CN101166065A - Deep sea remote water sound communication method - Google Patents

Abstract

This invention provides a blue water remote underwater communication method including: 1, combining frequency-expansion communication with a Pattern time delay difference coding underwater communication system and applying a work mode of M members, 2, applying a single array element PTRM channel balance technology at the receiving end, 3, analyzing character of blue-water tracks and pointing out that when a sound source is near a track shaft, regions along the shaft are gathered regions. Advantages: 1, communication rate is increased due to the frequency-expansion and the Pattern time delay difference coding method, 2, the single array element passive time reversing mirror can use multi-use expansion signals to suppress interference among codes and get gathered gain , 3, realizing stable remote communication by the character of blue-water communication.

Description

Deep sea remote water sound communication method

(1) technical field

The present invention relates to a kind of mechanics of communication, particularly a kind of water sound communication technique or rather, relates to a kind of method that realizes deep sea remote water sound communication.

(2) background technology

Information-based deep-sea resources exploitation, energy development are the projects of vital and lasting importance that is related to China's sustainable development.Develop the deep water hydrocarbon resource as early as possible, be related to and effectively alleviate the serious day by day petroleum resources of China situation in short supply, be related to the safety and the economic security of national petroleum resources.Exploitation deep-sea oil gas resource will have more complicated technology, needs lash ship, underwater operation robot and deep-sea fixing exploitation base station work compound.Deep sea remote water sound communication will provide transmission of monitoring, remote control and safety guarantee required information service, and its research is extremely urgent, will become one of central factor of restriction underwater information field development.

At present telecommunication just designs from communication technology angle, does not make full use of the deep-sea characteristic of channel, and remote water sound communication normally adopts spread spectrum technic or LFM signal, all is single by acquisition spread spectrum or related gain, with the raising communication distance.Though that spread spectrum communication has is anti-interference, anti-many ways, strong security and be easy to realize advantage such as code division multiple access, the underwater sound communication available band is limited, so the frequency expansion sequence pulsewidth is bigger usually, this will cause the traffic rate of spread-spectrum underwater sound communication very low.

The intersymbol interference that channel many ways expansion produces is one of major obstacle of underwater sound communication, especially prolongs, when each approach amplitude is big, underwater sound communication is had a strong impact on generation when many ways are expanded.As everyone knows, common filtering and raising transmitting power are inoperative to suppressing the interference of many ways.The simplest method that overcomes intersymbol interference is to leave sufficiently long wait time slot between each chip, make and expand maximum delay interval greater than many ways between its code element, promptly the multi-path signals of last code element disappears when next code element arrives, but this method can cause traffic rate very low.Adaptive channel equalizer is another technology that suppresses intersymbol interference, by estimation to channel impulse response, eliminate the channel effect in the received signal, thereby elimination intersymbol interference, but the common operand of blind equalization is big and need some prioris, but not blind equalization then needs to send learn sequence, does not reach the study stable state in case channel is too complicated, then can cause follow-up gross error.Above-mentioned anti-many ways interference method all is the angles from the inhibition multi-path signals, and fails to make full use of multi-path signals information.

In addition, communication sending and receiving internodal channel form is directly connected to the underwater sound communication quality, and the system function of channel is very responsive to the variation of the relative position of sound source and acceptance point, environmental parameter, velocity of sound distribution etc.Therefore, the research deep sea remote water sound communication is at first tackled the deep-sea characteristic of channel and is studied.Yet at present as yet not with the important research link of deep-sea characteristic of channel research as the realization deep sea remote water sound communication.

(3) summary of the invention

The object of the present invention is to provide a kind of shortcoming and defect that can overcome the remote water sound communication low rate of existing simple dependence spread spectrum; Can strengthen communication distance, improve communication quality; Can realize the deep sea remote water sound communication method of low bit error.

The object of the present invention is achieved like this:

(1) spread spectrum communication is combined with Pattern pattern time-delay coding underwater sound communication system, and adopt M unit working method;

(2) adopt single array element passive type mirror time reversal (PTRM) channel equalization technique at receiving terminal;

(3) analyze the deep ocean channel characteristic, point out when sound source is positioned near the sound channel axle, to be the convergence zone along the sound channel axle.

The present invention can also comprise:

1, described spread spectrum communication is combined with Pattern pattern time-delay coding underwater sound communication system, and adopt the cataloged procedure of M unit working method to be: produce M frequency expansion sequence, and generate spreading code with advantage correlated performance; By pre-transmission digital information b _cThe decision select a spreading code, and with it as Pattern, again by pre-transmission digital information b _pDetermine the time delay value of Pattern pattern time-delay coding; Encoded process obtains the information code signal, before emission information code signal, launches a LFM signal earlier, both as synchronous code, again as acquisition code.

2, describedly adopt single array element passive type mirror time reversal (PTRM) channel equalization technique to be at receiving terminal: at first receive detectable signal, and with its time counter-rotating as preprocessor; Subsequently with this preprocessor of information code signal process that receives; Its output is carried out convolution with acquisition code again, handles thereby finish passive type mirror time reversal.

3, before described analysis deep ocean channel characteristic is communication, carry out acoustic velocity measutement, obtain the sound channel shaft position degree of depth in pre-service area; The sending and receiving node is placed the sound channel axle.

Advantage of the present invention is mainly reflected in: compare with traditional spread spectrum communication (1), and spread spectrum and Pattern pattern time-delay coding communication means can effectively improve its traffic rate among the present invention; (2) compare with conventional anti-many ways interference method, single array element passive type mirror time reversal among the present invention can make full use of many ways spread signal, has both effectively suppressed intersymbol interference, obtains to assemble gain again and has improved signal to noise ratio; (3) by in conjunction with the deep-sea characteristic of channel, more help realizing sane telecommunication.

(4) description of drawings

Fig. 1 is the spread spectrum Pattern of M unit pattern time-delay coding Principle of Communication figure;

Fig. 2 is a passive type mirror time reversal theory diagram;

Fig. 3,4, the 5th, the deep-sea velocity of sound distributes and channel impulse response, and wherein: Fig. 3 is the sound velocity profile at the South Sea, and the sound channel axle is positioned under water about 1000m; Fig. 4 all is positioned at sound channel axle, horizontal range 30km for the sending and receiving node, the channel impulse response that utilizes ray models to obtain; Fig. 5 is positioned at the stationary nodes of sound channel axle and is positioned at channel impulse response between certain user node of 150m Hai Shen, and its horizontal range also is 30km;

Fig. 6 is the system block diagram of deep sea remote water sound communication;

Fig. 7, the 8th, the deep-sea ray picture, wherein: the ray picture when Fig. 7 is positioned at the sound channel axle for sound source; Fig. 8 is positioned at the dark ray picture of 150m for sound source;

Fig. 9,10 is deep-sea acoustic propagation loss curve, wherein: near the propagation loss when Fig. 9 is positioned at the sound channel axle for sound source, Figure 10 is positioned at the propagation loss of 150m when dark for sound source;

Figure 11,12 is channel time reversal, and wherein: Figure 11 is the time inverse channel of Fig. 4 correspondence, and Figure 12 is the time inverse channel of Fig. 5 correspondence;

Figure 13,14,15 is the relevant output of the copy under the different signal to noise ratios (the sending and receiving node all is positioned at the sound channel axle), wherein: Figure 13 SNR=0dB, Figure 14 SNR=-5dB, Figure 15 SNR=-10dB.

(5) embodiment

For example the present invention is done description in more detail below in conjunction with accompanying drawing:

1, the spread spectrum Pattern of M unit pattern time-delay coding communication

The M element spread spectrum communication is the multi-system spread spectrum communication, and a plurality of information bits transmit with a spreading code, and it has improved transmission rate with respect to traditional spread spectrum communication, is suitable for the underwater sound environment that bandwidth has strict restriction, has stronger antijamming capability.

This communication means selects for use the M element spread spectrum communication combined with Pattern pattern time-delay coding underwater sound communication system, promptly obtained the characteristic that spread spectrum communication can be competent at telecommunication, effectively improved spread spectrum communication speed again.The Pattern pattern time-delay coding (Pattern Time Delay Shift Coding, PDS) the underwater sound communication system belongs to arteries and veins position coding, and information is modulated in the delay inequality information that code element appears at the code element window, each symbol width T ₀By Pattern sign indicating number type pulsewidth T _pWith scramble time T _cConstitute, i.e. T ₀=T _p+ T _cIf with the Pattern code element of spreading code, carry out the PDS secondary coding again after then can finishing spread spectrum coding as the PDS system.Fig. 1 has provided the spread spectrum Pattern of M unit pattern time-delay coding Principle of Communication figure.

C among Fig. 1 ₁, c ₂..., c _MBe M spreading code, they have good auto-correlation and cross-correlation performance.The information code that sends is selected one as Pattern sign indicating number type by the coding selector according to the information that transmits from this M spreading code, this spreading code amount of information of carrying is log like this ₂M bit is designated as b _cCarry out the Pattern pattern time-delay coding with this spreading code as Pattern sign indicating number type, promptly finish coding digital information for the second time, be designated as b _pThe information code that receives is through M copy correlator, by detecting the type that the relevant peaks maximum rules out yard, the digital information b that translates this yard type correspondence _c, and measure the time delay difference of this spreading code correspondence, and finish PDS decoding, obtain digital information b _p

In addition, the code element duty ratio of spread spectrum Pattern pattern time-delay coding communication can be saved power consumption less than 1, and this is useful for the underwater sound communication node of pursuing in low-power consumption.

2, single array element passive type mirror time reversal technology

Time reversal, mirror mated " the best " room and time filter with the sound channel.This method proposes to adopt single array element to realize passive type mirror time reversal (PTRM), both can satisfy the underwater sound communication node and pursue the requirement of simple in structure and low-power consumption, can realize the effect of adaptive equalization sound channel again, when suppressing intersymbol interference, can improve signal to noise ratio, thereby increase communication distance.

Sound source is preceding at emission information code signal s (t), and first emission one detectable signal p (t) constructs a preposition preprocessor time reversal with the detectable signal that receives and realizes that passive type handles time reversal.Its theory diagram as shown in Figure 2.

The detectable signal p that receives _r(t) and information code signal s _r(t) be expressed as respectively:

$\left\{\begin{array}{c}{p}_r\left(t\right)=p\left(t\right)\⊗h\left(t\right)+n_p\left(t\right)\\ s_r\left(t\right)=s\left(t\right)\⊗h\left(t\right)+n_s\left(t\right)\end{array}\right.---\left(1\right)$

Symbol in the formula

The expression convolution algorithm, n _p(t), n _s(t) be respectively the local interference noise of stack; H (t) is the impulse response function of many ways sound channel, and total received signal is all the interference stacks along different approaches, the different signals that arrive constantly by acceptance point.

With P _r(t) obtain p time reversal _r(-t) stored the system function as preprocessor then, and with s _r(t) through preprocessor, be output as:

$r_1\left(t\right)=s_r\left(t\right)\⊗p_r(-t)(-t)]$

(2)

$=s\left(t\right)\⊗p(-t)\⊗[h\left(t\right)\⊗h(-t)]+n_1\left(t\right)$

In the formula $n_1\left(t\right)=s_r\left(t\right)\⊗n_p(-t)+p_r(-t)\⊗n_s\left(t\right)$ Be the noise jamming item;

Be the auto-correlation function of channel impulse response function, be equivalent in time the many ways spread signal that receives carried out compression, same-phase stack that its relevant peaks can be similar to it and be considered as the δ function apparently higher than secondary lobe, this up-to-date style (2) can be written as:

$r_1\left(t\right)\≅s\left(t\right)\⊗p(-t)\⊗\mathrm{\δ}\left(t\right)+n_1\left(t\right)---\left(3\right)$

Then preprocessor output is made convolution algorithm with p (t), is output as:

$r\left(t\right)=r_1\left(t\right)\⊗p\left(t\right)=s\left(t\right)\⊗p(-t)\⊗p\left(t\right)+n_1\left(t\right)\⊗p\left(t\right)---\left(4\right)$

Select for use linear FM signal as detectable signal p (t), its frequency band that takies should comprise the frequency band that information code signal s (t) takies.Because $p\left(t\right)\⊗p(-t)\≈\mathrm{\δ}\left(t\right),$ So formula (4) can be written as:

$r\left(t\right)\≅s\left(t\right)\⊗\mathrm{\δ}\left(t\right)+n\left(t\right)---\left(5\right)$

In the formula $n\left(t\right)=n_1\left(t\right)\⊗p\left(t\right)$ Be the noise jamming item.At this moment, the signal component among the r (t) has been approximately information code waveform s (t).

Single array element mirror time reversal can only utilize two internodal multi-path signalses, handles with basic matrix and compares, and the space-focusing gain that this has also sacrificed basic matrix causes secondary lobe to uprise.

Following analysis list array element mirror time reversal focuses on the focusing gain that multi-path signals obtains.If each approach noise component(s) signal to noise ratio independent and each approach signal is identical, the detectable signal p that receives after propagating of channel then _r(t) can be expressed as:

$p_r\left(t\right)=p\left(t\right)\⊗h\left(t\right)+n\left(t\right)=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}[A_{i}p(t-{\mathrm{\τ}}_i)+n_i\left(t\right)]---\left(6\right)$

Wherein the noise component(s) of each approach satisfies:

E[n _i(t)n _j(t)]＝0，i≠j?(7)

Each approach Signal-to-Noise satisfies:

${\mathrm{<figure-callout\; id="1"\; label="SNR"\; filenames="A20071007255600112.png,A20071007255600114.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_1=\frac{{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="A20071007255600112.png,A20071007255600114.png"\; state="\{\{state\}\}">A</figure-callout>}}_1^2}{{\mathrm{\&sigma;}}_1^2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="A20071007255600114.png,A20071007255600115.png"\; state="\{\{state\}\}">A</figure-callout>}}_2^2}{{\mathrm{\&sigma;}}_2^2}=......=\frac{A_i^2}{{\mathrm{\&sigma;}}_i^2}=\frac{A_{i+1}^2}{{\mathrm{\&sigma;}}_{i+1}^2}=......=\frac{{\mathrm{<figure-callout\; id="2"\; label="A\; N"\; filenames="A20071007255600114.png,A20071007255600115.png"\; state="\{\{state\}\}">A</figure-callout>}}_N^{}}{{\mathrm{\&sigma;}}_N^2}---\left(8\right)$

σ in the formula _i ²Be i approach noise component(s) n _i(t) variance.

After handling time reversal, the same-phase stack simultaneously of each multi-path signals, signal output can be expressed as after time reversal, mirror was handled:

$r\left(t\right)=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_{i}p\left(t\right)+\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{n}_i\left(t\right)---\left(9\right)$

Its signal to noise ratio is:

${\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="A20071007255600114.png,A20071007255600115.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_2={\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_i\right)}^2/\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_i^2\right)---\left(10\right)$

Can get by formula (8):

$\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_i^2=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{A_i^2}{A_1^2}{\mathrm{\&sigma;}}_1^2=\frac{{\mathrm{\&sigma;}}_1^2}{A_1^2}\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_i^2---\left(11\right)$

Then formula (10) can be expressed as:

${\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="A20071007255600114.png,A20071007255600115.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_2={\frac{A_1^2}{{\mathrm{\&sigma;}}_1^2}\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_i\right)}^2/\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_i^2\right)$

$=\frac{A_1^2}{{\mathrm{\&sigma;}}_1^2}(\underset{i=1}{\overset{\mathrm{<figure-callout\; id="2"\; label="N\; A\; i"\; filenames="A20071007255600114.png,A20071007255600115.png"\; state="\{\{state\}\}">N</figure-callout>}}{\mathrm{\&Sigma;}}}{A}_i^{}{}_2^{}+\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{j\&NotEqual;i}{\overset{N}{\underset{j=1}{\mathrm{\&Sigma;}}}}{A}_i{A}_j)/\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_i^2\right)---\left(12\right)$

$=\frac{A_1^2}{{\mathrm{\&sigma;}}_1^2}[1+\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{j\&NotEqual;i}{\overset{N}{\underset{j=1}{\mathrm{\&Sigma;}}}}{A}_i{A}_j\right)/\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_i^2\right)]$

Its decibel form is:

${\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="A20071007255600114.png,A20071007255600115.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_2={\mathrm{<figure-callout\; id="1"\; label="SNR"\; filenames="A20071007255600112.png,A20071007255600114.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_1+{10\log }_{10}[1+\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{j\&NotEqual;i}{\overset{N}{\underset{j=1}{\mathrm{\&Sigma;}}}}{A}_i{A}_j\right)/\left(\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{A}_i^2\right)]---\left(13\right)$

Can see that from the above analysis single array element mirror time reversal has been realized rake, signal to noise ratio snr after handling ₂〉=SNR ₁(during no multi-path signals, "=" sets up).Right second of formula is focusing gain, and its value is relevant with the quantity and the amplitude of multi-path signals, and promptly in the focusing process, many ways effect that the waveguide border produces has strengthened the energy of mirror focus signal time reversal, has more focusing effect than free field (Free-space) environment.So channel is complicated, single array element mirror time reversal focusing effect is good more.

In sum, though mirror time reversal that single array element constitutes can not get the spatial gain that time reversal, the mirror battle array was handled, causing secondary lobe to be higher than battle array handles, but still can be in the underwater sound communication with the multi-path signals same-phase stack simultaneously that produces via the sound channel if be applied to, compressed signal in time, eliminate intersymbol interference, and can improve signal to noise ratio, when especially near the node stationary cloth is put in the deep ocean channel axle, communicating, the mirror technology will be more suitable time reversal, help realizing long-range, high quality water sound communication.

3, deep-sea underwater acoustic channel specificity analysis

From the viewpoint of theory of communication, the ocean is exactly the sound channel, and the underwater sound communication quality is to a great extent by underwater acoustic channel characteristic decision, so to the research of the characteristic of channel and how to utilize the characteristic of channel be of great value to improve communication quality.

In resource mineral reserve district, the South Sea, the sea all has the typical deep ocean channel velocity of sound to distribute and appearance throughout the year deeply all above 2000m.There is a minimum in deep-sea velocity of sound distribution curve, and its residing degree of depth is called the sound channel axle.Refraction effect has reflected that sound ray is tending towards bending towards the little water layer of the velocity of sound in communication process, in deep ocean channel, the part sound ray that starts from the sound source that is positioned at the sound channel axle is not retained in sound channel owing to standing the caused acoustical energy losses of sea and sub-bottom reflection, propagation loss is less, can pass farly, and many ways effect of the convergence zone in sound channel is less relatively.Utilize the deep-sea characteristic of channel, this paper proposes the stationary nodes of underwater sound communication net is placed the communication plan of sound channel axle.Fig. 3 is the sound velocity profile at the South Sea, and the sound channel axle is positioned under water about 1000m; Fig. 4 all is positioned at sound channel axle, horizontal range 30km for the sending and receiving node, the channel impulse response that utilizes ray models to obtain; Fig. 5 is positioned at the stationary nodes of sound channel axle and is positioned at channel impulse response between certain user node of 150m Hai Shen, and its horizontal range also is 30km.

As can see from Figure 4, the sound ray of propagating along the sound channel axle arrives in evening because acoustic velocity is minimum, and since without boundary reflection the energy loss minimum, so energy wants big many than other multi-path signalses; In addition, the many ways expansion of the channel of Fig. 4 wants simple many with respect to Fig. 5.

In deep ocean channel, the impulse response function of channel is very stable, sound rises and falls little.For underwater sound communication, if the sending and receiving node is all placed near the sound channel axle, be that expansion intersymbol interference of causing in many ways is little on the one hand, be propagation loss is little on the other hand.So this paper proposition places stationary nodes near the sound channel axle, helps realizing long-range, high quality water sound communication, have important practical and be worth.

Fig. 6 shows the system block diagram of deep sea remote water sound communication of the present invention, with reference to this figure and embodiment, the present invention is described in further detail.

(1) carries out acoustic velocity measutement in pre-communication work district, obtain the sound channel shaft position degree of depth, the sending and receiving node is placed the sound channel axle.

Deep ocean channel is made of the characteristic that the deep-sea velocity of sound distributes.The deep-sea velocity of sound distributes and has a minimum, and the water layer at its place is called the sound channel axle.Refraction effect has determined sound ray to be tending towards bending towards the less water layer of the velocity of sound in communication process, thereby in deep ocean channel, a part of sound ray that starts from sound source is not retained in the sound channel owing to standing the caused acoustical energy losses of sea and sub-bottom reflection.Because propagation loss is less, when sound source is positioned near the sound channel axle, be the convergence zone especially along the sound channel axle, acoustical signal can pass farly along the sound channel axle, and less in the channel impulse response effective width of sound channel convergence zone.The sound velocity profile at certain South Sea as shown in Figure 3, its sound channel axle is about the 1000m degree of depth.Fig. 7,8 is for its sound source is positioned near the sound channel axle and ray picture when being positioned at the sea, and Fig. 9,10 is their corresponding propagation loss figure.

Can see along the sound channel axle by Fig. 7, on all distances, all be convergence zone almost, its propagation loss is shown in Fig. 9, can see along the propagation loss of sound channel axle very little, the propagation loss at 60km place has only 86dB, with Figure 10 contrast, under the same distance, the propagation loss when the sending and receiving node all is positioned at the sound channel axle is obviously little as can be seen.So, then can realize remote water sound communication if communication node is laid on the sound channel axle.

(2), produce M frequency expansion sequence, and generate spreading code, note c with advantage correlated performance at transmitting terminal ₁, c ₂..., c _MBy pre-transmission digital information b _cThe decision select a spreading code, and with it as Pattern, again by pre-transmission digital information b _pDetermine the time delay value of Pattern pattern time-delay coding, finish the PDS coding, obtain information code signal s (t).

The M value is 2 integral number power.With M=8 is example, if binary digital information b _cC is then selected in=[000] ₁As the Pattern sign indicating number, if b _cC is then selected in=[101] ₄As the Pattern sign indicating number.

Beg for below with embodiment the traffic rate of the spread spectrum Pattern of M unit pattern time-delay coding communication once is discussed.

If spreading code pulsewidth T _p=128ms; PDS scramble time T _c=32ms, time quantization layer Δ τ=1ms, then the PDS coding carries information n=log ₂(T _c/ Δ τ)=5bit.If adopt the communication of BPSK coding spread spectrum, then spread spectrum communication speed is about 1/T _p≈ 8bit/s; If press this paper scheme, each spreading code is increased the PDS scramble time of 32ms, then the pulsewidth T of each information code element ₀=160ms, each information code element carry amount of information increases 5bit, and this moment, the traffic rate of spread spectrum Pattern pattern time-delay coding was (1+5)/T ₀≈ 38bit/s, traffic rate improve about 3.5 times.If system adopts 8 systems (M=8) spread spectrum coding mode, then can further improve traffic rate, be (3+5)/T ₀=50bit/s; Adopt 16 systems (M=16) spread spectrum coding mode, traffic rate is (4+5)/T ₀=56.25bit/s.Frequency expansion sequence has good multiple access characteristic, if adopt multichannel to work simultaneously again, then traffic rate can be multiplied on this basis again.

Behind given Pattern sign indicating number pulsewidth and the coded quantization layer, can determine that best PDS coding bit counts n, so that spread spectrum Pattern pattern time-delay coding communication system traffic rate is the highest.By simulation analysis as can be known, along with the spreading code pulsewidth increases, the multiple that then combines back traffic rate raising with PDS coding system is obvious more.For example establishing the spreading code pulsewidth is 256ms, and then spread spectrum communication speed is about 4bit/s; It is 6 that at this moment best PDS coding bit counts n, and promptly each spreading code need be increased the PDS scramble time of 64ms, the pulsewidth T of each information code element ₀=320ms, this moment, the traffic rate of spread spectrum Pattern pattern time-delay coding was about (1+6)/T ₀≈ 22bit/s has improved 4.5 times.When especially less or desire improves communication distance when system bandwidth (spreading gain is the product of spread spectrum bandwidth and spreading code pulsewidth), the spreading code pulsewidth is about second-time, the PDS scramble time that increases a few tens of milliseconds then can increase a few bit information, is very significant to improving traffic rate.

(3) before emission information code signal, emission one LFM signal both as synchronous code, again as acquisition code, is remembered p (t) earlier.

(4) at receiving terminal, with detectable signal time reversal of receiving as preprocessor; Subsequently with this preprocessor of information code signal process that receives; Its output is carried out convolution with acquisition code p (t) again, handles thereby finish passive type mirror time reversal.The output signal of passive type mirror time reversal focuses on many ways spread signal, has both suppressed intersymbol interference, has improved signal to noise ratio again.

The channel impulse response of the deep-sea sound channel shown in Fig. 4,5, inverse channel when pairing

Shown in Figure 11,12.The time inverse channel

Be near desirable, it has only a main peak, and side lobe levels is very little, obtains " focusings " effect of multi-path signals energy, thus the time error rate of communicating by letter after the anti-mirror equilibrium can significantly reduce, and can improve signal to noise ratio.

(5) with time reversal the mirror output signal send into the copy correlator bank.With transmitting terminal b _c=[1 0 1], select c ₄Be example, then, can determine that Pattern is spreading code c by the maximum judgement ₄Thereby, demodulate digital information b _cMeasure the time delay difference of this spreading code correspondence simultaneously, finish PDS decoding, obtain digital information b _p

When Figure 13,14,15 has provided the sending and receiving node and all has been positioned at the sound channel axle, the output waveform figure of being correlated with of the copy under different signal to noise ratios.Emulation added up system at the deep-sea, the error rate of communication distance 30km: if single channel work (traffic rate 50bit/s), when received signal to noise ratio approaches 0 error code during greater than 0dB, when received signal to noise ratio during for-10dB the error rate be 10 ^-4About; If 6 passages work (traffic rate 300bit/s) simultaneously, when received signal to noise ratio during greater than 0dB, the error rate is about 10 ^-3

Claims (5)

1. deep sea remote water sound communication method is characterized in that:

(1) spread spectrum communication is combined with Pattern pattern time-delay coding underwater sound communication system, and adopt M unit working method;

(2) adopt single array element passive type mirror time reversal channel equalization technique at receiving terminal;

(3) analyze the deep ocean channel characteristic, utilize near the characteristic that when sound source is positioned at the sound channel axle, is the convergence zone along the sound channel axle.

2. deep sea remote water sound communication method according to claim 1, it is characterized in that: described spread spectrum communication is combined with Pattern pattern time-delay coding underwater sound communication system, and adopt the cataloged procedure of M unit working method to be: to produce M frequency expansion sequence, and generate spreading code with advantage correlated performance; By pre-transmission digital information b _cThe decision select a spreading code, and with it as Pattern, again by pre-transmission digital information b _pDetermine the time delay value of Pattem pattern time-delay coding; Encoded process obtains the information code signal, before emission information code signal, launches a LFM signal earlier, both as synchronous code, again as acquisition code.

3. deep sea remote water sound communication method according to claim 1 and 2 is characterized in that: describedly adopt single array element passive type mirror time reversal channel equalization technique to be at receiving terminal: at first receive detectable signal, and with its time counter-rotating as preprocessor; Subsequently with this preprocessor of information code signal process that receives; Its output is carried out convolution with acquisition code again, handles thereby finish passive type mirror time reversal.

4. deep sea remote water sound communication method according to claim 1 and 2 is characterized in that: before described analysis deep ocean channel characteristic is communication, carry out acoustic velocity measutement in pre-service area, obtain the sound channel shaft position degree of depth; The sending and receiving node is placed the sound channel axle.

5. according to claim 3 or 2 described deep sea remote water sound communication methods, it is characterized in that: before described analysis deep ocean channel characteristic is communication, carry out acoustic velocity measutement, obtain the sound channel shaft position degree of depth in pre-service area; The sending and receiving node is placed the sound channel axle.

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