Access point supporting wireless communication and operation method thereof

Abstract

A method of operation of an access point configured to provide wireless communication according to the present invention comprises the steps of: receiving channel response information from an external communication device; generating a beam adjustment matrix based on the channel response information; generating a power allocation matrix based on the average signal-to-noise ratio (SNR) for each of the plurality of streams included in the channel response information; and performing beamforming for the external communication device based on the generated power allocation matrix and the beam adjustment matrix. The channel response information is compressed beamforming feedback of a multiple input multiple output single user beamforming (MIMO SUBF) system, and a first power allocated to a first stream having an average SNR of a first value among the plurality of streams is greater than a second power allocated to a second stream having an average SNR of a second value greater than the first value among the plurality of streams.

Description

Technology Field

[0001] The present invention relates to wireless communication, and more specifically, to an access point that supports wireless communication and a method of operating the same. Background Technology

[0002] Wireless communication provides data communication between various devices via wireless channels. To meet the increasing demand for wireless data traffic, wireless communication is evolving to support higher data transmission rates.

[0003] Recently, wireless communication systems that increase the data transmission rate by using multiple transmission antennas and multiple transmitting antennas (e.g., MIMO; multi-input and multi-output) are used. In addition, beamforming techniques that localize the antenna beam to a specific user are used to improve the efficiency of wireless communication. The problem to be solved

[0004] The objective of the present invention is to provide an access point having improved reliability and improved performance and a method of operating the same. means of solving the problem

[0005] A method of operation for an access point configured to provide wireless communication according to an embodiment of the present invention comprises: receiving channel response information from an external communication device; generating a beam adjustment matrix based on the channel response information; generating a power allocation matrix based on the average signal-to-noise ratio (SNR) for each of the plurality of streams included in the channel response information; and performing beamforming for the external communication device based on the generated power allocation matrix and the beam adjustment matrix. The channel response information is compressed beamforming feedback of a multiple input multiple output single user beamforming (MIMO SUBF) system. A first power allocated to a first stream having an average SNR of a first value among the plurality of streams is greater than a second power allocated to a second stream having an average SNR greater than the first value among the plurality of streams.

[0006] A method of operation of an access point configured to provide wireless communication according to an embodiment of the present invention comprises: receiving channel response information from an external communication device; generating a beam adjustment matrix based on the channel response information; selecting a level of a modulation coding technique; selecting one of a first power allocation matrix and a second power allocation matrix based on the selected level of the modulation coding technique; and performing beamforming for the external communication device based on the selected one of the first and second power allocation matrices and the beam adjustment matrix. Each of the first and second power allocation matrices is generated based on the average signal-to-noise ratio (SNR) for each of the plurality of streams included in the channel response information. The first power allocation matrix has a diagonal matrix structure, and the second power allocation matrix has a block rotation matrix structure. The channel response information is compressed beamforming feedback of a multiple input multiple output single user beamforming (MIMO SUBF) system. The first power assigned to the first stream, in which the average SNR among the plurality of streams is a first value, is greater than the second power assigned to the second stream, in which the average SNR among the plurality of streams is a second value greater than the first value.

[0007] An access point configured to support wireless communication according to an embodiment of the present invention includes: a controller configured to receive channel state information from an external communication device, the channel state information including information on the average signal-to-noise ratio (SNR) for each of a plurality of streams and information on a beam adjustment matrix, and to output a power allocation matrix and a beam adjustment matrix based on the channel state information; a signal processor configured to process data to be transmitted to the external communication device; a power allocation engine configured to perform power allocation for a signal processed by the signal processor based on the power allocation matrix from the controller; a beamforming engine that performs beamforming based on the output of the power allocation engine and the beam adjustment matrix; and a plurality of antennas configured to transmit the output of the beamforming engine to the external communication device. The power allocation engine performs power allocation by applying the power allocation matrix equally to each of a plurality of subcarriers, and the access point performs wireless communication with the external communication device based on multiple input multiple output single user beamforming (MIMO SUBF). Effects of the invention

[0008] According to the present invention, a communication device can generate a power allocation matrix based on the average SNR per stream. Accordingly, in a communication environment where channel characteristics per subcarrier are unknown, the overall packet error performance can be improved by allocating relatively high power to streams having a relatively low average SNR. Thus, a communication device having improved reliability and improved performance and a method of operation thereof are provided. Brief explanation of the drawing

[0009] FIG. 1 is a block diagram illustrating an exemplary wireless communication system according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating the operation of the first communication device of FIG. 1 in an exemplary manner. FIG. 3 is a flowchart illustrating the operation of the wireless communication system of FIG. 1 in an exemplary manner. FIG. 4 is a block diagram exemplarily showing the first and second communication devices of FIG. 1. FIG. 5 is a block diagram exemplarily showing the controller of the first communication device of FIG. 4. Figures 6 and 7 are graphs that exemplarily show packet error performance with the diagonal power matrix applied, as described with reference to Figure 4. FIG. 8 is a block diagram exemplarily showing a controller included in a first wireless device according to an embodiment of the present invention. FIGS. 9 to 11 are graphs for explaining the rotational power matrix generated by the rotational power matrix generator of the controller of FIG. 8. FIGS. 12 and FIGS. 13 are graphs that exemplarily show packet error performance in a configuration with a diagonal power matrix applied, described with reference to FIG. 5, and packet error performance in a configuration with a rotating power matrix applied, described with reference to FIG. 8. FIG. 14 is a block diagram exemplarily showing a controller included in a first communication device according to an embodiment of the present invention. FIG. 15 is a diagram illustrating the operation of a first communication device including the controller of FIG. 14 in an exemplary manner. FIGS. 16 and FIGS. 17 are graphs illustrating the effect of adaptive power allocation in a first communication device including the controller of FIG. 14. FIG. 18 is a block diagram illustrating an exemplary electronic device according to the present invention. Specific details for implementing the invention

[0010] In the following, embodiments of the present invention will be described clearly and in detail so that a person skilled in the art can easily practice the present invention.

[0011] Terms such as "unit," "engine," and "module" used in the detailed description or drawings, or functional blocks performing various operations illustrated in the drawings, may be implemented as software, firmware, hardware circuits, or various combinations thereof.

[0012] FIG. 1 is a block diagram illustrating an exemplary wireless communication system according to an embodiment of the present invention. Referring to FIG. 1, the wireless communication system (10) may include a first communication device (100) and a second communication device (101). In an exemplary embodiment, the first and second communication devices (100, 101) may be one of various electronic devices configured to support wireless communication, such as an access point (AP), a base station, a repeater, a Wi-Fi router, a smartphone, a tablet, a laptop, etc. For convenience of explanation, the first communication device (100) is assumed to be an access point (AP) or a wireless access point (WAP) configured to be connected to a wired network and to provide a wireless network to the second communication device (101). The second communication device (101) is assumed to be a station (e.g., a smartphone, etc.) configured to perform wireless communication with the first communication device (100). In an exemplary embodiment, the first communication device (100) and the second communication device (101) may each be a wireless communication chipset based on a wireless local area network (WLAN) standard or may be included therein. However, the scope of the invention is not limited thereto.

[0013] The first communication device (100) and the second communication device (101) can perform wireless communication through a wireless channel (CH). The first communication device (100) and the second communication device (101) can configure a Multi-Input and Multi-Output Single-User Beamforming (MIMO SUBF) system. For example, the first communication device (100) may include a plurality of first antennas (ANT11~ANT1n), and the second communication device (101) may include a plurality of second antennas (ANT21~ANT2m). The first and second communication devices (100, 101) can perform wireless communication using a plurality of first and second antennas (ANT11~ANT1n, ANT21~ANT2m). At this time, the first communication device (100) can perform beamforming to form an antenna beam based on channel status information (CSI) from the second communication device (101).

[0014] For example, a first communication device (101), which may be an access point (AP), can transmit a sounding packet (e.g., NDP; null data packet) through a plurality of first antennas (ANT11 to ANT1n). The sounding packet from the first communication device (101) can be provided to a plurality of second antennas (ANT21 to ANT2m) of a second communication device (101) via a channel (CH). At this time, the received signal for the k-th subcarrier among the received signals at the second communication device (101) can be modeled as in Equation 1.

[0015]

[0016] Referring to mathematical formula 1, Y k is a received signal received from the second communication device (101), and S k Is N tx It is a sounding signal vector with a magnitude of ×1. At this time, N tx indicates the number of multiple first antennas (ANT11~ANT1n) of the first communication device (100) (i.e., the number of transmitting antennas). E S represents the total power available from a plurality of first antennas (ANT11~ANT1n) of the first communication device (101). H k is a channel matrix indicating the frequency response of a channel (CH), and the size of the channel matrix is N rx × N tx is. At this time, N rx indicates the number of multiple second antennas (ANT21~ANT2m) of the second communication device (101) (i.e., the number of transmitting antennas). N k is the received noise signal. The subscript of k indicates that these are factors relating to the k-th subcarrier. That is, Y k may refer to the received signal for the k-th subcarrier, and since the meaning of the subscripts in the remaining arguments is similar, a detailed explanation thereof is omitted. In the following, unless otherwise defined, the subscript of k may indicate a configuration regarding the k-th subcarrier.

[0017] The second communication device (101) uses a channel estimator to obtain the frequency response of the channel (CH) from the received signal. H k It can be estimated. The second communication device (101) is estimated H k Singular value decomposition (SVD) can be performed on . The result of the singular value decomposition can be as shown in Equation 2.

[0018]

[0019] Referring to mathematical formula 2, U k and V k H Each is a unitary matrix, and is a diagonal matrix containing singular values ​​of the channels (CH). V k H Is V k It is the conjugate transpose matrix of, and V k is a beam adjustment matrix used to perform beam forming.

[0020] In an exemplary embodiment, the second communication device (101) can feed back channel state information (CSI) to the first communication device (100). For example, the first and second communication devices (100, 101) can perform wireless communication based on a predetermined wireless communication protocol. The second communication device (101) can feed back channel state information (CSI) to the first communication device (100) according to the predetermined wireless communication protocol. In an exemplary embodiment, the predetermined wireless communication protocol may be based on at least one of various wireless communication methods such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), SC-FDMA (single carrier frequency division multiple access), NOMA (non-orthogonal multiple access), etc. CDMA can be implemented using radio technology such as UTRA (universal terrestrial radio access) or CDMA2000. TDMA can be implemented using radio technology such as GSM (global system for mobile communications) / GPRS (general packet radio service) / EDGE (enhanced data rates for GSM evolution). OFDMA can be implemented using radio technology such as IEEE 802.11 (Wi-Fi) (e.g., IEEE 802.11ac, IEEE 802.11ax, IEEE 802.11n, etc.), IEEE 802.16 (WiMAX), IEEE 802-20, EUTRA (evolved UTRA), etc.UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is part of E-UMTS (Evolved UMTS) that uses E-UTRA, employing OFDMA in the downlink and SC-FDMA in the uplink. LTE-A (Advanced) is an evolution of 3GPP LTE.

[0021] In an exemplary embodiment, channel state information (CSI) according to a predetermined wireless communication protocol may include information regarding a beam adjustment matrix. The second communication device (101) through singular value decomposition (SVD) described with reference to Equation 2 V k H Calculate , and the calculated V k H Beam adjustment matrix based on ( V k ) can be calculated. The second communication device (101) is a beam adjustment matrix ( V k The complex number elements included in ) can be converted into angle forms, and the converted information can be provided to the first communication device (100) as channel state information (CSI).

[0022] In an exemplary embodiment, channel state information (CSI) according to a predetermined wireless communication protocol may include information on the average signal-to-noise ratio (SNR) per stream. For convenience of explanation, the term "stream" is used below, but "stream" may refer to a channel of data transmitted and received between communication devices, such as a data stream or a spatial stream. The second communication device (101) may calculate information on the average signal-to-noise ratio (SNR) per stream based on Equation 3 and provide the calculated result to the first communication device (100) as channel state information (CSI).

[0023]

[0024] Referring to mathematical formula 3, AvgSNR db,i represents the average signal-to-noise ratio of the i-th stream. N SS indicates the number of streams to be transmitted by the first communication device (100) performing beamforming. σ n 2 represents noise variance. Hereinafter, to facilitate the explanation of the technical concept of the present invention, and for the convenience of explanation unless otherwise noted, the average signal-to-noise ratio of the i-th stream is expressed in linear units and referred to as the average SNR. That is, the average SNR of the i-th stream is "SNR i It can be referred to as ", and SNR i It can be expressed as in Equation 4. Also, for the sake of clarity in the explanation, the term average SNR is used, but average SNR may refer to the individual average signal-to-noise ratio for each of the multiple streams.

[0025]

[0026] The factors of mathematical formula 4 have been explained previously, so a detailed explanation thereof is omitted.

[0027] According to an embodiment of the present invention, a first communication device (100) can perform beamforming based on channel state information (CSI) provided by a second communication device (101). At this time, the first communication device (100) can individually allocate power to each of a plurality of streams based on the average SNR. In this case, the overall efficiency of wireless communication may be improved or the overall packet error performance may be improved.

[0028] For example, some wireless communication protocols (e.g., IEEE 802.11ac, IEEE 802.11ax) support the same modulation and coding techniques for each stream. In this case, if there is a large difference in average SNR between each of the multiple streams, the likelihood of errors occurring in the stream with a relatively small average SNR may increase. This reduces the overall packet error performance. To prevent a reduction in overall packet error performance, power may be allocated differently for each of the multiple streams. For example, the first communication device (100) has a beam adjustment matrix included in the channel state information (CSI) ( V k Beamforming can be performed using ). In an exemplary embodiment, the beam adjustment matrix ( V k ) may be a matrix computed through singular value decomposition. In this case, since the probability of an error occurring is high in a stream with a relatively low average SNR, the first communication device (100) has a power allocation matrix such as Equation 5 ( P k ) can be applied.

[0029]

[0030] Referring to mathematical formula 5, P k represents the power allocation matrix for the k-th subcarrier, and since the remaining arguments have been explained previously, a detailed explanation thereof is omitted. The power allocation method based on Equation 5 is such that the first communication device (100) has channel response characteristics (i.e., channel matrix () for each of the plurality of subcarriers H k Based on the assumption that )) is known, the singular value of the channel (CH) ( It is a method of applying water-filling power allocation or inverse water-filling power allocation using ).

[0031] In an exemplary embodiment, in a specific wireless communication system or a specific wireless communication protocol, the channel state information (CSI) fed back from the second communication device (101) to the first communication device (100) is a beam tuning matrix ( V k It may include only information regarding ) and average SNR per stream. In this case, the first communication device (101) includes singular values ​​for each of the plurality of subcarriers (e.g., Because ) is not received as feedback (in other words, the first communication device (100) has frequency response characteristics for each of the multiple subcarriers, i.e., the channel matrix ( H k Because ) is not recognized), the power allocation method per subcarrier based on mathematical formula 5 may not be applied.

[0032] A first communication device (100) according to an embodiment of the present invention can provide power allocation on a stream-by-stream basis based on the average SNR per stream. That is, in a specific wireless communication system (e.g., MIMO SUBF), even if the access point does not recognize the channel response or singularity per subcarrier, the total data packet error can be reduced by performing power allocation based on the average SNR per stream. The power allocation method of the first communication device (100) according to an embodiment of the present invention is described in more detail with reference to the drawings below.

[0033] FIG. 2 is a flowchart illustrating the operation of the first communication device of FIG. 1. Referring to FIG. 1 and FIG. 2, in step S110, the first communication device (100) may receive channel state information (CSI) from the second communication device (101). For example, the first communication device (100) may be an access point (AP), and the second communication device (101) may be a user terminal that performs wireless communication with the first communication device (100). In this case, the first communication device (100) may transmit a sounding packet. The second communication device (101) may receive the sounding packet from the first communication device (100), calculate information regarding the beam adjustment matrix and information regarding the average SNR per stream based on the received signal, and feed back the calculated information to the first communication device (100) as channel state information (CSI). In an exemplary embodiment, the second communication device (101) can provide feedback of channel status information (CSI) through a channel (CH) or a separate feedback channel.

[0034] In step S120, the first communication device (100) can compare the average SNR per stream included in the channel state information (CSI). In step S130, the first communication device (100) can perform power allocation for each of the streams such that the power allocated to the stream having a relatively small average SNR is relatively increased.

[0035] As described above, according to an embodiment of the present invention, the first communication device (100) can improve overall data packet error performance by relatively increasing the power allocated to a stream having a relatively small average SNR.

[0036] FIG. 3 is a flowchart illustrating the operation of the wireless communication system of FIG. 1. Referring to FIG. 1 and FIG. 3, in step S210, the first communication device (100) can transmit a sounding packet (e.g., NDP; null data packet).

[0037] In step S220, the second communication device (101) has a frequency response of the channel ( H k ) can be estimated. For example, the second communication device (101) receives a sounding packet (NDP) output from the first communication device (100) through a channel (CH), and based on the received signal, the frequency response or channel matrix ( H k ) can be estimated.

[0038] In step S230, the second communication device (101) has an estimated frequency response ( H k By performing singular value decomposition on ), the beam adjustment matrix ( V k ) and average SNR can be calculated. Beam adjustment matrix( V k The calculation process for ) and average SNR has been explained earlier, so a detailed explanation is omitted.

[0039] In step S240, the second communication device (101) has a beam adjustment matrix ( V k Channel state information (CSI) including information on ) and average SNR can be fed back to the first communication device (100).

[0040] In step S250, the first communication device (100) has a power allocation matrix based on information about the average SNR included in the channel state information (CSI). DP ) can be generated. In an exemplary embodiment, the power allocation matrix ( DP ) may be the same value or the same matrix for each of the plurality of subcarriers used in wireless communication between the first and second communication devices (100, 101).

[0041] In an exemplary embodiment, the power allocation matrix ( DP ) may have the form of a diagonal structure or a diagonal matrix, but the scope of the present invention is not limited thereto. For example, the power allocation matrix may have the form of a rotation structure or a rotation matrix. Referring to FIGS. 4 to 7, a power allocation matrix with a diagonal structure ( DP )(hereinafter referred to as the "diagonal power matrix" for convenience of explanation.) is described, and with reference to FIGS. 8 to 13, a power allocation matrix of a rotation structure ( RP )(Referred to as the "rotation power matrix" below for convenience of explanation.) is explained.

[0042] In step S260, the first communication device (100) is a diagonal power matrix ( DP ) and beam tuning matrix( V k Beamforming can be performed based on ). In an exemplary embodiment, the diagonal power matrix according to an embodiment of the present invention ( DP ) and beam tuning matrix(V k When beamforming is performed based on ), the power allocated to streams with a relatively low average SNR becomes relatively higher, thereby improving overall data packet error performance.

[0043] FIG. 4 is a block diagram illustrating the first and second communication devices of FIG. 1 as an example. For the sake of brevity of the drawings and convenience of explanation, the schematic configuration of the first and second communication devices (100, 101) is shown, but the scope of the invention is not limited thereto.

[0044] Referring to FIGS. 1 and FIGS. 4, a wireless communication system (10) may include a first communication device (100) and a second communication device (101). The first and second communication devices (100, 101) may communicate with each other through a channel (or wireless channel) (CH).

[0045] The first communication device (100) may include a signal processor (110), a power allocation engine (120), a beamforming engine (130), a controller (140), and first and second transmitting antennas (TX1, TX2). The second communication device (101) may include a channel estimator (101a), a singular value decomposer (101b), a channel state information extractor (101c), and first and second receiving antennas (RX1, RX2). For the sake of brevity of the drawings and convenience of explanation, the number of transmitting antennas and receiving antennas is depicted as two each, but the scope of the invention is not limited thereto, and the number of transmitting antennas and receiving antennas can be varied in many ways.

[0046] The signal processor (110) can perform various signal processing on data to be transmitted from the first communication device (100) to the second communication device (101). In an exemplary embodiment, the signal processor (110) may include various functional blocks that perform preprocessing on the data, such as an LDPC tone-mapper engine, a per-stream CSD (cyclic shift delay) engine, etc.

[0047] Data or signals processed by the signal processor (110) can be provided to the power allocation engine (120). The power allocation engine (120) is a diagonal power matrix ( generated by the controller) DP Power allocation for processed data or signals can be performed based on ).

[0048] For example, the second communication device (101) may feed back channel state information (CSI) to the first communication device (100). As previously described, the channel state information (CSI) may include information regarding the beam adjustment matrix (Vk) and the average SNR per stream. As a more detailed example, the first and second receiving antennas (RX1, RX2) of the second communication device (101) may receive sounding packets output through the first and second transmitting antennas (TX1, TX2). The channel estimation engine (101a) may, based on the received signal, the frequency response for the channel (CH) H k ) can be estimated. The singular value decomposition engine (101b) can estimate the estimated frequency response characteristics ( H k Through singular value decomposition for ), the beam adjustment matrix ( V k ) can be computed. The channel state information engine (101c) can compute the beam adjustment matrix ( V k Information on the average SNR per stream and channel can be fed back as channel state information (CSI).

[0049] The controller (140) has a diagonal power matrix ( based on feedback channel state information (CSI) DP ) and beam tuning matrix( V k It can generate ). As a more detailed example, the diagonal power matrix ( DP ) can be expressed as in mathematical formula 6.

[0050]

[0051] Referring to Equation 6, DP refers to a diagonal power matrix according to an embodiment of the present invention, and p1 to p Nss represents the diagonal elements of the diagonal power matrix, and SNR1 to SNR Nss Each is the 1st to the Nth SS It indicates the average SNR for each of the streams, and τ and α indicate constant values. In this case, τ can be set so as to satisfy the condition of Equation 7.

[0052]

[0053] The factors of mathematical formula 7 have been explained earlier, so a detailed explanation thereof is omitted.

[0054] α may be a constant that applies the magnitude of the average SNR per stream to the power allocation matrix (DP). In an exemplary embodiment, when α is 1 (i.e., α = 1), it may be considered as inverse power loading. In an exemplary embodiment, the larger the value of α, the more the deviation between the average SNRs per stream is reflected in the power allocation, and the smaller the value of α, the less the deviation between the average SNRs per stream is reflected in the power allocation. In an exemplary embodiment, the constant value of α may be a predetermined value or a value adjusted during the communication process of the wireless communication system (10). In an exemplary embodiment, the constant value of α may be a value greater than 0 and less than 1.

[0055] As described in mathematical formula 6, a diagonal power matrix according to an embodiment of the present invention ( DP ) may have the form of a diagonal structure or a diagonal matrix. For convenience of explanation, as shown in FIG. 4, the number of transmitting antennas and receiving antennas is 2 each, and the number of streams (i.e., N) in wireless communication between the first and second communication devices (100, 101) SS It is assumed that ) has 2. In this case, the diagonal power matrix( DP ) can take the form of a 2×2 diagonal matrix and can be expressed as in mathematical equation 8.

[0056] Referring to mathematical formula 8, SNR1 represents the average SNR for the first stream, and SNR2 may refer to the average SNR for the second stream, and since the remaining arguments have been explained previously, a detailed explanation thereof is omitted. The power allocation matrix of Equation 5 ( P k Unlike ), the diagonal power matrix of mathematical equation 8 ( DP In ), the subscript (k) indicating the subcarrier is omitted. This is the diagonal power matrix ( DP This is because ) is applied equally to each of the multiple subcarriers. That is, the first communication device (100) has the characteristics of each subcarrier of the channel (CH) (e.g., H k Even if ) is not recognized, the diagonal power matrix ( based on information about the average SNR per stream) DP ) can be generated.

[0057] delete

[0058] delete

[0059] Signals processed by the power allocation engine (120) (i.e., the results of the product of the signal processed by the signal processor (110) and the diagonal power matrix (DP)) can be provided to the beamforming engine (130). The beamforming engine (130) can perform beamforming based on the signals provided from the power allocation engine (120). For example, the beamforming engine (130) can obtain a beam adjustment matrix ( V k ) is received, and beamforming is performed based on the received beam adjustment matrix, so that data can be transmitted through the first and second antennas (TX1, TX2).

[0060] In an exemplary embodiment, a series of signal processing steps of the first communication device (100) may be similar to Equation 5, but the diagonal power matrix ( DP The difference may be that ) is applied equally to all of the multiple subcarriers. That is, according to an embodiment of the present invention, the first communication device (100) has a frequency response (CH) for a channel (CH). H k Even if ) is not recognized, generate a diagonal power matrix (DP) based on the average SNR per stream, and the generated diagonal power matrix ( DP Power allocation for each of multiple streams can be performed based on ). In this case, since more power is allocated to streams with a relatively small average SNR, overall packet error performance can be improved.

[0061] FIG. 5 is a block diagram exemplarily showing a controller of the first communication device of FIG. 4. Referring to FIG. 4 and FIG. 5, the controller (140) may include a beam tuning matrix generator (141), a variable calculator (142), a constant calculator (143), and a diagonal power matrix calculator (144). The beam tuning matrix calculator (141) is a beam tuning matrix ( V k Beam adjustment matrix based on information about ) V k It can generate the generated beam adjustment matrix ( V k ) can be provided as a beamforming engine (130).

[0062] The variable calculator (142) can generate a variable (γ) based on the stream-by-stream average SNR included in the channel state information (CSI). In an exemplary embodiment, the variable (γ) may refer to a deviation or ratio on the stream-by-stream average SNRs. For example, as previously described, the number of streams (N) in wireless communication between the first and second communication devices (100, 101) SS If there are 2 variables, the variable (γ) can be SNR1 / SNR2 or SNR2 / SNR1.

[0063] The constant operator (143) is a diagonal power matrix ( DP The constant (α1) required to generate ) can be computed. For example, the constant (α1) is the magnitude of the average SNR per stream in the diagonal power matrix ( DP It may be a constant applied to ). In an exemplary embodiment, the constant (α1) may be determined according to the coding scheme (e.g., MCS; modulation and coding scheme) and channel environment of the wireless communication system (10), or may be a value determined during the manufacturing process of the first communication device (100).

[0064] The diagonal power matrix generator (144) generates a diagonal power matrix based on variables (γ) and a constant (α1). DP ) can be generated. As previously explained, the generated diagonal power matrix ( DP ) is N SS ×N SS It can have the form of a diagonal matrix and can be applied equally to each of multiple subcarriers. The generated diagonal power matrix ( DP ) can be provided as a power allocation engine (120).

[0065] FIGS. 6 and 7 are graphs that exemplarily show packet error performance with the diagonal power matrix described with reference to FIG. 4. The horizontal axes of the graphs in FIGS. 6 and 7 indicate the signal-to-noise ratio, and the vertical axes indicate packet error performance.

[0066] Each of the graphs in FIGS. 6 and FIGS. 7 shows performance indicators for a configuration to which the diagonal power matrix-based power allocation technique according to an embodiment of the present invention is applied and a configuration to which the diagonal power matrix-based power allocation technique according to an embodiment of the present invention is not applied, according to various modulation coding conditions (MSC; modulation coding scheme) (e.g., MCS0~MCS8). For the brevity of the drawings and convenience of explanation, the configuration to which the diagonal power matrix-based power allocation technique according to an embodiment of the present invention is applied is labeled "DPA (Diagonal power allocation)", and the configuration to which the diagonal power matrix-based power allocation technique according to an embodiment of the present invention is not applied is labeled "NoPA (No Power Allocation)".

[0067] The graph in FIG. 6 relates to a wireless communication system in which the number of transmitting and receiving antennas is 2×2 and the number of streams is 2, and the graph in FIG. 7 relates to a wireless communication system in which the number of transmitting and receiving antennas is 4×2 and the number of streams is 2.

[0068] Referring to FIGS. 6 and 7, graphs corresponding to DPA (i.e., graphs relating to configurations to which the power allocation technique of the present invention is applied) have improved packet error performance compared to graphs corresponding to NoPA (i.e., graphs relating to configurations to which the power allocation technique of the present invention is not applied). For example, referring to the performance indicator based on the sixth modulation coding technique (MCS6), the packet error performance of DPA is higher than that of NoPA at the same SNR. Similarly, other modulation coding techniques (e.g., MCS0 to MCS8) may also have a similar difference in packet error performance depending on whether the power allocation technique of the present invention is applied (i.e., DPA has higher packet error performance than NoPA).

[0069] In an exemplary embodiment, in certain modulation coding techniques (e.g., MCS0, MCS1, MCS3, etc.), the packet error performance may show a tendency to decrease as the power allocation technique of the present invention is applied. According to an embodiment of the present invention, the packet error performance in the aforementioned specific modulation coding techniques may be improved by implementing the power allocation matrix in the form of a rotation matrix. Hereinafter, a power allocation matrix having the form of a rotation matrix, i.e., a rotation power matrix ( RP The composition of ) is explained.

[0070] FIG. 8 is a block diagram exemplarily showing a controller included in a first wireless device according to an embodiment of the present invention. FIGS. 9 through 11 are graphs for explaining a rotational power matrix generated by a rotational power matrix generator of the controller of FIG. 8. In an exemplary embodiment, the controller (140) of FIG. 5 has a diagonal power matrix ( DP While generating ), the controller (240) of FIG. 8 generates a rotational power matrix of a rotational structure ( RP Can generate ).

[0071] Referring to FIG. 8, the controller (240) may include a beam-adjustment matrix generator (241), a variable operator (242), a constant operator (243), and a power allocation matrix operator (244). Since the beam-adjustment matrix generator (241) is similar to that described with reference to FIG. 5, a detailed description thereof is omitted.

[0072] The variable calculator (242) can generate a variable (γ) based on information regarding the average SNR per stream included in the channel state information (CSI). In an exemplary embodiment, the variable (γ) may indicate a deviation or ratio on the average SNRs per stream. For example, similar to what was previously described, if the number of streams in wireless communication between the first and second communication devices (100, 101) is two, the variable (γ) may be SNR1 / SNR2 or SNR2 / SNR1 or, (SNR1 / SNR2) 1 / 2 or (SNR2 / SNR1) 1 / 2 It could be.

[0073] The constant operator (243) can generate the constant (α2) required to generate the power allocation matrix (RP). The power allocation matrix generator (244) generates a rotating power matrix ( based on the variable (γ) and the constant (α2). RP ) can be generated. Below, the rotation power matrix ( RP ) is explained in more detail. For the convenience of explanation, the number of streams (N SS It is assumed that ) is 2. The number of streams (N ss ) has 2, and channel characteristics for a specific channel( H Given ), and a singular matrix for a specific channel ( V ) and power allocation matrix( P When ) is applied, the channel capacity (C) may be equal to Equation 9.

[0074]

[0075] Since the arguments of Equation 9 have been explained previously, a detailed explanation thereof is omitted. Referring to Equation 9, the power allocation matrix ( P As such, a diagonal matrix form or a rotation matrix form can be considered. Power allocation matrix ( P ) is a diagonal matrix, that is, a diagonal power matrix( DP In the case of ), PVHH H V H P H The result of has the form of a diagonal matrix. On the other hand, the power allocation matrix ( P ) is the rotation matrix, that is, the rotation power matrix( RP In the case of ), PVHH H V H P H The result may include off-diagonal term values. The off-diagonal value described above acts as inter-stream interference at the receiving end (e.g., the second communication device (101)), and such inter-stream interference can reduce packet error performance.

[0076] In an exemplary embodiment, if the receiving end (e.g., the second communication device (101)) is a maximum likelihood (ML) receiver or includes a successive interference cancellation receiver, inter-stream interference can be eliminated at a low modulation order and a low code rate (e.g., a relatively low level MCS).

[0077] Therefore, if the non-diagonal values ​​of Equation 9 are ignored (e.g., assumed to be 0), the effective transmission amount can be defined. Power allocation matrix ( P ) is the rotation matrix, that is, the rotation power matrix( RP In the case of ), and the diagonal matrix, that is, the diagonal power matrix( DP The effective transmission amount in the case of ) can be expressed as Equation 10 and Equation 11, respectively.

[0078]

[0079]

[0080] Mathematical formula 10 is the rotation power matrix ( RP The first effective transmission amount (Tput) in the case where ) is applied RP Shows ), and Equation 11 is the diagonal power matrix( DP The second effective transmission amount (Tput) when ) is applied DP It shows ). Since the arguments of Equation 10 and Equation 11 have been explained previously, a detailed explanation thereof is omitted.

[0081] In an exemplary embodiment, the graphs of FIGS. 9 and 10 show the first effective transmission amount (Tput) according to the ratio of singular values ​​(ratio = σ1 / σ2). RP ) and the second effective transmission amount (Tput DP These are graphs showing ). In the graph of Fig. 9, the horizontal axis indicates the angle (θ) of Equation 10, and the vertical axis indicates the effective transmission amount (Tput RP It indicates ). The horizontal axis of the graph in Fig. 10 indicates the angle (p1) of Equation 11, and the vertical axis indicates the effective transmission amount (Tput DP It refers to ).

[0082] As illustrated in the graphs of Figures 9 and 10, the larger the ratio of singular values ​​(ratio = σ1 / σ2) (in other words, the larger the difference between singular values), the higher the effective transmission amount of the power allocation matrix (RP) having the form of a rotation matrix.

[0083] In an exemplary embodiment, when a rotational power matrix (RP) is applied, since the non-diagonal values ​​increase together as the effective transmission amount increases, in order to improve overall packet error performance, an appropriate coefficient is used for the rotational power matrix ( RP It must be reflected in ).

[0084] As described above, the rotational power matrix according to the present invention ( RP ) can be expressed as in Equation 12. In an exemplary embodiment, the rotation power matrix of Equation 12 ( RP ) is the number of streams (N SS Rotation power matrix in the case where ) are 2 ( RP Shows the schematic shape of ).

[0085]

[0086] The arguments of Equation 12 have been explained previously, so a detailed explanation thereof is omitted. The values ​​of θ or c in the power allocation matrix (RP) of Equation 12 may be determined or calculated based on information regarding the stream-by-stream average SNR included in the feedback channel state information (CSI). Alternatively, there may exist a predetermined set of candidates for the values ​​of θ or c, and the values ​​of θ or c may be selected from the predetermined set of candidates based on information regarding the stream-by-stream average SNR so that the expected maximum transmission amount for the stream-by-stream average SNR is realized.

[0087] In an exemplary embodiment, the geometric mean decomposition (GMD) of Equation 13 may be used to determine an appropriate θ or c value.

[0088]

[0089] Referring to Equation 13, χ is the inter-stream interference term, and since the remaining factors have been explained previously, a detailed explanation thereof is omitted. In Equation 13, the values ​​of c and s can be defined as shown in Equation 13.

[0090]

[0091] The arguments of Equation 14 have been explained previously, so a detailed explanation thereof is omitted. Referring to Equations 13 and 14, as the ratio of channel singularities (i.e., γ) increases, c (or cosθ) will become smaller. That is, through Equations 13 and 14, it can be confirmed that as the ratio of channel singularities (i.e., γ) increases, more rotation is required to produce the same effective channel gain, and consequently, the inter-stream interference term (χ) increases.

[0092] Based on the above-described mathematical formulas 11 to 14, a rotation power matrix according to an embodiment of the present invention ( RP ) can be defined as in mathematical formula 15.

[0093]

[0094] Since the factors of Equation 15 have been explained previously, a detailed explanation thereof is omitted. Referring to Equation 15, a rotation power matrix according to an embodiment of the present invention ( RP ) can be determined using a value of c based on the average SNR per stream. In an exemplary embodiment, the constant (α) may be a compensation factor for the rotational power matrix (RP). For example, the constant (α) may be a factor to compensate for the fact that, unlike the GMD method applied to each subcarrier at the transmitter (i.e., beamformer), the power allocation matrix (RP) in the form of a rotational matrix is ​​applied equally to all subcarriers.

[0095] In an exemplary embodiment, the constant (α) can be determined such that optimal packet error performance can be achieved. For example, referring to FIG. 11, the graph in FIG. 11 shows the packet error performance for the constant (α2) in a configuration where a rotation power matrix (RP) is applied (i.e., RPA; rotation power allocation) and a configuration where no power allocation is applied (i.e., NoPA). As illustrated in FIG. 11, when the constant (α2) is a first value (V1), the packet error performance may be optimal, and the first value (V1) may be determined as the constant (α2) for the power allocation matrix (RP).

[0096] As described above, the first communication device according to an embodiment of the present invention has a power allocation matrix based on stream-specific average SNR information ( DP or RP Generate ) and the generated power allocation matrix( DP or RP ) can be applied equally to all multiple subcarriers. In this case, by allocating relatively high power to streams with relatively low average SNR, the probability of error occurring in streams with relatively low average SNR can be reduced, and as a result, overall packet error performance can be improved.

[0097] In an exemplary embodiment, in the embodiments described above, the number of streams (N SS Although it has been described that ) is 2, the scope of the present invention is not limited thereto. For example, the number of streams (N SS If ) is more than 2, a power allocation matrix can be generated based on a configuration similar to that described above. For example, a diagonal power matrix ( DP ) is the number of streams (N SS Even if ) is more than 2, a diagonal power matrix in the form of a diagonal matrix based on mathematical formula 6 ( DP ) can be generated.

[0098] On the other hand, the number of streams (N SS If ) is more than 2, rotation power matrix( RP ) can be implemented using a unitary matrix or a block diagonal rotation matrix. For example, if the number of streams (NSS) is greater than 2 and beamforming based on Singular Value Decomposition (SVD) is applied, SNR1 > SNR2 > … Nss The condition is satisfied. In this case, by applying a 2×2 rotation matrix in units of 2 streams, the rotation power matrix ( RP ) can be generated. In this case, since the average packet error is predominantly determined by the performance of the stream with the lowest average SNR, a pair is formed with the stream having the highest average SNR to allocate the maximum amount of power to the stream with the lowest average SNR, and the formed pair can be applied to the rotation matrix. For example, N SS When α is 3, rotation power matrix ( RP ) can be expressed as in mathematical equation 16, and N SS When α is 4, rotation power matrix ( RP ) can be expressed as in mathematical formula 17.

[0099]

[0100]

[0101] In Equations 16 and 17, the left matrix (i.e., the matrix with elements 0 and 1) is a permutation matrix and is a matrix for forming pairs of streams. In Equation 16, the value of c can be determined by the difference of the pair (SNR1, SNR3). In Equation 17, the value of c1 can be determined by the difference of the pair (SNR1, SNR4), and the value of c2 can be determined by the difference of (SNR2, SNR3).

[0102] As a more general configuration, the rotation power matrix (RP) can be defined as in Equation 18.

[0103]

[0104]

[0105]

[0106]

[0107]

[0108] Referring to Equation 18, RP represents the rotational power matrix, and PM is N SS ×N SS Refers to an identity matrix of size R1 to R Nss / 2 represents a 2×2 rotation matrix (i.e., the structure of the rotation power matrix in Fig. 14). R1 ​​to R Nss / 2 The values ​​of (e.g., the value of c) can be determined based on pairs of average SNRs for two streams, as previously explained. That is, if the number of streams (Nss) is odd, the number of R in RM is (N SS If -1) / 2 and the number of streams (Nss) is even, the number of Rs in RM is N SS / It can be 2. R1 to R Nss / 2 The method of constructing the 2×2 rotation matrix is ​​similar to that described earlier, so a detailed explanation of it is omitted.

[0109] As described above, the number of streams (N SS Even if ) is greater than 2, pairs of streams are generated based on the average SNR per stream, and the values ​​of c can be determined based on the difference in SNR of the generated pairs. Based on the determined values ​​of c, the rotation power matrix ( RP ) can be generated.

[0110] FIGS. 12 and FIGS. 13 are graphs that exemplarily show packet error performance in a configuration with a diagonal power matrix applied, as described with reference to FIG. 5, and packet error performance in a configuration with a rotating power matrix applied, as described with reference to FIG. 8. The horizontal axes of the graphs in FIGS. 12 and FIG. 13 indicate the signal-to-noise ratio, and the vertical axes indicate packet error performance.

[0111] Each of the graphs in FIGS. 12 and 13 is a diagonal power matrix ( DP ) and rotation power matrix( RP It shows the packet error performance in a configuration where ) is applied. The graph in FIG. 12 relates to a wireless communication system in which the number of transmitting and receiving antennas is 2×2 and the number of streams is 2, and the graph in FIG. 13 relates to a wireless communication system in which the number of transmitting and receiving antennas is 3×2 and the number of streams is 2.

[0112] Referring to FIGS. 12 and 13, the graphs referred to as "DPA (diagonal power allocation)" are diagonal power matrices ( DP Refers to a configuration to which ) is applied, and the graphs referred to as "RPA (rotation power allocation)" are rotation power matrices ( RP Refers to a configuration to which ) is applied.

[0113] In some modulation coding techniques, DPA may have improved packet error performance than RPA, while in other modulation coding techniques, RPA may have improved packet error performance than DPA. For example, as illustrated in FIGS. 12 and 13, in the case of the seventh modulation coding technique (MSC7), DPA has improved packet error performance than RPA for the same SNR. On the other hand, in the case of the first modulation coding technique (MCS1), RPA has improved packet error performance than DPA.

[0114] This is the diagonal power matrix ( in the case of DPA) DP Since ) has a diagonal matrix form, it does not generate inter-stream interference. Accordingly, DPA has improved packet error performance compared to RPA in relatively high-level modulation coding techniques (e.g., MCS6, MCS7, MCS8, etc.). On the other hand, in the case of RPA, the rotation power matrix ( RP Because it has a rotation matrix form, it causes inter-stream interference. However, since RPA can produce a relatively higher effective SNR, it has improved packet error performance compared to DPA in modulation coding techniques with relatively low code rates (e.g., MSC0, MCS1, MCS3, etc.).

[0115] FIG. 14 is a block diagram illustrating, in an exemplary manner, a controller included in a first communication device according to an embodiment of the present invention. In an exemplary embodiment, the controller (340) of FIG. 14 may be applied to or included in the first communication device (100) described with reference to FIG. 1 and FIG. 2. Referring to FIG. 14, the controller (340) may include a beam adjustment matrix generator (341), a variable operator (342), a constant operator (343), and a power allocation matrix operator (344).

[0116] The beam adjustment matrix generator (341) generates a beam adjustment matrix based on channel state information (CSI). V k ) can be generated. The beam adjustment matrix generator (341) has been described previously, so a detailed description thereof is omitted.

[0117] The variable calculator (342) can generate a variable (γ) based on information about the average SNR per stream included in the channel state information (CSI). In an exemplary embodiment, the variable (γ) is the previously described diagonal power matrix ( DP ) or rotation power matrix( RP It may be information necessary to generate ). The variable (γ) may be a deviation, difference, or ratio for the average SNR of each of the multiple streams. Since the configuration of the variable (γ) according to the form of the power allocation matrix (DP or RP) has been described previously, a detailed explanation thereof is omitted.

[0118] The constant operator (343) is a power allocation matrix ( DP or RP A constant (α1 or α2) required to generate ) can be generated. In an exemplary embodiment, the constant operator (343) can output one of the constants (α1, α2) based on information about the modulation coding technique (MCSx) determined by the modulation coding technique discriminator (345).

[0119] The modulation coding technique discriminator (345) can select a modulation coding technique (MSCx) to be used in wireless communication based on channel state information (CSI). For example, in standards such as IEEE 802.11 of WLAN (wireless LAN), the modulation coding technique can be determined through various combinations of spatial streams, modulation types, coding rates, etc.

[0120] The power allocation matrix generator (344) generates a diagonal power matrix ( based on the modulation coding technique (MSCx) selected by the modulation coding technique discriminator (345). DP ) and rotation power matrix( RP You can output any one of the following.

[0121] For example, as described with reference to FIGS. 6 and 7, in some modulation coding techniques, diagonal power matrix ( DP A configuration (i.e., DPA) with ) applied can degrade packet error performance. Or, as described with reference to FIGS. 12 and 13, in some modulation coding techniques, DPA has relatively improved packet error performance, and in some other modulation coding techniques, the rotation power matrix ( RP A configuration with ) applied (i.e., RPA) can have relatively improved packet error performance. That is, by selectively applying either DPA or RPA depending on the modulation coding technique, the overall packet error performance of the wireless communication system can be improved.

[0122] FIG. 15 is a diagram exemplarily showing the operation of a first communication device including the controller of FIG. 14. For convenience of explanation, the operation according to the flowchart of FIG. 15 is described with reference to the first communication device (100) of FIG. 2. At this time, the first communication device (100) may include the configuration of the controller (340) of FIG. 14. That is, the first communication device (100) according to a modulation coding technique, a diagonal power matrix ( DP ) or rotation power matrix( RP ) can be used optionally.

[0123] Referring to FIGS. 1, FIGS. 14, and FIGS. 15, in step S310, the first communication device (100) can receive channel status information (CSI) from the second communication device (101).

[0124] In step S320, the first communication device (100) may select a level of modulation coding technique based on channel state information (CSI). However, the scope of the present invention is not limited thereto, and the first communication device (100) may select a level of modulation coding technique based on various information required in a wireless communication environment or other various information fed back from the second communication device (101).

[0125] In step S330, the first communication device (100) can make a diagonal selection based on the selected level of the modulation coding technique. For example, the first communication device (100) can select one of the power allocation matrix (DP) of the diagonal matrix and the power allocation matrix (RP) of the rotation matrix that corresponds to the selected level of the modulation coding technique.

[0126] In step S340, the first communication device (100) can perform beamforming based on the selected power allocation matrix.

[0127] As described above, according to embodiments of the present invention, overall packet error performance can be improved by selectively or adaptively applying DPA or RPA depending on the level of modulation coding techniques used in a wireless communication system. In an exemplary embodiment, the exemplary configuration of modulation coding techniques and the power allocation technique applied accordingly may be as shown in Table 1.

[0128] MCS Index Spatial Streams Modulation Type Coding Rate Adaptive PA 0 1 BPSK 1 / 2 RPA 1 1 QPSK 1 / 2 RPA 2 1 QPSK 3 / 4 DPA or (RPA in 2×2) 3 1 16QAM 1 / 2 RPA (α=0) 4 1 16QAM 3 / 4 DPA 5 1 64QAM 2 / 3 DPA 6 1 64QAM 3 / 4 DPA 7 1 64QAM 5 / 6 DPA

[0129] Referring to Table 1, the number of spatial streams, the modulation type, and the coding rate may differ depending on the level of the modulation code technique (e.g., MCS Index). In an exemplary embodiment, among the various levels of the modulation code technique, if the coding rate is relatively large, DPA may be applied, and if the coding rate is relatively small, RPA may be applied. For example, MCS0, MCS1, and MCS3 may have a relatively small coding rate (e.g., 1 / 2), and MCS2, MCS4, MCS5, MCS6, and MCS7 may have a relatively large coding rate (e.g., 3 / 4, 2 / 3, 5 / 6, etc.). In this case, if one of MCS0, MCS1, and MCS3 having a relatively low coding rate is selected as the level of the modulation coding technique, the first communication device (100) has a rotation power matrix ( RP Power allocation or beamforming can be performed based on ), and when one of MCS2, MCS4, MCS5, MCS6, and MCS7 having a relatively high coding rate is selected as the level of the modulation coding technique, the first communication device (100) is a diagonal power matrix ( DP Power allocation or beamforming can be performed based on ). That is, if the coding rate corresponding to the level of the determined modulation coding technique is greater than the reference value, the diagonal power matrix ( DP ) can be selected, and if the corresponding coding rate is not greater than the reference value, the rotation power matrix ( RP ) may be selected. However, the scope of the present invention is not limited thereto. For example, even if the level of the modulation coding technique is the same, DPA or RPA may be selectively applied depending on the communication environment or antenna configuration, etc. For example, when MCS2 is selected as the level of the modulation coding technique, the first communication device (100) has a diagonal power matrix ( DP ) can be selected. In this case, if the transmitting antenna and receiving antenna are configured as 2×2, the diagonal power matrix ( DP Instead of ) rotation power matrix( RP ) can be selected. That is, the first communication device (100) can selectively apply DPA or RPA based on the level of the modulation coding technique, the communication environment, the antenna configuration, etc.

[0130] In an exemplary embodiment, the diagonal power matrix ( DP ) or rotation power matrix( RP The configuration for selectively applying ) can be determined through various prior evaluations or actively adjusted through the measurement and evaluation of SNR or effective transmission amount during the communication process of the wireless communication system.

[0131] As described above, according to embodiments of the present invention, a first communication device (e.g., an access point) can generate a power allocation matrix based on the average SNR for each of a plurality of streams and perform beamforming based thereon. That is, even if the first communication device (e.g., an access point) does not recognize the channel characteristics for each of a plurality of subcarriers, power allocation for each of a plurality of streams can be performed based on the average SNR for each of a plurality of streams. In this case, by allocating relatively large power to streams having a relatively low average SNR, overall packet error performance can be improved.

[0132] In an exemplary embodiment, according to embodiments of the present invention, a power allocation matrix generated in a first communication device (e.g., an access point) may have a diagonal matrix structure or a rotated matrix structure. In this case, the first communication device, based on a selected level of a modulation coding technique, has a diagonal power matrix ( DP ) or rotation power matrix( RP ) can be applied selectively.

[0133] FIGS. 16 and FIGS. 17 are graphs illustrating the effect of adaptive power allocation in a first communication device including the controller of FIG. 14. The horizontal axes of the graphs in FIGS. 16 and FIGS. 17 indicate the signal-to-noise ratio, and the vertical axes indicate packet error performance.

[0134] Each of the graphs in FIGS. 16 and FIGS. 17 shows performance indicators for a configuration to which the power allocation technique described with reference to FIGS. 14 and FIGS. 15 (i.e., the adaptive application of the diagonal power matrix (DP) and the rotational power matrix (RP) according to the MCS level, hereinafter referred to as adaptive power allocation (APA) for convenience of explanation) is applied, and a configuration to which adaptive power allocation is not applied (i.e., NoPA), according to various modulation coding conditions (MSC; modulation coding scheme) (e.g., MCS0 to MCS8). For the sake of brevity of the drawings and convenience of explanation, a configuration to which the adaptive power allocation technique according to an embodiment of the present invention is applied is labeled "APA (Adaptive power allocation)", and a configuration to which the adaptive power allocation technique is not applied is labeled "NoPA (No Power Allocation)".

[0135] As illustrated in the graphs of FIGS. 16 and 17, the configuration to which the adaptive power allocation technique according to the present invention is applied (i.e., APA) exhibits improved packet error performance across all MCS levels compared to the configuration to which the adaptive power allocation technique is not applied (i.e., NoPA). This is because, as previously described, power allocation is performed without causing inter-stream interference by using a diagonal power matrix (DP) at MCS levels with a relatively high coding rate, and power allocation is performed to generate an improved effective SNR by using a rotating power matrix (RP) at MCS levels with a relatively low coding rate.

[0136] As described above, according to an embodiment of the present invention, the overall packet error performance can be improved by selectively applying a power allocation matrix according to the MCS level.

[0137] FIG. 18 is a block diagram illustrating an exemplary electronic device according to the present invention. Referring to FIG. 18, the electronic device (1000) may include a main processor (1100), a touch panel (1200), a touch driving circuit (1202), a display panel (1300), a display driving circuit (1302), a system memory (1400), a storage device (1500), an image processor (1600), a communication block (1700), an audio processor (1800), and a power management circuit (1900). In an exemplary embodiment, the electronic device (1000) may be one of various electronic devices such as a mobile communication terminal, a PDA (Personal Digital Assistant), a PMP (Portable Media Player), a digital camera, a smartphone, a tablet computer, a laptop computer, a wearable device, etc., or one of various communication devices that support wireless communication mediation, such as a wireless router, a wireless communication base station, etc. In an exemplary embodiment, the electronic device (1000) may include additional components other than those shown in FIG. 18, or some of the components shown in FIG. 18 may be omitted from the electronic device (1000).

[0138] The main processor (1100) can control the overall operations of the electronic device (1000). The main processor (1100) can control / manage the operations of the components of the electronic device (1000). The main processor (1100) can process various operations to operate the electronic device (1000).

[0139] The touch panel (1200) may be configured to detect touch input from a user under the control of the touch driving circuit (1202). The display panel (1300) may be configured to display image information under the control of the display driving circuit (1302).

[0140] The system memory (1400) can store data used for the operation of the electronic device (1000). For example, the system memory (1400) may include volatile memory such as SRAM (Static Random Access Memory), DRAM (Dynamic RAM), SDRAM (Synchronous DRAM), and / or non-volatile memory such as PRAM (Phase-change RAM), MRAM (Magneto-resistive RAM), ReRAM (Resistive RAM), FRAM (Ferro-electric RAM).

[0141] The storage device (1500) can store data regardless of power supply. For example, the storage device (1500) may include at least one of various non-volatile memories such as flash memory, PRAM, MRAM, ReRAM, FRAM, etc. For example, the storage device (1500) may include built-in memory and / or removable memory of the electronic device (1000).

[0142] The audio processor (1600) can process audio signals using the audio signal processor (1610). The audio processor (1600) can receive audio input through the microphone (1620) or provide audio output through the speaker (1630).

[0143] The communication block (1700) can exchange signals with an external device / system through an antenna (1710). The transceiver (1720) and MODEM (Modulator / Demodulator, 1730) of the communication block (1700) can process signals exchanged with an external device / system according to at least one of various wireless communication protocols such as LTE (Long Term Evolution), WiMax (Worldwide Interoperability for Microwave Access), GSM (Global System for Mobile communication), CDMA (Code Division Multiple Access), Bluetooth, NFC (Near Field Communication), Wi-Fi (Wireless Fidelity), and RFID (Radio Frequency Identification). In an exemplary embodiment, the antenna (1710) of the communication block (170) may include a plurality of antennas and can perform MIMO-based communication with an external communication device. In an exemplary embodiment, when the electronic device (1000) operates as an access point (AP), the communication block (1700) can perform stream-by-stream power allocation based on the method or structure described with reference to FIGS. 1 through 15.

[0144] The image processor (1800) can receive light through the lens (1810). The image device (1820) and image signal processor (1830) included in the image processor (1800) can generate image information regarding an external object based on the received light.

[0145] The power management circuit (1900) can be configured to receive power from a battery or other power source and to provide power to the main processor (1100) or various other components.

[0146] The above description describes specific embodiments for implementing the present invention. The present invention will include not only the embodiments described above, but also embodiments that can be simply modified or easily modified. Furthermore, the present invention will include technologies that can be easily modified and implemented using the embodiments. Accordingly, the scope of the present invention should not be limited to the embodiments described above, but should be defined by the claims set forth below as well as equivalents to the claims of this invention.

Claims

Claim 1 A method of operation for an access point configured to provide wireless communication, comprising: receiving channel response information from an external communication device; generating a beam adjustment matrix based on the channel response information; generating a power allocation matrix based on the average signal-to-noise ratio (SNR) for each of a plurality of streams included in the channel response information; and performing beamforming for the external communication device based on the generated power allocation matrix and the beam adjustment matrix, wherein the channel response information is compressed beamforming feedback of a multiple input multiple output single user beamforming (MIMO SUBF) system, and a first power allocated to a first stream having a first average SNR value among the plurality of streams is greater than a second power allocated to a second stream having a second average SNR value greater than the first value among the plurality of streams. Claim 2 In claim 1, the power allocation matrix is ​​applied equally to each of the plurality of subcarriers. Claim 3 In claim 1, the power allocation matrix is ​​generated based on a ratio and a constant value between the average SNRs for each of the plurality of streams. Claim 4 A method of operation in which, in claim 1, the power allocation matrix is ​​a first power allocation matrix having the structure of a diagonal matrix or a second power allocation matrix having the structure of a rotation matrix. Claim 5 A method of operation according to claim 4, further comprising the step of determining the level of a modulation and coding scheme (MCS) used in wireless communication with the external communication device. Claim 6 In claim 5, the operation method wherein the power allocation matrix is ​​determined as one of the first power allocation matrix and the second power allocation matrix based on the determined level of the modulation coding technique. Claim 7 A method of operation according to claim 6, wherein if the coding rate corresponding to the determined level of the modulation coding technique is greater than the reference value, the power allocation matrix is ​​determined as the first power allocation matrix, and if the coding rate corresponding to the determined level of the modulation coding technique is not greater than the reference value, the power allocation matrix is ​​determined as the second power allocation matrix. Claim 8 In claim 4, where the number of the plurality of streams is Nss, provided that Nss is a positive integer, the power allocation matrix is ​​a diagonal matrix of size Nss × Nss, and the power allocation matrix is ​​defined based on Equation 1, [Equation 1] The DP in the above mathematical formula 1 is the power allocation matrix, and the SNR1 to SNR Nss A method of operation in which each indicates the average SNR for the plurality of streams, and τ and α are constant values. Claim 9 In claim 8, the α in the above mathematical formula 1 is a value greater than 0 and less than 1, and the τ in the above mathematical formula 1 is defined to satisfy mathematical formula 2, and [mathematical formula 2] is a method of operation. Claim 10 In claim 4, where the number of the plurality of streams is Nss, provided that Nss is a positive integer, the power allocation matrix is ​​a block rotation matrix of size Nss × Nss, and the power allocation matrix is ​​defined based on Equation 3, [Equation 3] In the above mathematical formula 3, RP refers to the power allocation matrix, and PM is N SS ×N SS It is a permutation matrix of size R1 to R Nss / 2 is a method of operation that is a 2×2 rotation matrix.

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