CN108736931B - A kind of signal synchronization method and device - Google Patents

Abstract

This document discloses a signal synchronization method and apparatus. The signal synchronization method includes: when the automatic gain control AGC unit locks the received signal, delay autocorrelation processing is performed on the signals received by each receiving antenna, and after delaying for a first time length, the processed received signals of each channel are compared with each other. The reference thresholds corresponding to the received signals of this channel are compared, and whether the rough synchronization is completed is determined according to the comparison results of each channel; after the rough synchronization is completed, the local cross-correlation processing is performed on the received signals of each channel, and the results of the local cross-correlation processing of each channel are weighted Accumulate and filter, search for the maximum value from the filtered signal, and determine that the fine synchronization is completed when the maximum value is found. The technical solution in this paper can ensure the positioning accuracy when the received signal is synchronized in a multiple-input multiple-output system, and reduce the computational complexity.

Description

A kind of signal synchronization method and device

technical field

The present invention relates to the technical field of wireless communication, and in particular, to a signal synchronization method and device.

Background technique

The performance of synchronization technology is directly related to the performance of the entire communication system. It can be said that without an accurate synchronization algorithm, reliable data transmission is impossible, which is the premise of reliable information transmission. For an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM for short) system, the system has very high requirements on synchronization. Because of the inter-channel interference (ICI) and inter-symbol interference (ISI) introduced by various synchronization errors, the receiver cannot receive data correctly, and it will also destroy the sub-carriers in the OFDM system. Orthogonality.

As shown in Figure 1, in a common OFDM system receiver, after the automatic gain control (Automatic Gain Control, AGC) unit (301) triggers and locks the received signal, the signal received from each antenna (302) is sent to the modem ( Modem) (303), in the Modem, the symbol synchronizer (304) first performs positioning synchronization. The result of the symbol synchronizer positioning synchronization provides a reference point for the Fast Fourier Transformation (FFT) unit (305), so that the next series of operations (eg, demodulation) can be performed. In order not to affect the subsequent demodulation, the symbol synchronization positioning accuracy must be within a certain reasonable range.

Symbol positioning synchronization is to determine the starting position of the OFDM symbol, that is, the starting position of each FFT window. As shown in Figure 2, there may be four situations for symbol positioning synchronization: 1) FFT window 1 (Window1) indicates that the timing estimation point is correct, there is no deviation, and the demodulated data should also be correct; 3) FFT window 2 (Window2) indicates that the timing estimation point falls within the Cyclic Prefix (CP) of this symbol and is ahead of the optimal timing point; 3) FFT window 3 (Window3) indicates that the timing estimation point falls within the cyclic prefix of the next symbol 4) FFT window 4 (Window4) indicates that the timing estimation point falls within the data part of the previous symbol and is ahead of the cyclic prefix of this symbol.

In the above four cases, the first one is an ideal situation, which will not cause symbol positioning error; the second one is not much different from the ideal point, the introduced positioning deviation can be recovered by the equalizer, but if the difference is large, It will affect the performance of channel smoothing, thereby reducing the performance of the equalizer; the third and fourth cases will introduce ISI and ICI, which will greatly reduce the system performance, so it should be avoided.

In the case of multipath channels, it is difficult to locate on the ideal point, so a reasonable location range needs to be determined. First, determine the allowable positioning deviation according to the number of channel smoothing points. Assume that the number of smoothing points selected is 11. When smoothing, ensure that the phases of these 11 consecutive points are continuous, that is, the maximum phase difference of all frequency points does not exceed π. Then the allowable time deviation Δt is

In the case of 20MHz sampling frequency, the time interval between two points in the time domain is 50ns, Δf is equal to 312.5kHz, so Δt is equal to 150ns, and the range of the actual positioning point is 3 points ahead or behind the ideal positioning point. Affects smoothing performance.

In addition, in the case of a Multiple-Input Multiple-Output (MIMO) system, each antenna has a fixed delay, and not only multipath, but also the fixed delay of the antenna needs to be considered during synchronization. Time.

Therefore, how to provide a synchronization algorithm suitable for a multiple-input multiple-output system and reduce the computational complexity without affecting the positioning accuracy is a problem that needs to be solved.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a signal synchronization method and device, which can ensure the positioning accuracy when receiving the signal synchronization in a multiple-input multiple-output system, and reduce the computational complexity.

An embodiment of the present invention provides a signal synchronization method, including:

When the automatic gain control AGC unit locks the received signal, delay autocorrelation processing is performed on the signals received by each receiving antenna, and after delaying the first time length, the processed received signals of each channel are compared with the reference corresponding to the received signal of the channel. The thresholds are compared, and the coarse synchronization is determined according to the comparison results of each channel;

After the rough synchronization is completed, perform local cross-correlation processing on each channel of received signals, perform weighted accumulation and filtering on the results of each channel's local cross-correlation processing, search for the maximum value from the filtered signals, and determine completion when the maximum value is found. Fine sync.

An embodiment of the present invention provides a signal synchronization device, including:

The coarse synchronization module is used to perform delayed autocorrelation processing on the signals received by each receiving antenna when the automatic gain control AGC unit locks the received signal, and after delaying the first time length, the processed received signals of each channel are compared with the received signal. Compare the reference thresholds corresponding to the received signals of each channel, and determine whether the rough synchronization is completed according to the comparison results of each channel;

The fine synchronization module is used to perform local cross-correlation processing on each channel of received signals after the completion of the coarse synchronization, weighted accumulation and filtering of the results of each channel’s local cross-correlation processing, and searches for the maximum value from the filtered signals. When the maximum value is reached, it is determined that the fine synchronization is completed.

Compared with the prior art, the embodiment of the present invention provides a signal synchronization method and device, when the automatic gain control AGC unit locks the received signal, the delayed autocorrelation processing is performed on the signal received by each receiving antenna, After a period of time, the processed received signals of each channel are compared with the reference thresholds corresponding to the received signals of each channel, and whether the rough synchronization is completed is determined according to the comparison results of each channel; after the rough synchronization is completed, the local cross-correlation is performed on the received signals of each channel. processing, weighted accumulation and filtering are performed on the results of local cross-correlation processing of each channel, the maximum value is searched from the filtered signal, and it is determined that the fine synchronization is completed when the maximum value is found. The embodiments of the present invention can ensure the positioning accuracy when receiving signals are synchronized in a multiple-input multiple-output system, and reduce the computational complexity.

Description of drawings

1 is a schematic diagram of a digital receiver receiving a signal and demodulating it in the prior art;

2 is a schematic diagram of an anchor point for symbol positioning synchronization in the prior art;

3 is a flowchart of a signal synchronization method according to Embodiment 1 of the present invention;

4 is a schematic block diagram of a coarse synchronization process in Embodiment 1 of the present invention;

5 is a schematic time sequence diagram of delay-triggered coarse synchronization detection in Embodiment 1 of the present invention;

6 is a schematic block diagram of a fine synchronization process in Embodiment 1 of the present invention;

7 is a schematic diagram of triggering coarse synchronization detection using AGC locking time delay in Example 1 of the present invention;

8 is a schematic diagram of reference threshold generation and coarse synchronization detection triggering in Example 2 of the present invention;

FIG. 9 is a schematic diagram of a signal synchronization apparatus according to Embodiment 2 of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, the embodiments in the present application and the features in the embodiments may be arbitrarily combined with each other if there is no conflict.

Example 1

As shown in FIG. 3, an embodiment of the present invention provides a signal synchronization method, including:

In step S310, when the automatic gain control AGC unit locks the received signal, delay autocorrelation processing is performed on the signals received by each receiving antenna, and after delaying for a first time length, the processed received signals of each channel are compared with the received signal of the channel. The corresponding reference thresholds are compared, and it is determined whether the coarse synchronization is completed according to the comparison results of each channel;

Step S320, after the rough synchronization is completed, perform local cross-correlation processing on each channel of received signals, perform weighted accumulation and filtering on the results of each channel's local cross-correlation processing, search for the maximum value from the filtered signals, and search for the maximum value. When it is determined that the fine synchronization is completed.

In an implementation manner, performing delayed autocorrelation processing on the signal received by any channel of the receiving antenna includes:

Perform a symbol autocorrelation operation with a delay of N beats on the received signal r(n) according to the period N of the short training sequence to obtain the first signal Λ(m);

Wherein, the symbol autocorrelation operation with a delay of N beats can be expressed by the following formula (2-1):

Among them, N is the period of the short training sequence (Shorting Training Field, STF for short), if the sampling frequency is 20MHz, then N is equal to 16; r(n) is the received signal, and r ^* (n) is the conjugate of the received signal ; sign() is the sign function;

Among them, the short training sequence is used for signal detection, AGC power adjustment, coarse synchronization, etc. STF belongs to a sequence known to the transmitting side and the receiving side, through which the received signal can be judged, and can be used for Subsequent fine synchronization processing provides a certain reference and buffer.

In one embodiment, the first time length is the time length after the duration T1 of the short training sequence minus the maximum time T2 _max for the AGC unit to lock the received signal;

Wherein, in general, the time t2 when the AGC unit locks the received signal does not exceed T2 _max ;

In an implementation manner, the reference threshold corresponding to each channel of received signals is obtained by averaging the delay autocorrelation results of the channel of received signals within a short training sequence period and then multiplying by 0.5.

In one embodiment, the processed received signals of each channel are compared with the reference thresholds corresponding to the received signals of the channel, and whether the rough synchronization is completed is determined according to the comparison results of each channel, including:

If the processed received signal of one channel reaches the reference threshold corresponding to the received signal of the channel and reaches the reference threshold for a period of time, it is determined that the received signal of the channel meets the coarse synchronization requirement;

It is determined that the coarse synchronization is completed when there is at least one received signal that meets the coarse synchronization requirement.

Wherein, the continuous holding time is a preset value, such as 5 sampling points;

In an implementation manner, performing local cross-correlation processing on any channel of received signals includes:

Perform a local cross-correlation operation on the received signal r(m) according to the period N of the long training sequence to obtain the second signal Γ(m);

Wherein, the local cross-correlation operation can be represented by the following formula (2-2):

Wherein, c(n) is the tap coefficient of the filter, and the tap coefficient of the filter is designed according to the numerical value of the long training sequence; r ^* () is the conjugate of the received signal;

In one embodiment, weighted accumulation and filtering are performed on the results of each local cross-correlation process, including:

Equal weight accumulation is performed on the results of each local cross-correlation processing to obtain a third signal;

sending the third signal into a filter with a tap number a for filtering;

Wherein, the product of the number of taps a of the filter and the sampling interval of the received signal is greater than or equal to the maximum delay between the transmitting antennas; the value of the tap coefficient corresponding to the signal sent by the first transmitting antenna among the a tap coefficients is greater than that of the other taps The value of the coefficient; any other transmitting antenna except the first transmitting antenna sends signals ahead of the first transmitting antenna.

Among them, the maximum value is searched from the filtered signal, and the position where the maximum value appears is the position where the LTF ends, and it is also the beginning of the next symbol. Since there is a guard interval in front of each symbol, according to the position where the LTF ends and the guard interval The length can determine the starting position of each symbol, therefore, when the maximum value is searched, it is determined that the fine synchronization is completed.

In one embodiment, as shown in Figure 4, the coarse synchronization process may include the following steps:

1) After the AGC unit locks the received signal, a first trigger signal is generated by the trigger signal generator (401);

2) processing the signals received by each receiving antenna (402) according to the first trigger signal;

3) The received signal is processed in two ways, one of the signals is sent to the symbol-fetching unit for symbol-fetching operation, and the extracted symbol is stored in a first depth of N (N is the period of STF, for example, N=16). In the first-in-first-out (First Input First Output, FIFO for short) buffer (404), another signal is sent to the conjugation unit (405) for conjugation operation; the output signal of the first FIFO buffer is combined with the conjugation operation. The output signal of the yoke unit is multiplied;

4) Divide the multiplied signal into two channels, one of which is stored in a second first-in-first-out (First Input First Output, FIFO for short) with a depth of N (N is the period of STF, for example, N=16). In the buffer (406), another way of data is subtracted from the output signal of the second FIFO buffer, and the subtracted signal is sent to the accumulating modulo unit (407) for accumulating modulo operation, thus completing a Delayed autocorrelation operation with a window length of N (N=16);

5) Starting from the AGC unit locking the received signal, the trigger signal generator (401) delays the first time threshold T1 and then outputs a second trigger signal to the mean value operation unit (408), which extracts a delay of a certain window length. The autocorrelation results are averaged to obtain the reference threshold value, and the coarse synchronization detection is triggered at the same time;

6) the comparison unit (409) corresponding to each receiving antenna compares the autocorrelation result output by the accumulating modulo unit with the reference threshold output by the mean arithmetic unit to obtain a 1-bit comparison result;

7) The 1-bit comparison result output by the comparison unit (409) corresponding to each receiving antenna is sent to the OR logic operation unit (410) to generate a 1-bit coarse synchronization result; for example, when the coarse synchronization result is 1, it is determined that the coarse synchronization result is 1. synchronization completed;

Among them, as shown in Figure 5, for example, the AGC lock signal is used for delay triggering, the delay autocorrelation results of a certain window length are extracted and averaged to obtain the threshold value, and the coarse synchronization detection is triggered at the same time, and the results of the delay autocorrelation will be sequentially Compared with the threshold value, when a point is lower than the threshold value, the coarse synchronization will not be triggered, and the coarse synchronization will be triggered only when the result of the delayed autocorrelation is lower than the threshold value for 5 consecutive times. Because the coarse synchronization detection does not start when the AGC is locked, but starts when the reference threshold is obtained, which reduces the coarse synchronization detection during the period when the AGC is locked to the threshold, and can effectively reduce the occurrence of false synchronization.

The purpose of the above coarse synchronization is to trigger the fine synchronization calculation and provide a suitable calculation window length for the fine synchronization.

In the process of fine synchronization, a digital filter with 64 taps is designed by using the value of the Long Training Field (LTF) in one cycle. The tap coefficients of , do cross-correlation operation, and the cross-correlation operation can be expressed by the following formula (2-2):

Among them, N represents the length of the cross-correlation calculation, and N is equal to 64; r(m) is the received signal, and c(n) is the tap coefficient of the filter;

The period of the long training sequence LTF is 4 times that of the STF, which is the same as the period of an OFDM, and can be used for fine synchronization, fine frequency offset estimation, and signal estimation. The embodiment of the present invention utilizes its strong correlation characteristic to locally store a piece of processed LTF (ie, the tap coefficient of the filter).

In the process of fine synchronization, for the MIMO system, except for the first antenna, the other antennas will be advanced through time domain cyclic shift (the maximum advance is 200ns, and the sampling frequency is 4 points for 20MHz), which leads to The MIMO system cannot obtain the synchronization result simply by directly detecting the cross-correlation peak like the single-input single-output (SISO) system. For MIMO, the result of synchronization must be where the first peak occurs. In order to locate the ideal position more accurately, in the embodiment of the present invention, the cross-correlation calculation result is passed through a filter with 6 taps, and then the maximum value of the output result of the filter is searched within a certain range, which is the final precision Synchronized result.

In addition, it can be seen from Fig. 1 that the third situation may occur at the synchronization position, that is, the timing estimation point falls within the cyclic prefix of the next symbol and lags behind the optimal timing point, so positioning synchronization can be improved by positioning offset processing. dynamic range. For example, move the synchronization position forward 6 points to start extracting each OFDM symbol, before performing FFT, move the value of the first six points of the symbol to the last position of the symbol, which allows the positioning point to be located at the best position Swing left and right. This not only ensures that the positioning synchronization point can move left and right at the optimal positioning point, but also does not introduce inter-symbol interference, thereby improving the dynamic range of positioning synchronization.

In one embodiment, based on the above considerations, as shown in FIG. 6 , the fine synchronization process may include the following steps:

1) a rough synchronization completion trigger signal generator (601), the trigger signal generator generates a third trigger signal (equivalent to a time delay T2 after the AGC locking time);

2) According to the third trigger signal, the signals received by each receiving antenna are sent to the corresponding first filters (602) for filtering processing, and then sent to the corresponding modulo units (603) for filtering. Modulo processing;

Among them, the tap coefficients of the filter are processed according to the time domain signal of the long training sequence. First, the symbol of the time domain signal of the long training sequence is taken to determine the symbol of the filter tap coefficient, and then according to the time domain signal of the long training sequence. The magnitude of the amplitude, the filter coefficients are set to 0, 1, 2, because the amplitude is large, the anti-noise ability is strong, and the confidence is high, so a larger weight is given. The tap coefficient c(n) of such a filter is a complex number consisting of 0, 1, and 2 (for example, 1+2i);

3) sending the modulo signal of each antenna into an accumulator (604) for summation operation, which is equivalent to equal weight superimposition of the cross-correlation operation results of each antenna;

4) input the signal output by the accumulator into a second filter (605) for processing, and the processing is used to reduce the influence of different delays of multiple antennas and multipath;

Among them, the second filter is equivalent to a sliding window summation, and one of the values is weighted. The sliding window can reduce the influence of different delays and multipath of the antenna, and the weighting can improve the peak intensity of the first transmitting antenna. There are It is beneficial to locate the peak value of the first antenna and improve the accuracy of the positioning result.

5) the output signal of the second filter is input into the maximum value search unit (606) to carry out the maximum value search to obtain a precise synchronization result;

6) Input the result output by the maximum value search unit into the positioning offset unit (607), move the synchronization position forward by 6 points to start extracting each OFDM symbol, and before performing the FFT, extract the first six points of the symbol The numerical value of is moved to the last position of the symbol, and the starting position of the extracted FFT window is obtained after positioning the offset; in addition, the point of the positioning offset is moved to the last of the symbol by the periodic characteristic of the symbol after the data is extracted;

The processing in the coarse synchronization process and the fine synchronization process is further described below with some examples.

Example 1

As shown in Figure 7, after the AGC is locked, the received signal enters the modem. At this time, the coarse synchronization detection will not be performed immediately, but the detection will be performed after a certain time delay. The delay time (T) is obtained by subtracting the latest AGC lock time (701) from the time at which the short training sequence for coarse synchronization ends (702).

In actual work, after the AGC locks (703), the threshold (704) is obtained after the delay time (T), which makes the coarse synchronization detection (705) occur after the threshold is generated. In this way, after the AGC is locked (703), the coarse synchronization detection will not be performed before the coarse synchronization detection (705) is triggered, which will effectively reduce the occurrence of false synchronization.

Example 2

As shown in FIG. 8 , the received signal is subjected to delayed autocorrelation processing to obtain an output result (801). Using this output result (801), the AGC lock delay trigger starts to calculate the threshold value (802). The calculation of the threshold value starts from the trigger. Start to extract 16 values of the output result (801) and then take the average to obtain, after the threshold value calculation is completed, the threshold value becomes effective, the coarse synchronization detection starts, and then the output result (801) and the threshold value pass through the comparator (803) ) to compare and output a 1-bit comparison result, the comparison result passes through a 5-tap filter (804) whose tap coefficients are all 1, and the output data of the filter is compared with the value in the register (805), wherein the value in the register is If the value is set to 5, it is equal to prove that the coarse synchronization of the antenna is detected; the function of the 5-tap filter (804) is: it is considered as a coarse synchronization trigger only when 5 consecutive points reach the threshold value;

The coarse synchronization detection results of all antennas are processed through logical OR (806), that is, as long as one antenna coarse synchronization is detected, the coarse synchronization process is completed.

The completion of the coarse synchronization will trigger the calculation and detection of the fine synchronization.

Example 3

As shown in FIG. 6, the tap coefficients of the first filter (602) are designed according to the time domain value of the long training sequence, the real part and the imaginary part of the time domain value of the long training sequence are averaged respectively, and the average value is divided by 2 to get the threshold value, divide the real part and imaginary part of the time domain value of the long training sequence by its corresponding threshold value, and then round off the calculation result (2 if the absolute value exceeds 2) to obtain the final filter value. Tap coefficient c'(n).

In the above formula (3-1), c(n) is to compress the original LTF time-domain signal, that is to express the characteristics of the LTF time-domain signal with very small bits, X(n) is the LTF time-domain signal, N=64 represents the period of LTF, and round() is the rounding function;

In the above formula (3-2), c'(n) is the tap coefficient (ie the long training sequence stored locally);

For the second filter (605), the second filter has a total of 6 taps, and the tap coefficients are: {1, 1, 1, 1, 2, 1}, the second filter can resist multipath effects and different antennas At the same time, by increasing the weight value of the peak value of the first receiving antenna, the synchronization result is positioned on the first receiving antenna.

As shown in FIG. 9, an embodiment of the present invention provides a signal synchronization device, including:

The coarse synchronization module 901 is used to perform delayed autocorrelation processing on the signals received by each receiving antenna when the automatic gain control AGC unit locks the received signal, and after delaying the first time length, the processed received signals of each channel are compared with each other. The reference thresholds corresponding to the received signals of this channel are compared, and whether the rough synchronization is completed is determined according to the comparison results of each channel;

The fine synchronization module 902 is used to perform local cross-correlation processing on the received signals of each channel after the coarse synchronization is completed, perform weighted accumulation and filtering on the results of the local cross-correlation processing of each channel, search for the maximum value from the filtered signals, and When the maximum value is found, it is determined that the fine synchronization is completed.

In one embodiment, the coarse synchronization module is used to perform delayed autocorrelation processing on the signals received by any one of the receiving antennas in the following manner:

Perform a symbol autocorrelation operation with a delay of N beats on the received signal r(n) according to the period N of the short training sequence to obtain the first signal Λ(m);

Wherein, the symbol autocorrelation operation with a delay of N beats can be expressed by the following formula:

Wherein, N is the period of the short training sequence STF, r(n) is the received signal, r ^* (n) is the conjugate of the received signal; sign() is the sign function.

In one embodiment, the first time length is the time length after the duration T1 of the short training sequence minus the maximum time T2 _max for the AGC unit to lock the received signal.

In an implementation manner, the reference threshold corresponding to each channel of received signals is obtained by averaging the delay autocorrelation results of the channel of received signals within a short training sequence period and then multiplying by 0.5.

In one embodiment, the coarse synchronization module is used to compare the processed received signals of each channel with the reference thresholds corresponding to the received signals in the following manner, and determine whether to complete the coarse synchronization according to the comparison results of each channel:

If the processed received signal of one channel reaches the reference threshold corresponding to the received signal of the channel and reaches the reference threshold for a period of time, it is determined that the received signal of the channel meets the coarse synchronization requirement;

It is determined that the coarse synchronization is completed when there is at least one received signal that meets the coarse synchronization requirement.

In one embodiment, the fine synchronization module is used to perform local cross-correlation processing on any one of the received signals in the following manner:

Perform a local cross-correlation operation on the received signal r(m) according to the period N of the long training sequence to obtain the second signal Γ(m);

Wherein, the local cross-correlation operation can be expressed by the following formula:

Among them, c(n) is the tap coefficient of the filter, and the tap coefficient of the filter is designed according to the value of the long training sequence; r ^* () is the conjugate of the received signal.

In one embodiment, the fine synchronization module is used to perform weighted accumulation and filtering on the results of each local cross-correlation processing in the following manner:

Equal weight accumulation is performed on the results of each local cross-correlation processing to obtain a third signal;

sending the third signal into a filter with a tap number a for filtering;

Wherein, the product of the number of taps a of the filter and the sampling interval of the received signal is greater than or equal to the maximum delay between the transmitting antennas; the value of the tap coefficient corresponding to the signal sent by the first transmitting antenna among the a tap coefficients is greater than that of the other taps The value of the coefficient; any other transmitting antenna except the first transmitting antenna sends signals ahead of the first transmitting antenna.

It should be noted that the present invention can also have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these Corresponding changes and deformations should belong to the protection scope of the appended claims of the present invention.

Claims (14)

1. A method of signal synchronization, comprising:

when the automatic gain control AGC unit locks the received signals, the signals received by each receiving antenna are subjected to delay autocorrelation processing, after the first time length is delayed, the processed received signals of each path are compared with a reference threshold corresponding to the received signals of the path, and whether coarse synchronization is finished or not is determined according to the comparison result of each path;

after coarse synchronization is completed, local cross-correlation processing is carried out on each path of received signals, weighted accumulation and filtering are carried out on results of each path of local cross-correlation processing, a maximum value is searched from the filtered signals, and fine synchronization is judged to be completed when the maximum value is searched.

2. The method of claim 1, wherein:

the method for carrying out time delay autocorrelation processing on signals received by any path of receiving antenna comprises the following steps:

carrying out symbol autocorrelation operation of delaying N beats on a received signal r (N) according to the period N of the short training sequence to obtain a first signal Lambda (m);

the symbol autocorrelation operation of the delayed N beats can be represented by the following formula:

where N is the period of the short training sequence STF, r (N) is the received signal, r^*(n) is the conjugate of the received signal; sign () is a sign taking function.

3. The method of claim 1 or 2, wherein:

the first time length is the duration T1 of the short training sequence minus the maximum time T2 for the AGC unit to lock onto the received signal_maxThe latter time length.

4. The method of claim 2, wherein:

the reference threshold corresponding to each path of received signal is obtained by taking an average value according to the time delay autocorrelation result of the path of received signal in a short training sequence period and then multiplying the average value by 0.5.

5. The method of claim 1, wherein:

comparing the processed received signals with the reference threshold corresponding to the received signals, and determining whether coarse synchronization is completed according to the comparison result of each path, including:

if a path of processed received signals reaches a reference threshold corresponding to the path of received signals and reaches the reference threshold for a period of time, judging that the path of received signals meets the requirement of coarse synchronization;

and judging to finish coarse synchronization when at least one path of received signals meets the coarse synchronization requirement.

6. The method of claim 1, wherein:

carrying out local cross-correlation processing on any path of received signals, comprising the following steps:

performing local cross-correlation operation on the received signal r (m) according to the period N of the long training sequence to obtain a second signal (m);

wherein the local cross-correlation operation may be represented by the following formula:

wherein, c (n) is the tap coefficient of the filter, and the tap coefficient of the filter is designed according to the value of the long training sequence; r is^*() Is the conjugate of the received signal.

7. The method of claim 1, wherein:

performing weighted accumulation and filtering on the results of the local cross-correlation processing of each path, comprising the following steps:

performing equal weight accumulation on the results of the local cross-correlation processing of each path to obtain a third signal;

sending the third signal into a filter with the number of taps a for filtering;

the product of the tap number a of the filter and the sampling interval of the received signal is greater than or equal to the maximum delay among the transmitting antennas; the value of the tap coefficient corresponding to the signal sent by the first sending antenna in the a tap coefficients is larger than the values of other tap coefficients; any other transmission antenna than the first transmission antenna transmits a signal before the first transmission antenna transmits a signal.

8. A signal synchronization apparatus, comprising:

the coarse synchronization module is used for carrying out time delay autocorrelation processing on signals received by each path of receiving antenna when the automatic gain control AGC unit locks the receiving signals, comparing the processed receiving signals of each path with a reference threshold corresponding to the received signals of the path after delaying for a first time length, and determining whether coarse synchronization is finished or not according to comparison results of each path;

and the fine synchronization module is used for performing local cross-correlation processing on each path of received signals after coarse synchronization is completed, performing weighted accumulation and filtering on results of each path of local cross-correlation processing, searching a maximum value from the filtered signals, and judging that fine synchronization is completed when the maximum value is searched.

9. The apparatus of claim 8, wherein:

the coarse synchronization module is used for performing time-delay autocorrelation processing on signals received by any path of receiving antenna by adopting the following modes:

carrying out symbol autocorrelation operation of delaying N beats on a received signal r (N) according to the period N of the short training sequence to obtain a first signal Lambda (m);

the symbol autocorrelation operation of the delayed N beats can be represented by the following formula:

where N is the period of the short training sequence STF, r (N) is the received signal, r^*(n) is the conjugate of the received signal; sign () is a sign taking function.

10. The apparatus of claim 8 or 9, wherein:

the first time length is the duration T1 of the short training sequence minus the maximum time T2 for the AGC unit to lock onto the received signal_maxThe latter time length.

11. The apparatus of claim 9, wherein:

the reference threshold corresponding to each path of received signal is obtained by taking an average value according to the time delay autocorrelation result of the path of received signal in a short training sequence period and then multiplying the average value by 0.5.

12. The apparatus of claim 8, wherein:

the coarse synchronization module is used for comparing the processed receiving signals of each path with a reference threshold corresponding to the receiving signals of the path in the following mode, and determining whether coarse synchronization is finished according to the comparison result of each path:

if a path of processed received signals reaches a reference threshold corresponding to the path of received signals and reaches the reference threshold for a period of time, judging that the path of received signals meets the requirement of coarse synchronization;

and judging to finish coarse synchronization when at least one path of received signals meets the coarse synchronization requirement.

13. The apparatus of claim 8, wherein:

the fine synchronization module is used for performing local cross-correlation processing on any path of received signals in the following modes:

performing local cross-correlation operation on the received signal r (m) according to the period N of the long training sequence to obtain a second signal (m);

wherein the local cross-correlation operation may be represented by the following formula:

wherein, c (n) is the tap coefficient of the filter, and the tap coefficient of the filter is designed according to the value of the long training sequence; r is^*() Is the conjugate of the received signal.

14. The apparatus of claim 8, wherein:

and the fine synchronization module is used for performing weighted accumulation and filtering on the results of the local cross-correlation processing of each path by adopting the following modes:

performing equal weight accumulation on the results of the local cross-correlation processing of each path to obtain a third signal;

sending the third signal into a filter with the number of taps a for filtering;

the product of the tap number a of the filter and the sampling interval of the received signal is greater than or equal to the maximum delay among the transmitting antennas; the value of the tap coefficient corresponding to the signal sent by the first sending antenna in the a tap coefficients is larger than the values of other tap coefficients; any other transmission antenna than the first transmission antenna transmits a signal before the first transmission antenna transmits a signal.

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