CN104270227A - Null-shift-keying-based physical layer safety transmission method in multi-input single-output system - Google Patents

Abstract

The invention discloses a null-shift-keying-based physical layer safety transmission method in a multi-input single-output system. The physical layer safety transmission method includes the steps that (1) the multi-input single-output communication system comprises a source node, a destination node and a wiretapping node, M transmitting antennas are assembled on the source node, and the destination node and the wiretapping node are each provided with an antenna; (2) information of the source node is grouped, wherein bit grouping is carried out on bit information sequences to be transmitted through the source node according to the same bit length; (3) null shift keying is carried out, wherein bit information contained in information bit groups is mapped to the transmitting antennas with the corresponding serial numbers through the source node, and the source node transmits antenna serial numbers to serve as carriers of information source information through null shift keying; (4) precoding processing is carried out, wherein precoding processing is carried out on symbols transmitted by the transmitting antennas through the source node. According to the null-shift-keying-based physical layer safety transmission method, limitation of a single-antenna system to the physical layer safety can be broken, the structure of a transceiver can be simplified, and defects in a traditional multi-antenna physical layer safety transmission method are overcome.

Description

Move the safe transmission method of physical layer of keying based on sky in MISO system

Technical field

The present invention relates to be a kind of adopt sky to move keying (sky moves keying English: Space Shift Keying, be called for short in literary composition: SSK) safe transmission method of physical layer, specifically, relate to the safe transmission method of physical layer moving keying in a kind of multiple input single output (multiple input single output English is: Multiple-Input-Single-Output, is called for short in literary composition: MISO) system based on sky.

Background technology

Due to the opening of transmission medium, radio communication, while bringing great convenience to people's life, also makes the individual privacy of user, property safety is on the hazard.Therefore, how guaranteeing the fail safe of Wireless Data Transmission, make it not be stolen, decode, is the major issue that radio communication must solve.Traditionally, the security mechanism of cordless communication network is mainly referred from wired communication network, information privacy sex chromosome mosaicism wherein solves primarily of the cryptographic algorithm based on standard-key cryptography and RSA arithmetic, and the high computation complexity needed for decryption ensure that the validity of cryptographic algorithm.Although these cryptography methods achieve immense success in the application of information security field, for maintenance information has played safely important function, but along with the lifting of Computing ability and arithmetic speed, this fail safe be based upon on computation complexity is challenged just day by day.On the other hand, the important feature that wireless network is different from computer network is the broadcast characteristic of its Information Communication, and this causes the online distribution of key, maintenance management more difficult.

Summary of the invention

Technical problem: technical problem to be solved by this invention is: the safe transmission method of physical layer moving keying in a kind of MISO system based on sky is provided, the method can break through the restriction of a single aerial system to safety of physical layer on the one hand, can transceiver architecture be simplified again on the other hand, overcome the defect of traditional multiple antennas safe transmission method of physical layer.

Technical scheme: for solving the problems of the technologies described above, the technical solution used in the present invention is:

Move a safe transmission method of physical layer for keying in MISO system based on sky, this transmission method comprises the following steps:

The first step: the multiple input single output communication system under safety of physical layer scene, comprise a source node S and two information destination node, two information destination node are all the validated users of system; In communication process, source node sends information to an information destination node, node D for the purpose of this information destination node; This information of another information destination node intention eavesdropping is eavesdropping node E; Source node S is equipped with M root transmitting antenna, and destination node D and eavesdropping node E assembles 1 antenna respectively, and the m root transmitting antenna in source node S to the channel of destination node D is the transmitting antenna of source node S to the channel set of destination node D is m root transmitting antenna in source node S to the channel of eavesdropping node E is all channels are separate; Destination node D obtains channel by channel estimating eavesdropping node E obtains channel by channel estimating destination node D and eavesdropping node E by the feedback of channel information that obtains to source node S; The span of M be greater than 1 integer, m=1,2 ..., M; M be greater than 1 integer;

Second step: source node identification divides into groups: source node S, by bit information sequence x to be sent, is carried out bit groupings by same bits length p, had 2 ^pplant grouping situation, be designated as one_to_one corresponding between the transmitting antenna sequence number of bit groupings and source node, block length p meets p=log ₂m;

3rd step: sky moves keying: corresponding according between bit groupings and the transmitting antenna sequence number of source node, the bit information that packets of information bits comprises by source node is mapped on the transmitting antenna of corresponding sequence number; Based on the random unique trait of wireless channel, the process of carrying out transmitting antenna selection is equivalent to the process of Channel assignment; Move keying by sky, source node transmitting antenna sequence number becomes the supporting body of information source information, and the transmitting antenna of selected signal transmission always sends the symbol 1 in binary phase shift keying signal, and this symbol 1 is designated as x ₀, | x ₀| ²=1, not selected M-1 root antenna keeps mourning in silence, and does not send any signal;

4th step: precoding processing: source node carries out precoding processing to the symbol that each transmitting antenna sends, the m root transmitting antenna of selected signal transmission sends symbol x ₀time, to x ₀be multiplied by a precoding coefficients α _m, α _mmeet formula (1):

${\mathrm{\α}}_m{h}_{S_{m}E}={\mathrm{\α}}_{m_2}{h}_{S_{m_2}E}$ Formula (1)

Wherein, represent the m in M root transmitting antenna ₂the precoding coefficients of root transmitting antenna, and m ₂≠ m, represent m ₂root transmitting antenna is to the channel of eavesdropping node E.

Further, move the safe transmission method of physical layer of keying based on sky in described MISO system, also comprise the 5th step: detect sky and move keyed information: first precoding coefficients is sent to destination node by source node, source node has M root transmitting antenna, total M kind Received signal strength possibility, the actual signal received of hypothesis goal node is y _d, according to formula (2) measuring and calculating y _dand the Euclidean distance between various possibility Received signal strength:

${|y_D-\sqrt{P}{\mathrm{\α}}_m{h}_{S_{m}D}{x}_0|}^2$ Formula (2)

Wherein, P represents the transmitting power of source node, α _mrepresent the precoding coefficients of m root transmitting antenna;

From an above-mentioned gained M Euclidean distance, choose transmitting antenna sequence number corresponding to minimum value, be the source node transmitting antenna sequence number that source node identification is mapped to, thus obtain the packets of information bits that this source node corresponding to transmitting antenna sequence number sends; Destination node carries out infomation detection, adopts maximum likelihood algorithm according to formula (3):

formula (3)

Wherein, represent that destination node is to the detected value of transmitting antenna sequence number,

The average pairwise error probability of destination node is:

${\mathrm{APEP}}_D=\frac{1}{M(M-1)}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{\underset{m_2\≠m}{m_2=1}}{\overset{M}{\mathrm{\Σ}}}Q\left(\frac{|\sqrt{P}{\mathrm{\α}}_m{h}_{S_{m}D}-\sqrt{P}{\mathrm{\α}}_{m_2}{h}_{S_{m_2}D}|}{\sqrt{2}\mathrm{\σ}}\right)$ Formula (4)

Wherein, APEP _drepresent the average pairwise error probability of destination node, Q represents complementary error function, and σ represents noise power; represent the m in M root transmitting antenna ₂the precoding coefficients of root transmitting antenna, and m ₂≠ m, represent m ₂root transmitting antenna is to the channel of destination node D;

For eavesdropping node, due to the existence of formula (1), no matter which root transmitting antenna signal transmission source node selects, the Received signal strength y of eavesdropping node _efor:

$y_E=\sqrt{P}{\mathrm{\α}}_1{h}_{S_{1}E}{x}_0+v_E$ Formula (5)

Wherein, v _erepresent the reception noise of eavesdropping node;

The average pairwise error probability APEP of eavesdropping node _efor:

${\mathrm{APEP}}_E=\frac{1}{M(M-1)}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{\underset{m_2\≠m}{m_2=1}}{\overset{M}{\mathrm{\Σ}}}Q\left(0\right)=0.5.$

Beneficial effect: compared with prior art, technical scheme of the present invention has following beneficial effect: in transmission method of the present invention, source node adopts sky to move key control technology, information source information is mapped in transmitting antenna sequence number, eliminate the otherness of each transmitting antenna to eavesdropping node channel by sending precoding processing, thus realize the safety of physical layer transmission of information.On the one hand, this method, using the carrier of antenna serial number as information source information, can overcome safety of physical layer in traditional single antenna systems and restrict this shortcoming by channel, even if tapping channel quality is better than main channel, also can realize safety of physical layer transmission; On the other hand, this method only activates an antenna at every turn and sends signal, therefore compared to traditional multiple antennas safe transmission method of physical layer, this method hardware implementing is simpler, practicality is stronger, avoid the inter-antenna interference in conventional method, the problem such as synchronous, and only need a radio frequency link, save cost.

Accompanying drawing explanation

Fig. 1 is the scene schematic diagram of multiple input single output safety of physical layer of the present invention communication.

Fig. 2 is FB(flow block) of the present invention.

Fig. 3 is in embodiment provided by the invention, and source node adopts sky to move key control technology information source information packet map to be carried out sending pretreated schematic diagram to antenna serial number.

Fig. 4 is in embodiment provided by the invention, and destination node four kinds may Received signal strength and actual Received signal strength planisphere on a complex plane.

Fig. 5 is M=2 at transmitting antenna, under 4,8 conditions, through preliminary treatment and not through preliminary treatment gained safety mutual amount of information with signal to noise ratio change curve.

Fig. 6 is M=2 at transmitting antenna, under 4,8 conditions, and destination node, average pairwise error probability string diagram when eavesdropping node adopts Maximum Likelihood Detection.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in detail.

As shown in Figure 1, move the safe transmission method of physical layer of keying in a kind of MISO system of the present invention based on sky, comprise the following steps:

The first step: the multiple input single output communication system under safety of physical layer scene, comprise a source node S and two information destination node, two information destination node are all the validated users of system; In communication process, source node sends information to an information destination node, node D for the purpose of this information destination node; This information of another information destination node intention eavesdropping is eavesdropping node E.Eavesdropping node E eavesdrops the information that source node S flows to destination node D.Source node S is equipped with M root transmitting antenna, and destination node D and eavesdropping node E assembles 1 antenna respectively.M root transmitting antenna in source node S to the channel of destination node D is the transmitting antenna of source node S to the channel set of destination node D is m root transmitting antenna in source node S to the channel of eavesdropping node E is all channels are separate.Source node S is main channel to the channel of destination node D, and source node S is tapping channel to the channel of eavesdropping node E.Destination node D obtains channel by channel estimating eavesdropping node E obtains channel by channel estimating destination node and eavesdropping node adopt knows channel condition information based on the channel estimation methods of least mean-square error (MMSE), the detailed process of channel estimating can see Georgios B.Giannakis.Signal Processing Advances in Wireless and Mobile Communications Volume 1:Trends in Channel Estimation and Equalization.Beijing:Posts & Telecommunications Press, 2002,11.Certainly, channel estimation methods can also adopt other published methods.Destination node D and eavesdropping node E by the feedback of channel information that obtains to source node S; The span of M be greater than 1 integer, m=1,2 ..., M.M be greater than 1 integer

Second step: source node identification divides into groups: source node S, by bit information sequence x to be sent, is carried out bit groupings by same bits length p, had 2 ^pplant grouping situation, be designated as one_to_one corresponding between the transmitting antenna sequence number of bit groupings and source node, block length p meets p=log ₂m.When block length p meets p=log ₂during M, can ensure that each bit groupings can be mapped to different antenna serial number.

3rd step: sky moves keying: corresponding according between bit groupings and the transmitting antenna sequence number of source node, the bit information that packets of information bits comprises by source node is mapped on the transmitting antenna of corresponding sequence number, namely selects different transmitting antennas according to different packets of information bits.If current information bit groupings is x ₁, then the 1st antenna is selected to send signal, if current information bit groupings is x ₂, then select the 2nd antenna to send signal, the like.Based on the random unique trait of wireless channel, the process of carrying out transmitting antenna selection is equivalent to the process of Channel assignment, namely from channel set in choose a channel such as: when packets of information bits is x _mtime, select m root antenna to send signal, be namely equivalent to from channel set in choose channel carry out signal transmission.Therefore, at the receiving terminal of destination node, as long as detect signal is from which channel, just can know it is which root transmitting antenna is selected, also just can obtain source information bit groupings further.Keying is moved by sky, source node transmitting antenna sequence number becomes the supporting body of information source information, the transmitting antenna of selected signal transmission always sends the symbol 1 in binary phase shift keying (being called for short in binary phase shift keying literary composition: BPSK) signal, and this symbol 1 is designated as x ₀, | x ₀| ²=1, not selected M-1 root antenna keeps mourning in silence, and does not send any signal.Therefore, the symbol " 1 " that source node sends is constant, and itself does not carry any information, and source node identification has all been mapped in transmitting antenna sequence number.

4th step: precoding processing: source node carries out precoding processing to the symbol that each transmitting antenna sends, the m root transmitting antenna of selected signal transmission sends symbol x ₀time, to x ₀be multiplied by a precoding coefficients α _m,

α _mmeet formula (1):

${\mathrm{\α}}_m{h}_{S_{m}E}={\mathrm{\α}}_{m_2}{h}_{S_{m_2}E}$ Formula (1)

Wherein, represent the m in M root transmitting antenna ₂the precoding coefficients of root transmitting antenna, and m ₂≠ m, represent m ₂root transmitting antenna is to the channel of eavesdropping node E.

M root antenna is selected to send symbol x at source node ₀time, the Received signal strength y of destination node _dfor:

$y_D=\sqrt{P}{h}_{S_{m}D}{x}_0+v_D$ Formula (6)

In formula (6), P is the transmitted power of source node.V _dfor additive white Gaussian noise, obedience average is zero, variance is σ ²multiple Gaussian Profile.Suppose the general random distribution such as the information source information of source node is, then the probability that every root antenna is selected is equivalently, channel set in the selected probability of each channel be main channel transinformation content I can be obtained thus _dfor:

$I_D={\log }_{2}M-\frac{1}{M}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{E}_{v_D}\left\{{\log }_2\right[\underset{m_2=1}{\overset{M}{\mathrm{\Σ}}}\exp (-\frac{{|d_D+v_D|}^2-{\left|v_D\right|}^2}{{\mathrm{\σ}}^2})\left]\right\}$ Formula (7)

In formula (7), d _dfor the purpose of distance in node between different Received signal strength constellation point, for about destination node additive white Gaussian noise v _dmathematic expectaion. concrete reckoning process can see Xinrong Guan, Yueming Cai, and Weiwei Yang.On the Mutual Information and Precoding for Spatial Modulation with Finite Alphabet.IEEE Wireless Communications Letters, vol.2, no.4, pp.383-386, Aug.2013.In like manner, tapping channel transinformation content I _ecan be expressed as:

$I_E={\log }_{2}M-\frac{1}{M}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{E}_{v_E}\left\{{\log }_2\right[\underset{m_2=1}{\overset{M}{\mathrm{\Σ}}}\exp (-\frac{{|d_E+v_E|}^2-{\left|v_E\right|}^2}{{\mathrm{\σ}}^2})\left]\right\}$ Formula (8)

In formula (8), d _efor the distance in eavesdropping node between different Received signal strength constellation point, for about eavesdropping node additive white Gaussian noise v _emathematic expectaion.Based on main channel and tapping channel mutual information, system safety transinformation content I can be obtained _sfor: I _s=I _d-I _e.

From tapping channel transinformation content mathematical expression, tapping channel transinformation content I _esize and d _ebe closely related.Especially, if for any m and m ₂, have then there is I _e=0, namely eavesdrop node and cannot obtain any information sent about source node.

According to the 4th step, if m ₂=1, and then all the other precoding coefficients are:

${\mathrm{\α}}_m=h_{S_{1}E}/h_{S_{m}E}$

Through above-mentioned process, any antenna selected transmission symbol x of source node ₀time, the Received signal strength of eavesdropping node is namely to any m and m ₂, have d _e=0.Therefore, tapping channel transinformation content is I _e=0, and minor channel information amount is:

$I_D={\log }_{2}M-\frac{1}{M}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{E}_{v_D}\left\{{\log }_2\right[\underset{m_2=1}{\overset{M}{\mathrm{\Σ}}}\exp (-\frac{{|{d_D}^{\′}+v_D|}^2-{\left|v_D\right|}^2}{{\mathrm{\σ}}^2})\left]\right\}$

Wherein, ${d_D}^{\′}=\sqrt{P}({\mathrm{\α}}_m{h}_{S_{m}D}-{\mathrm{\α}}_{m_2}{h}_{S_{m_2}D})x_0.$ At high s/n ratio $(\frac{P}{{\mathrm{\σ}}^2}\→\∞)$ Under condition, there is I _d→ log ₂m.

Pass through, the 4th step precoding processing, eliminate the otherness of each transmitting antenna of source node to eavesdropping node channel, therefore eavesdrop node and cannot detect signal is from which root antenna, also cannot obtain source node and be mapped to information source information in transmitting antenna sequence number.

Further, move the safe transmission method of physical layer of keying based on sky in described MISO system, also comprise the 5th step: detect sky and move keyed information: first precoding coefficients is sent to destination node by source node, source node has M root transmitting antenna, total M kind Received signal strength possibility, the actual signal received of hypothesis goal node is y _d, according to formula (2) measuring and calculating y _dand the Euclidean distance between various possibility Received signal strength:

${|y_D-\sqrt{P}{\mathrm{\α}}_m{h}_{S_{m}D}{x}_0|}^2$ Formula (2)

Wherein, P represents the transmitting power of source node, α _mrepresent the precoding coefficients of m root transmitting antenna;

From an above-mentioned gained M Euclidean distance, choose transmitting antenna sequence number corresponding to minimum value, be the source node transmitting antenna sequence number that source node identification is mapped to, thus obtain the packets of information bits that this source node corresponding to transmitting antenna sequence number sends; Destination node carries out infomation detection, adopts maximum likelihood algorithm according to formula (3):

formula (3)

Wherein, represent that destination node is to the detected value of transmitting antenna sequence number.

The average pairwise error probability of destination node is:

${\mathrm{APEP}}_D=\frac{1}{M(M-1)}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{\underset{m_2\≠m}{m_2=1}}{\overset{M}{\mathrm{\Σ}}}Q\left(\frac{|\sqrt{P}{\mathrm{\α}}_m{h}_{S_{m}D}-\sqrt{P}{\mathrm{\α}}_{m_2}{h}_{S_{m_2}D}|}{\sqrt{2}\mathrm{\σ}}\right)$ Formula (4)

Wherein, APEP _drepresent the average pairwise error probability of destination node, Q represents complementary error function, and σ represents noise power; represent the m in M root transmitting antenna ₂the precoding coefficients of root transmitting antenna, and m ₂≠ m, represent m ₂root transmitting antenna is to the channel of destination node D.

For eavesdropping node, due to the existence of formula (1), no matter which root transmitting antenna signal transmission source node selects, the Received signal strength y of eavesdropping node _efor:

$y_E=\sqrt{P}{\mathrm{\α}}_1{h}_{S_{1}E}{x}_0+v_E$ Formula (5)

Wherein, v _erepresent the reception noise of eavesdropping node;

The average pairwise error probability APEP of eavesdropping node _efor:

${\mathrm{APEP}}_E=\frac{1}{M(M-1)}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{\underset{m_2\≠m}{m_2=1}}{\overset{M}{\mathrm{\Σ}}}Q\left(0\right)=0.5.$

Because all information is all carried in transmitting antenna sequence number, only need detect it is the x which root transmitting antenna is launched ₀, can source node identification be recovered.Adopt maximum likelihood algorithm, detect transmitting antenna sequence number according to formula (3).

If what select in modulated process is that m root antenna sends, then destination node Received signal strength is if that select in modulated process is m ₂root antenna sends, then destination node Received signal strength is m ₂≠ m.From maximum likelihood algorithm, destination node receives y based on reality _djudge into actual transmission antenna serial number m by accident m ₂pairwise error probability be:

In the process, destination node will use precoding coefficients α _m, informed by source node.Pr () presentation of events probability of happening.Therefore, the pairwise error probability (English full name is: Pairwise Error Probability, is called for short: PEP in literary composition) that can obtain destination node detection judgement in SSK scheme is:

Wherein, Q represents complementary error function, correspondingly, the average pairwise error probability (English full name is: Average Pairwise Error Probability, is called for short: APEP in literary composition) that can obtain destination node detection judgement is:

${\mathrm{APEP}}_D=\frac{1}{M(M-1)}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{\underset{M_2\≠n}{M_2=1}}{\overset{M}{\mathrm{\Σ}}}Q\left(\frac{|\sqrt{P}{\mathrm{\α}}_m{h}_{S_{m}D}-\sqrt{P}{\mathrm{\α}}_{m_2}{h}_{S_{m_2}D}}{\sqrt{2}\mathrm{\σ}}\right)$

For eavesdropping node, due to factor alpha _mdesign ensure that therefore have eavesdropping node:

$Q\left(\frac{|\sqrt{P}{\mathrm{\α}}_m{h}_{S_{m}E}-\sqrt{P}{\mathrm{\α}}_{m_{m_2}}{h}_{S_{m_2}E}|}{\sqrt{2}\mathrm{\σ}}\right)=0.5,\∀m,m_2$

So the average pairwise error probability of eavesdropping node is:

APEP _E＝0.5

The contrast of this error probability shows: the detection judgement of eavesdropping node is random completely, and destination node normally can receive source node identification.

In the present invention, the principle of safety of physical layer is from information theory view instead of increases computation complexity solution communication security sex chromosome mosaicism.As long as main channel (between source node and destination node channel) is better than tapping channel (source node and eavesdropping inter-nodal channel), source node and destination node just can not rely on key and realize being perfectly safe communicating, and namely maximum attainable secure communication speed be called as safe capacity; When main channel is inferior to tapping channel, then cannot realize absolute secure communication, namely safe capacity is zero.Intuitively, safety of physical layer is exactly utilize destination node relative to eavesdropping node to the advantage of source signal reception, and enable destination node obtain the information of source node transmission completely, eavesdropping node then cannot from eavesdropping the security information that obtain source node reception.In a single aerial system, safe capacity is subject to the restriction of channel link qualities completely: when tapping channel quality is better than main channel, and safe capacity is zero, namely cannot ensure the safety of physical layer transmission of data completely.Existing result of study shows, introducing multi-antenna technology can effectively improve this situation, even if tapping channel is better, also by the safe capacity of the signal transacting acquisition non-zero of multiple antennas.Such as, source node is designed by wave beam forming, makes signal beam main lobe aim at destination node, zero lobe aims at eavesdropping node, like this, even if main channel link-quality is not as tapping channel, destination node also can obtain the advantage relative to eavesdropping node when receiving source information; And for example, source node can, while utilizing some antennas to send security information, utilize residue antenna to send artificial interference signal, stops eavesdropping node to the intercepting of source node security information.But, from the implementation procedure of these multiple antennas safe transmission method of physical layer, often need comparatively complicated precoder design; And the radiofrequency signal owing to using many antennas to send same frequency simultaneously, there is the such as problem such as co-channel interference, sky line locking, this brings challenge to its practical application.Therefore, a kind of simple and effective multiple antennas safe transmission method of physical layer is sought significant to the practicalization promoting safety of physical layer.It is the simple multiple antenna transmission technique of a kind of way of realization that sky moves keying (Space Shift Keying, SSK).Be different from conventional art, sky moves keying and only activates an antenna transmission signal at every turn.Randomness based on wireless channel is supposed, different transmitting antenna is different to the channel of same reception antenna.Utilize this characteristic, at transmitting terminal, choose different antennae according to different source information and send signal, by antenna serial number as information carrier.At receiving terminal, as long as detect transmitting antenna sequence number, corresponding information can be recovered.Compared to traditional multiple antenna transmission technique, sky moves keying and has following advantage: 1) without problems such as interference, sky line lockings in band, because only have selected antenna to send signal at every turn, all the other antennas keep mourning in silence, 2) only need a radio frequency link, cost is lower; 3) receiver structure is simple, owing to adopting single data stream to detect, greatly reduces and detects reception complexity.Move the essence of keying from sky, which utilizes the otherness of channel between different transmitting antenna to reception antenna, the information that this otherness makes source node set up is uniquely reversible to the mapping of antenna serial number.If all channels not there are differences, receiving terminal just cannot detect signal is from which root transmitting antenna, also just cannot Restorer varieties node send be what information, this shows that sky moves keying and relies on channel diversity height.And on the other hand, safety of physical layer is also closely related with channel diversity: if tapping channel and main channel just the same, which kind of transmission method no matter that adopt, and all cannot realize safety of physical layer transmission.Therefore, channel diversity moves in keying and safety of physical layer at sky and all plays vital effect, this for utilize sky move keying carry out safety of physical layer transmission provide possibility.Specifically, eliminate each transmitting antenna to retain its otherness to destination node channel to the otherness of eavesdropping node channel as long as move in keying process at sky, safety of physical layer transmission can be realized.Sky, just based on above-mentioned consideration, is moved key control technology and safety of physical layer technology combines by the present inventor, proposes the concrete technical scheme of the present patent application.

Exemplify a specific embodiment below.

In a multiple input single output safety of physical layer communication system, there is a source node S, one destination node D and eavesdropping node E.Source node S has information to be sent to destination node D, and wishes that this information is not ravesdropping node E and eavesdrops.Suppose that source node S is equipped with 4 antennas, destination node D, eavesdropping node E are then only equipped with 1 antenna.Suppose that each transmitting antenna of source node is respectively to the channel of destination node: $h_{S_{1}D}=-0.1241+06715i,h_{S_{2}D}=1.4897-1.2075i,h_{S_{3}D}=1.4090+0.7172i,$ With the each antenna of source node is respectively to the channel of eavesdropping node: $h_{S_{1}E}=0.4889+0.2939i,h_{S_{2}E}=1.0347-0.7873i,h_{S_{3}E}=0.7269+0.8884i,$ With source node transmitted power is set to 1.Suppose source node known channel state information with and destination node is only known as shown in Figure 2, Figure 3 and Figure 4, the implementation procedure of whole example is as follows:

First-selection, source node carries out packets of information bits.Because source node has 4 transmitting antennas, therefore packets of information bits length is p=2.Four kinds of packets of information bits are respectively: x ₁=00, x ₂=01, x ₃=10 and x ₄=11.Such as, when source node identification bit sequence is 1001110011, it can be obtained x by 2 bit length groupings ₃x ₂x ₄x ₁x ₄five information block.

Secondly: carry out sky and move keying.4 kinds of different information block, according to certain mapping ruler, are mapped in source node transmitting antenna sequence number by source node.As shown in Figure 3, in this example, bit groupings x ₁=00 is mapped to first transmitting antenna, x ₂=01 is mapped to the 2nd transmitting antenna, x ₃=10 are mapped to the 3rd transmitting antenna, x ₄=11 are mapped to the 4th transmitting antenna.Such as: if current information block to be sent is x ₃=10, then select the 3rd antenna to send signal x ₀(x ₀for " 1 " in BPSK modulation symbol, do not carry any information).Move in keying process at sky, source node does not send information block x ₃=10 is own, but be carried to above antenna serial number " 3 ".If destination node correctly detects that its signal received is from source node the 3rd transmitting antenna, then destination node oppositely can infer that the packets of information bits that source node sends is x ₃=10.

Then: source node sends preliminary treatment.As shown in Figure 3, as the 1st antenna selected transmission x of source node ₀time, to x ₀be multiplied by precoding coefficients α ₁=1, namely do not do any phase rotating and Scalable; As the 2nd antenna selected transmission x of source node ₀time, to x ₀be multiplied by precoding coefficients:

${\mathrm{\α}}_2=\frac{h_{S_{1}E}}{h_{S_{2}E}}=\frac{0.4889+0.2939i}{1.0347-0.7873i}=0.1624+0.4076i$

As the 3rd antenna selected transmission x of source node ₀time, to x ₀be multiplied by precoding coefficients:

${\mathrm{\α}}_3=\frac{h_{S_{1}E}}{h_{S_{3}E}}=\frac{0.4889+0.2939i}{0.7269+0.8884i}=0.679-0.1675i$

As the 4th antenna selected transmission x of source node ₀time, to x ₀be multiplied by precoding coefficients:

${\mathrm{\α}}_4=\frac{h_{S_{1}E}}{h_{S_{4}E}}=\frac{0.4889+0.2939i}{-0.3034-1.1471i}=-0.3448+0.3350i$

Source node, after calculating above-mentioned precoding coefficients, is informed destination node, is convenient to it and detects reception.For eavesdropping node, through above-mentioned transmission preliminary treatment, no matter which root antenna source node selects send x ₀, that eavesdropping node receives is all y _e=0.4889+0.2939i+v _e, therefore eavesdrop node cannot detection signal from any root transmitting antenna.

Last: destination node detects and receives.Under noise free conditions, destination node is according to channel condition information with precoding coefficients α _m, four kinds of possible Received signal strength can be drawn in advance, be respectively:

$y_1={\mathrm{\α}}_1{h}_{S_{1}D}{x}_0=-0.1241+0.6715i$

$y_2={\mathrm{\α}}_2{h}_{S_{2}D}{x}_0=0.7340+0.4111i$

$y_3={\mathrm{\α}}_3{h}_{S_{3}D}{x}_0=0.7794+0.0995i$

$y_4={\mathrm{\α}}_4{h}_{S_{4}D}{x}_0=-1.0348-0.0874i$

Destination node calculates the actual signal y received _dand the Euclidean distance between above-mentioned various possibility Received signal strength, carries out maximum likelihood decision, thus draws source node transmitting antenna sequence number, and obtain corresponding bit groupings information.As shown in Figure 4, y ₁, y ₂, y ₃and y ₄four constellation point are corresponding above-mentioned 4 kinds of possible Received signal strength respectively.When the actual Received signal strength of destination node is y _dduring=0.8+0.01i, known y _dwith y ₃distance the shortest, can decision signal from the 3rd antenna, therefore know that the bit groupings information that source node sends is x ₃=10.

The present invention moves key control technology by sky, is carried on by source node identification in transmitting antenna sequence number, and by sending preliminary treatment, eliminating the otherness of each transmitting antenna to eavesdropping node channel, making eavesdropping node cannot recover the information source information be mapped in antenna serial number.Fig. 5 and Fig. 6 sets forth the present invention's carry, and to move keying safe transmission method of physical layer in number of transmit antennas based on sky be 2,4, the average pairwise error probability figure of the safety mutual amount of information under 8 conditions and destination node, eavesdropping node.In Fig. 5, abscissa represents transmitting signal to noise ratio, unit db, and ordinate represents safety mutual amount of information, unit bits/s.In Fig. 5, without precoding processing, refer to and adopt method of the present invention, but do not adopt the 4th step.Precoding processing, refers to and adopts method of the present invention, contain the 4th step.As shown in Figure 5, adopt that empty to move the maximum safety mutual amount of information that key control technology sends acquisition be at every turn the logarithm of number of transmit antennas.Fig. 5 also shows, sending precoding processing is move by sky the key that keying realizes safety of physical layer transmission, if do not carry out transmission precoding processing, under high s/n ratio condition, safety mutual amount of information will be tending towards 0.In Fig. 6, abscissa represents transmitting signal to noise ratio, unit db, and ordinate represents average pairwise error probability.Fig. 6 shows, the difference of each transmitting antenna of source node to eavesdropping node channel is eliminated owing to sending precoding processing, causing eavesdropping node to detect is the selected transmission signal of which root antenna, therefore under any any signal to noise ratio condition of number of antennas, eavesdropping node average pairwise error probability remains 0.5 constant, and destination node average probability of error then increases with signal to noise ratio and drops to tolerance interval.

Claims (2)

1. move a safe transmission method of physical layer for keying in MISO system based on sky, it is characterized in that: this transmission method comprises the following steps:

The first step: the multiple input single output communication system under safety of physical layer scene, comprise a source node S and two information destination node, two information destination node are all the validated users of system; In communication process, source node sends information to an information destination node, node D for the purpose of this information destination node; This information of another information destination node intention eavesdropping is eavesdropping node E; Source node S is equipped with M root transmitting antenna, and destination node D and eavesdropping node E assembles 1 antenna respectively, and the m root transmitting antenna in source node S to the channel of destination node D is the transmitting antenna of source node S to the channel set of destination node D is m root transmitting antenna in source node S to the channel of eavesdropping node E is all channels are separate; Destination node D obtains channel by channel estimating eavesdropping node E obtains channel by channel estimating destination node D and eavesdropping node E by the feedback of channel information that obtains to source node S; The span of M be greater than 1 integer, m=1,2 ..., M; M be greater than 1 integer;

Second step: source node identification divides into groups: source node S, by bit information sequence x to be sent, is carried out bit groupings by same bits length p, had 2 ^pplant grouping situation, be designated as one_to_one corresponding between the transmitting antenna sequence number of bit groupings and source node, block length p meets p=log ₂m;

3rd step: sky moves keying: corresponding according between bit groupings and the transmitting antenna sequence number of source node, the bit information that packets of information bits comprises by source node is mapped on the transmitting antenna of corresponding sequence number; Based on the random unique trait of wireless channel, the process of carrying out transmitting antenna selection is equivalent to the process of Channel assignment; Move keying by sky, source node transmitting antenna sequence number becomes the supporting body of information source information, and the transmitting antenna of selected signal transmission always sends the symbol 1 in binary phase shift keying signal, and this symbol 1 is designated as x ₀, | x ₀| ²=1, not selected M-1 root antenna keeps mourning in silence, and does not send any signal;

4th step: precoding processing: source node carries out precoding processing to the symbol that each transmitting antenna sends, the m root transmitting antenna of selected signal transmission sends symbol x ₀time, to x ₀be multiplied by a precoding coefficients α _m, α _mmeet formula (1):

${\mathrm{\α}}_m{h}_{S_{m}E}={\mathrm{\α}}_{m_2}{h}_{S_{m_2}E}$ Formula (1)

Wherein, represent the m in M root transmitting antenna ₂the precoding coefficients of root transmitting antenna, and m ₂≠ m, represent m ₂root transmitting antenna is to the channel of eavesdropping node E.

2. according to the safe transmission method of physical layer moving keying in MISO system according to claim 1 based on sky, it is characterized in that: also comprise the 5th step: detect sky and move keyed information: first precoding coefficients is sent to destination node by source node, source node has M root transmitting antenna, total M kind Received signal strength possibility, the actual signal received of hypothesis goal node is y _d, according to formula (2) measuring and calculating y _dand the Euclidean distance between various possibility Received signal strength:

${|y_D-\sqrt{P}{\mathrm{\α}}_m{h}_{S_{m}D}{x}_0|}^2$ Formula (2)

Wherein, P represents the transmitting power of source node, α _mrepresent the precoding coefficients of m root transmitting antenna;

From an above-mentioned gained M Euclidean distance, choose transmitting antenna sequence number corresponding to minimum value, be the source node transmitting antenna sequence number that source node identification is mapped to, thus obtain the packets of information bits that this source node corresponding to transmitting antenna sequence number sends; Destination node carries out infomation detection, adopts maximum likelihood algorithm according to formula (3):

formula (3)

Wherein, represent that destination node is to the detected value of transmitting antenna sequence number;

The average pairwise error probability of destination node is:

${\mathrm{APEP}}_D=\frac{1}{M(M-1)}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{\underset{m_2\≠m}{m_2=1}}{\overset{M}{\mathrm{\Σ}}}Q\left(\frac{|\sqrt{P}{\mathrm{\α}}_m{h}_{S_{m}D}-\sqrt{P}{\mathrm{\α}}_{m_2}{h}_{S_{m_2}D}|}{\sqrt{2}\mathrm{\σ}}\right)$ Formula (4)

Wherein, APEP _drepresent the average pairwise error probability of destination node, Q represents complementary error function, and σ represents noise power; represent the m in M root transmitting antenna ₂the precoding coefficients of root transmitting antenna, and m ₂≠ m, represent m ₂root transmitting antenna is to the channel of destination node D;

For eavesdropping node, due to the existence of formula (1), no matter which root transmitting antenna signal transmission source node selects, the Received signal strength y of eavesdropping node _efor:

$y_E=\sqrt{P}{\mathrm{\α}}_1{h}_{S_{1}E}{x}_0+v_E$ Formula (5)

Wherein, v _erepresent the reception noise of eavesdropping node;

The average pairwise error probability APEP of eavesdropping node _efor:

${\mathrm{APEP}}_E=\frac{1}{M(M-1)}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{\underset{m_2\≠m}{m_2=1}}{\overset{M}{\mathrm{\Σ}}}Q\left(0\right)=0.5.$