CN102932289B - Cyclic shifting-based method for estimating shifting number and channel response in orthogonal frequency division multiplexing (OFDM) system - Google Patents

Abstract

The invention relates to a cyclic shifting-based method for estimating shifting number and channel response in an orthogonal frequency division multiplexing (OFDM) system. The technical scheme is as follows: a PTS processing method based on time domain cyclic shifting is adopted to reduce the peak average power ratio (PAPR) of an OFMD symbol in an OFDM system model, and then a pilot frequency inserted method for estimating the cyclic shifting number of a sequence and the response of a transmission channel is provided. According to the method, the PAPR of the system is reduced while the sending of edge information is avoided, and a receiving end can estimate the cyclic shifting number of each sub-sequence in a time domain by using a small amount of pilot frequency information without using complex blind estimating, so that phase position rotating factors which are multiplied by each symbol in a frequency domain can be calculated, and the reliability and the effectiveness of the system are improved.

Description

Estimate the method for displacement number and channel response based on cyclic shift in ofdm system

Technical field

The invention belongs to wireless communication technology field, relate to reduction and the pilot design of peak-to-average power ratio (PAPR) in OFDM (OFDM) system.

Background technology

The concept of orthogonal frequency division multiplexi comes across mid-term the 1950's the earliest.The sixties, people have carried out much theoretic research to multi-carrier modulation technology, define the thought of parallel data transmission and frequency division multiplexing (FDM), and this makes OFDM technology first be applied in U.S. Military high frequency communication system.Use discrete Fourier transform (DFT) (DFT) and inverse discrete Fourier transformer inverse-discrete (IDFT) greatly reduce the complexity of multicarrier system after realizing the modulation and demodulation of base band.1985, Cimim introduced cell mobile communication systems, for the development of Wireless OFDM System is laid a good foundation the concept of OFDM first.The nineties in last century, the develop rapidly of Digital Signal Processing and large scale integrated circuit is that obstacle has been cleared away in the development of OFDM technology, and from then on OFDM has climbed up the wonderful stage of modern communications.

OFDM (OFDM) is a kind of special multi-carrier modulation, its basic thought be by the data flow of high-speed transfer by serial/parallel conversion, become the low rate data streams of parallel transmission in several orthogonal narrowband subchannels.The data message of transmission is distributed on each subcarrier by OFDM technology, thus considerably increases the duration of each symbol, makes symbol period be greater than multidiameter delay, thus has the ability of extraordinary antagonism ISI.OFDM technology utilizes the time-frequency orthogonality of signal, allows sub-channel spectra to overlap, and makes the availability of frequency spectrum improve nearly one times, thus has the very high availability of frequency spectrum.

The fundamental block diagram of ofdm system as shown in Figure 1, through QAM modulation, binary message modulation is become qam symbol in transmitting terminal information source, comprising pilot frequency information and data message, then carry out IFFT conversion, insertion Cyclic Prefix, parallel-serial conversion, D/A conversion, finally the OFDM time-domain signal of generation is sent.At receiving terminal, the inverse process of a transmitting terminal is carried out to the information received, estimate raw information, calculate the error rate.

Suppose in ofdm system, there is N number of subcarrier, then data flow X _kcan time domain OFDM signal be obtained after carrying out N point IFFT, can be expressed as:

$x\left(n\right)=\frac{1}{\sqrt{N}}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{X}_k{e}^{j2\mathrm{\πkn}/N},0\≤n\≤N-1---\left(1\right)$

Wherein, X _kbe through the complex signal after constellation modulation, N is counting of IFFT conversion.Because OFDM symbol is formed by stacking by multiple separate modulated sub-carriers, so just likely produce larger peak-to-average power ratio PAPR.The range of linearity of high PAPR to the power amplifier in transmitter and receiver proposes very high requirement, also add the complexity of the equipment such as A/D, D/A converter.If high PAPR makes signal beyond the range of linearity of amplifier, then signal can produce nonlinear distortion, destroys the performance of system.Reducing PAPR is an indispensable part in ofdm system.

The usual computing formula of peak-to-average power ratio is:

$\mathrm{PAPR}\left(\mathrm{dB}\right)=10\log \frac{\max \left\{{\left|y_n\right|}^2\right\}}{E\left[{\left|y_n\right|}^2\right]}---\left(2\right)$

Wherein y _nbe OFDM time domain sample signal, E [] represents the average asking signal.

The technology of current reduction PAPR mainly contains three classes: pre-distortion signal technology, coding class technology, probability class technology.The thought of signal distortion techniques is exactly directly carry out nonlinear operation to the peak value of signal.Although very simple, owing to being nonlinear operation, in-band noise and the outer interference of band can being produced, the error rate of system is raised.The thought of coding class technology only sends the code word with lower PAPR characteristic, thus avoid the code word sending and there will be higher PAPR.This type of technology is linear process, signal can not be made to produce distortion, but computation complexity is very high, has been only applicable to the situation that carrier number is less.The thought of probability class technology reduces the probability occurring large PAPR, and these class methods are linear processes, also comparatively complicated.

Document [G.R. Hill, M. Faulkner and J. Singh, " Reducing the peak-to-average power ratio in OFDM by cyclicallyshifting partial transmit sequences ", ELECTRONICS LETTERS 16th March 2000 Vol. 36 No. 6, pp.560-561.

] in propose the method adding time-domain cyclic shift in traditional PTS method, each sub-sequence carries out corresponding cyclic shift in time domain after being multiplied by corresponding phase rotation coefficient again, the number of such generation candidate sequence increases, the PAPR performance of system is improved, but do not mention effective demodulation method at receiving terminal, and computation complexity and operand are all larger, document [L. Yang, K. Soo, S. Q. Li, and Y. M. Siu, " PAPR Reduction Using Low Complexity PTS to Construct of OFDM Signals Without Side Information ", IEEE TRANSACTIONS ONBROADCASTING, VOL. 57, NO. 2, pp.284-290.JUNE 2011.] in have employed the method for time-domain cyclic shift equally, each subsequence only carries out cyclic shift in time domain, the candidate sequence of such generation is more than corresponding conventional P TS, system PAPR also improves, but what adopt is perfect channel estimation, computation complexity is high.The pilot design based on time-domain cyclic shift PTS that the present invention proposes solves the problem of channel estimating and the twiddle factor estimation splitting PTS at equal intervals, not only make system PAPR Performance Ratio conventional P TS make moderate progress, while reducing the error rate, also reduce computation complexity.

Be illustrated in figure 2 traditional PTS method based on time-domain cyclic shift.Traditional PTS method is that each subsequence is multiplied by a corresponding phase rotation coefficient, and each subsequence is added again asks minimum PAPR, for ensure data message integrality and produce W ^v-1plant candidate and send sequence.PAPR performance impact subtracts greatly, and OFDM symbol need add side information again, and receiving terminal also needs to carry out complicated blind estimate computing.

Summary of the invention

Technical problem to be solved by this invention is, the defect high for existing reduction PAPR technology complexity, error rate of system is high, based on time-domain cyclic shift PTS, proposes the deficiency that a kind of pilot design method improves conventional P TS suppression PAPR.This method avoid the transmission of side information in PTS method, reduce receiving terminal blind estimate algorithm complex simultaneously.While raising system effectiveness, also ensure that the reliability of system, after also avoiding PTS process because of the pilot tone that inserting channel is estimated before PTS process, pilots insertion is on the impact of system PAPR performance simultaneously.

The technical scheme that the present invention solves the problems of the technologies described above is:

For the ofdm system model under multipath channel, reduce on the basis of papr at the partial transmission sequence based on time-domain cyclic shift, a kind of pilot interposition method is proposed, reducing in OFDM symbol papr based on time-domain cyclic shift PTS method, inserting at transmitting terminal and estimate phase rotation coefficient pilot tone and channel estimation pilot.Specifically comprise step:

First between reduction PAPR performance and computational complexity, the suitable subsequence number V that will split is selected.Pilot tone (Equations of The Second Kind pilot tone) position estimating phase rotating is determined, at this position (i.e. frequency-domain OFDM symbol X in OFDM symbol _2Vafter position) after insert at equal intervals and be used for the pilot tone (first kind pilot tone) of channel estimating.OFDM symbol is become the subsequence of V non-overlapping copies at Dividing in frequency domain, wherein V is Equations of The Second Kind pilot tone number, inserts one for estimating the pilot tone (Equations of The Second Kind pilot tone) of phase rotation coefficient in each subsequence.Converted by IFFT, each sub-block superposes and asks minimum peak-to-average power ratio PAPR after time domain carries out cyclic shift, in the OFDM symbol with minimum PAPR for estimate phase rotation coefficient pilot tone before and after insert a pilot tone (the 3rd class pilot tone) respectively, finally the burst of above-mentioned insertion pilot tone is sent.

Wherein, one is inserted for estimating that the pilot tone particular content of phase rotation coefficient comprises: in the ofdm system comprising N number of subcarrier in each subsequence, transmitting data information is mapped to data flow X through ovennodulation, after determining subsequence number V, V+1 to the 2V position of data flow X vector is inserted and is used for the pilot tone estimating phase rotation coefficient, then adopt the method split at equal intervals data flow X to be divided into the subvector X of V non-overlapping copies ^v, v=1,2 ..., V, second non-zero in each like this subvector is exactly estimate the pilot tone of phase rotating.

Receiving terminal is sequence to the received signal carry out FFT computing, convert frequency-region signal sequence to , utilize the pilot frequency information estimating V phase rotating based on two the 3rd class pilot tones inserted after time-domain cyclic shift PTS process; By the at equal intervals split plot design same with transmitting terminal by frequency-region signal sequence be divided into V subsequence at equal intervals , estimate that the pilot tone of phase rotating can calculate the number of twiddle factor corresponding to each subsequence and time-domain cyclic shift according to V, corresponding phase place reduction carried out to each subsequence; Each subsequence superposes and utilizes pilot tone (first kind pilot tone) information after V estimation phase rotating pilot frequency locations to carry out channel estimating and interpolation, estimates raw information.

The present invention is a kind ofly carrying out phase rotating with pilot frequency information based on proposing on time-domain cyclic shift partial transmission sequence method and is estimating and the method for channel estimating, while guarantee system reliability, also reduce receiving terminal computational complexity, improve the validity of system.

Traditional PTS method is ensure that the integrality of data message produces W ^v-1plant candidate and send sequence.The present invention produces W ^vplant candidate and send sequence, reduction PAPR performance is better than conventional P TS method.Inserted before PTS process for the pilot tone of channel estimating in the present invention, the insertion of pilot tone in ofdm system is reduced the PAPR performance impact of the OFDM symbol after PTS process.OFDM symbol after PTS process does not need to add side information again, and receiving terminal also need not carry out complicated blind estimate computing, but utilizes pilot tone to estimate phase rotation coefficient, and the validity that improve system also ensure that the reliability of system simultaneously.

Accompanying drawing explanation

Fig. 1 is ofdm communication system theory diagram;

Fig. 2 is the theory diagram of conventional P TS method;

Fig. 3 is the schematic diagram based on time-domain cyclic shift PTS;

Fig. 4 is the theory diagram of the invention process process;

Fig. 5 is the PAPR Performance comparision analogous diagram of the inventive method;

Fig. 6 is the inventive method bit error rate performance under a multipath channel environment.

Embodiment

Ofdm system model under multipath channel, as shown in Figure 1, through QAM modulation, binary message modulation is become qam symbol in transmitting terminal information source, then carry out IFFT conversion, insertion Cyclic Prefix, parallel-serial conversion, D/A conversion, finally the OFDM time-domain signal of generation is sent.At receiving terminal, the inverse process of a transmitting terminal is carried out to the information received, estimate raw information.The present invention, based on the partial transmission sequence basis of time-domain cyclic shift, inserts response pilot tone.Figure 4 shows that the invention process procedural block diagram, specifically comprise the steps:

1, in the OFDM symbol of input, determine the position of the pilot tone (Equations of The Second Kind pilot tone) estimating phase rotating, after its position, insert the pilot tone (first kind pilot tone) being used for channel estimating at equal intervals.

As shown in Figure 1 for ofdm system, be divided into V subsequence at equal intervals to the data flow X after quadrature amplitude modulation (QAM), wherein the value of V is the number of the Equations of The Second Kind pilot tone for estimating phase rotating.After quadrature amplitude modulation, data flow X can be expressed as:

X=[X ₁,X ₂,...,X _V,X _V+1,X _V+2,...X _2V,X _2V+1,...X _N]

Wherein from X _v+1to X _2Vthis V data are defined as the pilot tone (Equations of The Second Kind pilot tone) estimating phase rotating, at X _2Vposition is afterwards inserted at equal intervals the pilot tone (first kind pilot tone) being used for channel estimating.

2, OFDM symbol (the data flow X after quadrature amplitude modulation) being become the subsequence of V non-overlapping copies at Dividing in frequency domain, in each subsequence, inserting one for estimating the Equations of The Second Kind pilot tone of phase rotation coefficient.

Transmitting data information is mapped in Dividing in frequency domain through ovennodulation and becomes a series of data flow, is inserted V+1 to the 2V position of data flow X vector and is used for the pilot tone estimating phase rotation coefficient, i.e. X _v+1to X _2Vthis V data are the pilot tone of the estimation phase rotation coefficient inserted, then by the method split at equal intervals, the data flow inserting pilot tone are divided into the subsequence X of V non-overlapping copies ^v, v=1,2 ..., V, wherein, the length of each subsequence is N/V, and in each subsequence, second non-zero is exactly the pilot tone for estimating phase rotating.

As shown in Equation (3), X is divided into the subsequence of V non-overlapping copies, after each subsequence superposition, still equals X.

$X=\underset{v=1}{\overset{V}{\mathrm{\Σ}}}{X}^v---\left(3\right)$

Wherein,

X ¹=[X ₁,0,0,...,X _V+1,0,0,...,X _2V+1,0,0,...X _N-V+1,0,...,0]

X ²=[0,X ₂,0,...,0,X _V+2,0,...,0,X _2V+2,0,...,0,X _N-V+2,...,0]

X ^V=[0,0,...,0,X _V,0,0,...,0,X _2V,0,...,0,0,...,0,X _N-V,0,...,0,X _N]

Data flow X is after being divided into V subsequence at equal intervals, and the data of its V+1 to 2V position become second non-zero of each subvector successively.

As mentioned above, the position of the V+1 to 2V of data flow X is the pilot tone for estimating phase rotating inserted, after being divided into V subsequence at equal intervals, at subsequence X ¹in second non-zero X _v+1with subsequence X ²in second non-zero X _v+2be exactly the Equations of The Second Kind pilot tone of corresponding estimation phase rotation coefficient, in like manner, subsequence X ^vin second non-zero X _2Valso be corresponding pilot tone.Can to learn in each subsequence that second non-zero is exactly the pilot tone for estimating phase rotating by this rule.

3, each subsequence superposes after carrying out cyclic shift, carries out IFFT conversion, is transformed into time domain and obtains the OFDM symbol with minimum PAPR.

Be illustrated in figure 3 the schematic diagram that the present invention is based on time-domain cyclic shift PTS.Each subsequence is transformed into time domain by IFFT and then carries out cyclic shift, and the symbol be equivalent in each sub-carrier positions has in a frequency domain carried out phase rotating.Suppose that time domain cyclic has moved m position, then in frequency domain, in each sub-block, the corresponding twiddle factor of each subcarrier is e ^{j2 π km/N}.When the number of OFDM symbol sub-carriers is 512, namely during N=512, be the twiddle factor e making different m value corresponding ^{j2 π km/N}phase place be convenient to receiving terminal and judge, the difference between different m value should not be less, and the difference herein between different m value can be set to the integral multiple (also can be set to other value) of 32.The selected scope of m can be reduced for reducing computational complexity, herein the selected scope of time-domain cyclic shift number m be set to 0,32},

1) the twiddle factor vector corresponding to each subsequence is determined.

Twiddle factor vector corresponding to each subsequence obtains according to following formula:

$b^v=[e^{j2\mathrm{\π}0m_v/N},e^{j2\mathrm{\π}1m_v/N},e^{j2\mathrm{\π}2m_v/N},e^{j2\mathrm{\π}3m_v/N},...,e^{j2\mathrm{\πk}{m}_v/N},...,e^{j2\mathrm{\π}(N-1)m_v/N}]$

Wherein, 1≤v≤V, m _v=0,32

2) then the twiddle factor vector that each subsequence dot product is corresponding is added to obtain vectorial Y:

$Y=\underset{v=1}{\overset{V}{\mathrm{\Σ}}}{b}^v*X^v,1\≤v\≤V,---\left(4\right)$

3) again IFFT conversion is carried out to vectorial Y and just obtain the OFDM time domain sample signal y after phase optimization _n, by y _nsubstitute into formula (2) and calculate corresponding PAPR value.The PAPR calculated and the PAPR value of the OFDM symbol after out of phase optimization are compared, to obtain the OFDM symbol with minimum PAPR value.

Repeat above-described three steps, by m corresponding for each subsequence _vvalue travels through in { 0,32 } scope, then can produce 2 ^vplant m _vthe combination of value, thus also can produce 2 ^vthe individual OFDM symbol through phase optimization.Calculate the PAPR value of each OFDM symbol, select the OFDM symbol wherein with minimum PAPR.

4, the Equations of The Second Kind pilot tone two ends after being multiplied by phase rotation coefficient in the OFDM symbol with minimum PAPR are inserted a pilot tone (the 3rd class pilot tone) more respectively and can be estimated the channel response at Equations of The Second Kind pilot tone place to make receiving terminal.

The OFDM symbol with minimum PAPR is transformed into frequency domain:

$X_{\mathrm{optimal}}=[X_1^{\′},X_2^{\′},...,X_V^{\′},X_{V+1}^{\′},X_{V+2}^{\′},...,X_{2V}^{\′},X_{2V+1}^{\′},...X_N^{\′}]$

Wherein, X _optimalin for being multiplied by the Equations of The Second Kind pilot tone after phase rotation coefficient, the front and back of the Equations of The Second Kind pilot tone after being multiplied by phase rotation coefficient are inserted two the 3rd class pilot tones again and are used for estimating the channel response at place, with two pilot tones are inserted in position.Last be transformed into time domain by IFFT conversion by frequency domain send inserting the OFDM symbol of above-mentioned pilot tone through above-mentioned process again.

Receiving terminal to the received signal sequence carries out FFT computing, converts frequency-region signal sequence to , two the 3rd class pilot tones utilizing transmitting terminal to insert estimate the pilot frequency information of V phase rotating; Adopt the at equal intervals split plot design same with transmitting terminal by receiving terminal frequency-region signal sequence be divided into V subsequence at equal intervals , estimate that the pilot tone of phase rotating can calculate the number of twiddle factor corresponding to each subsequence and time-domain cyclic shift according to V, corresponding phase place reduction carried out to each subsequence; Each subsequence superposes and utilizes the pilot frequency information after V estimation phase rotating pilot frequency locations to carry out channel estimating and interpolation, estimates the channel response at Equations of The Second Kind pilot tone place.

5, receiving terminal carries out rotatable phase estimation to the received signal.

1) OFDM symbol with optimum PAPR arrives receiving terminal through multipath channel, and receiving terminal carries out FFT computing to the OFDM symbol received, and is transformed into frequency domain

$\tilde{X}=[{\tilde{X}}_1,{\tilde{X}}_2,...,{\tilde{X}}_V,{\tilde{X}}_{V+1},{\tilde{X}}_{V+2},...{\tilde{X}}_{2V},{\tilde{X}}_{2V+1},...,{\tilde{X}}_N]$

Then ${\tilde{X}}_k=X_k\·H\left(k\right)\·e^{j2\mathrm{\π}(k-1)m/N}---\left(5\right)$

Wherein X _kfor original QAM modulation symbol, the response that H (k) is channel, e ^{j2 π (k-1) m/N}the rotatable phase factor corresponding to each subcarrier.

2) according to two the 3rd class pilot tones inserted, estimate receiving terminal and estimate phase rotating pilot tone the channel response at place , V+1≤k≤2V.

Phase rotation coefficient is not multiplied by, so the channel response at two the 3rd class pilot tone places is respectively by said process known two the 3rd class pilot tones:

The channel response of Equations of The Second Kind pilot tone can be estimated again by linear interpolation formula:

$\hat{H}\left(k\right)=\frac{[\hat{H}(2V+1)-\hat{H}\left(V\right))]}{V+1}(k-V)+\hat{H}\left(V\right),V+1\≤k\≤2V---\left(6\right)$

The Equations of The Second Kind pilot frequency information after being multiplied by phase rotation coefficient just can be estimated according to the channel response at the Equations of The Second Kind pilot tone place estimated:

${\stackrel{\‾}{X}}_k=\frac{{\tilde{X}}_k}{\hat{H}\left(k\right)}=\frac{X_k\·H\left(k\right)\·e^{j2\mathrm{\π}(k-1)m/N}}{\hat{H}\left(k\right)},V+1\≤k\≤2V---\left(7\right)$

3) differentiation of sub-sequences time-domain cyclic shift number.

Estimate that the pilot tone of phase rotating calculates the number of the twiddle factor determination time-domain cyclic shift corresponding to each subsequence according to receiving terminal V.The Equations of The Second Kind pilot tone being multiplied by phase rotation coefficient estimated is carried out phase place reverse rotation, is namely multiplied by phase place reverse rotation factor e ^{-j2 π (k-1) m/N}, and then do difference with the Equations of The Second Kind pilot tone not being multiplied by the phase place reverse rotation factor, difference is minimum, and corresponding m value is exactly be the time-domain cyclic shift number that the subsequence of transmitting terminal carries out:

$D=|{\stackrel{\‾}{X}}_k\·e^{-j2\mathrm{\π}(k-1)m/N}-X_k|,V+1\≤k\≤2V---\left(8\right)$

X _kfor transmitting terminal is for estimating the Equations of The Second Kind pilot frequency information of phase rotating, for the Equations of The Second Kind pilot frequency information be multiplied by after phase rotation coefficient that receiving terminal estimates.In { 0,32 } scope, choose the value making the m that D value is minimum in (8) formula, and this m value is judged to be the time-domain cyclic shift number that transmitting terminal kth-V subsequence carries out.

6, receiving terminal carry out to the received signal phase place reduction estimate primary signal.

To the received signal carry out the at equal intervals segmentation same with transmitting terminal, according to the time-domain cyclic shift number m of each sub-sequence estimated in step 5, phase place reduction is carried out to each subsequence.The first kind pilot tone for channel estimating inserted finally by transmitting terminal estimates channel response, thus estimates primary signal .

1) to the received signal carry out the at equal intervals segmentation same with transmitting terminal:

${\tilde{X}}^1=[{\tilde{X}}_1,\mathrm{0,0},...,{\tilde{X}}_{V+1},\mathrm{0,0},...,{\tilde{X}}_{2V+1},\mathrm{0,0},...,{\tilde{X}}_{V-V+1},0,...,0]$

${\tilde{X}}^2=[0,{\tilde{X}}_2,0,...,0,{\tilde{X}}_{V+2},0,...,0,{\tilde{X}}_{2V+2},0,...,0,{\tilde{X}}_{N-V+2},...,0]$

${\tilde{X}}^V=[\mathrm{0,0},...,0,{\tilde{X}}_V,\mathrm{0,0},...,0,{\tilde{X}}_{2V},0,...,\mathrm{0,0},...,0,{\tilde{X}}_{N-V},0,...,0,{\tilde{X}}_N]$

2) by the time-domain cyclic shift number of v the subsequence estimated in step 5 to determine that receiving terminal v subsequence to carry out when phase place is reduced the phase place reverse rotation that is multiplied by because of subvector:

${\hat{b}}^v=[e^{-j2\mathrm{\π}0{\hat{m}}_v/N},e^{-j2\mathrm{\π}1{\hat{m}}_v/N},e^{-j2\mathrm{\π}2{\hat{m}}_v/N},e^{-j2\mathrm{\π}3{\hat{m}}_v/N},...,e^{-j2\mathrm{\πk}{\hat{m}}_v/N},...,e^{-j2\mathrm{\π}(N-1){\hat{m}}_v/N}]$

Then the reverse rotation estimated corresponding to each subsequence dot product be added because of subvector:

$\stackrel{\‾}{Y}=\underset{v=1}{\overset{V}{\mathrm{\Σ}}}{\hat{b}}^v.*{\tilde{X}}^v,1\≤v\≤V---\left(9\right)$

3) signal after phase place reduction the first kind pilot tone for channel estimating that recycling transmitting terminal inserts carrys out the channel response in estimating OFDM symbol behind 2V+2 position, then channel response is out utilized estimated by the first kind and the 3rd class pilot tone to carry out linear interpolation, thus estimate response H (k) of whole channel, 1≤k≤N, finally estimates primary signal :

${\hat{X}}_k=\frac{{\stackrel{\‾}{Y}}_k}{H\left(k\right)},1\≤k\≤N---\left(10\right)$

Be the PAPR Performance comparision analogous diagram of the inventive method as shown in Figure 5, as can be seen from Figure, time-domain cyclic shift PTS method of the present invention is more superior in reduction PAPR performance than traditional PTS method.

Be the inventive method bit error rate performance under a multipath channel environment shown in Fig. 6, the present invention's bit error rate performance under a multipath channel environment, the bit error rate performance that in its bit error rate performance and conventional P TS, receiving terminal receives complete edge information is close.

Claims (6)

1. estimate a method for displacement number and channel response based on time-domain cyclic shift, it is characterized in that, comprise the steps:

Transmitting terminal: determine the Equations of The Second Kind pilot frequency locations estimating phase rotating in the OFDM symbol of input, insert the first kind pilot tone being used for channel estimating at equal intervals after this position; OFDM symbol being divided at equal intervals the subsequence of V non-overlapping copies at frequency domain, in each subsequence, inserting one for estimating the Equations of The Second Kind pilot tone of phase rotation coefficient; Each subsequence is added and asks minimum peak-to-average force ratio PAPR after time domain carries out cyclic shift, in the OFDM symbol with minimum PAPR, insert a 3rd class pilot tone respectively at Equations of The Second Kind pilot tone two ends, the OFDM symbol of above-mentioned insertion pilot tone is transformed into time domain by frequency domain and sends;

Receiving terminal: sequence converts frequency-region signal sequence to the received signal the 3rd class pilot tone utilizing transmitting terminal to insert estimates the pilot frequency information of V phase rotating; To frequency-region signal sequence carry out the at equal intervals segmentation identical with transmitting terminal, estimate that the pilot tone of phase rotating calculates the number of phase rotation coefficient vector corresponding to each subsequence and time-domain cyclic shift according to V, according to the subsequence obtained after segmentation and twiddle factor vector, signal is reduced, the pilot tone for channel estimating inserted by transmitting terminal estimates channel response, obtains primary signal.

2. method according to claim 1, is characterized in that: described for estimating that the Equations of The Second Kind pilot tone of phase rotating is: the subsequence X by the method split at equal intervals, the data flow inserting pilot tone being divided into V non-overlapping copies ^v, v=1,2 ..., V, in V subsequence after singulation, in each subsequence, second non-zero is exactly estimate the Equations of The Second Kind pilot tone of phase rotating.

3. method according to claim 1, is characterized in that: according to formula: $b^v=[b^{j2\mathrm{\π}0m_v/N},e^{j2\mathrm{\π}1m_v/N},e^{j2\mathrm{\π}2m_v/N},e^{j2\mathrm{\π}3m_v/N},...,e^{j2\mathrm{\πk}{m}_v/N},...,e^{j2\mathrm{\π}(N-1)m_v/N}]$ Determine the twiddle factor vector corresponding to each subsequence, wherein 1≤v≤V, m _vfor { value in 0,32} scope, N is the number of ofdm system sub-carriers.

4. method according to claim 1, is characterized in that: according to formula:

v+1≤k≤2V, carries out phase place reverse rotation by the Equations of The Second Kind pilot tone being multiplied by phase rotation coefficient estimated, then carries out difference operation with the Equations of The Second Kind pilot tone not being multiplied by the phase place reverse rotation factor, selects the m value making D value minimum as cyclic shift number, wherein, and X _kfor transmitting terminal is for estimating the Equations of The Second Kind pilot tone of phase rotating, for the Equations of The Second Kind pilot tone that receiving terminal estimates.

5. method according to claim 1, is characterized in that: according to two the 3rd class pilot tones inserted, and estimates receiving terminal and estimates phase rotating pilot tone the channel response at place according to formula estimate receiving terminal be multiplied by phase rotation coefficient after Equations of The Second Kind pilot frequency information, wherein, V+1≤k≤2V.

6. method according to claim 2, is characterized in that: ask smallest peaks average power PAPR to be specially: then twiddle factor vector corresponding to each subsequence dot product be added: again IFFT conversion is carried out to vectorial Y and obtain OFDM time domain sample signal y _n, according to formula: ask PAPR, calculate each group m _vcorresponding PAPR, until traveled through all m _vcombination, selects the OFDM symbol with minimum PAPR.