CN105227246A - A kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal - Google Patents

Abstract

The invention discloses a kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal.According to the time dependent feature of dolphin whistle signal frequency, utilize multiple LFM signal subsection combine analog dolphin whistle signal, adopt the modulates information of BOK method realization to LFM signal, and then realize the bionical underwater sound communication modulation based on dolphin whistle signal and LFM signal.In receiving terminal is to the reception data after equilibrium, the centre frequency of every section of LFM signal and frequency modulation rate are estimated, and based on the dolphin whistle signal sample adopted during modulation, carry out demodulation, obtain modulation intelligence.Adopt this segmentation LFM to imitate the underwater acoustic communication method of dolphin whistle signal, can realize utilizing simple linear FM signal to carry out the bionic camouflage underwater sound communication of high fidelity, strengthen disguise and the practicality of communication.

Description

A kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal

Technical field

The invention belongs to field of underwater acoustic communication, particularly relate to a kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal.

Background technology

In recent years, along with the development of modern Detection Techniques, concealed requirement is proposed to underwater sound communication.

Traditional concealed communication method makes signal of communication be hidden in background noise, the covert communications namely under Low SNR.But due to the temporal extension of underwater acoustic channel, frequency expansion and serious attenuation characteristic, the signal of identical sound source level can not realize the covert communications in different distance, when especially there is audiomonitor when between transmitting-receiving node, cannot realize covert communications.Different from the hidden underwater sound communication of low signal-to-noise ratio, segmentation LFM signal is utilized to imitate the camouflage underwater acoustic communication method of dolphin whistle signal, adopt dolphin whistle signal intrinsic in ocean as information carrier, permission signal of communication is detected, but in identifying, be taken as marine biological noise get rid of, reach the effect of covert communications, attempt solving covert communications problem under water.

A kind of bionical underwater acoustic communication method based on difference Pattern pattern time-delay coding is disclosed in Chinese patent CN103368660A.Dolphin is called signal and is applied in difference Pattern pattern time-delay coding communication system, to reach the object of bionical covert communications by the method.Disclose a kind of underwater acoustic communication method based on the bionical Signal coding of Virtual time reversal mirror M unit in Chinese patent specification CN103401619A, the method adopts dolphin to call signal equally and modulates, and realizes covert communications.But these two kinds of communication systems all adopt time delay to encode, instead of BOK modulation; Meanwhile, what these two kinds communication adopted is the ticktack acoustical signal of dolphin, not whistle signal.Real dolphin cry signal communicates, and communication efficiency depends on the sample quality of employing, and application is inconvenient.Chinese patent specification CN102355440A discloses a kind of underwater acoustic communication method based on very little linear frequency modulation keying modulation, the method utilizes the ultra-narrow band signal of very little linear frequency modulation keying modulation to realize high-rate information transmission, but does not emphasize the hidden performance of communication.

Summary of the invention

The object of this invention is to provide a kind of simple, amount of calculation is less, utilizes segmentation LFM signal to imitate the underwater acoustic communication method of dolphin whistle signal.

Utilize segmentation LFM signal to imitate a underwater acoustic communication method for dolphin whistle signal, comprise the following steps,

Step one: choose dolphin whistle signal, carries out Short Time Fourier Transform to dolphin whistle signal, obtains frequency spectrum profiles curve chart at that time;

Step 2: equidistantly get a little according to the time shaft of symbol width to dolphin whistle time-frequency spectrum curve, the instantaneous frequency values f of the corresponding dolphin whistle signal of each time point difference _i, obtain one group of frequency values f corresponding with time point;

Step 3: obtain coding to be sent by modulation, if coding number is not the integral multiple of the number of the class frequency value f medium frequency obtained, then after coding to be sent, supplement code element, make coding number after supplementing be the integral multiple of the number of the class frequency value f medium frequency obtained;

Step 4: carry out BOK modulation to sent coding, determines the frequency modulation rate value corresponding to each code element, obtains the tune group of frequencies k after one group of modulation;

Step 5: each frequency values in the class frequency value f obtained is circulated as the reference frequency of every section of LFM signal in order, duration using symbol width T as every section of LFM signal, adjust frequency values in order as the frequency modulation rate of every section of LFM signal each tune in group of frequencies k, produce every section of LFM signal, the LFM signal obtained is combined in time by the order of frequency values f, forms one section of segmentation LFM and imitate whistle data-signal;

Step 6: the multistage segmentation LFM of acquisition is imitated whistle data-signal and combines in order, adds blank protection interval, obtains total imitative whistle data-signal between every section of imitative whistle data-signal;

Step 7: synchronizing signal is the dolphin whistle signal obtained in step one, protecting interval to combine by adding one section of blank between synchronizing signal and total imitative whistle data-signal, obtaining bionical communications transmit frame signal;

Step 8: bionical communications transmit frame signal launched, after underwater acoustic channel, at receiving terminal Received signal strength;

Step 9: Received signal strength and dolphin whistle signal are carried out copy related operation, the time point finding peak-peak place corresponding is the starting point of synchronizing signal, add the duration of synchronizing signal in step 7 and the duration at blank protection interval, determine the start time point of bionic data signal;

Step 10: to determining that the bionic data signal of start time point carries out equilibrium, obtain the bionic data signal after equilibrium;

Step 11: to the bionic data signal after equilibrium is that length is intercepting with symbol width, and excludes blank protection interval;

Step 12: demodulation is carried out to every section of LFM signal after intercepting, obtains modulation intelligence.

A kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal of the present invention, can also comprise

1, every section of LFM signal is:

$s_i\left(t\right)=cos\left(2\mathrm{\π}t\right(f_i-\frac{k_{i}T}{2})+{\mathrm{\πk}}_i{t}^2)$

Wherein, T is symbol width, f _ibe i-th frequency values, k _icorresponding frequency modulation rate.

2, the bionic data signal after equilibrium is:

r(t)＝s _r(t)*h'(-t)

＝[s(t)*h(t)]*h'(-t)+n(t)*h'(-t)

＝s(t)*[h(t)]*h'(-t)+n(t)*h'(-t)

Wherein, s _r(t) signal for receiving, s (t) is bionical communications transmit frame signal, n (t) is noise signal, the impulse response function that h (t) is channel, h'(t) the channel impulse response function for estimating, by doing to copy relevant acquisition to the synchronizing signal received and original whistle signal.

The method of 3, carrying out demodulation to every section of LFM signal after intercepting is Fourier Transform of Fractional Order parameter Estimation demodulation method or coupling correlation demodulation method.

4, Fourier Transform of Fractional Order parameter Estimation demodulation method is:

According to symbol width, segmentation is carried out to bionic data signal, extract every section of LFM signal y successively _it (), asks y _i(t) Fourier Transform of Fractional Order Y under different order _pu (), carries out parameter Estimation and obtains

$\{p,u_0\}=\arg \underset{p,n}{\max }|Y_p\left(u\right){|}^2$

$\left\{\begin{array}{c}\hat{k}=-\cot \left(\frac{p\mathrm{\π}}{2}\right)\\ {\hat{f}}_0=u_0\csc \left(\frac{p\mathrm{\π}}{2}\right)\end{array}\right.$

Right carry out polarity judgement: if then i-th section of LFM signal receiving result if then i-th section of LFM signal receiving result

Finally all demodulation result carried out and close, obtaining final modulation intelligence

5, mating correlation demodulation method is:

According to symbol width, segmentation is carried out to bionic data signal, extract every section of LFM signal y successively _it (), produces respectively and corresponds to " 1 " every section of LFM signal s _1i(t) and every section of LFM signal s corresponding to " 0 " _0it (), then obtains y respectively _i(t) and s _1ithe correlation function R of (t) _1i, and y (τ) _i(t) and s _0ithe correlation function R of (t) _0i(τ):

$R_{1i}\left(\mathrm{\τ}\right)=\left|{\∫}_{-\mathrm{\∞}}^{+\mathrm{\∞}}{y}_i\left(t\right)s_{1i}(t-\mathrm{\τ})dt\right|$

$R_{0i}\left(\mathrm{\τ}\right)=\left|{\∫}_{-\mathrm{\∞}}^{+\mathrm{\∞}}{y}_i\left(t\right)s_{0i}(t-\mathrm{\τ})dt\right|$

Then R is contrasted _1i(τ) and R _0i(τ) size of relevant peaks, determines the code element that i-th section of LFM signal is corresponding: if R _1i(τ) >R _0i(τ), then i-th section of LFM signal receiving result if R _1i(τ) <R _0i(τ), then i-th section of LFM signal receiving result ${\hat{a}}_i=0;$

Finally the demodulation result of every section of LFM signal is combined, obtain final demodulation code

Beneficial effect:

By emulation experiment and tank experiments, the feasibility of the method obtains checking.Achieve zero error rate communication under-10dB signal to noise ratio condition in emulation experiment, tank experiments achieves zero error rate communication under 19 rice grain pattern communication distances, 20 milliseconds of symbol width conditions.

The communication means adopting the LFM of utilization of the present invention to imitate dolphin whistle signal to carry out communicating, can utilize segmentation LFM frequently signal carry out modulation /demodulation as carrier wave, simple, amount of calculation is less, and traffic rate is moderate.Meanwhile, the imitative dolphin whistle signal disguise after synthesis is higher, can realize pretending covert communications.

Accompanying drawing explanation

Fig. 1 is the flow chart utilizing segmentation LFM to imitate dolphin whistle signal to carry out communicating;

Fig. 2 is true dolphin whistle signal time-frequency spectrum curve chart;

Fig. 3 is the true dolphin whistle signal first-harmonic time-frequency spectrum curve chart extracted;

Fig. 4 is modulation principle figure;

Fig. 5 is bionical segmentation LFM spectrum diagram;

Fig. 6 is the frame structure schematic diagram that transmits;

Fig. 7 is the waveform time-frequency spectrum curve chart that transmits;

Fig. 8 is subjunctive mood mirror time reversal schematic diagram;

Fig. 9 is Fourier Transform of Fractional Order demodulation principle figure;

Figure 10 is coupling relative theory figure.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further details.

The technical problem to be solved in the present invention proposes one to utilize segmentation LFM signal to imitate dolphin whistle signal, realizes the method for bionical hidden underwater sound communication.

Realize the object of the invention technical scheme, as shown in Figure 1:

Utilize segmentation LFM signal to imitate a camouflage underwater acoustic communication method for dolphin whistle signal, it is characterized in that:

At transmitting terminal:

Step 1: choose suitable dolphin whistle signal, carry out Short Time Fourier Transform to dolphin whistle signal, obtains frequency spectrum profiles curve chart at that time;

Step 2: equidistantly get a little according to the time shaft of symbol width to the dolphin whistle time-frequency spectrum curve described in step 1, the instantaneous frequency values f of the corresponding dolphin whistle signal of each time point _i, thus the frequency values f that acquisition one group is corresponding with time point;

Step 3: obtain modulation intelligence;

Step 4: modulation intelligence step 3 obtained carries out BOK modulation, determines the frequency modulation rate value k corresponding to each code element ₀or k ₁, and its putting in order according to symbol order, obtain the tune group of frequencies k after one group of modulation, such as: 0 corresponds to k ₀=-40000Hz/s, 1 corresponds to k ₁=+40000Hz/s, is encoded to 011010, then the tune group of frequencies k obtained is: k ₀k ₁k ₁k ₀k ₁k ₀;

Step 5: each frequency values in class frequency value f step 2 obtained is in order as the reference frequency of every section of LFM signal, duration using symbol width T as every section of LFM signal, each in the tune group of frequencies k utilizing step 4 to obtain adjusts frequency values in order as the frequency modulation rate of every section of LFM signal, produce every section of LFM signal, the order of the frequency values f obtained by step 2 by these signals combines in time, forms one section of segmentation LFM and imitates whistle data-signal;

Step 6: obtain total bionic data signal, content comprises

(1) he number and the product of symbol width during the total duration of definition coding equals described in step 3 modulation intelligence, define total he number that code length is the coding described in step 3;

(2) if coding number is less than the number of the class frequency value f medium frequency that step 2 obtains, namely total duration of encoding is less than the length of whistle signal, so for ensureing the integrality of imitative whistle signal, the code element of supplementary some that should be suitable after original code element, make to supplement rear code length identical with the number of the class frequency value f medium frequency that step 2 obtains, and then carry out step 5;

(3) if code length is greater than the number of the class frequency value f medium frequency that step 2 obtains, namely total duration of encoding is greater than the length of whistle signal, the frequency values f that so step 2 can be obtained recycles, repeat step 5, until residue after code length is less than the number of f, is repeating (2) in step 6;

(4) supplement code element time, according to dolphin whistle signal time-frequency spectrum contour curve in step 1 in time variation tendency carry out complement code, such as: if time-frequency spectrum contour curve is on a declining curve in time, then should supplement 0 yard; If time-frequency spectrum contour curve is in rising trend in time, then should mend 1 yard;

(5) the multistage segmentation LFM of acquisition is imitated whistle data-signal to combine in order, add blank protection interval between every section of imitative whistle data-signal, obtain total imitative whistle data-signal;

Step 7: synchronizing signal is the real dolphin whistle signal described in step 1, adds one section of blank and protects interval to combine, obtain bionical communications transmit frame signal between imitative whistle data-signal synchronizing signal and step 6 obtained;

Step 8: frame emission signal step 7 obtained is launched, after underwater acoustic channel, at receiving terminal Received signal strength;

At receiving terminal:

Step 9: carry out synchronous to received signal, method is that the dolphin whistle signal described in Received signal strength and step 1 is carried out copy related operation, find the time point that peak-peak place is corresponding, be the starting point of synchronizing signal, and then add the duration of the synchronizing signal described in step 7 and the duration at blank protection interval, determine the start time point of bionic data signal;

Step 10: equilibrium is carried out to the bionic data signal of time of the determining starting point described in step 9, obtains the bionic data signal after equilibrium;

Step 11: the bionic data signal after the equilibrium obtain step 10 is that length is intercepting with symbol width, and exclude blank protection interval;

Step 12: demodulation is carried out to every section of LFM signal after the intercepting described in step 10, obtains modulation intelligence.

Above-mentioned utilize LFM to imitate dolphin whistle signal to carry out in the communication means communicated, the dolphin whistle signal used in step 1 is the whistle signal of all kinds of dolphins that actual acquisition arrives, by frequency spectrum profiles curve at that time on a timeline to choose the reference frequency of frequency values as every section of LFM signal of corresponding time point after symbol width equidistantly divides, duration using symbol width as every section of LFM signal, utilize the slope of every section of LFM signal to modulate, can obtain listening imitative whistle data-signal similar to dolphin whistle territory from time-frequency domain and people's ear.Before bionic data signal, add original whistle signal again as synchronizing signal, bionical communication frame can be formed.In transmitting procedure, even if this signal of communication is intercepted and captured by enemy, also can be called as biology intrinsic in ocean when identifying thus be excluded, be reached the object of bionical covert communications.When receiving terminal demodulation, first utilize subjunctive mood mirror time reversal to carry out equilibrium, then utilize Fourier Transform of Fractional Order or coupling to be correlated with and carry out demodulation, obtain modulation intelligence.

Do some to the present invention below to illustrate: the dolphin whistle signal in step 1 refers to the whistle signal of all kinds of dolphin.Time-frequency spectrum contour curve used in step 2 is dolphin whistle signal first-harmonic time-frequency spectrum contour curve.Described in step 5, the reference frequency of every section of LFM signal refers to the centre frequency of every section of LFM signal.The equalization methods adopted in step 10 is subjunctive mood mirror time reversal equalization methods.Blank protection gap length described in step 6 is 50ms.Blank protection gap length described in step 7 is 1s.Synchronizing signal described in step 7 is the whistle signal described in step 1.The demodulation method adopted in step 12 can be Fourier Transform of Fractional Order parameter Estimation demodulation method.The demodulation method adopted in step 12 can be coupling correlation demodulation method.

The present invention relates to a kind of camouflage underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal.

The signal of communication that during whistle signal of dolphin, dolphin is main, its video envelope and chirp class signal seemingly, therefore can utilize segmentation LFM signal to simulate dolphin whistle signal, utilize LFM signal to carry the communication information, communicate, realize imitative dolphin whistle signal covert communications.

At transmitting terminal:

Step 1: choose suitable dolphin whistle signal, carry out Short Time Fourier Transform to dolphin whistle signal, obtains frequency spectrum profiles curve chart at that time, as shown in Figures 2 and 3.

Step 2: equidistantly get a little according to the time shaft of symbol width to the dolphin whistle time-frequency spectrum curve described in step 1, the instantaneous frequency values f of the corresponding dolphin whistle signal of each time point _i, thus the frequency values f that acquisition one group is corresponding with time point;

Step 3: obtain modulation intelligence, as shown in Figure 4;

Step 4: modulation intelligence step 3 obtained carries out BOK modulation, determines the frequency modulation rate value k corresponding to each code element ₀or k ₁, and its putting in order according to symbol order, obtain the tune group of frequencies k after one group of modulation, such as: 0 corresponds to k ₀=-40000Hz/s, 1 corresponds to k ₁=+40000Hz/s, is encoded to 011010, then the tune group of frequencies k obtained is: k ₀k ₁k ₁k ₀k ₁k ₀;

If unipolar binary to be modulated is encoded to a={1,0,1,1,0,0,1 ..., BOK modulation is carried out to it, corresponding tune group of frequencies k={k ₁, k ₀, k ₁, k ₁, k ₀, k ₀, k ₁.

Step 5: each frequency values in class frequency value f step 2 obtained is in order as the reference frequency of every section of LFM signal, duration using symbol width T as every section of LFM signal, each in the tune group of frequencies k utilizing step 4 to obtain adjusts frequency values in order as the frequency modulation rate of every section of LFM signal, produce every section of LFM signal, the order of the frequency values f obtained by step 2 by these signals combines in time, form one section of segmentation LFM and imitate whistle data-signal, as shown in Figure 5;

If i-th frequency values is f _i, corresponding frequency modulation rate is k _i, then i-th section of linear FM signal s can be obtained _i(t) be:

$s_i\left(t\right)=cos\left(2\mathrm{\&pi;}t\right(f_i-\frac{k_{i}T}{2})+{\mathrm{\&pi;k}}_i{t}^2)---\left(1\right)$

Wherein, T is symbol width.The instantaneous frequency of this signal is:

$f=f_i-\frac{k_{i}T}{2}+k_{i}t---\left(2\right)$

Step 6: obtain total bionic data signal, content comprises

(1) he number and the product of symbol width during the total duration of definition coding equals described in step 3 modulation intelligence, define total he number that code length is the coding described in step 3;

(2) if coding number is less than the number of the class frequency value f medium frequency that step 2 obtains, namely total duration of encoding is less than the length of whistle signal, so for ensureing the integrality of imitative whistle signal, the code element of supplementary some that should be suitable after original code element, make to supplement rear code length identical with the number of the class frequency value f medium frequency that step 2 obtains, and then carry out step 5;

(3) if code length is greater than the number of the class frequency value f medium frequency that step 2 obtains, namely total duration of encoding is greater than the length of whistle signal, the frequency values f that so step 2 can be obtained recycles, repeat step 5, until residue after code length is less than the number of f, is repeating (2) in step 6;

(4) supplement code element time, according to dolphin whistle signal time-frequency spectrum contour curve in step 1 in time variation tendency carry out complement code, such as: if time-frequency spectrum contour curve is on a declining curve in time, then should supplement 0 yard; If time-frequency spectrum contour curve is in rising trend in time, then should mend 1 yard;

(5) the multistage segmentation LFM of acquisition is imitated whistle data-signal to combine in order, add blank protection interval between every section of imitative whistle data-signal, obtain total imitative whistle data-signal;

Step 7: synchronizing signal is the real dolphin whistle signal described in step 1, adds one section of blank and protects interval to combine, obtain bionical communications transmit frame signal, as shown in Figure 6 and Figure 7 between imitative whistle data-signal synchronizing signal and step 6 obtained;

Step 8: frame emission signal step 7 obtained is launched, after underwater acoustic channel, at receiving terminal Received signal strength;

At receiving terminal:

Step 9: carry out synchronous to received signal, method is that the dolphin whistle signal described in Received signal strength and step 1 is carried out copy related operation, find the time point that peak-peak place is corresponding, be the starting point of synchronizing signal, and then add the duration of the synchronizing signal described in step 7 and the duration at blank protection interval, determine the start time point of bionic data signal;

Step 10: equilibrium is carried out to the bionic data signal of time of the determining starting point described in step 9, obtains the bionic data signal after equilibrium;

Equalization methods adopts subjunctive mood mirror time reversal balancing technique.As shown in Figure 8, in this patent, detectable signal and synchronizing signal are same signal.At receiving terminal, to the detectable signal p received _rt () copies relevant to original detectable signal p (t) work, thus estimate the impulse response function h'(t of channel), then carried out obtaining h'(-t time reversal).By the data letter s received _r(t) number and h'(-t) make convolution, obtain finally virtual signal r (t) received, its waveform is similar to prime information waveform, reaches portfolio effect.Virtual time reversal mirror processing procedure expression formula is as follows:

s _r(t)＝s(t)*h(t)+n(t)(3)

r(t)＝s _r(t)*h'(-t)

＝[s(t)*h(t)]*h'(-t)+n(t)*h'(-t)(4)

＝s(t)*[h(t)]*h'(-t)+n(t)*h'(-t)

Note: be called virtual time reversal channel, can be used as " total channel " that signal eventually passes through.Signal is by after virtual time reversal channel, and direct signal is higher than multi-path signals energy a lot, and inhibit the intersymbol interference that underwater acoustic channel multi-path effect brings, meanwhile, because noise is non-coherent addition, this technology can also improve signal to noise ratio.

Step 11: the bionic data signal after the equilibrium obtain step 10 is that length is intercepting with symbol width, and exclude blank protection interval;

Step 12: demodulation is carried out to every section of LFM signal after the intercepting described in step 10, obtains modulation intelligence.

Demodulation method can be Fourier Transform of Fractional Order parameter Estimation demodulation method or coupling correlation demodulation method.

(1) Fourier Transform of Fractional Order parameter Estimation demodulation method:

When demodulation, first according to symbol width, segmentation is carried out to bionic data signal, extract every segment signal successively.As shown in Figure 9.Suppose the i-th section of LFM signal y extracted in bionic data signal _it (), asks y _i(t) Fourier Transform of Fractional Order Y under different order _pu (), then utilizes

$\{p,u_0\}=\arg \underset{p,u}{\max }|Y_p\left(u\right){|}^2$

$\left\{\begin{array}{c}\hat{k}=-\cot \left(\frac{p\mathrm{\&pi;}}{2}\right)\\ {\hat{f}}_0=u_0\csc \left(\frac{p\mathrm{\&pi;}}{2}\right)\end{array}\right.---\left(5\right)$

Formula (5) carries out parameter Estimation to it, obtains right carry out polarity judgement: if then i-th section of LFM signal receiving result if then i-th section of LFM signal receiving result finally all demodulation result carried out and close, obtaining final modulation intelligence

(2) correlation demodulation method is mated

Because LFM signal has good correlated performance, the correlation peak of its auto-correlation function is very precipitous, is similar to δ function, coupling correlation technique therefore can be utilized to carry out demodulation, as shown in Figure 10.

When demodulation, first according to symbol width, segmentation is carried out to bionic data signal, extract every segment signal successively.At receiving terminal, according to the frequency waypoint that step 2 obtains, produce the every section of LFM signal corresponding to " 1 " and correspond to " 0 " respectively.Suppose the i-th section of LFM signal y extracted in bionic data signal _it (), i-th section of LFM signal corresponding to " 1 " is s _1it (), i-th section of LFM signal corresponding to " 0 " is s _0it (), then obtains y respectively _i(t) and s _1ithe correlation function R of (t) _1i, and y (τ) _i(t) and s _0ithe correlation function R of (t) _0i(τ), its computing formula is as follows:

$R_{1i}\left(\mathrm{\&tau;}\right)=\left|{\&Integral;}_{-\mathrm{\&infin;}}^{+\mathrm{\&infin;}}{y}_i\left(t\right)s_{1i}(t-\mathrm{\&tau;})dt\right|---\left(6\right)$

$R_{0i}\left(\mathrm{\&tau;}\right)=\left|{\&Integral;}_{-\mathrm{\&infin;}}^{+\mathrm{\&infin;}}{y}_i\left(t\right)s_{0i}(t-\mathrm{\&tau;})dt\right|---\left(7\right)$

Then R is contrasted _1i(τ) and R _0i(τ) size of relevant peaks, determines the code element that i-th section of LFM signal is corresponding: if R _1i(τ) >R _0i(τ), then i-th section of LFM signal receiving result if R _1i(τ) <R _0i(τ), then i-th section of LFM signal receiving result finally the demodulation result of every section of LFM signal is combined, obtain final demodulation code

The present invention relates to a kind of camouflage underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal, it is characterized in that: according to the time dependent feature of dolphin whistle signal frequency, utilize multiple LFM signal subsection combine analog dolphin whistle signal, adopt the modulates information of BOK method realization to LFM signal, and then realize the bionical underwater sound communication modulation based on dolphin whistle signal and LFM signal.Receiving terminal by Fourier Transform of Fractional Order to the reception data after equilibrium in the centre frequency of every section of LFM signal and frequency modulation rate estimate, and based on the dolphin whistle signal sample adopted during modulation, carry out demodulation, obtain modulation intelligence.Adopt this segmentation LFM to imitate the underwater acoustic communication method of dolphin whistle signal, can realize utilizing simple linear FM signal to carry out the bionic camouflage underwater sound communication of high fidelity, strengthen disguise and the practicality of communication.

Claims (6)

1. utilize segmentation LFM signal to imitate a underwater acoustic communication method for dolphin whistle signal, it is characterized in that: comprise the following steps,

Step one: choose dolphin whistle signal, carries out Short Time Fourier Transform to dolphin whistle signal, obtains frequency spectrum profiles curve chart at that time;

Step 2: equidistantly get a little according to the time shaft of symbol width to dolphin whistle time-frequency spectrum curve, the instantaneous frequency values f of the corresponding dolphin whistle signal of each time point difference _i, obtain one group of frequency values f corresponding with time point;

Step 3: obtain coding to be sent by modulation, if coding number is not the integral multiple of the number of the class frequency value f medium frequency obtained, then after coding to be sent, supplement code element, make coding number after supplementing be the integral multiple of the number of the class frequency value f medium frequency obtained;

Step 4: carry out BOK modulation to sent coding, determines the frequency modulation rate value corresponding to each code element, obtains the tune group of frequencies k after one group of modulation;

Step 5: each frequency values in the class frequency value f obtained is circulated as the reference frequency of every section of LFM signal in order, duration using symbol width T as every section of LFM signal, adjust frequency values in order as the frequency modulation rate of every section of LFM signal each tune in group of frequencies k, produce every section of LFM signal, the LFM signal obtained is combined in time by the order of frequency values f, forms one section of segmentation LFM and imitate whistle data-signal;

Step 6: the multistage segmentation LFM of acquisition is imitated whistle data-signal and combines in order, adds blank protection interval, obtains total imitative whistle data-signal between every section of imitative whistle data-signal;

Step 7: synchronizing signal is the dolphin whistle signal obtained in step one, protecting interval to combine by adding one section of blank between synchronizing signal and total imitative whistle data-signal, obtaining bionical communications transmit frame signal;

Step 8: bionical communications transmit frame signal launched, after underwater acoustic channel, at receiving terminal Received signal strength;

Step 9: Received signal strength and dolphin whistle signal are carried out copy related operation, the time point finding peak-peak place corresponding is the starting point of synchronizing signal, add the duration of synchronizing signal in step 7 and the duration at blank protection interval, determine the start time point of bionic data signal;

Step 10: to determining that the bionic data signal of start time point carries out equilibrium, obtain the bionic data signal after equilibrium;

Step 11: to the bionic data signal after equilibrium is that length is intercepting with symbol width, and excludes blank protection interval;

Step 12: demodulation is carried out to every section of LFM signal after intercepting, obtains modulation intelligence.

2. a kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal according to claim 1, is characterized in that: every section of described LFM signal is:

$s_i\left(t\right)=cos\left(2\mathrm{\&pi;}t\right(f_i-\frac{k_{i}T}{2})+{\mathrm{\&pi;k}}_i{t}^2)$

Wherein, T is symbol width, f _ibe i-th frequency values, k _icorresponding frequency modulation rate.

3. a kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal according to claim 1, is characterized in that: the bionic data signal after described equilibrium is:

r(t)＝s _r(t)*h'(-t)

＝[s(t)*h(t)]*h'(-t)+n(t)*h'(-t)

＝s(t)*[h(t)]*h'(-t)+n(t)*h'(-t)

Wherein, s _r(t) signal for receiving, s (t) is bionical communications transmit frame signal, n (t) is noise signal, the impulse response function that h (t) is channel, h'(t) the channel impulse response function for estimating, by doing to copy relevant acquisition to the synchronizing signal received and original whistle signal.

4. a kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal according to claim 1, is characterized in that: described method of carrying out demodulation to every section of LFM signal after intercepting is Fourier Transform of Fractional Order parameter Estimation demodulation method or coupling correlation demodulation method.

5. a kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal according to claim 1, is characterized in that: described Fourier Transform of Fractional Order parameter Estimation demodulation method is:

According to symbol width, segmentation is carried out to bionic data signal, extract every section of LFM signal y successively _it (), asks y _i(t) Fourier Transform of Fractional Order Y under different order _pu (), carries out parameter Estimation and obtains

$\{p,u_0\}=\underset{p,u}{\mathrm{argmax}}|Y_p\left(u\right){|}^2$

$\left\{\begin{array}{c}\hat{k}=-\cot \left(\frac{p\mathrm{\&pi;}}{2}\right)\\ {\hat{f}}_0=u_0\csc \left(\frac{p\mathrm{\&pi;}}{2}\right)\end{array}\right.$

Right carry out polarity judgement: if then i-th section of LFM signal receiving result if then i-th section of LFM signal receiving result

Finally all demodulation result carried out and close, obtaining final modulation intelligence

6. a kind of underwater acoustic communication method utilizing segmentation LFM signal to imitate dolphin whistle signal according to claim 1, is characterized in that: described coupling correlation demodulation method is:

According to symbol width, segmentation is carried out to bionic data signal, extract every section of LFM signal y successively _it (), produces respectively and corresponds to " 1 " every section of LFM signal s _1i(t) and every section of LFM signal s corresponding to " 0 " _0it (), then obtains y respectively _i(t) and s _1ithe correlation function R of (t) _1i, and y (τ) _i(t) and s _0ithe correlation function R of (t) _0i(τ):

$R_{1i}\left(\mathrm{\&tau;}\right)=\left|{\&Integral;}_{-\mathrm{\&infin;}}^{+\mathrm{\&infin;}}{y}_i\left(t\right)s_{1i}(t-\mathrm{\&tau;})dt\right|$

$R_{0i}\left(\mathrm{\&tau;}\right)=\left|{\&Integral;}_{-\mathrm{\&infin;}}^{+\mathrm{\&infin;}}{y}_i\left(t\right)s_{0i}(t-\mathrm{\&tau;})dt\right|$

Then R is contrasted _1i(τ) and R _0i(τ) size of relevant peaks, determines the code element that i-th section of LFM signal is corresponding: if R _1i(τ) >R _0i(τ), then i-th section of LFM signal receiving result if R _1i(τ) <R _0i(τ), then i-th section of LFM signal receiving result

Finally the demodulation result of every section of LFM signal is combined, obtain final demodulation code