CN102624669A - Mixed distribution optimization-based orthogonal frequency division multiplexing (OFDM) signal peak-to-average power ratio suppression method - Google Patents

Abstract

The invention discloses a mixed distribution optimization-based orthogonal frequency division multiplexing (OFDM) signal peak-to-average power ratio suppression method, and mainly aims to solve the problems of low compromising efficiency between peak-to-average power ratio suppression and bit error rate performance and inflexibility of a companding curve form in the prior art. The method is implemented by the following steps of: (1) performing OFDM modulation on an input bit stream, and performing up-sampling to obtain an original OFDM signal; (2) constructing a companding function on the basis of a mixed distribution optimization object; (3) performing companding transformation on the original OFDM signal, and transmitting the companding-transformed signal; (4) calculating a de-companding function, and performing de-companding transformation on the received signal; and (5) performing down-sampling on the de-companding-transformed signal, and performing OFDM demodulation to recover the original bit stream. The peak-to-average power ratio suppression and bit error rate performance can be well compromised, and different system performance values can be obtained by rationally regulating parameters, so that a wireless OFDM system can be flexibly designed, and the method can be widely applied to various new-generation broadband wireless OFDM communication systems.

Description

Ofdm signal method for inhibiting peak-to-average ratio based on mixed distribution optimization

Technical field

The invention belongs to wireless communication technology field, relate to the peak-to-average ratio PAPR inhibition method of modulating in OFDM wireless signal transmission, can be widely used in all kinds of new generation broadband OFDM wireless communication systems.

Background technology

Modulating in OFDM is a kind of multi-carrier modulation technology, because subcarrier is a quadrature, so can significantly reduce the intersymbol interference of system.Compare with single-carrier modulated, its spectrum efficiency is higher.In addition, through inserting protection at interval, OFDM can resist multipath channel better.Because these advantages, the OFDM modulation is widely used in the wireless communication system.

Yet, still exist some shortcomings not solve in the ofdm system.One of sixty-four dollar question is exactly the high peak-to-average ratio PAPR of ofdm signal.In order to guarantee the linear amplification of signal, high peak-to-average ratio PAPR forces transmit power amplifier that a big rollback must be arranged, and this has just seriously reduced the efficient of amplifier.

Non-linear companding method is a kind of effective ways that reduce ofdm signal peak-to-average ratio PAPR, as: index companding, sectional companding and trapezoidal companding etc.Tao Jiang has proposed the index companding method in " Exponential Companding Technique for PAPR Reduction in OFDM Systems "; Its basic thought is that the amplitude distribution with original ofdm signal is converted into even distribution; But; This method can make small amplitude signal and the distribution increase of signal significantly, thereby causes peak-to-average ratio PAPR and error rate BER decreased performance; Jun Hou has proposed the sectional companding method in " Peak-to-Average Power Ratio Reduction of OFDM Signals With Nonlinear Companding Scheme " for this reason; Its basic thought is the small signal amplitudes Rayleigh distributed that makes behind the companding; The large-signal whose amplitude obeys evenly distributes; Though can effectively reducing signal peak-to-average, this method compares PAPR; And error rate of system BER is also lower, but the form of its companding curve lacks flexibility, is difficult to satisfy the performance requirement of different system; Shiann-Shiun Jeng has proposed trapezoidal companding method in " Efficient PAPR Reduction in OFDM Systems Based on a Companding Technique With Trapezium Distribution " for this reason; Its basic thought is that the amplitude distribution with original ofdm signal is converted into trapezoidal profile; But; This method can make the distribution of small amplitude signal increase, thereby causes peak-to-average ratio PAPR decreased performance.

Summary of the invention

The objective of the invention is to above-mentioned existing methods not enough; A kind of ofdm signal method for inhibiting peak-to-average ratio of optimizing based on mixed distribution has been proposed; With the good compromise between picked up signal peak-to-average ratio PAPR inhibition and the error rate of system BER performance; And for the wireless OFDM system design provides higher flexibility, to satisfy the performance requirement of different system.

Realize that basic thought of the present invention is: make that the probability density function of small signal amplitudes is a power function behind the companding, and the whose amplitude obeys of large-signal is evenly distributed, its technical scheme comprises the steps:

(1) incoming bit stream is carried out modulating in OFDM, obtain original ofdm signal x through up-sampling again _n, wherein, n=0,1 ..., JN-1, J represent the up-sampling factor, N representes the subcarrier number that ofdm system comprises;

(2) structure companding function is following:

$z=\left\{\begin{array}{cc}\mathrm{sign}\left(x\right){\left\{\frac{m+1}{k}\right[1-\exp (-\frac{{\left|x\right|}^2}{{\mathrm{\σ}}^2})\left\}\right]}^{\frac{1}{m+1}},& \left|x\right|\≤\sqrt{-{\mathrm{\σ}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\\ \mathrm{sign}\left(x\right)[\frac{1-\exp (-\frac{{\left|x\right|}^2}{{\mathrm{\σ}}^2})}{k{\left(\mathrm{cA}\right)}^m}+\frac{\mathrm{mcA}}{m+1}],& \left|x\right|>\sqrt{-{\mathrm{\σ}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\end{array}\right.$

Wherein, x is the input signal of companding function, and z is the output signal of companding function, k＞0th, and power control factor, m＞0th, the power of power function, c is the transfer point factor, and A is the peak amplitude of output signal z, and σ is original ofdm signal x _nStandard variance, exp () is a natural exponential function, ln () is the natural logrithm function, sign () is-symbol function,

Be the radical sign operator, || be modulo operator, $\left|x\right|\≤\sqrt{{-\mathrm{\σ}}^2\mathrm{Ln}[1-\frac{{k\left(\mathrm{CA}\right)}^{m+1}}{m+1}]}$ The input signal x that this condition is satisfied in expression is a small-signal, $\left|x\right|>\sqrt{{-\mathrm{\σ}}^2\mathrm{Ln}[1-\frac{{k\left(\mathrm{CA}\right)}^{m+1}}{m+1}]}$ The input signal x that this condition is satisfied in expression is a large-signal;

(3) according to the peak-to-average ratio PAPR of system requirements; Interval (0; 1) selects to make the transfer point factor c of error rate of system BER minimum in; In the interval (0,3] the interior power time m that selects to make error rate of system BER minimum, find the solution peak amplitude A and the power control factor k that exports signal z according to following formula more successively:

$A=\sqrt{{3\mathrm{\σ}}^2\frac{m+3}{m+1}\frac{m(1-c)+1}{m(1-c^3)+3}}$

$k=\frac{m+1}{c^m{A}^{m+1}(m+1-\mathrm{mc})};$

(4) with companding function z to original ofdm signal x _nCarry out companding transform, obtain companding transform signal y _n:

$y_n=\left\{\begin{array}{cc}\mathrm{sign}\left(x_n\right){\left\{\frac{m+1}{k}\right[1-\exp (-\frac{{\left|x_n\right|}^2}{{\mathrm{\σ}}^2})\left\}\right]}^{\frac{1}{m+1}},& \left|x_n\right|\≤\sqrt{-{\mathrm{\σ}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\\ \mathrm{sign}\left(x_n\right)[\frac{1-\exp (-\frac{{\left|x_n\right|}^2}{{\mathrm{\σ}}^2})}{k{\left(\mathrm{cA}\right)}^m}+\frac{\mathrm{mcA}}{m+1}],& \left|x_n\right|>\sqrt{-{\mathrm{\σ}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\end{array}\right.;$

(5) companding transform signal y is calculated in definition according to peak-to-average ratio PAPR _nPeak-to-average ratio PAPR;

(6) with companding transform signal y _nBe sent to channel, after transmission, obtain receiving signal r _n:

$r_n=y_n\⊗h_n+w_n,$

Wherein,

Be the convolution algorithm symbol, h _nBe channel impulse response, w _nIt is additive white Gaussian noise;

(7) to the companding function z function of negating, it is following to obtain separating the companding function:

$x^{\′}=\left\{\begin{array}{cc}\mathrm{sign}\left(z^{\′}\right)\sqrt{{-\mathrm{\σ}}^2\ln (1-\frac{k{\left|z^{\′}\right|}^{m+1}}{m+1}),}& \left|z^{\′}\right|\≤\mathrm{cA}\\ \mathrm{sign}\left(z^{\′}\right)\sqrt{-{\mathrm{\σ}}^2\ln [1-k{\left(\mathrm{cA}\right)}^m\left(\right|z^{\′}|-\frac{\mathrm{mcA}}{m+1})]},& \left|z^{\′}\right|>\mathrm{cA}\end{array}\right.$

Wherein, z ' is an input signal of separating the companding function, and x ' is an output signal of separating the companding function;

(8) with separating companding function x ' r to received signal _nSeparate the companding conversion, obtain separating companding figure signal x ' _n:

$x_n^{\′}=\left\{\begin{array}{cc}\mathrm{sign}\left(r_n\right)\sqrt{-{\mathrm{\σ}}^2\ln (1-\frac{k{\left|r_n\right|}^{m+1}}{m+1}),}& \left|r_n\right|\≤\mathrm{cA}\\ \mathrm{sign}\left(r_n\right)\sqrt{-{\mathrm{\σ}}^2\ln [1-k{\left(\mathrm{cA}\right)}^m\left(\right|r_n|-\frac{\mathrm{mcA}}{m+1})]},& \left|r_n\right|>\mathrm{cA}\end{array}\right.;$

(9) to separating companding figure signal x ' _nCarry out down-sampling, demodulation restores bit stream through OFDM again;

(10) bit stream that restores and incoming bit stream are mated, count error rate of system BER, the error rate BER of the more approaching original ofdm system of this error rate BER, then the error rate BER performance of method for inhibiting peak-to-average ratio is good more.

The present invention has been owing to made up the companding function, and is optimized for power function to the probability density function of small signal amplitudes with this companding function, and the whose amplitude obeys of large-signal is evenly distributed, thereby compared with prior art has following advantage:

(a) can between signal peak-to-average is than PAPR inhibition and error rate of system BER performance, obtain good trading off;

(b) can higher flexibility be provided for the wireless OFDM system design.

Simulation result shows that the present invention not only can obtain good trading off between signal peak-to-average is than PAPR inhibition and error rate of system BER performance, and can higher flexibility be provided for the wireless OFDM system design.

Description of drawings

Fig. 1 is the flow chart that the present invention suppresses the ofdm signal peak-to-average ratio;

Fig. 2 is the signal amplitude distribution map of the present invention and existing companding method;

Fig. 3 is the peak-to-average ratio performance comparison diagram of the present invention and existing companding method;

Fig. 4 is the bit error rate performance comparison diagram of the present invention and existing companding method.

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are described in detail.Present embodiment is that prerequisite is implemented with technical scheme of the present invention, provided detailed execution mode and specific operation process, but protection scope of the present invention is not limited to following embodiment.

With reference to Fig. 1, concrete performing step of the present invention is following:

Step 1: incoming bit stream is carried out the OFDM modulation, obtain original ofdm signal x through up-sampling again _n, wherein, n=0,1 ..., JN-1, J represent the up-sampling factor, N representes the subcarrier number that ofdm system comprises.

Step 2: make up the companding function.

2.1) definition companding function amplitude output signal | the probability density function f of z| (| z|):

$f\left(\right|z\left|\right)=\left\{\begin{array}{cc}k{\left|z\right|}^m,& 0\&le;\left|z\right|\&le;\mathrm{cA}\\ k{\left(\mathrm{cA}\right)}^m,& \mathrm{cA}<\left|z\right|\&le;A\end{array}\right.$

Wherein, z is the output signal of companding function, k＞0th, and power control factor, m＞0th, the power of power function, c is the transfer point factor, A is the peak amplitude of output signal z, || be modulo operator;

2.2) obtain companding function amplitude output signal | the cumulative distribution function F of z| (| z|) and inverse function F ^-1(| z|):

$F\left(\right|z\left|\right)=\left\{\begin{array}{cc}\frac{k{\left|z\right|}^{m+1}}{m+1},& 0\&le;\left|z\right|\&le;\mathrm{cA}\\ k{\left(\mathrm{cA}\right)}^m\left|z\right|-\frac{\mathrm{km}{\left(\mathrm{cA}\right)}^{m+1}}{m+1},& \mathrm{cA}<\left|z\right|\&le;\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="HDA0000155980860000012.png,HDA0000155980860000021.png"\; state="\{\{state\}\}">A</figure-callout>}\\ 1,& \left|z\right|>A\end{array}\right.,$

$F^{-1}\left(\right|z\left|\right)=\left\{\begin{array}{cc}{\left[\frac{(m+1)\left|z\right|}{k}\right]}^{\frac{1}{m+1}},& \left|z\right|\&le;\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}\\ \frac{\left|z\right|}{k{\left(\mathrm{cA}\right)}^m}+\frac{\mathrm{mcA}}{m+1},& \left|z\right|>\frac{k{\left(\mathrm{cA}\right)}^{m+1}}{m+1}\end{array}\right.;$

2.3) with F (| z|) and inverse function F ^-1(| solution formula g=sign (x) F of operation result substitution companding function z|) ^-1[F (| x|)] in, obtain companding function z:

$z=\left\{\begin{array}{cc}\mathrm{sign}\left(x\right){\left\{\frac{m+1}{k}\right[1-\exp (-\frac{{\left|x\right|}^2}{{\mathrm{\&sigma;}}^2})\left\}\right]}^{\frac{1}{m+1}},& \left|x\right|\&le;\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\\ \mathrm{sign}\left(x\right)[\frac{1-\exp (-\frac{{\left|x\right|}^2}{{\mathrm{\&sigma;}}^2})}{k{\left(\mathrm{cA}\right)}^m}+\frac{\mathrm{mcA}}{m+1}],& \left|x\right|>\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\end{array}\right.$

Wherein, x is the input signal of companding function, and z is the output signal of companding function, F (| x|)=1-exp (| x| ²/ σ ²) be companding function input signal amplitude | the cumulative distribution function of x|, σ is original ofdm signal x _nStandard variance, exp () is a natural exponential function, ln () is the natural logrithm function, sign () is-symbol function,

Be the radical sign operator, || be modulo operator, $\left|x\right|\&le;\sqrt{{-\mathrm{\&sigma;}}^2\mathrm{Ln}[1-\frac{{k\left(\mathrm{CA}\right)}^{m+1}}{m+1}]}$ The input signal x that this condition is satisfied in expression is a small-signal, $\left|x\right|>\sqrt{{-\mathrm{\&sigma;}}^2\mathrm{Ln}[1-\frac{{k\left(\mathrm{CA}\right)}^{m+1}}{m+1}]}$ The input signal x that this condition is satisfied in expression is a large-signal.

Step 3: confirm the inferior m of transfer point factor c, power in the companding function, peak amplitude A and the power control factor k of output signal z.

3.1) according to the peak-to-average ratio PAPR of system requirements, selection makes the minimum transfer point factor c of error rate of system BER in interval (0,1), in the interval (0,3] the interior power time m that selects to make error rate of system BER minimum;

3.2) equate that according to the input signal x of companding function and the average power of output signal z confirm the peak amplitude A of output signal z, derivation is following:

$E\left[{\left|x\right|}^2\right]=E\left[{\left|z\right|}^2\right]$

$\&DoubleRightArrow;{\&Integral;}_0^{\&infin;}{\left|x\right|}^{2}f\left(\right|x\left|\right)d\left(\right|x\left|\right)={\&Integral;}_0^{\&infin;}{\left|z\right|}^{2}f\left(\right|z\left|\right)d\left(\right|z\left|\right)$

$\&DoubleRightArrow;{\&Integral;}_0^{\&infin;}{\left|x\right|}^2\frac{2\left|x\right|}{{\mathrm{\&sigma;}}^2}\exp (-\frac{{\left|x\right|}^2}{{\mathrm{\&sigma;}}^2})d\left(\right|x\left|\right)={\&Integral;}_0^{\mathrm{cA}}{\left|z\right|}^{2}k{\left|z\right|}^{m}d\left(\right|z\left|\right)+{\&Integral;}_{\mathrm{cA}}^A{\left|z\right|}^{2}k{\left(\mathrm{cA}\right)}^{m}d\left(\right|z\left|\right),$

$\&DoubleRightArrow;{\mathrm{\&sigma;}}^2=\frac{{\mathrm{kc}}^m{A}^{m+3}}{3}(1-\frac{{\mathrm{mc}}^3}{m+3})$

$\&DoubleRightArrow;A=\sqrt{{3\mathrm{\&sigma;}}^2\frac{m+3}{m+1}\frac{m(1-c)+1}{m(1-c^3)+3}}$

Wherein, E [| x| ²] be the average power of input signal x, E [| z| ²] be the average power of output signal z, E [] is the expectation operator, $f\left(\right|x\left|\right)=\frac{2\left|x\right|}{{\mathrm{\&sigma;}}^2}\mathrm{Exp}(-\frac{{\left|x\right|}^2}{{\mathrm{\&sigma;}}^2})$ Be companding function input signal amplitude | the probability density function of x|;

3.3) by cumulative distribution function F (| character F z|) (A)=1 available power controlling elements k:

$k=\frac{m+1}{c^m{A}^{m+1}(m+1-\mathrm{mc})}.$

Step 4: with companding function z to original ofdm signal x _nCarry out companding transform, promptly be optimized for power function to the probability density function of small signal amplitudes, and the whose amplitude obeys of large-signal is evenly distributed, obtain companding transform signal y _n:

$y_n=\left\{\begin{array}{cc}\mathrm{sign}\left(x_n\right){\left\{\frac{m+1}{k}\right[1-\exp (-\frac{{\left|x_n\right|}^2}{{\mathrm{\&sigma;}}^2})\left\}\right]}^{\frac{1}{m+1}},& \left|x_n\right|\&le;\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\\ \mathrm{sign}\left(x_n\right)[\frac{1-\exp (-\frac{{\left|x_n\right|}^2}{{\mathrm{\&sigma;}}^2})}{k{\left(\mathrm{cA}\right)}^m}+\frac{\mathrm{mcA}}{m+1}],& \left|x_n\right|>\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\end{array}\right..$

Step 5: the defined formula according to peak-to-average ratio PAPR calculates companding transform signal y _nPeak-to-average ratio PAPR, promptly signal peak-to-average is than the average power of the peak power/signal of PAPR=signal, with result of calculation and original ofdm signal x _nPeak-to-average ratio PAPR compare, peak-to-average ratio PAPR is low more, shows that then the inventive method is to original ofdm signal x _nThe inhibition effect of peak-to-average ratio PAPR good, as shown in Figure 3 more.

Step 6: with companding transform signal r _nBe sent to channel, after transmission, obtain receiving signal r _n:

$r_n=y_n\&CircleTimes;h_n+w_n,$

Wherein,

Be the convolution algorithm symbol, h _nBe channel impulse response, w _nIt is additive white Gaussian noise.

Step 7: to the function of negating of the companding function z in the step 2, it is following to obtain separating the companding function:

$x^{\&prime;}=\left\{\begin{array}{cc}\mathrm{sign}\left(z^{\&prime;}\right)\sqrt{{-\mathrm{\&sigma;}}^2\ln (1-\frac{k{\left|z^{\&prime;}\right|}^{m+1}}{m+1}),}& \left|z^{\&prime;}\right|\&le;\mathrm{cA}\\ \mathrm{sign}\left(z^{\&prime;}\right)\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-k{\left(\mathrm{cA}\right)}^m\left(\right|z^{\&prime;}|-\frac{\mathrm{mcA}}{m+1})]},& \left|z^{\&prime;}\right|>\mathrm{cA}\end{array}\right.$

Wherein, z ' is an input signal of separating the companding function, and x ' is an output signal of separating the companding function.

Step 8: with separating companding function x ' r to received signal _nSeparate the companding conversion, promptly use this r _nSubstitute the input signal z ' that separates the companding function, obtain separating companding figure signal x ' _n:

$x_n^{\&prime;}=\left\{\begin{array}{cc}\mathrm{sign}\left(r_n\right)\sqrt{-{\mathrm{\&sigma;}}^2\ln (1-\frac{k{\left|r_n\right|}^{m+1}}{m+1}),}& \left|r_n\right|\&le;\mathrm{cA}\\ \mathrm{sign}\left(r_n\right)\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-k{\left(\mathrm{cA}\right)}^m\left(\right|r_n|-\frac{\mathrm{mcA}}{m+1})]},& \left|r_n\right|>\mathrm{cA}\end{array}\right..$

Step 9: to separating companding figure signal x ' _nCarry out down-sampling, demodulation restores bit stream through OFDM again.

Step 10: bit stream that restores and incoming bit stream are mated; Promptly be judged to identical bit in the bit stream that restores and the incoming bit stream correctly; Different bits are judged to error code, count error rate of system BER, the error rate BER of the more approaching original ofdm system of this error rate BER; Then the error rate BER performance of method for inhibiting peak-to-average ratio is good, as shown in Figure 4 more.

Above-mentioned steps has been described preferred embodiment of the present invention, and obviously the researcher of this area can make various modifications and replacement to the present invention with reference to preferred embodiment of the present invention and accompanying drawing, and these modifications and replacement all should fall within protection scope of the present invention.

Effect of the present invention can be described further through emulation.

1) simulated conditions: in modulating in OFDM, chooser carrier wave number is 1024, and selecting modulation mode is the QPSK modulation; Transmission channel adopts rician fading channel, and channel does not carry out encoding process.

2) emulation content and result:

Emulation 1 is carried out companding transform with the present invention and existing companding method to original ofdm signal, and the signal amplitude of its acquisition distributes as shown in Figure 2, and peak-to-average ratio PAPR performance is as shown in Figure 3.

Emulation 2 is separated the companding conversion to received signal with the present invention and existing companding method, and the error rate BER performance of its acquisition is as shown in Figure 4.

Visible by Fig. 2, compare with the trapezoidal companding method of exponential sum, the present invention has reduced the distribution of its small amplitude signal, therefore can improve its PAPR performance.

Visible by Fig. 3 and Fig. 4; The present invention can obtain good trading off between signal peak-to-average is than PAPR inhibition and error rate of system BER performance; And can obtain different systematic functions, thereby higher flexibility is provided for the wireless OFDM system design through reasonable adjustment parameter.

Claims (2)

1. wireless OFDM ofdm signal method for inhibiting peak-to-average ratio of optimizing based on mixed distribution may further comprise the steps:

(1) incoming bit stream is carried out modulating in OFDM, obtain original ofdm signal x through up-sampling again _n, wherein, n=0,1 ..., JN-1, J represent the up-sampling factor, N representes the subcarrier number that ofdm system comprises;

(2) structure companding function is following:

$z=\left\{\begin{array}{cc}\mathrm{sign}\left(x\right){\left\{\frac{m+1}{k}\right[1-\exp (-\frac{{\left|x\right|}^2}{{\mathrm{\&sigma;}}^2})\left\}\right]}^{\frac{1}{m+1}},& \left|x\right|\&le;\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\\ \mathrm{sign}\left(x\right)[\frac{1-\exp (-\frac{{\left|x\right|}^2}{{\mathrm{\&sigma;}}^2})}{k{\left(\mathrm{cA}\right)}^m}+\frac{\mathrm{mcA}}{m+1}],& \left|x\right|>\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\end{array}\right.$

Wherein, x is the input signal of companding function, and z is the output signal of companding function, k＞0th, and power control factor, m＞0th, the power of power function, c is the transfer point factor, and A is the peak amplitude of output signal z, and σ is original ofdm signal x _nStandard variance, exp () is a natural exponential function, ln () is the natural logrithm function, sign () is-symbol function,

Be the radical sign operator, || be modulo operator, $\left|x\right|\&le;\sqrt{{-\mathrm{\&sigma;}}^2\mathrm{Ln}[1-\frac{{k\left(\mathrm{CA}\right)}^{m+1}}{m+1}]}$ The input signal x that this condition is satisfied in expression is a small-signal, $\left|x\right|>\sqrt{{-\mathrm{\&sigma;}}^2\mathrm{Ln}[1-\frac{{k\left(\mathrm{CA}\right)}^{m+1}}{m+1}]}$ The input signal x that this condition is satisfied in expression is a large-signal;

(3) according to the peak-to-average ratio PAPR of system requirements; Interval (0; 1) selects to make the transfer point factor c of error rate of system BER minimum in; In the interval (0,3] the interior power time m that selects to make error rate of system BER minimum, find the solution peak amplitude A and the power control factor k that exports signal z according to following formula more successively:

$A=\sqrt{{3\mathrm{\&sigma;}}^2\frac{m+3}{m+1}\frac{m(1-c)+1}{m(1-c^3)+3}}$

$k=\frac{m+1}{c^m{A}^{m+1}(m+1-\mathrm{mc})};$

(4) with companding function z to original ofdm signal x _nCarry out companding transform, obtain companding transform signal y _n:

$y_n=\left\{\begin{array}{cc}\mathrm{sign}\left(x_n\right){\left\{\frac{m+1}{k}\right[1-\exp (-\frac{{\left|x_n\right|}^2}{{\mathrm{\&sigma;}}^2})\left\}\right]}^{\frac{1}{m+1}},& \left|x_n\right|\&le;\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\\ \mathrm{sign}\left(x_n\right)[\frac{1-\exp (-\frac{{\left|x_n\right|}^2}{{\mathrm{\&sigma;}}^2})}{k{\left(\mathrm{cA}\right)}^m}+\frac{\mathrm{mcA}}{m+1}],& \left|x_n\right|>\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-\frac{{k\left(\mathrm{cA}\right)}^{m+1}}{m+1}]}\end{array}\right.;$

(5) companding transform signal y is calculated in definition according to peak-to-average ratio PAPR _nPeak-to-average ratio PAPR;

(6) with companding transform signal y _nBe sent to channel, after transmission, obtain receiving signal r _n:

$r_n=y_n\&CircleTimes;h_n+w_n,$

Wherein,

Be the convolution algorithm symbol, h _nBe channel impulse response, w _nIt is additive white Gaussian noise;

(7) to the companding function z function of negating, it is following to obtain separating the companding function:

$x^{\&prime;}=\left\{\begin{array}{cc}\mathrm{sign}\left(z^{\&prime;}\right)\sqrt{{-\mathrm{\&sigma;}}^2\ln (1-\frac{k{\left|z^{\&prime;}\right|}^{m+1}}{m+1}),}& \left|z^{\&prime;}\right|\&le;\mathrm{cA}\\ \mathrm{sign}\left(z^{\&prime;}\right)\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-k{\left(\mathrm{cA}\right)}^m\left(\right|z^{\&prime;}|-\frac{\mathrm{mcA}}{m+1})]},& \left|z^{\&prime;}\right|>\mathrm{cA}\end{array}\right.$

Wherein, z ' is an input signal of separating the companding function, and x ' is an output signal of separating the companding function;

(8) with separating companding function x ' r to received signal _nSeparate the companding conversion, obtain separating companding figure signal x ' _n:

$x_n^{\&prime;}=\left\{\begin{array}{cc}\mathrm{sign}\left(r_n\right)\sqrt{-{\mathrm{\&sigma;}}^2\ln (1-\frac{k{\left|r_n\right|}^{m+1}}{m+1}),}& \left|r_n\right|\&le;\mathrm{cA}\\ \mathrm{sign}\left(r_n\right)\sqrt{-{\mathrm{\&sigma;}}^2\ln [1-k{\left(\mathrm{cA}\right)}^m\left(\right|r_n|-\frac{\mathrm{mcA}}{m+1})]},& \left|r_n\right|>\mathrm{cA}\end{array}\right.;$

(9) to separating companding figure signal x ' _nCarry out down-sampling, demodulation restores bit stream through OFDM again;

(10) bit stream that restores and incoming bit stream are mated, count error rate of system BER, the error rate BER of the more approaching original ofdm system of this error rate BER, then the error rate BER performance of method for inhibiting peak-to-average ratio is good more.

2. method according to claim 1, wherein step (9) is said matees bit stream that restores and incoming bit stream, is identical bit in the bit stream that restores and the incoming bit stream is judged to correctly, and different bits are judged to error code.

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