CN104618005A - Emission focusing type multi-antenna gap safety communication method - Google Patents

Emission focusing type multi-antenna gap safety communication method Download PDF

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CN104618005A
CN104618005A CN201510044229.XA CN201510044229A CN104618005A CN 104618005 A CN104618005 A CN 104618005A CN 201510044229 A CN201510044229 A CN 201510044229A CN 104618005 A CN104618005 A CN 104618005A
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antenna
phase
signal
transmitting
legitimate receipt
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CN104618005B (en
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殷勤业
俱莹
陈媛
杨骞
王慧明
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Xian Jiaotong University
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Xian Jiaotong University
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Abstract

The invention discloses an emission focusing type multi-antenna gap safety communication method. In the training phase, the legitimate users transmit training signals received, the transmitter phase value obtained for transmission through the next phase of testing and treatment; in the transmission signal phase, the transmitter select multiple antennas for transmitting signals based on the upward pattern, the training phase of the detected phase negated, after loading the information so that the signal came back and received legitimate users transmit antenna phase stack, so that the received energy to focus on legitimate user, legitimate users each receiving antenna separately within product-related testing, training signals for transmitting antenna can correctly demodulate the signal, the other antenna to eliminate bias based on correct demodulation of the antenna, on average receiving antenna and solving all the phase demodulating the correct information, but it is difficult eavesdropper correctly received and intercepted information. Simulation results show that the legitimate user receives symbol error rate is kept low level at low signal to noise ratio, and high eavesdropper symbol error rate.

Description

The multiple antennas gap safety communicating method of transmitting focusing formula
Technical field:
The present invention relates to secure wireless communication transmission method, particularly a kind of multiple antennas gap safety communicating method of transmitting focusing formula.
Background technology:
In recent years, radio communication brings facility to the life of people, but electromagnetic broadcast characteristic and the opening of wireless channel make the security facing communicated challenge, and thus wireless security communication becomes the focus of communications field research.Frequency hopping is a kind of method of conventional secure communication, but frequency hopping communications exists some shortcomings being difficult to overcome, as taken a large amount of frequency spectrum resources, antenna size needs change along with the change of frequency, hop rate is subject to phase-locked loop and the restriction etc. of antenna size pace of change.In addition, listener-in, can correct demodulating information in any position once steal frequency hopping pattern, and its basic reason is that frequency and position have nothing to do, and frequency hopping does not utilize the characteristic of radio communication.
Wireless channel has the Spatial characteristic outside time-frequency domain, if can by empty spectrum resource Appropriate application, the problem that frequency spectrum resource is day by day deficient can be solved, the diversity of empty spectrum can be utilized again to maximize the otherness between legitimate receipt user and listener-in's channel, just can realize the fail safe communicated under the prerequisite of communication quality ensureing legitimate receipt user.
0/1 formula gap technology a kind ofly utilizes empty spectrum resource to improve the method for the confidentiality of communication, transmitting terminal electronic switch switches fast between transmitting antenna, select different antenna transmission signals according to gap pattern at every turn, channel is constantly changed along with the change of antenna.
The 0/1 formula gap technology transmitting terminal based on forward direction training sends training sequence, and receiving terminal use training obtains weights and carries out demodulation when formal communication, just can obtain regular planisphere.But once listener-in is aware of gap pattern and can grasp opportunity and participate in together with legitimate receipt user training, so listener-in also can correct restituted signal.
0/1 formula gap technology of weight feedback type adopts the method for reverse train, by receiving terminal transmitting training sequence, transmitting terminal feeds back to receiving terminal after obtaining the channel information between dual-mode antenna, and receiving terminal utilizes the reciprocity design weights of channel, carrys out restituted signal by the correct weighting of gap pattern.But need the process of a feedback channel information, not only reduce efficiency, and likely can make mistakes in the process of feedback channel information, make the reliability communicated be difficult to ensure.
Summary of the invention:
The object of the present invention is to provide a kind of multiple antennas gap safety communicating method of transmitting focusing formula, this communication means is by utilizing the empty spectrum resource outside time-frequency domain, adopt the transmission method of transmitting focusing, signal is made to locate in-phase stacking legitimate receipt user, maximize the otherness between legitimate receipt user and listener-in's channel, under the prerequisite ensureing legitimate receipt user communication quality, realize the fail safe communicated.
For reaching above object, the present invention takes following technical scheme to be achieved:
The multiple antennas gap safety communicating method of transmitting focusing formula, adopts transmitting terminal and the legitimate receipt mode configuring multiple antennas per family, comprises the steps:
1) training stage:
A, by legitimate receipt user transmitting training signal;
B, transmitting terminal receive training signal, and carry out inner product coherent detection to the training signal that every root antenna receives, and obtain the stage of transmitting to be used for the phase value of processing signals;
2) transmit the stage:
It is radiofrequency signal that a, transmitting terminal choose the modulates information that a kind of modulation system will send, and chooses the antenna that will transmit according to gap pattern;
The phase place negate that training stage detects by b, transmitting terminal, the former road of the signal making legitimate receipt user send after load information returns, and at legitimate receipt, user locates in-phase stacking;
Every root antenna of c, legitimate receipt user carries out inner product coherent detection respectively, being used for the kth root antenna of transmitting training signal can correct restituted signal, the phase place that all the other antennas go out according to kth root antenna detection is asked for and eliminates phase deviation, the phase value that average all antennas solve, obtains final restituted signal.
The present invention further improves and is, transmitting terminal configuration M root antenna, M >=2, legitimate receipt user configures K root antenna, K >=2, and the adjacent antenna spacing of transmitting terminal and legitimate receipt user is all greater than a wavelength.
The present invention further improves and is, training signal is sent by the kth root antenna of legitimate receipt user, be reverse train, and the first phase of training signal is by legitimate receipt user random selecting, without the need to informing transmitting terminal.
The present invention further improves and is, transmitting terminal at every turn according to gap pattern random selecting many antenna transmission signals to realize transmitting focusing, the switching of antenna utilizes electronic switch to realize.
Compared with prior art, useful achievement of the present invention is:
1, core of the present invention is transmitting focusing, and what receive due to transmitting terminal many antennas is the same signal that legitimate receipt user sends, and former road returns will inevitably at the transmitting antenna place in-phase stacking of legitimate receipt user.And the signal that listener-in receives just can not ensure in-phase stacking, even if in the place of close together, also likely can oppositely offset.By transmitting focusing, the received signal to noise ratio of legitimate receipt user significantly improves, and the received signal to noise ratio eavesdropping user does not improve, and makes the signal to noise ratio of legitimate receipt user obviously be better than eavesdropping the signal to noise ratio of user, adds fail safe.In addition, had the technology of transmitting focusing, the gap pattern that just can adopt many antennas simultaneously to launch, comparatively front several at every turn can only the fail safe of gap technology of an antenna transmission higher.
2, the signal that legitimate receipt user sends only has legitimate receipt user oneself to know, without the need to informing transmitting terminal, transmitting terminal sends back to legitimate receipt user after being only responsible for load information, avoids the risk that in exchange message process, stolen hearer intercepts and captures.Even if listener-in receives signal and opportunity of grasping take part in training, do not know the primary signal that legitimate receipt user sends, can not correct information be demodulated.Legitimate receipt user sends the initial phase random selecting of signal at every turn, even if the accidental demodulation of listener-in is correct, after legitimate receipt user has changed and transmitted, listener-in still can not demodulation, is equivalent to " one-time pad ".
3, gap technology realizes the switching of transmitting antenna by switching electronic switch, the quick switching of antenna makes channel change rapidly, makes listener-in be difficult to acquisition of information.Hop rate and the skip frame of antenna are depended in the empty gain of expansion of gap technology, and electronic switch switches the level that hop rate can be made to reach very high, far above the accessible hop rate of frequency hopping.And the distributed arrangement of antenna, distance can be far, can obtain very large skip frame again, and therefore, gap technology can obtain the empty gain of high expansion, can improve again the fail safe of communication while ensureing communication quality.
Accompanying drawing illustrates:
Fig. 1 is the system model figure of transmitting focusing formula safety communication technology involved in the present invention.
Fig. 2 is legitimate receipt user and the error sign ratio figure of eavesdropping user under different signal to noise ratio, wherein, Fig. 2 (a) is the error sign ratio figure under different signal to noise ratio for the legitimate receipt user under linear coordinate and eavesdropping user, and Fig. 2 (b) is the error sign ratio figure under different signal to noise ratio for the legitimate receipt user under logarithmic coordinates and eavesdropping user.
Fig. 3 is the error sign ratio figure under transmitting terminal different transmit antennas number.
Embodiment:
Below in conjunction with the drawings and specific embodiments, the present invention is described in further details.
As shown in Figure 1, transmitting terminal Alice and legitimate receipt user Bob all configures multiple antennas to the system model of transmitting focusing formula safety communication technology involved in the present invention, and the side of intercepting Eve also sets up multiple antennas in order to obtaining information.Wherein, Eve only eavesdrops message and does not transmit.
When analyzing channel model, there is following hypothesis: 1. propagation medium is homogenous linear and isotropic; 2. each array element distance is from being greater than wavelength X, and the impact between array element can be ignored; 3. the noise in each array element and channel is Gauss's additive white noise, is separate, and has nothing to do with signal; 4. channel is slow change, and namely within a period of time of communication, the characteristic of channel is thought constant.
Communicating pair uses identical carrier frequency, adopt narrowband model, then parsingization transmit for s 0and φ 0be respectively the amplitude and first phase that transmit, ω is carrier frequency, and p (t) is the envelope of modulation signal.
Signal is in space through Multipath Transmission, and after different time delays and decay, suppose there is J paths (comprising direct projection footpath and reflection footpath), the signal of receiving terminal is:
x ( t ) = Σ i = 1 J b i s [ t - τ i ( x i , y i , z i ) ] + n ( t ) = Σ i = 1 J b i e - jω τ i ( x i , y i , z i ) s 0 e j ( ωt + φ 0 ) p [ t - τ i ( x i , y i , z i ) ] + n ( t ) - - - ( 1 )
In formula, b iand τ i(x i, y i, z i) represent the amplitude fading of i-th multipath and time delay respectively, wherein, (x i, y i, z i) be the three dimensions component of wave transmissions distance of equal value, the additive white Gaussian noise that n (t) is zero-mean.For the i-th paths, signal lag τ i(x i, y i, z i) arrive receiving terminal afterwards, before this, the arriving signal of the i-th paths is 0.
When symbol time is greater than multi-path delay spread, after the signal in all paths all arrives, have the plateau that one section of all path signal is superimposed, during detection, only consider the stable sinusoidal signal of this section, each antenna detects respectively.
1) training stage:
A, kth root antenna transmission training signal by legitimate receipt user Bob, first phase φ 0random selecting, the antenna k sending training signal is also random selecting.The signal that Alice receives is:
x A ( t ) = h k s 0 e j ( ωt + φ 0 ) + n A ( t ) - - - ( 2 )
In formula, h k = [ h k 1 , h k 2 , . . . h kM ] T = [ b k 1 e j θ k 1 , b k 2 e j θ k 2 , . . . b kM e j θ kM ] T , Wherein h kithe kth root antenna representing Bob to the amplitude fading of equal value of the mulitpath comprehensive function of i-th antenna of Alice and phase shift, b kiand θ kibe respectively amplitude fading and phase shift, n at () is white Gaussian noise.
B, transmitting terminal Alice carry out N times of over-sampling to the signal that every root antenna receives, and are the correlated series of 0 by the first phase that L cycle is long carry out inner product coherent detection to the signal after sampling, the correlated results of i-th antenna is:
R i ( m ) = < x Ai ( n ) , r A ( n ) > = E [ h ki s 0 e j 2 &pi; N ( n + m ) e j &phi; 0 r A * ( n ) ] = 1 LN &Sigma; n = 0 LN - 1 h ki s 0 e j 2 &pi; N ( n + m ) e j &phi; 0 e - j 2 &pi; N n = b ki s 0 e j ( &theta; ki + &phi; 0 ) e j 2 &pi; N m - - - ( 3 )
In formula, E [] is mathematic expectaion, can be obtained the phase value θ of training stage by formula (3) ki+ φ 0, this is also that the every root antenna of subsequent transmission signal phase is used for carrying out the phase value needed for signal weighting.
2) transmit the stage:
It is radiofrequency signal that a, transmitting terminal Alice choose the modulates information that a kind of modulation system will send, and chooses the antenna that G root will transmit, the set of the G root antenna serial number chosen is designated as ST according to gap pattern.
The phase theta that b, Alice will this G root antenna detect in the training stage ki+ φ 0negate, loads the communication information send back to Bob by original path afterwards, now Alice transmit for:
s A ( t ) = [ A s e j ( &omega;t + &theta; s ) ] diag { a } c - - - ( 4 )
In formula, diag{} represents that diagonal entry is the diagonal matrix of { }, represent the phase place negate detected by Alice, a=[a 1, a 2..., a m] tthe switch vector produced according to gap pattern, a when Alice selects i-th antenna transmission ia when=1, Alice does not select i-th antenna transmission i=0.
Suppose channel reciprocity, the signal that the kth root of Bob and l (l ≠ k) root antenna receive is respectively:
x Bk ( t ) = h k T s A ( t ) + n Bk ( t ) = A s e j ( &omega;t + &theta; s ) h k T diag { a } c + n Bk ( t ) = &Sigma; i &Element; S T b ki A s e j ( &omega;t + &theta; s ) e - j &phi; 0 + n Bk ( t ) - - - ( 5 )
x Bl ( t ) = h l T s A ( t ) + n Bl ( t ) = A s e j ( &omega;t + &theta; s ) h l T diag { a } c + n Bl ( t )
= &Sigma; i &Element; S T b li A s e j ( &omega;t + &theta; s ) e - j &phi; 0 e j ( &theta; li - &theta; ki ) + n Bl ( t ) - - - ( 6 )
In formula, n bk(t) and n blt () is white Gaussian noise.
Every root antenna of c, legitimate receipt user Bob carries out inner product coherent detection, respectively due to phase 0be sent by Bob the training stage, so Bob holds this phase place known, and use namely first phase is-φ 0correlated series carry out inner product coherent detection, the related test results of kth root and l (l ≠ k) root antenna is respectively:
&xi; Bk = e j &theta; s &Sigma; i &Element; S T A s b ki - - - ( 7 )
&xi; Bl = e j&theta; s &Sigma; i &Element; S T A s b li e j ( &theta; li - &theta; ki ) = e j &theta; s B l e j &beta; l - - - ( 8 )
Will be written as form, so far, being used for the kth root antenna of Bob of transmitting training signal obtains signal phase θ s, and can see, the signal that the G root antenna of Alice is sent has identical phase place at the kth root antenna place of Bob, can correct restituted signal, and achieves in-phase stacking; And except antenna k, after all the other antenna demodulation, the planisphere of signal all there occurs rotation, the phase place that l (l ≠ k) root antenna can go out according to kth root antenna detection tries to achieve oneself phase deviation β l, by eliminating deviation, just can correct demodulation.Each when gap change in pattern, solve the digital baseband input signal of an antenna l (l ≠ k), the follow-up symbol received is according to this deviate demodulation.The phase place that average all reception antennas solve obtains final phase value, thus demodulates correct information.
Level security of the present invention under Simulation experiments validate QPSK modulation system, wherein the side of intercepting Eve adopts the antenna with legitimate receipt user Bob equal number.
See Fig. 2, the error sign ratio of legitimate receipt user and the side of intercepting is contrasted under multiple state of signal-to-noise, can find: legitimate receipt user Bob all can recover primary signal with very little error sign ratio when more than signal to noise ratio-15dB, and the error sign ratio of the side of intercepting Eve is always about 0.75, so high error sign ratio makes Eve cannot steal any information at all, and the error sign ratio of Eve and signal to noise ratio have nothing to do, mainly the channel difference of Eve and Bob causes, and the transmission mechanism of gap make use of the diversity of empty spectrum just to maximize this species diversity.
See Fig. 3, the error sign ratio of Bob when transmitting terminal each random selecting different antennae number transmits, error sign ratio increases with number of transmit antennas object and reduces, performance when Alice chooses 1 antenna transmission is obviously not as choosing many antenna transmissions, thus transmitting focusing technology makes the signal of many antenna transmissions hold in-phase stacking to improve fail safe at Bob, and being better than at every turn can only by the gap technology of an antenna transmission.

Claims (4)

1. the multiple antennas gap safety communicating method of transmitting focusing formula, adopts transmitting terminal and the legitimate receipt mode configuring multiple antennas per family, it is characterized in that, comprise the steps:
1) training stage:
A, by legitimate receipt user transmitting training signal;
B, transmitting terminal receive training signal, and carry out inner product coherent detection to the training signal that every root antenna receives, and obtain the stage of transmitting to be used for the phase value of processing signals;
2) transmit the stage:
It is radiofrequency signal that a, transmitting terminal choose the modulates information that a kind of modulation system will send, and chooses the antenna that will transmit according to gap pattern;
The phase place negate that training stage detects by b, transmitting terminal, the former road of the signal making legitimate receipt user send after load information returns, and at legitimate receipt, user locates in-phase stacking;
Every root antenna of c, legitimate receipt user carries out inner product coherent detection respectively, being used for the kth root antenna of transmitting training signal can correct restituted signal, the phase place that all the other antennas go out according to kth root antenna detection is asked for and eliminates phase deviation, the phase value that average all antennas solve, obtains final restituted signal.
2. the multiple antennas gap safety communicating method of transmitting focusing formula according to claim 1, is characterized in that, transmitting terminal configuration M root antenna, M >=2, legitimate receipt user configures K root antenna, K >=2, and the adjacent antenna spacing of transmitting terminal and legitimate receipt user is all greater than a wavelength.
3. the multiple antennas gap safety communicating method of transmitting focusing formula according to claim 1, it is characterized in that, training signal is sent by the kth root antenna of legitimate receipt user, is reverse train, and the first phase of training signal is by legitimate receipt user random selecting, without the need to informing transmitting terminal.
4. the multiple antennas gap safety communicating method of transmitting focusing formula according to claim 1, it is characterized in that, transmitting terminal at every turn according to gap pattern random selecting many antenna transmission signals to realize transmitting focusing, the switching of antenna utilizes electronic switch to realize.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102970068A (en) * 2012-10-22 2013-03-13 西安交通大学 Distributed multi-antenna gap receiving and sending method for security and secrecy wireless communication
CN103236877A (en) * 2013-04-19 2013-08-07 西安交通大学 Weight value feedback reversal training method used for safety wireless communication
US20130301484A1 (en) * 2012-05-13 2013-11-14 Amir Keyvan Khandani Distributed Collaborative Signaling in Full Duplex Wireless Transceivers

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130301484A1 (en) * 2012-05-13 2013-11-14 Amir Keyvan Khandani Distributed Collaborative Signaling in Full Duplex Wireless Transceivers
CN102970068A (en) * 2012-10-22 2013-03-13 西安交通大学 Distributed multi-antenna gap receiving and sending method for security and secrecy wireless communication
CN103236877A (en) * 2013-04-19 2013-08-07 西安交通大学 Weight value feedback reversal training method used for safety wireless communication

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