Apparatus and method for fronthaul transmission in wireless communication system

Abstract

The present invention provides a 4G (4thGeneration) or pre-LTE (LongTermEvolution) communication system for supporting higher data rates after the 5G (5thgeneration) communication system. 5G.SOLUTION: According to an embodiment, an operation method of a digitalunit (DU) of a base station in a wireless communication system includes identifying a designated path among a plurality of paths of a fronthaul interface connecting the DU and a radiounit (RU), generating a control message for a plurality of layers, and transmitting the control message to the RU through the designated path, wherein the control message includes scheduling information for the plurality of layers.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to wireless communication systems, and more particularly to an apparatus and method for fronthaul transmission in a wireless communication system. [Background technology]

[0002] 4G(4 th Since the commercialization of the 5G (5th generation) communication system, improved 5G (5G) technology has been developed to meet the increasing demand for wireless data traffic. th Efforts are being made to develop 5G (5th generation) or pre-5G communication systems. For this reason, 5G or pre-5G communication systems are also called beyond 4G network communication systems or post-LTE (Long Term Evolution) systems.

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

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

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

[0006] As transmission capacity increases in wireless communication systems, function splitting, which separates base stations functionally, is being applied. With function splitting, a base station can be separated into a digital unit (DU) and a radio unit (RU), and a fronthaul is defined for communication between the DU and RU, requiring transmission via the fronthaul. Summary of the Invention [Problem to be solved by the invention]

[0007] Based on the above discussion, the present disclosure provides an apparatus and method for transmitting control messages over a fronthaul interface.

[0008] The present disclosure also provides an apparatus and method for integrating information common to layers in a wireless communication system into one message and transmitting the information.

[0009] The present disclosure also provides an apparatus and method for reducing processing burden and memory requirements when operating digital units (DUs) and radio units (RUs) in a wireless communication system. [Means for solving the problem]

[0010] According to various embodiments of the present disclosure, a method for operating a DU (digital unit) of a base station in a wireless communication system includes the steps of: identifying a designated path from among a plurality of paths of a fronthaul interface connecting the DU and a radio unit (RU); generating a control message for a plurality of layers; and transmitting the control message to the RU via the designated path, wherein the control message may include scheduling information for the plurality of layers.

[0011] According to various embodiments of the present disclosure, a method for operating an RU (radio unit) of a base station in a wireless communication system may include the steps of receiving a control message for multiple layers from the DU through a path selected from multiple paths of a fronthaul interface connecting the RU and a DU (digital unit), identifying scheduling information for the multiple layers based on the control message, and performing communication based on the scheduling information.

[0012] According to various embodiments of the present disclosure, a DU (digital unit) device of a base station in a wireless communication system includes at least one processor, and the at least one processor identifies a designated path from among multiple paths of a fronthaul interface connecting the DU and a radio unit (RU), generates a control message for multiple layers, and controls the fronthaul interface to transmit the control message to the RU via the designated path, and the control message can include scheduling information for the multiple layers.

[0013] According to various embodiments of the present disclosure, a device of a radio unit (RU) of a base station in a wireless communication system includes at least one transceiver and at least one processor, and the at least one processor controls a fronthaul interface connecting the RU and a digital unit (DU) to receive control messages for multiple layers from the DU through a path selected from multiple paths of the fronthaul interface, identifies scheduling information for the multiple layers based on the control message, and controls the at least one transceiver to perform communication based on the scheduling information. [Effects of the Invention]

[0014] The apparatus and method according to various embodiments of the present disclosure can reduce the operational burden on a digital unit (DU) and a radio unit (RU) by transmitting information for each layer using one control message.

[0015] The effects obtained by the present disclosure are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those having ordinary skill in the technical field to which the present disclosure pertains from the following description. [Brief explanation of the drawings]

[0016] [Figure 1A] 1 illustrates a wireless communication system in accordance with various embodiments of the present disclosure. [Figure 1B] FIG. 10 illustrates an example of a fronthaul structure with functional separation of a base station according to various embodiments of the present disclosure. [Figure 2] 1 is a diagram illustrating the configuration of a digital unit (DU) in a wireless communication system according to various embodiments of the present disclosure. [Figure 3] FIG. 2 is a diagram illustrating the configuration of a radio unit (RU) in a wireless communication system according to various embodiments of the present disclosure. [Figure 4] FIG. 1 illustrates an example of function split in a wireless communication system according to various embodiments of the present disclosure. [Figure 5] 10A-10C illustrate example control messages for multi-layer scheduling according to various embodiments of the present disclosure. [Figure 6] 1 illustrates an example of a DU and a RU for multi-layer scheduling according to various embodiments of the present disclosure. [Figure 7] 1A-1C illustrate examples of control message structures according to various embodiments of the present disclosure. [Figure 8] 10A-10C illustrate examples of control message transmissions according to various embodiments of the present disclosure. [Figure 9] 10A-10C illustrate other examples of control message transmission according to various embodiments of the present disclosure. [Figure 10A] FIG. 10 illustrates an example of a control plane during multi-layer scheduling according to various embodiments of the present disclosure. [Figure 10B] FIG. 10 is a diagram illustrating another example of a control plane during multi-layer scheduling according to various embodiments of the present disclosure. [Figure 11] FIG. 10 illustrates a flow of DU operations for multi-layer scheduling according to various embodiments of the present disclosure. [Figure 12]FIG. 1 illustrates a flow of RU operations for multi-layer scheduling according to various embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] The terms used in this disclosure are merely used to describe specific embodiments and are not intended to limit the scope of other embodiments. A singular expression can include a plural expression unless the context clearly dictates otherwise. Terms used herein, including technical or scientific terms, can have the same meaning as commonly understood by a person of ordinary skill in the art described in this disclosure. Terms used in this disclosure that are defined in a general dictionary can be interpreted as meanings that are the same as or similar to their meanings in the context of the relevant art, and should not be interpreted as idealized or overly formal unless explicitly defined in this disclosure. In some cases, even terms defined in this disclosure cannot be interpreted to exclude embodiments of the present disclosure.

[0018] In the various embodiments of the present disclosure described below, a hardware approach is described as an example, but since the various embodiments of the present disclosure include techniques that use both hardware and software, the various embodiments of the present disclosure do not exclude a software-based approach.

[0019] The following explanations use the following terms to refer to signals (e.g., message, information, preamble, signal, signaling, sequence, stream), resources (e.g., symbol, slot, subframe, radio frame, subcarrier, resource element (RE), resource block (RB), bandwidth part (BWP), occasion), operation states (e.g., step, operation, procedure), data (e.g., user stream, IQ data, information, bit, symbol, codeword), channels, control information (e.g., downlink control information (DCI), medium access control element (CE), radio resource control (RRC) signaling), and network entities. The terms referring to a device (entity), the terms referring to components of a device, etc. are provided as examples for the convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0020] Furthermore, in this disclosure, expressions such as "more than" or "less than" may be used to determine whether a particular condition is satisfied or fulfilled, but this is merely a description to express an example and does not exclude descriptions such as "more than" or "less than." A condition described as "more than" can be replaced with "more than," a condition described as "less than," and a condition described as "more than and less than" can be replaced with "more than and less than."

[0021] Although the present disclosure describes various embodiments using terminology used in some communication standards (e.g., 3GPP (3rd Generation Partnership Project), xRAN (extensible radio access network), and O-RAN (open-radio access network)), this is merely an example for the purpose of explanation. Various embodiments of the present disclosure may be easily modified and applied to other communication systems.

[0022] 1A 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 some of the nodes that utilize wireless channels in the wireless communication system. Although Fig. 1 illustrates only one base station, other base stations identical to or similar to base station 110 may also be included.

[0023] The base station 110 is a network infrastructure that provides wireless connectivity to the terminals 120 and 130. The base station 110 has coverage defined in a predetermined geographical area based on the distance over which signals can be transmitted. In addition to a base station, the base station 110 may also be referred to as an "access point (AP)," "eNodeB (eNB)," "5th generation node (5G node)," "next generation nodeB (gNB)," "wireless point," "transmission / reception point (TRP)," or other terms with equivalent technical meanings.

[0024] Each of the terminals 120 and 130 is a device used by a user and communicates with the base station 110 via a wireless channel. A link from the base station 110 to the terminal 120 or 130 is called a downlink (DL), and a link from the terminal 120 or 130 to the base station 110 is called an uplink (UL). The terminals 120 and 130 can also communicate with each other via a wireless channel. In this case, a link between the terminals 120 and 130 (device-to-device link; D2D) is called a sidelink, and the sidelink may be used interchangeably with a PC5 interface. In some cases, at least one of the terminals 120 and 130 can operate without user involvement. That is, at least one of the terminals 120 and 130 may be a device that performs machine type communication (MTC) and may not be carried by the user. Each of terminal 120 and terminal 130 may be referred to as a terminal, a "user equipment (UE)," a "customer premises equipment (CPE)," a "mobile station," a "subscriber station," a "remote terminal," a "wireless terminal," an "electronic device," or a "user device," or other terms with equivalent technical meanings.

[0025] The base station 110, the terminal 120, and the terminal 130 can perform beamforming. The base station 110, the terminal 120, and the terminal 130 can transmit and receive radio signals not only in a relatively low frequency band (e.g., FR1 (frequency range 1) of NR) but also in a high frequency band (e.g., FR2 of NR, millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, 60 GHz)). In this case, the base station 110, the terminal 120, and the terminal 130 can perform beamforming to improve channel gain. Here, beamforming can include transmit beamforming and receive beamforming. That is, the base station 110, the terminal 120, and the terminal 130 can impart directivity to a transmit signal or a receive signal. To this end, the base station 110 and the terminals 120 and 130 perform beam search or beam management. Serving beams 112, 113, 121, and 131 can be selected through a frequency management procedure. After the serving beams 112, 113, 121, and 131 are selected, subsequent communications can be performed using resources that are quasi-colocated (QCL) with the resources transmitting the serving beams 112, 113, 121, and 131. Base stations / terminals according to various embodiments of the present disclosure can also communicate within a frequency range corresponding to FR1. The base station / terminal may or may not perform beamforming.

[0026] A first antenna port and a second antenna port may be said to be in a QCL relationship if the large-scale characteristics of the channel carrying symbols on a first antenna port can be inferred from the channel carrying symbols on a second antenna port. For example, the large-scale characteristics may include at least one of a delay spread, a Doppler spread, a Doppler shift, an average gain, an average delay, and a spatial receiver parameter.

[0027] In this disclosure, a beam refers to a spatial flow of a signal in a wireless channel and is formed by one or more antennas (or antenna elements). This beam-forming process may be referred to as beamforming. Beamforming may include analog beamforming and digital beamforming (e.g., precoding). Reference signals transmitted based on beamforming may include, for example, a demodulation-reference signal (DM-RS), a channel state information-reference signal (CSI-RS), a synchronization signal / physical broadcast channel (SS / PBCH), and a sounding reference signal (SRS). In addition, an IE such as a CSI-RS resource or an SRS-resource may be used as a configuration for each reference signal, and such a configuration may include information associated with the beam. The information associated with the beam may indicate whether the corresponding configuration (e.g., CSI-RS resource) uses the same spatial domain filter as other configurations (e.g., other CSI-RS resources in the same CSI-RS resource set) or a different spatial domain filter, or which reference signal it is quasi-colocated with, and if so, what type it is (e.g., QCL type A, B, C, D).

[0028] When the base station stores a beam profile during the RU initialization process, it may store a common beam vector and each precoding vector in the order of each layer. Treating each of all terminals (i.e., users) as one layer and applying a weight vector (precoder) common to each terminal may be understood as forming a common beam applied to all terminals. Applying a specific precoder for multi-layers to each terminal may be understood as single-user beamforming for each terminal. On the other hand, even if a precoder is applied to a terminal, signals transmitted to some terminals may be spatially distinguished from signals transmitted to other terminals. In this case, applying the corresponding precoder may be understood as multi-user beamforming.

[0029] In the past, in communication systems where the cell radius of base stations was relatively large, each base station was installed to include the functions of a digital processing unit (or DU (digital unit)) and an RF (radio frequency) processing unit (or RU (radio unit)). th As higher frequency bands are used in communication systems of the previous generation and / or later, the cell radius of base stations has become smaller, and the number of base stations required to cover a specific area has increased, resulting in increased installation costs for operators to install the increased number of base stations. To minimize base station installation costs, a structure has been proposed in which the DU and RU of a base station are separated, one or more RUs are connected to one DU via a wired network, and one or more RUs are geographically distributed to cover a specific area. Hereinafter, base station deployment structures and extension examples according to various embodiments of the present disclosure will be described with reference to FIG. 1B.

[0030] 1B illustrates an example of a fronthaul structure based on functional separation of a base station according to various embodiments of the present disclosure. Unlike a backhaul between a base station and a core network, a fronthaul refers to an entity between a wireless LAN and a base station.

[0031] 1B, the base station 110 can include a DU 160 and an RU 180. A fronthaul 170 between the DU 160 and the RU 180 is x For operation of the fronthaul 170, an interface such as an enhanced common public radio interface (eCPRI) or a radio over ethernet (ROE) may be used.

[0032] As communication technology develops, mobile data traffic increases, which significantly increases the bandwidth required for the fronthaul between digital units and radio units. In a deployment such as C-RAN (centralized / cloud radio access network), the DU performs functions related to PDCP (packet data convergence protocol), RLC (radio link control), MAC (media access control), and PHY (physical layer), while the RU may be implemented to perform functions related to the PHY layer in addition to RF (radio frequency) functions.

[0033] The DU 160 may be responsible for higher layer functions of a wireless network. For example, the DU 160 may perform functions of the MAC layer and part of the PHY layer. Here, the part of the PHY layer refers to functions performed at a higher step of the PHY layer, and may include, for example, channel encoding (or channel decoding), scrambling (or descrambling), modulation (or demodulation), and layer mapping (or layer demapping). According to one embodiment, if the DU 160 complies with the O-RAN standard, it may be referred to as an O-DU (O-RAN DU). The DU 160 may be substituted for a first network entity for a base station (e.g., gNB) in embodiments of the present disclosure, as needed.

[0034] The RU 180 may be responsible for lower layer functions of the wireless network. For example, the RU 180 may perform part of the PHY layer and RF functions. Here, part of the PHY layer refers to PHY layer functions that are performed at a relatively lower step than the DU 160, and may include, for example, IFFT (or FFT) transformation, CP insertion (CP removal), and digital beamforming. A specific example of such functional separation is described in detail in FIG. 4. The RU 180 may be referred to as an "access unit (AU)," "access point (AP)," "transmission / reception point (TRP)," "remote radio head (RRH)," "radio unit (RU)," or other terms with equivalent technical meanings. According to one embodiment, if the RU 180 complies with the O-RAN standard, it may be referred to as an O-RU (O-RAN RU). The RU 180 may be substituted for a second network entity for a base station (e.g., gNB) in the embodiments of the present disclosure, as needed.

[0035] Although FIG. 1B illustrates the base station including a DU and an RU, various embodiments of the present disclosure are not limited thereto. In some embodiments, the base station may be implemented in a distributed deployment with a centralized unit (CU) configured to perform functions of upper layers (e.g., packet data convergence protocol (RRC) (PDCP)) of the access network and a distributed unit (DU) configured to perform functions of lower layers. In this case, the distributed unit (DU) may include the digital unit (DU) and radio unit (RU) of FIG. 1. Between the core (e.g., 5G core (5GC) or next generation core (NGC)) network and the radio network (RAN), the base station may be implemented in a structure in which the CU, DU, and RU are arranged in this order. The interface between the CU and the distributed unit (DU) may be referred to as an F1 interface.

[0036] A centralized unit (CU) is connected to one or more DUs and can handle higher layer functions than the DUs. For example, the CU can handle radio resource control (RRC) and packet data convergence protocol (PDCP) layer functions, while the DU and RU can handle lower layer functions. The DU can perform radio link control (RLC), media access control (MAC), and some of the physical layer (PHY) functions (high PHY), while the RU can handle the remaining PHY layer functions (low PHY). Also, as an example, a digital unit (DU) can be included in a distributed unit (DU) depending on the implementation of a distributed configuration of a base station. Hereinafter, unless otherwise specified, the operations of a digital unit (DU) and an RU are described. However, various embodiments of the present disclosure may be applied to both a base station configuration including a CU and a configuration in which a DU is directly connected to a core network without a CU (i.e., a CU and a DU are integrated into a single entity).

[0037] 2 shows the configuration of a DU in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 2 is part of a base station and can be understood as the configuration of the DU 160 in FIG. 1B. As used below, the terms "module," "device," etc. refer to a unit that processes at least one function or operation, and can be implemented in hardware, software, or a combination of hardware and software.

[0038] Referring to FIG. 2, the DU 160 includes a communication unit 210 , a storage unit 220 , and a control unit 230 .

[0039] The communication unit 210 can perform functions for transmitting and receiving signals in a wired communication environment. The communication unit 210 can include a wired interface for controlling a direct connection between devices via a transmission medium (e.g., copper wire, optical fiber). For example, the communication unit 210 can transmit an electrical signal to another device via a copper wire or convert between an electrical signal and an optical signal. The communication unit 210 can be connected to a radio unit (RU). The communication unit 210 can be connected to a core network or a CU in a distributed configuration.

[0040] The communication unit 210 may also perform functions for transmitting and receiving signals in a wireless communication environment. For example, the communication unit 210 may perform a conversion function between a baseband signal and a bit string in accordance with a system physical layer standard. For example, when transmitting data, the communication unit 210 generates complex symbols by encoding and modulating a transmission bit string. When receiving data, the communication unit 210 recovers a received bit string by demodulating and decoding the baseband signal. The communication unit 210 may also include multiple transmission and reception paths. According to an embodiment, the communication unit 210 may be connected to a core network or another node (e.g., an integrated access backhaul (IAB)).

[0041] The communication unit 210 can transmit and receive signals. To this end, the communication unit 210 can include at least one transceiver. For example, the communication unit 210 can transmit a synchronization signal, a reference signal, system information, a message, a control message, a stream, control information, or data. The communication unit 210 can also perform beamforming.

[0042] The communication unit 210 transmits and receives signals as described above. Therefore, all or part of the communication unit 210 may be referred to as a "transmitter," a "receiver," or a "transmitter / receiver." In the following description, transmission and reception via a wireless channel are used to mean that the above-described processing is performed by the communication unit 210.

[0043] Although not shown in FIG. 2, the communication unit 210 may further include a backhaul communication unit for connection with a core network or another base station. The backhaul communication unit provides an interface for communication with other nodes in the network. That is, the backhaul communication unit converts a bit string transmitted from the base station to another node, e.g., another access node, another base station, an upper node, or a core network, into a physical signal, and converts a physical signal received from another node into a bit string.

[0044] The storage unit 220 stores data such as basic programs, application programs, and setting information for the operation of the DU 160. The storage unit 220 may include a memory. The storage unit 220 may be configured as a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. The storage unit 220 provides the stored data in response to a request from the control unit 230. According to one embodiment, the storage unit 220 may store scheduling information (e.g., beam information, antenna port information) and flow information (e.g., eAxC) for each stream.

[0045] The control unit 230 controls the overall operation of the DU 160. For example, the control unit 230 transmits and receives signals via the communication unit 210 (or via the backhaul communication unit). The control unit 230 also records and reads data in the memory unit 220. The control unit 230 can perform the functions of a protocol stack required by a communication standard. To this end, the control unit 230 may include at least one processor. In some embodiments, the control unit 230 may include a control message generator including resource allocation information for multi-layer scheduling and a flow identifier for transmitting the corresponding control message. The control message generator and the flow identifier may be instruction sets or codes stored in the memory unit 220, instructions / codes that at least temporarily reside in the control unit 230, or memory space for storing instructions / codes, or may be part of circuitry constituting the control unit 230. According to various embodiments, the control unit 230 may control the DU 160 to perform operations according to various embodiments described below.

[0046] The configuration of the DU 160 shown in Fig. 2 is merely an example, and examples of DUs that perform various embodiments of the present disclosure are not limited to the configuration shown in Fig. 2. That is, according to various embodiments, some configurations may be added, deleted, or changed.

[0047] 3 shows the configuration of an RU in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 3 is part of a base station and can be understood as the configuration of RU 180 in FIG. 1B. As used below, the terms "module," "device," etc. refer to a unit that processes at least one function or operation, and can be implemented in hardware, software, or a combination of hardware and software.

[0048] Referring to FIG. 3, the RU 180 includes a communication unit 310 , a storage unit 320 , and a control unit 330 .

[0049] The communication unit 310 performs a function of transmitting and receiving signals through a wireless channel. For example, the communication unit 310 upconverts a baseband signal to an RF band signal and transmits the upconverted signal through an antenna, and downconverts an RF band signal received through the antenna back to a baseband signal. For example, the communication unit 310 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

[0050] The communication unit 310 may also include multiple transmission and reception paths. Furthermore, the communication unit 310 may also include an antenna unit. The communication unit 310 may also include at least one antenna array configured with multiple antenna elements. In terms of hardware, the communication unit 310 may be configured with 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 in a single package. The communication unit 310 may also include multiple RF chains. The communication unit 310 may perform beamforming. The communication unit 310 may apply beamforming weights to signals to be transmitted or received in order to impart directionality to the signals according to the settings of the control unit 330. According to an embodiment, the communication unit 310 may include a radio frequency (RF) block (or RF unit).

[0051] The communication unit 310 can transmit and receive signals. To this end, the communication unit 310 can include at least one transceiver. The communication unit 310 can transmit downlink signals. The downlink signals can include synchronization signals (SS), reference signals (RS) (e.g., CRS (cell-specific reference signal), DM (demodulation)-RS), system information (e.g., MIB, SIB, RMSI (remaining system information), OSI (other system information)), configuration messages, control information, downlink data, etc. The communication unit 310 can receive uplink signals. The uplink signal may include a random access related signal (e.g., a random access preamble (RAP) (or Msg1 (message 1)), Msg3 (message 3)), a reference signal (e.g., a sounding reference signal (SRS), DM-RS), or a power headroom report (PHR), etc.

[0052] The communication unit 310 transmits and receives signals as described above. Therefore, all or part of the communication unit 310 may be referred to as a "transmitter," a "receiver," or a "transmitter / receiver." In the following description, transmission and reception performed via a wireless channel are used to mean that the above-described processing is performed by the communication unit 310.

[0053] The memory unit 320 stores data such as basic programs, application programs, and setting information for the operation of the RU 180. The memory unit 320 may be configured as a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory. The memory unit 320 provides the stored data in response to a request from the control unit 330.

[0054] The control unit 330 controls the overall operation of the RU 180. For example, the control unit 330 transmits and receives signals via the communication unit 310. The control unit 330 also records and reads data in the memory unit 320. The control unit 330 can perform the functions of a protocol stack required by a communication standard. To this end, the control unit 330 can include at least one processor. The control unit 330 can include various modules for performing communication. According to various embodiments, the control unit 330 can control the terminal to perform operations according to various embodiments described below.

[0055] FIG. 4 illustrates an example of a function split in a wireless communication system according to various embodiments of the present disclosure. As wireless communication technology develops (e.g., 5G (5 th With the introduction of the 5G (5G generation) communication system (or new radio (NR) communication system), the number of RUs required to be installed has increased as the frequency bands used have increased and the cell radius of base stations has become significantly smaller. Furthermore, the amount of data transmitted in the 5G communication system has increased by more than tenfold, significantly increasing the transmission capacity of wired networks transmitted over the fronthaul. These factors could significantly increase the installation costs of wired networks in 5G communication systems. Therefore, in order to reduce the transmission capacity of wired networks and their installation costs, a technology has been proposed that transfers some of the functions of the DU's modem to the RU to reduce the fronthaul transmission capacity. This technology can be referred to as "function split."

[0056] To reduce the burden on the DU, methods are being considered to expand the role of the RU, which is currently responsible for RF functions, to include some physical layer functions. In this case, the higher the layer function the RU performs, the greater the RU's processing volume, increasing the fronthaul transmission bandwidth and lowering the latency requirements for response processing. On the other hand, the higher the layer function the RU performs, the less virtualization gain there is and the larger, weight, and cost of the RU increase. It is necessary to implement optimal functional separation by considering the trade-off between the above advantages and disadvantages.

[0057] Referring to Figure 4, functional separation in the physical layer below the MAC layer is illustrated. In the case of a downlink (DL) transmitting a signal to a terminal via a wireless network, a base station may sequentially perform channel encoding / scrambling, modulation, layer mapping, antenna mapping, RE mapping, digital beamforming (e.g., precoding), IFFT transformation / CP insertion, and RF conversion. In the case of an uplink (UL) receiving a signal from a terminal via a wireless network, a base station may sequentially perform RF conversion, FFT transformation / CP removal, digital beamforming (pre-combining), RE demapping, channel estimation, layer demapping, demodulation, and decoding / descrambling. The separation of uplink and downlink functions may be defined into various types depending on the needs of vendors, standard discussions, etc., depending on the trade-offs described above.

[0058] The first functional separation 405 may be a separation of RF functions and PHY functions. The first functional separation does not substantially implement PHY functions within the RU and may be referred to as Option 8, for example. The second functional separation 410 allows the RU to perform IFFT transformation / CP insertion in the DL and FFT transformation / CP removal in the UL, and the DU to perform the remaining PHY functions. For example, the second functional separation 410 may be referred to as Option 7-1. The third functional separation 420a allows the RU to perform IFFT transformation / CP insertion in the DL and FFT transformation / CP removal and digital beamforming in the UL, and the DU to perform the remaining PHY functions. For example, the third functional separation 420a may be referred to as Option 7-2x Category A. The fourth functional separation 420b allows the RU to perform up to digital beamforming in both the DL and UL, and the DU to perform higher-level PHY functions after digital beamforming. For example, the fourth functional separation 420b may be referred to as Option 7-2x Category B. In the fifth function separation 425, the RU performs up to RE mapping (or RE demapping) in both DL and UL, and the DU performs higher PHY functions after RE mapping (or RE demapping). For example, the fifth function separation 425 may be referred to as Option 7-2. In the sixth function separation 430, the RU performs up to modulation (or demodulation) in both DL and UL, and the DU performs higher PHY functions after modulation (or demodulation). For example, the sixth function separation 430 may be referred to as Option 7-3. In the seventh function separation 440, the RU performs up to encoding / scrambling (or decoding / descrambling) in both DL and UL, and the DU performs higher PHY functions after modulation (or demodulation). For example, the seventh function separation 440 may be referred to as Option 6.

[0059] According to one embodiment, when large-capacity signal processing is expected, such as in an FR1 MMU, functional separation at a relatively high layer (e.g., fourth functional separation 420b) may be required to reduce fronthaul capacity. Also, functional separation at an excessively high layer (e.g., sixth functional separation 430) may complicate the control interface and include multiple PHY processing blocks in the RU, which may burden the RU implementation. Therefore, appropriate functional separation may be required depending on the arrangement and implementation method of the DU and RU.

[0060] According to one embodiment, if the RU is unable to process precoding of data received from the DU (i.e., if the RU's precoding capability is limited), the third function separation 420a or a lower function separation (e.g., the second function separation 410) may be applied. Conversely, if the RU is able to process precoding of data received from the DU, the fourth function separation 420b or a higher function separation (e.g., the sixth function separation 430) may be applied. Hereinafter, various embodiments in this disclosure will be described based on the third function separation 420a or the fourth function separation 420b unless otherwise specified, but this does not exclude the configuration of embodiments based on other function separations. That is, in the sixth function separation 430 (Option 7-3) situation, the DU and RU operations for control message transmission described below in FIGS. 5 to 12 may also be applied.

[0061] Fronthaul Control message for multi-layer scheduling

[0062] To increase the transmission capacity within a cell, a base station can perform multi-layer transmission to a terminal. The base station generates multiple streams and transmits them to the terminal within one TTI. Each stream can be transmitted through a corresponding antenna. Each transmission stream is spatially separated via an antenna. As the number of layers increases, the amount of processing required in the fronthaul between the DU and RU by the base station increases. This problem can occur not only when the base station transmits data to the terminal, but also in the uplink where the terminal transmits data to the base station. Therefore, hereinafter, FIGS. 5 to 12 describe a method for more efficiently transmitting control information (e.g., resource allocation information, beam allocation information, scheduling information, etc.) during multi-layer scheduling in a fronthaul architecture with functional separation between the DU and RU.

[0063] To explain the Section types, the following Section types are supported within the C-plane:

[0064] [Table 1]

[0065] 5 shows an example of a control message for multi-layer scheduling according to various embodiments of the present disclosure. In the DL, the DU can transmit to the RU whether resources are scheduled (e.g., RE mapping pattern), beam information applied to the scheduled resources, and user data. In the UL, the DU transmits to the RU whether resources are scheduled and beam information for the scheduling resources, as in the DL, and the RU can transmit user data to the DU. To reduce the burden on the fronthaul between the DU and RU, a small-capacity, small-resource, and flexible DU-RU interface is required.

[0066] 5, a situation is described in which a base station transmits a data stream having N layers (N is an integer greater than 1) to a terminal. The DU 560 can transmit the N data streams to the RU 580. At this time, the DU 560 can also transmit control information corresponding to each data stream to the RU 580.

[0067] Since user data between the DU 560 and the RU 580 is differentiated by layer, the transmission path / reception path can be differentiated between layers. The layer-based differentiation can facilitate transmission and queue management by processing the transmission and reception of user data streams in parallel. Meanwhile, as the number of layers increases, the amount of control information to manage them inevitably increases. Assume a situation in which a control message is configured for each of N user data. The DU 560 can transmit a total of N control messages (first control message 510-1, second control message 510-2, ..., Nth control message 510-N) to the RU 580. The RU 580 is required to process individual control messages to process user data corresponding to each layer. This increase in the number of layers can result in an increase in memory and processing costs for control message processing in the RU. Furthermore, information included in the control messages that is commonly applied to each user data is received and processed redundantly by the RU, resulting in overhead.

[0068] When a beam common to all layers is applied, a method of transmitting a control message using an integrated extended antenna-carrier (eAxC) can be considered, but in this case, there is a difficulty in limited operation as in the case where the RU 580 does not have precoding capability (e.g., the third functional separation 420a in FIG. 4). Since designing a control message taking into account the capability and type of functional separation of the RU 580 can affect DU configuration, it is necessary to design a control message to integrate and transmit scheduling patterns for multiple layers in one control message even in other scenarios (e.g., the fourth functional separation 420b in FIG. 4).

[0069] To address the above-described problems, various embodiments of the present disclosure describe a method for a DU to transmit a simplified control message for multiple layers to an RU during scheduling for multiple layers. The DU 560 can transmit one control message 520 for multiple user data (N) through multi-layer transmission to the RU 580. This control message may be an integration of N control messages (first control message 510-1, second control message 510-2, ..., Nth control message 510-N) transmitted individually. The DU 560 can generate a control message including control information commonly applied to layers (user data) and control information applied to each layer. In this case, according to one embodiment, if there are no control parameters that are applied differently to each layer, the control information applied to each layer may be omitted from the control message. Also, according to one embodiment, if a control message is commonly applied to some layers (two or more layers) of all layers, the control message may include control information for the some layers. The control message may be referred to as a compact control message, a simplified control message, a representative control message, an integrated control message, or a multi-layer-based control message.

[0070] The control message design reduces repetitive overhead, reduces processing load, and memory requirements, thereby reducing the transmission capacity of the fronthaul. Furthermore, by defining relatively compact control messages not only when a common beam is applied to all layers, but also when a beam is assigned to each user (SU-MIMO case) and when spatially separated precoding is applied to each user (e.g., MU-MIMO case), fewer resources are required for information processing in the fronthaul.

[0071] Design for Fronthaul Control Message

[0072] Figure 6 shows an example of a DU and an RU for multi-layer scheduling according to various embodiments of the present disclosure. In Figure 6, eCPRI and O-RAN standards are illustratively described as fronthaul interfaces when transmitting messages between a DU and an RU. An eCPRI header, an O-RAN header, and additional fields may be included in the Ethernet payload of the message. Hereinafter, various embodiments of the present disclosure will be described using eCPRI or O-RAN standard terminology; however, other expressions having equivalent meanings to each term may be used instead of various embodiments of the present disclosure.

[0073] The fronthaul transport protocol may be Ethernet and eCPRI, which are easily shared with the network. The Ethernet payload may include an eCPRI header and an O-RAN header. The eCPRI header may be located at the front end of the Ethernet payload. The contents of the eCPRI header are as follows:

[0074] ecpriVersion (4 bits): 0001b (fixed value) ecpriReserved (3 bits): 0000b (fixed value) ecpriConcatenation (1 bit): 0b (fixed value) ecpriMessage (1 byte): Message type ecpriPayload (2 bytes): Payload size in bytes ecpriRtcid / ecpriPcid (2 bytes): x, y, z can be configured depending on the management plane (M-plane). This field can indicate the transmission path of the control message (eAxC (extended antenna carrier) in eCPRI) according to various embodiments during multi-layer transmission.

[0075] CU_Port_ID (x bits): Identifies the channel card. Can also identify the modem (2 bits for channel card, 2 bits for modem) BandSector_ID (y bits): Cell / Sector classification CC_ID (z bits): Classified by component carrier RU_Port_ID (w bits): Classified by layer, T, antenna, etc. ecpriSeqid (2 bytes): Sequence ID is managed separately for ecpriRtcid / ecpriPcid, and Sequence ID and subsequence ID are managed separately. Radio-transport-level fragmentation is possible using the subsequence ID (different from application-level fragmentation).

[0076] The fronthaul application protocol can include a control plane (C-plane), a user plane (U-plane), a synchronization plane (S-plane), and a management plane (M-plane).

[0077] The control plane may be configured to transmit section information and beam information via a control message. The section information is layer-specific information and may include information about resources allocated in one slot (e.g., 14 symbols). In the control plane / user plane, a section may refer to an area where resources are allocated. For example, one section may be a resource grid expressed as a time-frequency resource, and may indicate a resource allocation area for 1 to 273 RBs in the frequency domain and up to 14 symbols in the time domain. That is, the section information may include resource allocation information for communication between an RU and a UE.

[0078] The beam information may be section-specific / layer-specific beam information and may indicate a beam applied to a corresponding layer. The beam information is a method for indicating a beam and may include parameters directly indicating a weight vector (or a weight matrix, depending on the embodiment) applied to form a beam, or may include a predefined weight vector or an indicator (e.g., beam ID, precoding indicator) indicating a resource to which a specific beam is applied. In addition to information indicating which beam (which precoding) is applied, the beam information may include at least one of information indicating the type of beam applied to a layer, a user ID corresponding to the layer, or an antenna port number. The beam information is information regarding digital beamforming and indicates precoding. Precoding can determine how data streams corresponding to each layer are divided and transmitted to transmission antennas. The beam information for each layer may indicate an index indicating a weight vector of [1 × Nt] size, an indicator indicating a weight matrix (e.g., PMI, CRI, i1), or the weight vector value itself, where Nt is the number of antennas. The beam information in the i-th layer can correspond to the i-th column of the precoding matrix.

[0079] The user plane may include the user's downlink data or uplink data. The weight vector of the beam information described above may be multiplied by the user's data (IQ data).

[0080] The management plane may be associated with an initial setup, a non-real-time reset or a reset, and a non-real-time report.

[0081] Referring to FIG. 6, a situation in which the DU 660 transmits a control message to the RU 680 will be described. The control message may include section information and beam information for the corresponding data stream. Assume a multi-layer transmission situation. To transmit a total of N data streams, control information for each data stream needs to be provided to the RU 680. In this case, the processing unit of the DU 660 (e.g., the control plane CPU) can transmit a control message corresponding to each layer through the eAxC corresponding to each layer. In this case, the DU 660 can transmit a total of N control messages (first control message 610-1, second control message 610-2, ..., Nth control message 610-N) to the RU 680. A total of N pieces of section information and a total of N pieces of beam information may be provided to the RU 680. However, information generally transmitted in multi-layer transmission is the same or similar except for beam information. Therefore, if the RU 680 can share information with multiple eAxCs, transmission of the same information may be duplicated in the RU 680, resulting in overhead.

[0082] According to various embodiments, the DU 660 can transmit one control message 620 for a total of N layers to the RU 680. The DU 660 can identify a transmission path for transmitting the control message. The RU 680 can receive the control message through the identified reception path. The transmission path (or reception path) of each layer can correspond to an eAxC (extended antenna-carrier) in eCPRI. The eAxC can indicate the data flow for each antenna for each carrier in a sector. In other words, it can be a unit of signal flow that can be spatially distinguished. The DU 660 can identify the eAxC for transmitting the control message. A representative eAxC can be pre-designated for N eAxCs (N is an integer greater than or equal to 1).

[0083] According to various embodiments, a representative eAxC is pre-assigned to the DU and RU via the service non-real-time OAM domain (ORAN M-plane) interface, and the DU 660 can identify the designated eAxC when transmitting a multi-layer or control message. A management plane (M-plane) may be assigned multiple eAxCs and one representative eAxC ID, such as 'eAxC ID #A = {eAxC ID #0, eAxC ID #1, eAxC ID #2, eAxC ID #(N-1)}, where A is #0 to #(N-1)'. In some embodiments, a representative eAxC for each group among multiple eAC groups may be pre-assigned (e.g., a representative eAxC for a first group and a representative eAxC for a second group). In other embodiments, one or more eAxCs may be pre-assigned for all eAxCs (e.g., a set including one or more representative eAxCs exists). The one or more eAxCs may have a priority. The eAxCs can be used for control message transmission in the order of priority as many as necessary for transmitting the integrated control message.

[0084] According to various embodiments, the DU 660 can generate a control message to be transmitted via the identified path (representative eAxC). The control message can be an integrated message including information for a total of N layers. By configuring a control message to include section information for multiple layers and beam information for each layer, rather than including section information / beam information for one layer, overhead in the fronthaul can be reduced. To configure this control message, a new field can be added to the control message. The DU can attach a new extension field, 'section extension', and transmit the control message on the control plane section. According to one embodiment, the 'section extension' field can be added to the control message based on ExtType=8 of the ORAN WG4 CUS standard. ExtType defines a type for section extension on the control plane (C-plane). New types of extension formats can be defined based on ExtType=8. For example, this 'section extension' field can be applied when the section type of the control message is 1, 3, or 5. In addition, the beam ID field in a control message to which a 'section extension' field is attached may point to a weight matrix instead of a beam weight vector based on the beam group type information (beamGroupType) in the 'section extension' field. According to another embodiment, the 'section extension' field may be added to a control message based on ExtType=7 of the ORAN WG4 CUS standard. A new control message may also be configured by modifying some of the fields based on the existing ExtType.

[0085] An extension field in the control message may further include control information for the layer. For example, the extension field may be defined as shown in the table below.

[0086] [Table 2]

[0087] 'ef' may indicate the presence or absence of a section extension. For example, 'ef' may indicate the presence of a section extension field when it is 1, and 'ef' may indicate the absence of a section extension field when it is 0. 'extType' indicates the type of the extension field, and 'extLen' indicates the length of the extension field in bytes. According to an embodiment of the present disclosure, a 'beamGroupType' field may be added as a payload in the extension field. For example, the 'beamGroupType' field may be 2 bits and may be configured to indicate the scheduling method of the beamID in the control message.

[0088] In some embodiments, an extension field in the control message may further include control information for individual layers. For example, the extension field may be defined as shown in the table below.

[0089] [Table 3]

[0090] 'bif (beam identification field)' is an indicator that indicates the presence of the beam ID of the next octet, and the x-th port beamID indicates beam information for an individual layer. The beamID of the 1st port can be included in the O-RAN header in the control message. The 'beamGroupType' field is 2 bits and can be configured to indicate the scheduling method for the layer in the control message. For example, the 'beamGroupType' field can be configured as shown in the table below.

[0091] [Table 4]

[0092] 'numPortc' can indicate the number of ports (or number of layers, number of transmit / receive paths) indicated by the extension field. Depending on the standard, 64 ports may be indicated. 'bif' can be an indicator indicating the presence of a beamID in the next octet. The distinction between single user and multi-user is made by the presence or absence of overlap in scheduling within a specified frequency region (e.g., one or more RBs). For example, resource allocation within the same RB range can accommodate multi-user scheduling.

[0093] Meanwhile, the expansion fields and individual structures in Tables 2 to 4 are merely examples, and can be modified in a manner obvious to those skilled in the art.

[0094] 7 shows an example of a control message structure according to various embodiments of the present disclosure. A multi-layer transmission situation for four streams is taken as an example.

[0095] Referring to FIG. 7 , a control message set 700 includes layer-specific control messages 711, 712, 713, and 714 without extension fields according to various embodiments of the present disclosure. Octets 1 to 7 of the control messages may correspond to an eCPRI header. Here, parameters other than ecpriRtcid / ecpriPcid, which indicate the transmission path (eAxC) in the eCPRI header, may be common to all layers. Octets 9 to 24 of the control messages may correspond to an O-RAN header. In some embodiments, parameters of the O-RAN header may be common to all layers. In some embodiments, some parameters of the O-RAN header may be common to all layers, while other parameters, such as beamID, may be configured to be different for each layer. When transmitting layer-specific control messages 711, 712, 713, and 714, overhead may occur because information common to each layer is received and processed redundantly by the RU.

[0096] To solve the above problem, the DU can transmit a control message 750 to the RU. The control message 750 may be an integrated form of the control messages 711, 712, 713, and 714. According to one embodiment, the control messages 711, 712, 713, and 714 may share common header parameters except for ecpriRtcid / ecpriPcid. Therefore, the control message 750 may be configured using the existing eCPRI header and O-RAN header. Octets 1 to 4 and 6 to 24 of the control message 750 may be identical to those of the individual control messages 711, 712, 713, and 714, except for ecpriRtcid / ecpriPcid in Octet 5. Octet 5 may be configured to indicate the ID of the eAxC designated as the representative (e.g., eAxC ID=0). When performing multi-layer transmission, the DU can configure the control message 750 based on the header parameters of the representative eAxC and the individual layer transmission.

[0097] The control message 750 may include an extension field according to various embodiments of the present disclosure. According to one embodiment, when all control parameters are commonly applied to layers, the extension field may be configured as shown in Table 2. The extension field in Table 2 may be added to Octets 25 to 28. In this case, 'beamGroupType' may indicate 00b. The weight vector indicated by 'beamID' in Octets 23 to 24 may be commonly applied to layers. In addition, 'numPortc' is the number of ports for multi-layer transmission and may indicate 4.

[0098] 7 illustrates an embodiment in which an extension field according to Table 2 is added to a control message, but the embodiment of the present disclosure is not limited thereto. Other types of extension fields may be defined. According to one embodiment, the extension field may be configured as shown in Table 3.

[0099] According to one embodiment, the extension field may also include a beam group indicator. The weight vector (or weight matrix) applied during signal transmission may be configured in two stages. In the first stage, a beam group may be indicated, and in the second stage, a beam within the beam group may be indicated. The extension field may also include a beam group indicator. The beam ID in the header may be configured to indicate a beam within a beam group. If the beam group indicator does not need to be changed, the beam group indicator may be intermittently omitted from the extension field. Furthermore, by indicating a group and indicating individual beams within the group, the number of bits occupied by the beam ID for a layer may be reduced. This is because the beam group for each layer is the same, but the individual beams may be different. The two-stage indication reduces the number of beam IDs, allowing the beam ID information in the existing section to be recycled. According to a further embodiment, in the case of MU-MIMO, the extension field may further include individual beam IDs for each of the second and subsequent layers. The beam ID in the extension field may also be configured to indicate a beam within a beam group.

[0100] According to an embodiment, the extension field may include a group identifier. The group identifier may indicate a group to which a layer belongs. The group may indicate groups to which the same weight matrix is ​​applied. For example, the group identifier may be configured in the form of a bitmap according to the size of the layer. '0' may indicate the first group, and '1' may indicate the second group. The bitmap may indicate MU-MIMO scheduling. Also, if the bitmap is all 0s, the group identifier may indicate common beam scheduling. Also, if the bitmap is all 1s, it may indicate SU-MIMO scheduling. As another example, the group identifier may be configured as a layer classifier. For example, when a control message for a total of four layers is configured, a value of '0' may indicate common beam scheduling, '1' may indicate MU-MIMO scheduling with two layers per UE, and '4' may indicate single-user scheduling.

[0101] 8 illustrates an example of control message transmission according to various embodiments of the present disclosure. A situation in which resource allocation for four layers of a single user is performed is illustrated. The DU can generate a control message indicating resource allocation and beam information for each UE according to the scheduling result. The horizontal axis represents the frequency domain, and the vertical axis represents the layer.

[0102] 8, resources for UE #0 are allocated in a first frequency domain across layers #0 to #3, resources for UE #1 are allocated in a second frequency domain across layers #0 to #3, and resources for UE #2 are allocated in a third frequency domain across layers #0 to #3 (800). At this time, referring to the control plane 810, a total of four individual control messages are transmitted. Since the rank number of UE #0 is 4, the rank number of UE #1 is 4, and the rank number of UE #2 is 2, the maximum rank number of UE #0, UE #1, and UE #2 is 4. Since control messages need to be transmitted by layer and the maximum rank between UEs to be scheduled is 4, a total of four control messages may be required. Since the same beam (beam #0) is provided to the layers and UEs, transmitting four control messages on the control plane is inefficient, a single integrated control message may be proposed.

[0103] Referring to the control plane 820, one integrated control message is transmitted. To configure the control message, the parameters in Table 2 can be configured as follows:

[0104] Section Configuration: eCPRI header and O-RAN header can be used.

[0105] - eAxC ID=#0 (representative): Indicates a designated path among the multi-layers. Indicates a representative designated path, where #0 is merely an example, and according to one embodiment, any eAxC ID (e.g., #0, #1, ..., #N-1) can be mapped as a representative. -Beam ID=#0 (common beam): Indicates a beam that is commonly applied to all terminals.

[0106] Section Extension Configuration

[0107] -beamGroupType=00b: Specifies the beam scheduling method according to Table 4. -numPortc=4: The total number of layers is 4. According to one embodiment, when the beam scheduling method is 00b, the number of layers may be omitted.

[0108] 9 illustrates another example of control message transmission according to various embodiments of the present disclosure. This illustrates a situation in which resource allocation for up to eight layers is performed in a mixed situation of single-user scheduling and multi-user scheduling. The DU can generate a control message indicating resource allocation and beam information for each UE based on the scheduling result. The horizontal axis represents the frequency domain, and the vertical axis represents the layer.

[0109] Referring to FIG. 9, resources for UE #0 are allocated in the first frequency region across layers #0 to #3, resources for UE #0, UE #1, UE #2, and UE #3 are allocated in the second frequency region across layers #0 to #7, and resources for UE #1 are allocated in the third frequency region across layers #0 to #1 (900). Referring to the control plane 910, a total of 14 individual control messages are transmitted. Because UE #0 has a rank of 4, UE #1 has a rank of 2, and the rank in the second resource region is 8, 14 layers requiring overall scheduling can be distinguished. Since control messages must be transmitted for each layer, a total of 14 control messages may be required. Although scheduling is performed for SU-MIMO in the first and third resource regions and for MU-MIMO in the second resource region, configuring control messages for each layer can waste fronthaul resources. Therefore, one integrated control message can be proposed for each scheduling scheme.

[0110] Referring to the control plane 920, a total of three integrated control messages are transmitted. One integrated control message is transmitted for each frequency domain. To configure the control messages, the parameters in Table 2 or Table 3 can be configured as follows:

[0111] Section Configuration: eCPRI header and O-RAN header can be used.

[0112] - eAxC ID=#0 (representative): Indicates a designated path among the multi-layers. Indicates a representative designated path, where #0 is merely an example, and according to one embodiment, any eAxC ID (e.g., #0, #1, ..., #N-1) can be mapped as a representative. Beam ID=#0: Indicates a beam for a layer of a single terminal or a beam applied to the first layer.

[0113] Section Extension Configuration 1 - First Resource Area -beamGroupType=01b: Specifies the beam scheduling method according to Table 4. -numPortc=4: The total number of layers is 4. Second Section Extended Configuration - Second Resource Area -beamGroupType=10b: Specifies the beam scheduling method according to Table 4. -numPortc=8: The total number of layers is 4. Beam ID #1 to #7 (or UE IE #1 to #7): A beam ID is defined for each layer. The beam ID for the first layer may be included in the section configuration. Although it has been stated that beam IDs are configured for each layer, according to one embodiment, a reduced number of beam IDs may be included depending on the size of the beam matrix.

[0114] Third Section Extended Configuration - Third Resource Area -beamGroupType=01b: Specifies the beam scheduling method according to Table 4. -numPortc=2: The total number of layers is 2.

[0115] 10A illustrates an example of a control plane during multi-layer scheduling according to various embodiments of the present disclosure. This illustrates a situation in which resource allocation is performed in a situation where single-user scheduling and multi-user scheduling are mixed. The DU can generate a control message indicating resource allocation and beam information for each UE according to the scheduling result. The horizontal axis represents the frequency domain, and the vertical axis represents the layer.

[0116] 10A, resources for UE #0 are allocated in a first frequency region 1010 across layers #0 to #3, resources for UE #0, UE #1, UE #2, and UE #3 are allocated in a second frequency region 1020 across layers #0 to #7, and resources for UE #1 are allocated in a third frequency region 1030 across layers #0 to #1 (1000). When multi-user scheduling is performed in the second frequency region 1020, any beam may be assigned to regions with no user data, i.e., regions where user IQ data is all 0. Therefore, although UE #1, UE #2, and UE #3 do not use the entire second frequency region 1020 across layers #4 to #7, beams assigned to scheduled resources in the second frequency region 1020 may also be assigned to unscheduled resources to facilitate control message configuration.

[0117] 10B illustrates another example of a control plane during multi-layer scheduling according to various embodiments of the present disclosure. This illustrates a situation in which resource allocation is performed in a situation where single-user scheduling and multi-user scheduling are mixed. The DU can generate a control message indicating resource allocation and beam information for each UE based on the scheduling result. The horizontal axis represents the frequency domain, and the vertical axis represents the layer.

[0118] Referring to FIG. 10B, resources for UE#0 are allocated in a first frequency domain 1060 across layer#0 to layer#3, resources for UE#0, UE#1, UE#2, UE#3, and UE#4 are allocated in a second frequency domain 1070 across layer#0 to layer#7, and resources for UE#1 are allocated in a third frequency domain 1080 across layer#0 to layer#1 (1050).

[0119] When multi-user scheduling is performed in the second frequency region 1070, any beam may be assigned to a region with no user data, i.e., a region where the user IQ data is all zero. Although UE#1, UE#2, UE#3, and UE#4 do not use the entire second frequency region 1070 in layers 4 to 7, to facilitate the configuration of control messages, beams assigned to scheduled resources in the second frequency region 1070 may also be assigned to unscheduled resources. However, unlike FIG. 10A, in layer 7 of FIG. 10B, not only UE#3 but also UE#4 are scheduled within the second frequency region 1070. Because UE multiplexing is required for the layer of the resource region for MU-MIMO, section fragmentation may be required. According to one embodiment, the RU can fragment sections for a specific layer. The RU can configure a control message to include information regarding section fragmentation. For example, the extension field can include information regarding the layer to be fragmented (e.g., a port number indication). The extension field can also include location information of the RBs that require fragmentation (e.g., an RB offset).

[0120] 11 illustrates a flow of operations of a DU for multi-layer scheduling according to various embodiments of the present disclosure. The DU is exemplified by the DU 160 in FIG.

[0121] Referring to FIG. 11, in step 1101, a DU can identify a designated transmission path. The DU can identify one or more transmission paths among multiple layers. The identified path can be a path designated to represent multiple layers. According to one embodiment, the transmission path can be designated in the management plane (M-plane of O-RAN). The management plane can be designated as 'eAxC ID #A = {eAxC ID #0, eAxC ID #1, eAxC ID #2, eAxC ID #(N-1)}' (A is one of #0 to #(N-1)). A representative eAxC can be designated for a total of N layers.

[0122] In step 1103, the DU can generate a control message based on multi-layer scheduling. Multi-layer scheduling refers to the process of allocating resources for multiple streams. A stream can correspond to a port (e.g., antenna port) of an RU. A base station scheduler can allocate resources for multiple streams within a specified time-frequency region (e.g., section). Based on the scheduling result, the DU can generate a control message.

[0123] The DU may generate a control message including section information, beam information, and flow information. The DU may generate section information based on the scheduling result. For example, the section information may include information on the time domain (e.g., frame, subframe, slot, symbol), information on the frequency domain (e.g., RB, reMask), and information on the section (e.g., section ID). The DU may configure a control message to include the section information. The DU may generate beam information based on the scheduling result. Spatially distinguished resources may also be included in the scheduling result. For example, the DU may generate beam information to include at least one of parameters associated with the beam assigned to each UE (e.g., beamID), parameters for precoding applied to the UE layer (e.g., PMI), or parameters associated with MU-MIMO scheduling. The DU may generate flow information indicating the path identified in step 1101. For example, the 'ecpriRtcid / ecpriPcid' fields in the eCPRI header may be set to indicate the eAxC ID corresponding to the identified path, and the flow information may be generated to include the above-described setting.

[0124] In step 1105, the DU can transmit a control message via a fronthaul interface. For example, the DU can transmit a control message based on at least one of eCPRI and O-RAN among the fronthaul interfaces. For example, the DU can use an O-RAN header to transmit section information. The DU can also use an O-RAN section extension field to transmit beam information. The DU can also use the 'ecpriRtcid / ecpriPcid' field in the eCPRI header to transmit flow information.

[0125] 12 illustrates an operational flow of an RU for multi-layer scheduling according to various embodiments of the present disclosure. The RU is exemplified by the RU 180 of FIG.

[0126] 12, in step 1201, an RU may receive a control message via a fronthaul interface. For example, the RU may receive the control message based on at least one of eCPRI and O-RAN among the fronthaul interfaces. The RU may receive the control message based on at least one of eCPRI header information and O-RAN header information. The control message may include multi-layer scheduling information.

[0127] In step 1203, the RU may acquire multi-layer scheduling information. The multi-layer scheduling information may include section information, beam information, and flow information for multiple layers. For example, the RU may acquire multi-layer scheduling information based on at least one of eCPRI and O-RAN interfaces among the fronthaul interfaces. For example, the RU may identify an O-RAN header to receive the section information. The RU may acquire time-frequency resources for wireless communication from the section information. The RU may also identify an O-RAN section extension field to receive beam information. The RU may acquire a weight vector to be applied to each layer from the beam information. The weight vector may be a beam weight vector based on a common beam or a weight vector corresponding to one column of a precoding matrix. The RU may also identify the 'ecpriRtcid / ecpriPcid' field in the eCPRI header to receive flow information. The RU may confirm the transmission path of the corresponding control message from the flow information.

[0128] In step 1205, the RU may perform multi-layer communication. The RU may transmit scheduling information to a terminal and perform downlink communication for multi-layer transmission. The RU may transmit a data stream to the terminal by applying a weight matrix according to the scheduling information. Alternatively, the RU may transmit scheduling information to the terminal and perform uplink communication for receiving multi-layer transmission from the terminal. The RU may provide information on the weight matrix according to the scheduling information to the terminal.

[0129] According to various embodiments of the present disclosure, by constructing simplified control messages for multiple layers and transmitting the corresponding control messages through designated paths, resources consumed in the fronthaul interface between the DU and RU may be reduced. For example, the processing load may be reduced. The load for generating and processing control plane packets may be reduced in proportion to the number of sections reduced compared to the bandwidth (BW) of the existing control plane. Furthermore, for example, the memory requirement load may be reduced. The memory requirement may be reduced in proportion to the number of sections reduced compared to the bandwidth (BW) of the existing control plane. By reducing the bandwidth within the fronthaul, resources consumed may be saved, enabling efficient fronthaul operation. In particular, in an environment where the number of layers increases or multiple antennas are used (e.g., FR2), the amount of traffic that a base station must process during scheduling increases, so the gain of the integrated control message operation method of the present disclosure may be further increased. For example, performance by NR frequency range may be derived as shown in Table 5 below. Here, the performance indicator is the number of control plane sections required for cell support.

[0130] [Table 5]

[0131] According to an embodiment, a method for operating a digital unit (DU) of a base station in a wireless communication system, the method comprising: identifying a designated path from among multiple paths of a fronthaul interface connecting the DU and a radio unit (RU); and generating a control message for multiple layers, the control message being transmitted to the RU via the designated path, the control message including scheduling information for multiple layers.

[0132] In some embodiments, the plurality of layers includes a first layer and a second layer, and the control message includes information indicating some of the plurality of layers, a first weight vector of the first layer, and information indicating a second weight vector of the second layer.

[0133] In some embodiments, the scheduling information includes: Section information indicating common resource allocations for multiple layers; Beam information relating to weight matrices for multiple layers; Flow information indicating a designated path, where if the section information is included in an Open Radio Access Network (O-RAN) header of the control message, the beam information is included in a section extension field of the control message; Flow information is included in the "ecpriRtcid / ecpriPcid" of the enhanced Common Public Radio Interface (eCPRI) header of the control message.

[0134] In some embodiments, the control message includes type information indicating a scheduling scheme for multiple layers, the scheduling scheme including one of the following: a first scheme applying a common beam to each layer, a second scheme applying a precoding matrix to multiple layers, and a third scheme applying individual precoding to each of the multiple layers.

[0135] In some embodiments, if the type information indicates a first scheme, the weight matrix indicates a single-layer beamforming weight vector, and if the type information indicates a second scheme, the weight matrix indicates a multiple-layer weight matrix.

[0136] In some embodiments, if all control parameters apply generally to the layer, the control message includes an extension field.

[0137] In some embodiments, the extension fields include a beamGroupType, a weight vector indicated by the beamID, and a number of ports numPortc for multi-layer transmission.

[0138] In some embodiments, resources are allocated to multiple tiers of a single user, and the control message indicates resource allocation and beam information for each terminal according to the scheduling result.

[0139] In some embodiments, single-user scheduling and multi-user scheduling are mixed, and the control message indicates resource allocation and beam information for each terminal according to the scheduling result.

[0140] According to an embodiment, there is provided a method for operating a radio unit (RU) of a base station in a wireless communication system, the method comprising: transmitting control messages of multiple layers from a digital unit (DU) over multiple paths of a fronthaul interface connecting the RU and the DU; identifying scheduling information of multiple layers based on the control messages; and performing communication based on the scheduling information.

[0141] In some embodiments, the plurality of layers includes a first layer and a second layer, and the control message includes information indicating some of the plurality of layers, a first weight vector of the first layer, and information indicating a second weight vector of the second layer.

[0142] In some embodiments, the scheduling information includes: section information indicating common resource allocations for multiple layers; beam information relating to weight matrices for multiple layers; and flow information indicating a designated path, where the beam information is included in a section extension field of the control message if the section information is included in an Open Radio Access Network (O-RAN) header of the control message. The flow information is included in the "ecpriRtcid / ecpriPcid" of the enhanced Common Public Radio Interface (eCPRI) header of the control message.

[0143] In some embodiments, the control message includes type information indicating a scheduling scheme for multiple layers, the scheduling scheme including one of the following: a first scheme applying a common beam to each layer, a second scheme applying a precoding matrix to multiple layers, and a third scheme applying individual precoding to each of the multiple layers.

[0144] In some embodiments, if the type information indicates a first scheme, the weight matrix indicates a single-layer beamforming weight vector, and if the type information indicates a second scheme, the weight matrix indicates a multiple-layer weight matrix.

[0145] According to an embodiment, a device of a digital unit (DU) of a base station in a wireless communication system includes at least one processor, the at least one processor being configured to identify a designated path from among a plurality of paths, generate control messages of multiple layers of a fronthaul interface connecting the DU and a radio unit (RU), and control the fronthaul interface to transmit the control messages to the RU via the designated path, the control messages including scheduling information of the multiple layers.

[0146] In some embodiments, the plurality of layers includes a first layer and a second layer, and the control message includes information indicating some of the plurality of layers, a first weight vector of the first layer, and information indicating a second weight vector of the second layer.

[0147] In some embodiments, the scheduling information includes: section information indicating common resource allocations for multiple layers; beam information relating to weight matrices for multiple layers; and flow information indicating a designated path, where the beam information is included in a section extension field of the control message if the section information is included in an Open Radio Access Network (O-RAN) header of the control message. The flow information is included in the "ecpriRtcid / ecpriPcid" of the enhanced Common Public Radio Interface (eCPRI) header of the control message.

[0148] In some embodiments, the control message includes type information indicating a scheduling scheme for multiple layers, the scheduling scheme including one of the following: a first scheme applying a common beam to each layer, a second scheme applying a precoding matrix to multiple layers, and a third scheme applying individual precoding to each of the multiple layers.

[0149] In some embodiments, if the type information indicates a first scheme, the weight matrix indicates a single-layer beamforming weight vector, and if the type information indicates a second scheme, the weight matrix indicates a multiple-layer weight matrix.

[0150] According to an embodiment, a device of a radio unit (RU) of a base station in a wireless communication system includes: at least one processor, the at least one processor configured to control a fronthaul interface connecting the RU and a digital unit (DU) to receive control messages of multiple layers from the DU via designated paths therebetween; identify scheduling information of multiple layers based on the control messages via the multiple paths of the fronthaul interface; and control at least one transceiver to perform communication based on the scheduling information.

[0151] In some embodiments, the plurality of layers includes a first layer and a second layer, and the control message includes information indicating some of the plurality of layers, a first weight vector of the first layer, and information indicating a second weight vector of the second layer.

[0152] In some embodiments, the scheduling information includes: section information indicating common resource allocations for multiple layers; beam information relating to weight matrices for multiple layers; and flow information indicating a designated path, where the beam information is included in a section extension field of the control message if the section information is included in an Open Radio Access Network (O-RAN) header of the control message. The flow information is included in the "ecpriRtcid / ecpriPcid" of the enhanced Common Public Radio Interface (eCPRI) header of the control message.

[0153] In some embodiments, the control message includes type information indicating a scheduling scheme for multiple layers, the scheduling scheme including one of the following: a first scheme applying a common beam to each layer, a second scheme applying a precoding matrix to multiple layers, and a third scheme applying individual precoding to each of the multiple layers.

[0154] In some embodiments, if the type information indicates a first scheme, the weight matrix indicates a single-layer beamforming weight vector, and if the type information indicates a second scheme, the weight matrix indicates a multiple-layer weight matrix.

[0155] The methods according to the embodiments described in the claims or specification of the present disclosure can be implemented in the form of hardware, software, or a combination of hardware and software.

[0156] In the case of a software implementation, a computer-readable storage medium may be provided that stores one or more programs (software modules). The one or more programs stored on the computer-readable storage medium are configured for execution by one or more processors in an electronic device. The one or more programs include instructions that cause the electronic device to perform a method according to the embodiments described in the claims or specification of the present disclosure.

[0157] 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 device, compact disc-ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage, magnetic cassette, or in memory configured as a combination of some or all of these. Each of these memory configurations may also include multiple instances.

[0158] The program may also be stored in an attachable storage device accessible through a communication network such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), or a storage area network (SAN), or a combination thereof. Such a storage device may be accessible to a device that performs an embodiment of the present disclosure through an external port. A separate storage device on the communication network may also be accessible to a portable electronic device.

[0159] In the specific embodiments of the present disclosure described above, elements included in the disclosure are expressed in the singular or plural form according to the specific embodiments presented. However, the expressions "singular" or "plural" are selected to suit the presented circumstances for the convenience of explanation, and the present disclosure is not limited to singular or plural elements, and elements expressed in the plural form may be composed in the singular form, and elements expressed in the singular form may be composed in the plural form.

[0160] While the detailed description of the present disclosure has been given with reference to specific embodiments, it goes without saying that various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be determined by the following claims and their equivalents. [Explanation of symbols]

[0161] 210 Communications Department 220 Storage section 230 Control Unit 310 Communications Department 320 Storage section 330 Control Unit

Claims

1. 1. A method performed by a digital unit (DU) of a base station in a wireless communication system, comprising: generating a control plane message (C-plane message) for multiple ports, the control plane message including section information and a section extension; and transmitting the control plane message to a radio unit (RU) via a specific port among the multiple ports; The section information includes information on a beam identifier (ID), The section extension may be: Beam group type information for indicating the type of beam grouping; and including port information for indicating a total number of one or more extended antenna-carrier (eAxC) ports indicated by said section extension.

2. Each of the multiplexed ports corresponds to a corresponding layer or a corresponding transmission or reception (Tx / Rx) path; The method of claim 1 , wherein the specific port is identified by a management plane (M-plane).

3. The method of claim 1 , wherein each of the multiple ports shares the section information within the RU.

4. The type of beam grouping is: a first type for indicating the beam ID to be used as a common beam ID; a second type for indicating that the beam ID and subsequent beam IDs apply to the one or more eAxC ports; 2. The method of claim 1, wherein the listed beam IDs in the section extension are one of a third type to indicate that they apply to the one or more eAxC ports.

5. The method of claim 4 , wherein when the type of the beam grouping is the second type, the beam ID indicates a beam matrix.

6. The beam ID is associated with an index that indicates multiple beams; The method of claim 1 , wherein each of the multiple beams is applied to a corresponding one of the one or more eAxC ports and the particular port.

7. the beam ID is associated with the particular port; The method of claim 1 , wherein the section extension further comprises a beam ID or a user equipment (UE) ID of each of the one or more eAxC ports.

8. 1. A method performed by a radio unit (RU) of a base station in a wireless communication system, comprising: transmitting a control plane message from a distributed unit (DU) through a specific port among multiple ports; and identifying section information and section extension included in the control plane message; The section information includes information on a beam identifier (ID), The section extension may be: Beam group type information for indicating the type of beam grouping; and including port information for indicating a total number of one or more extended antenna-carrier (eAxC) ports indicated by said section extension.

9. Each of the multiplexed ports corresponds to a corresponding layer or a corresponding transmission or reception (Tx / Rx) path; The method of claim 8, wherein the specific port is identified by a management plane (M-plane).

10. The method of claim 8 , wherein each of the multiple ports shares the section information within the RU.

11. The type of beam grouping is: a first type for indicating the beam ID to be used as a common beam ID; a second type for indicating that the beam ID and subsequent beam IDs are applied to the one or more eAxC ports; 9. The method of claim 8, wherein the listed beam IDs in the section extension are one of a third type to indicate that they apply to the one or more eAxC ports.

12. The method of claim 11 , wherein when the type of the beam grouping is the second type, the beam ID indicates a beam matrix.

13. The beam ID is associated with an index that indicates multiple beams; The method of claim 8 , wherein each of the multiple beams is applied to a corresponding one of the one or more eAxC ports and the particular port.

14. the beam ID is associated with the particular port; The method of claim 8 , wherein the section extension further includes a beam ID or a user equipment (UE) ID for each of the one or more eAxC ports.

15. A distributed unit (DU) or radio unit (RU) device, comprising: at least one transceiver; and at least one processor; 15. Apparatus, wherein the at least one processor is configured to implement one of claims 1 to 14.

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