Electronic device and method for determining precoder in wireless communication system

Abstract

In embodiments, a device of a digital unit (DU) is provided. The device may comprise: a transceiver; a memory for storing instructions; and a processor. The instructions, when executed by the processor, may instruct the device to: obtain a channel frequency response through reference signals from a terminal; obtain eigenvectors through eigen decomposition for the channel frequency response; obtain transform vectors by performing a two-dimensional Fourier transform on the eigenvectors; identify basis vectors among a plurality of basis vectors for an enhanced Type 2 codebook through a decision metric according to the transform vectors; determine a precoding matrix using the identified basis vectors; and transmit downlink data to which the precoding matrix is applied to the terminal through a radio unit (RU).

Description

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

[0001] The present disclosure relates to a wireless communication system. For example, the present disclosure relates to an electronic device and method for determining a precoder in a wireless communication system.

[0002] To improve signal transmission and reception performance, multiple-input multiple-output (MIMO) technology is used. Wireless communication systems utilizing MIMO technology utilize multiple antennas at both the transmitter and receiver. The channel capacity of a wireless communication system utilizing MIMO technology can be significantly improved compared to single-antenna technology.

[0003] The above information may be provided as background art to aid in understanding the present disclosure. No claim or determination is made as to whether any of the above-described matters constitute prior art related to the present disclosure.

[0004] In embodiments, a device of a digital unit (DU) is provided. The device may include a transceiver, a memory storing instructions, and a processor. The instructions, when executed by the processor, may cause the device to obtain a channel frequency response through reference signals from a terminal, obtain eigenvectors through eigendecomposition for the channel frequency response, obtain transform vectors by performing a two-dimensional Fourier transform on the eigenvectors, identify basis vectors among a plurality of basis vectors for an enhanced Type 2 codebook through a decision metric according to the transform vectors, determine a precoding matrix using the identified basis vectors, and transmit downlink data to which the precoding matrix is ​​applied to the terminal through a radio unit (RU).

[0005] In embodiments, a terminal is provided. The terminal may include a transceiver, a memory storing instructions, and a processor. The instructions, when executed by the processor, may cause the device to receive reference signals from a network node through the transceiver, obtain a channel frequency response through the reference signals, obtain eigenvectors through eigendecomposition of the channel frequency response, obtain transform vectors by performing a two-dimensional Fourier transform on the eigenvectors, identify basis vectors among a plurality of basis vectors for an enhanced Type 2 codebook through a decision metric according to the transform vectors, determine a precoding matrix using the identified basis vectors, and transmit channel state information including the precoding matrix to the network node through the transceiver.

[0006] In embodiments, a method performed by a DU (digital unit) is provided. The method may include an operation of obtaining a channel frequency response through reference signals from a terminal, an operation of obtaining eigenvectors through eigen decomposition for the channel frequency response, an operation of obtaining transform vectors by performing a two-dimensional Fourier transform on the eigenvectors, an operation of identifying basis vectors among a plurality of basis vectors for an enhanced Type 2 codebook through a decision metric according to the transform vectors, an operation of determining a precoding matrix using the identified basis vectors, and an operation of transmitting downlink data to which the precoding matrix is ​​applied to the terminal through a RU (radio unit).

[0007] Figure 1 shows a wireless communication system.

[0008] Figure 2 shows an example of components of a base station.

[0009] Figure 3 shows an example of a resource structure in the time domain and frequency domain.

[0010] Figure 4 shows examples of channels in a communication standard.

[0011] Figure 5a shows the codebook indices of a Type 2 codebook.

[0012] Figure 5b shows the design principle of the enhanced Type 2 codebook.

[0013] Figure 5c shows the codebook indices of the enhanced Type 2 codebook.

[0014] Figure 6 shows signal flows for CSI (channel state information) reporting.

[0015] Figure 7 shows signal flows for precoding applied to downlink data.

[0016] Figures 8a, 8b, 9a, 9b, 10a, 10b, 11a, and 11b show examples of performance of precoder selection.

[0017] Figure 12a shows the functional components of a DU (digital unit).

[0018] Figure 12b shows the functional components of a radio unit (RU).

[0019] Figure 13 shows the functional components of the terminal.

[0020] The terms used in this disclosure are used only to describe specific embodiments and may not be intended to limit the scope of other embodiments. The singular expression may include plural expressions unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by those of ordinary skill in the art described in this disclosure. Terms defined in general dictionaries among the terms used in this disclosure may be interpreted as having the same or similar meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined in this disclosure. In some cases, even if a term is defined in this disclosure, it cannot be interpreted to exclude embodiments of the present disclosure.

[0021] The various embodiments of the present disclosure described below illustrate a hardware-based approach as an example. However, since the various embodiments of the present disclosure include techniques utilizing both hardware and software, the various embodiments of the present disclosure do not exclude a software-based approach.

[0022] In the following description, terms referring to signals (e.g., signal, information, message, signaling), terms referring to data types (e.g., list, set, subset), terms for operational states (e.g., step, operation, procedure), terms referring to data (e.g., packet, user stream, information, bit, symbol, codeword), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, resource element (RE), resource block (RB), bandwidth part (BWP), occasion), terms referring to channels, terms referring to network entities, terms referring to components of devices, etc. are examples for convenience of description. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0023] In the following description, terms referring to signals (e.g., signal, information, message, signaling), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, resource element (RE), resource block (RB), bandwidth part (BWP), occasion), terms for operational states (e.g., step, operation, procedure), terms referring to data (e.g., packet, user stream, information, bit, symbol, codeword), terms referring to channels, terms referring to network entities, terms referring to components of devices, etc. are examples for convenience of description. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0024] In addition, in the present disclosure, expressions such as "more than" or "less than" may be used to determine whether a specific condition is satisfied or fulfilled, but this is merely a description for expressing an example and does not exclude descriptions such as "more than" or "less than." A condition described as "more than" may be replaced with "more than," a condition described as "less than" may be replaced with "less than," and a condition described as "more than and less than" may be replaced with "more than and less than." In addition, hereinafter, "A" to "B" mean at least one of elements from A (including A) to B (including B). hereinafter, "C" and / or "D" mean at least one of "C" or "D," that is, including {"C", "D", "C" and "D"}.

[0025] Although the present disclosure describes various embodiments using terms used in some communication standards (e.g., 3rd Generation Partnership Project (3GPP), European Telecommunications Standards Institute (ETSI), extensible radio access network (xRAN), open-radio access network (O-RAN), etc.), these are merely examples for explanation. The various embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0026] Figure 1 shows a wireless communication system.

[0027] Referring to FIG. 1, FIG. 1 illustrates a base station (110) and a terminal (120) as some of the nodes utilizing a wireless channel in a wireless communication system. Although FIG. 1 illustrates only one base station, the wireless communication system may further include other base stations identical or similar to the base station (110).

[0028] The base station (110) is a network infrastructure that provides wireless access to the terminal (120). The base station (110) has coverage defined based on the distance at which a signal can be transmitted. In addition to the base station, the base station (110) may be referred to as an 'access point (AP)', 'eNodeB (eNB)', '5th generation node', 'next generation nodeB (gNB)', 'wireless point', 'transmission / reception point (TRP)', or other terms having equivalent technical meanings.

[0029] The terminal (120) is a device used by a user and communicates with the base station (110) via a wireless channel. The link from the base station (110) to the terminal (120) is referred to as a downlink (DL), and the link from the terminal (120) to the base station (110) is referred to as an uplink (UL). In addition, although not shown in FIG. 1, the terminal (120) and another terminal may communicate with each other via a wireless channel. In this case, the link between the terminal (120) and another terminal (device-to-device link, D2D) is referred to as a sidelink, and the sidelink may be used interchangeably with the PC5 interface. In some other embodiments, the terminal (120) may be operated without the involvement of a user. In one embodiment, the terminal (120) is a device that performs machine type communication (MTC) and may not be carried by the user. Additionally, according to one embodiment, the terminal (120) may be an MTC UE or an NB (narrowband)-IoT (internet of things) device.

[0030] The terminal (120) may be referred to as a terminal, or other terms such as 'user equipment (UE),' 'customer premises equipment (CPE),' 'mobile station,' 'subscriber station,' 'remote terminal,' 'wireless terminal,' 'electronic device,' or 'user device,' or other terms having equivalent technical meanings.

[0031] The base station (110) and the terminal (120) can perform beamforming. The base station (110) and the terminal (120) can transmit and receive wireless signals in a relatively low frequency band (e.g., FR 1 (frequency range 1) of NR). In addition, the base station (110) and the terminal (120) can transmit and receive wireless signals in a relatively high frequency band (e.g., FR 2 (or, FR 2-1, FR 2-2, FR 2-3), FR 3 of NR), millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, 60 GHz)). To improve channel gain, the base station (110) and the terminal (120) can perform beamforming. Here, the beamforming can include transmission beamforming and reception beamforming. The base station (110) and the terminal (120) can impart directionality to the transmitted or received signal. To this end, the base station (110) and the terminal (120) can select serving beams through a beam search or beam management procedure. After the serving beams are selected, subsequent communication can be performed through resources that have a QCL relationship with the resource that transmitted the serving beams.

[0032] If large-scale characteristics of a channel carrying a symbol on a first antenna port can be inferred from a channel carrying a symbol on a second antenna port, the first antenna port and the second antenna port can be evaluated to have a QCL relationship. For example, the large-scale characteristics may include at least one of delay spread, Doppler spread, Doppler shift, average gain, average delay, and a spatial receiver parameter.

[0033] Although both the base station (110) and the terminal (120) are described as performing beamforming in FIG. 1, the embodiments of the present disclosure are not necessarily 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, either only one of the base station and the terminal may perform beamforming, or neither the base station nor the terminal may perform beamforming.

[0034] In the present disclosure, a beam refers to a spatial flow of a signal in a wireless channel, and is formed by one or more antennas (or antenna elements), and this forming process may be referred to as beamforming. Beamforming may include at least one of analog beamforming and digital beamforming (e.g., precoding). Reference signals transmitted based on beamforming may include, for example, a demodulation-reference signal (DM-RS), a channel state information-reference signal (CSI-RS), a synchronization signal / physical broadcast channel (SS / PBCH), and a sounding reference signal (SRS). In addition, as a configuration for each reference signal, an IE such as a CSI-RS resource or an SRS-resource may be used, and this configuration may include information associated with the beam. Information associated with a beam may mean whether the configuration (e.g., a CSI-RS resource) uses the same spatial domain filter as another configuration (e.g., another CSI-RS resource within the same CSI-RS resource set) or a different spatial domain filter, or whether it is quasi-co-located (QCL) with a reference signal, and if so, what type it is (e.g., QCL type A, B, C, D).

[0035] FIG. 2 illustrates examples of components of a base station. FIG. 2 illustrates DUs and RUs, where the functions of the base station are implemented by different entities. A fronthaul interface may be used for communication between the DU and the RU. Unlike the backhaul between the base station and the core network, the fronthaul refers to the entity between the wireless LAN and the base station. FIG. 2 illustrates an example of a fronthaul structure between a DU (210) and one RU (220), but this is merely for convenience of explanation and the present disclosure is not limited thereto. In other words, embodiments of the present disclosure can also be applied to a fronthaul structure between one DU and multiple RUs. For example, embodiments of the present disclosure can be applied to a fronthaul structure between one DU and two RUs. Furthermore, embodiments of the present disclosure can also be applied to a fronthaul structure between one DU and three RUs.

[0036] Referring to FIG. 2, the base station (110) may include a DU (210) and a RU (220). The front hole (215) between the DU (210) and the RU (220) is F x It can be operated through an interface. For operation of the fronthaul (215), interfaces such as eCPRI (enhanced common public radio interface) and ROE (radio over ethernet) can be used, for example.

[0037] As communications technology advances, mobile data traffic increases, significantly increasing the bandwidth requirements for the fronthaul between the digital unit and the radio unit. In deployments such as C-RAN (centralized / cloud radio access network), the DU performs functions for the packet data convergence protocol (PDCP), radio link control (RLC), media access control (MAC), and physical layer (PHY), while the RU can be implemented to perform additional functions for the PHY layer in addition to its radio frequency (RF) functions.

[0038] DU (210) may be responsible for upper layer functions of a wireless network. For example, DU (210) may perform functions of the MAC layer and a part of the PHY layer. Here, a part of the PHY layer refers to functions performed at a higher level among the functions of the PHY layer, and may include, for example, channel encoding (or channel decoding), scrambling (or descrambling), modulation (or demodulation), and layer mapping (or layer demapping). According to an embodiment, if DU (210) complies with the O-RAN standard, it may be referred to as O-DU (O-RAN DU). DU (210) may be replaced with a first network entity for a base station (e.g., gNB) in embodiments of the present disclosure as needed.

[0039] The RU (220) may be responsible for lower layer functions of a wireless network. For example, the RU (220) may perform a part of the PHY layer, an RF function. Here, a part of the PHY layer refers to functions of the PHY layer that are performed at a relatively lower level than the DU (210), and may include, for example, iFFT transformation (or FFT transformation), CP insertion (CP removal), and digital beamforming. The RU (220) may be referred to as an 'access unit (AU)', an 'access point (AP)', a 'transmission / reception point (TRP)', a 'remote radio head (RRH)', a 'radio unit (RU)', or other terms having an equivalent technical meaning thereto. According to an embodiment, when the RU (220) complies with the O-RAN standard, it may be referred to as an O-RU (O-RAN RU). RU (220) may be replaced with a second network entity for a base station (e.g., gNB) in embodiments of the present disclosure as needed.

[0040] In FIG. 2, the base station (110) is described as including a DU (210) and a RU (220), but the embodiments of the present disclosure are not limited thereto. The base station according to the embodiments may be implemented in a distributed deployment according to a centralized unit (CU) configured to perform functions of upper layers of an access network (e.g., packet data convergence protocol (PDCP), radio resource control (RRC)) and a distributed unit (DU) configured to perform functions of lower layers. For example, the distributed unit (DU) may include a digital unit (DU) and a radio unit (RU) of FIG. 2. In addition, for example, the base station may be implemented in a structure in which the CU, the DU, and the RU are arranged in that order between a core (e.g., a 5G core (5GC) or a next generation core (NGC)) network and a radio network (RAN). The interface between CU and DU (distributed unit) can be referred to as the F1 interface.

[0041] A centralized unit (CU) can be connected to one or more DUs and can be responsible for functions at a higher layer than the DU. For example, the CU can be responsible for functions at the RRC (radio resource control) and PDCP (packet data convergence protocol) layers, while the DU and RU can be responsible for functions at lower layers. The DU can perform some functions (high PHY) of the RLC (radio link control), MAC (media access control), and PHY (physical) layers, while the RU can be responsible for the remaining functions (low PHY) of the PHY layer. In addition, for example, a digital unit (DU) can be included in a distributed unit (DU) depending on the implementation of a distributed deployment of the base station. Hereinafter, unless otherwise defined, the operations of DU (digital unit) and RU are described, but various embodiments of the present disclosure can be applied to both a base station arrangement including a CU and an arrangement in which a DU is directly connected to a core network (i.e., a base station in which the CU and DU are integrated into a single entity (e.g., an NG-RAN node)).

[0042] Figure 3 illustrates an example of a resource structure in the time and frequency domains. Figure 3 illustrates the basic structure of the time-frequency domain, which is a radio resource domain in which data or control channels are transmitted in the downlink or uplink.

[0043] Referring to Figure 3, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDM (orthogonal frequency division multiplexing) symbol, N symbA set of OFDM symbols (302) constitutes one 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 minimum transmission unit in the frequency domain may be a subcarrier.

[0044] The basic unit of resources in the time-frequency domain is a resource element (RE) (312), which can be represented by an OFDM symbol index and a subcarrier index. A resource block may include multiple resource elements. In the LTE system, a resource block (RB) (or physical resource block (PRB)) is N in the time domain. symb N consecutive OFDM symbols and frequency domain SC RB are defined as N consecutive subcarriers. In the NR system, a resource block (RB) (308) is defined as N in the frequency domain. SC RB can be defined as N consecutive subcarriers (310). In a wireless access network, the bandwidth constituting the resource grid is N RB DL Dog or N RB UL It may include RBs (304) of N RB DL represents the number of RBs corresponding to the downlink bandwidth, and N RB UL represents the number of RBs corresponding to the uplink bandwidth. One RB (308) is N on the frequency axis. SC RB It contains REs (312). In general, the minimum transmission unit of data is RB and the number of subcarriers is N. SC RB=12. The frequency domain may include common resource blocks (CRBs). Physical resource blocks (PRBs) may be defined in the bandwidth part (BWP) of the frequency domain. The CRB and PRB numbers may be determined based on the subcarrier spacing. The data rate may increase in proportion to the number of RBs scheduled to the terminal.

[0045] In the NR system, in the case of a frequency division duplex (FDD) system that operates the downlink and uplink by frequency division, the downlink transmission bandwidth and the uplink transmission bandwidth may be different. The channel bandwidth represents the radio frequency (RF) bandwidth corresponding to the system transmission bandwidth. [Table 1] shows part of the correspondence between the system transmission bandwidth, subcarrier spacing (SCS), and channel bandwidth defined in the NR system in a frequency band lower than x GHz (e.g., frequency range (FR) 1 (310 MHz to 7125 MHz)). And [Table 2] shows part of the correspondence between the transmission bandwidth, subcarrier spacing, and channel bandwidth defined in the NR system in a frequency band higher than y GHz (e.g., FR2 (24250 MHz - 52600 MHz) or FR2-2 (52600 MHz to 71000 MHz)). For example, an NR system with a 100 MHz channel bandwidth and a 30 kHz subcarrier spacing has a transmission bandwidth of 273 RBs. In [Table 1] and [Table 2], N / A may be a bandwidth-subcarrier combination not supported by the NR system.

[0046] Channel bandwidth [MHz] SCS 5 10 20 50 80 100 Transmission bandwidth configuration N RB15kHz2552106207N / AN / A30kHz11245113321727360kHzN / A112465107135

[0047] Channel bandwidth [MHz] SCS50100200400 Transmission bandwidth configuration N RB 60kHz66132264N / A120kHz3266132264

[0048] Figure 4 shows examples of channels in a communication standard.

[0049] Figure 4 illustrates examples of channels in a communication standard. The channels may include a physical channel (410), a transport channel (420), and a logical channel (430), depending on the layers defined in the communication standard.

[0050] Referring to FIG. 4, a physical channel (410) may provide functions (e.g., channel coding, HARQ processing, modulation, multi-antenna processing, resource mapping) necessary for generating physical signals at the physical layer. At the physical layer, physical signals are modulated using OFDM and may be transmitted in a wireless environment via time-frequency resources (e.g., resources of the resource grid of FIG. 3).

[0051] In downlink transmission, a physical channel (410) may include at least one of a physical broadcast channel (PBCH), a physical downlink shared channel (PDSCH), or a physical downlink control channel (PDCCH). The PDCCH may be used to carry downlink control information (DCI). Generally, downlink data refers to symbols transmitted through the PDSCH, and a downlink control signal may include symbols transmitted through the PDCCH. In addition, in the downlink, in addition to the channels illustrated in FIG. 4, a synchronization signal (e.g., a primary synchronization signal (PSS), a secondary synchronization signal (SSS)) and an SS / PBCH block including a broadcast signal (e.g., a PBCH)) may be transmitted for synchronization. In addition, in the downlink, a channel state information-reference signal (CSI-RS) for obtaining measurement or channel information, a demodulation reference signal (DMRS) for channel estimation and demodulation, and a phase tracking reference signal (PTRS) may be transmitted in the downlink.

[0052] In uplink transmission, the physical channel (410) may include at least one of a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), or a physical random access channel (PRACH). The PUSCH or PUCCH may be used to carry uplink control information (UCI). Generally, uplink data refers to symbols transmitted through the PUSCH, and the uplink control signal may include symbols corresponding to the UCI. For example, the UCI may include at least one of a scheduling request (SR), a hybrid automatic request (HARQ)-acknowledge (ACK) bit(s), or channel state information (CSI). In addition, in the uplink, in addition to the channels illustrated in FIG. 4, a DMRS and a PTRS for channel estimation and demodulation may be transmitted in the downlink for channel estimation.

[0053] The transmission channel (420) connects the physical layer and the medium access channel (MAC) layer located at an upper level of the physical layer, and can be classified according to how data is transmitted through the wireless interface. In the downlink, the transmission channel (420) may include at least one of a paging channel (PCH) for paging, a broadcast channel (BCH) for broadcasting system information, or a downlink shared channel (DL-SCH) for transmitting downlink data. In the uplink, the transmission channel (420) may include at least one of a random access channel (RACH) for transmitting a random access preamble or an uplink shared channel (UL-SCH) for transmitting downlink data.

[0054] The logical channel (430) is located above the transport channel and is mapped to the transport channel (420). The logical channel (430) can be divided into a control channel for transmitting control region information and a traffic channel for transmitting user region information. The control channel of the logical channel (430) can include at least one of a paging control channel (PCCH), a broadcast control channel (BCCH), a common control channel (CCCH), or a dedicated control channel (DCCH). The traffic channel of the logical channel (430) can include a dedicated traffic channel (DTCH).

[0055] In describing embodiments of the present disclosure, a random access signal may include sequences transmitted via a physical random access channel (PRACH). "Data" may include signals other than a reference signal. For example, "data" obtained by a receiver in uplink communication may include signals transmitted via a PDSCH. However, the PDSCH is exemplary, and it is understood that embodiments of the present disclosure may also be applied to channels to which a precoder can be applied (e.g., PUSCH, PDCCH, PUCCH).

[0056] Precoding may refer to an operation applied to a signal before the signal is transmitted from the transmitter. In a wireless communication system, the signal may be transmitted on a wireless channel between the transmitter and the receiver. In order for the receiver to receive the signal well, the transmitter may perform an operation of multiplying the signal by a specific matrix. The specific matrix may be referred to as a precoder or a precoding matrix. For example, in a 3GPP standard communication system, it is defined that a terminal (120) reports channel state information (CSI) to a base station (110). The channel state information refers to information related to the quality of a wireless channel or wireless link formed between the terminal (120) and an antenna port (e.g., a CSI-RS port) of the base station (110). The channel state information may include a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI). The above RI indicates information related to the rank of the channel and represents the number of streams that the terminal (120) can receive through the same resource. The above PMI is a value that reflects the spatial characteristics of the channel and represents information (e.g., an index) on a precoding matrix preferred by the terminal among a plurality of candidate precoding matrices. The plurality of candidate precoding matrices are defined as a codebook, and the candidate precoding matrices of the codebook can be defined in the standard in various ways depending on the codebook type.

[0057] The 3GPP NR standard defines Type 1 codebooks and Type 2 codebooks. Type 1 codebooks can be 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 up to Rank 2, the enhanced Type 2 codebook was introduced in Release 16. The enhanced Type 2 codebook can support up to Rank 4, and in the enhanced Type 2 codebook, the beam amplitude scaling and co-phasing values ​​(which can be referred to as beam combining coefficients) for all beams can be calculated in a similar manner to the Type 2 codebook. As ranks expand, feedback overhead may increase linearly with the number of subbands. Since uplink resources may be insufficient, a process called 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 combining coefficients.

[0058] According to the 3GPP standard, in the precoder of the enhanced Type 2 codebook, discrete Fourier transform (DFT) vectors can be utilized as basis vectors. The basis vector can be defined as the angle of the horizontal beam and the vertical beam within a two-dimensional antenna array. The enhanced Type 2 codebook includes a subband (SB)-based precoder, but the terminal (120) can be configured to convert the subband domain into a lag domain and then report limited coefficients through compression, instead of reporting information about the precoder for each subband. To improve the efficiency of uplink resources, the capacity of the channel state information (CSI) of the uplink control information (UCI) can be reduced.

[0059] The terminal (120) can determine the rank, precoding matrix, and / or modulation order based on mutual information (MI) or downlink throughput. For example, the terminal (120) can determine the mutual information. The terminal (120) can obtain an effective MIMO CFR matrix by multiplying a CFR (channel frequency response) matrix by a precoding matrix. The terminal (120) can obtain the mutual information from the MIMO CFR when the transmitter uses bit interleaved coded modulation (BICM) and the receiver uses maximum likelihood (ML) or linear minimum mean square error (LMMSE). The terminal (120) can determine the number of layers that maximize the mutual information. The number of layers can be associated with the rank. The terminal (120) can determine the precoding matrix that maximizes the mutual information as a precoder. The above precoder may be associated with codebook indices to be reported to the base station (110). The codebook indices may be used to form a specific precoder. The terminal (120) may determine a modulation order that maximizes the mutual information. The modulation order may be associated with a CQI indicating a modulation scheme. For example, the modulation scheme may 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.

[0060] Figure 5a shows the codebook indices of a Type 2 codebook.

[0061] Referring to Fig. 5a, the precoding matrix of a Type 2 codebook can be indicated through multiple codebook indices. The precoding matrix of layer l is W (l) It can be. The following terms can be defined to describe the precoding matrix. In the present disclosure, WB (wideband) represents the entire band (e.g., BWP) of the connected cell, and SB (subband) can represent a subset of WB. The subband can be set by the network (e.g., base station (110)), and the precoding matrix of the Type 2 codebook can include components in units of subbands. The plurality of codebook indices include a first codebook index (i 1,1 )(501), 2nd codebook index (i 1,2 )(502), 3rd Codebook Index (i 1,4,l )(503), 4th Codebook Index (i 2,1,l )(504), 5th Codebook Index (i 2,2,l )(505), and the 6th codebook index (i 1,3,l )(506) may be included. As a non-limiting example, the fifth codebook index (i 2,2,l )(505) may be omitted from reporting depending on network settings.

[0062] 1st codebook index (i 1,1 )(501) may represent the selection of oversampling. For example, the first oversampling factor in the first dimension (e.g., horizontal dimension) may be O1 and the second oversampling factor in the second dimension (e.g., vertical dimension) may be O2. The first codebook index (i 1,1 ) can represent oversampling as a combination of (o1, o2), where o1 can have a value greater than or equal to 0 and less than or equal to O1-1, and o2 can have a value greater than or equal to 0 and less than or equal to O2-1. The second codebook index (i 1,2) may represent the selection of the DFT beam. For example, the number of antenna ports in the first dimension (e.g., horizontal dimension) may be N1 and the number of antenna ports in the second dimension (e.g., vertical dimension) may be N2. The second codebook index (i 1,2 )(502) can represent a DFT beam as a combination of (n1, n2), where n1 can have a value greater than or equal to 0 and less than or equal to N1-1, and n2 can have a value greater than or equal to 0 and less than or equal to N2-1. The first codebook index (i 1,1 ) and the second codebook index (i 1,2 ) can be expressed as (m1, m2), and the combination for the i-th beam among the total L beams is (m1 (i) , m2 (i) ) can be expressed as the third codebook index (i 1,4,l )(503) can represent the WB amplitude. The WB amplitude of the i-th beam is p l,i (1) can be expressed as the 4th codebook index (i 2,1,l )(504) can represent the subband phase. The subband phase of the i-th beam is φ l,i can be expressed as the 5th codebook index (i 2,2,l )(505) can represent the SB amplitude. The SB amplitude of the i-th beam is p l,i (2) can be expressed as the 6th codebook index (i 1,3,l )(506) can represent the strongest beam.

[0063] Type 2 codebooks can provide a two-stage precoding matrix, where two matrices are multiplied. For example, a precoding matrix for a Type 2 codebook can have the following form:

[0064]

[0065] W1 is a precoding matrix of the WB component, and W2 represents a precoding matrix of the SB component. Considering the components represented through each codebook index, W1 is W specified through the first codebook index (501) and the second codebook index (502). m1 (i) , m2 (i) and p specified through the third codebook index (503). l,i (1) can be configured through. On the other hand, W2 can be configured through the 4th codebook index (504) and the 5th codebook index (505).

[0066] Figure 5b shows the design principle of the enhanced Type 2 codebook.

[0067] Referring to Fig. 5b, the first grid (551) represents beams and subbands in the spatial domain according to the Type 2 codebook. The second grid (552) represents beams and basis vectors in the spatial domain according to the enhanced Type 2 codebook. The second grid (552) is obtained by decompressing N3 subbands from the first grid (551) through frequency-domain compression. v can be transformed into basis vectors. The deformation due to the frequency-domain compression can be expressed as follows.

[0068]

[0069]

[0070]

[0071]

[0072] With frequency-domain compression, the number of non-zero coefficients (hereinafter, non-zero coefficients) can be limited by ignoring weaker beam coefficients.

[0073] Figure 5c shows the codebook indices of the enhanced Type 2 codebook.

[0074] Referring to Fig. 5c, the precoding matrix of the enhanced Type 2 codebook can be indicated through multiple codebook indices. As in Fig. 5a, WB (wideband) represents the entire band of the connected cell (e.g., BWP), and SB (subband) can represent a subset of WB. The precoding matrix of the enhanced Type 2 codebook can include components in units of subbands. For layer l, the precoding matrix including all subbands is It can be. The above precoding matrix can be composed of WB spatial information, SB amplitude and phase information, and delay information. The size of the above precoding matrix is ​​N AP When xN3, N AP 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 x2L. The size of the matrix corresponding to the above SB amplitude and phase information is 2LxM. v The size of the matrix corresponding to the above delay information is M v xN3. The operation of the above WB spatial information and the above SB amplitude and phase information can be understood as compression of the spatial domain. The operation of the above SB amplitude and phase information and the above delay information can be understood as compression of the frequency domain.

[0075] The above multiple codebook indices are first codebook indices (i 1,1 , i 1,2 ))(571), 2nd codebook index (i 2,3,l )(572), 3rd Codebook Index (i 2,5,l )(573), 4th Codebook Index (i 2,4,l )(574), 5th Codebook Indexes (i 1,5 , i 1,6,l )(575), 6th Codebook Index (i 1,7,l )(576) and the 7th codebook index (i 1,8,l)(577) may be included. The first codebook indices (i 1,1 , i 1,2 ))(571) can represent a 2D DFT beam. The first codebook indices (i 1,1 , i 1,2 ))(571) is as in Type 2 codebook, can represent a 2D DFT beam (or DFT basis vector, which can be referred to as basis vector) expressed as a second codebook index (i 2,3,l )(572) can represent the WB amplitude. The WB amplitude is p l,p (1) can be expressed as . For example, p can represent polarization (e.g., p=0, 1). l can represent a layer. The third codebook index (i 2,5,l )(573) represents the feedback phase. The feedback phase is can be expressed as the 4th codebook index (i 2,4,l )(574) represents the feedback amplitude. The feedback amplitude is p l,i,f (2) can be expressed as 5th codebook indices (i 1,5 , i 1,6,l )(575) indicates the delay due to frequency compression, can be expressed as f is M v represents one of the basis vectors of the dog. For example, f is from 0 to M v -1 has a value between 6th codebook index (i 1,7,l )(576) is a bitmap, and the 7th codebook index (i 1,8,l )(577) can represent the strongest beam.

[0076] PCA (principal component analysis) is a technique for compressing high-dimensional vectors. For example, through PCA, the terminal (120) can obtain multiple eigenvectors for an entire band (e.g., the entire BWP, wideband (WB)) and multiple eigenvectors for each subband. To explain the selection of a precoder using PCA, the necessary explanations are provided below.

[0077]

[0078]

[0079] By the above CFR matrix and precoding matrix, a new effective CFR can be defined.

[0080]

[0081] represents the new effective CFR matrix, and s represents the subband index.

[0082] The CFR matrix of the above mathematical expression 4 can be re-expressed as follows.

[0083]

[0084]

[0085] For broadband PMI reporting, the PCA technique can be expressed as follows:

[0086]

[0087]

[0088]

[0089]

[0090] For subband PMI reporting, the PCA technique can be expressed as follows:

[0091]

[0092]

[0093] In the present disclosure, techniques for determining an enhanced Type 2 precoder defined in the NR standard based on the PCA technique described above are described. FIG. 6 illustrates an example in which a terminal (120) selects an enhanced Type 2 precoding matrix according to the PCA technique, and FIG. 7 illustrates an example in which a base station (110) (e.g., DU (210)) selects an enhanced Type 2 precoding matrix according to the PCA technique.

[0094] Figure 6 illustrates signal flows for CSI (channel state information) reporting. In Figure 6, the operations of the base station (110) can be understood as operations of the DU (210) or the RU (220). For example, the operation of transmitting or receiving a signal of the base station (110) can be understood as the operation of the DU (210) via the RU (220).

[0095] Referring to FIG. 6, in operation (601), the base station (110) may transmit reference signals to the terminal (120). For example, the reference signals may include channel state information-reference signals (CSI-RS).

[0096] In operation (603), the terminal (120) may perform precoder selection based on the enhanced Type 2 codebook. According to one embodiment, the terminal (120) may obtain eigenvectors according to the PCA technique. The terminal (120) may determine the precoding matrix of the enhanced Type 2 codebook through the eigenvectors. For example, let us assume that the number of layers of the enhanced Type 2 codebook is 2. The terminal (120) may obtain two eigenvectors through the PCA technique. For example, the terminal (120) may obtain the eigenvectors of the following mathematical formula.

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107] The terminal (120) can obtain L basis vectors from the eigenvectors obtained through PCA.

[0108]

[0109]

[0110]

[0111]

[0112] WB for the second layer and the first pole 2D DFT can be performed. For example, 2D DFT can be performed based on the following mathematical formula.

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121] As another example, the above decision metric can be generated according to the following mathematical formula.

[0122]

[0123]

[0124]

[0125]

[0126]

[0127] optimal set can be defined as follows.

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140] By the eigenvectors exemplified through Equations 25 to 28, the enhanced Type 2 codebook The precoding matrix for can be approximated as follows. Before reporting, compression of the frequency domain may not be performed.

[0141]

[0142] The terminal (120) can calculate mutual information using the precoding matrix and CFR estimate. The above mathematical formula assumes two layers, i.e., rank 2. However, the terminal (120) can iteratively calculate mutual information while varying the rank. For example, the terminal (120) can select a rank that maximizes mutual information and report the PMI and CQI corresponding to the selected rank.

[0143] Unlike the case where the base station (110) determines the precoder, in the case where the terminal (120) determines the precoder to report CSI, additional operations such as frequency compression, quantization, and coefficient limitation may be required to be performed. For example, the terminal (120) The star coefficients can be FFTed based on the mathematical formula below.

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154]

[0155]

[0156]

[0157]

[0158] To quantize the global gain, the following tables can be defined.

[0159] Table 3 is a table listing the p1 values ​​defined in the specification.

[0160]

[0161] Table 4 is a table listing the p2 values ​​defined in the specification.

[0162]

[0163] Table 5 is a table that multiplies the p1 and p2 values ​​defined in the standard in any combination and lists them in order of magnitude. Table 4 contains a total of 29 values.

[0164]

[0165] 'Thre1' listed in Table 6 is the average of two adjacent values ​​in Table 5.

[0166]

[0167] Table 7 is the average of two adjacent values ​​in Table 4.

[0168]

[0169]

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176] For example, the amplitude for the second pole can be expressed with the following code.

[0177]

[0178] For PMI reporting, the phase by lag can also be quantized.

[0179]

[0180]

[0181]

[0182] Now, we can determine the SB precoder using the quantized limited number of coefficients and the WB basis vectors. The variables are as follows: Initializes.

[0183]

[0184]

[0185]

[0186] The precoding matrix of the enhanced Type 2 codebook can be determined as follows.

[0187]

[0188]

[0189] The terminal (120) can calculate mutual information using the calculated precoding matrix and CFR estimate. For example, the terminal (120) can repeatedly perform the calculation of mutual information while changing the rank. For example, the terminal (120) can select a rank that maximizes mutual information and report the PMI and CQI corresponding to the selected rank. While rank-2 is assumed in the above examples, this is merely an example and should not be construed as limiting other embodiments of the present disclosure. For example, embodiments of the present 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.

[0190] Fig. 7 illustrates signal flows for precoding applied to downlink data. In Fig. 7, operations of the base station (110) can be understood as operations of the DU (210) or the RU (220). For example, the operation of transmitting or receiving a signal of the base station (110) can be understood as the operation of the DU (210) via the RU (220). The operation of selecting a precoder of the base station (110) can be understood as the operation of the DU (210). In Fig. 7, it is assumed that channel reciprocity is satisfied in the wireless channel between the base station (110) and the terminal (120). For example, signals on the wireless channel can be transmitted or received in a TDD frequency band.

[0191] Referring to FIG. 7, in operation (701), the terminal (120) can transmit SRSs to the base station (110).

[0192] In operation (703), the base station (110) may perform enhanced Type 2 codebook-based precoder selection. In one embodiment, the base station (110) may obtain eigenvectors according to a technique. The base station (110) may determine a precoding matrix of the enhanced Type 2 codebook through the eigenvectors. For example, the base station (110) may determine the precoding matrix according to the method described in Equations 10 to 29. Meanwhile, when the base station (110) determines the enhanced Type 2 codebook, since a separate report is not required, there is no need to limit the number of compression, quantization, and / or non-zero coefficients. Accordingly, the computational processes of Equations 30 to 42 may be omitted. As a non-limiting example, it should be understood that determining a precoding matrix through the method of Equations 30 to 42 may also be understood as an embodiment of the present disclosure.

[0193] In operation (705), the base station (110) may perform data transmission to the terminal (120). The base station (110) may apply a precoding matrix according to the precoder selection to the transmission data. For example, the transmission data may include transmission streams for each antenna. The base station (110) may multiply the transmission vector including the transmission streams by the precoding matrix. The base station (110) may transmit the result of the multiplication to the terminal (120) via a plurality of antennas.

[0194] Figures 8a, 8b, 9a, 9b, 10a, 10b, 11a, and 11b show examples of performance of precoder selection.

[0195] Referring to FIG. 8A, a graph (800) represents throughput according to the number of layers. The horizontal axis of the graph (800) represents the number of layers. The vertical axis of the graph (800) represents throughput (unit: Mbps (megabits per second)). In the graph (800), it is assumed that the number of horizontal antenna ports of the base station (110) is 16, the number of vertical antenna ports of the base station (110) is 2, and the number of antenna ports of the terminal (120) is 4. It is assumed that under a 32x4 MIMO cluster delay line (CDL)-B channel, SCS = 30 kHz, the number of RBs is 53, all RBs are scheduled, SNR = -20 dB, and the speed of the UE is 0 km / h. It is assumed that the channel is a non-line of sight (NLOS) environment. The first line (801) shows the transmission performance when using a precoder of an enhanced Type 2 codebook that does not utilize frequency compression. The second line (802) shows the transmission performance when using a precoder of an enhanced Type 2 codebook that utilizes frequency compression according to embodiments. The third line (803) shows the transmission performance when using a Type 1 codebook. When the number of layers is 1, the first line (801) shows a performance gain of approximately 57% compared to the third line (803).

[0196] Referring to FIG. 8B, a graph (850) represents throughput according to the number of layers. The horizontal axis of the graph (850) represents the number of layers. The vertical axis of the graph (850) represents throughput (unit: Mbps). In the graph (850), it is assumed that the number of horizontal antenna ports of the base station (110) is 16, the number of vertical antenna ports of the base station (110) is 2, and the number of antenna ports of the terminal (120) is 4. It is assumed that under a 32x4 MIMO CDL-B channel, SCS = 30 kHz, the number of RBs is 53, all RBs are scheduled, SNR = 0 dB, and the speed of the UE is 0 km / h. The channel is assumed to be an NLOS environment. The first line (851) represents the transmission performance when using a precoder of an enhanced Type 2 codebook that does not use frequency compression. The second line (852) shows the transmission performance when using a precoder of an enhanced Type 2 codebook utilizing frequency compression according to embodiments. The third line (853) shows the transmission performance when using a Type 1 codebook. When the number of layers is 2, the first line (851) shows a performance gain of approximately 46% compared to the third line (853).

[0197] Referring to FIG. 9A, a graph (900) represents throughput according to the number of layers. The horizontal axis of the graph (900) represents the number of layers. The vertical axis of the graph (900) represents throughput (unit: Mbps). In the graph (900), it is assumed that the number of horizontal antenna ports of the base station (110) is 16, the number of vertical antenna ports of the base station (110) is 2, and the number of antenna ports of the terminal (120) is 4. It is assumed that under a 32x4 MIMO CDL-B channel, SCS = 30 kHz, the number of RBs is 53, all RBs are scheduled, SNR = 20 dB, and the speed of the UE is 0 km / h. The channel is assumed to be an NLOS environment. The first line (901) represents the transmission performance when using a precoder of an enhanced Type 2 codebook that does not use frequency compression. The second line (902) shows the transmission performance when using a precoder of an enhanced Type 2 codebook utilizing frequency compression according to embodiments. The third line (903) shows the transmission performance when using a Type 1 codebook. When the number of layers is three, the first line (901) shows a performance gain of approximately 31% compared to the third line (903).

[0198] Referring to FIG. 9B, a graph (950) represents throughput according to the number of layers. The horizontal axis of the graph (950) represents the number of layers. The vertical axis of the graph (950) represents throughput (unit: Mbps). In the graph (950), it is assumed that the number of horizontal antenna ports of the base station (110) is 16, the number of vertical antenna ports of the base station (110) is 2, and the number of antenna ports of the terminal (120) is 4. It is assumed that under a 32x4 MIMO CDL-B channel, SCS = 30 kHz, the number of RBs is 53, all RBs are scheduled, SNR = 30 dB, and the speed of the UE is 0 km / h. The channel is assumed to be an NLOS environment. The first line (951) represents the transmission performance when using a precoder of an enhanced Type 2 codebook that does not use frequency compression. The second line (952) shows the transmission performance when using a precoder of an enhanced Type 2 codebook utilizing frequency compression according to embodiments. The third line (953) shows the transmission performance when using a Type 1 codebook. When the number of layers is 3, the first line (951) shows a performance gain of approximately 7% compared to the third line (953).

[0199] Referring to FIG. 10a, a graph (1000) represents throughput according to the number of layers. The horizontal axis of the graph (1000) represents the number of layers. The vertical axis of the graph (1000) represents throughput (unit: Mbps). In the graph (1000), it is assumed that the number of horizontal antenna ports of the base station (110) is 16, the number of vertical antenna ports of the base station (110) is 2, and the number of antenna ports of the terminal (120) is 4. It is assumed that under a 32x4 MIMO CDL-D channel, SCS = 30 kHz, the number of RBs is 53, all RBs are scheduled, SNR = -20 dB, and the speed of the UE is 0 km / h. The channel is assumed to be a line of sight (LOS) environment. The first line (1001) represents the transmission performance when using a precoder of an enhanced Type 2 codebook that does not use frequency compression. The second line (1002) shows the transmission performance when using a precoder of an enhanced Type 2 codebook utilizing frequency compression according to embodiments. The third line (1003) shows the transmission performance when using a Type 1 codebook. When the number of layers is 1, the first line (1001) shows a performance gain of approximately 4% compared to the third line (1003).

[0200] Referring to FIG. 10b, a graph (1050) represents throughput according to the number of layers. The horizontal axis of the graph (1050) represents the number of layers. The vertical axis of the graph (1050) represents throughput (unit: Mbps). In the graph (1050), it is assumed that the number of horizontal antenna ports of the base station (110) is 16, the number of vertical antenna ports of the base station (110) is 2, and the number of antenna ports of the terminal (120) is 4. It is assumed that under a 32x4 MIMO CDL-B channel, SCS = 30 kHz, the number of RBs is 53, all RBs are scheduled, SNR = 0 dB, and the speed of the UE is 0 km / h. The channel is assumed to be a LOS environment. The first line (1051) represents the transmission performance when using a precoder of an enhanced Type 2 codebook that does not use frequency compression. The second line (1052) shows the transmission performance when using a precoder of an enhanced Type 2 codebook utilizing frequency compression according to embodiments. The third line (1053) shows the transmission performance when using a Type 1 codebook. When the number of layers is 2, the first line (1051) shows a performance gain of approximately 2% compared to the third line (1053).

[0201] Referring to Fig. 11a, a graph (1100) represents throughput according to the number of layers. The horizontal axis of the graph (1100) represents the number of layers. The vertical axis of the graph (1100) represents throughput (unit: Mbps). In the graph (1100), it is assumed that the number of horizontal antenna ports of the base station (110) is 16, the number of vertical antenna ports of the base station (110) is 2, and the number of antenna ports of the terminal (120) is 4. It is assumed that under a 32x4 MIMO CDL-B channel, SCS = 30 kHz, the number of RBs is 53, all RBs are scheduled, SNR = 20 dB, and the speed of the UE is 0 km / h. The channel is assumed to be a LOS environment. The first line (1101) represents the transmission performance when using a precoder of an enhanced Type 2 codebook that does not use frequency compression. The second line (1102) shows the transmission performance when using a precoder of an enhanced Type 2 codebook utilizing frequency compression according to embodiments. The third line (1103) shows the transmission performance when using a Type 1 codebook. When the number of layers is 3, the first line (1101) shows a performance gain of approximately 7% compared to the third line (1103).

[0202] Referring to FIG. 11b, a graph (1150) represents throughput according to the number of layers. The horizontal axis of the graph (1150) represents the number of layers. The vertical axis of the graph (1150) represents throughput (unit: Mbps). In the graph (1150), it is assumed that the number of horizontal antenna ports of the base station (110) is 16, the number of vertical antenna ports of the base station (110) is 2, and the number of antenna ports of the terminal (120) is 4. It is assumed that under a 32x4 MIMO CDL-B channel, SCS = 30 kHz, the number of RBs is 53, all RBs are scheduled, SNR = 30 dB, and the speed of the UE is 0 km / h. The channel is assumed to be a LOS environment. The first line (1151) represents the transmission performance when using a precoder of an enhanced Type 2 codebook that does not use frequency compression. The second line (1152) shows the transmission performance when using a precoder of an enhanced Type 2 codebook utilizing frequency compression according to embodiments. The third line (1153) shows the transmission performance when using a Type 1 codebook. When the number of layers is 4, the first line (1151) shows a performance gain of approximately 5% compared to the third line (1153).

[0203] Fig. 12a illustrates functional components of a DU (digital unit) (e.g., DU (210)). The configuration illustrated in Fig. 12a can be understood as the configuration of DU (210) of Fig. 12a as part of a base station. Terms such as "... unit" and "... unit" used hereinafter mean a unit that processes at least one function or operation, and this can be implemented by hardware, software, or a combination of hardware and software.

[0204] Referring to FIG. 12a, DU (210) includes a transceiver (1210), a memory (1220), and a processor (1230).

[0205] The transceiver (1210) can perform functions for transmitting and receiving signals in a wired communication environment. The transceiver (1210) can include a wired interface for controlling direct connections between devices via a transmission medium (e.g., copper wire, optical fiber). For example, the transceiver (1210) can transmit electrical signals to other devices via copper wire, or perform conversion between electrical signals and optical signals. The DU (210) can communicate with the RU (radio unit) via the transceiver (1210).

[0206] The transceiver (1210) may perform functions for transmitting and receiving signals in a wireless communication environment. For example, the transceiver (1210) may perform a conversion function between baseband signals and bit streams according to the physical layer specifications of the system. For example, when transmitting data, the transceiver (1210) generates complex symbols by encoding and modulating the transmitted bit stream. Furthermore, when receiving data, the transceiver (1210) restores the received bit stream by demodulating and decoding the baseband signal. Furthermore, the transceiver (1210) may include multiple transmission and reception paths.

[0207] The transceiver (1210) can transmit and receive signals. For example, the transceiver (1210) can transmit a management plane (M-plane) message. For example, the transceiver (1210) can transmit a management plane (S-plane) message. For example, the transceiver (1210) can transmit a control plane (C-plane) message. For example, the transceiver (1210) can transmit a user plane (U-plane) message. For example, the transceiver (1210) can receive a user plane message. Although only the transceiver (1210) is illustrated in FIG. 12A, in other implementations, the DU (210) may include two or more transceivers.

[0208] The transceiver (1210) transmits and receives signals as described above. Accordingly, all or part of the transceiver (1210) may be referred to as a 'communication unit', a 'transmitter', a 'receiver', or a 'transmitter-receiver'. In addition, in the following description, transmission and reception performed through a wireless channel are used to mean that processing as described above is performed by the transceiver (1210). According to one embodiment, the transceiver (1210) may obtain random access signals related to an NPRACH on which physical layer processing has been performed from an RU (e.g., RU (220)). For example, the transceiver (1210) may obtain signals (e.g., frequency domain signals) on which CP removal and FFT have been performed on the received signals.

[0209] Although not illustrated in FIG. 12A, the transceiver (1210) may further include a backhaul transceiver for connection to the core network or other base stations. The backhaul transceiver may provide an interface for communicating with other nodes within the network. That is, the backhaul transceiver converts a bit stream transmitted from the base station to other nodes, such as other access nodes, other base stations, upper nodes, the core network, etc., into a physical signal, and converts a physical signal received from other nodes into a bit stream.

[0210] The memory (1220) stores data such as basic programs, application programs, and setting information for the operation of the DU (210). The memory (1220) may be referred to as a storage unit. The memory (1220) may be configured as volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. In addition, the memory (1220) may provide stored data upon request of the processor (1230). The memory (1220) is a functional component and represents a storage space. For example, the memory (1220) may be understood not only to represent a memory (e.g., a hard disk, flash memory, RAM) arranged as a component within the DU (210), but also to represent a space for storing instructions and / or programs.

[0211] The processor (1230) controls the overall operations of the DU (210). The processor (1280) may be referred to as a control unit. For example, the processor (1230) transmits and receives signals through the transceiver (1210) (or through the backhaul communication unit). In addition, the processor (1230) records and reads data from the memory (1220). In addition, the processor (1230) may perform functions of a protocol stack required by a communication standard. Although only the processor (1230) is illustrated in FIG. 12A, the DU (210) may include two or more processors according to other implementation examples.

[0212] According to one embodiment, the processor (1230) may perform physical layer processing on signals received from an RU (e.g., RU (220)). For example, the processor (1230) may perform subcarrier demapping (RE demapping) on ​​the received signals. For example, the processor (1230) may obtain a noise-interference component (e.g., a noise-interference covariance matrix) based on the received reference signals. Furthermore, for example, the processor (1230) may perform channel estimation based on the received reference signals. The processor (1230) may determine weights for a receive combiner. The processor (1230) may determine data corresponding to an uplink signal.

[0213] The configuration of DU (210) illustrated in FIG. 12a is merely an example, and examples of DUs performing embodiments of the present disclosure are not limited to the configuration illustrated in FIG. 12a. In some embodiments, some configurations may be added, deleted, or changed.

[0214] Fig. 12b illustrates the functional components of a radio unit (RU). The configuration illustrated in Fig. 12b can be understood as the configuration of the RU (220) of Fig. 2 as part of a base station. Terms such as "... unit" and "... unit" used hereinafter mean a unit that processes at least one function or operation, and this can be implemented by hardware, software, or a combination of hardware and software.

[0215] Referring to FIG. 12b, the RU (220) includes an RF transceiver (1260), a fronthaul transceiver (1265), a memory (1270), and a processor (1280).

[0216] The RF transceiver (1260) performs functions for transmitting and receiving signals via a wireless channel. For example, the RF transceiver (1260) upconverts a baseband signal into an RF band signal and transmits it via an antenna, and downconverts an RF band signal received via the antenna into a baseband signal. For example, the RF transceiver (1260) may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like.

[0217] The RF transceiver (1260) may include multiple transmission and reception paths. Furthermore, the RF transceiver (1260) may include an antenna unit. The RF transceiver (1260) may include at least one antenna array composed of multiple antenna elements. In terms of hardware, the RF transceiver (1260) may be composed of digital circuits and analog circuits (e.g., a radio frequency integrated circuit (RFIC)). Here, the digital circuits and analog circuits may be implemented in a single package. In addition, the RF transceiver (1260) may include multiple RF chains. The RF transceiver (1260) may perform beamforming. The RF transceiver (1260) may apply beamforming weights to a signal to be transmitted and received in order to impart directionality according to the settings of the processor (1280). According to one embodiment, the RF transceiver (1260) may be equipped with multiple antennas.

[0218] According to one embodiment, the RF transceiver (1260) may transmit and receive signals on a radio access network. For example, the RF transceiver (1260) may transmit a downlink signal. The downlink signal may include a synchronization signal (SS), a reference signal (RS) (e.g., a cell-specific reference signal (CRS), a demodulation (DM)-RS), system information (e.g., a MIB, a SIB, remaining system information (RMSI), other system information (OSI)), a configuration message, control information, or downlink data. In addition, for example, the RF transceiver (1260) may receive an uplink signal. For example, the uplink signal may include a random access related signal (e.g., an NPRACH, an NPUSCH). According to one embodiment, the RF transceiver (1260) may receive signals including random access signals via multiple antennas provided in the RF transceiver (1260). Although only the RF transceiver (1260) is illustrated in FIG. 12B, according to other implementation examples, the RU (220) may include two or more RF transceivers.

[0219] The fronthaul transceiver (1265) can transmit and receive signals. According to one embodiment, the fronthaul transceiver (1265) can transmit and receive signals on the fronthaul interface. For example, the fronthaul transceiver (1265) can receive a management plane (M-plane) message. For example, the fronthaul transceiver (1265) can receive a management plane (S-plane) message. For example, the fronthaul transceiver (1265) can receive a control plane (C-plane) message. For example, the fronthaul transceiver (1265) can transmit a user plane (U-plane) message. For example, the fronthaul transceiver (1265) can receive a user plane message. According to one embodiment, the fronthaul transceiver (1265) may transmit a signal (e.g., a frequency domain signal) on which CP removal and FFT have been performed to the DU (e.g., the DU (210)). Although only the fronthaul transceiver (1265) is illustrated in FIG. 12B , in other implementations, the RU (220) may include two or more fronthaul transceivers.

[0220] The RF transceiver (1260) and the fronthaul transceiver (1265) transmit and receive signals as described above. Accordingly, all or part of the RF transceiver (1260) and the fronthaul transceiver (1265) may be referred to as a 'communication unit', a 'transmitter', a 'receiver', or a 'transmitter-receiver unit'. In addition, in the following description, transmission and reception performed through a wireless channel are used to mean that the processing as described above is performed by the RF transceiver (1260). In the following description, transmission and reception performed through a wireless channel are used to mean that the processing as described above is performed by the RF transceiver (1260).

[0221] The memory (1270) stores data such as basic programs, application programs, and setting information for the operation of the RU (220). The memory (1270) may be referred to as a storage unit. The memory (1270) may be configured as volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. In addition, the memory (1270) may provide stored data upon request of the processor (1280). The memory (1270) is a functional component and represents a storage space. For example, the memory (1270) may be understood not only to represent a memory (e.g., a hard disk, a flash memory, a RAM) arranged as a component within the RU (220), but also to represent a space for storing instructions and / or programs.

[0222] The processor (1280) controls the overall operations of the RU (220). The processor (1280) may be referred to as a control unit. For example, the processor (1280) transmits and receives signals through the RF transceiver (1260) or the fronthaul transceiver (1265). In addition, the processor (1280) writes and reads data to and from the memory (1270). In addition, the processor (1280) may perform functions of the protocol stack required by the communication standard. Although only the processor (1280) is illustrated in FIG. 12B, the RU (220) may include two or more processors according to other implementation examples. The processor (1280) may be a set of instructions or codes stored in the memory (1270), or may be a storage space storing instructions / codes or instructions / codes that are temporarily residing in the processor (1280), or may be a part of the circuitry constituting the processor (1280). In addition, the processor (1280) may include various modules for performing communication. The processor (1280) may control the RU (220) to perform operations according to the embodiments described below.

[0223] The configuration of RU (220) illustrated in FIG. 12b is merely an example, and examples of RUs performing embodiments of the present disclosure are not limited to the configuration illustrated in FIG. 12b. In some embodiments, some configurations may be added, deleted, or changed.

[0224] Figure 13 shows the functional components of a terminal (e.g., terminal (120)).

[0225] Referring to FIG. 13, the terminal (120) may include a transceiver (1310), a memory (1320), and a processor (1330). The transceiver (1310) performs functions for transmitting and receiving signals via a wireless channel. For example, the transceiver (1310) performs a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the system. For example, when transmitting data, the transceiver (1310) generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the transceiver (1310) restores a reception bit stream by demodulating and decoding the baseband signal. In addition, the transceiver (1310) upconverts a baseband signal into an RF (radio frequency) band signal and transmits it through an antenna, and downconverts an RF band signal received through the antenna into a baseband signal. For example, the transceiver (1310) may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc.

[0226] The transceiver (1310) may include multiple transmission and reception paths. Furthermore, the transceiver (1310) may include an antenna unit. The transceiver (1310) may include at least one antenna array composed of multiple antenna elements. In terms of hardware, the transceiver (1310) may be composed of digital circuits and analog circuits (e.g., a radio frequency integrated circuit (RFIC)). Here, the digital circuits and analog circuits may be implemented in a single package. In addition, the transceiver (1310) may include multiple RF chains. The transceiver (1310) may perform beamforming. The transceiver (1310) may apply beamforming weights to a signal to be transmitted and received in order to impart directionality to the signal according to the settings of the processor (1330). According to one embodiment, the transceiver (1310) may include a radio frequency (RF) block (or RF unit). The RF block may include first RF circuitry associated with the antenna and second RF circuitry associated with baseband processing. The first RF circuitry may be referred to as RF-A (antenna). The second RF circuitry may be referred to as RF-B (baseband).

[0227] The transceiver (1310) can transmit and receive signals. For this purpose, the transceiver (1310) can include at least one transceiver. The transceiver (1310) can receive a downlink signal. The downlink signal can include a synchronization signal (SS), a reference signal (RS) (e.g., a cell-specific reference signal (CRS), a demodulation (DM)-RS), system information (e.g., a MIB, a SIB, remaining system information (RMSI), other system information (OSI)), a configuration message, control information, or downlink data. In addition, the transceiver (1310) can transmit an uplink signal. The uplink signal may include a random access related signal (e.g., a random access preamble (RAP) (or Msg1 (message 1)), Msg3 (message 3)), a reference signal (e.g., a sounding reference signal (SRS), DM-RS), or a power headroom report (PHR).

[0228] Additionally, the transceiver (1310) may include different communication modules to process signals of different frequency bands. Furthermore, the transceiver (1310) may include multiple communication modules to support multiple different wireless access technologies. For example, different wireless access technologies may include Bluetooth low energy (BLE), Wireless Fidelity (Wi-Fi), WiFi Gigabyte (WiGig), cellular networks (e.g., Long Term Evolution (LTE), new radio (NR), etc.). Additionally, different frequency bands may include super high frequency (SHF) (e.g., 2.5 GHz, 5 GHz) bands, millimeter wave (mm wave) (e.g., 38 GHz, 60 GHz, etc.) bands. Additionally, the transceiver (1310) may use the same type of wireless access technology on different frequency bands (e.g., unlicensed bands for licensed assisted access (LAA), citizens broadband radio service (CBRS) (e.g., 3.5 GHz)).

[0229] The transceiver (1310) transmits and receives signals as described above. Accordingly, all or part of the transceiver (1310) may be referred to as a "transmitter," a "receiver," or a "transmitting and receiving unit." Furthermore, in the following description, transmission and reception performed via a wireless channel are used to mean processing performed by the transceiver (1310) as described above.

[0230] The memory (1320) stores data such as basic programs, application programs, and setting information for the operation of the terminal (120). The memory (1320) may be configured as volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. In addition, the memory (1320) provides stored data upon request of the processor (1330). According to one embodiment, the memory (1320) may store codebooks for CSI reporting. Each of the codebooks may include information on precoding matrices. The memory (1320) is a functional component and represents a storage space. For example, the memory (1320) may be understood to represent not only a memory (e.g., a hard disk, flash memory, RAM) arranged as a component within the terminal (120), but also a space for storing instructions and / or programs.

[0231] The processor (1330) controls the overall operations of the terminal (120). For example, the processor (1330) transmits and receives signals through the transceiver (1310). In addition, the processor (1330) records and reads data from the memory (1320). In addition, the processor (1330) can perform the functions of the protocol stack required by the communication standard. To this end, the processor (1330) may include at least one processor. The processor (1330) may include at least one processor or microprocessor, or may be a part of a processor. In addition, a part of the transceiver (1310) and the processor (1330) may be referred to as a CP. The processor (1330) may include various modules for performing communication. The processor (1330) may control the terminal (120) to perform operations according to the embodiments described above.

[0232] In embodiments, a device of a digital unit (DU) is provided. The device may include a transceiver, a memory storing instructions, and a processor. The instructions, when executed by the processor, may cause the device to obtain a channel frequency response through reference signals from a terminal, obtain eigenvectors and eigenvalues ​​through eigendecomposition for the channel frequency response, obtain transform vectors by performing a two-dimensional Fourier transform on the eigenvectors, identify basis vectors among a plurality of basis vectors for an enhanced Type 2 codebook through a decision metric according to the transform vectors, determine a precoding matrix using the identified basis vectors, and transmit downlink data to which the precoding matrix is ​​applied to the terminal through a radio unit (RU).

[0233] According to one embodiment, the plurality of basis vectors for the enhanced Type 2 codebook may be determined by the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, a first oversampling factor in the first dimension, and a second oversampling factor in the second dimension.

[0234] According to one embodiment, the reference signals include sounding reference signals (SRS), and the two-dimensional Fourier transform may include a fast Fourier transform (FFT) according to the number of transmission antennas in the first dimension and the number of transmission antennas in the second dimension.

[0235] In one embodiment, the decision metric according to the transformation vectors may represent the sum of the sizes of the transformation vectors. The identified basis vectors may be identified as the top L basis vectors when a plurality of basis vectors for the enhanced Type 2 codebook are sorted in descending order according to the decision metric.

[0236] In one embodiment, the instructions, when executed by the processor, cause the device to determine beam coefficients for the enhanced Type 2 codebook through the subband eigenvectors and the identified basis vectors among the eigenvectors, and to determine a precoding matrix using the basis vectors and the beam coefficients, wherein the beam coefficients may include, in each subband, a layer-specific amplitude coefficient and a layer-specific phase coefficient.

[0237] According to one embodiment, the instructions, when executed by the processor, may cause the device to obtain first eigenvectors for a wideband (WB) through eigen decomposition according to a bandwidth part (BWP), and to obtain second eigenvectors for a wideband (SB) through eigen decomposition according to each subband of the subbands of the BWP.

[0238] In one embodiment, the eigenvectors include the first eigenvectors and the second eigenvectors, the first eigenvectors being used to identify the basis vectors among a plurality of basis vectors for the enhanced Type 2 codebook, and the second eigenvectors being used to determine beam coefficients for the enhanced Type 2 codebook.

[0239] In embodiments, a terminal is provided. The terminal may include a transceiver, a memory storing instructions, and a processor. The instructions, when executed by the processor, may cause the device to receive reference signals from a network node through the transceiver, obtain a channel frequency response through the reference signals, obtain eigenvectors and eigenvalues ​​through eigendecomposition for the channel frequency response, obtain transform vectors by performing a two-dimensional Fourier transform on the eigenvectors, identify basis vectors among a plurality of basis vectors for an enhanced Type 2 codebook through a decision metric according to the transform vectors, determine a precoding matrix using the identified basis vectors, and transmit channel state information including the precoding matrix to the network node through the transceiver.

[0240] According to one embodiment, the plurality of basis vectors for the enhanced Type 2 codebook are determined by a number of transmit antennas in a first dimension, a number of transmit antennas in a second dimension, a first oversampling factor in the first dimension, and a second oversampling factor in the second dimension, wherein 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 a codebook configuration of the network node, and the codebook configuration can be obtained through an RRC (radio resource control) message.

[0241] According to one embodiment, the reference signals include channel state information-reference signals (CSI-RS), and the two-dimensional Fourier transform may include a fast Fourier transform (FFT) according to the number of transmission antennas in the first dimension and the number of transmission antennas in the second dimension.

[0242] According to one embodiment, the decision metric according to the transformation vectors represents the sum of the sizes of the transformation vectors, and the identified basis vectors can be identified as the top L basis vectors when a plurality of basis vectors for the enhanced Type 2 codebook are sorted in descending order according to the decision metric.

[0243] In one embodiment, the instructions, when executed by the processor, may cause the device to determine beam coefficients for the enhanced Type 2 codebook through the subband eigenvectors and the identified basis vectors among the eigenvectors, and to determine a precoding matrix using the basis vectors and the beam coefficients. The beam coefficients may include, for each subband, a layer-specific amplitude coefficient and a layer-specific phase coefficient.

[0244] According to one embodiment, the instructions, when executed by the processor, may cause the device to obtain first eigenvectors for a wideband (WB) through eigen decomposition according to a bandwidth part (BWP), and to obtain second eigenvectors for a wideband (SB) through eigen decomposition according to each subband of the subbands of the BWP.

[0245] In one embodiment, the eigenvectors include the first eigenvectors and the second eigenvectors, the first eigenvectors being used to identify the basis vectors among a plurality of basis vectors for the enhanced Type 2 codebook, and the second eigenvectors being used to determine beam coefficients for the enhanced Type 2 codebook.

[0246] In embodiments, a method performed by a DU (digital unit) is provided. The method may include an operation of obtaining a channel frequency response through reference signals from a terminal, an operation of obtaining eigenvectors and eigenvalues ​​through eigen decomposition for the channel frequency response, an operation of obtaining transform vectors by performing a two-dimensional Fourier transform on the eigenvectors, an operation of identifying basis vectors among a plurality of basis vectors for an enhanced Type 2 codebook through a decision metric according to the transform vectors, an operation of determining a precoding matrix using the identified basis vectors, and an operation of transmitting downlink data to which the precoding matrix is ​​applied to the terminal through a RU (radio unit).

[0247] According to one embodiment, the plurality of basis vectors for the enhanced Type 2 codebook may be determined by the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, a first oversampling factor in the first dimension, and a second oversampling factor in the second dimension.

[0248] In one embodiment, the reference signals may include sounding reference signals (SRS). The two-dimensional Fourier transform may include a fast Fourier transform (FFT) according to the number of transmission antennas in the first dimension and the number of transmission antennas in the second dimension.

[0249] According to one embodiment, the decision metric according to the transformation vectors represents the sum of the sizes of the transformation vectors, and the identified basis vectors can be identified as the top L basis vectors when a plurality of basis vectors for the enhanced Type 2 codebook are sorted in descending order according to the decision metric.

[0250] In one embodiment, the operation of determining the precoding matrix may include an operation of determining beam coefficients for the enhanced Type 2 codebook through subband eigenvectors and the identified basis vectors among the eigenvectors, and an operation of determining a precoding matrix using the basis vectors and the beam coefficients. The beam coefficients may include, in each subband, a layer-by-layer amplitude coefficient and a layer-by-layer phase coefficient.

[0251] According to one embodiment, the operation of obtaining the eigenvectors may include an operation of obtaining first eigenvectors for a wideband (WB) through eigen decomposition according to a bandwidth part (BWP), and an operation of obtaining second eigenvectors for a SB through eigen decomposition according to each subband of the subbands of the BWP.

[0252] For one or more embodiments, at least one of the components described in one or more of the preceding drawings may be configured to perform one or more operations, techniques, processes, and / or methods as described herein. For example, a processor (e.g., a baseband processor) described herein with respect to one or more of the preceding drawings may be configured to operate according to one or more examples described herein. For another example, circuitry associated with a user equipment (UE), a base station, a network element, and the like, as described above with respect to one or more of the preceding drawings, may be configured to operate according to one or more examples described herein.

[0253] Any of the embodiments described above may be combined with any other embodiment (or combination of embodiments) unless explicitly stated otherwise. The foregoing description of one or more implementations provides examples and descriptions, but is not intended to be exhaustive or limit the scope of the embodiments to the precise forms disclosed. Modifications and variations are possible in light of the above teachings or may be learned from practicing various embodiments.

[0254] The methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0255] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. 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 execute methods according to embodiments described in the claims or specification of the present disclosure. The one or more programs may be provided as a computer program product. The computer program product may be traded between a seller and a buyer as a commodity. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read only memory (CD-ROM)), or may be distributed online (e.g., downloaded or uploaded) via an application store (e.g., Play Store™) or directly between two user devices (e.g., smart phones). In the case of online distribution, at least a portion of the computer program product may be temporarily stored or temporarily created in a device-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or an intermediary server.

[0256] These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage devices, compact disc-ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage devices, magnetic cassettes, or may be stored in memories formed by a combination of some or all of these. In addition, each configuration memory may include multiple copies.

[0257] Additionally, the program may be stored on an attachable storage device that is accessible via a communication network, such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device implementing an embodiment of the present disclosure via an external port. Additionally, a separate storage device on the communication network may be connected to a device implementing an embodiment of the present disclosure.

[0258] In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed singularly or plurally, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in plural may be composed of singular elements, or components expressed in singular may be composed of plural elements.

[0259] According to embodiments, one or more of the components or operations of the aforementioned components may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (e.g., modules or programs) may be integrated into a single component. In such a case, the integrated component may perform one or more functions of each of the plurality of components identically or similarly to those performed by the corresponding component among the plurality of components prior to the integration. According to embodiments, the operations performed by a module, program, or other component may be executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be executed in a different order, omitted, or one or more other operations may be added.

[0260] Meanwhile, although the detailed description of the present disclosure has described specific embodiments, it is obvious that various modifications are possible within the scope of the present disclosure.

Claims

1. In the DU (digital unit) device, Transmitter and receiver; Memory for storing instructions; and Contains a processor, The above instructions, when executed by the processor, cause the device to: Obtain the channel frequency response through reference signals from the terminal, By performing eigen decomposition on the above channel frequency response, eigenvectors are obtained, By performing a two-dimensional Fourier transform on the above eigenvectors, transformation vectors are obtained, Through the decision metric according to the above transformation vectors, basis vectors are identified among multiple basis vectors for the enhanced Type 2 codebook, Determine a precoding matrix using the above identified basis vectors, Causing downlink data to which the above precoding matrix is ​​applied to be transmitted to the terminal through a RU (radio unit). device.

2. In claim 1, The plurality of basis vectors for the enhanced Type 2 codebook are determined by the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, the first oversampling factor in the first dimension, and the second oversampling factor in the second dimension. device.

3. In claim 2, The above reference signals include SRS (sounding reference signals), The above two-dimensional Fourier transform includes a fast Fourier transform (FFT) according to the number of transmission antennas in the first dimension and the number of transmission antennas in the second dimension. device.

4. In claim 3, The decision metric according to the above transformation vectors represents the sum of the sizes of the above transformation vectors, The above identified basis vectors are identified as the top L basis vectors when the plurality of basis vectors for the enhanced Type 2 codebook are sorted in descending order according to the decision metric. device.

5. In claim 3, the instructions, when executed by the processor, cause the device to: Among the above eigenvectors, beam coefficients for the enhanced Type 2 codebook are determined through the subband eigenvectors and the identified basis vectors, causing a precoding matrix to be determined using the above basis vectors and the above beam coefficients, The above beam coefficients include, in each subband, amplitude coefficients per layer and phase coefficients per layer. device.

6. In claim 1, the instructions, when executed by the processor, cause the device to: Through eigen decomposition according to BWP (bandwidth part), the first eigenvectors for WB (wideband) are obtained, Causing the second eigenvectors for SB(subband) to be obtained through eigenvalue decomposition according to each subband of the above BWP. device.

7. In claim 6, The above eigenvectors include the first eigenvectors and the second eigenvectors, The above first eigenvectors are used to identify the basis vectors among a plurality of basis vectors for the enhanced Type 2 codebook, The above second eigenvectors are used to determine beam coefficients for the enhanced Type 2 codebook. device.

8. At the terminal, Transmitter and receiver; Memory for storing instructions; and Contains a processor, The above instructions, when executed by the processor, cause the device to: Receive reference signals from a network node through the above transceiver, Obtain the channel frequency response through the above reference signals, By performing eigen decomposition on the above channel frequency response, eigenvectors are obtained, By performing a two-dimensional Fourier transform on the above eigenvectors, transformation vectors are obtained, Through the decision metric according to the above transformation vectors, basis vectors are identified among multiple basis vectors for the enhanced Type 2 codebook, Determine a precoding matrix using the above identified basis vectors, Causing the channel state information including the above precoding matrix to be transmitted to the network node through the transceiver, Terminal.

9. In claim 8, A plurality of basis vectors for the enhanced Type 2 codebook are determined by the number of transmit antennas in the first dimension, the number of transmit antennas in the second dimension, a first oversampling factor in the first dimension, and a second oversampling factor in the second dimension, The number of transmitting antennas in the first dimension, the number of transmitting antennas in the second dimension, the first oversampling factor, and the second oversampling factor are configured from a codebook configuration of the network node, The above codebook configuration is obtained through an RRC (radio resource control) message. Terminal.

10. In claim 9, The above reference signals include CSI-RS (channel state information-reference signals), The above two-dimensional Fourier transform includes a fast Fourier transform (FFT) according to the number of transmission antennas in the first dimension and the number of transmission antennas in the second dimension. Terminal.

11. In claim 10, The decision metric according to the above transformation vectors represents the sum of the sizes of the above transformation vectors, The above identified basis vectors are identified as the top L basis vectors when the plurality of basis vectors for the enhanced Type 2 codebook are sorted in descending order according to the decision metric. Terminal.

12. In claim 10, the instructions, when executed by the processor, cause the device to: Among the above eigenvectors, beam coefficients for the enhanced Type 2 codebook are determined through the subband eigenvectors and the identified basis vectors, causing a precoding matrix to be determined using the above basis vectors and the above beam coefficients, The above beam coefficients include, in each subband, amplitude coefficients per layer and phase coefficients per layer. Terminal.

13. In claim 8, the instructions, when executed by the processor, cause the device to: Through eigen decomposition according to BWP (bandwidth part), the first eigenvectors for WB (wideband) are obtained, Causing the acquisition of second eigenvectors for SB through eigenvalue decomposition according to each subband of the subbands of the above BWP. Terminal.

14. In claim 13, The above eigenvectors include the first eigenvectors and the second eigenvectors, The above first eigenvectors are used to identify the basis vectors among a plurality of basis vectors for the enhanced Type 2 codebook, The above second eigenvectors are used to determine beam coefficients for the enhanced Type 2 codebook. Terminal. In a method performed by 15.DU (digital unit), An operation of obtaining a channel frequency response through reference signals from a terminal, An operation of obtaining eigenvectors through eigen decomposition of the above channel frequency response, An operation of obtaining transformation vectors by performing a two-dimensional Fourier transform on the above eigenvectors, An operation of identifying basis vectors among multiple basis vectors for an enhanced Type 2 codebook through a decision metric according to the above transformation vectors, An operation of determining a precoding matrix using the above-identified basis vectors, An operation of transmitting downlink data to which the above precoding matrix is ​​applied to the terminal through a RU (radio unit), method.

Images