Apparatus and method for adaptive codebook for dual beamforming feedback

Abstract

A beamforming receiver apparatus and a beamforming feedback method are provided. The beamforming receiver apparatus includes a channel estimator, a first beamforming matrix provider and a second beamforming matrix provider, and a dimension reduction unit. The channel estimator receives an NDP through a channel and obtains channel information of the channel based on the NDP. The first beamforming matrix provider provides a wideband beamforming matrix based on the channel information. The dimension reduction unit generates equivalent channel information based on the wideband beamforming matrix. The second beamforming matrix provider provides a subcarrier beamforming matrix based on the equivalent channel information. The wideband beamforming matrix and the subcarrier beamforming matrix are fed back to a beamforming transmitter apparatus. Any one or any combination of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices is selected from a codebook.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 083,411 filed with the U.S. Patent and Trademark Office on September 25, 2020, and Korean Patent Application No. 10-2020-0174101 filed with the Korean Intellectual Property Office on December 14, 2020, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The methods, apparatus, and systems consistent with the example embodiments relate to semiconductor integrated circuits, and more specifically, to adaptive codebooks for dual-beamforming feedback. Background Technology

[0004] In wireless communication systems, a strong communication signal is crucial. Specifically, the receiver aims for the maximum possible signal-to-noise ratio (SNR). Similarly, in Wi-Fi systems, an increase in SNR at the receiver increases the likelihood of correctly receiving frames and reduces the amount of retransmissions required from the source. The receiver's SNR can be increased by increasing transmit power, decreasing the distance between the source and receiver, and increasing antenna gain.

[0005] In wireless local area network (WLAN) systems such as Wi-Fi, signals can be transmitted based on beamforming methods. In wireless communication systems, beamforming is a smart antenna technology used to direct beams to corresponding terminals. Beamforming feedback should precede beamforming transmission, and various methods for providing efficient beamforming feedback have been investigated. Summary of the Invention

[0006] At least one example embodiment provides a beamforming receiving device capable of adaptively utilizing a codebook to reduce the overhead of beamforming feedback while performing dual beamforming feedback.

[0007] At least one example embodiment provides a wireless communication system including a beamforming receiver.

[0008] At least one example embodiment provides a beamforming feedback method performed by a beamforming receiving device.

[0009] According to one aspect of an example embodiment, a beamforming receiving device includes a processor configured to implement: a channel estimator configured to receive null data packets (NDP) from a beamforming applicator via a channel and obtain multiple channel information associated with multiple subcarriers of the channel based on the NDP; a first beamforming matrix provider configured to provide multiple wideband beamforming matrices based on the multiple channel information; a dimensionality reduction unit configured to generate multiple equivalent channel information corresponding to the multiple channel information based on the multiple wideband beamforming matrices; and a second beamforming matrix provider configured to provide multiple subcarrier beamforming matrices based on the multiple equivalent channel information. The processor is further configured to feed back the multiple wideband beamforming matrices and the multiple subcarrier beamforming matrices to the beamforming applicator and select any one or any combination of the multiple wideband beamforming matrices and the multiple subcarrier beamforming matrices from multiple codebooks stored in the beamforming receiving device.

[0010] According to one aspect of an example embodiment, a wireless communication system includes: a beamforming applicator configured to transmit a Non-Device Proposal (NDP) via a channel; and a beamforming receiver configured to receive the NDP via the channel, estimate the channel based on the NDP, and feed back the estimated channel result to the beamforming applicator. The beamforming receiver includes a processor configured to implement: a channel estimator configured to obtain multiple channel information associated with multiple subcarriers based on the NDP; a first beamforming matrix provider configured to provide multiple wideband beamforming matrices based on the multiple channel information; a dimensionality reduction unit configured to generate multiple equivalent channel information corresponding to the multiple channel information based on the multiple wideband beamforming matrices; and a second beamforming matrix provider configured to provide multiple subcarrier beamforming matrices based on the multiple equivalent channel information. The processor is also configured to feed back the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices as the result of channel estimation to the beamforming applicator, and to select any one or any combination of the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices from a plurality of codebooks stored in the beamforming applicator.

[0011] According to one aspect of an example embodiment, a beamforming applicator includes a processor configured to implement: a channel estimator configured to receive null data packets (NDP) from the beamforming applicator via a channel and obtain multiple channel information associated with multiple subcarriers of the channel based on the NDP; a feedback mode selector configured to select one of a first feedback mode, a second feedback mode, or a third feedback mode as the selected feedback mode based on channel characteristics; and a first beamforming matrix provider configured to generate multiple broadband beamforming matrices by performing singular value decomposition (SVD) and compressing the multiple channel information based on the selected feedback mode being the second feedback mode, and based on the selected feedback mode being the first feedback mode or the third feedback mode, based on... The plurality of channel information selects one of a plurality of first codebooks as the selected first codebook and outputs the selected first codebook as one of the plurality of wideband beamforming matrices; a dimensionality reduction unit is configured to generate 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 is configured to generate a plurality of subcarrier beamforming matrices by performing SVD and compressing the plurality of equivalent channel information based on the selected feedback mode being a first feedback mode, and to select one of a plurality of second codebooks as the selected second codebook based on the plurality of equivalent channel information based on the selected feedback mode being a second feedback mode or a third feedback mode, and output the selected second codebook as one of the plurality of subcarrier beamforming matrices. The processor is also configured to feed back the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices to the beamforming application device, and the codebook index corresponding to the selected first codebook and the selected second codebook is fed back to the beamforming application device.

[0012] According to an example embodiment, a beamforming feedback method includes: obtaining multiple channel information associated with multiple subcarriers of a channel based on null data packets (NDP) received from a beamforming applicator via a channel; providing multiple wideband beamforming matrices based on the multiple channel information; generating multiple equivalent channel information corresponding to the multiple channel information based on the multiple wideband beamforming matrices; providing multiple subcarrier beamforming matrices based on the multiple equivalent channel information; and feeding back the multiple wideband beamforming matrices and the multiple subcarrier beamforming matrices to the beamforming applicator. Any one or any combination of the multiple wideband beamforming matrices and the multiple subcarrier beamforming matrices is selected from multiple codebooks stored in a memory.

[0013] According to an example embodiment, a beamforming receiving device includes a processor configured to: estimate a channel based on an NDP received from a beamforming applying device via the channel; provide a plurality of wideband beamforming matrices and a plurality of subcarrier beamforming matrices as a result of the channel estimation; select any one or any combination of the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices from a plurality of codebooks stored in the beamforming receiving device; generate a beamforming feedback report based on the plurality of wideband beamforming matrices and the plurality of subcarrier beamforming matrices; and feed back the beamforming feedback report to the beamforming applying device. The beamforming feedback report includes Media Access Control (MAC) header information, category information, Multiple-Input Multiple-Output (MIMO) control information, codebook index information, Compressed Beamforming Report (CBR) information, and feedback mode information.

[0014] In the beamforming receiving device, wireless communication system, and beamforming feedback method according to the example embodiments, dual beamforming feedback can be used when beamforming feedback is performed in feedback mode, and a codebook utilization scheme can be applied to at least one of multiple broadband beamforming matrices and multiple subcarrier beamforming matrices. Furthermore, an adaptive codebook utilization scheme can be implemented to select and / or change the feedback mode based on channel conditions and / or environment. Therefore, the feedback overhead of beamforming feedback can be efficiently reduced, and beamforming feedback can be performed with improved efficiency. Attached Figure Description

[0015] The above and other aspects will become more apparent from the following description of exemplary embodiments taken in conjunction with the accompanying drawings, in which:

[0016] Figure 1 This is a block diagram illustrating a beamforming receiver and a wireless communication system including the beamforming receiver according to an example embodiment.

[0017] Figure 2 and Figure 3 This is a diagram used to describe the dual-beamforming feedback according to an example embodiment.

[0018] Figure 4A , Figure 4B , Figure 4C , Figure 4D and Figure 5 This is a diagram used to describe the process of designing a codebook used in a beamforming device according to an example embodiment.

[0019] Figure 6 This is a block diagram illustrating a beamforming receiving device and a wireless communication system according to an example embodiment.

[0020] Figure 7 This is a diagram illustrating a beamforming feedback report generated by a beamforming receiving device according to an example embodiment.

[0021] Figure 8 This is a diagram illustrating the performance of a beamforming device according to an example embodiment.

[0022] Figure 9 This is a block diagram illustrating a beamforming receiving device and a wireless communication system according to an example embodiment.

[0023] Figure 10 This is a diagram illustrating a beamforming feedback report generated by a beamforming receiving device according to an example embodiment.

[0024] Figure 11 and Figure 12 This is a block diagram illustrating a beamforming receiving device and a wireless communication system according to an example embodiment.

[0025] Figure 13 This is a block diagram illustrating a feedback mode selector included in a beamforming receiving device according to an example embodiment.

[0026] Figure 14 This is a diagram illustrating the lookup table included in the feedback mode selector according to an example embodiment.

[0027] Figure 15 This is a block diagram illustrating a beamforming receiving device and a wireless communication system according to an example embodiment.

[0028] Figure 16 , Figure 17 and Figure 18 This is a flowchart illustrating a beamforming feedback method according to an example embodiment.

[0029] Figure 19 This is a block diagram illustrating an electronic device in a network environment according to an example embodiment. Detailed Implementation

[0030] Example embodiments will be described with reference to the accompanying drawings. However, this disclosure may be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Throughout this application, the same reference numerals refer to the same elements. Expressions such as “at least one of…” following a list of elements modify the entire list of elements, rather than individual elements in the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0031] Figure 1 This is a block diagram illustrating a beamforming receiver and a wireless communication system including the beamforming receiver according to an example embodiment.

[0032] Reference Figure 1The wireless communication system 10 includes a beamformer 100 and a beamformer receiver 200.

[0033] In some example embodiments, the wireless communication system 10 may be a wireless communication system implemented or formed based on a wireless local area network (WLAN). For example, the wireless communication system 10 may be a wireless communication system implemented or formed based on Wi-Fi. For example, the WLAN system may be implemented based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11ac standard or the IEEE 802.11ax standard, or it may be implemented based on the IEEE 802.11be standard as a next-generation standard.

[0034] In a WLAN system, beamforming transmission can be performed between beamforming applicator 100 and beamforming receiver 200. Beamforming transmission is a technique in a multi-antenna orthogonal frequency division modulation (OFDM) system where the beam of an antenna is guided and limited to a specific terminal. Beamforming transmission can be divided into techniques for forming transmission beams to increase the received data rate of a single user (e.g., single-user beamforming) and techniques for forming transmission beams to eliminate mutual interference during simultaneous transmission among multiple users (e.g., multi-user beamforming). Beamforming receiver 200 can decode packets sent from beamforming applicator 100 for channel measurements, compress channel information based on techniques specified in the WLAN standard, and feed back the compressed channel information to beamforming applicator 100. This operation of feeding back channel information can be referred to as beamforming feedback, and beamforming feedback can be performed in feedback mode.

[0035] According to an example embodiment, beamforming feedback performed in feedback mode can be dual-beamforming feedback or two-step beamforming feedback. Dual-beamforming feedback can be used to reduce feedback overhead. For example, one matrix can be used with broadband, and another matrix can be used with sub-bands (e.g., with subcarriers). Dual-beamforming feedback will refer to... Figure 2 and Figure 3 Detailed description.

[0036] The operation of the wireless communication system 10 and beamforming receiving device 200 according to the example embodiment will be described below based on the operation of reducing feedback overhead when performing dual beamforming feedback in feedback mode. However, the example embodiment is not limited thereto, and the wireless communication system 10 may perform normal beamforming transmission in normal operation mode after the feedback mode based on the channel information obtained through dual beamforming feedback.

[0037] Beamforming device 100 transmits null data packets (NDPs) for channel measurement. Beamforming device 100 may be referred to as a transmitter or access point (AP). NDPs may be referred to as probe packets.

[0038] The beamforming apparatus 100 may include a plurality of antennas (e.g., transmit antennas) 101. The beamforming apparatus 100 may use the plurality of antennas 101 to transmit or output NDP. For example, the number of the plurality of antennas 101 may be N. t , where N t It is a natural number greater than or equal to 2.

[0039] Beamforming receiver 200 receives the NDP (Network Targeting) from beamforming applicator 100 via the channel, estimates the channel based on the NDP, and feeds back the estimated channel result to beamforming applicator 100. Beamforming receiver 200 performs dual beamforming feedback to reduce the feedback overhead of beamforming feedback; therefore, it only feeds back multiple wideband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs), rather than the entire channel matrix. For example, as described later, the multiple wideband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs) can be fed back in the form of a beamforming feedback report. Beamforming receiver 200 may be referred to as a receiver or station (STA).

[0040] The beamforming receiver 200 includes a channel estimator 210, a first beamforming matrix provider 220, a dimensionality reduction unit 230, and a second beamforming matrix provider 240. The beamforming receiver 200 may also include a plurality of antennas (e.g., receiving antennas) 201.

[0041] The beamforming receiving device 200 can use multiple antennas 201 to receive NDP from the beamforming applying device 100 via a channel. For example, the number of antennas 201 can be N. r , where N r It is a natural number greater than or equal to 2. A channel (e.g., a wireless channel) can be formed between a plurality of antennas 101 of the beamforming applicator 100 and a plurality of antennas 201 of the beamforming receiver 200.

[0042] The channel estimator 210 obtains multiple channel information (ECI) associated with or related to multiple subcarriers by estimating the channel based on NDP. For example, one channel information can be estimated and obtained for one subcarrier. For example, individual channel information can be obtained in the form of a channel matrix representing the frequency response.

[0043] The first beamforming matrix provider 220 provides multiple wideband beamforming matrices (WBMs) based on multiple channel information (ECI). The first beamforming matrix provider 220 may be referred to as a wideband beamforming matrix (BM) provider.

[0044] The dimensionality reduction unit 230 generates multiple equivalent channel information EECIs corresponding to multiple channel information ECIs based on multiple broadband beamforming matrices (WBMs). For example, each equivalent channel information can be generated in the form of an equivalent channel matrix whose size is reduced compared to the size of the corresponding channel information (e.g., the size of the corresponding channel matrix).

[0045] The second beamforming matrix provider 240 provides multiple subcarrier beamforming matrices (SBMs) based on multiple equivalent channel information (EECI). The second beamforming matrix provider 240 may be referred to as a subcarrier beamforming matrix provider.

[0046] According to an example embodiment, at least one of a plurality of broadband beamforming matrices (WBMs) and a plurality of subcarrier beamforming matrices (SBMs) is selected from a plurality of pre-designed or pre-designed codebooks. In other words, a codebook utilization scheme can be applied to or employed on at least one of the plurality of broadband beamforming matrices (WBMs) and the plurality of subcarrier beamforming matrices (SBMs).

[0047] For example, the first beamforming matrix provider 220 may include a plurality of pre-designed first codebooks 221 corresponding to a plurality of wideband beamforming matrices (WBMs). The plurality of first codebooks 221 may be stored in memory. The second beamforming matrix provider 240 may include a plurality of pre-designed second codebooks 241 corresponding to a plurality of subcarrier beamforming matrices (SBMs). The plurality of second codebooks 241 may be stored in memory. The plurality of first codebooks 221 may be referred to as a plurality of wideband codebooks (WCBs), and the plurality of second codebooks 241 may be referred to as a plurality of subcarrier codebooks (SCBs).

[0048] In some example embodiments, such as referring to Figure 6 As described, when applying a codebook utilization scheme to multiple broadband beamforming matrices (WBMs), the first beamforming matrix provider 220 can select one of multiple first codebooks 221 based on multiple channel information (ECIs) and output the selected first codebook as one of the multiple broadband beamforming matrices (WBMs).

[0049] In other example embodiments, such as referring to Figure 9 As described, when a codebook utilization scheme is applied to multiple subcarrier beamforming matrices (SBMs), the second beamforming matrix provider 240 can select one of multiple second codebooks 241 based on multiple equivalent channel information (EECI), and can output the selected second codebook as one of the multiple subcarrier beamforming matrices (SBMs).

[0050] In other example embodiments, such as referring to Figure 11 The described method utilizes codebook techniques to apply to both multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs).

[0051] In some example embodiments, such as referring to Figure 12 The beamforming receiving device 200 is described as being able to operate in one of three feedback modes—a first feedback mode, a second feedback mode, and a third feedback mode—based on channel characteristics. The first feedback mode can be a feedback mode that applies a codebook utilization scheme to multiple broadband beamforming matrices (WBMs). The second feedback mode can be a feedback mode that applies a codebook utilization scheme to multiple subcarrier beamforming matrices (SBMs). The third feedback mode can be a feedback mode that applies a codebook utilization scheme to both the multiple broadband beamforming matrices (WBMs) and the multiple subcarrier beamforming matrices (SBMs). In other words, an adaptive codebook utilization scheme that selects the feedback mode based on channel conditions and / or environment can be implemented.

[0052] In some example embodiments, such as referring to Figure 4A , Figure 4B , Figure 4C , Figure 4D , Figure 5 and Figure 15 As described, multiple codebooks (e.g., at least one of a first codebook 221 and a second codebook 241) may be designed and stored in the beamforming device 200 during manufacturing and / or during initial operation.

[0053] In WLAN systems, beamforming can increase antenna gain while maintaining omnidirectional coverage, resulting in increased SNR and more stable, higher-bandwidth WLAN connections by focusing transmissions to the receiver. These benefits are achieved by transmitting signals via an antenna array and slightly altering the phase of the signal at each antenna in the array. For example, the IEEE 802.11ac standard (e.g., the wireless network standard in the 802.11 series developed by the IEEE Standards Association) provides protocols for calibrating antenna arrays to direct signals to any point covered by omnidirectional propagation. Beamforming applicator 100 can be a device that enhances the phase shift of the antenna to generate gain in the desired direction. Beamforming receiver 200 can be a device that is the target of beamforming applicator 100. Beamforming receiver 200 can participate in beamforming but does not enhance the timing of its antenna.

[0054] For beamforming transmission in a WLAN system, the beamforming applicator 100 should first obtain channel information (or channel state information) from the beamforming receiver 200. To obtain the channel information, the beamforming applicator 100 can transmit NDP (or probe packets) through multiple antennas 101. The beamforming receiver 200 can receive the NDP through multiple antennas 201 and obtain the channel information based on the NDP. The received signal can represent the result of passing through the channel, and the relationship between the transmitted signal and the received signal can satisfy Equation 1.

[0055] [Equation 1]

[0056] Y[k]=H[k]S[k]+N[k]

[0057] In Equation 1, Y[k] represents the vector of the received signal, S[k] represents the vector of the transmitted signal (e.g., the vector of the probe signal), H[k] represents the channel matrix representing the frequency response, N[k] represents the noise vector, and k represents the subcarrier index. Each of Y[k] and N[k] can be N r *1 vector, S[k] can be N t *1 vector, H[k] can be N r *N t Matrix. N t N represents the number of antennas 101 in the beamforming device 100. r This indicates the number of antennas 201 in the beamforming device 200.

[0058] The beamforming receiver 200 can use the channel estimator 210 to estimate the channel information H of each subcarrier, and the channel information H can correspond to one of a plurality of channel information ECIs. In addition, when the beamforming receiver 200 operates in feedback mode, the beamforming receiver 200 can perform singular value decomposition (SVD) on the channel information H based on Equation 2.

[0059] [Equation 2]

[0060] H[k]=U[k]∑[k]V[k] H

[0061] In Equation 2, each of U[k] and V[k] represents the identity matrix, ∑[k] is a diagonal matrix including the channel singular values, and V[k]... H Let V[k] be the conjugate transpose of V[k].

[0062] In a WLAN system, to reduce feedback overhead, the beamforming receiver 200 may not directly feed back V[k]. Instead, the beamforming receiver 200 may first perform the phase shift using a diagonal matrix based on Equation 3. Multiply by V[k] to obtain Q[k], where It is the phase value corresponding to the element in the i-th row and j-th column of V[k].

[0063] [Equation 3]

[0064]

[0065] Subsequently, the beamforming receiver 200 can use Givens rotation to compress and feed back the angle values ​​φ and ψ corresponding to the various elements of Q[k]. In other words, the beamforming receiver 200 can quantize the angle values ​​φ and ψ obtained based on Equation 4, and can feed back the quantized angle values ​​to the beamforming applicator 100.

[0066] [Equation 4]

[0067]

[0068] In equation 4, 1 i-1 It can be a vector that includes the element 1. Additionally, And Givens rotation G li (ψ) can be defined as in equations 5 and 6 respectively.

[0069] [Equation 5]

[0070]

[0071] [Equation 6]

[0072]

[0073] In other words, the multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs) fed back from the beamforming receiver 200 to the beamforming applicator 100 may include angle values ​​φ and ψ obtained based on Equation 4.

[0074] Figure 2 and Figure 3 This is a diagram used to describe dual-beamforming feedback.

[0075] Figure 2 This illustrates multiple subcarriers used for signal transmission between a beamforming applicator and a beamforming receiver in a wireless communication system. Figure 2 In the diagram, an arrow represents a subcarrier SC. Figure 3 An example of a wireless communication system that performs dual beamforming feedback is shown, for example, a dimensionality reduction scheme for reducing the size of the beamforming matrix.

[0076] Reference Figure 2 and Figure 3The wireless communication system 20 may include a beamforming applicator 105 and a beamforming receiver 205. The beamforming applicator 105 may include multiple antennas 101, a wideband precoder unit 120, and a subcarrier precoder unit 140. The beamforming receiver 205 may include multiple antennas 201, a channel estimator 210, a wideband precoder calculator 250, a dimensionality reduction unit 230, and a subcarrier precoder calculator 260. The wideband precoder calculator 250 may include a covariance calculator 252, a SVD unit 254, and a compression unit 256. The subcarrier precoder calculator 260 may include a SVD unit 262 and a compression unit 264. The multiple antennas 101 and 201, the channel estimator 210, and the dimensionality reduction unit 230 may be respectively connected to… Figure 1 The multiple antennas 101 and 201, the channel estimator 210, and the dimensionality reduction unit 230 are essentially the same.

[0077] The beamforming receiver 205 can receive NDP or probe packets and can obtain channel information (e.g., channel matrix) H[k] by estimating the channel using the channel estimator 210, where k = 0, 1, ..., N. fft -1. Here, N fft It can represent the number of multiple subcarriers (SC) in a DM symbol.

[0078] The beamforming receiver 205 can divide multiple subcarriers SC into M groups SCG, where M is a natural number greater than or equal to 2, so each group SCG can include Ng (= N fft / M) subcarriers. Beamforming receiver 205 can form a broadband beam with the same value for all groups of SCGs (e.g., broadband beamforming information or broadband beamforming matrix). Beamforming receiver 205 can obtain the broadband beam based on Equation 7 using covariance calculator 252.

[0079] [Equation 7]

[0080]

[0081] The beamforming receiver 205 can perform SVD on the covariance matrix (e.g., Cov[m]) obtained by Equation 7 using the SVD unit 254, and can obtain the identity matrix W of the broadband beam as in Equation 8. WB [m].

[0082] [Equation 8]

[0083] W WB [m] = SVD(Cov[m])

[0084] Beamforming receiver 205 can be used in unit matrix W WBFrom the multiple columns of [m], columns 1 to K can be selected using compression unit 256 based on the Givens rotation pair identity matrix W according to equations 3 to 6. WB [m] Perform compression and obtain the angle values ​​φ and ψ associated with the broadband beam. Here, K can be a design parameter and can be an adjustable parameter.

[0085] Next, the beamforming receiving device 205 can form a subcarrier beam (e.g., subcarrier beamforming information or subcarrier beamforming matrix) for each subcarrier SC.

[0086] First, the beamforming receiver 205 can use the dimension reduction unit 230 to combine the channel matrix H[k] with the identity matrix W of the broadband beam. WB [m] are multiplied, and equivalent channel information (e.g., equivalent channel matrix) can be obtained as in Equation 9.

[0087] [Equation 9]

[0088]

[0089] Equivalent channel matrix The size of H[k] can be reduced compared to the channel matrix H[k]. For example, H[k] can have N... r *N t The size of W, and W WB [m] can have N t The size of *K. Therefore, It can have N r The size of the matrix can be reduced by *K (e.g., dimensionality reduction). For example, when N t =16, N r When H[k] = 2 and K = 8, a 2*8 H[k] of size 2*16 can be generated. Since 2*8 is less than 2*16, the size of the matrix can be reduced.

[0090] Beamforming receiver 205 can use SVD unit 262 to apply the equivalent channel matrix obtained by equation 9. Perform SVD, and the identity matrix W of the subcarrier beam can be obtained as shown in Equation 10. SC [k].

[0091] [Equation 10]

[0092]

[0093] Beamforming device 205 can use compression unit 264 based on Givens rotation pair identity matrix W according to equations 3 to 6. SC [k] performs compression and obtains the angle values ​​φ and ψ associated with the subcarrier beam.

[0094] When feedback is provided for channel information used in beamforming transmission, the beamforming receiver 205 can provide feedback on the angle values ​​φ and ψ of the M broadband beams obtained through the compression unit 256, and can also provide feedback on the N values ​​obtained through the compression unit 264. fft The angle values ​​φ and ψ of each subcarrier beam. Figure 3 In the diagram, the arrows from the broadband pre-encoder calculator 250 to the broadband pre-encoder unit 120 represent the angle values ​​φ and ψ of M broadband beams, and the arrows from the subcarrier pre-encoder calculator 260 to the subcarrier pre-encoder unit 140 represent N... fft The angle values ​​φ and ψ of each subcarrier beam.

[0095] Wideband precoder unit 120 can recover M wideband beams based on angle values ​​φ and ψ fed back from wideband precoder calculator 250, and subcarrier precoder unit 140 can recover N beams based on angle values ​​φ and ψ fed back from subcarrier precoder calculator 260. fft There are M subcarrier beams, and can be based on the recovered M broadband beams and the recovered N fft The channel information is obtained by using subcarrier beams.

[0096] As described above, the broadband beamforming matrix can be determined by beamforming receiver 205 from the covariance matrix of the broadband channel. The broadband bandwidth can depend on channel conditions and MIMO mode. For single-user beamforming, the broadband bandwidth can be approximately 80 MHz. For multi-user beamforming, it may need to be less than approximately 80 MHz (e.g., approximately 5 to 10 MHz per user). After calculating the covariance matrix, the broadband beamforming matrix can be obtained by methods used in compressed beamforming (e.g., SVD). The design parameter K can be determined by beamforming receiver 205 or beamforming applicator 105. For example, in the case of single-user beamforming, K can be determined by beamforming receiver 205. In the case of multi-user beamforming or trigger-based feedback, K can be determined by beamforming applicator 105. The trade-off between complexity and performance influences the choice of K. Various factors include timing, delay spread, bandwidth edge, spatial correlation between antennas, etc.

[0097] According to an example embodiment, the broadband precoder calculator 250 and the subcarrier precoder calculator 260 may be replaced by the first beamforming matrix provider 220 and the second beamforming matrix provider 240, respectively. In other words, the replacement is based on a reference... Figure 2 and Figure 3The described operation calculates and feeds back multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs), and can apply a codebook to at least one of the WBMs and SBMs. Therefore, the computational load and the amount of data to be fed back can be reduced, thus reducing feedback overhead.

[0098] Figure 4A , Figure 4B , Figure 4C , Figure 4D and Figure 5 This is a diagram used to describe the process of designing a codebook used in a beamforming device according to an example embodiment.

[0099] Reference Figure 4A , Figure 4B , Figure 4C , Figure 4D and Figure 5 When generating multiple codebooks, the discrete-time Fourier transform (DFT) codebook can be used as the initial value to execute the Lloyd algorithm.

[0100] For example, the initial DFT codebook w(n) can be obtained based on Equation 11.

[0101] [Equation 11]

[0102]

[0103] In equation 11, N represents the number of codebooks, and B represents the number of columns in each codebook. The j-th vector of the i-th codebook can be derived from... Sure.

[0104] According to the example embodiment, Equation 11 can be used to generate N DFT codebooks. Furthermore, these N DFT codebooks can be used as initial values ​​to execute the Lloyd algorithm.

[0105] In some example embodiments, the Lloyd algorithm can be performed based on the following sequence (1), (2), (3), and (4). First, the Euclidean distance function ED(.) used to perform the Lloyd algorithm can be defined as in Equation 12.

[0106] [Equation 12]

[0107] ED(A, B) = ||AD - B||

[0108] In Equation 12, diag represents the function used to extract the diagonal elements of a matrix, uppercase letters represent the matrix, and lowercase letters represent the columns of the matrix.

[0109] (1) Based on the IEEE D-channel model, multiple (e.g., approximately 10,000) samples of the channel matrix H can be generated. This can be achieved by performing SVD on each sample of the channel matrix H.

[0110] (2) Next, for a given codebook (The initial codebook is a DFT codebook, i=1), and the V samples can be divided into N regions based on Euclidean distance as shown in Equation 13.

[0111] [Equation 13]

[0112]

[0113] (3) Next, for X n (n = 0, 1, ..., N-1), the W with the smallest average Euclidean distance can be calculated as in Equation 13 and can be set as the i-th codebook.

[0114] [Equation 14]

[0115]

[0116] (4) Next, steps (2) and (3) can be repeated until the convergence condition J is met. (i) In equation 15, It can be a set of V, that is

[0117] [Equation 15]

[0118] If J (i) >∈, then i = i+1

[0119] Else, Stop

[0120]

[0121] Figure 4A , Figure 4B , Figure 4C and Figure 4D This illustrates the process of detecting the centroid or geometric center using the Lloyd algorithm. Figure 4A , Figure 4B , Figure 4C and Figure 4D In the diagram, the part marked with a dot (.) represents the centroid of each region, and the part marked with a cross (+) represents the codebook corresponding to each region.

[0122] Figure 4A , Figure 4B , Figure 4C and Figure 4DThe results of the algorithm being iterated once, twice, three times, and fifteen times are shown respectively. As the algorithm is repeated... Figure 4A The five regions R11, R21, R31, R41, and R51 can be changed to Figure 4B The five regions R12, R22, R32, R42 and R52 in the text Figure 4C The five regions R13, R23, R33, R43 and R53 and Figure 4D The five regions R14, R24, R34, R44, and R54 are shown. Furthermore, it can be seen that the centroids of each region match the corresponding codebook and satisfy the convergence condition of Equation 15.

[0123] Figure 5 This illustrates the convergence process under the convergence condition of Equation 15 as the Lloyd algorithm is repeatedly executed. It can be seen that when the Lloyd algorithm is repeated approximately ten times or more, the corresponding codebook converges to the desired optimal codebook.

[0124] Figure 6 It is shown Figure 1 A block diagram illustrating an example of a beamforming device and a wireless communication system. Repeated descriptions will be omitted.

[0125] Reference Figure 6 The wireless communication system 10a includes a beamforming applicator 100 and a beamforming receiver 200a. The beamforming applicator 100 may include a plurality of antennas 101. The beamforming receiver 200a may include 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.

[0126] Figure 6 This example illustrates a codebook utilization scheme applied only to multiple broadband beamforming matrices (WBMs), therefore Figure 6 The configuration of the first beamforming matrix provider 220a in the example can be changed. The beamforming apparatus 100, the plurality of antennas 101 and 201, the channel estimator 210, and the dimensionality reduction unit 230 can be compared with a reference. Figure 1 and Figure 3 The descriptions are essentially the same.

[0127] The first beamforming matrix provider 220a may include a first storage unit (STG) 222 and a first selector (SEL) 224.

[0128] The first storage unit 222 can store multiple first codebooks WCB_1, WCB_2, ..., WCB_N. For example, the multiple first codebooks WCB_1 to WCB_N can be based on a reference. Figure 4A , Figure 4B , Figure 4C , Figure 4D and Figure 5 The Lloyd algorithm described is used for pre-design and pre-storage. For example, the first storage cell 222 may include volatile memory such as dynamic random access memory (DRAM), static random access memory (SRAM), mobile DRAM, etc., and / or non-volatile memory such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, phase-change random access memory (PRAM), resistive random access memory (RRAM), nanofloating gate memory (NFGM), polymer random access memory (PoRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), etc.

[0129] The first selector 224 can select multiple wideband beamforming matrices (WBMs) based on multiple first codebooks WCB_1 to WCB_N. For example, the first selector 224 can select the codebook that can achieve the maximum beamforming gain. For example, based on multiple channel information (ECI), the first selector 224 can select one of the multiple first codebooks WCB_1 to WCB_N as one of the multiple wideband beamforming matrices (WBMs), and the selected first codebook can be used to maximize the power of the channel.

[0130] In some example embodiments, the first selector 224 may select one of a plurality of broadband beamforming matrices (WBMs) based on Equation 16.

[0131] [Equation 16]

[0132]

[0133] In equation 16, W w N represents the selected broadband beamforming matrix. g H[k] represents the number of subcarriers corresponding to a broadband beam, and H[k] represents the channel matrix corresponding to one of the multiple channel information ECIs. H [k] denotes the conjugate transpose of H[k], W i codebook set The i-th codebook (e.g., the i-th codebook among multiple first codebooks WCB_1 to WCB_N), where k represents the index of the multiple subcarriers. The function argmax represents the argument of max (e.g., a function that returns the value that maximizes the function).

[0134] The second beamforming matrix provider 240a may include an SVD unit 242 and a compression unit (COMP) 244.

[0135] SVD unit 242 can perform SVD on multiple equivalent channel information (EECI). Compression unit 244 can compress the output of SVD unit 242. SVD unit 242 and compression unit 244 can be respectively connected to... Figure 3 The SVD unit 262 and compression unit 264 are essentially the same. In other words, when the codebook utilization scheme is applied only to multiple broadband beamforming matrices (WBMs), the second beamforming matrix provider 240a can be implemented in essentially the same way as the subcarrier precoder calculator 260.

[0136] Multiple broadband beamforming matrices (WBMs) provided from the first beamforming matrix provider 220a and multiple subcarrier beamforming matrices (SBMs) provided from the second beamforming matrix provider 240a can be fed back to the beamforming application device 100. For example, a beamforming feedback report (BFR) generated based on the multiple broadband beamforming matrices (WBMs) and the multiple subcarrier beamforming matrices (SBMs) can be fed back to the beamforming application device 100.

[0137] Figure 7 It is shown by Figure 6 A diagram showing an example of a beamforming feedback report generated by the device.

[0138] Reference Figure 7 The Beamforming Feedback Report (BFR) may include Media Access Control (MAC) header information 271, category information 272, Multiple Input Multiple Output (MIMO) control information 273, codebook index information 274a, Compressed Beamforming Report (CBR) information 275a, additional common phase information 276a, and feedback mode information 277a. Figure 7 The beamforming feedback report (BFR) may also include codebook index information 274a, additional common phase information 276a, and feedback mode information 277a.

[0139] Codebook index information 274a may correspond to multiple wideband beamforming matrices (WBMs), and CBR information 275a may correspond to multiple subcarrier beamforming matrices (SBMs). Feedback mode information 277a may represent the first feedback mode of the codebook utilization scheme applied to the multiple wideband beamforming matrices (WBMs).

[0140] Figure 7 The beamforming feedback report (BFR) may not include all information about multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs). Instead, Figure 7 The beamforming feedback report (BFR) may include only some or partial information about multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs). For example, for multiple subcarrier beamforming matrices (SBMs), feedback can be provided through compressed N... fftCBR information 275a (reference) is generated from the angle values ​​φ and ψ of each subcarrier beam. Figure 2 and Figure 3 (Description). For multiple broadband beamforming matrices (WBMs) using a codebook utilization scheme, codebook index information 274a representing the codebooks corresponding to the M broadband beams can be fed back. Therefore, the computational cost and the amount of data to be fed back can be reduced, thus reducing the feedback overhead.

[0141] Additionally, the additional common phase information 276a may include the components of equation 3. Public phase information φ common For calculation accuracy, the common phase information φ of the subcarrier beams is used. common It can be fed back separately along with the angle values ​​φ and ψ.

[0142] Figure 8 It is shown Figure 6 The diagram shows the performance of the beamforming device.

[0143] Reference Figure 8 CASE1 indicates a beamforming receiver that does not perform dual beamforming feedback, and CASE2 indicates a beamforming receiver that does not perform dual beamforming feedback. Figure 2 and Figure 3 The beamforming receiver shown is a beamforming receiver that performs only dual beamforming feedback. CASE3 indicates that... Figure 6 The beamforming receiver 200a shown implements dual beamforming feedback and applies a codebook utilization scheme to multiple broadband beamforming matrices (WBMs). It can be seen that in the beamforming receiver 200a according to the example embodiment, feedback overhead is reduced and data transmission volume is increased.

[0144] Figure 9 It is shown Figure 1 A block diagram of another example of a beamforming device and wireless communication system. Repeated descriptions will be omitted.

[0145] Reference Figure 9 The wireless communication system 10b includes a beamforming applicator 100 and a beamforming receiver 200b. The beamforming applicator 100 may include a plurality of antennas 101. The beamforming receiver 200b may include 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.

[0146] Figure 9 This example illustrates a codebook utilization scheme applied only to multiple subcarrier beamforming matrices (SBMs), therefore Figure 9 The configuration of the second beamforming matrix provider 240b in the example can be changed. The beamforming apparatus 100, the plurality of antennas 101 and 201, the channel estimator 210, and the dimensionality reduction unit 230 can be compared with a reference. Figure 1 and Figure 3 The descriptions are essentially the same.

[0147] The first beamforming matrix provider 220b may include a covariance calculator (COV) 225, an SVD unit 226, and a compression unit 228.

[0148] The covariance calculator 225 can calculate the covariance matrix based on multiple channel information (ECI). The SVD unit 226 can perform SVD on the output of the covariance calculator 225. The compression unit 228 can compress the output of the SVD unit 226. The covariance calculator 225, the SVD unit 226, and the compression unit 228 can be respectively connected to… Figure 3 The covariance calculator 252, SVD unit 254, and compression unit 256 are essentially the same. In other words, when the codebook utilization scheme is applied only to multiple subcarrier beamforming matrices (SBMs), the first beamforming matrix provider 220b can be implemented in essentially the same way as the broadband precoder calculator 250.

[0149] The second beamforming matrix provider 240b may include a second storage unit 246 and a second selector 248.

[0150] The second storage unit 246 can store multiple second codebooks SCB_1, SCB_2, ..., SCB_N. For example, the multiple second codebooks SCB_1 to SCB_N can be based on a reference. Figure 4A , Figure 4B , Figure 4C , Figure 4D and Figure 5 The Lloyd algorithm described is pre-designed and pre-stored. For example, the second storage unit 246 may include volatile memory and / or non-volatile memory.

[0151] The second selector 248 can select multiple subcarrier beamforming matrices (SBMs) based on multiple second codebooks SCB_1 to SCB_N. For example, the second selector 248 can select the codebook that yields the maximum beamforming gain. For example, based on multiple equivalent channel information (EECIs), the second selector 248 can select one of the multiple second codebooks SCB_1 to SCB_N as one of the multiple subcarrier beamforming matrices (SBMs), and the selected second codebook is closest to the multiple equivalent channel information (EECIs).

[0152] In some example embodiments, the second selector 248 may select one of a plurality of subcarrier beamforming matrices (SBMs) based on Equation 17.

[0153] [Equation 17]

[0154]

[0155] In equation 17, W s N represents the selected subcarrier beamforming matrix. g V represents the number of subcarriers corresponding to a broadband beam, ED(.) represents the Euclidean distance function, and V sc [k] represents the identity matrix of the channel matrix corresponding to one of the multiple equivalent channel information EECIs, W i codebook set In the context of the subcarriers, k represents the i-th codebook (e.g., the i-th codebook among multiple second codebooks SCB_1 to SCB_N), and k represents the index of the multiple subcarriers. The function argmin represents the argument of min (e.g., a function that returns the value that minimizes the function).

[0156] Multiple broadband beamforming matrices (WBMs) provided from the first beamforming matrix provider 220b and multiple subcarrier beamforming matrices (SBMs) provided from the second beamforming matrix provider 240b can be fed back to the beamforming application device 100. For example, a beamforming feedback report (BFR) generated based on the multiple broadband beamforming matrices (WBMs) and the multiple subcarrier beamforming matrices (SBMs) can be fed back to the beamforming application device 100.

[0157] Figure 10 It is shown by Figure 9 A diagram showing an example of a beamforming feedback report generated by the device.

[0158] Reference Figure 10 The Beamforming Feedback Report (BFR) may include MAC header information 271, category information 272, MIMO control information 273, codebook index information 274b, CBR information 275b, and feedback mode information 277b. Figure 10 The beamforming feedback report (BFR) may also include codebook index information 274b and feedback mode information 277b.

[0159] Codebook index information 274b may correspond to multiple subcarrier beamforming matrices (SBMs), and CBR information 275b may correspond to multiple broadband beamforming matrices (WBMs). Feedback mode information 277b may represent a second feedback mode for applying the codebook utilization scheme to multiple subcarrier beamforming matrices (SBMs).

[0160] Figure 10 The beamforming feedback report (BFR) may include only partial information from multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs). For example, for multiple broadband beamforming matrices (WBMs), feedback can be provided by compressing the angle values ​​φ and ψ of M broadband beams (refer to...). Figure 2 and Figure 3The generated CBR information 275b (description) is described. For multiple subcarrier beamforming matrices (SBMs) using the application codebook, feedback representation with N is possible. fft The codebook index information for each subcarrier beam is 274 bits. Therefore, the computational load and the amount of data to be fed back can be reduced, thus reducing the feedback overhead.

[0161] Figure 11 and Figure 12 It is shown Figure 1 Block diagrams of beamforming devices and other examples of wireless communication systems are shown. Repeated descriptions will be omitted.

[0162] Reference Figure 11 The wireless communication system 10c includes a beamforming applicator 100 and a beamforming receiver 200c. The beamforming applicator 100 may include a plurality of antennas 101. The beamforming receiver 200c may include 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.

[0163] Figure 11 An example of a codebook utilization scheme is shown for applying both multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs), thus the configurations of the first beamforming matrix provider 220c and the second beamforming matrix provider 240c can be changed. The beamforming apparatus 100, multiple antennas 101 and 201, channel estimator 210, and dimension reduction unit 230 can be used in conjunction with a reference... Figure 1 and Figure 3 The descriptions are essentially the same.

[0164] The first beamforming matrix provider 220c can be connected with Figure 6 The first beamforming matrix provider 220a is substantially the same as that in the second beamforming matrix provider 240c, and may include a first storage unit 222 and a first selector 224. Figure 9 The second beamforming matrix provider 240b is substantially the same as that in the second beamforming matrix provider and may include a second storage unit 246 and a second selector 248.

[0165] The beamforming feedback report generated based on multiple broadband beamforming matrices (WBMs) provided by the first beamforming matrix provider 220c and multiple subcarrier beamforming matrices (SBMs) provided by the second beamforming matrix provider 240c may include MAC header information, category information, MIMO control information, and related information. Figure 7 The first codebook index information corresponding to codebook index information 274a in the codebook, and Figure 10 The codebook index information 274b corresponds to the second codebook index information and the feedback mode information.

[0166] Reference Figure 12 The wireless communication system 10d includes a beamforming applicator 100 and a beamforming receiver 200d. The beamforming applicator 100 may include a plurality of antennas 101. The beamforming receiver 200d may include 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.

[0167] Figure 12 An example is shown of a scheme for selectively and / or adaptively applying codebook utilization to at least one of multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs). Therefore, the beamforming device 200d may also include a feedback mode selector 280, and the configurations of the first beamforming matrix provider 220d and the second beamforming matrix provider 240d may be varied. The beamforming device 100, the multiple antennas 101 and 201, the channel estimator 210, and the dimension reduction unit 230 may be referenced. Figure 1 and Figure 3 The descriptions are essentially the same.

[0168] The beamforming receiver 200d can operate in one of three feedback modes: a first feedback mode, a second feedback mode, and a third feedback mode. In the first feedback mode, one of a plurality of first codebooks 221 can be selected, and the selected first codebook can be output as one of a plurality of broadband beamforming matrices (WBMs). In the second feedback mode, one of a plurality of second codebooks 241 can be selected, and the selected second codebook can be output as one of a plurality of subcarrier beamforming matrices (SBMs). In the third feedback mode, one of a plurality of first codebooks 221 and one of a plurality of second codebooks 241 can be selected, and the selected first codebook and the selected second codebook can be output as one of a plurality of broadband beamforming matrices (WBMs) and a plurality of subcarrier beamforming matrices (SBMs), respectively.

[0169] To select and / or change the feedback mode, the first beamforming matrix provider 220d may include a first processing unit (PU1) 2202 and a second processing unit (PU2) 2204, and the second beamforming matrix provider 240d may include a third processing unit (PU3) 2402 and a fourth processing unit (PU4) 2404. The first processing unit 2202 and the second processing unit 2204 may respectively have... Figure 6 The first beamforming matrix provider 220a and Figure 9 The configuration is substantially the same as that of the first beamforming matrix provider 220b. The third processing unit 2402 and the fourth processing unit 2404 may respectively have the same configuration as... Figure 9 The second beamforming matrix provider 240b and Figure 6The second beamforming matrix provider 240a in the middle has essentially the same configuration.

[0170] The feedback mode selector 280 can select one of a first feedback mode, a second feedback mode, and a third feedback mode based on the characteristics of the channel, and can generate a mode signal MD representing the selected feedback mode. For example, the selected feedback mode can be a feedback mode predicted to have the maximum data transmission volume.

[0171] In some example embodiments, one of the first processing unit 2202 and the second processing unit 2204 may be enabled or activated, and one of the third processing unit 2402 and the fourth processing unit 2404 may be enabled or activated, depending on the feedback mode (e.g., based on the mode signal MD). For example, the first processing unit 2202 may be enabled in both a first feedback mode and a third feedback mode, and the second processing unit 2204 may be enabled in the second feedback mode. Additionally, the third processing unit 2402 may be enabled in both the second and third feedback modes, and the fourth processing unit 2404 may be enabled in the first feedback mode.

[0172] Figure 13 It is shown Figure 12 A block diagram of an example of a feedback mode selector included in a beamforming device.

[0173] Reference Figure 13 The feedback mode selector 280a may include an estimator 282 and a selector 284.

[0174] The estimator 282 can estimate the characteristics of the channel and generate a characteristic signal CCHA representing the estimated channel characteristics. For example, the channel characteristics may include at least one of the following: signal-to-noise ratio (SNR), modulation and coding scheme (MCS), physical data unit (PDU) length, bandwidth (BW), number of spatial streams (Nss), and coding scheme (including binary convolutional coding (BCC) and low-density parity-check (LDPC)).

[0175] Selector 284 can select one of the feedback modes based on the characteristics of the channel (e.g., based on the characteristic signal CCHA) and can generate the mode signal MD.

[0176] In some example embodiments, selector 284 may include a preset or predetermined lookup table (LUT) 286. For example, lookup table 286 may represent the relationship between estimated channel characteristics and feedback modes.

[0177] Figure 14 It is shown Figure 13 A diagram showing examples of lookup tables that can be included in the feedback mode selector.

[0178] Reference Figure 14The example shown is a lookup table 286, where SNR and MCS are used as characteristics of the channel.

[0179] exist Figure 14 In the example, lookup table 286 may include M different MCS cases for each SNR and the data rate for each MCS in the first feedback mode, the second feedback mode, and the third feedback mode.

[0180] For example, for the first SNR SNR_1 and the first MCS to the Mth MCS MCS_1, MCS_2, ..., MCS_M, lookup table 286 may include the data rates RATE_1_1_1, RATE_1_2_1, ..., RATE_1_M_1 under the first feedback mode, the data rates RATE_1_1_2, RATE_1_2_2, ..., RATE_1_M_2 under the second feedback mode, and the data rates RATE_1_1_3, RATE_1_2_3, ..., RATE_1_M_3 under the third feedback mode. Similarly, for the second SNR SNR_2 and the first MCS to the Mth MCS MCS_1, MCS_2, ..., MCS_M, lookup table 286 may include the data rates RATE_2_1_1, RATE_2_2_1, ..., RATE_2_M_1 under the first feedback mode, the data rates RATE_2_1_2, RATE_2_2_2, ..., RATE_2_M_2 under the second feedback mode, and the data rates RATE_2_1_3, RATE_2_2_3, ..., RATE_2_M_3 under the third feedback mode. For the Kth SNR SNR_K and the first MCS to the Mth MCS MCS_1, MCS_2, ..., MCS_M, lookup table 286 may include the data rates RATE_K_1_1, RATE_K_2_1, ..., RATE_K_M_1 under the first feedback mode, the data rates RATE_K_1_2, RATE_K_2_2, ..., RATE_K_M_2 under the second feedback mode, and the data rates RATE_K_1_3, RATE_K_2_3, ..., RATE_K_M_3 under the third feedback mode.

[0181] When the SNR estimated by estimator 282 is greater than SNR_m among SNR_1 to SNR_K and less than or equal to SNR_(m+1), SNR_m can be selected, and the corresponding MCS can be selected from MCS_1 to MCS_M. Among the data rates corresponding to the selected SNR and the selected MCS, the feedback mode corresponding to the maximum data rate (e.g., the data transmission volume is predicted to be maximum) can be selected.

[0182] Figure 15 It is shown Figure 1 A block diagram of another example of a beamforming device and wireless communication system. Repeated descriptions will be omitted.

[0183] Reference Figure 15 The wireless communication system 10e includes a beamforming applicator 100 and a beamforming receiver 200e. The beamforming applicator 100 may include a plurality of antennas 101. The beamforming receiver 200e may include 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 a codebook generator 290.

[0184] Figure 15 An example is shown where the beamforming apparatus 200e also includes a codebook generator 290. The beamforming apparatus 100, the plurality of antennas 101 and 201, the channel estimator 210, the first beamforming matrix provider 220, the dimensionality reduction unit 230, and the second beamforming matrix provider 240 are comparable to those shown in the reference diagram. Figure 1 and Figure 3 The descriptions are essentially the same.

[0185] The codebook generator 290 can design multiple first codebooks 221 and / or multiple second codebooks 241, and can generate codebook information (CBI) representing the designed codebooks. For example, the codebook generator 290 can be based on a reference... Figure 4A , Figure 4B , Figure 4C , Figure 4D and Figure 5 The Lloyd algorithm is described to design the codebook. The codebook information CBI can be provided to the first beamforming matrix provider 220 and the second beamforming matrix provider 240.

[0186] The first beamforming matrix provider 220 and the second beamforming matrix provider 240 can be referred to as follows Figure 6 , Figure 9 , Figure 11 and Figure 12 The implementation.

[0187] In some exemplary embodiments, at least a portion of the elements or components included in the beamforming receiving device according to the exemplary embodiments may be implemented as hardware. For example, at least a portion of the elements or components included in the beamforming receiving device may be included in a computer-based electronic system. In other exemplary embodiments, at least a portion of the elements or components included in the beamforming receiving device according to the exemplary embodiments may be implemented as instruction code or program routines (e.g., software programs). For example, the instruction code or program routines may be executed by a computer-based electronic system and may be stored in any storage device located inside or outside the computer-based electronic system.

[0188] In the beamforming receiving device and wireless communication system according to the example embodiments, dual beamforming feedback can be used when beamforming feedback is performed in feedback mode, and a codebook utilization scheme can be applied to at least one of a plurality of wideband beamforming matrices (WBMs) and a plurality of subcarrier beamforming matrices (SBMs). Furthermore, an adaptive codebook utilization scheme can be implemented to select and / or change the feedback mode based on channel conditions and / or environment. Therefore, the feedback overhead of beamforming feedback can be reduced efficiently, and beamforming feedback can be performed with improved efficiency.

[0189] Figure 16 , Figure 17 and Figure 18 This is a flowchart illustrating a beamforming feedback method according to an example embodiment.

[0190] Reference Figure 16 The beamforming feedback method according to the example embodiment can be executed by a wireless communication system including a beamforming applicator and a beamforming receiver. For example, the beamforming feedback method according to the example embodiment can be executed by a beamforming receiver. The wireless communication system and the beamforming receiver can be as described in reference to... Figures 1 to 15 The implementation.

[0191] In the beamforming feedback method according to the example embodiment, multiple channel information associated with multiple subcarriers is obtained by estimating the channel based on the NDP received from the beamforming apparatus via the channel (operation S100). For example, operation S100 may be performed by... Figure 1 The channel estimator 210 in the middle is executed.

[0192] Multiple broadband beamforming matrices are provided based on multiple channel information (operation S200). For example, operation S200 can be provided by... Figure 1 The first beamforming matrix provider 220 in the process is executed.

[0193] In some example embodiments, when operation S200 is performed, one of a plurality of pre-designed first codebooks can be selected based on multiple channel information, and the selected first codebook can be output as one of a plurality of broadband beamforming matrices. For example, based on multiple channel information, one of a plurality of first codebooks can be selected as one of a plurality of broadband beamforming matrices, and the selected first codebook can be used to maximize the power of the channel. For example, it can be based on a reference Figure 6 Equation 16 describes the selection of one of several broadband beamforming matrices.

[0194] Multiple equivalent channel information corresponding to multiple channel information is generated based on multiple broadband beamforming matrices (operation S300). For example, operation S300 can be performed by... Figure 1 The dimensionality reduction unit 230 in the middle is executed.

[0195] Multiple subcarrier beamforming matrices are provided based on multiple equivalent channel information (operation S400). For example, operation S400 can be provided by... Figure 1 The second beamforming matrix provider 240 in the process is executed.

[0196] In some example embodiments, when operation S400 is performed, one of a plurality of pre-designed second codebooks can be selected based on a plurality of equivalent channel information, and the selected second codebook can be output as one of a plurality of subcarrier beamforming matrices. For example, based on a plurality of equivalent channel information, one of a plurality of second codebooks can be selected as one of a plurality of subcarrier beamforming matrices, and the selected second codebook can be selected because it is closest to the plurality of equivalent channel information. For example, it can be based on a reference Figure 9 Equation 17 describes the selection of one of multiple subcarrier beamforming matrices.

[0197] Multiple broadband beamforming matrices and multiple subcarrier beamforming matrices are fed back to the beamforming application device. For example, the multiple broadband beamforming matrices and multiple subcarrier beamforming matrices can be fed back to the beamforming application device in the form of beamforming feedback reports.

[0198] At least one of multiple broadband beamforming matrices and multiple subcarrier beamforming matrices is selected from multiple pre-designed codebooks. For example, as shown in reference... Figure 6 , Figure 9 and Figure 11 The described scheme can apply a codebook utilization scheme to only multiple broadband beamforming matrices (WBMs), can apply a codebook utilization scheme to only multiple subcarrier beamforming matrices (SBMs), or can apply a codebook utilization scheme to both multiple broadband beamforming matrices (WBMs) and multiple subcarrier beamforming matrices (SBMs).

[0199] Reference Figure 17 In the beamforming feedback method according to the example embodiment, repeated descriptions will be omitted.

[0200] The beamforming receiver's feedback mode is selected based on the characteristics of the channel (operation S500). For example, as referenced... Figure 12 As described, one of a first feedback mode, a second feedback mode, and a third feedback mode can be selected based on the characteristics of the channel, and the selected feedback mode can be the feedback mode predicted to have the maximum data transmission volume. For example, operation S500 can be... Figure 12 The feedback mode selector 280 in the middle is executed.

[0201] Operations S100, S200, S300, and S400 following operation S500 can be referenced. Figure 16 The descriptions are essentially the same.

[0202] Reference Figure 18In the beamforming feedback method according to the example embodiment, repeated descriptions will be omitted.

[0203] Design multiple codebooks (operation S600). For example, refer to... Figure 4A , Figure 4B , Figure 4C , Figure 4D and Figure 5 As described, multiple codebooks can be designed based on the Lloyd algorithm. For example, operation S600 can be performed once during manufacturing and / or during the initial operation of the beamforming receiver, and can be omitted thereafter. For example, operation S600 can be... Figure 15 The codebook generator 290 in the middle is executed.

[0204] Operations S100, S200, S300, and S400 following operation S600 can be referenced. Figure 16 The descriptions are essentially the same.

[0205] In some example embodiments, it is possible to Figure 17 In the example, an additional operation S600 is performed.

[0206] As those skilled in the art will understand, the exemplary embodiments can be implemented as systems, methods, computer program products, and / or computer program products embodied in one or more computer-readable media, on which computer-readable program code is embodied. The computer-readable program code can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. For example, a computer-readable medium can be a non-transitory computer-readable medium.

[0207] Figure 19 This is a block diagram illustrating an electronic device in a network environment according to an example embodiment.

[0208] Reference Figure 19In network environment 300, electronic device 301 can communicate with electronic device 302 via a first network 398 (e.g., a short-range wireless communication network), or with electronic device 304 or server 308 via a second network 399 (e.g., a long-range wireless communication network). In some example embodiments, electronic device 301 can communicate with electronic device 304 via server 308. In some example embodiments, electronic device 301 may include processor 320, memory 330, input device 350, sound output device 355, display device 360, audio module 370, sensor module 376, interface 377, haptic module 379, camera module 380, power management module 388, battery 389, communication module 390, subscriber identification module (SIM) 396, and / or antenna module 397.

[0209] Processor 320 may execute, for example, software (e.g., program 340) to control at least one other component (e.g., hardware or software component) of electronic device 301 coupled to processor 320, and may perform various data processing or calculations. In some example embodiments, processor 320 may include a main processor 321 (e.g., a central processing unit (CPU) or application processor (AP)) and an auxiliary processor 323 (e.g., a graphics processing unit (GPU), image signal processor (ISP), sensor hub processor, or communication processor (CP)) that may operate independently of or in conjunction with the main processor 321.

[0210] The memory 330 may store various data used by at least one component of the electronic device 301 (e.g., processor 320 or sensor module 376). The various data may include, for example, software (e.g., program 340) and input or output data of commands associated therewith. The memory 330 may include volatile memory 332 or non-volatile memory 334.

[0211] The program 340 may be stored as software in the memory 330 and may include, for example, an operating system (OS) 342, middleware 344 and / or application 346.

[0212] Input device 350 can receive commands or data from outside electronic device 301 (e.g., a user) for use by another component of electronic device 301 (e.g., processor 320). Sound output device 355 can output sound signals to outside electronic device 301. Display device 360 ​​can visually provide information to outside electronic device 301 (e.g., to a user).

[0213] Audio module 370 can convert sound into electrical signals and vice versa. Sensor module 376 can detect the operating state of electronic device 301 (e.g., power supply or temperature) or the environmental state outside electronic device 301 (e.g., user state), and then generate electrical signals or data values ​​corresponding to the detected state. Interface 377 can support one or more specified protocols for direct (e.g., wired) or wireless connection of electronic device 301 to external electronic device (e.g., electronic device 302).

[0214] The connection terminal 378 may include a connector via which the electronic device 301 can be physically connected to an external electronic device (e.g., electronic device 302). The haptic module 379 can convert electrical signals into mechanical stimuli (e.g., vibration or movement) or electrical stimuli that can be recognized by a user through their touch or kinesthesia. The camera module 380 can capture still or moving images.

[0215] The power management module 388 manages the power supplied to other components of the electronic device 301. In some example embodiments, the power management module 388 may be implemented as at least part of, for example, a power management integrated circuit (PMIC). The battery 389 may power at least one component of the electronic device 301.

[0216] The communication module 390 can support the establishment of a direct (e.g., wired) or wireless communication channel between the electronic device 301 and an external electronic device (e.g., electronic device 302, electronic device 304, or server 308) and perform communication via the established communication channel. In some example embodiments, the communication module 390 may include a wireless communication module 392 (e.g., a cellular communication module, a short-range wireless communication module, or a Global Navigation Satellite System (GNSS) communication module) or a wired communication module 394 (e.g., a local area network (LAN) communication module or a power line communication (PLC) module).

[0217] In some example embodiments, the wireless communication module 392 included in the communication module 390 may include a beamforming applicator and a beamforming receiver according to an example embodiment, and may be implemented to perform a beamforming feedback method according to an example embodiment. For example, the wireless communication module 392 included in the electronic device 301 may include a beamforming receiver according to an example embodiment (e.g., Figure 1 The beamforming receiving device 200 in the electronic device 304, including the wireless communication module, may include a beamforming applicator (e.g., Figure 1The beamforming receiving device (100) in the electronic device 301 and the beamforming applying device (304) are connected by a second network 399 formed between the electronic devices 301 and 304, which may correspond to a channel between the beamforming receiving device and the beamforming applying device. The beamforming receiving device included in the electronic device 301 can communicate with the beamforming applying device included in the electronic device 304 and can operate based on a codebook utilization scheme and / or an adaptive codebook utilization scheme according to the exemplary embodiment while performing dual beamforming feedback. Similarly, the beamforming receiving device included in the electronic device 304 can communicate with the beamforming applying device included in the electronic device 301 and can operate based on a codebook utilization scheme and / or an adaptive codebook utilization scheme according to the exemplary embodiment while performing dual beamforming feedback.

[0218] Antenna module 397 can send or receive signals or power to or from outside the electronic device 301 (e.g., external electronic device).

[0219] The example embodiments are applicable to various communication devices and systems that perform beamforming, as well as various electronic devices and systems that include communication devices and systems. For example, the example embodiments are applicable to systems such as personal computers (PCs), workstations, mobile phones, smartphones, tablet computers, laptop computers, personal digital assistants (PDAs), portable multimedia players (PMPs), digital cameras, portable game consoles, music players, camcorders, video players, navigation devices, wearable devices, Internet of Things (IoT) devices, Internet of Everything (IoE) devices, e-book readers, virtual reality (VR) devices, augmented reality (AR) devices, robotic devices, drones, and the like.

[0220] The foregoing are illustrative examples and should not be construed as limiting. While some illustrative examples have been described, those skilled in the art will readily understand that many modifications can be made without substantially departing from the novel teachings and advantages of the illustrative examples. Therefore, all such modifications are intended to be included within the scope of the illustrative examples as defined in the claims. It will thus be understood that the foregoing are illustrative of various illustrative examples and should not be construed as limiting oneself to the specific illustrative examples disclosed, and modifications to the disclosed illustrative examples, as well as other illustrative examples, are intended to be included within the scope of the appended claims.

Claims

1. A beamforming receiver, comprising: The processor is configured to implement: A channel estimator is configured to receive empty data packets from a beamforming apparatus via a channel and obtain multiple channel information associated with multiple subcarriers of the channel based on the empty data packets; A first beamforming matrix provider is configured to provide multiple broadband beamforming matrices based on the multiple channel information; A dimensionality reduction unit is configured to generate multiple equivalent channel information corresponding to the multiple channel information based on the multiple broadband beamforming matrices; as well as A second beamforming matrix provider is configured to provide multiple subcarrier beamforming matrices based on the multiple equivalent channel information. The processor is further configured to feed back the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices to the beamforming apparatus. Specifically, any one or any combination of the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are selected from a plurality of codebooks stored in the beamforming receiving device. The beamforming receiver is configured to operate in a first feedback mode, a second feedback mode, and a third feedback mode. In the first feedback mode, one of a plurality of first codebooks is selected as the selected first codebook, and the output of the selected first codebook is used as one of the plurality of broadband beamforming matrices. In the second feedback mode, one of a plurality of second codebooks is selected as the chosen second codebook, and the output of the selected second codebook is used as one of the plurality of subcarrier beamforming matrices. In the third feedback mode, one of the plurality of first codebooks is selected as the selected first codebook and the output of the selected first codebook is used as one of the plurality of broadband beamforming matrices, and one of the plurality of second codebooks is selected as the selected second codebook and the output of the selected second codebook is used as one of the plurality of subcarrier beamforming matrices.

2. The beamforming receiver according to claim 1, wherein, The first beamforming matrix provider is configured to select one of the plurality of first codebooks as the selected first codebook based on the plurality of channel information, and output the selected first codebook as one of the plurality of broadband beamforming matrices.

3. The beamforming receiving apparatus according to claim 2, further comprising a first storage unit configured to store the plurality of first codebooks, in, The processor is also configured to implement a first selector, which is configured to select the selected first codebook to maximize the power of the channel.

4. The beamforming receiver according to claim 3, wherein, The first selector is configured to select the selected first codebook based on the following equation 1: [Equation 1] In equation 1, W w N represents the selected broadband beamforming matrix. g H[k] represents the number of subcarriers corresponding to a broadband beam, and H[k] represents the channel matrix corresponding to one of the multiple channel information. H [k] denotes the conjugate transpose of H[k], W i Let i represent the i-th codebook among the plurality of first codebooks, and k represent the index of the plurality of subcarriers.

5. The beamforming receiver according to claim 3, wherein, The processor is further configured to generate a beamforming feedback report based on the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices, and to control the beamforming receiver to feed back the beamforming feedback report to the beamforming applicator. The beamforming feedback report includes media access control header information, category information, multiple input multiple output control information, codebook index information corresponding to the multiple broadband beamforming matrices, compressed beamforming report information corresponding to the multiple subcarrier beamforming matrices, additional common phase information, and feedback mode information.

6. The beamforming receiver according to claim 3, wherein, The processor is also configured to implement: Singular value decomposition unit, configured to perform singular value decomposition on the plurality of equivalent channel information; and A compression unit is configured to compress the output of the singular value decomposition unit.

7. The beamforming receiver according to claim 1, wherein, The second beamforming matrix provider is further configured to select one of the plurality of second codebooks as the selected second codebook based on the plurality of equivalent channel information, and output the selected second codebook as one of the plurality of subcarrier beamforming matrices.

8. The beamforming receiver according to claim 7, further comprising a second storage unit configured to store the plurality of second codebooks, in, The processor is further configured to implement a second selector, which is configured to select the selected second codebook as the closest to the plurality of equivalent channel information.

9. The beamforming receiver according to claim 8, wherein, The second selector is configured to select the selected second codebook based on the following equation 2: [Equation 2] In equation 2, W s N represents the selected subcarrier beamforming matrix. g V represents the number of subcarriers corresponding to a broadband beam, ED(.) represents the Euclidean distance function, and V sc [k] represents the identity matrix of the channel matrix corresponding to one of the plurality of equivalent channel information, W i Let i represent the i-th codebook among the plurality of second codebooks, and k represent the index of the plurality of subcarriers.

10. The beamforming receiver according to claim 8, wherein, The processor is further configured to generate a beamforming feedback report based on the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices, and to control the beamforming receiver to feed back the beamforming feedback report to the beamforming applicator. The beamforming feedback report includes media access control header information, category information, multiple input multiple output control information, codebook index information corresponding to the multiple subcarrier beamforming matrices, compressed beamforming report information corresponding to the multiple broadband beamforming matrices, and feedback mode information.

11. The beamforming receiver according to claim 8, wherein, The processor is also configured to implement: A covariance calculator is configured to identify the covariance matrix based on the plurality of channel information; A singular value decomposition unit is configured to perform singular value decomposition on the output of the covariance calculator; as well as A compression unit is configured to compress the output of the singular value decomposition unit.

12. The beamforming receiver according to claim 1, wherein: The first beamforming matrix provider is further configured to select one of the plurality of first codebooks as the selected first codebook based on the plurality of channel information, and output the selected first codebook as one of the plurality of broadband beamforming matrices. The second beamforming matrix provider is further configured to select one of the plurality of second codebooks as the selected second codebook based on the plurality of equivalent channel information, and output the selected second codebook as one of the plurality of subcarrier beamforming matrices.

13. The beamforming receiver according to claim 1, wherein, The processor is also configured to implement a feedback mode selector, which is configured to select one of the first feedback mode, the second feedback mode, and the third feedback mode as the selected feedback mode based on the characteristics of the channel, the selected feedback mode being predicted to have the maximum data transmission volume.

14. The beamforming receiver according to claim 13, wherein, The characteristics of the channel indicate any one or any combination of the signal-to-noise ratio, modulation and coding scheme, physical data unit length, bandwidth, number of spatial streams, and coding schemes including binary convolutional coding and low-density parity checking.

15. The beamforming receiver according to claim 1, wherein, The processor is also configured to implement a codebook generator, which is configured to generate the plurality of codebooks.

16. The beamforming receiver according to claim 15, wherein, The codebook generator is configured to generate the plurality of codebooks by executing the Lloyd algorithm using discrete-time Fourier transform codebooks as initial values.

17. The beamforming receiver according to claim 1, wherein, The beamforming receiver is included in a wireless communication system based on a wireless local area network.

18. A beamforming receiver, comprising: The processor is configured to implement: A channel estimator is configured to receive empty data packets from a beamforming apparatus via a channel and obtain multiple channel information associated with multiple subcarriers of the channel based on the empty data packets; A feedback mode selector is configured to select one of a first feedback mode, a second feedback mode, or a third feedback mode as the selected feedback mode based on the characteristics of the channel. A first beamforming matrix provider is configured to generate a plurality of broadband beamforming matrices by performing singular value decomposition and compressing the plurality of channel information based on the selected feedback mode being the second feedback mode, and to select one of a plurality of first codebooks as the selected first codebook based on the plurality of channel information and output the selected first codebook as one of the plurality of broadband beamforming matrices based on the selected feedback mode being the first feedback mode or the third feedback mode. A dimensionality reduction unit is configured to generate multiple equivalent channel information corresponding to the multiple channel information based on the multiple broadband beamforming matrices; as well as A second beamforming matrix provider is configured to generate multiple subcarrier beamforming matrices by performing singular value decomposition and compressing the multiple equivalent channel information, based on the selected feedback mode being the first feedback mode; and to select one of multiple second codebooks as the selected second codebook based on the multiple equivalent channel information, and output the selected second codebook as one of the multiple subcarrier beamforming matrices, based on the selected feedback mode being the second feedback mode or the third feedback mode. The processor is further configured to feed back the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices to the beamforming apparatus, and The codebook index corresponding to the selected first codebook and the selected second codebook is fed back to the beamforming device.

19. A beamforming feedback method for a beamforming receiver, comprising: Multiple channel information associated with multiple subcarriers of the channel is obtained based on empty data packets received from the beamforming device via the channel. Multiple broadband beamforming matrices are provided based on the aforementioned channel information; Based on the multiple broadband beamforming matrices, multiple equivalent channel information corresponding to the multiple channel information is generated; Multiple subcarrier beamforming matrices are provided based on the aforementioned multiple equivalent channel information; as well as The plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are fed back to the beamforming application device. Specifically, any one or any combination of the plurality of broadband beamforming matrices and the plurality of subcarrier beamforming matrices are selected from a plurality of codebooks stored in the memory. The beamforming receiver operates in a first feedback mode, a second feedback mode, and a third feedback mode. In the first feedback mode, one of a plurality of first codebooks is selected as the selected first codebook, and the output of the selected first codebook is used as one of the plurality of broadband beamforming matrices. In the second feedback mode, one of a plurality of second codebooks is selected as the chosen second codebook, and the output of the selected second codebook is used as one of the plurality of subcarrier beamforming matrices. In the third feedback mode, one of the plurality of first codebooks is selected as the selected first codebook and the output of the selected first codebook is used as one of the plurality of broadband beamforming matrices, and one of the plurality of second codebooks is selected as the selected second codebook and the output of the selected second codebook is used as one of the plurality of subcarrier beamforming matrices.

Images