Method and apparatus for transmitting flow control information for dual connectivity in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting relatively high data transmission rates. Particularly, a method performed by a DU of a base station in a wireless communication system, according to various embodiments of the present disclosure, comprises the steps of: receiving, from a CU of the base station, first information related to a distribution state of a packet; determining a target buffer amount on the basis of the first information; and transmitting, to the CU, second information including a size and / or a variation value for each of the current buffer amount of the DU and the target buffer amount.

Description

Method and device for transmitting flow control information for dual connection in a wireless communication system

[0001] The present disclosure generally relates to a wireless communication system, and more specifically to an apparatus and method for performing appropriate distribution of packets in a dual-connection environment in a wireless communication system.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in frequency bands below 6 GHz ('Sub 6 GHz'), such as 3.5 gigahertz (3.5 GHz), but also in ultra-high frequency bands called millimeter waves (mmWave), such as 28 GHz and 39 GHz ('Above 6 GHz'). In addition, for 6G mobile communication technology, which is referred to as a system beyond 5G, implementation in the terahertz (THX) band (e.g., the 3 terahertz band at 95 GHz) is being considered to achieve transmission speeds 50 times faster and ultra-low latency reduced to one-tenth compared to 5G mobile communication technology.

[0003] In the early stages of 5G mobile communication technology, aiming to satisfy service support and performance requirements for enhanced Mobile BroadBand (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), technologies such as beamforming and Massive MIMO to mitigate path loss and increase transmission distance in ultra-high frequency bands, support for various numerologies (such as the operation of multiple subcarrier spacings) and dynamic operation of slot formats for the efficient utilization of ultra-high frequency resources, initial access techniques to support multi-beam transmission and broadband, definition and operation of Band-Width Parts (BWP), Low Density Parity Check (LDPC) codes for high-volume data transmission, new channel coding methods such as Polar Codes for the reliable transmission of control information, and L2 pre-processing (L2 Standardization has been carried out for pre-processing, network slicing which provides a dedicated network specialized for specific services, and other methods.

[0004] 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.

[0005] In addition, standardization is underway in the field of wireless interface architecture / protocols for technologies such as the Industrial Internet of Things (IIoT) for supporting new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) which provides nodes for expanding 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 (2-step RACH 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) for incorporating 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.

[0006] 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).

[0007] 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.

[0008] Various embodiments of the present disclosure aim to provide devices and methods capable of effectively providing services in a wireless communication system.

[0009] According to various embodiments of the present disclosure, a method performed by a distributed unit (DU) of a base station in a wireless communication system comprises: receiving first information regarding the distribution status of a packet from a central unit (CU) of the base station; determining a target buffer amount based on the first information; and transmitting to the CU a second information including at least one of a size or change amount value for each of the current buffer amount of the DU and the target buffer amount, wherein the DU may include a master cell group (MCG) DU or a secondary cell group (SCG) DU.

[0010] According to various embodiments of the present disclosure, a method performed by a central unit (CU) of a base station in a wireless communication system comprises: transmitting first information regarding the distribution status of a packet to a distributed unit (DU) of the base station; receiving second information from the DU, the second information including at least one of a size or change amount value for each of the current buffer amount of the DU and the target buffer amount of the DU based on the first information; and determining a packet transmission amount for the DU based on the second information to the DU, wherein the DU may include a master cell group (MCG) DU or a secondary cell group (SCG) DU.

[0011] According to various embodiments of the present disclosure, a distributed unit (DU) of a base station in a wireless communication system comprises: a transceiver; and at least one control unit connected to the transceiver, wherein the at least one control unit is configured to receive first information regarding the distribution status of a packet from a central unit (CU) of the base station, determine a target buffer amount based on the first information, and transmit second information to the CU, the second information comprising at least one of a size or change amount value for each of the current buffer amount of the DU and the target buffer amount, and the DU may include a master cell group (MCG) DU or a secondary cell group (SCG) DU.

[0012] According to various embodiments of the present disclosure, a central unit (CU) of a base station in a wireless communication system comprises: a transceiver; and at least one control unit connected to the transceiver, wherein the at least one control unit is configured to: transmit first information regarding the distribution status of a packet to a distributed unit (DU) of the base station; receive second information from the DU including at least one of a size or change amount value for each of the current buffer amount of the DU and the target buffer amount of the DU based on the first information; and determine a packet transmission amount for the DU based on the second information to the DU, wherein the DU may include a master cell group (MCG) DU or a secondary cell group (SCG) DU.

[0013] Various embodiments of the present disclosure aim to provide an apparatus and method capable of effectively providing services in a wireless communication system. More specifically, according to various embodiments of the present disclosure, end-to-end delay can be reduced by lowering the likelihood of increased reordering delay. Additionally, the likelihood of packet loss due to the expiration of a reordering timer can be lowered. Furthermore, the likelihood of transmission speed degradation due to buffer shortage can be reduced, thereby improving transmission speed quality.

[0014] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0015] FIG. 1 illustrates an example of a wireless communication environment according to embodiments of the present disclosure.

[0016] FIG. 2 illustrates an example of the configuration of a base station in a wireless communication system according to embodiments of the present disclosure.

[0017] FIG. 3 illustrates an example of the configuration of a terminal in a wireless communication system according to embodiments of the present disclosure.

[0018] FIG. 4 illustrates an example of a DC related to various embodiments of the present disclosure.

[0019] FIG. 5 illustrates the concept of a buffer underflow phenomenon related to various embodiments of the present disclosure.

[0020] FIG. 6 illustrates the concept of buffer delay occurrence in relation to various embodiments of the present disclosure.

[0021] FIG. 7 illustrates signaling for optimal traffic distribution in a wireless communication system according to various embodiments of the present disclosure.

[0022] FIG. 8 illustrates a method for transmitting the packet distribution status of a CU in a wireless communication system according to various embodiments of the present disclosure.

[0023] FIG. 9 illustrates an example of a field configuration including a packet distribution state in a wireless communication system according to various embodiments of the present disclosure.

[0024] FIG. 10 illustrates another example of a field configuration including a packet distribution state in a wireless communication system according to various embodiments of the present disclosure.

[0025] FIG. 11 illustrates methods for determining a target buffer amount in a wireless communication system according to various embodiments of the present disclosure.

[0026] FIG. 12 illustrates a method for reporting a current buffer amount and a target buffer amount to a CU in a wireless communication system according to various embodiments of the present disclosure.

[0027] FIG. 13 illustrates an example of reporting buffer amount-related information in a wireless communication system according to various embodiments of the present disclosure.

[0028] FIG. 14a illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0029] FIG. 14b illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0030] FIG. 14c illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0031] FIG. 14d illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0032] FIG. 14e illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0033] FIG. 14f illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0034] FIG. 14g illustrates another example of a field configuration including a packet distribution state in a wireless communication system according to various embodiments of the present disclosure.

[0035] FIG. 14h illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0036] FIG. 15a illustrates the sequence of packet distribution operations based on wireless communication buffer amount reporting according to various embodiments of the present disclosure.

[0037] FIG. 15b illustrates the sequence of packet distribution operations based on buffer amount reporting in a wireless communication system according to various embodiments of the present disclosure.

[0038] FIG. 15c illustrates the sequence of packet distribution operations based on buffer amount reporting in a wireless communication system according to various embodiments of the present disclosure.

[0039] FIG. 16 illustrates the operation of a DU for packet distribution based on buffer amount reporting in a wireless communication system according to embodiments of the present disclosure.

[0040] FIG. 17 illustrates the operation of a CU for packet distribution based on buffer amount reporting in a wireless communication system according to embodiments of the present disclosure.

[0041] In relation to the description of the drawings, the same or similar reference numerals may be used for identical or similar components.

[0042] 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.

[0043] 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.

[0044] Terms referring to components of a device used in the following description (control unit, processor, artificial intelligence (AI) model, encoder, decoder, autoencoder (AE), neural network (NN) model, etc.) and terms referring to data (signal, feedback, report, reporting, information, parameter, value, bit, codeword, 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 similar or equivalent technical meanings may be used.

[0045] Additionally, the present disclosure describes various embodiments using terms used in some communication standards (e.g., 3GPP (3rd Generation Partnership Project)), but this is merely illustrative. Various embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0046] In the present disclosure, the downlink channel may be either a physical downlink control channel (PDCCH) or a physical downlink shared channel (PDSCH). In the present disclosure, the uplink channel may be either a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). Additionally, in the present disclosure, uplink data may be data transmitted and / or received over the uplink channel described above, and downlink data may be data transmitted and / or received over the downlink channel described above.

[0047] FIG. 1 illustrates a wireless communication system according to various embodiments of the present disclosure. FIG. 1 illustrates a base station (110), a terminal (120), and a terminal (130) as part of nodes utilizing a wireless channel in a wireless communication system. FIG. 1 illustrates only one base station, but other base stations identical or similar to the base station (110) may be additionally included.

[0048] A base station (110) is a network infrastructure that provides wireless access to terminals (120, 130). The base station (110) has coverage defined as a certain geographical area based on the distance at 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)', 'gNodeB (gNB)', '5G node (5th generation node)', '6G node (6th generation node)', 'wireless point', 'transmission / reception point (TRP)', or other terms having an equivalent technical meaning.

[0049] Each of the terminal (120) and terminal (130) is a device used by a user and performs communication with the base station (110) via a wireless channel. In some cases, at least one of the terminal (120) and terminal (130) may be operated without user involvement. That is, at least one of the terminal (120) and terminal (130) is a device that performs machine type communication (MTC) and may not be carried by the user. Each of the terminal (120) and terminal (130) may be referred to as 'terminal', 'user equipment (UE)', 'mobile station', 'subscriber station', 'customer premises equipment (CPE)', 'remote terminal', 'wireless terminal', 'electronic device', or 'user device', or other terms having a similar or equivalent technical meaning.

[0050] A base station (110), a terminal (120), and a terminal (130) can transmit and receive wireless signals in a millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, 60 GHz, over 60 GHz, etc.). At this time, to improve channel gain, the base station (110), the terminal (120), and the terminal (130) can perform beamforming. Here, beamforming may include transmission beamforming and reception beamforming. That is, the base station (110), the terminal (120), and the terminal (130) can impart directivity to the transmission signal or the reception signal. To this end, the base station (110) and the terminal (120, 130) can select serving beams (112, 113, 121, 131) through a beam search or beam management procedure. After serving beams (112, 113, 121, 131) are selected, subsequent communication can be performed through a resource that is in a quasi-co-located (QCL) relationship with the resource that transmitted the serving beams (112, 113, 121, 131).

[0051] FIG. 2 illustrates an example of the configuration of a base station in a wireless communication system according to embodiments of the present disclosure. According to various embodiments of the present disclosure, the base station (110) may be referred to as a network for convenience. The configuration exemplified in FIG. 2 can be understood as the configuration of the base station (110). Terms such as '~unit', '~unit', etc. used below refer to a unit that processes at least one function or operation, and this may be implemented in hardware or software, or a combination of hardware and software.

[0052] Referring to FIG. 2, the base station (110) may include a wireless communication unit (210), a backhaul communication unit (220), a storage unit (230), and a control unit (240).

[0053] The wireless communication unit (210) performs functions for transmitting and receiving signals through a wireless channel. For example, the wireless communication unit (210) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the wireless communication unit (210) generates complex symbols by encoding and modulating the transmitted bit sequence. Also, when receiving data, the wireless communication unit (210) restores the received bit sequence by demodulating and decoding the baseband signal. Additionally, the wireless communication unit (210) upconverts the baseband signal into an RF (radio frequency) band signal and transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal.

[0054] To this end, the wireless communication unit (210) may include a transmitting filter, a receiving filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc. Additionally, the wireless communication unit (210) may include a plurality of transmitting and receiving paths. Furthermore, the wireless communication unit (210) may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the wireless communication unit (210) may be composed of a digital unit and an analog unit, and the analog unit may be composed of a plurality of sub-units depending on operating power, operating frequency, etc.

[0055] The wireless communication unit (210) can transmit and receive signals. To this end, the wireless communication unit (210) may include at least one transceiver. For example, the wireless communication unit (210) can transmit a synchronization signal, a reference signal, system information, a message, control information, or data. Additionally, the wireless communication unit (210) can perform beamforming.

[0056] The wireless communication unit (210) transmits and receives signals as described above. Accordingly, all or part of the wireless communication unit (210) may be referred to as a 'transmitter', a 'receiver', or a 'transmitter / receiver'. Furthermore, in the following description, transmission and reception performed through a wireless channel are used to mean that processing as described above is performed by the wireless communication unit (210).

[0057] The backhaul communication unit (220) provides an interface for communicating with other nodes within the network. That is, the backhaul communication unit (220) converts a bit sequence transmitted from the base station (110) to other nodes, such as other connection nodes, other base stations, upper nodes, core networks, etc., into a physical signal, and converts a physical signal received from other nodes into a bit sequence.

[0058] The storage unit (230) stores data such as basic programs, application programs, and configuration information for the operation of the base station (110). The storage unit (230) may include memory. The storage unit (230) may be composed of volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. Additionally, the storage unit (230) may provide the stored data upon request from the control unit (240).

[0059] The control unit (240) controls the overall operations of the base station (110). For example, the control unit (240) transmits and receives signals through the wireless communication unit (210) or through the backhaul communication unit (220). Additionally, the control unit (240) writes and reads data to and from the storage unit (230). Furthermore, the control unit (240) can perform the functions of a protocol stack required by the communication standard. To this end, the control unit (240) may include at least one processor.

[0060] Although not illustrated in FIG. 2, according to various embodiments of the present disclosure, the base station (110) may further include a receiving device for performing embodiments of the present disclosure. Specifically, the receiving device may be included in the wireless communication unit (210) or may be included in the base station (110) separately from the wireless communication unit (210). Alternatively, the receiving device may exist outside the base station (110) and be connected to the base station (110) wirelessly or via a wire. In this case, the receiving device may include at least one receiver. Additionally, the control unit (240) may control the receiving device to perform embodiments of the present disclosure below.

[0061] The configuration of the base station (110) shown in FIG. 2 is merely one example of a base station, and the examples of base stations for performing various embodiments of the present disclosure are not limited to the configuration shown in FIG. 2. That is, depending on various embodiments, some configurations may be added, deleted, or changed.

[0062] In FIG. 2, the base station is described as a single entity, but the present disclosure is not limited thereto. A base station according to various embodiments of the present disclosure may be implemented to form an access network having a distributed deployment as well as an integrated deployment. According to one embodiment, the base station may be distinguished into a central unit (CU) and a digital unit (DU), wherein the CU may be implemented to perform upper layer functions (e.g., radio link control (RLC), packet data convergence protocol (PDCP), and radio resource control (RRC)), and the DU may be implemented to perform lower layer functions (e.g., medium access control (MAC), physical (PHY)). The DU of the base station may form beam coverage on a radio channel.

[0063] FIG. 3 illustrates the configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure. The configuration exemplified in FIG. 3 can be understood as the configuration of a terminal (120). Terms such as ‘~part’, ‘~unit’ used below refer to a unit that processes at least one function or operation, and this may be implemented in hardware or software, or a combination of hardware and software.

[0064] Referring to FIG. 3, the terminal includes a communication unit (310), a storage unit (320), and a control unit (330).

[0065] The communication unit (310) performs functions for transmitting and receiving signals through a wireless channel. For example, the communication unit (310) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the communication unit (310) generates complex symbols by encoding and modulating the transmitted bit sequence. Also, when receiving data, the communication unit (310) restores the received bit sequence by demodulating and decoding the baseband signal. Additionally, the communication unit (310) upconverts the baseband signal into an RF band signal and transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. For example, the communication unit (310) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

[0066] Additionally, the communication unit (310) may include a plurality of transmission and reception paths. Furthermore, the communication unit (310) may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the communication unit (310) may be composed of a digital circuit and an analog circuit (e.g., a radio frequency integrated circuit (RFIC)). Here, the digital circuit and the analog circuit may be implemented as a single package. Additionally, the communication unit (310) may include a plurality of RF chains. Furthermore, the communication unit (310) may perform beamforming.

[0067] The communication unit (310) transmits and receives signals as described above. Accordingly, all or part of the communication unit (310) may be referred to as a 'transmitter', a 'receiver', or a 'transmitter / receiver'. Additionally, in the following description, transmission and reception performed via a wireless channel are used to mean that processing as described above is performed by the communication unit (310).

[0068] The storage unit (320) stores data such as basic programs, application programs, and setting information for the operation of the terminal. The storage unit (320) may be composed of volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. Additionally, the storage unit (320) provides the stored data upon the request of the control unit (330).

[0069] The control unit (330) controls the overall operations of the terminal. For example, the control unit (330) transmits and receives signals through the communication unit (310). Additionally, the control unit (330) writes and reads data to and from the storage unit (320). Furthermore, the control unit (330) can perform the functions of the protocol stack required by the communication standard. To this end, the control unit (330) may include at least one processor or microprocessor, or be part of a processor. Additionally, part of the communication unit (310) and the control unit (330) may be referred to as a communication processor (CP).

[0070] According to various embodiments, the control unit (330) can control the terminal to perform operations according to various embodiments described below.

[0071] Terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc., are examples provided for the convenience of explanation. Accordingly, the present disclosure is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0072] The configuration of the terminal (120) shown in FIG. 3 is merely an example of a terminal, and the examples of terminals performing various embodiments of the present disclosure are not limited to the configuration shown in FIG. 3. That is, depending on various embodiments, some configurations may be added, deleted, or changed.

[0073] Meanwhile, 5G NR (new radio) in wireless (or mobile) communication systems supports DC (dual connectivity) technology. 5G terminals can select two of 4G LTE (long term evolution), 5G FR1 (frequency range 1), and 5G FR2 (frequency range 2) to connect simultaneously. Depending on the connection method, DC is divided into EN-DC (evolved non-standalone dual connectivity), NE-DC (NR E-UTRA dual connectivity), and NR-DC (new radio dual connectivity). EN-DC refers to using 4G EPC (evolved packet core) in the core network (CN) and simultaneously connecting 4G LTE and 5G FR1 or 4G LTE and 5G FR2 in the radio access network (RAN). NE-DC refers to using 5G 5GC in the core network and simultaneously connecting 4G LTE and 5G FR1 or 4G LTE and 5G FR2 in the RAN. NR-DC refers to using 5GC in the core network and simultaneously connecting 5G FR1 and 5G FR2 in the RAN. Hereinafter, embodiments of the present disclosure propose a method for efficiently distributing packets in the above-described DC.

[0074] FIG. 4 illustrates an example of a DC related to various embodiments of the present disclosure.

[0075] Referring to FIG. 4, the flow of downlink (DL) signals in the protocol stacks of the master node and secondary node in a DC (e.g., (a) EN-DC and (b) NR-DC) can be described. In this case, the secondary node (e.g., SgNB or SeNB) connected to the master node (e.g., MeNB or MgNB) via an X2-U or Xn-U interface may be a node that provides additional radio resources for the terminal. More specifically, in a 5G DC, downlink traffic branching takes place at the gNB-CU (next generation Node B - central unit) responsible for the PDCP (packet data convergence protocol) layer. Then, traffic divided into the MCG (master cell group) path and the SCG (secondary cell group) path is transmitted to the radio interface via an LTE base station responsible for the RLC (radio link control) layer (e.g., eNB (enhanced Node B)) or gNB-DU (next generation Node B - distributed unit). In this case, the 3GPP 5G interface specification refers to the interface between the gNB-CU and the eNB as X2-U, the interface between the gNB-CU and gNB-DU belonging to the same gNB as F1-U, and the interface between the gNB-CU and gNB-DU belonging to different gNBs as Xn-U. Furthermore, an MCG bearer may be located only at the MeNB (or MgNB) to utilize only MeNB (or MgNB) resources within the DC. An SCG bearer may be located only at the SeNB (or SgNB) to utilize SeNB (or SgNB) resources within the DC.A split bearer can be located at both the MeNB (or MgNB) and SgNB (or SeNB) to utilize both MeNB (or MgNB) and SgNB (or SeNB) resources in the DC. For example, in the DC, the split bearer can be split at the PDCP layer of a master node (e.g., MeNB or MgNB) connected to a core network (e.g., EPC or 5GC). For the split bearer, the master node and the secondary node can be connected via an X2-U interface, and signals transmitted through the split bearer can be sent from the PDCP layer of the master node to the RLC layer of the secondary node. Referring again to Fig. 4, traffic can be transmitted or information for traffic transmission can be conveyed at the X2-U, F1-U, and Xn-U interfaces of the DC using the 3GPP TS38.425 standard. However, in order to achieve optimal performance in terms of throughput (or speed) and delay in the DC, it may be necessary to exchange various information in real time between the gNB-CU and the eNB or gNB-DU (hereinafter referred to as eNB / gNB-DU). However, the TS38.425 NR data user protocol used in the F1-U, X2-U, and Xn-U interfaces has a problem in that the information that can be exchanged is limited. Therefore, when using DC functions in wireless (or mobile) communication network systems including 5G NR, 6G, etc., a method may be required to define new traffic flow control information exchanged through interfaces such as F1-U, X2-U, and Xn-U, and to transmit this information.

[0076] FIG. 5 illustrates the concept of a buffer underflow phenomenon related to various embodiments of the present disclosure.

[0077] The eNB / gNB-DU responsible for the RLC layer needs to maintain an appropriate buffer amount considering the wireless interface transmission speed. For example, referring to the top graph of Fig. 5(a) and Fig. (b), if the buffer amount is insufficient, it can cause a situation where there is no data to transmit even if there is a scheduling opportunity, which may lead to a decrease in transmission speed (or throughput). On the other hand, referring to the bottom graph of Fig. 5(a), if the buffer amount is excessive as the target buffer amount is increased to prevent the problem of insufficient buffer amount, the reordering delay may increase due to the difference in PDCP COUNT (e.g., a value derived by combining the HFN (hyper frame number) and PDCP SN (sequence number) managed by the transmitting side of PDCP) between the MCG path and the SCG path. Therefore, in order to maintain an appropriate level of buffer volume, the eNB / gNB-DU transmits information such as the desired buffer size and desired data rate to the gNB-CU using the specifications defined in the standard document 3GPP TS38.425, and the gNB-CU needs to decide the distribution of packets to the MCG path and SCG path based on the received information and its own policy.

[0078] FIG. 6 illustrates the concept of buffer delay occurrence in relation to various embodiments of the present disclosure.

[0079] Referring to FIG. 6, the gNB-CU may not know how much buffering delay the packets transmitted to the eNB / gNB-DU will experience among the delays that the packets may experience (e.g., propagation delay between interfaces of D1 (610), buffering delay (or queueing delay) of D2 (620), and air delay of D3 (630). To minimize reordering delay, the gNB-CU needs to split the packets so that the delays experienced by the packets transmitted to the MCG and the packets transmitted to the SCG until they reach the UE are similar (or so that the reordering delay does not increase). However, since the gNB-CU cannot know how much buffering delay the packets transmitted to the eNB / gNB-DU will experience, it cannot optimally split the packets to the MCG and SCG. If the buffering delay of either the MCG or the SCG becomes relatively large, the reordering delay may increase.

[0080] Furthermore, eNB / gNB-DU faces the problem of difficulty in determining the optimal target buffer size because it is impossible to determine whether the gNB-CU is splitting traffic between the MCG and SCG or transmitting via only a single path. eNB / gNB-DU fundamentally assumes that the gNB-CU is transmitting simultaneously to both the MCG and SCG, and may minimize the target buffer size to reduce the possibility of reorder delays. However, as the target buffer size is minimized, the likelihood of transmission speed degradation due to buffer shortages increases. Therefore, even if the gNB-CU is connected to the DC, if it is transmitting traffic via only a single path (e.g., either the MCG or SCG) without splitting it between the MCG and SCG, eNB / gNB-DU can increase the target buffer size to lower the risk of buffer shortages without worrying about reorder delays. Additionally, when the gNB-CU switches from transmitting via only a single path to simultaneous transmission to the MCG and SCG, the target buffer size can be reduced to prevent an increase in reorder delays.

[0081] Accordingly, in order to prevent an increase in reorder delay and prevent buffer shortage, and to prevent an increase in end-to-end delay or a decrease in transmission speed, the present disclosure proposes a method in which the DC transmits the traffic distribution status of the gNB-CU to the eNB / gNB-DU, and the eNB / gNB-DU transmits information regarding its buffer amount to the gNB-CU. Accordingly, the eNB / gNB-DU can optimally set the target buffer amount, and the gNB-CU can optimally distribute traffic.

[0082] FIG. 7 illustrates signaling for optimal traffic distribution in a wireless communication system according to various embodiments of the present disclosure.

[0083] Referring to FIG. 7, the sequence of signalings for the gNB-CU to efficiently distribute traffic from the DC to the MCG and SCG is described. The DC in FIG. 7 may be an EN-DC or an NR-DC, but is not limited thereto. Accordingly, in the following embodiments including FIG. 7, the gNB-CU may be referred to as CU, and the eNB / gNB-DU may be briefly referred to as DU. Furthermore, although the following figures are illustrated as gNB-CU and eNB / gNB-DU, nodes or units performing the roles of CU and DU in a 6G communication system may be included. For example, this is merely an example to explain the state in which a packet transmission path branches from the CU of a base station (e.g., gNB) to the MCG (e.g., eNB / gNB-DU) and SCG (e.g., eNB / gNB-DU) in a 5G or 6G system, and is not limited to a specific DC structure. In addition, the branched paths from the CU of the base station (e.g., gNB) to the terminal (e.g., the path from the CU through the MCG and the path from the CU through the SCG) below may be briefly referred to as the MCG path and the SCG path, respectively.

[0084] In step 710, the CU may notify the eNB / gNB-DU of the MCG and / or the eNB / gNB-DU of the SCG of information regarding the packet distribution status. For example, the information regarding the packet distribution status transmitted by the CU may include information regarding the current packet distribution status and information regarding the packet distribution status after any period of time has elapsed (or information regarding the packet distribution status scheduled to change). More specific details are described in detail below in FIGS. 8 to 10.

[0085] In step 720, the eNB / gNB-DU, having received information regarding the packet distribution status from the CU, can determine the target buffer amount based on the packet distribution status of the CU. For example, considering the packet distribution status scheduled to change from the current packet distribution status of the CU, it can determine whether to decrease, maintain, or increase the target buffer amount. Although FIG. 7 illustrates the SCG's eNB / gNB-DU determining the target buffer amount, this is merely an example, and it is understood that this can also be performed by the MCG's eNB / gNB-DU. More specific details are explained below in FIG. 11.

[0086] In step 730, the eNB / gNB-DU can transmit information regarding the target buffer amount determined in step 720 and information regarding the current buffer amount of the eNB / gNB-DU to the CU. Although FIG. 7 illustrates that the eNB / gNB-DU of the MCG determines the target buffer amount, this is merely an example, and it is understood that this can be performed by the eNB / gNB-DU of the SCG. More specific details are described below in FIG. 12, 13, and FIG. 14a through 14h.

[0087] The signaling according to the DC and steps 710 through 730 of FIG. 7 described above is merely an example, and some or all of it may be applied identically or similarly to the embodiments of the present disclosure described below. Accordingly, configurations omitted or added in the following embodiments may be described based on FIG. 7 described above.

[0088] FIG. 8 illustrates a method for transmitting the packet distribution status of a CU in a wireless communication system according to various embodiments of the present disclosure.

[0089] Referring to FIG. 8, a method for transmitting information regarding the packet distribution status of a CU, which is transmitted by the CU to an eNB / gNB-DU (e.g., an eNB / gNB-DU of an MCG or an eNB / gNB-DU of an SCG) in step 710 of FIG. 7 described above, is explained. Accordingly, descriptions that overlap with FIG. 7 may be omitted.

[0090] The CU may transmit information regarding the packet distribution state of the CU to the eNB / gNB-DU using the DL user data format (810) defined in 3GPP TS38.425 or a similar format (820). In one embodiment, 810 may be a method of using a DL user data format with a PDU (protocol data unit) type=0 among the types of frame formats for the NR User Plane Protocol. In another embodiment, 820 may be a method of using a new frame format having a value of PDU type=3 to 15. A more specific configuration of the transmission format is described below in FIGS. 9 and 10.

[0091] Meanwhile, information regarding the packet distribution status of the CU may include information regarding the current packet distribution status and information regarding the packet distribution status after an arbitrary amount of time has elapsed (or information regarding the packet distribution status scheduled for change). For example, information regarding the packet distribution status may include information indicating which path the CU is currently transmitting the downlink packet to, either the MCG or the SCG path, and how the transmission path of the downlink packet is scheduled to change thereafter. Additionally, the aforementioned arbitrary amount of time may represent a state change time (hereinafter referred to as state change time) indicating the scheduled time for changing the transmission path of the downlink packet. For example, the state change time may represent the minimum value required for the CU to change the distribution status of the downlink packet (e.g., 10ms) or the time value until the transmission time of the next downlink packet. Of course, the transmitted information and the time for changing the transmission path are not limited to names such as the distribution state and state change time described above; they are merely used as unified names for convenience.

[0092] Distribution states can be defined as follows. Of course, they are not limited to the examples below. For instance, MM may indicate that it is distributing packets only to MCG and plans to distribute packets only to MCG even after the state change time. MD may indicate that it is distributing packets only to MCG and plans to distribute packets to both MCG and SCG after the state change time. MS may indicate that it is distributing packets only to MCG and plans to distribute packets only to SCG after the state change time. SS may indicate that it is distributing packets only to SCG and plans to distribute packets only to SCG even after the state change time. SD may indicate that it is distributing packets only to SCG and plans to distribute packets to both MCG and SCG after the state change time. SM may indicate that it is distributing packets only to SCG and plans to distribute packets only to MCG after the state change time. DD is distributing packets to both MCG and SCG, and can indicate that it plans to distribute packets to both MCG and SCG even after the state change time. DM is distributing packets to both MCG and SCG, and can indicate that it plans to distribute packets only to MCG after the state change time. DS is distributing packets to both MCG and SCG, and can indicate that it plans to distribute packets only to SCG after the state change time.

[0093] FIG. 9 illustrates an example of a field configuration including a packet distribution state in a wireless communication system according to various embodiments of the present disclosure.

[0094] Referring to FIG. 9, a method for transmitting information regarding the packet distribution status of the CU to the eNB / gNB-DU is described through the method described in FIG. 8 (e.g., 810: DL user data format defined in 3GPP TS38.425). For example, information regarding the packet distribution status can be transmitted based on the DL user data format corresponding to PDU type=0 among the types of frame formats for the NR User Plane Protocol of 3GPP TS38.425.

[0095] More specifically, the DL user data format may further include fields corresponding to 910 through 940. For example, the header of the DL user data format may include spare fields, and each field indicating whether to include information regarding the distribution state and state change time proposed in this disclosure (e.g., Distribution State Flag field (910) and Next State Time Flag field (930)) may be added to some of the spare fields. In this case, whether to include information regarding the distribution state and state change time may be indicated in the form of a flag. For example, the Distribution State Flag field (910) may include a value of 1 bit, and if the field includes a value of 0, it may indicate that the Distribution State field does not exist. On the other hand, if the Distribution State Flag field (910) includes a value of 1, it may indicate that the Distribution State field (920), which includes information regarding the distribution state, exists prior to the padding field. For example, the Next State Time Flag field (930) may contain a value of 1 bit, and if the field contains a value of 0, it may indicate that the Next State Time field does not exist. On the other hand, if the Next State Time Flag field (930) contains a value of 1, it may indicate that the Next State Time field (940), which contains information about the distribution state prior to the padding field, exists. In the example described above, the meaning of each flag field value is merely an example, and it may also indicate that the field exists when it has a value of 0.

[0096] And when the Distribution State Flag field (910) and the Next State Time Flag field (930) indicate that the Distribution State field (920) and the Next State Time field (940) exist, respectively, the configuration of each information field (920, 940) may be as follows. For example, the Distribution State field (920) contains 1 octet, and the information indicated by the corresponding values ​​may be represented in relation to the distribution state of the current packet described in detail in FIG. 8. On the other hand, when the Distribution State Flag field (910) indicates that the Distribution State field (920) does not exist, the Distribution State field (920) contains 0 octets. As an example, depending on each value of the Distribution State field (920), 0 = MM, 1 = MD, 2 = MS, 3 = SS, 4 = SD, 5 = SM, 6 = DD, 7 = DM, 8 = DS, and 9 to 255 = reserved values ​​may be represented, respectively. Additionally, the Next State Time field (940) contains 1 octet and can represent any one of the time values ​​between 0 and 255 ms. Meanwhile, if the Next State Time Flag field (930) indicates that the Next State Time field (940) does not exist, the Next State Time field (940) contains 0 octets.

[0097] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 9 are merely examples and may be changed differently from the illustrated and described embodiments.

[0098] FIG. 10 illustrates another example of a field configuration including a packet distribution state in a wireless communication system according to various embodiments of the present disclosure.

[0099] Referring to FIG. 10, a method for transmitting information regarding the packet distribution status of a CU to an eNB / gNB-DU using the method described in FIG. 8 (e.g., 820: a newly defined frame format) is described. For example, any one of the reserved PDU type values ​​(e.g., 3 to 15) in addition to the frame format types for the NR User Plane Protocol of 3GPP TS38.425 may be used. Accordingly, in addition to the configuration of the frame format, the values ​​of the fields for transmitting information regarding the distribution status and state change time proposed in this disclosure, and the meanings represented by those values, may be applied in FIG. 10 in the same or similar manner as those described in FIG. 9. Therefore, descriptions that overlap with FIG. 9 may be omitted.

[0100] In one embodiment, a frame format having a PDU type value of 15 may be used to convey information regarding the distribution state and state change time proposed in this disclosure. For example, the header of the new frame format may include fields (e.g., a Distribution State Flag field (1010) and a Next State Time Flag field (1030)) that indicate whether to include information fields regarding the distribution state and state change time proposed in this disclosure. In this case, whether to include information regarding the distribution state and state change time may be indicated in the form of a flag. For example, the Distribution State Flag field (1010) may include a value of 1 bit, and if the field includes a value of 0, it may indicate that the Distribution State field does not exist. On the other hand, if the Distribution State Flag field (1010) includes a value of 1, it may indicate that the Distribution State field (1020), which includes information regarding the distribution state, exists prior to the padding field. For example, the Next State Time Flag field (1030) may contain a value of 1 bit, and if the field contains a value of 0, it may indicate that the Next State Time Flag field does not exist. On the other hand, if the Next State Time Flag field (1030) contains a value of 1, it may indicate that the Next State Time field (1040), which contains information regarding the distribution state prior to the padding field, exists. In the example described above, the meaning of each flag field value is merely an example, and it may also indicate that the field exists when it has a value of 0.

[0101] And when the Distribution State Flag field (1010) and the Next State Time Flag field (1030) respectively indicate that the Distribution State field (1020) and the Next State Time field (1040) exist, the configuration of each information field (1020, 1040) may be as follows. For example, the Distribution State field (1020) contains 1 octet, and the information indicated by the corresponding values ​​may be represented in relation to the distribution state of the current packet described in detail in FIG. 8. On the other hand, when the Distribution State Flag field (1010) indicates that the Distribution State field (1020) does not exist, the Distribution State field (1020) contains 0 octets. For example, depending on each value of the Distribution State field (1020), 0 = MM, 1 = MD, 2 = MS, 3 = SS, 4 = SD, 5 = SM, 6 = DD, 7 = DM, 8 = DS, and 9 to 255 = reserved values, respectively. Additionally, the Next State Time field (1040) contains 1 octet and can represent any one of the time values ​​between 0 and 255 ms. Meanwhile, if the Next State Time Flag field (1030) indicates that the Next State Time field (1040) does not exist, the Next State Time field (1040) contains 0 octets.

[0102] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields assigned meaningful values, the order of the fields, the number of octets or bits, and whether fields are included within the format, etc., as illustrated in FIG. 10 are merely examples and may be changed differently from the illustrated and described embodiments. In addition, the new frame field proposed in FIG. 10 is exemplified by the case where PDU type=15, but is not limited thereto and may have any one of the reserved values ​​from 3 to 14.

[0103] Meanwhile, the packet distribution status of the CU described in FIGS. 9 and FIGS. 10 above may be transmitted periodically, or transmitted non-periodically according to a request from the eNB / gNB-DU or according to the judgment of the CU.

[0104] FIG. 11 illustrates methods for determining a target buffer amount in a wireless communication system according to various embodiments of the present disclosure.

[0105] Referring to FIG. 11, an eNB / gNB-DU that has received information regarding the packet distribution status from a CU according to the method of FIG. 9 and FIG. 10 described above can determine a target buffer amount based on the packet distribution status of the CU. The target buffer amount of the DRB (data radio bearer) related to downlink packets in the eNB / gNB-DU can be determined by considering the current or subsequent buffer status of the eNB / gNB-DU (e.g., including at least one of the maximum buffer size, average transmission rate, or target buffering time). And the target buffer amount can be changed based on the information regarding the packet distribution status received from the CU.

[0106] More specifically, the methods by which the eNB / gNB-DU changes the target buffer amount according to the packet distribution status of the CU may be as follows.

[0107] In a first embodiment, if an eNB / gNB-DU currently receiving downlink packets is receiving only through a single path (e.g., an MCG or SCG path) and is scheduled to continue doing so thereafter, the eNB / gNB-DU currently receiving downlink packets may maximize the target buffer amount to prevent buffer shortage.

[0108] In a second embodiment, if an eNB / gNB-DU currently receiving downlink packets is receiving them only through a single path (e.g., MCG or SCG path), but thereafter downlink packets are scheduled to be transmitted through another single path or all paths (e.g., MCG and SCG paths), the eNB / gNB-DU currently receiving downlink packets may minimize the target buffer amount to prevent an increase in reordering delay.

[0109] In a third embodiment, if the CU is only transmitting via another path and is not scheduled to transmit to an eNB / gNB-DU that is not currently receiving downlink packets, the eNB / gNB-DU that is not currently receiving downlink packets can minimize the target buffer amount.

[0110] In a fourth embodiment, if the CU is transmitting only through other paths and is subsequently scheduled to transmit through all paths (e.g., MCG and SCG paths), the eNB / gNB-DU that is not currently receiving downlink packets can minimize the target buffer amount to prevent an increase in reordering delay.

[0111] In the fifth embodiment, if the CU is only transmitting through other paths but is scheduled to transmit only to an eNB / gNB-DU that is not currently receiving downlink packets, the eNB / gNB-DU that is not currently receiving downlink packets may maximize the target buffer amount to prevent buffer shortage.

[0112] In the sixth embodiment, when the CU is being transmitted to all paths (e.g., MCG and SCG paths), each eNB / gNB-DU can minimize the target buffer amount to prevent an increase in reorder delay.

[0113] Of course, the above-described embodiments are merely examples, and examples of methods for changing the target buffer amount of eNB / gNB-DU according to the packet distribution status of the CU can be shown as in Table 1 below.

[0114]

[0115] Referring again to FIG. 11, based on the embodiments described above and Table 1, the method for setting the target buffer amount of MCG eNB / gNB-DU and SCG eNB / gNB-DU according to the current distribution state of the CU and the distribution state after the state change time may be as follows.

[0116] In (a), if the current CU is transmitting downlink packets only on a single path (e.g., SCG path) and is expected to continue doing so, the MCG eNB / gNB-DU can minimize the target buffer amount. On the other hand, the SCG eNB / gNB-DU can maximize the target buffer amount to prevent buffer shortage.

[0117] In (b), if the CU is currently transmitting downlink packets only through a single path (e.g., MCG path) but plans to transmit them through another single path (e.g., SCG path) or all paths (e.g., MCG and SCG paths) later, the MCG eNB / gNB-DU and SCG eNB / gNB-DU can minimize the target buffer amount to prevent an increase in reordering delay.

[0118] In (c), if the current CU is transmitting downlink packets only on a single path (e.g., SCG path) but plans to transmit them later on another single path (e.g., MCG path) or all paths (e.g., MCG and SCG paths), the MCG eNB / gNB-DU can maximize the target buffer amount to prevent buffer shortage. On the other hand, the SCG eNB / gNB-DU can minimize the target buffer amount to prevent an increase in reordering delay.

[0119] (d) In case CU is being transmitted to all paths (e.g., MCG and SCG paths), MCG eNB / gNB-DU and SCG eNB / gNB-DU can minimize the target buffer amount to prevent an increase in reorder delay.

[0120] Meanwhile, according to the embodiments described above, the method for determining the target buffer amount of the eNB / gNB-DU can be expressed as follows according to Equation 1.

[0121] [Mathematical Formula 1]

[0122] Target buffer size = max[max buffer size, average transfer rate × target buffering time]

[0123] In Equation 1, the target buffer amount can be determined as the larger of the maximum size of the eNB / gNB-DU buffer and the product of the average transfer rate and the target buffering time. Of course, Equation 1 is merely an exemplary method for determining the target buffer amount and is not limited thereto.

[0124] In addition, according to the embodiments described above, a method for changing the target buffer amount based on information regarding the packet distribution status received by the eNB / gNB-DU from the CU can be expressed as follows according to Equations 2 and 3.

[0125] [Mathematical Formula 2]

[0126] Maximize Target Buffer Size = max[Max Buffer Size, Average Transfer Rate × Target Buffering Time (110ms)]

[0127] Equation 2 may represent a method for maximizing the target buffer amount, and the maximum (or maximum value) of the target buffer amount may be determined by the larger of the maximum size of the eNB / gNB-DU buffer and the product of the average transfer rate and the target buffering time of 110ms. Of course, Equation 2 is merely an exemplary method for determining the maximum value of the target buffer amount and is not limited thereto. Furthermore, the target buffering time of 110ms in Equation 2 is merely an example, and it goes without saying that other values ​​may be used depending on the case.

[0128] [Mathematical Formula 3]

[0129] Minimize target buffer size = max[max buffer size, average transfer rate × target buffering time (20ms)]

[0130] Equation 3 may represent a method for minimizing the target buffer amount, and the minimization (or minimum value) of the target buffer amount may be determined by the larger of the maximum size of the eNB / gNB-DU buffer and the product of the average transfer rate and the target buffering time of 20ms. Of course, Equation 3 is merely an exemplary method for determining the minimum value of the target buffer amount and is not limited thereto. Furthermore, the target buffering time of 20ms in Equation 3 is merely an example, and it goes without saying that other values ​​may be used depending on the case.

[0131] FIG. 12 illustrates a method for reporting a current buffer amount and a target buffer amount to a CU in a wireless communication system according to various embodiments of the present disclosure.

[0132] Referring to FIG. 12, a method is described for transmitting information regarding the buffer amount of an eNB / gNB-DU (e.g., an eNB / gNB-DU of an MCG or an eNB / gNB-DU of an SCG) to a CU in step 730 of FIG. 7 described above (e.g., including information regarding the current buffer amount and the target buffer amount). Accordingly, descriptions that overlap with FIG. 7 may be omitted.

[0133] The eNB / gNB-DU can transmit information regarding the buffer amount of the eNB / gNB-DU to the CU using the DL data delivery status format (1210) defined in 3GPP TS38.425 or a similar format (1220). In one embodiment, 1210 may be a method using a DL data delivery status format with PDU type=1 among the types of frame formats for the NR User Plane Protocol. In one embodiment, 1220 may be a method using a new frame format having a value of PDU type=3 to 15. In this case, the newly defined frame format for transmitting information regarding the current buffer amount and target buffer amount of the eNB / gNB-DU may have a different PDU type value from the new frame format for transmitting information regarding the current distribution status of the CU described in FIG. 10 above. A more specific configuration of the transmission format is described below in FIG. 14a to 14h.

[0134] Meanwhile, the specific configuration of the buffer amount information of the eNB / gNB-DU transmitted by the eNB / gNB-DU to the CU is as follows. For example, the buffer amount information may include at least one of the eNB / gNB-DU's current buffer amount, target buffer amount, or target buffering time. In this case, the current buffer amount may represent the total size of downlink packets currently accumulated in the eNB / gNB-DU's buffer. The target buffer amount may represent the total size of downlink packets within the buffer targeted by the eNB / gNB-DU. The target buffering time may represent the estimated time required for the downlink packets within the buffer targeted by the eNB / gNB-DU to be exhausted. Additionally, as described above, the buffer amount information may be represented as the current corresponding value or as a change amount (Δ, delta) compared to previously transmitted values. For example, the current buffer amount (delta) may represent the change amount compared to the previously transmitted current buffer amount value. The target buffer amount (delta) may represent the change amount compared to the previously transmitted target buffer amount value. The target buffering time (delta) may represent the amount of change relative to the previously transmitted target buffering time value. The buffer amount information of the eNB / gNB-DU may include the current value and / or the amount of change for each of the included information (including at least one of the current buffer amount, target buffer amount, or target buffering time).

[0135] FIG. 13 illustrates an example of reporting buffer amount-related information in a wireless communication system according to various embodiments of the present disclosure.

[0136] Referring to FIG. 13, the current buffer amount, target buffer amount, or target buffering time can each have an index set for arbitrary intervals. Accordingly, the eNB / gNB-DU may transmit each piece of information as a current value and / or change amount value as described above, or transmit an index corresponding to the interval containing the current value and / or change amount value to the CU. Since the ranges of current values ​​and the corresponding indices in FIG. 13 are merely examples, the configuration of FIG. 13 is not limited thereto.

[0137] FIG. 14a illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0138] Referring to FIG. 14a, a method is described in which an eNB / gNB-DU transmits buffer amount information to a CU using the method described in FIG. 12 (e.g., 1210: DL data delivery status format defined in 3GPP TS38.425). For example, buffer amount information may be transmitted based on the DL data delivery status format corresponding to PDU type=1 among the frame format types for the NR User Plane Protocol of 3GPP TS38.425. In this case, the DL data delivery status format may be a frame format used when the eNB / gNB-DU transmits the result of receiving downlink packets and the result of transmission to the wireless interface (e.g., the result of transmission to the terminal) to the gNB-CU.

[0139] More specifically, the DL data delivery status format may further include fields corresponding to 1410 to 1470. For example, one bit of the spare fields included in the header of the DL data delivery status format may be used as a field indicating whether buffer amount-related information proposed in this disclosure is included (e.g., Buffer Information Indication field (1410)). In this case, whether buffer amount-related information is included may be indicated in the form of a flag. For example, the Buffer Information Indication field (1410) may include a value of 1 bit, and if the field includes a value of 0, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), Target Buffering Time field (1440), Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) do not exist. On the other hand, if the Buffer Information Indication field (1410) contains a value of 1, it may indicate that fields containing buffer amount information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), Target Buffering Time field (1440), Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) exist prior to the padding field.In the example described above, the meaning of each flag field value is merely an example, and a value of 0 may indicate that the field exists.

[0140] And if the Buffer Information Indication field (1410) indicates that there are fields containing information related to the buffer amount, the composition of each information field (1420 to 1470) may be as follows. For example, the Current Buffer Size field (1420) may contain 4 octets and may indicate the total size of downlink packets currently accumulated in the eNB / gNB-DU buffer (e.g., 0 to 2^32-1 bytes). The Target Buffer Size field (1430) may contain 4 octets and may indicate the total size of downlink packets within the buffer targeted by the eNB / gNB-DU (e.g., 0 to 2^32-1 bytes). The Target Buffering Time field (1440) may contain 2 octets and may indicate the average transmission speed (Target buffer size / avg throughput) for the target buffer size (e.g., 0 to 65,535 ms). The Current Buffer Size (delta) field (1450) contains 4 octets and can indicate a change amount (e.g., 0 to 2^32-1 bytes) relative to the previously transmitted current buffer size value. The Target Buffer Size (delta) field (1460) contains 4 octets and can indicate a change amount (e.g., 0 to 2^32-1 bytes) relative to the previously transmitted target buffer size value. The Target Buffering Time (delta) field (1470) contains 2 octets and can indicate a change amount (e.g., 0 to 2^32-1 bytes) relative to the previously transmitted target buffering time value. Of course, if the Buffer Information Indication field (1410) indicates that there are no fields containing buffer amount information, the fields described above (1420 to 1470) contain 0 octets.

[0141] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14a are merely examples and may be changed differently from the illustrated and described embodiments.

[0142] FIG. 14b illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0143] Referring to FIG. 14b, a method is described in which an eNB / gNB-DU transmits buffer amount information to a CU via the method described in FIG. 12 (e.g., 1210: DL data delivery status format defined in 3GPP TS38.425). For example, buffer amount information may be transmitted based on the DL data delivery status format corresponding to PDU type=1 among the frame format types for the NR User Plane Protocol of 3GPP TS38.425. Meanwhile, FIG. 14b may relate to an embodiment in which the buffer amount information in the field configuration of FIG. 14a described above is configured to include only the current value. Additionally, the fields included in the DL data delivery status format of FIG. 14b may refer to the same fields as those having the same reference numbers in FIG. 14a described above. Therefore, descriptions that overlap with FIG. 14a may be omitted.

[0144] More specifically, the DL data delivery status format may further include fields corresponding to 1410 to 1440. For example, one bit of the spare fields included in the header of the DL data delivery status format may be used as a field indicating whether buffer amount-related information proposed in this disclosure is included (e.g., Buffer Information Indication field (1410)). For example, the Buffer Information Indication field (1410) may include a value of 1 bit, and if the field includes a value of 0, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), and Target Buffering Time field (1440)) do not exist. On the other hand, if the Buffer Information Indication field (1410) contains a value of 1, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), and Target Buffering Time field (1440)) exist prior to the padding field. In the example described above, the meaning of each flag field value is merely one example, and it may also indicate that the corresponding field exists when it has a value of 0. Therefore, when the Buffer Information Indication field (1410) indicates that fields containing buffer amount-related information exist, the DL data delivery status format may further include the Current Buffer Size field (1420), Target Buffer Size field (1430), and Target Buffering Time field (1440).

[0145] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14b are merely examples and may be changed differently from the illustrated and described embodiments.

[0146] FIG. 14c illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0147] Referring to FIG. 14c, a method is described in which an eNB / gNB-DU transmits buffer amount information to a CU via the method described in FIG. 12 (e.g., 1210: DL data delivery status format defined in 3GPP TS38.425). For example, buffer amount information may be transmitted based on the DL data delivery status format corresponding to PDU type=1 among the frame format types for the NR User Plane Protocol of 3GPP TS38.425. Meanwhile, FIG. 14c may relate to an embodiment in which the buffer amount information in the field configuration of FIG. 14a described above is configured to include only the change amount value. Additionally, the fields included in the DL data delivery status format of FIG. 14c may refer to the same fields as the fields having the same reference numbers in FIG. 14a described above. Therefore, descriptions that overlap with FIG. 14a may be omitted.

[0148] More specifically, the DL data delivery status format may further include fields corresponding to 1410 and 1450 through 1470. For example, one bit of the spare fields included in the header of the DL data delivery status format may be used as a field indicating whether buffer amount-related information proposed in this disclosure is included (e.g., Buffer Information Indication field (1410)). For example, the Buffer Information Indication field (1410) may include a value of 1 bit, and if the field includes a value of 0, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) do not exist. On the other hand, if the Buffer Information Indication field (1410) contains a value of 1, it may indicate that fields containing buffer amount information (e.g., Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) exist prior to the padding field. In the example described above, the meaning of each flag field value is merely an example, and it may also indicate that the field exists when it has a value of 0.Accordingly, if the Buffer Information Indication field (1410) indicates that there are fields containing information related to the buffer amount, the DL data delivery status format may further include a Current Buffer Size (delta) field (1450), a Target Buffer Size (delta) field (1460), and a Target Buffering Time (delta) field (1470).

[0149] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14c are merely examples and may be changed differently from the illustrated and described embodiments.

[0150] FIG. 14d illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0151] Referring to FIG. 14d, a method is described in which an eNB / gNB-DU transmits buffer amount information to a CU via the method described in FIG. 12 (e.g., 1210: DL data delivery status format defined in 3GPP TS38.425). For example, buffer amount information may be transmitted based on the DL data delivery status format corresponding to PDU type=1 among the frame format types for the NR User Plane Protocol of 3GPP TS38.425. In this case, the change amount information included in the DL data delivery status format may be indicated by an index rather than an explicit value. Through this, the size of each field may be reduced. For example, the Current Buffer Size field (1420), Target Buffer Size field (1430), Target Buffering Time field (1440), Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470) can each be represented as 1 byte. Meanwhile, since FIG. 14d expresses buffer amount information in the field configuration of FIG. 14a described above as an index rather than an explicit value, the types of fields included in the DL data delivery status format and the meanings represented by each field can be applied identically in FIG. 14d, except that the size of each added field is different. Therefore, the fields included in the DL data delivery status format of FIG. 14d may refer to the same fields as the fields having the same reference number in FIG. 14a described above. Of course, as described above, there may be differences due to the fact that the value of each field is expressed as an index rather than an explicit value. Therefore, descriptions that overlap with Fig. 14a may be omitted.

[0152] More specifically, the DL data delivery status format may further include fields corresponding to 1410 to 1470. For example, one bit of the spare fields included in the header of the DL data delivery status format may be used as a field indicating whether buffer amount-related information proposed in this disclosure is included (e.g., Buffer Information Indication field (1410)). For example, the Buffer Information Indication field (1410) may include a value of 1 bit, and if the field includes a value of 0, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), Target Buffering Time field (1440), Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) do not exist. On the other hand, if the Buffer Information Indication field (1410) contains a value of 1, it may indicate that fields containing buffer amount information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), Target Buffering Time field (1440), Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) exist prior to the padding field. In the example described above, the meaning of each flag field value is merely an example, and it may also indicate that the field exists when it has a value of 0.

[0153] If the Buffer Information Indication field (1410) indicates that there are fields containing information related to the buffer amount, the configuration of each information field (1420 to 1470) may be as follows. For example, the Current Buffer Size field (1420) may contain 1 octet and represent an index corresponding to the total size of downlink packets currently accumulated in the eNB / gNB-DU buffer. The Target Buffer Size field (1430) may contain 1 octet and represent an index corresponding to the total size of downlink packets within the buffer targeted by the eNB / gNB-DU. The Target Buffering Time field (1440) may contain 1 octet and represent an index corresponding to the average transmission speed for the target buffer size. The Current Buffer Size (delta) field (1450) may contain 1 octet and represent an index corresponding to the change amount relative to the previously transmitted current buffer size value. The Target Buffer Size (delta) field (1460) contains 1 octet and may indicate an index corresponding to the amount of change relative to the previously transmitted target buffer size value. The Target Buffering Time (delta) field (1470) contains 1 octet and may indicate an index corresponding to the amount of change relative to the previously transmitted target buffering time value. Of course, if the Buffer Information Indication field (1410) indicates that there are no fields containing buffer amount information, the fields described above (1420 to 1470) contain 0 octets.

[0154] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14d are merely examples and may be changed differently from the illustrated and described embodiments.

[0155] FIG. 14e illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0156] Referring to FIG. 14e, a method is described in which an eNB / gNB-DU transmits buffer amount information to a CU via the method described in FIG. 12 (e.g., 1210: DL data delivery status format defined in 3GPP TS38.425). For example, buffer amount information may be transmitted based on the DL data delivery status format corresponding to PDU type=1 among the frame format types for the NR User Plane Protocol of 3GPP TS38.425. Meanwhile, FIG. 14e may relate to an embodiment in which the buffer amount information in the field configuration of FIG. 14d described above is configured to include only the current value. Additionally, the fields included in the DL data delivery status format of FIG. 14e may refer to the same fields as the fields having the same reference numbers in FIG. 14d described above. Therefore, descriptions that overlap with FIG. 14d may be omitted.

[0157] More specifically, the DL data delivery status format may further include fields corresponding to 1410 to 1440. For example, one bit of the spare fields included in the header of the DL data delivery status format may be used as a field indicating whether buffer amount-related information proposed in this disclosure is included (e.g., Buffer Information Indication field (1410)). For example, the Buffer Information Indication field (1410) may include a value of 1 bit, and if the field includes a value of 0, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), and Target Buffering Time field (1440)) do not exist. On the other hand, if the Buffer Information Indication field (1410) contains a value of 1, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), and Target Buffering Time field (1440)) exist prior to the padding field. In the example described above, the meaning of each flag field value is merely one example, and it may also indicate that the corresponding field exists when it has a value of 0. Therefore, when the Buffer Information Indication field (1410) indicates that fields containing buffer amount-related information exist, the DL data delivery status format may further include the Current Buffer Size field (1420), Target Buffer Size field (1430), and Target Buffering Time field (1440).

[0158] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14e are merely examples and may be changed differently from the illustrated and described embodiments.

[0159] FIG. 14f illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0160] Referring to FIG. 14f, a method is described in which an eNB / gNB-DU transmits buffer amount information to a CU via the method described in FIG. 12 (e.g., 1210: DL data delivery status format defined in 3GPP TS38.425). For example, buffer amount information may be transmitted based on the DL data delivery status format corresponding to PDU type=1 among the frame format types for the NR User Plane Protocol of 3GPP TS38.425. Meanwhile, FIG. 14f may relate to an embodiment in which the buffer amount information in the field configuration of FIG. 14d described above is configured to include only the change amount value. Additionally, the fields included in the DL data delivery status format of FIG. 14f may refer to the same fields as the fields having the same reference numbers in FIG. 14d described above. Therefore, descriptions that overlap with FIG. 14d may be omitted.

[0161] More specifically, the DL data delivery status format may further include fields corresponding to 1410 and 1450 through 1470. For example, one bit of the spare fields included in the header of the DL data delivery status format may be used as a field indicating whether buffer amount-related information proposed in this disclosure is included (e.g., Buffer Information Indication field (1410)). For example, the Buffer Information Indication field (1410) may include a value of 1 bit, and if the field includes a value of 0, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) do not exist. On the other hand, if the Buffer Information Indication field (1410) contains a value of 1, it may indicate that fields containing buffer amount information (e.g., Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) exist prior to the padding field. In the example described above, the meaning of each flag field value is merely an example, and it may also indicate that the field exists when it has a value of 0.Accordingly, if the Buffer Information Indication field (1410) indicates that there are fields containing information related to the buffer amount, the DL data delivery status format may further include a Current Buffer Size (delta) field (1450), a Target Buffer Size (delta) field (1460), and a Target Buffering Time (delta) field (1470).

[0162] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14f are merely examples and may be changed differently from the illustrated and described embodiments.

[0163] FIG. 14g illustrates another example of a field configuration including a packet distribution state in a wireless communication system according to various embodiments of the present disclosure.

[0164] Referring to FIG. 14g, a method is described in which an eNB / gNB-DU transmits buffer amount information to a CU via the method described in FIG. 12 (e.g., 1220: a newly defined frame format). For example, any one of the reserved PDU type values ​​(e.g., 3 to 15) may be used in addition to the frame format types for the NR User Plane Protocol of 3GPP TS38.425. Accordingly, in addition to the configuration of the frame format, the values ​​of the fields for transmitting buffer amount information proposed in this disclosure (e.g., fields having the same reference numbers 1420 to 1470) and the meanings represented by those values ​​may be applied in the same or similar manner as described in FIG. 14a. Therefore, descriptions that overlap with FIG. 14a may be omitted.

[0165] More specifically, the DL data delivery status format may further include fields corresponding to 1410 to 1416 indicating whether it contains buffer amount information and fields corresponding to 1420 to 1470 containing buffer amount information. For example, the header of the DL data delivery status format may include fields to indicate whether a spare field (1410) and fields containing buffer amount information (e.g., 1420 to 1470) exist (e.g., Current Buffer Size Indication field (1420), Target Buffer Size Indication field (1430), Target Buffering Time Indication field (1440), Current Buffer Size (delta) Indication field (1450), Target Buffer Size (delta) Indication field (1460), and Target Buffering Time (delta) Indication field (1470)).

[0166] For example, if the fields corresponding to 1411 to 1416 each contain a value of 0, it may indicate that the fields containing buffer amount information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), Target Buffering Time field (1440), Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) do not exist. On the other hand, if the fields corresponding to 1411 to 1416 each contain a value of 1, it may indicate that fields containing buffer amount-related information (e.g., Current Buffer Size field (1420), Target Buffer Size field (1430), Target Buffering Time field (1440), Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470)) exist prior to the padding field. In the example described above, the meaning of each flag field value is merely an example, and it may also indicate that the corresponding field exists when it has a value of 0.

[0167] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14g are merely examples and may be changed differently from the illustrated and described embodiments.

[0168] FIG. 14h illustrates an example of a field configuration including buffer amount related information in a wireless communication system according to various embodiments of the present disclosure.

[0169] Referring to FIG. 14h, the DL data delivery status format may further include fields corresponding to 1410 to 1416 indicating whether it contains buffer amount information, and fields corresponding to 1420 to 1470 containing buffer amount information. In this case, the change amount information included in the DL data delivery status format may be indicated by an index rather than an explicit value, as illustrated in FIG. 14g. Through this, the size of each field may be reduced. For example, the Current Buffer Size field (1420), Target Buffer Size field (1430), Target Buffering Time field (1440), Current Buffer Size (delta) field (1450), Target Buffer Size (delta) field (1460), and Target Buffering Time (delta) field (1470) may each be represented as 1 byte. Meanwhile, since FIG. 14h expresses buffer amount information in the field configuration of FIG. 14g described above as an index rather than an explicit value, the types of fields included in the DL data delivery status format and the meanings represented by each field can be applied identically in FIG. 14h, differing only in the size of each added field. Therefore, the fields included in the DL data delivery status format of FIG. 14h may refer to the same fields as those having the same reference numbers in FIG. 14g described above. Of course, as mentioned above, there may be differences due to the values ​​of each field being expressed as indices rather than explicit values. Therefore, explanations that overlap with FIG. 14g may be omitted.

[0170] When fields (e.g., 1411 to 1416) for indicating whether fields containing buffer amount information (e.g., 1420 to 1470) exist indicate that fields containing buffer amount information exist, the configuration of each information field (1420 to 1470) may be as follows. For example, the Current Buffer Size field (1420) may contain 1 octet and may indicate an index corresponding to the total size of downlink packets currently accumulated in the eNB / gNB-DU buffer. The Target Buffer Size field (1430) may contain 1 octet and may indicate an index corresponding to the total size of downlink packets within the buffer targeted by the eNB / gNB-DU. The Target Buffering Time field (1440) may contain 1 octet and may indicate an index corresponding to the average transmission speed for the target buffer size. The Current Buffer Size (delta) field (1450) contains 1 octet and may indicate an index corresponding to a change amount relative to the previously transmitted current buffer size value. The Target Buffer Size (delta) field (1460) contains 1 octet and may indicate an index corresponding to a change amount relative to the previously transmitted target buffer size value. The Target Buffering Time (delta) field (1470) contains 1 octet and may indicate an index corresponding to a change amount relative to the previously transmitted target buffering time value. Of course, if the fields (e.g., 1411 to 1416) for indicating whether fields containing buffer amount information (e.g., 1420 to 1470) exist indicate that fields containing buffer amount information do not exist, the above-described information fields (1420 to 1470) contain 0 octets.

[0171] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14h are merely examples and may be changed differently from the illustrated and described embodiments.

[0172] FIGS. 14g and 14h relate to a method of transmitting buffer amount information to a CU through a newly defined frame format (e.g., 1220) in FIG. 12, describing a method of reporting each value included in the buffer amount information as an explicit value and a method of reporting as an index corresponding to each value. However, FIGS. 14g and 14h are merely examples of a method of reporting buffer amount information using a newly defined frame format and are not limited thereto. Accordingly, an embodiment including only the current value or the change amount value may be applied, as described in FIGS. 14b, 14c, 14e, and 14f, respectively.

[0173] In addition, the reporting of information regarding the buffer amount of the eNB / gNB-DU according to the above-described FIGS. 12, 13 and FIGS. 14a to 14h may be performed periodically, or transmitted non-periodically at the request of the CU or at the judgment of the eNB / gNB-DU.

[0174] Meanwhile, FIGS. 15a to 15c below illustrate operations for performing efficient packet distribution between a CU, an MCG eNB / gNB-DU, and an SCG eNB / gNB-DU based on the embodiments of the present disclosure described above. Accordingly, the operations described in FIGS. 15a to 15c are merely examples based on the embodiments described above and may be applied differently based on the embodiments described above.

[0175] FIG. 15a illustrates the sequence of packet distribution operations based on wireless communication buffer amount reporting according to various embodiments of the present disclosure.

[0176] Referring to Fig. 15a, an example of a cycle is described in which, when the packet distribution state of the CU is maintained, the eNB / gNB-DU determines the target buffer amount and reports it to the CU.

[0177] In step 1501, the CU may transmit information regarding the packet distribution status to the SCG eNB / gNB-DU. At this time, the information regarding the packet distribution status may be transmitted via the DL user data format corresponding to PDU type=0. For example, the information regarding the packet distribution status may include information indicating that the current distribution status is a single path to the SCG eNB / gNB-DU and that the distribution status after the state change time (e.g., 10ms) will also be performed via the same single path (e.g., Distribution State=SS, and Next State Time=10ms).

[0178] In step 1502, the SCG eNB / gNB-DU can determine its target buffer amount based on information regarding the packet distribution status received from the CU. For example, the SCG eNB / gNB-DU can identify, based on the information regarding the packet distribution status from the CU, that packets will continue to be transmitted via a single path to the SCG eNB / gNB-DU even after the state change time. Therefore, the SCG eNB / gNB-DU can set the target buffer amount to the maximum. As an example, the maximum determined target buffer amount can be determined as 13.1 MB (megabit), which is the average transmission speed of 1 Gbps × the target buffering time of 110 ms, according to the above-described Equation 2.

[0179] In step 1503, the SCG eNB / gNB-DU can transmit buffer amount information to the CU. At this time, the buffer amount information can be transmitted via the DL data delivery status format corresponding to PDU type=1. For example, the buffer amount information may include the current buffer amount (e.g., 4MB), the target buffer amount (e.g., 13.1MB), and the target buffering time (e.g., 110ms).

[0180] FIG. 15b illustrates the sequence of packet distribution operations based on buffer amount reporting in a wireless communication system according to various embodiments of the present disclosure.

[0181] Referring to Fig. 15b, an example of a cycle is described in which, when the packet distribution state of the CU changes, the eNB / gNB-DU determines the target buffer amount and reports it to the CU.

[0182] In step 1504, the CU may transmit information regarding the packet distribution status to the SCG eNB / gNB-DU. In this case, the information regarding the packet distribution status may be transmitted via the DL user data format corresponding to PDU type=0. Additionally, the CU may inform the SCG eNB / gNB-DU that after the state change time, the transmission path will switch from single-path transmission to dual-path transmission to the SCG eNB / gNB-DU. For example, the information regarding the packet distribution status may include information indicating that the current distribution state is single-path to the SCG eNB / gNB-DU and that the distribution state will change to dual-path transmission after the state change time (e.g., 110ms) (e.g., Distribution State=SD, Next State Time=110ms).

[0183] In step 1505, the SCG eNB / gNB-DU can determine its target buffer amount based on information regarding the packet distribution status received from the CU. For example, the SCG eNB / gNB-DU can identify, based on the information regarding the packet distribution status from the CU, that packets will also be transmitted via the path to the MCG eNB / gNB-DU after the state change time. Therefore, the SCG eNB / gNB-DU can set the target buffer amount to a minimum. As an example, the minimum determined target buffer amount can be determined as 2.4 MB, which is the average transmission speed of 1 Gbps × the target buffering time of 20 ms, according to the above-described Equation 3.

[0184] In step 1506, the SCG eNB / gNB-DU can transmit buffer amount information to the CU. At this time, the buffer amount information can be transmitted via the DL data delivery status format corresponding to PDU type=1. For example, the buffer amount information may include the current buffer amount (e.g., 4MB), the target buffer amount (e.g., 2.4MB), and the target buffering time (e.g., 20ms).

[0185] In step 1507, the CU can identify whether to change the packet transmission path based on buffer amount information received from the SCG eNB / gNB-DU. For example, the CU can maintain single path transmission to the SCG eNB / gNB-DU because the target buffering time of the SCG eNB / gNB-DU is 20ms, but the current buffer amount (4MB) exceeds the target buffer amount (2.4MB).

[0186] FIG. 15c illustrates the sequence of packet distribution operations based on buffer amount reporting in a wireless communication system according to various embodiments of the present disclosure.

[0187] Referring to Fig. 15c, an example of a cycle in which the eNB / gNB-DU changes the packet transmission path according to the current buffer state and the packet distribution state of the changed CU is described.

[0188] In step 1508, while the packet transmission path to the SCG eNB / gNB-DU is maintained as a single path after step 1507 of FIG. 15b described above, the SCG eNB / gNB-DU may transmit buffer amount-related information to the CU to transmit the current buffer amount. For example, buffer amount-related information including the changed current buffer amount (e.g., 2.4 MB), the target buffer amount (e.g., 2.4 MB), and the target buffering time (e.g., 20 ms) may be transmitted to the CU. However, step 1508 may be omitted.

[0189] In step 1509, the CU can transmit packets to all paths according to the packet distribution status reported to the SCG eNB / gNB-DU in step 1504 of FIG. 15b described above. For example, the CU can identify from the buffer amount information received from the SCG eNB / gNB-DU in step 1508 that the current buffer amount of the SCG eNB / gNB-DU has decreased to the target buffer amount. Therefore, the CU can determine that no increase in reorder delay will occur and, accordingly, transmit packets to all paths. Additionally, the CU can transmit information regarding the changed packet distribution status (e.g., Distribution State=DD) to the MCG eNB / gNB-DU and SCG eNB / gNB-DU currently receiving packets. Information regarding the packet distribution status can be transmitted via the DL user data format corresponding to PDU type=0. However, even if step 1508 is omitted, CU may perform step 1509 when the change state time of step 1504 of FIG. 15b has elapsed.

[0190] In step 1510, the MCG eNB / gNB-DU can determine its target buffer amount based on the packet distribution status (1509) from the CU. For example, the MCG eNB / gNB-DU can identify, based on information regarding the packet distribution status of the CU, that both the current packet distribution status and the distribution status after the state change time are transmissions to all paths. Accordingly, the MCG eNB / gNB-DU can set the target buffer amount to a minimum. As an example, the minimum determined target buffer amount can be determined as 0.24 MB, which is the average transmission speed of 100 Mbps × target buffering time of 20 ms, according to the above-described Equation 3.

[0191] Meanwhile, the series of operations according to FIGS. 15a to 15c described above may be examples of application according to embodiments described in FIGS. 7 to 13 and FIGS. 14a to 14h. Accordingly, at least some of the operations of the SCG eNB / gNB-DU among the operations described above may be performed by the MCG eNB / gNB-DU, and vice versa.

[0192] FIG. 16 illustrates the operation of a DU for packet distribution based on buffer amount reporting in a wireless communication system according to embodiments of the present disclosure.

[0193] Referring to FIG. 16, the operation of a CU (e.g., gNB-CU) of a DU (e.g., referring to an MCG eNB / gNB-DU or an SCG eNB / gNB-DU) proposed in the present disclosure is illustrated, and some or all of the various embodiments related to the packet distribution operation described above may be applied to FIG. 16 in the same or similar manner.

[0194] In step 1610, the DU may receive first information from the CU. At this time, the first information may include information regarding the packet distribution status and may be transmitted via a DL user data format corresponding to PDU type=0 or a new frame format having any one of PDU type=3 to 15. At this time, the information regarding the packet distribution status may include information regarding the current distribution status and the distribution status after the state change time.

[0195] In step 1620, the DU can determine its target buffer amount based on the first information received from the CU. For example, the DU can determine the target buffer amount to be maximum or minimum by considering the packet transmission path that will change after the state change time according to the information regarding the packet distribution status of the CU. For example, if the packet transmission amount after the state change time decreases from the current packet transmission amount to the DU, the DU can determine the target buffer amount to be minimum. For another example, if the packet transmission amount after the state change time increases from the current packet transmission amount to the DU, the DU can determine the target buffer amount to be maximum.

[0196] In step 1630, the DU may transmit second information to the CU. At this time, the second information may include buffer amount information and may be transmitted via a DL data delivery status format corresponding to PDU type=1 or a new frame format having any one of PDU type=3 to 15. However, if a new frame format is used in steps 1610 and 1630, a format different from the PDU type used in step 1610 may be used. For example, the buffer amount information may include at least one of the DU's current buffer amount, target buffer amount, or target buffering time.

[0197] Meanwhile, although an embodiment of the operation of the DU has been described above based on the flowchart shown in FIG. 16, it is obvious that the operation of the DU may vary according to other embodiments described above.

[0198] FIG. 17 illustrates the operation of a CU for packet distribution based on buffer amount reporting in a wireless communication system according to embodiments of the present disclosure.

[0199] Referring to FIG. 17, the operation of a DU (e.g., referring to an MCG eNB / gNB-DU or an SCG eNB / gNB-DU) of a CU (e.g., gNB-CU) proposed in the present disclosure is illustrated, and some or all of the various embodiments related to the packet distribution operation described above may be applied in the same or similar way to FIG. 17.

[0200] In step 1710, the CU may transmit first information to the DU. At this time, the first information may include information regarding the packet distribution status and may be transmitted via a DL user data format corresponding to PDU type=0 or a new frame format having any one of PDU type=3 to 15. At this time, the information regarding the packet distribution status may include information regarding the current distribution status and the distribution status after the state change time.

[0201] In step 1720, the CU may receive second information from the DU. At this time, the second information may include buffer amount information and may be transmitted via a new frame format having a DL data delivery status format corresponding to PDU type=1 or a value of PDU type=3 to 15. However, if a new frame format is used in steps 1710 and 1720, a format different from the PDU type used in step 1710 may be used. For example, the buffer amount information may include at least one of the DU's current buffer amount, target buffer amount, or target buffering time. Additionally, the DU's target buffer amount and target buffering time may be determined based on the first information of step 1710.

[0202] In step 1730, the CU can determine the packet transmission amount for the DU based on the second information received from the DU. For example, if the current buffer amount level for the DU's target buffer amount is suitable for the packet distribution state scheduled for change and / or if the state change time included in the first information has elapsed, the CU can transmit downlink packets based on the transmission path changed to the DU.

[0203] Meanwhile, although an embodiment of the operation of the CU has been described above based on the flowchart illustrated in FIG. 17, it is obvious that the operation of the CU may vary according to other embodiments described above.

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

1. A method performed by a distributed unit (DU) of a base station in a wireless communication system, A step of receiving first information regarding the distribution status of a packet from the CU (central unit) of a base station; A step of determining a target buffer amount based on the first information above; and The method includes the step of transmitting second information to the CU, the second information comprising at least one of a size or change amount value for each of the current buffer amount of the DU and the target buffer amount, and A method in which the above DU includes a DU within an MCG (master cell group) or a DU within an SCG (secondary cell group).

2. In Paragraph 1, The first information above includes the current distribution status of the packet and the distribution status after any time, and A method in which the above first information is included in a first format having a value of 0 for the PDU (protocol data unit) type or a second format having a value of any one of 3 to 15.

3. In Paragraph 1, A method in which the target buffer amount is determined based on at least one of information regarding the buffer size, average transmission speed (throughput), or target buffering time of the DU.

4. In Paragraph 1, The above second information is included in a third format having a value where the PDU type is 1 or a fourth format having a value of any one of 3 to 15, and The above target buffer amount includes the size of the target buffer of the DU or a time value corresponding to the target buffer, and A method in which the current buffer amount and the target buffer amount are each indicated by an explicit value or by an index corresponding to the explicit value.

5. A method performed by a central unit (CU) of a base station in a wireless communication system, A step of transmitting first information regarding the distribution status of a packet to a DU (distributed unit) of a base station; A step of receiving second information from the DU, comprising at least one of a size or change amount value for each of the current buffer amount of the DU and the target buffer amount of the DU based on the first information; and The method includes the step of determining the packet transmission amount for the DU based on the second information using the DU, and A method in which the above DU includes a DU within an MCG (master cell group) or a DU within an SCG (secondary cell group).

6. In Paragraph 5, The first information above includes the current distribution status of the packet and the distribution status after any time, and A method in which the above first information is included in a first format having a value of 0 for the PDU (protocol data unit) type or a second format having a value of any one of 3 to 15.

7. In Paragraph 5, A method in which the target buffer amount is based on at least one of information regarding the buffer size, average transmission speed (throughput), or target buffering time of the DU.

8. In Paragraph 5, The above second information is included in a third format having a value where the PDU type is 1 or a fourth format having a value of any one of 3 to 15, and The above target buffer amount includes the size of the target buffer of the DU or a time value corresponding to the target buffer, and A method in which the current buffer amount and the target buffer amount are each indicated by an explicit value or by an index corresponding to the explicit value.

9. In a distributed unit (DU) of a base station in a wireless communication system, Transmitter / receiver; and It includes at least one control unit connected to the above-mentioned transmitting and receiving unit, and The above at least one control unit is: Receive first information regarding the distribution status of a packet from the CU (central unit) of the base station, and Determine the target buffer amount based on the above first information, and, The above CU is configured to transmit second information including at least one of a size or change amount value for each of the current buffer amount of the DU and the target buffer amount, and The above DU is a DU comprising a DU within an MCG (master cell group) or a DU within an SCG (secondary cell group).

10. In Paragraph 9, The first information above includes the current distribution status of the packet and the distribution status after any time, and The above first information is a DU included in a first format having a value of 0 for the PDU (protocol data unit) type or a second format having a value of any one of 3 to 15.

11. In Paragraph 9, The above target buffer amount is determined based on at least one of information regarding the buffer size, average transmission speed (throughput), or target buffering time of the DU.

12. In Paragraph 9, The above second information is included in a third format having a value where the PDU type is 1 or a fourth format having a value of any one of 3 to 15, and The above target buffer amount includes the size of the target buffer of the DU or a time value corresponding to the target buffer, and DU, wherein the current buffer amount and the target buffer amount are each indicated by an explicit value or by an index corresponding to the explicit value.

13. In a central unit (CU) of a base station in a wireless communication system, Transmitter / receiver; and It includes at least one control unit connected to the above-mentioned transmitting and receiving unit, and The above at least one control unit is: Transmits first information regarding the distribution status of a packet to the DU (distributed unit) of the base station, and Receiving second information from the DU, comprising at least one of a size or change amount value for each of the current buffer amount of the DU and the target buffer amount of the DU based on the first information, and The above DU is configured to determine the packet transmission amount for the DU based on the above second information, and The above DU comprises a DU within the MCG (master cell group) or a DU within the SCG (secondary cell group), CU.

14. In Paragraph 13, The first information above includes the current distribution status of the packet and the distribution status after any time, and The above first information is included in a first format having a value of 0 for the PDU (protocol data unit) type or a second format having a value of any one of 3 to 15, CU.

15. In Paragraph 13, The above target buffer amount is based on at least one of information regarding the buffer size, average throughput, or target buffering time of the DU, CU.

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