CN104320777A - Multi-antenna system communication safety improving method based on beam forming - Google Patents

Abstract

The invention discloses a multi-antenna system communication safety improving method based on beam forming. The method includes the following steps that a legal receiver sends a channel estimation sequence, and a legal sender estimates channel information of legal communication according to the sequence; the legal sender is multiplied by a weight when sending the information; in the communication process, an MPSK modulation method with symmetric symbol sets is adopted for modulation; the receiver demodulates signals by means of maximum likelihood; when a legal sender antenna is larger than a legal receiver antenna, a weight coefficient is processed by means of an array redundancy advantage, and finally the sent signals are obtained. The method has the advantages that higher safety is obtained at less cost than a traditional safety and physical layer safety system; by means of the array redundancy advantage, the weight coefficient of the sent signals is processed, the situation that an eavesdropping party attacks in a blind equalization mode is further prevented, and safety is improved.

Description

A kind of method of the raising multiaerial system communication security based on beam forming

Technical field

The present invention relates to wireless communication system security technology area, particularly relate to a kind of method of the raising multiaerial system communication security based on beam forming.

Background technology

The safety attention always of radio communication.Recently the mobile radio network developed rapidly makes it easily suffer the attack of the side of eavesdropping due to the broadcast characteristic of its wireless signal.Traditional safe practice based on password does not utilize radio communication physical layer characteristic when considering safety problem, when solving the modern various wireless network secure problem developed rapidly (as radio sensing network etc.) unable to do what one wishes.

Current multiple antennas safety of physical layer technology is based upon on some unpractical hypothesis bases mostly.Great majority need to know the channel information of eavesdropping side and legitimate correspondence both sides based on the method hypothesis legitimate sender sending beam forming, and this is difficult to realize in practical communication.The fail safe of man made noise's class methods of the array redundancy method that LI proposes and Goel is then be based upon on tapping channel and the strict irrelevant basis of legitimate channel, if the channel information of eavesdropping side and legitimate correspondence channel information is very close or the side's of eavesdropping obtaining portion divides legal channel information, its fail safe cannot ensure.

In layer security research, MIMO man made noise and upper stream password combine by H.WEN, but the method security performance fails to reach actual demand.The cross-layer scheme that STBC is combined with upper strata key can be reached good security performance, but its Space Time Coding needs fixing dual-mode antenna number of combinations to make it in practical application scene, receive a definite limitation.

Summary of the invention

Object of the present invention is overcoming the deficiencies in the prior art, a kind of method of the raising multiaerial system communication security based on beam forming is provided, adopt the safe practice that in mimo system, beam forming is combined with upper strata key, upper strata key is utilized to coordinate the beam forming technique of physical layer, even if also have no idea correct demodulation under eavesdropping side obtains legitimate correspondence both sides accurate channel information condition, thus ensure that eavesdropping side cannot obtain any useful information from physical layer.And the random decay fast rapidly of the transmission signal of physical layer, and be submerged in screen upper strata key in noise, make eavesdropping side comparatively legacy communications system be more difficult to attack acquisition key by blind estimate mode.

The object of the invention is to be achieved through the following technical solutions: a kind of method of the raising multiaerial system communication security based on beam forming, comprises the following steps:

S1: before a communication, legitimate receipt direction legitimate sender transmitting channel estimated sequence, legitimate sender estimates the channel information H of legitimate correspondence according to the channel estimation sequence received _bA, according to the reciprocity of TDD system channel, draw H _bA=H _aB, this sequencal estimation H steals in eavesdropping side _bE, cannot according to retrieval channel information H _bAand H _aE;

S2: legitimate sender sends information s (n), is multiplied by weight w (n), the information x (n) finally sent=w (n) s (n) when sending information s (n); In process of transmitting, legitimate correspondence both sides share binary sequence Q _control=(q ₁, q ₂..., q _n), q _i∈ GF (2), I _efor diagonal entry is the N of 1 _rdimension unit matrix, order

$\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& H_A{w}_i^0=I_E\\ \mathrm{if}& q_i=1,& H_A{w}_i^1=-I_E\end{array}\right.$

$w^0=\{w_1^0,w_2^0...,w_n^0\},w^1=\{w_1^1,w_2^1...,w_n^1\};$

S3: in communication process, adopts and has the MPSK modulation system of symmetrical symbols collection, namely to modulation glossary of symbols S, to wherein any one modulation symbol s _i∈ S, total exist one the mapping of constellation symbol and modulation bit is by following criterion:

U _i＝(u ₁,u ₂,...u _M) _i→s _i

$U_j=U_i\⊕(\mathrm{1,1},...1)\→s_j=-s_i$

Wherein, M is order of modulation, U _i(i=1,2 ..., M) for M-bit wait adjust bit vectors;

S4: work as U _imapping symbols s _iin time, ensures and U _ihamming distance vectorial U farthest _jbe mapped to-s _i, ensure that the average Hamming distance of bit vectors that adjacent symbol is corresponding is minimum, then legitimate receipt side receives signal y simultaneously _rn () utilizes maximum-likelihood demodulation s _ias follows:

${\hat{s}}_i=\underset{s_i\∈S}{\arg }\min {\left|\right|y_r-I_E{s}_i\left|\right|}^2$

$\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& {\stackrel{\‾}{s}}_i={\hat{s}}_i\\ \mathrm{if}& q_i=1,& {\stackrel{\‾}{s}}_i=-{\hat{s}}_i\end{array}\right.;$

Meanwhile, eavesdropping side receives signal y _e, the signal received with the same manner demodulation:

$\begin{array}{c}{\hat{s}}_i=\underset{s_i\∈S}{\arg }\min {\left|\right|y_e-I_E{s}_i\left|\right|}^2\\ =\underset{s_i\∈S}{\arg }\min {\left|\right|H_E{w}_{i}s\left(n\right)+v_E-I_E{s}_i\left|\right|}^2\end{array};$

S5: as legitimate sender antenna N _tbe greater than legitimate receipt side antenna N _rtime, become when order sends weight coefficient; Utilize array redundancy advantage, at each symbol sending time slots i for weight coefficient make following process:

$H_A=\left[H_0{H}_1\right],w=\left[\begin{array}{c}{w}_0\\ w_1\end{array}\right]$

Then have,

$H_{A}w=H_0{w}_0+H_1{w}_1=(\±1_{q_i})I_E$

$x\left(n\right)=w\·s\left(n\right)=\left[\begin{array}{c}{w}_{0}s\left(n\right)\\ w_{1}s\left(n\right)\end{array}\right]=\left[\begin{array}{c}{x}_0\left(n\right)\\ x_1\left(n\right)\end{array}\right];$

Wherein, $\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& (\±1_{q_i})=1\\ \mathrm{if}& q_i=1,& (\±1_{q_i})=-1\end{array}\right.;$ H ₀for N _r× N _rsubmatrix, H ₁for N _r× (N _t-N _r) submatrix; Make x ₁(n)=w ₁n () s (n) is stochastic variable, and obey gaussian random distribution, average μ, covariance matrix Σ; So solve an equation and can obtain $x_0\left(n\right)={H_0}^{-1}[(\±1_{q_i})I_{E}s\left(n\right)-H_1{x}_1\left(n\right)];$

S6: finally can send signal:

$x\left(n\right)=\left[\begin{array}{c}{H_0}^{-1}[(\±1_{q_i})I_{E}s\left(n\right)-H_1{x}_1\left(n\right)]\\ x_1\left(n\right)\end{array}\right].$

The beneficial effect of technical solution of the present invention is: the safe practice that in a kind of mimo system, beam forming is combined with upper strata key, upper strata key is utilized to coordinate the beam forming technique of physical layer, even if also have no idea correct demodulation under eavesdropping side obtains legitimate correspondence both sides accurate channel information condition, thus ensure that eavesdropping side cannot obtain any useful information from physical layer.And the random decay fast rapidly of the transmission signal of physical layer, and be submerged in noise to have screened upper strata key, make eavesdropping side comparatively legacy communications system be more difficult to attack acquisition key by blind estimate mode, the method obtains than conventional security and the higher fail safe of safety of physical layer system with less cost.This method adopts array redundancy advantage, processes, prevent eavesdropping side from utilizing blind equalization mode to attack further, improve fail safe transmission signal weight coefficient.

Accompanying drawing explanation

Fig. 1 is communication scenes figure of the present invention;

Fig. 2 is structural representation of the present invention;

Fig. 3 is the BER performance map when eavesdropping side obtains top level control secret key;

Fig. 4 is the BER performance map when eavesdropping side obtains precise channel information;

Fig. 5 is when eavesdropping side's channel is very close to BER performance map during legitimate correspondence both sides;

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail, but protection scope of the present invention is not limited to the following stated.

Based on a method for the raising multiaerial system communication security of beam forming, comprise the following steps:

S1: as shown in Figure 1, communication scenes: suppose legitimate correspondence transmit leg Alice, N _tfor transmit leg transmitting antenna, legitimate correspondence recipient Bob, N _rfor recipient's reception antenna, the side of eavesdropping Eve, N _efor the side's of eavesdropping reception antenna, legitimate correspondence both sides also do not know the existence of Eve.Before a communication, Bob is first to Alice transmitting channel estimated sequence, and Alice is according to the channel information H of the sequencal estimation legitimate correspondence received _bA, according to TDD system channel reciprocity, H _bA=H _aB, and Eve can steal this sequencal estimation H _bE, but cannot according to this retrieval H _bAand H _aE;

S2: as shown in Figure 2, legitimate sender sends information s (n), is multiplied by weight w (n), the information x (n) finally sent=w (n) s (n) when sending information s (n); In process of transmitting, legitimate correspondence both sides share binary sequence Q _control=(q ₁, q ₂..., q _n), q _i∈ GF (2), I _efor diagonal entry is the N of 1 _rdimension unit matrix, order

$\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& H_A{w}_i^0=I_E\\ \mathrm{if}& q_i=1,& H_A{w}_i^1=-I_E\end{array}\right.$

$w^0=\{w_1^0,w_2^0...,w_n^0\},w^1=\{w_1^1,w_2^1...,w_n^1\};$

S3: in communication process, adopts and has the MPSK modulation system of symmetrical symbols collection, namely to modulation glossary of symbols S, to wherein any one modulation symbol s _i∈ S, total exist one the mapping of constellation symbol and modulation bit is by following criterion:

U _i＝(u ₁,u ₂,...u _M) _i→s _i

$U_j=U_i\⊕(\mathrm{1,1},...1)\→s_j=-s_i;$

Wherein, M is order of modulation, U _i(i=1,2 ..., M) for M-bit wait adjust bit vectors;

S4: work as U _imapping symbols s _iin time, ensures and U _ihamming distance vectorial U farthest _jbe mapped to-s _i, ensure that the average Hamming distance of bit vectors that adjacent symbol is corresponding is minimum, then legitimate receipt side receives signal y simultaneously _rn () utilizes maximum-likelihood demodulation s _ias follows:

${\hat{s}}_i=\underset{s_i\∈S}{\arg }\min {\left|\right|y_r-I_E{s}_i\left|\right|}^2$

$\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& {\stackrel{\‾}{s}}_i={\hat{s}}_i\\ \mathrm{if}& q_i=1,& {\stackrel{\‾}{s}}_i=-{\hat{s}}_i\end{array}\right.;$

Meanwhile, eavesdropping side receives signal y _e, the signal received with the same manner demodulation:

$\begin{array}{c}{\hat{s}}_i=\underset{s_i\∈S}{\arg }\min {\left|\right|y_e-I_E{s}_i\left|\right|}^2\\ =\underset{s_i\∈S}{\arg }\min {\left|\right|H_E{w}_{i}s\left(n\right)+v_E-I_E{s}_i\left|\right|}^2\end{array};$

S5: as legitimate sender antenna N _tbe greater than legitimate receipt side antenna N _rtime, become when order sends weight coefficient; Utilize array redundancy advantage, at each symbol sending time slots i for weight coefficient make following process:

$H_A=\left[H_0{H}_1\right],w=\left[\begin{array}{c}{w}_0\\ w_1\end{array}\right]$

Then have,

$H_{A}w=H_0{w}_0+H_1{w}_1=(\±1_{q_i})I_E$

$x\left(n\right)=w\·s\left(n\right)=\left[\begin{array}{c}{w}_{0}s\left(n\right)\\ w_{1}s\left(n\right)\end{array}\right]=\left[\begin{array}{c}{x}_0\left(n\right)\\ x_1\left(n\right)\end{array}\right];$

Wherein, $\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& (\±1_{q_i})=1\\ \mathrm{if}& q_i=1,& (\±1_{q_i})=-1\end{array}\right.;$ H ₀for N _r× N _rsubmatrix, H ₁for N _r× (N _t-N _r) submatrix; Make x ₁(n)=w ₁n () s (n) is stochastic variable, and obey gaussian random distribution, average μ, covariance matrix Σ; So solve an equation and can obtain $x_0\left(n\right)={H_0}^{-1}[(\±1_{q_i})I_{E}s\left(n\right)-H_1{x}_1\left(n\right)];$

S6: finally can send signal:

$x\left(n\right)=\left[\begin{array}{c}{H_0}^{-1}[(\±1_{q_i})I_{E}s\left(n\right)-H_1{x}_1\left(n\right)]\\ x_1\left(n\right)\end{array}\right].$

As shown in Figure 3, Eve (K) represents performance curve during Eve acquisition top level control key, namely when eavesdropping side obtains top level control key, the method that the present invention proposes still can ensure that eavesdropping side cannot any information of demodulation, the error rate is tending towards 0.5, and in similar cross-layer system or conventional cipher safety, eavesdropping side is once obtain entirely collapsing of key means safe system.

As shown in Figure 4, in figure, CB is the inventive method, and AN is physical layer man made noise method, and AR is physical layer random array redundancy method; In figure (424), (426) represent recipient's antenna, transmit leg antenna, the side's of eavesdropping number of antennas i.e. (N _rn _tn _e); When eavesdropping side obtains precise channel information, AR (array redundancy method) during method and conventional physical that the present invention proposes are safe, AN (man made noise's method) systems approach Performance comparision, still can ensure that eavesdropping side cannot demodulation, and conventional physical safety method eavesdropping side can recover partial information.

As shown in Figure 5, in figure 10 °, 20 °, 45 ° represent the similarity of eavesdropping side's channel and legitimate channel respectively; When eavesdropping side's channel is very close to legitimate correspondence both sides, with traditional AR (array redundancy), AN (man made noise) method Performance comparision, the method that the present invention proposes still can ensure that eavesdropping side cannot demodulation, and conventional physical safety method eavesdropping side can recover partial information.

Claims (1)

1., based on a method for the raising multiaerial system communication security of beam forming, it is characterized in that: comprise the following steps:

S1: before a communication, legitimate receipt direction legitimate sender transmitting channel estimated sequence, legitimate sender estimates the channel information H of legitimate correspondence according to the channel estimation sequence received _bA, according to the reciprocity of TDD system channel, draw H _bA=H _aB, this sequencal estimation H steals in eavesdropping side _bE, cannot according to retrieval channel information H _bAand H _aE;

S2: legitimate sender sends information s (n), is multiplied by weight w (n), the information x (n) finally sent=w (n) s (n) when sending information s (n); In process of transmitting, legitimate correspondence both sides share binary sequence Q _control=(q ₁, q ₂..., q _n), q _i∈ GF (2), I _efor diagonal entry is the N of 1 _rdimension unit matrix, order

$\begin{array}{c}\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& H_A{w}_i^0=I_E\\ \mathrm{if}& q_i=1,& H_A{W}_i^1={-I}_E\end{array}\right.\\ W^0=\{w_1^0,w_2^0...,w_n^0\},W^1=\{w_1^1,w_2^1...,w_n^1\}\end{array};$

S3: in communication process, adopts and has the MPSK modulation system of symmetrical symbols collection, namely to modulation glossary of symbols S, to wherein any one modulation symbol s _i∈ S, total exist one the mapping of constellation symbol and modulation bit is by following criterion:

U _i＝(u ₁,u ₂,...u _M) _i→s _i

$U_j=U_i\⊕(\mathrm{1,1},...,)\→s_j={-s}_i;$

Wherein, M is order of modulation, U _i(i=1,2 ..., M) for M-bit wait adjust bit vectors;

S4: work as U _imapping symbols s _iin time, ensures and U _ihamming distance vectorial U farthest _jbe mapped to-s _i, ensure that the average Hamming distance of bit vectors that adjacent symbol is corresponding is minimum, then legitimate receipt side receives signal y simultaneously _rn () utilizes maximum-likelihood demodulation s _ias follows:

${\hat{s}}_i=\underset{s_i\∈S}{\arg }{\min \left|\right|y_r-I_E{s}_i\left|\right|}^2$

$\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& {\stackrel{\‾}{s}}_i={\hat{s}}_i\\ \mathrm{if}& q_i=1& {\stackrel{\‾}{s}}_i=-{\hat{s}}_i\end{array}\right.;$

Meanwhile, eavesdropping side receives signal y _e, the signal received with the same manner demodulation:

$\begin{array}{c}{\hat{s}}_i=\underset{s_i\∈S}{\arg }\min {\left|\right|y_e-I_E{S}_i\left|\right|}^2\\ =\underset{s_i\∈S}{\arg }\min {\left|\right|H_E{w}_{i}s\left(n\right)+v_E-I_E{s}_i\left|\right|}^2\end{array};$

S5: as legitimate sender antenna N _tbe greater than legitimate receipt side antenna N _rtime, become when order sends weight coefficient; Utilize array redundancy advantage, at each symbol sending time slots i for weight coefficient make following process:

$H_A=\left[H_0{H}_1\right],w=\left[\begin{array}{c}{w}_0\\ w_1\end{array}\right]$

Then have,

$\begin{array}{c}{H}_{A}w=H_0{w}_0+H_1{w}_1=(\±1_{\mathrm{qi}})I_E\\ x\left(n\right)=w\·s\left(n\right)=\begin{array}{c}\left[\begin{array}{c}{w}_{0}s\left(n\right)\\ w_{1}s\left(n\right)\end{array}\right]=\begin{array}{}\end{array}\left[\begin{array}{c}{x}_0\left(n\right)\\ x_1\left(n\right)\end{array}\right]\end{array}\end{array};$

Wherein, $\left\{\begin{array}{ccc}\mathrm{if}& q_i=0,& (\±1_{\mathrm{qi}})=1\\ \mathrm{if}& q_i=1,& (\±1_{\mathrm{qi}})=-1\end{array}\right.;$ H ₀for N _r× N _rsubmatrix, H ₁for N _r× (N _t-N _r) submatrix; Make x ₁(n)=w ₁n () s (n) is stochastic variable, and obey gaussian random distribution, average μ, covariance matrix Σ; So solve an equation and can obtain x ₀(n)=H ₀ ^-1[(± 1 _qi) I _es (n)-H ₁x ₁(n)];

S6: finally can send signal:

$x\left(n\right)=\left[\begin{array}{c}{H_0}^{-1}[(\±1_{\mathrm{qi}})I_{E}s\left(n\right)-H_1{x}_1\left(n\right)]\\ x_1\left(n\right)\end{array}\right].$