KR100962266B1 - Method and apparatus for decode hybrid STBC signals - Google Patents

Abstract

A method and apparatus for hybrid STBC signal demodulation that can be used in a MIMO OFDM system is disclosed.

A method for demodulating a hybrid STBC signal in which a space time block code (STBC) signal and a spatial multiplexing (SM) signal are mixed according to the present invention, the method comprising: receiving the hybrid STBC signal and including the received hybrid STBC signal in the received hybrid STBC signal Detecting the detected STBC signal, canceling the detected STBC signal from the received hybrid STBC signal, and detecting the SM signal, canceling the detected SM signal from the received hybrid STBC signal. And repeatedly detecting the STBC signal, and determining the STBC signal as the final STBC signal if the detected STBC signal and the repeatedly detected STBC signal are the same.

Description

Hybrid STBC signal demodulation method and apparatus {Method and apparatus for decode hybrid STBC signals}

The present invention relates to a demodulation method and apparatus thereof, and more particularly, to a hybrid STBC signal demodulation method and apparatus capable of effectively detecting a signal in a multiple input multiple output (MIMO) OFDM system having a hybrid space time block code (STBC) structure. will be.

Recently, as the demand for high-speed data transmission in a wireless environment is expected to increase, a shortage of frequency resources is expected, and as the importance of frequency bands becomes more important, an orthogonal frequency division mulitplexing (OFDM) system that can be used by sharing frequency is introduced. It is attracting much attention as the next generation wireless multimedia transmission technology. In the wireless environment, as the demand for high-speed data transmission and the simultaneous connection of many users increases, a lot of researches are being conducted to enable the use of a limited frequency more efficiently. In order to solve the high link budget required in the wireless Internet, researches on a transmission diversity scheme using multiple antennas at the transmitting end have been actively conducted. The most representative of the transmit diversity schemes is the STBC technique, which shows excellent performance at low speed, but degrades due to delay caused by feedback at high speed.

The Bell Lab Layered Space Time (MIMO) method of Bell Lab Layered Space Time (BMO) proposed by Bell Lab to increase the multiplexing gain is possible. This method transmits and receives in rich scattering environment. By using multiple antennas, multiple independent fading channels can be formed and different signals can be transmitted for each transmit antenna, resulting in a significant data rate. At this time, each receiving antenna detects only a specific signal and treats other signals as interference signals and detects the signal while minimizing the influence of other signals by forcing zero-forcing or nulling the minimum mean square error (MMSE). do.

In the MIMO scheme, the BLAST-OFDM scheme can be easily applied to a multipath environment because the transmission signal assumes flat fading having a bandwidth smaller than the coherence bandwidth of the channel. That is, the BLAST system using the OFDM scheme has the advantage that the effects of the multipath delay are reduced by the use of CP and approximated to the flat fading channel so that the receiver can detect the signal without additional hardware. In addition, when using multiple transmit / receive antennas by applying V-BLAST, it is possible to effectively increase the transmission rate even with low calculation amount.

In the MIMO OFDM system, the baseband signal is modulated using BPSK, QPSK, 16-QAM, 64-QAM, etc., and then processed using the components of IFFT / FFT. In this case, it is performed through a carrier synthesizer.

Hybrid STBC means applying STBC to each data stream in V-BLAST OFDM. This structure provides a diversity effect, which not only improves performance, but also reduces the number of receive antennas required.

In comparison with the performance of the general STBC, the hybrid STBC has a performance difference that is significantly different from that of the general STBC because other signals besides the signal to detect act as interference. Moreover, as the number of interfering signals increases, the difference becomes more pronounced. For example, hybrid STBCs having a mixture of STBC and SM signals exhibit more severe performance degradation due to interference than hybrid STBCs having two STBC signals.

In this case, the performance of general STBC is much better than that of hybrid STBC, and the performance difference between V-BLAST OSIC and DFE such as existing SM-related techniques is not big enough. It becomes unclear. Therefore, there is a need to increase the performance of the existing hybrid STBC detection technique.

The technical problem to be achieved by the present invention is a hybrid STBC received signal demodulation method that can improve the performance when detecting the STBC signal and SM signal according to each transmission technique in the hybrid STBC signal when the signal is detected at the receiving end and To provide a device.

The signal demodulation method according to the present invention for solving the above technical problem is a method for demodulating a hybrid STBC signal in which a space time block code (STBC) signal and a spatial multiplexing (SM) signal are mixed (a) the hybrid Receiving an STBC signal; (b) detecting an STBC signal included in the received hybrid STBC signal; (c) canceling the detected STBC signal from the received hybrid STBC signal to detect an SM signal; (d) canceling the detected SM signal from the received hybrid STBC signal to detect an STBC signal; And (e) if the STBC signal detected in step (b) and the STBC signal detected in step (d) are the same, determining the STBC signal as the final STBC signal.

In step (e), if the STBC signal detected in step (b) and the STBC signal detected in step (d) are not the same, the STBC signal detected in step (d) is detected in step (b). It is preferable to set the signal and repeat from the step (c).

Step (c) comprises: (c1) detecting a reference signal from the received hybrid STBC signal using a V-BLAST OSIC or V-BLAST DFE method; (c2) determining a plurality of signals having a shortest Euclidean distance on the reference signal and constellation as candidate signals; And (c3) selecting a signal having the smallest error among the candidate signals as the SM signal.

And, the number of the plurality of signals in the step (c2) is a maximum of 4 when the QPSK modulation is used for the hybrid STBC signal, and a maximum of 16 when 16-QAM modulation is used.

In accordance with another aspect of the present invention, there is provided a signal demodulation device for demodulating a hybrid STBC signal in which a space time block code (STBC) signal and a spatial multiplexing (SM) signal are mixed. Receiving unit for receiving; An STBC signal detector for detecting an STBC signal included in the received hybrid STBC signal; An SM signal detector for canceling the detected STBC signal from the received hybrid STBC signal to detect an SM signal; A repetitive STBC signal detector for canceling the detected SM signal from the received hybrid STBC signal and repeatedly detecting the STBC signal; And an STBC signal determiner for determining the STBC signal as the final STBC signal when the STBC signal detected by the STBC signal detector and the STBC signal detected by the repeated STBC signal detector are the same.

According to the present invention, it is possible to reduce the performance attenuation caused by the SM signal interference which cannot be reduced in the existing hybrid STBC demodulation scheme. This can improve the overall demodulation performance of the MIMO OFDM system.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 illustrates a flow of a method for demodulating a hybrid STBC signal in which a space time block code (STBC) signal and a spatial multiplexing (SM) signal are mixed according to an embodiment of the present invention.

Channel estimation is performed by receiving the hybrid STBC signal (step 100). Detecting the STBC signal included in the received hybrid STBC signal (step 110), canceling the detected STBC signal from the received hybrid STBC signal (cancellation) to detect the SM signal (step 120), and receiving the received hybrid STBC signal The detected SM signal is canceled from the cell and the STBC signal is repeatedly detected (step 130).

If the detected STBC signal and the repeatedly detected STBC signal are the same, the STBC signal is determined as the final STBC signal (step 140).

2 is a block diagram illustrating a configuration of an apparatus for demodulating a hybrid STBC signal in which a space time block code (STBC) signal and a spatial multiplexing (SM) signal are mixed according to an embodiment of the present invention. This apparatus has a configuration for implementing the method of FIG.

The apparatus includes an antenna array 200 which is a receiver for receiving the hybrid STBC signal, a channel estimator 210 for estimating a channel for the received signal, and a signal detector 220 for detecting a required signal from the signal. do.

The signal detector 220 detects an SM signal by canceling the detected STBC signal from the STBC signal detector 230 that detects an STBC signal included in the received hybrid STBC signal. The detected SM signal detector 240 and the repeated STBC signal detector 250 and STBC signal detector 230 which cancel the detected SM signal from the received hybrid STBC signal and repeatedly detect the STBC signal. If the STBC signal and the STBC signal detected by the repetitive STBC signal detection unit 250 are the same, the STBC signal determination unit 260 determines the STBC signal as the final STBC signal.

In the present invention, the concept of repetitive STBC signal detection is introduced to increase the performance of STBC signal detection, and the V-algorithm is applied to improve the performance of SM signal detection, thereby improving the overall performance of STBC and SM signal detection. Increasing the performance of the STBC, which will be described in detail below.

Hybrid STBC structure to be used in an embodiment of the present invention is shown in FIG. As shown in FIG. 3, the transmitting end 300 includes signal processing and / or modulation processing 305, and transmits a hybrid STBC signal mixed with an STBC signal and an SM signal through the STBC signal block 310 to four transmitting antennas ( 315 is used and transmitted, and the receiving end 350 receives the same using three receiving antennas 355.

In MIMO OFDM system, various techniques are proposed according to the use of multiple antennas. Space Time Block Code (STBC), spatial multiplexing (SM), hybrid STBC, and beamforming are techniques for using multiple antennas.

Whereas the existing BLAST system has a constraint that the number of receiving antennas must be equal to or greater than the number of transmitting antennas, in the hybrid STBC structure to which the present invention is applied, the receiving antennas are smaller than the number of transmitting antennas as illustrated in FIG. Even if it works.

In addition, as shown in FIG. 3, the transmitting end 300 mixes an STBC signal and an SM signal composed of different signals, and sends them to the receiving end 350. The receiving end 350 first detects the STBC signal (360). After canceling the detected STBC signal from the received signal, the MIMO detector 365 restores the SM signal to the MIMO detection method. (The function of the MIMO detector 365 is included in the function of the signal detector 220, and the description of the function of the MIMO detector is not described separately.)

The method of FIG. 1, which is the flow of one embodiment of the present invention, is described in more detail in the flowchart of FIG. 4.

When a hybrid STBC signal mixed with a STBC (Space Time Block Code) signal and a SM (Spatial Multiplexing) signal is received through an antenna array (step 400), the received signal is read and a K value is input (step 405). . This K value determines the maximum number of times that steps 415 to 445 of FIG. 4 are repeated, and may be set automatically or may be a value input from a user.

Then, i = 0 is set as a variable value for repeating the step of FIG. 4, and the STBC signal detection unit 230 detects an STBC signal (step 410).

In order to detect the STBC signal, a formal processing of the signal is required, which will be described below.

The equation at the receiving end is expressed as Equation 1 below.

과

는 3x1의 벡터로 구성되어있으며

는 다중경로 채널인 i.i.d 랜덤 복소수 벡터이다. 여기서 i 가 의미하는 바는 수신안테나의 개수를 나타내는 것이고 j가 나타내는 바는 송신안테나의 개수를 의미하는 것이라 할 수 있다. 여기서 n은 평균 '0'을 갖는 가우시안 잡음을 나타낸다.In this expression

and

Consists of vectors of 3x1,

Is an iid random complex vector that is a multipath channel. In this case, i means the number of reception antennas, and j means the number of transmission antennas. Where n represents Gaussian noise with an average of '0'.

The STBC signal is first detected from the received signal. The asymmetric channel matrix consisting of the 4x3 vector structure is converted into a 2x2 vector structure that is easy to operate.

Transmitted signals were also classified into new groups, classified according to the modulation scheme used for the signals.

The received signal is also modified to create a new received signal as shown in Equation 4.

This newly defined matrix can be expanded like this equation:

과

는 각각

과

에 더해진 잡음이며, 각각은 2x2의 행렬로 구성되어있다. 수학식 5를 통해서

과

라는 새로운 수신 신호를 정의한다. 그리고, 이를 이용하여 STBC 신호인

를 검출한다.

를 검출하기 위한 수학식은 다음과 같다.here

and

Respectively

and

Is the noise added to, and each consists of a matrix of 2x2. Through Equation 5

and

Define a new received signal. And, using this, the STBC signal

Detect.

The equation for detecting is as follows.

This equation can be written as in Equation 7 below.

를 의미한다. 수학식 7을 통해

과

를 새롭게 정의된

부터

까지의 값과 새롭게 정의된 채널 값으로 구할 수 있다. 수학식 8은 STBC 신호를 검출해 내는 수식으로써, 간단한 연산을 통해서 STBC 신호를 검출해 낼 수 있게 한다.here

Means. Through equation (7)

and

Newly defined

from

It can be obtained by up to and the newly defined channel value. Equation (8) is an equation for detecting the STBC signal, and makes it possible to detect the STBC signal through a simple operation.

를 곱한 후 양자화를 해줌으로써 STBC 검출을 완료하게 된다. 상기와 같이 4x3의 벡터구조로 되어있는 신호를 2x2의 벡터신호 값으로 만듦으로 인해 좀더 손쉽게 STBC 신호 값을 검출해 낼 수 있는 것이다.On the STBC signal obtained as above

After multiplying by quantization, STBC detection is completed. The STBC signal value can be detected more easily by making the signal having the 4x3 vector structure as the 2x2 vector signal as described above.

The next step to be performed is to detect the SM signal (step 420). Initially, if the value of K is 5, for example, the process proceeds from step 415 to step 420.

Since the STBC signal has already been detected, a process of canceling the detected STBC signal from the signal received in step 400 is first performed to detect the SM signal.

In order to detect the SM signal, the DFE method of V-BLAST has to be detected. If the first detected signal is correct due to the characteristics of V-BLAST, the signal to be obtained later is relatively accurately detected due to less interference. That is, in hybrid STBC, the STBC signal has better BER performance than the normal SM signal due to diversity gain. As such, since the first signal is detected relatively accurately, the performance of the SM signal is better than that of the conventional V-BLAST signal.

Unlike the STBC signal, since the SM signal is composed of different signals for each time slot, unlike the STBC signal detection, the SM signal must be detected for each time slot. In view of this, the conventional cancellation process to be performed first to detect the SM signal is shown in Equation (9).

과

는 수신 신호에서 STBC 신호가 소거 (cancellation) 된 신호이다.Where and

and

Is a signal in which the STBC signal is canceled from the received signal.

The next step to be performed is an ordering step, in which the value of the inverse matrix G of the channel used is MMSE and is expressed by Equation 10.

In ordering method, the inverse of the channel is arranged in the order of the smaller rows.

는 만족하게 되고 또한 sorting 된 신호는 2개 밖에 존재하지 않기 때문에

를 만족하게 된다. I is a variable representing a decoding step, and the order in which the SM signal is detected is the third and fourth because the STBC is detected. therefore

Is satisfied, and because there are only two sorted signals

Will be satisfied.

The matrix sorted according to G can be expressed by the following equation.

는 QR 분해 방법을 거처 다음과 같이 나타낼 수 있다.Ordered

Based on the QR decomposition method, can be expressed as follows.

를 곱한다. 이는 수학식 14와 같은 형태로 구성되게 된다.Next, the received received data

Multiply by This is configured in the form of equation (14).

Where t means time slot.

Finally, the final calculation work to detect the SM signal is performed.

In this case, Q () means an index indicating quantization, and the SM signal is demodulated only through this calculation process.

The SM signal demodulation method described so far can be referred to as a technique in which a detection method in a general V-BLAST technique is applied to a hybrid STBC.

Hereinafter, according to an embodiment of the present invention, a method for improving the performance of the existing SM signal detection technique will be described. This method is called the V-algorithm, and the main goal is to detect the first detection signal more accurately by characterizing that the overall signal detection performance depends on the capability of the first detection signal due to the characteristics of V-BLAST. do. According to the present invention, the biggest feature of the proposed method is to detect a signal using the number of candidate signals, V. By selecting and using an appropriate number of Vs, the performance improvement of the SM signal detection can be derived.

The candidate signal refers to a peripheral signal of the first detected signal in constellation according to the modulation technique for the received signal. The reason for considering the ambient signal is based on the assumption that if the first signal detected through V-BLAST OSIC or DFE is wrong, the surrounding signal on the constellation is likely to be the correct signal.

In addition, V is determined as the number of surrounding signals to be considered. In this case, V refers to the number of candidate signals to be considered. Therefore, the larger the value of V, the more signals to consider. But you can predict that performance will improve.

In the following, the overall algorithm steps of the V-algorithm are described.

The first step in this technique is to detect the signal using the V-BLAST OSIC or V-BLAST DFE technique. In this step, the first detected signal becomes a reference signal for determining the candidate signal. V-BLAST OSIC or V-BLAST DFE techniques are well known in the art to which the present invention pertains, and those skilled in the art can easily use these techniques as necessary, and thus a separate description of the techniques will be omitted.

The next step is to select the V value. The V value is a variable indicating how many candidate groups to use. The maximum number that can be selected depends on the modulation technique. For example, up to four Vs can be selected when using the QPSK modulation scheme, and up to 16 Vs can be selected using the 16-QAM modulation scheme.

After selecting V, candidate signals are detected next. The candidate signal is determined based on the detected first signal performed in the first step. 5 shows a method of selecting a candidate group, which shows a situation when V = 5 in a 16-QAM modulation scheme.

In FIG. 5, the first signal detected by the OSIC or the DFE technique is represented by a triangle in 1 + i coordinates. This signal is also a candidate signal, and V-1 signals having the shortest Euclidean distance are selected as candidate signals based on the triangle display. The selected candidate signals are as follows.

의 값을 후보 신호의 값으로 고정시키고 그

을

에 대입해 각 후보군 별 총 SM 신호 값을 검출하게 된다. 이렇게 후보 신호를 이용한 기법은 기존의 ML 방법의 단점인 높은 복잡도를 매우 효과적으로 낮추면서 기존의 OSIC나 DFE 방법 보다는 효과적으로 성능을 높이는 방법이라 할 수 있다. In the above example, since V = 5, there are four candidate signals. Each candidate signal is assumed to be the first detected signal and the remaining signals are detected. The method for detecting the remaining signal is expressed by Equation 15

Fix the value of to the value of the candidate signal

of

The total SM signal value of each candidate group is detected by substituting for. The technique using the candidate signal is a method of increasing the performance more effectively than the conventional OSIC or DFE method while effectively reducing the high complexity, which is a disadvantage of the conventional ML method.

 In this way, each candidate signal becomes the first detection signal to detect the remaining signals. This signal can be expressed as the following equation.

The last step is to select a signal having the least error among the candidate group signals shown in Equation 17.

The obtained signal can improve the BER performance of the SM signal by detecting the first signal more accurately. As mentioned above, the larger the number of Vs, the greater the number of signals that can be compared, resulting in a performance proportional to the number of Vs.

FIG. 6 is a BER performance result graph in which the V-algorithm is applied to the V-BLAST DFE when the number of transmit and receive antennas is three, respectively, and shows a change in the BER performance according to the change of the value of V. FIG. Here, the situation when V = 1 may be regarded as the performance of the general V-BLAST DFE without applying the V-algorithm according to the present invention. As shown in the graph of FIG. 6, as the number of V increases, the performance also improves. Therefore, it can be seen that it is advantageous to use a larger number of V to increase the detection capability of the SM signal.

Next, a repetitive STBC signal detector method according to the present invention will be described. Based on the STBC signal and SM signal obtained above, the STBC signal is repeatedly obtained.

The detected SM signal is canceled from the original received signal (step 430), and as a result, the STBC signal is detected again (step 435).

By comparing the STBC signal obtained in step 435 with the STBC signal obtained in step 410 (step 445), if the two STBC signals are equal to each other, the signal is set to the last detected STBC signal and the STBC detection is completed (450). step). If the two STBC signals are different from each other, the STBC signal obtained later is repeatedly set to the STBC signal detected in step 410 (step 440), and then the SM signal is obtained again in step 415 using the STBC signal (steps 420 and 425). step). After that, the STBC signal is repeatedly detected through the obtained SM signal (step 435), and it is again compared with the previously obtained STBC signal. Likewise, if these two STBC signals are equal to each other, the STBC signal detection is terminated, and if different, the repeat detection is repeated again.

The STBC signal thus obtained is compared with the STBC signal generally obtained by the conventional method in the hybrid STBC, and it can be seen that the interference effect is reduced due to repetitive detection.

The variable K in step 405 of FIG. 4 represents a threshold for how many times the routines from step 415 to step 445 should be repeated, and by appropriately selecting this value, the flow of FIG. It can be prevented and the method or apparatus according to the present invention can be prevented from having more complexity than necessary.

As described above, the simulation result when the transmission signal of the hybrid STBC structure is detected by the technique proposed in the embodiment of the present invention will be described below.

As a result graph of FIGS. 7 to 9, a convolutional channel code having a code rate of 1/2 is used as implemented in a MIMO OFDM system environment. We also consider the channel environment as a Rayleigh fading channel with a path of seven.

이라고 할 때 약 2 dB 정도 성능 차이가 벌어짐을 알 수 있다. FIG. 7 compares the performance between the proposed detection and the conventional hybrid STBC according to the present invention, wherein the number of antennas used is the same as the number of antennas of FIG. 4 and 3 receive antennas. As shown in the graph of FIG. 7, when the V-algorithm is applied to detect the repeated STBC signal and the SM signal, the target BER is determined.

It can be seen that the performance difference is about 2 dB.

FIG. 8 is a comparison graph of the result of a signal (proposed detector) using the repeated STBC detection technique according to the present invention, which is also the result of not using the conventional detection technique (ie, repeated STBC detection technique) as in FIG. Indicates a comparison. As shown in the graph of FIG. 8, it can be seen that the improvement of performance occurs even in a situation where the V-algorithm is not considered.

9 is a performance comparison graph according to the number of V in the considered hybrid STBC. Unlike the performance change of the V-algorithm according to the change of V in ZF V-BLAST, the performance difference according to the number of V is not so large. Since the SMBC signal is detected after the STBC signal has already been detected, the characteristics of the V-algorithm according to the present invention to accurately detect the first signal and minimize the interference with the signal afterwards are not met. It can be said to be the result. Although the performance difference according to the value of V is not large, the fact that the V-algorithm helps improve the performance compared to the situation where V = 1, that is, without the V-algorithm applied.

Therefore, based on the simulation results as described above, the results of using the proposed techniques according to the present invention can be effectively used in the MIMO OFDM system when detecting the transmission signal in the hybrid STBC structure. It can be seen that.

The invention can also be embodied as computer readable code. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD_ROM, magnetic tape, floppy disks, optical data storage devices, and the like, and also include those implemented in the form of carrier waves, for example, transmission over the Internet. 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.

As described above, optimal embodiments have been disclosed in the drawings and the specification. Herein, specific terms have been used, but they are used only for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The invention can be used in the field of communications, in particular in the field of MIMO OFDM.

Figure 1 illustrates the flow of signal detection in a hybrid STBC signal in accordance with the present invention.

2 is a block diagram showing the configuration of an apparatus for detecting a signal in a hybrid STBC signal according to the present invention.

3 is a simplified view of an environment in which the present invention is implemented, and illustrates an environment of three transmitting antennas and three receiving antennas.

FIG. 4 is a detailed view of FIG. 1 showing the flow in which the method according to the invention is carried out.

5 shows a candidate signal selection process in the 16-QAM modulation technique when using the V-algorithm according to the present invention.

FIG. 6 shows the performance of the bit error rate of the V-algorithm according to the number of Vs in V-BLAST when three transmitting antennas and three receiving antennas are used.

7 illustrates a comparison of bit error rates of the STBC signal detection scheme and the conventional hybrid STBC signal detection scheme according to the present invention in a MIMO OFDM system.

8 illustrates a comparison of the bit error rate of the STBC signal detection method and the STBC signal of the conventional hybrid STBC detection method according to the present invention in a MIMO OFDM system. FIG. 9 illustrates the performance change of the bit error rate of the technique according to the present invention according to the number of Vs according to the present invention assuming that STBC signal detection is perfect in a MIMO OFDM system.

Claims (8)

In the method for demodulating a hybrid STBC signal mixed with a space time block code (STBC) signal and a spatial multiplexing (SM) signal, (a) receiving the hybrid STBC signal; (b) detecting an STBC signal included in the received hybrid STBC signal; (c) canceling the detected STBC signal from the received hybrid STBC signal to detect an SM signal; (d) canceling the detected SM signal from the received hybrid STBC signal to detect an STBC signal; And (e) if the STBC signal detected in step (b) and the STBC signal detected in step (d) are the same, determining the STBC signal as a final STBC signal. The method of claim 1, In step (e), if the STBC signal detected in step (b) and the STBC signal detected in step (d) are not the same, the STBC signal detected in step (d) is detected in step (b). A signal demodulating method, characterized in that the signal is set and repeated from the step (c). The method according to claim 1 or 2, In step (c), (c1) detecting a reference signal from the received hybrid STBC signal using a V-BLAST OSIC or V-BLAST DFE method; (c2) determining a plurality of signals having a shortest Euclidean distance on the reference signal and constellation as candidate signals; And (c3) selecting a signal having the smallest error among the candidate signals as an SM signal. The method of claim 3, The number of the plurality of signals in the step (c2) is a maximum of 4 when the QPSK modulation is used for the hybrid STBC signal, and a maximum of 16 when 16-QAM modulation is used, signal demodulation method. In the apparatus for demodulating a hybrid STBC signal mixed with a space time block code (STBC) signal and a spatial multiplexing (SM) signal, A receiver configured to receive the hybrid STBC signal; An STBC signal detector for detecting an STBC signal included in the received hybrid STBC signal; An SM signal detector for canceling the detected STBC signal from the received hybrid STBC signal to detect an SM signal; A repetitive STBC signal detector for canceling the detected SM signal from the received hybrid STBC signal and repeatedly detecting the STBC signal; And And an STBC signal determiner for determining the STBC signal as the final STBC signal when the STBC signal detected by the STBC signal detector and the STBC signal detected by the repeated STBC signal detector are the same. The method of claim 5, The STBC signal determining unit sets the STBC signal detected by the repeating STBC signal detecting unit to the STBC signal detected by the STBC signal detecting unit if the STBC signal detected by the STBC signal detecting unit and the STBC signal detected by the repeating STBC signal detecting unit are not the same. And input the signal to the SM signal detection unit. The method according to claim 5 or 6, The SM signal detector, Detecting a reference signal from the received hybrid STBC signal using a V-BLAST OSIC or V-BLAST DFE method; Determine a plurality of signals having the shortest Euclidean distance on the reference signal and constellation as candidate signals; And And selecting a signal having the smallest error among the candidate signals as an SM signal. The method of claim 7, wherein Wherein the number of the plurality of signals is at most 4 when QPSK modulation is used for the hybrid STBC signal, and at most 16 when 16-QAM modulation is used.

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