CN105681323A - Information hiding wireless transmission method based on time reversal - Google Patents

Abstract

The invention discloses an information hiding wireless transmission method based on time reversal, and belongs to the field of electronic technology. The method comprises the following steps that: a cloak pulse H(t) is added in front of an encoded target signal T(t) to form a new pulse sequence X(t); the cloak pulse undergoes a multipath delay effect after passing through a first reverberation cavity, a waveform is extended, and the target signal is hidden to form a new signal Y(t); the Y(t) is transmitted, and time reversal waveform transform is performed on the signal Y(t) after the signal Y(t) is received by a receiving end to obtain Y(-t); and the Y(-t) is input into a second reverberation cavity being the same as the first reverberation cavity, and the cloak signal and the target signal are recovered. Through the scheme, information hiding transmission is realized. The information hiding wireless transmission method is applied to the field of secret communication.

Description

A kind of Information hiding formula radio transmitting method based on time reversal

Technical field

The invention belongs to person in electronics, be specifically related to a kind of Information hiding formula radio transmitting method based on time reversal.

Background technology

Along with development and the scientific and technical continuous renewal of society, the quantity of information of people's contact is also increasing, and information transmission is also enriched constantly with the means obtained. Wireless messages is current communication mode the most widely, in wireless communications, in order to prevent confidential information to be intercepted between communication object, it is necessary to by the method coding information of agreement in advance, allows information disguising, or communicates in the way of its true content hidden. In message transmitting procedure, transmitting terminal is accomplished by the information of required transmission is encrypted, and changes the form of expression of original information, hides real information; At receiving terminal, according to prior agreement, hiding real information is carried out DecryptDecryption process, recover raw information. Such that enable listener-in to receive, do not know about the information content representated by signal yet.

But, along with the development of electronic information technology, the especially raising of computer technology, to ery easy by adopting Digital Signal Processing to add cracking of confidential information. See as much mobile phone A PP is soft at present, so that it may moment cracks the password of hotspot (WIFI), causes damage. Accordingly, it is capable to information is encrypted by a kind of new mechanism of no searching, it is prevented that information is stolen in transmitting procedure, it it is a significant research topic. Such as 2010, J.M.Lukens has delivered on famous academic journal " Nature " and has been entitled as " Atemporalcloakattelecommunicationdatarate " (Nature, vol.498,205-208,2013) article, elaborates that utilization is warbled delay technology, the method of the stealthy cape of manufacturing time (Temporalcloak), allow Information hiding in time cape, it is achieved the concealed transmission of information, it is achieved secret communication. This method is based on pure physical mechanism, it is not necessary to Digital Signal Processing, and listener-in cannot obtain and add confidential information, therefore prevents the leakage of information.

Time reversal electromagnetism is a new electromagnetism subject branch. Here, so-called time reversal is not Back In Time, but the inverting of motion.For electromagnetic wave propagation, it is simply that received time domain electromagnetic signal waveform is done mirror image on a timeline, the process then launched again. Becoming better and approaching perfection day by day and the continuous renewal of signal processing technology of inverting electromagnetic theory over time, being with a wide range of applications of the electromagnetic superior space-time adaptive filtering characteristic of time reversal, it is possible to resolve puzzlement tradition electromagnetic theory some difficult problems for many years. The electromagnetism time reversal system of complete set is divided into two parts, and Part I is time reversal mirror system (Timereversalmirror, TRM), and Part II is reception system. The effect of TRM is that the channel signal received is carried out time reversal inversion, is then reversed by the waveform obtained and is encoded or shaping, re-emitting. The effect of reception system is to launch channel-sounding signal, and receives the inverting signal launched by TRM, washed to obtaining focusing at self. 2004, G.lerosey et al. delivers and is entitled as " TimeReversalofelectromagneticwaves " (Phys.Rev.Lett., vol.92, pp.1939041), in literary composition first to time reversal electromagnetic empty time synchronizing focus characteristic elaborate. G.Lerosey in 2007 et al. authority's academic journal " Science " deliver be entitled as " Focusingbeyongthediffractionlimitwithfar-fieldtimerevers al; " (Science, vol.315, pp.1119-1122, Feb.2007.), acquisition time reversal electromagnetic wave far field super-resolution rate sub-wavelength focus characteristics is described by literary composition, and gives experiment proof. 2013, fourth general et al. delivers and is entitled as " Sub-wavelengtharraywithembeddedchirpeddelaylinesbasedont imereversaltechnique " (IEEETrans.AntennasPropag., vol.61, no.5, pp.2868-2873), propose to utilize dispersion encoding channel, obtain the mode that time reversal sub-wavelength focuses on. 2015, fourth general et al. delivers and is entitled as " Enhancementoftimereversalsubwavelengthwirelesstransmissi onusingpulseshaping " (IEEETrans.AntennasPropag., vol.63, no.9, pp.4169-4174), it is proposed that based on the method that pulse-shaping technique obtains time reversal super-resolution focus.

Summary of the invention

The purpose of the present invention is intended to the time domain focus characteristics utilizing time reversal, creates time cape, makes signal to be transmitted can hide wherein, it is achieved the purpose that secrecy is wirelessly transferred.

The present invention is by the following technical solutions to achieve these goals:

A kind of Information hiding formula radio transmitting method based on time reversal, it is characterised in that comprise the following steps:

(1) launch wideband-short pulse A (t), do linear amplification through power amplifier, it is thus achieved that time domain cape signal C (t) of contraction;

(2) pulse of coding or train of pulse S (t) are launched, synthesizing road signal Y (t)=A (t)+S (t), S (t) and C (t) gathering interval with C (t) is Δ t;

(3) Y (t) is sent in the first reverberation chamber, due to multipath effect, cape signal C (t) wave distortion, stretch, form cape signal N (t), and signal S (t) of information is carried in annihilation, forms new signal Z (t);

(4) Z (t) is launched, received by receiving terminal after free space;

(5) at receiving terminal, Z (t) waveform is done time inversion, obtain signal Z (-t);

(6) sending in the second reverberation chamber by signal Z (-t) after inverting, inverting noise signal N (-t) of expansion focuses on again, and the information being hidden in cape is restored.In technique scheme, the time domain response in reverberation chamber can be expressed as,

$H\left(t\right)=\underset{i=1}{\overset{N}{\Σ}}{a}_i\mathrm{\δ}(t-{\mathrm{\Δt}}_i)---\left(2\right)$

Wherein, N is the quantity of multipath, a_iIt is the amplitude factor of the i-th paths, δ (t-Δ t_i) it is the shock response of the i-th paths, Δ t_iIt it is the time delay of the i-th paths.

In technique scheme, in step 3:

$Z\left(t\right)=N\left(t\right)+M\left(t\right)=\underset{i=1}{\overset{N}{\Σ}}{a}_{i}C(t-{\mathrm{\Δt}}_i)+\underset{i=1}{\overset{N}{\Σ}}{a}_{i}S(t-{\mathrm{\Δt}}_i).$

In technique scheme, in step 5, the expression formula of Z (-t) is:

$Z(-t)=N(-t)+M(-t)=\underset{i=1}{\overset{N}{\Σ}}{a}_{i}C(-t-{\mathrm{\Δt}}_i)+\underset{i=1}{\overset{N}{\Σ}}{a}_{i}S(-t-{\mathrm{\Δt}}_i).$

In technique scheme, in step 6

$\begin{array}{c}O(-t)=Z(-t)*\mathrm{\δ}(t-{\mathrm{\Δt}}_i)\\ =\underset{i=1}{\overset{N}{\Σ}}{a}_{i}C(-t-{\mathrm{\Δt}}_i)*a_i\mathrm{\δ}(t-{\mathrm{\Δt}}_i)+\underset{i=1}{\overset{N}{\Σ}}{a}_{i}S(-t-{\mathrm{\Δt}}_i)*a_i\mathrm{\δ}(t-{\mathrm{\Δt}}_i)\\ =\underset{i=1}{\overset{N}{\Σ}}{a}_i^{2}C(-t)+\underset{i=1}{\overset{N}{\Σ}}{a}_i^{2}S(-t)+\underset{i=1}{\overset{N}{\Σ}}\underset{j=1,i\≠j}{\overset{N}{\Σ}}{a}_i{a}_{j}C(-t+{\mathrm{\Δt}}_i-{\mathrm{\Δt}}_j)+\underset{i=1}{\overset{N}{\Σ}}\underset{j=1,i\≠j}{\overset{N}{\Σ}}{a}_i{a}_{j}S(-t+{\mathrm{\Δt}}_i-{\mathrm{\Δt}}_j)\end{array}.$

The present invention, because have employed technique scheme, therefore possesses following beneficial effect:

The present invention obtains higher secure wireless communication, to need the Information hiding transmitted in man-made environment's noise, and by time reversal technology, realize the waveform being hidden in Signal in Noise is recovered at receiving terminal, it is easily separated with noise signal, thus realizing the hidden wireless transmission of information, reach the effect of secrecy transmission.

Accompanying drawing explanation

Fig. 1 is basic block diagram of the present invention.

Fig. 2 is the waveform in the embodiment of the present invention after the cape signal combination of echo signal and contraction.

Fig. 3 is chaos reverberation chamber of the present invention model.

Cape signal is launched in the embodiment of the present invention by Fig. 4, the waveform of vanishing target signal.

Fig. 5 is the signal waveform after recovering in the embodiment of the present invention.

Detailed description of the invention

All features disclosed in this specification, or the step in disclosed all methods or process, except mutually exclusive feature and/or step, all can combine by any way.

Elaborate below in conjunction with-5 couples of present invention of Fig. 1.

A kind of Information hiding formula transmission method based on time reversal, scheme is as it is shown in figure 1, be made up of following several parts:

1. pulse generator 1, is used for launching cape pulse A (t).

2. power amplifier 2, amplify cape pulse for amplitude, obtain signal C (t).

3. power combiner 3, for being combined into a road signal by the cape pulse signal after signal to be transmitted X (t) and amplification.

4. chaos reverberation chamber 4. For the cape signal waveform after amplification is carried out multidiameter, it is achieved the process manufacturing environment noise of duration of run cape.

5. power amplifier 5, are used for the cape signal after amplifying expansion and echo signal, are used for launching signal.

6. reception antenna, is used for receiving signal.

7. free space radio channel.

8. time reversal module, for the signal waveform that inverting receives.

9. chaos reverberation chamber 2. There is identical time domain response with reverberation chamber 1, be used for recovering waveform.

10. reception terminal.

Its work process is, has following steps:

(1) pulse A (t) launched by impulse sender.

(2) amplify after the amplified device of A (t), obtain cape signal C (t), in power combiner, be combined into road signal Y (t) with signal to be transmitted X (t).

(3) Y (t) is sent in chaos reverberation chamber. In chaos reverberation chamber, cape signal C (t) waveform changes, form cape signal N (t), also can there is multipath effect in signal to be transmitted simultaneously, form new signal M (t), owing to the amplitude of M (t) is less than N (t), therefore, M (t) falls into oblivion and in cape signal N (t), forms new signal Z (t).

(4) Z (t) is launched by transmitting antenna, through free-space propagation, reception antenna receive.

(5) signal Z (t) received is sent in time reversal module, it is thus achieved that waveform inversion signal Z (-t).

(6) being sent into by Z (-t) in chaos reverberation chamber, due to the time reversal electromagnetic wave compensating action to multipath effect, environment cape signal and measured signal focus on respectively, and can be distinguish between.

In step (2), it is achieved that for the process of signal to be transmitted cape setup time.Now, the state of time cape is contraction state. At contraction state, it is possible to differentiated cape signal and signal to be transmitted by amplitude.

In step (3), it is achieved that time cape is opened, cover the process of echo signal, it is achieved that to the stealthy operation of echo signal time domain.

In step (5), it is achieved that the under operation to time cape.

In step (6), it is achieved that the shrinkage operation of time cape. Now, the state of time cape is contraction state, signal to be transmitted and cape Signal separator, displays from time cape.

Embodiment 1

Step 1, is launched pulse signal A (t) by pulse generator 1. Pulse generator shown in Fig. 1 can be realized by photoconductive switch or AWG (Arbitrary Waveform Generator).

Step 2, sends into pulse signal A (t) in amplifier 2, obtains cape signal C (t). Now, by cape signal C (t) with echo signal S (t) through power combiner 3, road signal Y (t) is synthesized, as shown in Figure 3. The mathematic(al) representation of signal Y (t) is,

Y (t)=C (t)+S (t) (1)

Step 3, send synthesized signal Y (t) in the reverberation chamber 4 shown in Fig. 3. In this embodiment, reverberation chamber is of a size of a=40cm, b=40cm, c=70cm. Owing to reverberation chamber is a multidiameter structure, its time domain response can be expressed as,

$H\left(t\right)=\underset{i=1}{\overset{N}{\Σ}}{a}_i\mathrm{\δ}(t-{\mathrm{\Δt}}_i)---\left(2\right)$

Wherein, N is the quantity of multipath, a_iIt is the amplitude factor of the i-th paths, δ (t-Δ t_i) it is the shock response of the i-th paths, Δ t_iIt it is the time delay of the i-th paths. After Y (t) sends into reverberation chamber, can there is multidiameter effect, output Z (t) in signal. Z (t) is:

$\begin{array}{c}Z\left(t\right)=N\left(t\right)+M\left(t\right)\\ =C\left(t\right)*\underset{i=1}{\overset{N}{\Σ}}{a}_i\mathrm{\δ}(t-{\mathrm{\Δt}}_i)+S\left(t\right)\underset{i=1}{\overset{N}{\Σ}}{a}_i\mathrm{\δ}(t-{\mathrm{\Δt}}_i)\\ =\underset{i=1}{\overset{N}{\Σ}}{a}_{i}A(t-{\mathrm{\Δt}}_i)+\underset{i=1}{\overset{N}{\Σ}}{a}_{i}S(t-{\mathrm{\Δt}}_i)\end{array}---\left(3\right)$

In above formula, * it is convolution symbol, N (t) is the signal obtained with H (t) convolution of the C (t) in (1) formula, and M (t) is the signal obtained with H (t) convolution of the S (t) in (1) formula.

Owing to cape signal amplitude is higher than echo signal, therefore, after multidiameter, the cape signal after waveform diffusion can cover echo signal, is similar to and echo signal is covered in a time cape, as shown in Figure 4.

Step 4, amplifies transmitting terminal antenna 6 again by Z (t) by amplifier 5 and is radiated in free space 7. Transmitting terminal antenna can be broadband Vivaldi antenna or the butterfly antenna of low dispersion, to ensure that waveform is undistorted.

Step 5, at receiving terminal, utilizes the low dispersive-antenna 8 in broadband to receive the signal transmitted by transmitting terminal, and send into wave filter 9 filtering noise signal, after low-noise amplifier 10 amplifies, send into time reversal module 11, deadline inversion, it is thus achieved that Z (-t). The expression formula of Z (-t) is:

$\begin{array}{c}Z(-t)=N(-t)+M(-t)\\ =\underset{i=1}{\overset{N}{\Σ}}{a}_{i}C(-t-{\mathrm{\Δt}}_i)+\underset{i=1}{\overset{N}{\Σ}}{a}_{i}S(-t-{\mathrm{\Δt}}_i)\end{array}---\left(4\right)$

Step 6, sends into time reversal signal Z (-t) in the reverberation chamber 12 identical with reverberation chamber 4, and gained signal is:

$\begin{array}{c}O(-t)=Z(-t)*\mathrm{\δ}(t-{\mathrm{\Δt}}_i)\\ =\underset{i=1}{\overset{N}{\Σ}}{a}_{i}C(-t-{\mathrm{\Δt}}_i)*a_i\mathrm{\δ}(t-{\mathrm{\Δt}}_i)+\underset{i=1}{\overset{N}{\Σ}}{a}_{i}S(-t-{\mathrm{\Δt}}_i)*a_i\mathrm{\δ}(t-{\mathrm{\Δt}}_i)\\ =\underset{i=1}{\overset{N}{\Σ}}{a}_i^{2}C(-t)+\underset{i=1}{\overset{N}{\Σ}}{a}_i^{2}S(-t)+\underset{i=1}{\overset{N}{\Σ}}\underset{j=1,i\≠j}{\overset{N}{\Σ}}{a}_i{a}_{j}C(-t+{\mathrm{\Δt}}_i-{\mathrm{\Δt}}_j)+\underset{i=1}{\overset{N}{\Σ}}\underset{j=1,i\≠j}{\overset{N}{\Σ}}{a}_i{a}_{j}S(-t+{\mathrm{\Δt}}_i-{\mathrm{\Δt}}_j)\end{array}---\left(5\right)$

It can be seen that due to the time reversal compensation to multipath effect, cape signal is resumed out with input signal in formula (5). Waveform as shown in Figure 5, cape signal shrinks again, is again represented by input signal. The process of wave recovery is completed, it is achieved that the concealed transmission of signal at receiving terminal.

Claims (5)

1. the Information hiding formula radio transmitting method based on time reversal, it is characterised in that comprise the following steps:

Step (1), transmitting wideband-short pulse A (t), do linear amplification through power amplifier, it is thus achieved that time domain cape signal C (t) of contraction;

Step (2), by coding pulse or train of pulse S (t) launch, synthesizing road signal Y (t)=C (t)+S (t), S (t) and C (t) gathering interval with time domain cape signal C (t) is Δ t;

Step (3), Y (t) is sent in the first reverberation chamber, due to multipath effect, cape signal C (t) wave distortion, stretch, form noise signal N (t), and fall into oblivion and carry signal S (t) of information, form new mixed signal Z (t);

Step (4), by mixed signal Z (t) launch, received by receiving terminal after free space;

Step (5), at receiving terminal, Z (t) waveform is done time inversion, obtains inverting mixed signal Z (-t);

Step (6), inverting mixed signal Z (-t) is sent in the second reverberation chamber, obtain signal O (t).

2. a kind of Information hiding formula radio transmitting method based on time reversal according to claim 1, it is characterised in that

The time domain response in reverberation chamber can be expressed as,

Wherein, N is the quantity of multipath, a_iIt is the amplitude factor of the i-th paths, δ (t-Δ t_i) it is the shock response of the i-th paths, Δ t_iIt it is the time delay of the i-th paths.

3. a kind of Information hiding formula radio transmitting method based on time reversal according to claim 2, it is characterised in that in step 3:

(2) in formula, * it is convolution symbol, N (t) is the noise signal obtained with H (t) convolution of the C (t) in step (2), and M (t) is the signal of the information of carrying of S (t) distortion obtained with H (t) convolution.

4. a kind of Information hiding formula radio transmitting method based on time reversal according to claim 1, it is characterised in that in step 5, the expression formula of Z (-t) is:

(3) in formula, C (-t-Δ t_i) implication is the delayed time Δ t of cape signal C (t)_iAfter time inversion signal, S (-t-Δ t_i) implication be carry the delayed time Δ t of signal S (t) of information_iAfter time inversion signal.

5. a kind of Information hiding formula radio transmitting method based on time reversal according to claim 1, it is characterised in that in step 6

Wherein, N is the quantity of multipath, a_iIt is the amplitude factor of the i-th paths, δ (t-Δ t_i) it is the shock response of the i-th paths, Δ t_iIt it is the time delay of the i-th paths.