An underwater bionic camouflage covert communication method and device based on quasi-orthogonal signals
Patent Information
- Application Number
- CN202311214528.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-20
- Publication Date
- 2026-09-25
- Estimated Expiration
- 2043-09-20
AI Technical Summary
但是，这种低信噪比的隐蔽通信方法会限制通信系统的通信距离，导致长远距离隐蔽通信的可靠性和有效性难以得到保障
[0014](1)本发明以真实鲸目动物哨声信号作为模仿对象，构造与真实鲸目动物哨声信号高度相似的通信信号，将检测到的通信信号视为原始鲸目动物叫声而作为海洋噪声滤除，以达到隐蔽通信的目的；
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Figure CN117220786B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of communication technology, and in particular to an underwater biomimetic camouflage and covert communication method and device based on quasi-orthogonal signals. Background Technology
[0002] Underwater acoustic communication technology, as the most effective underwater communication method, is widely used in communication between underwater platforms, surface platforms, and land-based systems; underwater telemetry and control; underwater local area network interconnection; remote control of marine platform equipment; underwater image transmission; and integrated underwater communication and navigation. In recent years, with the increasingly fierce competition among nations in the maritime domain, underwater acoustic communication technology has played an increasingly important role in maritime rights protection and marine area conservation. However, with the development of marine stealth technology by various countries, the stealth and security of underwater acoustic communication systems are facing increasingly severe challenges. Therefore, in recent years, countries have conducted extensive research on covert underwater acoustic communication.
[0003] Traditional covert underwater acoustic communication methods primarily employ Low Probability of Interception (LPI) and Low Probability of Detection (LPD) techniques. LPI mainly uses techniques such as frequency hopping and time hopping to alter the parameters of artificial communication signals, increasing the difficulty for underwater detection systems to intercept the communication information, thereby achieving the goal of covert communication. However, the communication signals used in this method are still traditional underwater communication signals such as single-frequency signals and linear frequency modulated signals, which have relatively obvious artificial characteristics and are easily noticed by reconnaissance systems, leading to the location of underwater military platforms.
[0004] The core idea of LPD (Low Signal-to-Noise Ratio) is to reduce the signal-to-noise ratio of communication signals, hiding them within noise to increase the difficulty for reconnaissance systems to detect them. However, this low signal-to-noise ratio covert communication method limits the communication distance of the system, making it difficult to guarantee the reliability and effectiveness of long-distance covert communication. Summary of the Invention
[0005] This invention provides an underwater biomimetic camouflage and covert communication method and device based on quasi-orthogonal signals. From a biomimetic perspective, this invention utilizes the splicing of multiple quasi-orthogonal signal segments to mimic the whistling signals of real cetaceans under conditions of continuous frequency and phase continuity. Communication information is transmitted through the quasi-orthogonality between the quasi-orthogonal signals, thus achieving covert underwater communication. See the description below for details:
[0006] An underwater biomimetic camouflage and covert communication method based on quasi-orthogonal signals, the method comprising:
[0007] Based on the characteristics of cetacean whistles, a communication coding method is designed based on quasi-orthogonal signals.
[0008] Each coded whistle segment is copied and correlated with the corresponding quasi-orthogonal signal in the quasi-orthogonal signal library to determine the quasi-orthogonal signal used and thus decode the communication information.
[0009] The communication transmission and reception platform enables the transmission and decoding of communication information.
[0010] An underwater covert communication device based on quasi-orthogonal signal coding, the device comprising:
[0011] Communication Transmission Platform: The cetacean whistle pulse library transmits the cetacean whistle to be imitated to the quasi-orthogonal signal generator. The quasi-orthogonal signal generator segments the cetacean whistle to be imitated and obtains the quasi-orthogonal signal library for encoding based on the instantaneous frequency value at the endpoint of the whistle segment. This library is then sent to the communication encoder. The communication encoder reads the communication information to be transmitted and selects the quasi-orthogonal signal to construct the biomimetic cetacean whistle pulse according to the encoding method of the communication information transmitter. The pulse is then transmitted to the underwater acoustic transducer, where it is converted into a sound wave signal and sent into the water to realize the transmission of communication information.
[0012] Communication receiving platform: The hydrophone is used to collect the whistling signals of cetaceans carrying communication information and convert them into electrical signals, which are then transmitted to the copy correlator. The copy correlator synchronizes and times the received signals and sends them to the communication decoder. The communication decoder decodes the received signals based on the decoding method and finally outputs the decoded communication information through the communication information output device.
[0013] The beneficial effects of the technical solution provided by this invention are:
[0014] (1) This invention uses real cetacean whistle signals as the object of imitation, constructs a communication signal that is highly similar to real cetacean whistle signals, and treats the detected communication signal as the original cetacean call and filters it as ocean noise in order to achieve the purpose of covert communication.
[0015] (2) The start and end frequencies of the quasi-orthogonal signals used by each symbol in this invention are the same as the instantaneous frequencies of the real cetacean whistle signals at the same time point. This achieves a high degree of similarity between the frequency changes of the bionic communication signal and the frequency changes of the real cetacean whistle signals, while ensuring the continuity of the frequency of the bionic communication signal and further improving the concealment of the designed method.
[0016] (3) When splicing the biomimetic communication signal, the starting phase of each symbol is compensated according to the ending phase of the previous symbol, which ensures the continuity of the phase of the biomimetic communication signal and further improves the concealment of the designed method. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the encoding method in this invention;
[0018] Figure 2 This is a time-frequency ridge diagram of the four types of nonlinear frequency modulation fundamental signals in this invention;
[0019] Wherein: 1 is the basic signal of frequency falling concave nonlinear frequency modulation; 2 is the basic signal of frequency rising concave nonlinear frequency modulation; 3 is the basic signal of frequency rising convex nonlinear frequency modulation; 4 is the basic signal of frequency falling convex nonlinear frequency modulation.
[0020] Figure 3 This is a time-frequency ridge diagram of four types of frequency-rising spliced signals composed of four types of nonlinear frequency-modulated basic signals in this invention.
[0021] Among them: 5 is a concave-convex frequency rise splicing signal; 6 is a convex-concave frequency rise splicing signal; 7 is a double concave frequency rise splicing signal; 8 is a double convex frequency rise splicing signal.
[0022] Figure 4 This is a time-frequency ridge diagram of four types of frequency-dropping spliced signals composed of four types of nonlinear frequency-modulated basic signals in this invention.
[0023] Among them, 9 is a convex-concave frequency-decreasing splicing signal; 10 is a concave-convex frequency-decreasing splicing signal; 11 is a double-concave frequency-decreasing splicing signal; 12 is a double-convex frequency-decreasing splicing signal; and 13 is the splicing node of the splicing signal.
[0024] Figure 5 This represents the maximum cross-correlation value between the spliced signals of different splicing nodes in this invention;
[0025] Figure 6 This is a time-frequency diagram of the bionic communication whistle signal encoded in this invention;
[0026] Figure 7 This is a schematic diagram of the communication transmission platform in this invention;
[0027] Among them, 14 is a library of cetacean whistle pulses; 15 is a quasi-orthogonal signal generator; 16 is a communication encoder; 17 is the communication information to be transmitted; and 18 is an underwater acoustic transducer.
[0028] Figure 8 A schematic diagram of the communication receiving platform in this invention is shown.
[0029] Among them, 19 is a hydrophone; 20 is a copy correlator; 21 is a communication decoder; and 22 is a communication information output device. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below.
[0031] Unlike traditional methods, this invention presents a method and device for covert underwater communication that mimics the whistles of cetaceans. Taking a biomimetic approach, it utilizes a multi-segment quasi-orthogonal signal splicing method to mimic the whistles of real cetaceans under conditions of continuous frequency and phase, and transmits communication information through the quasi-orthogonality between these signals. Since current mainstream underwater reconnaissance systems classify marine animal calls as noise and filter them out, the method and device proposed in this invention can achieve covert underwater communication.
[0032] Example 1
[0033] This invention provides a method for covert underwater communication that utilizes quasi-orthogonal signals for encoding, resulting in frequency and phase continuity. Figure 1 The diagram illustrates the encoding of this method, by... Figure 1 As can be seen, this method first segments the real cetacean whistles according to the code width to obtain multiple whistle segments to be encoded. Then, it extracts the instantaneous frequency value of the real cetacean whistles corresponding to the endpoints of each whistle segment to be encoded, and uses quasi-orthogonal signals with these instantaneous frequency values as start and end frequencies to replace the whistle segments to be encoded for encoding and transmitting communication information. The technical solution of this invention mainly consists of the following three steps:
[0034] Step 1: Based on the characteristics of cetacean whistles, design a communication coding method based on quasi-orthogonal signals:
[0035] 1) Based on the symbol width T S And the time width T of the real cetacean whistle signal w(t) that is being imitated. W Determine the number N of information symbols that can be encoded by the whistle w(t) of this cetacean. S :
[0036]
[0037] In the formula, This is for rounding down.
[0038] The number N of the encoded information symbols obtained is based on the S , with T S The time width divides the whistle signal w(t) into N. S +1 whistle segments, of which the first N S Each of the whistle segments is a whistle segment to be encoded, and the duration of each segment is T. SThe last whistle segment is the tail whistle segment, located at the tail of the whistle signal w(t), and its duration is less than T. S The tail whistle segment is not encoded; only the other N segments are encoded. S Encode the N whistle segments to be encoded. S There are N whistle segments to be encoded. S +1 endpoint P i (i = 1, 2, ..., N) S +1).
[0039] 2) Obtain each endpoint P using short-time Fourier transform. i instantaneous frequency value f at point i ;
[0040] 3) Let the encoding sequence number n = 1;
[0041] 4) For the nth whistle segment, based on its starting endpoint P n and termination endpoint P n+1 instantaneous frequency value f at point n and f n+1 Generate multiple spliced signals y(t);
[0042] Among them, the instantaneous frequency values at the start and end points of all generated spliced signals y(t) are the same as those at the start point P of the whistle segment. n and termination endpoint P n+1 instantaneous frequency value f at point n and f n+1 The same. A specific example is given below, if the symbol width T... S =20ms, the instantaneous frequency value f at the beginning and end of the nth whistle segment. n =100Hz, the instantaneous frequency value f at the termination point n+1 =500Hz, then for all spliced signals y(t) generated for this whistle segment, the time width should be equal to the symbol width T. S That is, 20ms, the start and end frequencies should both be 100Hz, and the end frequency should both be 500Hz. In other words, the time width of the spliced signal y(t) is equal to the symbol width T. S The bandwidth is the absolute value of the instantaneous frequency difference between the start and end points of the nth whistle segment |f n+1 -f n These spliced signals y(t) have the same time width and bandwidth, only the splicing nodes ( Figure 4 (13) The positions in the time-frequency plane are different.
[0043] Taking the splicing node as the boundary, each spliced signal y(t) is composed of two segments of the basic signal x(t) to be spliced, and these two segments x(t) also determine the splicing node position of the spliced signal y(t). Since the time width of y(t) is TS The bandwidth is |f n+1 -f n In order to successfully splice the two basic signals x(t), the total time width T of the two basic signals x(t) is... x1 +T x2 It should be T S Total bandwidth B x1 +B x2 It should be |f n+1 -f n Specifically, firstly, generate generators with different time widths T. x and bandwidth B x A linear or nonlinear frequency-modulated signal is used as the fundamental signal x(t), and then T x1 +T x2 =T S and B x1 +B x2 =|f n+1 -f n Under the condition of |, select two basic signals x1(t) and x2(t) that can be spliced into y(t) to form y(t), and repeat this process until enough y(t) are formed.
[0044] Figure 2 The time-frequency ridge diagrams of four types of nonlinear frequency-modulated signals are shown as examples of the basic signal x(t), where 1 is a frequency-decreasing concave basic signal; 2 is a frequency-rising concave basic signal; 3 is a frequency-rising convex basic signal; and 4 is a frequency-decreasing convex basic signal. Figure 3 and Figure 4 The diagram shows the time-frequency ridge outlines of four rising-frequency spliced signals y(t) and four falling-frequency spliced signals y(t) that can be constructed using these four types of nonlinear frequency-modulated signals as the base signal x(t). In actual implementation, only one rising-frequency type and one falling-frequency type need to be selected. Furthermore, from... Figure 3 and Figure 4 It can be seen that the difference in time width and bandwidth between the two fundamental signals x1(t) and x2(t) can be regarded as the splicing node (t) of y(t). n ,f n The changes in the horizontal and vertical coordinates in the time-frequency plane mean that the generated spliced signal y(t) can be considered as having the same start and end frequencies, with only the splicing nodes (t) being spliced together. n ,f n Different y(t).
[0045] 5) Set a quasi-orthogonality screening threshold ε to perform quasi-orthogonality screening on all generated spliced signals y(t) to obtain quasi-orthogonal signals z(t); Figure 5 Show splicing node (t) n ,f n ) along tn with f n The maximum cross-correlation coefficient between y(t) during movement. The number of quasi-orthogonal signals z(t) that can be selected determines the number of bits to be encoded for the nth whistle segment. Specifically, if 2 z(t) are selected, the whistle segment to be encoded can be encoded with 1 bit; if 4 z(t) are selected, the whistle segment to be encoded can be encoded with 2 bits; if 8 z(t) are selected, the whistle segment to be encoded can be encoded with 3 bits, and so on.
[0046] 6) Determine the specific quasi-orthogonal signal z to be used for the whistle segment n based on the information to be encoded. n (t);
[0047] 7) Let the encoding sequence number n = n + 1, and repeat steps 4) to 6) until all whistle segments to be encoded have been encoded using the quasi-orthogonal signal z(t). Then, splice all the whistle segments together to form the encoded bionic communication whistle signal s(t). During splicing, the phase of each whistle segment is adjusted. Through phase compensation factor Phase compensation is performed to ensure the phase continuity of the communication whistle. It can be defined by the following formula, Figure 6 The time-frequency image of a fully encoded bionic communication whistle signal s(t) is shown;
[0048]
[0049] Furthermore, the original cetacean whistle sound with good autocorrelation and poor crosscorrelation is selected as the communication synchronization code SC and added before the biomimetic communication whistle signal s(t) to achieve synchronous timing of the communication receiving system.
[0050] The second step is to design the decoding method for the communication information receiving end:
[0051] First, by performing synchronization timing through copy correlation processing of the synchronization code SC, the received biomimetic communication whistle signal s is obtained. r (t) is the time base; further, based on the symbol width T S The received bionic communication whistle signal s r (t) Perform symbol segmentation and extract each coded whistle segment; further, perform copy correlation processing on each coded whistle segment and its corresponding quasi-orthogonal signal z(t) in the quasi-orthogonal signal library Z to determine the quasi-orthogonal signal z to be used. n (t), thereby enabling the decoding of communication information.
[0052] The third step is the implementation of the communication transmission and reception platform:
[0053] 1) The communication transmission platform is implemented as follows:
[0054] like Figure 7 As shown, the cetacean whistle pulse library 14 transmits the cetacean whistle to be imitated to the quasi-orthogonal signal generator 15. The quasi-orthogonal signal generator 15 segments the cetacean whistle to be imitated and obtains the quasi-orthogonal signal library (i.e., the 2-way quasi-orthogonal signal library for encoding) based on the instantaneous frequency values at the endpoints of the whistle segments. n The quasi-orthogonal signal is sent to the communication encoder 16. The communication encoder 16 reads the communication information 17 to be transmitted and selects the quasi-orthogonal signal to construct a biomimetic cetacean whistle pulse according to the encoding method of the communication information sending end. Then it is transmitted to the underwater acoustic transducer 18, which converts it into a sound wave signal and sends it into the water to realize the transmission of communication information.
[0055] 2) The communication receiving platform is implemented as follows:
[0056] like Figure 8 As shown, the hydrophone 19 collects the whistling signal of the cetacean animal carrying communication information and converts it into an electrical signal, which is then transmitted to the copy correlator 20. The copy correlator 20 synchronizes and times the received signal and sends it to the communication decoder 21. The communication decoder 21 decodes the received signal based on the decoding method of the communication information receiving end, and finally outputs the decoded communication information through the communication information outputter 22, thus realizing the decoding of the communication information.
[0057] Example 2
[0058] The solution in Embodiment 1 will be further described below with reference to the accompanying drawings, as detailed in the following description:
[0059] Depend on Figure 1 As can be seen, this method first divides the real cetacean whistle sound into segments according to the code width to obtain multiple whistle sound segments to be encoded. Then, it extracts the instantaneous frequency value of the real cetacean whistle sound corresponding to the endpoint of each whistle sound segment to be encoded, and uses the quasi-orthogonal signal with the instantaneous frequency value as the start and end frequency to replace the whistle sound segment to be encoded to encode and transmit communication information.
[0060] The first step is to design a communication coding method based on quasi-orthogonal signals, according to the characteristics of cetacean whistles:
[0061] First, based on the symbol width T S And the time width T of the real cetacean whistle signal w(t) that is being imitated. W Determine the number N of information symbols that can be encoded by the whistle w(t) of this cetacean. S :
[0062]
[0063] In the formula, This is for rounding down.
[0064] The number N of the encoded information symbols obtained is based on the S , with T S The time width divides the whistle signal w(t) into N. S +1 whistle segments, of which the first N S Each of the whistle segments is a whistle segment to be encoded, and the duration of each segment is T. S The last whistle segment is the tail whistle segment, located at the tail of the whistle signal w(t), and its duration is less than T. S The tail whistle segment is not encoded; only the other N segments are encoded. S Encode the N whistle segments to be encoded. S There are N whistle segments to be encoded. S +1 endpoint P i (i = 1, 2, ..., N) S +1).
[0065] Here is a specific example: suppose the duration T of a cetacean whistle w(t) is... W =210ms, symbol width T S =20ms, then the number of information symbols N that w(t) can encode can be obtained. S =10, meaning w(t) can be divided into 11 whistle segments, of which the first 10 whistle segments are the whistle segments to be encoded, and the duration of each segment is T. S =20ms. The last whistle segment is the tail whistle segment, located at the tail of the whistle signal w(t), with a duration of 10ms. The tail whistle segment is not encoded. Only the other 10 whistle segments to be encoded are encoded. These 10 whistle segments to be encoded have a total of 11 endpoints.
[0066] Furthermore, the endpoint P is obtained through short-time Fourier transform. i instantaneous frequency value f at point i Let the encoding sequence number n = 1;
[0067] For the nth whistle segment, based on its starting endpoint P n and termination endpoint P n+1 instantaneous frequency value f at point n and f n+1 Multiple spliced signals y(t) are generated; the instantaneous frequency values at the start and end points of all generated spliced signals y(t) are the same as the start point P of the whistle segment. n and termination endpoint P n+1 instantaneous frequency value f at point n and f n+1 same.
[0068] Here is a specific example: if the symbol width T S=20ms, the instantaneous frequency value f at the beginning and end of the nth whistle segment. n =100Hz, the instantaneous frequency value f at the termination point n+1 =500Hz, then for all spliced signals y(t) generated for this whistle segment, the time width should be equal to the symbol width T. S That is, 20ms, the start and end frequencies should both be 100Hz, and the end frequency should both be 500Hz. In other words, the time width of the spliced signal y(t) is equal to the symbol width T. S The bandwidth is the absolute value of the instantaneous frequency difference between the start and end points of the nth whistle segment |f n+1 -f n These spliced signals y(t) have the same time width and bandwidth, only the splicing nodes ( Figure 4 (13) The positions in the time-frequency plane are different.
[0069] Taking the splicing node as the boundary, each spliced signal y(t) is composed of two segments of the basic signal x(t) to be spliced, and these two segments x(t) also determine the splicing node position of the spliced signal y(t). Since the time width of y(t) is T S The bandwidth is |f n+1 -f n In order to successfully splice the two basic signals x(t), the total time width T of the two basic signals x(t) is... x1 +T x2 It should be T S Total bandwidth B x1 +B x2 It should be |f n+1 -f n Specifically, firstly, generate generators with different time widths T. x and bandwidth B x A linear or nonlinear frequency-modulated signal is used as the fundamental signal x(t), and then T x1 +T x2 =T S and B x1 +B x2 =|f n+1 -f n Under the condition of |, select two basic signals x1(t) and x2(t) that can be spliced into y(t) to form y(t). Repeat this process until a sufficient number of y(t) are formed.
[0070] Figure 2 The time-frequency ridge diagrams of four types of nonlinear frequency-modulated signals are shown as examples of the basic signal x(t), where 1 is a frequency-decreasing concave basic signal; 2 is a frequency-rising concave basic signal; 3 is a frequency-rising convex basic signal; and 4 is a frequency-decreasing convex basic signal. Figure 3 and Figure 4The diagram shows the time-frequency ridge outlines of four rising-frequency spliced signals y(t) and four falling-frequency spliced signals y(t) that can be constructed using these four types of nonlinear frequency-modulated signals as the base signal x(t). In actual implementation, only one rising-frequency type and one falling-frequency type need to be selected. Furthermore, from... Figure 3 and Figure 4 It can be seen that the difference in time width and bandwidth between the two fundamental signals x1(t) and x2(t) can be regarded as the splicing node (t) of y(t). n ,f n The changes in the horizontal and vertical coordinates in the time-frequency plane mean that the generated spliced signal y(t) can be considered as having the same start and end frequencies, with only the splicing nodes (t) being spliced together. n ,f n Different y(t).
[0071] Furthermore, a quasi-orthogonality screening threshold ε is set to perform quasi-orthogonality screening on all generated spliced signals y(t) to obtain quasi-orthogonal signals z(t);
[0072] Figure 5 Show splicing node (t) n ,f n ) along t n with f n The maximum cross-correlation coefficient between y(t) during movement. The number of quasi-orthogonal signals z(t) that can be selected determines the number of bits to be encoded for the nth whistle segment. Specifically, if 2 z(t) are selected, the whistle segment to be encoded can be encoded with 1 bit; if 4 z(t) are selected, the whistle segment to be encoded can be encoded with 2 bits; if 8 z(t) are selected, the whistle segment to be encoded can be encoded with 3 bits, and so on.
[0073] Furthermore, the specific quasi-orthogonal signal z used for the whistle segment n is determined based on the information to be encoded. n (t); Let the encoding sequence number n = n + 1, and repeat the above steps until all whistle segments to be encoded have been encoded using quasi-orthogonal signals z(t). Then, splice all whistle segments together to form the encoded bionic communication whistle signal s(t). During splicing, the phase of each whistle segment is adjusted. Through phase compensation factor Phase compensation is performed to ensure the phase continuity of the communication whistle. Accessible via:
[0074]
[0075] definition, Figure 6 The time-frequency image of a fully encoded bionic communication whistle signal s(t) is shown.
[0076] Furthermore, the original cetacean whistle sound with good autocorrelation and poor crosscorrelation is selected as the communication synchronization code SC and added before the biomimetic communication whistle signal s(t) to achieve synchronous timing of the communication receiving system.
[0077] The second step is to design the decoding method for the communication information receiving end:
[0078] 1) First, the received biomimetic communication whistle signal s is obtained by performing synchronization timing through copy correlation processing of the synchronization code SC. r (t) is the time base;
[0079] The time reference is the position of the starting point of the received signal, which can be obtained by locating the SC. Only by accurately locating the starting point and starting symbol segmentation from the starting point can the segmentation point of the received signal be matched with the segmentation point of the transmitted signal, and symbol misalignment will not occur.
[0080] 2) Based on the symbol width T S The received bionic communication whistle signal s r (t) Perform symbol segmentation and extract each coded whistle segment;
[0081] 3) Perform copy correlation processing on each coded whistle segment and its corresponding quasi-orthogonal signal z(t) in the quasi-orthogonal signal library Z to determine the quasi-orthogonal signal z to be used. n (t), thereby enabling the decoding of communication information.
[0082] The third step is the implementation of the communication transmission and reception platform:
[0083] 1) The communication transmission platform is implemented as follows:
[0084] like Figure 7 As shown, the cetacean whistle pulse library 14 transmits the cetacean whistle to be imitated to the quasi-orthogonal signal generator 15. The quasi-orthogonal signal generator 15 segments the cetacean whistle to be imitated and obtains the quasi-orthogonal signal library for encoding based on the instantaneous frequency value at the endpoint of the whistle segment. The quasi-orthogonal signal library is then sent to the communication encoder 16. The communication encoder 16 reads the communication information 17 to be transmitted and selects the quasi-orthogonal signal to construct the biomimetic cetacean whistle pulse according to the encoding method of the communication information transmitter. The pulse is then transmitted to the underwater acoustic transducer 18, where it is converted into a sound wave signal and sent into the water to realize the transmission of the communication information.
[0085] 2) The communication receiving platform is implemented as follows:
[0086] like Figure 8As shown, the hydrophone 19 collects the whistling signal of the cetacean animal carrying communication information and converts it into an electrical signal, which is then transmitted to the copy correlator 20. The copy correlator 20 synchronizes and times the received signal and sends it to the communication decoder 21. The communication decoder 21 decodes the received signal based on the decoding method of the communication information receiving end described in this embodiment of the invention, and finally outputs the decoded communication information through the communication information outputter 22, thus realizing the decoding of the communication information.
[0087] Unless otherwise specified, the model numbers of the various devices in this embodiment of the invention are not limited, and any device that can perform the above functions is acceptable.
[0088] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.
[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for underwater biomimetic camouflage and covert communication based on quasi-orthogonal signals, characterized in that, The method includes: Based on the characteristics of cetacean whistles, a communication coding method is designed based on quasi-orthogonal signals. Each coded whistle segment is copied and correlated with the corresponding quasi-orthogonal signal in the quasi-orthogonal signal library to determine the quasi-orthogonal signal used and thus decode the communication information. The transmission and decoding of communication information are realized based on a communication transmission and reception platform; The communication coding method is as follows: For the first The whistle segment, based on its starting point and termination endpoint instantaneous frequency value at and Generate multiple spliced signals ; Generate nodes with different time widths, using the splicing nodes as boundaries. and bandwidth Linear or nonlinear frequency-modulated signals as the basic signal ,exist and Under the given conditions, select those that can be spliced into Two basic signals and constitute ; Two basic signals Total bandwidth Total bandwidth; The width of the symbol; Set quasi-orthogonality filtering threshold For all generated spliced signals Quasi-orthogonality screening is performed to obtain quasi-orthogonal signals. ; The whistle segment is determined based on the information to be encoded. The specific quasi-orthogonal signal used During splicing, the phase of each whistle segment is adjusted. Through phase compensation factor Phase compensation is performed to ensure the phase continuity of the communication whistle. for: 。 2. The underwater biomimetic camouflage and covert communication method based on quasi-orthogonal signals according to claim 1, characterized in that, The method uses real cetacean whistle signals as a model to construct a communication signal that is highly similar to the real cetacean whistle signals. The detected communication signal is regarded as the original cetacean call and filtered out as marine noise in order to achieve the purpose of covert communication.
3. The underwater biomimetic camouflage and covert communication method based on quasi-orthogonal signals according to claim 1, characterized in that, The frequency and phase of the method are both continuous.
4. The underwater biomimetic camouflage and covert communication method based on quasi-orthogonal signals according to claim 1, characterized in that, In the method described, the start and end frequencies of the quasi-orthogonal signals used by each symbol are the same as the instantaneous frequencies of the whistling signals of real cetaceans at the same point in time.
5. The underwater biomimetic camouflage and covert communication method based on quasi-orthogonal signals according to claim 1, characterized in that, In the method described above, when splicing the signals into a biomimetic communication signal, the starting phase of each symbol is compensated based on the ending phase of the preceding symbol.
6. The underwater biomimetic camouflage and covert communication method based on quasi-orthogonal signals according to claim 1, characterized in that, By splicing the basic signal at different splicing node positions, multiple quasi-orthogonal signals are obtained when the node positions are different, satisfying the quasi-orthogonality between signals under the condition of a certain time bandwidth.
7. An underwater covert communication device based on quasi-orthogonal signal coding, characterized in that, The device is used to perform the communication method according to any one of claims 1-6, the communication device comprising: Communication Transmission Platform: The cetacean whistle pulse library transmits the cetacean whistle to be imitated to the quasi-orthogonal signal generator. The quasi-orthogonal signal generator segments the cetacean whistle to be imitated and obtains the quasi-orthogonal signal library for encoding based on the instantaneous frequency value at the endpoint of the whistle segment. This library is then sent to the communication encoder. The communication encoder reads the communication information to be transmitted and selects the quasi-orthogonal signal to construct the biomimetic cetacean whistle pulse according to the encoding method of the communication information transmitter. The pulse is then transmitted to the underwater acoustic transducer, where it is converted into a sound wave signal and transmitted into the water, thus realizing the transmission of communication information. Communication receiving platform: The hydrophone is used to collect the whistling signals of cetaceans carrying communication information and convert them into electrical signals, which are then transmitted to the copy correlator. The copy correlator synchronizes and times the received signals and sends them to the communication decoder. The communication decoder decodes the received signals based on the decoding method and finally outputs the decoded communication information through the communication information output device.