KR101604871B1 - Communication system for mu-mimo scheme - Google Patents

Abstract

The present invention relates to a multi-user multi-input multi-output (MU-MIMO) scheme.

The MS selects a precoding vector from a plurality of column vectors included in the precoding matrix and feeds the precoded vector back to the BS, and the BS transmits the data to the MS using the precoding vector.

Precoding, precoding matrix index, PMI, feedback

Description

[0001] COMMUNICATION SYSTEM FOR MU-MIMO SCHEME [0002]

The present invention relates to a multi-user multi-input multi-output (MU-MIMO) scheme. The present invention has been derived from research carried out as part of the IT growth engine technology development project of the Ministry of Knowledge Economy and the Korea IT Industry Promotion Agency [assignment number: 2006-S-001-03, title: Development of adaptive wireless access and transmission technology].

A wireless communication system uses a multi-antenna transmission / reception scheme (MIMO) to increase the frequency efficiency of radio resources. As an example of a multi-antenna transmission / reception scheme, a codebook multi-antenna transmission / reception scheme is used.

In a codebook multi-antenna transmission / reception scheme, a terminal selects at least one column vector among a plurality of column vectors included in a precoding matrix as a precoding vector, and feeds back information of a precoding vector to a base station. The base station has the same codebook as the terminal. The base station identifies the precoding vector selected by the terminal based on the information of the fed-back precoding vector, and transmits the data to the terminal using the identified precoding vector.

A specific precoding vector concentrates transmission energy in a specific direction. Therefore, if different terminals receive data using the same precoding vector, the data transmission performance is degraded due to the influence of interference between the terminals.

The base station selects only one of the plurality of terminals that have selected the same column vector as the precoding vector as the data receiving terminal and transmits the data to the selected data receiving terminal.

Therefore, in order to maximize the data transmission performance, it is desirable that each terminal selects a column vector as a precoding vector as much as possible.

An object of the present invention is to efficiently transmit data of each user simultaneously to a plurality of users by using the same time or frequency resources in a multi-input multi-output (MIMO) system.

According to another aspect of the present invention, there is provided a mobile station including a channel estimator for estimating a channel state with a base station, Wherein the feedback information generating unit includes a precoding vector selecting unit for selecting a coding vector, a feedback information generating unit, and a transmitting unit, and when the precoding vector selecting unit selects a plurality of contiguous column vectors as the precoding vector, Selects the outermost vector among the coding vectors as a reference vector, generates information on the reference vector and information on the number of the selected column vectors as feedback information, and the transmitter transmits the feedback information to the base station Terminal.

According to an aspect of the present invention, there is provided a base station comprising: a receiver for receiving feedback information from a plurality of terminals belonging to the base station; a precoding vector identification unit for identifying a precoding vector selected by each terminal based on the feedback information; A terminal selection unit for selecting the terminals that do not overlap with the selected precoding vectors to the data reception terminal, and a transmission unit for transmitting data to the data reception terminal.

According to another aspect of the present invention, a terminal includes a channel estimator for estimating a channel state with a base station, a first column vector or a last column vector among column vectors included in a precoding matrix based on the channel state, A transmission unit for transmitting information on the precoding vector to the base station and a transmission unit for transmitting data transmitted from the base station on the basis of the precoding vector, And a receiving unit for receiving the received signal.

According to the present invention, a multi-input multi-output (MIMO) system can efficiently transmit data of each user simultaneously to a plurality of users by using the same time or frequency resources.

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

1 is a diagram illustrating a concept of a multiple input multiple output system according to the present invention.

The base station 110 transmits data to the terminals 141 and 142 or receives data from the terminals 141 and 142 using a plurality of antennas 121, 122, 123 and 124. The base station 110 can transmit data or receive data in a specific direction by using a plurality of antennas 121, 122, 123, and 124 and a precoding vector. The influence of the interference signal in the other direction is reduced, so that the data transmission efficiency of the base station 110 is improved.

In FIG. 1, the terminals 141 and 142 are located in different directions. The base station 110 generates different beams 131 and 132 using different precoding vectors for the terminals 141 and 142 and transmits the data to the terminals 141 and 142 using the generated beams. 142).

Each terminal 141, 142 may have the same codebook as the base station 110. The codebook includes a plurality of precoding matrices, and the precoding matrix includes a plurality of precoding vectors. Selects a precoding vector based on the channel state between each of the terminals 141 and 142 and the base station 110 and generates channel quality information when the base station transmits the selected precoding vector to each of the terminals 141 and 142 do. Each terminal 141 and 142 transmits information on the precoding vector and channel quality information to the base station 110. The information on the precoding vector may be information on the index and rank of the precoding matrix including the precoding vector.

The base station 110 receives information on the precoding vector and channel quality information from each terminal. The base station 110 can transmit data to the terminals 141 and 142 using the precoding vectors selected by the terminals 141 and 142 when the terminals 141 and 142 select different precoding vectors have. When each terminal 141 and 142 selects the same precoding vector, the base station 110 compares the channel quality information of each of the terminals 141 and 142 with each other. The base station 110 can transmit data to the terminal having better channel quality information.

The base station and the terminal have the same codebook. The codebook includes at least one precoding matrix.

The codebook S can be expressed by the following equation (1).

[Equation 1]

은 코드북을 구성하는 n번째 프리코딩 행렬이다.here,

Is an n-th precoding matrix constituting the codebook.

은 하기 수학식 2와 같이 표현할 수 있다.The nth precoding matrix

Can be expressed by the following equation (2).

&Quot; (2) "

은 n번째 프리코딩 행렬의 l (l =1, 2,…,L)번째 열 벡터이 다.From here

It is the n-th l of the precoding matrix (l = 1, 2, ... , L) th column bekteoyi.

The number of data symbols that a base station sends to one terminal using multiple transmit antennas is called a layer. When the terminal selects a plurality of precoding vectors, the terminal feeds back information on the selected precoding vector to the base station. The base station simultaneously transmits a plurality of symbols to the terminal using a layer corresponding to each precoding vector.

의

번째 열 벡터를 사용한다고 가정하면, 이 때 사용하는 프리코딩 행렬을 아래 [수학식 3]과 같이 정의할 수 있다.The number of data layers to be transmitted from a base station to one terminal is M, and a precoding matrix

of

Th column vector, the precoding matrix used at this time can be defined as Equation (3) below.

&Quot; (3) "

을 이용하여 프리코딩 벡터를 선택한다고 가정하자. 제1 단말기(141)는 레이어 개수가 1개일 때

의 1번째 열 벡터를 프리코딩 벡터로 선택하고, 레이어 개수가 2개일 때

의 1, 4번째 열 벡터를 프리코딩 벡터로 선택하고, 레이어 개수가 3개일 때 1, 2, 4번째 열 벡터를 프리코딩 벡터로 선택하고, 레이어 개수가 4개일 때 1, 2, 3, 4번째 열 벡터를 프리코딩 벡터로 선택한다고 가정하면 각각에 대해서 아래 하기 수학식 4와 같이 쓸 수 있다.The base station 110 notifies the first terminal 141 of the precoding matrix

And a precoding vector is selected using the following equation. When the number of layers is one, the first terminal 141

Is selected as a precoding vector, and when the number of layers is two

1, 2, and 4 column vectors are selected as precoding vectors when the number of layers is 3. When the number of layers is 4, 1, 2, 3, and 4 Th column vector is selected as a precoding vector, it is possible to use Equation (4) below for each.

&Quot; (4) "

라고 하고, 그 때 사용하는 프리코딩 행렬 정보를

라고 하면, 기지국은

을 전송한다.The base station 110 transmits a data vector to be transmitted

, And the precoding matrix information to be used at that time

, The base station

Lt; / RTI >

의 열 벡터를

의 순서로 사용한다고 하면, 아래 수학식 5와 같은 프리코딩 행렬

을 정의할 수 있다.The base station 110 transmits a precoding matrix

The column vector of

, The following equation (5) is used: < EMI ID =

Can be defined.

&Quot; (5) "

은 다음과 같이 쓸 수 있다.That is, if the base station 110 uses column vectors in the same order as in Equation 4,

Can be written as

&Quot; (6) "

에 기반하여 프리코딩 벡터를 선택한다고 가정하자. 제1 단말기(141)는 좌측에 위치한 열벡터들을 순서대로 선택할 수 있다. 즉, 제1 단말기(141)가 1개의 프리코딩 벡터를 선택하는 경우, 제1 단말기는

를 선택한다. 제1 단말기(141)가 2개의 프리코딩 벡터를 선택하는 경우, 제1 단말기(141)는

,

를 선택한다. 제1 단말기(141)가 3개의 프리코딩 벡터를 선택하는 경우, 제1 단말기(141)는

,

,

를 선택하고, 제1 단말기(141)가 4개의 프리코딩 벡터를 선택하는 경우, 제1 단말기는

,

,

,

를 선택한다.When the first terminal 141 receives the

And selects a precoding vector based on the precoding vector. The first terminal 141 can sequentially select column vectors located on the left side. That is, when the first terminal 141 selects one precoding vector, the first terminal

. When the first terminal 141 selects two precoding vectors, the first terminal 141 transmits

,

. When the first terminal 141 selects three precoding vectors, the first terminal 141 transmits

,

,

And the first terminal 141 selects four precoding vectors, the first terminal selects

,

,

,

.

에 포함된 열벡터의 순서를 변형하여 생성된

에 기반하여 프리코딩 벡터를 선택할 수 있다. 일실시예에 따르면, 제2 단말기(142)는 하기 수학식 7과 같은

에 기반하여 프리코딩 벡터를 선택할 수 있다.The second terminal 142

Lt; RTI ID = 0.0 > transformed < / RTI >

Lt; RTI ID = 0.0 > a < / RTI > According to one embodiment, the second terminal 142 may be configured as follows:

Lt; RTI ID = 0.0 > a < / RTI >

&Quot; (7) "

은

의 역순으로 열벡터를 사용하여 구성된 것이다.(7)

silver

In the reverse order of the column vectors.

의 좌측에 위치한 열벡터들을 순서대로 선택할 수 있다. 즉, 제2 단말기(142)가 1개의 프리코딩 벡터를 선택하는 경우, 제2 단말기(142)는

를 선택한다. 제2 단말기(142)가 2개의 프리코딩 벡터를 선택하는 경우, 제2 단말기(142)는

,

를 선택한다. 제2 단말기(142)가 3개의 프리코딩 벡터를 선택하는 경우, 제2 단말기(142)는

,

,

를 선택하고, 제2 단말기(142)가 4개의 프리코딩 벡터를 선택하는 경우, 제2 단말기는

,

,

,

를 선택한다.If the second terminal 142 is not shown in Equation 7 And a precoding vector is selected using the following equation. The second terminal 142

Can be selected in order. In other words, when the second terminal 142 selects one precoding vector, the second terminal 142

. If the second terminal 142 selects two precoding vectors, the second terminal 142 may

,

. When the second terminal 142 selects three precoding vectors, the second terminal 142 may determine

,

,

And if the second terminal 142 selects four precoding vectors, the second terminal selects < RTI ID = 0.0 >

,

,

,

.

,

를 선택하고, 선택한 프리코딩 벡터를 이용하여 기지국으로부터 데이터를 수신할 수 있다. 또한, 제2 단말기(142)는

,

를 선택하고, 선택한 프리코딩 벡터를 이용하여 기지국으로부터 데이터를 수신할 수 있다. 즉, 각 단말기(141, 142)가 프리코딩 벡터를 중복 선택하는 경우를 최대한 방지하여 데이터 전송 효율을 극대화할 수 있다.It is assumed that the first terminal 141 and the second terminal 142 respectively select two precoding vectors. The first terminal 141

,

And receive data from the base station using the selected precoding vector. Also, the second terminal 142

,

And receive data from the base station using the selected precoding vector. That is, it is possible to maximize the data transmission efficiency by preventing the terminals 141 and 142 from duplicatively selecting the precoding vectors.

FIG. 2 is a diagram illustrating a precoding matrix and a reference vector according to an embodiment of the present invention. Referring to FIG. In the embodiment shown in FIG. 2, for simplicity, it is assumed that the codebook includes only one precoding matrix.

을 프리코딩 벡터로 선택하였다고 가정하자. 제1 단말기는 프리코딩 벡터

의 프리코딩 행렬에서의 위치(인덱스)를 포함하는 피드백 정보를 생성할 수 있다.The first terminal selects at least one precoding vector from among a plurality of column vectors included in the precoding matrix. If the first terminal is a column vector

As a precoding vector. The first terminal includes a precoding vector

(Index) in the precoding matrix of < RTI ID = 0.0 >

As an example of generating the feedback information, the first terminal may assume a P matrix including column vectors in the same order as the order of the column vectors included in the precoding matrix. That is, the P matrix is the same matrix as the precoding matrix. In this case, the feedback information may include 1) the first terminal uses the P matrix, and 2) the precoding vector is the first vector (of the P matrix). The base station can use the feedback information to know that the precoding vector is the first vector of the P matrix.

,

를 프리코딩 벡터로서 선택할 수 있다. 이 경우에, 피드백 정보는 1) 제1 단말기가 P 행렬을 이용한다는 점, 2) 프리코딩 벡터는 (P행렬의) 2번째 벡터 및 3번째 벡터라는 점을 포함할 수 있다. 기지국은 피드백 정보를 이용하여 프리코딩 벡터가 P 행렬의 2번째, 3번째 벡터임을 알 수 있다.Assume that the first terminal selects two precoding vectors. The first terminal is a continuous column vector

,

Can be selected as a precoding vector. In this case, the feedback information may include 1) the first terminal uses the P matrix, and 2) the precoding vector is the second and third vector (of the P matrix). The base station can use the feedback information to know that the precoding vector is the second and third vectors of the P matrix.

,

를 프리코딩 벡터로서 선택한 경우에, 제1 단말기는 2-1) (P 행렬의) 2번째 벡터인

가 기준 벡터인 점, 2-2) 프리코딩 벡터의 개수는 2개인 점, 2-3) 기준벡터로부터 오른쪽에 위치한 열벡터들이 프리코딩 벡터로 선택되었다는 점을 피드백 정보로서 생성할 수 있다. 기지국은 2-1), 2-2), 2-3)을 이용하여 기준 벡터

의 좌측에 위치하는

도 프리코딩 벡터로 선택되었음을 알 수 있다. In order to simply generate the feedback information, the first terminal may select a reference vector from a plurality of precoding vectors and generate information feedback information on the number of precoding vectors. In other words,

,

Is selected as a precoding vector, the first terminal is 2-1) the second vector (of the P matrix)

Is a reference vector, 2-2) the number of precoding vectors is 2, and 2-3) the column vectors located on the right side from the reference vector are selected as precoding vectors as feedback information. The base station uses the 2-1), 2-2), and 2-3)

Located on the left side of

Is also selected as a precoding vector.

According to an exemplary embodiment, when the first terminal uses the P matrix, the first terminal may select the leftmost vector among the plurality of continuous column vectors as the reference vector. In this case, it is the same information that (1) the first terminal uses the P matrix and (2-3) the column vectors located to the right from the reference vector are selected as precoding vectors.

According to another embodiment of the present invention, the order of the column vectors of the P matrix may be determined by reflecting the order in which the column vectors are selected as precoding vectors.

를 프리코딩 벡터로 선택할 수 있다. 제1 단말기가 2개의 프리코딩 벡터를 선택하는 경우, 제1 단말기는 프리코딩 행렬의 좌측에 위치한

및

를 프리코딩 벡터로 선택한다. 제1 단말기가 복수의 프리코딩 벡터를 선택하는 경우, 선택된 프리코딩 벡터들은 반드시 연속적으로 위치한다.That is, when the first terminal selects one precoding vector, the first terminal is located at the leftmost position of the precoding matrix

Can be selected as a precoding vector. When the first terminal selects two precoding vectors, the first terminal is located on the left side of the precoding matrix

And

As a precoding vector. When the first terminal selects a plurality of precoding vectors, the selected precoding vectors are always located consecutively.

로 고정하여 피드백 정보를 간단히 구성할 수 있다. 즉, 1)제1 단말기가 P 행렬을 이용하여 프리코딩 벡터를 선택한다는 점과 2-1) (P 행렬의) 1번째 벡터인

가 기준 벡터라는 점은 동일한 정보이다.In this case, the first terminal uses the reference vector

So that the feedback information can be easily configured. That is, 1) the first terminal selects the precoding vector using the P matrix and 2-1) the first vector (of the P matrix)

Is a reference vector is the same information.

Therefore, in this case, the first terminal 1) selects the precoding vector using the P matrix, 2-2) the feedback information includes only the fact that the number of precoding vectors is two, can do. The number of selected precoding vectors can be referred to as rank information.

Although the first terminal selects the leftmost vector among the successive column vectors as the reference vector, it is also possible to select the rightmost vector as the reference vector according to another embodiment.

The Q matrix shown in FIG. 2 includes column vectors in the same order as the order of the column vectors included in the precoding matrix. That is, the P matrix and the Q matrix may be the same matrix. However, when the second terminal selects the precoding vector using the Q matrix, the reference vector may be the column vector located at the rightmost position among the plurality of column vectors included in the Q matrix. Also, when the second terminal selects a plurality of precoding vectors, the column vectors to the left of the reference vector are selected as precoding vectors.

가 프리코딩 벡터로 선택될 수 있다. 제2 단말기가 2개의 프리코딩 벡터를 선택하는 경우,

및

가 프리코딩 벡터로 선택될 수 있다.That is, when the second terminal selects only one precoding vector,

May be selected as a precoding vector. When the second terminal selects two precoding vectors,

And

May be selected as a precoding vector.

3 is a diagram illustrating a concept of selecting a terminal to receive data from among a plurality of terminals, according to an embodiment of the present invention. In FIG. 3, it is assumed that the codebook includes a plurality of precoding matrices. In this case, each terminal must include an index (PMI: Precoding Matrix Index) of a precoding matrix including a precoding vector selected by each terminal in the feedback information from a plurality of precoding matrices included in the codebook.

번째 프리코딩 행렬에 포함된다. 제1 단말기가 P 행렬에 기반하여 프리코딩 벡터를 선택한 경우에, P, Q타입 구별자는 '0'일 수 있다. 이 경우, 기준 벡터는 P 행렬의 복수의 열벡터들 중에서 가장 왼쪽에 위치한 열벡터일 수 있다. 레이어의 개수가 1개 이므로, 제1 단말기가 선택한 프리코딩 벡터의 개수는 1개임을 알 수 있다. 따라서, 기지국은 제1 단말기가

번째 프리코딩 행렬의 1번째 벡터를 프리코딩 벡터로서 선택하였음을 알 수 있다.Feedback information for the first terminal is shown in the first column of FIG. Referring to the feedback information of the first terminal, the precoding vector selected by the first terminal may be selected from a plurality of precoding matrices

Th precoding matrix. If the first terminal selects a precoding vector based on the P matrix, the P, Q type discriminator may be '0'. In this case, the reference vector may be the leftmost column vector among the plurality of column vectors of the P matrix. Since the number of layers is one, it can be seen that the number of precoding vectors selected by the first terminal is one. Therefore,

Th precoding matrix is selected as a precoding vector.

번째 프리코딩 행렬의 1번째, 2번째, 3번째 벡터를 프리코딩 벡터로 선택하였음을 알 수 있다.Feedback information for the second terminal is shown in the second column of FIG. Referring to the feedback information of the second terminal,

Th precoding matrix is selected as a precoding vector.

번째 프리코딩 벡터의 3번째, 4번째 열벡터를 프리코딩 벡터로 선택하였음을 알 수 있다.If the third terminal selects a precoding vector based on the Q matrix, the P, Q type distinguisher may be '1'. In this case, the reference vector may be the column vector located at the rightmost of the plurality of column vectors of the Q matrix. Since the number of layers is two,

Th precoding vector is selected as a precoding vector.

번째 프리코딩 행렬의 3번째, 4번째 벡터를 프리코딩 벡터로 선택하였음을 알 수 있다.The feedback information for the fourth terminal is shown in the fourth column of FIG. Referring to the feedback information of the fourth terminal,

Th precoding matrix is selected as a precoding vector.

번째 프리코딩 행렬의 1번째를 프리코딩 벡터로 선택하였음을 알 수 있다.Referring to the feedback information of the fourth terminal,

Th precoding matrix is selected as a precoding vector.

번째 프리코딩 벡터에 포함된 열벡터를 프리코딩 벡터로 선택하였다. 좀 더 구체적으로 살펴본다면, 제1 단말기는

번째 프리코딩 벡터의 1번째 열벡터를 프리코딩 벡터로 선택하고, 제3 단말기는

번째 프리코딩 벡터의 3번째, 4번째 열벡터를 프리코딩 벡터로 선택하였다. 즉, 제1 단말기와 제3 단말기가 선택한 프리코딩 벡터는 서로 중복되지 않는다. 이 경우, 기지국은 각 단말기가 선택한 프리코딩 벡터를 이용하여 각 단말기로 데이터를 전송할 수 있다.Referring to the feedback information of each terminal, the first terminal and the third terminal

Th precoding vector is selected as a precoding vector. To be more specific, the first terminal

Th precoding vector as a precoding vector, and the third terminal selects

Th precoding vector is selected as a precoding vector. That is, the precoding vectors selected by the first terminal and the third terminal do not overlap with each other. In this case, the base station can transmit data to each terminal using the precoding vector selected by each terminal.

번째 프리코딩 행렬에 포함된 열벡터를 프리코딩 벡터로 선택하였다. 좀 더 구체적으로 살펴본다면, 제2 단말기는 1번째, 2번째, 3번째 벡터를 프리코딩 벡터로 선택하고, 제4 단말기는 3번째 벡터 및 4번째 벡터를 프리코딩 벡터 로 선택하였다. 즉, 제2 단말기와 제4 단말기가 선택한 프리코딩 벡터는 서로 중복된다. 이 경우, 기지국은 제2 단말기와 제4 단말기 중에서 어느 하나의 단말기만을 선택하고, 선택된 단말기에 대하여 3번째 벡터를 프리코딩 벡터로 이용하여 데이터를 전송할 수 있다.Referring to the feedback information of the second terminal and the second terminal, the second terminal and the fourth terminal

Th precoding matrix is selected as a precoding vector. In more detail, the second terminal selects the first, second, and third vectors as precoding vectors, and the fourth terminal selects the third and fourth vectors as precoding vectors. That is, the precoding vectors selected by the second terminal and the fourth terminal are overlapped with each other. In this case, the base station may select only one of the second terminal and the fourth terminal, and transmit data using the third vector as a precoding vector to the selected terminal.

According to an embodiment, each terminal transmits channel quality information related to each precoding vector to the base station by including the feedback information in the feedback information, and the base station decides a terminal to receive data using each precoding vector based on the channel quality information You can decide.

According to an exemplary embodiment, the channel quality information may be a signal-to-noise ratio when each terminal receives data using each precoding vector. The BS may compare signal-to-noise ratios when each terminal receives data using a specific column vector, and may select a terminal with the highest SNR as a terminal to receive data using the column vector.

4 is a block diagram illustrating a structure of a terminal according to an embodiment of the present invention. The terminal 400 includes a receiving unit 410, a channel estimating unit 420, a precoding vector selecting unit 430, a feedback information generating unit 450, a channel quality information generating unit 440 and a transmitting unit 460 do.

The channel estimation unit 420 estimates the channel state between the base station 470 and the terminal 400. [

The receiver 410 receives the pilot signal from the base station 470 and the channel estimator 420 estimates the channel state between the base station 470 and the terminal 400 based on the pilot signal.

The precoding vector selector 430 selects a precoding vector based on the estimated channel state. According to an exemplary embodiment, the precoding vector selector 430 may select a precoding vector from a plurality of column vectors included in the precoding matrix.

The feedback information generator 450 may generate information on the precoding vector as feedback information. According to an exemplary embodiment, the precoding vector selector 430 may select a plurality of continuous column vectors among a plurality of column vectors included in the precoding matrix as precoding vectors. In this case, the feedback information generating unit 450 selects the column vector located at the outermost out of the selected plurality of precoding vectors as information on the reference vector and information on the number of column vectors selected as the precoding vector As feedback information.

According to an embodiment, the information on the reference vector may include information on the index of the reference vector. The index of the reference vector indicates which of the plurality of column vectors included in the precoding matrix is selected as the reference vector.

According to one embodiment, the information on the reference vector may include information on the position of the reference vector among the successive column vectors selected as the precoding vector. That is, the information on the mood vector can indicate which of the continuous column vectors is selected as the reference vector. If the rightmost or leftmost vector among the successive column vectors is selected as the reference vector, the feedback information can be simply generated.

The channel quality information generation unit 440 generates channel quality information between the base station 470 and the terminal 400 on the basis of the precoding vector. According to an embodiment, the channel quality information generator 440 generates a signal-to-noise ratio when channel data is received from the base station 470 using the precoding vector selected by the precoding vector selector 430 as channel quality information can do. The feedback information generating unit 450 may include the channel quality information in the feedback information.

The transmitting unit 460 transmits the feedback information to the base station 470.

The base station 470 receives feedback information from a plurality of terminals 400 and 480. The base station 470 identifies the precoding vectors selected by the terminals 400 and 480 using the feedback information. The base station 470 transmits data to the terminals 400 and 480 using the precoding vectors selected by the terminals 400 and 480.

The receiving unit 410 receives data from the base station 470 based on the feedback information.

When a plurality of terminals 400 and 480 select the same column vector as a precoding vector, the base station 470 selects one of the terminals as a data receiving terminal and transmits data to the data receiving terminal using the precoding vector send. According to an embodiment, the BS 470 may select a data receiving terminal based on the channel quality information transmitted by each of the terminals 400 and 480.

5 is a block diagram illustrating a structure of a base station according to an embodiment of the present invention. The base station 500 includes a receiving unit 510, a precoding vector identifying unit 520, a terminal selecting unit 530, and a transmitting unit 540.

The receiving unit 510 receives feedback information from a plurality of terminals 550 and 560 belonging to the base station 500, respectively.

The precoding vector selector 520 identifies a precoding vector selected by each terminal based on the feedback information. According to one embodiment, the precoding vector may be a contiguous column vector among the column vectors included in the precoding matrix. In this case, the feedback information may include information about a reference vector that is coded at the outermost precoding vector and the number of column vectors selected as a precoding vector.

According to an exemplary embodiment, the information on the reference vector may include information on the position of the reference vector in the precoding matrix and information on the position of the reference vector among the column vectors selected as the precoding vector.

For example, the index of the reference vector may be used as information on the position of the reference vector. Also, information on the leftmost or rightmost among the successive column vectors selected as the precoding vector may be used as information on the position of the reference vector among the column vectors selected as precoding vectors.

The terminal selection unit 530 selects the terminals that do not overlap with the selected precoding vectors as the data reception terminal. For example, if the first terminal 550 and the second terminal 560 select a column vector included in a different precoding matrix as a precoding vector, the terminal selection unit 530 selects the column vector included in the precoding matrix, 2 terminal 560 as the data receiving terminal.

In addition, if the first terminal 550 and the second terminal 560 select a column vector included in the same precoding matrix as a precoding vector, but the index of the precoding vector is different, each of the terminals 550 and 560 Different precoding vectors are selected. In this case, the terminal selection unit 530 may select both the first terminal 550 and the second terminal 560 as data receiving terminals.

However, when the first terminal 550 and the second terminal 560 select the same column vector included in the same precoding matrix as the precoding vector, the terminal selecting unit 530 selects the first column, 2 terminal 560 as a data receiving terminal.

According to one embodiment, the receiver 510 receives channel quality information related to a precoding vector selected by each of the terminals 550 and 560 from the terminals 550 and 560, and the terminal selector 530 selects channel quality information The data receiving terminal can be selected.

According to an embodiment, the channel quality information may be a signal-to-noise ratio when each terminal 550, 560 receives data using each precoding vector. The terminal selection unit 530 compares the signal-to-noise ratios when the terminals 550 and 560 receive data by using the column vectors selected by the terminals 550 and 560 as precoding vectors, Excellent terminals 550 and 560 can be selected as terminals to receive data using the corresponding column vectors.

The transmitting unit 540 transmits data to the data receiving terminal. The transmitting unit 540 can transmit data using the precoding vector selected by the data receiving terminal.

6 is a block diagram illustrating a structure of a terminal according to another embodiment of the present invention. The terminal 600 includes a receiving unit 610, a channel estimating unit 620, a precoding vector selecting unit 630, a channel quality information generating unit 640 and a transmitting unit 650.

The channel estimator 620 estimates a channel state between the base station 660 and the terminal 600. The receiver 610 receives the pilot signal from the base station 660 and the channel estimator 620 estimates the channel state between the base station 660 and the terminal 600 based on the pilot signal.

The precoding vector selector 630 selects at least one precoding vector among the column vectors included in the precoding matrix. According to an exemplary embodiment, the precoding vector selector 630 may select a plurality of continuous column vectors as precoding vectors. In this case, the precoding matrix selector 630 may select the column vectors including the first column vector or the last column vector among the column vectors included in the precoding matrix as precoding vectors. The first column vector means the leftmost column vector among the plurality of column vectors included in the precoding matrix and the last column vector is the rightmost column vector among the plurality of column vectors included in the precoding matrix it means.

The channel quality information generator 640 generates channel quality information related to the selected precoding vector. According to an exemplary embodiment, the channel quality information may be a signal-to-noise ratio when data is received using each precoding vector selected by each of the terminals 600 and 670.

The transmitting unit 650 transmits information on the precoding vector to the base station 660.

The base station 660 identifies the precoding vector selected by the terminal 600 based on the information on the precoding vector and transmits the data to the terminal 600 using the identified precoding vector.

According to one embodiment, the transmitter 650 transmits channel quality information related to the precoding vector selected by the precoding vector selector 630 to the base station 660. When the first terminal 600 and the second terminal 670 select the same column vector as the precoding vector, the base station determines whether any one of the first terminal 600 and the second terminal 670 May be selected as the data receiving terminal. The base station 660 transmits data to the terminal selected as the data receiving terminal.

According to one embodiment, the channel quality information is obtained by the first terminal 600 selecting the first column vector included in the precoding matrix as a precoding vector to receive the first data from the base station 660, To-noise ratio between the first terminal 600 and the base station 660 when a second column vector included in the precoding matrix is selected as a precoding vector and a second data is received from the base station 660 .

In this case, the channel quality information generator 640 generates the signal-to-noise ratio when the second terminal 670 does not receive the second data as the second channel quality information, and the transmitter 650 generates the second channel quality Information to the base station 660.

The base station 660 may select a data receiving terminal by comparing the case where the second terminal receives the second data and the case where the second terminal does not receive the second data.

According to another embodiment, the channel quality information generator 640 may select the first column vector included in the precoding matrix as a precoding vector by the first terminal 600, receive data from the base station 660, 2 terminal 670 can generate the signal-to-noise ratio between the base station 660 and the terminal 600 in the case where no data is received using another column vector included in the precoding matrix.

In this case, when the second terminal selects the second column vector included in the precoding matrix as a column vector and receives the second data from the base station 660, the channel quality information generator 630 transmits the channel quality information to the base station 660, To-noise ratio between the first terminal 600 and the first terminal 600 as second channel quality information.

The transmission unit 650 transmits the channel quality information and the second channel quality information to the base station 660. The base station 660 transmits the second data when the second terminal receives the second data, The data receiving terminal can be selected.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill 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. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

1 is a diagram illustrating a concept of a multiple input multiple output system according to the present invention.

2 is a diagram illustrating a precoding matrix and a reference vector according to the present invention.

3 is a diagram illustrating a concept of selecting a terminal to receive data from among a plurality of terminals, according to an embodiment of the present invention.

4 is a block diagram illustrating a structure of a terminal according to an embodiment of the present invention.

5 is a block diagram illustrating a structure of a base station according to an embodiment of the present invention.

6 is a block diagram illustrating a structure of a terminal according to another embodiment of the present invention.

Claims (18)

In the terminal, A channel estimator for estimating a channel state with a base station; A precoding vector selection unit for selecting a precoding vector among the column vectors included in the precoding matrix based on the channel state; A feedback information generating unit; And [0050] Lt; / RTI > When the precoding vector selection unit selects a plurality of contiguous column vectors as the precoding vector, Wherein the feedback information generator selects the outermost vector among the precoding vectors as a reference vector, generates information on the reference vector and information on the number of the selected column vectors as feedback information, And the transmitter transmits the feedback information to the base station. The method according to claim 1, A receiver for receiving a pilot signal from the base station Further comprising: Wherein the channel estimator estimates the channel state based on the pilot signal. The method according to claim 1, Wherein the information on the reference vector includes information on an index of the reference vector and information on a position of the reference vector in the continuous column vectors. The method according to claim 1, A channel quality information generator for generating channel quality information on a channel between the base station and the MS based on the precoding vectors, Further comprising: And the feedback information generation unit includes the channel quality information in the feedback information. The method according to claim 1, A receiver for receiving data from the base station based on the feedback information; Further comprising: In the base station, A receiver for receiving feedback information from a plurality of terminals belonging to the base station; A precoding vector identification unit that identifies a precoding vector selected by each of the terminals based on the feedback information; A terminal selection unit for selecting, as data reception terminals, the terminals whose selected precoding vectors do not overlap with each other; And A transmission unit for transmitting data to the data reception terminal, Lt; / RTI > Wherein the receiver receives channel quality information associated with a precoding vector from the terminals, Wherein the terminal selecting unit selects the data receiving terminal based on the channel quality information and selects a terminal having the better channel quality information among the terminals whose selected precoding vectors overlap each other as the data receiving terminal, Base station. delete delete delete delete In the terminal, A channel estimator for estimating a channel state with a base station; A precoding vector selection unit that selects at least one or more continuous column vectors including a first column vector or a last column vector among the column vectors included in the precoding matrix based on the channel state as a precoding vector; A transmitting unit for transmitting information on the precoding vector to the base station; And A receiver for receiving data transmitted from the base station based on the precoding vector; Lt; / RTI > 12. The method of claim 11, A channel quality information generating unit for generating channel quality information associated with the precoding vector, Further comprising: And the transmitter transmits the channel quality information to the base station. 13. The method of claim 12, Wherein the channel quality information generator receives the first data from the base station on the basis of the precoding vector and the second terminal receives the other data not selected as the precoding vector among the column vectors included in the precoding matrix, In case of receiving the second data from the base station based on the column vectors, And generating a signal-to-noise ratio between the base station and the terminal using the channel quality information. 14. The method of claim 13, Wherein the channel quality information generator further generates a signal-to-noise ratio when the second terminal does not receive the second data as second channel quality information. 13. The method of claim 12, Wherein the channel quality information generation unit receives the first data from the base station based on the precoding vector, and the other column vectors not selected as the precoding vector from among the column vectors included in the precoding matrix, If not used by the base station, And generating a signal-to-noise ratio between the base station and the terminal using the channel quality information. 16. The method of claim 15, Wherein the channel quality information generator generates the channel quality information based on the column vectors included in the precoding matrix when the second terminal receives the second data from the base station based on the other column vectors not selected as the precoding vector among the column vectors included in the precoding matrix, And a signal-to-noise ratio between the base station and the terminal is generated as second channel quality information. In the base station, A receiver for receiving feedback information from a plurality of terminals belonging to the base station; A precoding vector identification unit that identifies a precoding vector selected by each of the terminals based on the feedback information; A terminal selection unit for selecting, as data reception terminals, the terminals whose selected precoding vectors do not overlap with each other; And A transmission unit for transmitting data to the data reception terminal, Lt; / RTI > Wherein the precoding vector is contiguous column vectors contained in a precoding matrix, Wherein the feedback information includes information on an outermost reference vector among the precoding vectors, Base station. 18. The method of claim 17, Wherein the information on the reference vector includes information on the index of the reference vector and information on the position of the reference vector in the continuous column vectors.

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