminal, method.

15. In claim 14, the above method is, Based on transmitting the above reset response message to the second DU, the operation of performing a DU group setup process with the second DU is included. method.

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