KR20080101460A - Method and apparatus for efficient transmit using a partial feedback in mutiple antenna system - Google Patents

Abstract

A transmitting method using a partial feedback in a multiple antenna system and an apparatus thereof are provided to improve the performance of the system and reduce the complexity of reception terminal by allocating transmission power by using opposite angle ingredient of R matrices fed back in the base multiple antenna system. A channel matrix is disassembled with QR(401). The opposite angle ingredient of the disassembled R matrices is fed back(407). The opposite angle ingredient of R matrices is transmitted to the CQI(Channel Quality Indicator) information mapped to the predetermined bit. According to the feedback number of transmission, the channel matrix is disassembled with QR and the opposite angle of the disassembled R matrices is fed back.

Description

Efficient Transmission Method and Apparatus Using Partial Feedback in Multi-antenna Systems {METHOD AND APPARATUS FOR EFFICIENT TRANSMIT USING A PARTIAL FEEDBACK IN MUTIPLE ANTENNA SYSTEM}

1 is a flowchart illustrating an operation of a transmitter and a receiver for power allocation according to feedback information in a SQR decomposition-based multi-antenna system according to the related art.

2 is a block diagram of a transmitter and receiver for power allocation according to feedback information in a multiple antenna system according to an embodiment of the present invention;

3 is a flowchart illustrating a transmission operation for power allocation using feedback frequency control according to a channel change rate in a multi-antenna system according to an embodiment of the present invention;

4 is a flowchart illustrating a reception operation for power allocation using feedback frequency control according to a channel change rate in a multi-antenna system according to an embodiment of the present invention;

5 is a flowchart illustrating a reception operation for transmitting selective feedback information according to a channel value in a multi-antenna system according to an embodiment of the present invention;

6 is a flowchart illustrating a transmission operation for transmitting selective feedback information according to a channel value in a multi-antenna system according to an embodiment of the present invention;

7 is a graph comparing the BER performance of the prior art and the present invention based on the ZF detection technique in a 4x4 transmit / receive antenna;

8 is a graph comparing the BER performance of the prior art and the present invention based on the MMSE detection technique for a 4x4 transmit / receive antenna;

9 is a graph comparing the BER performance of the prior art and the present invention based on a ZF detection technique for an 8x8 transmit / receive antenna;

10 is a graph comparing the BER performance of the prior art and the present invention based on the MMSE detection technique for an 8x8 transmit / receive antenna;

11 is a BER performance graph when using the CQI information and transmission power control,

12 is a BER performance graph according to the feedback frequency compared to the channel change,

13 is a BER performance graph according to the selective feedback;

14 is a graph comparing feedback amounts according to selective feedback.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an efficient transmission method and apparatus using partial feedback in a multiple-input multiple-output ("MIMO") system, and in particular, to a closed-loop environment QR decomposition based MIMO. A method and apparatus for reducing the complexity of a receiving end using a small amount of feedback information in a system.

MIMO system is a technology that can increase the data transmission reliability or increase the reliability of data transmission by using multiple antennas in the transmitter and receiver. The MIMO system is divided into two types, an open-loop and a closed-loop type, which will be described with an emphasis on the closed-loop MIMO system. Various transmission power control methods have been proposed to improve system performance in the closed loop environment. For example, the Bit Error Rate (hereinafter referred to as "BER") of a MIMO system based on Ordered Successive Interference Cancellation (hereinafter referred to as "OSIC") by using a conventional pseudoinverse in the prior art. There is a transmission power control method that shows an improvement in performance. In addition, various precoding techniques that can be applied at the transmitting end have been proposed to improve the performance of the QR decomposition based MIMO system. In the conventional preprocessing technique, a preprocessing matrix obtained through singular value decomposition (hereinafter referred to as "SVD") fed back from a closed loop MIMO system is multiplied by a transmission signal and then transmitted. On the contrary, in order to reduce the complexity of the receiver in an open MIMO system, a receiver structure using QR decomposition of a channel matrix has been proposed. Here, the error rate may be lowered by considering the reordering technique of changing the signal detection order before the QR decomposition.

However, the above-described prior arts exhibit different problems when applied to actual MIMO systems. Since the transmission power control method requires the entire channel information for calculating the transmission power, instead of feeding back the entire channel information, the receiving end feeds back the calculated transmission power after calculating the transmission power. Has the disadvantage of increasing. The preprocessing technique is not suitable for real systems due to the increased complexity due to the SVD of the channel matrix for preprocessing and an increase in the amount of feedback due to the feedback of the entire channel matrix. In addition, the signal detection technique using the SQR decomposition has a problem in that the receiver complexity increases due to the channel matrix and the rearrangement of the received signal and shows limited system performance for a given channel.

1 is a flowchart illustrating an operation of a transmitter and a receiver for power allocation according to feedback information in a SQR decomposition-based multi-antenna system according to the related art.

Referring to FIG. 1, first, the transmitter receives power from the receiver in step 100 and allocates power such that reception power is constant.

Thereafter, in step 102, the transmitter receives a signal from the receiver to configure a channel matrix, aligns the channel matrix, and performs QR decomposition.

In step 104, the transmitter detects a transmission signal from the received signal by performing interference cancellation from the SQR decomposition result.

The algorithm of the present invention is then terminated.

As described above, the closed-loop system needs the channel information of the receiving end using the feedback, where the transmitting end can perform more efficient transmission based on the given channel information. Based on these advantages, closed-loop systems perform better than open-loop systems, but suffer from the amount of feedback information and delays.

Accordingly, in order to overcome the problems of the prior arts, there is a need for an efficient transmission method and apparatus for improving system performance by using partial channel information in a closed loop QR based MIMO system and reducing complexity of a receiver.

Accordingly, an object of the present invention is to provide a transmission method and apparatus using partial feedback in a multi-antenna system.

Another object of the present invention is to provide a method and apparatus for determining and transmitting an optimal transmission power for each transmission antenna by feeding back diagonal components of an R matrix in a multiple antenna system based on QR decomposition.

It is still another object of the present invention to provide an efficient transmission method and apparatus using feedback frequency control according to a change rate of a channel in a multi-antenna system based on QR decomposition.

Another object of the present invention is to provide an efficient transmission method and apparatus using selective feedback according to channel value in a multi-antenna system based on QR decomposition.

According to a first aspect of the present invention for achieving the above object, in a receiving method for partial feedback information in a multi-antenna system, the step of QR decomposition of the channel matrix, and the diagonal component of the decomposed R matrix feedback It characterized in that it comprises a process.

According to a second aspect of the present invention for achieving the above object, in the transmission method for partial feedback information in a multi-antenna system, receiving the diagonal component of the R matrix as feedback information during QR decomposition, and the R matrix And a step of allocating a transmission power by using a diagonal component of and transmitting data at the allocated transmission power.

According to a third aspect of the present invention for achieving the above objects, in a receiving method for partial feedback information in a multi-antenna system, receiving information about the number of feedback transmissions from a transmitter, and according to the number of feedback transmissions And feeding back the diagonal components of the decomposed R matrix by performing QR decomposition on the channel matrix.

According to a fourth aspect of the present invention for achieving the above objects, in a transmission method for partial feedback information in a multi-antenna system, a process of calculating the number of feedback transmissions and transmitting them to a receiver and the receivers according to the number of feedback transmissions Receiving the diagonal component of the R matrix decomposed from the feedback information, allocating a transmission power using the diagonal component of the R matrix, and transmitting data at the allocated transmission power. It is done.

According to a fifth aspect of the present invention for achieving the above objects, in a receiving method for partial feedback information in a multi-antenna system, determining whether the receiving power is constant, and when the receiving power is not constant, a channel QR decomposing the matrix to feed back the diagonal components of the decomposed R matrix.

According to a sixth aspect of the present invention for achieving the above objects, in a receiving apparatus for partial feedback information in a multi-antenna system, a QR decomposer for QR decomposing a channel matrix and a diagonal component of the decomposed R matrix are fed back. It characterized in that it comprises a feedback provider.

According to a seventh aspect of the present invention for achieving the above objects, a transmitter for partial feedback information in a multi-antenna system, comprising: a feedback checker for receiving diagonal information of an R matrix as feedback information during QR decomposition; And a power allocator for allocating transmission power using the diagonal component of the matrix, and an RF processor for transmitting data at the allocated transmission power.

According to an eighth aspect of the present invention for achieving the above objects, in a transmission apparatus for partial feedback information in a multi-antenna system, the number of feedback transmission is calculated and transmitted to the receiver, and decomposed from the receiver according to the number of feedback transmissions. A feedback checker for receiving the diagonal component of the R matrix as feedback information, a power allocator for allocating transmission power using the diagonal component of the R matrix, and an RF processor for transmitting data at the allocated transmission power; It is characterized by.

According to a ninth aspect of the present invention for achieving the above objects, in a receiving apparatus for partial feedback information in a multi-antenna system, a MIMO detecting unit for determining whether a receiving power is constant, and when the receiving power is not constant, And a feedback provider which feeds back the diagonal components of the decomposed R matrix by performing QR decomposition on the channel matrix.

According to a tenth aspect of the present invention for achieving the above object, in a multi-antenna system for allocating the transmission power using the partial feedback information, by QR decomposition of the channel matrix, the diagonal component of the decomposed R matrix is fed back. And a transmitter for receiving the diagonal components of the decomposed R matrix as feedback information and allocating transmission power.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, the present invention provides a method and apparatus for transmitting to reduce the complexity of the receiver while improving the performance of the system by determining the optimal transmission power by feeding back the diagonal component of the R matrix in a multi-antenna system based on QR decomposition. This will be explained.

1 to 6, a signal model will be described for explaining the operation of the present invention.

When the number of transmit antennas is M and the number of receive antennas is N, the transmission signal vector and the reception signal vector may be expressed by Equation 1 below.

는 수신신호 벡터로써

로 표현되고, 상기

는 송신신호로써

로 표현되고, 상기

는 잡음(Noise) 벡터로

으로 표현되고, 상기

는 채널행렬로써 하기 <수학식 2>와 같이 표현된다.Where

Is the received signal vector

Represented by

Is the transmission signal

Represented by

Is the noise vector

Represented by the above

Is a channel matrix represented by Equation 2 below.

는 수신안테나 i와 송신안테나 j 사이 채널계수이고 M은 송신안테나 수이고, N은 수신안테나 수를 나타낸다.Where

Is the channel coefficient between the reception antenna i and the transmission antenna j, M is the number of transmission antennas, and N is the number of reception antennas.

)을 QR 분해를 수행한다. 그리고, 더욱 정확한 신호검출을 위한 재정렬과정은 에러 전파 효과를 줄임으로써 시스템의 성능을 높여주는 반면, 수신기의 복잡도를 증가시키게 되며 주어진 채널행렬에 따라 시스템의 성능을 제한하는 한계점을 가진다. 상기 QR 분해에 따른 수신신호는 하기 <수학식 3>과 같이 표현될 수 있다.In order to detect the received signal of Equation 1 in a receiver, a channel matrix (

Perform QR decomposition. In addition, the realignment process for more accurate signal detection increases the performance of the system by reducing the error propagation effect, increases the complexity of the receiver, and has a limitation of limiting the performance of the system according to a given channel matrix. The received signal according to the QR decomposition may be expressed as Equation 3 below.

는 수신신호 벡터이고, 상기 Q는 유니터리(Unitary) 행렬이고 R은 상삼각(upper triangle) 행렬이고, 상기

는 송신신호 벡터. 상기

는 잡음 벡터이다. 여기서, 상기 <수학식 3>에 Q 행렬의 에르미트 행렬(Hermitian Matrix)을 곱하면 하기 <수학식 4>와 같은 형태의 수신신호를 얻을 수 있다.Where

Is a received signal vector, Q is a unitary matrix, R is an upper triangle matrix,

Is the transmission signal vector. remind

Is the noise vector. Here, by multiplying Hermitian Matrix of the Q matrix by Equation 3, a reception signal having a form as shown in Equation 4 can be obtained.

는 수신신호 벡터이고, 상기 R은 QR 분해시 상삼각 행렬이고, 상기

는 송신신호 벡터. 상기

는 잡음 벡터이다.Here, Q is a unitary matrix during QR decomposition,

Is a received signal vector, R is an upper triangular matrix during QR decomposition, and

Is the transmission signal vector. remind

Is the noise vector.

In the M, M-1 and M-2 stages of the QR decomposition based MIMO system, the bit error probability is assumed under a sufficiently high signal-to-noise ratio (hereinafter referred to as "SNR"). Can be approximated as

,

,

은 각각 M, M-1, M-2 번째 신호검출 과정에서의 비트에러 확률로써, 상기

은 M 번째 신호가 성공적으로 검출된 다음 M-1 번째 신호검출시 비트에러가 발생할 조건부 확률로 산출되고, 상기

은 M, M-1 번째 신호가 성공적으로 검출된 다음 M-2 번째 신호검출시 비트에러가 발생할 조건부 확률로 산출된다. 상기 <수학식 5>으로부터

는 k 번째 단계의 신호검출이 정확하게 이루어질 확률이고,

는 k 번째 단계의 신호검출에서 에러가 발생할 확률이라고 하면, 일반적인 k 번째 단계에서의 비트에러 확률은 하기 <수학식 6>으로 표현될 수 있다. Where

,

,

Is the bit error probability in the M, M-1 and M-2 signal detection processes, respectively.

Is calculated as a conditional probability that a bit error occurs when the M-th signal is successfully detected and then the M-1th signal is detected.

Is calculated as the conditional probability that a bit error will occur when the M-2th signal is successfully detected and the M-2th signal is detected. From Equation 5

Is the probability that the signal detection of the k- th step is made correctly,

It can be expressed by the following if said probability of error on the detection signal of the k-th step, the bit error probability in the general k-th stage is <Equation 6>.

은 M, M-1,...,k+1 번째 신호가 성공적으로 검출된 다음 k 번째 신호검출시 비트에러가 발생할 조건부 확률로 산출된다. That is, Equation 6 is a bit error probability in the k th signal detection step.

Is calculated as the conditional probability that a bit error will occur when the kth signal is detected after the M, M-1, ..., k + 1th signals are successfully detected.

Here, unlike the conventional signal detection method using Ordered Successive Interference Cancellation (OSIC), in the QR decomposition-based MIMO system, when the accurate signal detection is performed in the previous signal detection steps, the influence of the interference is completely eliminated. The bit error probability in the k th signal detection step can be expressed by Equation 7 below.

는 Q 함수이고, 상기

은 k 번째 송신신호에 할당된 송신전력 값이고, 상기

은 QR 분해시 R 행렬의 k 번째 행 k 번째 열에 있는 값이다. 상기

는 잡음의 표준편차이다.Where

Is a Q function,

Is a transmission power value assigned to the kth transmission signal, and

Is the value in the k th row of the k th row of the R matrix during QR decomposition. remind

Is the standard deviation of noise.

Based on Equation 7, the overall bit error probability of the QR decomposition-based MIMO system may be calculated by Equation 8 below.

는 전체 비트에러 확률이고, 상기

는 첫 번째 신호검출 단계에서의 비트에러 확률, 상기

은 두 번째 신호검출 단계에서의 비트에러 확률,

은 M 번째 신호검출 단계에서의 비트에러 확률이다.Where

Is the total bit error probability,

First Bit error probability in the first signal detection step,

Is the probability of bit error in the second signal detection phase,

Is the bit error probability in the M th signal detection step.

In order to find out the transmission power to minimize the BER of the QR decomposition based MIMO system, the Lagrange Multiplier is used. At this time, the transmission power of the transmitter must satisfy the following condition.

Where M is the number of transmit antennas and P _i is the transmit power value assigned to the i < th > That is, Equation (9) is a formula for limiting the transmission power. When there are M transmission antennas in total, and the limit of the transmission power is M, it is assumed that M has an average transmission power of 1 per antenna. The presence of a transmission antenna limits the total M transmission power at the transmitter.

A cost function having Equation 8 as an objective function and Equation 9 as a constraint function is shown in Equation 10 below.

을 만족하면서 상기 비트에러확률을 최소화하는 전력

를 구하는 것이다. 여기서,

와 같다. 이러한 비용함수의

를 만족하는 최적의 송신전력을 구하면 하기 <수학식 11>과 같다.Equation 10 is a formula for obtaining a transmission power for minimizing the probability of a bit error of a system.

To minimize the bit error probability

To obtain. here,

Same as Of these cost functions

Obtaining the optimal transmission power that satisfies the Equation (11).

는 k 번째 송신안테나에 할당되는 송신전력이고, 상기

는 수신기에서 채널행렬을 QR 분해하였을 때 얻어지는 R 행렬의 k번째 행 k번째 열의 값이다. 총 송신안테나가 M개가 있기 때문에 R 행렬은 M x M의 크기를 갖고 할당해야 할 송신전력 값 또한 M개의 값을 갖는다. 한편, 물리적으로 R 행렬은 송신기가 수신기 사이 채널환경을 수학적으로 나타내주는 수치이므로 이에 대응하여 송신기에서 주어진 채널환경에 적절한 송신전력을 할당해 주어야 시스템 성능을 향상시킬 수 있다. 상기

값은 R_{1 ,1} 내지 R_{M ,M}값에 의존적이며 k는 1부터 M까지의 송신안테나 인덱스이다.Where

Is the transmit power allocated to the kth transmit antenna, and

Is the value of the k th row k th column of the R matrix obtained when QR decomposition of the channel matrix at the receiver. Since there are M total transmit antennas, the R matrix has the size of M × M and the transmit power value to be allocated also has M values. On the other hand, physically, the R matrix is a numerical value representing the channel environment between the transmitters and the receivers. Accordingly, the system performance may be improved by allocating an appropriate transmission power to a given channel environment in the transmitter. remind

The value depends on the values of R _{1 , 1} to R _{M , M} and k is the transmission antenna index from 1 to M.

As described above, when performing the transmission power control so that the power of the received signal for each signal detection step in the QR decomposition-based MIMO system is the same, the BER performance of the system can be optimized.

2 is a block diagram of a transmitter and receiver for power allocation according to feedback information in a multiple antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the transmitter includes a preprocessor 200, a plurality of RF processors 202_1 to 202_M, a feedback checker 204, a power calculator 206, and a power allocator 208.

The preprocessor 200 calculates a beampome weight or a precoding weight by referring to the estimated channel matrix value, and multiplies the input data by the input data to output the RF data to the RF processors 202_1 to 202_M. That is, the preprocessor 200 may minimize signal interference by precoding input data and radiating an inter-symbol interference (ISI) or a directional beam. The RF processor 202 corresponds to each of the M transmit antennas, converts the baseband signal into an RF band signal, and transmits a precoded signal through a corresponding antenna to a wireless channel. In this case, the RF processor 202_1 to 202_M transmits the signal with the optimal transmission power from the power allocator 207. The optimal transmit power value allows the receive power to be constant. The feedback confirmation unit 204 receives feedback information (a diagonal component of the R matrix during QR decomposition) from the receiver and provides the diagonal component of the corresponding R matrix to the power calculator 206. According to the implementation, the number of feedback transmissions 240 is calculated and notified to the receiver by using the Doppler frequency and the transmission signal period. The power calculator 206 receives the diagonal component of the R matrix from the feedback checker 204 and calculates an optimal transmit power for each transmit antenna by using a Lagrange Multiplier. Will output The optimal transmission power is calculated by Equation 11 and is determined by the diagonal component 230 and the number of transmission antennas of the R matrix. The power allocator 208 supplies the optimal transmit power value calculated from the power calculator 206 to the plurality of RF processors 202_1 to 202_M.

The next receiver is configured to include an RF processor 201_1 to 201_N, a MIMO detector 210, and a feedback provider 215. The MIMO detector 210 is divided into a QR resolver 211 and a signal detector 213.

The RF processing units 201_1 to 201_N each correspond to each of the N reception antennas, and convert the RF band signal received through the corresponding antenna into a baseband signal. The RF processor 202 constructs a channel matrix through channel estimation and provides the channel matrix to the MIMO detector 206.

The MIMO detector 210 includes the QR decomposer 211 and the signal detector 213 to QR decompose the channel matrix from the RF processor 201 to detect a transmission signal from the received signal. The QR decomposed reception signal is represented by Equation 4.

The QR decomposer 211 decomposes the channel matrix H into a Q matrix and an R matrix according to a QR decomposition algorithm and outputs the same to the signal detector 213. Herein, the M matrix having a size of N × N is represented as a unitary matrix, and the R matrix having an size of M × M is represented as an upper triangle matrix. The signal detector 213 estimates a transmission signal from the received signal with reference to the QR decomposition result from the QR decomposer 211. Here, the signal detection unit 206 may estimate the transmission signal vector from the received signal vector according to a zero forcing (ZF) detector method or a minimum mean square error (MMSE) detector method. The feedback provider 215 receives the diagonal component of the R matrix from the QR decomposer 211 and feeds back to the transmitter according to the feedback transmission frequency information from the transmitter. In some implementations, the feedback provider 215 determines whether the reception power is constant. If the reception power is constant, the feedback provider 215 does not transmit the feedback information to the transmitter. If the reception power is not constant, the feedback provider 215 transmits the feedback information to the transmitter.

Power allocation using partial feedback will be described based on the operation of the receiver and the transmitter. First, the receiver performs QR decomposition on the channel matrix, and then feeds back the diagonal components of the R matrix to the transmitter. Under the assumption that the time-varying speed of the channel is slow, the transmitter has channel information close to the current channel state through feedback. By using the above-described transmission technique based on such channel information, the signal detection order does not affect the system performance because the same BER performance is shown for all orders during sequential signal detection. That is, even if error propagation exists, the influence is independent of the signal detection order. Therefore, rearrangement of the received signal vector and the channel matrix in the receiver is unnecessary, and the complexity of the receiver can be lowered than that of the existing SQR decomposition based MIMO system. In addition, while the SQR decomposition-based MIMO system exhibits limited performance for a given channel matrix, the present invention transmits at a transmission power optimized for a given channel, thereby enabling more accurate signal detection compared to existing techniques.

3 to 4 below, as an additional technique for reducing the amount of feedback in the system proposed by the present invention, a feedback frequency adjustment technique according to a change rate of a channel and a selective feedback technique according to a channel value will be described.

3 is a flowchart illustrating a transmission operation for power allocation using feedback frequency control according to a channel change rate in a multi-antenna system according to an exemplary embodiment of the present invention.

와 전송신호의 주기

의 곱으로 정의되며, 구현에 따라 수신기에 의해 산출되어 송신기가 수신할 수도 있다. 이러한 가변적인 피드백 빈도의 적용으로 채널의 변화속도에 따라 시스템의 성능은 유지하는 한편 피드백에 필요한 노력을 줄일 수 있다.Referring to FIG. 3, first, the transmitter determines the number of feedback transmissions FR using the Doppler frequency and the transmission signal period in step 300. That is, the feedback frequency is the maximum Doppler frequency

And period of transmission signal

It is defined as the product of and may be calculated by the receiver and received by the transmitter, depending on the implementation. By applying this variable feedback frequency, it is possible to reduce the effort required for feedback while maintaining the performance of the system according to the change rate of the channel.

Thereafter, in step 302, the transmitter receives diagonal components of an upper triangular matrix (R matrix) as feedback information during QR decomposition from the receiver.

In step 304, the transmitter calculates an optimal transmission power using Lagrange multipliers. This transmission power control can optimize the BER performance by making the power of the received signal the same at the time of signal detection.

Thereafter, the transmitter transmits data by allocating power according to the optimal transmission power calculated in step 306.

Thereafter, in step 308, the transmitter repeatedly performs steps 302 to 306 according to the number of feedback transmissions to calculate and allocate a transmission power.

The transmitter then terminates the algorithm of the present invention.

4 is a flowchart illustrating a reception operation for transmitting feedback information using feedback frequency control according to a channel change rate in a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 4, in step 401, the receiver receives a signal from a multiple reception antenna to configure a channel matrix, and then decomposes the channel matrix into a Q matrix and an R matrix by performing QR decomposition.

Thereafter, the receiver detects a transmission signal from the received signal by performing interference cancellation from the QR decomposition result in step 403.

Thereafter, the receiver determines whether the feedback information has been transmitted as many times as the number of feedback transmissions in step 405, and repeats steps 401 to 403 if the feedback information has been transmitted as many times as the feedback transmission times. According to the implementation, after the feedback information is transmitted according to the number of times, other operations may be performed.

If the feedback information is not transmitted as many times as the number of feedback transmissions, the receiver proceeds to step 407 to read a diagonal component of the R matrix, which is feedback information, and feed it back to the transmitter. Here, the diagonal component of the R matrix is transmitted in the form of channel quality indicator (CQI) information through 6-bit mapping. Table 1 below is a mapping table based on probability and statistical characteristics that the mapping of the CQI information is distributed within a certain range when the transmission power for each diagonal component or transmission antenna of the R matrix that is feedback information is positive.

Channel ( R ) or power value CQI mapping Channel ( R ) or power value CQI mapping 0.0 ~ 0.1 000000 3.1 ~ 3.2 100000 0.1-0.2 000001 3.2 to 3.3 100001 0.2 ~ 0.3 000010 3.3 ~ 3.4 100010 0.3 ~ 0.4 000011 3.4 ~ 3.5 100011 0.4-0.5 000100 3.5-3.6 100100 0.5 to 0.6 000101 3.6-3.7 100101 0.6-0.7 000110 3.7 ~ 3.8 100110 0.7 ~ 0.8 000111 3.8 ~ 3.9 100111 0.8 ~ 0.9 001000 3.9 to 4.0 101000 0.9-1.0 001001 4.0 ~ 4.1 101001 1.0-1.1 001010 4.1 ~ 4.2 101010 1.1 to 1.2 001011 4.2 ~ 4.3 101011 1.2 ~ 1.3 001100 4.3 ~ 4.4 101100 1.3 to 1.4 001101 4.4 ~ 4.5 101101 1.4-1.5 001110 4.5 ~ 4.6 101110 1.5 ~ 1.6 001111 4.6 ~ 4.7 101111 1.6-1.7 010000 4.7 ~ 4.8 110000 1.7 ~ 1.8 010001 4.8 ~ 4.9 110001 1.8-1.9 010010 4.9 ~ 5.0 110010 1.9 ~ 2.0 010011 5.0 ~ 5.1 110011 2.0 ~ 2.1 010100 5.1 ~ 5.2 110100 2.1 ~ 2.2 010101 5.2 ~ 5.3 110101 2.2 to 2.3 010110 5.3 ~ 5.4 110110 2.3 ~ 2.4 010111 5.4 to 5.5 110111 2.4 ~ 2.5 011000 5.5 ~ 5.6 111000 2.5-2.6 011001 5.6 ~ 5.7 111001 2.6 to 2.7 011010 5.7 to 5.8 111010 2.7 ~ 2.8 011011 5.8 to 5.9 111011 2.8 ~ 2.9 011100 5.9 to 6.0 111100 2.9 to 3.0 011101 6.0-6.1 111101 3.0 ~ 3.1 011110 6.1-6.2 111110 3.1 ~ 3.2 011111 6.2 ~ 111111

The receiver then terminates the algorithm of the present invention.

5 is a flowchart illustrating a reception operation for transmitting selective feedback information according to a channel value in a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 5, in step 500, the receiver receives a signal for multiple reception antennas to configure a channel matrix, and then decomposes the channel matrix into a Q matrix and an R matrix by performing QR decomposition.

In step 502, the receiver detects a transmission signal from the received signal by performing interference cancellation from the QR decomposition result.

Thereafter, in step 504, the receiver determines whether the reception power is constant for each reception antenna, and repeats steps 500 to 502 without transmitting feedback information when the reception power is constant. Here, the criterion for determining whether the reception power is constant is that the reception power is not constant when the difference between the diagonal components of the M, M-1th R matrices is greater than a predetermined threshold value, and the reception power is less than or equal to the threshold value. It is a constant case.

If the reception power is not constant, the receiver proceeds to step 506 where the diagonal component of the R matrix, which is feedback information, is read out and fed back to the transmitter.

The receiver then terminates the algorithm of the present invention.

6 is a flowchart illustrating a transmission operation for transmitting selective feedback information according to a channel value in a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 6, first, the transmitter determines whether reception power for each reception antenna is constant in step 600, and allocates transmission power without feedback information when reception power is constant in step 603.

If the reception power is not constant, the receiver proceeds to step 605 in which the diagonal component of the upper triangular matrix (R matrix) is received as feedback information from the receiver during QR decomposition.

In step 607, the transmitter calculates and allocates an optimal transmission power using a Lagrange multiplier.

Thereafter, the transmitter proceeds to step 609 to transmit data at the allocated transmission power.

The transmitter then terminates the algorithm of the present invention.

5 to 6 are selective feedback schemes according to channel values, and the purpose of the proposed system is to equalize the power of the received signal in each signal detection step. If provided, the system performance similar to the proposed scheme can be obtained even if the transmission power is transmitted by the same transmission antenna or star. Based on this, if the channel information measured by the receiver satisfies a predetermined criterion, the effort for feedback may be reduced by transmitting the same power instead of feedback.

6 to 14 show performance graphs according to the simulation. The environmental parameters for the simulation are shown in Table 2 below.

First, FIG. 7 to FIG. 10 are graphs comparing the system performance of the existing system with the present invention. 7 is a BER graph using QR decomposition, SQR decomposition, and the algorithm of the present invention based on the ZF detector method (V-BLAST, QPSK, 4Tx, 4Rx, ZF detection, and Rayleigh fading channel). 8 is a BER graph using QR decomposition, SQR decomposition, and the algorithm of the present invention based on the MMSE detector method (V-BLAST, QPSK, 4Tx, 4Rx, MMSE detection, and Rayleigh fading channel). 9 is a BER graph using QR decomposition, SQR decomposition, and the algorithm of the present invention based on the ZF detector method (V-BLAST, QPSK, 8Tx, 8Rx, ZF detection, and Rayleigh fading channel). 10 is a BER graph using QR decomposition, SQR decomposition, and the algorithm of the present invention based on the MMSE detector method (V-BLAST, QPSK, 8Tx, 8Rx, MMSE detection, and Rayleigh fading channel).

The results show that the proposed algorithm has an average gain of about 3dB over the BER 0.1% interval compared to the conventional SQR decomposition-based system. In particular, in a ZF detection environment where the number of transmit and receive antennas is 8, a gain of about 5 dB can be confirmed. In an MMSE detection environment, a diversity order increases regardless of the number of transmit and receive antennas. In addition, the present invention can also reduce the complexity of the receiver by eliminating the receiving signal and the channel matrix rearrangement process of the receiver in the existing SQR decomposition-based MIMO system.

11 illustrates a BER performance graph according to the CQI information and the transmission power controller method. Referring to the result of FIG. 11, a technique for calculating and allocating a transmit power by feeding back an R matrix and a method of allocating power by feeding back a calculated transmit power to a transmitter after calculating a transmit power at a receiver use CQI mapping. As a result of the performance verification, it can be seen that similar performance is shown. At this time, V-BLAST, QPSK, 4Tx, 4Rx, ZF detection, Rayleigh fading channel was used.

12 illustrates a BER performance graph according to a feedback frequency against a channel change, and FIG. 13 illustrates a BER performance graph according to selective feedback. 14 illustrates a graph comparing feedback amounts according to selective feedback. At this time, V-BLAST, QPSK, 4Tx, 4Rx, ZF detection, Rayleigh fading channel was used.

The performance results show that by maintaining the normalized feedback frequency per Doppler frequency using the feedback frequency adjustment method according to the channel change, the amount of feedback can be reduced while maintaining similar system performance according to the channel change rate. In addition, using a selective feedback method based on channel information, it is possible to reduce about 20% of the feedback amount while maintaining the approximate system performance. With a system degradation of about 1dB, the amount of feedback can be reduced by about 45%. Therefore, the present invention can be applied to a closed loop QR decomposition based MIMO system and various application systems.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, in the QR decomposition-based multi-antenna system, transmission power is allocated by using the diagonal component of the fed back R matrix, thereby reducing the receiver complexity and improving system performance. That is, the realistic feasibility of the QR decomposition-based MIMO system can be improved by reducing the complexity of the receiver and improving the system performance.

Claims (31)

In the receiving method for partial feedback information in a multi-antenna system, QR decomposition of the channel matrix, Feeding back a diagonal component of the decomposed R matrix. The method of claim 1, The diagonal component of the R matrix is transmitted as channel quality indicator (CQI) information mapped to predetermined bits. The method of claim 1, In the QR decomposition, the Q matrix is a unitary matrix, and the R matrix is represented by an upper triangular matrix. In the transmission method for partial feedback information in a multi-antenna system, Receiving the diagonal components of the R matrix as feedback information during QR decomposition; Allocating a transmission power using the diagonal component of the R matrix; Transmitting data at the allocated transmission power. The method of claim 4, wherein And a Lagrange multiplier method for allocating a transmission power using the diagonal component of the R matrix. The method of claim 5, The transmission power using the Lagrange multiplier method is calculated by the following equation (12).

Where

Is the transmit power allocated to the kth transmit antenna, and

Is the value of the k th row k th column of the R matrix obtained when QR decomposes the channel matrix at the receiver, and M is the index of the transmit antenna. The method of claim 5, In the Lagrangian multiplier method, the objective fuction is a system-wide bit error probability (

As a function, the constraint function (Constraint Fuction) is represented as a function to limit the transmission power. The method of claim 7, wherein The objective function and the constraint function are represented by Equation 13 and Equation 14 below.

Where

Is the total bit error probability,

First Bit error probability in the first signal detection step,

Is the probability of bit error in the second signal detection phase,

Is the bit error probability in the M th signal detection step,

Is a function.

Where M is the number of transmit antennas and P _i is the transmit power value assigned to the i &lt; th &gt; The method of claim 7, wherein The cost function of the objective function and the constraint function is represented by the following equation (15).

Where

Is a Q function,

Is a transmission power value assigned to the kth transmission signal, and

Is the value in the k th row k th column of the R matrix during QR decomposition, wherein M is the number of transmit antennas, and P _i is the transmit power value assigned to the i th transmit signal. In the receiving method for partial feedback information in a multi-antenna system, Receiving information about the number of feedback transmissions from a transmitter, And QR-decomposing the channel matrix according to the number of the feedback transmissions to feed back the diagonal components of the decomposed R matrix. In the transmission method for partial feedback information in a multi-antenna system, Calculating the number of feedback transmissions and transmitting them to a receiver; Receiving diagonal components of the R matrix decomposed from the receiver according to the number of feedback transmissions as feedback information; Allocating a transmission power using the diagonal component of the R matrix; Transmitting data at the allocated transmission power. The method of claim 11, The number of feedback transmissions is determined by the normalized Doppler frequency and the period of the transmission signal. In the receiving method for partial feedback information in a multi-antenna system, Determining whether the reception power is constant; And if the received power is not constant, feeding back the diagonal components of the decomposed R matrix by QR decomposing the channel matrix. The method of claim 13, And when the reception power is constant, feedback information is not transmitted. The method of claim 13, The criterion for determining whether the reception power is constant is characterized by comparing the difference between the M-th component of the R matrix, the M-1 component and the predetermined threshold value. In the receiver for partial feedback information in a multi-antenna system, With QR resolver to QR-decompose channel matrix, And a feedback provider for feeding back the diagonal components of the decomposed R matrix. The method of claim 16, And diagonal components of the R matrix are transmitted as channel quality indicator (CQI) information mapped to predetermined bits. The method of claim 16, In the QR decomposition, the Q matrix is a unitary matrix, and the R matrix is an upper triangular matrix. In the transmitter for partial feedback information in a multi-antenna system, A feedback checker that receives diagonal components of the R matrix as feedback information during QR decomposition; A power allocator for allocating transmission power using the diagonal components of the R matrix; And an RF processor for transmitting data at the allocated transmission power. The method of claim 19, And a Lagrange multiplier method for allocating a transmission power using the diagonal component of the R matrix. The method of claim 20, In the Lagrangian multiplier method, the objective fuction is a system-wide bit error probability (

Function, the constraint function appears as a transmission power constraint. The method of claim 19, The transmission power using the Lagrange multiplier method is calculated by the following equation (16).

Where

Is the transmit power allocated to the kth transmit antenna, and

Is the value of the k th row k th column of the R matrix obtained when QR decomposes the channel matrix at the receiver, and M is the index of the transmit antenna. The method of claim 21, The objective function and the constraint function are represented by Equation 17 and Equation 18 below.

Where

Is the total bit error probability,

First Bit error probability in the first signal detection step,

Is the probability of bit error in the second signal detection phase,

Is the bit error probability in the M th signal detection step,

Is a function.

Where M is the number of transmit antennas and P _i is the transmit power value assigned to the i &lt; th &gt; The method of claim 23, wherein The cost function of the objective function and the constraint function is represented by the following equation (19).

Where

Is a Q function,

Is a transmission power value assigned to the kth transmission signal, and

Is the value in the k th row k th column of the R matrix during QR decomposition, wherein M is the number of transmit antennas, and P _i is the transmit power value assigned to the i th transmit signal. In the receiver for partial feedback information in a multi-antenna system, An RF processor for receiving information about the number of feedback transmissions from a transmitter; And a feedback provider for feeding back the diagonal components of the decomposed R matrix by QR decomposing a channel matrix according to the number of feedback transmissions. In the transmitter for partial feedback information in a multi-antenna system, A feedback checker which calculates and transmits a number of feedback transmissions to a receiver and receives diagonal components of an R matrix decomposed from the receiver as feedback information according to the number of feedback transmissions; A power allocator for allocating transmission power using the diagonal components of the R matrix; And an RF processor for transmitting data at the allocated transmission power. The method of claim 26, And the number of feedback transmissions is determined by a normalized Doppler frequency and a period of a transmission signal. In the receiver for partial feedback information in a multi-antenna system, A MIMO detecting unit for determining whether the reception power is constant; And a feedback provider for feeding back the diagonal components of the decomposed R matrix by QR decomposing the channel matrix when the received power is not constant. The method of claim 28, And when the received power is constant, feedback information is not transmitted. The method of claim 28, The criterion for determining whether the reception power is constant is characterized in that the difference between the M-th component of the R matrix, the M-1 component and the size of the predetermined threshold value. In a multiple antenna system for allocating transmission power using partial feedback information, A receiver for performing QR decomposition on a channel matrix and feeding back a diagonal component of the decomposed R matrix; And a transmitter for receiving the diagonal components of the decomposed R matrix as feedback information and allocating transmission power.

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