CN108270492A - A kind of modulation and demodulation method for pretending sound communication - Google Patents
A kind of modulation and demodulation method for pretending sound communication Download PDFInfo
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- CN108270492A CN108270492A CN201710002090.1A CN201710002090A CN108270492A CN 108270492 A CN108270492 A CN 108270492A CN 201710002090 A CN201710002090 A CN 201710002090A CN 108270492 A CN108270492 A CN 108270492A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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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- 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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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B11/00—Transmission systems employing sonic, ultrasonic or infrasonic waves
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Abstract
The present invention relates to it is a kind of pretend sound communication modulator approach, including：Sub-frame processing is carried out to carrier audio signal, obtains multiframe data；DFT transform is done to each frame data, obtains spectral coefficient；Band spectrum modulation is done to spectral coefficient with reference to spreading code, obtains the spectral coefficient after band spectrum modulation；Time domain is transformed to by IDFT to the spectral coefficient after band spectrum modulation, then does windowing process again, finally reconfigures every frame time-domain signal by framing rule, synthesis emits after carrying the audio signal of information.The invention further relates to it is a kind of pretend sound communication demodulation method, including：Receiving terminal samples received signal, then carries out time synchronization and channel equalization to sampling obtained signal；The data slot containing information is intercepted, then carries out framing；DFT transform is done to each frame signal obtained after framing, obtains the spectral coefficient of each frame signal；Make relevant treatment with spreading code and spectral coefficient, obtain relative decoding result.
Description
Technical field
The present invention relates to sound communication field, more particularly to a kind of modulation and demodulation method for pretending sound communication.
Background technology
Under water in Acoustic channel, sound communication can realize the underwater nodes such as submarine, AUV/UUV, the subsurface communication network equipment
Between and the communication between surface vessel and underwater node device.However sound wave has opening in water, tradition is hidden
Underwater acoustic communication method is mostly using reducing transmitting signal power and signal of communication being designed like form of noise, if but intercepting and capturing
Equipment is less than a certain distance apart from sound source, and sound source will expose, and this method will lose concealment.
In air Acoustic channel, transmission information can realize music/shadow in carrier audio signal in a manner of Information hiding
Depending on Works copyright protection, broadcast monitoring, copy control etc., however there are poor reliability, information capacities for existing information hidden method
The shortcomings that small, anti-multipath channel disturbance poor performance.
Invention content
It is an object of the invention to overcome existing information hidden method there are poor reliability, information capacity is small, anti-multipath letter
The shortcomings that road jamming performance is poor, so as to provide a kind of modulation and demodulation method that concealment is high, anti-channel disturbance ability is strong that communicates.
To achieve these goals, the present invention provides it is a kind of pretend sound communication modulator approach, including：
Step 101 carries out sub-frame processing to carrier audio signal, obtains multiframe data；
Step 102, to step 101, obtained each frame data do DFT transform, obtain spectral coefficient；
Step 103 does band spectrum modulation with reference to spreading code to the spectral coefficient that step 102 obtains, after obtaining band spectrum modulation
Spectral coefficient；
Spectral coefficient after step 104, the band spectrum modulation obtained to step 103 transforms to time domain, Ran Houzai by IDFT
Windowing process is done, finally reconfigures every frame time-domain signal by framing rule, synthesis emits after carrying the audio signal of information.
In above-mentioned technical proposal, in a step 101, by the way of framing is overlapped or the mode of non-overlapping framing is to carrier
Audio signal carries out sub-frame processing.
In above-mentioned technical proposal, in step 103, band spectrum modulation is done to spectral coefficient by the way of amplitude modulation or phase modulation.
In above-mentioned technical proposal, band spectrum modulation is done to spectral coefficient by the way of amplitude modulation, expression formula is：
Or Yi(k)=Xi(k)·(1+bi·δi(k)·ω(k))；
Wherein, Yi(k) it is the spectral coefficient after band spectrum modulation；Xi(k) it is the spectral coefficient before band spectrum modulation；δi(k) it represents
The amplitude modulation factor, for measuring Yi(k) compared to Xi(k) knots modification of amplitude；ω (k) represents spreading code；bi∈ { ± 1 } represents the i-th frame
The information that data carry.
In above-mentioned technical proposal, band spectrum modulation is done to spectral coefficient by the way of phase modulation, expression formula is：
Wherein, Yi(k) it is the spectral coefficient after band spectrum modulation；Xi(k) it is the spectral coefficient before band spectrum modulation；λi(k) it represents
The phase modulation factor, for measuring Yi(k) compared to Xi(k) knots modification of phase；ω (k) represents spreading code.
The present invention also provides a kind of demodulation method for pretending sound communication, for being given birth to the modulator approach for pretending sound communication
Into signal be demodulated；This method includes：
Step 201, receiving terminal sample received signal, then same to sampling the obtained signal progress time
Step, the signal finally synchronized to the elapsed time do channel equalization；
Step 202 intercepts the data slot containing information from the signal after synchronous and channel equalization, then to containing
The data slot for having information carries out framing；
Step 203 does DFT transform to each frame signal obtained after framing, obtains the spectral coefficient of each frame signal；
Step 204, the spectral coefficient of each frame signal obtained with spreading code and step 203 make relevant treatment, obtain correlation
Decoding result.
In above-mentioned technical proposal, in step 201, include to sampling obtained signal progress time synchronization：With modulation
When used carrier audio signal obtained signal sampled to each array element make copy relevant treatment, and by maximum related value with
The thresholding of a certain setting is compared, and is then judged that signal is reached more than threshold value, is realized time synchronization.
In above-mentioned technical proposal, in step 201, channel equalization is done to the signal that the elapsed time synchronizes and is included：First will
Carrier audio signal generates training matrix, then carries out channel estimation using orthogonal matching pursuit method, and each array element is received number
Make convolution according to the time reversal conjugation with array element estimation channel, be superimposed all array numbers and factually show Virtual time reversal mirror channel
It is balanced.
In above-mentioned technical proposal, in step 204, the spreading code is to pretend employed in the modulator approach of sound communication
Spreading code.
In above-mentioned technical proposal, the step 204 further comprises：
The modulation system of the spectral coefficient of each frame signal that judgment step 203 obtains selects corresponding according to modulation system
Coding/decoding method, including：
(1) according toModulation format, coding/decoding method is as follows：
(2) according to Yi(k)=Xi(k)·(1+bi·δi(k) ω (k)) modulation format, coding/decoding method is as follows：
(3) according toModulation format, coding/decoding method is as follows
Wherein, CiFor decoding result；The spectral coefficient of each frame signal obtained for step 203.
The advantage of the invention is that：
The concealment that communicates is high, and traffic rate is high, and anti-channel disturbance ability is strong, good reliability, and can be neatly with adding
The communication system that the combinations such as close and channel coding realization more complicates, can effectively apply to hidden sound communication, Information hiding etc.
Field.
Description of the drawings
Fig. 1 (a) is the schematic diagram of non-overlapping framing；
Fig. 1 (b) is the schematic diagram for being overlapped framing；
Fig. 2 is the flow chart of the modulator approach of the camouflage sound communication of the present invention；
Fig. 3 is the flow chart of the demodulation method of the camouflage sound communication of the present invention.
Specific embodiment
In conjunction with attached drawing, the invention will be further described.
The modulator approach of the camouflage sound communication of the present invention is in the realization of signal transmitting terminal, the demodulation of camouflage sound communication of the invention
Method is realized in signal receiving end.After signal transmitting terminal modulator approach generation transmitting signal using the present invention, which is sent out
Propagation is penetrated, signal receiving end receives signal, then demodulation method demodulated signal using the present invention.
The demodulation method of the modulator approach to the camouflage sound communication of the present invention and camouflage sound communication illustrates in turn below.
Emit signal and include carrier audio signal, spreading code.Carrier audio signal is the signal of certain publicity, according to tool
Body application scenarios select；For example, under water, ocean background noise can be used as carrier audio signal, by Information hiding in load
Pretend ocean background noise (such as marine biological noise, ship-radiated noise) in body audio signal；In air, disclosure can be used
Audio signal (such as the open music played, movie and video programs) as carrier audio signal, by Information hiding its audio signal it
In.Spreading code can be any form of spreading codes such as pseudo-random sequence, chaos sequence, according to concrete application scene (such as from phase
Close characteristic, cross correlation, code sequence number and confidentiality etc.) carry out evaluation selection.
In one embodiment, carrier audio signal selection dolphin whistles signals, design parameter selection are as follows：Signal
Duration is 400ms, and frequency range is 50Hz~20kHz.Spreading code uses 8 rank m-sequences as modulation sequence.
With reference to figure 2, the modulator approach of camouflage sound communication of the invention includes the following steps：
Step 101 carries out sub-frame processing to carrier audio signal, obtains multiframe data.
Hereinbefore it has been noted that in the present embodiment, the carrier audio signal uses dolphin whistles signals, the letter
Number with s (n) represent, sample rate fs=48kHz.When doing sub-frame processing to carrier audio signal, overlapping point can be used
Frame or the mode of non-overlapping framing.Fig. 1 (a) is the schematic diagram of non-overlapping framing, and Fig. 1 (b) is the schematic diagram for being overlapped framing.It selects
Which kind of framing mode needs to determine according to traffic rate, camouflage property and application scenarios.Traffic rate is high and applies in air
When, the mode for being overlapped framing is typically chosen, this framing method can also be combined with the other technologies in Audio Signal Processing；And
In water in order to obtain higher camouflage effectiveness, it is typically chosen the mode of non-overlapping framing.
Assuming that the frame length of the obtained data frame of framing is FL, it is F that frame, which moves,S, D frames are shared, x is expressed as per frame datai(n)
(0≤n ＜ N, N represent the sampled point number that a frame signal includes, i ∈ { 1,2 ..., D }).Then in the present embodiment, dolphin
Whistles signals are handled using non-overlapping framing mode, frame length FL=85.3ms (4096 sampled points), frame are moved as FS
=85.3ms (4096 sampled points), obtains D=4 frame data, and x is expressed as per frame datai(n) (0≤n ＜ 4096, i ∈ 1,2,
3,4})。
Step 102, to step 101, obtained each frame data do DFT transform, obtain spectral coefficient.
Obtained spectral coefficient can use X in this stepi(k) it represents, wherein 0≤k ＜ N；In the present embodiment, N takes
Be worth is 4096, therefore 0≤k ＜ 4096.Step 103 does band spectrum modulation using spreading code to the spectral coefficient that step 102 obtains,
Obtain new spectral coefficient.
In this step, spreading code, the spectral coefficient that step 102 obtains are represented using ω (m) (0≤m ＜ M, code length M)
For Xi(k), the obtained new spectral coefficient of this step is Yi(k)。
When doing band spectrum modulation to spectral coefficient, the mode of amplitude modulation or phase modulation can be used.
According to the mode of amplitude modulation, thenOr Yi(k)=Xi(k)·(1+bi·δi(k)·ω
Or other mathematic(al) manipulations of equal value (k)).Wherein, δi(k) the amplitude modulation factor is represented, for measuring Yi(k) compared to Xi(k) amplitude
Knots modification；bi∈ { ± 1 } represent the information that the i-th frame data carry and spread spectrum code length M=N (it is without being limited thereto, code length M can take M≤
The arbitrary value of N).
According to the mode of phase modulation, thenOr other mathematic(al) manipulations of equal value.λi(k) table
Show the phase modulation factor, for measuring Yi(k) compared to Xi(k) knots modification of phase.
In the foregoing description, the amplitude modulation and phase modulation expression formula be using e the bottom of as, but not limited to this, it may be used and be with 10
Bottom is other exponential forms such as bottom with 2；The frequency range of the band spectrum modulation is Whole frequency band (i.e. M=N), but not limited to this, it can
Think certain band segment (i.e. M ＜ N), and frequency range position can arbitrarily select；The spread spectrum modulation technique includes but not limited to
Direct Sequence Spread Spectrum can be other spectrum spreading methods such as cyclic shift keying spread spectrum, M members spread spectrum, combination spread spectrum.
In one embodiment, spreading code uses 8 rank m-sequence ω (m), wherein, 0≤m ＜ 255, code length M=255.It is right
The mode that spectral coefficient does band spectrum modulation is amplitude modulation mode, and each frame carries information b1=+1, b2=-1, b3=+1, b4=-1 is adjusted
Width factor deltai(k)==0.1.
New spectral coefficient after step 104, the band spectrum modulation obtained to step 103 transforms to time domain by IDFT, so
It does windowing process again afterwards, finally reconfigures every frame time-domain signal by framing rule, synthesis is sent out after carrying the audio signal of information
It penetrates.
In this step, window function can be according to concealment, reliability and specific applied field used by windowing process
Scape is selected.In one embodiment, Hanning window can be used.
With reference to figure 3, the demodulation method of camouflage sound communication of the invention includes the following steps：
Step 201, receiving terminal sample the analog signal received, when then being carried out to sampling obtained signal
Between it is synchronous, the signal finally synchronized to the elapsed time does channel equalization.
Wherein, the receiving terminal is sensor array or single array element.In the present embodiment, the receiving terminal is 32 yuan of sensings
Device array.
In the present embodiment, the signal received to receiving terminal is according to sample rate fs=48kHz is sampled.
When doing time synchronization to sampling obtained signal, with carrier audio signal s (n) used when modulating to each battle array
Member samples obtained signal and makees copy relevant treatment, and maximum related value and the thresholding of a certain setting are compared, and is more than
Threshold value then judges that signal reaches, and realizes and synchronizes；
When doing channel equalization to the signal that the elapsed time synchronizes, carrier audio signal s (n) is generated into training matrix first,
Then channel estimation is carried out using OMP (orthogonal matching pursuit) method, each array element is received into data and array element estimation channel
Time reversal conjugation makees convolution, is superimposed all array numbers and factually shows Virtual time reversal mirror channel equalization.
Step 202 intercepts the data slot containing information from the signal after synchronous and channel equalization, then to containing
The data slot for having information carries out framing；
In this step, when doing framing operation, the framing method that is previously mentioned in step 101 before can be used, therefore not
It redescribes here.In one embodiment, a frame signal can be divided into D=4 frame signals.
Step 203 does DFT transform to each frame signal obtained after framing, obtains the spectral coefficient Y of each frame signali R
(k)。
Step 204, the spectral coefficient Y with spreading code ω (m) and each frame signali R(k) make relevant treatment, obtain relative decoding
As a result Ci。
Spreading code employed in this step is identical with the spreading code employed in modulator approach.Employed in this step
Spectral coefficient is the spectral coefficient for receiving signal, the spectral coefficient Y with transmitting signal involved in modulator approachi(k)
Difference, therefore using Yi R(k) it represents.
The step specifically includes：
Judge spectral coefficient Yi R(k) modulation system selects corresponding coding/decoding method according to modulation system, including：
(1) according toModulation format, coding/decoding method is as follows：
(2) according to Yi(k)=Xi(k)·(1+bi·δi(k) ω (k)) modulation format, coding/decoding method is as follows：
(3) according toModulation format, coding/decoding method is as follows
In one embodiment, the spreading code ω (m) in this step is 8 rank m-sequences, wherein, 0≤m ＜ 255, code length M
=255.
It should be noted last that the above embodiments are merely illustrative of the technical solutions of the present invention and it is unrestricted.Although ginseng
The present invention is described in detail according to embodiment, it will be understood by those of ordinary skill in the art that, to the technical side of the present 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
Right in.
Claims (10)
1. a kind of modulator approach for pretending sound communication, including：
Step 101 carries out sub-frame processing to carrier audio signal, obtains multiframe data；
Step 102, to step 101, obtained each frame data do DFT transform, obtain spectral coefficient；
Step 103 does band spectrum modulation with reference to spreading code to the spectral coefficient that step 102 obtains, and obtains the frequency spectrum after band spectrum modulation
Coefficient；
Spectral coefficient after step 104, the band spectrum modulation obtained to step 103 transforms to time domain by IDFT, then adds again
Window processing, finally reconfigures every frame time-domain signal by framing rule, and synthesis emits after carrying the audio signal of information.
2. the modulator approach of camouflage sound communication according to claim 1, which is characterized in that in a step 101, using overlapping
The mode of framing or the mode of non-overlapping framing carry out sub-frame processing to carrier audio signal.
3. the modulator approach of camouflage sound communication according to claim 1, which is characterized in that in step 103, using amplitude modulation
Or the mode of phase modulation does band spectrum modulation to spectral coefficient.
4. the modulator approach of camouflage sound communication according to claim 3, which is characterized in that frequency spectrum by the way of amplitude modulation
Coefficient does band spectrum modulation, and expression formula is：
Or Yi(k)=Xi(k)·(1+bi·δi(k)·ω(k))；
Wherein, Yi(k) it is the spectral coefficient after band spectrum modulation；Xi(k) it is the spectral coefficient before band spectrum modulation；δi(k) amplitude modulation is represented
The factor, for measuring Yi(k) compared to Xi(k) knots modification of amplitude；ω (k) represents spreading code；bi∈ { ± 1 } represents the i-th frame data
The information of carrying.
5. the modulator approach of camouflage sound communication according to claim 3, which is characterized in that frequency spectrum by the way of phase modulation
Coefficient does band spectrum modulation, and expression formula is：
Wherein, Yi(k) it is the spectral coefficient after band spectrum modulation；Xi(k) it is the spectral coefficient before band spectrum modulation；λi(k) phase modulation is represented
The factor, for measuring Yi(k) compared to Xi(k) knots modification of phase；ω (k) represents spreading code.
6. a kind of demodulation method for pretending sound communication, for the modulator approach institute of the camouflage sound communication to one of claim 1-5
The signal of generation is demodulated；This method includes：
Step 201, receiving terminal sample received signal, then carry out time synchronization to sampling obtained signal,
The signal finally synchronized to the elapsed time does channel equalization；
Step 202 intercepts the data slot containing information from the signal after synchronous and channel equalization, then to containing letter
The data slot of breath carries out framing；
Step 203 does DFT transform to each frame signal obtained after framing, obtains the spectral coefficient of each frame signal；
Step 204, the spectral coefficient of each frame signal obtained with spreading code and step 203 make relevant treatment, obtain relative decoding
As a result.
7. the demodulation method of camouflage sound communication according to claim 6, which is characterized in that in step 201, to sampling institute
Obtained signal carries out time synchronization and includes：Used carrier audio signal samples obtained letter to each array element during with modulation
Number make copy relevant treatment, and maximum related value and the thresholding of a certain setting are compared, then judge signal more than threshold value
It reaches, realizes time synchronization.
8. the demodulation method of camouflage sound communication according to claim 6, which is characterized in that in step 201, during to passing through
Between synchronous signal do channel equalization and include：Carrier audio signal is generated into training matrix first, is then chased after using orthogonal matching
Track method carries out channel estimation, and each array element is received data and the time reversal conjugation of array element estimation channel makees convolution, is superimposed
All array numbers factually show Virtual time reversal mirror channel equalization.
9. the demodulation method of camouflage sound communication according to claim 6, which is characterized in that in step 204, the spread spectrum
Spreading code employed in modulator approach of the code for the camouflage sound communication of one of claim 1-5.
10. the demodulation method of camouflage sound communication according to claim 6, which is characterized in that the step 204 is further wrapped
It includes：
The modulation system of the spectral coefficient of each frame signal that judgment step 203 obtains selects corresponding decoding according to modulation system
Method, including：
(1) according toModulation format, coding/decoding method is as follows：
(2) according to Yi(k)=Xi(k)·(1+bi·δi(k) ω (k)) modulation format, coding/decoding method is as follows：
(3) according toModulation format, coding/decoding method is as follows
Wherein, CiFor decoding result；Yi R(k) spectral coefficient of each frame signal obtained for step 203.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110166386A (en) * | 2019-05-30 | 2019-08-23 | 中国科学院声学研究所 | A kind of underwater sound communication equilibrium interpretation method based on recurrence Constructing Chaotic Code |
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| CN1863039A (en) * | 2005-05-11 | 2006-11-15 | 北京大学 | Hidden communication system and communication method based on audio frequency |
| US20140269201A1 (en) * | 2013-03-12 | 2014-09-18 | Zhiqiang Liu | Method for mobile underwater acoustic communications |
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