CN104468428B - Safety of physical layer method based on low complex degree difference channel estimation - Google Patents

Safety of physical layer method based on low complex degree difference channel estimation Download PDF

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CN104468428B
CN104468428B CN201410729165.2A CN201410729165A CN104468428B CN 104468428 B CN104468428 B CN 104468428B CN 201410729165 A CN201410729165 A CN 201410729165A CN 104468428 B CN104468428 B CN 104468428B
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channel estimation
authorized user
channel
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CN104468428A (en
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吕斌
杨震
冯友宏
王韦刚
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Nanjing Post and Telecommunication University
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses the safety of physical layer method based on low complex degree difference channel estimation, this method constructs low complex degree channel estimation to distinguish the channel estimating performance of authorized user and unauthorized user, realizes the secure communication between base station and authorized user.This method is effective combination of existing difference channel estimation methods and polynomial expansion method.This method realizes the performance difference of the channel estimation at authorized user and unauthorized user end first with reversed, forward direction difference channel estimation methods.Again for there is coherence between extensive antenna channel, the inverse operation of the big dimensional matrix of method approximate representation non-diagonal of polynomial expansion is introduced, reducing computation complexity, improves the real-time of system.Optimal system performance is realized finally by energetic optimum distribution.

Description

Safety of physical layer method based on low complex degree difference channel estimation
Technical field
The present invention relates to computer communication technology field, more particularly to a kind of object based on low complex degree difference channel estimation Manage layer safety method.
Background technology
At present, the broadband access method of mobile phone-base station is next main way with mobile communication system 5G broadband access One of.Wireless air interface between medium is subject to attack due to natural open nature.At present, the peace of wireless mobile communications Full property ensures that the security depends on key by upper layer security agreement, but depends on calculating safety.So And current key generates and distributes the security that can not be accomplished under Shannon information theory meaning.How future mobile communications are ensured The security of broadband wireless access has important research significance.
In recent years, safety of physical layer technology is fast-developing and obtains extensive concern.Research shows that the safety of information communication is asked Topic can be realized by the different characteristic of channel extracted between base station and authorized user, unauthorized user.As authorized user and Presence service quality (Quality of Service, QoS) difference, i.e., estimate between base station and authorized user between unauthorized user Performance is counted better than base station and unauthorized user, base station safely can send information to authorized user, and unauthorized user can not Therefrom intercept information.The existing difference channel estimation methods for radio MIMO system in document at present, utilize this method structure Build safe wireless communication system.I.e. by under reverse train (authorized user to the channel between the base station) estimation of pilot signal The channel state information (Channel State Information, CSI) of line linkIt is mutual according to the channel under tdd mode Yi Xing obtains the channel state information of base stationAccording to what is knownMan made noise (Artificial Noise, AN) is designed, Man made noise is placed onLeft kernel.(base station to authorized user, unauthorized user) is trained in the forward direction of pilot signal Stage, pilot signal are superimposed man made noise as training signal.Because of the influence of man made noise, the channel obtained at authorized user is estimated Count the estimation performance that performance is better than unauthorized user.Polynomial expansion (Polynomial Expansion, PE) is that one kind can be with The method for effectively reducing big dimensional matrix inverse operation.Polynomial expansion is by L ranks matrix polynomial come one matrix of approximate representation Function.L describes the levels of precision of each approximate characteristic value inverse, thus L with the increase of matrix dimension without increasing To realize approximate optimal performance.Under normal conditions, the selection needs of L are compromised between computation complexity and system performance.It is more Item formula expansion can be used for reducing computation complexity in extensive mimo system, optimize the multinomial of matrix by asymptotic analysis Formula is to ensure good system performance.
Extensive MIMO is a kind of important technology in next generation mobile communication.Thus, for extensive mimo system structure Difference channel estimation is built to realize that communication security also has great importance.When building difference channel estimation, it is necessary to calculate letter The least mean-square error matrix of road estimation, is directed to inverse of a matrix computing, under extensive mimo system, the calculating of the computing Complexity is high.And when the matrix involved in channel estimation is diagonal matrix, this high complexity computing can be avoided.But due to In extensive mimo system, the situation that distance between antennas is not enough is deposited, i.e., is had between the channel of extensive MIMO Apparent spatial coherence, the covariance matrix of channel is generally not diagonal matrix.Polynomial expansion can be reducing big dimension Spend the complexity of inverse of a matrix computing.Thus, if polynomial expansion structure can be utilized for extensive mimo wireless communication system The difference channel estimation of the low complex degree of system has realistic meaning.And present invention the problem of can well solving above.
The content of the invention
Present invention aims at provide a kind of safety of physical layer method based on low complex degree difference channel estimation, the party Method solves the problems, such as the secure communication of above-mentioned extensive mimo wireless communication system.This method assumes that application scenarios are in the time-division Under duplexing (Time Division Duplexing, TDD), sufficiently large distance cannot be provided between extensive antenna, antenna it Between there are spatial coherence, by building difference channel estimation so that the channel estimating performance between base station and authorized user is excellent Between base station and unauthorized user.To be non-right since there are coherences, the i.e. covariance matrix of channel matrix between antenna Angular moment battle array, inversion operation complexity are high.Carry out the process of approximate representation matrix inversion using multinomial, it is suitable by choosing Exponent number L reach compromise between computation complexity and system performance, be issued to realizing in relatively low computation complexity situation The system performance of near-optimization.
The technical scheme adopted by the invention to solve the technical problem is that：It is provided by the invention a kind of poor based on low complex degree The safety of physical layer method of different channel estimation, this method are made in authorized user using reversed, the forward direction training of pilot signal, non-awarded The channel state information performance difference estimated at user is weighed, even the channel estimating performance at authorized user is better than unauthorized user Place, to realize that base station safely can send information to authorized user, and unauthorized user can not therefrom intercept information.Pin There is a situation where matrix during to calculating least mean-square error for non-diagonal matrix, utilizing inverting for polynomial expansion approximate matrix Journey reduces computation complexity.Optimal system performance is realized finally by optimal energy distribution
Method flow：
Step 1：Authorized user sends pilot tone to base station, the channel of estimating uplink；According to the reciprocity of channel, obtain The estimation of downlink channel；
Step 2：According to the channel estimation of downlink, man made noise is designed.Base station is simultaneously to authorized user, unauthorized use Family sends pilot tone and the superposed signal of man made noise, and authorized user, unauthorized user obtain respective channel state information simultaneously Estimation, and calculate corresponding least mean-square error；
Step 3：Using before polynomial expansion approximate calculation into training authorized user, channel estimation at unauthorized user Least mean-square error；
Step 4：By the most optimal sorting that pilot signal and the energy of man made noise are trained to reverse train pilot signal, forward direction Match somebody with somebody, realize optimal difference channel estimating performance.
The present invention is applied to the extensive mimo wireless communication system under tdd mode, exists between antenna for base station apparent Spatial coherence.
Advantageous effect：
1st, the present invention can realize the secure communication between base station and authorized user.
2nd, the present invention utilizes the inversion process of polynomial expansion approximate representation matrix, on the premise of system performance is ensured, Significantly reduce the computation complexity of system.
Description of the drawings
Fig. 1 is the schematic diagram of a scenario of the present invention.
Fig. 2 is flow chart of the method for the present invention.
Specific embodiment
Patent of the present invention is described in further detail below in conjunction with Figure of description.
As shown in Figure 1, present system is that there are the extensive mimo wireless communication systems of unauthorized user (eavesdropping user) System.System includes a base station, an authorized user and a unauthorized user, exists wherein between the antenna of base station apparent Spatial coherence, and the antenna amount of base station is much larger than authorized user, unauthorized user.Base station sends signal to authorized user, Because there are unauthorized user, the communication between base station and authorized user may be intercepted by unauthorized user.Thus authorized user The reverse link channel estimation based on pilot tone is carried out between base station, obtains reverse chain channel HrEstimation.According under TDD Channel reciprocity, thus base station can obtain forward link channel HfEstimation.Base station is according to obtained channel estimation, designer Work noise sends the training signal for including man made noise to authorized user, and authorized user, unauthorized user obtain respective channel Hf、HuEstimation.Because of the presence of man made noise, it is ensured that reduced on the premise of authorized user is not disturbed at unauthorized user Channel estimating performance, that is, ensure that the communication between base station and authorized user is not eavesdropped by unauthorized user.It should for the present invention With, there are the characteristics of apparent spatial coherence, associated methods flow chart further illustrates between antenna for base station in scene.
As shown in Fig. 2, the method for the present invention mainly includes reverse link channel estimation, forward link channel is estimated, is multinomial Four parts such as formula expansion, optimal energy distribution.Reverse link channel estimation part, is based between authorized user and base station The reverse link channel estimation of pilot tone obtains reverse chain channel HrEstimation.According to the channel reciprocity under TDD, while base Forward link channel H can be obtained by standingfEstimation.Forward link channel estimating part, base station according to obtained channel estimation, if Man made noise is counted, the training signal for including man made noise is sent to authorized user, authorized user, unauthorized user are according to minimum equal Square error (Minimum Mean Square Error, MMSE) criterion, obtains respective channel Hf、HuEstimation and it is corresponding most Small mean square error.Because, there are the characteristics of apparent spatial coherence, being calculated most between antenna for base station in application scenarios of the present invention During small mean square error, matrix is generally non-diagonal matrix, i.e. the inversion process of matrix has high complexity.Thus, it can Using the inversion process of polynomial expansion approximate representation matrix, to obtain the approximate expression of least mean-square error.Finally by anti- To training pilot energy, forward direction training pilot energy, man made noise energy optimum allocation, obtain optimal be System performance.
Reverse train includes as follows：
Authorized user sends one group of pilot signal to base stationTo estimate the CSI of base station end, wherein pilot tone MatrixMeetPrAnd TrThe respectively energy and length of reverse train pilot signal.Base station connects The signal received is expressed as
Ybs=XrHr+Wbs (1)
Represent the channel matrix of uplink,For the additive white noise of receiving terminal.To formula (1) carry out converting and can obtaining
ybs=xrhf+wbs (2)
Wherein, Channel estimation is carried out according to linear MMSE criterion, can be obtained The estimate of channel matrix
Wherein,
Forward direction training includes as follows：
According to channel estimation valueArrangement obtainsDue to channel reciprocity, can obtainByDesign is artificial Noise matrixElement wherein in man made noise's matrix meets independent identically distributed zero-mean, variance is Gaussian variable.MatrixIts each column vector is located atLeft kernel, that is, meetMeet simultaneouslyBase station while pilot signal transmitted and man made noise at this time, reach To the channel estimating performance reduced on the premise of authorized user is not disturbed at unauthorized user.Transmission signal at this time can be with table It is shown as
WhereinMeetPfAnd TfRespectively preceding energy and length to training pilot signal Degree.The signal received at authorized user, unauthorized user is expressed as
WhereinRepresent base station and the channel matrix of unauthorized user downlink, It is additive white noise.Due toAnd it definesThen formula (5), formula (6) can be rewritten as
Yu=X 'bsHu+W′u (8)
Wherein, Formula (7), formula (8) can further be transformed to
yl=x 'bshr+w′l (9)
yu=x 'bshu+w′u (10)
Wherein, hr=vec (Hr), hu=vec (Hu),
Using minimum mean-square error forecast device, estimate of the channel matrix at authorized user, unauthorized user can be obtained
Wherein, It is minimum equal Square error is respectively
The approximate calculation of polynomial expansion includes as follows：
According to polynomial expansion, inverse of a matrix computing can be expressed as
Wherein, ρ must meet 0 ＜ ρ ＜, 2/ λmax(Q) to ensure the convergence of polynomial expansion, λmax(Q) it is matrix Q maximums Characteristic value.In order to reduce computation complexity, choose suitable P rank multinomials and carry out approximate representation inverse of a matrix computing, you can
Using formula (16), formula (11), formula (12) can be rewritten into respectively
It can further obtain
Wherein, It makes herein
,
To MMSElAnd MMSEuIt is normalized respectively, i.e.,
Optimal energy distribution includes as follows：
The channel estimating performance at the present invention optimal authorized user place in order to obtain, while prevent unauthorized user acquisition pair The accurate estimation of its channel, here by optimization reverse train pilot energy Pr, forward direction training pilot energy Pf, people The energy of work noiseIt realizes.It can obtain following equation
Wherein, γ NMSEuPreset minimum value,WithThe average energy respectively set is authorized and used Family and the highest energy of base station.The optimization problem is mainly realized, in NMSEuOn the premise of meeting preset minimum value, lead to Energy assignment constraints are crossed, obtain NMSElMinimum value.

Claims (5)

  1. A kind of 1. safety of physical layer method based on low complex degree difference channel estimation, which is characterized in that the described method includes with Lower step：
    Step 1：Authorized user sends pilot tone to base station, the channel of estimating uplink；According to the reciprocity of channel, downlink is obtained The estimation of link channel；
    Step 2：According to the channel estimation of downlink, man made noise is designed, base station is sent out simultaneously to authorized user, unauthorized user Pilot tone and the superposed signal of man made noise are sent, authorized user, unauthorized user obtain estimating for respective channel state information simultaneously Meter, and calculate corresponding least mean-square error；
    Step 3：Using before polynomial expansion approximate calculation into training authorized user, at unauthorized user channel estimation minimum Mean square error；
    Step 4：By training the optimum allocation of pilot signal and the energy of man made noise to reverse train pilot signal, forward direction, Realize optimal difference channel estimating performance；
    The optimum allocation of the energy includes following equation：
    <mrow> <munder> <mrow> <mi>m</mi> <mi>i</mi> <mi>n</mi> </mrow> <mrow> <msub> <mi>P</mi> <mi>f</mi> </msub> <mo>,</mo> <msub> <mi>P</mi> <mi>r</mi> </msub> <mo>,</mo> <msubsup> <mi>&amp;sigma;</mi> <mi>a</mi> <mn>2</mn> </msubsup> <mo>&amp;GreaterEqual;</mo> <mn>0</mn> </mrow> </munder> <msub> <mi>NMSE</mi> <mi>l</mi> </msub> </mrow>
    s.t.NMSEu≥γ,
    <mrow> <msub> <mi>P</mi> <mi>r</mi> </msub> <msub> <mi>T</mi> <mi>r</mi> </msub> <mo>+</mo> <mrow> <mo>(</mo> <msub> <mi>P</mi> <mi>f</mi> </msub> <mo>+</mo> <mo>(</mo> <mrow> <msub> <mi>N</mi> <mrow> <mi>b</mi> <mi>s</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>N</mi> <mi>l</mi> </msub> </mrow> <mo>)</mo> <msubsup> <mi>&amp;sigma;</mi> <mi>a</mi> <mn>2</mn> </msubsup> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>f</mi> </msub> <mo>&amp;le;</mo> <mover> <mi>P</mi> <mo>&amp;OverBar;</mo> </mover> <mrow> <mo>(</mo> <msub> <mi>T</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>T</mi> <mi>f</mi> </msub> <mo>)</mo> </mrow> <mo>,</mo> </mrow>
    <mrow> <msub> <mi>P</mi> <mi>r</mi> </msub> <msub> <mi>T</mi> <mi>r</mi> </msub> <mo>&amp;le;</mo> <msub> <mover> <mi>P</mi> <mo>&amp;OverBar;</mo> </mover> <mi>r</mi> </msub> <msub> <mi>T</mi> <mi>r</mi> </msub> <mo>,</mo> </mrow>
    <mrow> <mo>(</mo> <msub> <mi>P</mi> <mi>f</mi> </msub> <mo>+</mo> <msub> <mi>N</mi> <mrow> <mi>b</mi> <mi>s</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>N</mi> <mi>l</mi> </msub> <msubsup> <mi>&amp;sigma;</mi> <mi>a</mi> <mn>2</mn> </msubsup> <mo>)</mo> <msub> <mi>T</mi> <mi>f</mi> </msub> <mo>&amp;le;</mo> <msub> <mover> <mi>P</mi> <mo>&amp;OverBar;</mo> </mover> <mi>f</mi> </msub> <msub> <mi>T</mi> <mi>f</mi> </msub> <mo>,</mo> </mrow>
    Wherein, γ NMSEuPreset minimum value,WithThe average energy respectively set, authorized user and Ji The highest energy stood, MMSElFor the least mean-square error at authorized user, MMSEuIt is missed for the lowest mean square at unauthorized user Difference, NbsFor base station antenna amount, PfFor the preceding energy to training pilot signal, TfFor the preceding length to training pilot signal, Nl For antenna amount at authorized user, PrFor the energy of reverse train pilot signal, TrThe length of reverse train pilot signal,For The energy of man made noise.
  2. 2. a kind of safety of physical layer method based on low complex degree difference channel estimation according to claim 1, feature It is：The method is applied to the extensive mimo wireless communication system under tdd mode.
  3. 3. a kind of safety of physical layer method based on low complex degree difference channel estimation according to claim 1, feature It is：The method is the combination of difference channel estimation methods and polynomial expansion method.
  4. 4. a kind of safety of physical layer method based on low complex degree difference channel estimation according to claim 1, feature It is：The method is the process using polynomial expansion approximate representation non-diagonal matrix inversion.
  5. 5. a kind of safety of physical layer method based on low complex degree difference channel estimation according to claim 1, feature It is, when the method calculates the least mean-square error of channel estimation, matrix is non-diagonal matrix；It is approximate using polynomial expansion The inversion process of representing matrix obtains the approximate expression of least mean-square error.
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Citations (4)

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CN101039290A (en) * 2007-04-19 2007-09-19 西安电子科技大学 Method for estimating MIMO related channel based on self-adaptive training sequence
US20100238824A1 (en) * 2009-03-20 2010-09-23 Qualcomm Incorporated Feedback mechanisms for beamforming operation
CN103199909A (en) * 2013-04-16 2013-07-10 中国人民解放军信息工程大学 Signal transmission method, signal receiving method, signal transmission device, signal receiving device and signal communication system for achieving secure communication
CN103986545A (en) * 2014-05-09 2014-08-13 西安交通大学 Physical layer safety transmission method used for SIMO wireless communication system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101039290A (en) * 2007-04-19 2007-09-19 西安电子科技大学 Method for estimating MIMO related channel based on self-adaptive training sequence
US20100238824A1 (en) * 2009-03-20 2010-09-23 Qualcomm Incorporated Feedback mechanisms for beamforming operation
CN103199909A (en) * 2013-04-16 2013-07-10 中国人民解放军信息工程大学 Signal transmission method, signal receiving method, signal transmission device, signal receiving device and signal communication system for achieving secure communication
CN103986545A (en) * 2014-05-09 2014-08-13 西安交通大学 Physical layer safety transmission method used for SIMO wireless communication system

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