KR101100211B1 - Method for Transmitting Signal Using Multiple Antenna - Google Patents

Abstract

The present invention provides a signal transmission method applied to a multiple antenna system for transmitting a signal to two or more mobile stations using multiple antennas, the method comprising: linear distributed coding (LDC) corresponding to each mobile station according to a channel state of the two or more mobile stations; Linear Dispersion Coding) matrix and generating a signal using the generated matrix, the generated matrix is the power of the signal transmitted to each mobile station based on the channel conditions of the two or more mobile stations The present invention relates to a signal transmission method using a multi-antenna generated by including a variable for distributing a signal. In a multi-user multi-antenna system, an LDC matrix element is adaptively changed according to a channel state of each mobile station to efficiently perform communication. It can be effective.

Multiuser Multiantenna, LDC Matrix, Signal-to-Noise Ratio

Description

Signal transmission method using multiple antennas {Method for Transmitting Signal Using Multiple Antenna}

1 is a configuration diagram of an embodiment of a transmitter using multiple antennas.

2 is a diagram illustrating an embodiment of a receiver using multiple antennas.

3 is a diagram illustrating an embodiment of applying MIMO according to the position of a mobile station in a cell.

FIG. 4 is an exemplary explanatory diagram showing performance degradation according to a moving speed of a mobile station in a closed loop multiple input / output (CL-MIMO) system. FIG.

FIG. 5 is a diagram illustrating an embodiment of transmitting SINR versus receiving SINR in signal transmission according to Equations 9 and 10. FIG.

The present invention relates to a signal transmission method using a multi-antenna, and more particularly, to a method for transmitting a signal by adaptively performing LDC according to a channel state of a mobile station in a multi-user multi-antenna system.

1 is a configuration diagram of an embodiment of a transmitter using multiple antennas. Referring to FIG. 1, the channel encoder 11 performs channel encoding according to a predetermined algorithm on input data bits. The channel encoding is for adding information bits to input data bits to generate a more robust signal. Meanwhile, the mapper 12 performs a constellation mapping on bits that have undergone channel encoding and converts them into symbols. In addition, the serial / parallel converter 13 converts the symbols input in series in parallel so that the symbols output from the mapper can be transmitted through multiple antennas. In addition, the multi-antenna encoder 14 converts the channel symbols input in parallel into the multi-antenna symbols and transmits them.

2 is a diagram illustrating an embodiment of a receiver using multiple antennas. Referring to FIG. 2, the multi-antenna encoder 21 receives and converts a multi-antenna symbol into a channel symbol. Meanwhile, the parallel / serial converter 22 converts the channel symbols input in parallel to the serial. In addition, the demapper 23 performs constellation demapping on the serially input channel symbols and converts the bits into bits, and the channel decoder 24 decodes the bits received from the demapper. decoding is performed.

FIG. 3 is a diagram illustrating an embodiment of applying MIMO according to the position of a mobile station in a cell. As shown in FIG. 3, in the MIMO system, the most efficient MIMO application scheme may be determined according to the position of the mobile station in the cell or the user's Signal to Noise Ratio (SNR) geometry. That is, in the cell edge region 300, a transmit diversity scheme, a cell center region 100, a spatial multiplexing scheme, and a cell edge region 300 are provided. In the region 200 between the cell center regions 100, a mixed scheme of a transmit diversity scheme and a spatial multiplexing scheme is used. Accordingly, there is a problem in that all of the different types of MIMO systems must be implemented.

An object of the present invention is to more efficiently perform communication by using an LDC matrix corresponding to a channel state of each mobile station in a multiuser multiantenna system.

The present invention for achieving the above object is a signal transmission method applied to a multi-antenna system for transmitting a signal to two or more mobile stations using multiple antennas, corresponding to each of the mobile stations according to the channel state of the two or more mobile stations. Generating a Linear Dispersion Coding (LDC) matrix and transmitting a signal using the generated matrix.

The above-mentioned objects, features and advantages will become more apparent from the following detailed description in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Communication techniques via multiple antennas are used to increase the capacity, throughput and coverage of the system. As an example of a technique using multiple antennas, there are a spatial division multiplexing (SDM) scheme and a space time coding (STC) scheme. The SDM method is a method of maximizing a transmission rate by transmitting independent data through each antenna at a transmitting end. Meanwhile, the STC scheme is to obtain antenna diversity gain and coding gain by performing coding at the symbol level in the spatial domain and the time domain.

The generalization of the two methods is Linear Dispersion Coding (LDC). That is, the space-time coding scheme applied to the multiple antennas may be represented by an LDC matrix. That is, the multi-antenna encoding may be expressed as Equation 1.

는 q 번째 송신 데이터 심볼 곱해지는

분산 매트릭스이고, S 는 전송 매트릭스이다. 여기서, T 는 LDC 구간,

는 송신 안테나 개수를 의미한다. 한편, Q 는 하나의 LDC 구간 동안 전송하는 데이터의 수를 의미하고,

로 나타낼 수 있다. In Equation 1, S is a transmission matrix, an i th row of a transmission matrix S is symbols transmitted at an i th time, and a j th column means a symbol transmitted through a j th transmission antenna. Meanwhile,

Is multiplied by the q th transmitted data symbol

S is the dispersion matrix and S is the transmission matrix. Where T is the LDC interval,

Denotes the number of transmit antennas. On the other hand, Q refers to the number of data transmitted during one LDC interval,

It can be represented as.

의 실수부(

) 와 허부수(

)가 각각 다른 분산행렬에 의해 시공간 영역에 확산되는 경우, 전송행렬은 수학식 2 와 같이 나타낼 수 있다. Generally,

Real part of

) And imaginary numbers

) Is spread in the space-time region by different dispersion matrices, the transmission matrix can be expressed by Equation 2 below.

및

는 각각 실수부와 허수 부에 곱해지는

분산행렬(dispersion matrix)이다. 상기와 같은 방법으로 신호를 전송한 경우, 수신안테나를 통해 수신된 신호는

에 곱해지는 LDC 행렬이 같은 경우, 수학식 3 과 같이 나타낼 수 있다. In Equation 2,

And

Are multiplied by the real and imaginary parts, respectively.

It is a dispersion matrix. When the signal is transmitted in the above manner, the signal received through the receiving antenna is

When the LDC matrix to be multiplied by is the same, it can be expressed as Equation 3.

은 k 번째 안테나의 수신 잡음,

는 k 번째 수신안테나 신호 값이고,

는 송신측에서 전송한 신호를 나타낸다. 한편,

는 수학식 4 와 같이 나타낼 수 있다.In Equation 3,

Is the received noise of the k th antenna,

Is the k-th receiving antenna signal value,

Indicates a signal transmitted from the transmitting side. Meanwhile,

Can be expressed as in Equation 4.

In addition, in an LDC expressed as in Equation 1, an equivalence channel response may be represented as in Equation 5.

는 동등 채널 응답이고,

는

단위행렬이고,

는

채널행렬이다. here,

Is an equivalent channel response,

Is

Unit matrix,

Is

Channel matrix.

More generally, when the LDC is represented by Equation 2, the signal received by the receiving antenna may be represented by Equation 6.

In Equation 6, the subscript R represents a real part of the signal in a complex form, and the subscript I represents an imaginary part. In this case, the equivalent channel response H may be expressed as Equation (7).

,

,

를 나타낸다. 한편,

은 n 번째 수신 안테나를 통해 수신되는 채널 응답 벡터의 실수부이고,

은 n 번째 수신 안테나를 통해 수신되는 채널 응답 벡터의 허수부이다. 다중안테나 디코딩은 상기 수학식 3 또는 6 혹은 이와 동등한 식으로부터

및

를 추정하는 과정이다. In Equation 7,

,

,

Indicates. Meanwhile,

Is the real part of the channel response vector received through the nth receive antenna,

Is an imaginary part of the channel response vector received through the nth receive antenna. Multi-antenna decoding may be performed from Equation 3 or 6 or equivalent

And

Is the process of estimating.

In particular, in a multi-user multi-antenna system, a precoding matrix is determined according to a predetermined criterion. For example, the determination method may be achieved by maximizing a received signal to interference noise ratio (SINR), maximizing channel capacity, or minimizing interference. This system is called Close Loop MIMO (CL-MIMO). In addition, since multiple users (mobile stations) share frequency, time, and space, values corresponding to various users are added when creating the transmission matrix S of Equation 1. That is, the transmission matrix can be expressed as Equation (8).

은 n 번째 이동국에 상응하는 하나의 LDC 구간 동안 전송하는 데이터 개수이고,

를 의미한다. 이때, 수신신호는 수학식 6 에 나타낸 바와 같고, 특정 이동국을 기준으로 할 때, 자신에게 전송되는 데이터가 아닌 다른 이동국에 전송되는 데이터는 간섭(interference)으로 작용하게 된다. In Equation 8,

Is the number of data transmitted during one LDC interval corresponding to the nth mobile station,

Means. In this case, the received signal is as shown in Equation 6, and when a specific mobile station is referenced, data transmitted to a mobile station other than the data transmitted to the mobile station acts as an interference.

,

의 조합에 의해 구성될 수 있다. FIG. 4 is a diagram illustrating an exemplary embodiment of a performance degradation according to a moving speed of a mobile station in a closed loop multiple input / output (CL-MIMO) system. 4 shows an example of CL-MIMO applied to IEEE 802.16e, which is a portable Internet standard, as an example of a closed loop multiple input / output system. The CL-MIMO feeds back an index of a precoding matrix at a receiving end in order to maximize the received SINR.

,

It can be configured by a combination of.

However, if the mobile station's moving speed increases, the previous channel state and the channel state at the time of transmission change rapidly, and thus, the actual transmission cannot be considered to be performed using the best coding matrix having the best SINR characteristic. Therefore, it can be said that such CL-MIMO is not suitable when there is a high speed mobile station.

개의 이동국이 동시에 선택되고, 선택된 이동국들로 데이터가 전송될 경우, 각 이동국의 SNR(또는 SINR)에 따라서 각 사용자의 수신 성능이 달라진다. 이 경우, 선행코딩 행렬별로 전송 전력을 할당하거나(per user power control), 전송 레이트(rate)를 조절할 수 있다(per user rate control). 즉, 여러명의 선택된 이동국 중에, SNR(또는 SINR)이 매우 낮은 이동국에 보다 높은 전송 전력을 할당함으로써, 그 이동국에 대한 스루풋(throughput)을 증가시키고, 이에 따라, 시스템 전체의 스루풋을 증가시킬 수 있다.

When two mobile stations are selected at the same time and data is transmitted to the selected mobile stations, the reception performance of each user varies according to the SNR (or SINR) of each mobile station. In this case, transmission power may be allocated to each of the preceding coding matrix (per user power control) or the transmission rate may be adjusted (per user rate control). That is, among the several selected mobile stations, by assigning higher transmit power to a mobile station with a very low SNR (or SINR), the throughput for that mobile station can be increased, thereby increasing the throughput of the entire system. .

In general, for a mobile station having a low SNR (or SINR), the stability of the link should be increased by using the STTD method. However, the multi-user multi-antenna method may use the STTD method because several mobile stations share a MIMO channel. The system can be complex, with or without scheduling and switching between schemes.

If more power is allocated to a mobile station having a low SNR (or SINR) value and less power is allocated to a mobile station having a relatively low SNR (or SINR) value, a low SNR (or The channel response of the mobile station with SINR) has the same effect as using STTD, and the overall link throughput can be increased.

개의 수신안테나를 이용하여, 2 개의 이동국을 동시에 선택하는 경우, 다음과 같이 신호를 전송할 수 있다. For example, two transmit antennas

When two mobile stations are simultaneously selected using two reception antennas, a signal can be transmitted as follows.

및

은 제 1 이동국에 상응하는 행렬이고,

및

는 제 2 이동국에 상응하는 행렬이다. 각 사용자에 대하여, 각각 하나의 LDC 구간 동안에 2 개의 심볼을 전송한다. γ와 β는 각 이동국에 전력을 분배하는 변수로서, 수학식 10 의 조건을 만족한다.In Equation 9,

And

Is a matrix corresponding to the first mobile station,

And

Is a matrix corresponding to the second mobile station. For each user, two symbols are sent during each LDC interval. (gamma) and (beta) are variables which distribute electric power to each mobile station, and satisfy the condition of equation (10).

If the received SINR of the first mobile station is higher than the received SINR of the second mobile station, the received SINR of the second mobile station can be increased by decreasing γ and increasing β. On the other hand, when the reception SINR of the first mobile station is lower than the reception SINR of the second mobile station, it is possible to increase the reception SINR of the first mobile station by increasing γ and decreasing β.

및

는 속도에 따른 폐루프 다중입출력의 단점을 보완하기 위해서, 장기적으로 볼 때 가장 좋은 성능을 나타내는 행렬을 사용하였다. 수학식 9 에서는, 제 1 이동국에는 γ와 β를 제외한다면 STTD 방식인 알라무티(Alamouti) 방식의 행렬을 사용하였고, 제 2 이동국에는 이에 상응하는 변형된 STTD 방식을 사용하였다.In Equation 9

And

In order to make up for the shortcomings of closed-loop multi-input / output with speed, we used the best performance matrix in the long run. In Equation 9, except for γ and β, an Alamouti matrix, which is an STTD scheme, is used for the first mobile station, and a modified STTD scheme corresponding to the second mobile station is used.

When the receiving end has two receiving antennas, the received signal is as shown in Equation (11).

,

는 j 번째 시간에 i 번째 수신안테나에 들어오는 수신 신호와 잡음신호, s 는 송신 데이터 심볼을 벡터로 표현한 것이고, 두 이동국에 대한 동등 채널 응답(Equivalent Channel Response)은 수학식 12 에 나타낸 바와 같다.In Equation 11, * means a complex conjugate,

,

Denotes a received signal and a noise signal, and s denotes a transmission data symbol as a vector at the jth time, and an equivalent channel response for two mobile stations is shown in Equation 12.

는 k 번째 송신 안테나로부터 i 번째 수신 안테나로의 채널 응답을 의미한다. 이때, 제 1 이동국에 대한 동등 채널 응답은 의 첫번째 및 두번째 열(column)이 되고, 다른 두 행은 간섭으로 작용한다. 한편, 제 2 이동국에 대한 동등 채널 응답은

의 세번째 및 네번째 행이 되고, 다른 두 행은 간섭으로 작용한다.

Denotes a channel response from the k th transmit antenna to the i th receive antenna. At this time, the equivalent channel response to the first mobile station is The first and second columns of, and the other two rows act as interference. Meanwhile, the equivalent channel response for the second mobile station is

Become the third and fourth rows of, and the other two rows act as interference.

FIG. 5 is an exemplary diagram illustrating a transmission SINR versus a reception SINR in signal transmission according to Equations 9 and 10. FIG. As shown in FIG. 5, by adaptively changing the γ and β values of the LDC matrix as shown in Equation 9, a signal can be adaptively transmitted according to the channel state of each mobile station of the multi-antenna multi-user system.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

According to the present invention, in the multi-user multi-antenna system, the LDC matrix element is adaptively changed according to the channel state of each mobile station, so that communication can be efficiently performed.

Claims (7)

In the signal transmission method applied to a multi-antenna system for transmitting a signal to two or more mobile stations using a multi-antenna, Generating a Linear Dispersion Coding (LDC) matrix corresponding to each of the mobile stations according to the channel state of the two or more mobile stations; And Transmitting a signal using the generated matrix, Wherein the generated matrix includes a variable for distributing power of a signal transmitted to each mobile station based on channel conditions of the two or more mobile stations. The method of claim 1, And the number of the mobile stations is two. The method of claim 2, The transmission signal

A signal transmission method using multiple antennas, wherein S is a data symbol vector, q is a symbol index, and

Is the number of symbols to transmit to the first mobile station,

Is the number of symbols to transmit to the second mobile station,

And

Is a matrix corresponding to the first mobile station,

And

Is a matrix corresponding to the second mobile station). The method of claim 3, wherein

ego,

Signal transmission method using a multi-antenna, characterized in that. The method of claim 4, wherein The channel state is a signal transmission method using a multiple antenna, characterized in that measured by the Signal to Noise Ratio (SNR) or Signal to Interference Noise Ratio (SINR). The method of claim 4, wherein If the channel state for the first mobile station is better than the channel state for the second mobile station, β has a value greater than γ and the channel state for the second mobile station is greater than the channel state for the first mobile station. In a good case, the signal transmission method using multiple antennas, characterized in that γ has a value larger than β. The method of claim 4, wherein [Beta] and [gamma] is a signal transmission method using multiple antennas, characterized in that the variable for distributing the power of the signal transmitted to each mobile station.

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