CN101702705B - Synchronization method and system for multi-carrier system - Google Patents

Abstract

The present invention discloses a synchronization method and system for a multi-carrier system. The method comprises the following steps: S1, processing the signal frame received on each receiving antenna to obtain the connection point position of n identical training sequences on the strongest path of the received signal or finding the connection point position of the training sequence on each receiving antenna; S2, using the connection point position of n identical training sequences on the strongest path of the received signal or the connection point position of the training sequence found on each receiving antenna, obtaining the starting position of timing synchronization based on adaptive threshold estimation. The synchronization technical scheme of the multi-carrier system of the present invention greatly reduces the amount of calculation and complexity of timing synchronization without affecting the synchronization performance; and by using the noise signal ratio of the channel to calculate the multi-path discrimination coefficient of the multi-carrier system, the multi-path discrimination problem in synchronization is well solved.

Description

Synchronization method and system for multi-carrier system

technical field

The invention relates to the field of communication technology, in particular to a synchronization method and system for a multi-carrier system.

Background technique

With the development of wireless communication technology, multi-carrier technology, especially Orthogonal Frequency Division Multiplexing technology, has been widely used not only in the field of broadcast digital audio and video, but also because of its high spectrum utilization rate and effective resistance to multipath. , and has been introduced into the standards of wireless local area network and wireless metropolitan area network. In the Long Term Evolution (LTE) research initiated by the 3rd Generation Partnership Project (3GPP), Orthogonal Frequency Division Multiplexing (OFDM) technology has been adopted as the downlink multiple address mode.

The synchronization process of multi-carrier system includes frame synchronization, carrier synchronization and symbol synchronization. Frame synchronization is the first step at the receiving end of the system, which is to find the approximate starting position of the received signal through frame synchronization, and use this position for carrier synchronization; carrier synchronization ensures that the oscillation frequency of the receiving end is the same frequency and phase as the sending carrier. It is extremely sensitive to frequency offset, which requires the system to accurately estimate and compensate for frequency offset; and symbol synchronization is to ensure that Fast Fourier Transform (Fast Fourier Transformation, referred to as FFT) and Fast Fourier Transform (Inverse FFT, referred to as The start time of IFFT) is consistent, and the accuracy of its timing estimation has a great influence on the performance of the multi-carrier system.

The synchronization technology of a multi-carrier system generally uses a point-by-point correlation method to find the correlation maximum point between the received signal on each receiving antenna and the transmitted pilot signal, and use it as the starting position of timing synchronization. However, because the above method needs to calculate the relative transportation point by point, its computational complexity is high, which is not conducive to hardware implementation. In addition, since the timing synchronization will be affected by the multipath channel, the timing will be inaccurate.

Contents of the invention

The purpose of the present invention is to provide a synchronization method and system that can greatly reduce the calculation amount and complexity of timing synchronization of a multi-carrier system without affecting the synchronization performance.

In order to achieve the above object, the technical solution of the present invention provides a synchronization method for a multi-carrier system, which includes the following steps:

S1, process the signal frame received on each receiving antenna, and obtain the connection point positions of n sections of the same training sequence on the strongest path of the received signal or find the connection point position of the training sequence on each receiving antenna;

S2. Estimate the starting position of timing synchronization by using the connection point positions of n segments of the same training sequence on the strongest path of the received signal or the connection point positions of the training sequences found on each receiving antenna.

Wherein, before the step S1, a step may be further included: sending a signal frame on each transmitting antenna, the signal frame including a data frame and n training sequences with length L.

Wherein, the step S1 is specifically:

S11, start the signal frame received on each receiving antenna from a position, segment it according to the length of L first, and perform the FFT transformation of L point on each signal frame; perform the FFT transformation result with the local training sequence respectively Dot multiplication; the data after dot multiplication is multiplied by the training sequence length L, and then L-point IFFT is carried out; the IFFT output result is taken as a modulus value; wherein, the local training sequence is obtained in such a way: will receive from each receiving antenna After the received signal frame is inflected, the conjugate is taken, and then the FFT transformation of point L is performed;

S12, merge the modulus values, find the maximum peak position of the above merged results, and the result is the connection point positions of the two identical training sequences on the strongest path of the received signal; or do not perform the step of merging the modulus values, directly obtain The location of the attachment points for the training sequence on each receive antenna.

Wherein, the step S2 is specifically:

S21, intercepting a piece of data block with a length L from the connection point positions of n segments of the same training sequence on the strongest path of the received signal or before and after the connection point positions of the training sequences found on each receiving antenna, and dividing the Carrying out point multiplication and accumulation of two data blocks to obtain the correlation energy of the two data blocks, and summing the squares of the data points in one of the intercepted two data blocks to obtain the signal energy of the data block;

S22, using the correlation energy and signal energy of the data block to calculate the noise-to-signal ratio of the received signal;

S23, according to the noise-to-signal ratio and the ratio of the amplitude main-side lobe of the autocorrelation result of the training sequence after removing the virtual carrier, set an adaptive discrimination threshold, and calculate a higher noise-to-signal ratio at the position where the frame header does not appear The discriminant threshold is used to prevent false synchronization, and a lower discriminative threshold is calculated from a lower noise-to-signal ratio at the position where the frame header appears to prevent missing synchronization;

S24, using the above-mentioned adaptive discrimination threshold, starting from the position of the connection point on the strongest path, taking a search window whose size is half of the number of cyclic extension points, and searching for a numerical position exceeding the threshold in this window from back to front until Search the entire window, and the frontmost numerical position greater than the threshold in the window is the timing position of the first path, that is, the starting position of timing synchronization.

Wherein, after the step S2, a step is further included: compensating the received signal according to the start position of the timing synchronization, and completing the synchronization process.

The present invention also provides a synchronization system for a multi-carrier system, including:

The connection point position acquisition module is used to process the signal frame received on each receiving antenna to obtain the connection point position of n sections of the same training sequence on the strongest path of the received signal or to find the training sequence on each receiving antenna The location of the connection point;

The starting position estimation module of timing synchronization is used to estimate the timing by using the connection point positions of n sections of the same training sequence on the strongest path of the received signal or the connection point positions of the training sequences found on each receiving antenna A starting position for synchronization, using the starting position to perform timing synchronization on the received signal.

The above technical solution has the following advantages: by replacing point-by-point correlation operations with FFT and IFFT operations, the synchronization acquisition of the multi-carrier system is realized, and the calculation amount and calculation complexity of timing synchronization are greatly reduced without affecting the synchronization performance. And by using the noise-to-signal ratio of the channel to calculate the adaptive multipath discrimination coefficient of the multi-carrier system, the multipath discrimination problem in synchronization is well solved.

Description of drawings

Fig. 1 is the method flowchart of the embodiment of the present invention;

Fig. 2 is an algorithm flow chart of the receiving end in the method of the embodiment of the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Fig. 1 is the method flowchart of the embodiment of the synchronization method for multi-carrier system according to the present invention, the synchronization process is mainly completed at the receiving end, but at the sending end it is necessary to use a polynomial sequence (as a training sequence, which is 2 sections, with a length equal to L) is multiplexed with the modulated data sequence to finally obtain a signal frame with multiple sequences as synchronous symbols, and then send the signal frame. As shown in Figure 1, the synchronization process at the receiving end specifically includes:

A1, the data received on each receiving antenna starts from a random position, first segmented according to the length of L (same as the length of the training sequence at the sending end), and performs FFT transformation of each segment of serial data at point L; and then separately Carry out dot multiplication with the local training sequence symbols; then multiply the data after the dot multiplication by the training sequence length L, and then perform L-point IFFT; take the modulus value of the above IFFT output results; then merge the modulus values obtained by each receiving antenna; Find the maximum peak position of the above combined results, and the result is the connection point position of two identical training sequences on the strongest path of the received signal. The above step of merging the modulus values can be cancelled, so as to obtain the connection point position of the training sequence on each antenna.

A2, intercept a data block with a length of L from the front and back of the connection point, and perform point multiplication and accumulation of the two pieces of data to obtain the relevant energy of the two pieces of data. Calculate the sum of squares to obtain the signal energy of the data block;

A3, the difference obtained by subtracting the correlation energy of the data block from the signal energy of the data block is then divided by the correlation energy of the data block to obtain the noise-to-signal ratio of the received signal;

A4, according to the noise-to-signal ratio and the ratio of the amplitude main-side lobe of the autocorrelation result of the training sequence after removing the virtual carrier, set an adaptive discrimination threshold, and calculate a higher noise-to-signal ratio at the position where the frame header does not appear. The discriminant threshold is used to prevent false synchronization, and a lower discriminative threshold is calculated from a lower noise-to-signal ratio at the position where the frame header appears to prevent missing synchronization;

A5, using the above adaptive discrimination threshold, starting from the timing position of the strongest path, take a search window whose size is half of the number of cyclic extension points, and search for the numerical position exceeding the threshold in the window from back to front, until the full window search is completed, the window The most preceding numerical position greater than the threshold is the timing position of the first path (arrival position of the first path of the multipath channel), that is, the best timing acquisition position. Then use the above timing synchronization information to compensate the received signal and complete the synchronization process.

The following example illustrates. Without loss of generality, it is assumed that L=N/2 mentioned above. The synchronization sequence with ideal autocorrelation characteristics sent by the sending end may specifically be: a pseudorandom (PN) sequence, a constant amplitude zero autocorrelation (CAZAC) sequence, a generalized chirp chirp (GCL) sequence, and the like. For the sake of convenience, it is assumed in the following discussion that the polynomial sequence sent as the synchronization symbol (that is, the above-mentioned synchronization sequence) is a CAZAC sequence.

Suppose c(n) is a training sequence (synchronous pilot symbol) of length N, namely:

$\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1,2</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

Two repeated training sequences with a length of N/2 conforming to the structure of the training sequence can be obtained. When c(n) is sent from the time domain by the sending end during framing, the received signal of receiving antenna j can be expressed by r _j (n) as:

${\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

where N _t represents the number of transmitting antennas, h _{i, j, l} (n) represents the channel impulse response between transmitting antenna i and receiving antenna j, and L represents the number of multipath channels between transmitting antenna i and receiving antenna j , n _j (n) represents the additive white Gaussian noise on the receiving antenna j.

Assuming that the symmetric sequence of the sent training sequence c(n) is expressed as c _r (n)=c(N/2-1-n), after conjugating it and performing FFT transformation of N/2 points, we can get C _r ′(K), and store it as the local training sequence of the receiving end.

The algorithm flow of the receiving end is shown in Figure 2.

a. Segment the signal r _j (n) received by the receiving antenna j according to the block length of N/2 to obtain r _j,1 (d) and r _j,2 (d) respectively.

b. Perform N/2-point FFT transformation on the data blocks r _{j, 1} (d) and r _{j, 2} (d) respectively to obtain R _{j, 1} (K) and R _{j, 2} (K).

c. Dot product R _j (K) with the local training sequence to get 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 transformation respectively to obtain timing measurement function p' _{j, 1} (d) and p' _{j, 2} (d).

e. Merge p' _j,1 (d) and p' _j,2 (d) to obtain p' _j (d).

f. Find the connection point positions of two identical training sequences on the strongest path of the received signal, that is, obtain the initial estimated value of the timing capture position:

${{\mathrm{<span\; class="notranslate">\; d</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; arg</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; \{</span><span\; class="notranslate">\; |</span>{{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; \}</span>$

g. Solve the ratio of the main and side lobes of the amplitude of the autocorrelation result of the training sequence after removing the virtual carrier, denoted as α.

h. Estimate the noise-to-signal ratio (NSR) of the channel, the estimation formula is as follows,

$\stackrel{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}{\mathrm{<span\; class="notranslate">\; NSR</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}$

In the above formula,

$\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="N"\; filenames="H2009102380220E00021.png"\; state="\{\{state\}\}">N</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

i. Calculate the multipath discrimination threshold P _th according to the following formula,

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; th</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\frac{\stackrel{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}{\mathrm{<span\; class="notranslate">\; NSR</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; NSR</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}{{\mathrm{<span\; class="notranslate">\; NSR</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; NSR</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}$

In the above formula, NSR _L and NSR _U are the lowest and highest noise-to-signal ratios measured in the channel environment, respectively. When d is equal to the timing position, q(d) is the energy of the useful signal in the received signal. When d is far away from the timing position, its mathematical expectation is 0, which means that a higher NSR estimate is obtained where the frame header does not appear. A higher threshold can be obtained from a higher NSR estimation value to prevent false synchronization, and a lower NSR estimation value can be obtained from the position where the frame header appears, and a lower threshold can be obtained from a lower NSR estimation value to prevent leakage synchronization.

j. Estimate the timing position of the first path according to the following formula:

${\stackrel{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; arg</span>}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\stackrel{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\stackrel{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; th</span>}}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\stackrel{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; \}</span>$

In the above formula,

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\stackrel{\mathrm{<span\; class="notranslate">\; \&Lambda;</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; \{</span><span\; class="notranslate">\; |</span>{{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; ;</span>$

is the synchronization correlation value within the search window.

Finally, the received signal is compensated by using the timing estimated position information of the first path to complete the synchronization process.

All or part of the steps for realizing the method embodiment of the present invention can be completed by program-related hardware, and the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory (Read-only memory) , ROM), random access memory (Random Access Memory, RAM), magnetic disk or optical disk and other media that can store program code.

The present invention also provides a synchronization system for a multi-carrier system, including:

The connection point position acquisition module is used to process the signal frame received on each receiving antenna to obtain the connection point position of n sections of the same training sequence on the strongest path of the received signal or to find the training sequence on each receiving antenna The location of the connection point;

The starting position estimation module of timing synchronization is used to estimate the timing by using the connection point positions of n sections of the same training sequence on the strongest path of the received signal or the connection point positions of the training sequences found on each receiving antenna A starting position for synchronization, using the starting position to perform timing synchronization on the received signal.

It can be seen from the above embodiments that by replacing point-by-point correlation operations with FFT and IFFT operations, the synchronization acquisition of the multi-carrier system is realized, and the calculation amount and complexity of timing synchronization are greatly reduced without affecting the synchronization performance. And by using the noise-to-signal ratio of the channel to calculate the multipath discrimination coefficient of the multi-carrier system, the multipath discrimination problem in synchronization is well solved.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made, these improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (3)

1. A synchronization method for a multi-carrier system, characterized in that the method comprises the following steps: S1, process the signal frame received on each receiving antenna, and obtain the connection point positions of n sections of the same training sequence on the strongest path of the received signal or find the connection point position of the training sequence on each receiving antenna; S2, using the connection point positions of the n segments of the same training sequence on the strongest path of the received signal or the connection point positions of the training sequences found on each receiving antenna to estimate the starting position of timing synchronization; where n is positive integer; Before the step S1, a step is also included: sending a signal frame on each transmit antenna, the signal frame including a data frame and n sections of length L, which are training sequences as synchronization symbols; where L is a positive number; The step S1 is specifically: S11, start the signal frame received on each receiving antenna from a position, segment it according to the length of L first, and perform fast Fourier transform on point L for each signal frame; compare the results after the fast Fourier transform with the local training Perform dot multiplication of the sequence; multiply the data after the dot multiplication by the length L of the training sequence, and then perform L-point inverse fast Fourier transform; take the modulus value of the output result of the inverse fast Fourier transform; wherein, the local training sequence is obtained in this way : Take the conjugate after refolding the signal frame received from each receiving antenna, and then perform the fast Fourier transform of point L; S12, merge the modulus values, find the maximum peak position of the above merged results, and the result is the connection point positions of the two identical training sequences on the strongest path of the received signal; or do not perform the step of merging the modulus values, directly obtain the position of the connection point of the training sequence on each receive antenna; The step S2 is specifically: S21, intercepting a piece of data block with a length L from the connection point positions of n segments of the same training sequence on the strongest path of the received signal or before and after the connection point positions of the training sequences found on each receiving antenna, and dividing the Carrying out point multiplication and accumulation of two data blocks to obtain the correlation energy of the two data blocks, and summing the squares of the data points in one of the intercepted two data blocks to obtain the signal energy of the data block; S22, using the correlation energy and signal energy of the data block to calculate the noise-to-signal ratio of the received signal; S23, according to the noise-to-signal ratio and the ratio of the amplitude main-side lobe of the autocorrelation result of the training sequence after removing the virtual carrier, set an adaptive discrimination threshold, and calculate a higher noise-to-signal ratio at the position where the frame header does not appear The discriminant threshold is used to prevent false synchronization, and a lower discriminative threshold is calculated from a lower noise-to-signal ratio at the position where the frame header appears to prevent missing synchronization; S24, using the above-mentioned adaptive discrimination threshold, starting from the position of the connection point on the strongest path, taking a search window whose size is half of the number of cyclic extension points, and searching for a numerical position exceeding the threshold in this window from back to front until Search the entire window, and the frontmost numerical position greater than the threshold in the window is the timing position of the first path, that is, the starting position of timing synchronization. 2. The method for synchronizing a multi-carrier system as claimed in claim 1, further comprising a step after said step S2: compensating the received signal according to the starting position of said timing synchronization, and completing the synchronization process . 3. A synchronization system for a multi-carrier system, characterized in that the system comprises: A module for sending a signal frame on each transmit antenna, the signal frame including a data frame and n sections of length L, as a training sequence as a synchronization symbol, where L is a positive number; The connection point position acquisition module is used to process the signal frame received on each receiving antenna to obtain the connection point position of n sections of the same training sequence on the strongest path of the received signal or to find the training sequence on each receiving antenna The location of the connection point; the specific processing method is: S11, start the signal frame received on each receiving antenna from a position, segment it according to the length of L first, and perform fast Fourier transform on point L for each signal frame; compare the results after the fast Fourier transform with the local training Perform dot multiplication of the sequence; multiply the data after the dot multiplication by the length L of the training sequence, and then perform L-point inverse fast Fourier transform; take the modulus value of the output result of the inverse fast Fourier transform; wherein, the local training sequence is obtained in this way : Take the conjugate after refolding the signal frame received from each receiving antenna, and then perform the fast Fourier transform of point L; S12, merge the modulus values, find the maximum peak position of the above merged results, and the result is the connection point positions of the two identical training sequences on the strongest path of the received signal; or do not perform the step of merging the modulus values, directly obtain the position of the connection point of the training sequence on each receive antenna; The starting position estimation module of timing synchronization is used to estimate the timing by using the connection point positions of n sections of the same training sequence on the strongest path of the received signal or the connection point positions of the training sequences found on each receiving antenna The starting position of the synchronization, using the starting position to perform timing synchronization on the received signal, wherein n is a positive integer; the specific estimation method is: S21, intercepting a piece of data block with a length L from the connection point positions of n segments of the same training sequence on the strongest path of the received signal or before and after the connection point positions of the training sequences found on each receiving antenna, and dividing the Carrying out point multiplication and accumulation of two data blocks to obtain the correlation energy of the two data blocks, and summing the squares of the data points in one of the intercepted two data blocks to obtain the signal energy of the data block; S22, using the correlation energy and signal energy of the data block to calculate the noise-to-signal ratio of the received signal; S23, according to the noise-to-signal ratio and the ratio of the amplitude main-side lobe of the autocorrelation result of the training sequence after removing the virtual carrier, set an adaptive discrimination threshold, and calculate a higher noise-to-signal ratio at the position where the frame header does not appear The discriminant threshold is used to prevent false synchronization, and a lower discriminative threshold is calculated from a lower noise-to-signal ratio at the position where the frame header appears to prevent missing synchronization; S24, using the above-mentioned adaptive discrimination threshold, starting from the position of the connection point on the strongest path, taking a search window whose size is half of the number of cyclic extension points, and searching for a numerical position exceeding the threshold in this window from back to front until Search the entire window, and the frontmost numerical position greater than the threshold in the window is the timing position of the first path, that is, the starting position of timing synchronization.

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