KR20220041696A - Device and method using adaptive codebook for dual beamforming feedback and wireless communication system including the same - Google Patents

Abstract

A beamformer device includes a channel estimator, first and second beamforming matrix providers, and a dimension reduction unit. The channel estimator receives NDP through a channel from the beamformer device, estimates a channel based on the NDP, and acquires a plurality of pieces of channel information. The first beamforming matrix provider provides wideband beamforming matrices based on the plurality of pieces of channel information. The dimension reduction unit generates a plurality of pieces of equivalent channel information based on the wideband beamforming matrices. The second beamforming matrix provider provides subcarrier beamforming matrices based on the plurality of pieces of equivalent channel information. The wideband and subcarrier beamforming matrices are fed back to the beamformer device. At least one of the wideband and subcarrier beamforming matrices is selected from pre-designed codebooks.

Description

DEVICE AND METHOD USING ADAPTIVE CODEBOOK FOR DUAL BEAMFORMING FEEDBACK AND WIRELESS COMMUNICATION SYSTEM INCLUDING THE SAME

The present invention relates to a semiconductor integrated circuit, and more particularly, to an apparatus and method using an adaptive codebook for dual beamforming feedback, and a wireless communication system including the apparatus.

In a wireless communication system, it is important to have a strong communication signal. In particular, the largest possible signal-to-noise ratio (SNR) is required at the receiver. Likewise, increasing the SNR at the receiver increases the probability that frames are correctly received and reduces the amount of retransmission required from the source. Some methods to achieve better SNR at the receiver are to increase the transmit power, decrease the distance between the source and the receiver, and increase the antenna gain.

Meanwhile, a wireless local area network (WLAN) system such as wireless fidelity (WiFi) may transmit a signal based on a beamforming method. Beamforming is a method of a smart antenna, and is a technology that allows the beam of the antenna to shine only on a specific terminal. For beamforming transmission, beamforming feedback should be preceded, and various methods for providing efficient beamforming feedback are being studied.

One object of the present invention is to provide a beamformee apparatus capable of adaptively using a codebook while performing dual beamforming feedback in order to reduce the overhead of beamforming feedback.

Another object of the present invention is to provide a wireless communication system including the beamformer device.

Another object of the present invention is to provide a beamforming feedback method performed by the beamformer apparatus.

In order to achieve the above object, a beamformee apparatus according to embodiments of the present invention includes a channel estimator, a first beamforming matrix provider, a dimension reduction unit, and a second beamforming matrix provider. The channel estimator receives a Null Data Packet (NDP) through a channel from a beamformer device, and estimates the channel based on the NDP to obtain a plurality of channel information for a plurality of subcarriers. . The first beamforming matrix provider provides a plurality of wideband beamforming matrices based on the plurality of channel information. The dimension reduction unit generates a plurality of equivalent channel information corresponding to the plurality of channel information based on the plurality of wideband beamforming matrices. The second beamforming matrix provider provides a plurality of subcarrier beamforming matrices based on the plurality of equivalent channel information. The plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are fed back to the beamformer device. At least one of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices is selected from among a plurality of predesigned codebooks.

In order to achieve the above another object, a wireless communication system according to embodiments of the present invention includes a beamformer device and a beamformee device. The beamformer device transmits a Null Data Packet (NDP) for channel measurement. The beamformer device receives the NDP through the channel, and feeds back an estimation result of the channel based on the NDP to the beamformer device. The beamformer device includes a channel estimator, a first beamforming matrix provider, a dimension reduction unit, and a second beamforming matrix provider. The channel estimator receives the NDP, estimates the channel based on the NDP, and obtains a plurality of channel information for a plurality of subcarriers. The first beamforming matrix provider provides a plurality of wideband beamforming matrices based on the plurality of channel information. The dimension reduction unit generates a plurality of equivalent channel information corresponding to the plurality of channel information based on the plurality of wideband beamforming matrices. The second beamforming matrix provider provides a plurality of subcarrier beamforming matrices based on the plurality of equivalent channel information. The plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are fed back to the beamformer device. At least one of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices is selected from among a plurality of predesigned codebooks.

In order to achieve the above object, a beamformee apparatus according to embodiments of the present invention includes a channel estimator, a first beamforming matrix provider, a dimension reduction unit, a second beamforming matrix provider, and a feedback mode selector. include The channel estimator receives a Null Data Packet (NDP) through a channel from a beamformer device, and estimates the channel based on the NDP to obtain a plurality of channel information for a plurality of subcarriers. . The first beamforming matrix provider performs singular value decomposition (SVD) and compression on the plurality of channel information to generate a plurality of wideband beamforming matrices, or a predesigned design based on the plurality of channel information. One of the plurality of first codebooks is selected and outputted as one of the plurality of wideband beamforming matrices. The dimension reduction unit generates a plurality of equivalent channel information corresponding to the plurality of channel information based on the plurality of wideband beamforming matrices. The second beamforming matrix provider performs SVD and compression on the plurality of equivalent channel information to generate a plurality of subcarrier beamforming matrices, or a plurality of second codebooks designed in advance based on the plurality of equivalent channel information One of the subcarrier beamforming matrices is selected as one of the plurality of subcarrier beamforming matrices and output. The feedback mode selector selects all of the first feedback mode using the plurality of first codebooks, the second feedback mode using the plurality of second codebooks, and the plurality of first and second codebooks, based on the characteristics of the channel. One of the third feedback modes to be used, which is predicted to have the largest amount of data transmission, is selected. The plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices are fed back to the beamformer device, and a codebook index corresponding to a codebook used among the plurality of first and second codebooks is fed back.

In order to achieve the above another object, in the beamforming feedback method according to embodiments of the present invention, by estimating the channel based on the NDP (Null Data Packet) received through the channel from the beamformer device, A plurality of channel information for a plurality of subcarriers is obtained. A plurality of wideband beamforming matrices are provided based on the plurality of channel information. A plurality of equivalent channel information corresponding to the plurality of channel information is generated based on the plurality of wideband beamforming matrices. A plurality of subcarrier beamforming matrices are provided based on the plurality of equivalent channel information. The plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are fed back to the beamformer device. At least one of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices is selected from among a plurality of predesigned codebooks.

In order to achieve the above object, a beamformee device according to embodiments of the present invention estimates the channel based on a Null Data Packet (NDP) received through a channel from a beamformer device, providing a plurality of wideband beamforming matrices and a plurality of subcarrier beamforming matrices as a result of the channel estimation, wherein at least one of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices is pre-designed A beamforming feedback report is generated based on a plurality of codebooks selected from among the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices and fed back to the beamformer device. The beamforming feedback report includes MAC (Media Access Control) header information, category information, MIMO (Multiple Input Multiple Output) control information, codebook index information, CBR (Compressed Beamforming Report) information and feedback mode information. .

In the beamformer apparatus, the wireless communication system, and the beamforming feedback method according to the embodiments of the present invention as described above, dual beamforming feedback is used when beamforming feedback is performed in a feedback mode, and in particular, a plurality of wideband beamforming A codebook utilization technique may be applied to at least one of the matrices and the plurality of subcarrier beamforming matrices. In addition, an adaptive codebook utilization technique for selecting a feedback mode according to a channel situation/environment may be implemented. Therefore, it is possible to effectively reduce the feedback overhead of the beamforming feedback, and to perform the efficient beamforming feedback.

1 is a block diagram illustrating a beamformer device and a wireless communication system including the same according to embodiments of the present invention.
2 and 3 are diagrams for explaining dual beamforming feedback.
4A, 4B, 4C, 4D, and 5 are diagrams for explaining a process of designing a codebook used in a beamformer apparatus according to embodiments of the present invention.
6 is a block diagram illustrating an example of the beamformer device and the wireless communication system of FIG. 1 .
FIG. 7 is a diagram illustrating an example of a beamforming feedback report generated by the beamformer apparatus of FIG. 6 .
FIG. 8 is a view showing the performance of the beamformer of FIG. 6 .
9 is a block diagram illustrating another example of the beamformer device and the wireless communication system of FIG. 1 .
FIG. 10 is a diagram illustrating an example of a beamforming feedback report generated by the beamformer apparatus of FIG. 9 .
11 and 12 are block diagrams illustrating still other examples of the beamformer device and the wireless communication system of FIG. 1 .
13 is a block diagram illustrating an example of a feedback mode selector included in the beamformer of FIG. 12 .
14 is a diagram illustrating an example of a lookup table included in the feedback mode selector of FIG. 13 .
15 is a block diagram illustrating another example of the beamformer device and the wireless communication system of FIG. 1 .
16, 17 and 18 are flowcharts illustrating a beamforming feedback method according to embodiments of the present invention.
19 is a block diagram illustrating an electronic device in a network environment according to embodiments of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The same reference numerals are used for the same components in the drawings, and repeated descriptions of the same components are omitted.

1 is a block diagram illustrating a beamformer device and a wireless communication system including the same according to embodiments of the present invention.

Referring to FIG. 1 , a wireless communication system 10 includes a beamformer device 100 and a beamformee device 200 .

In one embodiment, the wireless communication system 10 may be a wireless local area network (WLAN)-based wireless communication system. For example, the wireless communication system 10 may be a wireless communication system based on WiFi (Wireless Fidelity). For example, the WLAN system may be implemented based on the IEEE 802.11ac or IEEE 802.11ax standard, or may be implemented based on the next standard, the IEEE 802.11be standard.

In the WLAN system, beamforming transmission may be performed between the beamformer device 100 and the beamformer device 200 . Beamforming transmission is a technique for limiting the beam of an antenna to a specific terminal in a multi-antenna orthogonal frequency division modulation (OFDM) system, and a technique for forming a transmission beam to increase the reception data rate of a single user. (ie, single-user beamforming) and a technique of forming a transmission beam for mutual interference cancellation during simultaneous transmission between multi-users (ie, multi-user beamforming). For single-user (or multi-user) beamforming transmission, the beamformer device 200 decodes a packet transmitted by the beamformer device 100 for channel measurement, and compresses channel information using a technique specified in the WLAN standard. and may be fed back to the beamformer device 100 . The operation of feeding back channel information as described above may be referred to as beamforming feedback, and such beamforming feedback may be performed in a feedback mode.

According to embodiments of the present invention, the beamforming feedback performed in the beamforming mode may be dual beamforming feedback or two-step beamforming feedback. The dual beamforming feedback may be used to reduce feedback overhead. For example, one matrix or matrix may be used with a wideband or wideband, and another matrix may be used with a subband or subband (i.e., a subcarrier or subcarrier). . The dual beamforming feedback will be described later with reference to FIG. 2 and the like.

Hereinafter, operations of the wireless communication system 10 and the beamformer apparatus 200 according to embodiments of the present invention will be mainly focused on an operation for reducing a feedback overhead when the dual beamforming feedback is performed in the feedback mode. to explain However, the present invention is not limited thereto, and the wireless communication system 10 may perform normal beamforming transmission based on channel information obtained by the dual beamforming feedback in the normal operation mode after the feedback mode.

The beamformer device 100 transmits a Null Data Packet (NDP) for channel measurement. The beamformer device 100 may be referred to as a transmitter or an access point (AP). The NDP may also be referred to as a sounding packet.

The beamformer apparatus 100 may include a plurality of antennas (or transmit antennas) 101 . The beamformer device 100 may output the NDP using a plurality of antennas 101 . For example, the number of the plurality of antennas 101 may be N _t (N _t is a natural number equal to or greater than 2).

The beamformer device 200 receives the NDP from the beamformer device 100 through a channel, estimates the channel based on the NDP, and feeds back an estimation result for the channel to the beamformer device 100 . . In this case, the beamformer 200 performs the dual beamforming feedback to reduce the feedback overhead of the beamforming feedback, and thus a plurality of wideband beamforming matrices (WBM) instead of the entire matrix for the channel ) and a plurality of subcarrier beamforming matrices (SBM). For example, as will be described later, a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM) may be fed back in the form of a beamforming feedback report. The beamformer apparatus 200 may be called a receiver or a station (STA).

The beamformer apparatus 200 includes a channel estimator 210 , a first beamforming matrix provider 220 , a dimension reduction unit 230 , and a second beamforming matrix provider 240 . The beamformer apparatus 200 may further include a plurality of antennas (or reception antennas) 201 .

The beamformer device 200 may receive the NDP from the beamformer device 100 through the channel using a plurality of antennas 201 . For example, the number of the plurality of antennas 201 may be N _r (N _r is a natural number equal to or greater than 2). Although not shown in detail, the channel (eg, a radio channel) may be formed between the plurality of antennas 101 of the beamformer apparatus 100 and the plurality of antennas 201 of the beamformer apparatus 200 . can

The channel estimator 210 estimates the channel based on the NDP to obtain a plurality of channel information ECIs for a plurality of subcarriers. For example, one channel information may be estimated and obtained for one subcarrier. For example, each channel information may be obtained in the form of a channel matrix indicating a frequency response.

The first beamforming matrix provider 220 provides a plurality of wideband beamforming matrices (WBM) based on the plurality of channel information pieces (ECI). The first beamforming matrix provider 220 may be referred to as a broadband beamforming matrix (BM) provider.

The dimension reduction unit 230 generates a plurality of equivalent channel information (EECI) corresponding to the plurality of channel information (ECI) based on the plurality of wideband beamforming matrices (WBM). For example, each equivalent channel information may be generated in the form of an equivalent channel matrix reduced in size than the corresponding channel information (ie, a channel matrix).

The second beamforming matrix provider 240 provides a plurality of subcarrier beamforming matrices SBM based on the plurality of equivalent channel information EECIs. The second beamforming matrix provider 240 may be referred to as a subcarrier beamforming matrix provider.

According to embodiments of the present invention, at least one of a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM) is selected from among a plurality of predesigned codebooks. In other words, the codebook utilization technique may be applied to at least one of a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM).

Specifically, the first beamforming matrix provider 220 may include a plurality of pre-designed first codebooks 221 corresponding to the plurality of wideband beamforming matrices (WBM). The second beamforming matrix provider 240 may include a plurality of pre-designed second codebooks 241 corresponding to the plurality of subcarrier beamforming matrices (SBM). The plurality of first codebooks 221 and the plurality of second codebooks 241 may be referred to as a plurality of wideband codebooks (WCB) and a plurality of subcarrier codebooks (SCB), respectively.

In an embodiment, as will be described later with reference to FIG. 6 , when the codebook utilization technique is applied to a plurality of wideband beamforming matrices (WBM), the first beamforming matrix provider 220 provides a plurality of channels One of the plurality of first codebooks 221 may be selected based on the information ECI and output as one of the plurality of wideband beamforming matrices WBM.

In another embodiment, as will be described later with reference to FIG. 9 , when the codebook utilization technique is applied to a plurality of subcarrier beamforming matrices (SBM), the second beamforming matrix provider 240 provides a plurality of equivalent One of the plurality of second codebooks 241 may be selected based on the channel information EECI and output as one of the plurality of subcarrier beamforming matrices SBM.

In another embodiment, as will be described later with reference to FIG. 11 , the codebook utilization technique may be applied to both a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM).

In one embodiment, as will be described later with reference to FIG. 12 , the beamformer apparatus 200 applies the codebook utilization technique to a plurality of wideband beamforming matrices (WBM) based on the channel characteristics. A feedback mode, a second feedback mode to which the codebook utilization technique is applied to a plurality of subcarrier beamforming matrices (SBM), and a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM) can be operated by selecting one of the third feedback modes to which the codebook utilization technique is applied. In other words, an adaptive codebook utilization technique for selecting a feedback mode according to a channel situation/environment may be implemented.

In one embodiment, as described below with reference to FIGS. 4, 5 and 15 , the plurality of codebooks (ie, at least one of the codebooks 221 , 241 ) are designed and beamed at the time of manufacture and/or at the beginning of operation. It may be stored in the bomi device 200 .

In a WLAN system, beamforming increases antenna gain while maintaining omnidirectional coverage, which results in a more stable and high-bandwidth WLAN connection by concentrating increased SNR and transmission to the receiver. This advantage is achieved by transmitting a signal through an array of antennas and slightly altering the phase of the signal at each antenna in the array. For example, a protocol may be provided for calibrating an array of antennas to direct a signal to some point that is covered under omni-directional propagation. The beamformer device 100 is a device that increases the phase shift of antennas to generate a gain in a required direction, and the beamformer device 200 is a target device of the beamformer device 100 . The beamformer 200 participates in beam setting, but does not increase the timing of antennas.

For beamforming transmission of the WLAN system, the beamformer device 100 must first obtain the channel information (or channel state information) from the beamformer device 200 . To this end, the beamformer device 100 transmits the NDP or sounding packet through the plurality of antennas 101 . The beamformer 200 receives the NDP through a plurality of antennas 201 to obtain the channel information. Received signals represent a result of undergoing the channel, and a relationship between transmitted signals and received signals may satisfy the following [Equation 1].

[Equation 1]

In Equation 1 above, Y[k] is the received signal vector, S[k] is the transmitted signal vector (ie, sounding signal vector), H[k] is the channel matrix indicating the frequency response, N [k] represents a noise vector, and k represents a subcarrier index. Y[k] and N[k] may be N _r *1 vectors, S[k] may be N _t *1 vectors, and H[k] may be N _r *N _t matrices. N _t represents the number of the plurality of antennas 101 of the beamformer apparatus 100 , and N _r represents the number of the plurality of antennas 201 of the beamformer apparatus 200 .

The beamformer 200 estimates channel information H for each subcarrier through the channel estimator 210 , which may correspond to one of a plurality of channel information ECIs. Also, when operating in the feedback mode, the beamformer 200 may perform singular value decomposition (SVD) on the channel information H as shown in Equation 2 below.

[Equation 2]

In [Equation 2] above, U[k] and V[k] are unitary matrices, Σ[k] is a diagonal matrix including a channel singular value, and V[k] ^H is It may be a conjugate transpose matrix of V[k].

(여기서,

는 V[k]의 i행, j열의 엘리먼트(element)에 해당하는 위상 값)를 V[k]에 곱하여 Q[k]를 획득할 수 있다. 그러면, Q[k]의 각 열의 마지막 행의 값은 실수 값을 가지게 된다.In the WLAN system, in order to reduce the feedback overhead, the beamformer 200 does not directly feed back V[k], but first performs a common-phase shift as shown in Equation 3 below. diagonal matrix for

(here,

can obtain Q[k] by multiplying V[k] by V[k] (a phase value corresponding to an element in row i and column j). Then, the value of the last row of each column of Q[k] has a real value.

[Equation 3]

Thereafter, angle values (φ, ψ) corresponding to each element of Q[k] may be compressed and fed back using Givens rotation. In other words, the beamformer apparatus 200 may quantize (φ, ψ) obtained by the following [Equation 4] and feed it back to the beamformer apparatus 100 .

[Equation 4]

및 기븐스 회전

는 각각 하기의 [수학식 5] 및 [수학식 6]과 같이 정의될 수 있다.In [Equation 4] above, 1 _i-1 may be a vector consisting of 1 having a length of . also,

and Gibbons rotation

may be defined as in [Equation 5] and [Equation 6], respectively.

[Equation 5]

[Equation 6]

In other words, the plurality of wideband beamforming matrices (WBM) and the plurality of subcarrier beamforming matrices (SBM) fed back to the beamformer apparatus 100 by the beamformer apparatus 200 are expressed in Equation 4 above. It may include the angle values (φ, ψ) obtained by

2 and 3 are diagrams for explaining dual beamforming feedback.

2 illustrates a plurality of subcarriers used for signal transmission between a beamformer device and a beamformer device of a wireless communication system, and one arrow indicates one subcarrier SC. 3 shows an exemplary structure of a wireless communication system that performs the dual beamforming feedback, that is, a dimension reduction technique for reducing the size of a beamforming matrix.

2 and 3 , the wireless communication system 20 may include a beamformer device 105 and a beamformer device 205 . The beamformer device 105 may include a plurality of antennas 101 , a wideband precoder unit 120 , and a subcarrier precoder unit 140 . The beamformer device 205 may include a plurality of antennas 201 , a channel estimator 210 , a wideband precoder operator 250 , a dimension reduction unit 230 , and a subcarrier precoder operator 260 . The wideband precoder operator 250 may include a covariance operator 252 , an SVD unit 254 , and a compression unit 256 . The subcarrier precoder operator 260 may include an SVD unit 262 and a compression unit 264 . The plurality of antennas 101 and 201, the channel estimator 210, and the dimension reduction unit 230 include the plurality of antennas 101 and 201 of FIG. 1, the channel estimator 210, and the dimension reduction unit 230, respectively. may be substantially the same.

The beamformer device 205 receives the NDP or sounding packet, and estimates the channel through the channel estimator 210 to obtain channel information (ie, channel matrix) H[k] (k=0, 1, ..., N _fft -1) can be obtained. Here, N _fft represents the number of a plurality of subcarriers (SC) present in one OFDM symbol.

The beamformer device 205 divides the plurality of subcarriers SC into M (M is a natural number greater than or equal to 2) groups SCG, and accordingly, Ng (=N _fft /M) in each group SCG. Subcarriers may be present. The beamformer device 205 may form a wideband beam (ie, wideband beamforming information or a wideband beamforming matrix) having the same value for each group SCG. The beamformer 205 may acquire the broadband beam as shown in Equation 7 below through the covariance operator 252 .

[Equation 7]

The beamformer 205 performs SVD on the covariance matrix (ie, Cov[m]) obtained by the above [Equation 7] through the SVD unit 254 to obtain the following [Equation 8] and Similarly, the unitary matrix W _WB [m] of the broadband beam can be obtained.

[Equation 8]

The beamformer 205 takes the first K (K is a natural number greater than or equal to 2)th column from among each column of the unitary matrix W _WB [m] through the compression unit 256, and the above [Equation 3] to [Equation 3] By performing Givens rotation-based compression according to Equation 6], it is possible to obtain angular values φ and ψ for the broadband beam. Here, K is a design parameter and may be an adjustable parameter.

Thereafter, the beamformer device 205 may form a per-subcarrier beam (ie, subcarrier beamforming information or a subcarrier beamforming matrix) for each subcarrier SC.

First, the beamformer 205 multiplies the channel matrix H[k] by the unitary matrix W _WB [m] of the broadband beam through the dimension reduction unit 230 to obtain equivalent channel information as shown in Equation 9 below. (ie, an equivalent channel matrix) may be obtained.

[Equation 9]

는 채널 매트릭스 H[k]에 비하여 크기가 감소될 수 있다. 예를 들어, H[k]는 N_r*N_t의 크기를 가지고, W_WB[m]은 N_t*K의 크기를 가지며, 따라서

는 N_r*K의 크기를 가지게 되어 크기가 감소될 수 있다(즉, 차원 축소). 예를 들어, N_t=16이고 N_r=2이고 K=8인 경우에, 2*16의 크기를 가지는 H[k]에 기초하여 2*8의 크기를 가지는

가 생성되어 매트릭스의 크기가 감소될 수 있다.Equivalent Channel Matrix

may be reduced in size compared to the channel matrix H[k]. For example, H[k] has size N _r *N _t , W _WB [m] has size N _t *K , so

has a size of N _r *K, so that the size can be reduced (ie, dimensionality reduction). For example, when N _t =16, N _r =2, and K = 8, based on H[k] having a size of 2*16, having a size of 2*8

can be generated to reduce the size of the matrix.

에 대한 SVD를 수행하여, 하기의 [수학식 10]과 같이 상기 부반송파 빔의 유니터리 매트릭스 W_SC[k]를 획득할 수 있다.The beamformer device 205 through the SVD unit 262, the equivalent channel matrix obtained by the above [Equation 9]

By performing SVD on , a unitary matrix W _SC [k] of the subcarrier beam can be obtained as shown in Equation 10 below.

[Equation 10]

The beamformer 205 performs the Givens rotation-based compression according to the above [Equation 3] to [Equation 6] on the basis of the unitary matrix W _SC [k] through the compression unit 264, Angle values (φ, ψ) for the subcarrier beam may be obtained.

In feeding back channel information for beamforming transmission, the beamformer device 205 feeds back angle values (φ, ψ) for the M wideband beams obtained by the compression unit 256, and the compression unit 264. It is possible to feed back the angle values (φ, ψ) for the N _fft subcarrier beams obtained by . In FIG. 3 , arrows fed back from the wideband precoder operator 250 to the wideband precoder unit 120 indicate angle values φ and ψ for the M wideband beams, and the subcarrier from the subcarrier precoder operator 260 . Arrows fed back to the precoder unit 140 indicate angle values φ and ψ for the N _fft subcarrier beams.

The wideband precoder unit 120 reconstructs the M wideband beams based on the fed back angle values φ and ψ, and the subcarrier precoder unit 140 is configured to reconstruct the M wideband beams based on the fed back angle values φ and ψ. N _fft subcarrier beams may be reconstructed, and the channel information may be obtained based on the reconstructed result.

As described above, the broadband beamforming matrix is determined by the beamformer 205 from the covariance matrix of the wideband channel. Wideband bandwidth may depend on channel conditions and MIMO mode. For single-user beamforming, about 80 MHz can give good results. For multi-user beamforming, less than about 80 MHz (eg, about 5 or 10 MHz per user) may be required. After calculating the covariance matrix, the broadband beamforming matrix may be obtained based on compressed beamforming. The design parameter K may be determined by the beamformer device 205 or the beamformer device 105 . For example, in the case of single-user beamforming, K may be determined by the beamformer device 205 . In the case of multi-user beamforming or trigger-based feedback, K may be determined by the beamformer device 105 . A tradeoff between complexity and performance analysis can affect the choice of K. Various factors may include timing, delay spread, aspects of bandwidth, and spatial correlation between antennas.

According to embodiments of the present invention, the wideband precoder operator 250 and the subcarrier precoder operator 260 may be replaced with the first beamforming matrix provider 220 and the second beamforming matrix provider 240 . there is. In other words, instead of calculating and feeding back all of the plurality of wideband beamforming matrices (WBM) and the plurality of subcarrier beamforming matrices (SBM) according to the above-described method, a plurality of wideband beamforming matrices (WBM) and a plurality of A codebook utilization technique may be applied to at least one of subcarrier beamforming matrices (SBM) of . Accordingly, the amount of computation and the amount of data fed back can be reduced, thereby reducing the feedback overhead.

4A, 4B, 4C, 4D, and 5 are diagrams for explaining a process of designing a codebook used in a beamformer apparatus according to embodiments of the present invention.

4A, 4B, 4C, 4D and 5 , in generating the plurality of codebooks, a Lloyd algorithm may be performed using a Discrete-time Fourier Transform (DFT) codebook as an initial value.

Specifically, the initial DFT codebook w(n) may be obtained based on the following [Equation 11].

[Equation 11]

이고, N은 코드북들의 개수이며, B는 각 코드북의 컬럼 수일 수 있다. i번째 코드북의 j번째 벡터는

에 의해서 결정될 수 있다.In the above [Equation 11],

, N may be the number of codebooks, and B may be the number of columns of each codebook. The j-th vector of the i-th codebook is

can be determined by

을 생성하며, 이를 초기 값으로 로이드 알고리즘을 수행할 수 있다.According to embodiments of the present invention, N DFT codebooks using Equation 11 above

, and the Lloyd's algorithm can be performed with this initial value.

In an embodiment, the Lloyd's algorithm may be performed based on the following order of (1), (2), (3), and (4). First, a Euclidean distance function ED(.) for performing the Lloyd's algorithm may be defined as in [Equation 12] below.

[Equation 12]

In the above [Equation 12], diag represents a function for extracting diagonal elements of a matrix, an uppercase letter indicates a matrix, and a lowercase letter indicates each column of the matrix.

를 생성할 수 있다.(1) A plurality of (eg, about 10000) channel matrix H samples may be generated based on the IEEE D-channel model. SVD was performed for each H sample,

can create

에 대해서 (초기 코드북은 DFT 코드북, i=1)에 대해서 V 샘플들을 하기의 [수학식 13]과 같이 유클리드 거리를 기준으로 N개의 영역들로 나눌 수 있다.(2) later, given codebook

For (the initial codebook is the DFT codebook, i = 1), V samples can be divided into N regions based on the Euclidean distance as shown in [Equation 13] below.

[Equation 13]

에 대해서 하기의 [수학식 14]와 같이 평균 유클리드 거리가 최소가 되는 W를 구하여 i번째 코드북으로 설정할 수 있다.(3) thereafter,

As shown in [Equation 14] below, W at which the average Euclidean distance is the minimum can be obtained and set as the i-th codebook.

[Equation 14]

를 만족할 때까지 반복할 수 있다. 하기의 [수학식 15]에서,

는

인 V의 집합일 수 있다.After (4), the process of (2) and (3) is used as a convergence condition

can be repeated until satisfied. In the following [Equation 15],

Is

It may be a set of V.

[Equation 15]

4A, 4B, 4C and 4D show the process of finding a centroid or geometric center through the Lloyd's algorithm. 4A, 4B, 4C, and 4D, a portion indicated by a dot (.) indicates the center of each region, and a portion indicated by a cross (+) indicates a codebook corresponding to each region.

4A, 4B, 4C and 4D show the results of iteration of the above-described algorithm 1 time, 2 times, 3 times, and 15 times, respectively. As the algorithm iterates, the five regions R11, R21, R31, R41, R51 in FIG. 4A become the five regions R12, R22, R32, R42, R52 in FIG. 4B, and the five regions in FIG. 4C. The fields R13, R23, R33, R43, R53 and the five regions R14, R24, R34, R44, R54 of FIG. 4D are changed, and the center of each region and the corresponding codebook coincide with the above [mathematics It can be confirmed that the convergence condition of Equation 15] is satisfied.

5 shows a process of converging to the convergence condition of [Equation 15] as the Lloyd's algorithm is repeatedly performed. If it is repeated about 10 times or more, it can be confirmed that the desired optimal codebook converges.

6 is a block diagram illustrating an example of the beamformer device and the wireless communication system of FIG. 1 . Hereinafter, descriptions overlapping those of FIG. 1 will be omitted.

Referring to FIG. 6 , the wireless communication system 10a includes a beamformer device 100 and a beamformer device 200a. The beamformer apparatus 100 may include a plurality of antennas 101 . The beamformer device 200a includes a plurality of antennas 201 , a channel estimator 210 , a first beamforming matrix provider 220a , a dimension reduction unit 230 , and a second beamforming matrix provider 240a . may include

The embodiment of FIG. 6 shows a case in which the codebook utilization technique is applied only to a plurality of wideband beamforming matrices (WBM), and accordingly, the configuration of the first beamforming matrix provider 220a may be changed compared to the existing one. . The beamformer apparatus 100 , the plurality of antennas 101 and 201 , the channel estimator 210 , and the dimension reduction unit 230 may be substantially the same as those described above with reference to FIG. 1 and the like.

The first beamforming matrix provider 220a may include a first storage (STG) 222 and a first selector (SEL) 224 .

The first storage unit 222 may store a plurality of first codebooks (WCB_1, WCB_2, ..., WCB_N). For example, the plurality of first codebooks WCB_1 to WCB_N may be designed and stored in advance based on the Lloyd's algorithm described above with reference to FIGS. 4 and 5 . For example, the first storage unit 222 may include a volatile memory such as a dynamic random access memory (DRAM), a static random access memory (SRAM), and/or an electrically erasable programmable read-only memory (EEPROM), a flash memory, or the like. ), PRAM (Phase Change Random Access Memory), RRAM (Resistance Random Access Memory), NFGM (Nano Floating Gate Memory), PoRAM (Polymer Random Access Memory), MRAM (Magnetic Random Access Memory), FRAM (Ferroelectric Random Access Memory) and non-volatile memory, such as

The first selector 224 may select a plurality of wideband beamforming matrices WBM based on the plurality of first codebooks WCB_1 to WCB_N. For example, the first selector 224 may select a codebook that can obtain the largest beamforming gain. For example, the first selector 224 selects one that maximizes the power of the channel from among the plurality of first codebooks WCB_1 to WCB_N based on the plurality of channel information ECI to a plurality of broadband beams. One of the forming matrices (WBM) may be selected.

In an embodiment, the first selector 224 may select one of the plurality of wideband beamforming matrices (WBM) based on Equation 16 below.

[Equation 16]

의 i번째 코드북, 즉 복수의 제1 코드북들(WCB_1~WCB_N) 중 i번째 코드북, k는 상기 복수의 부반송파들의 인덱스(index)를 나타낸다. argmax는 arguments of max, 즉 해당 함수를 최대로 만드는 값을 반환하는 함수를 나타낸다.In [Equation 16], W _w is the selected wideband beamforming matrix, N _g is the number of subcarriers corresponding to one wideband beam, and H[k] is one of the plurality of channel information (ECI). Channel matrix corresponding to one, H ^H [k] is the conjugate transpose matrix of H[k], W _i is the codebook set

The i-th codebook of , that is, the i-th codebook among the plurality of first codebooks WCB_1 to WCB_N, k indicates an index of the plurality of subcarriers. argmax represents arguments of max, that is, a function that returns a value that maximizes the function.

The second beamforming matrix provider 240a may include an SVD unit 242 and a compression unit (COMP) 244 .

The SVD unit 242 may perform SVD on a plurality of equivalent channel information EECIs. The compression unit 244 may compress the output of the SVD unit 242 . The SVD unit 242 and the compression unit 244 may be substantially the same as the SVD unit 262 and the compression unit 264 of FIG. 3 . In other words, when the codebook utilization technique is applied only to a plurality of wideband beamforming matrices (WBM), the second beamforming matrix provider 240a is substantially the same as the existing subcarrier precoder operator 260 . can be implemented.

The plurality of wideband beamforming matrices WBM provided from the first beamforming matrix provider 220a and the plurality of subcarrier beamforming matrices SBM provided from the second beamforming matrix provider 240a are formed by a beamformer. may be fed back to the device 100 . For example, a beamforming feedback report (BFR) generated based on a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM) may be fed back to the beamformer apparatus 100 .

FIG. 7 is a diagram illustrating an example of a beamforming feedback report generated by the beamformer apparatus of FIG. 6 .

7, the beamforming feedback report (BFR) is MAC (Media Access Control) header information 271, category information 272, MIMO (Multiple Input Multiple Output) control information 273, codebook index Information 274a, Compressed Beamforming Report (CBR) information 275a, additional common phase information 276a, and feedback mode information 277a may be included. The beamforming feedback report (BFR) of FIG. 7 may further include codebook index information 274a, additional common phase information 276a, and feedback mode information 277a compared to the existing codebook.

The codebook index information 274a may correspond to a plurality of wideband beamforming matrices (WBM), and the CBR information 275a may correspond to a plurality of subcarrier beamforming matrices (SBM). The feedback mode information 277a may indicate the first feedback mode to which the codebook utilization technique is applied with respect to a plurality of wideband beamforming matrices (WBM).

The beamforming feedback report (BFR) of FIG. 7 does not include all information on the plurality of wideband beamforming matrices (WBM) and the plurality of subcarrier beamforming matrices (SBM), but may include only some information. For example, for the plurality of subcarrier beamforming matrices (SBM), the CBR information 275a generated by compressing the angle values (φ, ψ) of the N _fft subcarrier beams described above with reference to FIGS. 2 and 3 is obtained. Codebook index information 274a indicating a codebook corresponding to M wideband beams may be fed back to the plurality of wideband beamforming matrices (WBM) to which the codebook utilization technique is applied. Accordingly, the amount of computation and the amount of data fed back can be reduced, thereby reducing the feedback overhead.

를 구성하고 있는 공통 위상 정보(φ_common)를 포함할 수 있다. 연산의 정확성을 위해, 상기 부반송파 빔들에 대해서 기존의 각도 값(φ, ψ)과 함께 공통 위상 정보(φ_common)를 추가적으로 피드백할 수 있다.In addition, the additional common phase information 276a is expressed in Equation 3 above.

It may include common phase information (φ _common ) constituting the . For accuracy of calculation, common phase information (φ _common ) may be additionally fed back together with the existing angle values (φ, ψ) for the subcarrier beams.

FIG. 8 is a view showing the performance of the beamformer of FIG. 6 .

Referring to FIG. 8 , CASE1 indicates a beamformer device that does not use dual beamforming feedback, CASE2 indicates a beamformer device that uses only dual beamforming feedback as shown in FIGS. 2 and 3 , and CASE3 indicates a dual beam device as shown in FIG. 6 . A beamformer apparatus 200a that uses forming feedback and applies the codebook utilization technique to a plurality of wideband beamforming matrices (WBM) is shown. In the beamformer apparatus 200a according to the embodiments of the present invention, it can be confirmed that the data transmission amount is increased by reducing the feedback overhead compared to the conventional method.

9 is a block diagram illustrating another example of the beamformer device and the wireless communication system of FIG. 1 . Hereinafter, descriptions overlapping those of FIGS. 1 and 6 will be omitted.

Referring to FIG. 9 , the wireless communication system 10b includes a beamformer device 100 and a beamformer device 200b. The beamformer apparatus 100 may include a plurality of antennas 101 . The beamformer apparatus 200b includes a plurality of antennas 201 , a channel estimator 210 , a first beamforming matrix provider 220b , a dimension reduction unit 230 , and a second beamforming matrix provider 240b . may include

The embodiment of FIG. 9 shows a case in which the codebook utilization technique is applied only to a plurality of subcarrier beamforming matrices (SBM), and accordingly, the configuration of the second beamforming matrix provider 240b may be partially changed. The beamformer apparatus 100 , the plurality of antennas 101 and 201 , the channel estimator 210 , and the dimension reduction unit 230 may be substantially the same as those described above with reference to FIG. 1 and the like.

The first beamforming matrix provider 220b may include a covariance operator (COV) 225 , an SVD unit 226 , and a compression unit 228 .

The covariance calculator 225 may calculate a covariance matrix based on the plurality of channel information ECI. The SVD unit 226 may perform SVD on the output of the covariance operator 225 . The compression unit 228 may compress the output of the SVD unit 226 . The covariance operator 225 , the SVD unit 226 , and the compression unit 228 may be substantially the same as the covariance operator 252 , the SVD unit 254 , and the compression unit 256 of FIG. 3 . In other words, when the codebook utilization technique is applied only to a plurality of subcarrier beamforming matrices (SBM), the first beamforming matrix provider 220b is substantially the same as the conventional wideband precoder operator 250 . can be implemented.

The second beamforming matrix provider 240b may include a second storage unit 246 and a second selector 248 .

The second storage unit 246 may store a plurality of second codebooks (SCB_1, SCB_2, ..., SCB_N). For example, the plurality of second codebooks SCB_1 to SCB_N may be designed and stored in advance based on the Lloyd's algorithm described above with reference to FIGS. 4 and 5 . For example, the second storage 246 may include any volatile and/or non-volatile memory.

The second selector 248 may select a plurality of subcarrier beamforming matrices SBM based on the plurality of second codebooks SCB_1 to SCB_N. For example, the second selector 248 may select a codebook that can obtain the largest beamforming gain. For example, the second selector 248 selects one of the plurality of second codebooks SCB_1 to SCB_N that is closest to the plurality of equivalent channel information EECIs as one of the plurality of subcarrier beamforming matrices SBM. can

In an embodiment, the second selector 248 may select one of the plurality of subcarrier beamforming matrices SBM based on Equation 17 below.

[Equation 17]

의 i번째 코드북, 즉 복수의 제2 코드북들(SCB_1~SCB_N) 중 i번째 코드북, k는 상기 복수의 부반송파들의 인덱스를 나타낸다. argmin은 arguments of min, 즉 해당 함수를 최소로 만드는 값을 반환하는 함수를 나타낸다.In [Equation 17], W _s is the selected subcarrier beamforming matrix, N _g is the number of subcarriers corresponding to one broadband beam, ED(.) is a Euclidean distance function, V _sc [k] ] is a unitary matrix for a channel matrix corresponding to one of a plurality of equivalent channel information (EECI), and W _i is a codebook set

The i-th codebook of , that is, the i-th codebook among the plurality of second codebooks SCB_1 to SCB_N, k indicates the indexes of the plurality of subcarriers. argmin represents arguments of min, that is, a function that returns a value that minimizes the function.

The plurality of wideband beamforming matrices WBM provided from the first beamforming matrix provider 220b and the plurality of subcarrier beamforming matrices SBM provided from the second beamforming matrix provider 240b are formed by a beamformer. may be fed back to the device 100 . For example, a beamforming feedback report (BFR) generated based on a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM) may be fed back to the beamformer apparatus 100 .

FIG. 10 is a diagram illustrating an example of a beamforming feedback report generated by the beamformer apparatus of FIG. 9 .

Referring to FIG. 10, the beamforming feedback report (BFR) includes MAC header information 271, category information 272, MIMO control information 273, codebook index information 274b, CBR information 275b, and feedback mode information. (277b). The beamforming feedback report (BFR) of FIG. 10 may further include codebook index information 274b and feedback mode information 277b compared to existing ones.

The codebook index information 274b may correspond to a plurality of subcarrier beamforming matrices (SBM), and the CBR information 275b may correspond to a plurality of wideband beamforming matrices (WBM). The feedback mode information 277b may indicate the second feedback mode to which the codebook utilization technique is applied with respect to a plurality of subcarrier beamforming matrices (SBM).

The beamforming feedback report (BFR) of FIG. 10 may include only some information about a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM). For example, with respect to the plurality of wideband beamforming matrices (WBM), the CBR information 275b generated by compressing the angle values (φ, ψ) for the M wideband beams described above with reference to FIGS. 2 and 3 is fed back. and, for the plurality of subcarrier beamforming matrices (SBM) to which the codebook utilization technique is applied, codebook index information 274b indicating a codebook corresponding to N _fft subcarrier beams may be fed back. Accordingly, the amount of computation and the amount of data fed back can be reduced, thereby reducing the feedback overhead.

11 and 12 are block diagrams illustrating still other examples of the beamformer device and the wireless communication system of FIG. 1 . Hereinafter, descriptions overlapping those of FIGS. 1, 6 and 9 will be omitted.

Referring to FIG. 11 , the wireless communication system 10c includes a beamformer device 100 and a beamformer device 200c. The beamformer apparatus 100 may include a plurality of antennas 101 . The beamformer device 200c includes a plurality of antennas 201 , a channel estimator 210 , a first beamforming matrix provider 220c , a dimension reduction unit 230 , and a second beamforming matrix provider 240c . may include

The embodiment of FIG. 11 shows a case in which the codebook utilization technique is applied to both a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM), and accordingly, the first and second beamforming The configuration of the matrix providers 220c and 240c may be partially changed. The beamformer apparatus 100 , the plurality of antennas 101 and 201 , the channel estimator 210 , and the dimension reduction unit 230 may be substantially the same as those described above with reference to FIG. 1 and the like.

The first beamforming matrix provider 220c is substantially the same as the first beamforming matrix provider 220a of FIG. 6 , and may include a first storage unit 222 and a first selector 224 . The second beamforming matrix provider 240c is substantially the same as the second beamforming matrix provider 240b of FIG. 9 , and may include a second storage unit 246 and a second selector 248 .

Meanwhile, although not shown, a plurality of broadband beamforming matrices WBM provided from the first beamforming matrix provider 220c and a plurality of subcarrier beamforming matrices provided from the second beamforming matrix provider 240c The beamforming feedback report generated based on (SBM) includes MAC header information, category information, MIMO control information, the first codebook index information corresponding to the codebook index information 274a of FIG. 7, and the codebook index information of FIG. 274b) may include second codebook index information and feedback mode information.

Referring to FIG. 12 , the wireless communication system 10d includes a beamformer device 100 and a beamformer device 200d. The beamformer apparatus 100 may include a plurality of antennas 101 . The beamformer device 200d includes a plurality of antennas 201 , a channel estimator 210 , a first beamforming matrix provider 220d , a dimension reduction unit 230 , a second beamforming matrix provider 240d and A feedback mode selector 280 may be included.

The embodiment of FIG. 12 shows a case in which the codebook utilization technique is selectively/adaptively applied to at least one of a plurality of wideband beamforming matrices (WBM) and a plurality of subcarrier beamforming matrices (SBM). It further includes a feedback mode selector 280, and the configuration of the first and second beamforming matrix providers 220d and 240d may be partially changed. The beamformer apparatus 100 , the plurality of antennas 101 and 201 , the channel estimator 210 , and the dimension reduction unit 230 may be substantially the same as those described above with reference to FIG. 1 and the like.

The beamformer 200d selects one of the plurality of first codebooks 221 and outputs the first feedback mode and the plurality of second codebooks 241 as one of the plurality of wideband beamforming matrices (WBM). The second feedback mode for selecting one of the plurality of subcarrier beamforming matrices (SBM) and outputting it as one of the plurality of subcarrier beamforming matrices (SBM), and a plurality of wideband beamforming matrices (WBM) by selecting one of the plurality of first codebooks (221) It may operate in one of the third feedback modes in which one of the plurality of second codebooks 241 is selected and outputted as one of the plurality of subcarrier beamforming matrices (SBM).

To this end, the first beamforming matrix provider 220d includes a first processing unit PU1 2202 and a second processing unit PU2 2204 , and the second beamforming matrix provider 240d includes a third It may include a processing unit (PU3) 2402 and a fourth processing unit (PU4) 2404 . The first processing unit 2202 and the second processing unit 2204 have substantially the same configuration as the first beamforming matrix provider 220a of FIG. 6 and the first beamforming matrix provider 220b of FIG. 9, respectively, The third processing unit 2402 and the fourth processing unit 2404 may have substantially the same configuration as the second beamforming matrix provider 240b of FIG. 9 and the second beamforming matrix provider 240a of FIG. 6 , respectively. there is.

The feedback mode selector 280 selects one of the first feedback mode, the second feedback mode, and the third feedback mode based on the characteristics of the channel, and generates a mode signal MD indicating the selected feedback mode. can do. For example, the feedback mode selector 280 may select one feedback mode that is predicted to have the highest data throughput based on the channel characteristics.

In one embodiment, one of the first and second processing units 2202 and 2204 is activated according to the feedback mode (ie, based on the mode signal MD) and the third and fourth processing units 2402 and 2404 are activated. ) can be activated. For example, the first processing unit 2202 may be activated in the first and third feedback modes, and the second processing unit 2204 may be activated in the second feedback mode. In addition, the third processing unit 2402 may be activated in the second and third feedback modes, and the fourth processing unit 2404 may be activated in the first feedback mode.

13 is a block diagram illustrating an example of a feedback mode selector included in the beamformer of FIG. 12 .

Referring to FIG. 13 , the feedback mode selector 280a may include an estimator 282 and a selector 284 .

The estimator 282 may estimate the characteristic of the channel and generate a characteristic signal CCHA indicating the estimated characteristic of the channel. For example, the characteristics of the channel include Signal-to-Noise Ratio (SNR), Modulation and Coding Scheme (MCS), Physical Data Unit (PDU) length, BW (bandwidth), Nss (Number of spatial stream). , and at least one of encoding techniques (Binary Convolution Coding (BCC)/Low Density Parity Check (LDPC)).

The selector 284 may select one feedback mode based on the channel characteristic (ie, based on the characteristic signal CCHA) and generate the mode signal MD.

In an embodiment, the selector 284 may include a preset look-up table (LUT) 286 . For example, the lookup table 286 may indicate a relationship between the estimated channel characteristic and the feedback mode.

14 is a diagram illustrating an example of a lookup table included in the feedback mode selector of FIG. 13 .

Referring to FIG. 14 , an exemplary configuration of a lookup table 286 is shown when SNR and MCS are used as characteristics of the channel.

In the example of FIG. 14 , the lookup table 286 may include M different MCS cases per SNR and data rates in the first, second and third feedback modes for each MCS. .

Specifically, the lookup table 286 shows the data rates RATE_1_1_1 and RATE_1_2_1 in the first feedback mode for the first SNR (SNR_1) and the first to M th MCSs (MCS_1, MCS_2, ..., MCS_M). , ..., RATE_1_M_1), data rates in the second feedback mode (RATE_1_1_2, RATE_1_2_2, ..., RATE_1_M_2) and data rates in the third feedback mode (RATE_1_1_3, RATE_1_2_3, ..., RATE_1_M_3 ) may be included. Similarly, the lookup table 286 shows the data rates RATE_2_1_1 in the first, second and third feedback modes for the second SNR (SNR_2) and the first to Mth MCSs (MCS_1 to MCS_M). , RATE_2_2_1, ..., RATE_2_M_1, RATE_2_1_2, RATE_2_2_2, ..., RATE_2_M_2, RATE_2_1_3, RATE_2_2_3, ..., RATE_2_M_3), including Kth SNR (SNR_Kth) and MCS (MCS_1 to MCS) Data rates (RATE_K_1_1, RATE_K_2_1, ..., RATE_K_M_1, RATE_K_1_2, RATE_K_2_2, ..., RATE_K_M_2, RATE_K_1_2_3, RATE... RATE_K_M_3) may be included.

When the SNR estimated by the estimator 282 is greater than SNR_m from among the SNRs SNR_1 to SNR_K and less than or equal to SNR_(m+1), SNR_m is selected, and the applied MCS from among the MCSs (MCS_1 to MCS_M) is selected. You can choose. Among data rates corresponding to the selected SNR and MCS, a feedback mode corresponding to the largest data rate (ie, a data transmission amount predicted to be the largest) may be selected.

15 is a block diagram illustrating another example of the beamformer device and the wireless communication system of FIG. 1 . Hereinafter, descriptions overlapping those of FIG. 1 will be omitted.

Referring to FIG. 15 , a wireless communication system 10e includes a beamformer device 100 and a beamformer device 200e. The beamformer apparatus 100 may include a plurality of antennas 101 . The beamformer device 200e includes a plurality of antennas 201 , a channel estimator 210 , a first beamforming matrix provider 220 , a dimension reduction unit 230 , a second beamforming matrix provider 240 , and It may include a codebook generator 290 .

The embodiment of FIG. 15 may further include a codebook generator 290 . The beamformer device 100 , the plurality of antennas 101 and 201 , the channel estimator 210 , the first beamforming matrix provider 220 , the dimension reduction unit 230 , and the second beamforming matrix provider 240 . ) may be substantially the same as described above with reference to FIG. 1 and the like.

The codebook generator 290 may design the plurality of first codebooks 221 and/or the plurality of second codebooks 241 , and may generate codebook information CBI indicating the designed codebooks. For example, the codebook generator 290 may design codebooks based on the Lloyd's algorithm described above with reference to FIGS. 4 and 5 . The codebook information CBI may be provided to the first and second beamforming matrix providers 220 and 240 .

The first and second beamforming matrix providers 220 and 240 may be implemented as described above with reference to FIGS. 6, 9, 11, 12, and the like.

Meanwhile, according to embodiments, some or all of the components included in the beamformer apparatus according to embodiments of the present invention may be implemented in the form of hardware. For example, some or all of the components may be included in a computer-based electronic system. In another embodiment, some or all of the components included in the beamformer apparatus according to embodiments of the present invention may be implemented in software, for example, in the form of instruction codes or program routines. For example, the instruction codes or program routines may be stored in any storage unit executed by a computer-based electronic system and disposed inside or external to the computer-based electronic system.

In a beamformer apparatus and a wireless communication system including the same according to embodiments of the present invention, dual beamforming feedback is used when beamforming feedback is performed in a feedback mode, and in particular, a plurality of wideband beamforming matrices (WBM) and a codebook utilization technique may be applied to at least one of a plurality of subcarrier beamforming matrices (SBM). In addition, an adaptive codebook utilization technique for selecting a feedback mode according to a channel situation/environment may be implemented. Therefore, it is possible to effectively reduce the feedback overhead of the beamforming feedback, and to perform the efficient beamforming feedback.

16, 17 and 18 are flowcharts illustrating a beamforming feedback method according to embodiments of the present invention.

Referring to FIG. 16 , a beamforming feedback method according to embodiments of the present invention is performed by a wireless communication system including a beamformer device and a beamformer device, and in particular, it is performed by the beamformer device. The wireless communication system and the beamformer device may be implemented as described above with reference to FIGS. 1 to 15 .

In the beamforming feedback method according to embodiments of the present invention, a plurality of channel information for a plurality of subcarriers is obtained by estimating a channel based on an NDP received from the beamformer device through a channel (step S100) . For example, step S100 may be performed by the channel estimator 210 of FIG. 1 .

A plurality of broadband beamforming matrices are provided based on the plurality of channel information (step S200). For example, step S200 may be performed by the first beamforming matrix provider 220 of FIG. 1 .

In an embodiment, in performing step S200, one of a plurality of first codebooks designed in advance based on the plurality of channel information may be selected and output as one of the plurality of wideband beamforming matrices. For example, one of the plurality of first codebooks that maximizes the power of the channel may be selected as one of the plurality of wideband beamforming matrices based on the plurality of channel information. For example, one of the plurality of broadband beamforming matrices may be selected based on Equation 16 described above with reference to FIG. 6 .

A plurality of equivalent channel information corresponding to the plurality of channel information is generated based on the plurality of wideband beamforming matrices (step S300). For example, step S300 may be performed by the dimension reduction unit 230 of FIG. 1 .

A plurality of subcarrier beamforming matrices are provided based on the plurality of equivalent channel information (step S400). For example, step S400 may be performed by the second beamforming matrix provider 240 of FIG. 1 .

In an embodiment, in performing step S400, one of a plurality of second codebooks designed in advance based on the plurality of equivalent channel information may be selected and output as one of the plurality of subcarrier beamforming matrices. For example, one of the plurality of second codebooks that is closest to the plurality of pieces of equivalent channel information may be selected as one of the plurality of subcarrier beamforming matrices. For example, one of the plurality of subcarrier beamforming matrices may be selected based on Equation 17 described above with reference to FIG. 9 .

The plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are fed back to the beamformer device. For example, it may be fed back in the form of a beamforming feedback report.

At least one of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices is selected from among a plurality of predesigned codebooks. For example, as described above with reference to FIGS. 6, 9 and 11, a codebook utilization technique is applied to a plurality of wideband beamforming matrices (WBM), or a codebook utilization technique is applied to a plurality of subcarrier beamforming matrices (SBM). The technique may be applied, or the codebook utilization technique may be applied to both the plurality of wideband beamforming matrices (WBM) and the plurality of subcarrier beamforming matrices (SBM).

Referring to FIG. 17 , in the beamforming feedback method according to embodiments of the present invention, a description overlapping with FIG. 16 will be omitted.

A feedback mode of the beamformer is selected based on the channel characteristics (step S500). For example, as described above with reference to FIG. 12 , a feedback mode predicted to have the largest amount of data transmission among the first feedback mode, the second feedback mode, and the third feedback mode is selected based on the channel characteristics. can For example, step S500 may be performed by the feedback mode selector 280 of FIG. 12 .

Subsequent steps S100, S200, S300 and S400 may be substantially the same as those described above with reference to FIG. 16 .

Referring to FIG. 18 , in the beamforming feedback method according to embodiments of the present invention, a description overlapping with FIG. 16 will be omitted.

The plurality of codebooks are designed (step S600). For example, as described above with reference to FIGS. 4 and 5 , codebooks may be designed based on the Lloyd's algorithm. For example, step S600 may be performed once during manufacturing and/or at the beginning of operation of the beamformer device and may be omitted thereafter. For example, step S600 may be performed by the codebook generator 290 of FIG. 15 .

Subsequent steps S100, S200, S300 and S400 may be substantially the same as those described above with reference to FIG. 16 .

Meanwhile, in the embodiment of FIG. 17 , step S600 may be additionally performed.

Meanwhile, embodiments of the present invention may be implemented in the form of products including computer-readable program codes stored in a computer-readable medium. The computer readable program code may be provided to the processor of various computers or other data processing devices. The computer-readable medium may be a computer-readable signal medium or a computer-readable recording medium. The computer-readable recording medium may be any tangible medium that can store or include a program in or connected to an instruction execution system, equipment, or device. For example, the computer-readable medium may be provided in the form of a non-transitory storage medium. Here, non-transitory means that the storage medium does not include a signal and is tangible, and does not distinguish that data is semi-permanently or temporarily stored in the storage medium.

19 is a block diagram illustrating an electronic device in a network environment according to embodiments of the present invention.

Referring to FIG. 19 , in the network environment 300 , the electronic device 301 communicates with the electronic device 302 through a first network 398 (eg, short-range wireless communication), or a second network 399 ( It may communicate with the electronic device 304 or the server 308 via (eg, remote wireless communication). In one embodiment, electronic device 301 may communicate with electronic device 304 via server 308 . In one embodiment, electronic device 301 includes processor 320 , memory 330 , input device 350 , sound output device 355 , display device 360 , audio module 370 , and sensor module 376 . ), interface 377 , haptic module 379 , camera module 380 , power management module 388 , battery 389 , communication module 390 , subscriber identification module 396 , and antenna module 397 . may include

The processor 320 may, for example, run software (eg, a program 340 ) to execute at least one other component (eg, a hardware or software component) of the electronic device 301 connected to the processor 320 . It can control and perform various data processing and operations. In one embodiment, the processor 320 may include a main processor 321 and a secondary processor 323 .

The memory 330 includes various data used by at least one component (eg, the processor 320 or the sensor module 376 ) of the electronic device 301 , for example, software (eg, a program 340 ). ) and input data or output data for commands related thereto. The memory 330 may include a volatile memory 332 or a non-volatile memory 334 .

The program 340 is software stored in the memory 330 , and may include, for example, an operating system (OS) 342 , middleware 344 , or an application 346 .

The input device 350 may receive a command or data to be used by a component (eg, the processor 320 ) of the electronic device 301 from the outside (eg, a user) of the electronic device 301 . The sound output device 355 may output a sound signal to the outside of the electronic device 301 . The display device 360 may visually provide information to a user of the electronic device 301 .

The audio module 370 may interactively convert a sound and an electrical signal. The sensor module 376 may generate an electrical signal or data value corresponding to an internal operating state (eg, power or temperature) of the electronic device 301 or an external environmental state. The interface 377 may support a designated protocol that may be connected to an external electronic device (eg, the electronic device 302 ) in a wired or wireless manner.

The connection terminal 378 may include a connector capable of physically connecting the electronic device 301 and an external electronic device (eg, the electronic device 302 ). The haptic module 379 may convert an electrical signal into a mechanical stimulus (eg, vibration or movement) or an electrical stimulus that the user can perceive through tactile or kinesthetic sense. The camera module 380 may capture still images and moving images.

The power management module 388 is a module for managing power supplied to the electronic device 301 , and may be configured as, for example, at least a part of a power management integrated circuit (PMIC). The battery 389 may be a device for supplying power to at least one component of the electronic device 301 .

The communication module 390 establishes a wired or wireless communication channel between the electronic device 301 and an external electronic device (eg, the electronic device 302 , the electronic device 304 , or the server 308 ), and establishes the established communication channel. It can support performing communication through In one embodiment, the communication module 390 may include a wireless communication module 392 or a wired communication module 394 .

In one embodiment, the wireless communication module 392 included in the communication module 390 includes a beamformer device and a beamformer device according to embodiments of the present invention, and may be implemented to perform a beamforming feedback method. . For example, the wireless communication module 392 included in the electronic device 301 and the wireless communication module (not shown) included in the electronic device 304 are each a beamformer device (eg, For example, the second network 399 including 200 of FIG. 1 and the beamformer apparatus (eg, 100 of FIG. 1 ), the second network 399 formed between the electronic devices 301 and 304 is the beamformer apparatus 200 . and a channel between the beamformer device 100 and the beamformer device 100 . The beamformer apparatus 200 included in the electronic device 301 may communicate with the beamformer apparatus 100 included in the electronic device 304, and at this time, while performing dual beamforming feedback, embodiments of the present invention It is possible to use a codebook utilization technique and/or an adaptive codebook utilization technique according to . Similarly, the beamformer apparatus 200 included in the electronic device 304 may communicate with the beamformer apparatus 100 included in the electronic device 301, and in this case, the present invention performs dual beamforming feedback. The codebook utilization technique and/or the adaptive codebook utilization technique according to the embodiments of may be used.

The antenna module 397 may receive a signal or power from the outside of the electronic device 301 (eg, an external electronic device), or may transmit a signal or power to the outside (eg, an external electronic device).

Embodiments of the present invention may be usefully used in various communication devices and systems for performing beamforming and any electronic devices and systems including the same. For example, embodiments of the present invention are PC (Personal Computer), notebook (laptop), cell phone (cellular), smart phone (smart phone), MP3 player, PDA (Personal Digital Assistant), PMP (Portable Multimedia Player), Digital TV, digital camera, portable game console, navigation device, wearable device, Internet of Things (IoT) device, Internet of Everything (IoE) device, e-book ), virtual reality (VR) devices, augmented reality (AR) devices, and electronic systems such as drones.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. you will understand that you can

Claims (20)

a channel estimator for receiving a Null Data Packet (NDP) from a beamformer device through a channel and estimating the channel based on the NDP to obtain a plurality of channel information for a plurality of subcarriers;
a first beamforming matrix provider providing a plurality of wideband beamforming matrices based on the plurality of channel information;
a dimension reduction unit generating a plurality of equivalent channel information corresponding to the plurality of channel information based on the plurality of wideband beamforming matrices; and
a second beamforming matrix provider providing a plurality of subcarrier beamforming matrices based on the plurality of equivalent channel information;
the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are fed back to the beamformer device;
At least one of the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices is selected from among a plurality of predesigned codebooks. The method of claim 1, wherein the first beamforming matrix provider comprises:
and selecting one of a plurality of first codebooks designed in advance based on the plurality of channel information and outputting the selected one of the plurality of wideband beamforming matrices as one of the plurality of broadband beamforming matrices. 3. The method of claim 2, wherein the first beamforming matrix provider comprises:
a first storage unit for storing the plurality of first codebooks; and
and a first selector for selecting one of the plurality of first codebooks that maximizes the power of the channel as one of the plurality of wideband beamforming matrices based on the plurality of channel information Beamformer device. 4. The method of claim 3, wherein the first selector comprises:
A beamformer apparatus, characterized in that it selects one of the plurality of broadband beamforming matrices based on the following [Equation 1].
[Equation 1]

In Equation 1 above, W _w is the selected wideband beamforming matrix, N _g is the number of subcarriers corresponding to one wideband beam, and H[k] is one of the plurality of channel information. A corresponding channel matrix, H ^H [k] is a conjugate transpose matrix of H[k], W _i is an i-th codebook among the plurality of first codebooks, and k is an index of the plurality of subcarriers. indicates. 4. The method of claim 3,
feeding back a beamforming feedback report generated based on the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices to the beamformer device;
The beamforming feedback report includes MAC (Media Access Control) header information, category information, multiple input multiple output (MIMO) control information, codebook index information corresponding to the plurality of wideband beamforming matrices, the plurality of A beamformer apparatus comprising: Compressed Beamforming Report (CBR) information corresponding to subcarrier beamforming matrices, additional common phase information, and feedback mode information. The method of claim 1, wherein the second beamforming matrix provider comprises:
and selecting one of a plurality of second codebooks designed in advance based on the plurality of equivalent channel information and outputting the selected one of the plurality of subcarrier beamforming matrices as one of the plurality of subcarrier beamforming matrices. 7. The method of claim 6, wherein the second beamforming matrix provider comprises:
a second storage unit for storing the plurality of second codebooks; and
and a second selector for selecting one of the plurality of second codebooks that is closest to the plurality of pieces of equivalent channel information as one of the plurality of subcarrier beamforming matrices. 8. The method of claim 7, wherein the second selector comprises:
A beamformer device, characterized in that it selects one of the plurality of subcarrier beamforming matrices based on the following [Equation 2].
[Equation 2]

In [Equation 2], W _s is the selected subcarrier beamforming matrix, N _g is the number of subcarriers corresponding to one broadband beam, ED(.) is a Euclidean distance function, V _sc [k] ] denotes a unitary matrix for a channel matrix corresponding to one of the plurality of equivalent channel information, W _i denotes an i-th codebook among the plurality of second codebooks, and k denotes an index of the plurality of subcarriers . 8. The method of claim 7,
feeding back a beamforming feedback report generated based on the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices to the beamformer device;
The beamforming feedback report includes MAC header information, category information, MIMO control information, codebook index information corresponding to the plurality of subcarrier beamforming matrices, CBR information corresponding to the plurality of wideband beamforming matrices, and a feedback mode. Beamformer device, characterized in that it includes information. The method of claim 1,
The first beamforming matrix provider selects one of a plurality of first codebooks designed in advance based on the plurality of channel information and outputs it as one of the plurality of wideband beamforming matrices,
The second beamforming matrix provider selects one of a plurality of second codebooks designed in advance based on the plurality of equivalent channel information and outputs the selected one of the plurality of subcarrier beamforming matrices as one of the plurality of subcarrier beamforming matrices. . The method of claim 1,
A first feedback mode in which one of a plurality of pre-designed first codebooks is selected and outputted as one of the plurality of wideband beamforming matrices, a plurality of subcarrier beamforming matrices by selecting one of a plurality of pre-designed second codebooks a second feedback mode for outputting one of the plurality of first codebooks, outputting one of the plurality of wideband beamforming matrices by selecting one of the plurality of first codebooks, and selecting one of the plurality of second codebooks to obtain the plurality of A beamformer device, characterized in that it operates in one of the third feedback modes for outputting one of the subcarrier beamforming matrices. 12. The method of claim 11,
and a feedback mode selector for selecting one of the first feedback mode, the second feedback mode, and the third feedback mode, which is predicted to have the largest amount of data transmission, based on the characteristics of the channel. Device. The method of claim 1,
The beamformer apparatus according to claim 1, further comprising a codebook generator for designing the plurality of codebooks. estimating the channel based on a null data packet (NDP) received through a channel from a beamformer device to obtain a plurality of channel information for a plurality of subcarriers;
providing a plurality of wideband beamforming matrices based on the plurality of channel information;
generating a plurality of equivalent channel information corresponding to the plurality of channel information based on the plurality of wideband beamforming matrices; and
providing a plurality of subcarrier beamforming matrices based on the plurality of equivalent channel information;
the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are fed back to the beamformer device;
At least one of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices is selected from among a plurality of predesigned codebooks. 15. The method of claim 14, wherein providing the plurality of broadband beamforming matrices comprises:
Selecting one of a plurality of first codebooks designed in advance based on the plurality of channel information and outputting it as one of the plurality of wideband beamforming matrices,
and selecting one of the plurality of first codebooks that maximizes the power of the channel as one of the plurality of wideband beamforming matrices based on the plurality of channel information. 15. The method of claim 14, wherein providing the plurality of subcarrier beamforming matrices comprises:
Selecting one of a plurality of second codebooks designed in advance based on the plurality of equivalent channel information and outputting it as one of the plurality of subcarrier beamforming matrices,
and selecting one closest to the plurality of pieces of equivalent channel information from among the plurality of second codebooks as one of the plurality of subcarrier beamforming matrices. 15. The method of claim 14,
Further comprising the step of selecting a feedback mode based on the characteristics of the channel,
The feedback mode is a first feedback mode for selecting one of a plurality of pre-designed first codebooks and outputting it as one of the plurality of wideband beamforming matrices, A second feedback mode for outputting one of the subcarrier beamforming matrices, and selecting one of the plurality of first codebooks to output one of the plurality of wideband beamforming matrices and selecting one of the plurality of second codebooks to include a third feedback mode outputting one of the plurality of subcarrier beamforming matrices,
The beamforming feedback method according to claim 1, wherein one of the first feedback mode, the second feedback mode, and the third feedback mode, which is predicted to have the largest amount of data transmission, is selected based on the characteristics of the channel. The channel is estimated based on a Null Data Packet (NDP) received through a channel from a beamformer device, and as a result of the channel estimation, a plurality of wideband beamforming matrices and a plurality of subcarrier beamforming matrices are wherein at least one of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices is selected from among a plurality of pre-designed codebooks, the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices A beamforming feedback report is generated based on the subcarrier beamforming matrices and fed back to the beamformer device,
The beamforming feedback report includes MAC (Media Access Control) header information, category information, MIMO (Multiple Input Multiple Output) control information, codebook index information, CBR (Compressed Beamforming Report) information and feedback mode information. Beamformer device. 19. The method of claim 18,
When one of a plurality of pre-designed first codebooks is selected and provided as one of the plurality of wideband beamforming matrices, the codebook index information corresponds to the plurality of wideband beamforming matrices, and the CBR information is The beamformer apparatus according to claim 1, comprising angle values for a plurality of subcarrier beamforming matrices, and wherein the beamforming feedback report further includes additional common phase information. 19. The method of claim 18,
When one of a plurality of pre-designed second codebooks is selected and provided as one of the plurality of subcarrier beamforming matrices, the codebook index information corresponds to the plurality of subcarrier beamforming matrices, and the CBR information is A beamformer device comprising angle values for a plurality of broadband beamforming matrices.

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