CN101753510A - Method and system used for precise timing synchronization of CMMB system mobile TV - Google Patents

Abstract

The invention discloses a method used for the precise timing synchronization of a CMMB system mobile TV, which comprises the following steps of: A. acquiring data used for precise timing synchronization; B. carrying out FFT conversion to convert the data used for precise timing synchronization into frequency domain data; C. carrying out channel estimation on the frequency domain data; D. carrying out phase compensation and selective merging on channel estimated values; and E. carrying out first effective path search according to the set search range to obtain a precise timing synchronization position. The invention also discloses a system used for the precise timing synchronization of the CMMB system mobile TV. The invention improves the timing synchronization robustness under the condition of non-integral multiple sampling by adopting a phase compensation technology and a selective merging technology and further increases the timing synchronization robustness and precision by adopting an average power and most effective energy joint detection technology. The invention can be widely applied to OFDM multiple-carrier systems, in particular to mobile multimedia broadcasting systems.

Description

A kind of accurate timing method for synchronous and system that is used for the CMMB standard mobile television

Technical field

The present invention relates to the synchronous reception technique of communication technical field, relate in particular to the accurate timing method for synchronous and the system that are used for the CMMB standard mobile television.

Background technology

Simultaneous techniques is the practical problem that any one communication system at first will solve, and its performance is directly connected to the performance of whole communication system.Do not have robust, synchronized algorithm accurately, just reliable transfer of data can not be arranged.

The process of signal Synchronization comprises synchronous and synchronous two processes of accurate timing of rough timing.Thick be synchronously utilize the slip auto-correlation then search peak obtain rough sync bit, and precise synchronization is to obtain further to obtain more definite signal Synchronization position after the coarse synchronization.Because the diversity of wireless channel, design a kind of robustness, timing synchronized algorithm that accuracy is high is a big difficult point of Communication System Design.

China Mobile multimedia broadcasting CMMB (China Mobile Multimedia Broadcasting) system has proposed a kind of new physical layer frame structure.As shown in Figure 1, provided the composition structural representation of beacon in each time slot of frame structure of CMMB system physical layer.In each time slot, each beacon is made up of a TxID (transmitter sign sequence) and two same synchronizing signals (SYNC).The time span of each synchronizing signal is 204.8 microseconds.

Because have two powers' footpath channel of long time delay expansion at present in the CMMB system, this has brought new challenge for regularly synchronous working.The synchronous target of accurate timing is to be synchronized to first to arrive position directly.If adopt the mode that directly detects most powerful path must bring bigger timing error, and adopt the scheme of the traditional detection that thresholding is set first effective diameter to detect the pure interference footpath of introducing easily by noise.In the dynamic fading environment of reality, existing time synchronization method is difficult to obtain perfect performance, when particularly being not most powerful path in the first arrival footpath.And traditional thin time synchronization method based on channel impulse response uses the IFFT module, has increased the complexity of system.

Summary of the invention

The objective of the invention is in order to overcome the deficiencies in the prior art, the accurate timing method for synchronous and the system that are used for the CMMB standard mobile television of a kind of high robust, pinpoint accuracy is provided.

The present invention is realized by the following technical programs:

A kind of accurate timing method for synchronous that is used for the CMMB standard mobile television comprises step:

A, obtain and be used for the accurate timing data in synchronization;

B, carry out FFT and be transformed into frequency domain data being used for the accurate timing data in synchronization;

C, frequency domain data is carried out channel estimating;

D, channel estimation value is carried out phase compensation and selectivity merge;

E, carry out the search of first effective diameter, obtain the accurate timing sync bit according to the hunting zone of setting.

Above-mentioned steps A is by according to thick synchronous searching result, 1024 sampling points that will thick regularly sync bit lag behind, and the accurate timing data in synchronization realized as being used for to obtain 2048 sampling points with this as starting point.

Above-mentioned steps B carries out channel estimating according to frequency domain data, local synchronizing sequence, and described local synchronizing sequence is that the synchronizing symbol frequency domain sequence of making a start is compensated the new sequence that obtains behind the 1024 sampling point timing slips.

Above-mentioned channel estimating adopts following LS channel estimating mode to realize:

Wherein, the described H of institute (k) is the domain channel response on each subcarrier, R _Sync(k) be the frequency domain receiving sequence, X _b(k) be local synchronizing sequence.

The phase compensation of above-mentioned steps C is to obtain new domain channel response and realized by the domain channel response on each subcarrier being multiply by different phase rotation coefficients; The selectivity of described step C merge be by domain channel response new after the phase compensation through the FFT conversion after, select to have that a road of maximum power value realized as the output result.

Spectrum power after select merging is carried out as follows frequency spectrum shift treatment step also comprising between above-mentioned steps D and the above-mentioned steps E: with the latter half frequency spectrum shift to negative semiaxis.

The hunting zone of setting among the above-mentioned steps E is to set according to the thick timing synchronization accuracy of concrete system; If after obtaining thick sync bit, next frame just carries out precise synchronization, the hunting zone of described setting also need add the sampling timing deviation that low precision crystal oscillator brings.

Above-mentioned steps D further may further comprise the steps:

D1, setting slide energy window;

The thresholding of D2, setting slide energy window;

D3, carry out first footpath according to the setting of slide energy window and thresholding and detect.

A kind of accurate timing synchro system that is used for the CMMB standard mobile television comprises, the synchrodata acquisition module is used to obtain and is used for the accurate timing data in synchronization; The FFT module is used for carrying out FFT and converting frequency domain data to being used for the accurate timing data in synchronization; Channel estimation module is used for frequency domain data is carried out channel estimating; Phase compensation and merging module are used for channel estimation value is carried out phase compensation and selectivity merging; The first effective diameter search module is used for carrying out the search of first effective diameter according to the hunting zone of setting, and obtains the accurate timing sync bit.

Above-mentioned synchrodata acquisition module also is used for slightly timing synchronous searching result of basis, and slightly 1024 sampling points of timing sync bit hysteresis obtain 2048 sampling points as being used for the accurate timing data in synchronization with this as starting point.

Above-mentioned channel estimation module also is used for carrying out channel estimating according to frequency domain data, local synchronizing sequence, and described local synchronizing sequence is that the synchronizing symbol frequency domain sequence of making a start is compensated the new sequence that obtains behind the 1024 sampling point timing slips.

Above-mentioned channel estimating adopts following LS channel estimating mode to obtain:

Wherein, described H (k) is the domain channel response on each subcarrier, R _Sync(k) be the frequency domain receiving sequence, X _b(k) be local synchronizing sequence.

Above-mentioned phase compensation and merging module comprise that at least one phase compensator and selectivity merge module, and described phase compensator is used for the domain channel response on each subcarrier be multiply by different phase rotation coefficients and obtains new domain channel response; Described selectivity merge module be used for by domain channel response new after the phase compensation through the FFT conversion after, select to have maximum power value a road as the output result.

Said system also comprises the frequency spectrum shift module, is used for the spectrum power after the selection merging is carried out frequency spectrum shift, and the latter half frequency spectrum shift is arrived negative semiaxis.

The hunting zone of above-mentioned setting is meant the scope of setting according to the thick timing synchronization accuracy of concrete system; If after obtaining thick sync bit, next frame just carries out precise synchronization, and the hunting zone of described setting also need add the sampling timing deviation that low precision crystal oscillator brings.

The above-mentioned first effective diameter search module comprises slide energy window module, thresholding module and the first footpath detection module, and described slide energy window module is used to be provided with the slide energy window; Described thresholding module is used to be provided with the thresholding of slide energy window; The described first footpath detection module is used for carrying out first footpath according to the setting of slide energy window and thresholding and detects.

The present invention's beneficial effect compared with prior art is:

(1) the present invention adopts phase compensation, selectivity merging technology to improve the synchronous robustness of timing under the non-integral multiple sampling situation;

(2) adopt average power, most powerful path energy associated detection technique further to improve regularly synchronous robustness and accuracy;

(3) adopt the slide energy window setting technique to reduce regularly synchronous detecting to the pure probability that disturbs the footpath;

(4) adopt FFT to realize, need not the IFFT module, convenient hardware or the software mode of adopting realized;

(5) the present invention can be widely used in OFDM multicarrier system, particularly mobile multimedia broadcast system.

Description of drawings

Fig. 1 is the composition structural representation of beacon in each time slot of frame structure of CMMB system physical layer in the prior art;

Fig. 2 is a specific embodiment of the invention system configuration schematic diagram;

Fig. 3 is a specific embodiment of the invention accurate timing method for synchronous flow chart.

Fig. 4 is that the specific embodiment of the invention is obtained and is used for the synchronous synchronizing symbol data method schematic diagram of accurate timing;

Embodiment

In conjunction with the accompanying drawings the present invention is done below by embodiment and to describe in further detail.

A kind of embodiment of system of the present invention, as shown in Figure 2, with the China Mobile multimedia broadcasting system is example, partly have two identical synchronizing signals at beacon, comprise synchrodata acquisition module, FFT module, channel estimation module, phase compensation and merging module, frequency spectrum shift module and the first effective diameter search module.

Thick regularly synchronization module carries out auto-correlation computation to list entries in a time slot, calculate the mould value of correlation, and searches for the thick regularly synchronous searching result of peak conduct of correlation and offer the synchrodata acquisition module.

The synchrodata acquisition module is used for obtaining to be used for the accurate timing data in synchronization, a kind of execution mode, according to thick timing synchronous searching result, slightly 1024 sampling points of timing sync bit hysteresis obtain 2048 sampling points as being used for the accurate timing data in synchronization with this as starting point.

The FFT module is used for that accurate timing data in synchronization piece is carried out FFT and is transformed into frequency domain data.

Channel estimation module is used for carrying out channel estimating according to frequency domain data, local synchronizing sequence, a kind of execution mode, and channel estimating adopts the LS channel estimating mode of low complex degree, obtains by following formula:

Wherein, described H (k) is the domain channel response on each subcarrier, R _Sync(k) be the frequency domain receiving sequence, X _b(k) be local synchronizing sequence, described local synchronizing sequence is that the synchronizing symbol frequency domain sequence of making a start is compensated the new sequence that obtains behind the 1024 sampling point timing slips.

Phase compensation and merging module are used for channel estimation value is carried out phase compensation and selectivity merging, and it comprises that further at least one phase compensator and selectivity merge module.In the present embodiment, phase compensator has two.Phase compensator is used for the domain channel response on each subcarrier be multiply by different phase rotation coefficients and obtains new domain channel response, and a kind of execution mode obtains by following formula:

$H_i^{\&prime;}\left(k\right)=H\left(k\right)\&CenterDot;e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;k}}{N}\&CenterDot;\frac{(i-1)}{M}},1\&le;i\&le;M$

Wherein i represents i phase compensator, and M represents the number of phase compensator.Selectivity merge module be used for by domain channel response new after the phase compensation through the FFT conversion after, the maximum power value on M road relatively, select to have maximum power value a road as the output result.Because non-integral multiple sampling can bring the serious leakage of main footpath energy, after merging, employing phase compensation can improve main footpath energy greatly, reduce secondary lobe, help the detection of first effective diameter.

Also comprise the frequency spectrum shift module in the present embodiment, be used for the spectrum power after the selection merging is carried out frequency spectrum shift, frequency spectrum shift is meant by the latter half frequency spectrum shift being arrived negative semiaxis, has made things convenient for the search of first effective diameter like this, also makes its physical significance clearer and more definite.

The first effective diameter search module is used for carrying out the search of first effective diameter according to the hunting zone of setting, and obtains the accurate timing sync bit.The first effective diameter search module further comprises slide energy window module, thresholding module and the first footpath detection module.Slide energy window module is used for the spectrum power value is added detection window, and described detection window is slided to the right successively from starting point, and when sliding into last point, this detection window is around to sequence starting point to be detected again; The thresholding module is used for setting first thresholding that detects the slide energy window that comprises first effective diameter and second thresholding that detects first effective diameter in the slide energy window according to average power, maximum power value; The first footpath detection module is used for carrying out first footpath according to the binary search strategy and detects, described binary search strategy is meant that searching for the slide energy window that comprises first effective diameter earlier determines the first effective diameter hunting zone, again search first effective diameter in the first effective diameter hunting zone.A kind of execution mode, this binary search strategy is:

A, search comprise the slide energy window of first effective diameter

1. detect from back to front successively, if slide energy window window self-energy is then returned its subscript greater than first thresholding, beginning from subscript to add that to subscript the long scope of window is as the first effective diameter hunting zone;

If 2. slide energy window window self-energy is then returned the subscript with ceiling capacity window all less than first thresholding, beginning from subscript to add that to subscript the long scope of window is as the first effective diameter hunting zone.

Search first effective diameter in b, the setting range

1. detect from back to front successively, if frequency spectrum spectral line energy, then returns its subscript greater than second thresholding as the first effective diameter position;

If 2. frequency spectrum spectral line energy is all less than second thresholding, then return have the ceiling capacity spectral line subscript as the first effective diameter position.

A kind of execution mode of the inventive method as shown in Figure 3, carries out auto-correlation computation to list entries in a time slot, calculate the mould value of correlation, and the peak of search correlation comprises the steps: as thick regularly sync bit

Step 301, the thick regularly sync bit of basis obtain the synchronizing symbol data block that is used for precise synchronization, cut method as shown in Figure 4,1024 sampling points that will thick regularly sync bit lag behind, with these 2048 sampling points that obtain the back as starting point as the synchronizing symbol data block that is used for precise synchronization;

Step 302,2048 the data of being taken out are FFT, obtain 2048 frequency domain response data, are shown below:

$R_{\mathrm{sync}}\left(k\right)=\frac{1}{\sqrt{N}}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{r}_{\mathrm{sync}}\left(n\right)\&CenterDot;e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;kn}}{N}},0\&le;k\&le;N-1$

Step 303, according to frequency domain data, local synchronizing sequence, calculate the domain channel response on each subcarrier, as shown in the formula:

Wherein H (k) is the domain channel response on each subcarrier, R _Sync(k) be the frequency domain receiving sequence, X _b(k) be local synchronizing sequence, this this locality synchronizing sequence is that the synchronizing symbol frequency domain sequence of making a start is compensated the new sequence that obtains behind the 1024 sampling point timing slips;

Step 304, H (k) is carried out different phase compensation, in the present embodiment, phase compensator has two,

Phase compensator 1:

Phase compensator 2:

Wherein, the phase place of phase compensator 1 compensation is 0 just, and former channel response remains unchanged, and former channel response through phase compensator 2 variation has taken place;

Step 305, with the revised channel response value of two-way through the FFT conversion, obtain its spectrum value;

Step 306, the maximum power value of two-way frequency spectrum relatively select bigger a road as output.

Wherein, performance number can adopt the following formula approximate calculation:

P′(n)＝max(|real(h(n))|，|imag(h(n))|)+min(|real(h(n))|，|imag(h(n))|)/2

Wherein, real () and imag () are respectively and get real and imaginary part, and max () and min () are respectively the maximum and the minimum value of fetch operand.H (n) is H _i' (k) passing through the frequency spectrum that obtains after the FFT conversion, described P ' is h (n) performance number (n).

Step 307, selectivity is merged the spectrum power value obtain, carry out frequency spectrum shift.

Wherein, the frequency spectrum shift mode is shown below:

$P\left(n\right)=\left\{\begin{array}{cc}{P}^{\&prime;}\left(n\right)& 0\&le;n\&le;1023\\ P^{\&prime;}(n+2048)& -1024\&le;n\&le;-1\end{array}\right.$

Step 308, the spectrum value after moving is carried out windowing process, and calculate window internal power energy and, concrete operations are as follows:

Wherein, slide energy window windowing mode is that detection window is slided to the right successively from starting point, and when sliding into last point, this window need be around to sequence starting point to be detected again, and the like.Be shown below:

$P_{\mathrm{win}}\left(k\right)=\underset{n=0}{\overset{\mathrm{win}\_\mathrm{len}-1}{\mathrm{\&Sigma;}}}{P}^{\&prime;}[(n+k)\%2048],{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&le;k\&le;{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">L</figure-callout>}}_2$

Wherein, L ₁And L ₂Be the hunting zone of setting, described % is the complementation operator, and described win_len is that the window of slide energy window is long, P _Win(k) for the spectrum power value through spectrum power in the new window that obtains behind the slide energy window and.

Wherein, the size of detection window is determined by channel circumstance, selects the maximum delay expansion long as window usually.

Step 309, threshold setting.Calculate P ' average power (k) earlier, and search out its maximum power value and subscript thereof, threshold value is set then.Average power obtains according to following formula:

$P_{\mathrm{avg}}=\frac{1}{L_2-{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+1}\underset{n=L_1}{\overset{L_2}{\mathrm{\&Sigma;}}}P\left(n\right)$

Maximum power value and subscript search procedure thereof are as follows:

${\hat{n}}_{\max }=\mathrm{<figure-callout\; id="1"\; label="arg\; max\; L"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">arg</figure-callout>}\underset{L_{}}{\max }\underset{}{{}_1\&le;n\&le;L_2}\left\{P\left(n\right)\right\}$

Threshold value is provided with the mode that adopts average power, maximum power joint-detection, as shown in the formula:

$\mathrm{th}=f(P_{\mathrm{avg}},P\left({\hat{n}}_{\max }\right))$

Wherein, functional relation f () should be according to concrete default.In the CMMB system, a kind of execution mode utilizes two threshold parameters to regulate average power and maximum power value respectively, and the big value of getting both then is as final threshold value.Two thresholdings can be provided with as shown in the formula:

${\mathrm{<figure-callout\; id="1"\; label="th"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">th</figure-callout>}}_1=f_1(P_{\mathrm{avg}},P\left({\hat{n}}_{\max }\right))=\max (a_1*P_{\mathrm{avg}},a_2*P\left({\hat{n}}_{\max }\right))$

${\mathrm{<figure-callout\; id="2"\; label="th"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">th</figure-callout>}}_2=f_2(P_{\mathrm{avg}},P\left({\hat{n}}_{\max }\right))=\max ({\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">b</figure-callout>}}_1*P_{\mathrm{avg}},{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="H2008102412778E0000022.png"\; state="\{\{state\}\}">b</figure-callout>}}_2*P\left({\hat{n}}_{\max }\right))$

Wherein, concrete thresholding is regulated parameter value a ₁, a ₂, b ₁, b ₂Determine by emulation according to real system.

Step 310, according to the thresholding that is provided with, adopt effective search strategy to retrieve first footpath.

S01, search comprise the slide energy window of first effective diameter

Detect from back to front successively, if slide energy window window self-energy is then returned its subscript greater than first thresholding, beginning from subscript to add that to subscript the long scope of window is as the first effective diameter hunting zone.

Then the hunting zone is:

If slide energy window window self-energy is then returned the subscript with ceiling capacity window all less than first thresholding, beginning from subscript to add that to subscript the long scope of window is as the first effective diameter hunting zone.

$\hat{n}=\arg \underset{n}{\max }\left\{P_{\mathrm{win}}\left(n\right)\right\}$

Then the hunting zone is:

Search first effective diameter in S02, the setting range

Detect from back to front successively, if frequency spectrum spectral line energy, then returns its subscript greater than second thresholding as the first effective diameter position.

If frequency spectrum spectral line energy all less than second thresholding, then return have the ceiling capacity spectral line subscript as the first effective diameter position, promptly

Step 311, the thick sync bit of basis, the first footpath effective diameter subscript adjustment obtain the precise synchronization position.

${\hat{d}}_f=d_c-{\hat{n}}_{\mathrm{first}}$

There is the not high problem of exceptional value, accuracy that detects easily at existing time synchronization method, signal synchronizing method of the present invention adopts technology such as phase compensation, slide energy window, joint-detection, binary search to greatly reduce and detects the pure false alarm probability of disturbing the footpath, improved the robustness of system.

Above content be in conjunction with concrete preferred implementation to further describing that the present invention did, can not assert that concrete enforcement of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.

Claims (16)

1. an accurate timing method for synchronous that is used for the CMMB standard mobile television is characterized in that, comprises step:

A, obtain and be used for the accurate timing data in synchronization;

B, carry out FFT and be transformed into frequency domain data being used for the accurate timing data in synchronization;

C, frequency domain data is carried out channel estimating;

D, channel estimation value is carried out phase compensation and selectivity merge;

E, carry out the search of first effective diameter, obtain the accurate timing sync bit according to the hunting zone of setting.

2. the accurate timing method for synchronous that is used for the CMMB standard mobile television according to claim 1, it is characterized in that: described steps A is by the thick synchronous searching result of basis, 1024 sampling points that will thick regularly sync bit lag behind, the accurate timing data in synchronization realized as being used for to obtain 2048 sampling points with this as starting point.

3. the accurate timing method for synchronous that is used for the CMMB standard mobile television according to claim 1, it is characterized in that: step B carries out channel estimating according to frequency domain data, local synchronizing sequence, and described local synchronizing sequence is that the synchronizing symbol frequency domain sequence of making a start is compensated the new sequence that obtains behind the 1024 sampling point timing slips.

4. the accurate timing method for synchronous that is used for the CMMB standard mobile television according to claim 3 is characterized in that, described channel estimating adopts following LS channel estimating mode to realize:

Wherein, described H (k) is the domain channel response on each subcarrier, R _Sync(k) be the frequency domain receiving sequence, X _b(k) be local synchronizing sequence.

5. the accurate timing method for synchronous that is used for the CMMB standard mobile television according to claim 1 is characterized in that: the phase compensation of described step C is to obtain new domain channel response and realized by the domain channel response on each subcarrier being multiply by different phase rotation coefficients; The selectivity of described step C merge be by domain channel response new after the phase compensation through the FFT conversion after, select to have that a road of maximum power value realized as the output result.

6. the accurate timing method for synchronous that is used for the CMMB standard mobile television according to claim 1 is characterized in that: the spectrum power after select merging is carried out as follows frequency spectrum shift treatment step also comprising between step D and the step e: with the latter half frequency spectrum shift to negative semiaxis.

7. according to the arbitrary described accurate timing method for synchronous that is used for the CMMB standard mobile television of claim 1 to 6, it is characterized in that: the hunting zone of setting in the described step e is to set according to the thick timing synchronization accuracy of concrete system; If after obtaining thick sync bit, next frame just carries out precise synchronization, the hunting zone of described setting also need add the sampling timing deviation that low precision crystal oscillator brings.

8. the accurate timing method for synchronous that is used for the CMMB standard mobile television according to claim 1 is characterized in that described step D further may further comprise the steps:

D1, setting slide energy window;

The thresholding of D2, setting slide energy window;

D3, carry out first footpath according to the setting of slide energy window and thresholding and detect.

9. an accurate timing synchro system that is used for the CMMB standard mobile television is characterized in that, comprises

The synchrodata acquisition module is used to obtain and is used for the accurate timing data in synchronization;

The FFT module is used for carrying out FFT and converting frequency domain data to being used for the accurate timing data in synchronization;

Channel estimation module is used for frequency domain data is carried out channel estimating;

Phase compensation and merging module are used for channel estimation value is carried out phase compensation and selectivity merging;

The first effective diameter search module is used for carrying out the search of first effective diameter according to the hunting zone of setting, and obtains the accurate timing sync bit.

10. the accurate timing synchro system that is used for the CMMB standard mobile television according to claim 9, it is characterized in that, described synchrodata acquisition module also is used for according to thick regularly synchronous searching result, slightly 1024 sampling points of timing sync bit hysteresis obtain 2048 sampling points as being used for the accurate timing data in synchronization with this as starting point.

11. the accurate timing synchro system that is used for the CMMB standard mobile television according to claim 9, it is characterized in that, described channel estimation module also is used for carrying out channel estimating according to frequency domain data, local synchronizing sequence, and described local synchronizing sequence is that the synchronizing symbol frequency domain sequence of making a start is compensated the new sequence that obtains behind the 1024 sampling point timing slips.

12. the accurate timing synchro system that is used for the CMMB standard mobile television according to claim 11 is characterized in that, described channel estimating adopts following LS channel estimating mode to obtain:

Wherein, described H (k) is the domain channel response on each subcarrier, R _Sync(k) be the frequency domain receiving sequence, X _b(k) be local synchronizing sequence.

13. the accurate timing synchro system that is used for the CMMB standard mobile television according to claim 9, it is characterized in that, described phase compensation and merging module comprise that at least one phase compensator and selectivity merge module, and described phase compensator is used for the domain channel response on each subcarrier be multiply by different phase rotation coefficients and obtains new domain channel response; Described selectivity merge module be used for by domain channel response new after the phase compensation through the FFT conversion after, select to have maximum power value a road as the output result.

14. the accurate timing synchro system that is used for the CMMB standard mobile television according to claim 9 is characterized in that, also comprises the frequency spectrum shift module, is used for the spectrum power after the selection merging is carried out frequency spectrum shift, and the latter half frequency spectrum shift is arrived negative semiaxis.

15., it is characterized in that the hunting zone of described setting is meant the scope of setting according to the thick timing synchronization accuracy of concrete system according to the arbitrary described accurate timing synchro system that is used for the CMMB standard mobile television of claim 9 to 14; If after obtaining thick sync bit, next frame just carries out precise synchronization, and the hunting zone of described setting also need add the sampling timing deviation that low precision crystal oscillator brings.

16. the accurate timing synchro system that is used for the CMMB standard mobile television according to claim 9, it is characterized in that, the described first effective diameter search module comprises slide energy window module, thresholding module and the first footpath detection module, and described slide energy window module is used to be provided with the slide energy window; Described thresholding module is used to be provided with the thresholding of slide energy window; The described first footpath detection module is used for carrying out first footpath according to the setting of slide energy window and thresholding and detects.

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