Disclosure of Invention
The invention aims to provide a distributed self-adaptive rank-reduction beam forming method, and aims to solve the problems that the complexity of a distributed array anti-interference self-adaptive algorithm is increased and the convergence speed is reduced when the number of array elements is large. The invention effectively combines the distributed adaptive strategy, the rank reduction technology and the beam forming method, and still adopts the thought of ATC, so that the nodes can effectively communicate with other nodes in the adaptive and combining processes, and the thought of rank reduction combined iterative optimization can be utilized to reduce the complexity of the algorithm and avoid unnecessary calculation cost under the condition of more array elements.
In order to achieve the purpose, the invention adopts the technical scheme that:
a distributed adaptive rank reduction beam forming method comprises the following steps:
step 1, obtaining array receiving signals of node k
Setting a desired far-field complex narrowband signal
Incident on the uniform linear array network and simultaneously subjected to P-1 complex narrow-band signals
Then the discrete complex baseband received signal vector of the kth node array is represented as:
wherein i represents the ith time, s
p(i) Is a narrow band signal
Discrete baseband form of (a); n is
k(i) Is a zero mean additive white gaussian noise vector; a (theta)
p) As a guide vector, a (θ)
1) As a guide vector of the desired signal, theta
pAngle of arrival for the p-th incident signal;
step 2, initializing the reduced rank weight vector, the reduced rank matrix and the related parameters
Initializing rank-reduced weight vector initial values for all node arrays
With initial values of the reduced rank matrix S
k(0) The condition constraint is satisfied:
and obtaining a switching matrix C and a combining matrix F, G according to the calculation rule:
wherein, c
l,kFor the (l, k) th element, f, of the switching matrix C
l,kFor the (l, k) -th element, g, of the combined matrix F
l,kIs the (l, k) th element of the combining matrix G;
a set of neighborhood nodes, r, representing the kth node array including itself
kIs composed of
The total number of nodes contained;
step 3, diffusing the received signals of each node array, and enabling the received signals of the node arrays to pass through a reduced rank beam former;
1) for array received signal x
l(i) And a desired signal steering vector a (theta)
1) Performing rank reduction processing to obtain the array receiving signal after rank reduction
Sum rank reduced desired signal steering vector
Wherein S isk(i-1) is a reduced rank matrix of the kth node array at the ith-1 moment;
2) obtained after rank reduction treatment
Obtaining an array output signal through a reduced rank filter:
wherein,
a rank reduction weight vector of the kth node array at the ith-1 moment;
and 4, diffusing the output signals of the node arrays and the array receiving signals after the rank reduction, and iteratively updating the rank reduction matrix Q of the kth node array
k(i) Intermediate estimation of sum rank reduced weight vector
Wherein,
and
are projection matrices;
and
respectively carrying out iteration step length of intermediate estimation of the reduced rank matrix and the reduced rank weight vector;
and 5, diffusing the intermediate estimation of the reduced rank weight vector of each node array, and randomly arranging the intermediate estimation of the reduced rank weight vector of the adjacent node including the node array of the kth node array to obtain:
and calculating a combination matrix of the reduced rank matrix estimation of the kth node array:
and 6, diffusing the combined matrix of the reduced rank matrix and the reduced rank matrix estimation of each node array, and updating to obtain the estimation of the reduced rank matrix of the kth node array:
and 7, calculating a combination matrix of the reduced rank weight vector estimation of the kth node array:
therein, unwecm,n{. is a matrixing function;
and 8, calculating the reduced rank weight vector estimation of the kth node array:
obtaining the optimal weight of the kth node array, and calculating a beam function:
wherein, wkFull rank weight vector for kth node array, Ek(θ) is the beam function, θ ∈ (-90 °,90 °).
A distributed adaptive rank reduction beam forming method comprises the following steps:
step 1, obtaining array receiving signals of node k
Setting a desired far-field complex narrowband signal
Incident on the uniform linear array network and simultaneously subjected to P-1 complex narrow-band signals
Then the discrete complex baseband received signal vector of the kth node array is represented as:
wherein i represents the ith time, s
p(i) Is a narrow band signal
Discrete baseband form of (a); n is
k(i) Is a zero mean additive white gaussian noise vector; a (theta)
p) As a guide vector, a (θ)
1) As a guide vector of the desired signal, theta
pAngle of arrival for the p-th incident signal;
step 2, initializing the reduced rank weight vector, the reduced rank matrix and the related parameters
Initializing rank-reduced weight vector initial values for all node arrays
With initial values of the reduced rank matrix S
k(0) The condition constraint is satisfied:
and obtaining a switching matrix C and a combining matrix F, G according to the calculation rule:
wherein, c
l,kFor the (l, k) th element, f, of the switching matrix C
l,kFor the (l, k) -th element, g, of the combined matrix F
l,kIs the (l, k) th element of the combining matrix G;
a set of neighborhood nodes, r, representing the kth node array including itself
kIs composed of
The total number of nodes contained;
step 3, diffusing the received signals of each node array, and enabling the received signals of the node arrays to pass through a reduced rank beam former;
1) for array received signal x
l(i) And a desired signal steering vector a (theta)
1) Performing rank reduction processing to obtain the array receiving signal after rank reduction
Sum rank reduced desired signal steering vector
Wherein S isk(i-1) is a reduced rank matrix of the kth node array at the ith-1 moment;
2) obtained after rank reduction treatment
Obtaining an array output signal through a reduced rank filter:
wherein,
a rank reduction weight vector of the kth node array at the ith-1 moment;
and 4, diffusing the output signals of the node arrays and the array receiving signals after the rank reduction, and iteratively updating the rank reduction matrix Q of the kth node array
k(i) Intermediate estimation of sum rank reduced weight vector
Wherein,
and
are projection matrices;
and
respectively carrying out iteration step length of intermediate estimation of the reduced rank matrix and the reduced rank weight vector;
step 5, diffusing the reduced rank matrix Q of each node arrayk(i) And randomly arranging the intermediate estimation of the reduced rank matrix of the adjacent nodes of the kth node array including the kth node array to obtain:
Σk(i)=[Ql(i),l∈Nk]T
and calculating a combination matrix of the reduced rank weight vector estimation of the kth node array:
and 6, diffusing the combined matrix of the intermediate estimation and the reduced rank weight vector estimation of each node array, and updating to obtain the reduced rank weight vector estimation of the kth node array:
and 7, calculating a combination matrix of the reduced rank matrix estimation of the kth node array:
therein, unwecm,n{. is a matrixing function;
and 8, calculating the reduced rank matrix estimation of the kth node array:
Sk(i)=Σk(i)Λk(i)
obtaining the optimal weight of the kth node array, and calculating a beam function:
wherein, wkFull rank weight vector for kth node array, Ek(θ) is the beam function, θ ∈ (-90 °,90 °).
The invention has the beneficial effects that:
the invention provides a distributed self-adaptive reduced rank beam forming method, which has the following advantages:
1) the invention combines the distributed adaptive strategy, the adaptive rank reduction technology and the beam forming method, and provides a basic framework of the distributed adaptive rank reduction beam former; in the framework, the rank reduction technology and the beam forming algorithm can be replaced or adjusted according to the requirements of users; has better flexibility.
2) Compared with a centralized algorithm, the distributed adaptive rank-reduction beamforming method can effectively utilize the difference of received signals caused by different geographic positions and mutual cooperation and information exchange among nodes, and avoids the situation that the anti-interference capability is weakened or even fails caused by the occurrence of problems in a fusion center.
3) The invention provides a self-adaptive distributed reduced rank beam forming method, wherein the reduced rank technology, the combination of node information and the beam forming are self-adaptive; when the arrival angle of the desired signal or the interference signal changes, the method provided by the invention can also adjust in a self-adaptive manner, and effectively suppresses the interference signal while ensuring the undistorted output of the desired signal.
4) The self-adaptive rank reduction method provided by the invention allows a user to set a proper rank reduction dimension according to requirements so as to obtain a better interference suppression effect; the information sharing method based on the adaptive combined matrix can utilize the differentiated information of the neighbor nodes, and is beneficial to improving the estimation performance of the reduced rank matrix and the reduced rank weight vector; after the distributed reduced rank matrix calculation is completed, the reduced rank beam forming method can obtain the interference suppression effect equivalent to that of the full rank beam forming method under the conditions of low calculation complexity and smaller communication bandwidth; has good practicability.
5) Compared with the existing distributed adaptive algorithm utilizing the adaptive combination coefficient, the invention provides the distributed adaptive algorithm based on the adaptive combination matrix; the method is not only related to the network topology, but also related to the reduced rank weight vector or the reduced rank matrix; by effectively utilizing the information of the neighbor nodes, the self-adaptive capacity and robustness of the distributed beam forming method can be further enhanced.
example 1
The embodiment provides a distributed rank-reduction beamforming method, as shown in fig. 3, on an arbitrary node k, the specific process is as follows:
step 1, obtaining array receiving signals of node k
Considering a network comprising N nodes, each node comprising an identical antenna array, wherein the number of array elements is M; the antenna array here may be any array, and for simplicity, the present embodiment is described by using a uniform linear array, as shown in fig. 1;
setting a desired far-field complex narrow-band signal
Incident on the uniform linear array network and simultaneously subjected to P-1 complex narrow-band signals
Then the discrete complex baseband received signal vector of the kth node array is represented as:
wherein i represents the ith time, s
p(i) Is a narrow band signal
Discrete baseband form of (a); n is
k(i) Is a variance of
Zero mean additive white Gaussian noise vector of (1) with n at different nodes or different times
l(i
1) Receiving signals x independently of each other and of the array
k(i) (ii) a The guide vector is
In particular, a (θ)
1) As a guide vector of the desired signal, theta
pThe arrival angle of the p-th incident signal is expressed as follows:
wherein phi isp=2πdsinθpλ, d denotes the spacing between adjacent array elements, λ is the carrier wavelength ·TRepresenting a transpose;
step 2, initializing the reduced rank weight vector, the reduced rank matrix and the related parameters
For an array of all
nodes k 1,2
And initial values of the reduced rank matrix S
k(0) And for the subsequent iteration update, the initial value of the reduced rank weight vector and the initial value of the reduced rank matrix need to satisfy the following condition constraint:
wherein the reduced rank matrix S
kThe dimension of the signal is M multiplied by D, the dimension of the reduced rank weight vector is D multiplied by 1, D represents the dimension after the reduced rank processing, and the physical meaning of the condition constraint is to enable the undistorted output of the expected signal; in addition, an array of all nodesAll of which are the same, and a switching matrix C and a combining matrix F, G need to be obtained according to the corresponding calculation rules,
a set of neighborhood nodes, r, including itself, representing node k
kThe specific calculation rule of the total number of nodes contained in the neighborhood node set representing the kth node is as follows:
step 3, the node receiving signal passes through the rank-reducing beam former
When the array element number or the sampling data of the array is many, the convergence speed of the self-adaptive method is greatly reduced, so that the rank reduction theory is introduced into the method, the complexity of the method can be effectively reduced through the rank reduction treatment, and the convergence speed of the method is improved; fig. 2 shows a schematic flow chart of spreading array receiving signals and performing rank reduction processing on node received signals, which includes the following specific steps:
1) for array received signal x
l(i) And a desired signal steering vector a (theta)
1) Performing rank reduction processing to obtain the array receiving signal after rank reduction
Sum rank reduced desired signal steering vector
The rank reduction is performed by multiplying by a rank reduction matrix S
kConjugate transpose (. cndot.) of (i-1)
H) The implementation is as follows:
2) obtained after rank reduction treatment
Obtaining an array output signal through a reduced rank filter:
and 4, diffusing the output signals of each node array and the array receiving signals after the rank reduction, and iteratively updating the rank reduction matrix Q of the node array k
k(i) Intermediate estimation of sum rank reduced weight vector
Wherein,
and
are all projection matrices;
and
respectively controlling the speed and the steady state of iterative convergence by using the intermediate estimated iterative step length of the reduced rank matrix and the reduced rank weight vector; coefficient c
l,kIs the (l, k) th element of the switching matrix C, which satisfies the constraint:
c
n,k=0,1
TC=1
Tc1 is 1, i.e. the sum of the column elements of the switching matrix C is 1, the sum of the row elements is also 1Is 1; i is
MAn identity matrix representing dimensions M x M; i is
DAn identity matrix representing dimensions D × D; x is the number of
l(i) Receiving signals for the array of the node l at the moment i;
and 5, diffusing the intermediate estimation of the rank-reduced weight vector of each node, and randomly arranging the intermediate estimation of the rank-reduced weight vector of the neighborhood nodes including the node k to obtain:
and calculating a combination matrix of the reduced rank matrix estimates for node k:
wherein the coefficient f
l,kIs the (l, k) th element of the combined matrix F, and the combined matrix F satisfies the constraint:
f
l,k=0,1
TF=1
Tthe sum of column elements of the combination matrix F is 1;
and 6, diffusing the combined matrix of the reduced rank matrix and the reduced rank matrix estimation of each node array, and updating to obtain the estimation of the reduced rank matrix of the node k array:
and 7, calculating a combination matrix of the reduced rank weight vector estimation of the node k:
wherein z is
k(i) Is a combination matrix T
k(i) The vectorized expression of (a) is,
representing the Kronecker product, a matrixing function unwec
m,n{. is an operator that converts a column vector of mn elements into an m × n matrix;
and 8, calculating the rank reduction weight vector estimation of the node k:
obtaining the optimal weight of the node array k, and calculating a beam function:
wherein, wkTo complete a sufficiently sufficient number of iterations of the full rank weight vector, E, of node kk(θ) is the beam function, θ ∈ (-90 °,90 °).
Example 2
The embodiment provides a distributed rank-reduction beamforming method, as shown in fig. 4, on an arbitrary node k, the specific process is as follows: the first 4 steps of this embodiment are the same as those of embodiment 1, and therefore are not described again, and will be started from step 5:
step 5, diffusing the reduced rank matrix Q of each node arrayk(i) Randomly arranging the reduced rank matrix of the neighborhood nodes including the node k to obtain:
Σk(i)=[Ql(i),l∈Nk]T
and calculating a combination matrix of the reduced rank weight vector estimates of the node k:
wherein the coefficient gl,kIs a combined matrix GThe (l, k) th element, and the combination matrix G satisfies the following constraint:
and 6, diffusing the combined matrix of the intermediate estimation of the reduced rank weight vector and the reduced rank weight vector estimation of each node array, and updating to obtain the reduced rank weight vector estimation of the node k:
and 7, calculating a combined matrix of the reduced rank matrix estimation of the node array k:
wherein v is
k(i) Is a combined matrix Λ
k(i) The vectorized expression of (a) is,
representing the Kronecker product, a matrixing function unwec
m,n{. is an operator that converts a column vector of mn elements into an m × n matrix;
and 8, calculating the reduced rank matrix estimation of the node array k:
Sk(i)=Σk(i)Λk(i)
obtaining the optimal weight of the node array k, and calculating a beam function:
wherein, wkTo complete a sufficiently sufficient number of iterations of the full rank weight vector, E, of node kk(θ) is the beam function, θ ∈ (-90 °,90 °).
The feasibility and superiority of the invention will be described by comparing the anti-interference effects of the algorithm DRACM-1 proposed in embodiment 1 and the algorithm proposed in embodiment 2 with the anti-interference effects of the D RACM-2 and the Beam coding algorithm through simulation experiments:
simulation experiment
Simulation 1: a network topology structure with 10 nodes interconnected, as shown in fig. 5, each node is a uniform linear array with an array element number M of 40, the spacing between adjacent array elements is half-wavelength, considering a desired single-tone signal, the arrival angle is 20 degrees, the power is 0dB, the frequency is 1kHz, three single-tone interference signals, the arrival angles are-60 degrees, 0 degrees, 60 degrees, the powers are all 10dB, the frequencies are 1.5kHz, 2kHz, 0.5kHz, the sampling rate is 8kHz, the iteration step sizes of the reduced-rank matrix and the reduced-rank weight vector in the algorithms of dramm-1 and dramm-2 are μ
sk=0.0002,k=1,2,..,N,μ
wk0.0003,
k 1,2, N, and the initial values of the reduced rank matrix and the reduced rank weight vector are I, respectively
M,D,
Iteration step size of BeamCoordination algorithm is mu
k0.0001,
k 1,2, N, the initial value of the weight vector is
The number of rapid beats was 50000, and the experimental results are shown in fig. 6, 7 and 8 after 100 independent repeated experiments.
As shown in fig. 6, the DRACM-1 and DRACM-2 algorithms proposed by the present invention can effectively suppress interference and enable undistorted output of a desired signal; as shown in fig. 7, compared with the Beam coding algorithm without information exchange, the dramm-1 and dramm-2 algorithms can improve the output signal to interference plus noise ratio, and compared with the distributed Beam coding algorithm, the dramm-1 and dramm-2 algorithms perform rank reduction, but the output signal to interference plus noise ratio thereof is basically consistent with the output signal to interference plus noise ratio of the Beam coding algorithm, that is, the rank reduction does not greatly reduce the performance of the algorithm, which can also be verified from the MSE learning curve shown in fig. 8.
While the invention has been described with reference to specific embodiments, any feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except mutually exclusive features and/or steps.