CN102215048A - Receiving method and receiving device of spread spectrum signals - Google Patents

Abstract

The invention discloses a receiving method of spread spectrum signals and belongs to the technical field of spread spectrum communication. The method comprises the following steps of: respectively receiving the spread spectrum signals by using at least two antennae; carrying out blind source separation by using at least two received signals as observation signals; and identifying separation signals which are obtained by the blind source separation, and determining useful signals and interference signals. The invention also discloses a receiving device of the spread spectrum signals and a spread spectrum communication system. By the invention, the anti-interference performance of the spread spectrum communication is effectively improved, an output signal to interference ratio is improved, and practicability and flexibility are relatively high.

Description

A kind of method of reseptance of spread spectrum signal and receiving system

Technical field

The present invention relates to a kind of method of reseptance of spread spectrum signal, relate in particular to a kind of method of reseptance that utilizes blind source to separate the spread spectrum signal that improves antijamming capability, belong to the spread spectrum technic field.

Background technology

In spread spectrum communication (spread spectrum communications is called for short spread spectrum communication or spread spectrum communication), the bandwidth W of transmission signals is much larger than the bandwidth R of primary signal, and promptly the bandwidth expansion factor G=W/R of spread-spectrum signal is much larger than 1.Current spread spectrum technic mainly comprises frequency hop spread spectrum and direct sequence spread spectrum skill.Frequency hopping (frequency hopping, FH) spread spectrum communication is meant transceiver communication both sides or each side under identical synchronized algorithm and pseudo-random hopping pattern algorithm controls, rf frequency in the frequency meter of agreement with the communication technology of discrete frequency form pseudorandom and saltus step synchronously.In frequency hopping communications, the bandwidth that radio frequency can cover in the saltus step process is far longer than the prime information bandwidth, thereby has expanded frequency spectrum.Direct sequence spread spectrum (direct sequence spread spectrum, DSSS) communication technology is carried out spread spectrum at the pseudo noise code (also claiming pseudo-code sequence, pseudo random sequence) that transmitting terminal adopts a speed to be far longer than information sequence to information sequence, with its video stretching, adopt identical pseudo noise code that spread-spectrum signal is carried out despreading, demodulation at receiving terminal, to recover primary signal.Spread spectrum communication has been introduced redundancy in the spread-spectrum process, make it have certain anti-interference capability.At present, spread spectrum communication has become the jamproof mainstream technology means of communication, has obtained extensive use in military and civilian communication.

In order to have solved the contradiction between ever-increasing number of users and the limited channel resource, multiple access technique is adopted in spread spectrum communication usually.Multiple access technique makes a large number of users can share the common transmission media with transmission information.The most basic multiple access technique has frequency division multiple access (frequency division multiple access, FDMA), time division multiple access (time division multiple access, TDMA) and code division multiple access (code division multiple access, CDMA).The frequency division multiple access technology is divided into the sub-band (also claiming subchannel) of some non-overlapping copies to channel band, uses to different users different subband allocation.Tdma is divided into the duration frame (period) of non-overlapping copies, again frame is divided into the time slot of non-overlapping copies, distribute a particular time-slot in the frame according to user's request for each user,, thereby realize that multiple access inserts according to the subscriber signal of time slot differentiation from different addresses.CDMA (Code Division Multiple Access) is distributed a unique signature sequence (signature sequence) for each user, and the signature sequence of different user is mutually uncorrelated or only have a less correlation.Above-mentioned three kinds of basic multiple access techniques can also mix employing, merge (FD/TDMA) as frequency division and time-division, and frequency division and sign indicating number divide merging (FD/CDMA) etc.Outstanding characteristics of above-mentioned multiple access technology are: mutually uncorrelated or only have a less correlation between the spread-spectrum signal of different user, make receiver from multi-user's mixed signal, effectively to extract active user's signal, suppress other subscriber signals or interference signal.

Aspect military communication, the battlefield electromagnetic environment is increasingly sophisticated, and the survival ability of spread spectrum communication has run into acid test.Aspect commercial communication, because the frequency spectrum resource growing tension, the probability that other signals of communication fall in the wideband spread-spectrum signal frequency spectrum also day by day improves, and is faced with the problem that keeps reliable communication under disturbed condition equally.But, the antijamming capability of spread spectrum communication is a cost to sacrifice frequency spectrum resource or transmission capacity, the finiteness of frequency spectrum resource and current big data quantity transmission requirements have limited the further raising of its antijamming capability, need seek new method to improve its antijamming capability.

Summary of the invention

Technical problem to be solved by this invention is to overcome blind source separate technology is used the many antennas that faced in spread spectrum communication technical bottleneck, a kind of method of reseptance and receiving system of spread spectrum signal are provided, only need less antenna (two antennas of minimum needs), can realize that blind source is separated in the application in the spread spectrum communication, thereby improve the antijamming capability of spread spectrum communication.

The present invention is specifically by the following technical solutions:

A kind of method of reseptance of spread spectrum signal, this method comprise that at least two antennas of utilization receive the step of spread spectrum signal respectively; Carry out blind source separation steps with the two paths of signals at least that receives as observation signal; And the separation signal that obtains is separated in blind source discern, identify the step of useful signal and interference signal.

One of preferred version, the method for reseptance of described spread spectrum signal specifically may further comprise the steps:

Step 1, at least two antennas of utilization receive spread spectrum signal respectively;

Step 2, the spread spectrum signal of two-way at least that receives is carried out despreading-demodulation process respectively;

Step 3, carry out blind source with the two paths of signals at least after despreading-demodulation as observation signal and separate, obtain the two-way separation signal;

Step 4, the two-way separation signal that obtains is separated in blind source discern, identify useful signal and interference signal; Then useful signal is deciphered, obtained source signal.

Two of preferred version, the method for reseptance of described spread spectrum signal specifically may further comprise the steps:

Step 1, at least two antennas of utilization receive spread spectrum signal respectively;

Step 2, the spread spectrum signal of two-way at least that receives is carried out despreading respectively handle;

Step 3, carry out blind source with the two paths of signals at least after the despreading as observation signal and separate, obtain the two-way separation signal; Step 4, the two-way separation signal that obtains is separated in blind source discern, identify useful signal and interference signal; Then useful signal is carried out demodulation, decoding, obtain source signal.

Above-mentioned two kinds of optimal technical scheme are utilized the nearly orthogonal characteristic of different user spread-spectrum signal in frequency domain, sign indicating number territory or time domain, earlier mixed signal is carried out despreading at receiving terminal, when effectively extracting active user's signal, suppress other subscriber signals and interference signal, thereby reduced the dimension of mixed signal.This scheme is specially adapted to the situation of multi-user's networking, the situation when also can be used for single user (being point-to-point communication).Consider point-to-point spread spectrum communication, have only one road spread-spectrum signal and one tunnel interference signal, receiving terminal is provided with two antennas can satisfy the suitable fixed condition that separate in blind source, therefore can directly carry out blind source to the spread spectrum signal that two antennas receive and separate, thereby it is as follows to obtain another optimal technical scheme of the present invention:

Described spread spectrum signal is single subscriber signal, and described method of reseptance specifically may further comprise the steps:

Step 1, at least two antennas of utilization receive spread spectrum signal respectively;

Step 2, carry out blind source with the spread spectrum signal of two-way at least that receives as observation signal and separate, obtain the two-way separation signal;

Step 3, the two-way separation signal that obtains is separated in blind source discern, identify useful signal and interference signal;

Step 4, useful signal is carried out despreading-demodulation, decoding, obtain source signal.

Further, this method also comprises the step of the characteristic parameter of the interference signal that identifies being analyzed and analysis result is fed back to signal sending end.Evade to realize disturbing, thereby further improve the antijamming capability of spread spectrum communication.

A kind of receiving system of spread spectrum signal, this device comprise according to the signal receive path of signal flow to the parallel connection of two-way at least that connects in turn, and blind source separative element, signal recognition unit, decoding unit; Described signal receive path comprises antenna and despreading-demodulating unit, is used to receive spread spectrum radio signal and despreading-demodulation; At least two paths of signals of described blind source separative element after with despreading-demodulation carries out blind source as observation signal to be separated; Described signal recognition unit is discerned the blind source isolated signal of separative element, identifies useful signal and interference signal; Described decoding unit is deciphered the useful signal that identifies, and obtains source information, and source information is sent to the stay of two nights.

A kind of receiving system of spread spectrum signal, described spread spectrum signal are single subscriber signal, and this device comprises according to signal flow to two antennas, blind source separative element, signal recognition unit, despreading-demodulating unit, the decoding unit that connect in turn at least; Described at least two antennas receive the spread spectrum radio signal respectively; Described blind source separative element carries out blind source with the spread spectrum signal of two-way at least that receives as observation signal to be separated; Described signal recognition unit is discerned the blind source isolated signal of separative element, identifies useful signal and interference signal; Described despreading-demodulating unit and decoding unit carry out despreading-demodulation, decoding to the useful signal that identifies respectively, obtain source information, and source information is sent to the stay of two nights.

Further, described signal recognition unit is also analyzed the characteristic parameter of the interference signal that identifies.

A kind of spread spectrum communication system comprises signal sending end and signal receiving end, and described signal receiving end comprises the receiving system of above-mentioned any one spread spectrum signal.

The present invention combines the separation of blind source with the inherent feature of spread spectrum communication, can be under the situation of two antennas of minimum only need, utilize blind source separate technology to realize effectively separating of useful signal and interference signal, strengthened the antijamming capability of spread spectrum communication, improved the output signal interference ratio.Compared to existing technology, the present invention has the following advantages:

The present invention can be separated from one another with spread-spectrum signal and interference signal, and when interference signal and spread-spectrum signal spectrum overlapping and power are better than spread-spectrum signal far away (for example pectination is disturbed, partial-band barrage jamming), this point is very favorable;

The present invention can realize effectively separating of multi-user's spread-spectrum signal and interference signal under the situation of two antennas, thereby has reduced the cost of system hardware and Installation and Debugging, has high practicality;

The present invention can realize effectively separating of spread-spectrum signal and multiple interference signal.Changed traditional anti-interference method and need take the inconvenience of different anti-interference methods, strengthened the flexibility of system at different interference types.

Description of drawings

Fig. 1 is a point-to-point spread spectrum communication system structural representation of the present invention, wherein is the receiving system of spread spectrum signal in the frame of broken lines;

Fig. 2 is multi-user's networking spread spectrum communication system structural representation of the present invention, wherein is the receiving system of spread spectrum signal in the frame of broken lines;

Fig. 3 is the principle schematic that separate in blind source;

Fig. 4 is a fastICA blind source separation algorithm flow chart;

When Fig. 5 is subjected to the partial-band barrage jamming for point-to-point spread spectrum communication, adopt the effect schematic diagram of the inventive method, the spectrogram, the two-way that are followed successively by Frequency Hopping Signal spectrogram, partial-band barrage jamming among the figure from top to bottom mix the spectrogram of received signal and the spectrogram of two-way separation signal;

When Fig. 6 disturbs for point-to-point spread spectrum communication is subjected to pectination, adopt the effect schematic diagram of the inventive method, be followed successively by the spectrogram of Frequency Hopping Signal spectrogram, pectination interference, the spectrogram of two-way mixing received signal and the spectrogram of two-way separation signal among the figure from top to bottom;

When Fig. 7 disturbs for point-to-point spread spectrum communication is subjected to frequency sweep, adopt the effect schematic diagram of the inventive method, be followed successively by time-frequency figure, the time-frequency figure that pectination is disturbed, the time-frequency figure of two-way mixing received signal and the time-frequency figure of two-way separation signal of Frequency Hopping Signal among the figure by (a) to (f);

When Fig. 8 disturbs for the communication of multi-user's networking frequency-hopping spread spectrum is subjected to partial-band barrage jamming, frequency sweep interference and pectination, adopt the method for reseptance of the present invention and the resulting error rate of traditional method of reseptance respectively with the signal-to-interference power ratio relation curve;

When Fig. 9 is subjected to relevant interference for multi-user's networking DS-CDMA communication, adopt the method for reseptance of the present invention and the resulting error rate of traditional method of reseptance respectively with the signal-to-interference power ratio relation curve.

Embodiment

Below in conjunction with accompanying drawing technical scheme of the present invention is elaborated:

Thinking of the present invention is blind source separate technology to be introduced the receiving terminal of spread spectrum communication, by the receiving spread frequency signal respectively of two paths of signals receive path at least, utilize blind source separate technology that useful signal is separated with interference signal then, thereby improve the antijamming capability of spread spectrum communication.

(blind source separation is separated in blind source, BSS) be the research focus of current demand signal processing and field of neural networks, refer to that source signal and transmission channel are unknown fully or only have under a small amount of priori situation, theory and technology that the observation mixed signal of only utilizing transducer output is estimated source signal and transmission channel.Blind source is separated under certain contrast function prerequisite of maximization (or minimization), linearity or non-linear mixed signal is separated, thereby reduced influencing each other between the signal.Separate in blind source can be with time domain, frequency domain is overlapping or nonoverlapping Signal Separation comes.If can utilize blind source separate technology that spread-spectrum signal and interference signal are separated, just can obviously improve the antijamming capability of spread spectrum communication not increasing under signal bandwidth (or reducing transmission capacity) condition.

For ease of the public understanding technical solution of the present invention, below the basic principle of earlier blind source being separated do one and briefly introduce:

Consider multidimensional source signal s (t)=[s ₁(t), s ₂(t), L, s _n(t)] ^T, s _i(t) be i (the source signal column vector of 1≤i≤n), [] ^TThe representing matrix transposition.If there be m transducer in receiving terminal, the transducer received signal is certain mixed form of source signal, and establishing received signal is x (t)=[x ₁(t), x ₂(t), L, x _m(t)] ^T, x _j(t) be j (the received signal column vector of transducer of 1≤j≤m).Received signal x (t) can be write as following form:

x(t)＝ξ(s(t))+n(t) (1)

In the formula (1), the situation of mixing between ξ () expression source signal and the mixed signal, promptly from

The space is arrived

The mapping in space, these mapping relations both can be linear, also can be non-linear.N (t) represents noise signal.The main task that separate in blind source is under the situation of only knowing mixed signal x (t), and source signal s (t) and mixing situation ξ () are estimated.

If can estimate the inverse mapping of ξ (), be made as ψ (), will receive mixed signal from

Spatial alternation is a source signal

Effective estimation of source signal can be realized in the space.

z(t)＝ψ(x(t)) (2)

As source signal s _i(t) and s _j(t) (i ≠ when j) adding up independent mutually, blind source separation problem is also referred to as independent component analysis for 1≤i≤n, 1≤j≤n.

1994, P.Comon delivered famous article and has set up the theoretical system that separate in blind source, and he points out: blind source separation problem can be equivalent to the dynamic optimization process under certain contrast function.

The separation of blind source estimates that to inverse mapping ψ () its principle as shown in Figure 3 usually under maximization (or minimization) some contrast function (being made as f (z (t))) situation.The contrast function that separate in blind source mainly comprises likelihood function, entropy, mutual information and non-Gauss etc., and the some of them contrast function has equivalence on mathematics.The dynamic optimization process that separate in blind source comprises alternative manners such as gradient method and fixing point method.

Separate owing to do not have or can there be qualifications in less prior information for utilizing in blind source, generally requires the receiving sensor number must not be less than the source signal number.Be less than the blind source separation problem of source signal number far away for number of sensors, do not find solution preferably at present as yet.

For point-to-point spread spectrum communication, owing to have only one road spread-spectrum signal and one tunnel interference signal, receiving terminal is provided with two antennas can satisfy the suitable fixed condition that separate in blind source, therefore can adopt spread spectrum communication system as shown in Figure 1, this system comprises transmitting terminal and receiving terminal, transmitting terminal encodes the source signal that information source provides, modulate-and sends behind the spread spectrum; Receiving terminal comprises two-way antenna, blind source separative element, signal recognition unit, despreading-demodulating unit, decoding unit in parallel as shown in frame of broken lines among the figure; The two-way antenna is the spread-spectrum signal of receiving end/sending end transmission respectively; Blind source separative element carries out blind source with this two-way spread-spectrum signal as observation signal to be separated, and isolated two paths of signals is sent to the signal recognition unit; The signal recognition unit identifies useful signal and interference signal from separation signal, useful signal is sent to despreading-demodulating unit, and the characteristic parameter (power, bandwidth etc.) of the interference signal that identifies is analyzed so that transmitting terminal disturbs according to this and evades; Despreading-demodulating unit, decoding unit carry out despreading-separate to the useful signal that identifies successively and are in harmonious proportion decoding, obtain source signal, and source signal is sent to the stay of two nights.

For the spread spectrum communication of multi-user's networking, because the antenna amount that subscriber signal quantity may be provided with much larger than receiving terminal, therefore can't be as above-mentioned scheme, directly the signal that fewer antennas is received carries out the separation of blind source.For this kind situation, spread spectrum communication system structure of the present invention comprises transmitting terminal and receiving terminal as shown in Figure 2, transmitting terminal encodes the source signal that information source provides, modulate-and sends behind the spread spectrum; Receiving terminal is as shown in frame of broken lines among the figure, comprise the signal receive path that two-way is made of antenna and despreading-demodulating unit respectively, two paths is the spread-spectrum signal that sends of receiving end/sending end and it is carried out despreading-demodulation respectively, to obtain baseband signal, the baseband signal after despreading-demodulation is sent into blind source separative element; The two paths of signals of blind source separative element after with despreading-demodulation carries out blind source as observation signal to be separated, and isolated two paths of signals is sent to the signal recognition unit; The signal recognition unit identifies useful signal and interference signal from separation signal, useful signal is sent to decoding unit; Decoding unit is deciphered useful signal can obtain the source signal that transmitting terminal sends, and it is delivered to the stay of two nights.

Below how the present invention being carried out blind source to spread-spectrum signal and interference signal separates and is further elaborated.

When spread spectrum communication was worked in point-to-point mode, source signal was encoded, become spread-spectrum signal s (t) behind modulation and the spread spectrum, supposes that interference side initiates one tunnel interference signal J (t), and both mix in wireless channel.At receiving terminal two antennas are set, owing to all contain interference signal, the influence that the spread spectrum communication performance is interfered in the received signal of every antenna.

Be mixed into example with linear instantaneous, the two-way received signal can be expressed as:

$\left\{\begin{array}{c}{x}_1\left(t\right)=a_{11}s\left(t\right)+a_{12}J\left(t\right)+n_1\left(t\right)\\ x_2\left(t\right)=a_{21}{s}_1\left(t\right)+a_{22}J\left(t\right)+n_2\left(t\right)\end{array}\right.---\left(3\right)$

In order to express easily, omit the time label " t " in the following formula, formula (3) be written as matrix form, obtain:

x＝A·s+n (4)

In the formula (4), x=[x ₁, x ₂] ^TBe two-way received signal, s=[s, J] ^TBe the two-way source signal, $A=\left[\begin{array}{c}{a}_{11},a_{12}\\ a_{21},a_{22}\end{array}\right]$ Be hybrid matrix, n=[n ₁, n ₂] ^TBe the noise signal set.Only there are two components in the formula (4), thereby can utilize blind source to separate and realize that useful signal s separates with the effective of interference signal J.

The present invention can use various existing algorithms that the two-way received signal is carried out the separation of blind source, is that example describes with SOBI, SONS, JADE, fastICA algorithm respectively below.

One, utilize the SOBI algorithm to realize blind separation

(second order blind identification algorithm, SOBI) algorithm realizes that by second order correlation matrix group associating diagonalization the hybrid matrix estimation separates with source signal to SOBI.

In the formula (4), noise satisfies following character:

E[n(m+k)n ^*(m)]＝δ(k)σ ²I (5)

In the formula (5), during and if only if k=0, δ (k)=1.Therefore, the second order correlation matrix of reception mixed signal can be expressed as:

R _xx(0)＝E[x(m)x ^*(m)]＝A·R _ss(0)·A ^H+σ ²I (6)

R _xx(k)＝E[x(m+k)x ^*(m)]＝A·R _ss(k)·A ^H，k≠0 (7)

In the formula (7), H represents that square reaches multiple transposition.Because each component of s is uncorrelated mutually in the source signal, R _Ss(k) be diagonal matrix.For the matrix form shown in the formula (7), can pass through methods such as characteristic value decomposition or singular value decomposition with its diagonalization, thereby realize effective estimation of hybrid matrix A.The concrete steps of SOBI algorithm are as follows:

A) utilize the T sampled data to estimate autocorrelation matrix

Ask for n maximum eigenvalue ₁, λ ₂, L, λ _nWith the characteristic of correspondence vector v ₁, v ₂, L, v _n

B) utilize

M-n minimum characteristic value estimate the white noise variance Calculate the albefaction matrix:

$U={[{({\mathrm{\&lambda;}}_1-{\widehat{\mathrm{\&sigma;}}}^2)}^{-1/2}{\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="110725133247.png,110725133258.png"\; state="\{\{state\}\}">v</figure-callout>}}_1,L,{({\mathrm{\&lambda;}}_n-{\widehat{\mathrm{\&sigma;}}}^2)}^{-1/2}{v}_n]}^H---\left(8\right)$

Obtain whitened signal y=Ux, y=[y ₁, y ₂, L, y _n] ^T

C) at a series of time interval k ∈ { k _j| j=1, L, K} estimate the covariance matrix of y down

D) will Carry out the associating diagonalization, try to achieve unit matrix

E) estimate separation signal and hybrid matrix.

$\left\{\begin{array}{c}z={\hat{W}}^H\&CenterDot;U\&CenterDot;x\\ \hat{A}=U^{\#}W\end{array}\right.---\left(9\right)$

Two, utilize the SONS algorithm to realize blind separation

SONS (second order nonstationary source separation, SONS) algorithm and the SOBI class of algorithms are seemingly, utilized the second order cumulant of signal equally, difference is that the SONS algorithm considered the non-stationary property of signal, can the coherent signal of non-stationary be separated.

For the noisy mixing observation signal shown in the formula (4), utilize observation data x calculation delay correlation matrix:

R _xx(k)＝E[x(m+k)x ^*(k)]＝AR _ss(k)A ^H，k≠0 (10)

Work as R _XxWhen (k) not satisfying the positive definite condition, can't some utilization in k ≠ 0

X carries out the albefaction processing to received signal.At this situation, the SONS algorithm utilizes a series of time delay correlation matrix M _Xx(k _i) linear combination make up second order correlation matrix C _Xx, make it to satisfy positive fixed condition, strengthened the stability of algorithm.

$M_{\mathrm{xx}}\left(k_i\right)=\frac{1}{2}\{R_{\mathrm{xx}}\left(k_i\right)+R_{\mathrm{xx}}^H\left(k_i\right)\}---\left(11\right)$

$C_{\mathrm{xx}}=\underset{i=1}{\overset{K}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i{M}_{\mathrm{xx}}\left(k_i\right)---\left(12\right)$

{ α _iFor making C _XxThe parameter sets of positive definite is to C _XxCarry out characteristic value decomposition, can obtain following form:

$C_{\mathrm{xx}}=[U_s,U_n]\left[\begin{array}{cc}{\mathrm{\&Lambda;}}_s& 0\\ 0& {\mathrm{\&Lambda;}}_n\end{array}\right]{[U_s,U_n]}^H---\left(13\right)$

Therefore, can utilize the albefaction matrix

Carry out whitening pretreatment to received signal,, and suppress The noise with the dimension of reduction signal.

y＝Qx＝Vs+Qn (14)

In the formula, V=QA, because albefaction data y is zero-mean and unit variance, VV ^H=I.

Consider that source signal is the second order non-stationary signal, and have relativity of time domain, therefore have:

M _xx(m _i，k _j)＝AM _ss(m _i，k _j)A ^H (15)

$M_{\mathrm{xx}}(m_i,k_j)=\frac{1}{2}\{R_{\mathrm{xx}}(m_i,k_j)+R_{\mathrm{xx}}^H(m_i,k_j)\}---\left(16\right)$

Matrix M in the formula (15) _Xx(m _i, k _j) satisfy the diagonalizable form of associating equally with the middle matrix of formula (7), can pass through M _Xx(m _i, k _j) the associating diagonalization come estimated mixing matrix A.Therefore, the concrete steps of SONS algorithm are as follows:

A) utilize x to calculate C _Xx, and then try to achieve the albefaction matrix Obtain whitened signal y;

B) y is divided into K nonoverlapping Frame, in each frame, calculates P different time relevant time delay matrix at interval, try to achieve M _Yy(m _i, k _j), i=1, L, K, j=1, L, P;

C) to M _Yy(m _i, k _j) carry out the associating diagonalization, try to achieve unit matrix D, make it satisfied:

D ^HM _yy(t _k，τ _i)D＝Δ _ki (17)

In the formula (17), { Δ _KiBe a series of diagonal matrix;

D) try to achieve separation matrix and separation signal.

$\left\{\begin{array}{c}W=D^{T}Q\\ z=\mathrm{Wx}\end{array}\right.---\left(18\right)$

Three, utilize the JADE algorithm to realize blind separation

(joint approximative diagonalization of eigenmatrix also is by matrix group associating diagonalization hybrid matrix to be estimated JADE) to the JADE algorithm.The difference of JADE algorithm and SOBI algorithm and SONS algorithm is that the JADE algorithm carries out on the fourth order cumulant basis.

Make that y is the n passage observed data of albefaction, y=[y ₁, y ₂, L, y _n] ^T, M is any n * n weight matrix.The capable j row of the i of the fourth order cumulant matrix of y (1≤i≤n, 1≤j≤n) element is:

${\left[Q_y\left(M\right)\right]}_{\mathrm{ij}}=\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}\underset{l=1}{\overset{n}{\mathrm{\&Sigma;}}}\mathrm{cum}(y_i,y_j,y_k,y_l)\&CenterDot;m_{\mathrm{kl}}---\left(19\right)$

In the formula (19), m _KlBe the capable l column element of k of matrix M, cum (y _i, y _j, y _k, y _l) be i among the vectorial y, j, k, the fourth order cumulant of four components of l, its computing formula is:

cum(y _i，y _j，y _k，y _l)＝E{y _iy _jy _ky _l}-E{y _iy _j}E{y _ky _l}-E{y _iy _k}E{y _jy _l}-E{y _iy _l}E{y _jy _k}

(20)

Q _y(M) be the cumulant matrix (cumulant matrix) of all fourth order cumulants formations of y, can be write as the long-pending form of two matrixes.

Through type (20) as can be known, Q _y(M) of matrix (i, j) element value has reflected given i, all fourth order cumulant cum (y under the j _i, y _j, y _k, y _l) weighted sum, its weight be Metzler matrix (k, l) element value, therefore, Q _y(M) whole fourth order cumulant information of multi-channel data y have been comprised.

N passage for albefaction is observed vectorial y, Q _y(M) can be expressed as:

Q _y(M)＝VΛ(M)V ^T (21)

In the formula (21), Λ (M) is the characteristic value diagonal matrix.

Λ(M)＝V ^TQ _y(M)V (22)

With the V matrix to Q _y(M) do quadratic form and handle, will obtain diagonal matrix Λ (M), this characteristic can be used for seeking the V matrix.

Therefore, can draw and utilize matrix group M=[M ₁, M ₂, L, M _P] associating diagonalization blind source separation method is as follows:

A) ask preconditioning matrix U, carry out albefaction, y=Ux receiving data x;

B) selected one group of matrix M=[M ₁, M ₂, L, M _P], calculate one group of cumulant matrix Q according to formula (19) _y(M _p);

C) ask " mixing-albefaction " matrix V=UA to each Q _y(M _p) the associating diagonalization, make non-diagonal angle index D _M(V) minimum;

$D_M\left(V\right)=\underset{M_p\&Element;M}{\mathrm{\&Sigma;}}\mathrm{off}\left[V^T{Q}_y\left(M_p\right)V\right]---\left(23\right)$

D) estimated mixing matrix and separation signal.

$\hat{A}=U^{T}V,$ $\hat{W}=V^{T}U,$ $z=\hat{W}x=V^T\mathrm{Ux}---\left(24\right)$

Four, utilize the fastICA algorithm to realize blind separation

Be that example describes with fastICA blind source separation method below based on negentropy.This method is the non-Gauss function in contrast with the maximization separation signal.

Carry out blind separating treatment in order to utilize fastICA to calculate, need carry out following centralization and whitening pretreatment step usually:

In the centralization preprocessing process, received signal is deducted its average:

x′＝x-E{x} (25)

In the formula (25), E{} represents to ask for mathematic expectaion.

In the albefaction process, at first need the covariance matrix of signal calculated, C _Xx=E{x ' [x '] ^T, covariance matrix is carried out characteristic value decomposition, C _Xx=EDE ^TUtilize eigenvectors matrix E and eigenvalue matrix D, according to following formula the signal of centralization is carried out albefaction and handle.

y＝ED ^-1/2E ^Tx′ (26)

Signal y after formula (26) is handled is a zero-mean unit variance signal, and uncorrelated mutually between each component.

According to central-limit theorem, a large amount of independent same distribution stochastic variables with the variable Gaussian distributed.When separation signal still was certain mixed form of source signal, its probability distribution still tended to Gaussian Profile; Separation signal that and if only if is during near source signal, and its probability distribution just can be away from Gaussian Profile.Therefore, can be with the non-Gauss of separation signal function in contrast, when the non-Gauss of separation signal that and if only if reached maximum, blind source was separated and has just been reached preferable performance.The negentropy of stochastic variable can be used for measuring its non-Gauss, and its definition is:

J(y)＝H(y _g)-H(y) (27)

In the formula (27), the negentropy of J (y) expression stochastic variable y, H (y)=-∫ p _y(η) logp _y(η) d η represents the differential entropy of y, y _gFor having the Gaussian random variable of identical variance (power) with y.From formula (27) as can be seen, negentropy has been measured the distance of differential entropy with the Gaussian random variable of identical variance (power) of stochastic variable.

The negentropy of stochastic variable can be estimated by nonlinear function:

J(y)∝[E{G(y)}-E{G(v)}] ² (28)

In the formula (28), G () is certain nonlinear function.A.

J.Karhunen and E.Oja adopt following non-line function in Independent Component Analysis document:

$\left\{\begin{array}{c}{G}_1\left(u\right)=\frac{1}{a}\log \cosh \mathrm{au}\\ G_2\left(u\right)=-\exp (-u^2/2)\end{array}\right.---\left(29\right)$

In the formula (29), a is a certain constant of value between 1 and 2.

Thus, as follows based on the fast fixed point blind source separation algorithm of negentropy:

w ⁺＝E{vg(w ^Tv)}-E{g′(w ^Tv)}w (30)

w＝w ⁺/||w ⁺|| (31)

In the formula (30), g () is the differential expression of G ().

FastICA blind source separation algorithm flow process is constantly carried out iteration to separation matrix w as shown in Figure 4, until making the negentropy shown in the formula (28) reach maximum, can obtain optimal separation matrix w _OptWith w _OptAct on the signal y after the albefaction, can realize effectively separating of active user's signal and interference signal.

In order in separation signal, to identify useful signal and interference signal, need increase the signal identifying at blind source after separating identifies useful signal and equivalent interference signal, for example can adopt the method for the customizing messages that inserts in advance commonly used, judge respectively promptly blind source separates in the two paths of signals that obtains whether comprise the customizing messages of making an appointment, the signal that comprises this customizing messages is a useful signal, and another road signal is an interference signal; Described customizing messages is inserted in the source signal that sends in advance by signal sending end.The signal recognition unit is also analyzed so that transmitting terminal disturbs according to this and evades the characteristic parameter (power, bandwidth etc.) of the interference signal that identifies, thereby further improves the antijamming capability of system.Decoding unit is deciphered the useful signal that identifies, and obtains final primary signal and sends to the stay of two nights.

Do you for the spread spectrum communication system of multi-user's networking shown in Figure 2, consider K (K? 2) the road spread-spectrum signal situation of communicating by letter simultaneously by multi-access mode, original user signal I ₁(n), I ₂(n), L, I _K(n) become K road spread-spectrum signal s through spread spectrum ₁(t), s ₂(t), L, s _K(t), suppose that spread-spectrum signal also is subjected to the influence of 1 tunnel interference signal J (t) in communication process.At k user's receiving terminal two antennas are set and receive, be mixed into example with linear instantaneous, the two-way received signal can be expressed as:

$\left\{\begin{array}{c}{r}_1\left(t\right)=a_{11}{s}_1\left(t\right)+a_{12}{s}_2\left(t\right)+L+a_{1K}{s}_K\left(t\right)+a_{1K+1}J\left(t\right)+n_1\left(t\right)\\ r_2\left(t\right)=a_{21}{s}_1\left(t\right)+a_{22}{s}_2\left(t\right)+L+a_{2K}{s}_K\left(t\right)+a_{2K+1}J\left(t\right)+n_2\left(t\right)\end{array}\right.---\left(32\right)$

In the formula (32), r ₁(t) be the 1st antenna receiving signal, r ₂(t) be the 2nd antenna receiving signal; Mixed coefficint a _IjRepresent j (the road source signal s of 1≤j≤K+1) _j(t) with i road received signal r _i(t) mapping relations between; n ₁(t) and n ₂(t) represent noise in the 1 tunnel received signal and the 2 tunnel received signal respectively.Herein, there is K+1 road source signal, but only obtains 2 road observation signals, be difficult to directly utilize blind source to be separated source signal is estimated.

At receiving terminal, at first to r ₁(t) and r ₂(t) carry out despreading-demodulation respectively and obtain baseband signal without 0-1 judgement with the redundant composition of removing its frequency spectrum.It is prerequisite that the method for the invention can be set up reliable synchronization with receiving terminal, and existing low signal interference ratio reliable synchronization technology can be this method provides technical support.Below, with k (1≤k≤K) individual user is that example further specifies:

$\left\{\begin{array}{c}{x}_1\left(m\right)=D_{\left(\right\{t_k\},\{f_k\},\{c_k\left\}\right)}\left(r_1\left(t\right)\right)\\ x_2\left(m\right)=D_{\left(\right\{t_k\},\{f_k\},\{c_k\left\}\right)}\left(r_2\left(t\right)\right)\end{array}\right.---\left(33\right)$

In the formula (33), x ₁(m), x ₂(m) be without the two-way baseband signal time series of adjudicating, m=1,2 ..., M is the seasonal effect in time series label.

Expression despreading-demodulation function, ({ t _k, { f _k, { c _k) the required relevant parameters such as time slot, frequency hopping pattern and signature sequence of expression receiving terminal despreading-demodulation.Because the spread-spectrum signal of different user has the nearly orthogonal characteristic in dimensions such as time, frequency or codings, the spread-spectrum signal of different user is uncorrelated mutually or only have a less correlation.After despreading-demodulation, can effectively recover active user's information, other subscriber signals and interference signal are then effectively suppressed.Because despreading-demodulation is based on multiply operation, the two-way baseband signal shown in the formula (33) can be approximately:

$\left\{\begin{array}{c}{x}_1\left(m\right)\&ap;b_{11}{I}_1^{\&prime;}\left(m\right)+L+b_{1k}{I}_k^{\&prime;}\left(m\right)+L{b}_{1K}{I}_K^{\&prime;}\left(m\right)+b_{1K+1}{J}^{\&prime;}\left(m\right)+{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="110725133247.png,110725133258.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^{\&prime;}\left(m\right)\\ x_2\left(m\right)\&ap;b_{21}{I}_1^{\&prime;}\left(m\right)+L+b_{2k}{I}_k^{\&prime;}\left(m\right)+L{b}_{2K}{I}_K^{\&prime;}\left(m\right)+b_{2K+1}{J}^{\&prime;}\left(m\right)+n_2^{\&prime;}\left(m\right)\end{array}\right.---\left(34\right)$

In the formula (34), I ' _k(m) be active user (k road) without the judgement baseband signal, I ' _j(m) (1≤j≤K, the baseband signal that the expression of j ≠ k) utilizes k customer parameter that j road source signal is carried out obtaining after despreading-demodulation.J ' is the baseband interference signal for utilizing k customer parameter that interference signal is carried out obtaining after despreading-demodulation (m).Owing to do not adopt correct parameter despreading-demodulation, I ' _j(m) (m) have similar probability distribution with J ', its numerical value is far smaller than I ' _k(m), can with

Equivalence is 1 road signal c _iG _k(m), c _iBe new mixed coefficint, 1≤i≤2.g _k(n) be equivalent signal, by forming of other subscriber signals and interference signal without correct parameter despreading-demodulated data.

Therefore, formula (34) can be write as:

$\left\{\begin{array}{c}{x}_1\left(m\right)\&ap;b_{1k}{I}_k^{\&prime;}\left(m\right)+c_1{g}_k\left(m\right)+{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="110725133247.png,110725133258.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^{\&prime;}\left(m\right)\\ x_2\left(m\right)\&ap;b_{2k}{I}_k^{\&prime;}\left(m\right)+c_2{g}_k\left(m\right)+n_2^{\&prime;}\left(m\right)\end{array}\right.---\left(35\right)$

Easy in order to describe, can omit time label m, further formula (35) is write as the form of matrix:

x＝A·s+n (36)

In the formula (36), x=[x ₁, x ₂] ^TBe two-way received signal, s=[I ' _k, g _k] ^TCan be considered the two-way source signal, $A=\left[\begin{array}{c}{b}_{1k},c_1\\ b_{2k},c_2\end{array}\right]$ Be hybrid matrix, n=[n ₁, n ₂] ^TFormula (36) shows: after receiving element was handled, the number of received signal was reduced to two, can utilize blind source to separate and realize useful information I ' _kWith interfere information g _kEffective separation, thereby remove the influence of other subscriber signals and interference signal to the active user.

Blind source separation methods such as foregoing JADE, SONS, SOBI, fastICA, maximum likelihood, minimum mutual information all can be applicable to herein, realize useful information I ' _kWith interfere information g _kEffective separation, detailed process repeats no more herein.

In order in separation signal, to identify useful signal and interference signal, need increase the signal identifying at blind source after separating identifies useful signal and equivalent interference signal, for example can adopt the method for the customizing messages that inserts in advance commonly used, judge respectively promptly blind source separates in two signals that obtain whether comprise the customizing messages of making an appointment, the signal that comprises this customizing messages is a useful signal, and another signal is an interference signal; Described customizing messages is inserted in the source signal that sends in advance by signal sending end.Decoding unit is deciphered the useful signal that identifies, and obtains final primary signal and sends to the stay of two nights.

Blind source of the present invention separate comprise independent component analysis (independent component analysis, ICA) and sparse component analysis (sparse component analysis, SCA).

Blind source of the present invention is separated the prior information that comprises spread spectrum communication and is applied to the separation of blind source to improve the half-blindness isolation technics of separating property.The prior information of spread spectrum communication of the present invention refers to carrier frequency, character rate, frequency hopping pattern and pseudo noise code etc.

The present invention separates with interference signal spread-spectrum signal at intermediate frequency or base band, reach the purpose that improves the spread spectrum communication antijamming capability.

Interference signal of the present invention can also can be some relevant interference for noncoherent jamming.Noncoherent jamming involved in the present invention refer to the waveform of interference signal and spread-spectrum signal do not have correlation or correlation a little less than, can comprise arrowband barrage jamming, broadband barrage jamming, single-tone interference, multitone interference, frequency sweep interference etc.Relevant interference involved in the present invention refers to that the waveform of interference signal and spread-spectrum signal have stronger correlation, pattern when it is jumped (or frequency hopping pattern, signature sequence) is identical with target spread spectrum user or part is identical, but information sequence is added up independence with spread spectrum user at present.

In order to verify performance of the present invention, utilize computer to write the simulated program checking that experimentizes.Because the error rate is to weigh the important indicator of communication system, keep the specific performance that the error rate numerical value that separates the front and back signal is measured the inventive method in mind.For the ease of realizing, do not adopt chnnel coding in the emulation experiment temporarily.After adopting chnnel coding, the performance of output signal will further be improved.

When Frequency Hopping Signal is worked in point-to-point mode, when being subjected to partial-band barrage jamming, frequency sweep interference and pectination interference effect, utilize the SOBI algorithm to adopt step of the present invention to separate to mixing received signal.

Fig. 5 is followed successively by the spectrogram of Frequency Hopping Signal and partial-band barrage jamming, spectrogram that two-way mixes received signal and the spectrogram of two-way separation signal from top to bottom.As can be seen, the power of partial-band barrage jamming signal is better than Frequency Hopping Signal far away from the mixed signal spectrogram, and in its bandwidth range, the spectral line of Frequency Hopping Signal is flooded fully; But after adopting the method for the invention (Fig. 1) to separate, the spectral line of Frequency Hopping Signal is clear again in the separation signal reveals, show that the method for the invention can realize effectively separating of Frequency Hopping Signal and partial-band barrage jamming signal, thereby improve the signal interference ratio of output signal, improved its antijamming capability.

Fig. 6 is followed successively by spectrogram that Frequency Hopping Signal and pectination disturb, spectrogram that two-way mixes received signal and the spectrogram of two-way separation signal from top to bottom.Similar to the result of Fig. 5, the method for the invention also can successfully realize Frequency Hopping Signal and effectively separating that pectination is disturbed.

Because Frequency Hopping Signal and frequency sweep interference signal in time and two dimension dynamic changes of frequency, adopt time-frequency figure to show the blind separate instance of Frequency Hopping Signal and frequency sweep interference signal.Fig. 7 (a) and (b) are respectively the time-frequency figure of Frequency Hopping Signal and frequency sweep interference signal, from the situation of change of time and two dimension aids of frequency; (c), (d) be respectively the time-frequency figure that two-way mixes received signal, therefrom as can be seen, all contains the frequency sweep interference component of Frequency Hopping Signal in the two-way received signal, communication performance is affected; (e), (f) be respectively and adopt the inventive method to obtain the time-frequency figure of two-way separation signal, therefrom as can be seen, Frequency Hopping Signal is separated fully with the frequency sweep interference.

When frequency hopping communications works in networking mode, exist partial-band barrage jamming, frequency sweep to disturb and during noncoherent jamming such as pectination interference, the error rate that adopts method of reseptance of the present invention and traditional method of reseptance respectively with the signal-to-interference power ratio relation curve as shown in Figure 8.Number of users is 10 in the emulation, and receiving terminal adopts the 2DPSK mode to modulate, and frequency hopping frequency number is 50, is respectively 21kHz, 22kHz ..., 70kHz, hop rate is 1000hops/s, information rate is 1000bps.The partial-band barrage jamming covers 30kHz～60kHz, and frequency sweep is disturbed at double bounce and swept in the time interval all over whole frequency hopping bandwidth, and pectination is disturbed four broach are set in the frequency hopping bandwidth.Fig. 8 is the average result of 200 Monte Carlo simulation experiments, and wherein blind separation algorithm adopts the JADE algorithm, and dotted line is for adopting the ber curve of traditional method of reseptance among the figure, and solid line is for adopting the ber curve of the inventive method.Contrast finds that under three kinds of noncoherent jamming, the inventive method all can obviously be improved the bit error rate performance of output signal.

Fig. 9 adopts method of reseptance of the present invention and traditional method of reseptance to receive the error rate of DS-CDMA signal and the relation curve of signal noise power ratio respectively when having relevant interference.Set in the emulation, number of users is 6, and the pseudo noise code cycle is 63, and the pseudo noise code spreading rate is 63MHz, information rate is 1Mbps, carrier frequency is 126MHz, and signal interference ratio is incremented to-8dB with the 8dB step-length from-40dB, every signal interference ratio point emulation 2000 times, in each emulation, the targeted customer of relevant interference chooses from 6 users at random, and parameter such as its pseudo noise code, symbol period, chip period and carrier frequency and targeted customer are identical.Dotted line is the ber curve that the targeted customer of relevant interference adopts traditional receiver among the figure, and solid line is respectively the ber curve that adopts JADE, SONS, SOBI and fastICA algorithm separation signal.Contrast finds that the inventive method can obviously be improved the bit error rate performance of DS-CDMA signal under relevant interference.

Claims (10)

1. the method for reseptance of a spread spectrum signal is characterized in that, this method comprises that at least two antennas of utilization receive the step of spread spectrum signal respectively; Carry out blind source separation steps with the two paths of signals at least that receives as observation signal; And the separation signal that obtains is separated in blind source discern, identify the step of useful signal and interference signal.

2. the method for reseptance of spread spectrum signal according to claim 1 is characterized in that, specifically may further comprise the steps:

Step 1, at least two antennas of utilization receive spread spectrum signal respectively;

Step 2, the spread spectrum signal of two-way at least that receives is carried out despreading-demodulation process respectively;

Step 3, carry out blind source with the two paths of signals at least after despreading-demodulation as observation signal and separate, obtain the two-way separation signal;

Step 4, the two-way separation signal that obtains is separated in blind source discern, identify useful signal and interference signal; Then useful signal is deciphered, obtained source signal.

3. the method for reseptance of spread spectrum signal according to claim 1 is characterized in that described spread spectrum signal is single subscriber signal, and described method of reseptance specifically may further comprise the steps:

Step 1, at least two antennas of utilization receive spread spectrum signal respectively;

Step 2, carry out blind source with the spread spectrum signal of two-way at least that receives as observation signal and separate, obtain the two-way separation signal;

Step 3, the two-way separation signal that obtains is separated in blind source discern, identify useful signal and interference signal;

Step 4, useful signal is carried out despreading-demodulation, decoding, obtain source signal.

4. the method for reseptance of spread spectrum signal according to claim 1 is characterized in that the method for reseptance of described spread spectrum signal specifically may further comprise the steps:

Step 1, at least two antennas of utilization receive spread spectrum signal respectively;

Step 2, the spread spectrum signal of two-way at least that receives is carried out despreading respectively handle;

Step 3, carry out blind source with the two paths of signals at least after the despreading as observation signal and separate, obtain the two-way separation signal;

Step 4, the two-way separation signal that obtains is separated in blind source discern, identify useful signal and interference signal; Then useful signal is carried out demodulation, decoding, obtain source signal.

5. the method for reseptance of spread spectrum signal according to claim 1, it is characterized in that, adopt following method that useful signal is discerned with interference signal: to judge respectively blind source separates whether comprise the customizing messages of making an appointment in the two paths of signals that obtains, the signal that comprises this customizing messages is a useful signal, and another road signal is an interference signal; Described customizing messages is inserted in the source signal that sends in advance by signal sending end.

6. as the method for reseptance of spread spectrum signal as described in the claim 3, it is characterized in that this method also comprises the step of the characteristic parameter of the interference signal that identifies being analyzed and analysis result is fed back to signal sending end.

7. the receiving system of a spread spectrum signal is characterized in that, this device comprises according to the signal receive path of signal flow to the parallel connection of two-way at least that connects in turn, and blind source separative element, signal recognition unit, decoding unit; Described signal receive path comprises antenna and despreading-demodulating unit, is used to receive spread spectrum radio signal and despreading-demodulation; At least two paths of signals of described blind source separative element after with despreading-demodulation carries out blind source as observation signal to be separated; Described signal recognition unit is discerned the blind source isolated signal of separative element, identifies useful signal and interference signal; Described decoding unit is deciphered the useful signal that identifies, and obtains source information, and source information is sent to the stay of two nights.

8. the receiving system of a spread spectrum signal, described spread spectrum signal is single subscriber signal, it is characterized in that this device comprises according to signal flow to two antennas, blind source separative element, signal recognition unit, despreading-demodulating unit, the decoding unit that connect in turn at least; Described at least two antennas receive the spread spectrum radio signal respectively; Described blind source separative element carries out blind source with the spread spectrum signal of two-way at least that receives as observation signal to be separated; Described signal recognition unit is discerned the blind source isolated signal of separative element, identifies useful signal and interference signal; Described despreading-demodulating unit and decoding unit carry out despreading-demodulation, decoding to the useful signal that identifies respectively, obtain source information, and source information is sent to the stay of two nights.

9. as the receiving system of spread spectrum signal as described in the claim 8, it is characterized in that described signal recognition unit is also analyzed the characteristic parameter of the interference signal that identifies.

10. a spread spectrum communication system comprises signal sending end and signal receiving end, it is characterized in that, described signal receiving end comprises the receiving system as spread spectrum signal as described in the claim 7,8 or 9.

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