Summary of the invention
For the deficiency of existing method, the invention proposes a kind of based on the extensive of uplink traffic channel information auxiliary
The Downlink channel estimation method of MIMO communication system.
Include the following steps: for realizing technical solution of the invention
Step 1: base station uses the uniform linear array with N root antenna, and mobile subscriber uses single antenna.It is mobile
User's pilot signal transmitted after base station receives signal, goes out uplink channel using classical Least Square Method, is denoted as
Step 2: base station pilot signal transmitted matrix X within T moment, the then signal that mobile subscriber receives are y=Φ
(β)w+n。
Step 3: setting the number of iterations counting variable l=1 initializes the precision vector of wIn each element be
1, initializationPrecision vectorIn each element be 1, initialize noise precisionβ is initialized simultaneously
For full neutral element.
Step 4: α is updated,γ and τ.
Step 5: updating β.
Step 6: judge whether iteration count variable l reaches whether the upper limit L or γ restrain, if be all unsatisfactory for, iteration
Counting variable l=l+1, and return step 4.
Step 7: setting thresholding η, and utilize the effective angle set omega of thresholding selection downlink channel.
Step 8: utilizing effective angle set omega, estimate final downlink channel.
Beneficial effects of the present invention:
Uplink traffic channel information is fused in Downlink channel estimation by the present invention, using uplink channel under
The joint sparse characteristic of Downlink channels, so that the available observation sample quantity of corresponding rarefaction representation optimization problem improves
One times.Compared with the conventional method, the present invention can significantly improve the performance of channel estimation
Specific embodiment
The present invention will be further explained below with reference to the attached drawings and specific examples.
As shown in Figure 1, the method for the present invention includes following steps:
(1) base station uses the uniform linear array with N root antenna, and mobile subscriber uses single antenna.It is mobile to use
Family pilot signal transmitted after base station receives signal, goes out uplink channel using classical Least Square Method, is denoted asAnd it is expressed as the form of sparse signal recovery:Wherein:
The referred to as calculation matrix of uplink,
Expression is evenly dividingN number of mesh point, i.e.,
dn, n=1,2 ..., N, the spacing of expression the n-th array element and the 1st array element,Indicate uplink electrical magnetic wave
Wavelength,
In element βiIndicate θiOn angular deviation,
It is channel in calculation matrixOn rarefaction representation vector,
E is that the mean value of a N-dimensional is 0, and precision isWhite Gaussian noise vector.
(2) base station pilot signal transmitted matrix X within T moment, the then signal that mobile subscriber receives are y=Φ (β)
W+n, wherein
Φ (β)=XA (β) is known as the calculation matrix of downlink,
A (β)=[a (θ1+β1),a(θ2+β2),...,a(θN+βN)],
λ indicates the wavelength of downlink electromagnetic wave,
W is rarefaction representation vector of the channel on calculation matrix Φ (β),
N is that the mean value of T dimension is 0, and precision is the white Gaussian noise vector of α.
(3) the number of iterations counting variable l=1 is set, the precision vector of w is initializedIn each element be 1, just
BeginningizationPrecision vectorIn each element be 1, initialize noise precisionIt is complete for initializing β simultaneously
Neutral element.
(4) α is updated,γ and τ, it may be assumed that
Wherein:
The mark of tr () representing matrix, | | | |22 norms of representing matrix, []iiI-th of representing matrix is diagonal
Line element, ()HExpression conjugate transposition, a=b=0.0001,
μ (α, γ, β)=α Σ (α, γ, β) ΦH(β) y, Σ (alpha, gamma, β)=(α ΦH(β)Φ(β)+diag(γ))-1
⊙ indicates Hadamard product,
Diag () indicates diagonal operation matrix, Ξ (alpha, gamma, β)=μ (alpha, gamma, β) μH(alpha, gamma, β)+Σ (alpha, gamma, β),
(5) β is updated, it may be assumed that
Wherein
Sign () expression takes sign operation,
Re () expression takes real part operation,
ci1=-α (χii+|μi|2),
μiIndicate i-th of element of μ (alpha, gamma, β), χjiIt indicates Σ (α, γ, β)
(j, i) a element,
(·)*Indicate conjugate operation, a'(θi+βi) indicate a (θi+βi) about βiDerivative,
It indicatesI-th of element,It indicates(j, i) a element,It indicatesAbout βiDerivative.
(6) judge whether iteration count variable l reaches upper limit L (such as L=100) or whether γ restrains (i.e. when secondary update
As a result whether equal result was updated with last time), if be all unsatisfactory for, iteration count variable l=l+1, and return to (4).
(7) thresholding is setWhereinIndicate the maximum element of i-th of value in μ (alpha, gamma, β), and
Using the thresholding choose downlink channel effective angle set omega=i | (μi)2>=η, i=1,2 ..., N }.
(8) effective angle set omega is utilized, estimates final downlink channel:Wherein
(·)ΩIndicate by the corresponding Column vector groups of set omega in matrix at submatrix,The generalized inverse of representing matrix.
Effect of the invention is described further below with reference to emulation experiment.
In order to assess the performance of this method, it is assumed that base station uses the homogenous linear battle array with N=150 root antenna
Column, the working frequency of downlink are 1980MHz, and the working frequency of downlink is 2170MHz, and wireless channel is by 3GPP
Spatial channel model (SCM) model is randomly generated, and each element of base station pilot signal transmitted matrix X obeys zero
The independent Gaussian of mean value unit variance is distributed, and ambient noise is assumed to be white Gaussian noise.
Experiment condition
Use the present invention in signal-to-noise ratio for 0dB, pilot tone moment T is estimated by carrying out 200 times to channel when 30 to 100 variation,
Simulation result is as shown in Figure 2.
Experimental analysis
Figure it is seen that the present invention can accurately estimate out the downlink channel of extensive MIMO communication system,
NMSE performance is substantially better than conventional method.
The series of detailed descriptions listed above only for feasible embodiment of the invention specifically
Protection scope bright, that they are not intended to limit the invention, it is all without departing from equivalent implementations made by technical spirit of the present invention
Or change should all be included in the protection scope of the present invention.