KR101447027B1 - Apparatus and method for beam forming in a multiple antenna system - Google Patents

Abstract

The present invention relates to a beamforming apparatus and method for a multi-antenna system, and a method for beamforming according to the present invention includes the steps of: (a) receiving a received signal through a plurality of antennas; (b) estimating channel information by decomposing a covariance matrix of the received signal, and obtaining a reception beamforming vector of the received signal based on the channel information; And (c) performing reception beamforming on the reception signal using the reception beamforming vector. In this way, even when an unspecified signal is received, channel information is estimated, and reception beamforming is performed using the calculated reception beamforming vector based on the estimated channel information, thereby improving the signal reception sensitivity.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a beamforming apparatus and method for a multi-

The present invention relates to a beamforming apparatus and method for a multi-antenna system for improving reception performance of an unspecified signal.

2. Description of the Related Art [0002] In recent years, research on a Multiple Input Multiple Output (MIMO) system has been actively conducted as a method for improving system performance and maximizing communication capacity while using the same frequency resources and power in a wireless communication environment.

A multi-input / output system is a multi-input / output antenna system that can improve transmission efficiency of transmission / reception data by adopting multiple transmission antennas and multiple reception antennas by avoiding use of a single transmission antenna and a reception antenna.

Transmit diversity, spatial multiplexing, and beamforming are examples of the multi-input / output system technology. The purpose of dual beamforming is to increase the SINR (Signal to Interference plus Noise Ratio) of a signal by applying a weight according to the channel state in multiple antennas.

The receive beamforming, which is a type of beamforming, is performed to improve the reception performance of a signal by matching the phase of the receiving end to the signal received when a signal is received by the multiple input / output system. The received beamforming is performed by multiplying the received signal by a received beamforming vector Lt; / RTI >

Most of the conventional reception beamforming techniques assume a wireless communication environment in which the communication standard between the transmitter and the reception period is fixed and basic radio signal information is mutually shared. Therefore, it is difficult to apply the conventional reception beamforming technique when the information on the received signal is unknown. For example, when an electronic warfare is performed, a receiver for Electronic Warfare Support (ES) receives information about a signal such as a signal transmitted from an enemy group, that is, an unspecified Most of them receive a signal. In this case, since it is impossible to estimate the information of the radio channel, there is a difficulty in improving the signal reception performance by using the conventional reception beamforming technique. A conventional beamforming apparatus for a multi-antenna system is disclosed in Korean Patent Application No. 10-2004-0054565.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a beamforming apparatus and method for a multi-antenna system capable of improving reception performance even in a wireless environment receiving an unspecified signal.

According to an aspect of the present invention, the above-mentioned object can be achieved by a method comprising: (a) receiving a received signal through a plurality of antennas; (b) estimating channel information by decomposing a covariance matrix of the received signal, and obtaining a reception beamforming vector of the received signal based on the channel information; And (c) performing reception beamforming on the reception signal using the reception beamforming vector.

The channel information may be estimated by removing a noise signal power value of the received signal from the covariance matrix using Singular Value Decomposition, and the channel information may be an eigenvector of the covariance matrix. A diagonal matrix having as elements a unitary matrix Q, an eigenvalue of the covariance matrix corresponding to a column vector constituting the Q matrix, and a product of a Hermitian matrix of the Q matrix ≪ / RTI >

The reception beamforming vector may be determined as a hermetian vector of an eigenvector of the Q matrix corresponding to an eigenvalue that maximizes a gain of the received signal among eigenvalues that are components of the diagonal matrix.

According to another aspect of the present invention, there is provided a receiver comprising: a receiver for receiving a received signal through a plurality of antennas; A channel information estimator for estimating channel information of the received signal by decomposing a covariance matrix of the received signal; A beamforming vector calculator for calculating a reception beamforming vector of the received signal based on the channel information; And a beamforming unit for performing reception beamforming with respect to the received signal using the calculated reception beamforming vector. The present invention can also be achieved by a beamforming apparatus for a multi-antenna system.

As described above, according to the present invention, channel information of an unspecified received signal is estimated and reception beamforming is performed using the calculated reception beamforming vector based on the channel information, thereby improving signal reception sensitivity.

1 is a block diagram of a beamforming apparatus of a multi-antenna system according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating a process of performing reception beamforming by the beamforming apparatus of FIG. 1; And
FIGS. 3 and 4 are graphs comparing reception performance of a conventional single antenna and multi-antenna reception performance when a beamforming method according to an embodiment of the present invention is applied.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the invention. It is also to be understood that the technical terms used herein are to be interpreted in a sense generally understood by a person skilled in the art to which the present invention belongs, Should not be construed to mean, or be interpreted in an excessively reduced sense. Further, when a technical term used herein is an erroneous technical term that does not accurately express the spirit of the present invention, it should be understood that technical terms that can be understood by a person skilled in the art are replaced. In addition, the general terms used in the present invention should be interpreted according to a predefined or prior context, and should not be construed as being excessively reduced.

Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In the present application, the term "comprising" or "comprising" or the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps.

Furthermore, terms including ordinals such as first, second, etc. used in this specification can be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the purpose of facilitating understanding of the present invention, and should not be construed as limiting the scope of the present invention with reference to the accompanying drawings.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

1 is a block diagram of a beamforming apparatus in a multi-antenna system according to an embodiment of the present invention.

Referring to FIG. 1, a beamforming apparatus of a multi-antenna system according to an embodiment of the present invention includes a receiver 10, a channel information estimator 20, a beamforming vector calculator 30, and a beamforming unit 40 ).

The receiving unit 10 receives signals using a plurality of antennas. The received signal may be a signal transmitted from an unspecified radiator in addition to a signal transmitted from a specific radiator in which information is shared, and may be an unspecified signal in which information on a received signal such as a frame size and channel information is not known.

The vector of the reception signal received through the receiving unit 10 when the called r, r is Can be expressed by the following mathematical expression. For reference, it is assumed that the receiving unit 10 receives signals using N _R multiple antennas.

채널 벡터, s는 송신된 데이터 심볼, n은

잡음 벡터이다.Here, h is the distance between the radiator and the receiver 10

Channel vector, s is the transmitted data symbol, n is

It is a noise vector.

The channel information estimator 20 estimates channel information between the radiator and the receiver 10 without sharing information such as a frame size of a received signal. At this time, the channel information estimation unit 20 estimates channel information by decomposing a covariance matrix of the received signal. The process of estimating the channel information is expressed as follows.

은 수신신호의 공분산 행렬, Q는 공분산 행렬의 고유벡터(Eigenvector)로 이루어지는 유니터리 행렬,

는 공분산 행렬의 고유값(Eigenvalue)을 성분으로 갖는 대각행렬,

는 Q행렬의 허미션(Hermitian)행렬,

은 잡음 신호의 평균전력이고,

은

단위행렬을 의미한다.here,

Quot; is a covariance matrix of received signals, Q is a unitary matrix consisting of eigenvectors of a covariance matrix,

A diagonal matrix having an eigenvalue of the covariance matrix as a component,

Is a Hermitian matrix of the Q matrix,

Is the average power of the noise signal,

silver

Unit matrix.

와 같이 특이값 분해(Singular Value Decomposition: SVD) 과정을 수행하여 채널정보를 추정한다. 채널정보는 위의 수학식 2에 나타난 바와 같이

로 표현될 수 있다.As shown in Equation 2, the channel information estimation unit 20 estimates the noise signal power value of the received signal in the covariance matrix,

And performs a singular value decomposition (SVD) process to estimate channel information. The channel information is expressed as shown in Equation (2)

. ≪ / RTI >

의 성분인 고유값(

)들 중 수신신호의 이득을 최대로 하는 고유값을 찾고, Q행렬의 열벡터 안에서 그 고유값에 대응되는 고유벡터(q)의 허미션 벡터인

를 수신 빔포밍 벡터로 결정한다. 예컨대, 수신신호의 이득을 최대로 하는 고유값이

이라면, Q행렬 중

에 대응되는 고유벡터인

를 수신 빔포밍 벡터로 결정한다.The beamforming vector calculator 30 calculates a beamforming vector based on the channel information of the received signal estimated through the channel information estimator 20. The beamforming vector calculator 30 calculates the beamforming vector < RTI ID = 0.0 >

The eigenvalues (

) Of the eigenvector ( q ) corresponding to the eigenvalue in the column vector of the Q matrix, which is a hermetian vector of the eigenvector

As a reception beamforming vector. For example, when the eigenvalue that maximizes the gain of the received signal is

Q matrix < RTI ID = 0.0 >

Is an eigenvector corresponding to

As a reception beamforming vector.

라 한다면, 이를 이용하여 수신 빔포밍을 수행하는 것은 다음의 수식을 이용하여 나타낼 수 있다.The beamforming unit 40 performs reception beamforming on the reception signal using the reception beamforming vector obtained by the beamforming vector calculator 30. [ The reception beamforming vector calculated by the beamforming vector calculator 30 is represented by w ,

, The reception beamforming can be performed using the following equation.

The beamforming performing unit 40 may improve the reception performance by performing the reception beamforming as described above to match the phase of the reception unit 10 to the reception signal.

2 is a flowchart illustrating a process of performing reception beamforming by the beamforming apparatus of FIG.

Referring to FIG. 2, a signal is received through a plurality of antennas (S10). At this time, the received signal may be an unspecified signal in which information on signals such as a frame standard and channel information is not shared.

In order to perform reception beamforming, channel information between a radiator and a receiver must be known, so channel information is estimated by decomposing a covariance matrix of a received signal (S11). That is, as shown in Equation (2), the channel information is estimated by performing singular value decomposition on the result of removing the noise signal power value of the received signal in the covariance matrix. The estimated channel information includes a unitary matrix Q made up of eigenvectors of a covariance matrix, a diagonal matrix Q having an eigenvalue Eigenvalue of a covariance matrix corresponding to a column vector forming a Q matrix, , And the Hermitian matrix of the Q matrix, as described above.

The obtained Q matrix is a matrix having candidates of the reception beamforming vector as column vectors, and performs reception beamforming using the selected column vectors. The selection of column vectors is done through the following steps.

)들을 성분으로 갖는다. 이 고유값들 중 수신신호의 이득을 최대로 하는 고유값을 찾는다(S13). 이때, 수신신호의 이득을 최대로 하는 고유값은 가장 큰 값을 찾음으로 얻을 수 있다.The diagonal matrix of the estimated channel information is the eigenvalue of the covariance matrix

). An eigenvalue that maximizes the gain of the received signal among the eigenvalues is searched (S13). At this time, the eigenvalue that maximizes the gain of the received signal can be obtained by finding the largest value.

If eigenvalues are selected in the diagonal matrix, an eigenvector corresponding to a selected eigenvalue of the column vectors of the Q matrix is found, and beamforming is performed using the hermetian vector of the eigenvector as a reception beamforming vector, The sensitivity can be improved (S15, S17).

Conventionally, when information of data such as a frame size is not shared between a transmitter and a receiver as in the case of receiving data of an enemy group in an electronic warfare, channel information can not be estimated, and thus it is difficult to perform reception beamforming. However, according to the beamforming apparatus and the beamforming method according to the embodiment of the present invention, even when an unspecified signal is received as described above, beamforming is performed using channel information estimated based on the covariance matrix, have.

FIG. 3 and FIG. 4 are graphs for comparing the reception performance of a signal with that of a conventional single antenna. FIG. 3 is for comparing the signal-to-noise ratio (SNR) of 0 dB, and FIG. 4 is for comparing the reception performance with the beamforming method according to the embodiment of the present invention at a relatively high signal-to-noise ratio of 16 dB. Note that the x-axis of the graph represents the number of samples of the received signal.

Referring to FIGS. 3 and 4, a reception performance gain of about 9 dB is generated when receiving a signal through multiple antennas by applying a beamforming method according to an embodiment of the present invention, compared to receiving a signal using a single antenna Can be confirmed.

As can be seen from the above analysis results, the beamforming apparatus and method according to the embodiment of the present invention can perform reception beamforming even when channel information is not shared between a transmitter and a receiver, It can be seen that it is worth using in wireless environment where information is not shared.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

10: Receiver 20: Channel information weight information
30: beamforming vector calculating unit 40: beamforming performing unit

Claims (8)

(a) receiving a received signal through a plurality of antennas;
(b) estimating channel information by decomposing a covariance matrix of the received signal, and obtaining a reception beamforming vector of the received signal based on the channel information; And
(c) performing receive beamforming on the received signal using the receive beamforming vector,
Wherein the channel information comprises:
Estimating a result of removing the noise signal power value of the received signal from the covariance matrix using Singular Value Decomposition,
A unitary matrix Q composed of eigenvectors of the covariance matrix, a diagonal matrix having as elements an eigenvalue of the covariance matrix corresponding to a column vector constituting the Q matrix, And a Hermitian matrix of the matrix. delete delete The method according to claim 1,
Wherein the reception beamforming vector is determined as a hermetian vector of an eigenvector of the Q matrix corresponding to an eigenvalue that maximizes a gain of the received signal among eigenvalues that are components of the diagonal matrix. / RTI > A receiver for receiving a received signal through a plurality of antennas;
A channel information estimator for estimating channel information of the received signal by decomposing a covariance matrix of the received signal;
A beamforming vector calculator for calculating a reception beamforming vector of the received signal based on the channel information; And
And a beamforming unit for performing reception beamforming on the received signal using the obtained reception beamforming vector,
Wherein the channel information estimator estimates channel information by performing a Singular Value Decomposition process on a result of removing the noise signal power value of the received signal in the covariance matrix,
The channel information estimated by the channel information estimator includes a unitary matrix Q made up of eigenvectors of the covariance matrix, an eigenvalue of the covariance matrix corresponding to a column vector constituting the Q matrix, ) And a Hermitian matrix of the Q matrix. ≪ RTI ID = 0.0 > 8. < / RTI > delete delete 6. The method of claim 5,
The beamforming vector calculator calculates the hermetian vector of the eigenvector of the Q matrix corresponding to the eigenvalue that maximizes the gain of the received signal among the eigenvalues that are components of the diagonal matrix as the reception beamforming vector Wherein the beamforming system is a multi-antenna system.

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