CN103634038B - Allied DOA estimation based on multiple antennas and the multipath signal reception method of Wave beam forming - Google Patents

Abstract

The invention discloses a kind of new use in conjunction DOA to estimate and the multipath signal reception method of Wave beam forming, the method is the characteristic utilizing spatial information that in multipath signal, each path signal carries different, use in conjunction DOA is estimated and beam-forming technology, the multipath signal of reception is processed, effectively estimate the arrival angle of each path signal, space angle is distinguished each path signal；The path signal of all angles is carried out Wave beam forming, thus each path signal is separated；In each path signal, extract main footpath signal, and it is demodulated, decodes.Its core concept is: DOA estimates and the use in conjunction of beam-forming technology, efficiently separate multipath signal, receiving terminal extracts main footpath signal and is demodulated, decodes, and has so been inherently eliminated the impact of multipath effect, improves the receptivity of ofdm communication system.

Description

Allied DOA estimation based on multiple antennas and the multipath signal reception method of Wave beam forming

Technical field

The present invention relates to mobile communication technology field, be specifically related to allied signal and arrive angle (Direction of Arrival, DOA) estimating should with Wave beam forming (Beamforming) technology one when multicarrier system receiving multipath signals Use field.

Technical background

Lead at wireless OFDM (Orthogonal Frequency Division Multiplexing, OFDM) In communication system, actual communication environment is multi-path environment, and the electric wave launching signal can arrive receiving terminal through different paths, multiple Propagation delay in path and decline are random, and receiving terminal received signal is the superposition of multiple path signal.Multipath Propagation can cause ofdm signal the extension of time domain waveform to occur in time domain, produces frequency selective fading on frequency domain.Meanwhile, Relative movement between node, result in the generation of Doppler frequency deviation, and these factors all can affect being properly received of ofdm signal, The receptivity causing receiving terminal declines.The focus that communication system performance is current research is improved under mobile multi-path environment, as Where receiving terminal eliminates the key that the impact of multipath effect is then problem as much as possible.The scheme that presently, there are is roughly divided into two Class: the first uses channel error correction encoding, Adaptive Modulation and channel equalization technique in wireless OFDM communication system；Wherein, letter Trace equalization technology is to insert special pilot in OFDM symbol when sending, and receiving terminal utilizes the special pilot inserted to enter signal Row equilibrium；Channel error correction technology and channel equalization technique add channel overhead, and frequency selective fading cannot be completely eliminated Impact on transmission reliability；Adaptive modulation technology can select the modulation methods that capacity of resisting disturbance is higher when channel conditions deteriorates Formula, also can reduce channel utilization；It two is diversity receiving technology based on multiple antennas, owing to same signal is through multipath transmisstion Issuable irrelevance, utilizes the multiple antennas at different spatial to go to receive one simultaneously and launches signal, then synthesize Or choose a strong signal, but this technology cannot be inherently eliminated the impact that multipath effect is brought.The present invention can be very Solve well problem above.

Summary of the invention

Goal of the invention is to be estimated and beam-forming technology by use in conjunction direction of arrival (DOA), to the multipath received Signal processes, and is inherently eliminated the impact of multipath effect, improves the receptivity of ofdm communication system.

The present invention solves its technical problem and is adopted the technical scheme that: the present invention provides a kind of associating based on multiple antennas DOA estimates and the multipath signal reception method of Wave beam forming, and the method utilizes each path signal in multipath signal to carry The characteristic that spatial information is different, the estimation of use in conjunction DOA and beam-forming technology, the multipath signal of reception is processed, Distinguish each path signal on space angle, separate multipath signal and extract main footpath signal, eliminate the impact of multipath effect, Thus improve the transmission performance of ofdm communication system.

Multipath signal reception scheme include the following: can estimate each path signal arrival angle, can be the most right Each path signal carries out Wave beam forming, efficiently separates multipath signal, efficiently extracts main footpath signal.Present invention introduces associating Application direction of arrival (DOA) is estimated and beam-forming technology, and the scheme proposed can fundamentally solve the shadow of multipath effect Ringing, and method is simple, easily realizes, in the scheme of current all open reports, receptivity is optimum.

In single-shot many receipts ofdm communication system, the allied DOA estimation based on multiple antennas of present invention proposition and wave beam shape The OFDM receiver system block diagram of the multipath signal reception method become as in figure 2 it is shown, main operational module by aerial array, DOA estimation, Beam-former and OFDM demodulation module composition；Wherein DOA estimates and Beam-former is multipath signal reception The core of scheme.The present invention proposes following technical scheme: utilize the spatial information that in multipath signal, each path signal carries Different characteristics, the receiving terminal docking collection of letters number carries out DOA estimation；Due to the coherence of multipath signal, by antenna array partition it is Some submatrixs, calculate each submatrix and receive the correlation matrix of signal, and try to achieve the meansigma methods of multiple submatrix correlation matrix, be Signal correlation matrix R after decoherence_X；By signal correlation matrix R_XCarry out Eigenvalues Decomposition, corresponding according to the little eigenvalue obtained The spatial spectrum of characteristic vector signal calculated, arrival angle, the space θ of each path signal corresponding of the spectral peak in spatial spectrum₁, θ₂,...,θ_K；Obtaining arrival angle, the space θ of path signal₁,θ₂,...,θ_KOn the basis of, the path signal to each Space Angle Carry out Wave beam forming respectively, respectively obtain each path signal, multipath signal is separated；In the multiple path signals obtained, Utilize the sign synchronization of OFDM demodulation, choose out by the path signal of minimum for synchronous point (path delay of time is minimum), lead the most by force Footpath signal y_max(t)；By the strongest main footpath signal y_maxT () is as the output signal of Beam-former；To output signal y_maxT () enters Row OFDM demodulation, including going Cyclic Prefix (CP), serial to parallel conversion, FFT and inverse mapping, is finally decoded.

Due to the coherence of multipath signal, decoherence process will be carried out in the receiving terminal docking collection of letters number, will aerial array It is divided into some submatrixs, calculates each submatrix and receive the correlation matrix of signal, and try to achieve the average of multiple submatrix correlation matrix Value, obtains the signal correlation matrix R after decoherence_X, N root antenna array partition is become the subarray being made up of m root antenna, submatrix Columns is L=N-m+1, and output signal vector Xl (t) of each subarray is respectively as follows:

$\left\{\begin{array}{c}{X}_1\left(t\right)={[x_1\left(t\right),x_2\left(t\right),...,x_m\left(t\right)]}^T\\ X_2\left(t\right)={[x_2\left(t\right),x_3\left(t\right),...,x_{m+1}\left(t\right)]}^T\\ ...\\ X_L\left(t\right)={[x_L\left(t\right),x_{L+1}\left(t\right),...,x_{L+m-1}\left(t\right)]}^T\end{array}\right.$

The correlation matrix R of l subarray_lFor: $R_l=E\left[X_l\left(t\right){X_l}^H\left(t\right)\right]=A_m{R}_X^l{A}_m^H+R_n^l$

Take the meansigma methods of the autocorrelation matrix of all subarrays, it may be assumed that

$R_X=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{R}_l=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{A}_m{R}_X^l{A}_m^H+R_n^l=A_m{R}_S{A}_m^H+R_n^l$

To carrying out the signal autocorrelation matrix R after decoherence process_XCarry out feature decomposition, respectively obtain big eigenvalue and little Eigenvalue, calculates characteristic vector U corresponding to little eigenvalue_n=[u_K+1,u_K+2,...,u_m], according to signal space spectrum definition Formula:

$P\left(\mathrm{\θ}\right)=\frac{1}{{\left|\mathrm{\α}{\left(\mathrm{\θ}\right)}^H{U}_n\right|}^2}=\frac{1}{\mathrm{\α}{\left(\mathrm{\θ}\right)}^H{U}_n{U}_n^H\mathrm{\α}\left(\mathrm{\θ}\right)}$

Obtain the spatial spectrum of signal, in the spatial spectrum of signal, search Space Angle θ corresponding to spectral peak₁,θ₂,...,θ_K。

Obtaining arrival angle, the space θ of path signal₁,θ₂,...,θ_KOn the basis of, the path signal to each Space Angle Carry out Wave beam forming respectively, i.e. Represent the best initial weights of the i-th paths Wave beam forming, obtain respectively To each path signal y₁(t),y₂(t),...,y_KT (), has separated multipath signal.

When each path signal is carried out Wave beam forming, drawn the optimum power of each path signal by following criterion Value, i.e. keeps this expected path angle, θ_iUnder conditions of gain is certain so that this output signal power minimizes.

The majorized function set up can be expressed as:

$\left\{\begin{array}{c}\min P_{\mathrm{out}}=E\left[{\left|y_i\left(t\right)\right|}^2\right]=w^H{R}_{X}w\\ s.t.w^{H}a\left({\mathrm{\θ}}_i\right)=1\end{array}\right.$

Majorized function is constructed Lagrangian: L (w)=w^HR_Xw+μ[w^Ha(θ_i)-1]；

W is carried out derivation and makesCan obtain

The best initial weights of the i-th paths Wave beam forming can be obtainedFor:

$w_{\mathrm{opt}}^i=\frac{R_X^{-1}a\left({\mathrm{\θ}}_i\right)}{a^H\left({\mathrm{\θ}}_i\right)R_X^{-1}a\left({\mathrm{\θ}}_i\right)}$

In K the path signal obtained, carry out choosing of main footpath signal, due to each path signal the path delay of time not With, so utilizing the sign synchronization module in OFDM demodulation, the path signal of minimum for synchronous point (path delay of time is minimum) is set to Main footpath signalThe strongest main footpath signal, w_{max_opt}Formed for the strongest main footpath signal beam Excellent weights, using the reservation of this path signal the output signal as Beam-former.

To the strongest main footpath signal y_maxT () carries out OFDM demodulation, including removing Cyclic Prefix (CP), serial to parallel conversion, FFT, inverse reflecting Penetrate, subsequently the signal after OFDM demodulation is decoded.

Beneficial effect:

1, the present invention can estimate the arrival angle of each path signal effectively.

2, the present invention can carry out Wave beam forming effectively to each path signal, separates multipath signal.

3, the present invention can efficiently extract out main footpath signal, is inherently eliminated the impact of multipath effect.

Accompanying drawing explanation

Fig. 1 is the multipath signal illustraton of model of single-shot many receipts ofdm communication system of the present invention.

Fig. 2 is the system block diagram of the OFDM receiver of the present invention.

Fig. 3 is the DOA estimation figure of the multipath signal reception of the present invention.

Fig. 4 is the Wave beam forming vectogram of the strongest main footpath signal of the present invention.

Fig. 5 is the bit error rate comparison diagram of the multipath signal reception of the present invention.

Detailed description of the invention

Below in conjunction with Figure of description, the invention is described in further detail.

1, signal model is derived

As it is shown in figure 1, the multipath signal model of single-shot many receipts ofdm communication system: assume to exist relatively between communication node Motion, the signal that node 1 is sent is received by node 2 after multipath channel.On each mobile node, there is single transmission Antenna and N root reception antenna, radio-frequency (RF) receiving and transmission module half-duplex works；N root reception antenna is arranged in uniform line-array, between adjacent antenna Away from for d.

I-th paths signal arrives the shock response h of n-th antenna_inT () is represented by:

$h_{\mathrm{in}}\left(t\right)=a_n\left({\mathrm{\θ}}_i\right)b_i\mathrm{\δ}(t-{\mathrm{\τ}}_i)e^{j{\mathrm{\ψ}}_i}---\left(1\right)$

Wherein, θ_iRepresent the arrival angle corresponding to the i-th paths signal；a_n(θ_i) represent that n-th antenna receives i-th road The steering vector of footpath signal,D is aerial array spacing, and λ is electromagnetic wavelength, b_i、 τ_iAnd ψ_iRepresent the path amplitudes of the i-th paths, path delay and path phase respectively.

The i-th paths signal x that n-th antenna of node receiving terminal receives_inT () is represented by:

$x_{\mathrm{in}}\left(t\right)=s\left(t\right)*h_{\mathrm{in}}\left(t\right)=a_n\left({\mathrm{\θ}}_i\right)b_{i}s(t-{\mathrm{\τ}}_i)e^{j{\mathrm{\ψ}}_i}=a_n\left({\mathrm{\θ}}_i\right)m_i\left(t\right)---\left(2\right)$

Wherein,Represent that the i-th paths signal arrives first reception antenna of receiving antenna array Expression formula；S (t) is the source signal of transmitting terminal.

Vector signal x on n-th antenna of node receiving terminal_nT () is the synthesis of K path signal, be represented by:

x_n(t)=x_1n(t)+x_2n(t)+...+x_Kn(t) (3)=a_n(θ₁)m₁(t)+a_n(θ₂)m₂(t)+...+a_n(θ_K) m_K(t)+n_n(t)

Wherein, n_nT () is the spatial noise on n-th antenna, for independent identically distributed white Gaussian noise.

Whole antenna array receiver signal phasor X (t) of node receiving terminal is represented by:

$\begin{array}{c}X\left(t\right)={[x_1\left(t\right)x_2\left(t\right)...x_N\left(t\right)]}^T=\left[\begin{array}{c}{a}_1\left({\mathrm{\θ}}_1\right)m_1\left(t\right)+a_1\left({\mathrm{\θ}}_2\right)m_2\left(t\right)+...+a_1\left({\mathrm{\θ}}_K\right)m_K\left(t\right)+n_1\left(t\right)\\ a_2\left({\mathrm{\θ}}_1\right)m_1\left(t\right)+a_2\left({\mathrm{\θ}}_2\right)m_2\left(t\right)+...+a_2\left({\mathrm{\θ}}_K\right)m_K\left(t\right)+n_2\left(t\right)\\ ...\\ a_N\left({\mathrm{\θ}}_1\right)m_1\left(t\right)+a_N\left({\mathrm{\θ}}_2\right)m_2\left(t\right)+...+a_N\left({\mathrm{\θ}}_K\right)m_K\left(t\right)+n_N\left(t\right)\end{array}\right]\\ =\begin{array}{c}\left[\begin{array}{c}{a}_1\left({\mathrm{\θ}}_1\right)a_1\left({\mathrm{\θ}}_2\right)...a_1\left({\mathrm{\θ}}_K\right)\\ a_2\left({\mathrm{\θ}}_1\right)a_2\left({\mathrm{\θ}}_2\right)...a_2\left({\mathrm{\θ}}_K\right)\\ ...\\ a_N\left({\mathrm{\θ}}_1\right)a_N\left({\mathrm{\θ}}_2\right)...a_N\left({\mathrm{\θ}}_K\right)\end{array}\right]\left[\begin{array}{c}{m}_1\left(t\right)\\ m_2\left(t\right)\\ ...\\ m_K\left(t\right)\end{array}\right]+\left[\begin{array}{c}{n}_1\left(t\right)\\ n_2\left(t\right)\\ ...\\ n_N\left(t\right)\end{array}\right]=\mathrm{AS}+N\end{array}\end{array}---\left(4\right)$

Wherein, A is expressed as the steering vector of aerial array, is:

$\begin{array}{c}A={\left[\begin{array}{c}{a}_1\left({\mathrm{\θ}}_1\right)a_1\left({\mathrm{\θ}}_2\right)...a_1\left({\mathrm{\θ}}_K\right)\\ a_2\left({\mathrm{\θ}}_1\right)a_2\left({\mathrm{\θ}}_2\right)...a_2\left({\mathrm{\θ}}_K\right)\\ ...\\ a_N\left({\mathrm{\θ}}_1\right)a_N\left({\mathrm{\θ}}_2\right)...a_N\left({\mathrm{\θ}}_K\right)\end{array}\right]}_{N\×K}\\ =\left[\begin{array}{cccc}1& 1& ...& 1\\ \exp \left(j\frac{2\mathrm{\π}d\sin {\mathrm{\θ}}_1}{\mathrm{\λ}}\right)& \exp \left(j\frac{2\mathrm{\π}d\sin {\mathrm{\θ}}_2}{\mathrm{\λ}}\right)& ...& \exp \left(j\frac{2\mathrm{\π}d\sin {\mathrm{\θ}}_K}{\mathrm{\λ}}\right)\\ ...& ...& ...& ...\\ \exp \left(j\frac{2\mathrm{\π}(N-1)d\sin {\mathrm{\θ}}_1}{\mathrm{\λ}}\right)& \mathrm{epx}\left(j\frac{2\mathrm{\π}(N-1)d\sin {\mathrm{\θ}}_2}{\mathrm{\λ}}\right)& ...& \mathrm{epx}\left(j\frac{2\mathrm{\π}(N-1)d\sin {\mathrm{\θ}}_K}{\mathrm{\λ}}\right)\end{array}\right]\end{array}$

S=[m₁(t),m₂(t),...,m_K(t)]^T, for K path signal vector of receiving terminal；

N=[n₁(t),n₂(t),...,n_N(t)]^T, for the spatial noise vector on aerial array.

Assume that antenna array receiver signal phasor X (t) exists correlation matrix R_X, R_XIt is represented by:

R_X=E [X (t) X^H(t)]=AR_SA^H+R_n(5) wherein, R_S=E [SS^H] it is signal autocorrelation matrix, R_n=E [NN^H] it is noise autocorrelation matrix.

2, the reception scheme of multipath signal

The OFDM receiver block diagram of the multipath signal reception scheme that the present invention proposes is as shown in Figure 2.Utilize in multipath signal The characteristic that spatial information that each path signal carries is different, receiving terminal carries out DOA estimation and Wave beam forming to multipath signal, Distinguish each path signal on space angle, separate multipath signal and extract main footpath signal, the most only to main footpath signal Carry out OFDM demodulation, decoding.Process prescription is as follows: be some submatrixs by antenna array partition, calculates each submatrix and receives letter Number correlation matrix, and try to achieve the meansigma methods of multiple submatrix correlation matrix, be the signal correlation matrix R after decoherence_X；Will letter Number correlation matrix R_XCarry out Eigenvalues Decomposition；According to the spatial spectrum of the little eigenvalue characteristic of correspondence vector signal calculated obtained, Arrival angle, the space θ of each path signal corresponding of the spectral peak in spatial spectrum₁,θ₂,...,θ_K；Arrive in the space obtaining path signal Reach angle θ₁,θ₂,...,θ_KOn the basis of, the path signal of each Space Angle is carried out Wave beam forming respectively, respectively obtains each road Footpath signal, separates multipath signal；In the multiple path signals obtained, utilize the sign synchronization of OFDM demodulation, by synchronous point The path signal of minimum (path delay of time is minimum) is chosen out, the strongest main footpath signal y_max(t)；By the strongest main footpath signal y_max T (), as the output signal of Beam-former, carries out OFDM demodulation, including removing Cyclic Prefix (CP), serial to parallel conversion, FFT and inverse Map, be finally decoded.

3, the DOA of multipath signal estimates

OFDM receiver first docking collection of letters number after receiving multipath signal carries out DOA estimation.Owing to multipath signal is phase Dry signal, so the first docking collection of letters number carries out decoherence process, will antenna array partition be that several subarrays go to process Receive signal；Again the reception signal autocorrelation matrix after carrying out decoherence process is carried out Eigenvalues Decomposition, draw the sky of signal Between compose, as shown in Figure 3.

Owing to multipath signal is coherent signal, multipath signal Correlation Moment rank of matrix is returned to number of path by 1, will antenna Array is divided into several subarrays and goes to process.Utilize the translation invariant shape of uniform line-array, N root antenna array partition is become by m The subarray of root antenna composition, submatrix columns is L=N-m+1, and each subarray comprises identical signal space information.Meter Calculate the signal correlation matrix of each subarray, then obtain the average of L sub-array signal correlation matrix, be decoherence and process After an equivalent sub-array signal correlation matrix R_X。

The output signal vector X of each subarray_lT () is respectively as follows:

$\left\{\begin{array}{c}{X}_1\left(t\right)={[x_1\left(t\right),x_2\left(t\right),...,x_m\left(t\right)]}^T\\ X_2\left(t\right)={[x_2\left(t\right),x_3\left(t\right),...,x_{m+1}\left(t\right)]}^T\\ ...\\ X_L\left(t\right)={[x_L\left(t\right),x_{L+1}\left(t\right),...,x_{L+m-1}\left(t\right)]}^T\end{array}\right.---\left(6\right)$

The correlation matrix R of l subarray_lFor:

$R_l=E\left[X_l\left(t\right){X_l}^H\left(t\right)\right]=A_m{R}_X^l{A}_m^H+R_n^l---\left(7\right)$

Wherein, A_mSteering vector for subarray；It it is the signal autocorrelation matrix of l subarray；It it is l The noise autocorrelation matrix of subarray.

Docking collection of letters decorrelation processes, and takes the meansigma methods of the autocorrelation matrix of all subarrays, it may be assumed that

$R_X=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{R}_l=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{A}_m{R}_X^l{A}_m^H+R_n^l=A_m{R}_S{A}_m^H+R_n^l---\left(8\right)$

The docking collection of letters number carries out DOA estimation, the signal autocorrelation matrix R after processing space smoothing_XCarry out feature decomposition,

Can be analyzed to:

$R_X=U_S{\mathrm{\Λ}}_S{U}_S^H+{\mathrm{\σ}}^2{U}_n{U}_n^H---\left(9\right)$

Wherein, Λ_S=diag (λ₁,λ₂,...,λ_K) it is the diagonal matrix being made up of K big eigenvalue；U_S=[u₁,u₂,..., u_K] it is the matrix being made up of big eigenvalue characteristic of correspondence vector；σ²It is m-K the little eigenvalue repeated；

U_n=[u_K+1,u_K+2,...,u_m] it is by little eigenvalue σ²The matrix that characteristic of correspondence vector is constituted.Signal space Spectrum expression formula is defined as:

$P\left(\mathrm{\θ}\right)=\frac{1}{{\left|\mathrm{\α}{\left(\mathrm{\θ}\right)}^H{U}_n\right|}^2}=\frac{1}{\mathrm{\α}{\left(\mathrm{\θ}\right)}^H{U}_n{U}_n^H\mathrm{\α}\left(\mathrm{\θ}\right)}---\left(10\right)$

According to formula (10) signal calculated spatial spectrum, the angle that K spectral peak of spatial spectrum is corresponding is arriving of each path signal Reach angle θ₁,θ₂,...,θ_K。

4, the Wave beam forming of multipath signal

Obtaining each path signal angle information θ₁,θ₂,...,θ_KOn the basis of, first separated by Beam-former Go out K path signal, be y₁(t),y₂(t),...,y_K(t), wherein Represent the i-th paths The best initial weights of Wave beam forming；Then, in the path signal obtained, choose out by the path signal that the path delay of time is minimum, The strongest main footpath signal, its Wave beam forming vector as shown in Figure 4, and as output signal y of Beam-former_max(t)；Finally Main footpath signal is carried out OFDM demodulation, decoding.

Respectively the path signal corresponding to each Space Angle is carried out Wave beam forming, obtain the wave beam of the i-th paths signal Form best initial weightsThis criterion is to keep this expected path angle, θ_iUnder conditions of gain is certain so that this output is believed Number minimum power, can be expressed as:

$\left\{\begin{array}{c}\min P_{\mathrm{out}}=E\left[{\left|y_i\left(t\right)\right|}^2\right]=w^H{R}_{X}w\\ s.t.w^{H}a\left({\mathrm{\θ}}_i\right)=1\end{array}\right.---\left(11\right)$

Wherein, a (θ_i) it is the steering vector of i-th path signal；P_outFor path signal output.

To formula (11) structure Lagrangian:

L (w)=w^HR_Xw+μ[w^Ha(θ_i)-1] (12)

W in above formula is carried out derivation and makesCan obtain:

$w_{\mathrm{opt}}^i=P_{\mathrm{out}\_\min }{R}_X^{-1}a\left({\mathrm{\θ}}_i\right)---\left(13\right)$

Formula (11) is substituted into above formula, the best initial weights of the i-th paths Wave beam forming can be obtainedFor:

$w_{\mathrm{opt}}^i=\frac{R_X^{-1}a\left({\mathrm{\θ}}_i\right)}{a^H\left({\mathrm{\θ}}_i\right)R_X^{-1}a\left({\mathrm{\θ}}_i\right)}---\left(14\right)$

In like manner, the Wave beam forming best initial weights of remaining K-1 path signal can be obtained, multipath signal be separated, obtains K Individual path signal.

In K the path signal obtained, carry out choosing of main footpath signal, due to each path signal the path delay of time not With, so utilizing the sign synchronization module in OFDM demodulation, the path signal of minimum for synchronous point (path delay of time is minimum) is set to Main footpath signal, the strongest main footpath signal.Using the reservation of this path signal the output signal as Beam-former, ignore other K- 1 path signal, the main footpath signal selected can be expressed as:

$y_{\max }\left(t\right)=w_{\max \_\mathrm{opt}}^{H}X\left(t\right)---\left(15\right)$

Wherein, y_maxT () is beamformer output signals (the strongest main footpath signal)；w_{max_opt}For the strongest main footpath signal wave The best initial weights that bundle is formed.

In the present invention, utilizing the characteristic that spatial information that in multipath signal, each path signal carries is different, receiving terminal is first Multipath signal first carries out DOA estimate on space angle, distinguish each path signal, then each path signal is carried out Wave beam forming, and the path signal of path selection time delay minimum is as final output signal, carries out OFDM demodulation, decoding.Therefore The present invention efficiently separates multipath signal and extracts main footpath signal, is inherently eliminated the impact of multipath, improves ofdm communication The transmission performance of system.

Scheme performance evaluation:

The parameter that simulating scenes of the present invention is used is described as follows:

Multipath channel models	M.1225A vehicular channel (six footpath signals)
		Maximum Doppler frequency offset	100Hz
Subcarrier number and FFT, IFFT point number	1024
		Subcarrier spacing	8K
Modulation system	QPSK
		Centre carrier frequency	300MHz
Sample rate	32MHz
		Antenna array columns	16
Space smoothing submatrix columns	8
		Array element distance	0.5 wavelength

Fig. 5 is the bit error rate comparison diagram (not adding Error Correction of Coding) of multipath signal reception.It will be clear that the present invention The bit error rate and theoretical calculation；In the OFDM receiver with single antenna contrasts, it can be seen that the OFDM receptivity of single antenna Along with the increase of signal to noise ratio has a declining tendency, but the amplitude inconspicuous declined after 15dB；And the bit error rate of the present invention Along with the increase of signal to noise ratio significantly decreases, after signal to noise ratio is 10dB, the bit error rate is almost close to 0.

Simulation result shows, the present invention program can efficiently separate multipath signal, extract main footpath signal.From acceptance The many-sides such as energy, practicality and implementation complexity consider, and in the communication environment of mobile multipath, the present invention program's is overall Performance is better than other reception schemes that presently, there are.

The ultimate principle of the present invention and principal character and advantages of the present invention have more than been shown and described.The present invention is not by upper State the principle that the present invention is simply described described in the restriction of embodiment, above-described embodiment and description, without departing from the present invention On the premise of spirit and scope, the present invention also has various changes and modifications, and these changes and improvements both fall within claimed In the scope of the invention, claimed scope is defined by its equivalent of appending claims.

Claims (8)

1. an allied DOA estimation based on multiple antennas and the multipath signal reception method of Wave beam forming, it is characterised in that described Method includes: utilize the characteristic that spatial information that in multipath signal, each path signal carries is different, receiving terminal docking to collect mail number Carry out DOA estimation；Due to the coherence of multipath signal, so being some submatrixs by antenna array partition, calculate each submatrix The correlation matrix of reception signal, and try to achieve the meansigma methods of multiple submatrix correlation matrix, it is the signal correlation matrix after decoherence R_X；By signal correlation matrix R_XCarry out Eigenvalues Decomposition, according to the sky of the little eigenvalue characteristic of correspondence vector signal calculated obtained Between compose, arrival angle, the space θ of spectral peak in spatial spectrum each path signal corresponding₁,θ₂,...,θ_K；Obtaining the sky of path signal Between arrive angle θ₁,θ₂,...,θ_KOn the basis of, the path signal of each Space Angle is carried out Wave beam forming respectively, respectively obtains each Individual path signal, separates multipath signal；In the multiple path signals obtained, utilize the sign synchronization module of OFDM demodulation, Choose out by the path signal that synchronous point is minimum, the strongest main footpath signal y_max(t)；By the strongest main footpath signal y_max(t) conduct The output signal of Beam-former；To output signal y_maxT () carries out OFDM demodulation, including go cyclic prefix CP, serial to parallel conversion, FFT and inverse mapping, be finally decoded；

Described method is obtaining each path signal angle information θ₁,θ₂,...,θ_KOn the basis of, by Beam-former first Isolate K path signal, be y₁(t),y₂(t),...,y_K(t), wherein Represent i-th The best initial weights that path beam is formed；Then, in the path signal obtained, the path signal that the path delay of time is minimum is selected Come, the strongest main footpath signal, and as output signal y of Beam-former_max(t)；Finally main footpath signal is carried out OFDM solution Adjust, decode；

Described method carries out Wave beam forming to the path signal corresponding to each Space Angle respectively, obtains the i-th paths signal Wave beam forming best initial weightsThis criterion is to keep this expected path angle, θ_iUnder conditions of gain is certain so that this output Signal power minimizes, and is expressed as:

$\left\{\begin{array}{cc}\min & P_{out}=E\[|y_i\left(t\right){|}^2\]=w^H{R}_{X}w\\ s.t.& w^{H}a\left({\mathrm{\θ}}_i\right)=1\end{array}\right.---\left(11\right)$

Wherein, a (θ_i) it is the steering vector of i-th path signal；P_outFor path signal output；

To formula (11) structure Lagrangian:

L (w)=w^HR_Xw+μ[w^Ha(θ_i)-1] (12)

W in above formula is carried out derivation and makesObtain:

$w_{opt}^i=P_{out\_min}{R}_X^{-1}a\left({\mathrm{\θ}}_i\right)---\left(13\right)$

Formula (11) is substituted into above formula, obtains the best initial weights of the i-th paths Wave beam formingFor:

$w_{opt}^i=\frac{R_X^{-1}a\left({\mathrm{\θ}}_i\right)}{a^H\left({\mathrm{\θ}}_i\right)R_X^{-1}a\left({\mathrm{\θ}}_i\right)}---\left(14\right)$

In like manner, obtain the Wave beam forming best initial weights of remaining K-1 path signal, multipath signal is separated, obtain K path letter Number；

Choosing of main footpath signal is carried out in K the path signal obtained, owing to the path delay of time of each path signal is different, institute To utilize the sign synchronization module in OFDM demodulation, synchronous point is minimum, the path signal that i.e. path delay of time is minimum is set to main footpath Signal, the strongest main footpath signal；Using the reservation of this path signal the output signal as Beam-former, ignore other K-1 Path signal, the main footpath signal selected is expressed as:

$y_{max}\left(t\right)=w_{\max \_opt}^{H}X\left(t\right)---\left(15\right)$

Wherein, y_maxT () is beamformer output signals, the strongest main footpath signal；w_{max_opt}For the strongest main footpath signal beam shape The best initial weights become；

Described method utilizes the characteristic that spatial information that in multipath signal, each path signal carries is different, and receiving terminal is first to many Footpath signal carries out DOA and estimates to distinguish each path signal on space angle, then each path signal is carried out wave beam shape Become, and the path signal of path selection time delay minimum is as final output signal, carries out OFDM demodulation, decoding.

A kind of allied DOA estimation based on multiple antennas the most according to claim 1 and the multipath signal reception of Wave beam forming Method, it is characterised in that: the spatial information entrained by each path signal in described multipath signal is different, is path letter Number arrival angle, space, utilize this characteristic to go to separate each path signal in multipath signal, at receiving terminal, docking is collected mail number Carry out DOA estimation, obtain the spatial spectrum of signal and arrival angle, the space θ of each path signal₁,θ₂,...,θ_K。

A kind of allied DOA estimation based on multiple antennas the most according to claim 2 and the multipath signal reception of Wave beam forming Method, it is characterised in that: due to the coherence of described multipath signal, so decoherence will be carried out in the receiving terminal docking collection of letters number Process, will antenna array partition be some submatrixs, calculate each submatrix and receive the correlation matrix of signal, and try to achieve many height The meansigma methods of battle array correlation matrix, obtains the signal correlation matrix R after decoherence_X, its derivation includes:

Assuming N root antenna array partition is become the subarray being made up of m root antenna, submatrix columns is L=N-m+1, every height The output signal vector X of array_lT () is respectively as follows:

$\left\{\begin{array}{c}{X}_1\left(t\right)={\[x_1\left(t\right),x_2\left(t\right),...,x_m\left(t\right)\]}^T\\ X_2\left(t\right)={\[x_2\left(t\right),x_3\left(t\right),...,x_{m+1}\left(t\right)\]}^T\\ ...\\ X_L\left(t\right)={\[x_L\left(t\right),x_{L+1}\left(t\right),...,x_{L+m-1}\left(t\right)\]}^T\end{array}\right.$

The correlation matrix R of l subarray_lFor:

Take the meansigma methods of the autocorrelation matrix of all subarrays, it may be assumed that

$R_X=\frac{1}{L}\underset{l=1}{\overset{L}{\Σ}}{R}_l=\frac{1}{L}\underset{l=1}{\overset{L}{\Σ}}{A}_m{R}_X^l{A}_m^H+R_n^l=A_m{R}_S{A}_m^H+R_n^l.$

4. connect according to the multipath signal of a kind of based on multiple antennas the allied DOA estimation described in Claims 2 or 3 and Wave beam forming Receiving method, it is characterised in that: described method is to carrying out the signal autocorrelation matrix R after decoherence process_XCarry out feature decomposition, Respectively obtain big eigenvalue and little eigenvalue, calculate characteristic vector U corresponding to little eigenvalue_n=[u_K+1,u_K+2,..., u_m], compose definition according to signal spaceObtain the spatial spectrum of signal, In the spatial spectrum of signal, search Space Angle θ corresponding to spectral peak₁,θ₂,...,θ_K。

A kind of allied DOA estimation based on multiple antennas the most according to claim 4 and the multipath signal reception of Wave beam forming Method, it is characterised in that: described method is obtaining arrival angle, the space θ of path signal₁,θ₂,...,θ_KOn the basis of, to each The path signal of Space Angle carries out Wave beam forming respectively, i.e. Represent the i-th paths Wave beam forming Best initial weights, respectively obtain each path signal y₁(t),y₂(t),...,y_KT (), has separated multipath signal.

A kind of allied DOA estimation based on multiple antennas the most according to claim 5 and the multipath signal reception of Wave beam forming Method, it is characterised in that: described method, when each path signal is carried out Wave beam forming, draws each road by following criterion The best initial weights of footpath signal, i.e. keeps this expected path angle, θ_iUnder conditions of gain is certain so that this output signal power is Littleization, its derivation is as follows:

The majorized function set up is expressed as:

$\left\{\begin{array}{cc}\min & P_{out}=E\[|y_i\left(t\right){|}^2\]=w^H{R}_{X}w\\ s.t.& w^{H}a\left({\mathrm{\θ}}_i\right)=1\end{array}\right.$

Majorized function is constructed Lagrangian: L (w)=w^HR_Xw+μ[w^Ha(θ_i)-1]；

W is carried out derivation and makesCan obtain

The best initial weights of the i-th paths Wave beam forming can be obtainedFor:

A kind of allied DOA estimation based on multiple antennas the most according to claim 6 and the multipath signal reception of Wave beam forming Method, it is characterised in that: described method carries out choosing of main footpath signal in K the path signal obtained, due to each path Path delay of time of signal is different, so utilizing the sign synchronization module in OFDM demodulation, (path delay of time is by minimum for synchronous point Little) path signal be set to main footpath signalThe strongest main footpath signal, w_{max_opt}For the strongest main footpath The best initial weights that signal beam is formed, using the reservation of this path signal the output signal as Beam-former.

A kind of allied DOA estimation based on multiple antennas the most according to claim 1 and the multipath signal reception of Wave beam forming Method, it is characterised in that: the synchronous point in described method is minimum for the minimum path delay of time.