Method and apparatus for determining predicted precoding matrix in wireless communication system

Abstract

The present disclosure relates to a method and apparatus for efficiently determining / selecting a predicted precoding matrix in a wireless communication system using precoding, and according to an embodiment of the present disclosure, a method by which a UE determines a precoding matrix comprises the steps of: receiving a CSI-RS from a base station; estimating a MIMO CFR on the basis of the CSI-RS; acquiring a WB eigenvector and an SB eigenvector for at least one slot duration configured after the current time point by using the estimated MIMO CFR; acquiring common information about at least one of each SB, each layer, each antenna pole, and each slot duration, on the basis of a base vector of the WB eigenvector; acquiring SB coefficients by projecting the SB eigenvector, on the basis of the common information; and determining, from the acquired SB coefficients, an SB PMI corresponding to a predicted precoding matrix for the at least one slot duration.

Description

Method and device for determining a predicted precoding matrix in a wireless communication system

[0001] The present disclosure relates to a method and apparatus for determining / selecting a precoding matrix in a wireless communication system using precoding.

[0002] To meet the increasing demand for wireless data traffic following the 4G system (i.e., the LTE (long-term evolution) system), the 5G system has been developed and commercialized. The 5G system can be implemented in the ultra-high frequency (mmWave) band. To mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, beamforming, massive MIMO (massive MIMO), full-dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large-scale antenna technologies are being discussed in the 5G system. In wireless communication systems such as the 5G system, various reference signals for estimating the channel state between the base station and the terminal are transmitted and received to ensure stable communication between the base station and the terminal, and channel state information (CSI) containing precoding-related information is reported from the terminal to the base station periodically or aperiodically. Research is also underway on various methods for efficient determination / selection of precoding matrices at terminals or base stations.

[0003] The present disclosure provides a method and device for efficiently determining / selecting a predicted precoding matrix in a wireless communication system using precoding, and a storage medium therefor.

[0004] Additionally, the present disclosure provides a method and device for determining / selecting a predicted precoding matrix in a terminal receiving a CSI-RS in a wireless communication system using precoding.

[0005] The present disclosure also provides a method and apparatus for determining / selecting a predicted precoding matrix at a base station receiving an SRS in a wireless communication system using precoding.

[0006] According to an embodiment of the present disclosure, a method for a terminal to determine a precoding matrix in a wireless communication system supporting precoding includes receiving a channel state information-reference signal (CSI-RS) from a base station. The method includes estimating a multiple-input multiple-output (MIMO) channel frequency response (CFR) based on the CSI-RS. The method includes obtaining a wideband (WB) eigenvector and a subband (SB) eigenvector for at least one slot period set after a current time using the estimated MIMO CFR. The method includes obtaining common information for at least one of SB-specific, layer-specific, antenna pole-specific, and slot-specific based on a basis vector of the WB eigenvector. The method includes obtaining SB coefficients by projecting the SB eigenvector based on the common information. The method includes determining an SB precoding matrix indicator (PMI) corresponding to a precoding matrix predicted for the at least one slot period from the obtained SB coefficients.

[0007] According to an embodiment of the present disclosure, in a wireless communication system supporting precoding, a user equipment (UE) includes a transceiver, one or more processors including processing circuitry, and a memory storing instructions, wherein the instructions, when individually or collectively executed by the one or more processors, cause the UE to receive a CSI-RS from a base station through the transceiver. In one embodiment, the instructions, when individually or collectively executed by the one or more processors, cause the UE to estimate a MIMO CFR based on the CSI-RS. In one embodiment, the instructions, when individually or collectively executed by the one or more processors, cause the UE to obtain a WB eigenvector and a SB eigenvector for at least one slot period set after a current time point using the estimated MIMO CFR. In one embodiment, the commands, when individually or collectively executed by the one or more processors, may cause the terminal to obtain common information for at least one of SB-wise, layer-wise, antenna pole-wise, and slot-wise based on a basis vector of the WB eigenvector. In one embodiment, the commands, when individually or collectively executed by the one or more processors, may cause the terminal to obtain SB coefficients by projecting the SB eigenvector based on the common information. In one embodiment, the commands, when individually or collectively executed by the one or more processors, may cause the terminal to determine an SB PMI corresponding to a predicted precoding matrix for the at least one slot-wise from the obtained SB coefficients.

[0008] In one embodiment, the commands, when individually or collectively executed by the one or more processors, may cause the terminal to repeatedly perform operations after acquiring the common information up to a maximum value of a predetermined rank.

[0009] In one embodiment, the instructions, when individually or collectively executed by the one or more processors, may further cause the terminal to compress the SB coefficients by transforming them from a frequency domain to a lag domain and from a time domain to a Doppler domain, perform quantization per SB, per layer, and per antenna pole, and obtain a limited number of quantized coefficients in the lag domain and the Doppler domain.

[0010] In one embodiment, the commands, when individually or collectively executed by the one or more processors, may further cause the terminal to select a rank that maximizes MI obtained from an effective MIMO CFR and to report, through the transceiver, CSI including SB PMI corresponding to the selected rank to the base station.

[0011] In one embodiment, the instructions, when individually or collectively executed by the one or more processors, may cause the terminal to perform a 2D FFT operation based on the basis vector of the WB eigenvector, and to obtain the common information for at least one of the SB-by-SB, layer-by-layer, antenna pole-by-pole, and slot-by-slot intervals that maximizes a decision metric.

[0012] According to an embodiment of the present disclosure, a method for a base station to determine a precoding matrix in a wireless communication system supporting precoding includes receiving an SRS from a terminal. The method includes estimating a MIMO CFR based on the SRS. The method includes obtaining a WB eigenvector and an SB eigenvector for at least one slot period set after a current time using the estimated MIMO CFR. The method includes obtaining common information for at least one of SB-specific, layer-specific, antenna pole-specific, and slot-specific based on a basis vector of the WB eigenvector. The method includes obtaining SB coefficients by projecting the SB eigenvector based on the common information. The method includes determining an SB PMI corresponding to a predicted precoding matrix for the at least one slot period from the obtained SB coefficients.

[0013] According to an embodiment of the present disclosure, in a wireless communication system supporting precoding, a base station includes a transceiver, one or more processors including processing circuitry, and a memory storing instructions, wherein the instructions, when individually or collectively executed by the one or more processors, cause the base station to receive an SRS from a terminal (UE) via the transceiver. In one embodiment, the instructions, when individually or collectively executed by the one or more processors, cause the base station to estimate a MIMO CFR based on the SRS. In one embodiment, the instructions, when individually or collectively executed by the one or more processors, cause the base station to obtain a WB eigenvector and a SB eigenvector for at least one slot period set after a current point in time using the estimated MIMO CFR. In one embodiment, the commands, when individually or collectively executed by the one or more processors, may cause the base station to obtain common information for at least one of SB-wise, layer-wise, antenna pole-wise, and slot-wise based on a basis vector of the WB eigenvector. In one embodiment, the commands, when individually or collectively executed by the one or more processors, may cause the base station to obtain SB coefficients by projecting the SB eigenvectors based on the common information. In one embodiment, the commands, when individually or collectively executed by the one or more processors, may cause the base station to determine an SB PMI corresponding to a predicted precoding matrix for the at least one slot-wise from the obtained SB coefficients.

[0014] In one embodiment, the instructions, when individually or collectively executed by the one or more processors, may cause the base station to repeatedly perform subsequent operations of obtaining the common information up to a maximum value of a predetermined rank.

[0015] In one embodiment, the instructions, when individually or collectively executed by the one or more processors, may further cause the base station to select a rank that maximizes the MI obtained from the effective MIMO CFR.

[0016] In one embodiment, the instructions, when individually or collectively executed by the one or more processors, may cause the base station to perform a 2D FFT operation based on the basis vector of the WB eigenvector and obtain the common information for at least one of the SB-by-SB, layer-by-layer, antenna pole-by-pole and slot-by-slot interval that maximizes a decision metric.

[0017] In one embodiment, the at least one slot period may include a time point at which the base station schedules a PDSCH to the terminal.

[0018] According to an embodiment of the present disclosure, a storage medium storing at least one computer-readable instruction may be provided. In one embodiment, the at least one instruction, when individually or collectively executed by one or more processors including processing circuitry of a terminal (UE), causes the terminal to perform at least one operation, wherein the at least one operation may include receiving a CSI-RS from a base station via the transceiver. In one embodiment, the at least one operation may include estimating a MIMO CFR based on the CSI-RS. In one embodiment, the at least one operation may include obtaining a WB eigenvector and a SB eigenvector for at least one slot interval set after a current time point using the estimated MIMO CFR. In one embodiment, the at least one operation may include obtaining common information for at least one of SB-wise, layer-wise, antenna pole-wise, and slot-wise based on a basis vector of the WB eigenvector. In one embodiment, the at least one operation may include an operation of obtaining SB coefficients by projecting the SB eigenvector based on the common information. In one embodiment, the at least one operation may include an operation of determining an SB PMI corresponding to a predicted precoding matrix for the at least one slot period from the obtained SB coefficients.

[0019] In one embodiment, the at least one operation may include an operation of repeatedly performing operations after obtaining the common information up to a maximum value of a predetermined rank.

[0020] In one embodiment, the at least one operation may further include an operation of compressing the SB coefficients by transforming them from a frequency domain to a lag domain and a time domain to a Doppler domain, an operation of performing quantization for each SB, each layer, and each antenna pole, and an operation of obtaining a limited number of quantized coefficients in the lag domain and the Doppler domain.

[0021] In one embodiment, the at least one operation may further include selecting a rank that maximizes MI obtained from an effective MIMO CFR and reporting CSI including SB PMI corresponding to the selected rank to the base station.

[0022] In one embodiment, the operation of obtaining the common information may include an operation of performing a 2D FFT operation based on the basis vector of the WB eigenvector, and an operation of obtaining the common information for at least one of the SB-specific, layer-specific, antenna pole-specific, and slot-specific sections that maximizes a decision metric.

[0023] Figure 1 is a diagram showing the time-frequency domain transmission structure in a 5G system.

[0024] Figure 2 is a diagram showing the frame, subframe, and slot structure in a 5G system.

[0025] Figure 3 is a drawing for explaining a beamforming method using precoding in a 5G system.

[0026] FIGS. 4A, 4B and 4C are diagrams showing an example of a prediction window for determining an eType II predicted precoder according to an embodiment of the present disclosure;

[0027] FIG. 5 is a diagram illustrating a method for determining an eType II predicted precoder in a terminal receiving a CSI-RS from a base station in a wireless communication system according to an embodiment of the present disclosure;

[0028] FIG. 6 is a diagram illustrating a method for determining an eType II predicted precoder at a base station receiving an SRS from a terminal in a wireless communication system according to an embodiment of the present disclosure;

[0029] FIG. 7 is a diagram illustrating an example of a specific method for determining an eType II predicted precoder in a terminal receiving a CSI-RS from a base station in a wireless communication system according to an embodiment of the present disclosure;

[0030] FIG. 8 is a diagram illustrating an example of a specific method for determining an eType II predicted precoder in a base station receiving an SRS from a terminal in a wireless communication system according to an embodiment of the present disclosure;

[0031] FIG. 9 is a diagram illustrating an example of a method for determining MI according to TDCQI settings when determining an eType II predicted precoder in a terminal receiving CSI-RS from a base station in a wireless communication system according to an embodiment of the present disclosure; and

[0032] FIG. 10 is a diagram illustrating an example configuration of a network entity in a wireless communication system according to an embodiment of the present disclosure.

[0033] The operating principles of the present disclosure are described in detail below with reference to the attached drawings. In the following description of the present disclosure, detailed descriptions of related known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the present disclosure. Furthermore, the terms described below are defined based on the functions of the present disclosure and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the overall content of this specification.

[0034] The advantages and features of the present disclosure, and methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present disclosure is complete and to fully inform those skilled in the art of the scope of the invention, and the present disclosure is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0035] At this time, it will be understood that each block of the processing flow diagrams and combinations of the flow diagrams can be performed by computer program instructions.

[0036] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0037] Here, the term '~ part' used in this embodiment means software or hardware components such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit), and the '~ part' performs certain roles. However, the '~ part' is not limited to software or hardware. The '~ part' may be configured to be on an addressable storage medium or may be configured to play one or more processors. Therefore, as an example, the '~ part' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and '~ parts' may be combined into a smaller number of components and '~ parts' or further separated into additional components and '~ parts'. Additionally, the components and '~parts' may be implemented to activate one or more CPUs within a device or secure multimedia card. In addition, in an embodiment, the '~parts' may include one or more processors.

[0038] In this disclosure, phrases such as "A / B", "A or B", "A and / or B", "at least one of A and B", "at least one of A or B", "A, B, or C", "at least one of A, B, and C", and "at least one of A, B, or C" can each include any one of the items listed together in that phrase, or all possible combinations thereof. Terms such as "first", "second", or "first" or "second" may be used merely to distinguish the corresponding component from other corresponding components and do not limit the corresponding components in any other respect (e.g., importance or order).

[0039] The terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, and terms referring to various identification information are provided as examples for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms referring to objects with equivalent technical meanings may be used.

[0040] In the present disclosure, a base station (BS) is a network entity that performs resource allocation of a terminal and can communicate with the terminal via a wireless network, and may be at least one of an eNode B, a Node B, a gNB, a RAN (Radio Access Network), an AN (Access Network), a RAN node, an IAB (Integrated Access / Backhaul) node, a radio access unit, a base station controller, a node on a network, or a TRP (transmission reception point). A user equipment (UE) may be at least one of a terminal, an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function.

[0041] For convenience of explanation, some terms and names defined in the 3GPP NR standard may be used. However, the present invention is not limited to these terms and names, and can be equally applied to systems conforming to other standards.

[0042] Figure 1 is a diagram illustrating an example of the basic structure of time-frequency resources of a 5G system.

[0043] Referring to Figure 1, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. In the time and frequency domains, the basic unit of resources is a resource element (RE, 101), which can be defined as 1 OFDM (Orthogonal Frequency Division Multiplexing) symbol (102) in the time axis and 1 subcarrier (103) in the frequency axis. In the frequency domain (For example, 12) consecutive REs can form one Resource Block (RB, 104). In one embodiment, multiple OFDM symbols can form one subframe (110). In FIG. 1 is the number of OFDM symbols per subframe (110) for setting the subcarrier spacing (μ), and a more specific description of the resource structure in a 5G system can be referred to the TS 38.211 section 4 specification.

[0044] Figure 2 is a diagram showing an example of the frame, subframe, and slot structure of a 5G system.

[0045] Referring to FIG. 2, one frame (Frame, 200) may be composed of one or more subframes (Subframe, 201), and one subframe may be composed of one or more slots (Slot, 202). For example, one frame (200) may be defined as 10 ms. One subframe (201) may be defined as 1 ms, in which case one frame (2-00) may be composed of a total of 10 subframes (201). One slot (202, 203) may be defined as 14 OFDM symbols (i.e., the number of symbols per slot ( )=14). 1 subframe (201) may be composed of one or more slots (202, 203), and the number of slots (202, 203) per 1 subframe (201) may vary depending on the setting value μ (204, 205) for the subcarrier spacing. In the example of Fig. 2, the cases where μ = 0 (204) and μ = 1 (205) as the subcarrier spacing setting value are illustrated. For example, when μ = 0 (204), 1 subframe (201) may be composed of one slot (202), and when μ = 1 (205), 1 subframe (201) may be composed of two slots (203). That is, the number of slots per 1 subframe ( ) may vary, and accordingly the number of slots per frame ( ) may vary.

[0046] Figure 3 is a diagram for explaining a beamforming method using precoding in a 5G system.

[0047] Beamforming can be applied to MIMO (multiple-input and multiple-output) technology that can support enhanced transmission capacity for a large number of users, thereby forming multiple beams. Referring to FIG. 3, in a 5G system, so-called hybrid beamforming (hybrid BF) (300) can be used, which combines digital beamforming (Digital BF) (310), which changes the phase and / or amplitude of a signal through digital signal processing, and analog beamforming (Analog BF) (320), which forms analog beams with various beam directions and beam widths by changing the phase and / or amplitude of an analog signal. The hybrid beamforming technology can provide a large antenna gain while reducing the complexity of implementation. As in the example of FIG. 3, a block for processing digital beamforming (Digital BF) (310) may include a baseband digital precoder (hereinafter simply referred to as a precoder) (311), an inverse fast Fourier transform (IFFT) unit, and a parallel / serial (P / S) conversion unit. The IFFT unit and the P / S conversion unit may be included in a number corresponding to the number of radio frequency (RF) chains, and each RF chain may be implemented by including a digital analog converter (DAC) and a mixer. In the example of FIG. 3, a block for processing analog beamforming (Analog BF) (320) may include a plurality of analog phase shifters (321), power amplifiers (PAs), and antenna arrays connected to each RF chain. Beam sweeping is possible over a wide range of angles through the above-described multiple analog phase shifters (321).The antenna array includes a plurality of antenna elements, and the number of RF chains increases corresponding to the number of antenna arrays. In a 5G system, a transmitter that forms a transmission beam may be implemented by including the above-described digital beamforming (Digital BF) block, a plurality of RF chains, and a plurality of analog beamforming (analog BF) blocks, and a receiver that forms a reception beam and receives a signal from the transmitter may be implemented by including a plurality of analog beamforming (analog BF) blocks, a plurality of RF chains, and a digital beamforming (Digital BF) block corresponding to the configuration of the transmitter. The precoder to be described in the embodiments of the present disclosure may be implemented in the baseband digital precoder (311). In the example of FIG. 3, the transmitter may be a transmitter of a base station that performs precoding, and the receiver may be a receiver of a terminal. As another example, the transmitter may be a transmitter of a terminal that performs precoding, and the receiver may be a receiver of a base station. The above precoding can be applied to downlink transmission in a downlink channel, such as a physical downlink shared channel (PDSCH) or a physical downlink control channel (PDCCH). In addition, the above precoding can be applied to uplink transmission in an uplink channel, such as a physical uplink shared channel (PUSCH) or a physical uplink control channel (PUCCH). The reference signal transmitted from the transmitter based on the beamforming can be, for example, at least one of a demodulation-reference signal (DM-RS), a channel state information-reference signal (CSI-RS), and a sounding reference signal (SRS).

[0048] In a wireless communication system, such as a 5G system defined in the 3GPP NR standard, a base station can transmit the CSI-RS, which is a terminal-specific reference signal, and the terminal can measure the received signal strength of the CSI-RS and transmit channel state information (CSI) to the base station. The CSI can include at least one of a Channel Quality Indicator (CQI), a Precoding Matrix Indicator (PMI), and a Rank Indication (RI) related to a channel state in the downlink. In addition, in the 5G system having the above structure, the terminal can transmit an SRS to the base station for the base station to estimate an uplink channel state. The uplink channel and the downlink channel can be reciprocal. Therefore, the base station can receive the SRS and perform downlink transmission based on the estimated channel state. In addition, in the 5G system, the base station can provide the terminal with configuration information for CSI-RS transmission and configuration information for SRS transmission. Transmission of the CSI-RS and the SRS in the terminal can be performed periodically or aperiodicly, respectively. The base station can activate, deactivate, or trigger SRS transmission to the terminal through signaling information.

[0049] In the above CSI, the RI indicates information related to the rank of the channel and represents the maximum number of streams that the terminal can receive through the same resource. The 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.

[0050] The 3GPP NR standard (TS 38.214) defines Type 1 codebooks and Type 2 codebooks. The Type 1 codebook can be divided into a single-panel codebook and a multi-panel codebook. The Type 2 codebook can be divided into the general Type 2 codebook and Type 2 port selection codebook introduced in 3GPP release 15, and the enhanced Type 2 codebook and enhanced Type 2 port selection codebook introduced in release 16. The Type 2 codebook in release 15 supports only up to rank 2, and the enhanced Type 2 codebook was introduced in release 16.

[0051] The precoding matrix of the above Type 2 codebook can support up to rank 2 and can be indicated by multiple codebook indices as defined in the 3GPP standard. The precoding matrix of the above enhanced Type 2 codebook can support up to rank 4, and in the enhanced Type 2 codebook, beam amplitude scaling and co-phasing values ​​(which may be referred to as beam combining coefficients) for all beams can be calculated in a similar manner to the Type 2 codebook. As the rank expands, the feedback overhead may linearly increase with the number of subbands. Therefore, the uplink resources for the terminal to report the PMI may not be sufficient, and a process referred to as discrete Fourier transform (DFT) compression or frequency-domain compression can be applied to the enhanced Type 2 codebook by utilizing the frequency domain correlation of the beam combining coefficients.

[0052] In the frequency band of the 5G system, WB (wideband) represents the entire band of the cell to which the terminal is connected (e.g., BWP ((bandwidth part)), and SB (subband) may represent a subset of WB. SB may be set by the base station, and the precoding matrix based on the Type 2 codebook and the enhanced Type 2 codebook may include components in units of SB. The Type 2 codebook may provide a precoding matrix in a double-stage form in which two matrices are multiplied. For example, the precoding matrix of the Type 2 codebook is It can be defined as follows. Here, W1 represents a precoding matrix of the WB component and W2 represents a precoding matrix of the SB component. And, W1 and W2 can be indicated through multiple codebook indices, respectively.

[0053] In the 3GPP standard, the enhanced Type 2 codebook-based precoder (hereinafter, eType II precoder) can use DFT vectors as basis vectors. The basis vector can be defined as the angle of the horizontal beam and the vertical beam within a 2-dimensional antenna array. In addition, the precoding matrix for the eType II precoder can be determined / selected using the PCA (principal component analysis) technique. PCA is a technique for compressing high-dimensional vectors, and through the PCA, the base station or terminal can obtain a plurality of eigenvectors for the WB and a plurality of eigenvectors for each SB. The eigenvectors are vectors used in the process of determining the precoding matrix. The above eType II precoder includes an SB-based precoder, and instead of reporting precoder information (i.e., PMI) for each subband to the base station, the terminal can be configured to transform the SB domain into a lag domain and report limited coefficients through compression. This can reduce the overhead of CSI to improve the efficiency of uplink resources.

[0054] The above NR eType II precoder is an SB-based precoder, but when the terminal provides feedback on CSI, rather than explicitly reporting the precoder for each SB, the coefficients of the entire SB are converted from the SB domain to the lag domain, and then compressed, quantized, and limited in number are applied, and the limited coefficients are reported to the UCI. Therefore, the precoding matrix used when the base station schedules the PDSCH is not the scheduled time, but the CSI from a past time.

[0055] When a terminal selects a precoding matrix using CSI-RS and transmits PMI for the precoding matrix to UL via UCI, the timing at which the base station schedules PDSCH for the terminal using the CSI feedback information transmitted to UL and the timing at which the terminal acquires DL CSI from the CSI-RS are different. In this case, the first delay is the time it takes for the terminal to receive the CSI-RS and transmit the UCI to UL, and the second delay is the time it takes for the base station to receive the UCI from the terminal and schedule the PDSCH. Therefore, since the existing NR eType II precoding matrix is ​​information that feeds back the CSI at the time the terminal receives the CSI-RS via UCI, the two delays mentioned above cannot be avoided.

[0056] Embodiments of the present disclosure propose a method for determining / selecting a predicted precoder matrix for a predicted precoder in a future slot period(s) at which the base station actually schedules a PDSCH, at the base station or the terminal. The present disclosure proposes an embodiment in which a terminal that receives a CSI-RS from a base station determines a predicted precoder matrix for a predicted precoder, and an embodiment in which a base station that receives an SRS from a terminal determines a predicted precoder matrix for a predicted precoder. In the present disclosure, the predicted precoder matrix will be referred to as an eType II predicted precoding matrix for convenience. In the embodiments of the present disclosure, the eType II predicted precoding matrix will be described by taking as an example application in the downlink. However, the eType II predicted precoding matrix can also be applied in the uplink.

[0057] In the present disclosure, a technique is proposed for determining / selecting / calculating PMI representing a predicted precoding matrix in two cases: when an SRS is received and when a CSI-RS is received. In the present disclosure, when an SRS is received and the PMI is determined / selected / calculated, the operating entity that determines / selects / calculates the PMI is a base station (BS), and when a CSI-RS is received and the PMI is determined / selected / calculated, the operating entity that determines / selects / calculates the PMI is a terminal (UE).

[0058] In the present disclosure, when a terminal receives a CSI-RS and determines / selects / calculates a PMI, it is necessary to define a prediction window expressed by at least one slot interval and offset.

[0059] FIGS. 4A, 4B, and 4C are diagrams illustrating an example of a prediction window for determining an eType II predicted precoder according to an embodiment of the present disclosure.

[0060] Figures 4a, 4b and 4c show the slot offset , the size of the slot interval is d=5 slots (i.e. one slot interval consists of 5 slots) and the prediction window is An example is shown having intervals (i.e., the number of slot intervals is 4). In Figs. 4a, 4b, and 4c, it is assumed that slot n is a slot in which a terminal transmits CSI including CQI and PMI. In this case, the CQI and PMI are predicted CQI and PMI for at least one slot after slot n (i.e., for a future time corresponding to the time at which the base station schedules the PDSCH).

[0061] Referring to Fig. 4a, when the index of the slot where CSI feedback information is transmitted to UCI is n, the prediction window is When the time domain channel quality indicator (TDCQI) set by the Radio resource control (RRC) message (i.e., configuration information) according to the 3GPP NR standard is 1-1, the CQI included in the UCI transmitted in slot n is slot The predicted channel in and the value can be determined from the PMI determined / selected / calculated for the first slot interval (let's define it as slot interval 0). That is, in the example of Fig. 4a, CQI is the predicted CQI associated with slot 0, which is located at a slot offset from slot n, and PMI is the predicted PMI associated with slot interval 0, which is located at a slot offset from slot n. The predicted PMI can be determined / selected / calculated for, for example, 5 slots within slot interval 0 (410).

[0062] Referring to Fig. 4b, when the TDCQI set with the above setting information is 1-2, the CQI included in the UCI transmitted in slot n is slot PMI determined / selected / calculated for the prediction channel and slot interval 0 in and slot Prediction channel and slot interval in The value can be determined from the PMI determined / selected / calculated for. At this time, the transmitted CQI and PMI can take the average value in two slot intervals (slot interval 0, slot interval 3), for example. That is, in the example of Fig. 4b, the CQI is the predicted CQI related to slot 0 and slot 19, and the PMI is the predicted PMI related to slot interval 0 and slot interval 3. The predicted PMI can be determined / selected / calculated for, for example, five slots within the corresponding slot interval (420).

[0063] Referring to Fig. 4c, when the TDCQI set with the above setting information is 2, the CQI included in the UCI transmitted in slot n is 2. Determine the value of the first CQI from the PMI determined / selected / calculated for the prediction channel and slot interval 0 in , and slot Prediction channel and slot interval in The value of the second CQI can be determined from the PMI determined / selected / calculated for. At this time, the CQI and PMI to be transmitted can be determined / selected / calculated for two slot intervals (slot interval 0, slot interval 3), for example. That is, in the example of Fig. 4c, the CQI is a predicted CQI related to slot 0 and slot 10, and the PMI is a predicted PMI related to slot interval 0 and slot interval 2. The predicted PMI can be determined / selected / calculated for, for example, five slots within the corresponding slot interval (430).

[0064] Embodiments of the present disclosure may provide a method for a terminal to receive a CSI-RS in a MIMO environment and determine / select / calculate an eType II predicted precoding matrix. In addition, when channel reciprocity is established in a time division duplex (TDD) system, a base station may receive an SRS and determine / select / calculate an eType II predicted precoding matrix. According to the 3GPP NR standard, an eType II predicted precoder uses a vector of an oversampled discrete Fourier transform (DFT) codebook as a basis vector, and the basis vector can be defined by an angle of a horizontal beam and an angle of a vertical beam. The above eType II predicted precoder is a SB-based and slot interval-based precoder, but when the terminal feeds back CSI to the base station, rather than explicitly reporting the precoder for each SB, the coefficients of the entire SB are converted from the SB domain to the lag domain and then converted from the interval domain to the Doppler domain, and then compressed, quantized, and number-limited are applied, and the limited coefficients are reported. This method is a method to reduce the amount of information included in the UCI. On the other hand, when the base station receives the SRS and uses multiple 2D DFT vectors per precoder as basis vectors to determine / select / calculate the precoder, compression, quantization, and number-limiting can be omitted.A terminal or a base station can select a specific rank and a MIMO precoder and modulation order corresponding to the rank that maximizes the mutual information (MI) or DL ​​throughput of the downlink (DL) when a PDSCH is scheduled. The MI can be obtained from an effective MIMO CFR (channel frequency response) matrix, and in the frequency domain, the effective MIMO CFR matrix can be obtained by multiplying the MIMO CFR matrix predicted from the SRS or CSI-RS in the configured slot period by the precoder determined / selected / calculated according to the present disclosure. Since the method of obtaining the MI from the effective MIMO CFR matrix itself can utilize a known technology, a detailed description thereof will be omitted. For example, when the effective MIMO CFR matrix is ​​given, the transmitter uses bit interleaved coded modulation (BICM), and the demodulator of the receiver has a reception structure such as maximum likelihood (ML) or linear minimum mean square error (LMMSE), the MI can be obtained.

[0065] In the present disclosure, a base station or a terminal can predict and determine a rank, a precoding matrix, and / or a modulation order to be applied at a future time (e.g., a time when a PDSCH is actually scheduled) based on the MI and / or downlink throughput. Specifically, an entity (a terminal or a base station) that determines / selects / calculates the eType II predicted Precoder (i.e., an eType II predicted precoding matrix) can select the number of layers (i.e., rank), PMI, and modulation order that maximize the MI (i.e., maximize DL throughput). The modulation order may be associated with a CQI indicating a modulation scheme. For example, the modulation scheme may be QPSK (quadrature phase shift keying) corresponding to a modulation order of 2, 16 QAM (quadrature amplitude modulation) corresponding to a modulation order of 4, 64 QAM corresponding to a modulation order of 6, or 256 QAM corresponding to a modulation order of 8.

[0066] In addition, PCA is a well-known technique that can compress and express a high-dimensional vector by expressing the high-dimensional vector as the product of a system matrix known to the transmitter and receiver and a low-dimensional coefficient vector. By utilizing this PCA technique, multiple eigenvectors representing one WB and multiple eigenvectors representing each SB can be obtained. Using the WB and SB eigenvectors obtained in this way, the WB and SB eigenvectors at the time of scheduling the PDSCH at the base station can be predicted. Alternatively, the MIMO CFR at the time of scheduling the PDSCH can be predicted from the MIMO CFR at the current time, and the WB and SB eigenvectors at the predicted time can be obtained. In this way, the method itself of obtaining the WB and SB eigenvectors used in the process of determining the eType II predicted Precoder at the time of scheduling the PDSCH (i.e., the future time) can utilize various known methods.

[0067] In the embodiments of the present disclosure below, a specific method of obtaining WB and SB eigenvectors at the time of scheduling a PDSCH from a base station or a terminal and determining / selecting / calculating an eType II predicted precoding matrix using the WB and SB eigenvectors is described.

[0068] FIG. 5 is a diagram illustrating a method for determining an eType II predicted precoder in a terminal receiving a CSI-RS from a base station in a wireless communication system according to an embodiment of the present disclosure.

[0069] Referring to FIG. 5, in step 501, the terminal can receive a CSI-RS from the base station and estimate a MIMO CFR based on the received CSI-RS. In step 502, the terminal can obtain a WB eigenvector and a SB eigenvector used for determining / selecting / calculating an eType II predicted precoder using the estimated MIMO CFR. The WB eigenvector and the SB eigenvector can be obtained for at least one slot period set after the current time, and the at least one slot period can correspond to a time point at which a PDSCH is scheduled for the terminal. Although not illustrated in FIG. 5, configuration information for the at least one slot period can be provided to the terminal in advance from the base station.

[0070] In step 502, the terminal can obtain common information for at least one of SB-wise, layer-wise, antenna pole-wise, and slot-wise that performs a 2D FFT operation based on a basis vector of a WB eigenvector and maximizes a decision metric. The terminal can obtain SB coefficients by projecting the SB eigenvector based on the common information, perform compression by performing transformation from the frequency domain to the lag domain and transformation from the time domain to the Doppler domain on the SB coefficients, perform quantization for SB-wise, layer-wise, and antenna pole-wise, and obtain a limited number of coefficients in the lag domain and the Doppler domain to determine the SB PMI for the eType II predicted precoder. The operation of step 502 can be performed for each rank.

[0071] In step 503, the terminal selects a rank that maximizes the above-mentioned MI and reports CSI including the SB PMI corresponding to the rank to the base station. Then, in step 504, the terminal can receive PDSCH data with the eType II predicted precoder applied to precoding based on the reported CSI.

[0072] A specific example of the embodiment of the above drawing 5 will be described in the embodiment of the following drawing 7.

[0073] FIG. 6 is a diagram illustrating a method for determining an eType II predicted precoder at a base station receiving an SRS from a terminal in a wireless communication system according to an embodiment of the present disclosure.

[0074] Referring to FIG. 6, in step 601, the base station can receive an SRS from the terminal and estimate a MIMO CFR based on the received SRS. In step 602, the base station can obtain a WB eigenvector and a SB eigenvector used for determining / selecting / calculating an eType II predicted precoder using the estimated MIMO CFR. The WB eigenvector and the SB eigenvector can be obtained for at least one slot period set after a current time, and the at least one slot period can correspond to a time point at which a PDSCH is scheduled for the terminal. The at least one slot period can be set by the base station and the setting information can be provided to the terminal in advance.

[0075] In step 602, the base station can obtain common information for at least one of SB-wise, layer-wise, antenna pole-wise, and slot-wise that performs a 2D FFT operation based on the basis vector of the WB eigenvector and maximizes the decision metric. The base station can obtain SB coefficients by projecting the SB eigenvector based on the common information, and determine the SB PMI for the eType II predicted precoder from the SB coefficients. The operation of step 602 can be performed for each rank. In the operation of the base station using SRS, the compression, quantization, and coefficient number limitation operations that perform transformation to the lag domain and transformation to the Doppler domain in the embodiment of FIG. 5 can be omitted. This is because the base station does not require overhead reduction for CSI reporting like the terminal.

[0076] And in step 603, the base station selects a rank that maximizes the above-mentioned MI, and transmits PDSCH data with an eType II predicted precoder applied to precoding based on the SB PMI corresponding to the rank.

[0077] A specific example of the embodiment of the above drawing 6 will be described in the embodiment of the following drawing 8.

[0078] FIG. 7 is a diagram illustrating an example of a specific method for determining an eType II predicted precoder in a terminal receiving a CSI-RS from a base station in a wireless communication system according to an embodiment of the present disclosure.

[0079] Referring to FIG. 7, in step 701, the terminal receives a CSI-RS from the base station, and in steps 702 and 703, estimates a MIMO CFR in at least one slot section set as described in FIGS. 4a to 4c based on the received CSI-RS, and extracts WB and SB Eigen vectors from the estimated MIMO CFR. At this time, the terminal may predict the WB and SB Eigen vectors within a prediction window corresponding to the at least one slot section from a series of WB and SB Eigen vectors up to the current point in time, or predict the MIMO CFR within the prediction window corresponding to the at least one slot section and extract the WB and SB Eigen vectors. In step 704, the terminal may start an operation of determining an eType II predicted precoder from rank (B) = 1. In step 705, the terminal obtains multiple WB basis vectors based on the WB eigenvector within the prediction window using 2D FFT, and in step 706, the terminal can obtain common information for at least one of SB-specific, layer-specific, antenna pole-specific, and slot-specific information that maximizes the decision metric. In step 707, the terminal can obtain SB coefficients by projecting the SB eigenvector onto the basis vector based on the common information.

[0080] In step 708, the terminal can perform 2DFFT on the SB coefficients to transform them from the SB domain to the lag domain and from the interval domain to the Doppler domain, and determine the per-layer lag value and the per-layer Doppler from the transformed coefficient values. In steps 709, 710, and 711, the terminal can quantize the global gain, quantize the per-lag and per-Doppler amplitude and phase, and limit the number of non-zero coefficients in the lag domain and the Doppler domain. In step 712, the terminal can determine / select / calculate the SB precoder (i.e., SB PMI) using the limited number of quantized coefficients and the WB basis vector, and then, in step 713, can change the rank of the determined SB PMI and calculate the MI. In steps 714 and 715, the terminal determines / selects / calculates a rank that maximizes the calculated MI for each Rank (B), and in step 716, the terminal may report to the base station at least one of the SB PMI (corresponding to the eType II predicted precoder) and the modulation order (QPSK, 16QAM, 64QAM, 256QAM, etc.) corresponding to the determined rank. In step 715, the terminal may repeat the operations of steps 705 to 714 until the Rank (B) reaches a predetermined maximum value. The terminal may receive PDSCH data to which the eType II predicted precoder is applied for precoding based on at least one of the reported SB PMI and modulation order.

[0081] FIG. 8 is a diagram illustrating an example of a specific method for determining an eType II predicted precoder at a base station receiving an SRS from a terminal in a wireless communication system according to an embodiment of the present disclosure.

[0082] Referring to FIG. 8, in step 801, the base station receives an SRS from the terminal, and in steps 802 and 803, estimates a MIMO CFR in at least one slot section set as described in FIGS. 4A to 4C based on the received SRS, and extracts WB and SB Eigen vectors from the estimated MIMO CFR. At this time, the base station may predict the WB and SB Eigen vectors within a prediction window corresponding to the at least one slot section from a series of WB and SB Eigen vectors up to the current point in time, or predict the MIMO CFR within the prediction window corresponding to the at least one slot section and extract the WB and SB Eigen vectors. In step 804, the base station may start an operation of determining an eType II predicted precoder from rank (B) = 1. In step 805, the base station obtains multiple WB basis vectors based on the WB eigenvector within the prediction window using 2D FFT, and in step 806, the base station can obtain common information for at least one of SB-wise, layer-wise, antenna pole-wise, and slot-wise that maximizes a decision metric. In step 807, the base station can obtain SB coefficients by projecting the SB eigenvectors onto the basis vectors based on the common information. In step 808, the base station determines / selects / calculates an SB precoder (i.e., SB PMI) using the SB coefficients and the WB basis vector for a given rank (B), and then in step 809, the base station can change the rank for the determined SB PMI and calculate MI.In steps 810 and 811, the base station determines / selects / calculates a rank that maximizes the calculated MI for each Rank (B), and in step 812, the base station can transmit PDSCH data with the eType II predicted precoder applied to precoding based on at least one of the SB PMI (corresponding to the eType II predicted precoder) and the modulation order (QPSK, 16QAM, 64QAM, 256QAM, etc.) corresponding to the determined rank.

[0083] FIG. 9 is a diagram illustrating an example of a method for determining MI based on TDCQI settings when determining an eType II predicted precoder in a terminal receiving a CSI-RS from a base station in a wireless communication system according to an embodiment of the present disclosure. The embodiment of FIG. 9 may be performed in combination with the embodiments of FIGS. 4a, 4b, 4c, FIG. 5, and / or FIG. 7.

[0084] In Fig. 9, the TDCQI can be set to one of three cases, 1-1, 1-2, or 2, depending on the configuration information of the base station, as described in Figs. 4a, 4b, and 4c. The three cases are briefly referred to as the first TDCQI, the second TDCQI, and the third TDCQI. In the case of the CSI-RS reception-based eType II predicted precoder according to the present disclosure, MI calculation can be performed differently depending on the TDCQI value, as in the embodiments of Figs. 4a, 4b, and 4c.

[0085] Referring to FIG. 9, in step 901, if the set TDCQI is the first TDCQI (i.e., 1-1), in step 902, the terminal MI can be calculated for each modulation order from the predicted channel and the PMI calculated for the first slot interval 0. Then, in step 903, the terminal can find the modulation order that maximizes MI and store the MI corresponding to the modulation order.

[0086] In step 911, the terminal sets the slot if the set TDCQI is the second TDCQI (i.e. 1-2) in step 912. MI0 can be calculated for each modulation order from the predicted channel and PMI calculated for slot interval 0. In addition, the terminal can calculate the MI0 for each slot Prediction channel and slot interval in MI1 can be calculated for each modulation order from the PMI calculated for . And at step 913, the terminal can store the modulation order that maximizes MI = MI0 + MI1 and the MI corresponding to the modulation order.

[0087] In step 921, if the set TDCQI is the second TDCQI (i.e. 2), the terminal selects slot in step 922. MI0 can be calculated for each modulation order from the PMI calculated for the prediction channel and slot interval 0 in step 923. In step 923, the terminal can store the modulation order that maximizes MI0 and the MI0 corresponding to the modulation order. In step 924, the terminal can store the modulation order that maximizes MI0 and the MI0 corresponding to the modulation order. Prediction channel and slot interval in MI1 can be calculated for each modulation order from the PMI calculated for . In step 925, the terminal can store the modulation order that maximizes MI1 and the MI1 corresponding to the modulation order. And in step 926, the terminal can store the MI that is the sum of MI0 + MI1.

[0088] Hereinafter, an example of a specific method of the present invention for approximating SB eigenvectors and WB eigenvectors in embodiments of the present disclosure and determining an eType II predicted precoder using the approximated SB eigenvectors and WB eigenvectors will be described.

[0089] Assuming that the number of layers in the precoder is 2 (i.e., the rank is 2), then the two predicted SB Eigenvectors ( ) can be approximated by the following [Mathematical Formula 1]. In the matrix on the right side of [Mathematical Formula 1] below, each column approximates the SB Eigen vector for each layer.

[0090] [Mathematical Formula 1]

[0091]

[0092] Here and are each SB Eigen vector for the first layer, SB Eigen vector for the second layer. and at (iota in Greek) is at least one slot interval (e.g., as described in FIGS. 4a, 4b and 4c). is a variable introduced for determining the predicted PMI (i.e., the predicted precoder matrix) for the predicted precoder in the slot interval 0, 1, 2 or 3 of the future time point. The base station can transmit signals via a two-dimensional antenna array. N1 is the number of antenna ports in the first dimension (e.g., horizontal direction) of the two-dimensional antenna array of the base station, and N2 is the number of antenna ports in the second dimension (e.g., vertical direction) of the two-dimensional antenna array of the base station. is the angle of the first dimension index corresponds to the second dimension angle index Represents the i-th basis vector consisting of a 2D DFT vector having ( ) In other words, N1 is the number of horizontal antenna ports, and N2 is the number of vertical antenna ports. is the index of the horizontal angle of the transmitted beam and the index of the vertical angle of the transmission beam The i-th basis vector (basis) formed by the Kronecker product of two DFT vectors having means. L means the number of basis. 2 index class can be expressed as follows [Mathematical Formula 2] and [Mathematical Formula 3].

[0093] [Equation 2]

[0094]

[0095] [Equation 3]

[0096]

[0097] Here go When it means the index of the horizontal angle of the th basis, and, is. Also, go When it means the index of the vertical angle of the th basis, and, am. is the oversampling factor for the horizontal beam, is the oversampling factor for the vertical beam. That is, is the oversampling factor in the first dimension, represents the oversampling factor in the second dimension. can be configured by an RRC message of the base station (110).

[0098] is the global gain (e.g. WB amplitude) for SB-common, basis-common, interval-common, layer 1, and pole 0, is the global gain (e.g. WB amplitude) for SB-common, basis-common, interval-common, layer 1, and pole 1 (second pole), are the global gains for SB-common, basis-common, interval-common, layer 2, and pole 0. is the global gain for SB-common, basis-common, interval-common, layer 2, and pole 1. In the present disclosure, the first pole may represent a first polarization, and the second pole may represent a second polarization. For example, since the first pole and the second pole have a phase difference, a parameter of a co-phase component may be multiplied to the precoding matrix of a specific pole (e.g., the second pole). In one implementation example, the poles of the transmitting antenna may be arranged to be orthogonal to each other.

[0099] is the number of layers When it is a dog, it is the number of lags. In the example above, am. is the number of Doppler waves. is layer 1, pole 0, basis , lag index And Doppler index is the amplitude for, is layer 1, pole 1, basis , lag index And Doppler index is the amplitude for, is layer 2, pole 0, basis , lag index And Doppler index is the amplitude for, is layer 2, pole 1, basis , lag index And Doppler index is the amplitude for . is layer 1, pole 0, basis , lag index And Doppler index is the phase for, is layer 1, pole 1, basis , lag index And Doppler index is the phase for, is layer 2, pole 0, basis , lag index And Doppler index is the phase for, is layer 2, pole 1, basis , lag index And Doppler index is the phase for . N3 is the number of SB. is the lag index for layer 1 is the lag value corresponding to is the lag index for layer 2 is the lag value corresponding to . N4 is the number of slot intervals mentioned above. is the Doppler index for layer 1 is the corresponding Doppler value, Doppler index for layer 2 is the corresponding Doppler value. In order to maintain the power of the precoding vector for each layer at a constant value, , slot interval Wow layer It doesn't really scale can be expressed as in [Mathematical Formula 4] below.

[0100] [Equation 4]

[0101]

[0102] [Equation 5a]

[0103]

[0104] Assuming that the number of layers of the precoder is 2 (i.e., the rank is 2), the WB Eigen vector is expressed as an approximate formula as in [Mathematical Formula 5a] above. We can obtain L basis vectors from layer 1 and slot interval for pole 0. WB Eigen vector of And, 2D FFT is performed as in [Mathematical Formula 5b] below.

[0105] [Equation 5b]

[0106]

[0107] Slot interval for layer 1 and pole 1 WB Eigen vector of 2D FFT is performed as follows.

[0108] [Equation 6]

[0109]

[0110] Slot interval for layer 2 and pole 0 WB Eigen vector of 2D FFT is performed as in [Mathematical Formula 7] below.

[0111] [Equation 7]

[0112]

[0113] interval for layer 2 and pole 1 WB Eigen vector of 2D FFT is performed as in [Mathematical Formula 8] below.

[0114] [Equation 8]

[0115]

[0116] Here am.

[0117] Calculated above Using this, the decision metric can be defined as in [Mathematical Formula 9] below.

[0118] [Equation 9]

[0119]

[0120] Here and is a design parameter, and as an example, both can have the value 1. Another metric can also be defined as in [Mathematical Formula 10] below.

[0121] [Equation 10]

[0122]

[0123] Then, as defined above By using The set of dogs is defined as shown in [Mathematical Formula 11] below.

[0124] [Equation 11]

[0125]

[0126] Then, from the metric as in [Mathematical Formula 12] You can choose.

[0127] [Equation 12]

[0128]

[0129] And, the optimal set is defined as in [Mathematical Formula 13] below.

[0130] [Equation 13]

[0131]

[0132] Here silver of is the th entry. Then, the horizontal angle index of L basis vectors and vertical angle index is obtained as shown in [Mathematical Formula 14].

[0133] [Equation 14]

[0134]

[0135] [Equation 15]

[0136]

[0137] The basis vector obtained from the Eigen vector above Projected as follows: layer 1, pole 0, and interval SB Eigen vector for As shown in [Mathematical Formula 16] below Projected onto.

[0138] [Equation 16]

[0139]

[0140] layer 1, pole 1, and interval SB Eigen vector for As shown in [Mathematical Formula 17] below Projected onto.

[0141] [Equation 17]

[0142]

[0143] layer 2, pole 0, and interval SB Eigen vector for As shown in [Mathematical Formula 18] below Projected onto.

[0144] [Equation 18]

[0145]

[0146] layer 2, pole 1, and interval SB Eigen vector for As shown in [Mathematical Formula 19] below Projected onto.

[0147] [Equation 19]

[0148]

[0149] In the present disclosure, in the case of the SRS reception-based eType II predicted precoder, eType II And interval The precoding matrix for can be approximated as follows [Mathematical Formula 20].

[0150] [Equation 20]

[0151]

[0152] In the present disclosure, MI can be calculated using the SB precoding matrix and the MIMO CFR estimate of a slot where a PDSCH will be scheduled in the future. MI can be calculated by varying the rank. Then, the rank that maximizes the calculated MI for each rank can be selected, and the SB PMI and the corresponding modulation order can be determined. The SB PMI and modulation order (QPSK, 16QAM, 64QAM, 256QAM, etc.) corresponding to that rank can be reported.

[0153] In the present disclosure, for the CSI-RS reception-based eType II predicted precoder, And interval In addition to obtaining the star coefficients, we perform frequency compression, time compression, quantization, and limiting the number of non-zero coefficients. And interval The star coefficients are 2D-FFTed as in [Mathematical Formula 21] below.

[0154] [Equation 21]

[0155]

[0156] Here And as shown in [Mathematical Formula 22] below, Defines.

[0157] [Equation 22]

[0158]

[0159] In addition, the following metric is calculated as [Mathematical Formula 23].

[0160] [Equation 23]

[0161]

[0162] second and fix it, Sort in descending order while changing the value. The first of the sorted items Select an entry and its set of lag values ​​as follows: It is indicated as .

[0163] In addition, the following metric is calculated as [Mathematical Formula 24].

[0164] [Equation 24]

[0165]

[0166] second and fix it, Sort in descending order while changing the value. The first of the sorted items Select an entry and its set of Doppler values ​​as follows: It is indicated as .

[0167] Layer and fix pole 0, class By changing Find the peak value and the location of that value It is indicated as Layer and fix pole 1, class By changing Find the peak value and the location of that value It is indicated as .

[0168] Variables as in [Mathematical Formula 25] Initializes.

[0169] [Equation 25]

[0170]

[0171] Here and am.

[0172] Layer and pole 0 corresponds to This Layer and pole 1 corresponds to If it is larger, it can be expressed as in [Equation 26] and [Equation 27].

[0173] [Equation 26]

[0174]

[0175] [Equation 27]

[0176]

[0177] Alternatively, it can be expressed as [Equation 28] and [Equation 29] below.

[0178] [Equation 28]

[0179]

[0180] [Equation 29]

[0181]

[0182] At this time, Is layer that satisfies for and, Is layer that satisfies for is. Also, Is layer that satisfies for and, Is layer that satisfies for is. Now, the global gain is quantized. [Table 1] below is a table listing the p1 values ​​defined in the specification.

[0183] [Table 1]

[0184]

[0185] [Table 2] below is a table listing the p2 values ​​defined in the standard.

[0186] [Table 2]

[0187]

[0188] [Table 3] below is a table that multiplies the p1 and p2 values ​​defined in the standard in any combination and lists them in order of magnitude. It has 29 values.

[0189] [Table 3]

[0190]

[0191] Below [Table 4], the listed Thre1 is the average of two adjacent values ​​in Table 2.

[0192] [Table 4]

[0193]

[0194] Layer and values ​​for pole 0 And Layer and values ​​for pole 1 We obtain the global gain value for each layer and pole. For example, The value of When creating the above value There are eight possible combinations: , should, On the other hand, p1 and p2, which express , have 1 and 1 as the only answers. And On the other hand, The eight ways above can be the answer to the question that can be expressed as follows. If p1 is 1, then p2 is This becomes. However, since p1 is the global gain for pole 1, layer And for pole 1 When, The quantized minimum of is It has to be the minimum value of p2. Note that layer And in order to express the values ​​for pole 1 in a wide range, The p1 value should be the minimum, which can minimize the quantization loss as much as possible. This becomes: Then, layer And for pole 1 The quantized minimum of is This is possible. this class In between, If it is close to, can be mapped to, this class In between, If it is close to, can be mapped to . With the same logic as above, global gain can be expressed in pseudo code as in [Table 5] below.

[0195] [Table 5]

[0196]

[0197] Here class are each quantized class is the index pointing to .

[0198] Now, we quantize the per-lag and per-Doppler amplitudes. Layer And for Pole 0 second Divide into Layer And for Pole 1 second Divide by , and map each divided value to the closest value of p2.

[0199] Thre2 listed in [Table 6] below is the average of two adjacent values ​​in Table 4.

[0200] [Table 6]

[0201]

[0202] For pole 0, it can be expressed in pseudo code as shown in [Table 7] below.

[0203] [Table 7]

[0204]

[0205] For pole 1, it can be expressed in pseudo code as shown in [Table 8] below.

[0206] [Table 8]

[0207]

[0208] Now, the per-lag and per-Doppler phases are quantized as in [Equation 30].

[0209] [Equation 30]

[0210]

[0211] Now we limit the number of non-zero coefficients in the lag domain.

[0212] given layer About of , and Sort in descending order while changing the value. Select the K0 with the largest value. All layers Repeat the above procedure for Collect the dog's entries. Sort the entries in descending order. The largest value is Select the entries of the dog and save the corresponding index of each entry as follows. ,

[0213] Now, we create an SB precoder using a limited number of quantized coefficients and a WB basis. The variables are as follows [Mathematical Equation 31]. Initializes.

[0214] [Equation 31]

[0215]

[0216] Here And this is it. And this is what I got from above. Enter the dog's entry as follows.

[0217] [Equation 32]

[0218]

[0219] Then, for the CSI-RS reception-based eType II predicted precoder, And layer The precoding matrix for is given as follows [Mathematical Formula 33].

[0220] [Equation 33]

[0221]

[0222] Here can be expressed as follows [Mathematical Formula 34].

[0223] [Equation 34]

[0224]

[0225] The MI is calculated using the above SB precoding matrix and MIMO CFR estimate. The MI is calculated by changing the rank. The rank that maximizes the calculated MI for each rank is selected, and the SB PMI and modulation order (QPSK, 16QAM, 64QAM, 256QAM, etc.) corresponding to the rank are reported. The fact that the MI is calculated differently depending on the TDCQI setting value set by the RRC message is explained in the embodiment of Fig. 9. When the set TDCQI is 1-1 or 1-2, only 1 modulation order is reported, and when the TDCQI is 2, 2 modulation orders are reported. Although not specified in the embodiment, the above method can be extended to easily select PMI for ranks = 1, 3, 4, 5, 6, 7, and 8 specified in the standard.

[0226] The NR eType II predicted precoding matrix selection algorithm proposed in the present disclosure described above allows the base station to receive feedback on the CSI at the time of scheduling the PDSCH. Therefore, rather than applying an already past precoding matrix at the time of scheduling the PDSCH due to time delay as in the conventional method, the PDSCH can be scheduled based on feedback on the CSI at the time of scheduling the PDSCH. Therefore, channel aging due to time delay can be minimized, and the PDSCH can be scheduled in a way that maximizes DL throughput.

[0227] FIG. 10 is a diagram illustrating an example configuration of a network entity in a wireless communication system according to an embodiment of the present disclosure. The configuration of FIG. 10 corresponds to the terminal or base station described in the embodiments of FIGS. 1 to 9.

[0228] The network entity of FIG. 10 may include a processor (1001), a transceiver (1003), and a memory (1005). The processor (1001), the transceiver (1003), and the memory (1005) of the network entity of FIG. 10 may operate according to at least one of the methods proposed in the embodiments of FIGS. 3 to 9. However, the components of the network entity are not limited to the examples described above. For example, the network entity may include more or fewer components than the components described above. In addition, the processor (1001), the transceiver (1003), and the memory (1005) may be implemented in the form of a single chip. The transceiver (1003) is a general term for a receiver of the network entity and a transmitter of the network entity, and may transmit and receive signals with a terminal or another network entity. At this time, the signal to be transmitted and received may include at least one of control information and data. To this end, the transceiver (1003) may include a wired or wireless transceiver and may include various configurations for transmitting and receiving signals. The transceiver (1003) may receive a signal, output it to the processor (1001), and transmit the signal output from the processor (1001). In addition, the transceiver (1003) may receive a communication signal, output it to the processor (1001), and transmit the signal output from the processor (1001) to another network entity through the network. The memory (1005) may store a program and data necessary for the operation of the network entity according to at least one of the embodiments of FIGS. 3 to 9. In addition, the memory (1005) may store control information or data included in a signal acquired from the network entity. The memory (1005) may be composed of a storage medium or a combination of storage media such as ROM, RAM, a hard disk, CD-ROM, and DVD.Additionally, the processor (1001) may control a series of processes so that a network entity can operate according to at least one of the embodiments of FIGS. 3 to 9. For example, the processor (1001) may include at least one processor and may control an eType II predicted precoder determination operation according to the present disclosure.

[0229] In a wireless communication system supporting precoding according to an embodiment of the present disclosure, a terminal (UE) includes a transceiver (1003), one or more processors (1001) including processing circuitry, and a memory (1105) storing instructions, wherein the instructions, when individually or collectively executed by the one or more processors, cause the terminal to receive a CSI-RS from a base station through the transceiver (1003) (501, 701), estimate a MIMO CFR based on the CSI-RS, obtain a WB eigenvector and an SB eigenvector for at least one slot section set after a current time point using the estimated MIMO CFR (702, 703), obtain common information for at least one of SB-wise, layer-wise, antenna pole-wise, and slot-wise based on a basis vector of the WB eigenvector (705, 706), and, based on the common information, derive the SB eigenvector. It can cause the SB coefficients to be obtained by projection (707), and the SB PMI corresponding to the predicted precoding matrix for at least one slot section to be determined from the obtained SB coefficients (502, 712).

[0230] In one embodiment, the commands, when individually or collectively executed by one or more processors (1001), may cause the terminal to repeatedly perform operations after acquiring the common information up to a maximum value of a predetermined rank.

[0231] In one embodiment, the instructions, when individually or collectively executed by the one or more processors (1001), may further cause the terminal to compress the SB coefficients by transforming them from a frequency domain to a lag domain and from a time domain to a Doppler domain (707, 708), perform quantization per SB, per layer, and per antenna pole (709, 710), and obtain a limited number of quantized coefficients in the lag domain and the Doppler domain (711).

[0232] In one embodiment, the commands, when individually or collectively executed by the one or more processors (1001), may further cause the terminal to select a rank that maximizes an MI obtained from an effective MIMO CFR and to report (713, 714, 715, 716) CSI including an SB PMI corresponding to the selected rank to the base station via the transceiver (1003).

[0233] In one embodiment, the instructions, when individually or collectively executed by the one or more processors (1001), may cause the terminal to perform a 2D FFT operation based on the basis vector of the WB eigenvector (705), and to obtain the common information for at least one of the SB-by-SB, layer-by-layer, antenna pole-by-pole, and slot-by-slot interval that maximizes a decision metric (706).

[0234] In a wireless communication system supporting precoding according to an embodiment of the present disclosure, a base station includes a transceiver, one or more processors including a processing circuit, and a memory storing instructions, wherein the instructions, when individually or collectively executed by the one or more processors, cause the base station to receive an SRS from a terminal (UE) through the transceiver (601, 801), estimate a MIMO CFR based on the SRS, and obtain a WB eigenvector and an SB eigenvector for at least one slot section set after a current time using the estimated MIMO CFR (802, 803), obtain common information for at least one of SB-wise, layer-wise, antenna pole-wise, and slot-wise based on a basis vector of the WB eigenvector (805, 806), obtain SB coefficients by projecting the SB eigenvector based on the common information (807), and predict a precoding matrix for the at least one slot section from the obtained SB coefficients. This may cause the corresponding SB PMI to be determined (602, 808).

[0235] In one embodiment, the instructions, when individually or collectively executed by the one or more processors, may cause the base station to repeatedly perform subsequent operations of obtaining the common information up to a maximum value of a predetermined rank.

[0236] In one embodiment, the instructions, when individually or collectively executed by the one or more processors, may further cause the base station to select (810, 811) a rank that maximizes an MI obtained from an effective MIMO CFR.

[0237] In one embodiment, the instructions, when individually or collectively executed by the one or more processors, may cause the base station to perform a 2D FFT operation based on the basis vector of the WB eigenvector and obtain the common information for at least one of the SB-by-SB, layer-by-layer, antenna pole-by-pole and slot-by-slot interval that maximizes a decision metric (806).

[0238] In one embodiment, the at least one slot period may include a time point at which the base station schedules a PDSCH to the terminal.

[0239] 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.

[0240] 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 for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present disclosure.

[0241] 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 device, compact disc ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage device, magnetic cassette. Or, they may be stored in a memory configured as a combination of some or all of these. In addition, each configuration memory may be included in multiple numbers.

[0242] Additionally, the program may be stored in an attachable storage device that is accessible via a communication network such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device performing 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 performing an embodiment of the present disclosure.

[0243] In the specific embodiments of the present disclosure described above, components included in the invention are expressed in the singular or plural form, 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 the plural form may be composed of singular elements, or components expressed in the singular form may be composed of plural elements.

[0244] While the detailed description of this disclosure has described specific embodiments, it should be understood that various modifications are possible without departing from the scope of this disclosure. Therefore, the scope of this disclosure should not be limited to the described embodiments, but should be defined not only by the scope of the claims described below, but also by equivalents thereof.

Claims

1. In a wireless communication system supporting precoding, in a terminal (user equipment: UE), Transmitter and receiver; One or more processors including processing circuitry; and A terminal comprising a memory for storing instructions, wherein the instructions are individually or collectively executed by one or more processors, Through the above transceiver, a CSI-RS (channel state information-reference signal) is received from the base station (501, 701), Estimate the MIMO (multiple-input multiple-output) CFR (channel frequency response) based on the above CSI-RS, Using the above estimated MIMO CFR, obtain the WB (wideband) eigenvector and the SB (subband) eigenvector for at least one slot section set after the current point in time (702, 703), Obtain common information for at least one of SB, layer, antenna pole and slot section based on the basis vector of the above WB eigenvector (705, 706), Based on the above common information, the SB coefficients are obtained by projecting the SB eigenvector (707), and A terminal causing the SB PMI (precoding matrix indicator) corresponding to the predicted precoding matrix for at least one slot section to be determined from the obtained SB coefficients (502, 712).

2. In paragraph 1, The above commands, when individually or collectively executed by one or more processors, cause the terminal to: A terminal that causes the operations after obtaining the above common information to be repeatedly performed up to the maximum value of a predetermined rank.

3. In paragraph 1, The above commands, when individually or collectively executed by one or more processors, cause the terminal to: Compress the above SB coefficients by converting them from the frequency domain to the lag domain and converting them from the time domain to the Doppler domain (707, 708). Perform quantization for each SB, layer, and antenna pole (709, 710), and A terminal further causing (711) to obtain a limited number of quantized coefficients in the lag domain and the Doppler domain.

4. In paragraph 1, The above commands, when individually or collectively executed by one or more processors, cause the terminal to: A terminal that selects a rank that maximizes MI (mutual information) obtained from an effective MIMO CFR and further causes the terminal to report CSI (channel state information) including SB PMI corresponding to the selected rank to the base station through the transceiver (713, 714, 715, 716).

5. In paragraph 1, The above commands, when individually or collectively executed by one or more processors, cause the terminal to: Performing a 2D FFT (fast Fourier transform) operation based on the basis vector of the above WB eigenvector (705), and A terminal that causes (706) the common information to be acquired for at least one of the SB-specific, layer-specific, antenna pole-specific and slot-specific segments that maximizes the decision metric.

6. In a wireless communication system supporting precoding, at a base station, Transmitter and receiver; One or more processors including processing circuitry; and A memory for storing instructions, wherein when the instructions are individually or collectively executed by one or more processors, the base station, Through the above transceiver, an SRS (sounding reference signal) is received from a terminal (user equipment: UE) (601, 801), Estimate the MIMO (multiple-input multiple-output) CFR (channel frequency response) based on the above SRS, Using the above estimated MIMO CFR, obtain the WB (wideband) eigenvector and the SB (subband) eigenvector for at least one slot interval set after the current point in time (802, 803), Obtain common information for at least one of SB, layer, antenna pole and slot section based on the basis vector of the above WB eigenvector (805, 806), Based on the above common information, the SB coefficients are obtained by projecting the SB eigenvector (807), and A base station causing (602, 808) to determine an SB PMI (precoding matrix indicator) corresponding to a predicted precoding matrix for at least one slot period from the obtained SB coefficients.

7. In paragraph 6, The above commands, when individually or collectively executed by one or more processors, cause the base station to: A base station that causes subsequent operations to be repeatedly performed up to the maximum value of a predetermined rank after obtaining the above common information.

8. In paragraph 6, The above commands, when individually or collectively executed by one or more processors, cause the base station to: A base station further causing (810, 811) to select a rank that maximizes the mutual information (MI) obtained from the effective MIMO CFR.

9. In paragraph 6, The above commands, when individually or collectively executed by one or more processors, cause the base station to: Perform a 2D FFT (fast Fourier transform) operation based on the basis vector of the above WB eigenvector (805), A base station that causes the common information to be acquired (806) for at least one of the SB-specific, layer-specific, antenna pole-specific and slot-specific segment-specific information that maximizes the decision metric.

10. In paragraph 6, A base station wherein at least one slot period includes a time point at which the base station schedules a physical downlink shared channel (PDSCH) to the terminal.

11. In a storage medium storing at least one instruction readable by a computer, The at least one command, when executed individually or collectively by one or more processors comprising processing circuitry of a user equipment (UE), causes the UE to perform at least one operation; At least one of the above actions: An operation of receiving a CSI-RS (channel state information-reference signal) from a base station through the above transceiver; An operation of estimating a MIMO (multiple-input multiple-output) CFR (channel frequency response) based on the above CSI-RS; An operation of obtaining a WB (wideband) eigenvector and a SB (subband) eigenvector for at least one slot section set after the current point in time using the above-mentioned estimated MIMO CFR; An operation of obtaining common information for at least one of SB-specific, layer-specific, antenna pole-specific, and slot-specific segment-specific information based on the basis vector of the above WB eigenvector; An operation of obtaining SB coefficients by projecting the SB eigenvector based on the above common information; and A storage medium including an operation of determining an SB PMI (precoding matrix indicator) corresponding to a predicted precoding matrix for at least one slot section from the obtained SB coefficients.

12. In paragraph 11, At least one of the above actions: A storage medium including an operation for repeatedly performing operations after obtaining the above common information up to a maximum value of a predetermined rank.

13. In paragraph 11, At least one of the above actions: An operation of compressing the above SB coefficients by converting them from the frequency domain to the lag domain and converting them from the time domain to the Doppler domain; An operation of performing quantization for each SB, each layer, and each antenna pole; and A storage medium further comprising an operation of obtaining a limited number of quantized coefficients in the lag domain and the Doppler domain.

14. In paragraph 11, At least one of the above actions: A storage medium further comprising an operation of selecting a rank that maximizes MI (mutual information) obtained from an effective MIMO CFR and reporting CSI (channel state information) including SB PMI corresponding to the selected rank to the base station.

15. In paragraph 11, The actions to obtain the above common information are: An operation of performing a 2D FFT (fast Fourier transform) operation based on the basis vector of the above WB eigenvector; and A storage medium comprising an operation for obtaining common information for at least one of the SB-specific, layer-specific, antenna pole-specific and slot-specific segments, which maximizes a decision metric.

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