Underwater acoustic communication method, device and equipment based on ship radiation noise and medium

Abstract

The invention discloses an underwater acoustic communication method, device and equipment based on ship radiation noise, and a medium, and the method comprises the steps: mapping a to-be-transmitted bit stream to a codebook sequence which is constructed and optimized based on the ship radiation noise, and generating a transmission signal consistent with the characteristics of the ship radiation noise through signal shaping processing; a receiving end realizes signal matching identification and inverse mapping recovery of an original bit stream through preprocessing, interference compensation, correlation detection and energy combination, and the identification probability of a non-destination receiver on a communication signal is remarkably reduced by means of the disguise characteristic of a ship radiation noise imitating signal. According to the method, the problem that the communication rate is limited due to the fact that a steganography method depends on camouflage signal hiding capacity is solved, the defect that a traditional spread spectrum sequence is easily observed and detected for a long time is overcome, and the requirement of modern ocean engineering for underwater acoustic communication concealment is met.

Description

Technical Field

[0001] This application relates to the field of underwater acoustic communication, specifically to an underwater acoustic communication method, apparatus, equipment, and medium based on ship radiated noise. Background Technology

[0002] Currently, the rapid development of "digital ocean" and "underwater Internet of Things" has driven underwater acoustic communication networks to become the core of research in the field of marine engineering. The demand for security and concealment of underwater data transmission continues to rise. Underwater acoustic covert communication, as a key technology to ensure that underwater information is not intercepted and communication behavior is not detected, directly affects the application effectiveness in scenarios such as marine resource exploration and underwater equipment interconnection. There is an urgent need for technical solutions with both high concealment and high efficiency to support the development of the industry.

[0003] In related technologies, to achieve covert underwater acoustic communication, some solutions employ low signal-to-noise ratio spread spectrum communication technology, which uses classical chaotic mapping to generate spread spectrum codes to broaden the signal bandwidth and reduce power spectral density; other solutions construct biomimetic communication signals based on the vocal characteristics of marine organisms, or use steganography to embed communication signals into camouflage signals, thereby improving concealment through signal camouflage.

[0004] However, the chaotic sequences in traditional low signal-to-noise ratio spread spectrum communication have a regular structure, making it easy for third parties to detect the communication signals through long-term listening, resulting in insufficient security. Biomimetic communication technology is limited by its biological friendliness and regional environmental constraints, limiting its applicability. Steganography methods are limited by the concealment capacity of the camouflaged signals, resulting in low communication rates that cannot meet the needs of modern marine engineering for the rapid transmission of large amounts of data. At the same time, underwater channels suffer from complex interference such as signal attenuation, multipath propagation, and Doppler shift, and the lack of targeted anti-interference design makes it difficult to guarantee communication reliability and fails to meet the comprehensive requirements of concealment, efficient transmission, and anti-interference capabilities. Summary of the Invention

[0005] This application provides a method, apparatus, equipment, and medium for underwater acoustic communication based on ship radiated noise, which can solve the technical problems of underwater acoustic covert communication in related technologies, such as easy long-term observation and detection, low communication rate, and insufficient decoding robustness under complex channels.

[0006] In a first aspect, embodiments of this application provide an underwater acoustic communication method based on ship radiated noise, the underwater acoustic communication method based on ship radiated noise comprising: The bit stream to be transmitted is mapped to a pre-built and optimized codebook sequence. The mapped codebook sequence is then processed to generate a transmission signal that conforms to the characteristics of ship radiated noise and is then transmitted. The system receives signals transmitted via an underwater acoustic channel, performs preprocessing and interference compensation on the received signals, achieves signal matching and identification through correlation detection and energy merging, and inversely maps the identification results back to the original bit stream to complete communication.

[0007] In conjunction with the first aspect, in one implementation, mapping the bit stream to be transmitted to a pre-constructed and optimized codebook sequence includes: Determine the number of codewords included in the pre-constructed and optimized codebook sequence, and set the corresponding binary code length based on the number of codewords; Define a fixed-length binary bit block, the length of which is consistent with the binary code length, and establish a one-to-one mapping relationship between the binary bit block and the unique index of each independent sequence in the codebook sequence; The bit stream to be transmitted is divided into multiple binary bit blocks according to the binary code length; Through the mapping relationship, each binary bit block is mapped to the corresponding codebook sequence, resulting in a set of codebook sequences that correspond one-to-one with the bit stream to be transmitted.

[0008] In conjunction with the first aspect, in one implementation, the signal shaping process for the mapped codebook sequence includes: For each codebook sequence obtained by mapping, a window function is applied to suppress spectral interference during sequence splicing; From the candidate signals extracted from ship radiated noise, segments with low correlation to the codebook sequence are selected as guard intervals; Each codebook sequence processed by the window function is combined with the guard interval to form multiple symbol-level waveforms, and the starting position of the guard interval in the symbol-level waveform is set with a random offset. The multiple symbol-level waveforms are spliced ​​together according to a preset timing rule to generate a frame-level transmission signal. The time-spectrum characteristics of the transmission signal are consistent with the ship's radiated noise.

[0009] In conjunction with the first aspect, in one embodiment, the preprocessing and interference compensation of the received signal includes: The received signal is whitened, and the whitening process is consistent with the pre-whitening standard in the codebook sequence construction stage to eliminate signal correlation interference introduced by the underwater acoustic channel. Based on the frequency shift range caused by relative motion in underwater acoustic communication scenarios, a micro-Doppler candidate set covering this frequency shift range is constructed; Based on each candidate coefficient in the microDoppler candidate set, the pre-constructed and optimized codebook sequence is resampled to obtain codebook sequence copies adapted to different frequency shifts; Based on the symbol timing of the received signal, the received window signal corresponding to each symbol is extracted to complete the interference compensation preparation.

[0010] In conjunction with the first aspect, in one implementation, the step of achieving signal matching and identification through correlation detection and energy merging, and inversely mapping the identification result back to the original bitstream, includes: For the received window signal corresponding to each symbol, calculate the normalized cross-correlation coefficient under different hysteresis with each codebook sequence copy adapted to different frequency shifts; From the cross-correlation coefficient sequence corresponding to each codebook sequence copy, select the multiple peaks with the largest amplitude; The selected peaks are accumulated and merged to obtain the merge score corresponding to each codebook sequence replica. The codebook sequence with the highest combined score among all codebook sequence copies is selected from the received window signals corresponding to each symbol as the matching and recognition result; By inversely mapping the relationship between binary bit blocks and codebook sequence indices, the matching and recognition results of each symbol are converted into corresponding binary bit blocks. All binary bit blocks are then concatenated to obtain the original bit stream.

[0011] In conjunction with the first aspect, in one implementation, prior to mapping the bit stream to be transmitted to a pre-constructed and optimized codebook sequence, the following steps are further included: Acquire the raw signal of ship radiated noise and extract multiple candidate signal segments according to preset length and step size; Each candidate signal segment is preprocessed to eliminate baseline offset and unify amplitude scale; Calculate the normalized cross-correlation coefficient between any two candidate signal segments, and construct an index of the degree of difference between segments based on the maximum normalized cross-correlation coefficient; An initial set of low-correlation sequences is selected based on the difference index to ensure that the starting interval of sequence segments within the set meets the preset constraints. An optimization algorithm is used to iteratively optimize the initial set of low-correlation sequences, minimizing the mutual coherence of the sequence set to obtain the optimal codebook sequence.

[0012] In conjunction with the first aspect, in one implementation, the iterative optimization of the initial low-correlation sequence set using an optimization algorithm includes: Define the initial set of low-correlation sequences as the initial state, and set the neighborhood structure of the sequence set to randomly swap a sequence within the set with a candidate signal segment outside the set; Construct an objective function, which includes the maximum correlation coefficient, the average correlation coefficient, and a penalty term for violating the starting interval constraint of the sequence set; Set the initial temperature, temperature reduction strategy, and state transition acceptance probability; Generate a new state based on the neighborhood structure, calculate the difference in the objective function between the new state and the current state, and determine whether to accept the new state based on the acceptance probability. The temperature is updated according to the cooling strategy, and the process of generating, judging and accepting states is repeated until the upper limit of iteration or the temperature threshold is reached, and the optimal codebook sequence is output.

[0013] Secondly, embodiments of this application provide an underwater acoustic communication device based on ship radiated noise, the underwater acoustic communication device based on ship radiated noise comprising: The bit-sequence mapping and signal shaping module is used to map the bit stream to be transmitted to a pre-built and optimized codebook sequence, perform signal shaping processing on the mapped codebook sequence, generate a transmission signal that conforms to the characteristics of ship radiated noise, and transmit it. The signal processing and decoding module is used to receive signals transmitted through the underwater acoustic channel, preprocess and compensate for interference in the received signals, achieve signal matching and recognition through correlation detection and energy merging, and inversely map the recognition results into the original bit stream to complete communication.

[0014] Thirdly, embodiments of this application provide an underwater acoustic communication device based on ship radiated noise. The underwater acoustic communication device based on ship radiated noise includes a processor, a memory, and an underwater acoustic communication program based on ship radiated noise stored in the memory and executable by the processor. When the underwater acoustic communication program based on ship radiated noise is executed by the processor, it implements the steps of the underwater acoustic communication method based on ship radiated noise as described in some of the above embodiments.

[0015] Fourthly, embodiments of this application provide a computer-readable storage medium storing an underwater acoustic communication program based on ship radiated noise, wherein when the underwater acoustic communication program based on ship radiated noise is executed by a processor, it implements the steps of the underwater acoustic communication method based on ship radiated noise as described in some of the above embodiments.

[0016] The beneficial effects of the technical solutions provided in this application include: By mapping the bitstream to be transmitted to a codebook sequence constructed and optimized based on ship radiated noise, and then generating a transmission signal consistent with the characteristics of ship radiated noise through signal shaping processing, the receiver achieves signal matching and identification and inverse mapping to recover the original bitstream through preprocessing, interference compensation, correlation detection, and energy combining. By leveraging the camouflage characteristics of the simulated ship radiated noise signal, the probability of non-target receivers recognizing the communication signal is significantly reduced. This method avoids the communication rate limitation caused by the reliance on the hiding capacity of camouflaged signals in steganography-based methods, and overcomes the deficiency of traditional spread spectrum sequences being easily detected by long-term observation. It can meet the concealment requirements of modern marine engineering for underwater acoustic communication, adapt to complex underwater channel environments, ensure decoding robustness, and provide efficient support for secure underwater information transmission. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of an embodiment of the underwater acoustic communication method based on ship radiated noise in this application. Figure 2 This is a schematic diagram of the signal time-domain waveform and cross-correlation results of the underwater acoustic communication method based on ship radiated noise according to an embodiment of this application; Figure 3 This is a schematic diagram comparing the signal spectrum characteristics of underwater acoustic communication methods based on ship radiated noise in embodiments of this application; Figure 4 This is a schematic diagram illustrating the relationship between pulse width and communication performance in an underwater acoustic communication method based on ship radiated noise, according to an embodiment of this application. Figure 5 This is a schematic diagram of the hardware structure of an underwater acoustic communication device based on ship radiated noise, which is involved in the embodiments of this application. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0019] This application provides a method, apparatus, device, and medium for underwater acoustic communication based on ship radiated noise, which can solve the technical problems of underwater acoustic covert communication in related technologies, such as easy long-term observation and detection, low communication rate, and insufficient decoding robustness under complex channels.

[0020] In a first aspect, embodiments of this application provide an underwater acoustic communication method based on ship radiated noise.

[0021] In one embodiment, reference is made to Figure 1, Figure 1 This is a flowchart illustrating the first embodiment of the underwater acoustic communication method based on ship radiated noise according to this application. Figure 1 As shown, underwater acoustic communication methods based on ship radiated noise include: S100: Map the bit stream to be transmitted to a pre-built and optimized codebook sequence, perform signal shaping processing on the mapped codebook sequence, generate a transmission signal that conforms to the characteristics of ship radiated noise, and transmit it. S200: Receives signals transmitted via an underwater acoustic channel, preprocesses and compensates for interference in the received signals, achieves signal matching and identification through correlation detection and energy merging, and inversely maps the identification results back to the original bit stream to complete communication.

[0022] In this embodiment, the bitstream to be transmitted is mapped to a codebook sequence constructed and optimized based on ship radiated noise. Signal shaping processing generates a transmission signal consistent with the characteristics of ship radiated noise. The receiver performs preprocessing, interference compensation, correlation detection, and energy combining to achieve signal matching and identification, and inverse mapping to recover the original bitstream. By leveraging the camouflage characteristics of the simulated ship radiated noise signal, the probability of non-target receivers recognizing the communication signal is significantly reduced. This method avoids the communication rate limitation caused by the reliance on the hiding capacity of camouflaged signals in steganography-based methods, and overcomes the vulnerability of traditional spread spectrum sequences to long-term observation and detection. It meets the concealment requirements of modern marine engineering for underwater acoustic communication, adapts to complex underwater channel environments, ensures decoding robustness, and provides efficient support for secure underwater information transmission.

[0023] Furthermore, in one embodiment, S100 includes the following steps: S101: Determine the number of codewords included in the pre-constructed and optimized codebook sequence, and set the corresponding binary code length based on the number of codewords; S102: Define a fixed-length binary bit block, the length of which is consistent with the binary code length, and establish a one-to-one mapping relationship between the binary bit block and the unique index of each independent sequence in the codebook sequence; S103: Divide the bit stream to be transmitted into multiple binary bit blocks according to the binary code length; S104: Through the mapping relationship, each binary bit block is mapped to the corresponding codebook sequence to obtain a set of codebook sequences that correspond one-to-one with the bit stream to be transmitted.

[0024] In this embodiment, the number of codewords contained in the pre-constructed and optimized codebook sequence is determined, and a corresponding binary code length is set based on the number of codewords. A fixed-length binary bit block with the same length as the binary code length is defined, and a one-to-one mapping relationship is established between the binary bit block and the unique index of each independent sequence in the codebook sequence. After the bit stream to be transmitted is divided into multiple binary bit blocks according to the binary code length, the mapping relationship is used to complete the mapping of each bit block to the corresponding codebook sequence and form a codebook sequence set. This ensures that the mapping logic between the bit stream and the codebook sequence is accurately matched, guaranteeing the orderliness and coherence of subsequent signal formation. Relying on the environmental compatibility characteristics of the codebook sequence and ship radiated noise, the communication concealment is enhanced while avoiding transmission efficiency loss caused by mapping mismatch, ensuring the high efficiency and stability of large-scale data transmission.

[0025] Furthermore, in one embodiment, S100 includes the following steps: S105: Apply a window function to each codebook sequence obtained by mapping to suppress spectral interference during sequence splicing; S106: Select segments with low correlation to the codebook sequence from the candidate signals extracted from ship radiated noise as guard intervals; S107: Each codebook sequence processed by the window function is combined with the guard interval to form multiple symbol-level waveforms, wherein the starting position of the guard interval in the symbol-level waveform is set with a random offset; S108: The multiple symbol-level waveforms are spliced ​​together according to a preset timing rule to generate a frame-level transmission signal. The time-spectrum characteristics of the transmission signal are consistent with the ship's radiated noise.

[0026] In this embodiment, a window function is applied to each codebook sequence obtained by mapping to suppress spectral interference generated by sequence splicing. A segment with low correlation to the codebook sequence is selected from the candidate signal extracted from the ship radiated noise as a guard interval. The codebook sequence after window function processing is combined with the guard interval and a random offset is set at the beginning position of the guard interval to form multiple symbol-level waveforms. The frame-level transmission signal with the spectral characteristics of the symbol-level waveforms that are consistent with the ship radiated noise when they are generated is spliced ​​according to a preset timing rule. This not only enhances the integration of communication signals with environmental noise to improve concealment, but also reduces the risk of being identified by suppressing spectral interference and breaking the periodicity of the signal. At the same time, it ensures the structural integrity and transmission stability of the transmitted signal and avoids the problems of reduced concealment and impaired transmission efficiency caused by signal distortion or periodic characteristics.

[0027] Furthermore, in one embodiment, step S200 includes the following steps: S201: Whiten the received signal, the whitening process being consistent with the pre-whitening standard in the codebook sequence construction stage, to eliminate signal correlation interference introduced by the underwater acoustic channel; S202: Based on the frequency shift range caused by relative motion in underwater acoustic communication scenarios, construct a micro-Doppler candidate set covering this frequency shift range; S203: Based on each candidate coefficient in the microDoppler candidate set, resample the pre-constructed and optimized codebook sequence to obtain codebook sequence copies adapted to different frequency shifts; S204: Based on the symbol timing of the received signal, extract the received window signal corresponding to each symbol to complete the interference compensation preparation.

[0028] In this embodiment, the received signal undergoes whitening processing consistent with the pre-whitening standard in the codebook sequence construction stage to eliminate signal correlation interference introduced by the underwater acoustic channel. A micro-Doppler candidate set covering the frequency shift range caused by relative motion in the underwater acoustic communication scenario is constructed. Based on each candidate coefficient in the micro-Doppler candidate set, the pre-constructed and optimized codebook sequence is resampled to obtain codebook sequence copies adapted to different frequency shifts. The received window signal corresponding to each symbol is extracted according to the symbol timing of the received signal to complete the interference compensation preparation. This effectively offsets the correlation interference and frequency shift effects during channel transmission, improves the matching accuracy between the received signal and the codebook sequence, provides high-quality input for subsequent signal identification, ensures the transmission reliability of covert communication in complex channel environments, and avoids decoding distortion caused by channel interference.

[0029] Furthermore, in one embodiment, step S200 includes the following steps: S205: For the received window signal corresponding to each symbol, calculate the normalized cross-correlation coefficient under different hysteresis with each codebook sequence copy adapted to different frequency shifts; S206: Select the multiple peaks with the largest amplitudes from the cross-correlation coefficient sequence corresponding to each codebook sequence copy; S207: Accumulate and merge the energy of the selected peaks to obtain the merge score corresponding to each codebook sequence copy; S208: Select the codebook sequence with the highest combined score among all codebook sequence copies of the received window signal corresponding to each symbol, and use it as the matching and recognition result; S209: By inversely mapping the mapping relationship between binary bit blocks and codebook sequence indices, the matching and recognition results of each symbol are converted into corresponding binary bit blocks, and all binary bit blocks are concatenated to obtain the original bit stream.

[0030] In this embodiment, the normalized cross-correlation coefficients of the received window signal corresponding to each symbol and each codebook sequence replica adapted to different frequency shifts under different hysteresis are calculated. From the cross-correlation coefficient sequence corresponding to each codebook sequence replica, the peaks with the largest amplitudes are selected and their energy is accumulated and merged to obtain the merging score of each codebook sequence replica. The codebook sequence with the highest merging score is selected as the matching and recognition result. The recognition result is converted into the corresponding binary bit block and spliced ​​to obtain the original bit stream through the inverse mapping relationship between binary bit blocks and codebook sequence index. The multi-peak energy merging is fully utilized to enhance the anti-interference capability of signal matching and ensure the accuracy of the recognition result in complex channel environments. Relying on the efficient mapping and inverse mapping mechanism between codebook sequences and bit streams, high transmission rate is ensured while maintaining communication concealment. This effectively solves the problems of easy detection or low decoding efficiency of traditional covert communication methods.

[0031] Furthermore, in one embodiment, before S100, there is S000, which includes the following steps: S001: Acquire the raw signal of ship radiated noise and extract multiple candidate signal segments according to preset length and step size; S002: Preprocess each candidate signal segment to eliminate baseline offset and unify amplitude scale; S003: Calculate the normalized cross-correlation coefficient between any two candidate signal segments, and construct an index of the degree of difference between segments based on the maximum normalized cross-correlation coefficient; S004: Based on the difference index, an initial set of low-correlation sequences is selected to ensure that the starting interval of the sequence segments in the set meets the preset constraints; S005: An optimization algorithm is used to iteratively optimize the initial low-correlation sequence set, minimizing the mutual coherence of the sequence set to obtain the optimal codebook sequence.

[0032] In this embodiment, the original ship radiated noise signal is acquired, and multiple candidate signal segments are extracted according to a preset length and step size. Each candidate signal segment is preprocessed to eliminate baseline offset and unify amplitude scale. The normalized cross-correlation coefficient between any two candidate signal segments is calculated, and a difference index is constructed based on the maximum normalized cross-correlation coefficient. Based on this difference index, an initial low-correlation sequence set that meets the preset starting interval constraint is selected. An optimization algorithm is used to iteratively optimize the initial low-correlation sequence set to minimize the cross-coherence of the sequence set, and finally obtain the optimal codebook sequence. This codebook sequence has the dual characteristics of low correlation and environmental adaptability, providing a high-quality basic sequence for subsequent signal mapping and shaping. It not only ensures a high degree of fit between the communication signal and the ship radiated noise to enhance concealment, but also improves communication reliability by reducing inter-sequence interference, avoiding the problem that traditional spread spectrum sequences are easily detected by long-term observation.

[0033] Further, in one embodiment, S005 includes the following steps: S005-1: Define the initial low-correlation sequence set as the initial state, and set the neighborhood structure of the sequence set to randomly exchange a sequence within the set with a candidate signal segment outside the set; S005-2: Construct an objective function, which includes the maximum correlation coefficient, the average correlation coefficient, and a penalty term for violating the starting interval constraint of the sequence set; S005-3: Set the initial temperature, temperature cooling strategy, and state transition acceptance probability; S005-4: Generate a new state according to the neighborhood structure, calculate the difference in the objective function between the new state and the current state, and determine whether to accept the new state based on the acceptance probability; S005-5: Update the temperature according to the cooling strategy, repeat the state generation, judgment and acceptance process until the upper limit of iteration or the temperature threshold is reached, and output the optimal codebook sequence.

[0034] In this embodiment, the initial low-correlation sequence set is defined as the initial state. The neighborhood structure of the sequence set is set as randomly exchanging a sequence within the set with a candidate signal segment outside the set. An objective function is constructed, including the maximum correlation coefficient, average correlation coefficient, and penalty term for violating the starting interval constraint of the sequence set. An initial temperature, a temperature cooling strategy, and a state transition acceptance probability are set. A new state is generated according to the neighborhood structure, and the difference between the objective function of the new state and the current state is calculated. Based on the acceptance probability, it is determined whether to accept the new state. The temperature is updated according to the cooling strategy, and the above state generation, judgment, and acceptance process is repeated until the iteration upper limit or temperature threshold is reached. The optimal codebook sequence is output. Through multi-dimensional objective functions and iterative optimization mechanisms, the mutual coherence of the codebook sequence is precisely controlled, while avoiding the problem of sequence segment overlap. This ensures that the codebook sequence maintains low correlation to reduce the bit error rate and has stable structural characteristics, providing core support for the covert transmission and reliable decoding of subsequent communication signals. This further compensates for the defect that traditional spread spectrum sequences are easily detected by long-term observation.

[0035] In summary, the underwater acoustic communication method based on ship radiated noise provided in the embodiments of this application is outlined in the following complete steps: I. Communication Codebook Sequence Construction and Optimization The codebook is the core carrier of information in a communication system. In this stage, by extracting, filtering and optimizing ship radiated noise, a communication codebook sequence with low correlation and high concealment is obtained, laying the foundation for subsequent signal transmission.

[0036] Step 1: Ship Radiated Noise Data Acquisition and Candidate Signal Extraction 1. Data Sampling: Acquiring continuous signals of measured ship radiated noise Discretize it at a fixed sampling frequency f to obtain a discrete time series:

[0037] Formula definition and explanation: x[n] represents the discretized ship radiated noise data. This means "defined as"; The discrete-time index n corresponds to the continuous time (in seconds), that is, the continuous signal corresponding to the nth sampling point in time. The value of time; Na is the total number of data points obtained after sampling. This formula clarifies the sampling mapping relationship from continuous signal to discrete signal.

[0038] 2. Candidate signal set extraction: The usage time of ship radiated noise is limited to 0.7s (corresponding to a data length of...). Segments are extracted from the sampled data at fixed step sizes h to form a set of candidate signals with indices 1, 2, ..., K:

[0039] Formula definition and explanation: P is the set of candidate signals, K is the total number of candidate signals, M is the number of sequences required for the communication codebook. K>M is required to ensure that there are enough candidate signals for subsequent screening and optimization. The length of each candidate signal is L.

[0040] 3. Candidate Signal Preprocessing: The truncated candidate signals are processed to remove the mean and unit norm, eliminate baseline offset, and unify the amplitude scale. The processed candidate signals are represented as follows:

[0041] Formula definition and explanation: The original candidate signal belongs to an L-dimensional real vector ( (representing L-dimensional real space). for The mean; This is the 2-norm of the mean-free signal (i.e., the Euclidean norm, used to calculate vector magnitude). For the preprocessed candidate signal, satisfying The unit norm constraint ensures that the amplitudes of all candidate signals are consistent.

[0042] The following text is omitted. The wavy line is the default. After normalization, the index is sequence.

[0043] Step 2: Calculation of candidate signal similarity and distance 1. Normalized cross-correlation calculation: Given an upper lag limit K, quantize two candidate signals using normalized cross-correlation. and Similarity:

[0044] Formula definition and explanation: Candidate signal and The normalized cross-correlation coefficient, where q is the signal lag (representing the time offset between two signal segments), and constraints. (K is the upper limit of lag); the numerator is the cross-correlation sum of the two signals under lag q, and the denominator is the product of the 2-norm of the two signals, which is used for normalization so that the correlation coefficient ranges between [-1,1]. The larger the absolute value, the higher the similarity between the two signals.

[0045] 2. Signal Distance Definition: The distance between candidate signals is defined based on the maximum correlation coefficient, used to describe the degree of signal difference.

[0046] Formula definition and explanation: for and The absolute value of the maximum normalized cross-correlation coefficient under all allowable hysteresis reflects the highest similarity between the two signals. The distance between signals. The larger the value, the greater the difference between the two signals and the lower the correlation.

[0047] Step 3: Initial selection of codebook sequences (farthest point sampling) Select M segments from the candidate set P, ensuring that the distance between segments is maximized and the starting point interval constraint is satisfied, to obtain an initial set of low-correlation sequences:

[0048] Formula (6) definition and explanation: The objective function is "to maximize the minimum distance between any two segments in M ​​segments" ( ), ensuring low correlation of the initially selected sequences; constraints This means that the difference between the starting indices (Sy, Sz) of any two segments is not less than the minimum interval. This avoids excessive overlap of fragments in the original noisy data.

[0049] Explanation of Formula (7): Let arg max be the initial set of low-relevance starting points obtained by sampling from the farthest point, and let arg max represent the set of indices that maximizes the pairwise minimum distance within the set. |=M indicates that the size of the set is M, which is the number of sequences required for the codebook.

[0050] Step 4: Codebook Sequence Optimization (Simulated Annealing Algorithm) 1. Definitions Related to Optimization Objectives: After pre-whitening the elements of the candidate set, the parameters to be optimized are defined based on the normalized cross-correlation:

[0051] Explanation of the Definition in Formula (8): is the maximum correlation coefficient of all pairwise sequences in the sequence set , reflecting the difference degree of the sequence pair with the highest correlation in the set.

[0052] Explanation of the Definition in Formula (9): is the average value of the correlation coefficients of all pairwise sequences in the set ( is the normalization coefficient of the summation term (since the number of combinations of i < j is ), reflecting the overall average correlation of the set.

[0053] Explanation of the Definition in Formula (10): is the number of sequence pairs that violate the starting point interval constraint, is the indicator function (taking the value of 1 when the condition in the parentheses is satisfied, otherwise 0), that is, counting the total number of sequence pairs with a starting point interval less than .

[0054] 2. Construction of the Objective Function: Construct an objective function that minimizes the mutual coherence, comprehensively weighing the maximum correlation, average correlation, and constraint violation:

[0055] Explanation of the Formula Definition: is the optimization objective function, which needs to be minimized by the algorithm; [0,1] is the weight coefficient, used to weigh (worst-case correlation) and (overall average correlation); is the penalty coefficient, used to punish the situation of violating the starting point interval constraint, ensuring that the optimized sequence meets the deployment requirements.

[0056] 3. Simulated Annealing Iterative Optimization State Definition: Any subset of sequence indices with size M is a "state", and the neighborhood structure is defined as "randomly swapping 1 index inside the set with 1 index outside the set" to generate a new state .

[0057] Acceptance Probability: Let the current temperature be T > 0, and the difference between the objective function of the new state and the current state be The probability of accepting the new state is:

[0058] Formula definition explanation: If <0 (new state is better), the probability of acceptance is 1, so the new state is accepted directly; if >0 (new state is poor) The probability of accepting a different solution increases with temperature T, which helps the algorithm escape local optima; conversely, the lower the temperature, the lower the probability of accepting a different solution, and the algorithm gradually converges.

[0059] Temperature Update: A geometric cooling strategy is used to update the temperature, ensuring that the algorithm converges gradually. , The formula definition and explanation are as follows: Let be the temperature of the t-th iteration. The temperature in the (k+1)th iteration. The cooling coefficient (between 0 and 1) is used to gradually reduce the temperature, allowing the algorithm to shift from "global exploration" to "local optimization".

[0060] Iteration process: Repeat t=1,2,... until the upper limit of iteration: sampling , ,make ,calculate ,by Accept or reject sampling, update the index of the optimal solution. The corresponding optimized codebook sequence is .

[0061] The final optimized codebook sequence is represented as:

[0062] Step 5: Selection of Guard Interval Sequence Based on the results of simulated annealing optimization, retain from the same optimization pool segment sequence And select a segment from it as the guard interval sequence (to suppress inter-symbol interference): 1. Calculation of sequence correlation indices: For each sequence j, calculate its maximum correlation coefficient and average correlation coefficient with other sequences:

[0063] Explanation of Formula (14): Let be the normalized cross-correlation coefficient between sequence i and sequence j; It is the maximum correlation coefficient of sequence j with all other sequences (reflecting the highest similarity between this sequence and other sequences). It is the average correlation coefficient of sequence j with all other sequences (reflecting the overall similarity of the sequence with other sequences).

[0064] 2. Guard Interval Sequence Selection: Select As a source of protective interval sequences; The corresponding protection interval sequence is:

[0065] Explanation of Formula (15): Index of the selected protection interval sequence; `g[n]` is the starting index of this sequence in the original ship radiated noise data; `g[n]` is the final guard interval sequence, which starts from the original noise data. It consists of segments of length L. By selecting low-correlation sequences as guard intervals, it is possible to avoid confusion with codebook sequences and improve communication reliability.

[0066] Accordingly, Figure 2 As shown, the upper "Original Signal" curve displays the time-domain waveform of the measured ship radiated noise (horizontal axis is time / s, vertical axis is amplitude), reflecting the random fluctuation characteristics of the original noise, which is the basis for the codebook sequence; the middle "Signal of Code 0000" and "Signal of Code 1001" curves are the time-domain waveforms of the two codebook sequences extracted and optimized from the original noise, respectively. Their fluctuation characteristics are highly consistent with the original signal, reflecting the environmental camouflage of the codebook sequence; the lower "Cross-Correlation" curve is the cross-correlation result of the above two codebook sequences (horizontal axis is hysteresis, vertical axis is correlation coefficient). The curve amplitude is close to 0 and the fluctuation is smooth, reflecting the low correlation between the codebook sequences, verifying the effectiveness of the codebook optimization process (such as farthest point sampling and simulated annealing), and ensuring the anti-interference capability of subsequent communication.

[0067] II. Signal Shaping and Transmission at the Transmitter Step 6: Bit-to-codebook sequence mapping The sending end converts the bit stream to be transmitted into a codebook sequence index using a "codeword count - code length - index mapping" method. 1. Definition of code length and mapping relationship: Suppose the codebook includes M sequences (number of codewords), and the corresponding binary code length is... Establish a mapping relationship between bit blocks and codebook sequence indices. .

[0068] 2. Bitstream to Index Mapping: Let the sequence of symbols to be transmitted be... , where each symbol It is a binary bit block of length B. The codebook sequence index corresponding to each bit block is obtained through the mapping relationship: .

[0069] Definition Explanation: Ns is the total number of symbols transmitted within a frame, and mq is the codebook sequence index corresponding to the q-th bit block. Subsequent transmissions will be based on the codebook sequence selected from this index.

[0070] Step 7: Signal Window Processing and Frame Structure Construction 1. Fade-in / fade-out window processing: To reduce spectral interference during sequence splicing, a fade-in / fade-out window is applied to the codebook sequence and the guard interval sequence. :

[0071] Formula definition and explanation: Let m be the sequence with index m in the codebook, and g[n] be the guard interval sequence. For fade-in and fade-out window functions (such as Hanning window, Hanning window); , These are the windowed codebook sequence and the guard interval sequence, respectively, which can effectively suppress amplitude abrupt changes at the splicing point.

[0072] 2. Symbol-level waveform construction: Construct the baseband transmission waveform for the q-th symbol, using a "codebook sequence + guard interval" structure, with a length of... (G is the length of the protection interval):

[0073] Formula definition and explanation: The transmitted waveform of the q-th symbol is given, and the first L sampling points are the codebook sequence after window processing. (Carrying information), the last G sampling points are the guard interval sequence after window processing. (Used to resist multipath interference); It is a random offset within [0, L - G], used to break the periodicity of the signal and improve its concealment.

[0074] 3. Frame-level transmission sequence generation: Multiple symbol-level waveforms are spliced ​​together to form a complete transmission sequence.

[0075] Formula definition and explanation: For the final transmission sequence, Represents a discrete-time index; through Implement time-domain shifting and splicing of the waveform of the qth symbol to ensure no overlap between symbols. Ns is the total number of symbols in a frame, and Ts is the length of a single symbol (unit: sampling points).

[0076] Accordingly, Figure 3As shown, this figure is a comparison of the spectral characteristics of underwater acoustic communication signals based on ship radiated noise. The "original signal" curve: the horizontal axis represents frequency (unit: Hz, scale 4×10). 4 The vertical axis represents the signal amplitude, showing the spectral distribution of the measured ship radiated noise. Overall, it exhibits the characteristic of "gradual attenuation of amplitude as frequency increases," without obvious sharp peaks (consistent with the "wideband and random" spectral characteristics of ship radiated noise), serving as the "environmental benchmark" for subsequent communication signal spectrum matching. The "communication signal" curve is the final communication signal spectrum generated by the transmitting end through "codebook sequence mapping → window processing → symbol / frame structure shaping." Its horizontal and vertical axis definitions are consistent with the "original signal," and its waveform trend is highly consistent with the original signal.

[0077] The spectral distributions of the two curves (amplitude decay trend, no sharp peaks) are almost identical, verifying the effectiveness of the design of "using ship radiated noise as the codebook source + signal shaping". The spectral characteristics of the communication signal are highly integrated with the environmental noise, giving the communication signal camouflage characteristics and achieving the core objective of "covert communication". The communication signal spectrum has no additional interference peaks (because the codebook sequence is processed by fade-in and fade-out windows, which suppresses splicing spectral interference), indicating that no new detectable features were introduced in the signal shaping stage. This ensures both the integrity of the information carried and the concealment, providing a basis for the subsequent "correlation detection-based decoding" at the receiver to identify that "the signal spectrum is consistent with the environmental noise spectrum, but has low correlation with the codebook sequence".

[0078] III. Signal Processing and Decoding at the Receiver The receiver recovers the original bit stream from the noisy received signal through preprocessing, Doppler compensation, correlation detection, and multi-peak merging, ensuring communication reliability.

[0079] Step 8: Received Signal Preprocessing. After transmission through the underwater acoustic channel, the received signal is affected by noise and interference. It undergoes pre-whitening processing consistent with that at the transmitting end to eliminate correlation interference introduced by the channel, resulting in the preprocessed received signal. [n].

[0080] Step 9: Doppler compensation Compensation is performed to address the Doppler frequency shift (which causes signal compression or stretching) present in the underwater acoustic channel: 1. Define a micro-Doppler candidate set to cover the possible frequency shift range:

[0081] Formula definition and explanation: The Doppler scaling factor; For the Doppler candidate set; This represents the scaling offset corresponding to the Doppler frequency shift. The maximum offset threshold is determined by covering. The range ensures that the actual Doppler shift is captured.

[0082] 2. Resample the codebook sequence to adapt to the Doppler-scaled received signal:

[0083] Formula definition and explanation: To adapt to Doppler coefficients The resampled codebook sequence; To perform a floor operation, the codebook sequence is stretched by adjusting the index of the sequence sampling points. <1) or compression ( >1), to compensate for signal distortion caused by Doppler frequency shift.

[0084] Step 10: Receive window truncation and cross-correlation calculation 1. Receive window truncation: Based on the sender's symbol length and redundancy design, truncate the receive window corresponding to the q-th symbol:

[0085] Formula definition explanation: r q [n] represents the received window signal of the q-th symbol, and r[n] represents the overall received signal, transmitted through qT. s + n locates the time-domain position of the q-th symbol; M s G is the redundancy length, and G is the protection interval length. For the maximum multipath delay, To reserve redundancy, f s Sampling frequency, To round down, the redundant length is designed to cover signal offsets caused by multipath delay and Doppler shift.

[0086] 2. Point-by-point normalized cross-correlation calculation: Within the allowable hysteresis range, calculate the point-by-point normalized cross-correlation between the receiving window and the resampled codebook sequence to detect the signal matching degree.

[0087] Formula definition and explanation: To receive signals [n] and the fitted Doppler coefficient Filtered codebook sequence The normalized cross-correlation coefficient under lag l; the numerator is the cross-correlation sum of the two under lag l, and the denominator is the square root product of the two energies (used for normalization). The larger the absolute value of the correlation coefficient, the higher the matching degree between the received signal and the codebook sequence.

[0088] Step 11: RAKE Multi-peak Energy Merging and Score Calculation 1. Multi-peak energy merging: Select K with the largest amplitude in the cross-correlation sequence. p Each peak value is used to accumulate energy using a RAKE merging strategy to improve multipath resistance.

[0089] Formula definition and explanation: The combined score for RAKE is l k K represents the lag position corresponding to the k-th peak. p The peak number of participants in the merger. The merging coefficient (e.g., when p=2, it is the square root of the sum of squares, i.e., energy merging); by merging the energy of multipath signals, the signal-to-noise ratio of the received signal and the reliability of detection are improved.

[0090] 2. Selection of Optimal Doppler Score: For each codebook sequence, select the maximum combined score among all Doppler candidate coefficients to ensure compensation for the impact of Doppler frequency shift.

[0091] Formula definition and explanation: The final score for codebook sequence m is obtained by... The result with the highest combined score among all Doppler candidate coefficients is selected to offset the adverse effect of Doppler frequency shift on signal detection.

[0092] Step 12: Decision and Bit Mapping Based on the final score of each codebook sequence, the codebook index corresponding to the received symbol is determined and then mapped back to the original binary bits:

[0093] Formula definition and explanation: The codebook index obtained from the judgment is obtained through... Select the index corresponding to the codebook sequence with the highest score; Mapping the sending end The inverse mapping, To ultimately recover the binary bit stream and achieve reliable information reception.

[0094] Accordingly, Figure 4 As shown in the figure, this is a performance correlation diagram of an underwater acoustic communication system based on ship radiated noise. The technical meanings of each part are explained below: Horizontal axis: Pulse width T p (Unit: seconds) is the duration parameter of the codebook sequence in the symbol-level waveform at the transmitting end (corresponding to the symbol length T at the transmitting end). s=L+G core components); Left vertical axis: communication rate (unit: bit / s), representing the number of bits that the system can transmit per unit time; Right vertical axis: bit error rate, representing the probability of decoding errors at the receiving end; Curves: the blue curve corresponds to "communication distance", and the orange curve corresponds to "bit error rate"; The relationship between pulse width and communication rate: As pulse width T... p As the pulse width increases, the communication rate decreases because an increase in pulse width means an increase in the duration of a single symbol, and a decrease in the number of symbols that can be transmitted per unit time (communication rate is inversely proportional to symbol duration), reflecting the trade-off between "signal duration and transmission efficiency". The relationship between pulse width and bit error rate: As pulse width T increases... p As the pulse width increases, the bit error rate decreases. This is because the longer the pulse width results in a longer time-domain length of the codebook sequence, which increases the integration time of the correlation detection at the receiver. This effectively suppresses noise and multipath interference, thereby reducing the probability of decoding errors. This demonstrates the positive correlation between "signal duration and anti-interference capability". Therefore, if the scenario requires "high transmission efficiency", a smaller T value should be selected. p (Shortening the duration of a single symbol and increasing the number of symbols per unit time) requires tolerating a higher bit error rate; if the scenario requires "high communication reliability", a larger T should be selected. p (Extending the integration time enhances anti-interference capabilities), but requires accepting a lower communication rate.

[0095] Secondly, embodiments of this application also provide an underwater acoustic communication device based on ship radiated noise. The underwater acoustic communication device based on ship radiated noise includes: a bit-sequence mapping and signal shaping module, which is used to map the bit stream to be transmitted to a pre-constructed and optimized codebook sequence, perform signal shaping processing on the mapped codebook sequence, generate a transmission signal that conforms to the characteristics of ship radiated noise, and transmit it; and a signal processing and decoding module, which is used to receive the signal transmitted through the underwater acoustic channel, perform preprocessing and interference compensation on the received signal, achieve signal matching and recognition through correlation detection and energy merging, and inversely map the recognition result back to the original bit stream to complete the communication.

[0096] The functions of each module in the above-mentioned underwater acoustic communication device based on ship radiated noise correspond to the steps in the above-mentioned underwater acoustic communication method based on ship radiated noise, and their functions and implementation processes will not be described in detail here.

[0097] Thirdly, embodiments of this application provide an underwater acoustic communication device based on ship radiated noise. The underwater acoustic communication device based on ship radiated noise can be a personal computer (PC), a laptop computer, a server, or other device with data processing capabilities.

[0098] Reference Figure 5 , Figure 5 This is a schematic diagram of the hardware structure of an underwater acoustic communication device based on ship radiated noise, as described in an embodiment of this application. In this embodiment, the underwater acoustic communication device based on ship radiated noise may include a processor, a memory, a communication interface, and a communication bus.

[0099] The communication bus can be of any type and is used to interconnect the processor, memory, and communication interface.

[0100] The communication interface includes input / output (I / O) interfaces, physical interfaces, and logical interfaces used for interconnecting internal components of the underwater acoustic communication equipment based on ship radiated noise, as well as interfaces used for interconnecting the underwater acoustic communication equipment based on ship radiated noise with other devices (such as other computing devices or user equipment). Physical interfaces can be Ethernet interfaces, fiber optic interfaces, ATM interfaces, etc.; user equipment can be displays, keyboards, etc.

[0101] Memory can be various types of storage media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), flash memory, optical storage, hard disk, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), etc.

[0102] The processor can be a general-purpose processor, which can call a hydroacoustic communication program based on ship radiated noise stored in memory and execute the hydroacoustic communication method based on ship radiated noise provided in the embodiments of this application. For example, the general-purpose processor can be a central processing unit (CPU). The method executed when the hydroacoustic communication program based on ship radiated noise is called can be referred to in the various embodiments of the hydroacoustic communication method based on ship radiated noise of this application, and will not be repeated here.

[0103] Those skilled in the art will understand that Figure 5 The hardware structure shown does not constitute a limitation of this application and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0104] Fourthly, embodiments of this application also provide a readable storage medium.

[0105] This application has a readable storage medium storing an underwater acoustic communication program based on ship radiated noise, wherein when the underwater acoustic communication program based on ship radiated noise is executed by a processor, it implements the steps of the underwater acoustic communication method based on ship radiated noise as described above.

[0106] The method implemented when the underwater acoustic communication program based on ship radiated noise is executed can be referred to in various embodiments of the underwater acoustic communication method based on ship radiated noise of this application, and will not be repeated here.

[0107] It should be noted that the sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0108] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus. The terms "first," "second," and "third," etc., are used to distinguish different objects, etc., and do not indicate a sequence, nor do they limit "first," "second," and "third" to different types.

[0109] In the description of the embodiments of this application, terms such as "exemplary," "for example," or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary," "for example," or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary," "for example," or "for instance" is intended to present the relevant concepts in a concrete manner.

[0110] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0111] In some processes described in the embodiments of this application, multiple operations or steps are included in a specific order. However, it should be understood that these operations or steps may not be executed in the order they appear in the embodiments of this application, or they may be executed in parallel. The sequence number of the operation is only used to distinguish different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed sequentially or in parallel, and these operations or steps may be combined.

[0112] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause a terminal device to execute the methods described in the various embodiments of this application.

[0113] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for underwater acoustic communication based on ship radiated noise, characterized in that, The underwater acoustic communication method based on ship radiated noise includes: The bit stream to be transmitted is mapped to a pre-built and optimized codebook sequence. The mapped codebook sequence is then processed to generate a transmission signal that conforms to the characteristics of ship radiated noise and is then transmitted. The system receives signals transmitted via an underwater acoustic channel, performs preprocessing and interference compensation on the received signals, achieves signal matching and identification through correlation detection and energy merging, and inversely maps the identification results back to the original bit stream to complete communication.

2. The underwater acoustic communication method based on ship radiated noise as described in claim 1, characterized in that, The process of mapping the bit stream to be transmitted to a pre-constructed and optimized codebook sequence includes: Determine the number of codewords included in the pre-constructed and optimized codebook sequence, and set the corresponding binary code length based on the number of codewords; Define a fixed-length binary bit block, the length of which is consistent with the binary code length, and establish a one-to-one mapping relationship between the binary bit block and the unique index of each independent sequence in the codebook sequence; The bit stream to be transmitted is divided into multiple binary bit blocks according to the binary code length; Through the mapping relationship, each binary bit block is mapped to the corresponding codebook sequence, resulting in a set of codebook sequences that correspond one-to-one with the bit stream to be transmitted.

3. The underwater acoustic communication method based on ship radiated noise as described in claim 1, characterized in that, The signal shaping process for the mapped codebook sequence includes: For each codebook sequence obtained by mapping, a window function is applied to suppress spectral interference during sequence splicing; From the candidate signals extracted from ship radiated noise, segments with low correlation to the codebook sequence are selected as guard intervals; Each codebook sequence processed by the window function is combined with the guard interval to form multiple symbol-level waveforms, and the starting position of the guard interval in the symbol-level waveform is set with a random offset. The multiple symbol-level waveforms are spliced ​​together according to a preset timing rule to generate a frame-level transmission signal. The time-spectrum characteristics of the transmission signal are consistent with the ship's radiated noise.

4. The underwater acoustic communication method based on ship radiated noise as described in claim 1, characterized in that, The preprocessing and interference compensation of the received signal includes: The received signal is whitened, and the whitening process is consistent with the pre-whitening standard in the codebook sequence construction stage to eliminate signal correlation interference introduced by the underwater acoustic channel. Based on the frequency shift range caused by relative motion in underwater acoustic communication scenarios, a micro-Doppler candidate set covering this frequency shift range is constructed; Based on each candidate coefficient in the microDoppler candidate set, the pre-constructed and optimized codebook sequence is resampled to obtain codebook sequence copies adapted to different frequency shifts; Based on the symbol timing of the received signal, the received window signal corresponding to each symbol is extracted to complete the interference compensation preparation.

5. The underwater acoustic communication method based on ship radiated noise as described in claim 4, characterized in that, The step of achieving signal matching and identification through correlation detection and energy merging, and inversely mapping the identification result back to the original bit stream, includes: For the received window signal corresponding to each symbol, calculate the normalized cross-correlation coefficient under different hysteresis with each codebook sequence copy adapted to different frequency shifts; From the cross-correlation coefficient sequence corresponding to each codebook sequence copy, select the multiple peaks with the largest amplitude; The selected peaks are accumulated and merged to obtain the merge score corresponding to each codebook sequence replica. The codebook sequence with the highest combined score among all codebook sequence copies is selected from the received window signals corresponding to each symbol as the matching and recognition result; By inversely mapping the relationship between binary bit blocks and codebook sequence indices, the matching and recognition results of each symbol are converted into corresponding binary bit blocks. All binary bit blocks are then concatenated to obtain the original bit stream.

6. The underwater acoustic communication method based on ship radiated noise as described in claim 1, characterized in that, Before mapping the bit stream to be transmitted to a pre-constructed and optimized codebook sequence, the following steps are also included: Acquire the raw signal of ship radiated noise and extract multiple candidate signal segments according to preset length and step size; Each candidate signal segment is preprocessed to eliminate baseline offset and unify amplitude scale; Calculate the normalized cross-correlation coefficient between any two candidate signal segments, and construct an index of the degree of difference between segments based on the maximum normalized cross-correlation coefficient; An initial set of low-correlation sequences is selected based on the difference index to ensure that the starting interval of sequence segments within the set meets the preset constraints. An optimization algorithm is used to iteratively optimize the initial set of low-correlation sequences, minimizing the mutual coherence of the sequence set to obtain the optimal codebook sequence.

7. The underwater acoustic communication method based on ship radiated noise as described in claim 6, characterized in that, The step of iteratively optimizing the initial set of low-correlation sequences using an optimization algorithm includes: Define the initial set of low-correlation sequences as the initial state, and set the neighborhood structure of the sequence set to randomly swap a sequence within the set with a candidate signal segment outside the set; Construct an objective function, which includes the maximum correlation coefficient, the average correlation coefficient, and a penalty term for violating the starting interval constraint of the sequence set; Set the initial temperature, temperature reduction strategy, and state transition acceptance probability; Generate a new state based on the neighborhood structure, calculate the difference in the objective function between the new state and the current state, and determine whether to accept the new state based on the acceptance probability. The temperature is updated according to the cooling strategy, and the process of generating, judging and accepting states is repeated until the upper limit of iteration or the temperature threshold is reached, and the optimal codebook sequence is output.

8. A hydroacoustic communication device based on ship radiated noise, characterized in that, The underwater acoustic communication device based on ship radiated noise includes: The bit-sequence mapping and signal shaping module is used to map the bit stream to be transmitted to a pre-built and optimized codebook sequence, perform signal shaping processing on the mapped codebook sequence, generate a transmission signal that conforms to the characteristics of ship radiated noise, and transmit it. The signal processing and decoding module is used to receive signals transmitted through the underwater acoustic channel, preprocess and compensate for interference in the received signals, achieve signal matching and recognition through correlation detection and energy merging, and inversely map the recognition results into the original bit stream to complete communication.

9. A hydroacoustic communication device based on ship radiated noise, characterized in that, The underwater acoustic communication device based on ship radiated noise includes a processor, a memory, and an underwater acoustic communication program based on ship radiated noise stored in the memory and executable by the processor, wherein when the underwater acoustic communication program based on ship radiated noise is executed by the processor, it implements the steps of the underwater acoustic communication method based on ship radiated noise as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores an underwater acoustic communication program based on ship radiated noise, wherein when the underwater acoustic communication program based on ship radiated noise is executed by a processor, it implements the steps of the underwater acoustic communication method based on ship radiated noise as described in any one of claims 1 to 7.

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