CN105119859A - Method and apparatus for eliminating amplitude limiting noise of ACO-OFDM system - Google Patents

Abstract

The invention provides a method and apparatus for eliminating amplitude limiting noise of an Asymmetrically Clipped Optical Orthogonal Frequency Division Multiplexing (ACO-OFDM) system. The method includes the steps of: carrying out modulation on input data sequences and obtaining time domain sequences of positive real numbers; carrying out threshold judgment on the time domain sequences of the positive real numbers so as to carry out amplitude limit on the part exceeding a predetermined threshold; obtaining transmitting signals; receiving the transmitting signals and obtaining the time domain signals; transforming the time domain signals and obtaining frequency domain observation sequences; obtaining frequency domain estimation sequences and noise estimation sequences; obtaining observation vectors and observation matrixes of a compressive sensing algorithm from a selection matrix; adopting the compressive sensing algorithm according to a compressive sensing algorithm mode, and obtaining the amplitude limiting noise sequences; and subtracting the amplitude limiting noise sequences from the time domain signals and obtaining the signals after the amplitude limiting noise signals are eliminated. In complex multipath channels having bad amplitude limit noises, the method can accurately and rapidly estimate and eliminate the amplitude limiting noises in high frequency spectrum efficiency, and can improve the system transmission robustness.

Description

The clipped noise removing method of ACO-OFDM system and device

Technical field

The present invention relates to digital signal transmission technique field, particularly a kind of clipped noise removing method of the ACO-OFDM system based on compressed sensing and device.

Background technology

OFDM (OrthogonalFrequencyDivisionMultiplexing) technology, high with its spectrum efficiency, that anti-multipath jamming ability strong, system realizes complexity is low, Bit and power allocation can be carried out, maximize the advantages such as transmission rate according to the characteristic of channel simultaneously, be widely applied in visible light communication.

But, because light intensity can not occur negative value, so for this bipolar signal of OFDM, the optical communication system of traditional intensity modulated cannot be directly applied to.One method is, direct current biasing is added into OFDM when electro-optical signal is changed, bipolar signal is made to become unipolar signal, thus can transmit on light, this method is called direct current biasing light ofdm system (DCbiasedOpticalOFDM), is called for short DCO-OFDM.Adopt DCO-OFDM system, the average power of output optical signal can be increased, reduce the power efficiency of system.Another kind method is, asymmetric amplitude limit light ofdm system (AsymmetricallyClippedOpticalOFDM), is called for short ACO-OFDM.ACO-OFDM is by a kind of data structure of design, make transmission time-domain signal have certain relevance, then directly in time domain, the part being less than 0 in former ofdm signal to be clipped, only retain on the occasion of, finally recover at receiving terminal, improve the dynamic range of signals of system with this.

But, the peak-to-average force ratio of ACO-OFDM time-domain signal is larger, very high to the requirement of power amplifier of making a start, the method of amplitude limit can be adopted, directly ofdm signal amplitude peak or near employing nonlinear operation reduce the peak value of signal, but inevitably produce signal distortion thus, introduce clipped noise, thus cause systematic function to decline.Therefore, estimation and the recovery of carrying out clipped noise is needed.

Summary of the invention

Object of the present invention is intended at least solve one of above-mentioned technological deficiency.

For this reason, one object of the present invention is the clipped noise removing method proposing a kind of ACO-OFDM system.The method in the complicated multipath channel that clipped noise is severe, with higher spectrum efficiency, accurately can be estimated and eliminate clipped noise, elevator system transmission robustness fast.

Another object of the present invention is the clipped noise cancellation element proposing a kind of ACO-OFDM system.

To achieve these goals, the embodiment of a first aspect of the present invention discloses a kind of clipped noise removing method of ACO-OFDM system, comprise the following steps: S1: ACO-OFDM modulation is carried out to the data sequence of input, obtain the time domain sequences of arithmetic number, and threshold judgement is carried out so that the part exceeding predetermined threshold is carried out amplitude limit to described arithmetic number time domain sequences, transmitted, will transmit and to be launched by LED; S2: transmit described in reception and obtain time-domain signal, discrete Fourier transform is carried out to obtain domain observations sequence to described time-domain signal, and obtain frequency domain estimated sequence and noise estimated sequence according to described domain observations sequence, and obtain selection matrix according to selection criterion, and obtain observation vector and the observing matrix of compressed sensing algorithm by described selection matrix; S3: adopt compressed sensing algorithm according to compressed sensing algorithm model, estimate to obtain clipped noise sequence to object vector; S4: the described time-domain signal received is deducted described clipped noise sequence, with the signal after the clipped noise signal that is eliminated.

In addition, the clipped noise removing method of ACO-OFDM system according to the above embodiment of the present invention can also have following additional technical characteristic:

In some instances, described S1 comprises further: S11: carry out constellation mapping to the described data sequence of input and obtain constellation mapping symbol, and forms Hermitian symmetrical structure according to the conjugation of described constellation mapping symbol and described constellation mapping symbol; S12: by odd subcarriers transmission data and by even subcarriers transmission zero; S13: serioparallel exchange is carried out to obtain the OFDM data block that length is N to the transmission result of described odd subcarriers and described even subcarriers, and inverse fast Fourier transform is carried out to described OFDM data block; S14: carry out asymmetric amplitude limit to the bipolarity data after described inverse fast Fourier transform, with the negative fraction zero setting by bipolar signal, and retains the positive portion of described bipolar signal.

In some instances, in described S2, also comprise: the rough estimate described time-domain signal received being carried out to clipped noise position, obtains the prior information of described clipped noise position.

In some instances, in described S2, described frequency domain estimated sequence obtains in the following way: when the element in described domain observations sequence is the data in odd subcarriers, is obtained the element of corresponding frequency domain estimated sequence by judgement; When element in described domain observations sequence is the data in even subcarriers, directly the element of the frequency domain estimated sequence of correspondence is set to 0, wherein, judgement mode is after the element in described domain observations sequence is multiplied by two, adjudicate according to minimum total error probability criterion, the element in the frequency domain estimated sequence obtained belongs to constellation mapping point.

In some instances, in described S2, described noise estimated sequence obtains in the following way: by described frequency domain estimated sequence divided by two, and obtains noise estimated sequence by the difference of described domain observations sequence and new frequency domain estimated sequence.

In some instances, in described S2, described selection matrix obtains in the following way: from the unit matrix of N rank, choose odd-numbered line vector obtain described selection matrix; Or, record in described noise estimated sequence and be less than predetermined threshold value and P the position altogether belonging to odd subcarriers, from the unit matrix of described N rank, choose corresponding P row vector obtain described selection matrix.

In some instances, in described S2, described observation vector is the product of selection matrix and noise estimated sequence, and described observing matrix is the product of selection matrix and Discrete Fourier transform.

In some instances, in described S3, described compressed sensing algorithm, comprising:

S31: hypothetical target vector length is N, and observation vector y length is M, and observing matrix Φ is M × N, then observing matrix Φ is expressed as [A ,-A], and the size of A is M × (N/2), object vector be expressed as $\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right],$ Wherein, x ₁, x ₂for the column vector of (N/2) × 1, then

$\hat{C}=\[A,-A\]\×\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right]=A(x_1-x_2),$

S32: observing matrix is become A, object vector becomes and meet

S33: utilize compressed sensing algorithm, tries to achieve the object vector after conversion

S34: according to positive and negatively try to achieve x ₁, x ₂, then:

$\left\{\begin{array}{cc}{x}_1\left(n\right)=0,x_2\left(n\right)=\tilde{x}\left(n\right)& \tilde{x}\left(n\right)>0\\ x_1\left(n\right)=\tilde{x}\left(n\right),x_2\left(n\right)=0& \tilde{x}\left(n\right)\≤0\end{array}\right.,$

Thus obtain described clipped noise sequence $\hat{c}=\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right].$

In some instances, in described S13, described compressed sensing algorithm is the one in compression sampling matching pursuit algorithm, orthogonal matching pursuit method and derivative algorithm thereof, sparse Adaptive matching back tracking method or subspace back tracking method, wherein, the prior information of described clipped noise position is for determining the initial condition of compressed sensing algorithm.

The embodiment of second aspect present invention discloses a kind of clipped noise cancellation element of ACO-OFDM system, comprise: signal emission module, for carrying out ACO-OFDM modulation to the data sequence of input, obtain the time domain sequences of arithmetic number, and threshold judgement is carried out so that the part exceeding predetermined threshold is carried out amplitude limit to described arithmetic number time domain sequences, transmitted; To transmit and to be launched by LED; Compressed sensing model generation module, time-domain signal is obtained for transmitting described in receiving, discrete Fourier transform is carried out to obtain domain observations sequence to described time-domain signal, and obtain frequency domain estimated sequence and noise estimated sequence according to described domain observations sequence, and obtain selection matrix according to selection criterion, and obtain observation vector and the observing matrix of compressed sensing algorithm by described selection matrix; Compressed sensing estimation module, for adopting compressed sensing algorithm according to compressed sensing algorithm model, estimates to obtain clipped noise sequence to object vector; Clipped noise cancellation module, for deducting described clipped noise sequence, with the signal after the clipped noise signal that is eliminated by the described time-domain signal received.

According to embodiments of the invention, the signal distortion that the clipped noise solving the ACO-OFDM in correlation technique brings and cause the problem of the decline of communication system performance, have the following advantages: be suitable for the occasion high and not high to signal power efficiency requirements to rate requirement, can in the complicated multipath channel that clipped noise is severe, with higher spectrum efficiency, accurately estimate and eliminate clipped noise, elevator system transmission robustness fast.

The aspect that the present invention adds and advantage will part provide in the following description, and part will become obvious from the following description, or be recognized by practice of the present invention.

Accompanying drawing explanation

The present invention above-mentioned and/or additional aspect and advantage will become obvious and easy understand from the following description of the accompanying drawings of embodiments, wherein,

Fig. 1 is the flow chart of the clipped noise removing method of ACO-OFDM system according to an embodiment of the invention;

Fig. 2 is the transmitting terminal signal flow graph of the clipped noise removing method of ACO-OFDM system according to an embodiment of the invention;

Fig. 3 is the receiving end signal flow chart of the clipped noise removing method of ACO-OFDM system according to an embodiment of the invention; And

Fig. 4 is the structured flowchart of the clipped noise cancellation element of ACO-OFDM system according to an embodiment of the invention.

Embodiment

Be described below in detail embodiments of the invention, the example of embodiment is shown in the drawings, and wherein same or similar label represents same or similar element or has element that is identical or similar functions from start to finish.Being exemplary below by the embodiment be described with reference to the drawings, only for explaining the present invention, and can not limitation of the present invention being interpreted as.

In describing the invention, it will be appreciated that, term " " center ", " longitudinal direction ", " transverse direction ", " on ", D score, " front ", " afterwards ", " left side ", " right side ", " vertically ", " level ", " top ", " end ", " interior ", orientation or the position relationship of the instruction such as " outward " are based on orientation shown in the drawings or position relationship, only the present invention for convenience of description and simplified characterization, instead of indicate or imply that the device of indication or element must have specific orientation, with specific azimuth configuration and operation, therefore limitation of the present invention can not be interpreted as.In addition, term " first ", " second " only for describing object, and can not be interpreted as instruction or hint relative importance.

In describing the invention, it should be noted that, unless otherwise clearly defined and limited, term " installation ", " being connected ", " connection " should be interpreted broadly, and such as, can be fixedly connected with, also can be removably connect, or connect integratedly; Can be mechanical connection, also can be electrical connection; Can be directly be connected, also indirectly can be connected by intermediary, can be the connection of two element internals.For the ordinary skill in the art, concrete condition above-mentioned term concrete meaning in the present invention can be understood.

Below in conjunction with accompanying drawing description according to the clipped noise removing method of the ACO-OFDM system of the embodiment of the present invention and device.

Fig. 1 is the flow chart of the clipped noise removing method of ACO-OFDM system according to an embodiment of the invention.

[embodiment 1]

As shown in Figure 1, composition graphs 2 and Fig. 3, according to an embodiment of the invention the clipped noise removing method of ACO-OFDM system be a kind of can be applicable in ACO-OFDM system based on compressed sensing clipped noise estimate and restoration methods, comprise the steps:

S1: ACO-OFDM modulation is carried out to the data sequence of input, obtain the time domain sequences of arithmetic number, and threshold judgement is carried out so that the part exceeding predetermined threshold is carried out amplitude limit to arithmetic number time domain sequences, transmitted, will transmit and to be launched by LED.

Particularly, comprising:

S11: constellation mapping is carried out to the data sequence of input and obtains constellation mapping symbol, and form Hermitian symmetrical structure according to the conjugation of constellation mapping symbol and constellation mapping symbol.

S12: by odd subcarriers transmission data and by even subcarriers transmission zero.

S13: serioparallel exchange is carried out to obtain the OFDM data block that length is N to the transmission result of odd subcarriers and even subcarriers, and inverse fast Fourier transform is carried out to OFDM data block.

S14: carry out asymmetric amplitude limit to the bipolarity data after inverse fast Fourier transform, with the negative fraction zero setting by bipolar signal, and retains the positive portion of bipolar signal.

That is, constellation mapping is carried out to the data sequence of input, obtains constellation mapping symbol.Get its conjugation symmetrical, form Hermitian symmetrical structure.Only in odd subcarriers transmission data, even subcarriers transmission zero.After carrying out serioparallel exchange, obtain the OFDM data block X that length is N, that is:

$X=(0,X_1,0,X_2,\mathrm{...}{X}_{N/2-1},0,X_{N/2-1}^{*},\mathrm{...},0,X_1^{*}),$

Wherein, the frequency domain symbol on X [k] the kth subcarrier that is data block X.

IFF conversion is carried out to X, obtains x _l(n).Carry out asymmetric amplitude limit to the bipolarity data after IFFT, by the negative fraction zero setting of bipolar signal, the positive portion of stick signal, obtains arithmetic number time domain sequences x (n), that is:

$x\left(n\right)=\left\{\begin{array}{cc}{x}_L\left(n\right)& x_L\left(n\right)>0\\ 0& x_L\left(n\right)\≤0\end{array}\right.,$

Carry out amplitude limit to x (n), width thresholding of limiting is A, is transmitted that is:

$\stackrel{\‾}{x}\left(n\right)=\{\begin{array}{cc}A& x\left(n\right)>A\\ x\left(n\right)& x\left(n\right)\≤A\end{array},$

To transmit and send into LED transmitting.

S2: receiving transmits obtains time-domain signal, discrete Fourier transform is carried out to obtain domain observations sequence to time-domain signal, and obtain frequency domain estimated sequence and noise estimated sequence according to described domain observations sequence, and obtain selection matrix according to selection criterion, and obtain observation vector and the observing matrix of compressed sensing algorithm by selection matrix.

Specifically, reception transmits, and obtains receiving time-domain signal being i.e. x (n)+c (n)+z (n), wherein z (n) is interchannel noise, and c (n) is clipped noise, meets:

$\stackrel{\‾}{x}\left(n\right)=x\left(n\right)+c\left(n\right),$

Discrete Fourier transform is carried out to it and obtains domain observations sequence X [k] ^*+ C [k]+Z [k].

According to maximal possibility estimation criterion, judgement is carried out to domain observations sequence and obtain frequency domain estimated sequence element wherein belongs to constellation mapping point, that is:

$\hat{X}\[k\]=\mathrm{argmin}|2(X{\[k\]}^{*}+C\[k\]+Z\[k\])-s|,s\∈\mathrm{\χ},$

In formula, χ is the set of constellation mapping point.

Noise estimated sequence is the difference of domain observations sequence and frequency domain estimated sequence, that is:

$\hat{C}\[k\]=X{\[k\]}^{*}+C\[k\]+Z\[k\]-\frac{\hat{X}\[k\]}{2},$

Be less than P the position altogether that predetermined threshold value belongs to odd subcarriers simultaneously in recording noise estimated sequence, from the unit matrix of N rank, choose corresponding P row vector obtain selection matrix S.

Observation vector is the product of selection matrix and noise estimated sequence, that is:

$y=S\hat{C},$

Observing matrix is the product of selection matrix and Discrete Fourier transform, that is:

φ＝S·F，

Wherein, matrix F is Discrete Fourier transform, and the element of its row k, the n-th row is:

$F_{k,n}=e^{-j\frac{2\mathrm{\π}kn}{N}},(k=0,1,2,\mathrm{...},N-1,n=0,1,2,\mathrm{...}N-1).$

S3: adopt compressed sensing algorithm according to compressed sensing algorithm model, estimate to obtain clipped noise sequence to object vector.

Specifically, object vector length is N, and suppose that observation vector y length is M, observing matrix φ is M × N.So observing matrix φ can be expressed as [A ,-A], and A is M × N/2; Object vector can be expressed as $\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right],$ X ₁, x ₂for the column vector of N/2 × 1, that is:

$\hat{C}=\[A,-A\]\×\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right]=A(x_1-x_2),$

Observing matrix is become A, and object vector becomes meet

Utilize CoSaMP compressed sensing algorithm, try to achieve the object vector after conversion

According to positive and negatively try to achieve x ₁, x ₂, that is:

$\left\{\begin{array}{cc}{x}_1\left(n\right)=0,x_2\left(n\right)=\tilde{x}\left(n\right)& \tilde{x}\left(n\right)>0\\ x_1\left(n\right)=\tilde{x}\left(n\right),x_2\left(n\right)=0& \tilde{x}\left(n\right)\≤0\end{array}\right.,$

Obtain clipped noise sequence $\hat{c}=\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right].$

S4: the time-domain signal of reception is deducted clipped noise sequence, with the signal after the clipped noise signal that is eliminated.

Specifically, time-domain signal is received in docking process, obtain the time-domain signal after clipped noise counteracting that is:

$\hat{x}\left(n\right)=\stackrel{\‾}{x}\left(n\right)+z\left(n\right)-\hat{c}\left(n\right),$

To time-domain signal carry out discrete Fourier transform, obtain frequency-region signal again utilize maximum Likelihood, obtain the signal after adjudicating that is:

$\hat{X}\[k\]=\arg min\left|2\hat{X}{\[k\]}^{*}-s\right|,s\∈\mathrm{\χ},$

Will middle even item zero setting, only retain odd term signal, be restored signal.

[embodiment 2]

As shown in Figure 1, composition graphs 2 and Fig. 3, the clipped noise removing method of ACO-OFDM system according to an embodiment of the invention, is that a kind of compressed sensing clipped noise auxiliary based on prior information that can be applicable in ACO-OFDM system is estimated and restoration methods, comprises:

S1: ACO-OFDM modulation is carried out to the data sequence of input, obtains arithmetic number time domain sequences; Carry out threshold judgement to the arithmetic number time domain sequences obtained, the part exceeding thresholding carries out amplitude limit, is transmitted; To transmit and send into LED transmitting, be specially:

Constellation mapping is carried out to the data sequence of input, obtains constellation mapping symbol.Get its conjugation symmetrical, form Hermitian symmetrical structure.Only in odd subcarriers transmission data, even subcarriers transmission zero.After carrying out serioparallel exchange, obtain the OFDM data block X that length is N, that is:

$X=(0,X_1,0,X_2,\mathrm{...}{X}_{N/2-1},0,X_{N/2-1}^{*},\mathrm{...},0,X_1^{*}),$

Wherein, the frequency domain symbol on X [k] the kth subcarrier that is data block X.

IFF conversion is carried out to X, obtains x _l(n).Carry out asymmetric amplitude limit to the bipolarity data after IFFT, by the negative fraction zero setting of bipolar signal, the positive portion of stick signal, obtains arithmetic number time domain sequences x (n), that is:

$x\left(n\right)=\left\{\begin{array}{cc}{x}_L\left(n\right)& x_L\left(n\right)>0\\ 0& x_L\left(n\right)\≤0\end{array}\right.,$

Carry out amplitude limit to x (n), width thresholding of limiting is A, is transmitted that is:

$\stackrel{\‾}{x}\left(n\right)=\left\{\begin{array}{cc}A& x\left(n\right)>A\\ x\left(n\right)& x\left(n\right)\≤A\end{array}\right..$

To transmit and send into LED transmitting.

S2: receive and transmit, obtains receiving time-domain signal, carries out discrete Fourier transform obtain domain observations sequence to it, and obtain frequency domain estimated sequence and noise estimated sequence thus; Obtain selection matrix according to selection criterion, and obtain observation vector and the observing matrix of compressed sensing algorithm by selection matrix, be specially:

Reception transmits, and obtains receiving time-domain signal being i.e. x (n)+c (n)+z (n), wherein z (n) is interchannel noise, and c (n) is clipped noise, meets:

$\stackrel{\‾}{x}\left(n\right)=x\left(n\right)+c\left(n\right).$

Time-domain signal is received in docking sampled point delivery value, exceedes the prior information of signal location as clipped noise position of decision threshold ε, obtains the rough estimate location sets Γ of clipped noise time-domain position, then have using modulus value:

$\mathrm{\Γ}=\left\{n\right||\stackrel{\‾}{x}\left(n\right)+z\left(n\right)|>\mathrm{\ϵ}\},$

Decision threshold is chosen for the constant times α of the mean value of current reception time-domain signal absolute value, that is:

$\mathrm{\ϵ}=\mathrm{\α}\×\frac{1}{N}\×\underset{k=0}{\overset{N-1}{\Σ}}|\stackrel{\‾}{x}\left(n\right)+z\left(n\right)|,$

Time-domain signal is received in docking carry out discrete Fourier transform and obtain domain observations sequence X [k] ^*+ C [k]+Z [k].

According to maximal possibility estimation criterion, judgement is carried out to domain observations sequence and obtain frequency domain estimated sequence element wherein belongs to constellation mapping point, that is:

$\hat{X}\[k\]=\mathrm{argmin}|2(X{\[k\]}^{*}+C\[k\]+Z\[k\])-s|,s\∈\mathrm{\χ},$

In formula, χ is the set of constellation mapping point.

Noise estimated sequence is the difference of domain observations sequence and frequency domain estimated sequence, that is:

$\hat{C}\[k\]=X{\[k\]}^{*}+C\[k\]+Z\[k\]-\frac{\hat{X}\[k\]}{2},$

Because even subcarriers part is zero in the frequency domain sequence that ACO-OFDM launches, set up a selection matrix S, S is the matrix choosing odd column formation from unit matrix Ι for this reason.

Observation vector is the product of selection matrix and noise estimated sequence, that is:

$y=S\hat{C},$

Observing matrix is the product of selection matrix and Discrete Fourier transform, that is:

φ＝S·F，

Wherein, matrix F is Discrete Fourier transform, and the element of its row k, the n-th row is:

$F_{k,n}=e^{-j\frac{2\mathrm{\π}kn}{N}},(k=0,1,2,\mathrm{...},N-1,n=0,1,2,\mathrm{...}N-1).$

S3: according to described compressed sensing algorithm model, adopts compressed sensing algorithm, estimates, namely obtain clipped noise sequence, be specially object vector:

Object vector length is N, and suppose that observation vector y length is M, observing matrix φ is M × N.So observing matrix φ can be expressed as [A ,-A], and A is M × N/2; Object vector can be expressed as $\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right],$ X ₁, x ₂for the column vector of N/2 × 1, that is:

$\hat{C}=\[A,-A\]\×\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right]=A(x_1-x_2),$

Observing matrix is become A, and object vector becomes meet

Rough estimate location sets Γ is shifted accordingly, that is:

$\left\{\begin{array}{cc}n=n-\frac{N}{2},& (n>\frac{N}{2})\\ n=n,& (n\≤\frac{N}{2})\end{array}\right.n\∈\mathrm{\Γ},$

Utilize based on the auxiliary compressed sensing algorithm of described prior information, as PA-CoSaMP algorithm, try to achieve the object vector after conversion the wherein rough estimate location sets Γ of prior information clipped noise time-domain position, for determining the initial condition of CoSaMP algorithm.

According to positive and negatively try to achieve x ₁, x ₂, that is:

$\left\{\begin{array}{cc}{x}_1\left(n\right)=0,x_2\left(n\right)=\tilde{x}\left(n\right)& \tilde{x}\left(n\right)>0\\ x_1\left(n\right)=\tilde{x}\left(n\right),x_2\left(n\right)=0& \tilde{x}\left(n\right)\≤0\end{array}\right.,$

Obtain clipped noise sequence $\hat{c}=\left[\begin{array}{c}{x}_1\\ x_2\end{array}\right].$

S4: deduct clipped noise sequence with reception time-domain signal, the signal after the clipped noise signal that is eliminated, is specially:

Time-domain signal is received in docking process, obtain the time-domain signal after clipped noise counteracting that is:

$\hat{x}\left(n\right)=\stackrel{\‾}{x}\left(n\right)+z\left(n\right)-\hat{c}\left(n\right),$

To time-domain signal carry out discrete Fourier transform, obtain frequency-region signal again utilize maximum Likelihood, obtain the signal after adjudicating that is:

$\hat{X}\[k\]=\arg \min \left|2\hat{X}{\[k\]}^{*}-s\right|,s\∈\mathrm{\χ},$

Will middle even item zero setting, only retain odd term signal, be restored signal.

According to the clipped noise removing method of the ACO-OFDM system of the embodiment of the present invention, the signal distortion that the clipped noise solving the ACO-OFDM in correlation technique brings and cause the problem of the decline of communication system performance, the method has the following advantages: be suitable for the occasion high and not high to signal power efficiency requirements to rate requirement, can in the complicated multipath channel that clipped noise is severe, with higher spectrum efficiency, accurately estimate and eliminate clipped noise, elevator system transmission robustness fast.

Fig. 4 is the structured flowchart of the clipped noise cancellation element of ACO-OFDM system according to an embodiment of the invention.As shown in Figure 4, the clipped noise cancellation element 400 of ACO-OFDM system according to an embodiment of the invention, comprising: signal emission module 410, compressed sensing model generation module 420, compressed sensing estimation module 430 and clipped noise cancellation module 440.

Wherein, signal emission module 410, for carrying out ACO-OFDM modulation to the data sequence of input, obtains the time domain sequences of arithmetic number, and carries out threshold judgement so that the part exceeding predetermined threshold is carried out amplitude limit to described arithmetic number time domain sequences, transmitted; To transmit and to be launched by LED.Compressed sensing model generation module 420 obtains time-domain signal for transmitting described in receiving, discrete Fourier transform is carried out to obtain domain observations sequence to described time-domain signal, and obtain frequency domain estimated sequence and noise estimated sequence according to described domain observations sequence, and obtain selection matrix according to selection criterion, and obtain observation vector and the observing matrix of compressed sensing algorithm by described selection matrix.Compressed sensing estimation module 430, for adopting compressed sensing algorithm according to compressed sensing algorithm model, is estimated to obtain clipped noise sequence to object vector.Clipped noise cancellation module 440 is for deducting described clipped noise sequence, with the signal after the clipped noise signal that is eliminated by the described time-domain signal received.

According to the clipped noise cancellation element of the ACO-OFDM system of the embodiment of the present invention, the signal distortion that the clipped noise solving the ACO-OFDM in correlation technique brings and cause the problem of the decline of communication system performance, this device has the following advantages: be suitable for the occasion high and not high to signal power efficiency requirements to rate requirement, can in the complicated multipath channel that clipped noise is severe, with higher spectrum efficiency, accurately estimate and eliminate clipped noise, elevator system transmission robustness fast.

It should be noted that, the specific implementation of the clipped noise removing method of the specific implementation of the clipped noise cancellation element of the ACO-OFDM system of the embodiment of the present invention and the ACO-OFDM system of the embodiment of the present invention is similar, specifically refer to the description of method part in the embodiment of the present invention, in order to reduce redundancy, do not repeat herein.

It should be noted that, the specific implementation of the device of the embodiment of the present invention and the specific implementation of method every similar, specifically referring to the description of method part, in order to reduce redundancy, not repeating.

Although illustrate and describe embodiments of the invention above, be understandable that, above-described embodiment is exemplary, can not be interpreted as limitation of the present invention, those of ordinary skill in the art can change above-described embodiment within the scope of the invention when not departing from principle of the present invention and aim, revising, replacing and modification.

Claims (10)

1. a clipped noise removing method for ACO-OFDM system, is characterized in that, comprise the following steps:

S1: ACO-OFDM modulation is carried out to the data sequence of input, obtain the time domain sequences of arithmetic number, and threshold judgement is carried out so that the part exceeding predetermined threshold is carried out amplitude limit to described arithmetic number time domain sequences, transmitted, will transmit and to be launched by LED;

S2: transmit described in reception and obtain time-domain signal, discrete Fourier transform is carried out to obtain domain observations sequence to described time-domain signal, and obtain frequency domain estimated sequence and noise estimated sequence according to described domain observations sequence, and obtain selection matrix according to selection criterion, and obtain observation vector and the observing matrix of compressed sensing algorithm by described selection matrix;

S3: adopt compressed sensing algorithm according to compressed sensing algorithm model, estimate to obtain clipped noise sequence to object vector;

S4: the described time-domain signal received is deducted described clipped noise sequence, with the signal after the clipped noise signal that is eliminated.

2. method according to claim 1, is characterized in that, described S1 comprises further:

S11: constellation mapping is carried out to the described data sequence of input and obtains constellation mapping symbol, and form Hermitian symmetrical structure according to the conjugation of described constellation mapping symbol and described constellation mapping symbol;

S12: by odd subcarriers transmission data and by even subcarriers transmission zero;

S13: serioparallel exchange is carried out to obtain the OFDM data block that length is N to the transmission result of described odd subcarriers and described even subcarriers, and inverse fast Fourier transform is carried out to described OFDM data block;

S14: carry out asymmetric amplitude limit to the bipolarity data after described inverse fast Fourier transform, with the negative fraction zero setting by bipolar signal, and retains the positive portion of described bipolar signal.

3. method according to claim 1, is characterized in that, in described S2, also comprises: the rough estimate described time-domain signal received being carried out to clipped noise position, obtains the prior information of described clipped noise position.

4. method according to claim 1, it is characterized in that, in described S2, described frequency domain estimated sequence obtains in the following way:

When the element in described domain observations sequence is the data in odd subcarriers, obtained the element of corresponding frequency domain estimated sequence by judgement;

When element in described domain observations sequence is the data in even subcarriers, directly the element of the frequency domain estimated sequence of correspondence is set to 0,

Wherein, judgement mode is that after the element in described domain observations sequence is multiplied by two, adjudicate according to minimum total error probability criterion, the element in the frequency domain estimated sequence obtained belongs to constellation mapping point.

5. method according to claim 1, it is characterized in that, in described S2, described noise estimated sequence obtains in the following way:

By described frequency domain estimated sequence divided by two, and obtain noise estimated sequence by the difference of described domain observations sequence and new frequency domain estimated sequence.

6. method according to claim 1, is characterized in that, in described S2, described selection matrix obtains in the following way:

From the unit matrix of N rank, choose odd-numbered line vector obtain described selection matrix; Or,

Record in described noise estimated sequence and be less than predetermined threshold value and P the position altogether belonging to odd subcarriers, from the unit matrix of described N rank, choose corresponding P row vector obtain described selection matrix.

7. method according to claim 1, is characterized in that, in described S2, described observation vector is the product of selection matrix and noise estimated sequence, and described observing matrix is the product of selection matrix and Discrete Fourier transform.

8. method according to claim 1, is characterized in that, in described S3, described compressed sensing algorithm, comprising:

S31: hypothetical target vector length is N, and observation vector y length is M, and observing matrix Φ is M × N, then observing matrix Φ is expressed as [A ,-A], and the size of A is M × (N/2), object vector be expressed as wherein, x ₁, x ₂for the column vector of (N/2) × 1, then

S32: observing matrix is become A, object vector becomes and meet

S33: utilize compressed sensing algorithm, tries to achieve the object vector after conversion

S34: according to positive and negatively try to achieve x ₁, x ₂, then:

Thus obtain described clipped noise sequence

9. method according to claim 2, it is characterized in that, in described S13, described compressed sensing algorithm is the one in compression sampling matching pursuit algorithm, orthogonal matching pursuit method and derivative algorithm thereof, sparse Adaptive matching back tracking method or subspace back tracking method, wherein, the prior information of described clipped noise position is for determining the initial condition of compressed sensing algorithm.

10. a clipped noise cancellation element for ACO-OFDM system, is characterized in that, comprising:

Signal emission module, for carrying out ACO-OFDM modulation to the data sequence of input, obtaining the time domain sequences of arithmetic number, and carrying out threshold judgement so that the part exceeding predetermined threshold is carried out amplitude limit to described arithmetic number time domain sequences, being transmitted; To transmit and to be launched by LED;

Compressed sensing model generation module, time-domain signal is obtained for transmitting described in receiving, discrete Fourier transform is carried out to obtain domain observations sequence to described time-domain signal, and obtain frequency domain estimated sequence and noise estimated sequence according to described domain observations sequence, and obtain selection matrix according to selection criterion, and obtain observation vector and the observing matrix of compressed sensing algorithm by described selection matrix;

Compressed sensing estimation module, for adopting compressed sensing algorithm according to compressed sensing algorithm model, estimates to obtain clipped noise sequence to object vector;

Clipped noise cancellation module, for deducting described clipped noise sequence, with the signal after the clipped noise signal that is eliminated by the described time-domain signal received.