A method and system for interference cancellation synchronization in a low signal-to-noise ratio scenario

Abstract

The application discloses a kind of low signal-to-noise ratio scene under interference cancellation synchronization method and system, belong to electronic communication technical field, by detecting first threshold signal, then interference path cluster energy is removed, then the maximum peak of multi-antenna is superposed, then the signal-to-noise ratio false alarm threshold is detected, and the second interference cancellation is carried out to the path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy path cluster energy

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronic communication, and particularly relates to a method and system for interference cancellation synchronization in a low signal-to-noise ratio (SNR) scenario. BACKGROUND

[0002] With the development of communication technology, synchronization technology as the basis of the receiver detection has attracted more and more attention. Under the condition of low SNR, it is often difficult to identify the signal from the strong interference background through simple threshold selection due to strong interference clutter and complex environmental interference. In addition, strong interference clutter and complex environment will greatly increase the false alarm probability (here, false alarm means that when no signal is received, it is detected as a signal received, which will cause the subsequent compensation and demodulation module to be abnormally started, greatly increasing the power consumption of the system and causing a large number of false detections). Therefore, under the condition of low SNR, a reliable detection method is needed to improve the correct probability of detection and reduce the false alarm probability, so as to improve the reliability of the system in complex environments and improve the competitiveness of the product.

[0003] Due to the very strong background noise under the condition of low SNR, a method for improving the signal-to-noise ratio is needed to improve the SNR in this scenario through appropriate methods to facilitate the pickup of signal components from the interference clutter. In addition, for interference components in complex environments, such as clutter interference and environmental interference, a method is needed to eliminate them to obtain cleaner time domain information and improve the overall synchronization performance. SUMMARY

[0004] In view of the problem of weak synchronization performance and low synchronization accuracy rate under the condition of low signal-to-noise ratio in the prior art, the application provides a method for interference cancellation synchronization in a low signal-to-noise ratio scenario, which comprises the following steps:

[0005] A1: detecting the first threshold signal;

[0006] A2: performing interference path cancellation on the path cluster energy;

[0007] A3: completing maximum peak superposition of multiple antennas;

[0008] A4: detecting the signal-to-noise ratio false alarm threshold;

[0009] A5: performing second interference cancellation on the path cluster energy path;

[0010] A6: calculating the energy of the signal in A1-A5 and obtaining the synchronization position, and the process ends.

[0011] Preferably, in step A1, the received time domain signal is first set as wherein , N represents the total data points of the received data, and M represents the number of symbols of the received data; N represents the total data points of the received data, and M represents the number of symbols of the received data;

[0012] and the multiple synchronization symbols to be transmitted are denoted as wherein wherein M represents the number of synchronization symbols; and the signals of multiple antennas are denoted as wherein wherein N represents the total number of antennas;

[0013] Then, the cross-correlation result of single-symbol single-antenna is calculated:

[0014]

[0015] wherein represents convolution;

[0016] Then, the correlation results of multiple symbols are superimposed:

[0017]

[0018] The noise is filtered according to the first threshold, and the first threshold is thr1,

[0019] If

[0020]

[0021] then

[0022]

[0023] More preferably, when the correlation results of multiple symbols are superimposed in the A1 step, the symbol data with smaller correlation result is directly discarded, that is, when the following condition is met:

[0024]

[0025] only then the subsequent superposition step is entered, otherwise the correlation result of the symbol is directly discarded and does not participate in subsequent calculation;

[0026] The noise is filtered according to the first threshold, and the first threshold is thr1,

[0027] If

[0028]

[0029] then

[0030]

[0031] Preferably, in the step A2, the threshold of interference cancellation is first set as , and is the third detection threshold, i.e. the threshold of signal-to-noise ratio; then the number of clusters of the jth antenna exceeding the threshold thr2 is detected, and the correlation result of the jth antenna exceeding the threshold is denoted as , and the number of clusters of the jth antenna exceeding the threshold is denoted as ;

[0032] Then the cluster energies are sorted from large to small, and the correlation results of the first X antennas from large to small are in turn as follows: ; ;

[0033] Then the largest X clusters are protected, and the X represents a natural number, wherein the un-protected jth cluster represents , and the un-protected cluster is identified as interference, and the interference cluster is eliminated, wherein the calculation process of the elimination of the X clusters is as follows:

[0034]

[0035] Then the calculation process of the elimination of the X clusters is repeated for multiple times, and the elimination of multiple clusters is completed until the signal-to-noise ratio of the jth cluster after elimination satisfies the threshold thr3;

[0036] , wherein the signal-to-noise ratio of the jth cluster after elimination is denoted as:

[0037]

[0038] When thr3, the interference cluster elimination algorithm is ended.

[0039] Preferably, in the step A3, the maximum values of the results of the second to the Jth antennas in the first cluster after the multi-antenna elimination are first aligned to the first antenna, wherein the maximum value index of the second antenna is:

[0040] , wherein arg represents the argument of

[0041] ; , and the maximum value index of the first antenna is:

[0042]

[0043]

[0044] ​​​​​​​​Then the 2nd antenna is cyclically shifted according to the maximum value deviation between the 2nd antenna and the 1st antenna:

[0045]

[0046] Wherein circshift represents cyclically shifting by idx2-idx1;

[0047] Then the results of the 3rd antenna to the Jth antenna are sequentially cyclically shifted as above to ensure that the maximum value results of the 2nd antenna to the Jth antenna are aligned, and then the multi-antenna results are superimposed:

[0048] .

[0049] Preferably, in the A3 step, after the results of the 3rd antenna to the Jth antenna are sequentially cyclically shifted as above, the combined antennas are subjected to a decision,

[0050] When

[0051]

[0052] only then enter the subsequent antenna superposition operation, otherwise discard the energy of the antenna;

[0053] Then the multi-antenna results are superimposed,

[0054]

[0055] Preferably, in the A4 step, first set the false alarm threshold to thr4,

[0056] If:

[0057]

[0058] Then mark the synchronization result as a synchronization failure, i.e. no valid signal arrives, wherein arg represents the argument of .

[0059] Preferably, in the A5 step, the is subjected to the elimination operation in the A2 step again, and the signal after the second elimination is set to .

[0060] Preferably, in the A6 step, the indexes of the strongest t paths are set to , and the corresponding energies are set to , and the energy calculation method of is:

[0061]

[0062] Where real represents taking the real part of the signal, and imag represents taking the imaginary part of the signal;

[0063] Then calculate the total energy:

[0064]

[0065] The precise synchronization position is obtained as follows:

[0066] This completes the interference cancellation and synchronization.

[0067] An interference cancellation synchronization system for low signal-to-noise ratio scenarios includes the following modules:

[0068] Threshold detection module: First, let the received time-domain signal be... And record the multiple synchronization symbols that need to be sent as Then, the signal representing multiple antennas is denoted as Next, the cross-correlation results for a single symbol and a single antenna are calculated:

[0069]

[0070] Then, the correlation results of multiple symbols are summed:

[0071]

[0072] Then filter out the noise according to the first threshold;

[0073] Interference cancellation module: First, set the interference cancellation threshold to 1. Then, the number of path clusters exceeding the threshold thr2 for the j-th antenna is detected, and the correlation result of the j-th antenna is set. The number of path clusters exceeding the threshold is ;

[0074] Then, the energy of the path clusters is sorted from largest to smallest, and the X largest paths are protected, with the unprotected paths being the... Each path represents Unprotected paths are identified as interference and are eliminated as interfering paths. The calculation process for eliminating individual paths is repeated multiple times to eliminate multiple path clusters until the elimination is complete. of When the threshold thr3 is satisfied, When thr3 is reached, this module stops the current calculation;

[0075] Antenna peak superposition module: First, it eliminates the peaks of multiple antennas. The maximum values ​​of the results from the second to the Jth antenna are aligned with the first antenna. Then, the results from the third to the Jth antenna are cyclically shifted to ensure that the maximum values ​​of the results from the second to the Jth antenna are aligned. Finally, the results from multiple antennas are superimposed.

[0076] False alarm detection module: First, set the false alarm threshold to thr4.

[0077] if:

[0078]

[0079] The synchronization result is then marked as synchronization failure, meaning no valid signal arrived, where arg represents the synchronization result. Find the independent variable;

[0080] Secondary interference cancellation module: for The signal is input to the interference cancellation module for recalculation, and the signal after the second cancellation is set to... ;

[0081] Synchronous detection module: Let the indices of the strongest t-th path be respectively The corresponding energies are respectively ,in ( The method for energy calculation is as follows:

[0082]

[0083] Where real represents taking the real part of the signal, and imag represents taking the imaginary part of the signal;

[0084] Then calculate the total energy:

[0085]

[0086] The precise synchronization position is obtained as follows:

[0087] This completes the interference cancellation and synchronization.

[0088] Compared with the prior art, the technical solution of the present invention has the following advantages / benefits:

[0089] 1. The multi-symbol superposition operation in step 1 and the multi-antenna superposition operation in step 3 can improve the synchronization performance under low SNR conditions.

[0090] 2. By eliminating fixed interference through steps 2 and 5, the impact of fixed interference on synchronization is reduced.

[0091] 3. By repeatedly checking the threshold, the probability of missed detections can be significantly reduced while improving the synchronization accuracy. Attached Figure Description

[0092] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation to the scope, and other related drawings can also be obtained by those skilled in the art without any creative effort.

[0093] Figure 1 is a flow chart of a synchronization method for interference cancellation in a low signal-to-noise ratio scenario.

[0094] Figure 2 is a system structure diagram of a synchronization system for interference cancellation in a low signal-to-noise ratio scenario. DETAILED DESCRIPTION

[0095] In order to make the objects, technical solutions and advantages of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely as follows. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of the present application. Therefore, the detailed description of the embodiments of the present application provided below is not intended to limit the scope of the claimed present application, but only to represent selected embodiments of the present application.

[0096] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it can not be further defined and explained in the subsequent drawings.

[0097] Embodiment 1:

[0098] As shown in the figure, a synchronization method for interference cancellation in a low signal-to-noise ratio scenario includes the following steps: Figure 1 A1: detecting a first threshold signal;

[0099] A2: performing interference path cancellation on path cluster energy;

[0100] A3: completing maximum peak superposition of multiple antennas;

[0101] A4: detecting a signal-to-noise ratio false alarm threshold;

[0102] A5: performing second interference cancellation on the path cluster energy path;

[0103] A6: calculating the energy of the signals in A1-A5 and obtaining a synchronization position, and the process ends.

[0104] A6: calculating the energy of the signals in A1-A5 and obtaining a synchronization position, and the process ends.

[0105] In step A1, first let the received time domain signal be wherein , represents the received time domain data of the first time, N represents the total number of data points of the received data, and here the waveform of the received data is not limited and can be an OFDM symbol or a chirp symbol.

[0106] Since the problem solved by the present patent is to improve under low conditions, various schemes need to be considered to improve the SNR of the system. In actual systems, multiple synchronization symbols are often sent, and the multiple synchronization symbols to be sent are denoted as wherein wherein represents the number of synchronization symbols; in actual systems, multiple antennas often exist, and then the signals representing multiple antennas are denoted as wherein wherein represents the total number of antennas;

[0107] Then, the cross-correlation result of a single symbol and a single antenna is calculated:

[0108]

[0109] wherein represents convolution; then, the correlation results of multiple symbols are superimposed, and through the signal correlation and the independent characteristics of noise, the SNR of the entire synchronization can be improved;

[0110] Then, the correlation results of multiple symbols are superimposed:

[0111]

[0112] Some relatively low noise needs to be filtered out according to the first threshold, so as to avoid the submersion of the main path due to the superposition of noise during subsequent superposition, and the first threshold is thr1,

[0113] If

[0114]

[0115] then

[0116]

[0117] When the correlation results of multiple symbols in step A1 are superimposed, the symbol data with a smaller correlation result is directly discarded, so as to avoid that some symbols are affected by strong noise and cause negative benefits, that is, when the following condition is met:

[0118]

[0119] Only after entering the subsequent superposition step, otherwise the symbol correlation results are discarded directly, not involved in subsequent calculation;

[0120] If the number of symbols is N, then through the combination of multiple symbols, the SNR can be improved by 10*log10(N)dB,

[0121] When N is equal to 2, the SNR is improved by 3dB; when N is equal to 3, the SNR is improved by 4.77dB, and when N is equal to 4, the SNR is improved by 6dB,

[0122] Then according to the first threshold, the noise is filtered out, and the first threshold is thr1,

[0123] If

[0124]

[0125] Then

[0126]

[0127] In the A2 step, first, the threshold for interference cancellation is , and is the third detection threshold, that is, the threshold of the signal-to-noise ratio; then the number of path clusters of the jth antenna that exceeds the threshold thr2 is detected, and the number of path clusters of the jth antenna that exceeds the threshold thr2 is detected. ;

[0128] Then the path cluster energy is sorted from large to small, and the related results of the first antenna from large to small are as follows: ;

[0129] Then the largest X paths are protected, X represents a natural number, and the un-protected jth path represents , and the un-protected path is identified as interference, and the interference path is eliminated, and the calculation process of the un-protected path is as follows:

[0130] Then the calculation process of the un-protected path is repeated several times, and the elimination of multiple path clusters is completed, until the of the

[0131] after elimination meets the threshold thr3; Wherein the signal-to-noise ratio of the path cluster j after elimination is represented as:

[0132]

[0133] ​​​​

[0134] When thr3, end the interference cancellation algorithm.

[0135] In A3, first align the maximum values of the results of the second to the Jth antennas to the first antenna, where the maximum value index of the second antenna is:

[0136]

[0137] where arg represents the argument of the complex number ; ;

[0138]

[0139]

[0140] Then, the second antenna is circularly shifted according to the maximum value deviation between the second antenna and the first antenna:

[0141]

[0142] where circshift represents circularly shifting the complex number by idx2-idx1 points;

[0143] Then, the results of the third to the Jth antennas are sequentially circularly shifted according to the above method, so that the maximum values of the second to the Jth antennas are aligned, thereby enhancing the performance of the multi-antenna superposition, and then the multi-antenna results are superposed:

[0144] .

[0145] Preferably, in A3, after the results of the third to the Jth antennas are sequentially circularly shifted according to the above method, in order to avoid the performance of the final multi-antenna combination being reduced due to the excessively low SNR of some antennas, a decision is made on the combined antennas,

[0146] When

[0147]

[0148] only then does the subsequent antenna superposition operation is performed, otherwise the energy of the antenna is discarded to avoid negative gain;

[0149] Then, the multi-antenna results are superposed,

[0150]

[0151] ​​In step A4, the false alarm threshold is first set to thr4.

[0152] if:

[0153]

[0154] The synchronization result is then marked as synchronization failure, meaning no valid signal arrived, where arg represents the synchronization result. Find the independent variable.

[0155] In step A5, for Perform the elimination operation in step A2 again, and let the signal after the second elimination be... .

[0156] In step A6, let the indices of the strongest t-th path be respectively... The corresponding energies are respectively ,in ( The method for energy calculation is as follows:

[0157]

[0158] Where real represents taking the real part of the signal, and imag represents taking the imaginary part of the signal;

[0159] Then calculate the total energy:

[0160]

[0161] The precise synchronization position is obtained as follows:

[0162] This completes the interference cancellation and synchronization.

[0163] Example 2:

[0164] An interference cancellation synchronization system for low signal-to-noise ratio scenarios, such as Figure 2 As shown, it includes the following modules:

[0165] Threshold detection module: First, let the received time-domain signal be... ,in , Representing the The received time-domain data at each moment, where N represents the total number of data points received;

[0166] And denote the multiple synchronization symbols that need to be sent as ,in ,in The number of symbols representing synchronization; then the signal representing multiple antennas is denoted as... ,in ,in Represents the total number of antennas;

[0167] Next, the cross-correlation results for a single symbol and a single antenna are calculated:

[0168]

[0169] in Represents convolution;

[0170] Then, the correlation results of multiple symbols are summed:

[0171]

[0172] Then filter out the noise according to the first threshold, let the first threshold be thr1.

[0173] if

[0174]

[0175] So

[0176] ;

[0177] Interference cancellation module: First, set the interference cancellation threshold to 1. Then, the number of path clusters exceeding the threshold thr2 for the j-th antenna is detected, and the correlation result of the j-th antenna is set. The number of path clusters exceeding the threshold is ;

[0178] Then, the energy of the radial clusters is sorted from largest to smallest, where the nth... The correlation results for the root antenna, from largest to smallest, are as follows: ;

[0179] Then protect the largest X paths, of which the unprotected path is the... Each path represents Unprotected paths are identified as interference and are eliminated as interference paths. The calculation process for eliminating individual paths is as follows:

[0180]

[0181] Then to The calculation process for eliminating individual paths is repeated multiple times to eliminate multiple path clusters until the elimination is complete. of The threshold thr3 is satisfied;

[0182] The signal-to-noise ratio after eliminating the radial cluster j Represented as:

[0183]

[0184] When thr3, this module stops this calculation;

[0185] Antenna peak superposition module: first, the maximum value of the results of the second to the Jth antenna after the multi-antenna elimination is aligned to the first antenna, where the maximum value index of the second antenna is:

[0186] arg represents the argument of the

[0187] ; ; ;

[0188] And let the maximum value index of the first antenna be:

[0189]

[0190] Then the second antenna is circularly shifted according to the maximum value deviation between the second antenna and the first antenna:

[0191]

[0192] Where circshift represents the circular shift of the , and the number of shifts is idx2-idx1;

[0193] Then the results of the third antenna to the Jth antenna are sequentially circularly shifted as described above to ensure that the maximum value results of the second antenna to the Jth antenna are aligned, and then the multi-antenna results are superimposed:

[0194] ;

[0195] False alarm detection module: first, let the false alarm threshold be thr4,

[0196] If:

[0197]

[0198] Then mark the synchronization result as a synchronization failure, that is, no valid signal arrives, where arg represents the argument of the ;

[0199] Secondary interference cancellation module: the input to the interference cancellation module is calculated again, and the secondary cancellation signal is ;

[0200] Synchronization detection module: let the index of the strongest tth path be , and the corresponding energy is wherein ( ) the method of energy calculation is:

[0201]

[0202] wherein real represents taking the real part of the signal, and imag represents taking the imaginary part of the signal;

[0203] Then the total energy is calculated:

[0204]

[0205] The accurate synchronization position is obtained as:

[0206] , and the interference cancellation synchronization is completed.

[0207] The above merely describes the preferred embodiments of the present application, and it should be noted that the above preferred embodiments should not be regarded as a limitation to the present application, and the protection scope of the present application should be defined by the scope of the claims. For those skilled in the art, several improvements and refinements can be made without departing from the spirit and scope of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A method for interference cancellation synchronization in low signal-to-noise ratio scenarios, characterized in that, Includes the following steps: A1: Calculate the cross-correlation results for a single symbol and a single antenna, then superimpose the correlation results for multiple symbols, and filter out noise from the superimposed correlation results; A2: Perform interference path elimination on path cluster energy, identify unprotected paths as interference, and perform interference path elimination on them; A3: Perform maximum peak summation on the multi-antenna results after interference path cancellation; A4: Set the signal-to-noise ratio false alarm threshold for the multi-antenna results after the maximum peak summation; A5: Perform a second interference cancellation on the energy of the path cluster; A6: Calculate the energy of the signal after the second interference cancellation in A1-A5, obtain the synchronization position, and the process ends.

2. The interference cancellation synchronization method in a low signal-to-noise ratio scenario according to claim 1, characterized in that, In step A1, the received time-domain signal is first set to... ,in , Representing the The received time-domain data at each moment, where N represents the total number of data points received; And denote the multiple synchronization symbols that need to be sent as ,in ,in The number of symbols representing synchronization; Then, the signal representing multiple antennas is denoted as... ,in ,in Represents the total number of antennas; Next, the cross-correlation results for a single symbol and a single antenna are calculated: in Represents convolution. This represents the transmitted pilot signal, where i represents the i-th symbol and j represents the j-th antenna; Then, the correlation results of multiple symbols are summed: This represents the correlation result for the i-th symbol and the j-th antenna; Then filter out the noise according to the first threshold, let the first threshold be thr1. if So 。 3. The interference cancellation synchronization method in a low signal-to-noise ratio scenario according to claim 2, characterized in that, When summing the correlation results of multiple symbols in step A1, the symbol data with smaller correlation results are discarded directly, i.e., when the following condition is met: Only if the result of the symbol is passed will it proceed to the subsequent superposition step; otherwise, the result of the symbol will be discarded and will not be included in the subsequent calculation. thr_select2 indicates that the threshold has been passed. Then filter out the noise according to the first threshold, let the first threshold be thr1. if So 。 4. The interference cancellation synchronization method in a low signal-to-noise ratio scenario according to claim 2, characterized in that, In step A2, the threshold for interference cancellation is first set to... ,make The third detection threshold is set; then the number of path clusters exceeding the threshold thr2 for the j-th antenna is detected, and the correlation result of the j-th antenna is set. The number of path clusters exceeding the threshold is ; Then, the energy of the radial clusters is sorted from largest to smallest, where the nth... The correlation results for the root antenna, from largest to smallest, are as follows: ; Then protect the largest X paths, where X represents a natural number, and the unprotected path is the Xth path. Each path represents Unprotected paths are identified as interference and are eliminated as interfering paths. The calculation process for eliminating individual paths is repeated multiple times to eliminate multiple path clusters until the elimination is complete. of Satisfy threshold thr3, That is, the signal after path elimination; when When thr3 is reached, the interference path elimination algorithm ends.

5. The interference cancellation synchronization method in a low signal-to-noise ratio scenario according to claim 4, characterized in that, In step A3, the first step is to eliminate the multiple antennas. The maximum values ​​of the results from the second to the Jth antennas are all aligned with the first antenna, where the index of the maximum value of the second antenna is: Where arg represents the pair Find the independent variable , This represents the correlation results after interference cancellation at the second antenna and the nth point; And let the index of the maximum value of the first antenna be: This represents the relevant results after interference cancellation at the first antenna and the nth point; Then, the second antenna is cyclically shifted according to the maximum deviation between the second antenna and the first antenna: Where cirshift represents the pair Perform a circular shift, shifting by the number of points idx2 - idx1; Then, the results from the 3rd antenna to the Jth antenna are sequentially shifted using the above-mentioned cyclic shift method to ensure that the maximum value results from the 2nd antenna to the Jth antenna are aligned. Finally, the results from multiple antennas are superimposed. 。 6. The interference cancellation synchronization method in a low signal-to-noise ratio scenario according to claim 5, characterized in that, In step A3, after sequentially performing the above-described cyclic shift on the results from the 3rd antenna to the Jth antenna, a decision is made on the merged antennas. when thr_select2 indicates the pass threshold; Only then will the subsequent antenna superposition operation proceed; otherwise, the energy of that antenna will be discarded. Then the results from multiple antennas are superimposed. 。 7. The interference cancellation synchronization method in a low signal-to-noise ratio scenario according to claim 5, characterized in that, In step A4, the false alarm threshold is first set to thr4. if: Then mark the synchronization result as a synchronization failure, where arg represents the result of the synchronization failure. Find the independent variable; This indicates the result of superimposing multiple antennas.

8. The interference cancellation synchronization method in a low signal-to-noise ratio scenario according to claim 7, characterized in that, In step A5, for Perform the elimination operation in step A2 again, and let the signal after the second elimination be... .

9. The interference cancellation synchronization method in a low signal-to-noise ratio scenario according to claim 8, characterized in that, In step A6, let the indices of the strongest t-th path be respectively The corresponding energies are respectively , , This represents the index of the strongest multipath. in The method for energy calculation is as follows: Where real represents taking the real part of the signal, and imag represents taking the imaginary part of the signal. ; Then calculate the total energy: The precise synchronization position is obtained as follows: Complete interference cancellation and synchronization. This represents the index of the strongest multipath.

10. A synchronization system for interference cancellation in low signal-to-noise ratio scenarios, characterized in that, Includes the following modules: Threshold detection module: First, let the received time-domain signal be... And record the multiple synchronization symbols that need to be sent as Then, the signal representing multiple antennas is denoted as Next, the cross-correlation results for a single symbol and a single antenna are calculated: This indicates the pilot signal to be transmitted, where i represents the i-th symbol and j represents the j-th antenna; Then, the correlation results of multiple symbols are summed: This represents the correlation result for the i-th symbol and the j-th antenna; Then filter out the noise according to the first threshold; Interference cancellation module: First, set the interference cancellation threshold to 1. Then, the number of path clusters exceeding the threshold thr2 for the j-th antenna is detected, and the correlation result of the j-th antenna is set. The number of path clusters exceeding the threshold is ; Then, the energy of the path clusters is sorted from largest to smallest, and the X largest paths are protected, with the unprotected paths being the... Each path represents Unprotected paths are identified as interference and are eliminated as interfering paths. The calculation process for eliminating individual paths is repeated multiple times to eliminate multiple path clusters until the elimination is complete. of When the threshold thr3 is satisfied, When thr3 is reached, this module stops the current calculation. This represents the SNR calculated for the j-th antenna; Antenna peak superposition module: First, it eliminates the peaks of multiple antennas. The maximum values ​​of the results from the second to the Jth antenna are aligned with the first antenna. Then, the results from the third to the Jth antenna are cyclically shifted to ensure that the maximum values ​​of the results from the second to the Jth antenna are aligned. Finally, the results from multiple antennas are superimposed. The correlation results for the j-th antenna after interference cancellation; False alarm detection module: First, set the false alarm threshold to thr4. if: The synchronization result is then marked as synchronization failure, meaning no valid signal arrived, where arg represents the synchronization result. Find the independent variable; Secondary interference cancellation module: for The signal is input to the interference cancellation module for recalculation, and the signal after the second cancellation is set to... ; Synchronous detection module: Let the indices of the strongest t-th path be respectively The corresponding energies are respectively , , This represents the index of the strongest multipath. in The method for energy calculation is as follows: Where real represents taking the real part of the signal, and imag represents taking the imaginary part of the signal. ; Then calculate the total energy: The precise synchronization position is obtained as follows: Complete interference cancellation and synchronization. This represents the index of the strongest multipath.

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