Disclosure of Invention
The technical problem to be solved by the invention is to provide a three-dimensional wireless sensor network non-cooperative positioning method based on RSS and AOA, which utilizes mixed measurement values to improve positioning accuracy, has high positioning accuracy and is less influenced by noise power of the mixed measurement values.
The technical scheme adopted by the invention for solving the technical problems is as follows: a three-dimensional wireless sensor network non-cooperative positioning method based on RSS and AOA is characterized by comprising the following steps:
the method comprises the following steps: establishing a space rectangular coordinate system as a reference coordinate system in a three-dimensional wireless sensing network environment, setting N anchor nodes and a target source in the three-dimensional wireless sensing network environment, and recording the coordinate position of the ith anchor node in the reference coordinate system as siThe coordinate position of the target source in the reference coordinate system is recorded as x, si=(si1,si2,si3),x=(x1,x2,x3) (ii) a Wherein N is a positive integer, N represents the total number of anchor nodes in the three-dimensional wireless sensor network environment, N is more than or equal to 4, i is a positive integer, i is more than or equal to 1 and less than or equal to N, si1、si2、si3Corresponding representation si1 st, 2 nd, 3 rd coordinate component, x1、x2、x3Correspondingly representing the 1 st coordinate component, the 2 nd coordinate component and the 3 rd coordinate component of x;
step two: transmitting a measuring signal by a target source in a three-dimensional wireless sensing network environment, and obtaining an RSS measuring value and an AOA measuring value after each anchor node receives the measuring signal transmitted by the target source; then, a measurement model of the RSS measurement value obtained by each anchor node is established, and the measurement model of the RSS measurement value obtained by the ith anchor node is described as follows:
and establishing respective measurement models of an azimuth angle measurement value and an elevation angle measurement value in the AOA measurement values obtained by each anchor node, and describing the measurement model of the azimuth angle measurement value in the AOA measurement values obtained by the ith anchor node as follows:
a measurement model of elevation measurements among AOA measurements obtained by the ith anchor node is described as:
wherein L is
iRepresents the RSS measurement obtained by the ith anchor node, i.e. the path loss, L, existing on the transmission path experienced by the measurement signal transmitted from the target source to the ith anchor node
0Representing the path loss existing on a transmission path from the transmission of a measurement signal from a target source to the reception of a reference point, gamma representing the path loss coefficient of the transmission distance from the transmission of the measurement signal from the target source to the reception of each anchor node, the value range of gamma being 2.2-2.8, the symbol "| | |" being the symbol of Euclidean norm, d
0Representing the distance of a reference point to a target source in a reference coordinate system, n
iRepresents L
iOf the measurement noise, n
iObeying a Gaussian distribution
Represents n
iPower of phi
iRepresenting azimuthal measurements, m, in AOA measurements obtained by the ith anchor node
iIs indicative of phi
iMeasurement noise present in, m
iObeying a Gaussian distribution
Represents m
iPower of alpha
iRepresenting elevation measurements, v, of AOA measurements obtained at the ith anchor node
iDenotes alpha
iOf the measurement noise, v
iObeying a Gaussian distribution
Denotes v
iThe power of (d);
step three: in that
m
i<<1、v
iWhen < 1, i.e. under the condition of high signal-to-noise ratio, for
Making approximate transformation to obtain n
iThe approximate expression of (c), described as:
and to
Making approximate transformation to obtain m
iThe weighted approximate expression is described as:
to pair
Making approximate transformation to obtain v
iThe approximate expression of (c), described as:
wherein the content of the first and second substances,
represents m
iWeighted value, c
i=[-sin(φ
i),cos(φ
i),0]
TThe term "[ 2 ]]"is a vector representing a symbol, k ═ 0,0,1]
TThe symbol "T" is transposed symbol, β, μ, λ
i、c
iK is an introduced intermediate variable;
step four: according to
And
and combining the least square criterion to obtain a non-convex positioning problem for solving x, which is described as:
wherein, min () is a minimum function;
step five: introducing auxiliary variables f, h, r and z and relaxation variables e, g and t into the description of solving the non-convex positioning problem of x to obtain an equivalent problem of solving the non-convex positioning problem of x, wherein the description is as follows:
wherein e is
iDenotes the i-th component in e, g
iDenotes the ith component in g, "s.t." means "constrained to … …", h
iDenotes the ith component in h, h
i=||x-s
i||
2,I
3Represents a 3-dimensional identity matrix, r
iDenotes the i-th component in r, r
i=||x-s
i||,f
iThe i-th component in f is represented,
step six: using a second order cone relaxation method, r in the description of the equivalence problem of the non-convex localization problem of x will be solved
i=||x-s
iRelaxation of | to r
i≥||x-s
iL; and a semi-positive definite relaxation method is adopted to relax the z-xTx in the description of solving the equivalence problem of the non-convex positioning problem of the x into a form of linear matrix inequality
Then according to r
i≥||x-s
iI and
and obtaining a mixed semi-positive definite/second order cone programming problem for solving x, wherein the description is as follows:
wherein the content of the first and second substances,
to represent
Is a semi-positive definite matrix;
step seven: and solving the mixed semi-positive definite/second-order cone programming problem of x by adopting an interior point method to obtain the global optimal solution of x, wherein the global optimal solution is used as the position estimation value of the target source in the reference coordinate system.
Compared with the prior art, the invention has the advantages that:
1) the method of the invention approximates the existing minimization problem based on the maximum likelihood criterion to the least square problem based on the least square criterion, namely, solves the non-convex positioning problem of x, and relaxes the non-convex positioning problem of x to the mixed semi-positive/second-order cone planning problem of x by combining the second-order cone relaxation technology and the semi-positive relaxation technology, thereby ensuring to obtain the global optimal solution of the position of the target source in the reference coordinate system and improving the positioning precision.
2) The method further improves the positioning accuracy by utilizing the RSS measurement value and the AOA measurement value, thereby more accurately estimating the position of the target source.
3) Experiments prove that the method of the invention has stable performance under the condition of large measurement noise power.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
The general implementation block diagram of the three-dimensional wireless sensor network non-cooperative positioning method based on RSS and AOA provided by the invention is shown in FIG. 1, and the method comprises the following steps:
the method comprises the following steps: establishing a space rectangular coordinate system as a reference coordinate system in a three-dimensional wireless sensing network environment, setting N anchor nodes and a target source in the three-dimensional wireless sensing network environment, and recording the coordinate position of the ith anchor node in the reference coordinate system as siThe coordinate position of the target source in the reference coordinate system is recorded as x, si=(si1,si2,si3),x=(x1,x2,x3) (ii) a N is a positive integer, N represents the total number of anchor nodes in the three-dimensional wireless sensor network environment, N is greater than or equal to 4, in this embodiment, N is 6, i is a positive integer, i is greater than or equal to 1 and less than or equal to N, and s isi1、si2、si3Corresponding representation si1 st, 2 nd, 3 rd coordinate component, x1、x2、x3Corresponding to the 1 st, 2 nd and 3 rd coordinate components representing x.
Fig. 2 is a schematic diagram showing positions of a target source and an ith anchor node in a reference coordinate system in an uncooperative three-dimensional wireless sensor network environment.
Step two: transmitting a measuring signal by a target source in a three-dimensional wireless sensing network environment, and obtaining an RSS measuring value and an AOA measuring value after each anchor node receives the measuring signal transmitted by the target source; then, a measuring model of RSS measured values obtained by each anchor node is established, and the ith anchor node is connected with the RSS measuring moduleThe measurement model of the point-obtained RSS measurements is described as:
and establishing respective measurement models of an azimuth angle measurement value and an elevation angle measurement value in the AOA measurement values obtained by each anchor node, and describing the measurement model of the azimuth angle measurement value in the AOA measurement values obtained by the ith anchor node as follows:
a measurement model of elevation measurements among AOA measurements obtained by the ith anchor node is described as:
wherein L is
iRepresents the RSS measurement obtained by the ith anchor node, i.e. the path loss, L, existing on the transmission path experienced by the measurement signal transmitted from the target source to the ith anchor node
0Representing the path loss present on the transmission path experienced by the measurement signal transmitted from the target source to the reference point, taken in the experiment L
0The value of gamma is 40dB, gamma represents the path loss coefficient of the transmission distance of the measurement signal transmitted from the target source to each anchor node, the value range of gamma is 2.2-2.8, if gamma is 2.6, the symbol "| | | |" is the symbol for solving the Euclidean norm, d
0Representing the distance from the reference point to the target source in the reference coordinate system, and taking d in the experiment
0Is 1 m, n
iRepresents L
iOf the measurement noise, n
iObeying a Gaussian distribution
Represents n
iPower of phi
iRepresenting azimuthal measurements, m, in AOA measurements obtained by the ith anchor node
iIs indicative of phi
iMeasurement noise present in, m
iObeying a Gaussian distribution
Represents m
iPower of alpha
iRepresenting elevation measurements, v, of AOA measurements obtained at the ith anchor node
iDenotes alpha
iOf the measurement noise, v
iObeying a Gaussian distribution
Denotes v
iOf the power of (c).
Step three: in that
m
i<<1、v
iWhen < 1, i.e. under the condition of high signal-to-noise ratio, for
Making approximate transformation to obtain n
iThe approximate expression of (c), described as:
and to
Making approximate transformation to obtain m
iThe weighted approximate expression is described as:
to pair
Making approximate transformation to obtain v
iThe approximate expression of (c), described as:
wherein the content of the first and second substances,
represents m
iWeighted value, c
i=[-sin(φ
i),cos(φ
i),0]
TThe term "[ 2 ]]"is a vector representing a symbol, k ═ 0,0,1]
TThe symbol "T" is transposed symbol, β, μ, λ
i、c
iAnd k are all introduced intermediate variables.
Step four: according to
And
and combining the least square criterion to obtain a non-convex positioning problem for solving x, which is described as:
wherein min () is a minimum function.
Step five: introducing auxiliary variables f, h, r and z and relaxation variables e, g and t into the description of solving the non-convex positioning problem of x to obtain an equivalent problem of solving the non-convex positioning problem of x, wherein the description is as follows:
wherein e is
iDenotes the i-th component in e, g
iDenotes the ith component in g, "s.t." means "constrained to … …", h
iDenotes the ith component in h, h
i=||x-s
i||
2,I
3Represents a 3-dimensional identity matrix, r
iDenotes the i-th component in r, r
i=||x-s
i||,f
iThe i-th component in f is represented,
step six: using a second order cone relaxation method, r in the description of the equivalence problem of the non-convex localization problem of x will be solved
i=||x-s
iRelaxation of | to r
i≥||x-s
iL; and adopting a semi-positive definite relaxation method to solve the problem that x is not the equal value of x in the description of the problem of the convex positioning
Tx relaxation is in the form of a Linear Matrix Inequality (LMI)
Then according to r
i≥||x-s
iI and
and obtaining a mixed semi-positive definite/second order cone programming problem for solving x, wherein the description is as follows:
wherein the content of the first and second substances,
to represent
Is a semi-positive definite matrix.
Step seven: and solving the mixed semi-positive definite/second-order cone programming problem of x by adopting an interior point method to obtain the global optimal solution of x, wherein the global optimal solution is used as the position estimation value of the target source in the reference coordinate system.
The feasibility, effectiveness and positioning performance of the method are verified through simulation experiments.
Setting that N is 6 anchor nodes exist in the three-dimensional wireless sensing network environment, and the coordinate positions of the target source and the 6 anchor nodes in the reference coordinate system are randomly selected in a cube of 15 x 15 cubic meters. The power of the measurement noise in the path loss present on the transmission path experienced by the measurement signal transmitted from the target source to any anchor node reception is assumed to be the same, i.e.
The power of the measurement noise present in the azimuth measurements in the AOA measurements obtained by any anchor node is the same, i.e.
The power of the measurement noise present in the elevation measurements in the AOA measurements obtained by any anchor node is the same, i.e.
Wherein the content of the first and second substances,
corresponding to the power representing the measurement noise in the path loss existing on the transmission path experienced by the measurement signal transmitted from the target source to the 1 st anchor node reception, the power representing the measurement noise in the path loss existing on the transmission path experienced by the measurement signal transmitted from the target source to the nth anchor node reception,
representing the power of the measurement noise in a given path loss,
representing the standard deviation of the measurement noise in a given path loss,
corresponding to the power representing the measurement noise present in the azimuth angle measurements in the AOA measurements obtained by the 1 st anchor node, the power of the measurement noise present in the azimuth angle measurements in the AOA measurements obtained by the Nth anchor node,
representing the power of measurement noise present in a given azimuth measurement,
to representThe standard deviation of the measurement noise present in a given azimuthal measurement,
corresponding to a power representing measurement noise present in elevation measurements in AOA measurements obtained by the 1 st anchor node, a power of measurement noise present in elevation measurements in AOA measurements obtained by the Nth anchor node,
represents the power of measurement noise present in a given elevation measurement,
representing the standard deviation of the measurement noise present in a given elevation measurement.
The performance of the method of the invention is tested along with the change situation of the increase of the number of the anchor nodes.
Fig. 3 is a graph showing that the root mean square error of the method of the present invention, the existing generalized confidence sub-domain method and the existing weighted least square method varies with the number of anchor nodes under the condition that the standard deviation of the measurement noise in the given path loss is 6dB, the standard deviation of the measurement noise in the given azimuth measurement value and the standard deviation of the measurement noise in the given elevation measurement value are both 5 degrees. It can be observed from fig. 3 that the Root Mean Square Error (RMSE) of the method of the present invention is smaller than the other two methods and closer to the cramer-Circle (CRLB), and the difference in RMSE values between the method of the present invention and the two existing methods increases as the number of anchor nodes increases, which indicates the superior performance of the method of the present invention in terms of positioning accuracy.
The performance of the method of the invention was tested as a function of increasing standard deviation of the measured noise.
Fig. 4 is a graph showing the variation of the root mean square error of the method of the present invention with the standard deviation of the measurement noise in the given path loss, compared with the existing generalized confidence sub-domain method and the existing weighted least square method, when the standard deviation of the measurement noise in the given azimuth measurement value and the standard deviation of the measurement noise in the given elevation measurement value are both 5 degrees and the number of anchor nodes is 6. Fig. 5 is a graph showing the variation of the root mean square error of the method of the present invention with the standard deviation of the measurement noise present in the given azimuth measurement value, which is 6dB, the standard deviation of the measurement noise present in the given elevation measurement value, which is 5 degrees, and the number of anchor nodes, which is 6, compared with the existing generalized confidence sub-domain method and the existing weighted least-squares method, with the standard deviation of the measurement noise present in the given azimuth measurement value. Fig. 6 shows a graphical representation of the root mean square error of the method of the invention versus the existing generalized confidence sub-domain method, the existing weighted least squares method as a function of the standard deviation of the measurement noise present in a given elevation measurement, given a standard deviation of the measurement noise in the path loss of 6dB, given a standard deviation of the measurement noise present in the azimuth measurement of 5 degrees, and given a number of anchor nodes of 6. It can be observed from fig. 4, 5 and 6 that the method of the present invention has more accurate positioning accuracy and is closer to the lower limit of cramer than the two existing methods within the standard deviation variation range of the measurement noise considered, and the positioning performance is more stable.
The first prior art method in fig. 3 to 6 is a 3-D Target Localization in Wireless Sensor Network Using RSS and AOA Measurements (three-dimensional object Localization based on RSS and AOA Measurements in Wireless Sensor networks), which is disclosed in IEEE Transactions on Vehicular Technology (institute of electrical and electronics engineers (IEEE) vehicle technologies) by slave Tomic et al, which is referred to as the generalized trust sub-domain method for short; the second existing method is a closed-form Solution for RSS/AOA Target Localization by spatial Coordinates mapping (RSS/AOA Target Localization based on Spherical coordinate transformation), which is disclosed in IEEE Wireless Communications Letters (institute of electrical and electronics engineers (IEEE) Wireless communication prompter) by slave Tomic et al, and is referred to as a weighted least square method for short.
The simulation result shows that the method has good positioning performance, can well meet the requirement of high positioning precision, and is less influenced by measurement noise.