KR101424697B1 - Apparatus and method for signal processing to eliminate interference in multi-user multiple input multiple output wireless communication system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a multi-user MIMO (Multi-User Multiple Input Multiple Output) wireless communication system, in which a base station, using channel information and interference information fed back from at least one terminal, A determiner for determining a percoding matrix and a weight matrix, a precoder for precoding a transmission signal to the terminals according to the precoding matrix, and a transmitter for transmitting the precoded signal through a plurality of antennas The transmission precoding matrix and the transmission weight matrix are repeatedly updated using the channel information and the interference information, thereby effectively eliminating the interference occurring in the outer cell and the inner cell .

A multi-user multiple input multiple output (MIMO), a precoding matrix, a weight matrix,

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a signal processing apparatus and a signal processing method for interference cancellation in a multi-user MIMO wireless communication system,

The present invention relates to a multi-user MIMO (Multi-User Multiple Input Multiple Output) wireless communication system, and more particularly, to a signal processing apparatus and method for interference cancellation in a multi-user MIMO wireless communication system.

2. Description of the Related Art [0002] Recently, as a demand for high-speed and high-quality data transmission has increased, a MIMO (Multiple Input Multiple Output) wireless communication system using a plurality of transmitting and receiving antennas has been attracting attention. The MIMO technique performs communication using a plurality of streams through a plurality of antennas, thereby greatly improving channel capacity as compared with the case of using a single antenna. For example, if both the transmitting and receiving ends use M transmit and receive antennas, the channel between each antenna is independent, and the bandwidth and total transmit power are fixed, the average channel capacity is increased by M times as compared to a single antenna . A multi-input / output system can be applied not only to a pair of transmitting and receiving ends but also between one transmitting end and a plurality of receiving ends. For example, a multi-user multiple input multiple output (MU MIMO) wireless communication system is constructed assuming a base station having a plurality of transmit antennas and a plurality of terminals having at least one antenna.

The multi-user MIMO wireless communication system increases frequency efficiency by allowing a plurality of users to simultaneously use space resources secured by using a plurality of antennas. In the case of a downlink for transmitting information from a base station to a mobile station, the base station pre-processes and transmits information to a plurality of users at the same time, and each of the plurality of users checks information from the signal received through each channel . To ensure high channel capacity, an alternative is needed to eliminate multi-user interference, which is interference between terminals, and interference from neighboring cells.

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

It is another object of the present invention to provide an apparatus and method for determining a transmit precoding matrix and a receive weight matrix through an iterative technique in a multi-user MIMO wireless communication system.

According to an aspect of the present invention, there is provided a base station apparatus in a multi-user multi-input multiple output (MIMO) multi-input multiple output (MIMO) A determiner for determining a percoding matrix and a weight matrix of the at least one mobile station using the information, a precoder for precoding a transmission signal to the terminals according to the precoding matrix, And a plurality of RF (Radio Frequency) processors for transmitting a coded signal through a plurality of antennas.

According to a second aspect of the present invention, there is provided a multi-user multi-input multiple output (MIMO) wireless communication system in which a terminal device receives a signal through at least one antenna A processor that removes interference caused by external signals by multiplying the received signal by an interference suppression matrix and eliminates interference due to a signal from the other terminal using a weights matrix provided from the base station; And an eliminator.

According to a third aspect of the present invention, there is provided a method of processing a signal of a base station in a multi-user multi-input multiple output (MIMO) Determining a percoding matrix and a weight matrix of the at least one UE using information and interference information; precoding a transmission signal to the UEs according to the precoding matrix; And transmitting the precoded signal through a plurality of antennas.

According to a fourth aspect of the present invention, there is provided a signal processing method of a terminal in a multi-user multi-input multiple output (MIMO) wireless communication system, And removing the interference caused by the signal to the other terminal by using a weights matrix provided from the base station. .

In a multi-user multi-input multiple output (MIMO) wireless communication system, a transmission precoding matrix and a transmission weight matrix are repeatedly updated using channel information and interference information, Interference can be effectively removed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, which illustrate a technique for eliminating interference to a mobile station in a multi-user multiple input multiple output (MU MIMO) wireless communication system. In particular, the present invention provides a technique for determining and using a transmit precoding matrix of a base station and a receive weight matrix of a terminal in a multi-user MIMO wireless communication system.

1 schematically illustrates a multi-user MIMO wireless communication system in accordance with the present invention,

Referring to FIG. 1, the BS 110 simultaneously transmits data signals to the MSs 120-1 to 120-K using a plurality of transmit antennas. At this time, the BS 110 transmits data signals to precoding matrices M ₁ , ... , M _K, and transmits the result. The data signal multiplied by the precoding matrix is received at each of the terminals 120-1 to 120-K via the corresponding channel _Hk . In addition, an interference signal from a neighboring cell is received at each of the terminals 120-1 to 120-K. Therefore, each of the terminals 120-1 to 120-K multiplies the reception signal by the weighting matrix _Wk to eliminate interference from neighboring cells and interference due to signals to other terminals.

Precoding matrix M ₁ to M _K and the weight matrix W ₁ to W _K is determined by the base station 110, the base stations 110 is the terminal to the weight matrix information (120-1 to 120-K) Feedforward < / RTI > To this end, each of the terminals 120-1 to 120-K feeds back the neighboring cell interference signal and the interference channel to the base station 110. [ The neighboring cell interference signal and the interference channel are measured by each of the terminals 120-1 to 120-K, and each of the terminals 120-1 to 120-K measures the adjacent And measures the interference signal and the interference channel. At this time, the neighboring cell interference signal and interference channel are not changed for a long time and are assumed to be the same while the terminal is receiving a signal. This assumption is made in that the interference from the neighboring cell is interference from the base station with a high power level and has a certain pattern.

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

2 illustrates a block diagram of a base station in a multi-user MIMO wireless communication system according to an embodiment of the present invention.

2, the base station includes a control information identifier 202, a matrix determiner 204, a control information generator 206, a modulator 208, a precoder 210, a signal buffer 212, A duplexer 214, and a plurality of RF (Radio Frequency) processors 216-1 to 216-N.

The control information verifier 202 confirms the control information received from the terminal. In particular, according to the present invention, the control information verifier 202 confirms channel information and interference information fed back from the UE and provides the channel information and the interference information to the matrix determiner 204. Herein, the channel information is a channel value between a BS and a UE, and the interference information indicates an interference channel value and an interference signal value of the UE. The type of feedback information may include at least one of channel quality information (CQI), adaptive modulation and coding information, user index, interference and noise covariance matrix (INCM) . Here, the channel quality information may be total channel state information (CSI), signal-to-noise ratio, channel capacity index, codebook index, and the like.

The matrix determiner 204 determines a precoding matrix to be used in the base station and a weight matrix to be used in the UE using the channel information and the interference information. Here, the precoding matrix and the weight matrix exist for each UE. The detailed function of the matrix determiner 204 will be described below with reference to FIG.

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 information bit streams to be transmitted to each terminal and converts the information bit streams 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 transmission signals to the inter-terminal by a corresponding precoding matrix. The signal buffer 212 temporarily stores precoded signals provided from the precoder 210 and outputs precoded signals to each terminal to be simultaneously transmitted.

The transceiver 214 performs transmission and reception conversion functions. For example, when following the time division duplex scheme, the repeater 214 transmits signals from the signal buffer 212 and the control information generator 206 to the plurality of RF processors 216-1 to 216- 216-N, and provides signals from the plurality of RF processors 216-1 through 216-N to the control information identifier 202 during the reception time. Each of the plurality of RF processors 216-1 to 216-N performs a function of converting between an RF band signal transmitted and received through a corresponding antenna and a baseband signal exchanged with the optical receiver 214. [

3 illustrates a block diagram of a matrix determiner 204 in a multi-user MIMO wireless communication system according to an embodiment of the present invention.

3, the matrix determiner 204 includes a combination set generator 302, a power allocation matrix calculator 306, an optimizer 308, and a final matrix determiner 310 .

The combination set generator 302 generates all possible beam assignment combinations. The number of beam assignment combinations is an iterative number for determining an optimal precoding matrix and a weighting matrix. For example, if the number of transmit antennas of the base station is 4, the number of receive antennas of the terminal A is 4, and the number of receive antennas of the terminal B is 4, possible beam allocation combinations are [4,0], [ 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 streams. Here, to smooth the respective streams of the channel means that the stream-specific signals are overlapped and received, and the specific-matrix is multiplied to the channels so that the signals for each stream are converted into the non-overlapping channels. For example, if the channel matrix is singular value decomposition (SVD), a diagonal matrix component appears. Therefore, if the channel matrix is multiplied by a specific matrix, only the diagonal matrix component is left. That is, the fact that the respective streams of the channel are to be canceled means that only the diagonal matrix component is left. The power is allocated so that the sum capacity is maximized.

The matrix calculator 306 generates a precoding matrix to be used in the base station and a weight matrix to be used in the UE for each combination generated in the combination set generator 302. [ The matrix calculator 306 generates one matrix set for each combination, and one matrix set includes precoding matrices and weight matrix pairs of each of the MSs. In order to generate one matrix set, the matrix calculator 306 initializes a precoding matrix and a weighting matrix, updates a precoding matrix using a weighting matrix, and calculates a weighting matrix using the updated precoding matrix Update. At this time, at the time of updating the precoding matrix, channel matrixes of all terminals and beam allocation information of the corresponding terminals are used in addition to weight matrices, and in addition to the updated precoding matrix at the time of updating the weight matrices, power allocation information, Allocation information, and channel matrixes of all terminals are used.

For example, the matrix calculator 306 initializes the precoding matrix and the weight matrix according to Equation (1).

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) above,

Is an initial weight matrix of the terminal k,

Is an initial precoding matrix of the terminal k,

Is the interference and noise covariance matrix of the terminal k,

Is the channel matrix of the terminal k,

The number of beams allocated to the terminal k,

Is the largest singular value of the matrix A

Left singular vectors corresponding to the singular values up to

Is the interference channel of the terminal k,

Is an interference signal of the terminal k,

Is the noise power.

The matrix calculator 306 performs an iterative step according to the determination of the optimization determiner 308 to update the precoding matrix and the weight matrix again. That is, the matrix calculator 306 repeatedly updates the precoding matrix and the weighting matrix until it is determined by the optimization determining unit 308 that the optimization is performed.

Then, the matrix calculator 306 calculates a sum capacity when using updated matrices in each iteration step. The summed capacitance is calculated according to the following Equation (1).

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) above,

The total capacity,

The number of terminals,

A diagonal matrix having an element as a singular value to be obtained at the time of singular value decomposition of a channel reflecting a precoding matrix and a weight matrix of the terminal k,

Denotes a power allocation matrix of the terminal k.

The optimization determiner 308 refers to the degree of change of the precoding matrix generated by the matrix calculator 306 to determine whether the precoding matrix and the weighting matrix are optimized. For example, the degree of change between the precoding matrix of the most recent iteration and the precoding matrix of the previous iteration is calculated by 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) above,

Is the operator of the frobenius norm,

The precoding matrix of the terminal k in the n < th >

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

That is, the optimization determiner 308 calculates the degree of change and compares it with a threshold value. If the degree of change is less than or equal to the threshold value, the optimization determiner 308 determines that the optimization is not optimized. If the degree of change is greater than or equal to the threshold value, the optimizer 308 determines that the optimization is not optimal. (306) to repeat the repetition step.

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

The operation of the matrix determiner 204 may be represented by a pseudo code as shown in Table 1 below.

code

Explanation

Perform on all combinations

Perform on all terminals

reset

Increase repeat steps

Perform on all terminals

Precoding matrix and

Update the weighting matrix

Calculate total capacity

Optimization judgment

Combination s
Determine Matrix and Sum Capacity

The final matrix and sum capacity
decision

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,

A beam allocation combination set,

A beam allocation combination index,

&Lt; / RTI >&lt; RTI ID = 0.0 &gt;

The number of scheduled terminals,

The terminal index,

The reception weight matrix of the terminal k in the n-th iteration step,

The transmission precoding matrix of the terminal k in the n-th iteration step,

Is the interference and noise covariance matrix of the terminal k,

The number of beams allocated to the terminal k,

Is the channel matrix of the terminal k,

The number of base station transmission antennas,

Is the largest singular value of the matrix A

Left singular vectors corresponding to the singular values up to

A channel matrix reflecting the weight matrix of the terminal k,

Is a tall matrix in which channel matrices of terminals other than the terminal k are sequentially stacked,

, remind

0 &quot; among the singular values of the matrix A

Right singular vectors corresponding to the number of singular values,

A channel matrix reflecting the precoding matrix and the weighting matrix of the terminal k,

Lt; RTI ID = 0.0 &gt; k &lt; / RTI &

×

Size diagonal matrix,

The

The sum of the diagonal components of

The total sum of the transmission powers,

The

A diagonal matrix having diagonal components of singular values obtained at the time of singular value decomposition,

The

As the providence man of

The square root of the diagonal combination of

The total capacity,

Is the sum capacity in the combination s,

The precoding matrix of the terminal k in the combination s,

Is the weight matrix of the terminal k in the combination s,

Is the index of the beam allocation combination having the maximum sum capacity,

The final sum capacity,

Is the final precoding matrix of the terminal k,

Denotes a final weighting matrix of the terminal k.

4 illustrates a block diagram of a UE in a multi-user MIMO wireless communication system according to an embodiment of the present invention.

4, the terminal includes a plurality of RF processors 402-1 through 402-N, a multiplexer 404, a signal classifier 406, a channel and an interference suppression matrix 408, Generator 410, a control information identifier 412, an ISM (Interference Suppression Matrix) processor 414, an interference canceller 416, and a demodulator 418.

Each of the plurality of RF processors 402-1 to 402-N performs a function of converting between an RF band signal transmitted and received through a corresponding antenna and a baseband signal exchanged with the optical receiver 404. The transceiver 404 performs transmission and reception conversion functions. For example, in the case of following the time division duplex method, the repeater 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 And provides signals from the plurality of RF processors 402-1 through 402-N to the signal classifier 406 during a receive time.

The signal classifier 406 classifies the signals received from the base station and outputs the classified signals to a 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, outputs a data signal to the ISM processor 414, And outputs a signal including the control information to the control information identifier 412. In addition, the signal classifier 406 outputs an interference signal received during a period in which a signal to the terminal itself is not received, to the channel and interference suppression matrix 408.

The channel and interference estimator 408 estimates a channel, an interference channel, and an interference signal of the terminal itself. The channel and interference estimator 408 estimates its own channel using a preamble or a pilot signal from the base station. The channel and interference estimator 408 estimates an interference channel and an interference signal using a signal received during a period in which a 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 the channel, the interference channel, and the interference signal information of the terminal itself 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 verifier 412 confirms control information received from the base station. For example, the control information identifier 412 identifies 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 OCI (Outer Cell Interference) from other cells. 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 weighting matrix. The demodulator 418 demodulates the interference-free signal according to the modulation scheme, and converts the demodulated signal into an information bit stream.

5 illustrates an operation procedure of a base station in a multi-user MIMO wireless communication system according to an embodiment of the present invention.

Referring to FIG. 5, in step 501, the BS determines whether channel information and interference information are received from the UEs. Herein, the channel information is a channel value between a BS and a UE, and the interference information indicates an interference channel value and an interference signal value of the UE. The type of information fed back from the UEs 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 BS proceeds to step 503 to generate a beam allocation combination set for the UEs to be scheduled. At this time, s is initialized to 1. Where s is a variable indicating the index of the beam allocation combination and is used for iterative execution of this procedure.

After generating the beam combining set, the BS proceeds to step 505 and initializes a matrix set for the s-th combination. The matrix set includes a precoding matrix M _k (n) and a weighting matrix W _k (n) pair of each of the UEs to be scheduled. That is, the precoding matrix M _k (n) and the weight matrix W _k (n) exist as many as the number of UEs. Here, n is an index indicating an update repetition 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 as shown in Equation (1).

After initializing the matrix set, the BS proceeds to step 507 and increments the iteration index n by one.

In step 509, the BS updates the precoding matrix M _k (n-1) and the weight matrix W _k (n-1) of the MSs. In this case, the precoding matrices M _k (n-1) is updated by using the weighting matrix W _k (n-1), the precoding matrix M _k (n-1) is the updated precoding matrix M _k ( n). At this time, at the time of updating the precoding matrix, channel matrixes of all terminals and beam allocation information of the corresponding terminals are used in addition to weight matrices, and in addition to the updated precoding matrix at the time of updating the weight matrices, power allocation information, Allocation information, and channel matrixes of all terminals are used. In addition, the base station calculates a sum capacity when updated matrices are used.

After updating the matrices in the matrix set, the BS proceeds to step 511 and determines whether the degree of change of the precoding matrix M _k (n-1) and the updated precoding matrix M _k (n) Check. That is, the BS determines whether the matrices updated at the current iteration step are optimized. E.g. The degree of change of the precoding matrix is calculated according to Equation (3).

If the degree of change of the precoding matrix is greater than or equal to the threshold value, the base station returns to step 507 and increments n by 1, and then proceeds to step 509. Here, the iterative update procedure through steps 507 through 511 may be performed independently for each terminal, or may be performed for all terminals if the matrices of one terminal are not optimized.

On the other hand, if the degree of change of the precoding matrix is smaller than the threshold, the BS proceeds to step 513 so that the precoding matrix _Mk (n) and the weighting matrix _Wk (n) As shown in FIG.

After determining the matrix set of the s-th combination, the BS proceeds to step 515 and determines whether a matrix set has been determined for all the combinations generated in step 503. In other words, the base station confirms whether the steps 505 to 513 have been performed for all the combinations.

If the matrix set is not determined for all the combinations, the BS proceeds to step 517 to increment s by 1, and then returns to step 505. [ That is, the base station repeats steps 505 to 513 for the next set of indices.

If the matrix set has been determined for all combinations, the BS proceeds to step 519 and determines a matrix set of combinations having a maximum sum capacity as a final matrix set.

After determining the final matrix set, the BS proceeds to step 521 and transmits the final matrix set information to each MS.

Then, the BS proceeds to step 523 and precodes the signals to the MSs using the precoding matrices in the final matrix set.

The final matrix set determination process of the BS shown in steps 503 to 519 of FIG. 5 is expressed by a numerical code as shown in Table 1 above.

6 illustrates an operation procedure of a UE in a multi-user MIMO wireless communication system according to an embodiment of the present invention.

Referring to FIG. 6, in step 601, the terminal determines whether a period in which no signal is received is displayed. Since the UE confirms the resource allocation result through a message received from the base station, the UE can know a period in which the signal to the UE is not received.

In step 603, the terminal measures an interference channel and an interference signal. Herein, the interference channel means a channel value with an adjacent base station, and the interference signal means a signal from an adjacent 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. Also, the terminal transmits channel information to the base station. However, channel information feedback with the base station may not be performed at the same period as the interference information feedback. Here, the type of feedback information may include at least one of channel quality information, adaptive modulation and coding information, a user index, and an interference and noise covariance matrix. Also, 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 MS determines whether weight matrix information is received from the BS.

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

In step 611, the MS eliminates interference by multiplying the received signal multiplied by the interference suppression matrix by the weight matrix.

After removing the interference, the UE proceeds to step 613 and demodulates the interference-free signal to recover the information bit stream.

Then, the MS proceeds to step 615 and transmits channel information to the BS through the BS. Here, the channel information transmitted to the base station is channel information updated in the interference cancellation process.

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

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

FIG. 7 (b) shows the DPC according to the number of iterative updates of the matrix and the difference in the sum rate of the present invention. In FIG. 7B, N _T denotes the number of transmit antennas, K denotes the number of terminals, SINR denotes the signal-to-interference and noise ratio, and N _R denotes the number of receive antennas. Referring to FIG. 7 (b), performance degradation occurs when the sum of the number of receive antennas is less than the number of transmit antennas in the case of using the existing technology, whereas the technique according to the present invention improves performance as the number of receive antennas is increased Is confirmed.

FIG. 7 (c) shows the sum rate according to the number of users. In FIG. 7C, N _R denotes the number of receiving antennas, α _k denotes the adjacent cell interference level, N _T denotes the number of transmitting antennas, and SINR denotes the signal-to-interference and noise ratio. Referring to FIG. 7C, when the technique of the present invention is used, it is confirmed that as the number of users increases, the sum rate increases at the same slope as the DPC.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

1 schematically illustrates a multi-user MIMO wireless communication system in accordance with the present invention,

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

3 is a block diagram of a matrix determiner in a multi-user MIMO wireless communication system according to an embodiment of the present invention.

4 is a block diagram of a UE in a multi-user MIMO wireless communication system according to an embodiment of the present invention;

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

6 is a diagram illustrating an operation procedure of a UE in a multi-user MIMO wireless communication system according to an embodiment of the present invention.

7 is a diagram showing a comparison between the performance of the technique according to the present invention and the performance of a DPC (Dirty Paper Coding) technique.

Claims (44)

A base station apparatus in a multi-user multiple input multiple output (MU MIMO) wireless communication system, A determiner for allocating power for each transmission stream and for determining a percoding 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 RF (Radio Frequency) processors for transmitting a precoded signal through a plurality of antennas. The method according to claim 1, The channel information is a channel value between a base station and a terminal, Wherein the interference information is an interference channel value and an interference signal value of the terminal. The method according to claim 1, The form of the feedback channel information and the interference information may include at least one of channel quality information (CQI), adaptive modulation and coding information, a user index, an interference and noise covariance matrix (INCM) Lt; RTI ID = 0.0 &gt; 1, &lt; / RTI &gt; The method of claim 3, Wherein the channel quality information includes at least one of a channel state information (CSI), a signal-to-noise ratio, a channel capacity index, and a codebook index. The method according to claim 1, Wherein the plurality of RF processors transmit control information including the weight matrix information. The method according to claim 1, The determiner, A generator for generating a beam allocation combination set for the at least one terminal, An operator for 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, A determiner for determining whether the precoding matrix and the weight matrix are optimized, A final matrix determiner for determining a combination of a precoding matrix and a weight matrix having a maximum sum capacity among the precoding matrices and weight matrices optimized for each beam allocation combination as a final precoding matrix and a weight matrix, &Lt; / RTI &gt; The method according to claim 6, And the determiner allocates the stream-specific power to maximize the sum capacity. The method according to claim 6, The computing unit includes: A weight matrix, a channel matrix of the at least one terminal, and beam allocation information of the corresponding terminal in updating the precoding matrix, And uses the updated precoding matrix, power allocation information, beam allocation information of the corresponding terminal, and the channel matrix of the at least one terminal at the updating of the weight matrix. The method according to claim 6, Wherein the operator repeatedly updates the precoding matrix and the weighting matrix until the precoding matrix and the weighting matrix are optimized. 10. 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) th iteration step is smaller than the threshold value, the determiner determines that the precoding matrix and the weight And determines that the matrix is optimized. 11. The method of claim 10, Wherein the determination unit calculates the degree of change as expressed by the following equation: &lt; EMI ID =

here,

Is the operator of the frobenius norm,

The precoding matrix of the terminal k in the (n) &lt; th &gt;

Is the trace operator, which means the sum of the diagonal components. The method according to claim 6, Wherein the arithmetic unit initializes the precoding matrix and the weighting matrix as: &lt; EMI ID =

Here,

Is an initial weight matrix of the terminal k,

Is an initial precoding matrix of the terminal k,

Is the interference and noise covariance matrix of the terminal k, Is the channel matrix of the terminal k,

The number of beams allocated to the terminal k,

Is the largest singular value of the matrix A

Left singular vectors corresponding to the singular values up to

Is the interference channel of the terminal k,

Is an interference signal of the terminal k,

Is the noise power. The method according to claim 6, Wherein the operator updates the precoding matrix and the weight matrix as follows: &lt; EMI ID =

Here,

The terminal index,

The reception weight matrix of the terminal k in the n-th iteration step,

The transmission precoding matrix of the terminal k in the n-th iteration step,

Is the interference and noise covariance matrix of the terminal k,

The number of beams allocated to the terminal k,

Is the channel matrix of the terminal k,

The number of base station transmission antennas,

Is the largest singular value of the matrix A

Left singular vectors corresponding to the singular values up to

A channel matrix reflecting the weight matrix of the terminal k,

Is a tall matrix in which channel matrices of terminals other than the terminal k are sequentially stacked,

, remind

0 &quot; among the singular values of the matrix A

Right singular vectors corresponding to the number of singular values,

A channel matrix reflecting the precoding matrix and the weighting matrix of the terminal k,

Lt; RTI ID = 0.0 &gt; k &lt; / RTI &

×

Size diagonal matrix,

The

The sum of the diagonal components of

The total sum of the transmission powers,

The

Of the singular values of the diagonal matrix. The method according to claim 6, Wherein the arithmetic unit calculates the sum capacity when using the updated precoding matrix and the updated weighting matrix. 15. The method of claim 14, Wherein the arithmetic unit calculates the summed capacity as follows:

Here,

The total capacity,

The number of terminals,

A diagonal matrix having an element as a singular value obtained in a singular value decomposition (SVD) of a channel reflecting a precoding matrix and a weighting matrix of the terminal k,

Denotes the power allocation matrix of the terminal k. A terminal apparatus in a multi-user multiple input multiple output (MU MIMO) wireless communication system, At least one RF (Radio Frequency) 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 including interference and noise covariance matrices of other terminals determined based on interference channels of other terminals and interference signals of other terminals, And a canceller for removing interference due to the signal to the other terminal using a weitz matrix provided from the base station. The method of claim 16, wherein Wherein the interference suppression matrix is a matrix as in the following equation:

Here,

Is the interference channel of the terminal k,

Is an interference signal of the terminal k,

Is the noise power. 17. The method of claim 16, &Lt; / RTI &gt; further comprising an estimator for measuring channel information and interference information. 19. The method of claim 18, The channel information is a channel value between a base station and a terminal, Wherein the interference information is an interference channel value and an interference signal value of the terminal. 19. The method of claim 18, Wherein the estimator estimates the interference channel and the interference signal using a signal received during a period in which a signal to the terminal itself is not received. 19. The method of claim 18, Wherein the at least one RF processor transmits control information including the channel information and the interference information to the base station. 22. The method of claim 21, The types of channel information and interference information transmitted to the base station include channel quality information (CQI), adaptive modulation and coding information, a user index, an interference-plus-noise covariance matrix (INCM) ). &Lt; / RTI &gt; A signal processing method of a base station in a multi-user multiple input multiple output (MU MIMO) wireless communication system, Determining a percoding matrix and a weight matrix of the at least one terminal using channel information and interference information fed back from at least one terminal; Precoding a transmission signal to the UEs according to the precoding matrix; And transmitting the precoded signal through a plurality of antennas, wherein the step of determining the precoding matrix and the weight matrix comprises allocating power for each transmission stream. 24. The method of claim 23, The channel information is a channel value between a base station and a terminal, Wherein the interference information is an interference channel value and an interference signal value of the terminal. 24. The method of claim 23, The form of the feedback channel information and the interference information may include at least one of channel quality information (CQI), adaptive modulation and coding information, a user index, an interference and noise covariance matrix (INCM) The method comprising at least one form. 26. The method of claim 25, Wherein the channel quality information includes at least one of channel state information (CSI), a signal-to-noise ratio, a channel capacity index, and a codebook index. 24. The method of claim 23, And transmitting control information including the weight matrix information. 24. The method of claim 23, Wherein the step of determining the precoding matrix and the weight matrix comprises: Generating a set of beam allocation combinations for the at least one terminal; Updating the weight matrix using the updated precoding matrix by updating the precoding matrix using the weight matrix after initializing the precoding matrix and the weight matrix, Determining whether the precoding matrix and the weight matrix are optimized; Determining a combination of a precoding matrix and a weighting matrix having a maximum sum capacity among the precoding matrices and weighting matrices optimized for each beam allocation combination as a final precoding matrix and a weighting matrix . &Lt; / RTI &gt; 24. The method of claim 23, Wherein the power allocation for each transmission stream is performed to maximize the sum capacity. 29. The method of claim 28, Wherein 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, Wherein the weight matrix update is performed using the updated precoding matrix, power allocation information, beam allocation information of the terminal, and channel matrix of the at least one terminal. 29. The method of claim 28, Wherein the updating of the precoding matrix and the weighting matrix is repeated until the precoding matrix and the weighting matrix are optimized. 32. The method of claim 31, Wherein the step of determining whether the precoding matrix and the weight matrix are optimized comprises: 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 smaller than the threshold value, the precoding matrix and the weighting matrix are optimized in the (n) th iteration step And determining whether or not the received signal is a signal. 33. The method of claim 32, Wherein the degree of change is calculated according to the following formula:

here,

Is the operator of the frobenius norm,

The precoding matrix of the terminal k in the (n) &lt; th &gt;

Is the trace operator, which means the sum of the diagonal components. 29. The method of claim 28, Wherein the precoding matrix and the weighting matrix are initialized as: &lt; EMI ID =

Here,

Is an initial weight matrix of the terminal k,

Is an initial precoding matrix of the terminal k,

Is the interference and noise covariance matrix of the terminal k,

Is the channel matrix of the terminal k,

The number of beams allocated to the terminal k,

Is the largest singular value of the matrix A

Left singular vectors corresponding to the singular values up to

Is the interference channel of the terminal k,

Is an interference signal of the terminal k,

Is the noise power. 29. The method of claim 28, Wherein the precoding matrix and the weighting matrix are updated as follows: &lt; EMI ID =

Here,

The terminal index,

The reception weight matrix of the terminal k in the n-th iteration step,

The transmission precoding matrix of the terminal k in the n-th iteration step,

Is the interference and noise covariance matrix of the terminal k,

The number of beams allocated to the terminal k,

Is the channel matrix of the terminal k,

The number of base station transmission antennas,

Is the largest singular value of the matrix A

Left singular vectors corresponding to the singular values up to

A channel matrix reflecting the weight matrix of the terminal k,

Is a tall matrix in which channel matrices of terminals other than the terminal k are sequentially stacked,

, remind

0 &quot; among the singular values of the matrix A

Right singular vectors corresponding to the number of singular values,

A channel matrix reflecting the precoding matrix and the weighting matrix of the terminal k,

Lt; RTI ID = 0.0 &gt; k &lt; / RTI &

×

Size diagonal matrix,

The

The sum of the diagonal components of

The total sum of the transmission powers,

The

Of the singular values of the diagonal matrix. 29. The method of claim 28, Further comprising the step of calculating a sum capacity when the updated precoding matrix and the updated weight matrix are used. 37. The method of claim 36, Characterized in that the summed capacitance is calculated according to the following equation:

Here,

The total capacity,

The number of terminals,

A diagonal matrix having an element as a singular value obtained in a singular value decomposition (SVD) of a channel reflecting a precoding matrix and a weighting matrix of the terminal k,

Denotes the power allocation matrix of the terminal k. A signal processing method of a terminal in a multi-user multiple input multiple output (MU MIMO) wireless communication system, Receiving a signal through at least one antenna; Removing interference from an external cell by multiplying a received signal by an interference suppression matrix including interference and noise covariance matrixes of other terminals determined based on interference channels of other terminals and interference signals of other terminals; And removing the interference due to the signal to the other terminal using a weitz matrix provided from the base station. 39. The method of claim 38, wherein Wherein the interference suppression matrix is a matrix as in the following equation:

Here,

Is the interference channel of the terminal k,

Is an interference signal of the terminal k,

Is the noise power. 39. The method of claim 38, And measuring channel information and interference information. 41. The method of claim 40, The channel information is a channel value between a base station and a terminal, Wherein the interference information is an interference channel value and an interference signal value of the terminal. 41. The method of claim 40,  Wherein the measurement of the interference channel and the interference signal value is performed using a signal received during a period in which a signal to the terminal itself is not received. 41. The method of claim 40, And transmitting control information including the channel information and the interference information to the base station. 44. The method of claim 43, The types of channel information and interference information transmitted to the base station may include channel quality information (CQI), adaptive modulation and coding information, user index, interference and noise covariance matrix (INCM) Matrix. &Lt; / RTI &gt;

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