KR101021700B1 - Beamforming apparatus and method for multiuser mimo system - Google Patents

Abstract

The present invention relates to a beamforming apparatus and method for a multi-user multi-input / output system, the apparatus comprising: a matrix operator for calculating a transmission beamforming matrix and a reception coupling matrix, and performing a calculation using the transmission beamforming matrix and symbols to transmit It includes a beam forming unit for generating a signal. In this case, the matrix operator updates the reception coupling matrix of the first reception device while fixing the reception coupling matrix of other reception devices other than the first reception device. According to the present invention, performance can be improved while effectively eliminating interference between users in a multi-user MIMO environment.

Multiuser, Multiple Input / Output System, Beamforming, Channel Matrix, Multiple Antennas

Description

Beamforming apparatus and method for multi-user multi-input / output system {BEAMFORMING APPARATUS AND METHOD FOR MULTIUSER MIMO SYSTEM}

The present invention relates to a beamforming apparatus and method for a multi-user multi-input / output system.

Recently, in a multi-user environment in which one base station supports multiple terminals, a multi-transmit / receive antenna transmission technology considering multi-users to increase the total channel capacity of a multi-input multiple-output (MIMO) system considering multi-users Research on the back is active. The multi-user channel environment should ensure that all of the multi-user MIMO schemes are in good condition so that they can take full advantage of the spatial degrees of freedom, so that the multi-users can communicate simultaneously at the desired rate without being limited by interference. Should be In multi-user MIMO, the uplink means that multiple users transmit data to the same base station (many-to-one), and the downlink means that the base station sends signals to multiple users (one-to-many). The lack of coordination is the difference from a typical single-user MIMO process.

In the downlink channel, the base station transmits signals to multiple users at the same time, so that each user receives an interference signal other than the desired signal. Since a technique for suppressing such interference is difficult in terms of complexity and cost for use in a terminal receiver, interference can be mitigated by intelligently designing a transmission signal in a base station transmitter. If the transmitter knows channel information in advance, the simplest way to handle user-to-user interference is to use zero-forcing or block diagonalization techniques to zero all interfering signals. Preprocess the transmitted signal with a pseudoinverse. However, there is a restriction that the number of base station transmit antennas must be larger than the total number of data streams of other users in order for the pseudo inverse of the channel to always exist, and power consumption to eliminate these interferences in a bad channel environment such as when users are located nearby A power inefficiency problem occurs, leading to performance degradation.

An object of the present invention is to provide an apparatus and method for beamforming a multi-user multi-input / output system that can optimize performance while effectively eliminating interference between users in a multi-user MIMO environment.

In order to solve the above technical problem, a beamforming apparatus of a multiple input / output system for a plurality of receivers including a first receiver according to an embodiment of the present invention includes a matrix calculator configured to calculate a transmission beamforming matrix and a reception coupling matrix; And a beamforming unit configured to generate a transmission signal by performing an operation using the transmission beamforming matrix and the symbol, wherein the matrix operation unit generates a reception coupling matrix of a reception device other than the first reception device among the plurality of reception devices. The reception coupling matrix of the first receiving device is updated in the fixed state.

The matrix calculator may calculate at least one phase value, and the beamformer may transmit the at least one phase value to the receiving device.

The reception device may calculate the reception coupling matrix using the at least one phase value from the beamformer.

은

으로 계산되며, 상기

는

으로 계산되고, 상기

는 상기 수신 결합 행렬이며, 상기

는 채널 행렬이다.The transmit beamforming matrix

silver

Is calculated as above

Is

Calculated as above

Is the receive coupling matrix, and

Is the channel matrix.

번째 수신 장치에 대한 수신 결합 벡터

는 행렬

의 최대 고유값(maximum eigenvalue)에 대응하는 단위 놈 고유벡터(unit-norm eigenvector)에 기초하여 결정될 수 있다.When the receiving device has two receiving antennas and one stream is provided to each receiving device

Join vector for the first receiver

Is a matrix

It may be determined based on the unit-norm eigenvector corresponding to the maximum eigenvalue of.

는 행렬

의 어느 한 행으로 나타낼 수 있으며, 상기 행렬 연산부는 상기 어느 한 행의 원소를 이용하여 두 개의 위상 값을 추출할 수 있다.The receive combining vector

Is a matrix

The matrix operation unit may extract two phase values using the elements of any one row.

번째 수신 장치에 대한 수신 결합 벡터

는 행렬

의 최대 고유값에 대응하는 단위 놈 고유벡터에 기초하여 결정될 수 있다.When the receiving device has two receiving antennas and one stream is provided to each receiving device

Join vector for the first receiver

Is a matrix

It may be determined based on the unit norm eigenvectors corresponding to the maximum eigenvalue of.

는 결합되어 있는 두 개의 복소 회전 행렬

중 어느 하나의 행으로 나타낼 수 있으며, 상기 행렬 연산부는 상기 어느 하나의 행의 원소를 이용하여 한 개의 위상 값을 추출할 수 있다.The receive combining vector

Is the two complex rotation matrices combined

The matrix operation unit may extract one phase value by using an element of the one row.

A beamforming method of a multiple input / output system for a plurality of receiving apparatuses including a first receiving apparatus according to another aspect of the present invention, the method comprising: calculating a transmission beamforming matrix and a reception coupling matrix, and the transmission beamforming matrix and a symbol Generating a transmission signal by performing an operation using the first reception device, wherein the first reception device is fixed while the reception coupling matrix of the reception device other than the first reception device is fixed among the plurality of reception devices. Updating the receive coupling matrix of < RTI ID = 0.0 >

As described above, according to the present invention, performance can be improved while effectively eliminating interference between users in a multi-user MIMO environment.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

와

는 각각 복소수

의 실수부와 허수부를 나타내고,

는 행렬

의 (m, n)번째 성분을 나타내며,

,

,

는 각각 행렬

의 복소공액(complex conjugate), 공액전치(conjugate transpose), 전치(transpose)를 나타내고,

는 행렬

의 트레이스(trace)를 나타내는 것으로 한다.Ordinary characters are referred to below as scalars, bold lowercase letters as vectors, and bold uppercase letters as matrices. And

Wow

Is a complex number each

Represents the real and imaginary parts of,

Is a matrix

Represents the (m, n) th component of,

,

,

Are each matrix

Complex conjugate, conjugate transpose, transpose of

Is a matrix

Assume a trace of.

First, a beamforming apparatus of a multi-user multi-input / output system according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 1.

1 is a block diagram illustrating a beamforming apparatus of a multi-user multi-input / output system according to an exemplary embodiment of the present invention.

개 존재한다고 가정한다.As shown in FIG. 1, the multi-user multi-input / output system includes a transmitter 100 and a plurality of receivers 200, and the transmitter 100 and the receiver 200 are connected through a wireless communication network. The transmitting device 100 is located in a base station, and each receiving device 200 is located in a terminal of a multi-user distributed in a wide range. The number of receiving devices 200 is not limited,

Suppose there is a dog.

The transmitting apparatus 100 includes a beam forming unit 110, a matrix calculating unit 120, and a plurality of transmitting antennas 130, and each receiving apparatus 200 includes a receiving combiner 210 and a plurality of receiving antennas 230. ). The transmitter 100 may further include a channel encoder (not shown), a bit interleaver (not shown), a serial-to-parallel converter (not shown), and a plurality of mapping units (not shown). The receiver 200 may further include a channel decoder (not shown), a bit deinterleaver (not shown), a parallel-to-serial converter (not shown), and a demapping unit (not shown). The beamforming apparatus according to the embodiment of the present invention includes the beam forming unit 110 and the matrix computing unit 120 in a narrow sense, but may further include a channel coder, a bit interleaver, a serial and a parallel converter, and a mapping unit in a broad sense. have.

The channel coder encodes information bits to be transmitted to the receiving device. That is, the channel coder inserts a cyclic redundancy check code (CRC) code, a convolutional code, and the like into the information bits so that the reception device can correct a random error that may occur during radio wave transmission.

The bit interleaver changes the arrangement of the bit stream provided from the channel coder so that the receiving device can correct the burst error or the fading caused by the fading. The bit interleaver may change the arrangement of the bit stream using methods such as block interleaving, helical interleaving, random interleaving, and the like.

The serial-to-parallel converter converts the bit stream serially input from the bit interleaver into a plurality of parallel bit streams according to the number of mapping units and sends the bit streams to the corresponding mapping units. Each parallel stream is generated by cutting the serial bit stream by a predetermined number of bits corresponding to the modulation level of the mapping unit. Herein, the modulation level is determined according to the modulation scheme used in the mapping unit. For example, if the number of mapping units is two and the modulation scheme is 16-QAM, the serially input bit stream may be converted into two parallel bit streams in units of 4 bits.

로 변환한다.The mapping unit uses a modulation scheme such as quadrature amplitude modulation (QAM) and quadrature phase shift keying (QPSK).

Convert to

을 계산하고 송신 빔형성 행렬

를 계산한다. 또한 행렬 연산부(120)는 전력 손실률(power loss factor)과 위상 값(phase values) 등을 포함하는 피드포워드 정보(feedforward information)를 생성한다.The matrix operation unit 120 performs a channel matrix based on the feedback information from the receiver 200.

Calculate the transmit beamforming matrix

Calculate In addition, the matrix operator 120 generates feedforward information including a power loss factor, phase values, and the like.

과 행렬 연산부(120)로부터 제공받은 송신 빔형성 행렬

을 이용하여 송신 신호를 생성하고, 송신 안테나(130)를 통하여 송신 신호를 전송한다. 또한 빔형성부(110)는 행렬 연산부(120)로부터 제공받은 피드포워드 정보를 송신 안테나(130)를 통하여 수신 장치(200)로 전송한다.The beam forming unit 110 is a symbol provided from the mapping unit

And the transmission beamforming matrix received from the matrix operator 120

Generates a transmission signal by using, and transmits the transmission signal through the transmission antenna 130. In addition, the beamformer 110 transmits the feedforward information provided from the matrix calculator 120 to the receiver 200 through the transmit antenna 130.

및 피드포워드 정보를 수신한다.The receiving device 200 transmits a signal transmitted from the transmitting device 100 through the receiving antenna 230.

And feedforward information.

을 계산하고, 수신 빔형성 행렬

과 수신된 신호

를 이용하여 필터 출력

를 생성한다. 그리고 필터 출력

과 전력 손실률을 이용하여 심벌

를 추정한다.The reception combiner 210 receives a reception beamforming matrix using a phase value.

And receive beamforming matrix

And received signals

Filter output using

. And filter output

And symbol using power loss rate

Estimate

를 비트 스트림으로 변환한다. 즉, 디매핑부는 수신 결합부(210)로부터 제공받은 심벌

를 복조하여 비트 스트림으로 변환한다.The demapping unit is a symbol estimated by the demodulation method corresponding to the modulation method used in the mapping unit.

To a bit stream. That is, the demapping unit is a symbol provided from the reception combiner 210.

Demodulate to convert to a bit stream.

The parallel converter converts a bit stream input in parallel from the demapping unit into a serial bit stream.

The bit deinterleaver changes the arrangement of the bit stream provided from the parallel-to-serial conversion unit according to the interleaving method used by the transmission apparatus 100 and converts the bit stream into the original bit stream.

The channel decoder checks whether there is an error using a CRC code, a convolutional code, etc. inserted in the bit stream provided from the bit deinterleaver, corrects the error if there is an error, and finally transmits it from the transmitting apparatus 100. Generate an estimated bit corresponding to the information bit to be made.

, 전력 손실률 및 위상 값을 계산하는 방법에 대하여 상세하게 설명한다.Then, the matrix beam forming unit 120 of the transmitting apparatus 100 according to the embodiment of the present invention transmit matrix formation beam

The method of calculating the power loss rate and the phase value will be described in detail.

개 존재하는 것으로 하고,

는 수신 장치(200)를 식별하기 위한 정보로서

번째 수신 장치(200)의 수신 안테나(230)는

개 존재하는 것으로 한다(

). 그러면 모든 수신 장치(200)의 수신 안테나(230)의 개수의 합은

으로 나타낼 수 있다. 그리고

는

번째 수신 장치(200)에 제공되는 공간 스트림(spatial streams)의 개수를 나타내고, 송신 장치(100)와

번째 수신 장치(200) 사이의 채널은

채널 행렬

로 모델링되며,

는 송신 장치(100)의

번째 안테나(130)와

번째 수신 장치의

번째 안테나(230) 사이의 채널 이득(channel gain)을 나타내고,

는

번째 수신 장치(200)에 대한

송신 데이터 심벌 벡터를 나타내는 것으로 한다. 그리고 각 수신 장치(200)는 자신의 채널을 통해 모든 스트림의 조합인

심벌 스트림을 수신한다.Hereinafter, the transmission antenna 130

Let's exist

Is information for identifying the receiving apparatus 200.

The receiving antenna 230 of the first receiving device 200

It is said that there exists dog

). Then the sum of the number of receiving antennas 230 of all receiving apparatuses 200

It can be represented as And

Is

The number of spatial streams provided to the first receiving device 200, and the transmitting device 100 and

The channel between the first receiving device 200 is

Channel matrix

Modeled as

Of the transmitting device 100

With the first antenna (130)

Of the first receiving device

Channel gain between the first antenna 230,

Is

For the first receiving device 200

It is assumed that the transmission data symbol vector is represented. Each receiving device 200 is a combination of all streams through its own channel.

Receive symbol stream.

번째 수신 장치(200)에 대한 송신 빔형성 행렬을

라고 하면

번째 수신 장치(200)에 수신되는 신호

는 [수학식 1]과 같다.first

The transmission beamforming matrix for the first receiving device 200

Say

Received by the first receiving device 200

Is the same as [Equation 1].

는 잡음 벡터(noise vector)이고, 항목

는

번째 수신 장치(200)에 대한 다른(

) 수신 장치(200)로부터의 간섭을 나타낸다.here,

Is a noise vector, and

Is

For the first receiving device 200 (

) Represents interference from the receiving apparatus 200.

번째 수신 장치(200)에 대한 수신 신호

에 수신 행렬

를 곱하여 생성된 필터 출력

는 [수학식 2]와 같다.

Signal for the first receiving device 200

Receive matrix

Filter output generated by multiplying

Is the same as [Equation 2].

, 수신 빔형성 행렬

, 송신 빔형성 행렬

을 다음과 같이 각각 정의한다.Network channel matrix for convenience of explanation

Receive beamforming matrix

Transmission beamforming matrix

Define each as follows:

은 [수학식 3]과 같이 나타낼 수 있다.Then, the filter output of all the receiving device 200

Can be expressed as shown in [Equation 3].

는

로 나타낼 수 있고,

는

로 나타낼 수 있으며,

이다.here

Is

Can be represented by

Is

Can be represented by

to be.

A block diagonalization (BD) algorithm for a multi-user MIMO system will be briefly described.

Block diagonalization algorithm

In the block diagonalization algorithm, a constraint such as Equation 4 is used to remove interference between all receiving apparatuses 200.

는 행렬

의 영공간(nullspace)에 놓여 있어야 한다. 여기서 행렬

는

로 정의된다.

를

로 나타내면 행렬

의 특이값 분해(Singular Value Decomposition, SVD)를

로 정의할 수 있다. 여기서 유니타리 행렬(unitary matrix)

는 좌특이 벡터(left singular vector)를 포함하고, 행렬

는 행렬

의 정렬된 특이값(ordered singular value)으로 이루어져 있으며, 행렬

는 처음

개의 우특이 벡터(right singular vector)로 이루어져 있고, 행렬

는 마지막

개의 우특이 벡터를 유지한다. 행렬

는 행렬

의 영공간에 대하여 직교 기저(orthogonal basis)를 형성하므로, 행렬

의 칼럼 조합을 이용하여

번째 수신 장치(200)에 대한 빔형성 행렬

를 구성할 수 있다.Matrix to satisfy Zero Forcing (ZF) constraint of Equation 4

Is a matrix

It must be placed in the nullspace of. Where matrix

Is

Is defined as

To

If expressed as

Singular Value Decomposition (SVD) of

Can be defined as Where the unitary matrix

Contains a left singular vector, and the matrix

Is a matrix

Matrix of ordered singular values

First

Matrix consisting of two right singular vectors

Last

Maintain the right side vector of the dog. procession

Is a matrix

Matrix forms an orthogonal basis of the zero space of

Using a column combination of

Beamforming matrix for the first receiving device 200

Can be configured.

번째 수신 장치(200)에 대한 전송이 제로 포싱(ZF) 제약 하에서 일어나기 위하여

의 랭크(rank)인

는 1 이상이어야 한다.

에 대한 충분 조건은 행렬

의 적어도 하나의 행이 행렬

의 다른 행들에 선형 독립이라는 것이다. 행렬

의 모든 행이 행렬

에 선형 독립이라고 가정하면 이 조건은 충족된다.

For the first receiving device 200 to occur under zero forcing (ZF) constraint

Rank of

Must be at least 1.

Sufficient condition for the matrix

At least one row of the matrix

In other rows of is linear independence. procession

All rows of a matrix

This condition is met if we assume linear independence.

이외의 수신 장치(200)에 대한 채널 행렬

의 영공간을

번째 수신 장치(200)에 대한 채널 행렬

에 적용한 후의 수신 신호는

로 나타낼 수 있다. 여기서

이다.

번째 수신 장치(200)는 다른 수신 장치(200)로부터의 간섭 없이 자신의 데이터 스트림을 수신할 수 있으므로 단일 사용자 MIMO 시스템의 어떠한 기법도 적용될 수 있다.

Channel matrix for non-receiving device 200

Spirit space

Channel matrix for the first receiving device 200

The received signal after applying to

It can be represented as. here

to be.

Since the first receiving device 200 may receive its own data stream without interference from other receiving devices 200, any technique of the single user MIMO system may be applied.

는 [수학식 5]와 같이 정의할 수 있다.By analyzing the dimensions of the zero space used to form the beam, taking into account the receive coupling matrix,

Can be defined as shown in [Equation 5].

을 계산하는 방법에 대하여 설명한다.Next, an optimal receive matrix that minimizes the power used to eliminate all multi-user interference

It will be described how to calculate.

), 각 수신 장치(200)에 하나의 스트림이 제공되는 것으로 가정한다. 물론, 본 발명은 수신 안테나(230)의 개수가 세 개 이상인 경우 에도 동일하게 적용될 수 있다. 이 경우 수신 행렬

은 행벡터가 되므로 이하에서는 이를 수신 결합 벡터

로 나타낸다.For convenience of explanation, it is assumed that each receiving apparatus 200 has two receiving antennas 230 (

It is assumed that one stream is provided to each receiving apparatus 200. Of course, the present invention can be equally applied even when the number of receiving antennas 230 is three or more. In this case the reception matrix

Since is a row vector,

Respectively.

는 [수학식 6]과 같이 나타낼 수 있다.In order to satisfy the zero forcing (ZF) constraint, the pseudo inverse of the effective channel matrix can be selected in consideration of the reception coupling vector of all the receiving devices 200, and accordingly, the transmission beam of Equation 3 Formation matrix

Can be expressed as shown in [Equation 6].

을 대입하면 필터 출력 벡터

는 [수학식 7]과 같이 나타낼 수 있다.Transmit Beamforming Matrix in Equation 3

Is substituted, the filter output vector

Can be expressed as shown in [Equation 7].

은 전력 손실률을 나타내고, 파워 제약에 의하면 전력 손실률

는 [수학식 8]과 같이 계산될 수 있다.here

Represents the power loss rate, and according to the power constraint, the power loss rate

May be calculated as shown in [Equation 8].

는 전체 전송 전력(total transmitted power)을 나타낸다.here

Denotes total transmitted power.

을 최소화하면서 최적의 수신 벡터를 구하는 문제를 식으로 표현하면 [수학식 9]와 같다.Power loss rate

The problem of finding the optimal reception vector with the minimum expression is expressed as [Equation 9].

First, the permutation of the effective channel matrix does not change the metric.

의 조건을 충족하는 순열 행렬

을 정의한다. 여기서 순열로 배치된 유효 채널 행렬

는

로 정의 된다.From [Equation 3] and [Equation 5],

Permutation matrix that satisfies

Define. Where the effective channel matrix arranged in permutation

Is

Is defined as

Representation of the optimization metric from this relationship is expressed by Equation 10.

과

의 성질을 이용하면 위의 메트릭은 [수학식 11]과 같이 풀린다.

and

Using the property of, the above metric is solved as shown in [Equation 11].

It can be seen from Equation 11 that the metric is not affected by the permutation of the effective channel matrix.

Algorithm 1

번째 이외의 다른 수신 장치(200)의 수신 결합 벡터

를 고정시킨 상태에서

번째 수신 장치(200)에 대한 최적의 수신 벡터

를 반복하여 계산함으로써 수신 빔형성 행렬

을 계산할 수 있다. 이에 따라 [수학식 9]는 [수학식 12]와 같이 나타낼 수 있다.Next, a method of solving [Equation 9] will be described. The method described below is called algorithm 1.

Receive combining vector of the receiving device other than the second

With fixed

Optimal reception vector for the first receiving device 200

Receive beamforming matrix by iteratively calculating

Can be calculated. Accordingly, Equation 9 may be expressed as Equation 12.

의 QR 분해(QR factorization)는

로 정의되고,

는

의 최대 고유값(maximum eigenvalue)에 대응하는 고유 벡터(eigenvector)를 나타낸다. [수학식 12]로부터

에 대하여 수신 벡터

를 구하고 이러한 과정을 반복하면, 전력 손실률을 최소화하는 최적의 수신 벡터의 집합을 결정할 수 있다.here

QR factorization of

Defined as

Is

An eigenvector corresponding to the maximum eigenvalue of. From Equation 12

Receive vector against

By repeating this process, we can determine the optimal set of received vectors that minimize the power loss rate.

Algorithm 1 can be summarized as follows.

를 (

)에 대하여

으로 초기화Step 1) Receive Vector

(

)about

Reset to

Step 2) Set the variable iter_count for the outer loop to 0

를 0으로 설정Step 3) Variable for Inner Loop

Is set to 0

로부터

와

를 구함Step 4)

from

Wow

Wanted

를 QR 분해하여

와

을 계산Step 5)

QR decomposition

Wow

Calculate

를 행렬

의 최대 고유값(maximum eigenvalue)에 대응하는 단위 놈 고유벡터(unit-norm eigenvector)로 결정Step 6)

Matrix

Determined by the unit-norm eigenvector corresponding to the maximum eigenvalue of

가

보다 작거나 같으면,

에 1을 더하고 단계 4)로 이동Step 7)

end

Is less than or equal to

Add 1 to and go to step 4)

Step 8) If iter_count is less than max_iteration, add 1 to iter_count and go to step 3)

On the other hand, using QR-updates instead of QR decomposition in step 5) can reduce the computational complexity.

가 계산되면, 계산된

는 [수학식 13]과 같이 일반 복소 유니타리 행렬(general complex unitary maxtrix)을 이용하여 나타낼 수 있다.Receive Beamforming Vector by Algorithm 1

Is calculated,

Can be represented using a general complex unitary maxtrix as shown in [Equation 13].

과

는 다음과 같이 정의되며,

는

이다.here

and

Is defined as:

Is

to be.

를 표현하면 [수학식 14]와 같다. 물론 두 번째 행을 이용할 수도 있다.Receive beamforming vector using first row in matrix [Equation 13]

Is expressed as in [Equation 14]. Of course, you can also use the second line.

를 식별할 수 있는 두 개의 위상 값

과

는 [수학식 15]와 같이 계산할 수 있다.Using the relationship between the components of Equation 14,

Two phase values to identify

and

Can be calculated as shown in [Equation 15].

과

는 각각 수신 벡터

의 첫 번째와 두 번째 원소를 나타낸다.here

and

Each receive vector

Represents the first and second elements of.

를 계산하고, 계산된 수신 빔형성 벡터

를 이용하여 [수학식 15]와 같이 두 개의 위상 값

과

를 계산할 수 있다. 계산된 위상 값

과

는

번째 수신 장치(200)로 전송되고, 이 수신 장치(200)는 두 개의 위상 값

과

를 이용하여 [수학식 14]를 통해 수신 빔형성 벡터

를 계산할 수 있으며, 일반화시면 수신 빔형성 행렬

을 계산할 수 있게 된다.In summary, the matrix calculating unit 120 of the transmitting apparatus 100 uses the algorithm 1 to receive a beamforming vector.

Is computed and the calculated received beamforming vector

Using two phase values as shown in [Equation 15]

and

Can be calculated. Calculated phase value

and

Is

Is transmitted to the first receiving device 200, which receives two phase values.

and

Receive beamforming vector using Equation (14)

Can be computed, and in generalization, the reception beamforming matrix

Can be calculated.

을 알고 있으므로 [수학식 3]에서의

를 계산할 수 있으며, [수학식 6]을 이용하여 송신 빔형성 행렬

을 계산할 수 있다. 그리고 송신 장치(100)는 [수학식 8]을 이용하여 전력 손실률

을 계산하고 이를 수신 장치(200)로 전송한다. 수신 장치(200)는 [수학식 7]의 전력 손실률

과 필터 출력

을 이용하여 심벌

를 추출한다.In addition, the transmitter 100 calculates a channel matrix calculated using the feedback information from the receiver 200.

Because we know that

Can be calculated, and the transmission beamforming matrix using Equation 6

Can be calculated. The transmitter 100 transmits power loss using Equation 8.

Calculate and transmit it to the receiving device 200. The receiving device 200 has a power loss rate of Equation 7

And filter output

Symbol using

Extract

를 계산할 수 있도록 하는 방법(이하, 알고리즘 2라 함)에 대해 설명한다.Using this algorithm 1, two phase values should be transmitted to each receiving apparatus 200. Then, in order to reduce such overhead, each receiving apparatus 200 uses only one phase value to receive a matrix.

It will be described a method (hereinafter referred to as Algorithm 2) that can be calculated.

Algorithm 2

Algorithm 2 is based on the complex rotation matrix of Equation 13 consisting of two matrices as follows.

로 이용한다. 따라서

번째 수신 장치(200)의 수신 벡터

는 [수학식 16]과 같이 나타낼 수 있다.By selecting one of two matrices of the complex rotation matrix, the phase value transmitted to each receiving apparatus 200 may be reduced from two to one. Since selecting either of the two matrices has no effect on the overall performance, the first vector of the first matrix

Use as. therefore

Reception vector of the first reception device 200

Can be expressed as shown in [Equation 16].

의 성분은 실수 값으로 되어 있는 것을 알 수 있다.Compared to Equation 14 of Algorithm 1, the reception vector in Equation 16 is obtained.

It turns out that the component of becomes a real value.

Equation 12 can be derived using the following well-known results.

If the above expression is expressed as a real-valued representation, Equation 17 is used.

는

이고,

은

(

)이다. 그리고 알고리즘 2에서 수신 벡터

는 실수 값 벡터 (

)이므로 [수학식 17]의 해는

로 줄어든다.here

Is

ego,

silver

(

)to be. And receive vector in algorithm 2

Is a real value vector (

), So the solution of [Equation 17]

Decreases to.

Therefore, using these results, algorithm 2 can be obtained by modifying only step 6) of algorithm 1 as follows.

Step 6 of Algorithm 2)

를 행렬

의 최대 고유값에 대응하는 단위 놈 고유벡터로 결정

Matrix

Determined by the unit norm eigenvectors corresponding to

를 계산하고, 계산된 수신 빔형성 벡터

를 이용하여 [수학식 16]과 같이 쉽게 위상 값

를 계산할 수 있다. 계산된 위상 값

은

번째 수신 장치(200)로 전송되고, 이 수신 장치(200)는 위상 값

를 이용하여 [수학식 16]을 통해 수신 결합 벡터

를 계산할 수 있다.As in Algorithm 1, the transmitting device 100 uses the Algorithm 2 to receive the beamforming vector.

Is computed and the calculated received beamforming vector

Phase value as shown in [Equation 16] using

Can be calculated. Calculated phase value

silver

Is sent to the first receiving device 200, the receiving device 200 is a phase value.

Receive combining vector through [Equation 16] using

Can be calculated.

Next, the performance of the beamforming scheme and the conventional scheme of the multi-user MIMO system according to the embodiment of the present invention will be described with reference to FIG. 2.

일 때 대략 5dB의 전력 이득을 제공하며, 알고리즘 2를 이용한 빔형성 방식도 기존의 제로 포싱 선처리 방식에 비하여 2dB 이득을 얻을 수 있음을 알 수 있다.2 is a graph showing simulation results for comparing the performance of a multi-user MIMO system and an existing system according to an embodiment of the present invention, where the horizontal axis represents a signal-to-noise ratio (SNR) and the vertical axis represents Bit Error Rate (BER). It can be seen that the beamforming method using Algorithm 1 and Algorithm 2 has a small performance difference of less than 0.5 dB. However, the beamforming method using Algorithm 1 has a bit error rate compared to the conventional block diagonalization (BD) technique.

It provides a power gain of approximately 5dB, and the beamforming method using Algorithm 2 can also obtain a 2dB gain compared to the conventional zero forcing preprocessing method.

Next, a beamforming method of a multi-user MIMO system according to an embodiment of the present invention will be described with reference to FIG. 3.

3 is a flowchart illustrating a beamforming method of a multi-user MIMO system according to an embodiment of the present invention.

First, the transmitter 100 of the MIMO system according to an embodiment of the present invention performs channel encoding for inserting a CRC code, a convolutional code, etc. in an information bit so that the receiver may correct a random error that may occur during radio wave transmission. The interleaving is performed by changing the arrangement of the bit stream using a method such as block interleaving, helical interleaving, random interleaving, and the like so that the error caused by the burst error or fading can be corrected by the receiving apparatus.

로 변환한다(S310).The transmitting device 100 then converts the serially altered serial bit stream into at least one parallel bit stream based on the modulation level, and uses modulation schemes such as quadrature amplitude modulation (QAM) and quadrature phase shift modulation (QPSK). Symbolize a parallel bit stream

Convert to (S310).

을 추출해 내고, 알고리즘 1 또는 2를 이용하여 수신 빔형성 행렬

를 계산하며, 두 개의 위상 값(알고리즘 1) 또는 한 개의 위상 값(알고리즘 2)과 전력 손실률

을 포함하는 피드포워드 정보를 연산한다(S320). 그리고 송신 장치(100)는 [수학식 6]을 이용하여 송신 빔형성 행렬

을 계산한다(S330).The transmitting device 100 receives the feedback information from the receiving device 200 and performs a channel matrix.

And extract the received beamforming matrix using algorithm 1 or 2.

Calculates two phase values (algorithm 1) or one phase value (algorithm 2) and power loss rate

Compute feedforward information including a (S320). In addition, the transmitting apparatus 100 transmits a transmission beamforming matrix using Equation 6

To calculate (S330).

과 심벌

를 곱하여 송신 신호를 생성하고(S340), 송신 안테나(130)를 통하여 생성된 송신 신호와 피드포워드 정보를 전송한다(S350).Then, the transmitting device 100 transmits a transmission beamforming matrix.

And the symbol

To generate a transmission signal by multiplying (S340), and transmits the transmission signal and the feedforward information generated through the transmission antenna 130 (S350).

Next, a method of processing the signal received by the reception apparatus 200 from the transmission apparatus 100 will be described.

및 피드포워드 정보를 수신한다. 수신 장치(200)는 송신 장치(100)에서 사용된 알고리즘 종류에 따라 두 개 또는 한 개의 위상 값을 이용하여 [수학식 14] 또는 [수학식 16]을 통해 수신 빔형성 행렬

를 계산한다. 그리고 수신 장치(200)는 수신 빔형성 행렬

과 수신된 신호

를 이용하여 필터 출력

를 생성한다. 수신 장치(200)는 [수학식 7]의 전력 손실률

과 필터 출력

을 이용하여 심벌

를 추출한다.The reception device 200 receives a signal through the reception antenna 230.

And feedforward information. The receiving device 200 uses the two or one phase values according to the type of algorithm used in the transmitting device 100 through [Equation 14] or [Equation 16].

Calculate In addition, the receiving apparatus 200 receives a reception beamforming matrix.

And received signals

Filter output using

. The receiving device 200 has a power loss rate of Equation 7

And filter output

Symbol using

Extract

를 복조하여 비트 스트림으로 변환한다. 그런 후 수신 장치(200)는 변환된 병렬 비트 스트림을 직렬 비트 스트림으로 변환한다. 수신 장치(200)는 송신 장치(100)에서 이용한 인터리빙 방법에 따라 직렬 비트 스트림의 배열 등을 변경하고, 비트 스트림 내에 삽입되어 있는 CRC 코드, 컨볼루셔널 코드 등을 이용하여 에러 여부를 체크하고, 에러가 존재하는 경우 에러를 정정하여 추정 비트를 생성한다. 수신 장치(200)는 추정 비트를 생성하는 과정과는 별도로 송신 장치(100)에 채널 상태 정보를 전송하여 송신 장치(100)로 하여금 채널 행렬을 추출할 수 있도록 한다.The receiving device 200 is a symbol in a demodulation method corresponding to the modulation method used in the transmitting device 100.

Demodulate to convert to a bit stream. The receiving device 200 then converts the converted parallel bit stream into a serial bit stream. The receiving device 200 changes the arrangement of the serial bit stream according to the interleaving method used by the transmitting device 100, checks whether there is an error using a CRC code, a convolutional code, etc. inserted in the bit stream, If an error exists, the error is corrected to generate an estimate bit. The reception apparatus 200 transmits the channel state information to the transmission apparatus 100 separately from the process of generating the estimated bits so that the transmission apparatus 100 may extract the channel matrix.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a block diagram illustrating a beamforming apparatus of a multi-user multi-input / output system according to an exemplary embodiment of the present invention.

2 is a graph illustrating simulation results in order to compare the performance of a multi-user MIMO system and an existing system according to an exemplary embodiment of the present invention.

3 is a flowchart illustrating a beamforming method of a multi-user MIMO system according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: transmitting apparatus, 110: beam forming unit,

120: matrix calculation unit, 130: transmit antenna,

200: receiving device, 210: receiving coupler,

230: receiving antenna

Claims (16)

A beam forming apparatus of a multiple input / output system for a plurality of receiving apparatuses including a first receiving apparatus, A matrix operation unit for calculating a transmission beamforming matrix and a reception combining matrix, and A beamforming unit configured to generate a transmission signal by performing an operation using the transmission beamforming matrix and the symbol; The matrix calculator updates the reception coupling matrix of the first reception device while the reception coupling matrix of the reception devices other than the first reception device is fixed among the plurality of reception devices. Beamforming apparatus. In claim 1, And the matrix calculator calculates at least one phase value, and the beamformer transmits the at least one phase value to the receiving device. In claim 2, And the reception device calculates the reception coupling matrix using the at least one phase value from the beamforming unit. In claim 1, The transmit beamforming matrix

silver

Is calculated as above

Is

Calculated as above

Is the receive coupling matrix, and

Is a channel matrix. delete delete delete delete A beamforming method of a multiple input / output system for a plurality of receiving apparatuses including a first receiving apparatus, Computing a transmit beamforming matrix and a receive coupling matrix, and Generating a transmission signal by performing an operation using the transmission beamforming matrix and symbols; The calculating may include updating the reception coupling matrix of the first receiving device while fixing the reception coupling matrix of the receiving device except the first receiving device among the plurality of receiving devices. Beamforming method. The method of claim 9, The calculating step includes calculating at least one phase value, The generating step includes transmitting the at least one phase value to the receiving device. In claim 10, And the reception apparatus calculates the reception coupling matrix using the at least one phase value. The method of claim 9, The transmit beamforming matrix

silver

Is calculated as above

Is

Calculated as above

Is the receive coupling matrix, and

Is a channel matrix. delete delete delete delete

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