KR20090023879A - Apparatus and method for signal processing to eliminate interference in multi-user multiple input multiple output wireless communication system - Google Patents

Abstract

A signal processing apparatus and a method thereof are provided to update a transmission precoding matrix and transmission weight matrix, repetitively by using channel information and interference information, thereby effectively removing the interference generated in the external cell and internal cell. A base station apparatus in an MU MIMO(Multi-User Multiple Input Multiple Output) wireless communication system comprises a control information checkup device(202), a matrix decider(204), a control information generator(206), a modulator(208), a precoder(210), a signal buffer(212), a multiplexer(214), and a plurality of RFs(216-1_216-N). The control information checkup device confirms the control information received from a terminal. The matrix decider determines a precoding matrix to be used in the base station and a weight matrix to be used in the terminal by using the channel information and interference information. The control information generator produces the control information to be transmitted to the terminal. The modulator modulates information bit strings to be transmitted to each terminal to produce complex symbols. The precoder multiplies transmission signals to each terminal by a corresponding precoding matrix.

Description

Signal processing apparatus and method for interference cancellation in a multi-user multi-input / output wireless communication system

The present invention relates to a multi-user multiple input multiple output (MU MIMO) wireless communication system, and more particularly, to a signal processing apparatus and method for interference cancellation in a multi-user multi-input multiple input wireless communication system.

Recently, as the demand for high-speed and high-quality data transmission has increased, a multiple input multiple output (MIMO) wireless communication system using a plurality of transmit / receive antennas has been attracting attention as one of techniques for satisfying this. The multiple input / output technology is a technology that can significantly improve channel capacity than when using a single antenna by performing communication using a plurality of streams through a plurality of antennas. For example, if both transmitter and receiver use M transmit and receive antennas, and the channels between the antennas are independent, and the bandwidth and the total transmit power are fixed, the average channel capacity is increased by M times compared to a single antenna. . The multi-input / output system can be applied not only to a pair of transceivers but also between one transmitter and multiple receivers. For example, assuming a base station having a plurality of transmit antennas and a plurality of terminals having at least one antenna, a multi-user multiple input multiple output (MU MIMO) wireless communication system is constructed.

A multi-user multi-input / output wireless communication system is a system that increases frequency efficiency by allowing a plurality of users to simultaneously use the space resources secured by using a plurality of antennas. In the case of downlink transmission of information from a base station to a terminal, the base station preprocesses and transmits information to a plurality of users at the same time, and each of the plurality of users confirms information from the signal received through each channel to itself. . In order to ensure high channel capacity, there is a need for an alternative for eliminating multi-user interference, which is interference between terminals, and interference from adjacent cells.

Accordingly, an object of the present invention is to provide an apparatus and method for eliminating interference between users and interference from adjacent cells in a multi-user multiple input multiple output (MU MIMO) wireless communication system.

Another object of the present invention is to provide an apparatus and method for determining a transmission precoding matrix and a reception weight matrix through an iterative technique in a multi-user multi-input / output wireless communication system.

According to a first aspect of the present invention for achieving the above object, a base station apparatus in a multi-user multiple input multiple output (MU MIMO) wireless communication system, the channel information and interference fed back from at least one terminal A determiner for determining a precoding matrix and a weight matrix of the at least one terminal using information; a precoder for precoding a transmission signal to the terminals according to the precoding matrix; And a plurality of Radio Frequency (RF) processors for transmitting the coded signal through a plurality of antennas.

According to a second aspect of the present invention for achieving the above object, in a multi-user multiple input multiple output (MU MIMO) wireless communication system, a terminal device receives a signal through at least one antenna At least one RF (Radio Frequency) processor, a processor for removing external cell interference by multiplying an interference suppression matrix by a received signal, and using a weight matrix provided from a base station to remove interference due to a signal to another terminal It characterized in that it comprises a remover.

According to a third aspect of the present invention for achieving the above object, a signal processing method of a base station in a multi-user multiple input multiple output (MU MIMO) wireless communication system, the channel fed back from at least one terminal Determining a precoding matrix and a weight matrix of the at least one terminal using information and interference information, and precoding a transmission signal to the terminals according to the precoding matrix. The method may include transmitting a precoded signal through a plurality of antennas.

According to a fourth aspect of the present invention for achieving the above object, a signal processing method of a terminal in a multi-user multiple input multiple output (MU MIMO) wireless communication system, the signal through at least one antenna Receiving the signal, removing the external cell interference by multiplying the received signal by the interference suppression matrix, and removing the interference due to the signal to the other terminal by using a weight matrix provided from the base station. It is done.

Multi-User Multiple Input Multiple Output (MU MIMO) In a wireless communication system, by repeatedly updating the transmission precoding matrix and the transmission weighting matrix using channel information and interference information, Interference can be effectively removed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, the present invention describes a technique for eliminating interference to a terminal in a multi-user multiple input multiple output (MU MIMO) wireless communication system. In particular, the present invention describes a technique for determining and using a transmission precoding matrix of a base station and a reception weight matrix of a terminal in a multi-user multi-input / output wireless communication system.

1 schematically shows a multi-user multi-input / output wireless communication system according to the present invention.

Referring to FIG. 1, the base station 110 simultaneously transmits a data signal to a plurality of transmission antennas to the terminals 120-1 through 120 -K. In this case, the base station 110 transmits data signals to a precoding matrix M ₁ corresponding to each of the terminals. … Multiply by, M _K to send. The data signal multiplied by the precoding matrix is received at each of the terminals 120-1 through 120-K through a corresponding channel H _k . In addition, an interference signal from an adjacent cell is received at each of the terminals 120-1 to 120 -K. Accordingly, each of the terminals 120-1 through 120-K eliminates interference from neighbor cells and signals from other terminals by multiplying the received signal by the weight matrix W _k .

Precoding matrices M ₁ to M _K and weight matrices W ₁ to W _K are determined by the base station 110, and the base station 110 transmits the weight matrix information to the terminals 120-1 to 120 -K. Feedforward. To this end, each of the terminals 120-1 through 120 -K feeds back an adjacent cell interference signal and an interference channel to the base station 110. The neighbor cell interference signal and the interference channel are measured by each of the terminals 120-1 through 120-K, and each of the terminals 120-1 through 120-K is adjacent to the signal while not receiving a signal. Measure a cell interference signal and the interference channel. In this case, it is assumed that the neighbor cell interference signal and the interference channel do not change for a long time, so that the terminal is the same while receiving the signal. This assumption holds in that interference from adjacent cells is interference from base stations with high power levels and has a specific pattern.

Hereinafter, the present invention will be described in detail with reference to the drawings the structure and operation of the base station, the terminal for removing interference as described above.

2 is a block diagram of a base station in a multi-user multi-input / output wireless communication system according to an exemplary embodiment of the present invention.

As shown in FIG. 2, the base station includes a control information checker 202, a matrix determiner 204, a control information generator 206, a modulator 208, a precoder 210, a signal buffer 212, The combiner 214 is configured to include a plurality of RF (Radio Frequency) processors 216-1 to 216-N.

The control information checker 202 confirms the control information received from the terminal. In particular, according to the present invention, the control information checker 202 checks the channel information and the interference information fed back from the terminal and provides it to the matrix determiner 204. Here, the channel information is a channel value between the base station and the terminal, the interference information means the interference channel value and the interference signal value of the terminal. The form of the feedback information may include at least one of channel quality information (CQI), adaptive modulation and coding information, a user index, and an interference-plus-noise covariance matrix (INCM). It may include. In this case, the channel quality information may be channel state information (CSI), signal to noise ratio, channel capacity index, codebook index, and the like.

The matrix determiner 204 determines the precoding matrix to be used in the base station and the weight matrix to be used in the terminal using the channel information and the interference information. Here, the precoding matrix and the weight matrix are present for each terminal. Detailed functions of the matrix determiner 204 will be described below with reference to FIG. 3.

The control information generator 206 generates control information to be transmitted to the terminal. In particular, according to the present invention, the control information generator 206 generates control information including weight matrix information of each terminal determined by the matrix determiner 204.

The modulator 208 modulates the information bit streams to be transmitted to each terminal and converts them into complex symbols. The precoder 210 precodes the transmission signals to each terminal according to the precoding matrix determined by the matrix determiner 204. That is, the precoder 210 multiplies the transmission signals to the terminal by the corresponding precoding matrix. The signal buffer 212 temporarily stores the precoded signals provided from the precoder 210, and outputs the sum of the precoded signals to each terminal to be transmitted simultaneously.

The copy device 214 performs transmission and reception conversion functions. For example, when the time division duplex scheme is used, the copyer 214 outputs the signals from the signal buffer 212 and the control information generator 206 to the plurality of RF processors 216-1 through time. 216-N) and a signal from the plurality of RF processors 216-1 to 216-N to the control information checker 202 during a reception time. Each of the plurality of RF processors 216-1 to 216 -N performs a conversion function between an RF band signal transmitted and received through a corresponding antenna and a baseband signal exchanged with the copyer 214.

3 is a block diagram of a matrix determiner 204 in a multi-user multi-input / output wireless communication system according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the matrix determiner 204 includes a combination set generator 302, a power allocator 304, a matrix operator 306, an optimizer 308, and a final matrix determiner 310. It is configured by.

The combination generator 302 generates all possible beam assignment combinations. The number of beam allocation combinations is the number of iterations to determine the optimal precoding matrix and the weight matrix. For example, when the number of transmission antennas of the base station is 4, the number of reception antennas of the terminal A is 4, and the number of reception antennas of the terminal B is 4, the possible beam allocation combinations are [4,0], [3,1], [ 2, 2], [1, 3], [0, 4], and the number of elements in the beam allocation combination set is five.

The power allocator 304 parallelizes each stream of the channel and allocates power to each of the horizontalized streams. In this case, the leveling of each stream of the channel means converting a channel in which the signals of the streams are overlapped and multiplying a specific matrix to a channel in which the signals of the streams do not overlap. For example, when the channel matrix is singular value decomposition (SVD), a diagonal matrix component appears. Therefore, multiplying the channel matrix by a specific matrix leaves only the diagonal matrix components. That is, horizontalizing each stream of the channel means leaving only the diagonal matrix component. The power is allocated such that the sum capacity is maximized.

The matrix operator 306 generates a precoding matrix to be used at the base station and a weight matrix to be used at the terminal for each combination generated by the combination generator 302. The matrix operator 306 generates one matrix set for each combination, and one matrix set includes a precoding matrix and weight matrix pairs of respective terminals. To generate one matrix set, the matrix operator 306 initializes the precoding matrix and the weighting matrix, updates the precoding matrix using the weighting matrix, and uses the updated precoding matrix to generate the weighting matrix. Update In this case, when updating the precoding matrix, in addition to the weighting matrix, channel matrixes of all terminals and beam allocation information of the corresponding terminals are used, and in addition to the updated precoding matrix, power allocation information and beams of the corresponding terminal are updated when the weighting matrix is updated. Allocation information, channel matrix of all terminals is used.

For example, the matrix operator 306 initializes the precoding matrix and the weight matrix as shown in Equation 1 below.

는 단말k의 초기 가중치 행렬, 상기

는 단말k의 초기 프리코딩 행렬, 상기

는 단말k의 간섭 및 잡음 공분산 행렬, 상기

는 단말k의 채널행렬, 상기

는 단말k에게 할당된 빔 개수, 상기

는 행렬 A의 특이 값(singular value)들 중 가장 큰 것부터

개까지의 특이 값에 대응되는 좌 특이 벡터(left singular vector)들, 상기

는 단말k의 간섭 채널, 상기

는 단말k의 간섭 신호, 상기

는 잡음 전력을 의미한다.In Equation 1,

Is the initial weight matrix of terminal k,

Is the initial precoding matrix of terminal k,

Is an interference and noise covariance matrix of terminal k,

Is the channel matrix of terminal k,

Is the number of beams allocated to terminal k,

Is the largest of the singular values of matrix A

Left singular vectors corresponding to up to singular values,

Is the interference channel of the terminal k,

Is the interference signal of the terminal k,

Means noise power.

Then, the matrix operator 306 updates the precoding matrix and the weight matrix again by performing an iterative step according to the determination of the optimization determination unit 308. That is, the matrix operator 306 iteratively updates the precoding matrix and the weighting matrix until it is determined to be optimized by the optimization decision unit 308.

In addition, the matrix operator 306 calculates a sum capacity when using the updated matrices in each iteration step. The sum capacity is calculated as in Equation 1 below.

는 합 용량, 상기

는 단말 개수, 상기

는 단말k의 프리코딩 행렬 및 가중치 행렬을 반영한 채널의 특이 값 분해시 얻어지 는 특이 값을 원소로 하는 대각행렬, 상기

는 단말k의 전력할당행렬을 의미한다.In Equation 2,

Is the sum capacity, said

Is the number of terminals, the

Is a diagonal matrix whose element is a singular value obtained when the singular value decomposition of the channel reflecting the precoding matrix and the weight matrix of the terminal k is performed.

Denotes the power allocation matrix of the terminal k.

The optimization determiner 308 determines whether the precoding matrix and the weighting matrix are optimized by referring to the degree of change of the precoding matrix generated by the matrix operator 306. For example, the degree of change between the precoding matrix of the recent iteration step and the precoding matrix of the previous iteration step is calculated as shown in Equation 2 below.

는 프로비니어스 놈(frobenius norm) 연산자, 상기

은 n번째 단복단계에서 단말k의 프리코딩 행렬, 상기

은 트레이스(trace) 연산자로, 대각성분의 합을 의미한다.In Equation 3,

Is the frobenius norm operator,

Is the precoding matrix of the terminal k in the nth single step,

Is a trace operator, the sum of the diagonal components.

That is, the optimizer 308 calculates the degree of change and compares it with the threshold. The optimization determiner 308 determines that the change is less than the threshold value has been optimized, and if the change is greater than or equal to the threshold value is determined that the optimization is not optimized by notifying the matrix operator 306, the matrix operator 306 causes the repetition step to be performed again.

The final matrix determiner 310 compares the sum capacities of the respective combinations to determine the precoding matrix and the weight matrix of the combination having the highest sum capacity as the final matrix.

If the operation of the matrix determiner 204 is represented by pseudo code, it is as shown in Table 1 below.

code Explanation

For all combinations

Perform for all terminals

    reset

Incremental iterations

Perform for all terminals

       Calculate sum of precoding matrix and weight matrix update capacity

Optimization judgment

Determining matrix and sum capacity of combinations

  Final matrix and sum capacity determination

는 빔 할당 조합 집합, 상기

는 빔 할당 조합 인덱스, 상기

은 행렬 갱신 반복단계 인덱스, 상기

는 스케줄링 대상 단말 개수, 상기

는 단말 인덱스, 상기

는 n번째 반복단계에서 단말k의 수신 가중치 행렬, 상기

는 n번째 반복단계에서 단말k의 송신 프리코딩 행렬, 상기

는 단말k의 간섭 및 잡음 공분산 행렬, 상기

는 단말k에게 할당된 빔 개수, 상기

는 단말k의 채널행렬, 상기

는 기지국 송신 안테나 개수, 상기

는 행렬 A의 특이 값(singular value)들 중 가장 큰 것부터

개까지의 특이 값에 대응되는 좌 특이 벡터(left singular vector)들, 상기

는 단말k의 가중치 행렬을 반영한 채널행렬, 상기

는 단말k를 제외한 나머지 단말들의 채널행렬을 차례대로 쌓은 톨 행렬(tall matrix)로서,

, 상기

는 행렬 A의 특이 값들 중 '0' 값인

개의 특이 값에 대응되는 우 특이 벡터(right singular vector)들, 상기

는 단말k의 프리코딩 행렬 및 가중치 행렬을 반영한 채널행렬, 상기

는 단말k의 전력할당을 위한

×

크기의 대각행렬,

는

의 대각성분의 합, 상기

는 송신전력의 총 합, 상기

는

의 특이 값 분해 시 얻어지는 특이 값들을 대각성분으로 갖는 대각행렬, 상기

는

의 프로비니어스 놈으로서,

의 대각성분 합의 제곱근(square root), 상기

는 합 용량, 상기

는 조합s에서 합 용량, 상기

는 조합s에서 단말k의 프리코딩 행렬, 상기

는 조합s에서 단말k의 가중치 행렬, 상기

는 합 용량이 최대인 빔 할당 조합의 인덱스, 상기

는 최종 합 용량, 상기

는 단말k의 최종 프리코딩 행렬, 상기

는 단말k의 최종 가중치 행렬을 의미한다.In Table 1,

Is a beam allocation combination set, the

Is the beam allocation combination index,

Is the matrix update iteration index,

Is the number of terminal to be scheduled,

Is the terminal index, the

Is a reception weight matrix of terminal k in the n th iteration,

Is the transmission precoding matrix of the terminal k in the n th iteration,

Is an interference and noise covariance matrix of terminal k,

Is the number of beams allocated to terminal k,

Is the channel matrix of terminal k,

Is the number of base station transmit antennas,

Is the largest of the singular values of matrix A

Left singular vectors corresponding to up to singular values,

Is a channel matrix reflecting the weight matrix of terminal k,

Is a toll matrix in which channel matrices of the other terminals except for k are sequentially stacked.

, remind

Is the zero value among the singular values of matrix A.

Singular vectors corresponding to two singular values,

Is a channel matrix reflecting a precoding matrix and a weighting matrix of terminal k,

Is for power allocation of terminal k.

×

Diagonal matrix of size,

Is

Sum of the diagonal components of

Is the total sum of the transmit powers,

Is

Diagonal matrix having the singular values obtained by decomposing the singular values of as diagonal components,

Is

As a Provenius guy,

Square root of the sum of the diagonal components of,

Is the sum capacity, said

Is the sum capacity in combinations,

Is the precoding matrix of terminal k in combinations,

Is a weighting matrix of terminal k in combination s,

Is the index of the beam allocation combination whose sum capacity is maximum,

Is the final sum capacity, said

Is the final precoding matrix of terminal k,

Denotes the final weight matrix of the terminal k.

4 is a block diagram of a terminal in a multi-user multi-input / output wireless communication system according to an exemplary embodiment of the present invention.

As shown in FIG. 4, the terminal includes a plurality of RF processors 402-1 to 402-N, a combiner 404, a signal classifier 406, a channel and interference suppression matrix 408, and control information. The generator 410 includes a control information checker 412, an interference suppression matrix (ISM) processor 414, an interference canceller 416, and a demodulator 418.

Each of the plurality of RF processors 402-1 to 402-N performs a conversion function between an RF band signal transmitted and received through a corresponding antenna and a baseband signal exchanged with the copyer 404. The decompressor 404 performs transmission and reception conversion functions. For example, when following a time division duplex scheme, the copyer 404 provides a signal from the control information generator 410 to the plurality of RF processors 402-1 to 402-N during a transmission time. During the reception time, signals from the plurality of RF processors 402-1 to 402-N are provided to the signal classifier 406.

The signal classifier 406 classifies the signal received from the base station and outputs the signal to the corresponding processing path. For example, the signal classifier 406 outputs a signal used for channel estimation, such as a pilot signal and a preamble, to the channel and interference suppression matrix 408, and outputs a data signal to the ISM processor 414. A signal including control information is output to the control information checker 412. In addition, the signal classifier 406 outputs the interference signal received during the period in which the signal to the terminal itself is not received to the channel and interference suppression matrix 408.

The channel and interference estimator 408 estimates the terminal's own channel, interference channel, and interference signal. The channel and interference estimator 408 estimates its channel using the preamble or pilot signal from the base station. The channel and interference estimator 408 estimates the interference channel and the interference signal by using the signal received during the period in which the signal to the terminal itself is not received.

The control information generator 410 generates control information to be transmitted to the base station. For example, the control information generator 410 generates control information including channel, interference channel, and interference signal information of the terminal own estimated by the channel and interference estimator 408. The type of information to be transmitted to the base station may include at least one of channel quality information, adaptive modulation and coding information, a user index, and an interference and noise covariance matrix. Here, the channel quality information may be total channel state information, signal to noise ratio, channel capacity index, codebook index, and the like.

 The control information checker 412 confirms the control information received from the base station. For example, the control information checker 412 checks the weight matrix information received from the base station and provides the weight matrix information to the interference canceller 416.

The ISM processor 414 multiplies the received signal by an interference suppression matrix for suppressing outer cell interference (OCI) from another cell. For example, the interference suppression matrix is an interference and noise covariance matrix of Equation (1).

The interference canceller 416 performs interference cancellation according to the weight matrix information received from the base station. That is, the interference canceller 416 multiplies the output from the ISM processor 414 by a weight matrix. The demodulator 418 demodulates the interference canceled signal into an information bit string according to a modulation method.

5 is a flowchart illustrating an operation procedure of a base station in a multi-user multi-input / output wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the base station determines whether channel information and interference information are received from terminals in step 501. Here, the channel information is a channel value between the base station and the terminal, the interference information means the interference channel value and the interference signal value of the terminal. The form of the information fed back from the terminals may include at least one of channel quality information, adaptive modulation and coding information, a user index, and an interference and noise covariance matrix. Here, the channel quality information may be total channel state information, signal to noise ratio, channel capacity index, codebook index, and the like.

When the channel information and the interference information are received, the base station proceeds to step 503 to generate a possible beam allocation combination set for the scheduling target terminals. At this time, s is initialized to 1. S is a variable representing an index of the beam allocation combination and is used for repeating the present procedure.

After generating the beam combination set, the base station proceeds to step 505 to initialize the matrix set for the s-th combination. The matrix set includes a precoding matrix M _k (n) and a weight matrix W _k (n) pairs of each of the scheduling target terminals. That is, the precoding matrix M _k (n) and the weight matrix W _k (n) exist as many as the number of terminals. Here, n is an index indicating an update repeating step of the matrices and is set to '0' at initialization. For example, the initial weight matrix W _k (0) and the initial precoding matrix M _k (0) are shown in Equation 1 above.

After initializing the matrix set, the base station proceeds to step 507 and increases the iteration index n by one.

In step 509, the base station updates the precoding matrix M _k (n-1) and the weight matrix W _k (n-1) of each of the terminals. In this case, the precoding matrix M _k (n-1) is updated using the weighting matrix W _k (n-1), and the precoding matrix M _k (n-1) is updated with the updated precoding matrix M _k ( is updated using n). In this case, when updating the precoding matrix, in addition to the weighting matrix, channel matrixes of all terminals and beam allocation information of the corresponding terminals are used, and in addition to the updated precoding matrix, power allocation information and beams of the corresponding terminal are updated when the weighting matrix is updated. Allocation information, channel matrix of all terminals is used. The base station also calculates the sum capacity when using the updated matrices.

After updating the matrices in the matrix set, the base station proceeds to step 511 whether the degree of change of the pre-coding matrix M _k (n-1) and the post-update precoding matrix M _k (n) is less than a threshold value. Check it. That is, the base station checks whether the matrices updated in the current repetition step are optimized. E.g. The degree of change of the precoding matrix is calculated as shown in Equation 3 above.

If the degree of change of the precoding matrix is greater than or equal to a threshold value, the base station returns to step 507 and increases n by 1, and then proceeds to step 509. In this case, the iterative update procedure through steps 507 to 511 may be performed independently for each terminal, or for all terminals unless the matrixes of one terminal are optimized.

On the other hand, if the degree of change of the precoding matrix is less than a threshold value, the base station proceeds to step 513 and the s-th combination of the precoding matrix M _k (n) and the weight matrix W _k (n) of the current iteration step. Determined by the matrix set of.

After determining the matrix set of the s-th combination, the base station proceeds to step 515 and determines whether the matrix set is determined for all combinations generated in step 503. In other words, the base station checks whether steps 505 to 513 are performed for all combinations.

If the matrix set has not been determined for all combinations, the base station proceeds to step 517 and increases s by 1 and then returns to step 505. That is, the base station repeats steps 505 to 513 for the next set of indexes.

If the matrix set is determined for all combinations, the base station proceeds to step 519 to determine the matrix set of the combination having the maximum sum capacity as the final matrix set.

After determining the final matrix set, the base station proceeds to step 521 and transmits the final matrix set information to each terminal.

In step 523, the base station precodes and transmits a signal to each terminal by using precoding matrices in the final matrix set.

When the final matrix set determination process of the base station shown in steps 503 to 519 of FIG. 5 is expressed by a water code, it is shown in Table 1 below.

6 illustrates an operation procedure of a terminal in a multi-user multi-input / output wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the terminal determines whether a section in which a signal to the terminal is not received appears in step 601. Since the terminal checks the resource allocation result through the message received from the base station, it can know the section in which the signal to the self is not received.

If the section in which the signal to the self is not received appears, the terminal proceeds to step 603 to measure the interference channel and the interference signal. Here, the interference channel means a channel value with a neighbor base station, and the interference signal means a signal from a neighbor base station.

After measuring the interference channel and the interference signal, the terminal proceeds to step 605 and transmits the interference channel information and the interference signal information to the base station. In addition, the terminal transmits channel information with the base station. However, the channel information feedback with the base station may not be performed at the same period as the interference information feedback. Here, the form of the feedback information may include at least one of channel quality information, adaptive modulation and coding information, a user index, an interference and noise covariance matrix. In addition, the channel quality information may be total channel state information, signal to noise ratio, channel capacity index, codebook index, and the like.

In step 607, the terminal determines whether weight matrix information is received from the base station.

When the weight matrix information is received, the terminal proceeds to step 609 to multiply the received signal received from the base station by the interference suppression matrix, thereby suppressing interference from adjacent cells. For example, the interference suppression matrix is an interference and noise covariance matrix of Equation (1).

In step 611, the terminal removes interference by multiplying the weighted matrix by a received signal multiplied by the interference suppression matrix.

After removing the interference, the terminal proceeds to step 613 to demodulate the interference canceled signal to restore the information bit stream.

In step 615, the terminal transmits channel information with the base station to the base station. Here, the channel information with the base station transmitted is the channel information updated during the interference cancellation process.

7 illustrates the performance of the technique according to the present invention and the DPC (Dirty Paper Coding) technique.

FIG. 7A illustrates a sum rate according to signal to interference and noise ratio (SINR). In FIG. 7A, one base station having four transmit antennas and three terminals having four receive antennas are assumed, and 'INR = [-10, 0, 10] dB' is three terminals. Each interference level is -10dB, 0dB, 10dB. Referring to FIG. 7 (a), when using the technique of the present invention, it is confirmed that a difference in sum rate less than 1bps / Hz occurs as compared to the DPC technique having optimal performance.

FIG. 7B illustrates the difference between the sum rates of the DPC and the present invention according to the number of iteration updates of the matrix. In FIG. 7B, N _T is the number of transmitting antennas, K is the number of terminals, SINR is the signal-to-interference and noise ratio, and N _R is the number of receiving antennas. Referring to (b) of FIG. 7, in the case of using the existing technology, performance degradation occurs when the sum of the number of receive antennas is smaller than the number of transmit antennas, whereas the technique according to the present invention improves performance as the number of receive antennas increases. It is confirmed that this occurs.

7 (c) shows the sum rate according to the number of users. In FIG. 7C, N _R is the number of receive antennas, α _k is the neighbor cell interference level, N _T is the number of transmit antennas, and SINR is a signal-to-interference and noise ratio. Referring to FIG. 7C, when the technique of the present invention is used, as the number of users increases, the sum rate increases with the same slope as the DPC.

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.

1 is a diagram schematically showing a multi-user multi-input / output wireless communication system according to the present invention;

2 is a block diagram of a base station in a multi-user multi-input / output wireless communication system according to an embodiment of the present invention;

3 is a block diagram of a matrix determiner in a multi-user multi-input / output wireless communication system according to an embodiment of the present invention;

4 is a block diagram of a terminal in a multi-user multi-input / output wireless communication system according to an embodiment of the present invention;

5 is a diagram illustrating an operation procedure of a base station in a multi-user multi-input / output wireless communication system according to an embodiment of the present invention;

6 is a diagram illustrating an operation procedure of a terminal in a multi-user multi-input / output wireless communication system according to an embodiment of the present invention;

7 shows a comparison of the performance of the technique according to the present invention and the DPC (Dirty Paper Coding) technique.

Claims (44)

In a base station apparatus in a multi-user multiple input multiple output (MU MIMO) wireless communication system, A determiner for determining a precoding matrix and a weight matrix of the at least one terminal using channel information and interference information fed back from at least one terminal; A precoder for precoding a transmission signal to the terminals according to the precoding matrix; And a plurality of radio frequency (RF) processors for transmitting the precoded signal through a plurality of antennas. The method of claim 1, The channel information is a channel value between the base station and the terminal, The interference information is characterized in that the interference channel value and the interference signal value of the terminal. The method of claim 1, The form of the fed back channel information and interference information may include channel quality information (CQI), adaptive modulation and coding information, user index, interference and noise covariance matrix (INCM). And at least one form. The method of claim 3, wherein The channel quality information includes at least one of overall channel state information (CSI), signal to noise ratio, channel capacity index, and codebook index. The method of claim 1, And the plurality of RF processors transmit control information including the weight matrix information. The method of claim 1, The determinant, A generator for generating a beam allocation combination set for the at least one terminal; An allocator for allocating power for each transmission stream; An initializer for initializing the precoding matrix and the weight matrix, updating the precoding matrix using the weight matrix, and updating the weight matrix using the updated precoding matrix; A determiner for determining whether the precoding matrix and the weight matrix are optimized; Among the precoding matrices and the weighting matrices optimized for each beam allocation combination, a final matrix determinant for determining the precoding matrix and the weighting matrix of the combination having the maximum sum capacity as the final precoding matrix and the weighting matrix. Apparatus comprising a. The method of claim 6, And the power allocator allocates the power per stream to maximize the sum capacity. The method of claim 6, The calculator, When updating the precoding matrix, using a weight matrix, the channel matrix of the at least one terminal, the beam allocation information of the corresponding terminal, And updating the weight matrix, using the updated precoding matrix, power allocation information, beam allocation information of a corresponding terminal, and a channel matrix of the at least one terminal. The method of claim 6, And the operator repeatedly updates the precoding matrix and the weight matrix until the precoding matrix and the weight matrix are optimized. The method of claim 9, If the degree of change of the precoding matrix of the (n-1) -th iteration step and the precoding matrix of the (n)-iteration step is smaller than a threshold, the determiner may determine the precoding matrix and the weight in the (n) -th iteration step. And determine that the matrix is optimized. The method of claim 10, The determiner is characterized in that for calculating the degree of change as shown in the following formula,

here,

Is the frobenius norm operator,

Is the precoding matrix of terminal k in the (n) -th step,

Is a trace operator, the sum of the diagonal components. The method of claim 6, The calculator, characterized in that for initializing the precoding matrix and the weight matrix as shown in the following equation,

Where

Is the initial weight matrix of terminal k,

Is the initial precoding matrix of terminal k,

Is an interference and noise covariance matrix of terminal k,

Is the channel matrix of terminal k,

Is the number of beams allocated to terminal k,

Is the largest of the singular values of matrix A

Left singular vectors corresponding to up to singular values,

Is the interference channel of the terminal k,

Is the interference signal of the terminal k,

Means noise power. The method of claim 6, The calculator is characterized in that for updating the precoding matrix and the weight matrix as shown in the following code

Where

Is the terminal index, the

Is a reception weight matrix of terminal k in the n th iteration,

Is the transmission precoding matrix of the terminal k in the n th iteration,

Is an interference and noise covariance matrix of terminal k,

Is the number of beams allocated to terminal k,

Is the channel matrix of terminal k,

Is the number of base station transmit antennas,

Is the largest of the singular values of matrix A

Left singular vectors corresponding to up to singular values,

Is a channel matrix reflecting the weight matrix of terminal k,

Is a toll matrix in which channel matrices of the other terminals except for k are sequentially stacked.

, remind

Is the zero value among the singular values of matrix A.

Singular vectors corresponding to two singular values,

Is a channel matrix reflecting a precoding matrix and a weighting matrix of terminal k,

Is for power allocation of terminal k.

×

Diagonal matrix of size,

Is

Sum of the diagonal components of

Is the total sum of the transmit powers,

Is

Means the diagonal matrix with the singular values obtained by decomposing the singular value of as a diagonal component. The method of claim 6, And the calculator calculates a sum capacity when using the updated precoding matrix and the updated weight matrix. The method of claim 14, The calculator is characterized in that for calculating the sum capacity as shown in the following formula,

Where

Is the sum capacity, said

Is the number of terminals, the

Is a diagonal matrix whose element is a singular value obtained by singular value decomposition (SVD) reflecting a precoding matrix and a weight matrix of terminal k.

Denotes the power allocation matrix of the terminal k. In a terminal device in a multi-user multiple input multiple output (MU MIMO) wireless communication system, At least one radio frequency (RF) processor for receiving a signal through at least one antenna; A processor for removing external cell interference by multiplying the received signal by an interference suppression matrix; And a canceler for canceling interference due to signals to other terminals by using a weight matrix provided from the base station. The method of claim 16 The interference suppression matrix is an apparatus according to the following formula,

Where

Is the interference channel of the terminal k,

Is the interference signal of the terminal k,

Means noise power. The method of claim 16, And an estimator for measuring channel information and interference information. The method of claim 18, The channel information is a channel value between the base station and the terminal, The interference information is characterized in that the interference channel value and the interference signal value of the terminal. The method of claim 18, The estimator is characterized in that for estimating the interference channel and the value of the interference signal using a signal received during a period in which no signal to the terminal itself. The method of claim 16, The at least one RF processor, characterized in that for transmitting the control information including the channel information and interference information to the base station. The method of claim 21, Types of channel information and interference information transmitted to the base station include channel quality information (CQI), adaptive modulation and coding information, user indexes, interference and noise covariance matrix (INCM). Apparatus, characterized in that it comprises at least one form. In a multi-user multiple input multiple output (MU MIMO) wireless communication system, a signal processing method of a base station, Determining a precoding matrix and a weight matrix of the at least one terminal by using channel information and interference information fed back from at least one terminal; Precoding a transmission signal to the terminals according to the precoding matrix; Transmitting the precoded signal through a plurality of antennas. The method of claim 23, wherein The channel information is a channel value between the base station and the terminal, The interference information is characterized in that the interference channel value and the interference signal value of the terminal. The method of claim 23, wherein The form of the fed back channel information and interference information may include channel quality information (CQI), adaptive modulation and coding information, user index, interference and noise covariance matrix (INCM). At least one form. The method of claim 25, The channel quality information includes at least one of overall channel state information (CSI), signal-to-noise ratio, channel capacity index, and codebook index. The method of claim 23, wherein Transmitting control information including the weight matrix information. The method of claim 23, wherein The process of determining the precoding matrix and the weight matrix, Generating a beam allocation combination set for the at least one terminal; Allocating power for each transmission stream; After initializing the precoding matrix and the weighting matrix, updating the precoding matrix using the weighting matrix, and updating the weighting matrix using the updated precoding matrix; Determining whether the precoding matrix and the weight matrix are optimized; Determining, among the precoding matrices and the weighting matrices optimized for each beam allocation combination, a precoding matrix and a weighting matrix of the combination having the largest sum capacity as the final precoding matrix and the weighting matrix. Characterized in that. The method of claim 28, Wherein the power allocation per transmission stream is performed to maximize the sum capacity. The method of claim 28, The precoding matrix update is performed using a weight matrix, a channel matrix of the at least one terminal, and beam allocation information of the corresponding terminal. The weight matrix update is performed using the updated precoding matrix, power allocation information, beam allocation information of a corresponding terminal, and a channel matrix of the at least one terminal. The method of claim 28, The updating of the precoding matrix and the weighting matrix is iteratively performed until the precoding matrix and the weighting matrix are optimized. The method of claim 31, wherein Determining whether the precoding matrix and the weight matrix are optimized, If the degree of change of the precoding matrix of the (n-1) -th iteration step and the precoding matrix of the (n) -th iteration step is less than the threshold, it is determined that the precoding matrix and the weighting matrix are optimized in the (n) -th iteration step. And determining the process. The method of claim 32, The change degree is calculated by the following formula,

here,

Is the frobenius norm operator,

Is the precoding matrix of terminal k in the (n) -th step,

Is a trace operator, the sum of the diagonal components. The method of claim 28, Wherein the precoding matrix and the weight matrix are initialized as in the following equation,

Where

Is the initial weight matrix of terminal k,

Is the initial precoding matrix of terminal k,

Is an interference and noise covariance matrix of terminal k,

Is the channel matrix of terminal k,

Is the number of beams allocated to terminal k,

Is the largest of the singular values of matrix A

Left singular vectors corresponding to up to singular values,

Is the interference channel of the terminal k,

Is the interference signal of the terminal k,

Means noise power. The method of claim 28, Wherein the precoding matrix and the weight matrix are updated as shown below.

Where

Is the terminal index, the

Is a reception weight matrix of terminal k in the n th iteration,

Is the transmission precoding matrix of the terminal k in the n th iteration,

Is an interference and noise covariance matrix of terminal k,

Is the number of beams allocated to terminal k,

Is the channel matrix of terminal k,

Is the number of base station transmit antennas,

Is the largest of the singular values of matrix A

Left singular vectors corresponding to up to singular values,

Is a channel matrix reflecting the weight matrix of terminal k,

Is a toll matrix in which channel matrices of the other terminals except for k are sequentially stacked.

, remind

Is the zero value among the singular values of matrix A.

Singular vectors corresponding to two singular values,

Is a channel matrix reflecting a precoding matrix and a weighting matrix of terminal k,

Is for power allocation of terminal k.

×

Diagonal matrix of size,

Is

Sum of the diagonal components of

Is the total sum of the transmit powers,

Is

Means the diagonal matrix with the singular values obtained by decomposing the singular value of as a diagonal component. The method of claim 28, Calculating a sum capacity when using the updated precoding matrix and the updated weight matrix. The method of claim 36, The sum capacity is calculated as in the following formula,

Where

Is the sum capacity, said

Is the number of terminals, the

Is a diagonal matrix whose element is a singular value obtained by singular value decomposition (SVD) reflecting a precoding matrix and a weight matrix of terminal k.

Denotes the power allocation matrix of the terminal k. Multi-User Multiple Input Multiple Output (MU MIMO) In a signal processing method of a terminal in a wireless communication system, Receiving a signal through at least one antenna, Removing external cell interference by multiplying the received signal by an interference suppression matrix; And removing interference due to signals to other terminals by using a weight matrix provided from the base station. The method of claim 38 Wherein the interference suppression matrix is a matrix such as

Where

Is the interference channel of the terminal k,

Is the interference signal of the terminal k,

Means noise power. The method of claim 38, And measuring channel information and interference information. The method of claim 40, The channel information is a channel value between the base station and the terminal, The interference information is characterized in that the interference channel value and the interference signal value of the terminal. The method of claim 40,  The method of measuring the interference channel and the interference signal value, characterized in that performed using a signal received during a period in which no signal to the terminal itself. The method of claim 38, And transmitting control information including the channel information and the interference information to the base station. The method of claim 43, Types of channel information and interference information transmitted to the base station include channel quality information (CQI), adaptive modulation and coding information, user index, interference and noise covariance matrix (INCM). Matrix) at least one form.

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