CN101425848B - Timing estimation method in single carrier frequency domain equalization system - Google Patents

Abstract

The invention discloses a timing estimation method in a single carrier frequency range equilibrium system; after the block synchronization, sample points closest to the timing position are obtained through a data auxiliary ML search algorithm and through setting a specific lead data structure, the timing deviation is locked to the deviation of one sample point, the rest timing deviation is estimated by an improved data-free auxiliary O&M algorithm; and the further timing correction is carried out by interpolating modules. With the method, a fully digital receiver is capable of acquiring the result of timing estimation in the time domain with high precision; moreover, the whole timing estimation process just needs less auxiliary data, so the practical value is very high.

Description

Timing estimation method in a kind of single-carrier frequency domain equalization system

Technical field

The present invention relates to moving communicating field, relate in particular to the timing estimation method in a kind of single-carrier frequency domain equalization system.

Background technology

At present; Along with new communication service demand increases rapidly; Transmission rate to wireless communication system and WLAN is had higher requirement; And the raising of transmission rate has brought bigger carrier wave frequency deviation, more serious ISI problems such as (intersymbol-interference, intersymbol interference) for conventional single-carrier system.OFDM (Orthogonal Frequency Division Multiplexing; OFDM) technology can effectively overcome the intersymbol interference that the weak channel of frequency selectivity brings; Become the research focus of radio communication and moving communicating field gradually, in multiple standards, be called as support technology.But the OFDM technology is relatively more responsive to carrier synchronization, and PAPR (Peak-to-Average Power Ratio, peak-to-average power ratio) is bigger, so the single-carrier frequency domain equalization system scheme is suggested.SC-FDE (single carrier system withfrequency domain equalization; Single carrier frequency domain equalization) is the method that a kind of up-and-coming anti-multipath disturbs in the broadband wireless transmission; The same piecemeal of taking with OFDM transmits, and adopts CP (CyclicPrefix, Cyclic Prefix) mode; So just can be converted into circular convolution to the linear convolution of signal and channel impulse response, and eliminate the interference of the data block that multipath causes.Adopt simple frequency-domain equalization technology just can eliminate intersymbol interference at receiving terminal.The SC-FDE system compares ofdm system and does not have the PAPR problem, thus need not use expensive linear power amplifier, simultaneously neither be responsive especially to carrier synchronization, so the SC-FDE technology receives increasing attention at present.

A most crucial problem in the digital communication technology field is exactly a stationary problem, is divided into carrier synchronization technically with regularly synchronously.In the baseband sampling signal that obtains through the receiving terminal behind the wireless mobile channel, exist carrier frequency offset, phase deviation and timing offset; These deviations generally derive from crystal oscillator between the transmitter and receiver do not match with wireless mobile channel in Doppler effect and these several aspects of frequency selectivity; Even if in the indoor environment of channel relatively flat, also can there be these deviations.Use the SC-FDE system of piece transmission technology that these synchronous deviations are had higher requirement.The simultaneous techniques of SC-FDE system be divided into carrier synchronization with regularly synchronously, its receiving terminal mainly contain following task synchronously:

1) frame arrive to detect, and is used for judging whether detect signal, and this is the synchronous first step, has only and judges that what receive is that useful signal just can carry out the processing of back;

2) carrier wave frequency deviation is caught;

3) carrier frequency tracking;

4) the symbol original position is estimated (piece is synchronous), promptly before equilibrium, accurately knows original position (initial Fourier transform FFT position), for obtaining more accurate position, needs timing estimation;

5) tracking of sampling clock frequency.

Can there be time-delay deviation in the SC-FDE radiofrequency signal owing to receive the influence reception signal of channel delay in separating the process of being transferred to baseband signal.Time-delay deviation can cause many-sided influence to the SC-FDE system; The one, make the planisphere of signal that rotation take place; The 2nd, brought inter symbol interference (ISI); The 3rd, inclined to one side correction can't be carried out accurate frequency offset estimating when not carrying out, and the 4th, the existence of time-delay deviation causes obtaining the original position of Fourier transform window accurately, causes channel estimating, frequency domain equalization precise decreasing; The 5th, the big more channel tracking of initial time-delay deviation, timing are followed the trail of, the effect of carrier tracking is poor more, and these all will cause system normally to move.The accuracy of therefore initial timing estimation will influence the performance of system to a great extent.Initial time-delay deviation should be controlled in 5% the symbol time in the general SC-FDE system, therefore in order to keep the superperformance of SC-FDE system, needs accurate timing.

Existing SC-FDE system piece synchronously after, mainly contain dual mode for processing regularly, a kind of processing mode is directly compensation in regularly following the tracks of, and is put into remaining time-delay deviation in the tracking to solve.Another kind of processing mode is to carry out timing estimation; The frequency offset estimating thinking is identical in existing timing estimation algorithm thinking and the ofdm system; Through utilizing two sections corresponding reception signal phase differences on frequency domain of identical auxiliary data to obtain timing offset, this timing estimation algorithm is specific as follows: the length of establishing unique word (UW) sequence A is the L Baud Length.Make two adjacent identical UW sequence A form new sequence [A A], obtain its sampled signal sequence and be respectively R in the correspondence of receiving terminal ₁=[r (1) ..., r (L)], R ₂=[r (L+1) ..., r (2L)], r (t) t={1,2 ... } expression receiving terminal signal sampling value.Owing to there is timing offset, the Fourier transform of R1, R2 sequence just is converted into the phase deviation on the frequency domain with the time-delay deviation on the time domain in theory, utilize this phase deviation just can obtain the time-delay deviation that will estimate.

Do not carry out the algorithm that timing estimation directly changes the timing tracking over to for above-mentioned synchronously at piece; Because the initial timing offset of wireless mobile channel is bigger; Cause channel estimating, frequency domain equalization module and tracing module estimated accuracy to reduce; Poor stability is to the demands for higher performance of module at the back.

Receive the algorithm that the phase difference of signal on frequency domain carries out timing estimation for above-mentioned utilization; Because this type algorithm need just can reach good effect under the very little situation of frequency deviation; And receiving terminal has only carried out thick frequency offset estimating before algorithm application; Also have bigger frequency deviation, the timing estimation results precision that therefore obtains is very low.Algorithm needs more auxiliary data simultaneously, can reduce the transmission rate of valid data, and algorithm need can increase the operand of algorithm and the complexity of realization in the enterprising line translation of frequency domain simultaneously.

Summary of the invention

The present invention provides the timing estimation method in a kind of SC-FDE system; Through setting distinctive lead data block structure; After the completion piece is synchronous; Combine through ML (Maximum Likelihood, the maximum likelihood) searching algorithm of the auxiliary type of data and O&M (the Oerder and Meyr) algorithm of the auxiliary type of free of data, directly on time domain, obtain timing estimation.

Technical scheme according to the invention is following:

Timing estimation method in a kind of single-carrier frequency domain equalization system, the sample rate of receiving terminal is 4 samplings, comprises step:

A, utilize maximum likelihood searching algorithm based on the BAKER sign indicating number to obtain sampled point Q near timing position;

B, be original position with Q, the data intercept section [r (Q) ..., r (Q+4M-1)]; With symbol S=[s (1) ..., s (4M)] and expression, i.e. S=[s (1);, s (4M)]=[r (Q) ..., r (Q+4M-1)]; Wherein M is the code element number in the data segment of intercepting, and the length of the data block of sending with transmitting terminal is identical, and S is carried out obtaining behind the bandpass filtering through first band pass filter

${\stackrel{\→}{S}}_1\left(z\right)=[s_1\left(1\right),\·\·\·,s_1\left(4M\right)];$

C, calculating $F\left(\left|{\stackrel{\→}{S}}_1\left(z\right)\right|\right)={\left|s_1\left(z\right)\right|}^2+\left|s_1\left(z\right)\right|$ , z=1.....4M, F () is a nonlinear function, with what obtain Carry out obtaining behind the bandpass filtering through second band pass filter

${\stackrel{\→}{S}}_2\left(z\right)=[s_2\left(1\right),\·\·\·,s_2\left(4M\right)];$

D, calculating residue timing offset $\widehat{\mathrm{\&epsiv;}}=-\frac{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2008102276735E00011.png,H2008102276735E00021.png"\; state="\{\{state\}\}">T</figure-callout>}}{2\mathrm{\&pi;}}\mathrm{Arg}\left(\underset{z=1}{\overset{\mathrm{VM}}{\mathrm{\&Sigma;}}}{s}_2\left(z\right)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008102276735E00011.png,H2008102276735E00021.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{V}z}\right),$ Make V=4 represent that the sample rate of receiving terminal is 4 samplings, promptly $\widehat{\mathrm{\&epsiv;}}=-\frac{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2008102276735E00011.png,H2008102276735E00021.png"\; state="\{\{state\}\}">T</figure-callout>}}{2\mathrm{\&pi;}}\mathrm{Arg}\left(\underset{z=1}{\overset{4M}{\mathrm{\&Sigma;}}}{s}_2\left(z\right)e^{-j\frac{\mathrm{\&pi;}}{2}z}\right),$ Total timing estimation value does

Wherein T is the code element transmission time, the side-play amount of the estimated value P of the original position of BAKER sign indicating number in the lead data that K-I-1 obtains for the sampling point position determined synchronously according to piece.

Preferably, said steps A specifically comprises step:

A1, after the auxiliary data that piece uses synchronously, add the auxiliary data of the lead data of N Baud Length as the maximum likelihood searching algorithm, said lead data is made up of the invalid code element of N-L Baud Length and the BAKER sign indicating number of L Baud Length;

A2, the sampling point position of determining synchronously according to piece obtain the estimated value P of the original position of BAKER sign indicating number in the lead data;

A3, confirmed that by estimated value P the hunting zone of the original position of BAKER sign indicating number is: with the P point is the center, and front and back each I sampled point is determined with the BAKER sign indicating number by the hunting zone and to be made the needed receiving sequence R of correlation computations;

The mould square C (k) of the correlation of A4,2I+1 BAKER sign indicating number sequence B of calculating and receiving sequence R, $C\left(k\right)={\left|\underset{n=1}{\overset{n}{\mathrm{\&Sigma;}}}\stackrel{\&OverBar;}{r}[k+4(n-1)]B^{*}\left(n\right)\right|}^2,$ K=1....2I+1;

A5, ask C (k) maximum corresponding sequence number K, obtain the offset T=K-I-1 of relative estimated position P, confirm the new original position Q of BAKER sign indicating number thus, its position is Q=P+ Δ T, and this position is near timing position.

Preferably, preceding 3 code elements of the Chu sequence that said invalid code element is 8 Baud Lengths, said BAKER sign indicating number is the sequence B of 13 Baud Lengths, B=[B (1) ... ..B (13)]=[1-1-1-1-111-1-11-11-1], i.e. N=16, L=13.

Preferably, said R be [r (P-I) ..., r (P+52+I)], with formula R=[r (1);, r (52+2I)] expression, promptly R=[r (1) ..., r (52+2I)]=[r (P-I);, r (P+52+I)], R is 2I+L*4=2I+52 sampled point altogether, and wherein r () is for receiving signal sampling value.

Preferably, the value of said position offset Δ T be on the occasion of the time, the expression timing position need squint to data transfer direction, when the value of said position offset Δ T was negative value, the expression timing position need be to the skew of the opposite direction of transfer of data.

Preferably, said first band pass filter is that centre frequency is the band pass filter of 1/2T, and said second band pass filter is that centre frequency is the band pass filter of 1/T.

Beneficial effect of the present invention is following:

The present invention is through setting distinctive lead data block structure; After the completion piece is synchronous; ML searching algorithm through the auxiliary type of data obtains the sampled point near timing position; Timing offset is locked onto the deviation of a sampled point, utilize the O&M algorithm estimated remaining timing offset of the auxiliary type of free of data after improving this moment again, carry out further correction of timing through interpolating module.All-digital receiver can directly obtain timing estimation results after adopting the present invention on time domain, and its precision is very high, and only needs less auxiliary data in the whole timing estimation process, and very high practical value is arranged.

Description of drawings

Fig. 1 is the flow chart of the timing estimation method in the SC-FDE according to the invention system;

Fig. 2 is for when the value of D is 4, calculates the peaked sketch map of mould square C (k) of the correlation of 9 BAKER sign indicating number sequence B and receiving sequence R;

Fig. 3 is for utilizing the sketch map of the further estimated remaining timing offset of O&M algorithm after improving among the present invention.

Embodiment

Because the all-digital receiver utilization in the reality is that interpolation algorithm recovers timing data, so receiving terminal generally all is at least 4 samplings, and promptly a code element has 4 sampled points at least.After piece is accomplished synchronously, can obtain rough sampling point position, but just be locked in a small range with original position this moment.In order to obtain accurate original position, need carry out further timing estimation, promptly smart timing estimation.The present invention is through setting distinctive lead data structure, accomplish piece synchronously after, the ML searching algorithm through the auxiliary type of data obtains the sampled point near timing position; Timing offset is locked onto the deviation of a sampled point, this moment treat estimation range narrowed down to (T/V, T/V); T is the code element transmission time, and V is the sample rate of receiving terminal, is 4 samplings generally speaking; Be scope narrow down to (T/4, T/4).Utilize the O&M algorithm estimated remaining timing offset of the auxiliary type of free of data after improving this moment again, carry out further correction of timing through interpolating module.All-digital receiver can directly obtain timing estimation results after adopting the present invention on time domain, and its precision is very high, and only needs less auxiliary data in the whole timing estimation process, and very high practical value is arranged.

Below in conjunction with each accompanying drawing concrete implementation procedure of the present invention is done further detailed explanation.

See also Fig. 1, this figure is the flow chart of the timing estimation method in the SC-FDE according to the invention system, and its concrete implementation procedure is following:

Step 10, after the auxiliary data that piece uses synchronously, add the auxiliary data of the lead data of N Baud Length as the ML searching algorithm, said lead data is made up of the invalid code element of N-L Baud Length and the BAKER sign indicating number of L Baud Length.

Adopt specific lead data structural reason following among the present invention:

The BAKER sign indicating number has strong autocorrelation performance; Length is that energy is L the most by force in the auto-correlation position for the BAKER sign indicating number of L; And the energy of all the other positions all is 1, even just because of this point makes the sampled point that also can accurately search under certain frequency deviation and the weak condition near timing position existing.The invalid code that increases is in order to ensure the strong correlation in the hunting zone.

Can select for use preceding 3 code elements in the Chu sequence of 8 Baud Lengths as invalid code element in the reality; The BAKER sign indicating number is 13 Baud Length B=[B (1); ... ..B (13)]=[1-1-1-1-111-1-11-11-1], this moment, the sample rate of receiving terminal was 4 samplings, the reception signal sampling value is r (t) t={1; 2 ... }.

Step 11, the sampling point position of determining synchronously according to piece obtain the estimated value P of the original position of BAKER sign indicating number in the lead data.

Step 12, confirmed that by estimated value P the hunting zone of the original position of BAKER sign indicating number is: with the P point is the center, front and back each I sampled point.Determine with the BAKER sign indicating number by the hunting zone and to make the needed receiving sequence R of correlation computations;

Said R be [r (P-I) ..., r (P+52+I)], with formula R=[r (1) ..., r (52+2I)] expression, promptly R=[r (1) ..., r (52+2I)]=[r (P-I) ..., r (P+52+I)], R is 2I+L*4=2I+52 sampled point altogether, and wherein r () is for receiving signal sampling value.

The mould square C (k) of the correlation of step 13,2I+1 BAKER sign indicating number sequence B of calculating and receiving sequence R, $C\left(k\right)={\left|\underset{n=1}{\overset{n}{\mathrm{\&Sigma;}}}\stackrel{\&OverBar;}{r}[k+4(n-1)]B^{*}\left(n\right)\right|}^2,$ K=1....2I+1.

If I value selected in the step 12 is 4, then need calculate R ₁=[r (1), r (5) ..., r (49)] with the mould square C (1) of the correlation of sequence B, R ₂=[r (2), r (6) ..., r (50)] with the mould square C (2) of the correlation of sequence B ... .., calculate R ₉=[r (9), r (13) ..., r (57)] with the mould square C (9) of the correlation of sequence B.

Step 14, ask the maximum corresponding sequence number K of C (k); Obtain the offset T=K-I-1 of relative estimated position P, confirm the new original position Q of BAKER sign indicating number thus, its position is Q=P+ Δ T; This position is adjusted the original position of Fourier transform window near timing position with this.

In this step, the value of said position offset Δ T be on the occasion of the time, the expression timing position need squint to data transfer direction, when the value of said position offset Δ T was negative value, the expression timing position need be to the skew of the opposite direction of transfer of data.

See also Fig. 2, this figure is when the value of I is 4, calculates the peaked sketch map of mould square C (k) of the correlation of 9 BAKER sign indicating number sequence B and receiving sequence; By visible among the figure; Input data r (n) are by the input of sampling beat, and data are put in the buffering area of four sampling time-delays, after four samplings of continuous input; This unit begins to calculate (at this moment importing data is r (4), and delay line is output as r (0)).Four samplings of every input (also being a symbol), the BARKER sign indicating number is updated to next bit.Calculating 13 so altogether takes turns.After last took turns beginning, the summer result that will add up square outputed to the MAX unit through mould, compares, and from all 9 accumulation results, determines maximum, determined the sampled point Q near timing position with this.

After above-mentioned steps is accomplished, can access near the sampled point of timing position, can timing offset be locked onto the deviation of a sampled point, i.e. the deviation of 1/4 code element.Utilize the further estimated remaining timing offset of O&M algorithm after improving below, to reach the purpose that accurate timing is estimated.

See also Fig. 3; This figure is the sketch map that utilizes the further estimated remaining timing offset of O&M algorithm after improving among the present invention; The O&M algorithm is insensitive to frequency deviation, does not need data auxiliary, simple in structure; Precision is higher under the situation of the certain less timing offset of the comparatively accurate i.e. existence of original position, implements more or less freely.The non-linear form of adjustment O&M algorithm not only can not reduce the shake variance under the non-weak channel, and can reduce the shake variance under the wireless mobile channel, improves estimated accuracy.Have the cyclic stationary characteristic if the O&M algorithm basic principle is the signal of matched filtering output through the signal after the Nonlinear Processing, just have spectral line to produce so in the symbol rate position.This just can use the Fourier series expansion to calculate spectral line.Input at the O&M algorithm carries out the bandpass filtering first time to signal, after non-linear, carries out the bandpass filtering second time, can reduce noise to estimation effect, reduces shake, improves estimated accuracy.Utilize the detailed process of the further estimated remaining timing offset of O&M algorithm after improving following among the present invention:

Step 15, be original position with Q, the data intercept section [r (Q) ..., r (Q+4M-1)]; With symbol S=[s (1) ..., s (4M)] and expression, i.e. S=[s (1);, s (4M)]=[r (Q) ...; R (Q+4M-1)], wherein M is the code element number in the data segment of intercepting, the length of the data block of sending with transmitting terminal is identical;

Step 16, S is carried out obtaining behind the bandpass filtering through first band pass filter

${\stackrel{\&RightArrow;}{S}}_1\left(z\right)=[s_1\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,s_1\left(4M\right)].$

Step 17, calculating $F\left(\left|{\stackrel{\&RightArrow;}{S}}_1\left(z\right)\right|\right)={\left|s_1\left(z\right)\right|}^2+\left|s_1\left(z\right)\right|$ , z=1.....4M, F () are nonlinear function, original O&M algorithm use be quadratic nonlinearity $F\left(\left|{\stackrel{\&RightArrow;}{S}}_1\left(z\right)\right|\right)={\left|s_1\left(z\right)\right|}^2$ , z=1.....4M among the present invention is adjusted into it $F\left(\left|{\stackrel{\&RightArrow;}{S}}_1\left(z\right)\right|\right)={\left|s_1\left(z\right)\right|}^2+\left|s_1\left(z\right)\right|,z=1.....4M.$

Step 18, with what obtain in the step 17 Carry out obtaining behind the bandpass filtering through second band pass filter

${\stackrel{\&RightArrow;}{S}}_2\left(z\right)=[s_2\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,s_2\left(4M\right)].$

Step 19, calculating residue timing offset $\widehat{\mathrm{\&epsiv;}}=-\frac{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2008102276735E00011.png,H2008102276735E00021.png"\; state="\{\{state\}\}">T</figure-callout>}}{2\mathrm{\&pi;}}\mathrm{Arg}\left(\underset{z=1}{\overset{\mathrm{VM}}{\mathrm{\&Sigma;}}}{s}_2\left(z\right)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008102276735E00011.png,H2008102276735E00021.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{V}z}\right),$ Make V=4 represent that the sample rate of receiving terminal is 4 samplings, promptly $\widehat{\mathrm{\&epsiv;}}=-\frac{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2008102276735E00011.png,H2008102276735E00021.png"\; state="\{\{state\}\}">T</figure-callout>}}{2\mathrm{\&pi;}}\mathrm{Arg}\left(\underset{z=1}{\overset{4M}{\mathrm{\&Sigma;}}}{s}_2\left(z\right)e^{-j\frac{\mathrm{\&pi;}}{2}z}\right),$ Wherein T is the code element transmission time.

Step 20, proofread and correct the signal after obtaining regularly according to

through the interpolation mould.Total timing estimation value of determining through the present invention is

Above-mentioned first band pass filter is that centre frequency is the band pass filter of 1/2T, and above-mentioned second band pass filter is that centre frequency is the band pass filter of 1/T.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, belong within the scope of claim of the present invention and equivalent technologies thereof if of the present invention these are revised with modification, then the present invention also is intended to comprise these changes and modification interior.

Claims (6)

1. the timing estimation method in the single-carrier frequency domain equalization system, the sample rate of receiving terminal is 4 samplings, it is characterized in that, comprises step:

A, utilize maximum likelihood searching algorithm based on the BAKER sign indicating number to obtain sampled point Q near timing position;

B, be original position with Q, the data intercept section [r (Q) ...; R (Q+4M-1)], with symbol S=[s (1) ... S (4M)] expression, promptly S=[s (1) ... S (4M)]=[r (Q); ..., r (Q+4M-1)], wherein M is the code element number in the data segment of intercepting; The length of the data block of sending with transmitting terminal is identical, S is carried out obtaining behind the bandpass filtering

r () through first band pass filter be the reception signal sampling value with s ();

C, calculating

Z=1 ... .., 4M, F () is a nonlinear function, with what obtain

Carry out obtaining behind the bandpass filtering through second band pass filter

${\stackrel{\&RightArrow;}{S}}_2\left(z\right)=[s_2\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,s_2\left(4M\right)];$

D, calculating residue timing offset Make V=4 represent that the sample rate of receiving terminal is 4 samplings, promptly Total timing estimation value does

Wherein T is the code element transmission time; The side-play amount of the estimated value P of the original position of BAKER sign indicating number in the lead data that K-I-1 obtains for the sampling point position determined synchronously according to piece; K is the maximum corresponding sequence number of C (k); C (k) is the mould square of the correlation of 2I+1 BAKER sign indicating number sequence B and receiving sequence R $C\left(k\right)={\left|\underset{n=1}{\overset{n}{\mathrm{\&Sigma;}}}\stackrel{\&OverBar;}{r}\right[k+4(n-1)\left]B^{*}\left(n\right)\right|}^2,$ K=1 ...., 2I+1, n=4L, $R=[\stackrel{\&OverBar;}{r}\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,\stackrel{\&OverBar;}{r}(52+2I)]=[r(P-I),\&CenterDot;\&CenterDot;\&CenterDot;,r(P+52+I)],$ Wherein, P is a central point, and I is for the P point being front and back, center each I sampled point.

2. the method for claim 1 is characterized in that, said steps A specifically comprises step:

A1, after the auxiliary data that piece uses synchronously, add the auxiliary data of the lead data of N Baud Length as the maximum likelihood searching algorithm, said lead data is made up of the invalid code element of N-L Baud Length and the BAKER sign indicating number of L Baud Length;

A2, the sampling point position of determining synchronously according to piece obtain the estimated value P of the original position of BAKER sign indicating number in the lead data;

A3, confirmed that by estimated value P the hunting zone of the original position of BAKER sign indicating number is: with the P point is the center, and front and back each I sampled point is determined with the BAKER sign indicating number by the hunting zone and to be made the needed receiving sequence R of correlation computations;

The mould square C (k) of the correlation of A4,2I+1 BAKER sign indicating number sequence B of calculating and receiving sequence R, $C\left(k\right)={\left|\underset{n=1}{\overset{n}{\mathrm{\&Sigma;}}}\stackrel{\&OverBar;}{r}\right[k+4(n-1)\left]B^{*}\left(n\right)\right|}^2,$ K=1 ...., 2I+1, n=4L;

A5, ask C (k) maximum corresponding sequence number K, obtain the offset T=K-I-1 of relative estimated position P, confirm the new original position Q of BAKER sign indicating number thus, its position is Q=P+ Δ T, and this position is near timing position.

3. method as claimed in claim 2 is characterized in that, preceding 3 code elements of the Chu sequence that said invalid code element is 8 Baud Lengths; Said BAKER sign indicating number is the sequence B of 13 Baud Lengths; B=[B (1) ... .., B (13)]=[1-1-1-1-1 1 1-1-1 1-1 1-1]; Be N=16, L=13.

4. method as claimed in claim 2 is characterized in that, said R be [r (P-I) ..., r (P+52+I)], use formula Expression, promptly $R=[\stackrel{\&OverBar;}{r}\left(1\right),\&CenterDot;\&CenterDot;\&CenterDot;,\stackrel{\&OverBar;}{r}(52+2I)]=[r(P-I),\&CenterDot;\&CenterDot;\&CenterDot;,r(P+52+I)],$ R is 2I+L*4=2I+52 sampled point altogether, and wherein r () is for receiving signal sampling value.

5. method as claimed in claim 2; It is characterized in that, the value of said offset T be on the occasion of the time, the expression timing position need squint to data transfer direction; When the value of said offset T was negative value, the expression timing position need be to the opposite direction skew of transfer of data.

6. method as claimed in claim 2 is characterized in that, said first band pass filter is that centre frequency is the band pass filter of 1/2T, and said second band pass filter is that centre frequency is the band pass filter of 1/T.

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