CN1984110B - Method for decreasing peak equilibrium ratio and orthogonal frequency division multiplexing system - Google Patents

Abstract

This invention relates to a method to reduce the peak-to-average and orthogonal frequency division multisystem with low peak-to-average, the core of the invention is: before anti-Fourier IFFT transform, the transmitter completely removes or retains part of the initial phase of modulated transmit sequence, and add the transfer function; the receiver removes the transfer function obtained after fast Fourier FFT transform in the frequency domain sequences, carry through the initial phase processing to the frequency domain sequences removed the transfer function, then resume to this transmit sequence. The invention only does N times complex multiplication when adding the transfer function, so it can reduce the implementation complexity of the transmitter and receiver under the premise to effectively reduce peak-to-average. In addition, through the use of this method of keeping part initial phase of transmit sequence by multiply initial phase of transmit sequence with phase factor, the source do not need to send any redundant information like side band information, therefore further lower the implementation complexity of transmitter and receiver.

Description

Reduce the method and ofdm system of peak-to-average force ratio with low peak average ratio

Technical field

The present invention relates to wireless communication field, relate in particular to based on OFDM (OrthogonalFrequency Division Multiplexing, OFDM) technology of technology reduction peak-to-average force ratio.

Background technology

Development along with mobile communication business, various multimedia services continue to bring out, the OFDM technology is applied in digital audio broadcasting (DAB), digital video broadcasting (DVB), ADSL (Asymmetric Digital Subscriber Line) (ADSL), wireless lan (wlan) based on IEEE802.11 and 802.16 standards, and becomes the main candidate technologies of 4G.

The OFDM technology is a kind of multi-carrier broadband digital modulation technique.It is divided into the experimental process bit stream with data flow, makes each sub data flow have lower transmission bit rate, and utilizes these data diffluences to modulate several quadrature carriers.The message transmission rate of each subcarrier after modulated is relatively low, and code-element period is longer, as long as the time delay expansion is compared less than certain ratio with code-element period, just can not produce intersymbol interference.In addition, the OFDM technology owing to the time-frequency orthogonality of having utilized signal allow each sub-channel spectra have 1/2 overlapping, make the availability of frequency spectrum improve nearly one times with respect to single carrier transmitting system.When a certain frequency range produced decline in the transmission channel, affected was those modulated carrier signals that fall into this frequency range, and the modulated carrier signal of other frequency range is unaffected.The ofdm system of employing OFDM technology is compared with traditional single carrier transmitting system (as time division multiple access TDMA) has tangible anti-multipath interference performance, also can form single frequency network, thereby be particularly suitable for the requirement of terrestrial broadcasting channel, can also realize the purpose that reduces cost with digital signal processor (DSP) chip.

The block diagram of ofdm system as shown in Figure 1, it comprises transmitter 100 and receiver 150.Transmitter 100 comprises channel encoder 102, sign map unit 104, deserializer 106, frequency pilot sign inserter 108, unit 114, D/A converter 116, radio frequency unit 118 are at interval protected in inverse-Fourier transform (IFFT) unit 110, parallel-to-serial converter 112, insertion fast.

Channel encoder 102 receives the input data, and the input data are carried out sending into sign map unit 104 after the chnnel coding.Chnnel coding can adopt the form of RS sign indicating number, convolution code, TURBO sign indicating number or LDPC sign indicating number or the cascade of multiple sign indicating number.

Sign map unit 104 code stream of self-channel encoder 102 in the future shines upon the symbol that forms after modulating according to predetermined constellation mapping mode, delivers in the deserializer 106.The constellation mapping mode includes but not limited to following several: BPSK, QPSK, 16QAM, 64QAM.

Each subcarrier of ofdm system can use different modulation according to the condition of channel, is criterion with the optimum balance between the availability of frequency spectrum and the error rate.The best modulation system that certain error rate is satisfied in selection can obtain maximum spectral efficiency.The frequency selective attenuation meeting of multipath channel causes received signal power to decline to a great extent, and uses the modulation system that is complementary with signal to noise ratio can improve the availability of frequency spectrum.As everyone knows, whether good reliability be communication system operation important performance assessment criteria, so system selects BPSK or QPSK modulation usually, can guarantee that like this system also can obtain good performance under the channel worst case.But the spectrum efficiency of these two kinds of modulation is too low.If the use Adaptive Modulation, terminal just can be used higher modulation when channel is good so, and the availability of frequency spectrum of whole system is significantly improved, and self adaptation can make power system capacity significantly increase.

Deserializer 106 is converted to parallel modulation symbol with the serial modulation symbol.The output parallel data is in frequency pilot sign inserter 108.

Pilot tone inserter 108 inserts frequency pilot sign in parallel modulation symbol, output to IFFT unit 110 then.

N point IFFT computing is carried out in IFFT unit 110, finishes the multi-carrier orthogonal modulation, and dateout is in parallel-to-serial converter 112.

The parallel data of parallel-to-serial converter 112 after with the IFFT conversion is converted to serial data and is transported to and inserts protection at interval in the unit 114.

Insert protection and insert corresponding protection at interval for each symbol in unit 114 at interval, dateout is in D/A converter 116.As long as protection greater than the maximum delay expansion of channel, just can be avoided the intersymbol interference (ISI) that is brought by multipath at interval.Inserting protection concrete mode at interval can be that 0 mode is inserted in employing entirely, but this mode can cause interchannel interference (ICI).Another kind of mode is to adopt the mode of Cyclic Prefix or cyclic suffix.The method of inserting Cyclic Prefix (Cyclic Prefix) is exactly the repetition numerical value that adds this symbol back segment of certain-length before each symbol.

D/A converter 116 converts digital signal to analog signal, delivers to radio frequency unit 118.

Radio frequency unit 118 comprises a formed filter and front end unit, and Analog signals is launched signal by antenna then.

Receiver comprises radio frequency unit 152, A/D converter 154, lock unit 156, frequency offset correction unit 158, unit 160, deserializer 162, FFT unit 164, frequency pilot sign withdrawal device 166, channel estimating unit 168, parallel-to-serial converter 170, symbol remove map unit 172, channel decoder 174 at interval to go protection.Receiver processing procedure fundamental sum transmitter is opposite, is not described in detail here.

A major defect of ofdm system is exactly that (promptly the instantaneous value of the output signal of OFDM transmitter has bigger fluctuation for Peak toAverage Power Ratio, PAPR) too high problem for peak power and average power ratio.This is because OFDM is the stack of a plurality of sine waves, and when the subcarrier number arrived to a certain degree more, by central-limit theorem, OFDM symbol waveform was a Gaussian random process.Its envelope is inconstant like this.This just requires parts such as power amplifier, A/D, D/A converter to have the very big range of linearity.And the non-linear meeting of these parts produces nonlinear distortion to signal conversely, thereby causes the raising of the error rate and the increase of band external leakage.Thereby cause the whole system performance decrease.Therefore, systematic function be improved, PAPR will be managed to reduce.

In ofdm system, the method that typically reduces PAPR comprises slicing, selects mapping (SLM), part transmission sequence (PTS) coding method etc.

The prior art one relevant with the present invention proposed the simplest method of the simplest a kind of reduction PAPR, and its core is: the peak amplitude by the restriction ofdm signal reduces PAPR.Its basic principle is: at signal through before the amplifier, directly the ofdm signal amplitude peak or near the employing nonlinear operation reduce PAPR value, make its dynamic change scope that can not exceed amplifier, thereby avoid the appearance of PAPR greatly.Briefly, can think to allow former ofdm signal by a rectangular window function, the amplitude of this window is the maximum amplitude of signal.

In ofdm system, because the probability that big peak value occurs is very little, therefore adopt the method for prior art one can be very directly, effectively reduce PAPR, yet amplitude limit is a non-linear process, from the angle of signal processing, the introducing of rectangular window will inevitably exert an influence to the frequency spectrum of original signal, causes distorted signals easily, thereby will cause disturbing in the serious band and the outer interference of band, and then cause the reduction and the band external leakage of the bit error rate performance of whole system.

The prior art two relevant with the present invention proposed the technology of another kind of reduction PAPR, its core is: reduce PAPR by the method for selecting mapping (SLM), the principle of this method is at transmitting terminal, produce M earlier and add up independently random sequence r1, r2 ..., rM, after doing XOR with former sequence respectively then, M different sequence of output selected transmitting of PAPR minimum at last from each road modulation signal.

By prior art two as can be seen, there is following defective in it:

1, needs side information

Prior art two needs transmitter transmission side information to be used to recover initial data, and this needs the outer bandwidth of occupying volume.Need the integrity problem in the transmission of extra consideration side information simultaneously, generally increase power and solve or increase error correcting code, this all brings extra expense.At receiving terminal, need extra receiver processing module, receive side information and be used for recovering correct data from the data flow that receives.

2, complexity height

When adopting prior art two, need to calculate extra M-1 group I FFT computing.Along with the increase of M, system carries out the also corresponding increase of searching times, makes the amount of calculation of system be linear growth with M, so the algorithm complex height of prior art two.

Summary of the invention

The purpose of this invention is to provide a kind of ofdm system that reduces the method for peak-to-average force ratio and have low peak average ratio, by the present invention, effectively reducing under the prerequisite of the peak-to-average force ratio that sends data sequence, can reduce the implementation complexity of transmitter and receiver effectively.

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

The invention provides a kind of method that reduces peak-to-average force ratio, it comprises:

A, before carrying out quick inverse-Fourier transform IFFT conversion, transmitter is removed processing to the initial phase of the transmission sequence after ovennodulation, and adds transfer function;

B, receiver will be removed through the transfer function in the frequency domain sequence that obtains behind the fast fourier transform FFT, and the described frequency domain sequence of removing transfer function is carried out initial phase processing, recover the transmission sequence that described transmitter sends;

Wherein, when transmitter was removed fully to the initial phase that sends sequence, described transmitter sent the initial phase information that comprises each subcarrier when sending treated transmission sequence; Described receiver adds initial phase according to received phase information to the described frequency domain sequence after the removal transfer function;

Or when transmitter was partly removed the initial phase that sends sequence, all initial phases in the transmission sequence after described transmitter will be modulated were multiplied by phase factor respectively, obtain Orders Corrected; Described receiver is removed phase factor to the described frequency domain sequence of removing after the transfer function.

Wherein, before described steps A, comprise:

Generation has the transmission sequence of initial phase.

The invention provides a kind of ofdm system with low peak average ratio, comprise transmitter and receiver, wherein said transmitter comprises the IFFT unit, and described receiver comprises the FFT unit,

Described transmitter also comprises first band pass filter, is used for the initial phase that enters IFFT unit transmission sequence is before removed processing, and adds transfer function, sends the IFFT unit then to;

Described receiver also comprises second band pass filter, be used for transfer function removal to the frequency domain sequence that obtains after the process FFT unit conversion, and the described frequency domain sequence of removing transfer function carried out initial phase processing, recover the transmission sequence that described transmitter sends.

Wherein, comprise when described first band pass filter:

The first initial phase processing module, when being used for the initial phase that enters the transmission sequence before the IFFT unit got rid of fully, described second band pass filter comprises:

The second initial phase processing module is used for adding the initial phase that receives from described transmitter through removing the sequence that obtains after transfer function is handled;

Or, when described first band pass filter comprises:

The first initial phase processing module, be used for will enter all initial phases of transmission sequence before the IFFT unit when multiply by phase factor, described second band pass filter comprises:

The second initial phase processing module is used for removing through removing the described phase factor of the sequence that obtains after transfer function is handled.

As seen from the above technical solution provided by the invention, among the present invention, before carrying out quick inverse-Fourier transform IFFT, transmitter is removed processing to the initial phase that sends sequence, and adds transfer function; Receiver will be removed through the transfer function in the frequency domain sequence that obtains behind the fast fourier transform FFT, and the frequency domain sequence of removing transfer function is carried out initial phase processing, recover the transmission sequence then.Because transmitting terminal only need carry out N time complex multiplication operation when adding transfer function, so the present invention can reduce the complexity that transmitter and receiver is realized under the prerequisite of the peak-to-average force ratio that effectively reduces the transmission data sequence.

In addition, the present invention keeps the part initial phase that sends sequence by the way that adopts the initial phase that will send sequence to be multiplied by phase factor, thereby do not need any redundant informations such as transmitting terminal transmitted sideband information, receiving terminal just can recover original series from send sequence, therefore further reduced the complexity that transmitter and receiver is realized.

Description of drawings

Fig. 1 is the frame diagram of ofdm system in the background technology;

Fig. 2 is the frame diagram of first embodiment provided by the invention;

Fig. 3 is the flow chart of second embodiment provided by the invention;

The flow chart of the 3rd embodiment that Fig. 4 passes through for the present invention;

Fig. 5 is the simulated effect figure behind enforcement the present invention.

Embodiment

According to the definition of peak-to-average force ratio, cause that big peak-to-average force ratio is because the consistency of sub-carrier phase if can keep suitable phase relation between each subcarrier, just can reduce peak-to-average force ratio effectively.Document (Newman D J.A n L 1 extremal problem forpolynominals.Proc.Amer.Math.Soc. in the Newman proposition, 1965,16:1287～1290.) and the document that proposes of Boyd (Boyd S.Multitone Signals with Low Crest Factor[J] .IEEETrans.Circuits Syst.1986, CAS-33:1018～1022.) point out in, when the distribution of the sub-carrier phase in the multicarrier met the newman distribution, the OFDM time-domain signal after the IFFT conversion had minimum peak-to-average force ratio.Therefore, in a kind of information scrambling method that reduces the multicarrier peak-to-average force ratio provided by the invention, transmitting terminal utilizes the multinomial of newman phase sequence to change the PHASE DISTRIBUTION that sends frequency domain sequence, thereby can change the power probability density distribution, can significantly reduce PAPR after the IFFT conversion.

First embodiment provided by the invention is a kind of ofdm system with low peak average ratio, and this system has increased band pass filter respectively in the transmitter and receiver of prior art, and its implementation framework comprises transmitter 100 and receiver 150 as shown in Figure 2.Described transmitter 100 comprises that transmitter 100 comprises channel encoder 102, sign map unit 104, deserializer 106, frequency pilot sign inserter 108, first band pass filter 109, unit 114, D/A converter 116, radio frequency unit 118 are at interval protected in inverse-Fourier transform (IFFT) unit 110, parallel-to-serial converter 112, insertion fast.Comprise the first initial phase processing module in wherein said first band pass filter 109, be used for the initial phase that enters IFFT unit transmission sequence is before got rid of fully; Or all initial phases that are used for entering IFFT unit transmission sequence before multiply by phase factor.

Channel encoder 102 receives the input data, and the input data are carried out sending into sign map unit 104 after the chnnel coding.Sign map unit 104 code stream of self-channel encoder 102 in the future shines upon the symbol that forms after modulating according to predetermined constellation mapping mode, delivers in the deserializer 106.The constellation mapping mode includes but not limited to following several: BPSK, QPSK, 16QAM, 64QAM.Deserializer 106 is converted to parallel modulation symbol with the serial modulation symbol.Output parallel data sequence is in frequency pilot sign inserter 108.Pilot tone inserter 108 inserts frequency pilot sign in parallel modulation symbol, generate and send sequence, sends into first band pass filter 109 then.

The transfer function of described first band pass filter 109 is shown in formula 1 and formula 2:

$H_{\left(\mathrm{\ω}\right)}=e^{-j\·\frac{{\mathrm{\ω}}^2}{4\mathrm{\α}}}$ Formula 1

$\mathrm{\&alpha;}=\frac{N\&CenterDot;\mathrm{\&pi;}}{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H06176003920060429E000031.png,H06176003920060429E000041.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}$ Formula 2

Wherein said N refers to the maximum number of subcarrier, and T refers to the OFDM symbol lengths.

To bigger N, no matter why T is worth, for any OFDM symbol, this phase relation can obtain lower identical peak-to-average force ratio.

Formula 2 is brought in the formula 1:

$H_{\left(f\right)}=e^{-j\&CenterDot;\frac{\mathrm{\&pi;}\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H06176003920060429E000031.png,H06176003920060429E000041.png"\; state="\{\{state\}\}">T</figure-callout>}}^2\&CenterDot;f^2}{\mathrm{<figure-callout\; id="3"\; label="N\; Formula"\; filenames="H06176003920060429E000031.png"\; state="\{\{state\}\}">N</figure-callout>}}}$ Formula 3

In baseband signal, described f is:

$f=(n-1)\&CenterDot;\frac{1}{\mathrm{<figure-callout\; id="4"\; label="T\; Formula"\; filenames="H06176003920060429E000031.png"\; state="\{\{state\}\}">T</figure-callout>}}$ Formula 4

Formula 4 brought in the formula 3 obtains:

$H_{\left(n\right)}=e^{-j\&CenterDot;\frac{\mathrm{\&pi;}\&CenterDot;{(n-1)}^2}{\mathrm{<figure-callout\; id="5"\; label="N\; Formula"\; filenames="H06176003920060429E000031.png,H06176003920060429E000041.png"\; state="\{\{state\}\}">N</figure-callout>}}}$ Formula 5

Formula 6

Above-mentioned formula 5 is the transfer function of first band pass filter, is exactly the newman phase sequence shown in the formula 6, n=1 wherein, and 2,3 ..., N is the subcarrier sequence number.

After described first band pass filter 109 receives the transmission sequence that pilot tone inserter 108 sends to, phase factor is wherein handled, utilize the transfer function in it that described transmission sequence is carried out complex multiplication operation N time then, obtain frequency domain sequence to be sent, output to IFFT unit 110 then.

Here first band pass filter 109 adopts two kinds of algorithms that the transmission sequence that pilot tone inserter 108 sends to is handled.

First kind is: the initial phase that removes earlier each subcarrier in the transmission sequence after ovennodulation by the first initial phase processing module, and it is separately preserved, then transmission sequence and the transfer function in it of removing initial phase are carried out complex multiplication operation N time, obtain frequency domain sequence to be sent, and give IFFT unit 110 the initial phase message transmission of described time domain sequences and each subcarrier.

Second kind is: be multiplied by a phase factor by the first initial phase processing module for all initial phases of each subcarrier in the transmission sequence after ovennodulation, carry out N complex multiplication computing with the transfer function of described first band pass filter then, obtain frequency domain sequence to be sent, and give IFFT unit 110 the initial phase message transmission of described time domain sequences and each subcarrier.

N point IFFT computing is carried out in IFFT unit 110, finishes the multi-carrier orthogonal modulation, and dateout is in parallel-to-serial converter 112.The parallel data of parallel-to-serial converter 112 after with the IFFT conversion is converted to serial data and is transported to and inserts protection at interval in the unit 114.Insert protection and insert corresponding protection at interval for each symbol in unit 114 at interval, dateout is in D/A converter 116.D/A converter 116 converts digital signal to analog signal, delivers to radio frequency unit 118.Radio frequency unit 118 comprises a formed filter and front end unit, and Analog signals is launched signal by antenna then.

Receiver comprises radio frequency unit 152, A/D converter 154, lock unit 156, frequency offset correction unit 158, unit 160, deserializer 162, FFT unit 164, second band pass filter 165, frequency pilot sign withdrawal device 166, channel estimating unit 168, parallel-to-serial converter 170, symbol remove map unit 172, channel decoder 174 at interval to go protection.Wherein said second band pass filter 165 comprises the second initial phase processing module, is used for adding the initial phase that receives through removing the sequence that obtains after transfer function is handled; Or, be used for removing through removing the described phase factor of the sequence that obtains after transfer function is handled.

Receiver processing procedure fundamental sum transmitter is opposite; after passing through radio frequency unit 152, A/D converter 154, lock unit 156, frequency offset correction unit 158, going to unit 160, protection interval, deserializer 162 and FFT unit 164 to handle successively; recover frequency domain sequence, then described frequency domain sequence is transferred to second band pass filter 165.

The processing procedure of first band pass filter 109 in described second band pass filter 165 and the transmitter is corresponding, also can adopt two kinds of Processing Algorithm:

First kind of algorithm at the initial phase of each subcarrier of removal in the transmitter carries out, and its operation principle is:

Remove transfer function H _(n), and, send frequency pilot sign withdrawal device 166 then to by the phase information that the second initial phase processing module is added the corresponding subcarrier that receives.

Second kind is to carry out at the algorithm that is multiplied by phase factor for the initial phase of each subcarrier in the transmitter, and its operation principle is:

Remove the transfer function of band pass filter, and remove phase factor α, send frequency pilot sign withdrawal device 166 then to by the second initial phase processing module.

After process frequency pilot sign withdrawal device 166, channel estimating unit 168, parallel-to-serial converter 170, symbol go map unit 172 and channel decoder 174 to handle successively, recover the original series that transmitter sends to.

Second embodiment provided by the invention is a kind of information scrambling method that reduces peak-to-average force ratio, as shown in Figure 3, comprises the steps:

Step 1 generates the transmission sequence that has initial phase, as shown in Equation 7:

$S_{\left(k\right)}=A_k\&CenterDot;e^{-j\&CenterDot;{\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="7"\; label="k\; Formula"\; filenames="H06176003920060429E000041.png"\; state="\{\{state\}\}">k</figure-callout>}}}$ Formula 7

θ wherein _kBe the initial phase of subcarrier k, A _kAmplitude for subcarrier k.

Step 2, described transmission sequence after modulation, and was removed earlier original phase information before the IFFT conversion, and then add transfer function by band pass filter: $H_{\left(n\right)}=e^{-j\&CenterDot;\frac{\mathrm{\&pi;}\&CenterDot;{(n-1)}^2}{N}},$ Frequency domain sequence before the IFFT conversion that obtains is as shown in Equation 8:

$S_{\left(k\right)}=A_k\&CenterDot;e^{-j\&CenterDot;\frac{{(n-1)}^2\&CenterDot;\mathrm{\&pi;}}{N}}$ Formula 8

Step 3 is to the S shown in the described formula 8 _(k)Sequence is carried out the IFFT conversion, obtains time domain sequences to be sent.

Step 4, with described time domain sequences to be sent, and the phase information of each subcarrier sends.

Receive the time domain sequences of transmitter transmission when receiver after, carry out following steps:

Step 5 is carried out the FFT conversion to the time domain sequences that receives, and recovers the S of correspondence as shown in Equation 8 _(k)Frequency domain sequence.

Step 6 is removed transfer function H by band pass filter _(n), and the phase information of adding the corresponding subcarrier that receives, recover the transmission sequence that has initial phase as shown in Equation 7.

Among second embodiment provided by the invention, because no longer comprise the phase information of original series in the transmission sequence, therefore the transmitter of transmitting terminal must send the receiver of the supplementary of the phase information that comprises each subcarrier to receiving terminal, receiver recovers the transmission sequence that transmitting terminal sends, i.e. the transmission sequence that has initial phase as shown in Equation 7 according to the phase information of the corresponding subcarrier that receives.

The 3rd embodiment provided by the invention does not need transmitter to transmit the supplementary of the phase information that comprises each subcarrier.Its main thought is: suitably keep a part of original phase information in sending sequence, the phase approximation newman that sends sequence is distributed, the transmitter of transmitting terminal does not need to send any redundant information like this, receiver also can recover the phase information of original series fully, thereby obtains the original series that transmitter sends.The specific implementation process of this embodiment comprises the steps: as shown in Figure 4

At transmitter terminal:

Step 1 generates the transmission sequence that has initial phase, still as shown in Equation 7:

$S_{\left(k\right)}=A_k\&CenterDot;e^{-j\&CenterDot;{\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="7"\; label="k\; Formula"\; filenames="H06176003920060429E000041.png"\; state="\{\{state\}\}">k</figure-callout>}}}$ Formula 7

θ wherein _kBe the initial phase of subcarrier k, A _kAmplitude for subcarrier k.

Step 2 is the phase theta of all subcarriers in the transmission sequence after ovennodulation _kBe multiplied by a phase factor α, obtain Orders Corrected S ' _(k), as shown in Equation 9:

${S^{\&prime;}}_{\left(k\right)}=A_k\&CenterDot;e^{-j\&CenterDot;\mathrm{\&alpha;}\&CenterDot;{\mathrm{\&theta;}}_k}$ Formula 9

Step 3 is added transfer function by band pass filter, obtains frequency domain sequence S to be sent " _(k), as shown in Equation 10:

${S^{\&prime;\&prime;}}_{\left(k\right)}=A_k\&CenterDot;e^{-j\&CenterDot;(\frac{{(n-1)}^2\&CenterDot;\mathrm{\&pi;}}{N}+\mathrm{\&alpha;}\&CenterDot;{\mathrm{\&theta;}}_k)}$ Formula 10

Because the transfer function of band pass filter is: $H_{\left(n\right)}=e^{-j\&CenterDot;\frac{\mathrm{\&pi;}\&CenterDot;{(n-1)}^2}{N}},$ With Orders Corrected S ' _(k)Carry out N CM computing with the transfer function of described band pass filter, obtain the frequency domain sequence S to be sent shown in above-mentioned formula 10 " _(k)

Step 4 is to described frequency domain sequence S to be sent " _(k)Carry out the IFFT conversion, obtain time domain sequences s to be sent _(k), as shown in Equation 11:

$S_{\left(k\right)}=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{S}_{\left(i\right)}\&CenterDot;e^{j\&CenterDot;2\&CenterDot;\mathrm{\&pi;}\&CenterDot;i\&CenterDot;k/N}$ Formula 11

Step 5 is launched described time domain sequences.

At receiver end

Step 6 after receiver receives described time domain sequences, is carried out the FFT conversion to described time domain sequences, obtains the frequency domain sequence S to be sent of the correspondence shown in above-mentioned formula 10 " _(k)

Step 7 is removed the transfer function of band pass filter, obtains the Orders Corrected S ' of correspondence as shown in Equation 9 _(k)

Step 8 is removed phase factor α, recovers the transmission sequence S that has initial phase _(k)

The original series S that obtains by the described method of the 3rd embodiment provided by the invention _(k)Have lower peak-to-average force ratio, and when adopting this method, transmitting terminal does not need specially to transmit the redundant information of the phase information that comprises each subcarrier.

Technology provided by the invention can be applied in any multi-carrier communications systems, includes but not limited to: DVB, DMB, DAB, ADSL, WLAN, next generation mobile communication system etc.

By the embodiment of the foregoing description as can be seen, the present invention compares with clipping method with the SLM method of available technology adopting and has the following advantages:

1, complexity reduces

The complexity that transmitting terminal increases is lower, only need carry out N time complex multiplication operation, than low many of SLM and PTS method complexity; Algorithm implements also fairly simple.

2, performance is good

Simulated effect has as shown in Figure 5 provided the newman distribution and has reduced the peak-to-average force ratio performance curve, as can be seen, by the present invention, the peak-to-average force ratio of the time domain sequences that obtains after the process IFFT conversion is significantly reduced.

3, do not need side information

When adopting the 3rd embodiment, owing to kept the part initial phase of each subcarrier, transmitting terminal does not need to send any redundant information, and receiving terminal just can recover original series from send sequence, thereby can improve transmission information processing speed.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Claims (3)

1. a method that reduces peak-to-average force ratio is characterized in that, comprising:

A, before carrying out quick inverse-Fourier transform IFFT conversion, transmitter is removed processing to the initial phase of the transmission sequence after ovennodulation, and adds transfer function;

Described transfer function is Wherein

Be the newman phase sequence, and N is the maximum number of subcarrier;

B, receiver will be removed through the transfer function in the frequency domain sequence that obtains behind the fast fourier transform FFT, and the described frequency domain sequence of removing transfer function is carried out initial phase processing, recover the transmission sequence that described transmitter sends;

Wherein, when transmitter was removed fully to the initial phase that sends sequence, described transmitter sent the initial phase information that comprises each subcarrier when sending treated transmission sequence; Described receiver adds initial phase according to received phase information to the described frequency domain sequence after the removal transfer function;

Or when transmitter was partly removed the initial phase that sends sequence, all initial phases in the transmission sequence after described transmitter will be modulated were multiplied by phase factor respectively, obtain Orders Corrected; Described receiver is removed phase factor to the described frequency domain sequence of removing after the transfer function.

2. method according to claim 1 is characterized in that, comprises before described steps A:

Generation has the transmission sequence of initial phase.

3. the ofdm system with low peak average ratio comprises transmitter and receiver, and wherein said transmitter comprises the IFFT unit, and described receiver comprises the FFT unit, it is characterized in that:

Described transmitter also comprises first band pass filter, is used for the initial phase that enters IFFT unit transmission sequence is before removed processing, and adds transfer function, sends the IFFT unit then to,

Described transfer function is Wherein Be the newman phase sequence, and N is the maximum number of subcarrier;

Described receiver also comprises second band pass filter, be used for transfer function removal to the frequency domain sequence that obtains after the process FFT unit conversion, and the described frequency domain sequence of removing transfer function carried out initial phase processing, recover the transmission sequence that described transmitter sends;

Wherein, comprise when described first band pass filter:

The first initial phase processing module, when being used for the initial phase that enters the transmission sequence before the IFFT unit got rid of fully, described second band pass filter comprises:

The second initial phase processing module is used for adding the initial phase that receives from described transmitter through removing the sequence that obtains after transfer function is handled;

Or, when described first band pass filter comprises:

The first initial phase processing module, be used for will enter all initial phases of transmission sequence before the IFFT unit when multiply by phase factor, described second band pass filter comprises:

The second initial phase processing module is used for removing through removing the described phase factor of the sequence that obtains after transfer function is handled.

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