Synchronous processing method based on joint judgment of underwater sound multi-frame signals and related characteristics

Abstract

The invention discloses a synchronous processing method based on joint judgment of underwater acoustic multi-frame signals and related characteristics, which comprises the following steps of: performing copy correlation on received signals by using locally stored synchronous signals, and performing joint validity judgment of related peak characteristics by using prior characteristic information of related peaks, namely characteristics of high peak values and low side lobes; a multi-frame signal combining coarse and fine synchronization is adopted as a synchronization frame format, and coarse synchronization judgment is performed by using a correlation peak relation and a relative position relation among the multi-frame signal, so that false synchronization caused by the influence of ocean burst noise is prevented; positioning a fine synchronization position according to a relative position relation between prior coarse and fine synchronization, judging whether the relation between a correlation peak value at the fine synchronization position and the relative position meets a set threshold value or not, and performing fine synchronization judgment; and finally, the initial position of the information signal can be calculated according to the position of establishing the fine synchronization. On the premise of ensuring the synchronous detection probability, the false synchronization probability can be effectively reduced, and the method adapts to the actual marine environment.

Description

Technical Field

[0001] The present invention relates to underwater acoustic communication technology, and in particular to a synchronization processing method based on joint judgment of underwater acoustic multi-frame signals and correlation features. Background Art

[0002] Underwater acoustic communication plays a crucial role in information transmission in the underwater environment. In an underwater acoustic communication network, signal synchronization is a prerequisite for accurate reception of communication signals and has an indispensable position in the communication system. Once synchronization is incorrect, signal demodulation fails, thus affecting the reliability of the entire underwater acoustic communication network. Existing underwater acoustic signal synchronization methods are often copy correlation synchronization methods. A frame of synchronization signal that is relatively easy to detect, such as an LFM signal, etc., is added before the communication signal for transmitting information. At the receiving end, the received signal is subjected to copy correlation with the locally stored synchronization signal. When the correlation peak exceeds a set threshold, it is considered that the synchronization signal has been detected. At this time, the synchronization start position can be deduced through the position where the correlation peak is located.

[0003] Existing methods rely on the high auto-correlation of the synchronization signal itself and are mainly for relatively stable and high signal-to-noise ratio channel conditions. However, the actual underwater acoustic channel is a well-known complex space-time-frequency varying channel. Changes in environmental factors cause signal fading effects, making the underwater acoustic channel state usually very unstable. This feature may cause serious distortion of the signal after passing through the underwater acoustic channel, resulting in a decrease in its correlation with the locally stored signal, thereby increasing the probability of missed synchronization, that is, in the presence of a synchronization signal, successful synchronization fails. In addition, due to the complex marine environment, specific scenario noises such as ship noises, specific location fish school foraging noises, and ice cracks in polar regions, etc., most of them are significant pulses with short-term distortion and have obvious non-Gaussian components. If the synchronization signal is only a single-frame signal, once such a high-intensity burst noise appears, it is very likely to be misdetected, increasing the probability of false synchronization, that is, in the absence of a synchronization signal, synchronization is erroneously performed. At the same time, the multi-path effect caused by sound waves propagating through different paths may very likely generate pseudo-correlation peaks at positions other than the true position after copy correlation, resulting in misjudgment of the synchronization position even if synchronization is captured. Therefore, the copy correlation method using a single-frame signal as the synchronization signal does not have sufficient robustness in the underwater acoustic channel. Summary of the Invention

[0004] The object of the present invention is a synchronization processing method based on joint judgment of underwater acoustic multi-frame signals and correlation features.

[0005] The technical solution for realizing the present invention is: A synchronization processing method based on joint judgment of underwater acoustic multi-frame signals and correlation features, including the following steps:

[0006] Step S1: Receive underwater acoustic signals in real time through an underwater transducer, convert the synchronous signals into electrical signals through acoustic-electric conversion, perform analog-to-digital conversion and sampling, then intercept the sampled received signals in a sliding window, and perform correlation operations on the received signals of each sliding window using the synchronous signals saved locally to obtain a correlation function;

[0007] Step S2: Use the sharpness of the correlation peak to perform joint feature judgment, set a decision threshold. If the peak value of the correlation function is greater than the set threshold and the average value of the sidelobes is not greater than 0.5 times the correlation peak value, then consider this correlation peak as a valid correlation peak, and record this peak value and its relative peak position;

[0008] Step S3: If 3 or more frames of valid correlation peaks are continuously detected and their peak values and corresponding positions are all within the same range, then it is considered that the synchronous signal is basically captured and coarse synchronization is established;

[0009] Step S4: After coarse synchronization is established, use the relative position of the reference peak value at the time of establishing coarse synchronization as a benchmark to narrow the search range of the correlation peak value, so as to resist the influence of burst noise and multipath;

[0010] Step S5: After capturing the end of the coarse synchronization, locate the sliding window where the fine synchronization is located, perform correlation operations on the data of this window. If the correlation peak value of the obtained correlation function is greater than the threshold and is within the same range as the reference peak value at the time of establishing coarse synchronization; at the same time, the relative peak position obtained is within the same range as the relative position of the reference peak value at the time of establishing coarse synchronization, then it is considered that fine synchronization is established;

[0011] Step S6: Based on the relative peak position at the time of establishing fine synchronization, deduce the starting position of the information signal, and the synchronization process ends.

[0012] Further, in Step S1: Receive underwater acoustic signals in real time through an underwater transducer, convert the synchronous signals into electrical signals through acoustic-electric conversion, perform analog-to-digital conversion and sampling, then intercept the received signals through a sliding window, and perform correlation operations on the received signals of each sliding window using the synchronous signals saved locally to obtain a correlation function. The specific method is as follows:

[0013] Assume that the acoustic signal received by the underwater transducer is sig(t), and its expression is:

[0014] sig(t) = [sync(t), Intvl(t), x(t)]

[0015] Among them, sync(t) is a continuous synchronous signal, and x(t) is the information signal that truly carries information. The guard interval Intvl(t) between sync(t) and x(t) is a blank segment with a known duration.

[0016] The discrete synchronization signal sync(n) is obtained by performing acoustic - electrical conversion, analog - digital conversion, and sampling on the continuous synchronization signal sync(t), and the sampling rate is f s , the sliding window length is T, and the received signal after the sliding window intercepts sync(n) is sync Rec (n), with a length of L1, then it can be obtained that:

[0017]

[0018] Let the locally saved discrete copy signal be sync Loc (n), perform copy correlation on it, that is:

[0019]

[0020] Among them, is the convolution operation, and the relationship between sync Loc (n) and the discrete synchronization signal sync(n) can be expressed as:

[0021] sync Loc (n) = sync(L1 - n)

[0022] Furthermore, in step S2, using the sharpness of the correlation peak, perform feature joint judgment, set a decision threshold. If the peak value of the correlation function is greater than the set threshold, and the average value of the sidelobes is not greater than 0.5 times the correlation peak value, then this correlation peak is considered a valid correlation peak, and record the peak value and its relative position of the peak. The specific method is as follows:

[0023] Step 2.1, set the decision threshold Th sync , and the threshold is set to 6 - 10 times the standard deviation of the background noise;

[0024] Step 2.2, calculate the correlation peak value and its relative position after the correlation operation, that is:

[0025] [Peak, idx] = max(sync Xcorr (n))

[0026] Among them, Peak is the maximum value of sync Xcorr (n), and idx is the relative position where Peak is located; if it satisfies:

[0027] Peak > Th sync

[0028] Then it is considered that this correlation peak satisfies the high - peak - value feature. Take 50 - 150 sampling points on the left and right of the correlation peak value, and calculate the average value at its left and right sidelobes, that is

[0029]

[0030] Among them, mean() represents taking the average value; if the following conditions are met:

[0031] sub left , sub right <0.5 * Peak

[0032] Then it is considered that the relevant peak simultaneously meets the characteristics of high peak value and low sidelobe, and is an effective relevant peak. Record the idx corresponding to Peak, otherwise, do not record, that is, set idx to 0.

[0033] Furthermore, in step S3, if 3 or more frames of effective relevant peaks are continuously detected, and their peak values and corresponding positions are all within the same range, it is considered that the synchronization signal is basically captured and coarse synchronization is established. The specific method is as follows:

[0034] Let the current sliding window be i, and its corresponding peak value and relative position be [Peak i , idx i . If Peak i-1 , Peak i-2 are both within the same range as Peak i , that is, the following conditions are met:

[0035] Peak i-1 , Peak i-2 ∈[Peak i *0.7, Peak i *1.3]

[0036] At the same time, idx i-1 , idx i-2 are both within the same range as idx i , that is, the following conditions are met:

[0037] idx i-1 , idx i-2 ∈[idx i -10, idx i +10]

[0038] Then it is considered that the synchronization signal is basically captured and coarse synchronization is established, and [Peak i , idx i is used as the reference peak value and the relative position of the reference peak value.

[0039] Furthermore, in step S4, after coarse synchronization is established, the search range of the relevant peak value is narrowed based on the relative position of the reference peak value at the time of establishing coarse synchronization, so as to resist the influence of burst noise and multipath. The specific method is as follows:

[0040] Based on the relative position of the reference peak value idx iTaking [ID] as a reference, narrow down the peak search range, expressed as:

[0041]

[0042] Furthermore, in step S5, after capturing the end of the coarse synchronization, locate the sliding window where the fine synchronization is located, perform a correlation operation on the received signal of this window. If the correlation peak of the obtained correlation function is greater than the threshold and within the same range as the reference peak when the coarse synchronization is established; at the same time, the relative position of the obtained peak is within the same range as the correlation position of the reference peak when the coarse synchronization is established, then it is considered that the fine synchronization is established. The specific method is as follows:

[0043] Step 5.1, according to the search range selected in step S4, if the received signals of several consecutive sliding windows afterwards do not detect a correlation peak that satisfies the threshold, that is, Peak i+1 < Th sync , then it is considered that the end of the coarse synchronization has been captured and the guard interval area has been entered;

[0044] Step 5.2, after a period of time of the guard interval, since the length of the guard interval is known, that is, locate the sliding window i where the fine synchronization is located fine ;

[0045] Step 5.3, perform a correlation operation on the received signal of the sliding window i fine and find the peak and its corresponding position within the restricted search range If it satisfies At the same time, satisfy:

[0046]

[0047] Then it is considered that the fine synchronization is established, otherwise return to step S1 and start the synchronization again.

[0048] Furthermore, in step S6, based on the relative position of the peak when the fine synchronization is established, deduce the starting position of the information signal, and the synchronization process ends. The specific method is as follows:

[0049] When the fine synchronization is established and is obtained, determine that the initial position of the synchronization signal is at the of the received signal. Assuming that the interval between the fine synchronization and the information signal x(t) is L2, then the starting position of the information signal is determined as:

[0050]

[0051] In this way, the synchronization process ends.

[0052] A synchronization processing system based on the joint judgment of underwater acoustic multi-frame signals and related features implements the synchronization processing method based on the joint judgment of underwater acoustic multi-frame signals and related features, realizes the synchronization processing based on the joint judgment of underwater acoustic multi-frame signals and related features, and executes steps S1 to S6 respectively in six modules.

[0053] A computer device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, it implements the synchronization processing method based on the joint judgment of underwater acoustic multi-frame signals and related features, and realizes the synchronization processing based on the joint judgment of underwater acoustic multi-frame signals and related features.

[0054] A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, it implements the synchronization processing method based on the joint judgment of underwater acoustic multi-frame signals and related features, and realizes the synchronization processing based on the joint judgment of underwater acoustic multi-frame signals and related features. Compared with the prior art, the remarkable advantages of the present invention are:

[0055] Compared with the prior art, the remarkable advantage lies in that: under the simulated ocean channel, while this synchronization algorithm can effectively reduce the false synchronization probability of the copy correlation synchronization method, it also has a good missed synchronization probability and can adapt to the actual ocean environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is the main step flow of the present invention.

[0057] Figure 2 It is the time-domain waveform of the transmitted synchronization signal.

[0058] Figure 3 It is the waveform of the correlation function after copy correlation.

[0059] Figure 4 It is the time-domain waveform of the received synchronization signal after passing through the simulated shallow sea channel.

[0060] Figure 5 It is the time-domain waveform of the received synchronization signal after passing through the simulated deep sea channel.

[0061] Figure 6 It is a schematic diagram of the simulated shallow sea channel environment of the implementation example.

[0062] Figure 7 It is a schematic diagram of the simulated deep sea channel environment of the implementation example.

[0063] Figure 8 It is a comparison chart of the missed synchronization probabilities of this algorithm and the copy correlation synchronization method under the simulated shallow sea channel.

[0064] Figure 9This is a comparison graph of the missed synchronization probability between the present algorithm and the copy correlation synchronization method under simulated deep-sea channels. Detailed implementation manners

[0065] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0066] A synchronization processing method based on the joint judgment of underwater acoustic multi-frame signals and correlation features, characterized by including the following steps:

[0067] Step S1: First, the underwater acoustic signal is received in real time through an underwater transducer, and the acoustic signal is converted into an electrical signal through acoustic-electric conversion. After analog-digital conversion and sampling, the received signal is intercepted through a sliding window (window length is T), and the data of each sliding window is subjected to a correlation operation with the locally stored synchronization signal to obtain a correlation function;

[0068] Assume that the acoustic signal received by the underwater transducer is sig(t), and its expression is:

[0069] sig(t) = [sync(t), Intvl(t), x(t)]

[0070] Among them, sync(t) is a continuous synchronization signal, and x(t) is an information signal that truly carries information. The guard interval Intvl(t) between sync(t) and x(t) is a blank segment with a known duration. The discrete synchronization signal obtained after converting the continuous synchronization signal sync(t) through acoustic-electric conversion, analog-digital conversion and sampling is sync(n). Assume that the sampling rate is f s , the sliding window length is T, and the received signal after the sliding window intercepts sync(n) is sync Rec (n), with a length of L1, then it can be obtained that:

[0071]

[0072] Let the locally stored discrete copy signal be sync Loc (n), and perform copy correlation on it, that is:

[0073]

[0074] Among them, is a convolution operation, and the relationship between sync Loc (n) and the discrete synchronization signal sync(n) can be expressed as:

[0075] sync Loc (n) = sync(L1 - n)

[0076] Step S2: Using the sharpness of the correlation peak, i.e., the characteristics of high peak value and low sidelobe, perform feature joint judgment, set a decision threshold, which is usually set to 6-10 times the standard deviation of the background noise. If the peak value of the correlation function is greater than the set threshold and the average value of its sidelobes (in the present invention, the sidelobes usually take the range of 50-150 sampling points around the correlation peak value) is not greater than 0.5 times the correlation peak value, then it is considered that the correlation peak meets the prior features of high peak value and low sidelobe, and is an effective correlation peak, and record the peak value and its relative position.

[0077] Calculate the correlation peak value and its relative position after the correlation operation, that is:

[0078] [Peak, idx] = max(sync Xcorr (n))

[0079] where Peak is the maximum value of sync Xcorr (n), and idx is the relative position where Peak is located. Set the threshold Th sync to 6.8σ, where σ is the standard deviation of the background noise signal. If it satisfies:

[0080] Peak > Th sync

[0081] then it is considered that the correlation peak meets the high peak value feature. Calculate the mean value at its left and right sidelobes, that is

[0082]

[0083] where mean() represents taking the average value. If it satisfies:

[0084] sub left , sub right < 0.5 * Peak

[0085] then it is considered that the correlation peak simultaneously meets the features of high peak value and low sidelobe, and is an effective correlation peak, record the idx corresponding to Peak, otherwise, do not record, that is, set idx to 0.

[0086] Step S3: If 3 or more frames of effective correlation peaks are continuously detected and their peak values and corresponding positions are all within the same range (in the present invention, if the ratio between the two values is between 0.7 and 1.3 times, it is considered to be within the same range), then it is considered that the synchronization signal is basically captured and coarse synchronization is established.

[0087] Let the current sliding window be i, and its corresponding peak value and relative position be [Peak i , idx i . If Peak i-1,Peak i-2 are all related to Peak i within the same range, that is, satisfying:

[0088] Peak i-1 ,Peak i-2 ∈[Peak i *0.7, Peak i *1.3]

[0089] Meanwhile, idx i-1 , idx i-2 are all related to idx i within the same range, that is, satisfying:

[0090] idx i-1 , idx i-2 ∈[idx i -10, idx i +10]

[0091] Then it is considered that the synchronization signal is basically captured and the coarse synchronization is established. And use [Peak i , idx i as the relative position of the reference peak and the reference peak.

[0092] Step S4: After the coarse synchronization is established, based on the relative position of the reference peak at the time of establishing the coarse synchronization, narrow the search range of the correlation peak, that is, only search for the peaks within the range of m points before and after the relative position of the reference peak, so as to resist the influence of burst noise and multipath.

[0093] Taking idx i the relative position of the reference peak to narrow the peak search range, which is expressed as:

[0094]

[0095] Step S5: According to the search range selected in Step S4, if no correlation peak satisfying the threshold is detected in the data of several consecutive frames of the sliding window afterwards, it is considered that the end of the coarse synchronization has been captured and the protection interval area has been entered. After the time period of the protection interval, the sliding window where the fine synchronization is located can be located. Perform correlation operation on the data of this window. If the correlation peak of the obtained correlation function is greater than the threshold and is within the same range as the reference peak at the time of establishing the coarse synchronization; at the same time, the relative position of the obtained peak is within the same range as the relative position of the reference peak at the time of establishing the coarse synchronization, then it is considered that the fine synchronization is established.

[0096] If Peak i+1 <Th sync , it is considered that the protection interval area has been entered. Since the length of the protection interval is known, the sliding window i where the fine synchronization is located can be located finePerform the relevant operations in step (1) on the data in this sliding window, and use the formula in step (4) to find the peak value and its corresponding position within the restricted search range. If it satisfies Simultaneously satisfy:

[0097]

[0098] It is considered that the fine synchronization is established; otherwise, return to step (1) and start the synchronization again.

[0099] Step S6: According to the relative position of the peak value when the fine synchronization is established, the starting position of the information signal can be deduced, and the synchronization process ends.

[0100] Assume that the length of the synchronized signal after sampling is L1. Then, when the fine synchronization is established and is obtained, the initial position of the synchronized signal in the received signal can be determined at . Assume that the interval between the fine synchronization and the information signal x(t) is L2. Then, the starting position of the information signal can be determined as:

[0101]

[0102] In this way, the synchronization process ends.

[0103] Embodiment

[0104] To verify the effectiveness of the proposed solution of the present invention, simulations are carried out taking typical shallow sea and deep sea environments as examples.

[0105] Without loss of generality, in view of the prior art, chaotic spread-spectrum signals have good anti-interference and anti-multipath capabilities and are suitable for complex underwater acoustic channels. Therefore, chaotic spread-spectrum signals are used as synchronized signals in this embodiment. The spread-spectrum sequence used in the MATLAB simulation is the Chebyshev chaotic sequence with a length of 256, the sampling frequency f s is 48 kHz, the carrier frequency f c is 8 kHz, and the bandwidth B is 4 kHz. The roll-off factor β of the raised cosine filter used is set to 0.5. In terms of the synchronized signal structure, the coarse synchronization is set to 5 consecutive frames of chaotic spread-spectrum signals, and the duration of the guard interval between the coarse and fine synchronizations is 0.256 seconds. The time-domain waveform of the generated transmitted synchronized signal is as shown in Figure 2 , and the waveform obtained after performing copy correlation with the copy signal saved locally is as shown in Figure 3 .

[0106] When simulating the ocean channel environment through BELLHOP, the parameters of the shallow sea are set as follows: sea depth 200m, transmitting sound source depth 20m, receiver depth 20m, and the distance between the transmitter and the receiver is 5km; the parameters of the deep sea are set as: sea depth 4000m, transmitting sound source depth 1000m, receiver depth 1000m, and the distance between the transmitter and the receiver is 5km. The time-domain waveforms of the received synchronization signals after simulating the shallow sea and deep sea channels are as shown in Figure 4 , Figure 5 shown. The simulated shallow sea channel environment is as shown in Figure 6 shown, and the deep sea channel environment is as shown in Figure 7 shown. It can be seen that the underwater acoustic channel in the shallow sea environment has more serious multipath effects.

[0107] The copy correlation synchronization method is used as a comparison. For the copy correlation method, when the correlation peak Peak after copy correlation is greater than Th sync , it is considered that the signal has been captured. When fine synchronization is captured, if the number of coarse synchronization signal frames captured is greater than or equal to 3, it is considered that the fine synchronization is valid and the synchronization is established. Through Monte Carlo simulation, the false synchronization probability comparison between the underwater acoustic signal synchronization method based on joint judgment of multi-frame features proposed in the present invention and the copy correlation synchronization method and its leakage synchronization probability comparison at different signal-to-noise ratios are calculated. When calculating the false synchronization probability, the input signal is the Gaussian white noise signal n(t). The false synchronization situation obtained by simulation is shown in Table 1. It can be seen that under the same Th sync condition, the false synchronization probability of the copy correlation synchronization method is about 1.99%, while the false synchronization probability of the multi-frame feature joint judgment method is about 0.0001%, and its false synchronization probability is significantly reduced.

[0108] Table 1 Comparison of false synchronization probabilities between the present algorithm and the copy correlation synchronization method

[0109]

[0110]

[0111] The comparison of the leakage synchronization probability of the algorithm under the shallow sea channel is as shown in Figure 8 shown, and the comparison of the leakage synchronization probability of the algorithm under the deep sea channel is as shown in Figure 9 shown. Whether under the shallow sea condition or the deep sea condition, when the signal-to-noise ratio is lower than -22dB, the leakage synchronization probability of the multi-frame feature joint judgment method is only slightly lower than that of the copy correlation method; when the signal-to-noise ratio is higher than -22dB, the leakage synchronization probability of the multi-frame feature joint judgment method is almost the same as that of the traditional copy correlation method. When the signal-to-noise ratio is greater than -18dB, the leakage synchronization probabilities of both are reduced to 0%. This proves that the multi-frame feature joint judgment synchronization method can still have a good leakage synchronization probability on the premise of effectively reducing the false synchronization probability. At the same time, this method has good synchronization performance whether in the shallow sea or in the deep sea, proving that it can be applied to different ocean environments.

[0112] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0113] The above-described embodiments merely represent several implementation manners of the present application, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A synchronous processing method based on joint judgment of underwater acoustic multi-frame signals and related features, characterized in that: The steps include: Step S1, receiving underwater acoustic signals in real time through an underwater transducer, converting synchronization signals into electrical signals through acoustic-electrical conversion, performing analog-to-digital conversion and sampling, intercepting the sampled received signals in a sliding window, and performing correlation operations on the received signals of each sliding window with the locally stored synchronization signals to obtain a correlation function; Step S2, using the sharpness of the correlation peak, perform feature joint judgment, set the judgment threshold, if the peak value of the correlation function is greater than the set threshold, and the average value of the side lobe is not greater than 0.5 times the correlation peak value, then the correlation peak is considered to be a valid correlation peak, and the peak value and its relative position are recorded; Step S3: If three or more effective correlation peaks are detected continuously, and the peak values ​​and their corresponding positions are within the same range, it is considered that the synchronization signal is basically captured and coarse synchronization is established; Step S4: After the coarse synchronization is established, the relative position of the reference peak when the coarse synchronization is established is used as a reference to narrow the search range of the correlation peak, thereby resisting the influence of burst noise and multipath; Step S5, after capturing the end of the coarse synchronization, locate the sliding window where the fine synchronization is located, and perform correlation operation on the window data. If the correlation peak value of the obtained correlation function is greater than the threshold value and is in the same range as the reference peak value when the coarse synchronization is established; and at the same time, the obtained peak relative position is in the same range as the reference peak correlation position when the coarse synchronization is established, it is considered that the fine synchronization is established; Step S6: According to the relative position of the peak value when the fine synchronization is established, the starting position of the information signal is deduced, and the synchronization process ends.

2. The synchronous processing method based on joint judgment of underwater acoustic multi-frame signals and related features according to claim 1 is characterized in that: Step S1, receiving underwater acoustic signals in real time through an underwater transducer, and converting the synchronization signal into an electrical signal through acoustic-electrical conversion, performing analog-to-digital conversion and sampling, intercepting the received signal through a sliding window, and using the locally stored synchronization signal to perform correlation operation on the received signal of each sliding window to obtain a correlation function. The specific method is: Assuming that the acoustic signal received by the underwater transducer is sig(t), its expression is: sig(t)=[sync(t),Intvl(t),x(t)] Wherein, sync(t) is a continuous synchronization signal, x(t) is an information signal that actually carries information, and the protection interval Intvl(t) between sync(t) and x(t) is a blank segment of known duration; The continuous synchronization signal sync(t) is converted from sound to electricity, converted from analog to digital, and then sampled to obtain a discrete synchronization signal sync(n). The sampling rate is f s , the sliding window length is T, and the received signal after the sliding window intercepts sync(n) is sync Rec (n), with a length of L1, we get: Set the locally saved discrete copy signal to sync Loc (n), and copy it, that is: in, For convolution operation, sync Loc The relationship between (n) and the discrete synchronization signal sync(n) is expressed as: sync Loc (n)=sync(L1-n)。 3. The synchronous processing method based on joint judgment of underwater acoustic multi-frame signals and related features according to claim 2 is characterized in that: Step S2: Use the sharpness of the correlation peak to perform feature joint judgment and set a judgment threshold. If the peak value of the correlation function is greater than the set threshold and the average value of the side lobe is not greater than 0.5 times the correlation peak value, the correlation peak is considered to be a valid correlation peak. Record the peak value and its relative position. The specific method is as follows: Step 2.1, set the decision threshold Th sync , the threshold is set to 6-10 times the standard deviation of the background noise; Step 2.2, calculate the correlation peak value and its relative position after the correlation operation, that is: [Peak,idx]=max(sync Xcorr (n)) Among them, Peak is sync Xcorr (n), idx is the relative position of Peak; if it satisfies: Peak>Th sync It is considered that the correlation peak meets the high peak feature, and 50-150 sampling points around the correlation peak are taken to calculate the mean of the left and right side lobes, that is, Among them, mean() means taking the average value; if it satisfies: sub left ,sub right <0.5*Peak It is considered that the correlation peak satisfies the characteristics of high peak value and low side lobe at the same time, and is a valid correlation peak. The idx corresponding to the Peak is recorded. Otherwise, it is not recorded, that is, idx is set to 0.

4. The synchronous processing method based on joint judgment of underwater acoustic multi-frame signals and related features according to claim 3 is characterized in that: Step S3: If three or more effective correlation peaks are detected continuously, and the peak values ​​and their corresponding positions are within the same range, it is considered that the synchronization signal is basically captured and coarse synchronization is established. The specific method is as follows: Assume that the current sliding window is i, and its corresponding peak value and its relative position are [Peak i ,idx i ], if Peak i-1 ,Peak i-2 Both with Peak i In the same scope, that is, satisfying: Peak i-1 ,Peak i-2 ∈[Peak i *0.7,Peak i *1.3] At the same time idx i-1 ,idx i-2 Both with idx i In the same scope, that is, satisfying: idx i-1 ,idx i-2 ∈[idx i -10,idx i +10] It is considered that the synchronization signal is basically captured, the rough synchronization is established, and [Peak i ,idx i ] as the reference peak relative position to the reference peak.

5. The synchronous processing method based on joint judgment of underwater acoustic multi-frame signals and related features according to claim 4 is characterized in that: Step S4: After the rough synchronization is established, the relative position of the reference peak when the rough synchronization is established is used as a reference to narrow the search range of the correlation peak, thereby resisting the influence of burst noise and multipath. The specific method is as follows: Take the reference peak relative position idx i As a benchmark, the peak search range is narrowed, expressed as:

6. The synchronous processing method based on joint judgment of underwater acoustic multi-frame signals and related features according to claim 5 is characterized in that: Step S5: After capturing the end of the coarse synchronization, locate the sliding window where the fine synchronization is located, and perform correlation operation on the received signal of the window. If the correlation peak value of the obtained correlation function is greater than the threshold value and is in the same range as the reference peak value when the coarse synchronization is established; and the relative position of the obtained peak value is in the same range as the reference peak correlation position when the coarse synchronization is established, it is considered that the fine synchronization is established. The specific method is: Step 5.1: According to the search range selected in step S4, if the received signals of the sliding window for several consecutive frames do not detect the correlation peak that meets the threshold, that is, Peak i+1 <Th sync , it is considered that the end of the coarse synchronization has been captured and the protection interval area has been entered; Step 5.2: After the guard interval has passed, since the guard interval length is known, the sliding window i where the fine synchronization is located is located. fine ; Step 5.3, for sliding window i fine The received signal is correlated and the peak value and its corresponding position within the restricted search range are found. If it satisfies At the same time: It is considered that fine synchronization is established, otherwise it returns to step S1 and restarts synchronization.

7. The synchronous processing method based on joint judgment of underwater acoustic multi-frame signals and related features according to claim 6 is characterized in that: Step S6: According to the relative position of the peak value when the fine synchronization is established, the starting position of the information signal is deduced, and the synchronization process ends. The specific method is: After fine synchronization is established, we get After that, determine the initial position of the synchronization signal at the received signal Assuming that the interval between the fine synchronization and the information signal x(t) is L2, the starting position of the information signal is determined as: Thus, the synchronization process ends.

8. A synchronous processing system based on the joint judgment of underwater acoustic multi-frame signals and related features, implementing the synchronous processing method based on the joint judgment of underwater acoustic multi-frame signals and related features as described in any one of claims 1-7, realizing synchronous processing based on the joint judgment of underwater acoustic multi-frame signals and related features, and executing steps S1 to S6 respectively in six modules.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the synchronous processing method based on the joint judgment of underwater acoustic multi-frame signals and related features as described in any one of claims 1 to 7 is implemented to realize synchronous processing based on the joint judgment of underwater acoustic multi-frame signals and related features.

10. A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the synchronous processing method based on the joint judgment of underwater acoustic multi-frame signals and related features as described in any one of claims 1 to 7 is implemented to realize synchronous processing based on the joint judgment of underwater acoustic multi-frame signals and related features.

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