Quadrature amplitude modulation-based high-speed bionic covert communication method and system

Abstract

The invention discloses a high-speed bionic covert communication method and system based on quadrature amplitude modulation. The method comprises the steps that a transmitting end transmits a bionic communication signal, a receiving end receives the bionic communication signal, and the bionic communication signal is generated through the following steps that information to be transmitted is coded in the form of a binary sequence, and a standard orthogonal amplitude mapping constellation diagram is adopted; mapping the coded binary sequence into a corresponding complex exponential sequence; converting an original dolphin click signal into a corresponding analytic signal based on Hilbert transform, and multiplying the analytic signal with the obtained complex exponential sequence to complete orthogonal amplitude modulation to obtain a code element sequence; dividing a plurality of adjacent code elements into a group, and inserting a training symbol in front of each group to obtain a frame of signal; and inserting the synchronizing signal into the front end of a frame of signal to obtain a bionic communication signal. According to the method, the high-bandwidth dolphin signal is selected as a carrier wave, the Hilbert transform is utilized to carry out amplitude and phase regulation and control on the signal in a time domain, the information is modulated in the amplitude and phase of click, the bandwidth utilization rate is high, the communication rate is up to 22.162 kbit / s under the hexadecimal system, and the data transmission capability of bionic covert communication is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of covert communication technology, and in particular to a high-speed bionic covert communication method and system based on orthogonal amplitude modulation. Background Art

[0002] Underwater acoustic communication technology is a key technology for human exploration of the ocean. With the development of underwater monitoring and reconnaissance technology, the security and concealment of underwater acoustic communication have gradually received attention. However, in order to ensure that the receiving end can accurately decode the signal, the sound signal emitted by the transmitting end often has a sound source level that is significantly higher than the ocean background noise. However, due to the openness and unreliability of the underwater acoustic communication channel, the underwater acoustic communication signal with a high sound source level is very easy to be intercepted by eavesdroppers. Therefore, how to ensure the concealment and security of communication has become a key issue to be solved in underwater acoustic communication.

[0003] Traditional underwater covert acoustic communication mostly uses the method of reducing the acoustic power of the transmitting end signal so that the communication signal is submerged in the background noise to achieve the effect of covert communication. However, this method inevitably limits the communication distance and cannot achieve long-distance underwater acoustic communication. Unlike low signal-to-noise ratio covert underwater acoustic communication, bionic covert communication emphasizes the use of bionic camouflage to induce the enemy to exclude the receiving signal to achieve the effect of concealment. This method does not need to reduce the signal-to-noise ratio of the communication signal and can achieve covert communication at a long distance underwater. Existing bionic communication technologies based on toothed whale biological signals are all based on actual sampled acoustic signal samples. By performing spectrum shifting, frequency compression and expansion, and segment replacement on the time-frequency curve of the signal sample, the information is modulated into the bionic signal to achieve bionic communication. However, the maximum communication rate of the existing method is only 200bps, which can only transmit short texts, and there is still a lot of room for improvement from practical application. Summary of the invention

[0004] In view of this, the purpose of the present invention is to propose a high-speed bionic covert communication method and system based on orthogonal amplitude modulation, which can solve the problem of low rate of existing bionic covert communication.

[0005] According to one aspect of the present invention, a high-speed bionic covert communication method based on orthogonal amplitude modulation is provided, comprising: a transmitting end transmitting a bionic communication signal, and a receiving end receiving the bionic communication signal, wherein the bionic communication signal is generated by the following steps:

[0006] The information to be transmitted is encoded in the form of a binary sequence, and a standard orthogonal amplitude mapping constellation is used to map the encoded binary sequence into a corresponding complex exponential sequence;

[0007] Based on Hilbert transform, the original dolphin click carrier signal is transformed into the corresponding analytical signal, and multiplied with the obtained complex exponential sequence to complete the orthogonal amplitude modulation and obtain the code element sequence;

[0008] A number of adjacent code elements are divided into a group, and a training symbol is inserted in front of each group to obtain a frame signal; a synchronization signal is inserted into the front end of a frame signal to obtain a bionic communication signal.

[0009] In the above technical solution, a high-bandwidth dolphin signal is innovatively selected as the carrier, and the orthogonal amplitude modulation method is used for information embedding. The Hilbert transform is used to control the amplitude and phase of the signal in the time domain, and the information is modulated in the amplitude and phase of the click, which has high bandwidth utilization. On the one hand, this method modulates information in the two orthogonal dimensions of the phase and amplitude of the biological signal, which can obtain greater bandwidth utilization. On the other hand, due to the use of amplitude modulation, the amplitude of the generated bionic communication signal changes irregularly, which is more similar to the distribution of biological signals in nature, so it has better camouflage and concealment. The communication rate in hexadecimal is as high as 22.162kbit / s, which greatly improves the data transmission capacity of bionic covert communication.

[0010] In some embodiments, the information to be transmitted is encoded in the form of a binary sequence, and a standard orthogonal amplitude mapping constellation is used to map the encoded binary sequence to a corresponding complex exponential sequence, specifically:

[0011] Use UTF-8 encoding to encode the information to be transmitted into a binary sequence with a size of DataSize bits;

[0012] The encoded binary sequence is bits are grouped into a group, M is the modulation base, and q code elements are obtained.

[0013] Map all code elements into corresponding complex exponential sequences according to the standard orthogonal amplitude modulation constellation diagram

[0014]

[0015] In some embodiments, the original dolphin click carrier signal is transformed into a corresponding analytical signal based on the Hilbert transform, and is multiplied with the obtained complex exponential sequence to complete the orthogonal amplitude modulation to obtain a symbol sequence, specifically:

[0016] The dolphin click signal is used as the carrier signal, denoted as c(t), and the carrier signal c(t) is Hilbert transformed to obtain the corresponding analytical signal The calculation formula is as follows:

[0017]

[0018] Where H[·] represents the Hilbert transform, * represents the convolution operator, and j is the imaginary unit;

[0019] The parsed signals will be After multiplying them with the complex exponential sequence and taking the real part, we can get the code element X(t)=[x1(t),x2(t),...,x q (t)], where the i-th codeword x i The calculation formula of (t) is as follows:

[0020]

[0021] In the formula, is the ith complex exponential.

[0022] In the above technical solution, since the dolphin click signal is a broadband signal, it cannot be modulated using the traditional quadrature amplitude modulation (QAM) method for a single carrier. Therefore, the Hilbert transform is used here to obtain the analytical signal of the broadband signal, and the amplitude and phase of the signal are modulated using a complex exponential method. This is an innovative method.

[0023] In some embodiments, the training symbol is a carrier signal.

[0024] In the above technical solution, since the carrier signal is the original signal that has not undergone any amplitude and phase changes, the receiving end can obtain the phase rotation and amplitude change of the training symbol in the channel by comparing the amplitude ratio and phase difference of the locally stored original signal with the received training symbol, and perform phase compensation and amplitude compensation for the subsequent code elements.

[0025] In some embodiments, the synchronization signal is obtained by encoding a carrier signal based on a Barker code.

[0026] In the above technical solution, a 13-bit Barker code is used to encode a carrier signal as a synchronization header. The Barker code is a bipolar sequence with excellent autocorrelation characteristics. The processed synchronization signal can obtain excellent autocorrelation characteristics like the Barker code and can be used for frame synchronization.

[0027] In some embodiments, after receiving the bionic communication signal, the receiving end specifically:

[0028] The received signal is cross-correlated with the synchronization header, and the bionic communication signal carrying information is extracted according to the cross-correlation peak position to complete frame synchronization;

[0029] Calculate the amplitude ratio and phase difference between each training symbol and the carrier signal c(t) in sequence;

[0030] The amplitude ratio and phase difference between each code element and the carrier signal c(t) are calculated in sequence, and the amplitude ratio and phase difference between each training symbol and the carrier signal c(t) are used to perform channel equalization;

[0031] The codewords after channel equalization are mapped to the corresponding binary sequence and the transmitted information is obtained after decoding.

[0032] In the above technical solution, the main purpose of this step is equalization, because the signal is an equalized signal, or a training signal, followed by several code elements. During the transmission process in the channel, the signal will be affected by changes in amplitude and phase. If it is not equalized, it will be wrong to use it directly for demodulation. By adding an equalized signal, the change in amplitude and phase of the equalized signal in the phase can be detected. Then, the amplitude and phase of the following code elements are compensated. The specific compensation is to find the change in amplitude and phase between the received equalized signal and the known equalized signal to ensure the accuracy of the result.

[0033] According to another aspect of the present invention, a high-speed bionic covert communication system based on quadrature amplitude modulation is provided, comprising a transmitting end and a receiving end for mutual communication, wherein the transmitting end comprises the following modules:

[0034] The encoding module is used to encode the information to be transmitted in the form of a binary sequence, and use a standard orthogonal amplitude mapping constellation diagram to map the encoded binary sequence into a corresponding complex exponential sequence;

[0035] A modulation module is used to transform the original dolphin click carrier signal into a corresponding analytical signal based on Hilbert transform, and multiply it with the obtained complex exponential sequence to complete orthogonal amplitude modulation to obtain a code element sequence;

[0036] The generation module is used to group several adjacent code elements into a group, insert a training symbol in front of each group to obtain a frame signal; insert a synchronization signal into the front end of a frame signal to obtain a bionic communication signal.

[0037] In the above technical scheme, in order to better use the above method, the present application proposes a high-speed bionic covert communication system based on orthogonal amplitude modulation. Each module corresponds to each step of the above method. The specific principles have been described above and will not be repeated here.

[0038] According to another aspect of the present invention, there is provided a high-speed bionic covert communication device based on quadrature amplitude modulation, comprising:

[0039] at least one processor and a memory communicatively coupled to the at least one processor;

[0040] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can perform the above method.

[0041] In the above technical solution, in order to better run and process the method, the above method is stored in a memory, and the stored method is executed by a processor. It should be noted that the principle and effect of each step have been described above and will not be described in detail here.

[0042] According to another aspect of the present invention, a computer-readable storage medium is provided, storing a computer program, wherein the computer program implements the above method when executed by a processor.

[0043] In the above technical solution, in order to better run and use the method, the above method is stored in a computer-readable storage medium, and the above method is implemented by a processor. It should be noted that the principle and effect of each step have been described above and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is a flow chart of an embodiment of a high-speed bionic covert communication method based on orthogonal amplitude modulation of the present invention;

[0046] Figure 2 It is a schematic diagram of the complete sending and receiving process of an embodiment of a high-speed bionic covert communication method based on orthogonal amplitude modulation of the present invention;

[0047] Figure 3 It is a standard mapping constellation diagram of hexadecimal quadrature amplitude modulation of an embodiment of a high-speed bionic covert communication method based on quadrature amplitude modulation of the present invention;

[0048] Figure 4 It is a schematic diagram of transmission signal generation and frame structure of an embodiment of a high-speed bionic covert communication method based on orthogonal amplitude modulation of the present invention;

[0049] Figure 5 This is a comparison diagram of constellations before and after equalization of an embodiment of a high-speed bionic covert communication method based on orthogonal amplitude modulation of the present invention;

[0050] Figure 6 It is a structural schematic diagram of an embodiment of a high-speed bionic covert communication system based on orthogonal amplitude modulation of the present invention. DETAILED DESCRIPTION

[0051] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention. Similarly, the following examples are only partial embodiments of the present invention rather than all embodiments, and all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0052] The present invention provides a high-speed bionic covert communication method and system based on orthogonal amplitude modulation, which can solve the problem of low rate of existing bionic covert communication.

[0053] Embodiment 1

[0054] See also Figure 1 A high-speed bionic covert communication method based on orthogonal amplitude modulation comprises: a transmitting end transmits a bionic communication signal, and a receiving end receives the bionic communication signal, wherein the bionic communication signal is generated by the following steps:

[0055] S1. The information to be transmitted is encoded in the form of a binary sequence, and a standard orthogonal amplitude mapping constellation is used to map the encoded binary sequence into a corresponding complex exponential sequence;

[0056] In this embodiment, S1, the information to be transmitted is encoded in the form of a binary sequence, and a standard orthogonal amplitude mapping constellation is used to map the encoded binary sequence to a corresponding complex exponential sequence, specifically:

[0057] S11, using UTF-8 encoding to encode the information to be transmitted into a binary sequence with a size of DataSize bits;

[0058] S12, the encoded binary sequence bits are grouped into a group, M is the modulation base, and q code elements are obtained. Map all code elements into corresponding complex exponential sequences according to the standard orthogonal amplitude modulation constellation diagram

[0059] S2, based on Hilbert transform, the original dolphin click carrier signal is transformed into the corresponding analytical signal, and multiplied with the obtained complex exponential sequence to complete the orthogonal amplitude modulation to obtain the code element sequence;

[0060] In this embodiment, S2, based on the Hilbert transform, the original dolphin click carrier signal is transformed into a corresponding analytical signal, and the orthogonal amplitude modulation is completed by multiplying the obtained complex exponential sequence to obtain a code element sequence, specifically:

[0061] S21, the dolphin click signal), the carrier signal c(t) is Hilbert transformed to obtain the corresponding analytical signal The calculation formula is as follows:

[0062]

[0063] Where H[·] represents the Hilbert transform, * represents the convolution operator, and j is the imaginary unit;

[0064] S22, analyze the signals in sequence Respectively with the complex exponential sequence After multiplication, take the real part and we can get the code element X(t)=[x1(t),x2(t),...,x q (t)], where the i-th codeword x i The calculation formula of (t) is as follows:

[0065]

[0066] In the formula, is the ith complex exponential.

[0067] S3. Group several adjacent code elements into a group, insert a training symbol in front of each group to obtain a frame signal; insert a synchronization signal into the front end of a frame signal to obtain a bionic communication signal.

[0068] In this embodiment, the training symbol is a carrier signal. Specifically, the training symbol insertion process is: each TSinterval adjacent codewords are grouped into a group, and the training symbol is inserted in front. In this method, the carrier signal c(t) is selected as the training symbol. Since c(t) is the original signal without any amplitude and phase changes, the receiving end can obtain the phase rotation and amplitude change of the training symbol in the channel by comparing the amplitude ratio and phase difference of the locally stored original signal and the received training symbol, and perform phase compensation on the TSinterval codewords that follow it. The number of training symbols is p.

[0069] In this embodiment, the synchronization signal is obtained by encoding the carrier signal based on the Barker code. Specifically, the carrier signal c(t) is encoded using a 13-bit Barker code as a synchronization header. The Barker code is a bipolar sequence with excellent autocorrelation characteristics. The 13-bit Barker code is specifically {1,1,1,1,1,-1,-1,1,1,-1,1,-1,1}. Each Barker code is multiplied by the carrier signal c(t) to obtain the synchronization signal ClickSync encoded by the click signal through the Barker code. Its expression is as follows:

[0070] ClickSync=[c(t),c(t),c(t),c(t),c(t),-c(t),-c(t),c(t),c(t),-c(t),c(t)-c(t),c(t)]

[0071] This signal can obtain excellent autocorrelation characteristics like the Barker code and can be used for frame synchronization.

[0072] The transmission rate calculation formula of this communication method is as follows

[0073] Rb=DataSize / [Len syn +(p+q)*Len click )]

[0074] Among them, Len syn The length of the synchronization signal ClickSync, Len click The length of the original click signal.

[0075] In this embodiment, currently, in the research on bionic covert communication based on toothed whale sound signals, most of them modulate information into bionic signals by performing spectrum shifting, frequency compression and expansion, segmented replacement and other processing on the time-frequency curve of the signal sample, thereby realizing bionic communication. For example, Liu Bingjie and others from Harbin Engineering University proposed to perform overall frequency shifting on the time-frequency curve of toothed whale whistle signals, and use the frequency shift amplitude to transmit information, with a communication rate of about 40bps. Jia Yuqing and others from Zhejiang University divided the toothed whale whistle signals into equally spaced small segments, and superimposed mutually orthogonal Chebyshev chaotic signals on each segment of the signal, and used cross-correlation operations for decoding, achieving a communication rate of 120bps. However, the existing methods are only stacking and modifying the collected toothed whale sound signals, and it is difficult to efficiently load information into the signal, so the communication rate is generally low. This implementation innovatively selects a high-bandwidth dolphin signal as the carrier, uses the Hilbert transform to control the amplitude and phase of the signal in the time domain, and modulates the information in the amplitude and phase of the click. It has high bandwidth utilization and a communication rate of up to 22.162 kbit / s in hexadecimal, which greatly improves the data transmission capacity of bionic covert communication.

[0076] In this embodiment, after the receiving end receives the bionic communication signal, specifically:

[0077] S21, cross-correlate the received signal with the synchronization header, extract the bionic communication signal carrying information according to the cross-correlation peak position, and complete frame synchronization; specifically:

[0078] Generate a synchronization signal ClickSync that is consistent with the transmitter locally, perform convolution operation with the received signal, and obtain the cross-correlation peak. According to the peak position and the length of the ClickSync signal, extract p training symbols and q code elements in the received signal to complete frame synchronization. Assume that the kth training symbol is z k (t), the i-th received codeword is y i (t), with sampling rate fs for zk (t) and y i (t) Perform equal-interval sampling to obtain a discrete signal and

[0079] S22, sequentially calculating the amplitude ratio and phase difference between each training symbol and the carrier signal c(t); specifically:

[0080] The phase difference between each received training symbol and the local carrier signal is calculated in turn for channel equalization. Assume that the discretized local carrier signal is c = [c1, c2, c3, ... c n ], for z k After Hilbert transform with c, the corresponding analytical signal is obtained and as follows:

[0081]

[0082]

[0083] in, and They are and The complex exponential form of the nth sampling point in A zn With A cn Respectively and The instantaneous amplitude of the nth sampling point in , θ zn With θ cn Respectively and The instantaneous phase of the i-th sampling point in , e is the natural logarithm, and j is the imaginary unit. and The inner product operation is performed to obtain the complex exponent m, which is calculated as follows:

[0084]

[0085] In the formula, * represents the conjugation operation, S is and The modulus of the inner product result, θ k for and According to this method, the amplitude ratio and phase difference of the received training symbol and the local carrier signal can be obtained in turn.

[0086]

[0087] S23, calculate the amplitude ratio and phase difference between each code element and the carrier signal c(t) in turn, and use the amplitude ratio and phase difference between each training symbol and the carrier signal c(t) to perform channel equalization; specifically, the calculation method of the amplitude ratio and phase difference between each code element and the carrier signal c(t) is consistent with the method of step S22, which will not be repeated here. Finally, the amplitude ratio and phase difference between each code element and the carrier signal c(t) are obtained as follows:

[0088] Amplitude ratio and phase difference obtained using S22 The amplitude ratio and phase difference obtained for S23 Perform equalization to obtain the equalized code element Each element in Equ is responsible for equalizing the TSinterval symbols that follow it. The amplitude and phase of the i-th symbol after equalization The calculation formula is as follows:

[0089]

[0090] S24, mapping the channel equalized code element to the corresponding binary sequence, and decoding to obtain the transmission information. The standard orthogonal amplitude modulation constellation is inversely mapped into a binary sequence. The binary sequence decoding process is consistent with S11.

[0091] In the embodiment of this city, the high-bandwidth dolphin signal is innovatively selected as the carrier, the orthogonal amplitude modulation method is used for information embedding, the Hilbert transform is used to control the amplitude and phase of the signal in the time domain, and the information is modulated in the amplitude and phase of the click, with high bandwidth utilization. On the one hand, this method modulates information in the two orthogonal dimensions of the phase and amplitude of the biological signal, which can obtain greater bandwidth utilization. On the other hand, due to the use of amplitude modulation, the amplitude of the generated bionic communication signal changes irregularly, which is more similar to the distribution of biological signals in nature, so it has better camouflage and concealment. The communication rate in hexadecimal is as high as 22.162kbit / s, which greatly improves the data transmission capacity of bionic covert communication. This embodiment is a high-speed bionic covert communication method based on orthogonal amplitude modulation. In order to verify this method, this embodiment simulates the communication performance under different signal-to-noise ratios under Rayleigh channel, and transmits one picture each time. The amount of data after encoding is 3000 bits, and the constellation mapping is performed using hexadecimal. The training sequence interval TSinterval is 50 code elements, and the simulation signal-to-noise ratio range is [-10dB, 15dB]. Each group of signal-to-noise ratios is simulated 100 times, and the transmission bit error rate is counted. The information modulation and demodulation steps of this system are as follows: Figure 2 As shown, the following steps are included:

[0092] Transmitter part:

[0093] S1: Encode the information to be transmitted by the sender in the form of a binary sequence;

[0094] S2: Use the standard orthogonal amplitude mapping constellation diagram to map the encoded binary sequence to the corresponding complex number. The specific mapping method is as follows: Figure 3 As shown;

[0095] S3: Use the original dolphin click signal as a carrier and perform quadrature amplitude modulation to obtain code elements;

[0096] S4: Group several adjacent code elements into a group, insert a training symbol in front of each group for channel equalization, and obtain a frame signal. Then insert the synchronization signal into the front end of a frame signal to obtain the bionic communication signal that the transmitter needs to send. The modulation process is as follows: Figure 4 shown.

[0097] Receiver part:

[0098] S5: cross-correlate the received signal with the synchronization header, extract the bionic communication signal carrying information according to the cross-correlation peak position, and complete frame synchronization;

[0099] S6: Calculate the amplitude ratio and phase difference between each training symbol and the carrier signal c(t) in sequence, for subsequent channel equalization of the code element;

[0100] S7: Calculate the amplitude ratio and phase difference of each code element and the carrier signal c(t) in turn, and use the result obtained in S6 to perform channel equalization;

[0101] S8: Map the code elements after channel equalization to the corresponding binary sequence, decode them to obtain the transmission information, and complete the bionic underwater acoustic communication.

[0102] Furthermore, the S1 is specifically:

[0103] S1-1: Use UTF-8 encoding to encode the information to be transmitted into a binary sequence with a size of 3000 bits;

[0104] Furthermore, the S2 is specifically:

[0105] S2-1: Assuming the modulation base is 16, divide the encoded binary sequence into groups of 4 bits each, obtaining 750 code elements. Map all code elements to corresponding complex exponentials according to the standard orthogonal amplitude modulation constellation diagram.

[0106] Furthermore, the orthogonal amplitude modulation method in S3 is specifically:

[0107] S3-1: Take the dolphin click signal as the carrier signal, denoted as c(t) (hereinafter, the carrier signal c(t) refers to the original dolphin click signal), perform Hilbert transform on the carrier signal c(t), and obtain the corresponding analytical signal The calculation formula is as follows:

[0108]

[0109] Where H[] represents the Hilbert transform, * represents the convolution operator, and j is the imaginary unit. Then, the analytical signal is transformed into The complex exponential obtained by S2-1 After multiplication, take the real part and you can get the code element X(t)=[x1(t),x2(t),...,x 750 (t)], where the i-th codeword x i The calculation formula of (t) is as follows:

[0110]

[0111] Since the dolphin click signal is a broadband signal, it cannot be modulated using the traditional single-carrier quadrature amplitude modulation (QAM) method. Therefore, the Hilbert transform is used here to obtain the analytical signal of the broadband signal, and the amplitude and phase of the signal are modulated using a complex exponential method. This is an innovative method.

[0112] Furthermore, the training symbol insertion process in S4 is specifically as follows:

[0113] S4-2: Divide every 50 adjacent code elements into a group and insert a training symbol in front. In this method, the carrier signal c(t) is selected as the training symbol. Since c(t) is the original signal without any amplitude and phase change, the receiving end can obtain the phase rotation and amplitude change of the training symbol in the channel by comparing the amplitude ratio and phase difference of the locally stored original signal and the received training symbol, and perform phase compensation on the 50 code elements that follow. The number of training symbols is 15.

[0114] Furthermore, the synchronization header in S4 is specifically:

[0115] S4-3: Use 13-bit Barker code to encode the carrier signal c(t) as the synchronization header. Barker code is a bipolar sequence with excellent autocorrelation characteristics. The 13-bit Barker code is {1,1,1,1,1,-1,-1,1,1,-1,1,-1,1}. Multiply each Barker code by the carrier signal c(t) to obtain the synchronization signal ClickSync encoded by the click signal through the Barker code. Its expression is as follows

[0116] ClickSync=[c(t),c(t),c(t),c(t),c(t),-c(t),-c(t),c(t),c(t),-c(t),c(t)-c(t),c(t)]

[0117] This signal can obtain excellent autocorrelation characteristics like the Barker code and can be used for frame synchronization.

[0118] Furthermore, the transmission rate calculation formula of this communication method is as follows:

[0119] Rb=3000 / [Len syn +(750+15)*Len click )]

[0120] Among them, Len click =0.174ms is the length of the original click signal, Len syn =13×Len click =2.262ms is the length of the synchronization signal ClickSync, and the calculated communication rate is 22.161kbit / s.

[0121] Furthermore, the frame synchronization process in S5 is specifically as follows:

[0122] S5-1: Generate a synchronization signal ClickSync locally that is consistent with the transmitter, perform convolution operation with the received signal, obtain the cross-correlation peak, and extract 15 training symbols and 750 code elements from the received signal based on the peak position and the length of the ClickSync signal to complete frame synchronization. Assume that the kth training symbol is z k (t), the i-th received codeword is y i (t), with sampling rate fs for z k (t) and y i (t) Perform equal-interval sampling to obtain a discrete signal and

[0123] Furthermore, the process of calculating the amplitude ratio and the phase difference in S6 is specifically as follows:

[0124] S6-1: Calculate the phase difference between each received training symbol and the local carrier signal in turn for channel equalization. Assume that the discretized local carrier signal is c = [c1, c2, c3, ... c n ], for z k After Hilbert transform with c, the corresponding analytical signal is obtained and as follows:

[0125]

[0126]

[0127] In the formula, and They are and The complex exponential form of the nth sampling point in A zn With A cn Respectively and The instantaneous amplitude of the nth sampling point in , θ zn With θ cn Respectively and The instantaneous phase of the i-th sampling point in , e is the natural logarithm, and j is the imaginary unit. and The inner product operation is performed to obtain the complex exponent m, which is calculated as follows:

[0128]

[0129] In the formula, * represents the conjugation operation, S is and The modulus of the inner product result, θ k for and According to this method, the amplitude ratio and phase difference of the received training symbol and the local carrier signal can be obtained in turn.

[0130] Furthermore, the calculation method of the amplitude ratio and phase difference between the code element and the carrier signal c(t) in S7 is consistent with S6-1, and the amplitude ratio and phase difference between each code element and the carrier signal c(t) are finally obtained as follows:

[0131] Furthermore, the channel equalization process in S7 is specifically as follows:

[0132] S7-1: Amplitude ratio and phase difference obtained using S6 The amplitude ratio and phase difference of S7 Perform equalization to obtain the equalized code element Each element in Equ is responsible for equalizing the 50 code elements that follow it. The amplitude and phase of the i-th code element after equalization are The calculation formula is as follows:

[0133]

[0134] Furthermore, the inverse mapping process in S8 is specifically as follows:

[0135] S7-1 The standard quadrature amplitude modulation constellation is inversely mapped into a binary sequence.

[0136] Furthermore, the binary sequence decoding process in S8 is consistent with S1-1;

[0137] The transmission bit error rate of this method under different signal-to-noise ratios is shown in Table 1:

[0138] Table 1 Communication bit error rate under different signal-to-noise ratios

[0139]

[0140] It can be seen from Table 1 that under Rayleigh channel, the bit error rate of this method at a lower signal-to-noise ratio is only 10 -4 , has excellent communication performance, greatly improving the information transmission rate of bionic covert communication. At the same time, the constellation diagram before and after equalization is as follows Figure 5 As shown, it can be seen that due to the influence of channel multipath effect, the unbalanced constellation diagram has a certain rotation and diffusion, while the equalized constellation diagram has clearer clustering and the bit error rate is significantly reduced.

[0141] Embodiment 2

[0142] See also Figure 6 A high-speed bionic covert communication system based on quadrature amplitude modulation includes a transmitting end and a receiving end for mutual communication, wherein the transmitting end includes the following modules connected in sequence:

[0143] The encoding module is used to encode the information to be transmitted in the form of a binary sequence, and use a standard orthogonal amplitude mapping constellation diagram to map the encoded binary sequence into a corresponding complex exponential sequence;

[0144] A modulation module is used to transform the original dolphin click carrier signal into a corresponding analytical signal based on Hilbert transform, and multiply it with the obtained complex exponential sequence to complete orthogonal amplitude modulation to obtain a code element sequence;

[0145] The generation module is used to group several adjacent code elements into a group, insert a training symbol in front of each group to obtain a frame signal; insert a synchronization signal into the front end of a frame signal to obtain a bionic communication signal.

[0146] The receiving end includes the following modules connected in sequence:

[0147] The cross-correlation module is used to cross-correlate the received signal with the synchronization header, extract the bionic communication signal carrying information according to the cross-correlation peak position, and complete frame synchronization;

[0148] A first calculation module is used to sequentially calculate the amplitude ratio and phase difference between each training symbol and the carrier signal c(t);

[0149] The second calculation module is used to calculate the amplitude ratio and phase difference between each code element and the carrier signal c(t) in sequence, and use the amplitude ratio and phase difference between each training symbol and the carrier signal c(t) to perform channel equalization;

[0150] The decoding module is used to map the code elements after channel equalization to the corresponding binary sequence and obtain the transmission information after decoding.

[0151] In this embodiment, in order to better use the method described in one of the embodiments, the present application proposes a high-speed bionic covert communication system based on orthogonal amplitude modulation. Each module corresponds to each step of the above method. The specific principles have been described above and will not be repeated here.

[0152] Embodiment 3

[0153] A high-speed bionic covert communication device based on orthogonal amplitude modulation, comprising:

[0154] at least one processor and a memory communicatively coupled to the at least one processor;

[0155] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method described in one of the embodiments.

[0156] In the above technical solution, in order to better run and process the method described in one of the embodiments, the above method is stored in a memory, and a processor is used to execute the stored method. It should be noted that the principle and effect of each step have been described above and will not be described in detail here.

[0157] Embodiment 4

[0158] A computer-readable storage medium stores a computer program, and the computer program implements the above method when executed by a processor.

[0159] In the above technical solution, in order to better run and use the method described in one of the embodiments, the above method is stored in a computer-readable storage medium, and a processor is used to implement the method described in one of the embodiments. It should be noted that the principle and effect of each step have been described above and will not be described in detail here.

[0160] The above descriptions are only some embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any equivalent device or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-speed bionic covert communication method based on orthogonal amplitude modulation, characterized in that: The method comprises: a transmitting end transmits a bionic communication signal, and a receiving end receives the bionic communication signal, wherein the bionic communication signal is generated by the following steps: The information to be transmitted is encoded in the form of a binary sequence, and a standard orthogonal amplitude mapping constellation is used to map the encoded binary sequence into a corresponding complex exponential sequence; Based on Hilbert transform, the original dolphin click carrier signal is transformed into the corresponding analytical signal, and multiplied with the obtained complex exponential sequence to complete the orthogonal amplitude modulation and obtain the code element sequence; A number of adjacent code elements are divided into a group, and a training symbol is inserted in front of each group to obtain a frame signal; a synchronization signal is inserted into the front end of a frame signal to obtain a bionic communication signal.

2. A high-speed bionic covert communication method based on orthogonal amplitude modulation as claimed in claim 1, characterized in that: The information to be transmitted is encoded in the form of a binary sequence, and the standard orthogonal amplitude mapping constellation is used to map the encoded binary sequence to the corresponding complex exponential sequence. Specifically: Use UTF-8 encoding to encode the information to be transmitted into a binary sequence with a size of DataSize bits; The encoded binary sequence is bits are grouped into a group, M is the modulation base, and q code elements are obtained. Map all code elements into corresponding complex exponential sequences according to the standard orthogonal amplitude modulation constellation diagram 3. A high-speed bionic covert communication method based on orthogonal amplitude modulation as claimed in claim 1, characterized in that: Based on the Hilbert transform, the original dolphin click carrier signal is transformed into the corresponding analytical signal, and multiplied with the obtained complex exponential sequence to complete the orthogonal amplitude modulation and obtain the code element sequence. Specifically: The dolphin click signal is used as the carrier signal, denoted as c(t), and the carrier signal c(t) is Hilbert transformed to obtain the corresponding analytical signal The calculation formula is as follows: Where H[·] represents the Hilbert transform, * represents the convolution operator, and j is the imaginary unit; The parsed signals will be After multiplying them with the complex exponential sequence and taking the real part, we can get the code element X(t)=[x1(t),x2(t),...,x q (t)], where the i-th codeword x i The calculation formula of (t) is as follows: In the formula, is the ith complex exponential.

4. A high-speed bionic covert communication method based on quadrature amplitude modulation as claimed in claim 1, characterized in that: The training symbol is a carrier signal.

5. A high-speed bionic covert communication method based on orthogonal amplitude modulation as claimed in any one of claims 1, characterized in that: The synchronization signal is obtained by encoding the carrier signal based on the Barker code.

6. A high-speed bionic covert communication method based on quadrature amplitude modulation as claimed in any one of claims 1 to 5, characterized in that: After the receiving end receives the bionic communication signal, specifically: The received signal is cross-correlated with the synchronization header, and the bionic communication signal carrying information is extracted according to the cross-correlation peak position to complete frame synchronization; Calculate the amplitude ratio and phase difference between each training symbol and the carrier signal c(t) in sequence; The amplitude ratio and phase difference between each code element and the carrier signal c(t) are calculated in sequence, and the amplitude ratio and phase difference between each training symbol and the carrier signal c(t) are used to perform channel equalization; The codewords after channel equalization are mapped to the corresponding binary sequence and the transmitted information is obtained after decoding.

7. A high-speed bionic covert communication system based on quadrature amplitude modulation, characterized in that: It includes a transmitting end and a receiving end that communicate with each other, wherein the transmitting end includes the following modules connected in sequence: The encoding module is used to encode the information to be transmitted in the form of a binary sequence, and use a standard orthogonal amplitude mapping constellation diagram to map the encoded binary sequence into a corresponding complex exponential sequence; A modulation module is used to transform the original dolphin click carrier signal into a corresponding analytical signal based on Hilbert transform, and multiply it with the obtained complex exponential sequence to complete orthogonal amplitude modulation to obtain a code element sequence; The generation module is used to group several adjacent code elements into a group, insert a training symbol in front of each group to obtain a frame signal; insert a synchronization signal into the front end of a frame signal to obtain a bionic communication signal.

8. A high-speed bionic covert communication system based on quadrature amplitude modulation as claimed in any one of claim 7, characterized in that: The receiving end includes the following modules connected in sequence: The cross-correlation module is used to cross-correlate the received signal with the synchronization header, extract the bionic communication signal carrying information according to the cross-correlation peak position, and complete frame synchronization; A first calculation module is used to sequentially calculate the amplitude ratio and phase difference between each training symbol and the carrier signal c(t); The second calculation module is used to calculate the amplitude ratio and phase difference between each code element and the carrier signal c(t) in sequence, and use the amplitude ratio and phase difference between each training symbol and the carrier signal c(t) to perform channel equalization; The decoding module is used to map the code elements after channel equalization to the corresponding binary sequence and obtain the transmission information after decoding.

9. A high-speed bionic covert communication device based on quadrature amplitude modulation, characterized in that: include: at least one processor and a memory communicatively coupled to the at least one processor; The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method as claimed in any one of claims 1 to 6.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

Images