KR101679429B1 - Adaptive OSIC (ordered successive interference cancellation)-SD(sphere decoder) decoder and decoding method using the same - Google Patents

Abstract

The present invention relates to an adaptive OSIC-SD decoder and a decoding method using the adaptive OSIC-SD decoder, and an adaptive OSIC-SD decoder and a decoding method using the same.
An adaptive OSIC-SD decoder according to the present invention includes: a receiver for receiving an external signal through an antenna and converting the received signal into a form suitable for decoding; A channel estimator for estimating a channel of the received symbol based on the signal converted by the receiver; And a decoding unit decoding the received symbols estimated by the channel estimating unit according to the SNR range using the OSIC decoding method or the SD decoding method.
According to the present invention, by using an ordered successive interference cancellation (OSIC) decoder instead of a conventional sphere decoder having a large complexity in a low SNR range, the complexity of the conventional SD can be remarkably reduced .

Description

The adaptive OSIC-SD decoder and the decoding method using the adaptive OSIC-SD decoder (Adaptive OSIC-sphere decoder)

The present invention relates to a decoder, and more particularly to a decoder using an ordered successive interference cancellation (OSIC) decoder instead of a conventional sphere decoder having a large complexity in a low signal-to-noise ratio (SNR) SD decoder and a decoding method using the adaptive OSIC-SD decoder, which can significantly reduce the complexity of the conventional SD.

ML (maximum likelihood) decoder in additive white Gaussian noise (AWGN) or fading channel shows optimal performance results. However, in ML decoder, complexity exponentially increases as the number of antennas increases or the modulation order increases.

범위 내에 놓여있는 좌표의 신호들에 한해서 최소 거리를 갖는 신호를 찾아 검파하기 때문에 ML에 비해 계산량이 훨씬 적다. 여기서,

는 초기에 설정된 반지름으로 유효한 심볼을 찾을 때까지 반지름 길이는 갱신된다.The ML decoder performs a process of finding a transmission vector x that minimizes a norm square value such as? Y-Hx? ² during demodulation. That is, the ML decoder compares the received signal with all signal coordinates, and detects a symbol of a coordinate having the shortest distance as an original transmission symbol. On the other hand, in the case of the SD (sphere decoder), as shown in FIG. 1, the radius

Since the signal with the minimum distance is detected and detected only for the signals within the range, the calculation amount is much smaller than the ML. here,

The radius length is updated until a valid symbol is found with the initially set radius.

를 설정하기 위한 많은 연구가 이루어지고 있다.It is very important that at least one valid coordinate is included in the initially set radius range since the position of the received signal on all signal coordinates will change from time to time due to noise. For that reason,

Have been investigated.

In a MIMO (Multi Input Multi Output) system, the received signal is expressed as y = Hx + n. Here, y denotes a symbol received from the N _r reception antennas, and H denotes an N _r × N _t channel. And x is the number of transmission symbols transmitted in N _t transmission antennas, and n is N _r received AWGNs.

Conventional SD describes the SD decoding process by dividing the real part and the complex part as shown in the following equation (1).

The received signal is represented by r = Ms + v by the above equation 1 and the received signal r is expressed by dividing it into a real part and an imaginary part as shown in the following equation (2).

Where Re {·} denotes the real part, Im {·} denotes the imaginary part, and (·) T denotes the transpose matrix.

The number of symbols to be detected is 2N _t since the real number and the imaginary part are separated and the decoding process is performed. Where 2N _t is simply denoted by m.

To apply SD, we first find the approximate coordinate position of the received symbol using ZF (zero forcing) or MMSE (minimum mean square error) decoder. In the case of ZF, [M ^H M] ^-1 M ^H is obtained and multiplied by the received vector r to estimate the received signal as shown in Equation 3 below.

For MMSE, G is calculated and applied as G = [M ^H M + σ ² I] ^-1 M ^H.

After MMSE ∥r-Ms∥ ² may be rewritten as the following equation 4, ML is expressed as equation (5).

Therefore, the coordinates of the valid symbol are located within the radius d as shown in Equation (6) below.

In Equation (6), the Cholesky factorization is applied to M ^T M to obtain an upper diagonal matrix having a matrix of m × m. Equation (6) can be expressed as Equation (7) below.

로 초기 설정되고, u_i = ρ_m의 조건을 가지고 다음의 수식 8과 같이 하한(lower bound)과 상한(upper bound)을 만족하는 값을 선택한다.The decoding proceeds in descending order from i = m to i = 1. When i = m, the radius d _i is

And a value satisfying a lower bound and an upper bound is selected as shown in the following Equation 8 with the condition of u _i = ρ _m .

는 x와 가까운 정수로 올림(round up)을 의미하며,

는 x와 가까운 정수로 내림(round down)을 의미한다. SD의 경우 복호 과정을 단순화 하기위해 기준 신호의 실수 집합만으로 복호 과정을 수행한다. 예를 들어서, 16QAM(quadrature amplitude modulation)로 전송하는 경우 SD를 수행할 때 오직 p = {-3, -1, 1, 3}과 같이 네 가지 가능성만 따지게 된다.In Equation 8 above

Means round up to an integer close to x,

Means round down to an integer close to x. In the case of SD, the decoding process is performed using only a real set of reference signals to simplify the decoding process. For example, in the case of 16QAM (Quadrature Amplitude Modulation) transmission, only four possibilities are given when performing SD, such as p = {-3, -1, 1, 3}.

In the case of 16QAM, we reduce one of the four elements of the p-set in the radius d _i through Eq. When i = m (after one cycle), d _i and u _i can be obtained by the following equation (9).

Finally, when i = 1 (last cycle), the radius is calculated as follows.

인 경우, 새로 계산된 길이를 반지름으로 하여 위의 과정을 다시 반복한다. If the

, Repeat the above procedure with the newly calculated length as the radius.

와 상관없이 복잡도를 일정한 수준으로 유지시킨다. Chan-Lee SD는 기존 SD에서 크게 2가지를 개선하였는데, 그 중 첫 번째는 상·하한 계산 후에 후보 벡터 z_i를 u_i와 유클리디언 거리 (euclidean distance)를 계산하고 오름차순으로 정렬시킨다. 이와 같은 과정을 통해 첫 번째 순환 과정 동안 원래 심볼을 찾을 수 있는 가능성이 커지게 되고, 디코딩 시간을 상당히 줄일 수 있게 된다. 두 번째는 복호 과정을 통해 하나의 후보 벡터가 찾아지면 반지름 및 상·하한 경계, N_i가 다시 새롭게 갱신된다. 벡터 z_i는 그대로 유지되지만 기존의 SD와 달리 k_i는 0으로 설정되지 않고 마지막 순환 과정의 값 그대로 유지시킨다. 이와 같이 함으로써 다음 복호 시 k_i지점을 고려하지 않게 되고, 이로 인해 복호 시간을 줄일 수 있다. However, since the computation becomes large when the radius length is large, the complexity is considerably sensitive to the radius length. Chan-Lee (Albert M. Chan and Inkyu Lee) The SD algorithm improves the SD to improve the radial length

And keeps the complexity at a constant level. In Chan-Lee SD, two improvements are made in the existing SD. First, after calculating the upper and lower bounds, the candidate vector z _i is calculated in ascending order by calculating u _i and euclidean distance. This process increases the likelihood of finding the original symbol during the first cyclic process and significantly reduces the decoding time. Second, if one candidate vector is found through the decoding process, the radius and the upper and lower bounds, N _i, are renewed again. The vector z _i remains unchanged, but unlike the conventional SD, k _i is not set to 0 and the value of the last cycle is maintained. By doing so, the point k _i is not considered in the next decoding, thereby reducing the decoding time.

However, since the Chan-Lee SD has a certain complexity, the complexity increases in a high SNR range.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and it is an object of the present invention to provide an apparatus and method for reducing complexity of a conventional SD by using an ordered successive interference cancellation (OSIC) decoder instead of a conventional sphere decoder having a large complexity in a low SNR range And an object of the present invention is to provide an adaptive OSIC-SD decoder and a decoding method using the adaptive OSIC-SD decoder.

According to an aspect of the present invention, there is provided an adaptive OSIC-SD decoder,

A receiver for receiving a signal from the outside via an antenna and converting the received signal into a form suitable for decoding;

A channel estimator for estimating a channel of the received symbol based on the signal converted by the receiver; And

And a decoding unit decoding the received symbols estimated by the channel estimating unit according to the SNR range using the OSIC decoding method or the SD decoding method.

Here, the decoding unit includes an MMSE decoder that finds a coarse coordinate position of a received symbol estimated by the channel estimation unit, an OSIC decoder and a Chan-Lee SD decoder that decode the received symbol through the MMSE decoder according to the SNR range can do.

The receiver receives signals through four receive antennas. In a low SNR range, received symbols for two antennas of the four receive antennas are decoded by the OSIC decoder, and received symbols for the remaining two antennas Is decoded by the Chan-Lee SD decoder.

In the intermediate SNR range, only symbols of one of the four receive antennas are decoded by the OSIC decoder, and received symbols for the remaining three antennas are decoded by the Chan-Lee SD decoder.

Also, in the high SNR range, all symbols of the four reception antennas are decoded by the Chan-Lee SD decoder.

In addition, the adaptive OSIC-SD decoder of the present invention may further include a demodulation unit that receives and demodulates the signal decoded by the decoding unit.

According to another aspect of the present invention, there is provided a decoding method using an adaptive OSIC-SD decoder,

A decoding method using an adaptive OSIC-SD decoder including a receiver for receiving a signal from the outside, a channel estimator for estimating a channel of the received symbol, and a decoder for decoding the received symbol according to the SNR range,

a) receiving a signal from the outside through the antenna by the receiving unit, and converting the received signal into a form suitable for decoding;

b) estimating a channel of the received symbol by the channel estimator based on the signal transformed through the receiver; And

and c) decoding the received symbol estimated by the channel estimation unit by the decoding unit according to the SNR range using the OSIC decoding method or the SD decoding method.

The decoding of step c) includes: searching for an approximate coordinate position of the received symbol estimated by the channel estimation unit by an MMSE decoder; and determining a co-ordinated position of a received symbol found by the MMSE decoder, Decoding the received symbols by the OSIC decoder and the Chan-Lee SD decoder according to the SNR range, respectively.

The receiver receives signals through four receive antennas. In a low SNR range, received symbols for two antennas of the four receive antennas are decoded by the OSIC decoder, and received symbols for the remaining two antennas Is decoded by the Chan-Lee SD decoder.

In the intermediate SNR range, only symbols of one of the four receive antennas are decoded by the OSIC decoder, and received symbols for the remaining three antennas are decoded by the Chan-Lee SD decoder.

Also, in the high SNR range, all symbols of the four reception antennas are decoded by the Chan-Lee SD decoder.

The method may further include receiving a signal decoded by the decoding unit in step c) and demodulating the signal by a demodulation unit.

According to the present invention, by using an ordered successive interference cancellation (OSIC) decoder instead of a conventional sphere decoder having a large complexity in a low SNR range, the complexity of the conventional SD can be remarkably reduced .

FIG. 1 is a diagram showing a geometric process of finding a received symbol of a conventional SD; FIG.
FIG. 2 is a schematic view showing the configuration of an adaptive OSIC-SD decoder according to the present invention; FIG.
FIG. 3 is a flowchart illustrating a decoding method using an adaptive OSIC-SD decoder according to the present invention; FIG.
4 is a graph showing bit error rate performance of Chan-Lee SD based on ZF and MMSE of a MIMO 4 × 4 system using a 16QAM modulation technique.
5 illustrates the complexity of Chan-Lee SD based on ZF and MMSE of a MIMO 4x4 system using a 16QAM modulation scheme.
FIG. 6 is a diagram showing a result of bit error rate performance analysis of a conventional SD and a Chan-Lee SD in a 4 × 4 MIMO system using a 16QAM modulation technique. FIG.
FIG. 7 is a diagram showing the complexity of an existing SD and a Chan-Lee SD in a 4x4 MIMO system using a 16QAM modulation technique.
8 is a graph showing the bit error rate performance analysis results of SD (Original or Chan-Lee) and OSIC algorithm and Hybrid OSIC-SD combined with OSIC and SD in a 4x4 MIMO system using 16QAM modulation technique.
FIG. 9 is a diagram showing complexity due to the amount of algorithm computation according to the SNR of the original SD and the algorithms of FIG. 8; FIG.
10 is a graph showing the bit error rate performance of the OSIC algorithm and the SD, and the adaptive OSIC-SD of the present invention in the 4x4 MIMO system using the 16QAM modulation technique.
11 is a diagram showing the complexity of the OSIC algorithm and SD and the adaptive OSIC-SD of the present invention in a 4x4 MIMO system using a 16QAM modulation technique;

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

FIG. 2 is a diagram schematically showing a configuration of an adaptive OSIC-SD decoder according to the present invention.

2, the adaptive OSIC-SD decoder according to the present invention includes a receiver 210, a channel estimator 220, and a decoder 230.

The receiving unit 210 receives an external signal through the antenna 205 and converts the received signal into a form suitable for decoding. For example, the receiver 210 removes a guard interval of a signal received through the antenna 205, and then performs an FFT (fast Fourier transform). The receiver 210 is based on an OFDMA (Orthogonal Frequency Division Multiplexing Access) system.

The channel estimator 220 estimates a channel of the received symbol based on the signal transformed through the receiver 210. [

The decoding unit 230 decodes the received symbols estimated by the channel estimation unit 220 according to the SNR range using the OSIC decoding method or the SD decoding method.

Here, the decoding unit 230 includes an MMSE decoder 231 for finding a coarse coordinate position of a received symbol estimated by the channel estimation unit 220 and a reception symbol passing through the MMSE decoder 231 in an SNR range And an OSIC decoder 232 and a Chan-Lee SD decoder 233 for decoding.

The receiver 210 receives a signal through the four receive antennas 205 and generates a receive symbol for two antennas of the four receive antennas 205 in a low SNR range (for example, less than 10 dB) Is decoded by the OSIC decoder 232 and the received symbols for the remaining two antennas are decoded by the Chan-Lee SD decoder 233. [

In the intermediate SNR range (for example, 10 dB to 15 dB), only the symbols of one reception antenna of the four reception antennas 205 are decoded by the OSIC decoder 232, and the remaining three antennas The received symbols are decoded by the Chan-Lee SD decoder 233.

All symbols of the four reception antennas 205 are decoded by the Chan-Lee SD decoder 233 in a high SNR range (for example, more than 15 dB). The Chan-Lee SD decoder 233 decodes all the symbols of the four reception antennas 205 in the high SNR range in such a manner that the complexity of the Chan-Lee SD decoder 233 is low .

In addition, the adaptive OSIC-SD decoder of the present invention may further include a demodulator 240 for demodulating a signal decoded by the decoder 230.

Hereinafter, a decoding method using the adaptive OSIC-SD decoder according to the present invention having the above-described configuration will be briefly described.

3 is a flowchart illustrating a decoding method using an adaptive OSIC-SD decoder according to the present invention.

2 and 3, a decoding method using an adaptive OSIC-SD decoder according to the present invention includes a receiving unit 210 for receiving signals from outside as described above, a channel estimating unit 210 for estimating a channel of a received symbol, A decoding method using an adaptive OSIC-SD decoder including a decoding unit 220 and a decoding unit 230 decoding a received symbol according to an SNR range. First, the receiving unit 210 transmits a signal from the outside to an antenna 205 ), And converts the received signal into a form suitable for decoding (step S310).

Then, the channel estimator 220 estimates the channel of the received symbol based on the signal converted by the receiver 210 (step S320).

Then, the decoding unit 230 decodes the received symbol estimated by the channel estimating unit 220 according to the SNR range using the OSIC decoding method or the SD decoding method (step S330).

The step of decoding in step S330 includes a step of searching for an approximate coordinate position of the received symbol estimated by the channel estimation unit 220 by the MMSE decoder 231, Decoding the received symbols by the OSIC decoder 232 and the Chan-Lee SD decoder 233 according to the SNR range based on the approximate coordinate positions of the symbols.

The receiver 210 receives a signal through the four receive antennas 205 and generates a receive symbol for two antennas of the four receive antennas 205 in a low SNR range (for example, less than 10 dB) Is decoded by the OSIC decoder 232 and the received symbols for the remaining two antennas are decoded by the Chan-Lee SD decoder 233. [

In the intermediate SNR range (for example, 10 dB to 15 dB), only the symbols of one reception antenna of the four reception antennas 205 are decoded by the OSIC decoder 232, and the remaining three antennas The received symbols are decoded by the Chan-Lee SD decoder 233.

All symbols of the four reception antennas 205 are decoded by the Chan-Lee SD decoder 233 in a high SNR range (for example, more than 15 dB).

In addition, the demodulating unit 240 may further demodulate the signal decoded by the decoding unit 230 in step S330 (S340).

4 to 11 are graphs showing performance analysis results of the adaptive OSIC-SD decoder and the conventional SD decoder of the present invention.

The parameters used for simulation for performance analysis are shown in Table 1 below. The experimental parameters in Table 1 are based on WiBro MIMO-OFDM.

Simulation parameter               Parameter                 Value            Transmission OFDM symbol                  42               MIMO technique             Layered 4x4                                                     Decryption algorithm SD
Hybrid OSIC-SD
Adaptive OSIC-SD               Channel environment       Quasi-static Flat Fading                  Noise                 AWGN                Modulation technique                 16QAM FFT size
(Data Carrier + Pilot Carrier +
DC + band)                                                1024 (720 + 120 + 1 + 183) 1 OFDM symbol size
(FFT + CP)             1152 (1024 + 128)            1 OFDM symbol time 115.2 μs
(102.4 mu s: FFT + 12.8 mu s: CP)              1 frame time                   5ms

4 is a graph showing bit error rate performance of Chan-Lee SD based on ZF and MMSE of a MIMO 4 × 4 system using a 16QAM modulation technique. In terms of bit error rate, the performance of the two algorithms is almost the same. However, as shown in FIG. 5, when the simulation time is measured in seconds according to each SNR, the MMSE has a smaller computation amount in the SNR range lower than ZF I can confirm.

FIG. 6 is a graph showing the bit error rate performance analysis results of a conventional SD and a Chan-Lee SD in a 4 × 4 MIMO system using a 16QAM modulation technique.

As shown in FIG. 6, it can be seen that the bit error rate performance is the same. However, when the calculation amount (complexity) is compared as shown in FIG. 7, it can be seen that Chan-Lee SD is quite good in the complex drawings.

FIG. 8 is a diagram showing bit error rate performance of SD (Original or Chan-Lee, see FIG. 6) and OSIC algorithm and Hybrid OSIC-SD in which OSIC and SD are combined in a 4 × 4 MIMO system using 16QAM modulation technique .

Referring to FIG. 8, in the case of Hybrid OSIC-SD (1), one of the four symbols is decoded by the OSIC and the remaining three symbols are decoded by SD.

In the case of the Hybrid OSIC-SD (2), two of the four symbols are decoded by the OSIC and the remaining two are decoded by the SD. Therefore, as shown in FIG. 8, the bit error rate performance of the hybrid OSIC-SD (1) having a large number of symbols decoded by the SD algorithm close to the ML performance is better than that of the hybrid OSIC-SD (2) . Hybrid algorithms do not satisfy ML performance like SD after about 12dB, but 3dB better performance than Hybrid OSIC-SD (2) and 6dB better Hybrid OSIC-SD (1) You can see what you see.

FIG. 9 is a diagram showing the complexity of the original SD and the algorithms according to the SNRs of the respective algorithms in FIG. 8 according to the algorithm operation amount.

As shown in FIG. 9, in the bit error rate performance, the same performance as the ML can be achieved in the case of the original SD, but the complexity is considerably larger than other algorithms. In the case of Chan-Lee SD Shows ML performance similar to that of original SD, and shows a significant improvement in complexity. As shown in FIG. 8, in the case of the existing OSIC algorithm, the bit error rate performance is the lowest compared to other algorithms, but the complexity is the lowest. Hybrid OSIC-SD, which combines OSIC and Chan-Lee SD, shows low complexity in the range of 22dB smaller than Chan-Lee SD by using low-complexity OSIC. Hybrid OSIC-SD (1) The complexity is greater because there are many symbols to be decoded by Chan-Lee SD compared to SD (2). However, since there are many symbols to be decoded by Chan-Lee SD, which provides ML performance, it is possible to confirm that the bit error rate performance is better as shown in FIG.

FIG. 10 is a graph showing the bit error rate performance of the OSIC algorithm and the SD, and the adaptive OSIC-SD of the present invention in the 4 × 4 MIMO system using the 16QAM modulation technique.

Referring to FIG. 10, in the adaptive OSIC-SD of the present invention, a decoding algorithm is adaptively used according to a channel state. When the channel condition is poor, Hybrid OSIC-SD (2) algorithm with lower complexity and the best bit error rate performance than the SD (Chan-Lee, Original) is selected in the low SNR range (<10dB). Hybrid OSIC-SD (1) with the best bit error rate performance is selected in the medium SNR range between 10dB and 15dB. And, in the high SNR range (> 15dB), the Chan-Lee SD algorithm satisfying the bit error rate performance such as ML and satisfying the performance of other SD in the complexity and SNR range is selected and decoded. As described above, the present invention adaptively uses a decoding algorithm according to a channel to satisfy the same performance as a conventional SD (Chan-Lee, Original) in terms of bit error as shown in FIG. 11, which shows the complexity of each algorithm, the Adaptive OSIC-SD of the present invention has the lowest complexity following OSIC. Although the complexity is the lowest in the OSIC, considering the trade-off between the bit error rate in FIG. 10 and the complexity in FIG. 11, the adaptive OSIC-SD algorithm of the present invention finds that the system satisfies the most optimal complexity and bit error rate .

As described above, the adaptive OSIC-SD decoder according to the present invention uses an ordered successive interference cancellation (OSIC) decoder instead of the conventional SD having a large complexity in a low SNR range and selectively uses a decoding algorithm according to a channel The complexity of the conventional SD can be remarkably reduced by reducing the amount of computation of the decoder.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Accordingly, the true scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of the same should be construed as being included in the scope of the present invention.

210 ... reception unit 220 ... channel estimation unit
230 ... Decoding section 231 ... MMSE decoder
232 ... OSIC decoder 233 ... SD decoder
240 ... demodulator

Claims (12)

A receiver for receiving a signal from the outside via an antenna, removing a guard interval of the received signal, and performing a fast Fourier transform;
A channel estimator for estimating a channel of the received symbol based on the signal converted by the receiver; And
And a decoder for decoding the received symbols estimated by the channel estimation unit according to an SNR range using an ordered successive interference cancellation (OSIC) decoding scheme or a sphere decoder (SD) decoding scheme. The method according to claim 1,
The decoder includes an MMSE decoder for calculating the coordinates of the received symbol estimated by the channel estimator, an adaptive OSIC decoder including an OSIC decoder and a Chan-Lee SD decoder for decoding the received symbol through the SNR range according to the SNR range, -SD decoder. 3. The method of claim 2,
The receiver receives a signal through four receive antennas. In the SNR range of less than 10 dB, received symbols received through two of the four receive antennas are decoded by the OSIC decoder, And the received symbol is decoded by the Chan-Lee SD decoder. 3. The method of claim 2,
The receiver receives a signal through the four receive antennas, and in the SNR range of 10 dB to 15 dB, only received symbols received through one receive antenna of the four receive antennas are decoded by the OSIC decoder, And the received symbols received through the Chan-Lee SD decoder are decoded by the Chan-Lee SD decoder. 3. The method of claim 2,
The receiving unit receives a signal through four receiving antennas,
And the received symbols received through the four receive antennas are decoded by the Chan-Lee SD decoder in an SNR range exceeding 15 dB. 6. The method according to any one of claims 1 to 5,
And a demodulator for receiving a signal decoded by the decoder and demodulating the signal. An adaptive OSIC-SD (Orthogonal Frequency Division Multiplexer) decoder, which includes a receiver for receiving a signal from the outside, a channel estimator for estimating a channel of the received symbol, and a decoder for decoding the received symbol according to the SNR range, As a decoding method using,
a) receiving an external signal through an antenna by the receiving unit, removing a guard interval of the received signal, and performing a fast Fourier transform;
b) estimating a channel of the received symbol by the channel estimator based on the signal transformed through the receiver; And
c) decoding the received symbol estimated by the channel estimating unit according to an SNR range using an ordered successive interference cancellation (OSIC) decoding scheme or a sphere decoder (SD) decoding scheme by the decoding unit; Decoding method using SD decoder. 8. The method of claim 7,
The decoding of step c) comprises the steps of: calculating the coordinates of the received symbol estimated by the channel estimation unit by an MMSE decoder; calculating a SNR range of the received symbol based on the coordinates of the received symbol calculated by the MMSE decoder And decoded by an OSIC decoder and a Chan-Lee SD decoder, respectively, in accordance with the OSIC-SD decoder. 9. The method of claim 8,
The receiver receives a signal through four receive antennas. In the SNR range of less than 10 dB, received symbols received through two of the four receive antennas are decoded by the OSIC decoder, And the received symbol is decoded by the Chan-Lee SD decoder. 9. The method of claim 8,
The receiver receives a signal through four receive antennas. In the SNR range of 10 dB to 15 dB, only the symbols received through one of the four receive antennas are decoded by the OSIC decoder, and the remaining three antennas Wherein the received symbols are decoded by the Chan-Lee SD decoder. 9. The method of claim 8,
The receiver receives a signal through four receive antennas, and, in an SNR range of more than 15 dB, the receive symbols received through the four receive antennas are all decoded by the Chan-Lee SD decoder. Decoding method. 12. The method according to any one of claims 7 to 11,
Further comprising receiving a signal decoded by the decoding unit of step c) and demodulating the signal by a demodulation unit, using the adaptive OSIC-SD decoder.

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