KR100830229B1 - Apparatus for efficient signal detection in multiple antenna system and method therof - Google Patents

Abstract

An effective signal detection method is disclosed in a wireless communication system using multiple antennas. The antenna array is composed of a plurality of antenna stages having M transmit antennas and N receive antennas, and are received through a plurality of receive antennas after the signals transmitted from each transmit antenna are added together. The candidate group setting unit determines the number V of candidate groups to be temporarily detected in order to detect a signal received through the multiplex antenna. The signal detecting unit detects the first V symbols detected according to the number of temporary candidate groups determined by the candidate group setting unit, and detects the remaining M-1 transmission signals by V using the first detected symbol, so that the entire detected signal sequence is V. Be a dog. The final signal selector selects one signal sequence closest to the received signal among the V signal sequences detected by the signal detector through a maximum likelihood (ML) test to determine the final detection signal. According to the present invention, in a wireless digital communication system using multiple antennas, a signal can be detected with a performance substantially similar to that of an optimal detection method while greatly reducing the complexity, and the complexity and detection of the system is controlled by adjusting V, the number of candidate groups detected. You can adjust the performance.

Description

Apparatus for efficient signal detection in multiple antenna system and method therof}

1 is a block diagram showing the configuration of a receiver including a signal detection apparatus in a multiple transmission and reception system according to the present invention;

2 is a flowchart illustrating a process of performing an efficient signal detection method in a multiple transmission / reception system according to the present invention;

3 is a diagram illustrating an operation procedure of a function for determining V candidate groups;

4 is a diagram illustrating a result of detecting V columns according to the first detected V symbols;

5 is a graph showing the performance of the 3 × 3 multi-antenna system to which the efficient signal detection technique according to the present invention,

6 is a graph showing the performance of the 2 × 2, 4 × 4 multi-antenna system to which the efficient signal detection technique according to the present invention is applied.

7 is a reference view for explaining the constellation.

The present invention relates to an apparatus and method for detecting a received signal in a multiple digital transmission / reception system using a vertical Bell Labs. Layered space time (V-BLAST) method, and more particularly, to a signal transmitted using multiple antennas. The present invention relates to an apparatus and a method for detecting V columns according to the first V symbols received and selecting an optimal signal sequence therefrom.

Recently, due to the quantitative growth in the wireless mobile communication market, the demand for the use of multimedia services as well as the spread of the high-speed Internet and generalization of the telephone market, the wireless mobile communication system has evolved from the voice-oriented service to the multimedia data-oriented service. In addition, due to the integration of wired and wireless networks, increasing mobility and ultra-high speed / capacity data transmission networks are being established. In line with this situation, wireless peronal area network (WPAN) and wireless broadband (WiBro) services have attracted much attention. These wireless near field communication and portable Internet services aim at transmission rates up to 1Gbps using wireless. However, it is very difficult to increase the existing transmission rate due to the interference of multiple users and the limited frequency band. In this situation, V-BLAST technique using multiple antennas can greatly increase the data rate. V-BLAST is a technique that can achieve high data rate by dividing serial data by the number of transmission antennas and transmitting them in parallel.

While the V-BLAST system can obtain a high data rate through parallel transmission, there is a disadvantage of high complexity and performance deterioration that occur in the process of separating and detecting parallel transmitted data. In order to overcome this disadvantage, many studies on V-BLAST signal detection have been made.

The existing V-BLAST system signal detection method uses a maximum likelihood (ML) detection method that is an optimal signal detection method or a subtractive interference cancellation method for interference cancellation. The ML detection method is a method of estimating a difference between a received signal and a symbol combination checked by the receiver through ML inspection, and estimating a transmission signal by selecting a combination having the smallest difference from the received signal among the symbol combinations. The ML method selects the optimal symbol combination by checking the combination of all transmittable symbols and thus exhibits optimal detection performance. However, as the number of transmit antennas increases or the signal modulation level increases, the complexity increases exponentially, resulting in a large detection delay in a real system. Therefore, it is practically impossible to use in a real-time transmission / reception system or a multi-antenna system using a large number of antennas.

The subtractive interference cancellation technique arranges the received signal power in large order to determine the signal with the largest power, then multiplies the estimated received signal by the channel parameter to create a transmission signal, and subtracts the generated signal from the existing received signal. Subtractive interference cancellation has the advantage of excellent performance and simple structure.However, since it is a sequential subtraction detection method, the detection performance of the remaining signals is highly dependent on the accuracy of the first signal detected and it is optimized by the influence of noise diffusion. The transmission efficiency is greatly reduced because it has a large performance difference from the ML detection method.

In order to solve the above problems, an apparatus and method of a multiple transmit / receive digital system capable of efficiently detecting a signal transmitted through a multiple transmit antenna to increase the performance of the multiple transmit and receive system and accordingly increase the capacity of the system. For the purpose of providing it.

In order to achieve the above object, the signal detection apparatus in a multiple transmission and reception system according to the present invention comprises an antenna array consisting of a plurality of antennas, the antenna array for receiving signals transmitted through the M multiplex antenna; A candidate group setting unit that determines the number V of candidate groups to be temporarily detected to detect the received signal; First means for detecting the first V symbols detected according to the number of candidate groups V set by the candidate group setting unit, and detecting the remaining detection sequences of the remaining M-1 lengths by V and having a final M length. A signal detector having second means for detecting the V candidate groups; Among the detected candidate groups, a final signal selection unit for selecting one signal sequence closest to the received signal through a maximum likelihood (ML) test and determining the final signal as the final detection signal.

In addition, according to another aspect of the present invention, a signal detection method in a multiplex transmission and reception system includes: receiving signals transmitted through M multiplex antennas; A candidate group setting step of determining the number V of candidate groups to be temporarily detected to detect a received signal; A first step of detecting the first V symbols detected according to the number V of the candidate groups set in the candidate group setting step, and detecting the remaining detection sequences of the remaining M-1 lengths by V and having a final M length. A signal detecting step having a second step of detecting the V candidate groups; And a final signal selection step of selecting one signal sequence closest to the received signal through a maximum likelihood (ML) test among the detected candidate groups and determining the final signal as the final detection signal.

Hereinafter, with reference to the drawings will be described an embodiment of a signal detection apparatus and method in a multiple transmission and reception system according to the present invention.

1 shows a configuration of a signal detection apparatus according to the present invention. In FIG. 1, the signal transmitting end is omitted, and only the signal receiving end is shown.

An efficient signal detection apparatus in a multiple transmission / reception system according to the present invention comprises a plurality of antennas (5), and receives signals in which transmission signals independently modulated by each transmission antenna are transmitted through M multiple transmission antennas (not shown). An antenna array 10; A candidate group setting unit 20 for determining the number V of candidate groups to be temporarily detected to detect the received signal; A signal detector which detects V symbols that are detected for the first time according to the set number V of candidate groups, and then detects V detection sequences of the remaining M-1 lengths and detects V candidate groups having a length of final M ( 30); Among the detected candidate groups, the final signal selector 40 selects one signal sequence closest to the received signal through a maximum likelihood (ML) test and determines it as the final detection signal.

2 illustrates the function of each component of FIG. 1 and shows the processing flow of the signal detection method according to the present invention. In FIG. 2, the transmitting end generates a transmission signal using independent coding and modulation for each transmission antenna, and transmits the transmission signal through multiple transmission antennas (the transmission end is omitted in FIG. 1). The receiving end receives a transmission signal through each antenna 5 of the antenna array 10 (100). The candidate group setting unit 20 of the receiver determines the number V of temporary signal strings to be detected (200). The signal detector 30 of the receiving end detects the V signal sequences (300), and the final signal selector 40 determines the final detection signal sequence closest to the received signal among the V signals through the ML test (400).

Hereinafter, specific technical matters will be described with reference to the drawings and the equations for each step.

는 수학식 1과 같이 주어진다.Transmission signal of V-BLAST system using M transmit antennas and N receive antennas

Is given by Equation 1.

는 i번째 전송안테나를 통해 전송된 신호를 나타내며

는 행렬의 트랜스포즈(transpose)를 나타냄). (here

Denotes the signal transmitted through the i th transmission antenna

Represents the transpose of the matrix).

The transmitted signal is received by the receiving antenna array 10 via multiple channels. The received signal is represented by the following equation.

(Where H is an N × M channel coefficient matrix and each element of the matrix is independent of each other, w represents N × 1 Additive White Gaussian Noise (AWGN))

The receiving end uses a basic subtractive interference cancellation scheme to detect the transmission signal s from the received signal y . Moore-Penrose pseudo inverse of the channel coefficient H is performed, which can be represented by the following equation.

는 Moore-Penrose 의사역행렬변환을 나타내고

는 Hermitian변환을 나타냄.) (here

Represents Moore-Penrose pseudoinverse transformation

Represents Hermitian transformation.)

The inverse matrix thus obtained is expandable to a minimum mean square error (MMSE) inverse matrix and can be expressed as the following equation.

는 (N+M)×M의 확장된 행렬로 다음 수학식과 같다.)(

Is an extended matrix of (N + M) × M, which is expressed as:

은 잡음의 분산을 나타낸다.) (here

Represents the variance of the noise.)

행렬의 norm값인

을 가장 큰 열부터 작은 열로 정렬한다. 확장된 채널 계수

의 열 역시

의 정렬 순서와 동일하게 정 렬하여

를 만든다. 정렬된

를 QR 분해를 통해 다음 수학식과 같이 Q와 R로 분해한다.Obtained above

The norm of the matrix

Sorts from the largest column to the smallest column. Extended Channel Count

The heat of

Sort in the same order as

Make Aligned

Is decomposed into Q and R as shown in the following equation through QR decomposition.

를 만족하는 정규직교 행렬(orthonormal matrix)임).( R is the upper triangular matrix and Q is

Is an orthonormal matrix that satisfies.

를 이용해 수신된 신호에서 Q성분이 제거된 M×1 벡터를 아래의 수학식과 같이 구한다.

Using M to obtain the M × 1 vector from which the Q component is removed from the received signal as shown in the following equation.

이고

이다.)(here

ego

to be.)

As described above, when the subtractive interference cancellation technique is used, the first detected signal affects the entire signal from the next detected signal to the last detected signal. Therefore, the first detected signal is accurately detected. very important. To compensate for this, the present invention detects the first V symbols detected. The number V of candidate symbols to be detected is determined by the candidate group setting unit 20 of FIG. 1. After determining the number V of candidate symbols to be detected in the post-group setting unit, the signal detection unit detects the first signal. First, before detecting a signal for the first time, the signal detector removes a channel component of a symbol to be first detected, which is expressed by the following equation.

As described above, V candidate signals are determined using the signal from which channel components are removed. The procedure for determining the V symbols is as follows.

는 k부터 각 심볼 사이의 유클리디안 거리를 측정하여 L-QAM 또는 L-PSK를 이용하는 시스템에서 V(V∈L)개의 심볼을 결정하는 결정함수). 도 3은 V=4인 경우의 결정함수

의 결정절차를 예시하고 있다. 채널의 영향이 제거된 후의 심볼인 k를 전송심볼로 맵핑을 하게 된다. 이때 V는 4이므로 맵핑되는 심볼이 유클리디안 거리에 따라 4개가 선택된다. 수학식 9의 결정함수는, 본 발명에서 정의한 것으로서, 이 결정함수가 하는 일은 처음으로 검출될 신호를 V개만큼 결정하는 역할을 한다. (

Is a decision function for determining V (V∈L) symbols in a system using L-QAM or L-PSK by measuring the Euclidean distance between k and each symbol. 3 is a decision function when V = 4

The procedure for determining is given. After the influence of the channel is removed, the symbol k is mapped to the transmission symbol. In this case, since V is 4, four symbols are selected according to Euclidean distance. The decision function of Equation 9 is defined in the present invention, and the function of the decision function is to determine as many as V signals to be detected for the first time.

After passing through the decision function, the first detected signal is V and can be expressed as the following equation.

는

으로부터 v번째로 가까운 심볼)(

Is

Vth nearest symbol from)

After the first detected symbol is determined, V signal strings having a length M are detected according to the first detected signal as shown in FIG. 4. In FIG. 4, the first V symbols 310 detected and the V signal sequences 320 detected according to the first V symbols detected are shown. The procedure for detecting the V signal strings is as follows.

Here, Q [·] means a quantization function based on the constellation used. The constellation indicates the position of a symbol for transmitting a signal. For example, binary signals of 0 and 1 are mapped to QAM symbols and sent as shown in FIG. 7, which is called a constellation diagram. The quantization function refers to a function of mapping a received signal to one point of the constellation according to the Euclidean distance.

All signals detected according to the above procedure can be represented by the following equation.

)(From the above expression

)

Finally, the ML sequence selects the signal sequence closest to the transmission signal among the V columns obtained as described above. ML test can be expressed as the following equation.

이 최종적으로 검출된 신호가 된다.Obtained by the above equation

This finally becomes a detected signal.

In the present invention, when V = L, detection performance can be greatly improved through reverse ordering. Earlier, we described the sorting that is done in a typical system. The reason for performing the pure sort in the general system is to minimize the error probability by detecting the symbol with the highest received power first. However, the main factor that greatly affects the performance of the system is the symbol with the lowest received power. In a system using L symbols, if V <L, all symbols are not considered as a candidate group, and therefore, the probability that the first signal is detected is not high. Therefore, the error probability is minimized by first detecting the symbol with the high reception power according to the pure alignment.

If V = L, all symbols are considered as candidates, so the first detected signal can be detected very accurately. Therefore, the system detects the symbol with the lowest received power, which greatly influences the performance of the system. It can be greatly increased. Therefore, in the present invention, when V <L, the highest power symbol is first detected to perform a pure sort to minimize an error probability, and when V = L, the first detected signal is detected very accurately. As a result, reverse alignment is performed to detect a signal having the lowest received power for the first time, which greatly influences the performance of the system.

In other words, in addition to the first detected symbol, another factor that determines the detection performance is the symbol received at the lowest power. Symbols received at the lowest power cause a significant drop in the detection performance of the receiver. Therefore, if the symbol received at the lowest power can be accurately detected first, the detection performance of the receiver can be greatly improved. As described above, a simple method of improving the detection performance using the symbol received at the lowest power is reverse alignment. In general subtractive interference cancellation, the signal with the largest received power is detected first so that the first detected symbol can be detected accurately.

을 계산하여 높은 값부터 정렬하여 정렬된 값에 따라 H를 정렬하는 일반적인 정렬과 반대로,

을 계산하여 낮은 값부터 정렬하고 그에 따라 H를 정렬하여 수행된다. 이렇게 역정렬을 수행한 후에는 수학식 6~12까지의 절차를 다른 변경없이 수행하게 된다. 이렇게 V=L인 경우에는 간단한 정렬의 변환인 역정렬을 통해 시스템의 성능을 크게 높이는 것이 가능하다.However, in the present invention, when V = L, all possible symbols are considered as candidate groups, so it is possible to detect the first detected symbol very accurately, thereby accurately detecting a low power received signal that influences the performance of the system through reverse alignment. The performance of the system can be improved similarly to the ML detection technique. Reverse alignment

Contrary to the usual sorting that computes a, sorts from the highest value to sort H according to the sorted value,

This is done by calculating and sorting from the lowest value and then sorting H accordingly. After the reverse alignment is performed, the procedures of Equations 6 to 12 are performed without any other changes. In the case of V = L, it is possible to greatly increase the performance of the system through reverse sorting, which is a conversion of a simple sort.

In the present invention, it is possible to perform the present invention with a zero forcing (ZF) detector using ordinary H without using the extension matrix specified in Equation 5. It is also possible to carry out the invention.

The present invention described above can be embodied as computer readable codes (programs) stored in a computer recording medium. Computer record carriers include any type of recording device that stores data that can be read by a computer system. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, which are also implemented in the form of carrier waves (for example, transmission over the Internet). It also includes. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

FIG. 5 is a graph showing BER (beat error rate) performance according to the number of V of the V-BLAST system using M = N = 3 using 16QAM. As the number of V increases, the first symbol can be accurately detected by considering more candidate groups, and thus the BER performance is improved. In the case of V = 16, all 16 possible symbols are considered as candidate groups, so the performance of the MMSE and ZF detector is very similar. In the case of reverse alignment, since it is possible to detect the received signal of the lowest power very accurately, the performance of the detector according to the present invention has a value very similar to that of the ML detector which is the optimum detector. 6 is a graph showing the BER performance according to the number of V of the V-BLAST system using M = N = 2, M = N = 4 using 16QAM. Regardless of the number of antennas, it can be seen that the detection performance increases as V increases in all cases. In addition, when the reverse alignment is performed as shown in FIG. 5, the detection performance is greatly increased.

According to an efficient signal detection apparatus and method in a multi-transmission / reception system according to the present invention, an effective signal detection method is effectively applied to more accurately detect a transmission signal in a digital wireless communication system using multiple antennas, thereby effectively increasing signal detection performance. The reverse alignment provides very low complexity and provides performance similar to that of optimal detection, resulting in stable signal detection and increased system capacity.

Claims (11)

An antenna array configured of an antenna stage including a plurality of antennas and receiving signals transmitted through M multiplex antennas; A candidate group setting unit that determines the number V of candidate groups to be temporarily detected to detect the received signal; First means for detecting the first V symbols detected according to the number of candidate groups V set by the candidate group setting unit, and detecting the remaining detection sequences of the remaining M-1 lengths by V and having a final M length. A signal detector having second means for detecting the V candidate groups; Receiving signal detection apparatus of the digital wireless multiplex transmission and reception system, characterized in that it comprises a final signal selection unit for selecting one of the signal sequence closest to the received signal by the maximum likelihood (ML) test among the detected candidate group to determine as the final detection signal . 2. The apparatus of claim 1, wherein the first means for detecting the signal detects V symbols first detected according to the following equation.

here

Is a decision function for determining V (V≤L, where L is the total number of symbols detectable at the receiving end) in a system using L-QAM or L-PSK by measuring the Euclidean distance between k and each symbol.

and

Is the signal from which channel components have been removed

Represents the first detected signal as determined by V. The method of claim 2, wherein

silver

ego, remind

Is

Is the vth closest symbol to The second means of the signal detection unit detects V candidate strings having a length of M by detecting V detection strings having a length of M-1, according to the following equation. Reception signal detection apparatus.

(Where Q [·] means quantization function by constellation used) The apparatus of claim 3, wherein the final signal selector selects one column closest to the transmission signal according to the following ML test according to the ML test.

Where y is the signal received in the receiving antenna array, H is the N × M channel coefficient matrix

Is the final detection signal selected as the signal sequence closest to the transmission signal. The signal detection unit according to any one of claims 1 to 4, wherein the signal detection unit When the number of candidate groups V is smaller than the number of symbols L, a symbol having a high reception power is detected first, and when V = L, the symbols are arranged in reverse order to detect a symbol having a low reception power first. Received signal detection device. Receiving signals transmitted through the M multiplex antennas; A candidate group setting step of determining the number V of candidate groups to be temporarily detected to detect a received signal; A first step of detecting the first V symbols detected according to the number V of the candidate groups set in the candidate group setting step, and detecting the remaining detection sequences of the remaining M-1 lengths by V and having a final M length. A signal detecting step having a second step of detecting the V candidate groups; Receiving a received signal of a digital wireless multiplex transmission and reception system, characterized in that it comprises a final signal selection step of selecting one signal sequence closest to the received signal through a maximum likelihood (ML) test among the detected candidate groups to determine as the final detection signal Way. 7. The method of claim 6, wherein the first step of the signal detection step detects V symbols first detected according to the following equation.

here

Is a decision function for determining V (V≤L, where L is the total number of symbols detectable at the receiving end) in a system using L-QAM or L-PSK by measuring the Euclidean distance between k and each symbol.

and

Is the signal from which channel components have been removed

Represents the first detected signal as determined by V. 8. The method of claim 7, wherein

silver

ego, remind

Is

Is the vth closest symbol to  In the second step of the signal detection step, the digital wireless multiplex transmission and reception is characterized by detecting V candidate groups having a length of M by detecting V detection strings having a length of M-1 according to the following equation. Received signal detection method of system.

(Where Q [·] means quantization function by constellation used) The method of claim 8, wherein the final signal selection step selects one column closest to the transmission signal according to the following ML test according to the ML test.

Where y is the signal received in the receiving antenna array, H is the N × M channel coefficient matrix

Is the final detection signal selected as the signal sequence closest to the transmission signal. The method according to any one of claims 6 to 9, wherein the signal detection step When the number of candidate groups V is smaller than the number of symbols L, a symbol having a high reception power is detected first, and when V = L, the symbols are arranged in reverse order to detect a symbol having a low reception power first. Received signal detection method. A computer recording medium storing a program for implementing the method of detecting a received signal according to any one of claims 6 to 9.

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