Electronic device and method for determining a precoder in a wireless communication system

Abstract

In an embodiment, an apparatus of a digital unit (DU) is provided. The apparatus can include a transceiver, a memory to store instructions, and a processor. The instructions, when executed by the processor, can direct the apparatus to obtain a channel frequency response from a reference signal from a terminal, obtain an eigenvector by eigen decomposition of the channel frequency response, obtain a transformed vector by performing a two-dimensional Fourier transform on the eigenvector, identify, according to the transformed vector, a basis vector of a plurality of basis vectors of an enhanced type 2 codebook by a decision metric, determine a precoding matrix using the identified basis vector, and transmit, by a radio unit (RU), downlink data to the terminal to which the precoding matrix is applied.

Description

Technical Field

[0001] This disclosure relates to a wireless communication system. For example, this disclosure relates to an electronic device and method for determining a pre-encoder in a wireless communication system. Background Technology

[0002] To improve signal transmission / reception performance, Multiple-Input Multiple-Output (MIMO) technology is used. Wireless communication systems using MIMO technology employ multiple antennas at both the transmitting and receiving ends. Compared to single-antenna technology, the channel capacity of wireless communication systems using MIMO technology can be significantly increased.

[0003] The above information is provided as related technology for the purpose of aiding understanding of this disclosure. No judgment or assertion is made as to whether anything described above can be used as prior art in connection with this disclosure. Summary of the Invention

[0004] Technical solutions

[0005] In one embodiment, a digital unit (DU) device is provided. The device may include a transceiver, a memory storing instructions, and a processor. When executed by the processor, the instructions enable the device to: obtain a channel frequency response from a reference signal from a terminal; obtain a feature vector by eigenvalue decomposition of the channel frequency response; obtain a transform vector by performing a two-dimensional (2D) Fourier transform on the feature vector; identify a basis vector among a plurality of basis vectors of an enhanced type 2 codebook based on the transform vector using a decision metric; determine a precoding matrix using the identified basis vectors; and transmit downlink data to which the precoding matrix is ​​applied via a radio unit (RU) to the terminal.

[0006] In one embodiment, a terminal is provided. The terminal may include a transceiver, a memory storing instructions, and a processor. When executed by the processor, the instructions enable the device to: receive a reference signal from a network node via the transceiver; obtain a channel frequency response via the reference signal; obtain a feature vector by eigenvalue decomposition of the channel frequency response; obtain a transform vector by performing a two-dimensional (2D) Fourier transform on the feature vector; identify a basis vector among multiple basis vectors of an enhanced type 2 codebook based on the transform vector using a decision metric; determine a precoding matrix using the identified basis vectors; and transmit channel state information including the precoding matrix to the network node via the transceiver.

[0007] In one embodiment, a method performed by a digital unit (DU) is provided. The method may include: obtaining a channel frequency response from a reference signal from a terminal; obtaining a feature vector by eigenvalue decomposition of the channel frequency response; obtaining a transform vector by performing a two-dimensional (2D) Fourier transform on the feature vector; identifying a basis vector among a plurality of basis vectors of an enhanced type 2 codebook based on the transform vector using a decision metric; determining a precoding matrix using the identified basis vectors; and transmitting downlink data to which the precoding matrix is ​​applied to the terminal via a radio unit (RU). Attached Figure Description

[0008] Figure 1 A wireless communication system is shown.

[0009] Figure 2 An example of the components of a base station is shown.

[0010] Figure 3 Examples of resource structures in the time and frequency domains are shown.

[0011] Figure 4 An example of a channel in a communication standard is shown.

[0012] Figure 5a The codebook index of type 2 codebook is shown.

[0013] Figure 5b The design principles of the enhanced Type 2 codebook are shown.

[0014] Figure 5c The codebook index of the enhanced type 2 codebook is shown.

[0015] Figure 6 The signal flow used for Channel State Information (CSI) reporting is shown.

[0016] Figure 7 The pre-coded signal flow applied to downlink data is shown.

[0017] Figure 8a , Figure 8b , Figure 9a , Figure 9b , Figure 10a , Figure 10b , Figure 11a and Figure 11b An example of performing precoder selection is shown.

[0018] Figure 12a The functional components of the digital unit (DU) are shown.

[0019] Figure 12b The functional components of the radio unit (RU) are shown.

[0020] Figure 13 The functional components of the terminal are shown. Detailed Implementation

[0021] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly indicates otherwise. The terms used herein (including technical or scientific terms) may have the same meaning as commonly understood by one of ordinary skill in the art as described in this disclosure. Among the terms used in this disclosure, terms defined in general dictionaries may be interpreted as having the same or similar meaning as in the context of related art, and are not to be interpreted as having an ideal or overly formal meaning unless explicitly defined in this disclosure. In some cases, even terms defined in this disclosure should not be construed as excluding embodiments of this disclosure.

[0022] In the various embodiments of this disclosure described below, hardware methods will be described as examples. However, since the various embodiments of this disclosure include techniques using both hardware and software, software-based methods are not excluded.

[0023] The terms used in the following description to refer to signals (e.g., signals, information, messages, signaling), data types (e.g., lists, sets, subsets), states used for calculation (e.g., steps, operations, procedures), data (e.g., packets, user streams, information, bits, symbols, codewords), resources (e.g., symbols, time slots, subframes, radio frames, subcarriers, resource elements (REs), resource blocks (RBs), bandwidth portions (BWPs), timings), channels, network entities, and components of devices are illustrative for ease of description. Therefore, this disclosure is not limited to the terms described below, and other terms with equivalent technical meanings may be used.

[0024] The terms used in the following description that refer to signals (e.g., signals, information, messages, signaling), resources (e.g., symbols, time slots, subframes, radio frames, subcarriers, resource elements (REs), resource blocks (RBs), bandwidth portions (BWPs), timings), terms used for calculating states (e.g., steps, operations, processes), terms referring to data (e.g., packets, user streams, information, bits, symbols, codewords), terms referring to channels, terms referring to network entities, terms referring to components of devices, etc., are illustrative for ease of description. Therefore, this disclosure is not limited to the terms described below, and other terms with equivalent technical meanings may be used.

[0025] Furthermore, in this disclosure, the terms "greater than" or "less than" can be used to determine whether a specific condition is met or satisfied, but this is merely a description of examples and does not exclude descriptions of "greater than or equal to" or "less than or equal to". A condition described as "greater than or equal to" can be replaced with "greater than", a condition described as "less than or equal to" can be replaced with "less than", and a condition described as "greater than or equal to and less than" can be replaced with "greater than and less than or equal to". Additionally, in the following, "A" to "B" refers to at least one of the elements from A (inclusive) to B (inclusive). In the following, "C" and / or "D" means including at least one of "C" or "D", i.e., {"C", "D" and "C and D"}.

[0026] Although this disclosure uses terms used in some communication standards (e.g., 3GPP, ETSI, xRAN, O-RAN) to describe various embodiments, these are merely examples for illustrative purposes. The various embodiments of this disclosure can be readily modified and applied to other communication systems.

[0027] Figure 1 A wireless communication system is shown.

[0028] refer to Figure 1 , Figure 1 Base station 110 and terminal 120 are shown as part of a node utilizing a wireless channel in a wireless communication system. Figure 1 Only one base station is shown, but the wireless communication system may further include another base station that is the same as or similar to base station 110.

[0029] Base station 110 is a network infrastructure that provides wireless access to terminal 120. Base station 110 has a coverage range defined based on the distance over which the signal can be transmitted. In addition to "base station", base station 110 may also be referred to as "access point (AP)", "eNodeB (eNB)", "fifth generation node", "next generation node B (gNB)", "wireless point", "transmit / receive point (TRP)" or other terms with equivalent technical meanings.

[0030] Terminal 120, used as a user device, communicates with base station 110 via a wireless channel. The link from base station 110 to terminal 120 is called the downlink (DL), and the link from terminal 120 to base station 110 is called the uplink (UL). Furthermore, although... Figure 1Not shown, but terminal 120 and another terminal can communicate with each other via a wireless channel. In this case, the link between terminal 120 and the other terminal (device-to-device link (D2D)) is called a side link, and this side link can be used interchangeably with the PC5 interface. In some other embodiments, terminal 120 can operate without user intervention. According to embodiments, terminal 120, as a device performing machine-type communication (MTC), may not be carried by a user. Additionally, according to embodiments, terminal 120 may be an MTC UE or a narrowband (NB)-Internet of Things (IoT) device.

[0031] In addition to "terminal", terminal 120 may also be referred to as "user equipment (UE)", "customer premises equipment (CPE)", "mobile station", "user station", "remote terminal", "wireless terminal", "electronic device", "user equipment" or other terms with equivalent technical meaning.

[0032] Base station 110 can perform beamforming with terminal 120. Base station 110 and terminal 120 can transmit and receive radio signals in relatively low frequency bands (e.g., NR frequency range 1 (FR 1)). Furthermore, base station 110 and terminal 120 can transmit and receive radio signals in relatively high frequency bands (e.g., FR 2 (or FR 2-1, FR 2-2, FR 2-3) or FR 3) and millimeter-wave frequency bands (e.g., 28 GHz, 30 GHz, 38 GHz, 60 GHz). Base station 110 and terminal 120 can perform beamforming to improve channel gain. In this document, beamforming can include transmit beamforming and receive beamforming. Base station 110 and terminal 120 can provide directionality to the transmitted or received signals. To this end, base station 110 and terminal 120 can select a serving beam through a beam search or beam management process. After selecting a serving beam, subsequent communication can be performed using resources that have a QCL relationship with the resources of the transmit serving beam.

[0033] If the large-scale characteristics of the channel carrying symbols at the first antenna port can be inferred from the channel carrying symbols at the second antenna port, then the first and second antenna ports can be evaluated as being in a QCL relationship. For example, large-scale characteristics may include at least one of delay spread, Doppler spread, Doppler shift, average gain, average delay, and spatial receiver parameters.

[0034] although Figure 1The description describes both base station 110 and terminal 120 performing beamforming, but embodiments of this disclosure are not limited thereto. In some embodiments, the terminal may or may not perform beamforming. Furthermore, the base station may or may not perform beamforming. That is, only one of the base station and the terminal may perform beamforming, or neither the base station nor the terminal may perform beamforming.

[0035] In this disclosure, a beam refers to the spatial flow of a signal in a wireless channel and is formed by one or more antennas (or antenna elements), and this forming process may be referred to as beamforming. Beamforming may include at least one of analog beamforming or digital beamforming (e.g., precoding). Reference signals transmitted based on beamforming may include, for example, demodulation reference signals (DM-RS), channel state information reference signals (CSI-RS), synchronization signal / physical broadcast channel (SS / PBCH), and sounding reference signals (SRS). Furthermore, IEs such as CSI-RS resources or SRS resources may be used as configurations for each reference signal, and these configurations may include beam-associated information. The beam-associated information may indicate whether the corresponding configuration (e.g., a CSI-RS resource) uses the same spatial filter as another configuration (e.g., another CSI-RS resource within the same CSI-RS resource set) or a different spatial filter, or which reference signal it is quasi-co-located (QCL) with, and if so, what type it is (e.g., QCL type A, B, C, D).

[0036] Figure 2 An example of a base station component is shown. Figure 2 The document describes how the base station's functions are divided and implemented by different entities: DU and RU. For communication between DU and RU, a fronthaul interface can be used. Unlike backhaul between the base station and the core network, fronthaul refers to the link between the wireless LAN and the base station. Figure 2 An example of a fronthaul structure between a DU 210 and an RU 220 is shown, but this is merely for illustrative purposes and the disclosure is not limited thereto. In other words, embodiments of the disclosure can also be applied to a fronthaul structure between a DU and multiple RUs. For example, embodiments of the disclosure can be applied to a fronthaul structure between a DU and two RUs. Furthermore, embodiments of the disclosure can also be applied to a fronthaul structure between a DU and three RUs.

[0037] refer to Figure 2 Base station 110 may include DU 210 and RU 220. Fronthaul 215 between DU 210 and RU 220 may operate via Fx interface. For operation of fronthaul 215, an interface such as enhanced universal public radio interface (eCPRI) or Ethernet radio (ROE) may be used.

[0038] With the development of communication technology and the increase in mobile data traffic, the bandwidth requirements for fronthaul between digital units and radio units have increased significantly. In deployments such as centralized / cloud radio access networks (C-RAN), the DU can be implemented to perform Packet Data Convergence Protocol (PDCP), Radio Link Control (RLC), Media Access Control (MAC), and Physical (PHY) functions, and the RU can be implemented to further perform PHY layer functions in addition to radio frequency (RF) functions.

[0039] DU 210 can be responsible for the upper-layer functions of the wireless network. For example, DU 210 can perform a portion of the PHY layer and MAC layer functions. In this document, a portion of the PHY layer refers to functions performed at a higher level within the PHY layer and may include, for example, channel coding (or channel decoding), scrambling (or descrambling), modulation (or demodulation), and layer mapping (or layer demapping). According to embodiments, if DU 210 conforms to the O-RAN standard, it can be referred to as an O-RAN DU (O-DU). In embodiments of this disclosure, DU 210 may be replaced as a first network entity of a base station (e.g., gNB) as needed, and is referred to as that first network entity.

[0040] RU 220 can be responsible for lower-layer functions of the wireless network. For example, RU 220 can perform a portion of the PHY layer and RF functions. In this document, "a portion of the PHY layer" refers to functions performed at a relatively lower level than DU 210 within the PHY layer and may include, for example, iFFT conversion (or FFT conversion), cyclic prefix (CP) insertion (or CP removal), and digital beamforming. RU 220 may be referred to as an Access Unit (AU), Access Point (AP), Transmit / Receive Point (TRP), Remote Radio Headend (RRH), Radio Unit (RU), or other terms with equivalent technical meanings. According to embodiments, if RU 220 conforms to the O-RAN standard, it may be referred to as an O-RAN RU (O-RU). In embodiments of this disclosure, RU 220 may be replaced as a second network entity of a base station (e.g., gNB) as needed, and is referred to as such second network entity.

[0041] although Figure 2Base station 110 is described as including DU 210 and RU 220, but embodiments of this disclosure are not limited thereto. The base station according to embodiments can be implemented in a distributed deployment based on a centralized unit (CU) and a distributed unit (DU), wherein the centralized unit is configured to perform upper-layer functions of the access network (e.g., Packet Data Convergence Protocol (PDCP), Radio Resource Control (RRC)), and the distributed unit is configured to perform lower-layer functions. As an example, the distributed unit (DU) may include... Figure 2 The base station consists of a Digital Unit (DU) and a Radio Unit (RU). Furthermore, as an example, between the core network (e.g., a 5G core (5GC) or Next Generation Core (NGC)) and the Radio Access Network (RAN), the base station can be implemented in a structure where CU, DU, and RU are arranged in sequence. The interface between the CU and the Distributed Unit (DU) can be referred to as the F1 interface.

[0042] By connecting to one or more DUs, a centralized unit (CU) can handle functions at higher layers than the DUs. For example, a CU can handle functions at the Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP) layers, while DUs and RUs can handle functions at lower layers. A DU can perform Radio Link Control (RLC), Media Access Control (MAC), and some functions at the PHY layer (high PHY), while an RU can perform the remaining functions at the PHY layer (low PHY). Furthermore, as an example, depending on the implementation of a distributed deployment of the base station, digital units (DUs) can be included within distributed units (DUs). Hereinafter, unless otherwise defined, the description refers to the operation of digital units (DUs) and RUs; however, various embodiments of this disclosure can be applied to both base station arrangements including CUs and arrangements where DUs are directly connected to the core network (i.e., CUs and DUs are integrated into a base station as a single entity (e.g., an NG-RAN node)).

[0043] Figure 3 Examples of resource structures in the time and frequency domains are shown. Figure 3 The basic structure of the time-frequency domain is shown. The time-frequency domain is the radio resource domain for transmitting data or control channels in the downlink or uplink.

[0044] refer to Figure 3 The horizontal axis represents the time domain, and the vertical axis represents the frequency domain. The smallest unit of transmission in the time domain is an Orthogonal Frequency Division Multiplexing (OFDM) symbol, and Nsymb OFDM symbols 302 are aggregated to form a time slot 306. The length of a subframe is defined as 1 ms, and the length of a radio frame 314 is defined as 10 ms. The smallest unit of transmission in the frequency domain can be a subcarrier.

[0045] The basic unit of resources in the time-frequency domain is a resource element (hereinafter referred to as "RE") 312, which can be represented as an OFDM symbol index and a subcarrier index. A resource block can include multiple resource elements. In LTE systems, a resource block (RB) (or physical resource block, hereinafter referred to as "PRB") is defined as Nsymb consecutive OFDM symbols in the time domain and NSCRB consecutive subcarriers in the frequency domain. In NR systems, a resource block (RB) 308 can be defined as NSCRB consecutive subcarriers 310 in the frequency domain. In radio access networks, the bandwidth for configuring the resource grid can include NRBDL or NRBUL RBs 304. NRBDL represents the number of RBs corresponding to the downlink bandwidth, and NRBU represents the number of RBs corresponding to the uplink bandwidth. An RB 308 includes NSCRB REs 312 on the frequency axis. Typically, the smallest unit of data transmission is an RB, and the number of subcarriers is NSCRB=12. The frequency domain can include common resource blocks (CRBs). Physical resource blocks (PRBs) can be defined in the bandwidth portion (BWP) in the frequency domain. The number of CRBs and PRBs can be determined based on the subcarrier spacing. The data rate can be increased proportionally to the number of RBs scheduled for the terminal.

[0046] In NR systems, in the case of frequency division duplex (FDD) systems that operate by dividing the downlink and uplink by frequency, the downlink transmission bandwidth and uplink transmission bandwidth can be different. Channel bandwidth indicates the radio frequency (RF) bandwidth corresponding to the system transmission bandwidth. Table 1 shows a portion of the correspondence between system transmission bandwidth, subcarrier spacing (SCS), and channel bandwidth defined in NR systems in frequency bands below x GHz (e.g., Frequency Range (FR) 1 (310 MHz to 7125 MHz)). Table 2 shows a portion of the correspondence between transmission bandwidth, subcarrier spacing, and channel bandwidth defined in NR systems in frequency bands above y GHz (e.g., FR2 (24250 MHz–52600 MHz) or FR2-2 (52600 MHz–71,000 MHz)). For example, in an NR system with a channel bandwidth of 100 MHz and a subcarrier spacing of 30 kHz, the transmission bandwidth is configured with 273 RBs. In Tables 1 and 2, N / A can be a bandwidth-subcarrier combination that is not supported in the NR system.

[0047] [Table 1]

[0048]

[0049] [Table 2]

[0050]

[0051] Figure 4 An example of a channel in a communication standard is shown.

[0052] Figure 4 An example of a channel in a communication standard is shown. Depending on the layers defined in the communication standard, a channel may include a physical channel 410, a transport channel 420, and a logical channel 430.

[0053] refer to Figure 4 Physical channel 410 can provide the functions necessary for generating physical signals in the physical layer (e.g., channel coding, HARQ processing, modulation, multi-antenna processing, and resource mapping). In the physical layer, physical signals are modulated in an OFDM scheme and can be transmitted via time-frequency resources (e.g., Figure 3 The resources of the resource grid are transmitted in the wireless environment.

[0054] In downlink transmission, physical channel 410 may include at least one of the physical broadcast channel (PBCH), physical downlink shared channel (PDSCH), or physical downlink control channel (PDCCH). The PDCCH may be used to carry downlink control information (DCI). Typically, downlink data may refer to symbols transmitted via the PDSCH, and downlink control signals may include symbols transmitted via the PDCCH. Furthermore, in the downlink, besides… Figure 4 In addition to the channels shown, SS / PBCH blocks, including synchronization signals (e.g., primary synchronization signal (PSS) or secondary synchronization signal (SSS)) and broadcast signals (e.g., PBCH), can also be transmitted. Furthermore, in the downlink, channel state information reference signals (CSI-RS) for obtaining measurement or channel information, demodulation reference signals (DMRS) for channel estimation and demodulation, and phase tracking reference signals (PTRS) can be transmitted.

[0055] In uplink transmission, physical channel 410 may include at least one of the Physical Uplink Shared Channel (PUSCH), Physical Uplink Control Channel (PUCCH), or Physical Random Access Channel (PRACH). PUSCH or PUCCH may be used to carry uplink control information (UCI). Typically, uplink data may refer to symbols transmitted via PUSCH, and uplink control signals may include symbols corresponding to UCI. For example, UCI may include at least one of Scheduling Request (SR), (multiple) Hybrid Automatic Request (HARQ)-Acknowledgement (ACK) bits, or Channel State Information (CSI). Furthermore, in the uplink, besides… Figure 4 In addition to the channels shown, DMRS for channel estimation and demodulation and PTRS for channel estimation can be transmitted in the downlink.

[0056] Transport channel 420 can connect the physical layer and a higher-level media access channel (MAC) layer, and can be classified according to the manner in which data is transmitted via the wireless interface. In the downlink, transport channel 420 may include at least one of a paging channel (PCH) for paging, a broadcast channel (BCH) for broadcasting system information, and a downlink shared channel (DL-SCH) for downlink data transmission. In the uplink, transport channel 420 may include at least one of a random access channel (RACH) for transmitting random access preambles or an uplink shared channel (UL-SCH) for transmitting downlink data.

[0057] Logical channel 430 is located above the transport channel and is mapped to transport channel 420. Logical channel 430 can be classified as a control channel for transmitting control area information and a traffic channel for transmitting user area information. The control channel of logical channel 430 may include at least one of paging control channel (PCCH), broadcast control channel (BCCH), common control channel (CCCH), or dedicated control channel (DCCH). The traffic channel of logical channel 430 may include a dedicated traffic channel (DTCH).

[0058] In describing embodiments of this disclosure, random access signals may include sequences transmitted via PRACH. "Data" may include signals that are not reference signals. As an example, in uplink communication, "data" received by a receiver may include signals transmitted via PDSCH. However, PDSCH is merely illustrative, and it will be apparent that embodiments of this disclosure can also be applied to channels where precoders can be applied (e.g., PUSCH, PDCCH, and PUCCH).

[0059] Precoding can represent the operations applied to a signal before it is transmitted by the transmitter. In a wireless communication system, a signal can be transmitted over a wireless channel between a transmitter and a receiver. For the receiver to correctly receive the signal, the transmitter can perform an operation of multiplying the signal by a specific matrix. This specific matrix can be called a precoder or precoding matrix. For example, in a 3GPP standard communication system, terminal 120 is defined to report Channel State Information (CSI) to base station 110. Channel State Information refers to information related to the quality of the wireless channel or wireless link formed between terminal 120 and the antenna ports (e.g., CSI-RS ports) of base station 110. Channel State Information can include a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), and a Channel Quality Indicator (CQI). The RI indicates information related to the rank of the channel and represents the number of streams that terminal 120 can receive through the same resources. The PMI is a value reflecting the spatial characteristics of the channel, representing information (e.g., an index) about the precoding matrix preferred by the terminal among multiple candidate precoding matrices. Multiple candidate precoding matrices are defined as codebooks, and the candidate precoding matrices of a codebook can be defined in various ways in the standard depending on the codebook type.

[0060] The 3GPP NR standard defines Type 1 and Type 2 codebooks. Type 1 codebooks can be further divided into single-panel codebooks and multi-panel codebooks. Type 2 codebooks can be divided into the general Type 2 codebook and Type 2 port selection codebook introduced in Release 15, and the enhanced Type 2 codebook and enhanced Type 2 port selection codebook introduced in Release 16. Since the Type 2 codebook in Release 15 only supports a maximum rank of 2, the enhanced Type 2 codebook was introduced in Release 16. The enhanced Type 2 codebook can support a maximum rank of 4, and in the enhanced Type 2 codebook, the beam amplitude scaling and in-phase values ​​(which can be called beam coefficients) of all beams can be calculated in a manner similar to that of the Type 2 codebook. With the expansion of the rank, the feedback overhead can increase linearly with the number of subbands. Due to potentially insufficient uplink resources, a process known as Discrete Fourier Transform (DFT) compression or frequency domain compression can be applied to the enhanced Type 2 codebook by utilizing the frequency domain correlation of the beam coefficients.

[0061] According to the 3GPP standard, in the precoder of the enhanced Type 2 codebook, the Discrete Fourier Transform (DFT) vector can be used as the basis vector. The basis vector can be defined as the angles of the horizontal and vertical beams in a two-dimensional antenna array. The enhanced Type 2 codebook includes a sub-band (SB) based precoder; however, the terminal 120 can be configured to report a limited number of coefficients by compression after transforming the sub-band domain into the hysteresis domain, rather than reporting information about the precoder for each sub-band. For uplink resource efficiency, the capacity of the CSI of the uplink control information (UCI) can be reduced.

[0062] Terminal 120 can determine the rank, precoding matrix, and / or modulation order based on mutual information (MI) or downlink throughput. For example, terminal 120 can determine the mutual information. Terminal 120 can obtain an effective MIMO CFR matrix by multiplying the channel frequency response (CFR) matrix by the precoding matrix. When the transmitter uses bit-interleaved coded modulation (BICM) and the receiver uses maximum likelihood (ML) or linear minimum mean square error (LMMSE), terminal 120 can obtain the mutual information from the MIMO CFR. Terminal 120 can determine the number of layers that maximize the mutual information. The number of layers may be related to the rank. Terminal 120 can determine the precoding matrix that maximizes the mutual information as a precoder. The precoder can be associated with a codebook index to be reported to base station 110. The codebook index can be used to form a specific precoder. Terminal 120 can determine the modulation order that maximizes the mutual information. The modulation order can be associated with the CQI representing the modulation scheme. For example, the modulation scheme can be quadrature phase shift keying (QPSK) corresponding to modulation order 2, 16 quadrature amplitude modulation (QAM) corresponding to modulation order 4, 64 QAM corresponding to modulation order 6, or 256 QAM corresponding to modulation order 8.

[0063] Figure 5a The codebook index of type 2 codebook is shown.

[0064] refer to Figure 5a The precoding matrix for type 2 codebooks can be indicated by multiple codebook indices. The precoding matrix for layer l can be W. (l) To describe the precoding matrix, the following terms may be defined. In this disclosure, wideband (WB) represents the entire frequency band of the cell being connected (e.g., BWP), and subband (SB) may represent a subset of WB. Subbands may be configured by the network (e.g., base station 110), and the precoding matrix of a type 2 codebook may include components in subband cells. Multiple codebook indices may include a first codebook index (i... 1,1 501, Second Codebook Index (i 1,2 502, Third Codebook Index (i 1,4,l 503, Fourth Codebook Index (i 2,1,l 504, Fifth Codebook Index (i 2,2,l )505 and the sixth codebook index (i 1,3,l 506. As a non-restrictive example, in the fifth codebook index (i 2,2,l In 505, reports can be omitted based on network settings.

[0065] First codebook index (i 1,1501 can represent the choice of oversampling. For example, the first oversampling factor for the first dimension (e.g., the horizontal dimension) could be O1, and the second oversampling factor for the second dimension (e.g., the vertical dimension) could be O2. First codebook index (i 1,1 Oversampling can be represented as a combination of (o1, o2), where O1 can have a value equal to or greater than 0 and equal to or less than O1-1, and O2 can have a value equal to or greater than 0 and equal to or less than O2-1. The second codebook index (i...) 1,2 The second codebook index (i) can represent the selection of the DFT beam. For example, the number of antenna ports in the first dimension (e.g., the horizontal dimension) can be N1, and the number of antenna ports in the second dimension (e.g., the vertical dimension) can be N2. 1,2 )502 can represent the DFT beam as a combination of (n1, n2), where n1 can have a value equal to or greater than 0 and equal to or less than N1-1, and n2 can have a value equal to or greater than 0 and equal to or less than N2-1. First codebook index (i 1,1 ) and second codebook index (i 1,2 The combination of beams can be represented as (m1, m2), and the combination of the i-th beam out of a total of L beams can be represented as (m1, m2). (i) m2 (i) Third codebook index (i) 1,4,l 503 can represent the WB amplitude. The WB amplitude of the i-th beam can be represented as p. l,i (1) Fourth codebook index (i 2,1,l 504 can represent the sub-band phase. The sub-band phase of the i-th beam can be represented as φ. l,i。 Fifth codebook index (i 2,2,l 505 can represent the SB amplitude. The SB amplitude of the i-th beam can be represented as p. l,i (2) The sixth codebook index (i 1,3,l 506 can represent the strongest beam.

[0066] Type 2 codebooks can provide a two-level form of precoding matrix consisting of the product of two matrices. For example, a Type 2 codebook precoding matrix can have the following form.

[0067] [Equation 1]

[0068]

[0069] W1 is the precoding matrix for the WB component, and W2 represents the precoding matrix for the SB component. Considering the components represented by each codebook index, W1 can be defined by W specified by the first codebook index 501 and the second codebook index 502.m1 (i) , m2 (i) and p specified by the third codebook index 503 l,i (1) Alternatively, W2 can be configured via the fourth codebook index 504 and the fifth codebook index 505.

[0070] Figure 5b The design principles of the enhanced Type 2 codebook are shown.

[0071] refer to Figure 5b The first grid 551 represents the beams and subbands in the spatial domain according to the Type 2 codebook. The second grid 552 represents the beams and basis vectors in the spatial domain according to the enhanced Type 2 codebook. In the second grid 552, the N3 subbands from the first grid 551 can be transformed into Mv basis vectors through frequency domain compression. The transformation caused by frequency domain compression can be expressed as follows.

[0072] [Equation 2]

[0073]

[0074] This represents the DFT matrix used for frequency domain compression.

[0075] Terminal 120, configured with an enhanced Type 2 codebook, can report to base station 110... The codebook index is related to the component of W2, not the component of W2. Equation 1 can be restated as follows.

[0076] [Equation 3]

[0077]

[0078] Along with frequency domain compression, the number of non-zero coefficients (hereinafter referred to as non-zero coefficients) can be limited by ignoring weaker beam coefficients.

[0079] Figure 5c The codebook index of the enhanced type 2 codebook is shown.

[0080] refer to Figure 5c The precoding matrix of an enhanced type 2 codebook can be indicated by multiple codebook indices. For example... Figure 5a As shown, wideband (WB) represents the entire frequency band of the cell being connected (e.g., BWP), and subband (SB) can represent a subset of WB. The precoding matrix of an enhanced type 2 codebook can include components at the subband level. For layer 1, the precoding matrix including all subbands can be... The precoding matrix can be configured with WB spatial information, SB amplitude and phase information, and delay information. When the size of the precoding matrix is ​​N... AP When the value is ×N3, NAP represents the number of antennas, and N3 represents the number of subbands. The size of the matrix corresponding to the WB spatial information is N. AP ×2L. The size of the matrix corresponding to the amplitude and phase information of SB is 2L×M. v The size of the matrix corresponding to the delay information is M. v ×N3. Operations on WB spatial information and SB amplitude and phase information can be understood as compression in the spatial domain. Operations on SB amplitude and phase information and delay information can be understood as compression in the frequency domain.

[0081] Multiple codebook indices may include the first codebook index (i 1,1 i 1,2 571. Second codebook index (i 2,3,l 572. Third Codebook Index (i 2,5,l 573, Fourth Codebook Index (i 2,4,l 574, Fifth Codebook Index (i 1,5 i 1,6,l 575, Sixth Codebook Index (i 1,7,l )576 and the seventh codebook index (i 1,8,l 577. First codebook index (i 1,1 i 1,2 571 can represent a 2DDFT beam. First codebook index (i 1,1 i 1,2 )571 can represent a 2D DFT beam (or can be called a DFT basis vector or basis vector), which is expressed as For example, in type 2 codebooks. Second codebook index (i 2,3,l 572 can represent the WB amplitude. The WB amplitude can be represented as p. l,p (1) For example, p can represent polarization (e.g., p = 0, 1). l can represent a layer. Third codebook index (i 2,5,l 573 represents the feedback phase. The feedback phase can be represented as... Fourth codebook index (i 2,4,l 574 represents the feedback amplitude. The feedback amplitude can be expressed as p. l,i,f (2) Fifth codebook index (i 1,5 i 1,6,l )575 indicates the delay based on frequency compression, and can be expressed as f represents M v One of the basis vectors. For example, f has vectors in 0 and M.v Values ​​between -1 and 1. Sixth codebook index (i 1,7,l )576 is a bitmap, and the seventh codebook index (i 1,8,l 577 can represent the strongest beam.

[0082] Principal Component Analysis (PCA) is a technique used to compress high-dimensional vectors. For example, through PCA, terminal 120 can obtain multiple eigenvectors for a complete frequency band (e.g., the entire BWP or wideband (WB)) and multiple eigenvectors for each subband. To describe the choice of precoder using PCA, the necessary descriptions are given below.

[0083] [Equation 4]

[0084]

[0085] Indicates subcarrier index, This represents the OFDM symbol index within a time slot. Indicates the number of transmit antenna ports. Indicates the number of receive antenna ports, and Indicates the transmit antenna port and receiving antenna port . Subcarrier index and OFDM symbols The CFR matrix at that location, and Indicates the transmit antenna port CFR vector and subcarrier index at the location and OFDM symbols .

[0086] A new effective CFR can be defined by the CFR matrix and the precoding matrix.

[0087] [Equation 5]

[0088]

[0089] represents the new valid CFR matrix, and s represents the subband index.

[0090] The CFR matrix in Equation 4 can be restated as follows.

[0091] [Equation 6]

[0092]

[0093] In this article, yes The Row vectors.

[0094] For the Broadband PMI report, PCA techniques can be expressed as follows.

[0095] [Equation 7]

[0096]

[0097] In Equation 7, the second equation starting from the top can be derived from... The definition is derived from the eigenvalues, and the third equation can be obtained through eigenvalue decomposition. λ[l] is the l-th eigenvalue and can satisfy the following inequality.

[0098] [Equation 8]

[0099]

[0100] Indicates and The corresponding feature vectors.

[0101] For subband PMI reports, PCA techniques can be expressed as follows.

[0102] [Equation 9]

[0103]

[0104] This represents the set of subcarrier indices corresponding to subband s, and Representation set The base number. It is the l-th eigenvalue of subband s, and Is with The corresponding feature vectors.

[0105] In this disclosure, based on the aforementioned PCA technique, a technique for determining the enhanced type 2 precoder as defined in the NR standard is described. Figure 6 The text describes an example of terminal 120 selecting an enhanced type 2 precoding matrix based on PCA technology, and... Figure 7 The example described is of a base station 110 (e.g., DU 210) selecting an enhanced type 2 precoding matrix according to the PCA technique.

[0106] Figure 6 The signal flow used for Channel State Information (CSI) reporting is shown. Figure 6 In this context, the operation of base station 110 can be understood as the operation of DU 210 or RU 220. For example, the operation of transmitting signals or receiving signals from base station 110 can be understood as the operation of DU 210 through RU 220.

[0107] refer to Figure 6 In operation 601, base station 110 may send a reference signal to terminal 120. For example, the reference signal may include a channel state information reference signal (CSI-RS).

[0108] In operation 603, terminal 120 can perform precoder selection based on the enhanced Type 2 codebook. According to an embodiment, terminal 120 can obtain feature vectors using PCA technology. Terminal 120 can determine the precoding matrix of the enhanced Type 2 codebook using the feature vectors. For example, assuming the enhanced Type 2 codebook has 2 layers, terminal 120 can obtain two feature vectors using PCA technology. For example, terminal 120 can obtain feature vectors according to the following equation.

[0109] [Equation 10]

[0110]

[0111] In this article, and They are the first layer SB SB feature vectors and second-layer SB The SB eigenvectors are given. E is the error matrix. The transmitting end (e.g., base station 110 or RU 220) can transmit signals through a two-dimensional antenna array. It is the number of antenna ports in the first dimension (e.g., the horizontal domain) of the two-dimensional antenna array at the transmitting end, while It is the number of antenna ports in the second dimension (e.g., the vertical domain) of the two-dimensional antenna array at the transmitting end. This represents the i-th basis vector configured by the 2D DFT vectors, where the angle of the first dimension (e.g., the horizontal domain) is related to the index. Correspondingly, the angle of the second dimension (e.g., the vertical domain) has an index. (i=0,1,…,L-1). L refers to the number of basis vectors. Index and It can be expressed as follows.

[0112] [Equation 11]

[0113]

[0114] [Equation 12]

[0115]

[0116] when When representing the index of the angle of the first dimension of the i-th basis vector, ,and Furthermore, when When representing the index of the second dimension of the i-th basis vector, ,and . It is the oversampling factor of the first dimension, and This represents the oversampling factor for the second dimension. It can be configured via RRC messages from base station 110.

[0117] In the equation, It is the global gain (e.g., WB amplitude) of SB-common, base-common, first layer, and first pole, and The global gain (e.g., WB amplitude) represents the SB common, base common, first layer, and second pole. In this disclosure, the first pole represents the first polarization, and the second pole can represent the second polarization. For example, due to the phase difference between the first and second poles, the parameters of the in-phase component can be multiplied by the precoding matrix of a particular pole (e.g., the second pole). As an implementation example, the poles of the transmit antennas can be set to be orthogonal to each other.

[0118] In the equation, It is the global gain (e.g., WB amplitude) of SB common, base common, second layer, and first pole, and Represents the global gain (e.g., WB amplitude) of SB common, base common, second layer and second pole.

[0119] This represents the amount of hysteresis when the number of layers is v. Hysteresis represents... Figure 5c The DFT basis vectors in the codebook. In this disclosure, hysteresis represents the delay information used for partitioning in the enhanced type 2 codebook (e.g., Figure 5c The number of rows (of delayed information). In Equation 10, the number of layers can be 2. It represents the magnitudes of the first layer, the first pole, the basis vector i, and the hysteresis index f. It represents the magnitudes of the first layer, the second pole, the basis vector i, and the hysteresis index f. It is the magnitude of the second layer, the first pole, the basis vector i, and the hysteresis index f, and It represents the magnitudes of the second layer, the second pole, the basis vector i, and the hysteresis index f. It is the phase of the first layer, the first pole, the basis vector i, and the hysteresis index f. It is the phase of the first layer, the second pole, the basis vector i, and the hysteresis index f. It is the phase of the second layer, the first pole, the basis vector i, and the hysteresis index f, and It is the phase of the second layer, the second pole, the basis vector i, and the hysteresis index f.

[0120] It represents the number of sub-bands. It is the lag value corresponding to the lag index f of the first level, and This is the hysteresis value corresponding to the hysteresis index f of the second layer. To maintain a constant power for the precoding vectors of each layer, each SB... and layer l Scaling can be expressed as follows.

[0121] [Equation 13]

[0122]

[0123] Terminal 120 can obtain L basis vectors from the feature vectors obtained through PCA.

[0124] The WB feature vectors of the first layer and the first pole can be used ( , and Perform a 2D FFT. For example, a 2D DFT can be performed based on the following equation.

[0125] [Equation 14]

[0126]

[0127] We can analyze the WB feature vectors of the first and second layers ( Perform a 2D DFT. For example, a 2D DFT can be performed based on the following equation.

[0128] [Equation 15]

[0129]

[0130] We can analyze the WB feature vectors of the second layer and the first layer. Perform a 2D DFT. For example, a 2D DFT can be performed based on the following equation.

[0131] [Equation 16]

[0132]

[0133] We can analyze the WB feature vectors of the second layer and the second pole (WB feature vectors). Perform a 2D DFT. For example, a 2D DFT can be performed based on the following equation.

[0134] [Equation 17]

[0135]

[0136] In this article, ,and .

[0137] This represents the oversampling factor in the first dimension. This represents the oversampling factor in the second dimension. This indicates the number of antennas in the first dimension, and This indicates the number of antennas in the second dimension. It can be configured via RRC messages from base station 110.

[0138] Decision metrics can be calculated using the equation above. , , , To generate it. For example, decision metrics can be generated based on the following equation.

[0139] [Equation 18]

[0140]

[0141] In this article, and These are design parameters. For example, It can be 1, and It can be 1.

[0142] As another example, a decision metric can be generated based on the following equation.

[0143] [Equation 19]

[0144]

[0145] Using the definition above , A set can be defined as follows.

[0146] [Equation 20]

[0147]

[0148] This represents the decision metric illustrated in Equations 18 and 19. Based on the following equations, you can choose... .

[0149] [Equation 21]

[0150]

[0151] Best Collection It can be defined as follows.

[0152] [Equation 22]

[0153]

[0154] In this article, Represents the i-th entry The index of the angle of the first dimension (e.g., the horizontal domain) of the L basis vectors. Index of the angle of the second dimension (e.g., the vertical domain) The following can be confirmed.

[0155] [Equation 23]

[0156]

[0157] [Equation 24]

[0158]

[0159] For each SB The obtained eigenvectors can be applied to the basis vectors. The SB eigenvectors of the first layer and the first pole ( ) can be projected onto the determined basis vectors ( For example, the SB eigenvector can be projected based on the following equation.

[0160] [Equation 25]

[0161]

[0162] SB feature vectors of the first and second layers ( ) can be projected onto the determined basis vectors ( For example, the SB eigenvector can be projected based on the following equation.

[0163] [Equation 26]

[0164]

[0165] SB feature vectors of the second layer and the first pole ( ) can be projected onto the determined basis vectors ( For example, the SB eigenvector can be projected based on the following equation.

[0166] [Equation 27]

[0167]

[0168] The SB feature vector of the second layer and the second pole ( ) can be projected onto the determined basis vectors ( For example, the SB eigenvector can be projected based on the following equation.

[0169] [Equation 28]

[0170]

[0171] The precoding matrix of the enhanced type 2 codebook can be approximated by the eigenvectors illustrated by equations 25 to 28 as follows. Frequency domain compression may not be performed before reporting.

[0172] [Equation 29]

[0173]

[0174] Terminal 120 can compute mutual information using a precoding matrix and CFR estimation. This equation assumes two levels, i.e., rank 2, but terminal 120 can repeat the computation of mutual information while changing the rank. For example, terminal 120 can select the rank that maximizes mutual information and can report the PMI and CQI corresponding to the selected rank.

[0175] Unlike the case where base station 110 determines the precoder, in the case where terminal 120 determines the precoder to report CSI, additional operations such as frequency compression, quantization, and coefficient limiting may need to be performed. For example, terminal 120 may perform operations on each based on the following equation: Perform an FFT on the coefficients.

[0176] [Equation 30]

[0177]

[0178] In this article, ,and Terminal 120 can calculate the following metrics.

[0179] [Equation 31]

[0180]

[0181] It is possible to sort in descending order while keeping l fixed and changing u. Among the sorted vectors, the first few can be selected. There are 10 entries. The lag value of an entry can be expressed as: .

[0182] When fixing layer l and the first pole, and when changing and hour, The peak value can be identified. (Compared to...) The position corresponding to the peak can be When fixing layer l and the second pole, and when changing... and hour, The peak value can be identified. (Compared to...) The position corresponding to the peak can be .variable It can be initialized as follows.

[0183] [Equation 32]

[0184]

[0185] In this article, , ,and .

[0186] For example, corresponding to layer l and the first pole It can be greater than that corresponding to layer l and the second pole. In this case, the variable The position can be determined according to the following equation.

[0187] [Equation 33]

[0188]

[0189] [Equation 34]

[0190]

[0191] For example, corresponding to layer l and the first pole It can be less than or equal to the layer corresponding to the second pole. In this case, the variable The position can be determined according to the following equation.

[0192] [Equation 35]

[0193]

[0194] [Equation 36]

[0195]

[0196] It is to satisfy The hysteresis f of layer l, and It is to satisfy The lag of layer l is f.

[0197] To quantify the global gain, the following table can be defined.

[0198] Table 3 lists the p1 values ​​defined in the standard.

[0199] [Table 3]

[0200]

[0201] Table 4 lists the p2 values ​​defined in the standard.

[0202] [Table 4]

[0203]

[0204] Table 5 is a table obtained by multiplying the p1 and p2 values ​​defined in the standard in any combination and listing them in order of magnitude. Table 4 has a total of 29 values.

[0205] [Table 5]

[0206]

[0207] The “Thre1” listed in Table 6 is the average of two adjacent values ​​in Table 5.

[0208] [Table 6]

[0209]

[0210] Table 7 is the average of two adjacent values ​​in Table 4.

[0211] [Table 7]

[0212]

[0213] Using the values ​​of layer l and the first pole and the values ​​of layer l and the second pole This allows us to calculate the global gain for each layer and each pole. For example, when When the value is 0.088388, the following conditions are met for this value to be true. It may have the following eight combinations: (0.088388,1), (0.125,0.717107), (0.176777,0.5), (0.25,0.353553), (0.353553,0.25), (0.5,0.176777), (0.717107,0.125), (1,0.088388).

[0214] if ,express p1 and p2 become 1 and 1 as unique solutions. For example, if Then it can represent The method can be to use the previous eight combinations as the solution. If p_1 is 1, then p_2 becomes 0.088388.

[0215] However, since p_1 is the global gain of the second pole, when considering layer l and the second pole... hour, The quantized minimum value inevitably becomes 0.088388. Note that the minimum value of p_2 is 0.088388. In order to represent the values ​​of layer l and the second pole over a wide range, The p_1 should be minimized, and p_1 = 0.088388 should be obtained to minimize the quantization loss to the greatest extent. Then, layer l and the second pole The quantized minimum value can be .if At 0.088388 and If it is between and close to 0.088388, then it can be mapped to ; and if At 0.088388 and If it is between and close to 0.088388, then it can be mapped to The global gain can be identified based on the logic described above. For example, the identification of the global gain can be expressed in the following code.

[0216] [Table 8]

[0217]

[0218] In Table 8, and They refer to quantified and The index.

[0219] Not only the global gain, but also the magnitude of each hysteresis can be quantized. For layer l and the first pole, this can be achieved by quantizing | Divide by Obtain the first value. For layer l and the second pole, this can be achieved by... Divide by Obtain the second value. The amplitudes of layer l and the first pole can be quantized as the value closest to the first value among the p2 values ​​in Table 2. The amplitudes of layer l and the second pole can be quantized as the value closest to the second value among the p2 values ​​in Table 2. For example, the amplitude of the first pole can be expressed as follows:

[0220] [Table 9]

[0221]

[0222] For example, the amplitude of the second pole can be expressed as the following code.

[0223] [Table 10]

[0224]

[0225] For the PMI report, each lagged phase can also be quantified.

[0226] [Equation 37]

[0227]

[0228] In the hysteresis domain, the non-zero coefficients may be finite. For a given layer l, It is possible to sort in descending order while simultaneously changing i and f. In the sorting... Among them, you can choose the one with the maximum value. indivual For all layers ( By repeating the above process, terminal 120 can obtain the total 120 entries. Terminal 120 can sort the total in descending order. Sort the entries. You can select the one with the maximum value. There are 100 entries, and each index can be stored as follows.

[0229] [Equation 38]

[0230]

[0231] Now, the SB precoder can be determined using a quantized, finite number of coefficients and WB basis vectors. Variables It can be initialized as follows.

[0232] [Equation 39]

[0233]

[0234] In this article, , ,and Furthermore, the above-obtained... The following can be applied to each item.

[0235] [Equation 40]

[0236]

[0237] The precoding matrix of the enhanced type 2 codebook can be determined as follows.

[0238] [Equation 41]

[0239]

[0240] [Equation 42]

[0241]

[0242] Terminal 120 can calculate mutual information using the calculated precoding matrix and CFR estimation. For example, terminal 120 can repeat the calculation of mutual information while changing the rank. For example, terminal 120 can select the rank that maximizes mutual information and can report the PMI and CQI corresponding to the selected rank. In the above example, rank 2 has been assumed, but this is merely an example and should not be construed as limiting other embodiments of this disclosure. For example, embodiments of this disclosure can be applied not only to ranks 1, 3, and 4 specified in the standard, but also to ranks 5, 6, 7, and 8.

[0243] Figure 7 The pre-coded signal flow applied to downlink data is shown. Figure 7 In this context, the operation of base station 110 can be understood as the operation of DU 210 or RU 220. For example, the operation of transmitting or receiving signals from base station 110 can be understood as the operation of DU 210 through RU 220. The operation of selecting the precoder of base station 110 can be understood as the operation of DU 210. Figure 7 In this context, it is assumed that channel reciprocity is satisfied in the radio channel between base station 110 and terminal 120. For example, signals on the radio channel can be transmitted or received in the TDD band.

[0244] refer to Figure 7 In operation 701, terminal 120 can send SRS to base station 110.

[0245] In operation 703, base station 110 can perform precoder selection based on the enhanced Type 2 codebook. According to an embodiment, base station 110 can obtain feature vectors according to a scheme. Base station 110 can determine the precoding matrix of the enhanced Type 2 codebook using the feature vectors. For example, base station 110 can determine the precoding matrix according to the methods described in Equations 10 to 29. Meanwhile, since base station 110 aims to determine the enhanced Type 2 codebook, compression, quantization, and / or limiting the number of non-zero coefficients are unnecessary since separate reporting is not required. Therefore, the calculation process in Equations 30 to 42 can be omitted. As a non-limiting example, determining the precoding matrix using the methods in Equations 30 to 42 can also be understood as an embodiment of this disclosure.

[0246] In operation 705, base station 110 can perform data transmission to terminal 120. Base station 110 can apply a precoding matrix to the transmitted data according to a precoder selection. For example, the transmitted data may include the transport stream of each antenna. Base station 110 can multiply the transport vector including the transport stream by the precoding matrix. Base station 110 can send the result of the multiplication to terminal 120 through multiple antennas.

[0247] Figure 8a , Figure 8b , Figure 9a , Figure 9b , Figure 10a , Figure 10b , Figure 11a and Figure 11b An example of performing precoder selection is shown.

[0248] refer to Figure 8a Graph 800 represents the throughput based on the number of layers. The horizontal axis of graph 800 represents the number of layers. The vertical axis of graph 800 represents the throughput (in megabits per second (Mbps)). In graph 800, it is assumed that the number of horizontal antenna ports of base station 110 is 16, the number of vertical antenna ports of base station 110 is 2, and the number of antenna ports of terminal 120 is 4. Under a 32×4 MIMO trunked delay line (CDL)-B channel, it is assumed that the SCS = 30kHz, the number of RBs is 53, all RBs are scheduled, the SNR = -20dB, and the UE speed is 0km / h. It is assumed that the channel is in a non-line-of-sight (NLOS) environment. The first line 801 represents the transmission performance when using a precoder with an enhanced type 2 codebook without frequency compression. The second line 802 represents the transmission performance when using a precoder with an enhanced type 2 codebook with frequency compression according to an embodiment. The third line 803 represents the transmission performance when using a type 1 codebook. When the number of layers is 1, approximately 57% of the performance gain of the first line 801 is identified compared to the third line 803.

[0249] refer to Figure 8b Graph 850 represents the throughput based on the number of layers. The horizontal axis of graph 850 represents the number of layers. The vertical axis of graph 850 represents the throughput (in Mbps). In graph 850, it is assumed that the number of horizontal antenna ports of base station 110 is 16, the number of vertical antenna ports of base station 110 is 2, and the number of antenna ports of terminal 120 is 4. Under a 32×4 MIMO CDL-B channel, it is assumed that the SCS = 30kHz, the number of RBs is 53, all RBs are scheduled, the SNR = 0dB, and the UE speed is 0km / h. It is assumed that the channel is an NLOS environment. The first line 851 represents the transmission performance when using a precoder with an enhanced Type 2 codebook without frequency compression. The second line 852 represents the transmission performance when using a precoder with an enhanced Type 2 codebook using frequency compression according to an embodiment. The third line 853 shows the transmission performance when using a Type 1 codebook. When the number of layers is 2, approximately 46% of the performance gain of the first line 851 is identified compared to the third line 853.

[0250] refer to Figure 9a Graph 900 represents the throughput based on the number of layers. The horizontal axis of graph 900 represents the number of layers. The vertical axis of graph 900 represents the throughput (in Mbps). In graph 900, it is assumed that the number of horizontal antenna ports of base station 110 is 16, the number of vertical antenna ports of base station 110 is 2, and the number of antenna ports of terminal 120 is 4. Under a 32×4 MIMO CDL-B channel, it is assumed that the SCS = 30kHz, the number of RBs is 53, all RBs are scheduled, the SNR = 20dB, and the UE speed is 0km / h. It is assumed that the channel is an NLOS environment. The first line 901 represents the transmission performance when using a precoder with an enhanced Type 2 codebook without frequency compression. The second line 902 represents the transmission performance when using a precoder with an enhanced Type 2 codebook using frequency compression according to an embodiment. The third line 903 represents the transmission performance when using a Type 1 codebook. When the number of layers is 3, approximately 31% performance gain of the first line 901 is identified compared to the third line 903.

[0251] refer to Figure 9b Graph 950 represents the throughput based on the number of layers. The horizontal axis of graph 950 represents the number of layers. The vertical axis of graph 950 represents the throughput (in Mbps). In graph 950, it is assumed that the number of horizontal antenna ports of base station 110 is 16, the number of vertical antenna ports of base station 110 is 2, and the number of antenna ports of terminal 120 is 4. Under a 32×4 MIMO CDL-B channel, it is assumed that the SCS = 30kHz, the number of RBs is 53, all RBs are scheduled, the SNR = 30dB, and the UE speed is 0km / h. It is assumed that the channel is an NLOS environment. The first line 951 represents the transmission performance when using a precoder with an enhanced Type 2 codebook without frequency compression. The second line 952 represents the transmission performance when using a precoder with an enhanced Type 2 codebook using frequency compression according to an embodiment. The third line 953 represents the transmission performance when using a Type 1 codebook. When the number of layers is 3, an approximately 7% performance gain is identified in the first line 951 compared to the third line 953.

[0252] refer to Figure 10aGraph 1000 represents the throughput based on the number of layers. The horizontal axis of Graph 1000 represents the number of layers. The vertical axis of Graph 1000 represents the throughput (in Mbps). In Graph 1000, we assume the following conditions: base station 110 has 16 horizontal antenna ports, base station 110 has 2 vertical antenna ports, and terminal 120 has 4 antenna ports. Under a 32×4 MIMO CDL-D channel, we assume the following conditions: SCS = 30kHz, number of RBs is 53, all RBs are scheduled, SNR = -20dB, and UE speed is 0km / h. We assume the channel is in a line-of-sight (LOS) environment. The first line 1001 represents the transmission performance when using a precoder with an enhanced Type 2 codebook without frequency compression. The second line 1002 represents the transmission performance when using a precoder with an enhanced Type 2 codebook using frequency compression according to an embodiment. The third line 1003 represents the transmission performance when using a Type 1 codebook. When the number of layers is 1, an approximately 4% performance gain is identified in the first line 1001 compared to the third line 1003.

[0253] refer to Figure 10b Graph 1050 represents the throughput based on the number of layers. The horizontal axis of graph 1050 represents the number of layers. The vertical axis of graph 1050 represents the throughput (in Mbps). In graph 1050, it is assumed that the number of horizontal antenna ports of base station 110 is 16, the number of vertical antenna ports of base station 110 is 2, and the number of antenna ports of terminal 120 is 4. Under a 32×4 MIMO CDL-B channel, it is assumed that the SCS = 30kHz, the number of RBs is 53, all RBs are scheduled, the SNR = 0dB, and the UE speed is 0km / h. It is assumed that the channel is in a LOS environment. The first line 1051 represents the transmission performance when using a precoder with an enhanced Type 2 codebook without frequency compression. The second line 1052 represents the transmission performance when using a precoder with an enhanced Type 2 codebook using frequency compression according to an embodiment. The third line 1053 represents the transmission performance when using a Type 1 codebook. When the number of layers is 2, an approximately 2% performance gain is identified in the first line 1051 compared to the third line 1053.

[0254] refer to Figure 11aGraph 1100 represents the throughput based on the number of layers. The horizontal axis of graph 1100 represents the number of layers. The vertical axis of graph 1100 represents the throughput (in Mbps). In graph 1100, it is assumed that the number of horizontal antenna ports of base station 110 is 16, the number of vertical antenna ports of base station 110 is 2, and the number of antenna ports of terminal 120 is 4. Under a 32×4 MIMO CDL-B channel, it is assumed that the SCS = 30kHz, the number of RBs is 53, all RBs are scheduled, the SNR = 20dB, and the UE speed is 0km / h. It is assumed that the channel is in a LOS environment. The first line 1101 represents the transmission performance when using a precoder with an enhanced Type 2 codebook without frequency compression. The second line 1102 represents the transmission performance when using a precoder with an enhanced Type 2 codebook using frequency compression according to an embodiment. The third line 1103 represents the transmission performance when using a Type 1 codebook. When the number of layers is 3, an approximately 7% performance gain is identified in the first line 1101 compared to the third line 1103.

[0255] refer to Figure 11b Graph 1150 represents the throughput based on the number of layers. The horizontal axis of graph 1150 represents the number of layers. The vertical axis of graph 1150 represents the throughput (in Mbps). In graph 1150, it is assumed that the number of horizontal antenna ports of base station 110 is 16, the number of vertical antenna ports of base station 110 is 2, and the number of antenna ports of terminal 120 is 4. Under a 32×4 MIMO CDL-B channel, it is assumed that the SCS = 30kHz, the number of RBs is 53, all RBs are scheduled, the SNR = 30dB, and the UE speed is 0km / h. It is assumed that the channel is in a LOS environment. The first line 1151 represents the transmission performance when using a precoder with an enhanced Type 2 codebook without frequency compression. The second line 1152 represents the transmission performance when using a precoder with an enhanced Type 2 codebook using frequency compression according to an embodiment. The third line 1153 represents the transmission performance when using a Type 1 codebook. When the number of layers is 4, an approximately 5% performance gain is identified in the first line 1151 compared to the third line 1153.

[0256] Figure 12a The functional components of a digital unit (DU) (e.g., DU 210) are shown. Figure 12a The configuration shown can be understood as part of a base station. Figure 12aThe configuration of the DU 210. In the following text, terms such as “...unit” or “...equipment” refer to a unit for performing at least one function or operation, and can be implemented by hardware, software, or a combination of hardware and software.

[0257] refer to Figure 12a The DU 210 includes a transceiver 1210, a memory 1220, and a processor 1230.

[0258] Transceiver 1210 can perform functions for transmitting and receiving signals in a wired communication environment. Transceiver 1210 may include a wired interface for controlling direct connections between devices via a transmission medium (e.g., copper wire, optical fiber). For example, transceiver 1210 can transmit electrical signals to another device via copper wire, or it can perform conversion between electrical and optical signals. DU 210 can communicate with a radio unit (RU) via transceiver 1210.

[0259] Transceiver 1210 can also perform functions for transmitting and receiving signals in a wireless communication environment. For example, transceiver 1210 can perform functions for converting between baseband signals and bit sequences according to the system's physical layer specifications. For example, when transmitting data, transceiver 1210 generates complex symbols by encoding and modulating the transmitted bit sequence. Furthermore, when receiving data, transceiver 1210 recovers the received bit sequence by demodulating and decoding the baseband signal. In addition, transceiver 1210 may include multiple transmit and receive paths.

[0260] Transceiver 1210 can send and receive signals. For example, transceiver 1210 can send management plane (M-plane) messages. For example, transceiver 1210 can send management plane (S-plane) messages. For example, transceiver 1210 can send control plane (C-plane) messages. For example, transceiver 1210 can send user plane (U-plane) messages. For example, transceiver 1210 can receive user plane messages. Although in Figure 12a Only transceiver 1210 is shown in the figure, but according to another embodiment, DU 210 may include two or more transceivers.

[0261] Transceiver 1210 transmits and receives signals as described above. Accordingly, all or part of transceiver 1210 may be referred to as a "communication unit," "transmitting unit," "receiving unit," or "transceiver unit." Furthermore, in the following description, transmission and reception performed via a radio channel are used to indicate that the processing described above is performed by transceiver 1210. According to an embodiment, transceiver 1210 may obtain random access signals associated with NPRACH for which physical layer processing is performed from an RU (e.g., RU 220). For example, transceiver 1210 may obtain a signal (e.g., a frequency domain signal) and perform CP removal and FFT on that signal for the received signal.

[0262] although Figure 12a Not shown, but transceiver 1210 may further include a backhaul transceiver for connecting to the core network or another base station. The backhaul transceiver can provide an interface for performing communication with other nodes in the network. That is, the backhaul transceiver converts a bit sequence sent from the base station to another node (e.g., another access node, another base station, an upper-layer node, or the core network) into a physical signal, and converts a physical signal received from another node into a bit sequence.

[0263] Memory 1220 stores data, such as basic programs, application programs, and configuration information for the operation of DU 210. Memory 1220 may be referred to as a storage unit. Memory 1220 may be configured as volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. Furthermore, memory 1220 can provide stored data according to requests from processor 1230. Memory 1220 represents storage space as a functional component. For example, memory 1220 can be understood not only to represent the memory of components configured within DU 210 (e.g., hard disk, flash memory, RAM), but also to represent space used for storing instructions and / or programs.

[0264] Processor 1230 controls the overall operation of DU 210. Processor 1230 can be referred to as a control unit. For example, processor 1230 sends and receives signals via transceiver 1210 (or via a return communication unit). Furthermore, processor 1230 writes data to memory 1220 and reads data from memory 1220. Additionally, processor 1230 can perform the functions of the protocol stack required in the communication standard. Although in Figure 12a Only processor 1230 is shown in the diagram, but according to another embodiment, DU 210 may include two or more processors.

[0265] According to an embodiment, processor 1230 can perform physical layer processing on signals received from an RU (e.g., RU 220). For example, processor 1230 can perform subcarrier demapping (RE demapping) on ​​the received signals. For example, processor 1230 can obtain noise interference components (e.g., noise interference covariance matrix) based on the received reference signal. Furthermore, for example, processor 1230 can perform channel estimation based on the received reference signal. Processor 1230 can determine the weights of the combiner. Processor 1230 can determine the data corresponding to the uplink signal.

[0266] Figure 12a The configuration of DU 210 shown is merely an example, and examples of DUs used to perform embodiments of this disclosure are not limited to this. Figure 12a The configuration is shown in the figure. In some embodiments, some configurations can be added, deleted, or changed.

[0267] Figure 12b The functional components of the radio unit (RU) are shown. Figure 12b The configuration shown can be understood as part of a base station. Figure 2 The configuration of the RU 220. In the following text, terms such as “...unit” or “...equipment” refer to a unit for performing at least one function or operation, and can be implemented by hardware, software, or a combination of hardware and software.

[0268] refer to Figure 12b The RU 220 includes an RF transceiver 1260, a fronthaul transceiver 1265, a memory 1270, and a processor 1280.

[0269] RF transceiver 1260 performs the function of transmitting and receiving signals via a radio channel. For example, RF transceiver 1260 up-converts a baseband signal to an RF band signal and then transmits the RF band signal through an antenna, and down-converts the RF band signal received through the antenna back to a baseband signal. For example, RF transceiver 1260 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.

[0270] RF transceiver 1260 may include multiple transmit and receive paths. Furthermore, RF transceiver 1260 may include antenna elements. RF transceiver 1260 may include at least one antenna array configured with multiple antenna elements. In terms of hardware, RF transceiver 1260 may be configured as digital and analog circuitry (e.g., radio frequency integrated circuit (RFIC)). Hereinafter, the digital and analog circuitry may be implemented in a single package. Furthermore, RF transceiver 1260 may include multiple RF chains. RF transceiver 1260 may perform beamforming. RF transceiver 1260 may apply beamforming weights to signals according to the configuration of processor 1280 to provide directionality to signals to be transmitted and received. According to embodiments, RF transceiver 1260 may include multiple antennas.

[0271] According to an embodiment, RF transceiver 1260 can transmit and receive signals on a radio access network. For example, RF transceiver 1260 can transmit downlink signals. Downlink signals may include synchronization signals (SS), reference signals (RS) (e.g., cell-specific reference signals (CRS), demodulation (DM)-RS), system information (e.g., MIB, SIB, remaining system information (RMSI), other system information (OSI)), configuration messages, control information, or downlink data, etc. Furthermore, for example, RF transceiver 1260 can receive uplink signals. For example, uplink signals may include random access related signals (e.g., NPRACH, NPUSCH). According to an embodiment, RF transceiver 1260 can receive signals including random access signals through multiple antennas included in RF transceiver 1260. Although in Figure 12b Only RF transceiver 1260 is shown in the figure, but according to another embodiment, RU 220 may include two or more RF transceivers.

[0272] The fronthaul transceiver 1265 can transmit and receive signals. According to an embodiment, the fronthaul transceiver 1265 can transmit and receive signals on a fronthaul interface. For example, the fronthaul transceiver 1265 can receive management plane (M-plane) messages. For example, the fronthaul transceiver 1265 can receive management plane (S-plane) messages. For example, the fronthaul transceiver 1265 can receive control plane (C-plane) messages. For example, the fronthaul transceiver 1265 can transmit user plane (U-plane) messages. For example, the fronthaul transceiver 1265 can receive user plane messages. According to an embodiment, the fronthaul transceiver 1265 can transmit signals (e.g., frequency domain signals) to a DU (e.g., DU 210) to which CP removal and FFT have been performed. Figure 12b Only the fronthaul transceiver 1265 is shown in the figure, but according to another embodiment, RU 220 may include two or more fronthaul transceivers.

[0273] RF transceiver 1260 and fronthaul transceiver 1265 transmit and receive signals as described above. Accordingly, all or part of RF transceiver 1260 and fronthaul transceiver 1265 may be referred to as a "communication unit," "transmitting unit," "receiving unit," or "transceiver unit." Furthermore, in the following description, transmission and reception performed via a radio channel are used to indicate that the processes described above are performed by RF transceiver 1260.

[0274] Memory 1270 stores data, such as basic programs, application programs, and configuration information for the operation of RU 220. Memory 1270 may be referred to as a storage unit. Memory 1270 may be configured as volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. Furthermore, memory 1270 can provide stored data upon request from processor 1280. Memory 1270 represents storage space as a functional component. For example, memory 1270 can be understood not only to represent the memory of components configured within RU 220 (e.g., hard disk, flash memory, RAM), but also to represent space used for storing instructions and / or programs.

[0275] Processor 1280 controls the overall operation of RU 220. Processor 1280 can be referred to as a control unit. For example, processor 1280 transmits and receives signals via RF transceiver 1260 or fronthaul transceiver 1265. Furthermore, processor 1280 writes data to memory 1270 and reads data from memory 1270. Additionally, processor 1280 can perform the functions of the protocol stack required in communication standards. Although in Figure 12b Only processor 1280 is shown, but according to another embodiment, RU 220 may include two or more processors. Processor 1280 may be a set of instructions or code stored in memory 1270, which resides at least temporarily in processor 1280, or it may be part of storage space for storing instructions / code or circuitry configuring processor 1280. Furthermore, processor 1280 may include various modules for performing communications. Processor 1280 may control RU 220 to perform operations according to embodiments described later.

[0276] Figure 12b The configuration of RU 220 shown is merely an example, and examples of RUs used to perform embodiments of this disclosure are not limited to. Figure 12b The configuration is shown in the figure. In some embodiments, some configurations can be added, deleted, or changed.

[0277] Figure 13The functional components of a terminal (e.g., terminal 120) are shown.

[0278] refer to Figure 13 Terminal 120 may include transceiver 1310, memory 1320, and processor 1330. Transceiver 1310 performs the function of transmitting and receiving signals via a radio channel. For example, transceiver 1310 performs the function of converting between baseband signals and bit sequences according to the system's physical layer specifications. For example, when transmitting data, transceiver 1310 generates complex symbols by encoding and modulating the transmitted bit sequence. Furthermore, when receiving data, transceiver 1310 recovers the received bit sequence by demodulating and decoding the baseband signal. In addition, transceiver 1310 up-converts the baseband signal to a radio frequency (RF) band signal and then transmits the RF band signal through an antenna, and down-converts the RF band signal received through the antenna back to a baseband signal. For example, transceiver 1310 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), and an analog-to-digital converter (ADC).

[0279] Transceiver 1310 may include multiple transmit and receive paths. Furthermore, transceiver 1310 may include antenna elements. Transceiver 1310 may include at least one antenna array configured with multiple antenna elements. In terms of hardware, transceiver 1310 may be configured as digital and analog circuitry (e.g., a radio frequency integrated circuit (RFIC)). Hereinafter, the digital and analog circuitry may be implemented in a single package. Furthermore, transceiver 1310 may include multiple RF chains. Transceiver 1310 may perform beamforming. Transceiver 1310 may apply beamforming weights to signals according to the configuration of processor 1330 to provide directionality to signals to be transmitted and received. According to embodiments, transceiver 1310 may include a radio frequency (RF) block (or RF unit). The RF block may include a first RF circuitry associated with an antenna and a second RF circuitry associated with baseband processing. The first RF circuitry may be referred to as an RF antenna (A). The second RF circuitry may be referred to as an RF baseband (B).

[0280] Transceiver 1310 can transmit and receive signals. For this purpose, transceiver 1310 may include at least one transceiver. Transceiver 1310 can receive downlink signals. Downlink signals may include synchronization signals (SS), reference signals (RS) (e.g., cell-specific reference signals (CRS), demodulation (DM)-RS), system information (e.g., MIB, SIB, remaining system information (RMSI), other system information (OSI)), configuration messages, control information, or downlink data, etc. Furthermore, transceiver 1310 can transmit uplink signals. Uplink signals may include random access related signals (e.g., random access preamble (RAP) (or message 1 (Msg1), message 3 (Msg3)), reference signals (e.g., sounding reference signals (SRS), DM-RS), or power headroom reports (PHR), etc.

[0281] Furthermore, transceiver 1310 may include different communication modules to process signals in different frequency bands. Additionally, transceiver 1310 may include multiple communication modules to support a variety of different radio access technologies. For example, different radio access technologies may include Bluetooth Low Energy (BLE), Wi-Fi, WiFi Gigabit (WiGig), and cellular networks (e.g., LTE, New Radio (NR)). Furthermore, different frequency bands may include UHF (High Frequency) bands (e.g., 2.5 GHz, 5 GHz) and millimeter-wave bands (e.g., 38 GHz, 60 GHz). Moreover, transceiver 1310 can use the same radio access technology in different frequency bands (e.g., unlicensed bands for Licensed Assisted Access (LAA), Citizens Broadband Radio Service (CBRS) (e.g., 3.5 GHz)).

[0282] Transceiver 1310 transmits and receives signals as described above. Accordingly, all or part of transceiver 1310 may be referred to as a "transmitting unit," a "receiving unit," or a "transceiver unit." Furthermore, in the following description, transmission and reception performed via a radio channel are used to indicate that the processing described above is performed by transceiver 1310.

[0283] Memory 1320 stores data for the operation of terminal 120, such as basic programs, application programs, and configuration information. Memory 1320 can be configured as volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. Furthermore, memory 1320 provides stored data upon request from processor 1330. According to an embodiment, memory 1320 may store codebooks for CSI reporting. Each codebook may include information about a pre-encoded matrix. Memory 1320 represents storage space as a functional component. For example, memory 1320 can be understood to represent not only the memory of components configured within terminal 120 (e.g., hard disk, flash memory, RAM), but also space for storing instructions and / or programs.

[0284] Processor 1330 controls the overall operation of terminal 120. For example, processor 1330 sends and receives signals via transceiver 1310. Furthermore, processor 1330 writes data to memory 1320 and reads data from memory 1320. Additionally, processor 1330 can perform the functions of the protocol stack required in the communication standard. For this purpose, processor 1330 may include at least one processor. Processor 1330 may include at least one processor or microprocessor, or may be part of a processor. Furthermore, transceiver 1310 and part of processor 1330 may be referred to as CP. Processor 1330 may include various modules for performing communication. Processor 1330 can control terminal 120 to perform operations according to the above embodiments.

[0285] In one embodiment, a digital unit (DU) device is provided. The device may include a transceiver, a memory storing instructions, and a processor. When executed by the processor, the instructions enable the device to: obtain a channel frequency response from a reference signal from a terminal; obtain a feature vector by eigenvalue decomposition of the channel frequency response; obtain a transform vector by performing a two-dimensional (2D) Fourier transform on the feature vector; identify a basis vector among a plurality of basis vectors of an enhanced type 2 codebook based on the transform vector using a decision metric; determine a precoding matrix using the identified basis vectors; and transmit downlink data to which the precoding matrix is ​​applied via a radio unit (RU) to the terminal.

[0286] According to an embodiment, multiple basis vectors of the enhanced type 2 codebook can be determined based on the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, a first oversampling factor, and a second oversampling factor.

[0287] According to an embodiment, the reference signal may include a sounding reference signal (SRS), and the 2D Fourier transform may include a fast Fourier transform (FFT) depending on the number of transmit antennas in the first dimension and the number of transmit antennas in the second dimension.

[0288] According to an embodiment, the decision metric of the transform vector can indicate the sum of the magnitudes of the transform vectors, and when the decision metrics are sorted in descending order, the identified basis vectors can be identified as the first L basis vectors among the multiple basis vectors of the enhanced type 2 codebook.

[0289] According to an embodiment, when executed by a processor, the instruction enables the device to: determine the beam coefficients of an enhanced type 2 codebook using sub-band feature vectors and identified basis vectors in the feature vectors, and to determine a precoding matrix using the beam coefficients and the identified basis vectors, wherein in each sub-band, the beam coefficients may include amplitude coefficients and phase coefficients for each layer.

[0290] According to an embodiment, when executed by a processor, the instruction enables the device to: obtain a first feature vector of the bandwidth (WB) by feature decomposition based on the bandwidth portion (BWP); and obtain a second feature vector of the subband by feature decomposition based on each subband in the subband (SB) of the BWP.

[0291] According to an embodiment, the feature vector may include a first feature vector and a second feature vector. The first feature vector can be used to identify the basis vectors among a plurality of feature vectors of the enhanced type 2 codebook, and the second feature vector can be used to identify the beam coefficients of the enhanced type 2 codebook.

[0292] In one embodiment, a terminal is provided. The terminal may include a transceiver, a memory storing instructions, and a processor. When executed by the processor, the instructions enable the device to: receive a reference signal from a network node via the transceiver; obtain a channel frequency response via the reference signal; obtain a feature vector by eigenvalue decomposition of the channel frequency response; obtain a transform vector by performing a two-dimensional (2D) Fourier transform on the feature vector; identify a basis vector among a plurality of basis vectors of an enhanced type 2 codebook based on the transform vector using a decision metric; determine a precoding matrix using the identified basis vectors; and transmit channel state information including the precoding matrix to the network node via the transceiver.

[0293] According to an embodiment, multiple basis vectors of the enhanced type 2 codebook can be determined based on the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, a first oversampling factor, and a second oversampling factor. The number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, the first oversampling factor, and the second oversampling factor can be configured from the codebook configuration of the network node, and the codebook configuration can be obtained through radio resource control (RRC) messages.

[0294] According to an embodiment, the reference signal may include a channel state information reference signal (CSI-RS), and the 2D Fourier transform may include a fast Fourier transform (FFT) depending on the number of transmit antennas in the first dimension and the number of transmit antennas in the second dimension.

[0295] According to an embodiment, the decision metric can indicate the sum of the magnitudes of the transform vectors, and when the decision metrics are sorted in descending order, the identified basis vectors can be identified as the first L basis vectors among a plurality of basis vectors in an enhanced type 2 codebook.

[0296] According to an embodiment, when executed by a processor, the instruction enables the device to: determine the beam coefficients of an enhanced type 2 codebook using subband feature vectors and identified basis vectors in the feature vectors, and to determine a precoding matrix using the beam coefficients and the identified basis vectors, wherein the beam coefficients may include amplitude coefficients and phase coefficients for each layer.

[0297] According to an embodiment, when executed by a processor, the instruction enables the device to: obtain a first feature vector of the bandwidth (WB) by feature decomposition based on the bandwidth portion (BWP); and obtain a second feature vector of the subband (SB) by feature decomposition based on the subband (SB) of the BWP.

[0298] According to an embodiment, the feature vector may include a first feature vector and a second feature vector. The first feature vector can be used to identify the basis vectors among a plurality of feature vectors of the enhanced type 2 codebook, and the second feature vector can be used to identify the beam coefficients of the enhanced type 2 codebook.

[0299] In one embodiment, a method performed by a digital unit (DU) is provided. The method may include: obtaining a channel frequency response from a reference signal from a terminal; obtaining a feature vector by eigenvalue decomposition of the channel frequency response; obtaining a transform vector by performing a two-dimensional (2D) Fourier transform on the feature vector; identifying a basis vector among a plurality of basis vectors of an enhanced type 2 codebook based on the transform vector using a decision metric; determining a precoding matrix using the identified basis vectors; and transmitting downlink data to which the precoding matrix is ​​applied to the terminal via a radio unit (RU).

[0300] According to an embodiment, multiple basis vectors of the enhanced type 2 codebook can be determined based on the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, a first oversampling factor, and a second oversampling factor.

[0301] According to an embodiment, the reference signal may include a sounding reference signal (SRS), and the 2D Fourier transform may include a fast Fourier transform (FFT) depending on the number of transmit antennas in the first dimension and the number of transmit antennas in the second dimension.

[0302] According to an embodiment, the decision metric of the transform vector can indicate the sum of the magnitudes of the transform vectors, and when the decision metrics are sorted in descending order, the identified basis vectors can be identified as the first L basis vectors among the multiple basis vectors of the enhanced type 2 codebook.

[0303] According to an embodiment, determining the precoding matrix may include: determining the beam coefficients of an enhanced type 2 codebook using sub-band feature vectors and basis vectors identified among the feature vectors; and determining the precoding matrix using the beam coefficients and the identified basis vectors. In each sub-band, the beam coefficients may include amplitude coefficients and phase coefficients for each layer.

[0304] According to an embodiment, obtaining the feature vector may include: obtaining a first feature vector of the bandwidth (WB) by eigenvalue decomposition of the bandwidth portion (BWP); and obtaining a second feature vector of the subband by eigenvalue decomposition of each subband (SB) in the BWP.

[0305] For one or more embodiments, at least one component of the components described in one or more of the foregoing figures may be configured to perform one or more operations, techniques, processes, and / or methods as described in this disclosure. For example, a processor (e.g., a baseband processor) described in this disclosure in conjunction with one or more of the foregoing figures may be configured to operate according to one or more examples described in this disclosure. As another example, circuitry associated with user equipment (UE), base stations, network elements, etc., as described above in conjunction with one or more of the foregoing figures may be configured to operate according to one or more examples described herein.

[0306] Unless otherwise expressly stated, any of the above embodiments may be combined with any other embodiment (or combination of embodiments). The foregoing description of one or more implementations is provided for illustration and description and is not intended to limit the scope of the embodiments or to exhaustively describe the precise forms disclosed. Modifications and variations are possible in accordance with the above teachings, or may be obtained from practice with various embodiments.

[0307] The methods described in the embodiments of the claims or specification of this disclosure can be implemented in hardware, software, or a combination of hardware and software.

[0308] When implemented as software, a computer-readable storage medium may be provided for storing one or more programs (software modules). The one or more programs stored in the computer-readable storage medium are configured to be executed by one or more processors in an electronic device. The one or more programs include instructions that cause the electronic device to perform methods according to embodiments described in the claims or specification of this disclosure. The one or more programs may be included in and provided therein in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., an optical disc read-only memory (CD-ROM)), or distributed online (e.g., downloaded or uploaded) via an app store (e.g., Play Store™), or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product may be temporarily generated or at least temporarily stored in a machine-readable storage medium (such as the memory of a manufacturer's server, an app store's server, or a relay server).

[0309] Such programs (software modules, software) can be stored in random access memory, non-volatile memory including flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), disk storage devices, optical storage devices (e.g., optical disc read-only memory (CD-ROM), digital versatile disc (DVD), or other formats), or cassette tape. Alternatively, it can be stored in a memory configured with some or all of these. Furthermore, multiple configuration memories may be included.

[0310] Additionally, the program can be stored in an attachable storage device that can be accessed via a communication network such as the Internet, intranet, local area network (LAN), wide area network (WAN), or storage area network (SAN), or a combination thereof. Such a storage device can be connected to a device executing embodiments of this disclosure via an external port. Furthermore, a separate storage device on a communication network can also be connected to a device executing embodiments of this disclosure.

[0311] In the specific embodiments described above, the components included in this disclosure are expressed in a singular or plural form according to the presented embodiments. However, the singular or plural expression may be appropriately chosen for ease of explanation, and this disclosure is not limited to singular or plural components; even components expressed in a plural form may be configured in a singular form, or vice versa.

[0312] According to various embodiments, one or more of the aforementioned components or operations may be omitted, or one or more other components or operations may be added. Alternatively or additionally, multiple components (e.g., modules or programs) may be integrated into a single component. In this case, the integrated component can still perform one or more functions of each of the multiple components in the same or similar manner as it was performed by a corresponding component among the multiple components prior to integration. According to various embodiments, operations performed by a module, program, or other component may be performed sequentially, in parallel, repeatedly, or heuristically, or one or more operations may be performed in a different order or omitted, or one or more other operations may be added.

[0313] Furthermore, specific embodiments have been described in the detailed description of this disclosure, and various modifications are possible without departing from the scope of this disclosure.

Claims

1. A device for a digital unit (DU), comprising: transceiver; Memory, storing instructions; as well as processor, Wherein, the instructions, when executed by the processor, cause the device to: The channel frequency response is obtained by using a reference signal from the terminal; The feature vector is obtained by eigenvalue decomposition of the channel frequency response; The transform vector is obtained by performing a two-dimensional (2D) Fourier transform on the eigenvectors; Based on the transformation vector, the basis vectors among multiple basis vectors of the enhanced type 2 codebook are identified by the decision metric; The precoding matrix is ​​determined using the identified basis vectors; and The precoding matrix is ​​transmitted to the terminal via the radio unit (RU) to the downlink data to which it is applied.

2. The device according to claim 1, wherein, The multiple basis vectors of the enhanced type 2 codebook are determined based on the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, the first oversampling factor, and the second oversampling factor.

3. The device according to claim 2, in, The reference signal includes the sounding reference signal (SRS), and The 2D Fourier transform includes the Fast Fourier Transform (FFT) based on the number of transmit antennas in the first dimension and the number of transmit antennas in the second dimension.

4. The device according to claim 3, in, The decision metric of the transformed vector indicates the sum of the magnitudes of the transformed vectors, and When the decision metrics are sorted in descending order, the identified basis vectors are identified as the first L basis vectors among the multiple basis vectors of the enhanced type 2 codebook.

5. The device according to claim 3, wherein, When the instruction is executed by the processor, it causes the device to: The beam coefficients of the enhanced type 2 codebook are determined using the sub-band eigenvectors and the identified basis vectors within those eigenvectors. The precoding matrix is ​​determined using the beam coefficients and the identified basis vectors, and In each subband, the beam coefficients include the amplitude coefficients and phase coefficients of each layer.

6. The device according to claim 1, wherein, When the instruction is executed by the processor, it causes the device to: The first eigenvector of the wideband (WB) is obtained by eigendecomposition of the bandwidth portion (BWP), and The second eigenvector of a subband is obtained by eigenvalue decomposition of each subband in the subband (SB) of the BWP.

7. The device according to claim 6, in, The eigenvectors include a first eigenvector and a second eigenvector. The first feature vector is used to identify the basis vectors among multiple feature vectors in the enhanced type 2 codebook, and The second feature vector is used to identify the beam coefficients of the enhanced type 2 codebook.

8. A terminal, comprising: transceiver; Memory, storing instructions; as well as processor, The instructions, when executed by the processor, cause the terminal to: Receive reference signals from network nodes via transceivers. The channel frequency response is obtained by using a reference signal; The feature vector is obtained by eigenvalue decomposition of the channel frequency response; The transform vector is obtained by performing a two-dimensional (2D) Fourier transform on the eigenvectors; Based on the transformation vector, the basis vectors among multiple basis vectors of the enhanced type 2 codebook are identified by the decision metric; The precoding matrix is ​​determined using the identified basis vectors; and The transceiver sends channel state information, including the precoding matrix, to the network nodes.

9. The terminal according to claim 8, wherein, The multiple basis vectors of the enhanced type 2 codebook are determined based on the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, a first oversampling factor, and a second oversampling factor. The number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, the first oversampling factor, and the second oversampling factor are configured from the codebook configuration of the network nodes. The codebook configuration is obtained through Radio Resource Control (RRC) messages.

10. The terminal according to claim 9, in, Reference signals include Channel State Information Reference Signal (CSI-RS). The 2D Fourier transform includes the Fast Fourier Transform (FFT) based on the number of transmit antennas in the first dimension and the number of transmit antennas in the second dimension.

11. The terminal according to claim 10, in, The decision metric indicates the sum of the magnitudes of the transformed vectors, and When the decision metrics are sorted in descending order, the identified basis vectors are identified as the first L basis vectors among the multiple basis vectors of the enhanced type 2 codebook.

12. The terminal according to claim 10, wherein, The instructions, when executed by the processor, cause the terminal to: The beam coefficients of the enhanced type 2 codebook are determined using the sub-band eigenvectors and the identified basis vectors within those eigenvectors. The precoding matrix is ​​determined using the beam coefficients and the identified basis vectors, and The beam coefficients include the amplitude coefficients and phase coefficients of each layer.

13. The terminal according to claim 8, wherein, The instructions, when executed by the processor, cause the terminal to: The first eigenvector of the wideband (WB) is obtained by eigendecomposition of the bandwidth portion (BWP), and The second eigenvector of the subband is obtained by eigenvalue decomposition of the subband (SB) of BWP.

14. The terminal according to claim 13, in, The eigenvectors include a first eigenvector and a second eigenvector. The first feature vector is used to identify the basis vectors among multiple feature vectors in the enhanced type 2 codebook, and The second feature vector is used to identify the beam coefficients of the enhanced type 2 codebook.

15. A method performed by a digital unit (DU), the method comprising: The channel frequency response is obtained by using a reference signal from the terminal; The feature vector is obtained by eigenvalue decomposition of the channel frequency response; The transform vector is obtained by performing a two-dimensional (2D) Fourier transform on the eigenvectors; Based on the transformation vector, the basis vectors among multiple basis vectors of the enhanced type 2 codebook are identified by the decision metric; The precoding matrix is ​​determined using the identified basis vectors; and The precoding matrix is ​​transmitted to the terminal via the radio unit (RU) to the downlink data to which it is applied.

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