CN102215184A - Method and system for estimating uplink timing error - Google Patents

Abstract

The invention discloses a method and system for estimating an uplink timing error. The method comprises the following steps of: estimating a channel frequency domain response of a pilot frequency position by using frequency domain data of an orthogonal frequency division multiplexing (OFDM) symbol; converting the estimated channel frequency domain response to a time domain so as to obtain a channel time domain response and carrying out zero resetting a tap determined as a noise item in the channel time domain response; converting the channel time domain response, which is obtained after the tap of the noise item is subjected to zero resetting, to a frequency domain so as to obtain a converted channel frequency domain response; carrying out conjugate correlation on pilot frequency points spaced in the converted channel frequency domain response and carrying out sequence averaging on a conjugate correlation result to obtain a sequence average value; and reconstructing a noise interference item by using rest taps after the tap of the noise item is subjected to zero resetting and estimating a timing error after subtracting the noise interference item from the sequence average value. According to the invention, the estimation precision of the timing error can be effectively improved and the demodulation property of the uplink channel can be assured.

Description

A kind of method of estimation of up timing offset and system

Technical field

The present invention relates to communication technical field, relate in particular to the method for estimation and the system of up timing offset in a kind of OFDM (Orthogonal FrequencyDivision Multiplexing, OFDM) system.

Background technology

In wireless communication system, the performance of simultaneous techniques is directly connected to the performance of whole communication system, and it is the prerequisite of information reliable transmission.OFDM (Orthogonal Frequency DivisionMultiplexing, OFDM) system can be divided into sample-synchronous, carrier synchronization and timing synchronously synchronously.

In ofdm system, comprise synchronously that regularly timing synchronization and sample value are regularly synchronously.The purpose of timing synchronization is to make receiving terminal determine the start-stop moment of each OFDM symbol, promptly determines FFT (fast Fourier transform) window position accurately, and further realizes the synchronous or frame synchronization of piece; Sample value regularly synchronously then is in order to make receiving terminal determine the start-stop moment of each sample value symbol.The realization sign synchronization need be determined symbol timing offset and sample value timing offset in ofdm system, as shown in Figure 1, the sample value symbol distribution the during sampling of first behavior ideal, there is symbol timing offset Δ t in second behavior with respect to the ideal sampling _fThe time sample value symbol distribution determined, there is sample value timing offset Δ t when sampling with respect to ideal in the third line _yThe time sample value symbol distribution determined, there is symbol timing offset Δ t when sampling with respect to ideal in fourth line _fWith sample value timing offset Δ t _yThe time sample value symbol distribution determined.

For symbol timing offset Δ t _f, as long as initial moment of symbol drop on Cyclic Prefix (CyclicPrefix, CP) in, just can not destroy the orthogonality between each subcarrier, only can cause the phase place rotation.Otherwise, can destroy the orthogonality between each subcarrier, also can crosstalk between created symbol simultaneously.Sample value timing offset Δ t _yCan equivalence be a fixing time delay.Therefore generally with symbol timing offset Δ t _fWith sample value timing offset Δ t _yThe equivalence that influences be a total timing offset value, by estimating this value ofdm system is carried out best timing, obtain the performance an of the best to guarantee ofdm system.

At present about estimating that the synchronous method of timing offset realization timing mainly is divided into following two classes:

1) based on the time domain correlation method of CP

This method is to utilize the redundancy of Cyclic Prefix, carries out auto-correlation in time domain and comes tracking symbol, promptly intercepts CP and OFDM symbol afterbody counterpart and carries out relevantly, obtains the largest peaks point, can determine the position of synchronization timing deviation.

Adopt the timing offset method of estimation of this kind mode, because the influence of channel multi-path, in the front portion of CP, the hangover of previous OFDM symbol has partly produced certain interference, that is to say that to utilize the data of CP front portion unreliable, thereby need obtain the starting point of CP valid data.Yet when system bandwidth hour because the number of samples of whole C P is smaller, if remove some sampling points that disturbed again, this moment available effective sampling point just still less, just have the not high problem of timing offset estimated accuracy.

2) based on the frequency domain correlation method of pilot tone

This algorithm is to utilize pilot signal in the received signal and local pilot signal to carry out frequency domain correlation to realize symbol tracking, the reception data and the local pilot frequency sequence that are about to pilot frequency locations on the same OFDM symbol multiply each other, eliminate the influence of local pilot frequency sequence, the frequency domain channel that has also promptly obtained the pilot tone place is estimated, calculate the conjugation correlation of adjacent pilot frequencies channel estimating afterwards, the phase place of this conjugation correlation is introduced by timing offset, thereby can obtain the timing offset value.

Adopt the timing offset method of estimation of this kind mode, less when the bandwidth that takies, when signal to noise ratio was low simultaneously, the estimated accuracy of timing offset was lower.Usually the frequency-region signal that will eliminate local pilot frequency sequence transforms to time domain, the signal value of determining noise in the time domain is put 0, afterwards again by DFT (Direct FourietTransformer, discrete Fourier transform) transforms to frequency domain, carry out the calculating of conjugation correlation of the adjacent pilot frequencies channel estimating of back again.The uplink channel estimation that transforms from the time domain to frequency domain adopts DFT (DirectFouriet Transformer, discrete Fourier transform) algorithm, promptly get window and carry out noise suppression raising channel estimated accuracy in time domain, but there is very big influence in this operation to the estimation of timing offset, when low signal-to-noise ratio even can't follow the tracks of, estimate timing offset.

Adopt existing timing offset method of estimation because the accurate timing offset of estimating OFDM system, when ofdm system life period deviation, the influence that brings is mainly reflected in: increase the sensitivity of ofdm system to the time delay expansion, and cause that thereby phase deviation causes demodulation performance to descend, error rate increase.

Summary of the invention

The invention provides a kind of up timing offset method of estimation and system, be used for effectively improving the estimated accuracy of timing offset, guaranteed the demodulation performance of up channel.

The invention provides a kind of method of estimation of up timing offset, comprising:

Utilize the frequency domain data of the orthogonal frequency division multiplex OFDM symbol that receives and the channel frequency domain response of local pilot data estimating pilot frequency position;

The estimated channel frequency domain response is transformed to time domain obtain the channel time domain response, and will determine it is the tap zero setting of noise item in the described channel time domain response;

The channel time domain response transform that will obtain after noise item tap zero setting is to frequency domain, obtains channel frequency domain response after the conversion;

It is relevant that at interval pilot tone point in the channel frequency domain response after the described conversion is carried out conjugation, and ask sequence average to obtain serial mean to the relevant result of conjugation;

Remaining tap reconstructs the noise jamming item after utilizing noise item tap zero setting, estimates timing offset deduct described noise jamming item in described serial mean after.

The present invention also provides a kind of estimating system of up timing offset, comprising:

The first channel frequency domain response estimation unit is used to utilize the frequency domain data of orthogonal frequency division multiplex OFDM symbol of reception and the channel frequency domain response of local pilot data estimating pilot frequency position;

The first channel time domain response unit is used for that the estimated channel frequency domain response is transformed to time domain and obtains the channel time domain response;

Tap zero setting unit is used for described channel time domain response is determined it is the tap zero setting of noise item;

Second channel frequency domain response unit is used for the channel time domain response transform that will obtain to frequency domain after noise item tap zero setting, obtain channel frequency domain response after the conversion;

The conjugation correlation unit is used for that the pilot tone point at interval of channel frequency domain response after the conversion is carried out conjugation and is correlated with;

All value cell is used for asking sequence average to obtain serial mean to the relevant result of conjugation;

Interference reconstruction unit, be used to utilize noise item tap zero setting after remaining tap reconstruct the noise jamming item;

The timing offset estimation unit is used for estimating timing offset after described serial mean deducts described noise jamming item.

Utilize the method for estimation and the system of up timing offset provided by the invention, has following beneficial effect: contain the noise jamming item and eliminate to getting behind the window frequency domain conjugation sequence of correlation values average packet, efficiently solve and utilize the frequency domain channel value get behind the window when low signal-to-noise ratio, can't carry out the problem of reliable timing estimation, effectively improve the precision that timing offset is estimated, guaranteed the demodulation performance of up channel.

Description of drawings

There is the schematic diagram of up timing offset in Fig. 1 for ofdm system;

Fig. 2 is the existing flow chart of estimating timing offset based on the frequency domain correlation method of pilot tone;

Fig. 3 is the method for estimation flow chart of up timing offset in the embodiment of the invention;

Fig. 4 is the estimating system structured flowchart of up timing offset in the embodiment of the invention.

Embodiment

Method of estimation and system to the up timing offset of the present invention's proposition illustrates in greater detail below in conjunction with drawings and Examples.

In ofdm system, suppose that the frequency domain reception data of an a certain moment OFDM symbol are:

R _k＝H _kS _k+W _k?k＝0，1，…，N-1 (1)

Wherein k represents OFDM symbol subcarrier sequence number, R _kThe frequency domain of pilot tone correspondence position receives data, H on the expression OFDM symbol _kThe frequency domain channel impulse response of expression pilot frequency locations, S _kThe pilot data of expression transmitting terminal, W _kThe expression additive white Gaussian noise, N represents useful subcarrier number, the i.e. number of OFDM symbol subcarrier in the ofdm system bandwidth.

Provide the principle that to estimate up timing offset based on the frequency domain correlation method of pilot tone below.According to existing frequency domain correlation method, as shown in Figure 2, carry out following flow process based on pilot tone:

Step S201 carries out conjugate multiplication with frequency domain data and the local pilot data of the orthogonal frequency division multiplex OFDM symbol that receives, thereby the influence of elimination pilot frequency sequence has also promptly obtained the channel frequency domain response of pilot sub-carrier position

$\hat{H}=R_k{S}_k^{*}=H_k{S}_k{S}_k^{*}+W_k{S}_k^{*}=P_s{H}_k+W_k^{\′}---\left(2\right)$

Suppose that signal carries out power normalization, then

Step S202 is to channel frequency domain response

Carry out Inverse Discrete Fourier Transform IDFT, obtain the estimated channel time-domain response

That is:

${\hat{h}}_n=\mathrm{IDFT}{\left(\hat{H}\right)}_n=h_n+w_n$ n＝0，1，…，N-1 (3)

Step S203 will determine it is the tap zero setting of noise item in the channel time domain response among the step S202, obtains the channel time domain response

The sample point of correspondence when the tap here refers to promptly that n gets different value.

Above-mentioned definite channel time domain response The existing method of the concrete employing of middle noise item no longer is described in detail here.

${\tilde{h}}_n=\left\{\begin{array}{cc}{\hat{h}}_n& n\∈\mathrm{\Ω}\\ 0& \mathrm{others}\end{array}\right.---\left(4\right)$

Wherein, Ω is the tap position set that is kept after the tap zero setting.

Step S204 is to the result of step S203

Carry out leaf transformation DFT in the N point discrete Fourier, obtain the channel frequency domain response estimation value on all subcarriers

${\tilde{H}}_k=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{\tilde{h}}_n{e}^{-j\·\frac{2\mathrm{\π}}{N}\·n\·k}=\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}\tilde{h}{e}^{-j\·\frac{2\mathrm{\π}}{N}\·n\·k}=H_k+\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{w}_n{e}^{-j\·\frac{2\mathrm{\π}}{N}\·n\·k}=H_k+{\tilde{W}}_k---\left(5\right)$

Wherein: k=0,1 ..., N-1

Step S205 is to being spaced apart two pilot tone point k of Δ k ₁, k ₂It is relevant to do conjugation:

${\tilde{H}}_{k_1}\·{\tilde{H}}_{k_2}^{*}=(H_{k_1}+{\tilde{W}}_{k_1}){(H_{k_2}+{\tilde{W}}_{k_2})}^{*}$

$=H_{k_1}\·H_{k_2}^{*}+\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}\underset{m\∈\mathrm{\Ω}}{\mathrm{\Σ}}{w}_n{w}_m^{*}{e}^{j\·\frac{2\mathrm{\π}}{N}\·({\mathrm{mk}}_2-{\mathrm{nk}}_1)}+H_{k_1}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{w}_n{e}^{j\·\frac{2\mathrm{\π}}{N}\·n\·k_2}+H_{k_2}^{*}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{w}_n{e}^{-j\·\frac{2\mathrm{\π}}{N}\·n\·k_1}---\left(6\right)$

Wherein, k ₂=k ₁+ Δ k, k ₁=0 ..., N-1-Δ k

Step S206, the sequence to conjugation after relevant is asked serial mean:

$E({\tilde{H}}_{k_1}\·{\tilde{H}}_{k_2}^{*})=E(H_{k_1}\·H_{k_2}^{*})+\frac{1}{N}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{\left|\right|w_n\left|\right|}^2{e}^{j\·\frac{2\mathrm{\π}}{N}\·\mathrm{n\Δk}}=1+\frac{{\mathrm{\σ}}^2}{N}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{e}^{-j\·\frac{2\mathrm{\π}}{N}\·n\·\mathrm{\Δk}}---\left(7\right)$

Obtain formula (7) by formula (6) and be based on following hypothesis:

1) Xiang Guan adjacent pilot frequencies point channel estimation value is approximate identical:

Promptly have:

$E(H_{k_1}\·H_{k_2}^{*})=1;$

2) w _nBe additive white Gaussian noise, and || w _n|| ²=σ ², σ ²Power for additive white Gaussian noise;

3) signal and noise are uncorrelated;

Step S201～step S206 is based on the derivation that does not have timing offset, supposes that there is timing offset Δ n in ofdm system, then:

Formula (1) should be modified to:

K=0,1 ..., N-1 (1 ')

Then according to the channel frequency domain response of pilot sub-carrier position among the step S201

Should be:

$\hat{H}=R_k{S}_k^{*}=H_k{e}^{\frac{j2\mathrm{\π\Δnk}}{N}}+W_k^{\′}---\left(2^{,}\right)$

According to the derivation of above-mentioned steps S202～step S205, the serial mean in can determining step S206 should be:

$E({\tilde{H}}_{k_1}\·{\tilde{H}}_{k_2}^{*})=W_N^{\mathrm{\Δn\Δk}}+\frac{{\mathrm{\σ}}^2}{N}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{W}_N^{\mathrm{n\Δk}}---\left(7^{,}\right)$

Wherein $W_N^{\mathrm{nk}}=e^{-j\·\frac{2\mathrm{\π}\·n\·k}{N}}.$

Step S207, the sequence of utilizing step S206 to obtain asks serial mean to estimate timing offset:

$\mathrm{\Δn}=\frac{\mathrm{angle}\left(Q\right)*N_{\mathrm{FFT}}}{2\mathrm{\π\Δk}}---\left(8^{,}\right)$

Wherein, angle is for asking phase bit arithmetic, N _FFTFor carrying out counting of fast Fourier transform FFT window that the OFDM symbolic blocks uses when synchronous, Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

Do not get window if do not carry out time domain when spatial transform is to the channel estimating of frequency domain after the denoising in step S204, then second in the formula (7 ') equals 0, otherwise this is not 0, then can estimate at certain influence to synchronization timing.After process was got window, the serial mean that frequency domain adjacent pilot frequencies point conjugation is relevant not only comprised the phase rotation coefficient that timing offset brings, and also comprises the noise jamming item simultaneously as can be seen.This is if the noise power that keeps is excessive, and playing main contribution in the relevant serial mean of frequency domain adjacent pilot frequencies point conjugation will be noise jamming, thereby utilizes existing method can't carry out timing offset and estimate.

At the problem that the channel estimating time domain is got curtain heading tape, the method for estimation of up timing offset proposed by the invention is at first revised the relevant serial mean of frequency domain adjacent pilot frequencies point conjugation, eliminates the distracter that noise path is brought.In embodiments of the invention one, a kind of method of estimation of up timing offset is provided, as shown in Figure 3, this method may further comprise the steps:

Step S301, the frequency domain data R of the orthogonal frequency division multiplex OFDM symbol that utilization receives _kChannel frequency domain response with local pilot data estimating pilot frequency position.

Preferably, according to the frequency domain reception data R of formula (2) with pilot frequency locations on the same OFDM symbol _kMultiply each other the channel frequency domain response of the pilot frequency locations that obtains estimating with local pilot frequency sequence

Step is 302, with the estimated channel frequency domain response

Transform to time domain and obtain the channel time domain response

Preferably, by Inverse Discrete Fourier Transform IDFT, according to formula (3) with the estimated channel frequency domain response

Transform to time domain and obtain the channel time domain response

Step S303 is with described channel time domain response

In determine it is the tap zero setting of noise item;

Wherein determine the channel time domain response

The existing method of the concrete employing of middle noise item no longer is described in detail here.

${\tilde{h}}_n=\left\{\begin{array}{cc}{\hat{h}}_n& n\∈\mathrm{\Ω}\\ 0& \mathrm{others}\end{array}\right.$

Wherein, Ω is the tap position set that is kept after the tap zero setting.

Step S304, the channel time domain that will after noise item tap zero setting, obtain response

Transform to frequency domain, obtain channel frequency domain response after the conversion

The channel time domain response that will after noise item tap zero setting, obtain in the present embodiment Carry out according to formula (5) that leaf transformation DFT transforms to frequency domain in the N point discrete Fourier, described N is the number of OFDM symbol subcarrier.

Step S305 is to channel frequency domain response after the conversion

Middle pilot tone point at interval carries out conjugation and is correlated with;

Specifically can carry out conjugation to the pilot tone point that is spaced apart Δ k and be correlated with according to formula (6), preferably, to channel frequency domain response after the conversion

Middle pilot tone point at interval carries out conjugation is correlated with, and is specially channel frequency domain response after the conversion

In adjacent pilot tone point to carry out conjugation relevant

Step S306 is in step S305

The result that conjugation is relevant asks sequence average to obtain serial mean;

Specifically ask serial mean according to formula (7 ')

Step S307 utilizes channel time domain response after the noise item tap zero setting Remaining tap reconstructs the noise jamming item.

Specifically can determine the channel time domain response according to the noise item of tap zero setting among the step S303

The position of stick signal tap and number, thus reconstruct the noise jamming item (being second in the formula (7)) of reservation noise tap introducing and deduct this distracter from serial mean, obtain amended serial mean:

$I=\frac{{\mathrm{\σ}}^2}{N}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{W}_N^{\mathrm{n\Δk}}$

$Q=E({\tilde{H}}_{k_1}\·{\tilde{H}}_{k_2}^{*})-I=W_N^{\mathrm{\Δn\Δk}}$

Wherein

I is the noise jamming item, σ ²Be the power of additive white Gaussian noise, N is the number of OFDM symbol subcarrier, and Ω is the tap position set that is kept after the tap zero setting, and Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

By this step, the conjugation sequence of correlation values of adjacent pilot frequencies point is average just only relevant with timing offset, thereby can estimate timing offset accurately.

Step S308, utilize amended serial mean to estimate timing offset Δ n:

$\mathrm{\Δn}=\frac{\mathrm{angle}\left(Q\right)*N_{\mathrm{FFT}}}{2\mathrm{\π\Δk}}=\frac{\mathrm{angle}\left(E({\tilde{H}}_{k_1}\·{\tilde{H}}_{k_2}^{*})-I\right)*N_{\mathrm{FFT}}}{2\mathrm{\π\Δk}}$

Wherein, angle is for asking phase bit arithmetic, N _FFTFor carrying out counting of fast Fourier transform FFT window that the OFDM symbolic blocks uses when synchronous, be the subcarrier number that exists in the ofdm system bandwidth, Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

As seen, the present invention contains the noise jamming item and eliminates getting behind the window frequency domain conjugation sequence of correlation values average packet, efficiently solve and utilize the frequency domain channel value get behind the window when low signal-to-noise ratio, can't carry out the problem of reliable timing estimation, effectively improve the precision that timing offset is estimated, guaranteed the demodulation performance of up channel.

In embodiments of the invention two, a kind of estimating system of up timing offset is provided, as shown in Figure 4, this system comprises: the first channel frequency domain response estimation unit 401 is used to utilize the frequency domain data of orthogonal frequency division multiplex OFDM symbol of reception and the channel frequency domain response of local pilot data estimating pilot frequency position; The first channel time domain response unit 402 is used for that the estimated channel frequency domain response is transformed to time domain and obtains the channel time domain response; Tap zero setting unit 403 is used for described channel time domain response is determined it is the tap zero setting of noise item; Second channel frequency domain response unit 404 is used for the channel time domain response transform that will obtain to frequency domain after noise item tap zero setting, obtain channel frequency domain response after the conversion; Conjugation correlation unit 405 is used for that the pilot tone point at interval of channel frequency domain response after the conversion is carried out conjugation and is correlated with; All value cell 406 is used for asking sequence average to obtain serial mean to the relevant result of conjugation; Interference reconstruction unit 407, be used to utilize noise item tap zero setting after remaining tap reconstruct the noise jamming item; Timing offset estimation unit 408 is used for estimating timing offset after described serial mean deducts described noise jamming item.

Preferably, the first channel frequency domain response estimation unit 401 specifically is used for the frequency domain reception data and the local pilot frequency sequence of pilot frequency locations on the same OFDM symbol are multiplied each other the channel frequency domain response of the pilot frequency locations that obtains estimating.The first channel time domain response unit 402 specifically is used for by Inverse Discrete Fourier Transform IDFT, the estimated channel frequency domain response is transformed to time domain obtain the channel time domain response.Second channel frequency domain response unit 404 specifically be used for will after noise item tap zero setting, obtain the channel time domain response carry out that leaf transformation DFT transforms to frequency domain in the N point discrete Fourier, described N is the number of OFDM symbol subcarrier.Conjugation correlation unit 405 specifically carries out conjugation to pilot tone point adjacent in the channel frequency domain response after the conversion and is correlated with.

Interference reconstruction unit 407 in the present embodiment specifically is used for by the described noise jamming item of following formula reconstruct:

$I=\frac{{\mathrm{\σ}}^2}{N}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{e}^{-j\frac{2\mathrm{\π}\·n\·\mathrm{\Δk}}{N}}$

Wherein I is the noise jamming item, σ ²Be the power of additive white Gaussian noise, N is the number of OFDM symbol subcarrier, and Ω is the tap position set that is kept after the tap zero setting, and Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

Timing offset estimation unit 408 specifically comprises in the present embodiment: revise the unit, be used for deducting the noise jamming item that reconstructs in serial mean, obtain revised serial mean Q; The timing offset computing unit is used to utilize revised serial mean Q to estimate timing offset Δ n by following formula:

$\mathrm{\Δn}=\frac{\mathrm{angle}\left(Q\right)*N_{\mathrm{FFT}}}{2\mathrm{\π\Δk}}$

Wherein, angle is for asking phase bit arithmetic, N _FFTFor carrying out counting of fast Fourier transform FFT window that the OFDM symbolic blocks uses when synchronous, Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

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, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims (10)

1. the method for estimation of a up timing offset is characterized in that, comprising:

Utilize the frequency domain data of the orthogonal frequency division multiplex OFDM symbol that receives and the channel frequency domain response of local pilot data estimating pilot frequency position;

The estimated channel frequency domain response is transformed to time domain obtain the channel time domain response, and will determine it is the tap zero setting of noise item in the described channel time domain response;

The channel time domain response transform that will obtain after noise item tap zero setting is to frequency domain, obtains channel frequency domain response after the conversion;

It is relevant that at interval pilot tone point in the channel frequency domain response after the described conversion is carried out conjugation, and ask sequence average to obtain serial mean to the relevant result of conjugation;

Remaining tap reconstructs the noise jamming item after utilizing noise item tap zero setting, estimates timing offset deduct described noise jamming item in described serial mean after.

2. the method for claim 1 is characterized in that, described utilize noise item tap zero setting after remaining tap reconstruct the noise jamming item, be specially by the described noise jamming item of following formula reconstruct:

$I=\frac{{\mathrm{\σ}}^2}{N}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{e}^{-j\frac{2\mathrm{\π}\·n\·\mathrm{\Δk}}{N}}$

Wherein I is the noise jamming item, σ ²Be the power of additive white Gaussian noise, N is the number of OFDM symbol subcarrier, and Ω is the tap position set that is kept after the tap zero setting, and Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

3. method as claimed in claim 1 or 2 is characterized in that, describedly estimates timing offset deduct described noise jamming item in serial mean after, specifically comprises:

In serial mean, deduct the noise jamming item that reconstructs, obtain revised serial mean Q;

Utilize revised serial mean Q to estimate timing offset Δ n by following formula:

$\mathrm{\Δn}=\frac{\mathrm{angle}\left(Q\right)*N_{\mathrm{FFT}}}{2\mathrm{\π\Δk}}$

Wherein, angle is for asking phase bit arithmetic, N _FFTFor carrying out counting of fast Fourier transform FFT window that the OFDM symbolic blocks uses when synchronous, Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

4. method as claimed in claim 1 or 2 is characterized in that, the channel frequency domain response of described estimating pilot frequency position specifically comprises:

The frequency domain reception data and the local pilot frequency sequence of pilot frequency locations on the same OFDM symbol are multiplied each other the channel frequency domain response of the pilot frequency locations that obtains estimating.

5. method as claimed in claim 1 or 2 is characterized in that, describedly the estimated channel frequency domain response is transformed to time domain obtains channel time domain response, specifically comprises:

By Inverse Discrete Fourier Transform IDFT, the estimated channel frequency domain response is transformed to time domain obtain the channel time domain response.

6. method as claimed in claim 1 or 2 is characterized in that, the channel time domain response transform that will obtain after noise item tap zero setting specifically comprises to frequency domain:

The channel time domain that will obtain after noise item tap zero setting response carries out that leaf transformation DFT transforms to frequency domain in the N point discrete Fourier, and described N is the number of OFDM symbol subcarrier.

7. method as claimed in claim 1 or 2 is characterized in that, described pilot tone point to interval in the channel frequency domain response after the conversion carries out conjugation is correlated with, and specifically comprises:

Pilot tone point adjacent in the channel frequency domain response after the conversion is carried out conjugation is correlated with.

8. the estimating system of a up timing offset is characterized in that, comprising:

The first channel frequency domain response estimation unit is used to utilize the frequency domain data of orthogonal frequency division multiplex OFDM symbol of reception and the channel frequency domain response of local pilot data estimating pilot frequency position;

The first channel time domain response unit is used for that the estimated channel frequency domain response is transformed to time domain and obtains the channel time domain response;

Tap zero setting unit is used for described channel time domain response is determined it is the tap zero setting of noise item;

Second channel frequency domain response unit is used for the channel time domain response transform that will obtain to frequency domain after noise item tap zero setting, obtain channel frequency domain response after the conversion;

The conjugation correlation unit is used for that the pilot tone point at interval of channel frequency domain response after the conversion is carried out conjugation and is correlated with;

All value cell is used for asking sequence average to obtain serial mean to the relevant result of conjugation;

Interference reconstruction unit, be used to utilize noise item tap zero setting after remaining tap reconstruct the noise jamming item;

The timing offset estimation unit is used for estimating timing offset after described serial mean deducts described noise jamming item.

9. system as claimed in claim 8 is characterized in that, described interference reconstruction unit specifically is used for by the described noise jamming item of following formula reconstruct:

$I=\frac{{\mathrm{\σ}}^2}{N}\underset{n\∈\mathrm{\Ω}}{\mathrm{\Σ}}{e}^{-j\frac{2\mathrm{\π}\·n\·\mathrm{\Δk}}{N}}$

Wherein I is the noise jamming item, σ ²Be the power of additive white Gaussian noise, N is the number of OFDM symbol subcarrier, and Ω is the tap position set that is kept after the tap zero setting, and Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

10. system as claimed in claim 8 or 9 is characterized in that described timing offset estimation unit specifically comprises:

Revise the unit, be used for deducting the noise jamming item that reconstructs, obtain revised serial mean Q in serial mean;

The timing offset computing unit is used to utilize revised serial mean Q to estimate timing offset Δ n by following formula:

$\mathrm{\Δn}=\frac{\mathrm{angle}\left(Q\right)*N_{\mathrm{FFT}}}{2\mathrm{\π\Δk}}$

Wherein, angle is for asking phase bit arithmetic, N _FFTFor carrying out counting of fast Fourier transform FFT window that the OFDM symbolic blocks uses when synchronous, Δ k is the interval of carrying out between the relevant pilot tone point of conjugation.

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