CN115173953A - Method for improving performance of hybrid HACO-OFDM (hybrid automatic repeat-orthogonal frequency division multiplexing) by applying predistortion technology - Google Patents
Method for improving performance of hybrid HACO-OFDM (hybrid automatic repeat-orthogonal frequency division multiplexing) by applying predistortion technology Download PDFInfo
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Abstract
The invention discloses a method for improving mixed HACO-OFDM performance by applying a predistortion technology, which comprises the steps of firstly carrying out FFT (fast Fourier transform) on an ACO-OFDM time domain signal after amplitude limiting again to obtain an ACO-OFDM frequency domain signal before the ACO-OFDM time domain signal and a PAM-DMT time domain signal are superposed to form the HACO-OFDM time domain signal, extracting interference noise at an imaginary part position in an even number subcarrier of the ACO-OFDM frequency domain signal, then applying the predistortion technology to subtract the ACO-OFDM frequency domain interference noise from the PAM-DMT frequency domain data at the even number of the subcarrier to obtain the PAM-DMT predistorted frequency domain data, then carrying out IFFT (inverse fast Fourier transform) on the PAM-DMT predistorted frequency domain data to obtain the PAM-DMT predistorted time domain signal, and finally superposing the PAM-DMT predistorted time domain signal and the ACO-OFDM time domain signal to form the HACO-OFDM time domain signal so as to eliminate the interference of the ACO-DMT modulation on the PAM-DMT. The method provided by the invention has the advantages of low complexity, strong reliability and high error rate performance.
Description
Technical Field
The invention belongs to the field of visible light communication subjects, and particularly relates to a method for improving hybrid asymmetric amplitude limiting optical orthogonal frequency division multiplexing (HACO-OFDM) performance by applying a predistortion technology.
Background
The hybrid HACO-OFDM is a technology combining asymmetric Clipped Optical Orthogonal Frequency Division Multiplexing (ACO-OFDM) and Pulse Amplitude Modulation-Discrete MultiTone (PAM-DMT), and its main idea is to use odd carriers to perform ACO-OFDM Modulation and even carriers to perform PAM-DMT Modulation, so as to balance power efficiency and spectrum utilization. But due to mutual interference between the ACO-OFDM and the PAM-DMT, the system performance is greatly affected. In order to reduce the influence, the traditional scheme adopts a Serial Interference Cancellation (SIC) technology to counteract the interference of the ACO-OFDM to the PAM-DMT, but the SIC technology also has the problems of high complexity, extra delay, error code propagation and the like. The problem to be solved by the present invention is how to effectively solve the mutual interference between ACO-OFDM and PAM-DMT while reducing the system complexity.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the HACO-OFDM has great influence on the system performance due to mutual interference between the ACO-OFDM and the PAM-DMT. In order to reduce the influence, the traditional scheme adopts the SIC technology to counteract the interference of the ACO-OFDM on the PAM-DMT, but the SIC technology also brings the problems of high complexity, extra delay, error code propagation and the like. The problem to be solved by the present invention is how to effectively solve the mutual interference between ACO-OFDM and PAM-DMT while reducing the system complexity.
The technical scheme adopted by the invention is as follows:
a method for improving the performance of a hybrid HACO-OFDM by applying a predistortion technology comprises the following steps:
before the ACO-OFDM time domain signal and the PAM-DMT time domain signal are superposed to form an HACO-OFDM time domain signal, firstly, fast Fourier Transform (FFT) is carried out on the amplitude-limited ACO-OFDM time domain signal again to obtain an ACO-OFDM frequency domain signal, interference noise at an imaginary part position in an even number subcarrier of the ACO-OFDM frequency domain signal is extracted, then, a predistortion technology is applied, the frequency domain interference noise of the ACO-OFDM is subtracted from the frequency domain data of the PAM-DMT at the position of the even number subcarrier to obtain frequency domain data after PAM-DMT predistortion, then, inverse Fast Fourier Transform (IFFT) is carried out on the frequency domain data to obtain a time domain signal after the PAM-DMT predistortion, and finally, the time domain signal after the PAM-DMT predistortion and the ACO-OFDM time domain signal are superposed to form the HACO-OFDM time domain signal, so that the interference of the ACO-OFDM modulation on the PAM-DMT is eliminated.
Further, the method comprises the steps of:
step 1) carrying out data layering on an information source, wherein ACO-OFDM modulation is carried out on first-layer data, and the modulated data are correspondingly placed at odd subcarrier positions; carrying out PAM-DMT modulation on the second layer data, and correspondingly placing the modulated data at the position of even number of subcarriers;
step 2) FFT transformation is carried out on the ACO-OFDM time domain signal again, the frequency domain interference noise of the ACO-OFDM is subtracted from the frequency domain data of the PAM-DMT at the position of an even number of subcarriers by applying a predistortion technology to obtain the frequency domain data after PAM-DMT predistortion, IFFT transformation is carried out on the frequency domain data after PAM-DMT predistortion to obtain the time domain signal after PAM-DMT predistortion, and then the time domain signal after PAM-DMT predistortion and the ACO-OFDM time domain signal are superposed to form an HACO-OFDM time domain signal so as to eliminate the interference of the ACO-OFDM modulation on the PAM-DMT;
step 3), adding a Cyclic Prefix (CP) to the superimposed HACO-OFDM time domain signal, and sending out the HACO-OFDM time domain signal through DA digital-to-analog conversion and a Bias Tee coupling circuit by using a photoelectric intensity modulator;
step 4), the modulated optical signal reaches a receiving end, and the receiving end performs photoelectric conversion, filtering amplification and AD (analog-to-digital) conversion on the received signal to obtain a signal to be demodulated of HACO-OFDM (Haco-orthogonal frequency division multiplexing);
and step 5) carrying out HACO-OFDM demodulation on the HACO-OFDM signal to be demodulated, wherein the first layer of data is subjected to ACO-OFDM demodulation, and because the interference of the first layer of ACO-OFDM modulation on the second layer of PAM-DMT is eliminated at the transmitting end, the second layer of data can be directly subjected to PAM-DMT demodulation, and finally the demodulated and recovered binary data is sent back to a signal sink.
The invention has the technical characteristics and obvious effects that:
the invention provides a method for improving mixed HACO-OFDM performance by applying a predistortion technology for the first time, which is different from the traditional HACO-OFDM processing method, wherein the mutual interference of ACO-OFDM modulation to PAM-DMT is eliminated from the angle of a frequency domain at a transmitting end, and the mutual interference of the ACO-OFDM modulation to PAM-DMT is counteracted by using a SIC technology from the angle of a time domain at a receiving end. The method provided by the invention has the advantages of low complexity, strong reliability and high error rate performance, because the interference of ACO-OFDM modulation on PAM-DMT is eliminated at the transmitting end, the receiving end can directly carry out parallel demodulation on data without SIC processing, the problems of high complexity, extra delay, error code propagation and the like caused by the traditional SIC serial interference elimination are effectively avoided, and the error rate performance of the method is superior to that of the HACO-OFDM scheme adopting SIC, and a certain reference value can be provided for improving the mixed HACO-OFDM performance by applying a predistortion technology.
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FIG. 1 is a flow chart illustrating a method for improving the performance of hybrid HACO-OFDM using predistortion technique according to an embodiment.
Detailed Description
The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present invention and should not be construed as limiting the present invention.
The embodiment is as follows:
a method for improving the performance of hybrid HACO-OFDM by applying a predistortion technology comprises the following steps:
before the ACO-OFDM time domain signal and the PAM-DMT time domain signal are superposed to form an HACO-OFDM time domain signal, firstly, FFT conversion is carried out on the amplitude-limited ACO-OFDM time domain signal again to obtain an ACO-OFDM frequency domain signal, interference noise at the position of an imaginary part in an even number subcarrier of the ACO-OFDM time domain signal is extracted, then, a predistortion technology is applied, the frequency domain interference noise of the ACO-OFDM is subtracted from the frequency domain data of the PAM-DMT at the position of the even number subcarrier to obtain frequency domain data after PAM-DMT predistortion, IFFT conversion is carried out on the frequency domain data to obtain a time domain signal after the PAM-DMT predistortion, and finally, the time domain signal after the PAM-DMT predistortion and the ACO-OFDM time domain signal are superposed to form the HACO-OFDM time domain signal, so that the interference of the PAO-OFDM modulation on the PAM-DMT is eliminated.
As shown in fig. 1, the method comprises the steps of:
step 1) carrying out data layering on an information source, wherein ACO-OFDM modulation is carried out on first-layer data, and the modulated data are correspondingly placed at odd-numbered subcarrier positions; carrying out PAM-DMT modulation on the second layer data, and correspondingly placing the modulated data at the position of even number of subcarriers;
the step 1) comprises the following steps:
1-1) suppose that the source data transmits N/2-1 data per frame, wherein the sequence numbers of the data are respectively from X 1 To X N/2-1 Then (X) 1 ,X N/2-1 ) The odd-numbered data in the first layer is divided into first layers, and Quadrature Amplitude Modulation (QAM) is performed to obtain X ACO,k1 Wherein k1= (1, 2, \8230;, N/4) is an odd number; and (X) 1 ,X N/2-1 ) The data with even serial number in the second layer is divided into the second layer, and Pulse Amplitude Modulation (PAM for short) is carried out to obtain X PAM,k2 Wherein k2= (1, 2,.., N/4-1);
1-2) QAM mapping data X to the first layer ACO,k1 Hermitian conjugate symmetry is carried out to obtain conjugate data X * ACO,k1 To map data X ACO,k1 And conjugate data X * ACO,k1 The requirement for conjugate symmetry is mapped as follows:
X odd ＝[0,X ACO,1 ,0,X ACO,2 ,0,X ACO,3 ,...,X ACO,N/4 ,0,X * ACO,N/4 ,...,X * ACO,3 ,0,X * ACO,2 ,0,X * ACO,1 ]
1-3) for data X satisfying Hermitian symmetry odd IFFT transformation is carried out to generate an ACO-OFDM real signal x which is in accordance with Intensity Modulation/Direct Detection (IM/DD) transmission ACO-OFDM ：
x ACO-OFDM ＝IFFT(X odd )
1-4) PAM mapping data X to second layer PAM,k2 Performing Hermitian co-treatmentYoke symmetry to obtain X * PAM,k2 Then the original value X is compared PAM,k2 And conjugate data X * PAM,k2 The requirement for conjugate symmetry is mapped as follows:
X even ＝[0,0,X PAM,1 ,0,X PAM,2 ,0,X PAM,3 ,...,X PAM,N/4-1 ,0,0,0,X * PAM,N/4-1 ,...,X * PAM,3 ,0,X * PAM,2 ,0,X * PAM,1 ]；
step 2) FFT conversion is carried out on the ACO-OFDM time domain signal again, the frequency domain interference noise of the ACO-OFDM is subtracted from the frequency domain data of the PAM-DMT at the positions of even number subcarriers by applying the predistortion technology to obtain the frequency domain data after PAM-DMT predistortion, and then the frequency domain data X 'after PAM-DMT predistortion is carried out' PAM-DMT IFFT conversion is carried out to obtain a time domain signal x 'after PAM-DMT predistortion' PAM-DMT Pre-distorted time-domain signal x 'for PAM-DMT' PAM-DMT Carry out ' zero-crossing amplitude limiting ' to obtain x ' PAM-DMT Finally, the data x after the zero-crossing clipping is obtained " PAM-DMT And ACO-OFDM time domain signal x' ACO-OFDM Overlapping to form HACO-OFDM time domain signal x HACO-OFDM Thus eliminating the interference of the ACO-OFDM modulation on the PAM-DMT;
the step 2) comprises the following steps:
2-1) ACO-OFDM real signal x transmitted by first layer ACO-OFDM Performing zero-crossing amplitude limiting, and removing a negative value signal in the ACO-OFDM real number signal to obtain x' ACO-OFDM ，
2-2) then p' ACO-OFDM FFT conversion is carried out to obtain a new frequency domain signal X 'of ACO-OFDM' ACO-OFDM Then extracting the interference noise of the imaginary part position in the even number subcarrier;
2-3) subtracting the frequency domain interference noise of ACO-OFDM from the frequency domain data of PAM-DMT at the position of even number subcarriers to obtain frequency domain data X 'after PAM-DMT predistortion' PAM-DMT ，
Wherein X PAM-DMT Frequency domain data representing PAM-DMT, 2 × imag (X' ACO-OFDM ) Represents to signal X' ACO-OFDM Taking data of an imaginary part and multiplying by 2 times, wherein i represents a complex number;
2-4) Pre-distorted frequency-domain data X 'of PAM-DMT' PAM-DMT IFFT conversion is carried out to obtain a time domain signal x 'after PAM-DMT predistortion' PAM-DMT ，
x' PAM-DMT ＝IFFT(X' PAM-DMT )＝(x' PAM-DMT,0 ,x' PAM-DMT,1 ,...,x' PAM-DMT,j ,...,x' PAM-DMT,N-1 )
Wherein x' PAM-DMT,j J = (0, n-1) represents the j-th PAM-DMT time domain signal of the IFFT output;
2-5) Pre-distorted time-domain Signal x 'of PAM-DMT' PAM-DMT Performing zero-crossing amplitude limiting operation to remove negative value part in PAM-DMT to obtain x " PAM-DMT ：
2-6) time-domain signal x after PAM-DMT predistortion " PAM-DMT And ACO-OFDM time domain signal x' ACO-OFDM Overlapping to obtain HACO-OFDM time domain signal x HACO-OFDM Therefore, the interference of the ACO-OFDM modulation on the PAM-DMT is eliminated;
x HACO-OFDM ＝x” PAM-DMT +x' ACO-OFDM ；
step 3), adding a cyclic prefix to the superimposed HACO-OFDM time domain signal, and sending the signal out by a photoelectric intensity modulator through DA (digital-to-analog) conversion and a Bias Tee coupling circuit;
the step 3 comprises the following steps:
3-1) to HACO-OFDM time domain signal x HACO-OFDM Inserting a cyclic prefix to obtain modulation data of HACO-OFDM;
3-2) after DA digital-to-analog conversion is carried out on the modulation data of HACO-OFDM, adding the modulation data and DC direct current Bias into a Bias Tee coupling circuit together to drive an optical transmitter to complete conversion from an electric signal to an optical signal;
3-3) the optical signal reaches a receiving end through direct, scattering and reflecting paths in a Visible Light Communication (VLC) channel, and then is sent to the next step for processing;
step 4), the modulated optical signal reaches a receiving end, and the receiving end performs photoelectric conversion, filtering amplification and AD (analog-to-digital) conversion on the received signal to obtain a signal to be demodulated of HACO-OFDM (Haco-orthogonal frequency division multiplexing);
step 5) HACO-OFDM demodulation is carried out on the HACO-OFDM signals to be demodulated, wherein ACO-OFDM demodulation is carried out on the first layer of data, and because the interference of the first layer of ACO-OFDM modulation on the second layer of PAM-DMT is eliminated at the transmitting end, PAM-DMT demodulation can be directly carried out on the second layer of data, and finally the demodulated and recovered binary data is sent back to a signal sink;
the step 5 comprises the following steps:
5-1) after receiving the signal to be demodulated of the HACO-OFDM, firstly removing a Cyclic Prefix (CP) signal to obtain an N-point original HACO-OFDM signal;
5-2) carrying out FFT (fast Fourier transform) on the HACO-OFDM signal of the N points to obtain complex data of the N points again;
5-3) taking out first layer ACO-OFDM data X 'to be demodulated output by FFT' 1，ACO-OFDM And a second layer of PAM-DMT data X 'to be demodulated' 2，PAM-DMT ；
5-4) data X 'to be demodulated in the first layer' 1，ACO-OFDM And second layer data X 'to be demodulated' 2，PAM-DMT Demodulating, judging the minimum Euclidean distance between the received constellation point and the theoretical constellation point by adopting a maximum likelihood ratio algorithm, and recovering the demodulated binary data X of the first layer (1) And recovering the demodulated binary data X of the second layer (2) ；
5-5) demodulating the first layer binary data X (1) And second layer demodulated binary data X (2) The position adjustment is performed and then sent back to the sink.
Through the implementation case, the method has the advantages that: and 2) subtracting the frequency domain interference noise of the ACO-OFDM from the frequency domain data of the PAM-DMT to obtain the frequency domain data after the PAM-DMT is pre-distorted, performing FFT conversion on the frequency domain data after the PAM-DMT is pre-distorted again to obtain a time domain signal after the PAM-DMT is pre-distorted, and then overlapping the amplitude-limited ACO-OFDM time domain signal with the PAM-DMT time domain signal to obtain a time domain signal after the HACO-OFDM is pre-distorted. In conclusion, the invention effectively improves the system performance of the hybrid HACO-OFDM.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (5)
1. A method for improving the performance of a hybrid HACO-OFDM system by using a predistortion technology is characterized by comprising
Before the ACO-OFDM time domain signal and the PAM-DMT time domain signal are superposed to form a HACO-OFDM time domain signal, firstly, fast Fourier Transform (FFT) is carried out on the amplitude-limited ACO-OFDM time domain signal again to obtain an ACO-OFDM frequency domain signal, interference noise at an imaginary part position in an even number subcarrier of the ACO-OFDM frequency domain signal is extracted, then, predistortion technology is applied, the frequency domain interference noise of the ACO-OFDM is subtracted from the frequency domain data of the PAM-DMT at the position of the even number subcarrier to obtain frequency domain data after the PAM-DMT predistortion, then, fast Fourier Transform (IFFT) is carried out on the frequency domain data to obtain the time domain signal after the PAM-DMT predistortion, and finally, the time domain signal after the PAM-DMT predistortion and the ACO-OFDM time domain signal are superposed to form the HACO-OFDM time domain signal, so that the interference of the ACO-OFDM modulation on the PAM-DMT is eliminated.
2. The method of claim 1 for improving hybrid HACO-OFDM performance using predistortion technique, comprising the steps of:
step 1) carrying out data layering on an information source, wherein ACO-OFDM modulation is carried out on first-layer data, and the modulated data are correspondingly placed at odd-numbered subcarrier positions; carrying out PAM-DMT modulation on the second layer data, and correspondingly placing the modulated data at the position of even number of subcarriers;
step 2) carrying out FFT transformation on the ACO-OFDM time domain signal again, subtracting the ACO-OFDM frequency domain interference noise from the PAM-DMT frequency domain data at the position of an even number of subcarriers by applying a predistortion technology to obtain the PAM-DMT predistorted frequency domain data, carrying out IFFT transformation on the PAM-DMT predistorted frequency domain data to obtain the PAM-DMT predistorted time domain signal, and then superposing the PAM-DMT predistorted time domain signal and the ACO-OFDM time domain signal to form a HACO-OFDM time domain signal so as to eliminate the interference of the ACO-OFDM modulation on the PAM-DMT;
step 3), adding a Cyclic Prefix (CP) to the superimposed HACO-OFDM time domain signal, and sending out the HACO-OFDM time domain signal through DA digital-to-analog conversion and a Bias Tee coupling circuit by using a photoelectric intensity modulator;
step 4), the modulated optical signal reaches a receiving end, and the receiving end performs photoelectric conversion, filtering amplification and AD (analog-to-digital) conversion on the received signal to obtain a signal to be demodulated of HACO-OFDM (Haco-orthogonal frequency division multiplexing);
and step 5) carrying out HACO-OFDM demodulation on the HACO-OFDM signal to be demodulated, wherein the first layer of data is subjected to ACO-OFDM demodulation, and because the interference of the first layer of ACO-OFDM modulation on the second layer of PAM-DMT is eliminated at the transmitting end, the second layer of data can be directly subjected to PAM-DMT demodulation, and finally the demodulated and recovered binary data is sent back to a signal sink.
3. The method of claim 2, wherein step 1) comprises the steps of:
1-1) suppose that the source data transmits N/2-1 data per frame, wherein the sequence numbers of the data are respectively from X 1 To X N/2-1 Then (X) 1 ,X N/2-1 ) The odd-numbered data in the first layer is divided into the first layer, and Quadrature Amplitude Modulation (QAM) is performed to obtain X ACO,k1 Wherein k1= (1, 2., N/4) is an odd number; and (X) 1 ,X N/2-1 ) The data with even serial number in the second layer is divided into the second layer, and Pulse Amplitude Modulation (PAM for short) is carried out to obtain X PAM,k2 Wherein k2= (1, 2,.., N/4-1);
1-2) QAM mapping data X to the first layer ACO,k1 Hermitian conjugation symmetry is carried out to obtain conjugation data X * ACO,k1 To map data X ACO,k1 And conjugate data X * ACO,k1 The requirement for conjugate symmetry is mapped as follows:
X odd ＝[0,X ACO,1 ,0,X ACO,2 ,0,X ACO,3 ,...,X ACO,N/4 ,0,X * ACO,N/4 ,...,X * ACO,3 ,0,X * ACO,2 ,0,X * ACO,1 ]
1-3) for data X satisfying Hermitian symmetry odd IFFT transformation is carried out to generate an ACO-OFDM real signal x which is in accordance with Intensity Modulation/Direct Detection (IM/DD) transmission ACO-OFDM ：
x ACO-OFDM ＝IFFT(X odd )
1-4) PAM mapping data X to the second layer PAM,k2 Hermitian conjugation symmetry to obtain X * PAM,k2 Then the original value X is added PAM,k2 And conjugate data X * PAM,k2 The requirement for conjugate symmetry is mapped as follows:
X even ＝[0,0,X PAM,1 ,0,X PAM,2 ,0,X PAM,3 ,...,X PAM,N/4-1 ,0,0,0,X * PAM,N/4-1 ,...,X * PAM,3 ,0,X * PAM,2 ,0,X * PAM,1 ]。
4. the method of claim 2 for improving the performance of a hybrid HACO-OFDM using predistortion technique, wherein step 2) comprises the steps of:
2-1) ACO-OFDM real signal x transmitted by first layer ACO-OFDM Carrying out zero-crossing amplitude limiting, and removing a negative value signal in the ACO-OFDM real number signal to obtain x' ACO-OFDM ，
2-2) then to x' ACO-OFDM FFT conversion is carried out to obtain a new frequency domain signal X 'of ACO-OFDM' ACO-OFDM Then extracting the interference noise of the imaginary part position in the even number subcarrier;
2-3) subtracting the frequency domain interference noise of ACO-OFDM from the frequency domain data of PAM-DMT at the positions of even subcarriers to obtain frequency domain data X 'after PAM-DMT predistortion' PAM-DMT ，
Wherein X PAM-DMT Frequency domain data representing PAM-DMT, 2 × imag (X' ACO-OFDM ) Represents to signal X' ACO-OFDM Taking data of an imaginary part and multiplying by 2 times, wherein i represents a complex number;
2-4) Pre-distorted frequency-domain data X 'to PAM-DMT' PAM-DMT IFFT conversion is carried out to obtain a time domain signal x 'after PAM-DMT predistortion' PAM-DMT ，
x' PAM-DMT ＝IFFT(X' PAM-DMT )＝(x' PAM-DMT,0 ,x' PAM -DMT,1,...,x' PAM -DMT,j,...,x' PAM-DMT,N-1 )
Wherein x' PAM-DMT,j J = (0, n-1) represents the j-th PAM-DMT time domain signal of the IFFT output;
2-5) Pre-distorted time-domain Signal x 'of PAM-DMT' PAM-DMT Performing zero-crossing amplitude limiting operation to remove the negative value part in PAM-DMT to obtain x " PAM-DMT ：
2-6) time-domain signal x after PAM-DMT predistortion " PAM-DMT And ACO-OFDM time domain signal x' ACO-OFDM Overlapping to obtain HACO-OFDM time domain signal x HACO-OFDM Thus eliminating the interference of the ACO-OFDM modulation on the PAM-DMT;
x HACO-OFDM ＝x” PAM-DMT +x' ACO-OFDM 。
5. the method of claim 2, wherein step 5 comprises the steps of:
5-1) after receiving the signal to be demodulated of the HACO-OFDM, firstly removing a Cyclic Prefix (CP) signal to obtain an N-point original HACO-OFDM signal;
5-2) carrying out FFT (fast Fourier transform) on the HACO-OFDM signal of the N points to obtain complex data of the N points again;
5-3) taking out first layer ACO-OFDM data X 'to be demodulated output by FFT' 1，ACO-OFDM And a second layer of PAM-DMT data X 'to be demodulated' 2，PAM-DMT ；
5-4) data X 'to be demodulated in the first layer' 1，ACO-OFDM And a second layer of data X 'to be demodulated' 2，PAM-DMT Demodulating, adopting maximum likelihood ratio algorithm, judging minimum Euclidean distance between received constellation point and theoretical constellation point, recovering first layer demodulation binary data X (1) And recovering the demodulated binary data X of the second layer (2) ；
5-5) demodulating the first layer binary data X (1) And second layer demodulated binary data X (2) The position adjustment is performed and then sent back to the sink.
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