CN110266344A - A kind of chaotic mixing spread spectrum secrecy underwater acoustic communication method - Google Patents
A kind of chaotic mixing spread spectrum secrecy underwater acoustic communication method Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/692—Hybrid techniques using combinations of two or more spread spectrum techniques
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
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- H04B13/00—Transmission systems characterised by the medium used for transmission, not provided for in groups H04B3/00 - H04B11/00
- H04B13/02—Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy
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Abstract
The invention discloses a kind of chaotic mixings to spread secrecy underwater acoustic communication method, the described method includes: the binary sequence even group-division that step 1) transmitting terminal issues information source, every group is divided into three pieces, first piece of progress BPSK modulation and Gray mapping, second piece of progress M member chaos phase modulation CPM frequency expansion sequence mapping, third block are modulated to chaotic fm spread spectrum CFM signal；Then the three classes orthogonal signalling of output are subjected to hybrid modulation, obtain chaotic mixing spread spectrum CHSS signal to be launched, CHSS signal is converted into analog signal and is emitted；The underwater sound analog signal received is converted to digital signal by step 2) receiving end, using the in-phase branch BPSK spread-spectrum signal in chaos phase modulation spread spectrum as pilot signal, using the spreading gain of chaos phase modulation spreading code, time-frequency two-dimensional search is carried out to signal and completes Time and Frequency Synchronization；Signal after Time and Frequency Synchronization is demodulated, M member CPM and CFM are spread and use incoherent maximum-likelihood demodulation algorithm, BPSK uses Coherent Demodulation, completes the despreading of M member and coherent demodulation, obtains binary sequence.
Description
Technical field
The present invention relates to technical field of underwater acoustic communication, and in particular to a kind of chaotic mixing spread spectrum secrecy underwater acoustic communication method.
Background technique
Increase with people to the enhancement of ocean development and to marine resources demand realizes that steady, secrecy the underwater sound is logical
Letter becomes new research hotspot.Seawater causes underwater channel transmission bandwidth relatively narrow the stronger attenuation characteristic of signal, the underwater sound
The lower spread speed of complicated and changeable and underwater sound signal of environment, so that underwater acoustic channel becomes one of channel the most complicated.Expand
Frequency communication has good antinoise and anti-multipath jamming characteristic, is widely used in long-range water due to the presence of spreading gain
Sound communication field.However the stronger noise robustness of spread spectrum communication is the communication data rate to sacrifice the availability of frequency spectrum as cost
It is usually very low；Conventional pseudorandom (Pseudo-Noise, PN) sequence that traditional spread spectrum communication uses has apparent week
The features such as phase property and two-value, once signal is trapped, the individual features such as spreading rate and code period be easy by enemy extract and
It utilizes, leads to information leakage.
In the prior art, M member Direct Sequence Spread Spectrum (Direct-Sequence Spread Spectrum, DSSS) communicates
Mode carries information bit using the combination of multiple frequency expansion sequences, improves the data transfer rate of spread spectrum communication to a certain extent；Combination
It is difficult to protect between the spread spectrum communication mode spreading code that data transfer rate is further improved, but is overlapped mutually on the basis of M member
End of certificate is entirely orthogonal, therefore exists and interfere with each other, and reduces the bit error rate performance of system；The cyclic shift keying in biorthogonal channel
(Cyclic Shift Keying, CSK) spread spectrum communication mode utilizes the big of symbol phases by modulates information in symbol phases
Small expression information, on the one hand improves the bandwidth availability ratio of spread spectrum communication system, on the other hand solves by orthogonal channel logical
The problem of being interfered between road, but bandwidth availability ratio is still limited.
Above-mentioned communication mode is the communication mode under unclassified environment, does not account for the ability of anti-interception of signal, adopts
Conventional Gold code or Kasami sequence are replaced with chaos sequence, utilize chaos sequence noise like, pseudorandom, aperiodic and to first
It is worth extremely sensitive characteristic, solves the problems, such as that conventional PN code is periodic, greatly improves the safety of communication, however due to letter
Two-value quantization is carried out to original chaos sequence in number generating process, lead to that treated chaos sequence and common PN sequence sheet
Matter is identical, and quantifies that correlation is caused to decline, and quantity available is reduced；Reduce what signal was detected by the way of burst communication
Probability, although intercept probability can be reduced to a certain extent, efficient communication rate will be greatly reduced in this method.
Summary of the invention
It is an object of the present invention to further increase the logical of underwater sound spread-spectrum communication to solve above-mentioned the deficiencies in the prior art
Believe rate, while improving the security performance of spread-spectrum signal, provides a kind of high reliablity, good confidentiality, communication efficiency the high underwater sound
Communication means.
In order to achieve the above objectives, a kind of chaotic mixing spread spectrum secrecy underwater acoustic communication method is provided, which comprises
The binary sequence even group-division that step 1) transmitting terminal issues information source, every group is divided into three pieces, first piece of progress
BPSK modulation and Gray mapping, second piece of progress M member chaos phase modulation CPM frequency expansion sequence mapping, third block are modulated to chaotic fm
Spread CFM signal；Then the three classes orthogonal signalling of output are subjected to hybrid modulation, obtain chaotic mixing spread spectrum CHSS to be launched
CHSS signal to be launched is finally converted to underwater sound analog signal and emitted by signal；
The underwater sound analog signal received is converted to digital signal by step 2) receiving end, using same in chaos phase modulation spread spectrum
Phase branch BPSK spread-spectrum signal is as pilot signal, using the spreading gain of chaos phase modulation spreading code, carries out time-frequency two to signal
Time and Frequency Synchronization is completed in dimension search；Signal after Time and Frequency Synchronization is demodulated, incoherent maximum is used for CPM and CFM spread spectrum
Likelihood demodulating algorithm, BPSK use Coherent Demodulation, complete the despreading of M member and coherent demodulation, obtain binary sequence.
As a kind of improvement of the above method, the step 1) is specifically included:
Step 1-1) it maps to obtain original chaos sequence using Quadratic, thus generate M1+ 1 CPM spreading code and M2
A CFM spreading code, the length of spreading code are N；The CPM spreading code of generation and CFM spreading code are separately constituted into a chaos phase modulation
Frequency expansion sequence setWith a chaotic fm frequency expansion sequence set
Step 1-2) transmitting terminal will input information according to (1+K1+K2) bit progress serioparallel exchange, to every 1+K1+K2Bit
1st progress BPSK maps to obtain BPSK symbol d0(t), chaos phase modulation spreading code c is utilized0(t)=P0To d0(t) it is spread
Modulation, is used for in-phase branch for modulated signal, wherein P0For the 1st spreading code in chaos phase modulation frequency expansion sequence set；To the 2nd
To K1+ 1 progress M member mapping, obtains M1Binary data d1(t), the d in chaos phase modulation frequency expansion sequence set is selected1(t)+2
A spreading codeSpread-spectrum signal as output, for quadrature branch；To K1+ 2 to K1+K2+ 1 progress
The mapping of M member, obtains M2Binary data d2(t), the d in chaotic fm frequency expansion sequence set is selected2(t)+1 spreading codeAs output；Wherein d1(t) and d2It (t) is respectively entrained by M member chaos phase modulation spread spectrum and chaotic fm
Information；d1(t) value be 0,1 ... M1- 1 }, d2(t) value be 0,1 ... M2-1}；
Step 1-3) by the c of generation0(t) it is modulated in in-phase branch,It is modulated in quadrature branch,
Then being modulated at frequency is f0Carrier wave on, obtain modulated CHSS time-domain signal, be expressed as follows:
WhereinExpression takes real part, and T is the length of a symbol:
T=NTc (8)
Wherein, N is spread code length, then the length T of each chipcAre as follows:
Wherein, B is signal bandwidth；
Step 1-4) CHSS signal s (t) to be launched is converted into underwater sound analog signal emits.
As a kind of improvement of the above method, the step 1-1) it specifically includes:
Step 1-1-1) it maps to obtain original chaos sequence using Quadratic, mapping equation indicates are as follows:
G (m+1)=U-Qg2(m) (1)
Wherein, as 3/4 < UQ < 2, g (m) ∈ (- 2/Q, 2/Q) takes Q=4 here, U=1/4, g (0) ∈ (- 0.5,
0.5), (- 0.5,0.5) g (m) ∈；
Step 1-1-2) by M different chaos initial values M mutually orthogonal chaos sequence is generated, it is denoted as:
G0,G2,...,Gk,...,GM (2)
Wherein,It is the chaos sequence of N for length；
Step 1-1-3) the above-mentioned chaos sequence quantified without two-value is modulated in carrier phase, it generates chaos phase modulation and expands
Frequency code, as shown in formula (3):
Step 1-1-4) by M1+ 1 mutually orthogonal chaos phase modulation spreading code forms a chaos phase modulation Spread Spectrum Sequence Set
It closesWherein+1 chaos phase modulation spreading code of kth is expressed asFor n-th of chip in chaos phase modulation spreading code；
Step 1-1-5) chaos sequence quantified without two-value is modulated on a carrier frequency, chaotic fm code is generated, such as
Shown in formula (4):
Wherein B is signal bandwidth, ξn(t)=u [t-nT0]-u[t-(n+1)T0] it be the duration is T0Unit pulse letter
Number, u (t) are jump function；
Step 1-1-6) by M2A mutually orthogonal chaotic fm spreading code forms a chaotic fm frequency expansion sequence setWherein k-th of chaotic fm spreading code is expressed asFor chaos
N-th of chip in frequency hopping spread spectrum code.
As a kind of improvement of the above method, the step 1-2) in K1Value are as follows:
K1=log2M1 (5)
K2Value is
K2=log2M2 (6)。
As a kind of improvement of the above method, the step 2) is specifically included:
Step 2-1) receiving end carries out Time and Frequency Synchronization to it after receiving CHSS signal；
Step 2-2) carrier frequency and symbol phases are obtained by Time and Frequency Synchronization after, using time domain resampling methods to broadband
Signal carries out frequency deviation compensation, while accordingly being compensated symbol phases, is demodulated to BPSK branch using Coherent Demodulation；
Step 2-3) incoherent maximum-likelihood demodulation algorithm, connecing after Time and Frequency Synchronization are used for CPM spread spectrum and CFM spread spectrum
Number orthogonal complex carrier signal being from a locally generated respectively of collecting mail is multiplied with the spreading code that M member chaos spread spectrum sequence is concentrated, and acquires product
Energy, and choose output result of the corresponding spreading code of maximum value in the position that frequency expansion sequence is concentrated as maximum-likelihood demodulation；
Step 2-4) Gray mapping is carried out to the demodulation result of BPSK branch and is adjudicated, to the solution of M member CPM and CFM branch
It adjusts result to carry out the mapping of M member and adjudicates, three road demodulating informations progress parallel-serial conversion is obtained into final demodulating information.
As a kind of improvement of the above method, the step 2-1) it specifically includes:
Step 2-1-1) the receiving end local that generates respective frequencies with the Doppler factor of frequency domain search step-length is orthogonal
Complex carrier signal, while with the CPM spreading code c of the displacement generation corresponding phase of a time domain step-size in search0(t), just by above-mentioned local
It hands over complex carrier signal multiplied by the CPM spreading code, receives signal and be multiplied with above-mentioned product, product filters off frequency multiplication by a low-pass filter
Component is shown below:
WhereinIt is the corresponding frequency deviation of Doppler factor,It is for generating CPM spreading code c0(t) original chaos sequence
By displacement after as a result, γ (t) is white noise part as a result, RBPSKThe processing result of corresponding bpsk signal, IMAnd ICFMPoint
Not Wei chaos phase modulation and chaotic fm modulating part result；
The output for taking the energy value of η (t) to search for as this；
Step 2-1-2) keep the Doppler factor of frequency domain search constant, CPM spread spectrum is updated with above-mentioned time domain step-size in search
The phase of code finds out the maximum of each secondary time domain search result according to the process iterative search of step 2-1-1) in search range
Value is used as search result.
Step 2-1-3) the orthogonal complex carrier signal in local for corresponding to Doppler factor is updated with above-mentioned frequency domain search step-length, it is searching for
It is iterated search according to the process of step 2-1-1) to step 2-1-2) in range, finds out the maximum of each secondary frequency domain search result
Value, and calculate this time and search for corresponding carrier frequency and spread spectrum code phase, and then obtain Time and Frequency Synchronization point, it is same to complete time-frequency two-dimensional
Step.
The present invention has the advantages that
1, method of the invention overcomes the binary feature and cyclophysis that tradition is random sequence, is not losing communication speed
Secrecy underwater sound communication is realized under conditions of rate；Using the good cross correlation of chaotic signal, the logical of hybrid spread spectrum is reduced
It is interfered between road, ensure that the bit error rate performance of system；
2, method of the invention improves the traffic rate of underwater sound spread-spectrum communication, while improving the security performance of spread-spectrum signal,
Have the advantages that high reliablity, good confidentiality, communication efficiency are high.
Detailed description of the invention
Fig. 1 is that chaotic mixing of the invention spreads secrecy underwater acoustic communication method flow chart；
Fig. 2 is that chaotic mixing of the invention spreads secrecy underwater sound communication Time and Frequency Synchronization realization schematic diagram；
Fig. 3 is that the incoherent maximum-likelihood demodulation of chaotic fm signal of the invention realizes schematic diagram.
Specific embodiment
Below with reference to specific drawings and examples to a kind of chaotic mixing spread spectrum secrecy underwater sound communication side provided by the invention
Method does further explaination.
Chaotic mixing spread spectrum secrecy underwater acoustic communication method flow chart provided by the invention is as shown in Figure 1, be described in detail below:
Step 1: mapping to obtain original chaos sequence using Quadratic, mapping equation is indicated are as follows:
G (m+1)=U-Qg2(m) (1)
Wherein, as 3/4 < UQ < 2, g (m) ∈ (- 2/Q, 2/Q) takes Q=4 here, U=1/4, g (0) ∈ (- 0.5,
0.5), (- 0.5,0.5) g (m) ∈；
M mutually orthogonal chaos sequence is generated by M different chaos initial values, is denoted as:
G0,G2,...,Gk,...,GM (2)
Wherein,It is the chaos sequence of N for length；
The above-mentioned chaos sequence quantified without two-value is modulated in carrier phase, chaos phase modulation spreading code is generated, such as formula
(3) shown in:
By M1+ 1 mutually orthogonal chaos phase modulation spreading code forms a chaos phase modulation frequency expansion sequence setWherein+1 chaos phase modulation spreading code of kth is expressed as It is mixed
N-th of chip in ignorant phase modulation spreading code；
On a carrier frequency by the chaos sequence quantified without two-value modulation, chaotic fm code is generated, as shown in formula (4):
Wherein B is signal bandwidth, ξn(t)=u [t-nT0]-u[t-(n+1)T0] it be the duration is T0Unit pulse letter
Number, u (t) are jump function；
By M2A mutually orthogonal chaotic fm spreading code forms a chaotic fm frequency expansion sequence setWherein k-th of chaotic fm spreading code is expressed asFor chaos
N-th of chip in frequency hopping spread spectrum code.
CPM and CFM frequency expansion sequence is non-quantized complex exponential sequence, and not only quantity available is more, correlation number, Er Qieke
The shortcomings that having taken the periodicity and two-value that tradition is random sequence, has stronger confidentiality.
Step 2: transmitting terminal will input information according to (1+K1+K2) bit progress serioparallel exchange, to every 1+K1+K2Bit
1st progress BPSK maps to obtain BPSK symbol d0(t), chaos phase modulation spreading code c is utilized0(t)=P0To d0(t) it is spread
Modulation, is used for in-phase branch for modulated signal, wherein P0For the 1st spreading code in chaos phase modulation frequency expansion sequence set；To the 2nd
To K1+ 1 progress M member mapping, obtains M1Binary data d1(t), the d in chaos phase modulation frequency expansion sequence set is selected1(t)+2
A spreading codeSpread-spectrum signal as output, for quadrature branch；To K1+ 2 to K1+K2+ 1 progress
The mapping of M member, obtains M2Binary data d2(t), the d in chaotic fm frequency expansion sequence set is selected2(t)+1 spreading codeAs output；Wherein d1(t) and d2It (t) is respectively entrained by M member chaos phase modulation spread spectrum and chaotic fm
Information；d1(t) value be 0,1 ... M1- 1 }, d2(t) value be 0,1 ... M2-1}；
M1=log2M (5)
Similarly for CFM sequence, from K group CFM sequence, mapping obtains corresponding CFM sequence, therefore each chaotic fm
Signal carries M2Bit information:
M2=log2K (6)
Step 3: the c that will be generated in step 20(t) it is modulated in in-phase branch, c1(t) it is modulated in quadrature branch, c2
(t) being then modulated at frequency is f0Carrier wave on, obtain modulated CHSS time-domain signal, be expressed as follows:
Wherein d0(t) the entrained information of BPSK modulation, d are represented0(t) value is+1 or -1.Expression takes real part, T
For the length of a symbol:
T=NTc (8)
Wherein, N is spread code length, then the length T of each chipcAre as follows:
Wherein, B is signal bandwidth；
Step 4: receiving end carries out Time and Frequency Synchronization to it after receiving CHSS signal, as shown in Figure 2:
4.1 receiving ends generate the orthogonal complex carrier signal in local of respective frequencies with the Doppler factor of a frequency domain search step-length,
The CPM spreading code of corresponding phase is generated with the displacement of a time domain step-size in search simultaneously.By the orthogonal complex carrier signal in above-mentioned local multiplied by
The CPM spreading code receives signal and is multiplied with above-mentioned product, and product filters off harmonic, such as following formula by a low-pass filter
It is shown:
Wherein γ (t) is white noise part as a result, RBPSKThe processing result of corresponding bpsk signal, IMAnd ICFMRespectively M
The result of member modulation and chaotic fm modulating part.
The output for taking the energy value of η (t) to search for as this.
4.2 keep the Doppler factor of frequency domain search constant, and the phase of CPM spreading code is updated with above-mentioned time domain step-size in search
Position repeats 4.1 in search range, finds out the maximum value of each secondary time domain search result as search result.
4.3 update the orthogonal complex carrier signal in local of corresponding Doppler factor with above-mentioned frequency domain search step-length, in search range
The process for repeating 4.1-4.2, finds out the maximum value of each secondary time domain search result, and calculate this time search for corresponding carrier frequency with
Code phase is spread, and then obtains Time and Frequency Synchronization point, it is synchronous to complete time-frequency two-dimensional.
Step 5: after obtaining carrier frequency and symbol phases by Time and Frequency Synchronization, using time domain resampling methods to broadband
Signal carries out frequency deviation compensation, while accordingly being compensated symbol phases, is demodulated to BPSK branch using Coherent Demodulation；
Step 6: spreading M member CPM and CFM and use incoherent maximum-likelihood demodulation algorithm, and Fig. 3 show CFM spread spectrum
Incoherent maximum-likelihood demodulation block diagram, orthogonal complex carrier signal that the reception signal after Time and Frequency Synchronization is from a locally generated respectively and
The CFM spreading code that M member chaotic fm spreading code frequency expansion sequence is concentrated is multiplied, and acquires the energy of product, and it is corresponding to choose maximum value
Output result of the CFM spreading code in the position that frequency expansion sequence is concentrated as maximum-likelihood demodulation；
Step 7: Gray mapping is carried out to the demodulation result on the road of BPSK and is adjudicated, the demodulation to M member CPM and CFM branch
As a result it carries out the mapping of M member and adjudicates, three road demodulating informations progress parallel-serial conversion is obtained into final demodulating information.
It should be noted last that the above examples are only used to illustrate the technical scheme of the present invention and are not limiting.Although ginseng
It is described the invention in detail according to embodiment, those skilled in the art should understand that, to technical side of the invention
Case is modified or replaced equivalently, and without departure from the spirit and scope of technical solution of the present invention, should all be covered in the present invention
Scope of the claims in.
Claims (6)
1. a kind of chaotic mixing spreads secrecy underwater acoustic communication method, which comprises
The binary sequence even group-division that step 1) transmitting terminal issues information source, every group is divided into three pieces, first piece of progress BPSK tune
System and Gray mapping, second piece of progress M member chaos phase modulation CPM frequency expansion sequence mapping, third block are modulated to chaotic fm spread spectrum CFM
Signal；Then the three classes orthogonal signalling of output are subjected to hybrid modulation, obtain chaotic mixing spread spectrum CHSS signal to be launched, most
CHSS signal to be launched underwater sound analog signal is converted to afterwards to emit；
The underwater sound analog signal received is converted to digital signal by step 2) receiving end, using the same phase branch in chaos phase modulation spread spectrum
Road BPSK spread-spectrum signal carries out time-frequency two-dimensional to signal and searches as pilot signal using the spreading gain of chaos phase modulation spreading code
Rope completes Time and Frequency Synchronization；Signal after Time and Frequency Synchronization is demodulated, incoherent maximum likelihood is used for CPM and CFM spread spectrum
Demodulating algorithm, BPSK use Coherent Demodulation, complete the despreading of M member and coherent demodulation, obtain binary sequence.
2. chaotic mixing according to claim 1 spreads secrecy underwater acoustic communication method, which is characterized in that the step 1) tool
Body includes:
Step 1-1) it maps to obtain original chaos sequence using Quadratic, thus generate M1+ 1 CPM spreading code and M2A CFM
Spreading code, the length of spreading code are N；The CPM spreading code of generation and CFM spreading code are separately constituted into a chaos phase modulation spread spectrum sequence
Column setWith a chaotic fm frequency expansion sequence set
Step 1-2) transmitting terminal will input information according to (1+K1+K2) bit progress serioparallel exchange, to every 1+K1+K2The 1st of bit
BPSK is carried out to map to obtain BPSK symbol d0(t), chaos phase modulation spreading code c is utilized0(t)=P0To d0(t) band spectrum modulation is carried out,
Modulated signal is used for in-phase branch, wherein P0For the 1st spreading code in chaos phase modulation frequency expansion sequence set；To the 2nd to K1+1
Position carries out the mapping of M member, obtains M1Binary data d1(t), the d in chaos phase modulation frequency expansion sequence set is selected1(t)+2 spread spectrums
CodeSpread-spectrum signal as output, for quadrature branch；To K1+ 2 to K1+K2+ 1 progress M member is reflected
It penetrates, obtains M2Binary data d2(t), the d in chaotic fm frequency expansion sequence set is selected2(t)+1 spreading codeAs output；Wherein d1(t) and d2It (t) is respectively entrained by M member chaos phase modulation spread spectrum and chaotic fm
Information；d1(t) value be 0,1 ... M1- 1 }, d2(t) value be 0,1 ... M2-1}；
Step 1-3) by the c of generation0(t) it is modulated in in-phase branch,It is modulated in quadrature branch,Then adjust
System is f in frequency0Carrier wave on, obtain modulated CHSS time-domain signal, be expressed as follows:
WhereinExpression takes real part, and T is the length of a symbol:
T=NTc (8)
Wherein, N is spread code length, then the length T of each chipcAre as follows:
Wherein, B is signal bandwidth；
Step 1-4) CHSS signal s (t) to be launched is converted into underwater sound analog signal emits.
3. chaotic mixing according to claim 2 spreads secrecy underwater acoustic communication method, which is characterized in that the step 1-1)
It specifically includes:
Step 1-1-1) it maps to obtain original chaos sequence using Quadratic, mapping equation indicates are as follows:
G (m+1)=U-Qg2(m) (1)
Wherein, as 3/4 < UQ < 2, g (m) ∈ (- 2/Q, 2/Q) takes Q=4, U=1/4, g (0) ∈ (- 0.5,0.5), g here
(m)∈(-0.5,0.5)；
Step 1-1-2) by M different chaos initial values M mutually orthogonal chaos sequence is generated, it is denoted as:
G0,G2,...,Gk,...,GM (2)
Wherein,It is the chaos sequence of N for length；
Step 1-1-3) the above-mentioned chaos sequence quantified without two-value is modulated in carrier phase, generate chaos phase modulation spread spectrum
Code, as shown in formula (3):
Step 1-1-4) by M1+ 1 mutually orthogonal chaos phase modulation spreading code forms a chaos phase modulation frequency expansion sequence setWherein+1 chaos phase modulation spreading code of kth is expressed as For
N-th of chip in chaos phase modulation spreading code；
Step 1-1-5) chaos sequence quantified without two-value is modulated on a carrier frequency, chaotic fm code is generated, such as formula (4)
It is shown:
Wherein B is signal bandwidth, ξn(t)=u [t-nT0]-u[t-(n+1)T0] it be the duration is T0Unit impulse function, u
It (t) is jump function；
Step 1-1-6) by M2A mutually orthogonal chaotic fm spreading code forms a chaotic fm frequency expansion sequence setWherein k-th of chaotic fm spreading code is expressed as For chaos
N-th of chip in frequency hopping spread spectrum code.
4. chaotic mixing according to claim 2 spreads secrecy underwater acoustic communication method, which is characterized in that the step 1-2)
In K1Value are as follows:
K1=log2M1 (5)
K2Value is
K2=log2M2 (6)。
5. chaotic mixing according to claim 2 spreads secrecy underwater acoustic communication method, which is characterized in that the step 2) tool
Body includes:
Step 2-1) receiving end carries out Time and Frequency Synchronization to it after receiving CHSS signal；
Step 2-2) carrier frequency and symbol phases are obtained by Time and Frequency Synchronization after, using time domain resampling methods to broadband signal
Frequency deviation compensation is carried out, while symbol phases are accordingly compensated, BPSK branch is demodulated using Coherent Demodulation；
Step 2-3) incoherent maximum-likelihood demodulation algorithm is used for CPM spread spectrum and CFM spread spectrum, the reception letter after Time and Frequency Synchronization
Number orthogonal complex carrier signal being from a locally generated respectively is multiplied with the spreading code that M member chaos spread spectrum sequence is concentrated, and acquires the energy of product,
And choose output result of the corresponding spreading code of maximum value in the position that frequency expansion sequence is concentrated as maximum-likelihood demodulation；
Step 2-4) Gray mapping is carried out to the demodulation result of BPSK branch and is adjudicated, to the demodulation knot of M member CPM and CFM branch
Fruit carries out the mapping of M member and adjudicates, and three road demodulating informations progress parallel-serial conversion is obtained final demodulating information.
6. chaotic mixing according to claim 5 spreads secrecy underwater acoustic communication method, which is characterized in that the step 2-1)
It specifically includes:
Step 2-1-1) receiving end generates the orthogonal multiple loads in local of respective frequencies with the Doppler factor of frequency domain search step-length
Wave, while with the CPM spreading code c of the displacement generation corresponding phase of a time domain step-size in search0(t), above-mentioned local is orthogonal multiple
Carrier wave receives signal and is multiplied with above-mentioned product, product filters off times frequency division by a low-pass filter multiplied by the CPM spreading code
Amount, is shown below:
WhereinIt is the corresponding frequency deviation of Doppler factor,It is for generating CPM spreading code c0(t) original chaos sequence passes through
It is after displacement as a result, γ (t) is white noise part as a result, RBPSKThe processing result of corresponding bpsk signal, IMAnd ICFMRespectively
The result of chaos phase modulation and chaotic fm modulating part；
The output for taking the energy value of η (t) to search for as this；
Step 2-1-2) keep the Doppler factor of frequency domain search constant, CPM spreading code is updated with above-mentioned time domain step-size in search
Phase, according to the process iterative search of step 2-1-1) in search range, the maximum value for finding out each secondary time domain search result is made
For search result；
Step 2-1-3) the orthogonal complex carrier signal in local for corresponding to Doppler factor is updated with above-mentioned frequency domain search step-length, in search range
The interior process according to step 2-1-1) to step 2-1-2) is iterated search, finds out the maximum value of each secondary frequency domain search result,
And calculate this time and search for corresponding carrier frequency and spread spectrum code phase, and then obtain Time and Frequency Synchronization point, it is synchronous to complete time-frequency two-dimensional.
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