CN106998586B - The synchronization acquiring method of wireless communication system in a kind of high dynamic environment - Google Patents

Abstract

The invention belongs to the technical field of communication, and in particular relates to a synchronization acquisition method of a wireless communication system in a high dynamic environment. In the method of the present invention, the differential demodulation soft information sequence of the received signal is firstly correlated with the local synchronous acquisition sequence, and the differential demodulation can effectively overcome the influence of the large frequency offset on the correlation peak value; The pattern and the local secondary capture pattern perform secondary correlation. If the secondary correlation peak value is greater than the threshold, it is considered that the time synchronization capture is successful; after the time synchronization capture is successful, the received synchronization signal waveform and the local synchronization capture waveform are used for multi-level frequency offset estimation. and compensation to complete the frequency synchronization, thereby completing the synchronous acquisition of the system; compared with the traditional synchronous acquisition method, the method of the present invention can improve the synchronous acquisition probability under the same false alarm probability, and can greatly improve the frequency offset estimation range and frequency Partial estimation accuracy, which can do well in synchronous capture in high dynamic environments.

Description

A Synchronization Acquisition Method for Wireless Communication System in High Dynamic Environment

technical field

The invention belongs to the technical field of communication, and in particular relates to a synchronization acquisition method of a wireless communication system in a high dynamic environment.

Background technique

In a wireless communication system, synchronization is the prerequisite for correct data transmission. As the most important part of synchronization technology, synchronization acquisition includes two parts: time synchronization and frequency synchronization. Usually, the receiving end does not know the starting position of the signal, and cannot directly receive and demodulate the data information, so time synchronization is required; the carrier of the received signal is not completely synchronized with the local carrier, and there is a frequency offset (frequency offset for short) ), so frequency synchronization is required; especially when the receiver is in a highly dynamic environment, the Doppler effect generated by the relative motion of the transceiver will cause a large frequency offset between the received signal and the transmitted signal, and the large frequency offset will affect the traditional synchronization method. The performance of time synchronization acquisition has a great impact, so how to realize the time synchronization and frequency synchronization of wireless communication systems in a highly dynamic environment is a difficult problem of synchronization acquisition.

Aiming at the problem of synchronous acquisition of wireless communication systems in high dynamic environments, many scholars at home and abroad have carried out a lot of research work, usually using the following methods: 1) Multi-channel time domain (or frequency domain) parallel acquisition method, this method simultaneously acquires the received signal Carry out frequency compensation for different branches, and use the time position, Doppler change rate and frequency offset corresponding to the branch where the maximum value in the correlation value greater than the threshold is located as the result of time synchronization and frequency synchronization; 2) Synchronization based on time domain sliding correlation The serial acquisition method, which is to perform sliding correlation on the received signal and the local synchronization sequence in the time domain. When the correlation value is greater than the threshold, it is considered that the time synchronization acquisition is completed, and the frequency offset is estimated according to multiple correlation values; 3) Based on the fast Fourier The fast acquisition method of FastFourier Transformation (FFT), which is the rapid implementation of method 2 in the frequency domain, uses the multiplication operation in the frequency domain to equivalently complete the correlation operation in the time domain. Compared with the sliding correlation operation in the time domain, this The method greatly reduces the capture time; 4) PMF-FFT algorithm based on Partial Matched Filtering (Partial Matched Filtering, PMF), this method selects a part of the long sequence in the time domain for correlation, which can resist the frequency offset to a certain extent The impact of the sequence, and then use the partial correlation value to do FFT to estimate the frequency, can improve the frequency estimation range.

The principle of the multi-channel time-domain (or frequency-domain) parallel acquisition method is relatively simple, and it can complete time and frequency synchronization in a highly dynamic environment, but in an environment with a large frequency offset, multi-channel parallel processing is required, and the implementation complexity is too high; based on The time-domain sliding correlation synchronous serial acquisition method and the FFT-based fast acquisition method are simple in structure, and the complexity of the FFT method is much lower than the time-domain sliding correlation, but the performance of the two is the same, and both methods are suitable for full-period pseudo-random For sequence capture, when the frequency offset is small, the longer the synchronization sequence, the better the correlation, but when the frequency offset is large, the correlation of the long sequence is greatly affected by the frequency offset, which will reduce the synchronization capture performance. Therefore, the large frequency These two methods are only suitable for shorter sequences to capture. Compared with long sequences, the frequency offset estimation range of short sequences is larger, but its correlation is poor, and it cannot meet the requirements of low signal-to-noise ratio and small frequency offset. System synchronization acquisition performance requirements, therefore, the selection of the synchronization acquisition sequence length should take into account the sequence correlation and frequency offset estimation range, too long or too short can not meet the system requirements; PMF-FFT is a commonly used long code acquisition algorithm at present, based on Taking into account the needs of better correlation and larger frequency offset estimation range, the partial correlation of long sequences is selected, but the operation of partial correlation destroys the good correlation characteristics of long sequences, causes a certain loss to the correlation peak, and reduces the performance of time synchronization capture , at the same time, the length of part of the relevant time also determines the frequency offset estimation range, and the ability to resist large frequency offsets is limited. Therefore, although these three methods can deal with environments with certain frequency offsets, they are difficult to deal with high-speed air-to-ground communications and air-to-air communications. Such as high dynamic environment with larger frequency deviation.

SUMMARY OF THE INVENTION

In order to solve the deficiencies of the prior art, the present invention provides a method for synchronous acquisition of a wireless communication system in a highly dynamic environment. In this method, the designed synchronous signal adopts a modulation method capable of differential demodulation, and the timing is performed at the receiving end. When synchronizing, the differential demodulation soft information sequence of the received signal is first correlated with the local synchronous acquisition sequence, and the differential demodulation can effectively overcome the influence of large frequency offset on the correlation peak; then the pattern composed of multiple primary correlation values Perform secondary correlation with the local secondary capture pattern, if the secondary correlation peak value is greater than the threshold, it is considered that the time synchronization capture is successful; after the time synchronization capture is successful, then use the received synchronization signal waveform and the local synchronization capture waveform to perform multi-level frequency offset estimation and Compensation to complete frequency synchronization, thereby completing the synchronization acquisition of the system; compared with the traditional synchronization acquisition method, this method can improve the synchronization acquisition probability under the same false alarm probability, and can greatly improve the frequency offset estimation range and frequency offset estimation accuracy , which can do well in synchronous capture in highly dynamic environments.

In order to describe the content of the present invention conveniently, the local synchronous acquisition pattern and the local synchronous signal waveform are firstly explained: the local synchronous acquisition pattern is composed of L ₂ local synchronous acquisition sequences X, and each synchronous acquisition sequence includes L ₁ modulation symbols, The phases of L ₂ local synchronous acquisition sequences form a local secondary acquisition pattern B, therefore, the local synchronous acquisition pattern includes L ₁ L ₂ modulation symbols; if each modulation symbol has N _samp sampling points, after N _samp times The sampled local synchronization capture pattern forms a local synchronization signal waveform S, wherein L ₁ , L ₂ , and N _samp are all non-zero natural numbers.

A method for synchronous acquisition of a wireless communication system in a highly dynamic environment, the specific steps are as follows:

S1, setting the capture threshold factor G _t and the differential symbol array λ of length K, λ=[λ(1)λ(2)...λ(K)];

S2. Initialize the sliding related initial position n, n=1;

S3. Perform symbol-level differential demodulation on the received signal at the current sample point position n to obtain differential demodulation soft information d _n ;

S4. Determine whether the current position n is greater than (L ₁ -1)N _samp , if so, calculate a first-order correlation value: correlate the sequence D formed by L ₁ differential demodulation soft information with the local synchronous capture sequence X, and obtain the current sample The first-order correlation value z _n corresponding to point position n; otherwise, go to S7;

S5. Determine whether the current position n is greater than (L ₁ L ₂ -1)N _samp , if so, calculate the secondary correlation value: correlate L ₂ primary correlation values Z with the local secondary capture pattern B to obtain the current sample point The second-level correlation value c _n corresponding to the position; otherwise, go to S7;

S6, judging whether the modulus of the secondary correlation value c _n is greater than the threshold: if so, turn to S8; otherwise, turn to S7;

S7, slide to the next position, n=n+1, turn to S3;

S8. Time synchronization capture position positioning: calculate the secondary correlation value corresponding to N _samp -1 sample points after the current sample point position n, and find the sample point position with the largest correlation value modulus among the N _samp secondary correlation values Time-synchronized capture completes as accurate time-synchronized capture position;

S9. Frequency synchronization: perform multi-level frequency offset estimation and compensation according to the received synchronization signal waveform R corresponding to the time synchronization capture position and the local synchronization signal waveform S.

Further, the specific steps of calculating the first-order correlation value in S4 are as follows:

S41. The symbol-level differential demodulation soft information d _n of the current sample point position n and the first L ₁ -1 differential demodulation soft information at equal intervals constitute the current differential demodulation soft information sequence D, The interval is N _samp sampling points;

S42, the current differential demodulation soft information sequence D and the local synchronous capture sequence Conjugate multiplication and summation and then divide by L ₁ to obtain the first-order correlation value z n corresponding to the current sample point position _n ,

Further, the specific steps for calculating the secondary correlation value in S5 are as follows:

S51. The first-order correlation value z _n of the current sample point position n and the first L ₂ -1 first-order correlation values at equal intervals constitute the current second-order capture pattern The interval is L ₁ N _samp sampling points;

S52, the current secondary capture pattern Z and the local secondary capture pattern Conjugate multiplication and summation and then divide by L ₂ to get the secondary correlation value c n corresponding to the current sample point position _n ,

Further, the specific steps of time synchronization capture position positioning in S8 are as follows:

S81. Calculate the symbol-level differential demodulation soft information corresponding to N _samp -1 sample point positions after the current sample point position n, and obtain

S82. Calculate the first-order correlation value corresponding to sample point positions n+1, n+2,..., n+N _samp -1 The calculation method is the same as S4;

S83. Calculate the secondary correlation value corresponding to sample point positions n+1, n+2,..., n+N _samp -1 The calculation method is the same as S5;

S84, the modulus of N _samp secondary correlation values Find the sample point position corresponding to the maximum value in , as the accurate time synchronization capture position, and the time synchronization capture is completed;

Further, the specific steps of frequency offset estimation described in S9 are as follows:

S91. Initialize frequency offset estimation series k=1;

S92. Correction waveform: according to the accurate time synchronization capture position obtained in S8, the received synchronization signal waveform R corresponding to the time synchronization capture position is conjugate-multiplied by the local synchronization signal waveform S to obtain the correction waveform A;

S93. Calculating the segmented mean value of the corrected waveform: Segment the corrected waveform according to the number of differential symbols λ(k) corresponding to the current frequency offset estimation series k, and calculate the mean value for each segment of the corrected waveform to obtain the segmented mean value sequence M _A of the corrected waveform ;

S94. Calculating the k-th stage phase difference: calculating the k-th stage phase difference △θ _k according to the mean value of the conjugate multiplication of adjacent values of _MA ;

S95. Estimating the frequency offset of the kth level: according to △θ _k , calculate the estimated value of the frequency offset of the kth level

S96. Compensating for frequency offset: performing k-th frequency offset compensation on the waveform R of the received synchronization signal, and updating R;

S97. Judging whether the current differential grade k is greater than or equal to the total grade K: if k≥K, go to S99; otherwise, go to S98;

S98. Update frequency offset estimation series k=k+1, go to S92;

S99. Accumulate multi-level frequency offset estimation results as the final frequency offset estimation result

The beneficial effects of the present invention are:

The invention can realize reliable time synchronization and frequency synchronization of the wireless communication system in a high dynamic environment, and first correlates the received signal differentially demodulated soft information sequence with the local synchronous capture sequence to overcome the influence of large frequency offset on the correlation value of the longer sequence ; and then use the secondary correlation mechanism to further improve the probability of synchronous acquisition in a high dynamic environment; then use the received synchronous signal waveform and the local synchronous signal waveform to perform multi-level frequency offset estimation and compensation, which greatly improves the frequency offset estimation range and frequency offset estimation accuracy, and is not sensitive to frequency offset, it is suitable for both small frequency offset environment and large frequency offset environment; compared with the traditional synchronous acquisition method, the present invention is in a high dynamic environment with large frequency offset and low signal-to-noise ratio. The synchronization acquisition probability, frequency offset estimation range and frequency offset estimation accuracy of a wireless communication system can be significantly improved, and the implementation complexity is low, so it has strong application value.

Description of drawings

Fig. 1 is a general flowchart of the synchronous acquisition method of the wireless communication system in the high dynamic environment of the present invention;

Fig. 2 is a flow chart of calculating the first-order correlation value;

Fig. 3 is a flow chart of secondary correlation value calculation;

Fig. 4 is a flow chart of time synchronization capture position positioning;

Fig. 5 is a flow chart of frequency synchronization;

Fig. 6 is a schematic diagram of a comparison of acquisition performance between a specific embodiment of the present invention and a traditional synchronous acquisition method under an additive white Gaussian noise channel (Additive White Gaussian Noise, AWGN);

Fig. 7 is a schematic diagram of frequency offset estimation performance comparison between a specific embodiment of the present invention and a traditional synchronization acquisition method in an AWGN channel.

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings.

Taking the MSK-modulated wireless communication system and the AWGN channel environment as an example, to carry out synchronous acquisition in a highly dynamic environment, the selected local acquisition sequence is an m-sequence with a cycle length of L ₁ =127, and the corresponding generator polynomial is: g(x )=x ⁷ +x ³ +1, the local secondary acquisition pattern is an m-sequence of length L ₂ =7: {-1,-1,-1,1,1,-1,1}, modulation symbol rate R _s = 1MBaud, oversampling multiple N _samp = 5, let {s _n } be the baseband oversampled waveform sequence for transmission, {w _n } be the noise sequence, △f is the frequency offset of the transceiver, that is, the carrier frequency of the received signal minus the carrier frequency of the transmitted signal frequency is △f, △θ is the carrier phase difference between transceivers, T _samp is the sampling time, and T _samp =1/(R _s N _samp ), then the received baseband oversampled waveform sequence is {r _n },n =1,2,..., r _n =s _n exp(j(2π△fnT _samp +△θ))+w _n , as shown in Figure 1, the specific steps of the synchronous capture method adopted in this embodiment are:

S1. Set the capture threshold factor G _t and the differential symbol array λ of length K=3, G _t =0.052, under this threshold factor, when E _s /N ₀ =0dB, the false alarm probability of this method is 2×10 ^-5 , λ=[λ(1) λ(2) ... λ(3)]=[4 50 444], its value is the number of symbols corresponding to each level of difference;

S2. Initialize the sliding related initial position n, n=1;

S3. Perform symbol-level differential demodulation on the received signal at the current sample point position n to obtain differential demodulation soft information d _n ;

S4, judge whether the current position n is greater than (L ₁ -1)N _samp , if so, then calculate the first-level correlation value, otherwise turn to S7, as shown in Figure 2, the first-level correlation value calculation includes:

S41. The symbol-level differential demodulation soft information d _n of the current sample point position n and the first L ₁ -1 differential demodulation soft information at equal intervals constitute the current differential demodulation soft information sequence D, The interval is N _samp sampling points;

S42, the current differential demodulation soft information sequence D and the local synchronous capture sequence Conjugate multiplication and summation and then divide by L ₁ to obtain the first-order correlation value z n corresponding to the current sample point position _n ,

S5, judging whether the current position n is greater than (L ₁ L ₂ -1)N _samp , if so, then calculate the secondary correlation value, otherwise turn to S7, as shown in Figure 3, the secondary correlation value calculation includes:

S51. The first-order correlation value z _n of the current sample point position n and the first L ₂ -1 first-order correlation values at equal intervals constitute the current second-order capture pattern The interval is L ₁ N _samp sampling points;

S52, the current secondary capture pattern Z and the local secondary capture pattern Conjugate multiplication and summation and then divide by L ₂ to get the secondary correlation value c n corresponding to the current sample point position _n ,

S6. Determine whether the modulus of the secondary correlation value c _n is greater than the threshold V _T , if so, go to S8; otherwise, go to S7; wherein, the threshold is the estimated value of the average power of the received signal, calculated as:

Take the received signal waveform of (L ₁ L ₂ -1) N _samp samples forward from the current sample point position n, and average its modulus value to obtain the average power of the signal

S7, slide to the next position, n=n+1, turn to S3;

S8, time synchronous capture location positioning, as shown in Figure 4, including:

S81. Calculate the symbol-level differential demodulation soft information corresponding to N _samp -1 sample point positions after the current sample point position n, and obtain

S82. Calculate the first-order correlation value corresponding to sample point positions n+1, n+2,..., n+N _samp -1 in, The calculation method of z _n+m is the same as S4;

S83. Calculate the secondary correlation value corresponding to sample point positions n+1, n+2,..., n+N _samp -1 in, The calculation method of c _n+m is the same as S5;

S84, the modulus of N _samp secondary correlation values Find the sample point position corresponding to the maximum value in , as the accurate time synchronization capture position, and the time synchronization capture is completed;

S9. Frequency synchronization: perform multi-level frequency offset estimation and compensation according to the received synchronization signal waveform R corresponding to the time synchronization capture position and the local synchronization signal waveform S, as shown in Figure 5, including:

S91. Initialize frequency offset estimation series k=1;

S92, correction waveform: according to the accurate time synchronization capture position obtained in S8, receive the synchronization signal waveform corresponding to the time synchronization capture position Synchronize with the local signal waveform Conjugate multiplication to get the corrected waveform in

S93. Calculating the segmented mean value of the corrected waveform: Segment the corrected waveform according to the number of differential symbols λ(k) corresponding to the current frequency offset estimation series k, and each segment contains λ(k) symbols, for a total of segments, of which Indicates rounding down, and calculating the mean value of the segmented correction waveform, and the obtained U mean values constitute the correction waveform segment mean value sequence in,

S94. Calculating the k-th stage phase difference: calculate the k-th stage phase difference △θ _k according to the mean value of the conjugate multiplication of adjacent values of _MA ,

S95. Estimating the frequency offset of the kth level: according to △θ _k , calculate the estimated value of the frequency offset of the kth level

S96. Compensate frequency offset: for receiving synchronous signal waveform Perform frequency offset compensation for the kth time to obtain the received synchronization signal waveform after frequency offset compensation in n=1,2,...,L ₁ L ₂ N _samp , update the received synchronization signal waveform R, let R=R′;

S97. Judging whether the current differential grade k is greater than or equal to the total grade K: if k≥K, go to S99; otherwise, go to S98;

S98. Update frequency offset estimation series k=k+1;

S99. Accumulate multi-level frequency offset estimation results as the final frequency offset estimation result

Fig. 6 is a performance comparison between this embodiment and the traditional synchronous serial acquisition method based on time-domain sliding correlation in the AWGN channel, where the abscissa is the normalized symbol-to-noise ratio E _s /N ₀ , The ordinate is the acquisition probability P _d and the false alarm probability P _f ; the modulation method adopts MSK, the modulation symbol rate R _s is 1MBaud, the oversampling multiple N _samp is 5, and the local synchronous acquisition sequences of the two methods are of length L ₁ =127 m sequence, the false alarm probability corresponding to the set correlation threshold is the same, both are 2×10 ^-5 ; the local capture pattern of the traditional method is repeated L ₂ =7 synchronization capture sequences, and the correlation values of L ₂ synchronization capture sequences are greater than the threshold Only then is that captured, where, In the present invention, the local secondary capture pattern selects an m-sequence whose length is L ₂ =7: {-1,-1,-1,1,1,-1,1}, wherein, 1 represents a local synchronous capture sequence, and -1 Represents the reverse phase sequence of the local synchronous capture sequence, the differential demodulation method adopts one-bit differential demodulation, and the threshold factor G _t is 0.052; the initial frequency offset is selected from two cases of △f=3.5kHz and △f=100kHz; the simulation results show that, When the initial frequency offset is 3.5kHz, the traditional method is greatly affected by the frequency offset, and cannot capture the synchronization signal when E _s /N ₀ ≤ -2dB, and reaches 95% when E _s /N ₀ = 1.25dB acquisition probability, and the synchronous acquisition method suitable for high dynamic environment of the present invention can reach 95% correct acquisition probability when E _s /N ₀ is-2.5dB, when the acquisition probability is 95%, it is better than the traditional method by about 3.75dB ; Because the sequence length L ₁ =127, the symbol rate R _s is 1MBaud, the frequency offset estimation range of the traditional method is ± 3.94kHz, in the dynamic environment greater than the frequency offset range, the traditional method has been unable to capture the synchronization signal, and the present invention Even when the initial frequency deviation is 100kHz, when E _s /N ₀ ≥ -1.5dB, the correct synchronization acquisition probability can still reach 95%, and the synchronization acquisition performance is far better than the traditional correlation synchronization acquisition method;

Figure 7 is a comparison of frequency offset estimation performance between this embodiment and the traditional synchronous serial acquisition method based on time-domain sliding correlation in an AWGN channel. The simulation parameters are set the same as those in Figure 6, and the traditional method uses sequence-level phase difference to divide the frequency offset. Estimation method, its theoretical frequency offset estimation range is [-R _s /(2L ₁ ), R _s /(2L ₁ )], which is [-3.94kHz, 3.94kHz]; and the multi-level phase difference in the present invention Frequency offset estimation method, differential symbol array λ=[λ(1) λ(2) ... λ(3)]=[450 444], the estimation range is [-R _s /(2λ(1)),R _s /( 2λ(1))], λ(1) represents the number of differential symbols of the first stage, and the theoretical frequency offset estimation range of this embodiment is [-125kHz, 125kHz]; the abscissa is E _s /N ₀ , and the ordinate is the frequency The root mean square error (Root Mean Square Error, RMSE) of offset estimation; Simulation result shows, the frequency offset estimation performance of the inventive method is far better than the frequency offset estimation performance of traditional method, in synchronous acquisition pattern by 7 127 long When the m-sequence is formed, the traditional method cannot estimate the frequency offset above 3.8kHz; while the synchronization acquisition method suitable for high dynamic environments proposed in the present invention can estimate a large-scale frequency offset of 120kHz, and the frequency offset estimation accuracy is affected by the initial frequency offset In the case of initial frequency offset of 3.5kHz and 100kHz, the RMSE of frequency offset estimation is almost the same, and there is only a 1dB gap from the Cramer-Rao Lower Bound (CRLB), while the frequency of the traditional method The accuracy of bias estimation is far worse than that of the embodiment of the present invention; the CRLB of frequency offset estimation is

Wherein, s[x] represents the standard deviation of x, and M is the number of symbols used for frequency offset estimation; therefore, under the same synchronization sequence length and the same false alarm probability requirement, the inventive method has better synchronization than the traditional method Acquisition performance, and can greatly improve the frequency offset estimation range and frequency offset estimation accuracy, can well complete time synchronization and frequency synchronization in a high dynamic environment, has a strong application value.

Claims (5)

1. A method for synchronization acquisition in a wireless communication system in a highly dynamic environment, comprising the steps of:

s1, setting an acquisition threshold factor G_tAnd a differential sign array λ of length K, [ λ (1) λ (2) … λ (K)]；

S2, initializing a sliding related initial position n, wherein n is 1;

s3, carrying out symbol-level differential demodulation on the received signal of the current sampling point position n to obtain differential demodulation soft information d_n；

S4, judging whether the current position n isWhether or not greater than (L)₁-1)N_sampIf yes, calculating a first-level correlation value: mixing L with₁A sequence D formed by differential demodulation soft information is correlated with a local synchronous capture sequence X to obtain a primary correlation value z corresponding to the current sampling point position n_n(ii) a Otherwise, go to S7;

s5, judging whether the current position n is larger than (L)₁L₂-1)N_sampIf yes, calculating a secondary correlation value: mixing L with₂The first-level correlation value Z is correlated with the local second-level capture pattern B to obtain a second-level correlation value c corresponding to the current sampling point position_n(ii) a Otherwise, turning to S7;

s6, judging a secondary correlation value c_nWhether the norm of (d) is greater than a threshold: if yes, go to S8; otherwise, go to S7;

s7, sliding to the next position, wherein n is n +1, and turning to S3;

s8, time synchronization acquisition position positioning: calculating N after the current sampling point position N_sampA secondary correlation value for 1 sample point, where N is_sampFinding out the sample point position with the maximum module of the correlation value from the secondary correlation values as an accurate time synchronization capturing position, and completing the time synchronization capturing;

s9, frequency synchronization: and performing multistage frequency offset estimation and compensation according to the received synchronous signal waveform R and the local synchronous signal waveform S corresponding to the time synchronization acquisition position.

2. The method for acquiring synchronization of a wireless communication system in a highly dynamic environment as claimed in claim 1, wherein the step S4 is implemented by the following steps:

s41 symbol-level differential demodulation soft information d of current sampling point position n_nWith front L equally spaced₁-the 1 differentially demodulated soft information forms a current differentially demodulated soft information sequence D,interval of N_sampSampling points;

s42, current differential demodulation soft information sequence D and local synchronous capture sequenceConjugate multiplied sum divided by L₁Obtaining a first-order correlation value z corresponding to the current sampling point position n_n，

3. The method for acquiring synchronization of a wireless communication system in a highly dynamic environment as claimed in claim 2, wherein the step S5 is implemented by the following steps:

s51, first-order correlation value z of current sampling point position n_nWith front L equally spaced₂-1 primary correlation values constituting the current secondary capture patternInterval L₁N_sampSampling points;

s52, current secondary capture pattern Z and local secondary capture patternConjugate multiplied sum divided by L₂Obtaining a second-level correlation value c corresponding to the current sampling point position n_n，

4. The method of claim 3, wherein the step S8 of locating the time synchronization acquisition position comprises the following steps:

s81, calculating N after the current sampling point position N_samp-1 symbol level differential demodulation soft information corresponding to the sampling point position to obtain

S82, calculating the positions N +1, N +2, …, N + N of the sampling points_samp-1 corresponding primary correlation valueThe calculation method is the same as S4;

s83, calculating the positions N +1, N +2, …, N + N of the sampling points_samp-1 corresponding secondary correlation valueThe calculation method is the same as S5;

s84 at N_sampModulo square of the second order correlation valueAnd finding out the sampling point position corresponding to the maximum value as an accurate time synchronization capturing position, and completing the time synchronization capturing.

5. The method of claim 4, wherein the frequency offset estimation in step S9 specifically comprises the following steps:

s91, initializing a frequency offset estimation stage number k equal to 1;

s92, correction waveform: according to the accurate time synchronization capturing position obtained by S8, carrying out conjugate multiplication on a received synchronization signal waveform R corresponding to the time synchronization capturing position and a local synchronization signal waveform S to obtain a correction waveform A;

s93, calculating a correction waveform segmentation mean value: segmenting the correction waveform according to the differential symbol number lambda (k) corresponding to the current frequency offset estimation series k, and averaging each segment of the correction waveform to obtain a correction waveform segmentation average value sequence M_A；

S94, calculating the phase difference of the kth level: according to M_AThe mean value of conjugate multiplication of adjacent values is used for calculating the k-th-stage phase difference △ theta_k；

S95, estimating the k-th order frequency deviation according to △ theta_kCalculating the estimated value of the kth frequency offset

S96, frequency offset compensation: performing frequency offset compensation on the wave form R of the received synchronous signal for the kth time, and updating the R;

s97, judging whether the current differential stage number K is more than or equal to the total stage number K: if K is more than or equal to K, turning to S99; otherwise, go to S98;

s98, updating the frequency offset estimation series k to k +1, and turning to S92;

s99, accumulating the multi-stage frequency deviation estimation result as the final frequency deviation estimation result