CN101867921A - Communication method capable of improving hiding performance of wireless sensor network - Google Patents

Abstract

The invention relates to a communication method capable of improving the hiding performance of a wireless sensor network, which comprises: a step 1, in which a link node sends an original impact signal to a common node; a step 2, in which the common node receives a multi-path impact signal influenced by multiple paths and compares the multi-path impact signal with the original impact signal by using a clean algorithm to calculate a channel impact response parameter indicating the characteristics of the paths between the link node and the common node; and a step 3, in which the common node stores the received multi-path impact signal into a storage of the common node and performs time reversal treatment of the multi-path impact signal to obtain a time reversal multi-path impact signal. The method has the advantages of preventing illegal snooping by improving the hiding performance of the link node according to the spatial and temporal focusing characteristic of a time reversal technique, thereby improving communication safety.

Description

The concealed communication means of a kind of raising wireless sensor network

Technical field

The invention belongs to the wireless sensor network technology field, relate in particular to a kind of communication means that can improve wireless sensor network security.

Background technology

Along with MEMS (micro electro mechanical system) (Micro-Electro-Mechanism System, MEMS), SOC (system on a chip) (System on Chip, SOC), the develop rapidly of radio communication and low-power-consumption embedded technology, be pregnant with wireless sensor network (Wireless Sensor Networks, and brought a change of information perception with its low-power consumption, low cost, characteristics distributed and self-organizing WSN).Wireless sensor network is exactly to form by being deployed in cheap microsensor nodes a large amount of in the monitored area, by a multihop self-organizing network of communication formation.

Wireless sensor network need to improve its information and mainly concentrates on aspects such as the key management of the routing safety agreement of safe MAC (Media Access Control) agreement, network layer of the efficient cryptographic algorithm of physical layer, the anti-DOS of data link layer (Denial of Service) attack and application layer and safe multicasting in disguised present most of wireless sensor network securities researchs of spatial transmission for the purpose of safety.

Though above-mentioned method can improve the fail safe of system effectively, but it improves concealed method all is that transmission signals is encrypted, the eavesdropping node still can receive these signals, as long as obtain corresponding the encryption or decipherment algorithm, still can eavesdrop these signals, therefore still have potential safety hazard.

Summary of the invention

The objective of the invention is fail safe for the communication process that improves wireless sensor network, the concealed communication means of a kind of raising wireless sensor network has been proposed, this method is utilized time reversal technology (TimeReversal, TR) space-time focus characteristics, by improving the disguise of link nodes, prevent illegal wiretapping, thereby improved communications security.

In order to achieve the above object, technical scheme of the present invention is: the concealed communication means of a kind of raising wireless sensor network, be applied to wireless sensor network, and described wireless sensor network comprises at least one link nodes and at least one ordinary node, it is characterized in that, comprise step:

Step 1: link nodes sends an original impact signal s (t) to ordinary node;

Step 2: ordinary node receives through the multipath impact signal s ' that arrives behind the multi-path influence (t), and multipath impact signal s ' (t) is compared by the Clean algorithm with original impact signal s (t) and calculates the channel impulse response parameter h that represents path characteristics between link nodes and the ordinary node _n(t), wherein n is an ordinary node quantity;

Step 3: ordinary node (t) stores the multipath impact signal s ' that receives in the memory of himself into, and ordinary node is to the multipath impact signal

Do time reversal and handle, obtain time reversal multipath impact signal

Step 4: the heat transfer agent i (t) that ordinary node collects himself sensing device and inverting multipath impact signal s ' (t) carry out the time reversal that convolution obtains ordinary node and send signal

And send it back link nodes;

Step 5: link nodes receives the multipath time reversal received signal through arriving behind the multi-path influence $r^{\′}\left(t\right)=i\left(t\right)\⊗s(-t)\⊗h_n(-t)\⊗h_n\left(t\right);$

Step 6: link nodes is extracted heat transfer agent i (t) from multipath time reversal received signal r ' (t), multipath time reversal received signal r ' (t) is carried out carrying out summation operation after the convolution operation with original impact signal s (t), obtain final multipath time reversal received signal

R (t) is exactly i (t) and two auto-correlation functions thus

The result of convolution, because two auto-correlation functions are similar to impulse function, therefore, it is right to go up from the time

Carrying out summed result is 1, so R (t) is exactly the reproduction of i (t) at the receiving terminal place, by aforesaid operations, just obtains heat transfer agent i (t).

Beneficial effect of the present invention: because after adopting technical scheme of the present invention, the channel response that each transducer write down has taken into full account the influence that space phase postpones and non-uniform dielectric brought that introduce in different path, so, from the signal of each transducer of periphery except can spatially converging at a bit, arrive but also can be implemented in synchronization, promptly realize the focusing on the time and space simultaneously.Thereby realized the space-time focusing of time reversal technology.Because the space-time focusing of time reversal technology only determined in very little spatial dimension, in the very narrow time range, it is the strongest that signal reaches, and exceed its space-focusing scope and time focusing range, signal is extremely faint.So, this Space Time focus characteristics of time reversal technology makes signal only can detect at the link nodes place, and other ground square signals outside link nodes are difficult to be detected, and therefore, the time reversal communication technology has fabulous safe and secret transmission characteristic.This also is a kind of new method that is different from the traditional wireless sensor networks security study.

Description of drawings

Fig. 1 is the space schematic diagram of link nodes when ordinary node sends an original impact signal.

Fig. 2 is the space schematic diagram of ordinary node when link nodes sends a time reversal transmission signal.

Fig. 3 is the signal eavesdropping Principle of Process schematic diagram of link nodes.

Fig. 4 is the space schematic diagram of two-dimensional simulation process of the test of the present invention.

Fig. 5 is the spatial distribution map of the verification and measurement ratio of I group l-G simulation test.

Fig. 6 is the spatial distribution map of the verification and measurement ratio of II group l-G simulation test.

Fig. 7 is the spatial distribution map of the verification and measurement ratio of III group l-G simulation test.

Fig. 8 is the spatial distribution map of the verification and measurement ratio of V group l-G simulation test.

Fig. 9 is the spatial distribution map of the verification and measurement ratio of VI group l-G simulation test.

Figure 10 is the spatial distribution map of the verification and measurement ratio of VII group l-G simulation test.

Figure 11 is the time distribution map of the verification and measurement ratio of I group l-G simulation test.

Figure 12 is the time distribution map of the verification and measurement ratio of II group l-G simulation test.

Figure 13 is the time distribution map of the verification and measurement ratio of III group l-G simulation test.

Figure 14 is the time distribution map of the verification and measurement ratio of V group l-G simulation test.

Figure 15 is the time distribution map of the verification and measurement ratio of VI group l-G simulation test.

Figure 16 is the time distribution map of the verification and measurement ratio of VII group l-G simulation test.

Embodiment

The present invention is described further below in conjunction with the drawings and specific embodiments.

At first, theoretical foundation of the present invention is done detailed description, as depicted in figs. 1 and 2, be illustrated in the wireless sensor network, have at least one link nodes and at least one ordinary node, also have at least one eavesdropping node.If do not adopt time reversal technology of the present invention, link nodes sends in the process of a time reversal transmission signal to link nodes to original impact signal of ordinary node transmission or ordinary node, the eavesdropping node can be equal receive these signals, just these signals can be cracked out to these Signal Processing methods as long as can obtain.

The signal processing principle of ordinary node, link nodes and eavesdropping node is identical.As shown in Figure 3, existing is that example elaborates to its process with the link nodes.

At first, reception waveform g (the t)=r ' of link nodes (t)+n (t), wherein r ' is a multipath time reversal received signal (t), n (t) is a noise.To receive waveform g (t) band pass filter that to send into a bandwidth be W and obtain filtered reception waveform z (t), then z (t) sent into square z that a squarer obtains the filtered reception waveform of link nodes ²(t), just obtain link nodes at the integrator that is T by a time of integration and receive waveform energy V, with the cut-off energy V of V and comparator _tCompare cut-off energy V _tA predefined parameter in comparator.If the reception waveform energy V of integrator is than cut-off energy V _tThe higher position thinks and has useful signal, otherwise just thinks and do not have useful signal.In the present invention, use verification and measurement ratio p _dWeigh the probability of the correct received signal of node, with the alert rate p of mistake _FaWeigh the probability of node mistake received signal, verification and measurement ratio p _dWith the alert rate p of mistake _FaBy the signal to noise ratio snr decision, signal to noise ratio snr is again by receiving waveform energy V decision.Below to verification and measurement ratio p _d, the alert rate p of mistake _FaBe described in detail with the theoretical derivation process of signal to noise ratio snr.

The cut-off energy V of comparator _tSelection to satisfy the alert rate p of mistake _FaRequirement, with the V that obtains _tBring formula (4) into and so just obtained verification and measurement ratio p _dRelation with signal to noise ratio.A given verification and measurement ratio is the different signal to noise ratio of correspondence in different communication systems, and the signal to noise ratio that obtains is considered to weigh the concealed more interested amount of communication system.

When not having useful signal among the reception waveform g (t) of link nodes, having only the power in power spectral density (PSD, Power Spectral Density) the unit frequency band is N ₀/ 2 (N ₀For noise " make a constant obtaining behind the Fourier transform) additive white Gaussian noise (AWGN; Additive White GaussianNoise) be input in the link nodes; statistically this noise is a radio noise at random, is characterized in that signal distributions on its communication channel is in very wide frequency band range.The reception waveform energy V of link nodes to power N ₀/ 2 do normalization, have so just obtained normalization stochastic variable Y=2V/N ₀, Y is the signal to noise ratio snr of link nodes, and then Y satisfies the χ that the degree of freedom is v=2TW ²Distribute, the T here is the time of integration, and W is the bandwidth of filter, and this moment, the probability density of Y was:

$p\left(y\right)=\frac{1}{2^{v/2}\mathrm{\Γ}\left(\frac{v}{2}\right)}{y}^{(v-2)/2}{e}^{-y/2},y\≥0$ Formula (1)

In the formula (1), y is any arithmetic number,

For parameter is

Gamma function, its expression formula is:

When having a signal that has ENERGY E in the T in the time of integration to be sent to radiometer among the reception waveform g (t) of link nodes, the stochastic variable Y clothes degree of freedom is v=2TW, and non-centrality parameter is λ=2E/N ₀Non-central χ ²Distribute, this moment, the probability density of Y was:

$p^{\′}\left(y\right)=\frac{1}{2}{\left(\frac{y}{\mathrm{\λ}}\right)}^{(v-2)/4}{e}^{-(y+\mathrm{\λ})/2}{I}_{(v-2)/2}\left(\sqrt{\mathrm{y\λ}}\right),y\≥0$ Formula (2)

In the formula (2)

Be that Bezier (Bessel) function is revised on the first kind (v-2)/2 rank.The verification and measurement ratio p of link nodes _FaWith the alert rate p of mistake _dValue, can determine by following two integration types now:

$p_{\mathrm{fa}}={\&Integral;}_{2V_T/{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000158461600022.png,HSA00000158461600052.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}^{\&infin;}p\left(y\right)\mathrm{dy}$ Formula (3)

$p_d={\&Integral;}_{2V_T/{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000158461600022.png,HSA00000158461600052.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}^{\&infin;}{p}^{\&prime;}\left(y\right)\mathrm{dy}$ Formula (4)

V _tBe the cut-off energy of comparator, the reception waveform energy V of comparator just and it compare.Link nodes will receive useful signal, and then received reception waveform g (t) need satisfy certain requirement, its signal to noise ratio snr and verification and measurement ratio p _dNeed reach certain threshold value.

Ordinary node and eavesdropping node the signal processing principle identical with link nodes, so be not described in detail.

On the above-mentioned theory basis, the concealed communication means of a kind of raising wireless sensor network provided by the invention is applied to wireless sensor network, and described wireless sensor network comprises at least one link nodes and at least one ordinary node, comprises step:

Step 1: link nodes sends an original impact signal s (t) to ordinary node;

Step 2: ordinary node receives through the multipath impact signal s ' that arrives behind the multi-path influence (t), and multipath impact signal s ' (t) is compared by the Clean algorithm with original impact signal s (t) and calculates the channel impulse response parameter h that represents path characteristics between link nodes and the ordinary node _n(t), wherein n is an ordinary node quantity; Clean algorithm (time domain deconvolution algorithm) is a kind of iterative algorithm that sampled data is deconvoluted, and is used to extract channel in this step and impacts relevant parameter h _n(t), because the clean algorithm belongs to prior art, therefore discuss no longer in detail.

Step 3: ordinary node (t) stores the multipath impact signal s ' that receives in the memory of himself into, and ordinary node is to the multipath impact signal

Do time reversal and handle, obtain time reversal multipath impact signal

Step 4: the heat transfer agent i (t) that ordinary node collects himself sensing device and inverting multipath impact signal s ' (t) carry out the time reversal that convolution obtains ordinary node and send signal

And send it back link nodes;

Step 5: link nodes receives the multipath time reversal received signal through arriving behind the multi-path influence $r^{\&prime;}\left(t\right)=i\left(t\right)\&CircleTimes;s(-t)\&CircleTimes;h_n(-t)\&CircleTimes;h_n\left(t\right);$

Step 6: link nodes is extracted heat transfer agent i (t) from multipath time reversal received signal r ' (t), multipath time reversal received signal r ' (t) is carried out carrying out summation operation after the convolution operation with original impact signal s (t), obtain final multipath time reversal received signal

R (t) is exactly i (t) and two auto-correlation functions thus The result of convolution, because two auto-correlation functions are similar to impulse function, therefore, it is right to go up from the time

Carrying out summed result is 1, so R (t) is exactly the reproduction of i (t) at the receiving terminal place, by aforesaid operations, just obtains heat transfer agent i (t).

Below, in conjunction with l-G simulation test the space-time focus characteristics that communication means of the present invention had is described.As shown in Figure 4, the invention provides a kind of space schematic diagram of two-dimensional simulation process of the test.In the embodiment shown in this figure, the length in the space of two-dimensional simulation process of the test is 6m, and wide is 3m.Among the figure, ε _rBe relative dielectric constant, constitute by real part and imaginary part that real part is the DIELECTRIC CONSTANT of material because the plural number of broad sense dielectric constant is expressed _r, imaginary part and conductivity are directly proportional, and in l-G simulation test, when conductivity was infinity, real part was a DIELECTRIC CONSTANT _rCan ignore, the broad sense dielectric constant of this moment is conductivity.PEC has been a simple metal, and its conductivity is infinitely great, so the broad sense dielectric constant is conductivity, through test, obtains the relative dielectric constant ε of body of wall _rBe 9, the relative dielectric constant ε of desk _rBe 2, the relative dielectric constant ε of stool _rBe 1.3.Round dot among the figure is represented ordinary node, and Diamond spot is represented link nodes.

Test by 6 groups of numerical simulations and to carry out emulation, these 6 groups experiments are respectively:

I. removing the next ordinary node of situation of all obstacles such as body of wall, desk and stool and communicating of a link nodes " one to one " under the simulation space as shown in Figure 4 according to communication means of the present invention; Verification and measurement ratio p under this group l-G simulation test _dSpatial distribution as shown in Figure 5, the time distributes as shown in figure 11.

II. communicate according to existing communication means at the next ordinary node of simulation space as shown in Figure 4 and a link nodes; Verification and measurement ratio p under this group l-G simulation test _dSpatial distribution as shown in Figure 6, the time distributes as shown in figure 12.

III. communicating of a next ordinary node of simulation space as shown in Figure 4 and a link nodes " one to one " according to above-mentioned communication means; Verification and measurement ratio p under this group l-G simulation test _dSpatial distribution as shown in Figure 7, the time distributes as shown in figure 13.

IV. under simulation space as shown in Figure 4, only keep under the situation of two ordinary nodes and a link nodes communicating according to above-mentioned communication means; Verification and measurement ratio p under this group l-G simulation test _dSpatial distribution as shown in Figure 8, the time distributes as shown in figure 14.

V. under simulation space as shown in Figure 4, only keep under the situation of four ordinary nodes and a link nodes communicating according to above-mentioned communication means; Verification and measurement ratio p under this group l-G simulation test _dSpatial distribution as shown in Figure 9, the time distributes as shown in figure 15.

VI. under simulation space as shown in Figure 4, only keep under the situation of eight ordinary nodes and a link nodes communicating according to above-mentioned communication means; Verification and measurement ratio p _dWith the alert rate p of mistake _FaDetermine verification and measurement ratio p under this group l-G simulation test by signal to noise ratio snr _dSpatial distribution as shown in figure 10, the time distributes as shown in figure 16.

Can obtain the verification and measurement ratio p when link nodes receives signal by above-mentioned 6 groups of emulation experiments _dSpatial distribution, shown in Fig. 5,6,7,8,9 and 10, W and L axle are represented longly and wide respectively among the figure, unit is meter p _dAxle is a verification and measurement ratio.As can be seen from the figure, guaranteeing that link nodes can receive under the situation of signal, introduce the verification and measurement ratio p of communication means of the present invention shown in Fig. 5,7,8,9 and 10 of time reversal technology _dSpatial distribution compare as shown in Figure 6 with adopting the existing communication method, communication means of the present invention has bigger influence to the safe transmission of signal.Adopting under the existing communication means situation, when link nodes receives useful signal, other many places can detect the existence of useful signal too in the space, if place the eavesdropping node in these positions, just be easy to receive these useful signals, so just be unfavorable for the safe transmission of information.When the communication means of the present invention that adopts after introducing the time reversal technology, situation has just been made a world of difference, has only the existence that can detect useful signal on every side in the very narrow scope of link nodes, and it is just very faint to exceed this range signal, therefore just detect existence less than useful signal, so just reduce the probability that signal is illegally detected when spatial transmission, improved the safe transmission of information.Illustrated that the space-focusing characteristic of time reversal technology can improve the information security of wireless sensor network.

Below by the further analyzing and testing rate of emulation experiment p _dTime distribute, shown in Figure 11,12,13,14,15 and 16.Adopting under the existing communication means situation, as shown in figure 12, signal all can be detected at emission initial stage useful signal in emulation finishes during this period of time, and communication means of the present invention such as Figure 11 of employing time reversal technology, 13,14, shown in 15 and 16, the time that can receive signal along with the increase of common node quantity is reducing, after common node quantity reaches certain value as can be seen from Figure 16, signal is in whole transmission course, useful signal only focuses in time reversal and constantly just can be detected out, and signal is difficult to be detected in At All Other Times.Thereby, illustrated and adopted the communication means of the present invention of time reversal technology to have the time focusing, so just reduced the probability that signal is illegally intercepted in time, improved of the fail safe of the information of wireless sensor network in the time propagation.

Those of ordinary skill in the art will appreciate that embodiment described here is in order to help reader understanding's principle of the present invention, should to be understood that protection scope of the present invention is not limited to such special statement and embodiment.Those of ordinary skill in the art can make various other various concrete distortion and combinations that do not break away from essence of the present invention according to these technology enlightenments disclosed by the invention, and these distortion and combination are still in protection scope of the present invention.

Claims (1)

1. one kind is improved the concealed communication means of wireless sensor network, is applied to wireless sensor network, and described wireless sensor network comprises at least one link nodes and at least one ordinary node, it is characterized in that, comprises step:

Step 1: link nodes sends an original impact signal s (t) to ordinary node;

Step 2: ordinary node receives through the multipath impact signal s ' that arrives behind the multi-path influence (t), and multipath impact signal s ' (t) is compared by the Clean algorithm with original impact signal s (t) and calculates the channel impulse response parameter h that represents path characteristics between link nodes and the ordinary node _n(t), wherein n is an ordinary node quantity;

Step 3: ordinary node (t) stores the multipath impact signal s ' that receives in the memory of himself into, and ordinary node is to the multipath impact signal

Do time reversal and handle, obtain time reversal multipath impact signal

Step 4: the heat transfer agent i (t) that ordinary node collects himself sensing device and inverting multipath impact signal s ' (t) carry out the time reversal that convolution obtains ordinary node and send signal

And send it back link nodes;

Step 5: link nodes receives the multipath time reversal received signal through arriving behind the multi-path influence $r^{\&prime;}\left(t\right)=i\left(t\right)\&CircleTimes;s(-t)\&CircleTimes;h_n(-t)\&CircleTimes;h_n\left(t\right);$

Step 6: link nodes is extracted heat transfer agent i (t) from multipath time reversal received signal r ' (t), multipath time reversal received signal r ' (t) is carried out carrying out summation operation after the convolution operation with original impact signal s (t), obtain final multipath time reversal received signal

R (t) is exactly i (t) and two auto-correlation functions thus

The result of convolution, because two auto-correlation functions are similar to impulse function, therefore, it is right to go up from the time

Carrying out summed result is 1, so R (t) is exactly the reproduction of i (t) at the receiving terminal place, by aforesaid operations, just obtains heat transfer agent i (t).

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