CN110336763A - A kind of method and system for the ACE inhibiting high order modulation ofdm signal peak-to-average force ratio - Google Patents
A kind of method and system for the ACE inhibiting high order modulation ofdm signal peak-to-average force ratio Download PDFInfo
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Abstract
The invention belongs to technical field of electronic communication, disclose the method and system of ACE for inhibiting high order modulation ofdm signal peak-to-average force ratio a kind of, redefine in extension rule of the frequency domain to constellation；And peak clipping thresholding is dynamically adjusted according to the peak-to-average force ratio of current demand signal, it obtains effective peak-to-average force ratio and inhibits gain, while making error rate of system severe exacerbation off guard；After obtaining effective peak-to-average force ratio and inhibiting gain, suitable spreading factor is obtained by amendment Least squares approximation formula, original time domain signal is amplified, signal peak-to-average ratio inhibitory effect is enhanced.The present invention is based on above-mentioned optimisation strategies, the peak-to-average force ratio of OFDM transmission signal is significantly reduced in the case where only needing an iteration, greatly reduce the implementation complexity of system, ensure that simultaneously the bit error rate and out-of-band power spectrality can loss within an acceptable range, the overall performance of ofdm system is effectively promoted.
Description
Technical field
The invention belongs to technical field of electronic communication more particularly to a kind of inhibit high order modulation ofdm signal peak-to-average force ratio
The method and system of ACE.
Background technique
Currently, the immediate prior art:
Orthogonal frequency division multiplex OFDM multi-carrier modulation technology with the advantages that its high spectrum utilization, high-transmission reliability by
It is widely used in various wireless communication systems, and becomes one of the key technology of the 5th Generation Mobile Communication System.Ofdm system
Using data parallel transmission mode, data are transmitted using mutually orthogonal subcarrier, when the signal of modulation passes through discrete fourier
After inverse transformation IFFT, when multiple phases are close or identical Signal averaging, biggish instantaneous power, priming signal will be generated
Higher peak-to-average force ratio PAPR problem.
One of the problem of high PAPR problem of ofdm signal is exactly ofdm system urgent need to resolve for a long time.High PAPR signal is wanted
It asks radio-frequency power amplifier HPA with extremely wide dynamic range and digital analog converter DAC has high precision, increase and be
The cost and implementation complexity of system.If the relevant parameter of HPA and DAC is not able to satisfy the requirement of ofdm signal, letter will result in
Number out of band spectrum extension and non-linear distortion, to deteriorate the performance of system.For ofdm system high peak-to-average power ratio problem, scholar
Have been presented for numerous solutions, such as dynamic constellation extension technology (Active Constellation Extension,
ACE).The basic thought of dynamic constellation extension technology is: in the feelings for not changing the Euclidean distance between planisphere inner constellation point
Under condition, guarantee that the minimum euclidean distance between peripheral planisphere is constant, extends the position of peripheral constellation point suitably to reduce signal
The value of peak-to-average force ratio.Its essential idea is that additional frequency offset is superimposed on corresponding subcarrier to change the width of transmission signal
Degree and phase reduce the same or similar probability of phase after subcarrier-modulated, and then reduce the peak-to-average force ratio of signal.
Up to now, a variety of ACE methods have been proposed in scholar.Such as the POCS that D.L.Jones is proposed
(Projection Onto the Convex Sets, convex set mapping) ACE method, is absolutely received well although this method has
Characteristic is held back, but convergence rate is slower, needs that just the peak-to-average force ratio of signal target value can be down to hereinafter, thus making by successive ignition
It is increased at the complexity of system.
For the disadvantage that POCS method convergence rate is slow, Krongold B S proposes a kind of SGP (Smart Gradient
Projection, intelligent gradient projection) ACE method, this method accelerates convergence rate by amplification original time domain signal, but
Additional complexity is needed to calculate gradient step.In the case, Mounira Laabidi proposes a kind of LSA (Least
SquareApproximation, Least squares approximation) ACE method, this method is with faster convergence rate and does not need additional
Complexity go the material calculation factor, but sacrifice a large amount of bit error rate performance.
Generally, for big subcarrier, the ofdm system of high order modulation, excessive the number of iterations means to increase a large amount of
Computation complexity, cause its application cost in practical communication system to be difficult to bear.Meanwhile above-mentioned traditional ACE method
Mainly for the ofdm system of low-order-modulated (QPSK~64-QAM) and less subcarrier, high-order M- extremely above to 64-QAM
The wideband OFDM system of QAM modulation, big number of subcarriers will consume more system resources and cannot obtain considerable
PAPR inhibits gain.
In conclusion problem of the existing technology is:
For the orthogonal frequency division multiplex OFDM system of big subcarrier, high order modulation, the prior art needs successive ignition just may be used
So that the peak-to-average force ratio of signal is dropped to target value hereinafter, increasing the implementation complexity of system, and be unable to the real-time ensuring bit error rate and
The loss of out-of-band power spectrality energy within an acceptable range, causes the overall performance of orthogonal frequency division multiplex OFDM system very low.
Solve the difficulty of above-mentioned technical problem:
(1) since the sub-carrier number of orthogonal frequency division multiplex OFDM system increases, cause the calculating of discrete Fourier transform multiple
Miscellaneous degree increases, and the existing ACE technology that successive ignition reduces ofdm system peak-to-average force ratio has not been suitable for engineer application.How to design repeatedly
For process, it is made to can be obtained first difficult point that significant peak-to-average force ratio gain is urgent need to resolve in the case where an iteration.
(2) as the order of modulation that orthogonal frequency division multiplex OFDM system uses increases, planisphere becomes increasingly complex, can expand
The constellation point ratio of exhibition reduces.How extension rule for high-order constellation point is designed, so that reducing the same of signal peak-to-average ratio
When guarantee system the bit error rate not severe exacerbation be urgent need to resolve second difficult point.
Solve the meaning of above-mentioned technical problem: if can guarantee that error rate of system and out-of-band power spectrality can not be serious
While deterioration, an iteration is achieved with considerable peak-to-average force ratio gain, then can substantially reduce orthogonal frequency division multiplex OFDM system
The implementation complexity of system, to reduce the application cost of communication system.
Summary of the invention
In view of the problems of the existing technology, the present invention provides a kind of inhibition high order modulation ofdm signal peak-to-average force ratios
The method and system of ACE.Present invention relates particularly to one of wireless communication technology fields to inhibit high order modulation OFDM
The ACE of (Orthogonal FrequencyDivision Multiplexing, orthogonal frequency division multiplexing) signal peak-to-average ratio
(Active Constellation Extension, dynamic constellation extension) scheme.High order modulation suitable for wirelessly communicating
Ofdm system realizes PAPR (Peak-to-Average Power, the peak of signal by extending transmitting terminal frequency-region signal constellation point
Compare) inhibit, it works to avoid high peak-to-average power ratio signal in the non-of HPA (HighPowerAmplifier, radio-frequency power amplifier)
Linear zone and caused by out of band spectrum extension and non-linear distortion, deteriorate system performance.
The invention is realized in this way a method of inhibit the ACE of high order modulation ofdm signal peak-to-average force ratio, comprising:
Redefine the extended mode for high-order constellation；Using adaptive peak clipping policy dynamic change peak clipping thresholding with suitable
The ofdm signal of different peak-to-average force ratios is answered, to guarantee that bit error rate performance will not severe exacerbation while reducing peak-to-average force ratio；Pass through
Amendment Least squares approximation formula generates suitable spreading coefficient and amplifies to original time domain signal, to accelerate this programme
Convergence rate.
Specific step is as follows:
Step 1 carries out quadrature amplitude modulation to the binary bit stream of orthogonal frequency division multiplex OFDM system transmitting terminal, obtains
To original frequency domain signal X=[X0,X1,...,Xk]T, wherein then k=0,1 ..., N-1 carry out J times to original frequency domain signal
After interpolation operation through inverse discrete Fourier transform be over-sampling time domain original OFDM signal x=[x0,x1,...,xn]T, wherein
N=0, the subcarrier number that 1 ..., JN-1, J indicate the up-sampling factor and J >=4, N include by ofdm system；Signal x will
Carry out following peak-to-average force ratio inhibition processing；
Step 2, the peak-to-average ratio for calculating current demand signal are denoted as ξ, and according to the peak-to-average force ratio ξ of system requirementstarAnd system is missed
Initial clipping rate CR is arranged in code rate BERinit, initial compensation factor gammainitAnd η；
Step 3 adjusts peak clipping thresholding A according to the peak-to-average ratio ξ of current demand signal, and cuts to original oversampled signals
Peak, the signal after obtaining peak clippingWith peak clipping noise cclip=[cclip,0,cclip,1,…,cclip,n]T, wherein
N=0,1 ..., JN-1；
Step 4, if p is peak clipping noise cclip,nThe set of the serial number of sampled point of the middle amplitude not equal to zero, i.e. p=n | |
cclip,n| ≠ 0 }, then peak clipping signal cclip,nThe set that middle serial number n belongs to the amplitude of the sampled point of p is denoted as ce, i.e. ce=| cclip,n
| | n ∈ p }, calculate ceThe mean value of middle all elements is denoted as τ；
Step 5, using leaf transformation FFT in JN point discrete Fourier by signalAnd cclipIt is converted into frequency domain, obtains frequency domain peak clipping
SignalWith frequency domain peak clipping noise Cclip=[Cclip,0,Cclip,1,...,Cclip,k]T, wherein k=0,
1,...,JN-1；
Step 6, in frequency domain to peak clipping signalPlanisphere be extended, the frequency domain peak clipping noise after being expanded
Step 7, using leaf inverse transformation IFFT in JN point discrete Fourier by frequency domain peak clipping noiseTime domain peak clipping is transformed into make an uproar
SoundWherein n=0,1 ..., JN-1；
Step 8, the peak clipping noise after extensionThe set that middle serial number n belongs to the amplitude of the sampled point of p is denoted asI.e.It calculatesThe mean value of middle all elements is denoted as
Step 9, Introduced Malaria factor k, utilizes the c in above-mentioned processe、τ、WithSpreading coefficient μ is calculated, and to original
Time-domain signal x is amplified, and is obtained peak-to-average force ratio and is inhibited signal
Step 10, the signal after peak-to-average force ratio is inhibitedIt send after insertion protection interval to radio frequency amplifier HPA and is emitted to channel
In.
Further, the present invention only needs an iteration, alternative manner specifically includes the following steps:
Binary bit stream is modulated to original over-sampling ofdm signal；
Corresponding Optimal Parameters are set；
Adaptive peak clipping processing；
Calculate amplitude vector mean value；
Fourier transformation FFT；
Constellation extension；
Inverse Fourier transform IFFT；
Amplitude vector mean value after calculating constellation extension；
It calculates spreading coefficient and amplifies original OFDM signal；
Send the signal after peak-to-average force ratio inhibits.
Further, quadrature amplitude modulation described in step 1 includes 16-QAM, 64-QAM, 256-QAM and 1024-QAM；
The J times of interpolation operation is frequency domain data X=[X after modulation0,X1,...,Xk]T, the insertion of the centre k=0,1 ..., N-1
(J-1) × N number of zero, thus after inverse discrete Fourier transform IFFT available J times of over-sampling original time domain signal x=
[x0,x1,...,xn]T, n=0,1 ..., JN-1 can be used following formula to indicate:
Wherein XkIt is the pervious frequency domain data of non-interpolation, Xk' it is frequency domain data after interpolation.
Further, the peak-to-average ratio ξ of current demand signal described in step 2 is calculated by following formula:
Wherein, n=0,1 ..., JN-1, max | xn|2Indicate signal x maximum power, E | xn|2Indicate signal x's
Mean power.
Further, adaptive peak clipping strategy described in step 3 is initial according to the adjustment of the peak-to-average force ratio PAPR value of current demand signal
Clipping rate, and then adjust peak clipping thresholding, avoid cutting away excessive non-peak point.The pass of the peak clipping thresholding A and clipping rate CR
System is shown below:
Wherein, σ is the mean power of signal x:
The clipping rate CR is adjusted by following formula:
CR=CRinit+(γ-1)·α·(ξ-ξtar)
Wherein,
γ and η is compensation factor, peak-to-average ratio ξ and initial clipping rate of the selection of value depending on current demand signal
CRinit。
The specific steps of the clipping operation include:
The first step is right | xn| all sampled points of > A carry out peak clipping operation, the signal after obtaining peak clipping
Wherein, n=0,1 ..., JN-1,Indicate imaginary unit, exp () is indicated using natural constant e the bottom of as
Index operation, θnFor original time domain signal xnPhase, | | be the operation of modulus value；
Second step, with the signal after peak clippingIt subtracts original time domain signal x and obtains peak clipping noise:
Further, described in step 6 in frequency domain to peak clipping signalPlanisphere be extended and include:
The first step, reservation inner constellation point, which is not done, to be extended；
Second step, apex angle constellation point are extended to the region far from planisphere center；
Third step, boundary constellation point are extended to along change in coordinate axis direction far from the region at planisphere center.
Further, the k of the Introduced Malaria factor described in step 9 utilizes the c in above-mentioned processe、τ、WithCalculate extension system
Number μ, and original time domain signal x is amplified and includes:
The first step, the suitable modifying factor k of selection in [- 1,2]；
Second step, corrects Least squares approximation formula, and optimization aim can indicate are as follows:
Wherein, min { } expression is minimized operator,Indicate two norm operator of vector, l indicate length and to
Measure ceEqually, but element be all 1 row vector, μ be wait seek optimal spreading coefficient；
Third step seeks the optimal spreading coefficient μ for meeting optimization aim described in second step:
It enables
The gradient for enabling f (μ) is zero:
Gradient algorithm is sought in wherein ▽ { } expression, then optimal spreading coefficient μ are as follows:
4th step, with optimal spreading coefficient amplification original time domain signal x to accelerate convergence rate, after obtaining peak-to-average force ratio inhibition
Time-domain signal
Another object of the present invention is to provide inhibition high order modulation ofdm signal peak described in a kind of implementation claim is equal
The system of the ACE of the inhibition high order modulation ofdm signal peak-to-average force ratio of the method for the ACE of ratio.
In conclusion advantages of the present invention and good effect are as follows:
The method and system of ACE inhibiting high order modulation ofdm signal peak-to-average force ratio provided by the invention a kind of, mainly solve
Big subcarrier, high order modulation orthogonal frequency division multiplex OFDM system in occur signal high peak-to-average power ratio the problem of.The present invention couple
The extended mode of high-order constellation is defined, and dynamically adjusts peak clipping thresholding according to the peak-to-average force ratio of current demand signal, is guaranteed
Error rate of system will not severe exacerbation while obtaining effective peak-to-average force ratio inhibition gain.In addition to this, the present invention is by correcting most
Small square regression formulas obtains suitable spreading factor, amplifies to original time domain signal, to accelerate the convergence of algorithm
Speed simultaneously enhances the signal peak-to-average ratio inhibitory effect of algorithm.The present invention is based on above-mentioned optimisation strategies, are only needing an iteration
In the case of significantly reduce the peak-to-average force ratio of OFDM transmission signal, greatly reduce the implementation complexity of system, while ensure that mistake
The loss of code rate and out-of-band power spectrality energy is within an acceptable range.
Since the present invention redefine in extension rule of the frequency domain to constellation and carries out in time domain to original signal
Amplification appropriate can obtain considerable PAPR gain in an iteration, overcome of the existing technology to high-order orthogonal
The ofdm system signal peak-to-average ratio of amplitude modulation system inhibits the disadvantage of gain deficiency.Meanwhile the present invention significantly reduces
The number of iterations and computational complexity needed for PAPR gain needed for obtaining allow to preferably be applied to high order modulation, big son
The orthogonal frequency division multiplex OFDM system of carrier wave.
Since present invention uses adaptive peak clipping strategies, can dynamically be adjusted according to the peak-to-average force ratio PAPR value of current demand signal
Whole peak clipping thresholding avoids excessive non-peak point from being reamed, and then can obtain error rate BER performance and peak-to-average force ratio PAPR inhibition
It is improved while performance, to further promote the overall performance of ofdm system.
Detailed description of the invention
Fig. 1 is the method flow diagram of the ACE provided in an embodiment of the present invention for inhibiting high order modulation ofdm signal peak-to-average force ratio.
Fig. 2 is constellation expandable area and extended mode schematic diagram provided in an embodiment of the present invention.
Fig. 3 is the present invention provided in an embodiment of the present invention and three kinds of existing ACE methods in high order modulation and big subcarrier
Peak-to-average ratio inhibition performance comparison diagram in ofdm system.
Fig. 4 is provided in an embodiment of the present invention under additive white Gaussian noise channel, the present invention and three kinds of existing ACE methods
Bit error rate performance comparison diagram in high order modulation and big subcarrier ofdm system.
Fig. 5 is the present invention provided in an embodiment of the present invention and three kinds of existing ACE methods in high order modulation and big subcarrier
Power spectral density performance comparison figure in ofdm system.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to embodiments, to the present invention
It is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, it is not used to
Limit the present invention.
In the prior art, big subcarrier, high order modulation orthogonal frequency division multiplex OFDM system in the signal peak that occurs it is equal
It is poorer than inhibitory effect, it not can be reduced the implementation complexity of system, and be unable to the real-time ensuring bit error rate and out-of-band power spectrality energy
Loss within an acceptable range, keep the overall performance of ofdm system very low.In the prior art, the application cost in communication system
It is high.
To solve the above problems, below with reference to concrete scheme, the present invention is described in detail.
For convergence rate existing for current conventional dynamic extension ACE scheme slow, the number of iterations and computation complexity it is high and
The bit error rate deteriorates serious problem, and the present invention only needs an iteration to can be obtained considerable peak-to-average force ratio inhibition gain, greatly reduces
Computation complexity, meanwhile, the present invention takes into account peak-to-average ratio inhibition performance and bit error rate performance, using special optimisation strategy, make
Its bit error rate will not severe exacerbation while reducing signal peak-to-average ratio.
As shown in Figure 1, it is provided in an embodiment of the present invention inhibit high order modulation ofdm signal peak-to-average force ratio ACE method include with
Lower step:
S101: binary bit stream is modulated to original over-sampling ofdm signal；
S102: corresponding Optimal Parameters are set；
S103: adaptive peak clipping processing；
S104: amplitude vector mean value is calculated；
S105: Fourier transformation FFT；
S106: constellation extension；
S107: inverse Fourier transform IFFT；
S108: the amplitude vector mean value after calculating constellation extension；
S109: it calculates spreading coefficient and amplifies original OFDM signal；
S110: the signal after peak-to-average force ratio inhibits is sent.
In step S101, quadrature amplitude tune is carried out to the binary bit stream of orthogonal frequency division multiplex OFDM system transmitting terminal
System, obtains original frequency domain signal X=[X0,X1,...,Xk]T, wherein k=0,1 ..., N-1, then to original frequency domain signal into
After J times of interpolation operation of row through inverse discrete Fourier transform be over-sampling time domain original OFDM signal x=[x0,x1,...,xn]T,
Wherein, n=0, the subcarrier number that 1 ..., JN-1, J indicate the up-sampling factor and J >=4, N include by ofdm system are intended
The modulation system of use includes 16-QAM, 64-QAM, 256-QAM and 1024-QAM；Signal x inhibits following peak-to-average force ratios is carried out
Processing；
The J times of interpolation operation carries out as the following formula:
Wherein, N indicates the subcarrier number of orthogonal frequency division multiplex OFDM system, and J is indicated according to the up-sampling for requiring selection
The factor, XkAnd Xk' respectively indicate the frequency-region signal up-sampled on preceding k-th of subcarrier with after up-sampling, 0≤k≤JN-1.
In step S102, the peak-to-average ratio for calculating current demand signal is denoted as ξ, and according to the peak-to-average force ratio ξ of system requirementstarAnd it is
Initial clipping rate CR is arranged in error rate BER of unitinginit, initial compensation factor gammainitAnd η；
The calculation formula of the peak-to-average force ratio ξ is as follows:
Wherein, n=0,1 ..., JN-1, max | xn|2Indicate original time domain signal x maximum power, E | xn|2Table
Show the mean power of original time domain signal x.
In step S103, according to the peak-to-average ratio ξ of current demand signal, adjust peak clipping thresholding A, and to original oversampled signals into
Row peak clipping, the signal after obtaining peak clippingWith peak clipping noise cclip=[cclip,0,cclip,1,...,cclip,n]T,
Wherein n=0,1 ..., JN-1, specifically includes:
3a) according to the peak-to-average ratio ξ of current demand signal, clipping rate is adjusted according to the following formula:
CR=CRinit+(γ-1)·α·(ξ-ξtar)
Wherein, γ and η is compensation factor, and the selection of value depends on the peak-to-average ratio ξ and initial clipping of current demand signal
Rate CRinit；
3b) calculate peak clipping thresholding A at this time:
Wherein, σ is the mean power of original time domain signal x, is calculated as follows:
Peak clipping operation 3c) is carried out to original time domain signal x, the signal after obtaining peak clipping
Wherein, n=0,1 ..., JN-1,Indicate imaginary unit, exp () is indicated using natural constant e the bottom of as
Index operation, θnFor original time domain signal xnPhase, | | be the operation of modulus value；
3d) the signal after peak clippingIt subtracts original time domain signal x and obtains time domain peak clipping noise cclip:
In step S104, if p is peak clipping noise cclip,nThe set of the serial number of sampled point of the middle amplitude not equal to zero, i.e. p=
{n||cclip,n| ≠ 0 }, then peak clipping signal cclip,nThe set that middle serial number n belongs to the amplitude of the sampled point of p is denoted as ce, i.e. ce=|
cclip,n| | n ∈ p }, calculate ceThe mean value of middle all elements is denoted as τ；
In step S105, using leaf transformation FFT in JN point discrete Fourier by signalAnd cclipIt is converted into frequency domain, obtains frequency domain
Peak clipping signalWith frequency domain peak clipping noise Cclip=[Cclip,0,Cclip,1,...,Cclip,k]T, wherein k=
0,1,...,JN-1；
The signalDiscrete Fourier transform FFT carry out according to the following formula:
The peak clipping noise cclipDiscrete Fourier transform FFT carry out according to the following formula:
In step S101, in frequency domain to peak clipping signalPlanisphere be extended, the frequency domain peak clipping after being expanded is made an uproar
SoundPlanisphere expandable area provided by the invention is as shown in Fig. 2, if by peak clipping
Signal after processingFrequency domain constellation point fall in expandable area, then retain the constellation point, otherwise according to following Rule Extended stars
Seat point: vertex constellation point is extended to dash area far from the region of complex plane coordinate far point, and boundary constellation point is to arrow meaning side
To the Directional Extension far from complex plane coordinate origin, inner constellation point does not have to extension, specifically includes:
Constellation point 6a) is divided into two parts according to the position distribution of constellation point in planisphere: inner constellation point and boundary star
Seat point；
6b) inner constellation point is corrected in the following manner as shown in C in Fig. 2:
6c) boundary constellation point is corrected in the following manner as shown in A, B, D in Fig. 2:
Wherein, Real () expression takes real part operation, and Imag () expression takes imaginary-part operation, and X indicates original frequency domain signal,
XkIndicate the corresponding original frequency domain signal of k-th of sampled point,Indicate by clipping peak clipping treated extension frequency-region signal,Indicate revised extension frequency-region signal；
Signal after 6d) extendingSubtract the frequency domain peak clipping noise after original frequency domain signal X is expanded
In step S107, using leaf inverse transformation IFFT in JN point discrete Fourier by the frequency domain peak clipping noise after extensionTransformation
At time domain peak clipping noiseWherein n=0,1 ..., JN-1；
The frequency domain peak clipping noiseInverse discrete Fourier transform IFFT carried out by following formula:
Wherein,Indicate extraction of square root operation；∑ indicates sum operation；Indicate multiplication operations；Exp is indicated with naturally normal
Number e is the index operation at bottom；For imaginary unit；π indicates pi.
Peak clipping noise in step S108, after extensionThe set that middle serial number n belongs to the amplitude of the sampled point of p is denoted as
I.e.It calculatesThe mean value of middle all elements is denoted as
In step S109, Introduced Malaria factor k utilizes the c in above-mentioned processe、τ、WithSpreading coefficient μ is calculated, and right
Original time domain signal x is amplified, and is obtained peak-to-average force ratio and is inhibited signalIt specifically includes:
Suitable modifying factor k, the present invention 9a) are selected in [- 1,2] according to the convergence rate of system requirements and the bit error rate
In, k value is bigger, and convergence rate is faster；
Least squares approximation formula 9b) is corrected, optimization aim can indicate are as follows:
Wherein, min { } expression is minimized operator,Indicate two norm operator of vector, l indicate length and to
Measure ceEqually but element be all 1 row vector, μ be wait seek optimal spreading coefficient；
The optimal spreading coefficient μ for meeting optimization aim 9c) is sought, is enabled
The gradient for enabling f (μ) is 0:
Gradient algorithm is sought in wherein ▽ { } expression, then optimal spreading coefficient μ are as follows:
9d) with the peak clipping noise after optimal spreading coefficient μ and extensionAmplification original time domain signal x is to accelerate convergence speed
Degree obtains the time-domain signal after peak-to-average force ratio inhibits
Signal in step S110, after peak-to-average force ratio is inhibitedIt send after insertion protection interval to radio frequency amplifier HPA and is emitted to
In channel.
Effect of the invention is described further below by emulation experiment.
1) simulated conditions:
Emulation experiment of the invention uses Matlab R2017b simulation software, and modulation system is 256-QAM quadrature amplitude tune
System, sub-carrier number N are set as 8192, and up-sampling multiple J is set as 4, initial clipping rate CRinitBe set as 4.68dB, compensation because
Sub- γinit=1.3 and η=1.3, regulatory factor k=2.
2) emulation content and interpretation of result:
Emulation 1, it is dynamic with the present invention and existing convex set mapping dynamic constellation extension method POCS-ACE, intelligent gradient projection
State constellation extension method SGP-ACE, Least squares approximation dynamic constellation extension method LSA-ACE respectively to original OFDM signal into
Row peak-to-average force ratio inhibits, and the peak-to-average force ratio PAPR obtained inhibits gain as shown in Figure 3.
Emulation 2 maps dynamic constellation extension method with the present invention and existing convex set under additive white Gaussian noise channel
POCS-ACE, intelligent gradient project dynamic constellation extension method SGP-ACE, Least squares approximation dynamic constellation extension method LSA-
ACE carries out peak-to-average force ratio inhibition to original OFDM signal respectively, and the bit error rate performance obtained is as shown in Figure 4.
Emulation 3, it is dynamic with the present invention and existing convex set mapping dynamic constellation extension method POCS-ACE, intelligent gradient projection
State constellation extension method SGP-ACE, Least squares approximation dynamic constellation extension method LSA-ACE respectively to original OFDM signal into
Row peak-to-average force ratio inhibits, and the out of band spectrum performance obtained is as shown in Figure 5.
By the simulation result of Fig. 3 it is found that the present invention given complementary cumulative distribution function value be 10-4When, the side POCS-ACE
It can get the peak-to-average force ratio gain of 1.80dB after method iteration 60 times, the peak that SGP-ACE method iteration once can get 3.10dB is equal
Than gain, iteration can get the peak-to-average force ratio gain of 3.20dB twice, and the peak that LSA-ACE method iteration once can get 3.10dB is equal
Than gain, iteration can get the peak-to-average force ratio gain of 3.05dB twice, and the present invention can get the peak-to-average force ratio gain of 3.4dB.Thus may be used
See.The present invention can reduce the peak-to-average force ratio of ODFM transmission signal compared to traditional constellation extension method significantly.
By the simulation result of Fig. 4 it is found that being 10 in bit error rate-4When, snr loss of the invention is less than an iteration
Lower LSA-ACE method bring snr loss is identical with SGP-ACE method bring snr loss under an iteration.It examines
Consider bring peak-to-average force ratio of the present invention and inhibit gain, snr loss is within the acceptable range.
By the simulation result of Fig. 5 it is found that the present invention can obtain it is several with LSA-ACE and SGP-ACE method under an iteration
The same power spectral density.
In conjunction with Fig. 3, Fig. 4 and Fig. 5 it is found that the present invention can be obtained under an iteration than POCS-ACE, SGP-ACE and
Better peak-to-average ratio inhibition performance under LSA-ACE method successive ignition, substantially reduces the computation complexity of system, while may be used also
To guarantee bit error rate performance and power spectrum performance not severe exacerbation.In conclusion compared with existing skill, scheme pair of the present invention
There is preferably overall performance in the orthogonal frequency division multiplex OFDM system of big carrier wave, high order modulation.
The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the invention, all in essence of the invention
Made any modifications, equivalent replacements, and improvements etc., should all be included in the protection scope of the present invention within mind and principle.
Claims (10)
1. a kind of method for the ACE for inhibiting high order modulation ofdm signal peak-to-average force ratio, which is characterized in that the inhibition high order modulation
The method of the ACE of ofdm signal peak-to-average force ratio includes:
It is redefined in extension rule of the frequency domain to constellation；
And peak clipping thresholding is dynamically adjusted according to the peak-to-average force ratio of current demand signal, obtain effective peak-to-average force ratio and inhibit gain, at the same make be
System bit error rate severe exacerbation off guard；
After obtaining effective peak-to-average force ratio and inhibiting gain, suitable spreading factor is obtained by amendment Least squares approximation formula, it is right
Original time domain signal amplifies, and enhances signal peak-to-average ratio inhibitory effect.
2. inhibiting the method for the ACE of high order modulation ofdm signal peak-to-average force ratio as described in claim 1, which is characterized in that described
The method of the ACE of inhibition high order modulation ofdm signal peak-to-average force ratio further comprises:
Binary bit stream is modulated to original over-sampling ofdm signal by step 1；
Corresponding Optimal Parameters are arranged in step 2；
Step 3, adaptive peak clipping processing；
Step 4 calculates amplitude vector mean value；
Step 5, Fourier transformation FFT；
Step 6, constellation extension；
Step 7, inverse Fourier transform IFFT；
Step 8, the amplitude vector mean value after calculating constellation extension；
Step 9 calculates spreading coefficient and amplifies original OFDM signal；
Step 10 sends the signal after peak-to-average force ratio inhibits.
3. inhibiting the method for the ACE of high order modulation ofdm signal peak-to-average force ratio as claimed in claim 2, which is characterized in that step
One further comprises: carrying out quadrature amplitude modulation to the binary bit stream of orthogonal frequency division multiplex OFDM system transmitting terminal, obtains
Original frequency domain signal X=[X0,X1,...,Xk]T, wherein then k=0,1 ..., N-1 carry out J times to original frequency domain signal and insert
After Value Operations through inverse discrete Fourier transform be over-sampling time domain original OFDM signal x=[x0,x1,...,xn]T, wherein n
=0,1 ..., JN-1, J indicate the up-sampling factor and J >=4, the N subcarrier number that includes by ofdm system；Signal x will
Carry out following peak-to-average force ratio inhibition processing；
The quadrature amplitude modulation includes 16-QAM, 64-QAM, 256-QAM and 1024-QAM, the J times of interpolation operation be
Modulated frequency domain data X=[X0,X1,...,Xk]T, k=0,1 ..., N-1 centre insertion (J-1) × N number of zero, thus by
Original time domain signal x=[the x of available J times of over-sampling after inverse discrete Fourier transform IFFT0,x1,...,xn]T, n=0,
1 ..., JN-1 can be used following formula to indicate:
Wherein XkIt is the pervious frequency domain data of non-interpolation, Xk' it is frequency domain data after interpolation.
4. inhibiting the method for the ACE of high order modulation ofdm signal peak-to-average force ratio as claimed in claim 2, which is characterized in that step
Two further comprise: the peak-to-average ratio for calculating current demand signal is denoted as ξ, and according to the peak-to-average force ratio ξ of system requirementstarAnd system error code
Initial clipping rate CR is arranged in rate BERinit, initial compensation factor gammainitAnd η；
Step 3 further comprises according to the peak-to-average ratio ξ of current demand signal, adjusting peak clipping thresholding A, and to original oversampled signals
Carry out peak clipping, the signal after obtaining peak clippingWith peak clipping noise cclip=[cclip,0,cclip,1,...,
cclip,n]T, wherein n=0,1 ..., JN-1.
Step 4, if p is peak clipping noise cclip,nThe set of the serial number of sampled point of the middle amplitude not equal to zero, i.e. p=n | |
cclip,n| ≠ 0 }, then peak clipping signal cclip,nThe set that middle serial number n belongs to the amplitude of the sampled point of p is denoted as ce, i.e. ce=| cclip,n
| | n ∈ p }, calculate ceThe mean value of middle all elements is denoted as τ.
5. inhibiting the method for the ACE of high order modulation ofdm signal peak-to-average force ratio as claimed in claim 2, which is characterized in that step
Five further comprise: using leaf transformation FFT in JN point discrete Fourier by signalAnd cclipIt is converted into frequency domain, obtains frequency domain peak clipping letter
NumberWith frequency domain peak clipping noise Cclip=[Cclip,0,Cclip,1,...,Cclip,k]T, wherein k=0,
1,...,JN-1。
6. inhibiting the method for the ACE of high order modulation ofdm signal peak-to-average force ratio as claimed in claim 2, which is characterized in that step
Six further comprise: in frequency domain to peak clipping signalPlanisphere be extended, the frequency domain peak clipping noise after being expanded
It is described in frequency domain to peak clipping signalPlanisphere be extended and include:
The first step, reservation inner constellation point, which is not done, to be extended；
Second step, apex angle constellation point are extended to the region far from planisphere center；
Third step, boundary constellation point are extended to along change in coordinate axis direction far from the region at planisphere center；
Step 7 further comprises: using leaf inverse transformation IFFT in JN point discrete Fourier by frequency domain peak clipping noiseIt is transformed into time domain
Peak clipping noiseWherein n=0,1 ..., JN-1；
Step 8 further comprises:, the peak clipping noise after extensionThe set that middle serial number n belongs to the amplitude of the sampled point of p is denoted as
I.e.It calculatesThe mean value of middle all elements is denoted as
7. inhibiting the method for the ACE of high order modulation ofdm signal peak-to-average force ratio as claimed in claim 2, which is characterized in that step
Nine further comprise: Introduced Malaria factor k utilizes the c in above-mentioned processe、τ、WithCalculate spreading coefficient μ, and to it is original when
Domain signal x is amplified, and is obtained peak-to-average force ratio and is inhibited signal
Step 10 further comprises: the signal after peak-to-average force ratio is inhibitedIt send after insertion protection interval to radio frequency amplifier HPA and emits
Into channel.
8. inhibiting the method for the ACE of high order modulation ofdm signal peak-to-average force ratio as claimed in claim 4, which is characterized in that step
Adaptive peak clipping strategy described in three is initial clipping rate to be adjusted according to the peak-to-average force ratio PAPR value of current demand signal, and then adjust and cut
Peak thresholding avoids cutting away excessive non-peak point.The relationship of the peak clipping thresholding A and clipping rate CR are as follows:
Wherein, σ is the mean power of signal x:
The clipping rate CR is adjusted by following formula:
CR=CRinit+(γ-1)·α·(ξ-ξtar)；
Wherein,
γ and η is compensation factor, and the selection of value depends on the peak-to-average ratio ξ and initial clipping rate CR of current demand signalinit；
The specific steps of the clipping operation include:
The first step is right | xn| all sampled points of > A carry out peak clipping operation, the signal after obtaining peak clipping
Wherein, n=0,1 ..., JN-1,Indicate imaginary unit, exp () is indicated using natural constant e as the index at bottom
Operation, θnFor original time domain signal xnPhase, | | be the operation of modulus value；
Second step, with the signal after peak clippingIt subtracts original time domain signal x and obtains peak clipping noise:
9. inhibiting the method for the ACE of high order modulation ofdm signal peak-to-average force ratio as claimed in claim 7, which is characterized in that step
The k of the Introduced Malaria factor described in nine, utilizes the c in above-mentioned processe、τ、WithSpreading coefficient μ is calculated, and original time domain is believed
Number x, which is amplified, includes:
1), the suitable modifying factor k of selection in [- 1,2]；
2) Least squares approximation formula, is corrected, optimization aim indicates are as follows:
Wherein, min { } expression is minimized operator,Indicate two norm operator of vector, l indicates length and vector ceOne
Sample, but element is all 1 row vector, and μ is wait seek optimal spreading coefficient；
3) the optimal spreading coefficient μ for 2) meeting optimization aim described in step, is sought:
It enables
The gradient for enabling f (μ) is zero:
Gradient algorithm is sought in wherein ▽ { } expression, then optimal spreading coefficient μ are as follows:
4), the time domain letter after peak-to-average force ratio inhibits is obtained to accelerate convergence rate with optimal spreading coefficient amplification original time domain signal x
Number
10. a kind of implement the method for the ACE of inhibition high order modulation ofdm signal peak-to-average force ratio described in claim 1-9 any one
Inhibit the system of the ACE of high order modulation ofdm signal peak-to-average force ratio.
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