CN103441769A - PTS method for reducing PAPR of OFDM system - Google Patents

Abstract

The invention belongs to the technical field of wireless communication, and particularly relates to a PTS method for reducing the PAPR of an OFDM system. After an OFDA signal is partitioned, autocorrelation with different autocorrelation coefficients is respectively added according to the plus or minus characteristic of a first data point real part of each piece, so that the aims that the PAPR of the OFDM signal is reduced and a receiving end detects the signal without sideband auxiliary information are achieved. The receiving end recovers a correlation coefficient according to the plus and minus characteristic of an autocorrelation value of each piece, a piece signal without autocorrelation and the autocorrelation coefficient corresponding to the piece signal are multiplied, and the phase rotation sequence timing the piece is judged according to the plus and minus characteristic of a product. The receiving end can recover an original signal without the sideband auxiliary information while the PAPR of the OFDM signal is effectively reduced through the self-correlation matching-PTS, so that band width is saved, and frequency spectrum utilization efficiency is effectively improved.

Description

A kind of PTS method that reduces the PAPR of ofdm system

Technical field

The invention belongs to wireless communication technology field, be specifically related to a kind of PTS method that reduces the PAPR of ofdm system.

Background technology

OFDM (Orthogonal Frequency Division Multiplexing, OFDM) be a kind of multi-carrier modulation technology of superior performance, because of its can effectively resist intersymbol interference (Inter-symbol Interference, ISI) and multidiameter delay in widespread attention.Exist the subcarrier of a plurality of quadratures in ofdm system, its output signal is the stack of a plurality of subsignals, thereby there will be very high peak-to-average power ratio (Peak-to-average Power Ratio, PAPR).High PAPR can cause the out-of-band power radiation, the hardware nonlinear distortion, and the phase mutual interference between subcarrier etc., make the systematic function severe exacerbation.Therefore, the PAPR of reduction ofdm system has very important meaning.

The method that reduces at present ofdm system PAPR is broadly divided into three classes: signal predistortion technology, coding class methods and probability class methods.The probability class methods are emphasis of studying at present.The inreal peak power that reduces ofdm signal of probability class methods, but by original ofdm signal being implemented to the purpose that linear partition or linear transformation reach reduction high-peak power probability of occurrence.The probability class methods comprise a lot of algorithms, as tone reservation (Tone Reservation, TR), selectivity mapping (Selective Mapping, SLM), partial transmission sequence (Partial Transmit Sequence, PTS) etc.In order to recover primary signal at receiving terminal, the PTS Technology Need transmits the secondary information of certain sideband, and this has just reduced the spectrum utilization efficiency of system.In order exactly the secondary information of sideband to be recovered at receiving terminal, usually can adopt extra technology to process the secondary information of sideband as coding techniques, this may cause the rising again of system PAPR, and has further reduced again the availability of frequency spectrum of system.Autocorrelation matching in this paper-PTS method is in effective reduction system PAPR, by the Information Embedding of the rotatable phase factor in the middle of the autocorrelation of signal, transmission without the secondary information of sideband just can realize the recovery of signal, has greatly improved spectrum utilization efficiency.

Summary of the invention

The object of the present invention is to provide a kind of PTS method that reduces the PAPR of ofdm system, the discriminant information of rotatable phase sequence is implanted in the middle of the autocorrelation of signal, just primary signal can be recovered without the secondary information of transmission sideband, improve spectrum utilization efficiency.

The objective of the invention is to be achieved through the following technical solutions:

S1, the frequency-region signal of establishing after serial to parallel conversion and baseband modulation are X, according to the division rule of conventional P TS, it are divided into to V sub-block X ^(m), wherein, m=1,2 ..., V, then pass through the auto-correlation coefficient arbiter by all sub-blocks, judges coefficient correlation G (z);

S2, the auto-correlation coefficient G (z) that S1 is determined and the described all sub-blocks of S1 by the autocorrelation signal generator, obtain auto-correlation frequency domain sub-block signal together;

S3, S2 gained auto-correlation frequency domain sub-block signal is carried out to the IFFT conversion, frequency domain auto-correlation sub-block signal is transformed to time domain, all sub-block signals after conversion are multiplied by respectively phase rotation coefficient b (m), b (m) ∈ (+1 ,-1), m=1,2,, V, suppose that time domain frequency domain sub-block signal is

by b (m) with

multiply each other and can obtain alternative transfer sequence

S4, according to the PAPR computing formula, calculate each alternative transfer sequence

pAPR, and select the signal of wherein minimum PAPR minimum

for transmission;

S5, suppose that the signal of receiving at receiving terminal is y,

y is carried out to the FFT operation, be transformed into frequency-region signal;

S6, according to the described partitioned mode of S1, y is carried out to piecemeal, be divided into V sub-block, each sub-block is expressed as Y ^(m), m=1,2 ..., V, to Y ^(m)carry out auto-correlation computation, recover the rotatable phase that auto-correlation coefficient and each sub-block are taken advantage of, the signal after the autocorrelation that is eliminated 1≤i≤V, described auto-correlation computation rule is, if the autocorrelation value of a sub-block for just, the auto-correlation coefficient of this sub-block reverts to k (k>0); If its autocorrelation value is negative, revert to-k of the autocorrelation value of this sub-block (k>0);

S7, by the S6 gained

with this

corresponding rotatable phase

1≤i≤V multiplies each other, and obtains final each sub-block signal recovered, and by each sub-block signal plus of described final recovery, obtains the final data block Y recovered ^*,

S8, to S7 gained Y ^*carry out base band demodulating and parallel serial conversion, the signal that obtains finally recovering.

Further, the number of the described alternative transfer sequence of S3 is n=2 ^v-1.

The invention has the beneficial effects as follows: be after the ofdm signal piecemeal, according to the positive and negative different autocorrelation of auto-correlation coefficient that adds respectively of first data point real part of each sub-block, with this, reach and reduce ofdm signal PAPR and the receiving terminal purpose without the secondary information detection signal of sideband.The positive and negative auto-correlation coefficient that recovers at receiving terminal according to each sub-block autocorrelation value, and the sub-block signal auto-correlation coefficient corresponding with it that will eliminate after autocorrelation multiply each other, according to the positive and negative phase rotating sequence that judges that this sub-block is taken advantage of of product.Autocorrelation matching-PTS, when effectively reducing ofdm signal PAPR, can recover primary signal at receiving terminal without the secondary information of sideband, has saved bandwidth, has effectively improved spectrum utilization efficiency.

The accompanying drawing explanation

The system block diagram that Fig. 1 is PTS-OFDM.

Fig. 2 is autocorrelation matching-PTS system block diagram.

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described:

A typical ofdm signal can be expressed as follows:

wherein, the number that N is the ofdm system sub-carriers, X (n) is the frequency domain data that n subcarrier uploaded defeated process baseband modulation, f _nbe the frequency of n subcarrier, the cycle that T is an OFDM symbol.

The PAPR of signal is defined as the instantaneous peak value power of signal and the ratio of average power:

$\mathrm{PAPR}=\frac{\max \left\{{\left|x\left(t\right)\right|}^2\right\}}{E\left\{{\left|x\left(t\right)\right|}^2\right\}}$

The dB of take rewrites during as unit as follows:

wherein, | x (t) | ²the instantaneous power that means signal, max[] the expression maximizing, E[] mean to average.

Use traditionally CCDF (Complementary Cumulative Distribution Function, CCDF) weigh the PAPR distribution situation in ofdm system, in all PAPR sampled values, be greater than the probability sum of the part sampled value appearance of threshold value: P{PAPR z}=1-P{PAPR≤z}=1-(1-e ^-z) ⁿ, wherein, z means the threshold value of PAPR.Can find out, number of sub carrier wave N is larger, and P (PAPR>z) is just larger.

As shown in Figure 1, N subcarrier in OFDM data is divided into V sub-block X to traditional PTS technology ^(m), m=1,2 ..., V.Division rule is as follows; The first, each sub-block vector length equates; The second, for each sub-block, the position that is not divided into the former OFDM symbolic information in this piece supplements 0.Each sub-block includes the data of different frequent points in N/V X.

In traditional PTS method, it is X=[X (0) that X is expressed as vector form, X (1) ..., X (N-1)], X can be divided into V sub-block according to random, adjacent, the three kinds of division rules that interweave, and each sub-block is expressed as to X ^(m), m=1,2 ..., V, X can be expressed as:

then each sub-block external reservoir is with suitable phase rotation coefficient, and selects one group and make to transmit and have the phase factor of minimum peak-to-average power ratio

wherein, b (m), m=1,2 ..., V is phase rotation coefficient, b (m)=exp (j φ (m)) m=1, and 2 ..., V.Especially, when the rotatable phase factor is restricted to b (m) ∈ (+1 ,-1), m=1,2 ..., during V, can obtain U=2 ^v-1individual alternative transfer sequence, and the ratio number of the secondary information of sideband that need to transmit is specially for log ₂u=log ₂2 ^v-1=V-1.

Time-domain signal is obtained through inverse fast fourier transform (Inverse Fast Fourier Transform, IFFT) by frequency-region signal: $\hat{x}=\mathrm{IFFT}\left(\underset{m=1}{\overset{v}{\mathrm{\Σ}}}b\left(m\right)X^{\left(m\right)}\right)=\underset{m=1}{\overset{v}{\mathrm{\Σ}}}b\left(m\right)*\mathrm{IFFT}\left(X^{\left(m\right)}\right)=\underset{m=1}{\overset{v}{\mathrm{\Σ}}}b\left(m\right)x^{\left(m\right)}$ According to $\mathrm{PAPR}\left(\mathrm{dB}\right)=10\log 10\frac{\max \left\{{\left|x\left(t\right)\right|}^2\right\}}{E\left\{\right|{x\left(t\right)|}^2\}}$ Calculate respectively the PAPR of each alternative signal, select the signal of PAPR minimum wherein for transmission, and the secondary information of sideband of the phase rotating of transmission identification simultaneously sequence.

The system block diagram of the autocorrelation matching that the present invention proposes-PTS method as shown in Figure 2.Suppose that the frequency-region signal after serial to parallel conversion and baseband modulation is X, according to the division rule of conventional P TS, it is divided into to V sub-block, X ^(m), m=1,2 ..., V.Then all sub-blocks are passed through to the auto-correlation coefficient arbiter.The auto-correlation coefficient arbiter is according to the positive and negative auto-correlation coefficient of determining this sub-block of first data point real part in each sub-block, if its real part is for just, the auto-correlation coefficient of this sub-block is judged to be α=k, (k>0), otherwise, the auto-correlation coefficient of this sub-block differentiate for α=-k, (k>0).

In the present invention, the transfer function of autocorrelation signal generator used is: G (z)=1+ α ^*z ^-1, wherein, z ^-1transfer operation backward, as z ^-1s (t)=s (t-1).By the autocorrelation signal generator, obtain autocorrelative frequency domain sub-block signal together with the coefficient correlation that all sub-blocks are judged with the auto-correlation coefficient arbiter.Then we are processed autocorrelative frequency domain sub-block signal by the subsequent treatment after conventional P TS method piecemeal.At first, by IFFT, convert frequency domain auto-correlation sub-block signal is transformed to time domain, then each sub-block is multiplied by respectively phase rotation coefficient.Now we limit b (m) ∈ (+1 ,-1), m=1, and 2 ..., V, so, according to the analysis to conventional P TS method, we can obtain U=2 ^v-1individual alternative signal transmission.Foundation

| x (t) | ²the instantaneous power that means signal, max[] the expression maximizing, E[] mean to average, the PAPR of signal is defined as the instantaneous peak value power of signal and the ratio of average power:

$\mathrm{PAPR}=\frac{\max \left\{{\left|x\left(t\right)\right|}^2\right\}}{E\left\{{\left|x\left(t\right)\right|}^2\right\}}$

The dB of take rewrites during as unit as follows:

$\mathrm{PAPR}\left(\mathrm{dB}\right)=10\log 10\frac{\max \left\{{\left|x\left(t\right)\right|}^2\right\}}{E\left\{\right|{x\left(t\right)|}^2\}}$

Calculate respectively the PAPR of each alternative signal transmission, and select the wherein signal of PAPR minimum

for transmission.We implicitly are implanted to the information of rotatable phase sequence in the middle of the autocorrelation of signal, therefore do not need to transmit the secondary information of sideband, have saved bandwidth, have improved spectrum utilization efficiency.

Suppose that the signal received at receiving terminal is y, it can be expressed as

receive signal through after the FFT operation, be transformed into frequency-region signal.

To receive division of signal according to the partitioned mode identical with transmitting terminal is that V sub-block is expressed as Y by each sub-block ^(m), m=1,2 ..., V Y can be expressed as:

then, each sub-block, by the autocorrelation signal adaptation, is done respectively to auto-correlation computation to each sub-block signal, the rotatable phase of being taken advantage of to recover auto-correlation coefficient and each sub-block.The recovery of auto-correlation coefficient rule is as follows: if the autocorrelation value of a sub-block for just, the auto-correlation coefficient of this sub-block reverts to k (k>0); If its autocorrelation value is negative, revert to-k of the autocorrelation value of this sub-block (k>0).Each sub-block signal Y that then will recover _i, 1≤i≤V and its corresponding auto-correlation coefficient recovered 1≤i≤V is in the lump by autocorrelation signal inverse transformation generator, and the signal after autocorrelation is eliminated in passable arriving

1≤i≤V.

And then, eliminated autocorrelation each sub-block signal afterwards

1≤i≤V and its corresponding auto-correlation coefficient

1≤i≤V is simultaneously by the rotatable phase arbiter.Rotatable phase decision rule corresponding to each sub-block is as follows: by the auto-correlation coefficient of each sub-block

1≤i≤V and this sub-block signal

the real part of first data point in 1≤i≤V multiplies each other, if product is greater than 0, and rotatable phase sequence corresponding to this sub-block

1≤i≤V is+1; Otherwise

1≤i≤V is-1.

Afterwards, each sub-block signal of autocorrelation will have been eliminated

the rotatable phase that 1≤i≤V is corresponding with it

1≤i≤V multiplies each other, and can obtain final each sub-block signal recovered, and then by each sub-block signal plus, just obtains the final data block Y recovered ^*,

pass through again base band demodulating and parallel serial conversion, the signal that just can obtain finally recovering.

Claims (2)

1. a PTS method that reduces the PAPR of ofdm system, it is characterized in that: its step is as described below:

S1, the frequency-region signal of establishing after serial to parallel conversion and baseband modulation are X, according to the division rule of conventional P TS, it are divided into to V sub-block X ^(m), wherein, m=1,2 ..., V, then pass through the auto-correlation coefficient arbiter by all sub-blocks, judges coefficient correlation G (z);

S2, the auto-correlation coefficient G (z) that S1 is determined and the described all sub-blocks of S1 by the autocorrelation signal generator, obtain auto-correlation frequency domain sub-block signal together;

S3, S2 gained auto-correlation frequency domain sub-block signal is carried out to the IFFT conversion, frequency domain auto-correlation sub-block signal is transformed to time domain, all sub-block signals after conversion are multiplied by respectively phase rotation coefficient b (m), b (m) ∈ (+1 ,-1), m=1,2,, V, suppose that time domain frequency domain sub-block signal is

by b (m) with

multiply each other and can obtain alternative transfer sequence

S4, according to the PAPR computing formula, calculate each alternative transfer sequence

pAPR, and select the signal of wherein minimum PAPR minimum for transmission;

S5, suppose that the signal of receiving at receiving terminal is y,

y is carried out to the FFT operation, be transformed into frequency-region signal;

S6, according to the described partitioned mode of S1, y is carried out to piecemeal, be divided into V sub-block, each sub-block is expressed as Y ^(m), m=1,2 ..., V,

to Y ^(m)carry out auto-correlation computation, recover the rotatable phase that auto-correlation coefficient and each sub-block are taken advantage of, the signal after the autocorrelation that is eliminated

1≤i≤V, described auto-correlation computation rule is, if the autocorrelation value of a sub-block for just, the auto-correlation coefficient of this sub-block reverts to k (k>0); If its autocorrelation value is negative, revert to-k of the autocorrelation value of this sub-block (k>0);

S7, by the S6 gained

with this

corresponding rotatable phase

1≤i≤V multiplies each other, and obtains final each sub-block signal recovered, and by each sub-block signal plus of described final recovery, obtains the final data block Y recovered ^*,

S8, to S7 gained Y ^*carry out base band demodulating and parallel serial conversion, the signal that obtains finally recovering.

2. a kind of PTS method that reduces the PAPR of ofdm system according to claim 1, it is characterized in that: the number of the described alternative transfer sequence of S3 is n=2 ^v-1.

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