CN102546511A - Underwater sound communication device and method based on time reversal and orthogonal frequency division multiplexing (OFDM) combined treatment - Google Patents

Abstract

The invention discloses an underwater sound communication device and a method based on time reversal and orthogonal frequency division multiplexing (OFDM) combined treatment. The underwater sound communication device comprises a signal transmitter, a power amplifier, a transmitting transducer, a receiving hydrophone array, a signal receiver and a signal processor, wherein the signal processor comprises a broadband Doppler estimation and compensation module, a time reversal processing module, an OFDM demodulation module, a channel estimation and compensation module and a frequency deviation estimation and compensation module. In the underwater sound communication device, the space time focusing characteristics of the time reversal are utilized to eliminate the multipath influence of the channel; a pulse channel response length can be shortened by the time reversal so as to reduce the length of an OFDM symbol guard interval and improve the communication efficiency; and because the guard interval is reduced, the length of the OFDM symbol can be shortened so as to enlarge a subcarrier frequency interval. With the method disclosed by the invention, interference among subcarriers can be reduced, and the available rate of the OFDM underwater sound communication is further improved.

Description

A kind of based on the time anti-and OFDM Combined Treatment the underwater sound communication device and method

Technical field

The present invention relates to the underwater sound communication device and method of anti-and OFDM when a kind of, belong to the water sound communication technique field.

Background technology

Since the middle and later periods nineties in last century; The people is just arranged progressively with orthogonal frequency utilization (Orthogonal Frequency Division Multiplexing; Abbreviation " OFDM ") technology is applied in the underwater sound communication, because the OFDM technology availability of frequency spectrum is high, traffic rate is fast; Transmit and receive hardware and realize that simply, ofdm communication has become the focus of underwater sound communication area research now.In order to realize reliable communication, the protection gap length of OFDM requires greater than channel maximum delay extension length, and the expansion of the time delay of underwater acoustic channel is more serious, has therefore reduced the efficient of OFDM underwater sound communication.Existing way is the length that promotes the OFDM symbol; Though this has promoted communication efficiency; But also reduced the sub-carrier frequencies interval of OFDM symbol, in dynamic underwater acoustic channel, increased and disturbed (inter-carrier interference between subcarrier; Be called for short " ICI "), reduced communication reliability.

Summary of the invention

The objective of the invention is to overcome that the protection of OFDM underwater sound communication in the prior art is long at interval, disturb bigger defective between subcarrier, provide a kind of based on the time anti-and OFDM Combined Treatment the underwater sound communication device and method.

For realizing above-mentioned purpose, the technical scheme that the present invention taked is:

Underwater sound communication device anti-and the OFDM Combined Treatment comprises when the present invention is based on:

Signal transmitter; Be used to form signal of communication; Said signal of communication comprises linear FM signal and ofdm signal, and is inserted with protection between Linear Frequency Modulation signal and the ofdm signal at interval, and said ofdm signal is through the PERCOM peripheral communication data being inserted pilot data after the OFDM modulation forms;

Power amplifier is used for said signal of communication is carried out power amplification;

Transmitting transducer is used for the signal of communication after amplifying is converted into acoustical signal, and acoustical signal is emitted in the water;

The receiving hydrophone battle array is used for receiving the acoustical signal that transmitting transducer is emitted to water, and converts said acoustical signal into the signal of telecommunication;

Signal receiver, being used for said electrical signal conversion is digital signal and storage;

Signal processor, this signal processor comprises:

---broadband Doppler estimates and compensating module, is used for signal receiver stored numbers signal is carried out the estimation and the broadband Doppler effect correction of Doppler's factor;

---the time anti-processing module, be used for carry out anti-processing when passive through the signal behind the Doppler effect correction of broadband;

---the OFDM demodulation module is used for the anti-signal of handling when passive is carried out the OFDM demodulation;

---channel estimating and compensating module, be used to utilize after the OFDM demodulation signal with adopt the least square channel estimation methods to estimate the response of underwater acoustic channel, and the influence of eliminating the signal of underwater acoustic channel after to the OFDM demodulation;

---frequency offset estimating and compensating module are used for carrying out frequency offset estimating and compensation through the signal after channel estimating and the compensating module processing.

Underwater acoustic communication method anti-and the OFDM Combined Treatment comprised the steps: when the present invention utilized above device to carry out

1) signal transmitter produces linear FM signal l (i); And externally insert pilot data in the communication data and obtain being inserted with the communication data x (k) of pilot data; The communication data x (k) that is inserted with pilot data is modulated into the first ofdm signal s (j) through OFDM, inserts protection then between Linear Frequency Modulation signal l (i) and the ofdm signal s (j) and form signal of communication at interval; I=1 wherein, 2 ..., I, I are the length of linear FM signal; K=1,2 ..., K, K are the length that is inserted with the communication data x (k) of pilot data; J=1,2 ..., J, J are the length of ofdm signal s (j), I, K, J are the positive integer greater than 1;

2) said signal of communication sends to the transmitting transducer that is positioned in the water after amplifying through power amplifier;

3) signal of communication after transmitting transducer will amplify is converted into acoustical signal and is emitted in the water;

4) utilize the receiving hydrophone battle array that is positioned in the water to receive transmitting transducer and be emitted to the acoustical signal in the water, and convert said acoustical signal into the signal of telecommunication;

5) signal receiver converts receiving hydrophone battle array institute electrical signal converted into digital signal Y (n) and stores;

6) the broadband Doppler in the signal processor estimates earlier said digital signal Y (n) and linear FM signal l (i) to be carried out related operation with compensating module, utilizes the result of said related operation to estimate T blanking time between all two the adjacent linear FM signals among the digital signal Y (n) then ₂, obtain suc as formula the interpolation factor D shown in that Doppler's factor-alpha shown in (1-1) and the formula (1-2):

α＝1-T ₂/T ₁ (1-1)

D＝1+α (1-2)

In the formula (1-1), T ₁The blanking time of two adjacent linear FM signals that the expression signal transmitter produces;

Then, utilize said interpolation factor D that said digital signal Y (n) is carried out the signal Y after interpolation is compensated ₁(n);

7) the time anti-processing module in the signal processor utilizes linear FM signal l (i) as detection source, to the signal Y after the said compensation ₁(n) carry out on frequency domain that anti-the processing obtains the second ofdm signal s when passive ₁(j);

8) the OFDM demodulation module in the signal processor is to the said second ofdm signal s ₁(j) carry out demodulation, obtain the communication data x after the demodulation ₁(k);

9) channel estimating in the signal processor and compensating module utilize the pilot data among the said communication data x (k) that is inserted with pilot data

With the communication data x after the said demodulation ₁The data of the pilot frequency locations (k) On frequency domain, utilize least square method that underwater acoustic channel is estimated, obtain estimated value suc as formula the channel response at the pilot frequency locations place shown in (2-1)

${\stackrel{\widehat{\→}}{H}}_{\mathrm{LS}}={\stackrel{\→}{y}}_p/{\stackrel{\→}{x}}_p---(2-1)$

Then; Utilize the linear interpolation method shown in the formula (2-2); Between all two adjacent elements

of said estimated value

and

, carry out linear interpolation, obtain complete channel response h (k);

$\hat{H}(\mathrm{mL}+l)=(1-\frac{l}{L})\hat{H}\left(\mathrm{mL}\right)+\frac{l}{L}\hat{H}(\mathrm{mL}+L),$ l＝0，1，…L-1 (2-2)

In the formula (2-2); The estimated value of the m * L channel response of the complete channel response of

expression; The estimated value of the m * L+L channel response of the complete channel response of

expression; The estimated value of the m * L+l channel response of the complete channel response of expression; M=1,2 ... M; L=1,2 ... L; M representes to be inserted with the quantity of the pilot data in the communication data x (k) of pilot data, and L representes to be inserted with the pilot interval of the communication data x (k) of pilot data;

Then, utilize the method shown in the formula (3) to eliminate the communication data x of underwater acoustic channel after to demodulation ₁(k) influence and obtain the communication data x through channel compensation ₂(k),

x ₂(k)＝x ₁(k)/h(k) (3)

10) frequency offset estimating in the signal processor and compensating module utilize the method shown in the formula (4) to estimate the communication data x through channel compensation ₂(k) frequency deviation

Utilize the method shown in the formula (5) to communication data x then through channel compensation ₂(k) carry out compensate of frequency deviation and obtain new communication data x ₃(k):

$\mathrm{\Δ}\hat{f}=\mathrm{angle}[\underset{M}{\mathrm{\Σ}}{x}_{\mathrm{mL}}^{*}\·p_{\mathrm{mL}}]/(2\mathrm{\π}\·T)---\left(4\right)$

$x_3\left(k\right)=x_2\left(k\right)\&CenterDot;\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="120112130407.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\&CenterDot;\mathrm{\&Delta;}\hat{f}\&CenterDot;T)---\left(5\right)$

In the formula (4), x _MLExpression is inserted with m pilot data among the communication data x (k) of pilot data,

Be x _MLConjugation, p _MLExpression is through the communication data x of channel compensation ₂The data of m pilot frequency locations (k), angle representes to get the phase angle of formula in the square brackets, and T representes the duration of ofdm signal s (j); In the formula here (5), j representes imaginary symbols.

Preferably, the present invention is in step 1), and the time span of said linear FM signal l (i) and the product of bandwidth are greater than 100.

Compared with prior art; The invention has the beneficial effects as follows: anti-focus characteristics when empty when the present invention utilizes; Eliminated the multi-path influence of channel, eliminated the time delay of channel, the time instead can the chopped pulse channel response length; Shorten ofdm signal s (j) protection length at interval, improved communication efficiency; Shorten the length of ofdm signal s (j) simultaneously, increased the subcarrier spacing of ofdm signal s (j), reduced between subcarrier and disturbed, further promoted the admissible rate of OFDM underwater sound communication, improved communication performance.Linear FM signal can be used for carrying out the estimation of Doppler's factor, and, as detection source, carry out that anti-processing does not bring the loss on the efficient when passive with linear FM signal.

Description of drawings

Fig. 1 is the structured flowchart of the underwater sound communication device of anti-and OFDM Combined Treatment when the present invention is based on;

Fig. 2 is the structural representation of signal processor of the present invention;

Fig. 3 be in the signal processor of the present invention the time anti-processing module fundamental diagram;

Fig. 4 is the form of the signal of communication that produces of signal transmitter of the present invention;

Fig. 5 is the typical waveguide environment sketch map of one of them embodiment of the present invention;

Fig. 6 is under form shown in Figure 4, the time-domain diagram of the signal of communication that signal transmitter produced;

Fig. 7 is the figure as a result that the broadband Doppler among the present invention estimates to carry out with compensating module related operation;

The planisphere of Fig. 8 after out-of-date anti-and OFDM Combined Treatment.

Embodiment

Below in conjunction with accompanying drawing and instantiation the present invention is done further description.

As shown in Figure 1, underwater sound communication device anti-and the OFDM Combined Treatment comprises signal transmitter, power amplifier, transmitting transducer, receiving hydrophone battle array, signal receiver and signal processor when the present invention is based on.Wherein:

Signal transmitter is used to produce signal of communication; Said signal of communication comprises linear FM signal and ofdm signal; And be inserted with protection between linear FM signal and the ofdm signal at interval, wherein, ofdm signal is through the PERCOM peripheral communication data being inserted pilot data after the OFDM modulation forms;

Power amplifier is used for signal of communication is carried out power amplification;

Transmitting transducer is used for the signal of communication after amplifying is converted into acoustical signal, and acoustical signal is emitted in the water;

The receiving hydrophone battle array is used for receiving the communication acoustical signal that transmitting transducer is emitted to water, and converts said acoustical signal into the signal of telecommunication;

It is digital signal and storage that signal receiver is used for said electrical signal conversion;

Signal processor comprise broadband Doppler's estimation and compensating module, the time anti-processing module, OFDM demodulation module, channel estimating and compensating module and frequency offset estimating and compensating module.Wherein, broadband Doppler estimation and compensating module are used for the signal of telecommunication of signal receiver storage is carried out the estimation and the broadband Doppler effect correction of Doppler's factor; The time anti-processing module be used for carry out anti-processing when passive through the signal behind the Doppler effect correction of broadband; The OFDM demodulation module is used for the anti-signal of handling when passive is carried out the OFDM demodulation; Channel estimating and compensating module are used to utilize the signal after least square channel estimation methods and the OFDM demodulation to estimate the response of underwater acoustic channel, and eliminate the influence of the signal of underwater acoustic channel after to the OFDM demodulation; Frequency offset estimating and compensating module are used for carrying out frequency offset estimating and compensation through the signal after channel estimating and the compensating module processing.

As shown in Figure 2, signal processor of the present invention mainly by broadband Doppler's estimation and compensating module, the time anti-processing module, OFDM demodulation module, channel estimating and compensating module and frequency offset estimating and compensating module form.

Underwater sound communication apparatus and method of the present invention are applicable to various environment, such as the underwater sound communication of environment such as shallow sea, lake.PERCOM peripheral communication data of the present invention comprise the coded data of voice, video, text etc.Specify technical scheme of the present invention with typical waveguide environment shown in Figure 5 and with QPSK (QPSK) coded data as the PERCOM peripheral communication data instance below.

In Fig. 5, the waveguide environment is made up of two parts: aqueous medium layer and sedimentary deposit.And in the present embodiment, the degree of depth of aqueous medium layer is 1.42 meters, and the degree of depth of sedimentary deposit is 0.22 meter; The receiving hydrophone battle array is a vertical battle array that 16 array elements are arranged, 0.08 meter of the spacing of adjacent two array elements, and uppermost array element is apart from 0.04 meter of the water surface; Transmitting transducer in the waveguide is apart from 0.6 meter of the water surface, and the horizontal range of transmitting transducer and receiving hydrophone battle array is 8 meters.In addition, c representes the velocity of sound, and ρ representes Media density, and α representes the acoustical absorptivity of medium.Below specify when carrying out the underwater sound communication step of anti-and OFDM Combined Treatment:

1. signal transmitter produces signal of communication:

The present invention need design signal of communication especially, and Fig. 4 shows a kind of concrete form of signal of communication: from left to right be followed successively by linear FM signal, protection interval, ofdm signal, protection interval, linear FM signal.The time domain form of signal of communication shown in Figure 4 is then as shown in Figure 6.As preferred version of the present invention, the time span of linear FM signal l (i) and the product of bandwidth can make Doppler's factor evaluated error be less than 1% greater than 100 like this.Certainly, in the present invention, the time span of linear FM signal l (i) and the product of bandwidth also can be less than or equal to 100 when transmitting transducer and receiving hydrophone battle array are static relatively.

Signal transmitter produces linear FM signal l (i); And externally insert pilot data in the communication data and obtain being inserted with the communication data x (k) of pilot data; The communication data x (k) that is inserted with pilot data is modulated into the first ofdm signal s (j) through OFDM, and the protection of inserting time span then between Linear Frequency Modulation signal l (i) and the ofdm signal s (j) and be T forms signal of communication at interval.Among the present invention, insert the L that is spaced apart of pilot data.Wherein, i=1,2 ... I, k=1,2 ..., K, j=1,2 ..., J; I is the length of linear FM signal l (i), and K is the length that is inserted with the communication data x (k) of pilot data, and J is the length of ofdm signal s (j), and I, K, J, L be arbitrarily the positive integer greater than 1, and T is any nonnegative number.

As just an example of the present invention; In the present embodiment, can the related parameter that have of signal of communication be done following the setting: the length I=800 of linear FM signal l (i), initial frequency is 6000 hertz; Cut-off frequency is 14000 hertz; 8000 hertz of bandwidth, time span are 0.02 second, and the time span of linear FM signal l (i) and bandwidth product are 0.02 * 8000=160.After in the QPSK coded data, inserting pilot tone, resulting length K=600 that are inserted with the communication data x (k) of pilot data, and the interval L=10 of insertion pilot data.Communication data x (k) modulates the length J=4096 of formed ofdm signal s (j) through OFDM, and the initial frequency of ofdm signal s (j) is 7000 hertz, and cut-off frequency is 13000 hertz, and time span is 0.1 second; Insert time span T between Linear Frequency Modulation signal l (i) and the ofdm signal s (j) and be 0.02 second 0 form signal of communication as shown in Figure 6 at interval as protection.

2. be input in the transmitting transducer that is positioned in the water after the signal of communication amplification of power amplifier with the signal transmitter generation, be converted into acoustical signal by transmitting transducer again and launch.

3. the receiving hydrophone battle array converts the acoustical signal that received transmitting transducer sends into the signal of telecommunication in water; Signal receiver is digital signal Y (n) with electrical signal conversion again and stores, and digital signal Y (n) is input in the signal processor handles.

4. estimation of the broadband Doppler in the signal processor and compensating module carry out the broadband Doppler effect correction to the digital signal Y (n) that receives.In signal of communication form shown in Figure 4; When the product of the time span of linear FM signal l (i) and bandwidth greater than 100 the time; Can utilize digital signal Y (n) and linear FM signal l (i) to carry out suc as formula the related operation shown in (1); Xcor is as shown in Figure 7 as a result for it, and its peak intervals is exactly the time interval T of the two adjacent linear FM signals of digital signal Y (n) ₂After through type (2) obtains the Doppler's factor-alpha between each two the adjacent linear FM signal among the digital signal Y (n), again according to corresponding each the interpolation factor D that obtains of formula (3).Then; Utilize each interpolation factor D between two corresponding with it adjacent linear FM signals, to carry out interpolation respectively; Until between all two adjacent linear FM signals, all having carried out corresponding interpolation, eliminated channel thus to the influence of digital signal Y (n) and the signal Y after being compensated ₁(n).Below bright specifically there to be three linear FM signals to be that example is carried out among the Y (n):

If three linear FM signals are arranged among the Y (n), so digital signal Y (n) and linear FM signal l (i) are carried out obtaining the interval T of preceding two adjacent linear FM signals respectively suc as formula the related operation shown in (1) ₂=b, the time interval T of latter two adjacent linear FM signal ₂=c.Utilize formula (2) to obtain Doppler's factor-alpha 1=1-b/T of preceding two adjacent linear FM signals ₁, utilize interpolation factor D1=1+ α 1 between preceding two adjacent linear FM signals, to carry out interpolation again; Equally, utilize formula (2) to obtain Doppler's factor-alpha 2=1-c/T of latter two adjacent linear FM signal ₁, utilize interpolation factor D2=1+ α 2 interpolation between latter two adjacent linear FM signal again.Thus, resulting signal is exactly Y after all having carried out corresponding interpolation between all adjacent two linear FM signals ₁(n).When the quantity of the linear FM signal among the Y (n) is other numerical value, between all two adjacent linear FM signals, carries out corresponding interpolation by the method for above-mentioned example and get final product.

$\mathrm{xcor}=Y\left(n\right)\&CircleTimes;l^{*}(-i)---\left(1\right)$

α＝1-T ₂/T ₁ (2)

D＝1+α (3)

In the formula (1),

The expression convolution algorithm, l ^*Anti-conjugation during the said linear FM signal l of (-i) expression (i).T in the formula (2) ₁The interval of the two adjacent linear FM signal l (i) that produce for signal transmitter.

In the signal processor the time anti-processing module to through the signal Y of Doppler effect correction ₁(n) utilize linear FM signal l (i) as detecting the source, each road signal is carried out anti-processing when passive according to flow process shown in Figure 3.Its way is: from the signal Y through Doppler effect correction ₁(n) the linear FM signal l that intercepting receives in _r(i) and ofdm signal s _r(j).Utilize method shown in the formula (4), obtain the ofdm signal s after anti-processing when passive ₁(j).

$s_1\left(j\right)=\mathrm{ifft}\{\underset{Q}{\mathrm{\&Sigma;}}{\left[\mathrm{fft}(l_{\mathrm{qr}}\left(i\right)\right]}^{*}\&CenterDot;\mathrm{fft}\left(l\left(i\right)\right)\&CenterDot;\mathrm{fft}\left(s_{\mathrm{qr}}\left(j\right)\right)\}---\left(4\right)$

In the formula (3), ifft representes inverse fourier transform, and fft representes Fourier transform, l _Qr(i) the said linear FM signal l of expression _r(i) the capable signal of q, s _Qr(j) be said ofdm signal s _r(j) the capable signal of q; The linear FM signal that l (i) expression signal transmitter produces, [fft (l _Qr(i))] ^*Expression fft (l _Qr(i)) conjugation, q is the positive integer smaller or equal to Q, Q is for receiving element number of array, Q=16 in this embodiment.Because the present invention's anti-processing module when being provided with, therefore allow signal transmitter to produce the ofdm signal s (j) of shorter time length, increase the subcarrier spacing of said ofdm signal s (j), reduced between the subcarrier of ofdm signal s (j) and disturbed.And linear FM signal Doppler's factor estimate and compensating module in be used for the estimating Doppler factor-alpha, again the time be used as the source of detecting in the anti-processing module, do not bring the loss on the efficient.

6. the ofdm signal s of the OFDM demodulation module in the signal processor after to anti-processing the when passive ₁(j) carry out demodulation operation, obtain communication data x ₁(k).

7. channel estimating in the signal processor and compensating module utilization are inserted with the pilot data among the communication data x (k) of pilot data

With communication data x ₁The data of the pilot frequency locations (k)

On frequency domain, utilize the least square method shown in the formula (5) that underwater acoustic channel is estimated, obtain the estimated value of the channel response at pilot tone place

${\stackrel{\widehat{\&RightArrow;}}{H}}_{\mathrm{LS}}={\stackrel{\&RightArrow;}{y}}_p/{\stackrel{\&RightArrow;}{x}}_p---\left(5\right)$

Then; Between two every adjacent elements

of said estimated value and

, utilize the linear interpolation method shown in the formula (6) to carry out interpolation respectively; Can obtain complete channel response h(k after passing through M * L interpolation altogether)

$\hat{H}(\mathrm{mL}+l)=(1-\frac{l}{L})\hat{H}\left(\mathrm{mL}\right)+\frac{l}{L}\hat{H}(\mathrm{mL}+L),$ l＝0，1，…L-1 (6)

In the formula (6); The m * L channel response estimated value of the complete channel response of

expression; The m * L+L channel response estimated value of the complete channel response of

expression; The m * L+l channel response estimated value of the complete channel response of

expression; M=1,2 ... M; L=1,2 ... L; M representes to be inserted with the quantity of the pilot data in the communication data x (k) of pilot data, and L is the pilot interval of communication data x (k), and M and L are any greater than 1 positive integer.In the present embodiment, M=60, L=10.

Then, utilize the method shown in the formula (7) to eliminate the communication data x of underwater acoustic channel after to demodulation ₁(k) influence and obtain the communication data x through channel compensation ₂(k),

x ₂(k)＝x ₁(k)/h(k) (7)

8. frequency offset estimating in the signal processor and compensating module utilize formula (8) to estimate frequency deviation

Utilize formula (9) to communication data x then through channel compensation ₂(k) carry out compensate of frequency deviation and obtain communication data x ₃(k):

$\mathrm{\&Delta;}\hat{f}=\mathrm{angle}[\underset{M}{\mathrm{\&Sigma;}}{x}_{\mathrm{mL}}^{*}\&CenterDot;p_{\mathrm{mL}}]/(2\mathrm{\&pi;}\&CenterDot;T)---\left(8\right)$

$x_3\left(k\right)=x_2\left(k\right)\&CenterDot;\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="120112130407.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\&CenterDot;\mathrm{\&Delta;}\hat{f}\&CenterDot;T)---\left(9\right)$

In the formula (4), x _MLExpression is inserted with m pilot data among the communication data x (k) of pilot data, Be x _MLConjugation, p _MLExpression is through the communication data x of channel compensation ₂The data of m pilot frequency locations (k), angle representes to get the phase angle of formula in the square brackets, and T representes the duration of ofdm signal s (j); In the formula here (9), j representes imaginary symbols.

In order to verify effect of the present invention, to the resulting communication data x of process signal processor processes ₃(k) the communication data x (k) with the signal transmitter generation compares, and its error rate is 0, and it is as shown in Figure 8 to draw planisphere.Can find out that from planisphere shown in Figure 8 communication efficiency of the present invention is fine.

Claims (3)

1. One kind based on the time anti-and OFDM Combined Treatment the underwater sound communication device; It is characterized in that; Comprise: signal transmitter, be used to form signal of communication, said signal of communication comprises linear FM signal and ofdm signal; And be inserted with protection between Linear Frequency Modulation signal and the ofdm signal at interval, said ofdm signal is through the PERCOM peripheral communication data being inserted pilot data after the OFDM modulation forms.

   Power amplifier is used for said signal of communication is carried out power amplification;

   Transmitting transducer is used for the signal of communication after amplifying is converted into acoustical signal, and acoustical signal is emitted in the water;

   The receiving hydrophone battle array is used for receiving the acoustical signal that transmitting transducer is emitted to water, and converts said acoustical signal into the signal of telecommunication;

   Signal receiver, being used for said electrical signal conversion is digital signal and storage;

   Signal processor, this signal processor comprises:

   ---broadband Doppler estimates and compensating module, is used for signal receiver stored numbers signal is carried out the estimation and the broadband Doppler effect correction of Doppler's factor;

   ---the time anti-processing module, be used for carry out anti-processing when passive through the signal behind the Doppler effect correction of broadband;

   ---the OFDM demodulation module is used for the anti-signal of handling when passive is carried out the OFDM demodulation;

   ---channel estimating and compensating module, be used to utilize after the OFDM demodulation signal with adopt the least square channel estimation methods to estimate the response of underwater acoustic channel, and the influence of eliminating the signal of underwater acoustic channel after to the OFDM demodulation;

   ---frequency offset estimating and compensating module are used for carrying out frequency offset estimating and compensation through the signal after channel estimating and the compensating module processing.
2. 2. the underwater acoustic communication method of anti-and OFDM Combined Treatment is characterized in that comprising the steps: when a device that utilizes claim 1 carried out

   1) signal transmitter produces linear FM signal l (i); And externally insert pilot data in the communication data and obtain being inserted with the communication data x (k) of pilot data; The communication data x (k) that is inserted with pilot data is modulated into the first ofdm signal s (j) through OFDM, inserts protection then between Linear Frequency Modulation signal l (i) and the ofdm signal s (j) and form signal of communication at interval; I=1 wherein, 2 ..., I, I are the length of linear FM signal; K=1,2 ..., K, K are the length that is inserted with the communication data x (k) of pilot data; J=1,2 ..., J, J are the length of ofdm signal s (j), I, K, J are the positive integer greater than 1.

   2) said signal of communication sends to the transmitting transducer that is positioned in the water after amplifying through power amplifier;

   3) signal of communication after transmitting transducer will amplify is converted into acoustical signal and is emitted in the water;

   4) utilize the receiving hydrophone battle array that is positioned in the water to receive transmitting transducer and be emitted to the acoustical signal in the water, and convert said acoustical signal into the signal of telecommunication;

   5) signal receiver converts receiving hydrophone battle array institute electrical signal converted into digital signal Y (n) and stores;

   6) the broadband Doppler in the signal processor estimates earlier said digital signal Y (n) and linear FM signal l (i) to be carried out related operation with compensating module, utilizes the result of said related operation to estimate T blanking time between all two the adjacent linear FM signals among the digital signal Y (n) then ₂, obtain suc as formula the interpolation factor D shown in that Doppler's factor-alpha shown in (1-1) and the formula (1-2):

   α＝1-T ₂/T ₁ (1-1)

   D＝1+α (1-2)

   In the formula (1-1), T ₁The blanking time of two adjacent linear FM signals that the expression signal transmitter produces;

   Then, utilize said interpolation factor D that said digital signal Y (n) is carried out the signal Y after interpolation is compensated ₁(n);

   7) the time anti-processing module in the signal processor utilizes linear FM signal l (i) as detection source, to the signal Y after the said compensation ₁(n) carry out on frequency domain that anti-the processing obtains the second ofdm signal s when passive ₁(j);

   8) the OFDM demodulation module in the signal processor is to the said second ofdm signal s ₁(j) carry out demodulation, obtain the communication data x after the demodulation ₁(k);

   9) channel estimating in the signal processor and compensating module utilize the pilot data among the said communication data x (k) that is inserted with pilot data

   

   With the communication data x after the said demodulation ₁The data of the pilot frequency locations (k)

   

   On frequency domain, utilize least square method that underwater acoustic channel is estimated, obtain estimated value suc as formula the channel response at the pilot frequency locations place shown in (2-1)

   ${\stackrel{\widehat{\&RightArrow;}}{H}}_{\mathrm{LS}}={\stackrel{\&RightArrow;}{y}}_p/{\stackrel{\&RightArrow;}{x}}_p---(2-1)$

   Then; Utilize the linear interpolation method shown in the formula (2-2); Between all two adjacent elements

   

   of said estimated value and

   

   , carry out linear interpolation, obtain complete channel response h (k);

   $\hat{H}(\mathrm{mL}+l)=(1-\frac{l}{L})\hat{H}\left(\mathrm{mL}\right)+\frac{l}{L}\hat{H}(\mathrm{mL}+L),$ l＝0，1，…L-1 (2-2)

   In the formula (2-2); The estimated value of the m * L channel response of the complete channel response of

   

   expression; The estimated value of the m * L+L channel response of the complete channel response of expression; The estimated value of the m * L+l channel response of the complete channel response of

   

   expression; M=1; 2;, M, l=1; 2; L, M represent to be inserted with the quantity of the pilot data in the communication data x (k) of pilot data, and L representes to be inserted with the pilot interval of the communication data x (k) of pilot data;

   Then, utilize the method shown in the formula (3) to eliminate the communication data x of underwater acoustic channel after to demodulation ₁(k) influence and obtain the communication data x through channel compensation ₂(k),

   x ₂(k)＝x ₁(k)/h(k) (3)

   10) frequency offset estimating in the signal processor and compensating module utilize the method shown in the formula (4) to estimate the communication data x through channel compensation ₂(k) frequency deviation

   

   Utilize the method shown in the formula (5) to communication data x then through channel compensation ₂(k) carry out compensate of frequency deviation and obtain new communication data x ₃(k):

   $\mathrm{\&Delta;}\hat{f}=\mathrm{angle}[\underset{M}{\mathrm{\&Sigma;}}{x}_{\mathrm{mL}}^{*}\&CenterDot;p_{\mathrm{mL}}]/(2\mathrm{\&pi;}\&CenterDot;T)---\left(4\right)$

   $x_3\left(k\right)=x_2\left(k\right)\&CenterDot;\exp (-j2\mathrm{\&pi;}\&CenterDot;\mathrm{\&Delta;}\hat{f}\&CenterDot;T)---\left(5\right)$

   In the formula (4), x _MLExpression is inserted with m pilot data among the communication data x (k) of pilot data,

   

   Be x _MLConjugation, p _MLExpression is through the communication data x of channel compensation ₂The data of m pilot frequency locations (k), angle representes to get the phase angle of formula in the square brackets, and T representes the duration of ofdm signal s (j); In the formula (5), j representes imaginary symbols.
3. 3. underwater acoustic communication method according to claim 2 is characterized in that: in step 1), the time span of said linear FM signal l (i) and the product of bandwidth are greater than 100.

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