CN103179067B - A kind of multi-system digital communication carrier modulation method - Google Patents

Abstract

The invention discloses a kind of multi-system digital communication carrier modulation method, step comprises: step 1, split linear frequency modulation phase shift keying carrier signal, and disassembly principle is, 1.1) paragraph header of each segment is identical with section tail; 1.2) carrier signal that each phase shift is corresponding is identical with the number of the binary number will encoded under this phase shifting scenarios by the hop count split; Step 2, will the carrier signal segment that obtains be split, successively be numbered according to its position in former linear frequency modulation phase shift keying carrier signal; Step 3, reconfiguring end to end for numbered for the tool obtained in step 2 carrier wave segment, requiring that the little segment number of the carrier wave of each recombination signal in same order is different, in order to make the otherness between each carrier signal waveform maximum.

Description

A kind of multi-system digital communication carrier modulation method

Technical field

The invention belongs to communication technical field, for linear frequency modulation phase shift keying carrier signal is carried out the difference splitting and reconfigure to improve different coding carrier signal, realize the method efficiently communicated with low error rate, be specifically related to a kind of multi-system digital communication carrier modulation method.

Background technology

Ocean area takes up an area more than 70% of sphere area, and along with human economy and social development, development and utilization ocean has become the important development strategy of various countries.The exploitation of marine resources be unable to do without subsurface communication, and underwater wireless communication becomes the new hot issue of Communication Studies.Communicate compared with (as mobile communication) with free space radio, because underwater acoustic channel is serious to electromagnetic wave attenuation, even if the ultralow frequency of selecting (being less than 10KHz), mix the transmitting power of MW class and huge antenna, also about 100 meters can only be transmitted in the seawater, data transmission rate is only about 100bits/s, and therefore subsurface communication generally adopts voice signal, i.e. underwater sound communication.Underwater acoustic channel has the features such as multi-path effect is remarkable, noise is complicated, Doppler frequency shift is serious, available bandwidth is little, and therefore, the communication means of a lot of free space maturation cannot be applicable to underwater acoustic channel.

At present, adopt the subsurface communication scheme that quaternary phase-shift keying (QPSK) is modulated, the equilibrium of passive type mirror time reversal is carried out decoding in conjunction with matched filtering to be widely used, but program error rate in low signal-to-noise ratio situation is larger.

Summary of the invention

The object of the present invention is to provide a kind of multi-system digital communication carrier modulation method, be reduced in the probability of matched filtering output error coupling under very noisy by the difference increased between modulation signal waveform thus reduce the error rate, also more information can be made to be encoded in carrier wave by increasing carrier wave difference simultaneously, improve the bit rate of information transmission.

The technical solution adopted in the present invention is, a kind of multi-system digital communication carrier modulation method, and the method is specifically implemented according to the following steps:

Step 1, linear frequency modulation phase shift keying carrier signal to be split

Disassembly principle is,

1.1) paragraph header of each segment is identical with section tail;

1.2) carrier signal that each phase shift is corresponding is identical with the number of the binary number will encoded under this phase shifting scenarios by the hop count split;

Step 2, to be numbered splitting the carrier signal segment that obtains

The carrier signal segment obtained will be split in step 1, successively be numbered according to its position in former linear frequency modulation phase shift keying carrier signal;

Step 3, by different order rearrange combination obtain multiple new carrier signal

Reconfigure end to end for numbered for the tool obtained in step 2 carrier wave segment, require that the little segment number of the carrier wave of each recombination signal in same order is different, make the otherness between each carrier signal waveform maximum.

The beneficial effect of the inventive method it is possible in underwater acoustic channel, realizes high rate of information transmission, low error rate underwater sound communication, and concrete advantage is:

1) obtain multiple different carrier signal achieve multilevel code on former phase shift keying carrier basis and modulation by splitting and recombinating on the basis of former phase shift keying carrier signal, improve the information transmission bit rate within the same carrier wave period exponentially, and then significantly improve communication speed.

2) compared with former phase shift keying carrier signal, expand the difference between different information carrier, thus distinguish more obvious after making to decode between different information carrier signal, easy matching and decoding, reduces the error rate of communication.

Accompanying drawing explanation

Fig. 1 is existing underwater sound communication system block diagram;

Fig. 2 is existing single-frequency frequency modulation carrier phase keying modulation waveform;

Fig. 3 is existing linear frequency modulation carrier phase keying modulation waveform;

Fig. 4 is existing passive type mirror time reversal channel equalization method schematic diagram;

Fig. 5 is that existing underwater sound communication information sends form schematic diagram;

Fig. 6 is the quaternary modulation carrier waveform of the inventive method embodiment;

Fig. 7 be the inventive method embodiment adopt initial phase be 0 the part octal system modulated carrier waveform that obtains through splitting and reorganizing of conventional linear frequency modulation quaternary carrier signal;

Fig. 8 is that the inventive method embodiment adopts initial phase to be the part octal system modulated carrier waveform that the conventional linear frequency modulation quaternary carrier signal of π obtains through splitting and reorganizing;

Fig. 9 be the inventive method embodiment adopt initial phase be 0 the new carrier waveform of part hexadecimal that obtains through splitting and reorganizing of linear frequency modulation quaternary carrier signal;

Figure 10 is that the inventive method embodiment adopts initial phase to be the new carrier waveform of part hexadecimal that the linear frequency modulation quaternary carrier signal of pi/2 obtains through splitting and reorganizing; ;

Figure 11 is that the inventive method embodiment adopts initial phase to be the new carrier waveform of part hexadecimal that the linear frequency modulation quaternary carrier signal of π obtains through splitting and reorganizing; ;

Figure 12 is that the inventive method embodiment adopts initial phase to be the new carrier waveform of part hexadecimal that the linear frequency modulation quaternary carrier signal of 3 pi/2s obtains through splitting and reorganizing; ;

Figure 13 is the inventive method underwater sound communication channel multi-path schematic diagram used;

Figure 14 is above-mentioned several embodiments error rate change curves in different state of signal-to-noise.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

As shown in Figure 1, be a typical underwater sound communication system structured flowchart of decoding based on the modulation of linear frequency modulation phase shift keying, the equilibrium of passive time reversal mirror and matched filtering.This underwater sound communication system is made up of emission system, underwater acoustic channel and receiving system.Emission system is encoded to digital binary signal, modulate, convert underwater sound signal to by underwater acoustic transducer again to send, the signal sent is through underwater acoustic channel, the underwater acoustic transducer of received system receives, Received signal strength is balanced and matched filtering decoding through passive time reversal mirror, recovers transmission signal.Simply introduce traditional quaternary phase shift keying modulator approach, passive time reversal mirror equalization methods and matched filtering coding/decoding method below.

As shown in Figure 2, be that a 11.5K hertz single-frequency cosine carrier has modulated two binary systems (00,01,10,11) information by different initial phase (0, pi/2, π, 3 pi/2s), corresponding to different subgraphs, code-element period is 0.348 millisecond; Fig. 3 then adopts linear frequency modulation cosine signal carrier wave to modulate two binary systems (00,01,10,11) information by different initial phase (0, pi/2, π, 3 pi/2s), and code-element period is 0.348 millisecond.In Fig. 3, carrier signal and Fig. 2 change to 18K hertz by 5K unlike adopted cosine signal frequency within four cycles.Contrast visible, in Fig. 3 between different information carrier waveform diversity ratio Fig. 2 in different information carrier different wave shape larger.

Passive type mirror time reversal channel equalization (PTRM) is the new technology occurred in Underwater acoustic signal processing in recent years, its maximum advantage can mate Acoustic channel adaptively when not having channel priori, and implementation space focuses on and time compress.

As shown in Figure 4, PTRM side's ratio juris is, arranges transmitting terminal and first launches known detectable signal p (t), and the impulse response of underwater acoustic channel is h (t), and detectable signal P (t) that receiving terminal receives is expressed as:

$P\left(t\right)=h\left(t\right)\⊗p\left(t\right)---\left(1\right)$

Symbol represent convolution algorithm.

P (t) elapsed time inversion structure preprocessor, the form of preprocessor is P (-t) and input signal convolution; Behind overprotection interval, launch information signal is s (t), and information signal S (t) that receiving terminal receives is:

$S\left(t\right)=s\left(t\right)\⊗h\left(t\right)---\left(2\right)$

S (t), through preprocessor, namely with P (-t) convolution, obtains preprocessor and exports:

$R\left(t\right)=S\left(t\right)\⊗P(-t)=s\left(t\right)\⊗h\left(t\right)\⊗p(-t)\⊗h(-t)=s\left(t\right)\⊗p(-t)\⊗\mathrm{\δ}\left(t\right)=s\left(t\right)\⊗p(-t)---\left(3\right)$

R (t) again with known detectable signal p (t) convolution, the equilibrium obtained export be:

$r\left(t\right)=R\left(t\right)\⊗p\left(t\right)=s\left(t\right)\⊗p(-t)\⊗p\left(t\right)=s\left(t\right)\⊗\mathrm{\δ}\left(t\right)=s\left(t\right)---\left(4\right)$

From deriving above, signal r (t) ideally after equilibrium is the s (t) that transmits, and therefore, utilizes PTRM equilibrium can recover transmitting after by underwater acoustic channel effect distortion at receiving terminal.

Become when underwater acoustic channel is, detectable signal original after certain hour just can not characterize the feature of present underwater acoustic channel, again will launch a detectable signal.Multipath component in order to avoid detectable signal interferes with the information signal launched subsequently, and detectable signal will wait for a protection interval T after launching ₁launch information signal again; In like manner, the multipath component in order to avoid information signal interferes with the detectable signal again launched, and will add a protection interval T after information signal ₂launch new detectable signal again.Protection interval T after information signal ₂be greater than the protection interval T after detectable signal ₁, because the number that information signal is launched is many, the strength ratio after multipath signal adds up is comparatively large, could not have influence on detectable signal subsequently behind longer protection interval.The form transmitted as shown in Figure 5, wherein T _pfor the emission duration of detectable signal, T ₁for the protection interval after detectable signal, T _sfor the emission duration of information signal, T ₂for the protection interval after information signal, the code-element period of detectable signal and information signal is T.

Matched filtering be used for the signal after to equilibrium carry out demodulation with obtain send information, concrete method obtains one group of reference signal at waveform time reversal of each information carrier signal of receiving terminal pre-stored (as shown in Figure 2 or Figure 3), passive type mirror time reversal equalizer exports and carries out matched filtering (namely carrying out convolution algorithm) with each reference signal respectively, there is peak-peak in the Waveform Matching filter result of the waveform of Received signal strength and which reference signal, then adjudicates as receiving this reference signal corresponding informance.

The present invention is directed to the modulating part of existing communication system, propose a kind of new multi-system digital communication carrier modulation method, traditional linear frequency modulation phase shift keying carrier signal is split as several sections according to the mode being convenient to be connected, and give different numberings to each section, then reconfigured according to different sequencings by these sections, the waveform obtained using different orders and different phase shifts is as the modulation waveform of different information coding.

Multi-system digital communication carrier modulation method of the present invention, specifically implement according to following steps:

Step 1, linear frequency modulation phase shift keying carrier signal to be split

Disassembly principle is,

1.1) paragraph header of each segment is identical with section tail (numerical value);

1.2) carrier signal that each phase shift is corresponding is identical with the number of the binary number will encoded under this phase shifting scenarios by the hop count split,

Such as select the carrier wave (upper left subgraph) of symbol 00 in Fig. 3, method for splitting is: get each peak point as fractionation point (as long as or to meet step 1.1 herein just passable, need not be peak point), can obtain four carrier wave segments, these four segments can obtain quaternary coding after step process below;

Note being peak value in quaternary embodiment, the fractionation point that just can have in octal system example is 0, also can obtain class sinusoidal signal.

Step 2, to be numbered splitting the carrier signal segment that obtains

To the carrier signal segment that obtains be split, successively be numbered according to its position in former linear frequency modulation phase shift keying carrier signal.

Such as the embodiment of step 1, the numbering of part between first peak point to second peak point is class cosine signal 1; In like manner, the part between the part between the part between second peak point to the 3rd peak point, the 3rd peak point to the 4th peak point, the 4th peak point to the 5th peak point is numbered class cosine signal 2, class cosine signal 3, class cosine signal 4 respectively;

Step 3, by different order rearrange combination obtain multiple new carrier signal

Reconfiguring end to end for numbered for the tool obtained in step 2 carrier wave segment, in order to make the otherness between each carrier signal waveform maximum, in the process reconfigured, requiring that the little segment number of the carrier wave of each recombination signal in same order is different,

Such as the signal segment that two step embodiments above obtain, rearrange according to the method provided in table 1, obtain four kinds of different carrier signals, be encoded to two bits, namely realize quaternary coding, the order provided according to table 1 carries out encoding the distinct symbols carrier waveform that obtains as shown in Figure 6.

The quaternary carrier wave coding restructuring sequence list of table 1, the inventive method embodiment

Carrier wave	Sequence number 1	Sequence number 2	Sequence number 3	Sequence number 4
					The carrier wave of information 00	Class cosine signal 1	Class cosine signal 2	Class cosine signal 3	Class cosine signal 4
The carrier wave of information 01	Class cosine signal 2	Class cosine signal 4	Class cosine signal 1	Class cosine signal 3
					The carrier wave of information 10	Class cosine signal 3	Class cosine signal 1	Class cosine signal 4	Class cosine signal 2
The carrier wave of information 11	Class cosine signal 4	Class cosine signal 3	Class cosine signal 2	Class cosine signal 1

So far, waveform corresponding to a symbol (00) of conventional linear frequency modulation phase shift keying carrier signal is only used just to achieve quaternary coding, by that analogy, the combination if corresponding waveforms of other symbols of further employing conventional linear frequency modulation phase shift keying carrier signal as above split and resequence, just can obtain 8 scale coding signals and 16 scale coding signals, corresponding distinct symbols coding waveforms is respectively as Fig. 7-Figure 12 provides.

Signal before splitting in Fig. 7-Fig. 8 adopts conventional linear frequency modulation quaternary carrier signal initial phase for 0 and two signals (in Fig. 3 signal shown in the subgraph of two, the left side) of π respectively, herein, carrier signal (in Fig. 3 signal shown in two subgraphs in the right) effect using initial phase to be pi/2 and 3 pi/2s is identical.

Fig. 9-Figure 12 is the new carrier signal adopting all four carrier signals in Fig. 3 to carry out splitting and reorganizing to obtain.Can to be encoded quaternary signal from carrier signal each in Fig. 9-12, Fig. 3,4 carrier signals just can obtain carrier waveforms different in 16, thus realize hexadecimal code.

The multi-system carrier wave more than obtained improves the efficiency of coding, makes the carrier signal in same time section to transmit more information, improves information transmission bit rate; Meanwhile, improve the difference between carrier signal, make through transmission distortion and very noisy environment under transmission, decode after can obtain lower transmission error rates.

In order to verify the superiority of the inventive method, under underwater acoustic channel environment, carried out contrast simulation, simulated environment is as follows: underwater acoustic channel design parameter is the depth of water 30 meters, and the water surface is tranquil, and water-bed smooth, in whole range of channels, the velocity of sound is 1480m/s; Horizontal range between transmitter and receiver is 650 meters; Transmitter adopts single transducer, and the degree of depth is 15 meters; Receiver adopts the transducer array of 9 transducer compositions, receiver using 9 receive MUT to signal carry out demodulation respectively through being superimposed again after PTRM equilibrium as Received signal strength, transducer array is bilateral symmetry distribution up and down centered by depth of water midpoint, 1.7 meters are spaced apart between transducer, transducer array receives relative to single transducer, greatly can improve the effect of PTRM equilibrium; Relative motion (Doppler frequency shift namely only caused by wave of the sea, marine turbulent flow, the Doppler frequency shift do not caused by relative motion between transmitter and receiver) is not had between transmitter and receiver; If multiple paths has three, its geometric representation as shown in figure 13.The time variable factor of three paths transmission losses meets rayleigh distributed, gets the parameter σ of rayleigh distributed respectively ₁=0.5, σ ₂=1.0, σ ₃=2.0.The time variable factor of propagation delay meets the white noise that average is 0, and variance is the Gaussian Profile of 0.01, represents that transmitter and receiver is between 1 centimetre to 5 centimetres with the distance that ripples fluctuate.Underwater acoustic channel noise average is 0, and signal to noise ratio is variable.Transmit form as shown in Figure 5, wherein T _p=0.348 millisecond, T ₁=50 milliseconds, T _s=250 milliseconds, T ₂=150 milliseconds, code-element period T=0.348 millisecond.

Under different state of signal-to-noise contrast simulation mono-frequency phase shift keyed carrier, conventional linear frequency modulation quaternary phase shift keying (QPSK) carrier wave, adopt the inventive method (as shown in Figure 6) quaternary carrier wave, adopt the inventive method (as shown in Figs. 7-8) octal system carrier wave and adopt the error rate of the inventive method (as shown in Fig. 9-Figure 12) hexadecimal carrier wave underwater sound communication system, result is as shown in figure 14.

In Figure 14, quaternary carrier method of the present invention is after signal to noise ratio is more than or equal to-12dB, and the error rate is 0, and transmission bit rate is identical with conventional linear frequency modulation quaternary phase-shift-keying method.Octal system carrier method of the present invention is after signal to noise ratio is more than or equal to 0dB, and the error rate is 0, and transmission bit rate is higher by 50% than conventional linear frequency modulation quaternary phase-shift-keying method.Hexadecimal carrier method of the present invention is suitable with the conventional linear frequency modulation quaternary phase-shift-keying method error rate, also basically identical with signal to noise ratio variation tendency, but information transmission bit rate is more than the twice of conventional linear frequency modulation quaternary phase-shift-keying method.Contrast simulation result is visible, and the inventive method has the lower error rate and the bit rate of Geng Gao than conventional linear frequency modulation QPSK method.

Claims (1)

1. a multi-system digital communication carrier modulation method, is characterized in that, the method is specifically implemented according to the following steps:

Step 1, linear frequency modulation phase shift keying carrier signal to be split

Disassembly principle is,

1.1) paragraph header of each segment is identical with section tail;

1.2) carrier signal that each phase shift is corresponding is identical with the number of the binary number will encoded under this phase shifting scenarios by the hop count split,

For quaternary modulation carrier waveform, method for splitting is: get each peak point as fractionation point, can obtain four carrier wave segments;

Step 2, to be numbered splitting the carrier signal segment that obtains

The carrier signal segment obtained will be split in step 1, successively be numbered according to its position in former linear frequency modulation phase shift keying carrier signal,

Be class cosine signal 1 by the numbering of part between first peak point to second peak point; In like manner, the part between the part between the part between second peak point to the 3rd peak point, the 3rd peak point to the 4th peak point, the 4th peak point to the 5th peak point is numbered class cosine signal 2, class cosine signal 3, class cosine signal 4 respectively;

Step 3, by different order rearrange combination obtain multiple new carrier signal

Reconfigure end to end for numbered for the tool obtained in step 2 carrier wave segment, be encoded to two bits, namely realize quaternary coding, the order provided according to table 1 carries out the distinct symbols carrier waveform obtained of encoding,

Table 1, quaternary carrier wave coding restructuring sequence list

Carrier wave Sequence number 1 Sequence number 2 Sequence number 3 Sequence number 4 The carrier wave of information 00 Class cosine signal 1 Class cosine signal 2 Class cosine signal 3 Class cosine signal 4 The carrier wave of information 01 Class cosine signal 2 Class cosine signal 4 Class cosine signal 1 Class cosine signal 3 The carrier wave of information 10 Class cosine signal 3 Class cosine signal 1 Class cosine signal 4 Class cosine signal 2 The carrier wave of information 11 Class cosine signal 4 Class cosine signal 3 Class cosine signal 2 Class cosine signal 1

, require that the little segment number of the carrier wave of each recombination signal in same order is different, make the otherness between each carrier signal waveform maximum.