CN101702705A - Synchronizing method and system for multi-carrier system - Google Patents

Abstract

The invention discloses a synchronizing method and a system for a multi-carrier system. The method comprises the following steps: S1, processing signal frames received by each receiving antenna, and acquiring a connecting point position of n sections of same training sequences on a maximum path of the received signals or finding out a connecting point position of a training sequence on each receiving antenna; and S2, by using the connecting point position of n sections of the same training sequences on the maximum path of the received signals or the connecting point position of the training sequence found out on each receiving antenna, based on the adaptive threshold, estimating and acquiring an initial position of timing synchronization. The synchronizing technical scheme of the multi-carrier system of the invention greatly reduces the operation amount and the operation complexity of timing synchronization under the condition that the synchronizing performance can not be influenced, and the multi-path distinguishing coefficients of the multi-carrier system are calculated by using the signal to noise ratio of channels, thereby well solving the multi-path distinguishing problem in the synchronizing process.

Description

The method for synchronous and the system that are used for multicarrier system

Technical field

The present invention relates to communication technical field, particularly a kind of method for synchronous and system that is used for multicarrier system.

Background technology

Along with development of wireless communication devices, multi-transceiver technology, especially orthogonal frequency division multiplexi, with its high spectrum utilization, effectively the characteristics to anti-multipath etc. have not only obtained using widely in broadcast type digital audio and video field, and be introduced in the standard of WLAN (wireless local area network) and wireless MAN.At third generation partner program (3rd GenerationPartnership Project, abbreviation 3GPP) Long Term Evolution (the Long Term Evolution that starts, abbreviation LTE) in the research, OFDM (Orthogonal Frequency DivisionMultiplexing is called for short OFDM) technology has been adopted as descending multi-access mode.

The synchronizing process of multicarrier system comprises frame synchronization, carrier synchronization and sign synchronization.Frame synchronization is the first step operation of system receiving terminal, promptly finds the general original position of received signal by frame synchronization, and utilizes this position to carry out carrier synchronization; The frequency of oscillation that carrier synchronization guarantees receiving terminal with send carrier wave with homophase frequently because multicarrier system itself is to frequency deviation sensitivity very, this just requires system to make frequency deviation to estimate accurately and compensate; And sign synchronization is in order to guarantee fast fourier transform (Fast Fourier Transformation, be called for short FFT) and invert fast fourier transformation (Inverse FFT, abbreviation IFFT) zero-time unanimity, the precision of its timing estimation has very big influence to the performance of multicarrier system.

The simultaneous techniques of multicarrier system generally at first adopts the relevant method of pointwise to find received signal on each root reception antenna with the maximum correlation point of pilot signal transmitted, and with it as regularly synchronous original position.But above method is transported owing to needing pointwise to ask relevant, so its computational complexity is higher, is unfavorable for the hardware realization.In addition, owing to regularly can be subjected to the influence of multipath channel synchronously, and then cause regularly inaccurate.

Summary of the invention

Purpose of the present invention is at the deficiencies in the prior art, and providing a kind of can reduce the regularly synchronous operand of multicarrier system and the method for synchronous and the system of computational complexity greatly under the prerequisite that does not influence net synchronization capability.

For achieving the above object, technical scheme of the present invention provides a kind of method for synchronous that is used for multicarrier system, and it may further comprise the steps:

S1 handles the signal frame that receives on the every reception antenna, obtains the tie point position of the identical training sequence of n section on the received signal most powerful path or find the tie point position of training sequence on every reception antenna;

S2 utilizes the tie point position of the identical training sequence of n section on the described received signal most powerful path or the tie point position of the training sequence that finds on every reception antenna, estimate to obtain regularly synchronous original position.

Wherein, can also comprise step before the described step S1: send signal frame on every transmit antennas, described signal frame comprises that Frame and n segment length are the training sequence of L.

Wherein, described step S1 is specially:

S11 since a position, according to the length segmentation of L, carries out the FFT conversion that L is ordered with every segment signal frame with the signal frame received on the every reception antenna earlier; Result after the FFT conversion is carried out dot product with local training sequence respectively; Data after the dot product be multiply by the training sequence length L, carry out L point IFFT again; IFFT is exported delivery value as a result; Wherein, described local training sequence obtains by this way: get conjugation behind the signal frame reflexed that will receive from every reception antenna, carry out the FFT conversion that L is ordered again;

S12 merges each mould value, the peak-peak position of searching above amalgamation result, and gained is the tie point position of two sections identical training sequences on the received signal most powerful path; Perhaps do not carry out the step that each mould value merges, directly obtain the tie point position of the training sequence on the every reception antenna.

Wherein, described step S2 is specially:

S21, intercept the data block that a block length is L respectively before and after the tie point position of the tie point position of the training sequence that the n section from described received signal most powerful path is identical or the training sequence that finds at every reception antenna, these two data blocks are carried out the correlation energy that a multiply accumulating obtains two data blocks, data point in one of two data blocks being intercepted is asked quadratic sum, obtain the signal energy of this data block;

S22 utilizes the correlation energy of this data block and the jam-to-signal that signal energy computation obtains received signal;

S23, the ratio of amplitude master's secondary lobe of training sequence auto-correlation result according to this jam-to-signal and after removing virtual carrier, a self adaptation judgement threshold is set, calculate higher judgement threshold to prevent that vacation from synchronously, calculating lower judgement threshold in case leak-stopping is synchronous in the position that frame head occurs by lower jam-to-signal in the position that frame head do not occur by higher jam-to-signal;

S24, utilize above-mentioned self adaptation judgement threshold, tie point position from the most powerful path, get a size and be count half search window of cyclic extensions, in this window from after forward search surpass the numerical value position of described thresholding, up to complete window of search, the most forward numerical value position greater than thresholding is the timing position in first footpath in the window, promptly regularly synchronous original position.

Wherein, also comprise step after described step S2: the original position synchronous according to described timing compensates to received signal, finishes synchronizing process.

The present invention also provides a kind of synchro system that is used for multicarrier system, comprising:

Tie point position acquisition module is used for the signal frame that receives on the every reception antenna is handled, and obtains the tie point position of the identical training sequence of n section on the received signal most powerful path or find the tie point position of training sequence on every reception antenna;

Regularly synchronous original position estimation module, the tie point position of the training sequence that is used to utilize the tie point position of the identical training sequence of n section on the described received signal most powerful path or on every reception antenna, finds, estimate to obtain regularly synchronous original position, it is synchronous to utilize described original position to carry out timing to received signal.

Technique scheme has following advantage: by replacing the synchronization acquistion that the pointwise related operation has been realized multicarrier system with FFT and IFFT computing, under the prerequisite that does not influence net synchronization capability, greatly reduce regularly synchronous operand and computational complexity.And by utilizing the jam-to-signal of channel, calculate the self adaptation multipath discriminant coefficient of multicarrier system, thereby the multipath in having solved is synchronously well differentiated problem.

Description of drawings

Fig. 1 is the method flow diagram of the embodiment of the invention;

Fig. 2 is the algorithm flow chart of receiving terminal in the method for the embodiment of the invention.

Embodiment

Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples are used to illustrate the present invention, but are not used for limiting the scope of the invention.

Fig. 1 is the method flow diagram according to the embodiment of the method for synchronous that is used for multicarrier system of the present invention, synchronizing process is mainly finished at receiving terminal, but need be with polynomial sequence (as training sequence at transmitting terminal, it is 2 sections, length is L) carry out multiplexing with modulated data sequence, finally obtaining with multinomial sequence is the signal frame of synchronizing symbol, sends this signal frame then.As shown in Figure 1, the synchronous flow process of receiving terminal specifically comprises:

A1 since a random site, according to the length segmentation (identical with the training sequence length of transmitting terminal) of L, carries out the FFT conversion that L is ordered with every section serial data with the data received on the every reception antenna earlier; Carry out dot product with local training sequence symbols respectively again; Then the data after the dot product be multiply by the training sequence length L, carry out L point IFFT again; Above IFFT is exported delivery value as a result; The mould value that each reception antenna is obtained merges afterwards; Search the peak-peak position of above amalgamation result, gained is the tie point position of two sections identical training sequences on the received signal most powerful path.The above-mentioned step that the mould value is merged can be cancelled, thereby obtains the tie point position of the training sequence on the every antenna.

A2, before and after this tie point position, intercept the data block that a block length is L respectively, this two blocks of data is carried out the correlation energy that a multiply accumulating obtains two blocks of data, the data point in any block length of intercepting data that are L is asked quadratic sum, obtain the signal energy of this data block;

A3, the difference of correlation energy gained that deducts data block with the signal energy of data block obtains the jam-to-signal of received signal again divided by the correlation energy of data block;

A4, the ratio of amplitude master's secondary lobe of training sequence auto-correlation result according to this jam-to-signal and after removing virtual carrier, a self adaptation judgement threshold is set, calculate higher judgement threshold to prevent that vacation from synchronously, calculating lower judgement threshold in case leak-stopping is synchronous in the position that frame head occurs by lower jam-to-signal in the position that frame head do not occur by higher jam-to-signal;

A5, utilize above self adaptation judgement threshold, from the most powerful path timing position, get a size and be count half search window of cyclic extensions, in window from after forward search surpass the numerical value position of thresholding, finish up to full window search, that the most forward numerical value position greater than thresholding is the timing position (in-position, the first footpath of multipath channel) in first footpath, promptly best timing acquisition position in the window.Utilize above regularly synchronizing information then, compensate to received signal, finish synchronizing process.

Below illustrate.Be without loss of generality, suppose the L=N/2 that above mentions.The synchronizing sequence with desirable autocorrelation performance that transmitting terminal sends can be specially: pseudorandom (PN) sequence, normal amplitude zero auto-correlation (CAZAC) sequence, generalized chirp (GCL) sequence etc.For simplicity, suppose all that in the following discussion the polynomial sequence as synchronizing symbol (being above-mentioned synchronizing sequence) that sends is the CAZAC sequence.

Suppose that c (n) is that length is the training sequence (synchronizing pilot symbol) of N, that is:

$c\left(n\right)=c(n+\frac{N}{2}),n=\mathrm{0,1,2},...,\frac{N}{2}-1$

Two segment length that can obtain meeting training sequence structure are the training sequence of the repetition of N/2.C (n) is sent from time domain when the framing by transmitting terminal, and then the received signal of reception antenna j can be used r _j(n) be expressed as:

$r_j\left(n\right)=\underset{i=1}{\overset{N_t}{\mathrm{\Σ}}}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{h}_{i,j,l}\left(n\right)c\left(n\right)+n_j\left(n\right)$

N wherein _tThe number of expression transmitting antenna, h _{I, j, l}(n) expression transmitting antenna i is to the channel impulse response between the reception antenna j, and L represents the multipath number of transmitting antenna i to channel between the reception antenna j, n _j(n) additive white Gaussian noise on the expression reception antenna j.

The symmetric sequences of supposing the training sequence c (n) of transmission is expressed as c _r(n)=and c (N/2-1-n), it is carried out carrying out the FFT conversion that N/2 is ordered again after the conjugation, can obtain C _r' (K), and it is stored as the local training sequence of receiving terminal.

The algorithm flow of receiving terminal as shown in Figure 2,

A. the signal r that reception antenna j is received _j(n) according to the block length segmentation of N/2, obtain r respectively _{J, 1}(d) and r _{J, 2}(d).

B. to data block r _{J, 1}(d) and r _{J, 2}(d) carry out the FFT conversion that N/2 orders respectively and obtain R _{J, 1}(K) and R _{J, 2}(K)

C. with R _j(K) carry out dot product with local training sequence, obtain P ' _{J, 1}(K)=R _{J, 1}(K) C ' _r(K) and P ' _{J, 2}(K)=R _{J, 2}(K) C ' _r(K).

D. to P ' _{J, 1}(K) and P ' _{J, 2}(K) do N/2 point IFFT conversion respectively and obtain regularly metric function p ' _{J, 1}(d) and p ' _{J, 2}(d)

E. merge p ' _{J, 1}(d) and p ' _{J, 2}(d) obtain p ' _j(d).

F. find the tie point position of two sections identical training sequences on the received signal most powerful path, promptly obtain the initial estimate of timing acquisition position:

d′ _j＝arg?max{|p _j′(d)|}

G. find the solution the ratio that removes amplitude master's secondary lobe of training sequence auto-correlation result behind the virtual carrier, be designated as α.

H. estimate the jam-to-signal (NSR) of channel, estimation equation is as follows,

$\stackrel{\mathrm{\Λ}}{\mathrm{NSR}}=\frac{\left|R\left(d\right)\right|-\left|q\left(d\right)\right|}{\left|q\left(d\right)\right|}$

In the following formula,

$q\left(d\right)=\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}{r}^{*}(d+n)r(d+\frac{N}{2}+n)$

$R\left(d\right)=\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\left|r(d+n)\right|}^2$

I. calculate multipath judgement threshold P according to following formula _Th,

$P_{\mathrm{th}}=\mathrm{\α}+(1-\mathrm{\α})\frac{\stackrel{\mathrm{\Λ}}{\mathrm{NSR}}-{\mathrm{NSR}}_L}{{\mathrm{NSR}}_U-{\mathrm{NSR}}_L}$

In the following formula, NSR _LAnd NSR _UBe respectively the minimum and strong noise signal ratio that channel circumstance is surveyed.Q when d equals timing position (d) is the energy of useful signal in the received signal, at d during away from timing position, its mathematic expectaion is 0, this means and obtain higher NSR estimated value in the place that frame head do not occur, it is synchronously false to prevent to obtain higher thresholding by higher NSR estimated value, and the position that frame head occurs obtains lower NSR estimated value, can obtain lower thresholding in case leak-stopping is synchronous by lower NSR estimated value.

J. estimate the timing position in first footpath according to following formula:

${\stackrel{\mathrm{\Λ}}{d}}^{\′}=\min \left\{\arg \right\{M\left(\stackrel{\mathrm{\Λ}}{d}\left(m\right)\right),M\left(\stackrel{\mathrm{\Λ}}{d}\left(m\right)\right)>P_{\mathrm{th}}M\left(\stackrel{\mathrm{\Λ}}{d}\right)\left\}\right\}$

In the following formula,

$M\left(\stackrel{\mathrm{\Λ}}{d}\right)=\max \left\{\right|{p_j}^{\′}\left(d\right)\left|\right\};$

Be the sync correlation value in the search window.

Utilize the timing estimation positional information in above-mentioned first footpath to compensate to received signal at last, finish synchronizing process.

Realize that all or part of step of method embodiment of the present invention can finish by the relevant hardware of program, this program can be stored in the computer read/write memory medium, and this storage medium can comprise: read-only memory (Read-only memory, ROM), random access memory (Random Access Memory, RAM), various media that can be program code stored such as magnetic disc or CD.

The present invention also provides a kind of synchro system that is used for multicarrier system, comprising:

Tie point position acquisition module is used for the signal frame that receives on the every reception antenna is handled, and obtains the tie point position of the identical training sequence of n section on the received signal most powerful path or find the tie point position of training sequence on every reception antenna;

Regularly synchronous original position estimation module, the tie point position of the training sequence that is used to utilize the tie point position of the identical training sequence of n section on the described received signal most powerful path or on every reception antenna, finds, estimate to obtain regularly synchronous original position, it is synchronous to utilize described original position to carry out timing to received signal.

As can be seen from the above embodiments, by replacing the synchronization acquistion that the pointwise related operation has been realized multicarrier system, under the prerequisite that does not influence net synchronization capability, greatly reduce regularly synchronous operand and computational complexity with FFT and IFFT computing.And by utilizing the jam-to-signal of channel, calculate the multipath discriminant coefficient of multicarrier system, thereby the multipath in having solved is synchronously well differentiated problem.

The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the technology of the present invention principle; can also make some improvement and modification, these improve and modification also should be considered as protection scope of the present invention.

Claims (6)

1. a method for synchronous that is used for multicarrier system is characterized in that, said method comprising the steps of:

S1 handles the signal frame that receives on the every reception antenna, obtains the tie point position of the identical training sequence of n section on the received signal most powerful path or find the tie point position of training sequence on every reception antenna;

S2 utilizes the tie point position of the identical training sequence of n section on the described received signal most powerful path or the tie point position of the training sequence that finds on every reception antenna, estimate to obtain regularly synchronous original position; Wherein n is a positive integer.

2. the method for synchronous that is used for multicarrier system as claimed in claim 1, it is characterized in that, also comprising step before the described step S1: on every transmit antennas, send signal frame, described signal frame comprise Frame and n segment length be L, as the training sequence of synchronizing symbol; Wherein L is a positive number.

3. the method for synchronous that is used for multicarrier system as claimed in claim 2 is characterized in that, described step S1 is specially:

S11 since a position, according to the length segmentation of L, carries out the fast fourier transform that L is ordered with every segment signal frame with the signal frame received on the every reception antenna earlier; Result after the fast fourier transform is carried out dot product with local training sequence respectively; Data after the dot product be multiply by the training sequence length L, carry out the L point, inverse fast Fourier transform again; Invert fast fourier transformation is exported delivery value as a result; Wherein, described local training sequence obtains by this way: get conjugation behind the signal frame reflexed that will receive from every reception antenna, carry out the fast fourier transform that L is ordered again;

S12 merges each mould value, the peak-peak position of searching above amalgamation result, and gained is the tie point position of two sections identical training sequences on the received signal most powerful path; Perhaps do not carry out the step that each mould value merges, directly obtain the tie point position of the training sequence on the every reception antenna.

4. the method for synchronous that is used for multicarrier system as claimed in claim 1 is characterized in that, described step S2 is specially:

S21, intercept the data block that a block length is L respectively before and after the tie point position of the tie point position of the training sequence that the n section from described received signal most powerful path is identical or the training sequence that finds at every reception antenna, these two data blocks are carried out the correlation energy that a multiply accumulating obtains two data blocks, data point in one of two data blocks being intercepted is asked quadratic sum, obtain the signal energy of this data block;

S22 utilizes the correlation energy of this data block and the jam-to-signal that signal energy computation obtains received signal;

S23, the ratio of amplitude master's secondary lobe of training sequence auto-correlation result according to this jam-to-signal and after removing virtual carrier, a self adaptation judgement threshold is set, calculate higher judgement threshold to prevent that vacation from synchronously, calculating lower judgement threshold in case leak-stopping is synchronous in the position that frame head occurs by lower jam-to-signal in the position that frame head do not occur by higher jam-to-signal;

S24, utilize above-mentioned self adaptation judgement threshold, tie point position from the most powerful path, get a size and be count half search window of cyclic extensions, in this window from after forward search surpass the numerical value position of described thresholding, up to complete window of search, the most forward numerical value position greater than thresholding is the timing position in first footpath in the window, promptly regularly synchronous original position.

5. as each described method for synchronous that is used for multicarrier system of claim 1～4, it is characterized in that also comprise step after described step S2: the original position synchronous according to described timing compensates to received signal, finishes synchronizing process.

6. a synchro system that is used for multicarrier system is characterized in that, described system comprises:

Tie point position acquisition module is used for the signal frame that receives on the every reception antenna is handled, and obtains the tie point position of the identical training sequence of n section on the received signal most powerful path or find the tie point position of training sequence on every reception antenna;

Regularly synchronous original position estimation module, the tie point position of the training sequence that is used to utilize the tie point position of the identical training sequence of n section on the described received signal most powerful path or on every reception antenna, finds, estimate to obtain regularly synchronous original position, it is synchronous to utilize described original position to carry out timing to received signal.

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