KR101547421B1 - Method for hybrid beamforming on statistical channel informaion, and apparatuses performing the same - Google Patents

Abstract

A mixed beamforming method and apparatus for performing the same are disclosed. A mixed beamforming method of a communication apparatus according to an exemplary embodiment includes obtaining statistical channel correlation matrices for a channel between an array antenna of the communication apparatus and each terminal apparatus, Determining an RF beamforming coefficient corresponding to the device, and performing RF beamforming on symbol streams to be transmitted to each terminal device based on the RF beamforming coefficient.

Description

METHOD FOR HYBRID BEAM FORMING ON STATISTICAL CHANNEL INFORMAION, AND APPARATUSES PERFORMING THE SAME. [0001] The present invention relates to a mixed beamforming method based on statistical channel information,

The following embodiments relate to a mixed beamforming method for determining an RF beamforming coefficient based on statistical channel information, and to devices performing the same.

One of the important design considerations in wireless communication systems is to achieve a theoretical capacity (Sahnnon Capacity) of a given channel between the base station and the terminal. To do this, it is necessary to use a transmission scheme suitable for a given channel. The MU-MIMO (Multi-User Multiple Input Multiple Output) transmission scheme accommodates terminals with small channel correlation at different positions simultaneously through the same radio frequency resource, High frequency efficiency can be obtained. However, since the channel correlation of the terminals is generally larger than zero, multi-user interference occurs and the ideal frequency efficiency can not be achieved.

Conventional methods for obtaining an ideal frequency efficiency include a Zero-Forcing Block Diagonalization (ZF-BD) method and a Channel Inversion (CI) method as a baseband precoding method. There is a hybrid beamforming scheme that prevents complex multi-user interference in a baseband (or frequency band). The ZF-BD scheme and the CI scheme are preprocessing methods in the baseband to prevent interference between multi-user symbol streams transmitted through RF chains. The CI scheme is a scheme for preventing interference between all streams, and the ZF-BD scheme is a method for preventing interference between terminals. In a method for preventing interference between two or more symbol streams transmitted to the same terminal, .

Meanwhile, by performing beamforming in the RF stage using two or more antennas for each RF chain of the base station, a high beamforming gain can be obtained and the quality of a received signal of the terminal can be improved. For such a base station, a composite beamforming scheme has been proposed. In this composite beamforming scheme, a high beamforming gain is obtained by performing beamforming (hereinafter referred to as 'RF beamforming') for each RF chain with a large number of transmitting antennas at an RF stage, and baseband precoding is performed to obtain multi- . The RF beamforming has a function of spatially separating a signal transmitted from the base station to the terminals.

Embodiments can reduce the overhead associated with collecting channel information by obtaining a statistical channel correlation matrix to determine the RF end beamforming coefficients in a complex beamforming base station using an array antenna with a very large number of antennas, Can be provided effectively.

A mixed beamforming method of a communication apparatus according to an exemplary embodiment of the present invention includes a step of generating an RF beam corresponding to each of the plurality of terminal devices based on statistical channel correlation matrices for an channel between an array antenna of the communication device and a plurality of terminal devices And performing RF beamforming on the symbol streams to be transmitted to the plurality of terminal devices based on the RF beamforming coefficient.

The method may further comprise performing baseband precoding on the symbol streams.

Wherein the step of determining the RF beamforming coefficients further comprises using a first channel correlation matrix among the statistical channel correlation matrices to calculate a signal-subspace-specific vector of the average of the effective channel responses for the subchannels of the communication device and the plurality of terminal devices Calculating a first matrix including signal subspace singular vectors, and noise subspace singular vectors of the average using the second channel correlation matrix among the statistical channel correlation matrices. Calculating a third matrix using a third channel correlation matrix from among the first matrix, the second matrix, and the statistical channel correlation matrices; Determining the RF beamforming coefficient based on the first matrix, the second matrix, and the third matrix.

The step of calculating the third matrix may include calculating the third matrix using the first matrix, the second matrix, and the third channel correlation matrix according to the number of columns of the RF beamforming coefficient .

When the number of columns is 1, the third matrix is an eigenvector, and when the number of columns is greater than 1, the third matrix may include eigenvectors of the number of columns as a column vector.

The number of columns may be independent of the subchannel.

The second matrix may include the noise quasi-spatial singular vectors as column vectors.

The method may further comprise obtaining the statistical channel correlation matrices.

Wherein the obtaining of the statistical channel correlation matrices comprises calculating the statistical channel correlation matrices using at least one of an arithmetic mean of an expectation operation and an angle of arrival of a signal received from the plurality of terminal devices . ≪ / RTI >

The obtaining of the statistical channel correlation matrices may further include reconstructing the statistical channel correlation matrix by performing eigenvalue decomposition on the statistical channel correlation matrix.

A communication apparatus according to an embodiment includes an array antenna and a plurality of terminal apparatuses each corresponding to each of the plurality of terminal apparatuses based on statistical channel correlation matrices for channels between the array antenna and a plurality of terminal apparatuses communicating with the communication apparatus A mixed beamforming determining unit that determines an RF beamforming coefficient and an RF beamforming unit that performs RF beamforming on symbol streams to be transmitted to the plurality of terminal devices based on the RF beamforming coefficient.

The apparatus may further comprise a baseband precoder for performing baseband precoding on the symbol streams.

Wherein the mixed beamforming determining unit calculates the statistical channel correlation matrices using at least one of an arithmetic mean of an expectation value calculation and an arrival angle of a signal received from the plurality of terminal apparatuses, To reconstruct the statistical channel correlation matrix.

The device may be a base station.

A communication system according to an exemplary embodiment includes a plurality of terminal devices and an array antenna, and each of the plurality of terminal devices, using statistical channel correlation matrices for the channel between the array antenna and the plurality of terminal devices, And a communication device that determines an RF beamforming coefficient corresponding to the RF beamforming coefficient.

The communication device may perform RF beamforming on symbol streams to be transmitted to the plurality of terminal devices based on the RF beamforming coefficient.

1 shows a communication system according to one embodiment.
2 is a flowchart for explaining a method of calculating an RF beamforming coefficient for a Kth terminal.
3 illustrates a beam pattern and constellation diagram of a multi-user RF beamforming according to an embodiment in a Rayleigh fading channel environment.

It is to be understood that the specific structural or functional descriptions of embodiments of the present invention disclosed herein are presented for the purpose of describing embodiments only in accordance with the concepts of the present invention, May be embodied in various forms and are not limited to the embodiments described herein.

Embodiments in accordance with the concepts of the present invention are capable of various modifications and may take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It should be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms disclosed, but includes all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

The terms first, second, or the like may be used to describe various elements, but the elements should not be limited by the terms. The terms may be named for the purpose of distinguishing one element from another, for example without departing from the scope of the right according to the concept of the present invention, the first element being referred to as the second element, Similarly, the second component may also be referred to as the first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Expressions that describe the relationship between components, for example, "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises ", or" having ", or the like, specify that there is a stated feature, number, step, operation, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

1 shows a communication system according to one embodiment.

Referring to FIG. 1, a communication system 10 may include a communication device 100 and a plurality of terminal devices 200-1 to 200-K, where K is a natural number of 1 or more. For example, the number of the plurality of terminal devices 200-1 to 200-K may be K.

The communication system 10 can perform communication in a wireless communication environment. For example, communication system 10 may perform communication in the 3GPP (3 ^rd Generation Partnership Project), LTE (Long-Term Evolution), and WiMAX (World Interoperability for Microwave Access) based.

The communication device 100 and the plurality of terminal devices 200-1 to 200-K can communicate with each other. For example, the communication device 100 and the plurality of terminal devices 200-1 to 200-K can exchange signals (or data) with each other. The communication device 100 may be a base station.

The communication apparatus 100 calculates RF beamforming coefficients W ₁ to W _K corresponding to each of the plurality of terminal devices 200-1 to 200-K based on statistical channel information, for example, statistical channel correlation matrices, And performs RF beamforming on the symbol streams s ₁ to s _K to be transmitted to each of the plurality of terminal devices 200-1 to 200-K. For example, the communication apparatus 100 may perform statistical channel correlation (hereinafter, referred to as " statistical channel correlation ") on the channel between the array antenna, for example, a plurality of antennas ANT-1 to ANT- Matrices can be obtained.

By obtaining statistical channel correlation matrices that can be collected in a relatively low period instead of using instantaneous channel information, the communication device 100 can mitigate the overhead of real-time instantaneous channel estimation for RF beamforming. In addition, the communication apparatus 100 can improve the sensitivity to the channel estimation error.

User interference may be eliminated by performing multiuser RF beamforming using the RF beamforming coefficients (W ₁ to W _K ) based on the communication device 100 statistical channel correlation matrices.

The communication apparatus 100 can perform baseband precoding on the symbol streams s ₁ to s _K to be transmitted to each of the plurality of terminal devices 200-1 to 200-K. The communication apparatus 100 may perform baseband precoding using instantaneous channel information to remove redundant multi-user interference components that could not be removed through RF beamforming.

The communication apparatus 100 includes a baseband precoder 130, RF chains (not shown), an RF beamforming unit 150 and a plurality of antennas ANT-1 to ANT-N .

개일 수 있다.The baseband precoder 130 may receive the symbol streams s ₁ to s _K. For example, each of the symbol streams s ₁ to s _K

.

The baseband precoder 130 may baseband precode the symbol streams s ₁ to s _K to produce output signals d ₁ to d _K. For example, the baseband precoder 130 may comprise a plurality of precoders, e.g., K precoders.

Baseband precoder 130 is sent to the respective output signals (d ₁ ~ d _K) of each RF (radio frequency), each output through a chain signals (d ₁ ~ d _K) for RF beam forming section 150 corresponding to the . For example, each RF chain may include an inverse fast fourier transform (IFFT), a parallel-to-serial converter, and a digital-to-analog converter (DAC).

RF beam forming unit 150 RF beamforming coefficients (W ₁ ~ W _K) of the symbol stream to be transmitted to a plurality of terminal devices (200-1 ~ 200-K), respectively on the basis of ₍₁ s ~ s _K) Lt; RTI ID = 0.0 > RF beamforming. ≪ / RTI > For example, RF beamforming unit 150 based on the RF beamforming coefficients (W ₁ ~ W _K) of the output signal of the baseband precoder 130 is transmitted over a respective RF chain (d ₁ ~ d _K And transmits the formed beam to the plurality of terminal devices 200-1 to 200-K through the plurality of antennas ANT-1 to ANT-N.

The RF beamformer 150 may include RF beam former 151-1 to 151-K corresponding to each RF chain, and a signal combiner 153.

Each RF beamformer (151-1 ~ 151-K) separates the signals transmitted through each of the RF chains (d ₁ ~ d _K) each of N signal, RF beamforming in the separated N signals The coefficients (W ₁ to W _K ) can be applied to generate signals (x ₁ to x _K ). For example, each of the signals x ₁ to x _K may be N signals. Also, each of the signals x ₁ to x _K may be signals whose phase has been changed in accordance with the RF beamforming coefficients W ₁ to W _K. Each of the RF beam formers 151-1 to 151-K may include a frequency converter, a phase shifter, and a power amplifier.

For example, the RF beamformer 1 (151-1) is separated on the signal (d ₁₎ transmitted over the corresponding RF chain to the N signal, RF beamforming coefficients in separate N signals (W ₁ ) May be applied to generate N signals (x ₁ ). The K-K RF beam former 151-K separates the transmitted signal ( _dK ) through the corresponding RF chain into N signals and applies the RF beamforming coefficient ( _WK ) to the separated N signals It is possible to generate N signals (x _K ).

The signal combining unit 153 combines the signals x ₁ to x _K to form a beam and transmits N beams of transmitted signals x to the plurality of antennas ANT-1 to ANT-N . For example, the signal combining unit 153 may transmit N transmission signals x to corresponding antennas ANT-1 to ANT-N.

The plurality of antennas ANT-1 to ANT-N may be implemented as a uniform linear array (ULA) or a uniform plane array (UPA).

The mixed beamforming determining unit 170 determines a statistical channel correlation matrix for a channel between an array antenna, for example, a plurality of antennas ANT-1 to ANT-N and each of the terminal apparatuses 200-1 to 200- .

The mixed beamforming determining unit 170 can determine the RF beamforming coefficients W ₁ to W _K corresponding to the plurality of terminal devices 200-1 to 200-K based on the statistical channel correlation matrices .

Effective channels H ₁ to H _K may be formed between the communication device 100 and a plurality of terminal devices 200-1 to 200-K. Each of the plurality of terminal devices 200-1 to 200-K can receive the corresponding reception signals y ₁ to y _k through the corresponding effective channel.

로 표현되고, 제K 단말장치(200-K)의 등화기(210-K)는

로 표현될 수 있다.

는 vector 또는 matrix의 Herimitan transposition을 나타낼 수 있다.Each of the received signals y ₁ to y _k can be canceled by the equalizers 210-1 to 210-K of the terminal devices 200-1 to 200-K. For example, the equalizer 210-1 of the first terminal device 200-1

, And the equalizer 210-K of the Kth terminal device 200-K is represented by

. ≪ / RTI >

Can represent a Herimitan transposition of a vector or matrix.

The symbol detectors 230-1 to 230-K of each of the terminal devices 200-1 to 200-K are connected to the equalizers 210-1 to 210-K of the terminal devices 200-1 to 200- It is possible to detect a desired symbol from the output signals r ₁ to r _K.

을 동시에 K개의 단말장치들(200-1~200-K)로 송신하는 경우를 가정한다.A method for determining the RF beamforming coefficients W ₁ to W _K of the mixed beamforming determining unit 170 of the communication apparatus 100 will be described in detail below. At this time, when the communication apparatus 100 transmits the symbol streams < RTI ID = 0.0 >

To the K terminals 200-1 to 200-K at the same time.

로 표현될 수 있다. 이때, 출력 신호들(d₁~d_K)은 수학식 1을 통해 표현될 수 있다.
The baseband precoder 130 may baseband precode the symbol streams s ₁ to s _K to generate precoded signals d ₁ to d _K. For example, the baseband precoder 130 corresponding to subchannel f

. ≪ / RTI > At this time, the output signals d ₁ to d _K can be expressed by Equation (1).

At this time, the transmission signal x of the communication device 100 can be expressed by Equation (2).

The received signal y _K received through the sub-channel f in the K-th terminal 200-K may be expressed by Equation (3).

는 제K 단말 장치(200-K)의 부채널 f에서의 유효 채널 응답을 의미할 수 있다.

는 부가 잡음(additive noise)을 의미할 수 있다. 또한,

는

로 정의될 수 있다. 이때, 모든 단말장치에서 수신된 신호들은 수학식 4와 같이 표현될 수 있다.
here,

May refer to an effective channel response on the subchannel f of the Kth terminal 200-K.

May mean additive noise. Also,

The

. ≪ / RTI > At this time, the signals received from all the terminal devices can be expressed by Equation (4).

Each matrix of Equation (4) can be defined as Equation (5).

Equation (4) can be summarized as shown in Equation (6) through Equation (5).

을 결정하는 것에 한하여 설명한다.
For the sake of convenience of explanation, the mixed beamforming determination unit 170 of the communication device 100 determines whether the mixed beamforming decision unit 170 is an RF beamforming matrix for the Kth terminal apparatus 200-

As shown in Fig.

는 다음과 같은 3가지 조건을 만족해야 한다.The RF beamforming matrix for the K < th > terminal apparatus 200-K

Must meet the following three conditions.

는 제K 단말장치(200-K)를 목적지로 송신되는 신호(y_K), 즉

가 제K 단말장치(200-K)를 제외한 다른 단말장치들에 도달하지 않도록 해야 한다.1) RF beamforming matrix

K is the terminal equipment signals (y _K) which is transmitted to (200-K) to the destination, that is,

Should not reach other terminal devices except for the K-th terminal device 200-K.

는 제K 단말장치(200-K)를 목적지로 송신되는 신호

가 제K 단말장치(200-K)로 도달할 수 있도록 해야 한다.2) RF beamforming matrix

Is transmitted to the K < th > terminal device 200-K

So that it can reach the K-th terminal device 200-K.

는 제K 단말장치(200-K)를 목적지로 송신되는 신호

가 제K 단말장치(200-K)로 도달하는 수신 전력이 최대가 되도록 해야 한다.
3) RF beamforming matrix

Is transmitted to the K < th > terminal device 200-K

K terminal apparatus 200-K is maximized.

는 부채널 f와 독립적인 값일 수 있다. 부채널 f에 대한 유효 채널 응답인

대신에 모든 부채널 f에 대한 평균치에 기초하여 RF 빔포밍 행렬

의 최적치를 계산하고, 부채널별

의 분산으로 인한 여분의 다중사용자 간섭은 기저대역 프리코더(130)의 기저대역 프리코딩을 통해 제거될 수 있다. 이때,

의 모든 부채널 f에 대한 평균치를

로 정의할 수 있다.
The RF beamforming matrix satisfying the above three conditions

May be a value independent of the subchannel f. The effective channel response for subchannel f

Instead, an RF beamforming matrix < RTI ID = 0.0 >

And calculates the optimum value for each subchannel

The extra multiuser interference due to the dispersion of the baseband precoder 130 may be eliminated through baseband precoding of the baseband precoder 130. At this time,

0.0 > f < / RTI >

.

은 수학식 7과 같이 표현될 수 있다.
The effective channel response for subchannel f

Can be expressed by Equation (7).

The average value of the correlation matrix for each subchannel can be expressed as Mathematical Expression 8.

Equations (3) and (6) can be summarized from Equation (7) to Equation (9) and Equation (10).

이고,

이다.
In the equations (9) and (10)

ego,

to be.

는 정리된 수신 신호 모델과 상술한 조건에 기초하여 구해질 수 있다.RF beamforming matrix

Can be obtained based on the summarized received signal model and the above-described conditions.

가 다른 단말장치들로 도달하지 않도록 하기 위해서는, 수학식 10으로부터 RF 빔포밍 행렬

가

의 null space에 존재하는 column vector들로 구성되어야 한다.

는 수학식 11과 같이 Singular Value Decomposition으로 표현될 수 있다.
Condition 1), that is, the signal transmitted to the destination of the K-th terminal apparatus 200-K

The RF beamforming matrix < RTI ID = 0.0 >

end

It must consist of column vectors in null space of.

Can be expressed by Singular Value Decomposition as shown in Equation (11).

는

의 signal subspace singular vector들을 의미할 수 있다.

는

의 noise subspace singular vector들을 column vector로 가지는 행렬을 의미할 수 있다. 따라서, 조건 1)을 만족하기 위한 RF 빔포밍 행렬

는 수학식 12와 같이 표현될 수 있다.
here,

The

Signal subspace singular vectors.

The

Can be a matrix with noise subspace singular vectors as column vectors. Therefore, the RF beamforming matrix for satisfying the condition 1)

Can be expressed by Equation (12).

는

의 noise subspace eigenvector들을 column vector로 가지는 행렬을 의미할 수 있고, 수학식 11로부터 수학식 13과 같이 표현될 수 있다.
Also,

The

And may be expressed as Equation (13) from Equation (11). &Quot; (13) "

는 모든 부채널에 대한

를 평균한 값을 나타낼 수 있다.
Here, the first channel correlation matrix

Lt; RTI ID = 0.0 >

Can be expressed as averages.

에 대한 해를 결정하기 위해 조건 2)를 이용할 수 있다. 수학식 12를 수학식 9에 대입하면, 제K 단말장치(200-K)가 수신하는 신호는 수학식 14와 같이 다시 표현될 수 있다.
Next, in Equation 12,

Condition 2) can be used to determine the solution to the problem. When Equation (12) is substituted into Equation (9), the signal received by the Kth terminal device (200-K) can be expressed again as in Equation (14).

가 제K 단말장치(200-K)로 도달할 수 있도록 하기 위해서는

가

의 signal subspace에 존재하는 column vector들로 구성되어야 한다.

는 수학식 15와 같이 Singular Value Decomposition으로 표현될 수 있다.
(Condition 2) from this equation (14), that is, the signal transmitted from the K terminal device 200-K to the destination

To be able to reach the K-th terminal device 200-K

end

And the column vectors present in the signal subspace.

Can be represented by Singular Value Decomposition as shown in Equation (15).

는

의 signal subspace singular vector들을 column vector로 가지는 행렬을 의미할 수 있다. 따라서, 조건 2)를 만족하기 위한

는

일 수 있다. 즉, 수학식 12는 수학식 16과 같이 다시 표현될 수 있다.
here,

The

Can be a matrix with signal subspace singular vectors as column vectors. Therefore, in order to satisfy the condition 2)

The

Lt; / RTI > That is, Equation (12) can be expressed again as Equation (16).

는

의 signal subspace eigenvector들을 column vector로 가지는 행렬을 의미하고, 수학식 17과 같이 표현될 수 있다.
here,

The

And the signal subspace eigenvectors as a column vector, and can be expressed as Equation (17).

는 모든 부채널에 대한

를 평균한 값을 나타낸다.
Here, the second channel correlation matrix

Lt; RTI ID = 0.0 >

Is averaged.

에 대한 해를 결정하기 위해 조건 3)을 이용할 수 있다. 수학식 16을 수학식 9에 대입하면, 제K 단말장치(200-K)가 수신하는 신호는 수학식 18과 같이 다시 표현될 수 있다.
Finally,

3) can be used to determine the solution for Substituting Equation (16) into Equation (9), the signal received by the Kth terminal device (200-K) can be expressed again as in Equation (18).

은 수학식 19와 같이 표현될 수 있다.
Here, the power of the desired signal

Can be expressed as: " (19) "

는

의 i번째 column vector를 의미할 수 있다.

로 가정할 때,

의 최적치는 수학식 20과 같이 표현될 수 있다.
here,

The

Can be defined as an i-th column vector.

Assuming that,

Can be expressed by Equation (20).

의 최적치는

의 가장 큰 eigenvalue를 갖는 eigenvector일 수 있다. 따라서,

의 최적치는

의 가장 큰

개의 eigenvalue를 갖는

개의 eigenvector들을 column vecotr로 가질 수 있다. 여기서,

는 부채널 f와 독립적인 값으로서 RF 빔포밍 행렬

의 column 수에 해당하고,

는 수학식 21과 같이 표현될 수 있다.

The optimal value of

Lt; RTI ID = 0.0 > eigenvalue of < / RTI > therefore,

The optimal value of

The largest of

Have eigenvalues of

We can have eigenvectors of a column as vecotr. here,

Is an RF beamforming matrix < RTI ID = 0.0 >

Of the number of columns,

Can be expressed as: " (21) "

는 제3 채널 상관 행렬일 수 있다.
here,

May be a third channel correlation matrix.

를 각 단말장치(200-1~200-K)로부터 미리 수집할 수 있다.The communication apparatus 100, for example, the mixed beamforming determination unit 170 may calculate the required statistical channel correlation matrices in Equation (13), Equation (17) and Equation (21)

Can be collected in advance from each of the terminal devices 200-1 to 200-K.

대신에

를 적용하거나 다른 방법으로

와 유사한 속성을 갖는 값을 적용할 수 있다.At this time,

Instead of

Or by other means

A value having an attribute similar to that of FIG.

을 계산함에 있어,기대치(expectation) 연산에 산술 평균을 적용하거나 또는 각 단말장치(200-1~200-K)에서 통신 장치(100)로 수신되는 신호의 도달각(angle of arrival)을 사용하는 다양한 방법으로 계산할 수 있다.According to one embodiment, the mixed beamforming determination unit 170 determines a channel correlation matrix for each of the terminal devices 200-1 to 200-K

An arithmetic mean is applied to an expectation calculation or an angle of arrival of a signal received by each of the terminal apparatuses 200-1 to 200-K to the communication apparatus 100 is used It can be calculated in various ways.

을 계산하고, eigenvalue decomposition을 수행한 다음, eigenvalue가 큰 dominant component만으로 채널 상관 행렬

을 재구성할 수 있다. 채널 상관 행렬

의 eigenvalue decomposition이

과 같이 표현되고, eigenvalue들 중 처음 L개가 dominant component 일 때, 수학식 22과 같이 채널 상관 행렬을 재구성할 수 있다.
According to another embodiment, the mixed beamforming determination unit 170 determines a channel correlation matrix for each of the terminal devices 200-1 to 200-K

, Eigenvalue decomposition is performed, and then a dominant component having a large eigenvalue is used to calculate a channel correlation matrix

Lt; / RTI > Channel correlation matrix

Eigenvalue decomposition of

And the channel correlation matrix can be reconstructed as shown in Equation (22) when the first L of eigenvalues is a dominant component.

이 수학식 13에 대입될 경우,

이 Full Rank를 갖거나 Rank가 매우 크게 되거나 그 null space의 dimension이 영(zero) 또는 매우 작게 되는 것을 방지할 수 있다.The reconstructed channel correlation matrix

When this is applied to Equation (13)

It is possible to avoid having a full rank, a very large rank, or a zero or very small dimension of the null space.

,

, 및 행렬

등을 산출하는 과정에 적용될 수 있다. 산출하는 과정은 상술한 바와 실질적으로 같을 수 있다.
Equation (22) is substituted into Equation (13)

,

, And matrix

And so on. The calculation process may be substantially the same as that described above.

2 is a flowchart for explaining a method of calculating an RF beamforming coefficient for a Kth terminal.

를 산출하기 위하여 수집된 채널 상관 행렬들에 기초하여

의 null space eigenvector들을 column vector로 가지는

을 계산할 수 있다(410). 이는, 수학식 12와 수학식 13에서 상술한 바와 같을 수 있다.1 and 2, the mixing beamforming determining unit 170 determines an RF beamforming coefficient for the Kth terminal 200-K,

On the basis of the collected channel correlation matrices

Null space eigenvectors as a column vector

(410). This can be as described above in Equations (12) and (13).

의 signal subspace eigenvector들을 column vector로 가지는 행렬

을 계산할 수 있다(420). 이는, 수학식 15와 수학식 18에서 상술한 바와 같을 수 있다.Next, the mixed beamforming determining unit 170

Of the signal subspace eigenvectors as a column vector

(420). This can be as described above in Equations (15) and (18).

, 즉

의 column 수를 설정값과 비교할 수 있다(430).The mixed beamforming determining unit 170

, In other words

(430).

가 1인 경우, 즉

의 column 수가 하나인 경우, 행렬

는 I일 수 있다(440). 이때, 제K 단말장치(200-K)를 위한 RF 빔포밍 계수

는

와 같을 수 있다(460).

Is 1, that is,

If the number of columns in a matrix is one,

May be I (440). At this time, the RF beamforming coefficient for the Kth terminal device 200-K

The

(460).

가 보다 큰 경우,

의 가장 큰

개의 eigenvalue를 갖는

개의 eigenvector들을 column vecotr로 갖는 행렬

fmf 산출할 수 있다(450). 이때, 제K 단말장치(200-K)를 위한 RF 빔포밍 계수

는

와 같을 수 있다(460).

Lt; RTI ID = 0.0 >

The largest of

Have eigenvalues of

Matrix with eigenvectors in column vecotr

fmf can be calculated (450). At this time, the RF beamforming coefficient for the Kth terminal device 200-K

The

(460).

The above procedure can be performed for all k = 1, 2, ..., K.

3 illustrates a beam pattern and constellation diagram of a multi-user RF beamforming according to an embodiment in a Rayleigh fading channel environment.

Referring to FIG. 3, simulation results are shown for an RF beamforming scheme according to an embodiment of the Rayleigh channel using an OFDM signal according to the LTE standard. The communication apparatus 100 has 32 transmission antennas and assumes a multi-user MIMO channel in which each of the four terminal apparatuses has one reception antenna. Since it is an experiment to verify the multiuser interference prevention performance, it is assumed that the signal-to-noise ratio (SNR) at the receiving end is 30 dB.

The OFDM symbol has 1024 subchannels, and the communication apparatus 100 performs D / A conversion and OFconversion of the OFDM symbols for each terminal device encoded by 16-QAM, and then transmits and combines the RF beam formers for each terminal device .

As shown in FIG. 3, the bit error rate (BER) of a multi-user RF beam former according to an embodiment may be 0.0246, which is better than the conventional method.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA) , A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing unit may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (16)

A mixed beamforming method for a communication apparatus,
Determining an RF beamforming coefficient corresponding to each of the plurality of terminal devices based on statistical channel correlation matrices for a channel between an array antenna of the communication device and a plurality of terminal devices; And
Performing RF beamforming on symbol streams to be transmitted to the plurality of terminal devices based on the RF beamforming coefficient
Lt; / RTI >
Wherein determining the RF beamforming coefficient comprises:
And signal subspace singular vectors of an average value of effective channel responses for a subchannel of the communication apparatus and the plurality of terminal apparatuses using a first channel correlation matrix among the statistical channel correlation matrices. Calculating a first matrix;
Calculating a second matrix including noise subspace singular vectors of the average using a second channel correlation matrix among the statistical channel correlation matrices;
Calculating a third matrix using a third channel correlation matrix among the first matrix, the second matrix, and the statistical channel correlation matrices; And
Determining the RF beamforming coefficient based on the first matrix, the second matrix, and the third matrix,
Wherein the mixed beamforming method comprises the steps of:
The method according to claim 1,
Performing baseband precoding on the symbol streams
Wherein the mixed beamforming method further comprises:
delete The method according to claim 1,
Wherein the calculating the third matrix further comprises:
Calculating the third matrix using the first matrix, the second matrix, and the third channel correlation matrix according to the number of columns of the RF beamforming coefficient;
Wherein the mixed beamforming method comprises the steps of:
5. The method of claim 4,
The third matrix is an eigenvector when the number of columns is 1,
And when the number of columns is greater than 1, the third matrix includes the column vectors as eigenvectors of the number of columns.
5. The method of claim 4,
Wherein the number of columns is independent of the subchannel.
The method according to claim 1,
Wherein the second matrix includes the noise quasi-spatial singular vectors as column vectors.
The method according to claim 1,
Obtaining the statistical channel correlation matrices
Wherein the mixed beamforming method further comprises:
9. The method of claim 8,
Wherein obtaining the statistical channel correlation matrices comprises:
Computing the statistical channel correlation matrices using at least one of an arithmetic mean of an expected value operation and an angle of arrival of a signal received from each terminal device
Wherein the mixed beamforming method comprises the steps of:
10. The method of claim 9,
Wherein obtaining the statistical channel correlation matrices comprises:
Performing eigenvalue decomposition on the statistical channel correlation matrix to reconstruct the statistical channel correlation matrix
Wherein the mixed beamforming method further comprises:
A communication device comprising:
Array antenna;
And a mixing beamforming determining unit for determining an RF beamforming coefficient corresponding to each of the plurality of terminal devices based on statistical channel correlation matrices for channels between the array antenna and a plurality of terminal devices communicating with the communication device, ; And
An RF beamforming unit for performing RF beamforming on symbol streams to be transmitted to the plurality of terminal devices based on the RF beamforming coefficient;
Lt; / RTI >
The mixed beamforming determination unit may determine,
And signal subspace singular vectors of an average value of effective channel responses for a subchannel of the communication apparatus and the plurality of terminal apparatuses using a first channel correlation matrix among the statistical channel correlation matrices. Calculating a first matrix,
Calculating a second matrix including noise subspace singular vectors of the average value using a second channel correlation matrix among the statistical channel correlation matrices,
Calculating a third matrix using a third channel correlation matrix among the first matrix, the second matrix, and the statistical channel correlation matrices,
And determines the RF beamforming coefficient based on the first matrix, the second matrix, and the third matrix.
12. The method of claim 11,
A baseband precoder for performing baseband precoding on the symbol streams,
Further comprising:
12. The method of claim 11,
The mixed beamforming determination unit may determine,
Calculating the statistical channel correlation matrices using at least one of an arithmetic mean of an expected value arithmetic operation and an arrival angle of a signal received from the plurality of terminal devices, and performing eigenvalue decomposition on the statistical channel correlation matrix, A communication device for reconstructing a correlation matrix.
12. The method of claim 11,
Wherein the communication device is a base station.
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