KR100936483B1 - Transmission antenna selection method in multi-transmission and reception system - Google Patents

Abstract

The present invention relates to a transmission antenna selection method in a multi-transmission and reception system, and does not feed back a large amount of channel information to a transmitting end. Its characteristic purpose is to provide a method with a small amount of complexity without this many matrix decomposition operations.

를 추출하는 단계; (b) 상기 추출된 L개의 sub-matrix

의 고유 값들의 합을 산출하는 단계; (c) 선택 가능한 sub-matrix

에 대하여

를 계산하는 단계; 및 (d) 상기 (c) 단계를 통해 계산된

값을 최대화 시킬 수 있는 sub-matrix

를 선택하는 단계; 를 포함한다. The present invention for achieving this purpose is (a) L sub-matrix from the channel matrix H

Extracting; (b) the extracted L sub-matrix

Calculating a sum of eigenvalues of; (c) selectable sub-matrix

about

Calculating; And (d) calculated through step (c).

Sub-matrix to maximize the value

Selecting a; It includes.

MIMO, transmit antenna, system capacity

Description

Transmit antenna selection scheme in multi-transmit / receive system {Transmit antenna selection scheme for spatial multiplexing in MIMO system}

The present invention relates to a transmission antenna selection method, and more specifically, a large amount of channel information is not fed back to a transmitting end, and only the index of the transmitting antenna selected by the transmitting antenna selecting technique at the proposed receiving end is fed back so that the amount of computation is increased. The present invention relates to a method of selecting a transmission antenna in a multi-transmission / reception system having a small amount of complexity and optimizing for all SNR regions without many matrix decomposition operations.

As is well known, a multiple-input multiple-output (MIMO) system can improve performance of a system by installing multiple antennas at a transmitter and a receiver. MIMO transmission technology is largely classified into a space-time code for obtaining diversity gain and a spatial multiplexing technique for obtaining multiplexing gain. Among these, spatial multiplexing is a method of maximizing the capacity of a system by simultaneously transmitting and receiving multiple data streams through multiple transmit / receive antennas.

Assuming a MIMO system having M transmit antennas and N receive antennas, the received signal y for the transmitted signal s, the channel matrix H (N × M), and the received noise vector n can be expressed by Equation 1 below. have.

[Equation 1]

When the transmitter allocates the same transmission power to each data stream, the channel capacity of the given system is given by the first system capacity equation as shown in Equations 2 and 3 below.

.............. [수식 2]

.............. [Equation 2]

...................................... [수식 3]

Equation 3

The capacity given in the above equation can be obtained by using Singular Value Decomposition (SVD) when the transmitter knows the channel information. In addition, by using a power allocation technique using SVD and water filling, an optimum capacity can be obtained, and the water filling technique is particularly effective in a low SNR region.

의 고유 값(eigenvalue)의 개수 L개만큼 data stream을 동시에 전송할 수 있다.) On the other hand, in the MIMO system having M transmit antennas and N receive antennas, when the number of transmit antennas is larger than the number of receive antennas, the transmitter cannot transmit M data streams simultaneously and can transmit up to N data streams. . (Given in [Equation 2]

A data stream can be transmitted at the same time as L number of eigenvalues.)

를 얻게 된다.FIG. 1A is an exemplary diagram illustrating a method of selecting L transmit antennas among M transmit antennas. FIG. 1A is a sub-matrix extracting L columns from H from a given channel matrix H. FIG.

You get

The selection technique of the transmitting antenna is performed at the receiving end. The conventionally proposed technique is summarized as follows.

중에서 용량(capacity)을 최대화할 수 있는 matrix를 찾는 것인데, 이는 원래 channel matrix H에서 어느 column을 뽑아내느냐 하는 것이고, 곧 송신안테나의 인덱스를 결정하는 것이 된다. 이것을 설명하기 위한 기본적인 가정은 다음과 같다.The basic concept is a selectable sub-matrix

It is to find a matrix that can maximize the capacity from among them, which column to extract from the original channel matrix H, and determine the index of the transmission antenna. The basic assumptions for explaining this are as follows.

를 찾기 위한 [수식 4] 및 [수식 5]와 같은 '제 2 시스템 용량식'을 나타낸다.Under the same assumption, sub-matrix can maximize the capacity

Denotes a 'second system dose formula' such as [Equation 4] and [Equation 5] to find.

..... [수식 4]

..... [Equation 4]

............................ [수식 5]

Equation 5

 Maximizing the addition of the log function is equivalent to maximizing each product, and can be expressed as shown in [Equation 5] above.

는 SNR (Signal to Noise Ratio)을 나타내는데, SNR값이 충분히 큰 영역에서는 다음과 같은 근사식, [수식 6]을 사용할 수 있다. In [Equation 4]

Represents a Signal to Noise Ratio (SNR). In the region where the SNR value is sufficiently large, the following approximation equation (Equation 6) can be used.

............................ [수식 6]

Equation 6

If the value of x is large enough, it has a relationship as shown in [Equation 6]. Using this approximation equation, [Equation 4] shown above can be approximated as [Equation 7] below.

.......................... [수식 7]

Equation 7

A method of finding a sub-matrix using an approximation can be expressed as the product of L eigenvalues as shown in [Equation 7]. This result can be expressed by Equation 8 below.

................. [수식 8]

...... [Equation 8]

를 찾기 위해서는, 선택 가능한 sub-matrix

에 대하여

를 계산하여, 이 값을 최대화 시킬 수 있는 sub-matrix

를 선택하는 것이다.Since the product of L eigenvalues has the same relationship as [Equation 8], the sub-matrix can maximize the capacity.

To find, selectable sub-matrix

about

Sub-matrix to maximize this value

To select.

를 계산하여 최적의 sub-matrix

를 찾는다. In summary, the prior art does not perform the calculation as shown in [Equation 4] for each sub-matrix (matrix decomposition is required to do the same as Equation 4), and as shown in [Equation 8].

Calculate the optimal sub-matrix

Find it.

However, since this is proposed under the assumption that the SNR value is large, it may be effective in a region where the SNR is sufficiently large, but may not be an optimal transmission antenna selection method in a region where the SNR value is low.

The present invention was devised in view of the above problems, and a first object of the present invention is not to feed back a large amount of channel information to a transmitting end, but only an index of a transmitting antenna selected by a transmitting antenna selecting technique at the proposed receiving end. By providing feedback, the object is to provide a method having a small amount of complexity without a large amount of matrix decomposition operations.

A second object of the present invention is to provide a transmission antenna selection method that is optimized for all SNR regions, rather than being optimized only in a region where the SNR value is sufficiently large.

를 추출하는 단계; (b) 상기 추출된 L개의 sub-matrix

의 고유 값들의 합을 산출하는 단계; (c) 선택 가능한 sub-matrix

에 대하여

를 계산하는 단계; 및 (d) 상기 (c) 단계를 통해 계산된

값을 최대화 시킬 수 있는 sub-matrix

를 선택하는 단계; 를 포함한다. The present invention for achieving this purpose is (a) L sub-matrix from the channel matrix H

Extracting; (b) the extracted L sub-matrix

Calculating a sum of eigenvalues of; (c) selectable sub-matrix

about

Calculating; And (d) calculated through step (c).

Sub-matrix to maximize the value

Selecting a; It includes.

According to the present invention as described above, by feeding back only the index of the transmission antenna selected by the transmission antenna selection technique of the proposed receiver without feeding back a large amount of channel information to the transmitter, it is possible to select a transmission antenna with a small amount of calculation. It works.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. Prior to this, the terms or words used in the present specification and claims are defined in the technical spirit of the present invention on the basis of the principle that the inventor can appropriately define the concept of the term in order to explain his invention in the best way. It should be interpreted to mean meanings and concepts. In addition, when it is determined that the detailed description of the known function and its configuration related to the present invention may unnecessarily obscure the subject matter of the present invention, it should be noted that the detailed description is omitted.

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

2 is a schematic configuration diagram of a multi-transmission / reception system according to the present invention, and FIG. 3 is a flowchart illustrating a transmission antenna selection method in a multi-transmission / reception system according to the first aspect of the present invention. As shown in FIG. 2, there are M transmit antennas and N receive antennas. At this time, the signal received at the receiving end is as shown in [Equation 1].

를 찾아서 이에 해당하는 송신안테나를 선택하는 방법으로 서, SNR이 낮은 경우를 가정한다.In the transmission antenna selection method in the multi-transmission / reception system according to the first aspect of the present invention, a sub-matrix is obtained by extracting L columns that can maximize capacity from the channel matrix H.

It is assumed that SNR is low as a method of searching for and selecting a corresponding transmission antenna.

를 추출한다(S10).Thus, L sub-matrix from channel matrix H

To extract (S10).

........................ [수식 9]

Equation 9

를 찾는 알고리즘을 유도해보면 아래의 [수식 10]과 같다.Thus, when the value of x is sufficiently small, it can be seen that an approximation equation such as [Equation 9] holds, and the sub-matrix is obtained from [Equation 4] using [Equation 9].

Deriving the algorithm to find is as shown in Equation 10 below.

........................ [수식 10]

............. Equation 10

의 고유 값(eigenvalue)들의 합을 산출하며(S20), [수식 10]은 아래와 같은 [수식 11]과 같이 나타낼 수 있다.Since, L sub-matrix

The sum of the eigenvalues is calculated (S20), and Equation 10 may be expressed as Equation 11 below.

...................... [수식 11]

Equation 11

를 찾기 위해서는, 선택 가능한 sub-matrix

에 대하여

를 계산함으로 써(S30), 상기

값을 최대화 시킬 수 있는 sub-matrix

를 선택한다(S40). That is, in the region with low SNR, the sum of L eigenvalues has the relation as shown in [Equation 11], so the sub-matrix can maximize the capacity.

To find, selectable sub-matrix

about

By calculating the (S30), said

Sub-matrix to maximize the value

Select (S40).

을 구하기 위해서는

와 마찬가지로 matrix decomposition이 필요 없고,

는

에 비교할 때 매우 적은 계산량을 가지면서도 더 좋은 성능을 갖는다. Such,

To save

Like matrix decomposition is unnecessary

Is

Compared to, it has very little calculation and better performance.

를 계산하여 송신안테나를 효과적으로 선택할 수 있지만, 이 기법 역시 SNR값이 낮은 영역에서만 효과적으로 동작하는 문제점을 갖고 있다. 즉, SNR의 값에 관계없이 효과적으로 송신안테나를 선택할 수 있는 방법이 필요하다. But,

Although the transmission antenna can be effectively selected by calculating, the technique also has a problem of operating effectively only in the region with low SNR value. That is, there is a need for a method capable of effectively selecting a transmission antenna regardless of the value of the SNR.

Accordingly, the present invention proposes a transmission antenna selection method in a multiplex transmission and reception system according to the second aspect. 4 is a flowchart illustrating a method of selecting a transmission antenna in a multi-transmission system according to a second aspect of the present invention.

Equation 12 is developed from Equation 4 to find a transmission antenna method that can effectively operate in the entire SNR region.

Equation 12

항과

항과 상수항 그리고 나머지 항

으로 이루어짐을 볼 수 있다. If we develop a given capacity equation, we can use

Section

Term, constant term, and rest term

It can be seen that.

는 쉽게 얻을 수 없는 값이므로 고려하지 않는다. 여기서, 주목해서 볼 점은

에는

이 계수로 곱해지고

에는

가 계수로 곱해진다는 점이다.The constant term is irrelevant to selecting a sub-matrix,

Is not taken into account because it is not easily obtained. At this point,

On

Multiplied by this coefficient

On

Is multiplied by a coefficient.

는 SNR값을 나타내는 변수로서, 이 값에 따라서

와

가 송신안테나를 결정하는데 서로 다른 비중을 갖게 됨을 알 수 있다. 즉,

가 작은 값을 가질 때는,

의 관계를 가지므로,

가 지배적인 역할을 하게 됨을 알 수 있다.

Is the variable representing the SNR value,

Wow

It can be seen that the different weights are used to determine the transmit antenna. In other words,

Has a small value,

Has a relationship with

Can be seen as a dominant role.

가 큰 값을 가질 때는,

의 관계를 가지므로,

가 중요한 역할을 하게 된다. Contrary,

Has a large value,

Has a relationship with

Will play an important role.

를 계산하여 송신안테나를 선택하고, SNR이 낮은 영역에서는

를 통해서 송신안테나를 선택한다는 것을 설명해준다.This result has been described in Eq. 8 and Eq. 11 in areas with large SNR.

To select the transmitting antenna, and in the region with low SNR

Explain that select the transmit antenna through.

와

의 조합으로 이루어진 다음의 [수식 13]과 같은 조합 값을 산출한다(S50).That is, the entire SNR region is considered from the 'second system capacity' ([Equation 4] and [Equation 5]).

Wow

A combination value of the following Equation 13 consisting of a combination of the following is calculated (S50).

Equation 13

와

의 조합 값을 최대화 시킬 수 있는 sub-matrix

를 선택한다(S60). As such,

Wow

Sub-matrix to maximize the combination of

Select (S60).

That is, by using this equation (13) as a new transmission antenna selection method, it is possible to obtain better performance than the results of the conventional technique and [11] in the entire SNR region.

의 계산과 비교했을 때 거의 동일한 계산량을 갖는다.In addition, the transmission antenna selection method in the multi-transmission system according to the second aspect also does not require matrix decomposition and is used in the prior art.

Compared with the calculation of has almost the same amount of calculation.

또는

의 결과만으로 송신안테나를 결정하는 것보다 좋은 성능을 가질 수 있으나,

항을 고려하지 않았으므로

= 0 이 되는 경우를 제외하면 최적의 결과에 비해 성능 저하가 있을 수 있다.However, the transmission antenna selection method according to [Equation 13]

or

Although the result can be better than determining the transmission antenna,

I didn't consider the terms

Except for the case where = 0, there may be a performance degradation compared to the optimal result.

Accordingly, the present invention proposes a transmission antenna selection method in a multiplex transmission and reception system according to a third aspect. 5 is a flowchart illustrating a method of selecting a transmission antenna in a multi-transmission system according to a third aspect of the present invention.

The same results as in [Equation 14] can be obtained from the aforementioned 'second system capacity formula' ([Equations 4] and [Equation 5]) and basic assumptions.

[Equation 14]

를 계산하여(S70),

값을 최대화 시킬 수 있는 sub-matrix

를 선택한다(S80). 이와 같이 송신안테나를 결정하는 것은 이론적인 최적의 알고리즘과 동일함을 알 수 있다. 이 방법 역시 위에서 설명된 다른 방법과 마찬가지로, matrix decomposition을 필요로 하지 않으며 종래의 기술에서 쓰이는

의 계산과 거의 동일한 계산량을 갖는다. Therefore, from [Formula 14]

By calculating (S70),

Sub-matrix to maximize the value

Select (S80). As described above, it can be seen that determining the transmission antenna is the same as the theoretical optimal algorithm. This method, like the other methods described above, does not require matrix decomposition and is used in the prior art.

It has almost the same amount of calculation as.

Although described and illustrated in connection with a preferred embodiment for illustrating the technical spirit of the present invention above, the present invention is not limited to the configuration and operation as shown and described as such, and the deviation from the scope of the technical spirit It will be appreciated by those skilled in the art that many changes and modifications can be made to the invention without departing from the scope of the invention, and therefore, all such suitable changes and modifications and equivalents should be considered to be within the scope of the invention.

1A is an exemplary view illustrating a method of selecting L transmit antennas among M transmit antennas.

2 is a block diagram of a multiplex transmission and reception system according to the present invention.

3 is a flowchart of a method of selecting a transmission antenna in a multi-transmission system according to a first aspect of the present invention.

4 is a flow chart related to a transmission antenna selection method in a multiplex transmission and reception system according to a second aspect of the present invention.

5 is a flowchart of a method of selecting a transmission antenna in a multi-transmission system according to a third aspect of the present invention.

Claims (5)

In the transmission antenna selection method in a multi-transmission and reception system, (a) L sub-matrix from channel matrix H

Extracting; (b) L sub-matrix extracted through step (a)

Calculating a sum of eigenvalues of (c) selectable sub-matrix

)about

Calculating; And (d) calculated through step (c)

Sub-matrix to maximize values

Selecting); Transmission antenna selection method in a multi-transmission system comprising a. here,

S is short for 'sub-matrix', sub-matrix

Is the extracted partial matrix,

Is

Complex conjugate transpose of

Is a matrix (

Sum of diagonal element of) delete delete delete delete

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