CN101399795A - Modulating and demodulating method for orthogonal differential chaos phase shift-keying of digital signal - Google Patents

Abstract

The invention discloses a digital signal orthogonal differential chaos shift keying modulation and demodulation method, namely, chaos phase is used for coding a multidigit binary number, orthogonal transform is carried out on a chaos sequence for generating a new sequence, and mutually orthogonally orthogonal basis functions which are used as carriers are formed with the original chaos sequence for modulation and demodulation. Compared with a quadruple chaos shift keying (QCSK), the invention improves the bandwidth utility ratio, increases the transmission speed, and reduces the error rate to a certain extent.

Description

Modulating and demodulating method for orthogonal differential chaos phase shift-keying of digital signal

Technical field

The invention belongs to the chaotic signal communications field, is that a kind of CHAOTIC PHASE and orthogonal method of utilizing carries out the method for modulation and demodulation to digital signal, is a kind of modulating and demodulating method for orthogonal differential chaos phase shift-keying of digital signal specifically.Because chaotic signal makes this modulation system have the good broadband characteristic, can be applied in the various wireless communication system.

Technical background

In recent years, the chaotic communication technology has become one of research focus.With respect to conventional communication techniques, chaotic communication system has good confidentiality, advantages such as strong interference immunity.Because up to now, under actual channel condition, still lack effectively reliable method and realize that at receiving terminal chaos is synchronous, thereby carry out the demodulation of signal.Therefore, existing research is many based on asynchronous method.Wherein, the method that difference is relevant is exactly a perfect method, as differential Chaos Shift Keying (Differential Chaos Shift-Keying:DCSK), can reach the best bit-error rate performance of chaos digital communication system under Gaussian channel at that time.But because when transmitting signal, half is a reference signal to differential Chaos Shift Keying (DCSK) in one-period, and second half is only real modulation signal, so its band efficiency is low.So, the two kinds of modulation-demo-demodulation methods that can increase operation rate have been developed out, four phase chaos shift keyings (Quadrature Chaos Shift-Keying:QCSK) and difference chaotic phase shift keying (Differential Chaos Phase Shift-Keying:DCPSK).The former utilizes the two-way chaotic signal of quadrature to modulate and transmit simultaneously, reach the effect that channel utilization becomes differential Chaos Shift Keying (DCSK) twice, but its bit error rate performance is unsatisfactory.The mode that the latter utilizes CHAOTIC PHASE and traditional M unit's phase shift keying (Phase Shift-Keying:PSK) to combine has especially improved band efficiency to a certain extent, and has also reached effect preferably.But these two kinds of methods still have improved space, and under the situation of current band resource growing tension, also need the higher modulation-demo-demodulation method of band efficiency to produce.Simultaneously, it is just feasible that its bit error rate performance also will reach certain level, even it is then better to surpass existing chaos modulation.

Summary of the invention

The objective of the invention is to overcome the technological deficiency that prior art exists, in conjunction with four phase chaos shift keyings (QCSK) and difference chaotic phase shift keying (DCPSK), a kind of digital signal orthogonal differential chaos phase shift keying (Quadrature Differential Chaos Phase Shift-Keying:QDCPSK) modulation-demo-demodulation method is proposed, when having both advantages, make the availability of frequency spectrum further improve, the broadband character of better utilization chaotic signal.And better anti-interchannel noise ability is arranged under certain condition.

The definition CHAOTIC PHASE is the particular state on the chaos locus, is exactly the specific moment in time.By information being embedded in the transmission of the information that can realize on the different CHAOTIC PHASE points.Chaos shift keying (QCSK) is similar mutually with four for the orthogonal differential chaos phase shift keying (QDCPSK) that the present invention proposes, and the chaos waveform of each sign bit correspondence all comprises reference signal section and information carrying signal section.But the modulation of information is to realize by the phase deviation between information-bearing section and reference field.Add mutually orthogonal two-way and transmit information simultaneously.

Two key technologies:

1, orthogonal differential chaos phase shift keying (QDCPSK) has two paths of signals to transmit simultaneously, is respectively in-phase signal and orthogonal signalling.The information that two-way is transmitted is not disturbed mutually, needs orthogonal basis function C=[c _x(t), c _y(t)], its orthogonality satisfies in the cycle in half symbols

${\∫}_0^{T/2}{c}_x^2\left(t\right)\mathrm{dt}={\∫}_0^{T/2}{c}_y^2\left(t\right)\mathrm{dt}=1$

${\∫}_0^{T/2}{c}_x\left(t\right)c_y\left(t\right)\mathrm{dt}=0$

And c _x(t), c _y(t) two signals all have the characteristic of chaotic signal.Its realization can be by c _x(t) produce c through the Hilbert conversion _y(t), also can directly use iir filter to carry out conversion in time domain.

2, a mistake! Do not find Reference source.It is one tunnel signal structure in the orthogonal differential chaos phase shift keying (QDCPSK) modulated mutually of M.Choose M phase point p in the reference signal section ₀, p ₁..., p _M-1,,, from reference field, select the start-phase p of a phase place as the message segment chaotic signal according to the symbol that transmits in the information-bearing section _m, circulation sends the chaotic signal p in the reference field then _m, p _M+1..., p _M+j..., p _M+M-1, wherein, p _M+j=p _{(m+j) mod M}, can represent log altogether ₂M bit.In the start-phase of receiving terminal, just can demodulate the information that is transmitted like this by detection received signal message segment.

The modulation of digital signal orthogonal differential chaos phase shift keying:

1, the chaotic signal that produces according to chaos signal generator uses orthogonal transform to produce the two-way orthogonal basis;

2, produce various CHAOTIC PHASE signal respectively according to the two-way orthogonal basis;

3, carry out CHAOTIC PHASE MODULATED according to the information that will transmit, select corresponding CHAOTIC PHASE signal respectively according to the symbol that is transmitted with two phase encoders; Each phase encoder is represented log ₂M bit, two phase encoders can be represented 2log altogether ₂M bit;

4, the two-way of quadrature is passed through the signal plus of CHAOTIC PHASE MODULATED, and send transmission signals as requested; Be specially: the preceding half period sends the reference signal section; The later half cycle sends the information carrying signal section through the modulation of quadrature chaos phase shift keying;

Transmission signals is expressed as the linear combination of orthogonal basis, i.e. c _x(t+p _Mx)+c _y(t+p _My); Can obtain the signal of QDCPSK thus through ovennodulation

$S_{\mathrm{QDCPSK}}\left(k\right)=\left\{\begin{array}{cc}\sqrt{E_b}{c}_x\left(k\right),& 0\&le;k<L\\ \begin{array}{c}\sqrt{E_b}(c_x\left((k-L+p_{\mathrm{mx}})\mathrm{mod}L\right)\\ +c_y\left((k-L+p_{\mathrm{my}})\mathrm{mod}L\right))\end{array}& ,L\&le;k<2L\end{array}\right.$

Wherein, L is the chaos sample value number that is produced in the half symbols cycle (T/2), E _bBe the energy of sample value function in the symbol period, p _MxAnd p _MyBe respectively the expression of Chaos Modulation phase place under discrete time of in-phase branch and quadrature branch, be equivalent to one section time-delay of signal;

5, at last modulation signal is gone out by antenna transmission.

The demodulation of digital signal orthogonal differential chaos phase shift keying

1, by antenna receiving signal, the preceding half period of received signal wherein, promptly the reference signal section produces the two-way orthogonal basis after by orthogonal transform again;

2, reference field signal and message segment signal are defeated by two CHAOTIC PHASE detection modules respectively; In in-phase branch, import former reference field signal and message segment signal; In quadrature branch, reference field signal and message segment signal after the input orthogonal transform are with the contained information of the quadrature component in the demodulated received signal;

3, CHAOTIC PHASE detection module produces M different CHAOTIC PHASE signal with the reference field signal, and carries out relevantly with the message segment signal respectively, and the M that an obtains correlation selects wherein the maximum correlation value corresponding symbol (as z0 correspondence s ₀, z ₁Corresponding s ₁..., z _M-1Corresponding s _M-1) as information symbol output, promptly

$Z=z_i=\underset{j}{\max }{z}_j,$ S＝s _i

Wherein, j=0,1 ..., M-1.

4, orthogonal differential chaos phase shift keying (QDCPSK) has the two-way CHAOTIC PHASE to detect; The output z of j correlator of homophase and quadrature branch in the demodulator _Jx, z _JyBe respectively

$z_{\mathrm{jx}}=\underset{k=0}{\overset{L-1}{\mathrm{\&Sigma;}}}[S_{\mathrm{QDCPSK}}(k+p_{\mathrm{jx}})+n\left(k\right)][S_{\mathrm{QDCPSK}}(k+L)+n\left(k\right)]$

$z_{\mathrm{jy}}=\underset{k=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{[S_{\mathrm{QDCPSK}}(k+p_{\mathrm{jy}})+n\left(k\right)]}^{*}[S_{\mathrm{QDCPSK}}(k+L)+n\left(k\right)]$

Wherein [] ^*The expression orthogonal transform.Judge that through above-mentioned maximum the back obtains symbol S again _x=s _IxAnd S _y=s _Iy, combination is finished demodulation after parallel/serial conversion restores the information bit of transmission.

The present invention can improve the speed and the band efficiency of transmission, and the bit number that each symbol comprised rises to 2log ₂M.By adjusting parameter M, the bit number that each symbol is comprised is much higher than 1 bit of DCSK, 2 bits of QCSK and the log of DCPSK ₂The M bit.

The bit error rate performance aspect, the chaos sample value number L that is produced in the half symbols cycle (T/2) is bigger, and parameter M is better than other chaos communication method under Gaussian channel also bigger the time.

Description of drawings

Fig. 1, be orthogonal differential chaos phase shift keying (QDCPSK) modulating signal phase structure.

Fig. 2, CHAOTIC PHASE generation module block diagram.

The modulation block diagram of Fig. 3, orthogonal differential chaos phase shift keying (QDCPSK).

Fig. 4, CHAOTIC PHASE detection module block diagram.

The demodulation block diagram of Fig. 5, orthogonal differential chaos phase shift keying (QDCPSK).

Fig. 6, orthogonal differential chaos phase shift keying (QDCPSK) and differential Chaos Shift Keying (DCSK), four mutually chaos shift keying (QCSK) and difference chaotic phase shift keying (DCPSK) bit error rate performance relatively.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail.

Embodiment: select orthogonal transform to use the Hilbert conversion, during the chaos sample value number L=64 that produced in the half symbols cycle (T/2), adopt the condition of getting M=4 and to implement respectively at 8 o'clock.

Transmitting terminal

1, the chaotic signal that produces according to chaos signal generator uses the Hilbert conversion to produce the two-way orthogonal basis, in [0, T] in the time, and c _x(t) be to produce chaos sequence, its Fourier is launched and can get with chaos generator

Then produce by the Hilbert conversion

Wherein, ω=2 π/T, f _kBe the amplitude of each frequency component after the Fourier series expansion,

Be the phase place of each frequency component, E _bIt is the energy of sample value function in the symbol period.

2, produce M different CHAOTIC PHASE signal respectively according to the two-way orthogonal basis, as mistake! Do not find Reference source.Wherein use M time-delay T _pThe delayer of=T/2M extracts M CHAOTIC PHASE of reference signal, and T is called symbol period for sending the time span of a symbol.When t＜T/2, switch switched input signal one side, buffering signals reference field; At t〉during T/2, switch switches to the circular buffering end, produces different phase delay.When M=4, c _x(t), c _y(t) can there be p prime minister position respectively ₀, p ₁, p ₂, p ₃Four kinds of situations.

3, the digital information that will transmit, promptly bits switch is carried out CHAOTIC PHASE MODULATED behind symbol, as mistake! Do not find Reference source.In two phase encoders select corresponding CHAOTIC PHASE signal respectively according to the symbol that is transmitted.Each phase encoder can be represented log ₂M bit, two phase encoders can be represented 2log altogether so ₂M bit.When M=4, each phase encoder can transmit 00,01,10 and 11 4 kind of situation respectively, the information of two bits, and those two phase encoders can transmit four bit informations altogether.

4, the two-way of quadrature is passed through the signal plus of CHAOTIC PHASE MODULATED, and sends signal as requested, as mistake! Do not find Reference source.Be specially when time t＜T/2, switch switches to a side who makes that chaotic signal can lead directly among the figure, promptly sends the reference signal section; At t〉during T/2, switch switches to a side who produces message segment, and at this moment, system sends the information carrying signal section of modulating through quadrature chaos phase shift keying.

Transmission signals can be expressed as the linear combination of orthogonal basis, i.e. c _x(t+p _Mx)+c _y(t+p _My).Can obtain the signal of QDCPSK thus through ovennodulation

$S_{\mathrm{QDCPSK}}\left(k\right)=\left\{\begin{array}{cc}\sqrt{E_b}{c}_x\left(k\right),& 0\&le;k<L\\ \begin{array}{c}\sqrt{E_b}(c_x\left((k-L+p_{\mathrm{mx}})\mathrm{mod}L\right)\\ +c_y\left((k-L+p_{\mathrm{my}})\mathrm{mod}L\right))\end{array}& ,L\&le;k<2L\end{array}\right.$

Wherein, L is the chaos sample value number that is produced in the half symbols cycle (T/2), p _MxAnd p _My) be respectively the expression of Chaos Modulation phase place under discrete time of in-phase branch and quadrature branch, be equivalent to one section time-delay of signal.When M=4, p _MxAnd p _MyPhase place four kinds of situations, i.e. p can be arranged respectively ₀, p ₁, p ₂, p ₃

5, at last modulation signal is gone out by antenna transmission.

Receiving terminal

1,, use the Hilbert conversion to produce orthogonal signalling by antenna receiving signal.The preceding half period of received signal wherein, promptly the reference signal section has produced the two-way orthogonal basis after by the Hilbert conversion again.

2, reference field signal and message segment signal are defeated by two CHAOTIC PHASE detection modules respectively, specifically connect as mistake! Do not find Reference source.Shown in.In in-phase branch, reference field signal and message segment signal are the serial inputs, and therefore, actual two signals all are received signals; In quadrature branch, the reference field signal demand carries out the Hilbert conversion, the contained information of quadrature component in the ability demodulated received signal.

3, CHAOTIC PHASE detection module such as a mistake! Do not find Reference source.Shown in.Produce M different CHAOTIC PHASE signal with the reference field signal, carry out relevant with the message segment signal respectively simultaneously.When t=T, the M that an obtains correlation selects wherein the maximum correlation value corresponding symbol (as z ₀Corresponding s ₀, z ₁Corresponding s ₁..., z _M-1Corresponding s _M-1) export as information symbol.Promptly

$Z=z_i=\underset{j}{\max }{z}_j,$ S＝s _i

Wherein, j=0,1 ..., M-1.When M=4, z is arranged ₀, z ₁, z ₂, z ₃Four kinds of outputs, corresponding respectively S can be 00,01,10,11.

4, orthogonal differential chaos phase shift keying (QDCPSK) has the two-way CHAOTIC PHASE to detect, as mistake! Do not find Reference source.Shown in.The output z of j correlator of homophase and quadrature branch in the demodulator _Jx, z _JyBe respectively

$z_{\mathrm{jx}}=\underset{k=0}{\overset{L-1}{\mathrm{\&Sigma;}}}[S_{\mathrm{QDCPSK}}(k+p_{\mathrm{jx}})+n\left(k\right)][S_{\mathrm{QDCPSK}}(k+L)+n\left(k\right)]$

$z_{\mathrm{jy}}=\underset{k=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{[S_{\mathrm{QDCPSK}}(k+p_{\mathrm{jy}})+n\left(k\right)]}^{*}[S_{\mathrm{QDCPSK}}(k+L)+n\left(k\right)]$

Wherein [] ^*Expression Hilbert conversion.Judge that through above-mentioned maximum the back obtains s again _IxAnd s _Iy, combination is finished demodulation after parallel/serial conversion just can restore the information bit of transmission.When M=4, z _Jx, z _JyFour kinds of outputs are arranged, corresponding s respectively _Ix, s _IyFour kinds of values are also arranged respectively, totally 4 bit informations that combine, consistent with transmission information.

The single carrier transmission design parameter of employing and wireless lan (wlan) system compatibility, centre frequency is 36MHz, the RF frequency range is taken as 17MHz.To 5 * 10 ⁴Bit information carries out transmission experiment, can obtain the situation of bit error rate performance.As mistake! Do not find Reference source.Shown in be when the chaos sample value number L=64 that produced in the half symbols cycle (T/2), adopt M=4 respectively, the orthogonal differential chaos phase shift keying (QDCPSK) of 8 yuan of modulation and differential Chaos Shift Keying (DCSK), four mutually chaos shift keying (QCSK) and difference chaotic phase shift keying (DCPSK) bit error rate performance relatively.As we know from the figure, under each situation, about greater than 8dB the time, orthogonal differential chaos phase shift keying (QDCPSK) all is best to performance in signal to noise ratio.And its each symbol comprises 2log as previously mentioned ₂M bit, transmission rate and band efficiency all are improved.

Claims (3)

1, a kind of digital signal orthogonal differential chaos phase shift keying modulator approach the steps include:

A, according to the chaotic signal that chaos signal generator produces, use orthogonal transform to produce the two-way orthogonal basis;

B, produce M different CHAOTIC PHASE signal respectively according to the two-way orthogonal basis;

The information that C, basis will transmit is carried out CHAOTIC PHASE MODULATED, selects corresponding CHAOTIC PHASE signal with two phase encoders respectively according to the symbol that is transmitted; Each phase encoder is represented log ₂M bit, two phase encoders can be represented 2log altogether ₂M bit;

D, with the two-way of quadrature signal plus through CHAOTIC PHASE MODULATED, and send transmission signals as requested; Be specially: the preceding half period sends the reference signal section; The later half cycle sends the information carrying signal section through the modulation of quadrature chaos phase shift keying.

2, digital signal orthogonal differential chaos phase shift keying modulator approach according to claim 1, it is characterized in that: described orthogonal basis, orthogonal basis function are C=[c _x(t), c _y(t)], its orthogonality satisfies in the cycle in half symbols

${\&Integral;}_0^{T/2}{c}_x^2\left(t\right)\mathrm{dt}={\&Integral;}_0^{T/2}{c}_y^2\left(t\right)\mathrm{dt}=1$

${\&Integral;}_0^{T/2}{c}_x\left(t\right)c_y\left(t\right)\mathrm{dt}=0$

And c _x(t), c _y(t) two signals all have the characteristic of chaotic signal;

Described transmission signals is expressed as the linear combination of orthogonal basis, promptly

$S_{\mathrm{QDCPSK}}\left(k\right)=\left\{\begin{array}{cc}\sqrt{E_b}{c}_x\left(k\right),& 0\&le;k<L\\ \begin{array}{c}\sqrt{E_b}(c_x\left((k-L+p_{\mathrm{mx}})\mathrm{mod}L\right)\\ +c_y\left((k-L+p_{\mathrm{my}})\mathrm{mod}L\right))\end{array}& ,L\&le;k<2L\end{array}\right.$

Wherein, L is the chaos sample value number that is produced in the half symbols cycle (T/2), E _bBe the energy of sample value function in the symbol period, p _MxAnd p _MyBe respectively the expression of Chaos Modulation phase place under discrete time of in-phase branch and quadrature branch, be equivalent to one section time-delay of signal.

3, a kind of digital signal orthogonal differential chaos phase shift keying demodulation method

A, by antenna receiving signal, the preceding half period of received signal wherein, promptly the reference signal section produces the two-way orthogonal basis after by orthogonal transform again;

B, reference field signal and message segment signal are defeated by two CHAOTIC PHASE detection modules respectively; In in-phase branch, import former reference field signal and message segment signal; In quadrature branch, reference field signal and message segment signal after the input orthogonal transform are with the contained information of the quadrature component in the demodulated received signal;

C, CHAOTIC PHASE detection module produce M different CHAOTIC PHASE signal with the reference field signal, and carry out relevantly with the message segment signal respectively, and the M that an obtains correlation selects wherein the maximum correlation value corresponding symbol (as Z ₀Corresponding S ₀, Z ₁Corresponding S ₁..., Z _M-1Corresponding S _M-1) as information symbol output, promptly

$Z=z_i=\underset{j}{\max }{z}_j,$ S＝s _i

Wherein, j=0,1 ..., M-1;

D, orthogonal differential chaos phase shift keying have the two-way CHAOTIC PHASE to detect; The output Z of j correlator of homophase and quadrature branch in the demodulator _Jx, Z _JyBe respectively

$z_{\mathrm{jx}}=\underset{k=0}{\overset{L-1}{\mathrm{\&Sigma;}}}[S_{\mathrm{QDCPSK}}(k+p_{\mathrm{jx}})+n\left(k\right)][S_{\mathrm{QDCPSK}}(k+L)+n\left(k\right)]$

$z_{\mathrm{jy}}=\underset{k=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{[S_{\mathrm{QDCPSK}}(k+p_{\mathrm{jy}})+n\left(k\right)]}^{*}[S_{\mathrm{QDCPSK}}(k+L)+n\left(k\right)]$

Wherein [] ^*The expression orthogonal transform.Judge that through above-mentioned maximum the back obtains symbol S again _x=S _IxAnd S _y=S _Iy, combination is finished demodulation after parallel/serial conversion restores the information bit of transmission.

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