CN103207381A - Multipath interference elimination method applied to indoor location based on signal strength - Google Patents

Abstract

The invention discloses a multipath interference elimination method applied to indoor location based on signal strength. According to the method, by establishing a corresponding model through an overlying system in a location system, a solving equation set is established so as to solve a distance from a real transmitting terminal to a receiving terminal in indoor location. Through the method, interference caused by overlying of direct path signals caused by signals of a reflection path in the indoor environment can be overcome, and accuracy in indoor location based on the electromagnetic strength is greatly improved.

Description

Be applied to the multipath interference elimination method based on the signal intensity indoor positioning

Technical field

The present invention relates to a kind of indoor ranging technology, be specifically related to the method that a kind of elimination multipath that is applied to the indoor positioning technology disturbs.

Background technology

Along with the development of target localization technology, present advanced person's gps satellite location technology has rule of thumb been developed into the map location by ancient in the location of target.In actual applications, thus the positioning error that can reach the whole world less than 10m in military affairs, civilian, a lot of fields such as space flight play an important role.But GPS has obvious defects in indoor location.Because the outer shell of building has disturbed the transmission of gps satellite signal, so can not receive gps signal in indoor environment, perhaps the error of GPS location can be very big.The indoor positioning technology puts forward in order to address this problem.Present indoor orientation method mainly comprises the signal intensity localization method, arrive the angle localization method and time of arrival localization method.

Arriving the angle localization method is to position according to the angle that signal arrives.3 smart antennas at first are set on indoor roof.When a localizing objects enters locating area, 3 smart antennas begin the arrival angle of measurement and positioning signal that target is sent.Through the integration of over-angle, indoor locating system will know that the position of target inside the perception zone is to reach the purpose of location.Based on the localization method that arrives angle 3 deficiencies are arranged.At first, the antenna that can cognitive radio arrives angle is very expensive.This is not conducive to the laying of extensive indoor locating system and popularizes.Secondly, still do not overcome the influence of multipath effect based on the indoor locating system of angle.Through the reflection of multiple reflectings surface such as wall or desktop, signal will be divided into multihop path to be transmitted.And at receiving end, can not identify which paths is exactly the path that straight line arrives.So the accuracy of location will descend greatly.At last, the present smart antenna floor area that can take measurement of an angle is big, is not suitable for installing in indoor environment.

Then be based on the localization method of time of arrival.This method utilizes the transmission time of signal to carry out measuring distance.And position according to the distance of measuring.Having widely in the underwater sonar system of this method used.This is because the character of particular surroundings under water and sound uniqueness determines.Sound is very rare in the environment under water arbitrarily is easy to pick out target sound.And the speed of sound is 340m/s.So can be by the form location of finishing target under water of reflection.But sound is more noisy in indoor environment, is difficult to go out respectively target sound.So being operated in of having utilizes find range electromagnetic time of arrival in the indoor environment.As everyone knows, electromagnetic wave propagation speed is 3 * 10e8m/s.In indoor of short duration transmission range, because electromagnetic wave propagation speed is very fast, so be difficult to determine the electromagnetic transmission time.So this method has limitation.In addition, bigger based on the hardware spending of the localization method of time of arrival, be difficult to form large-scale popularizing.

Also have a kind of more traditional method, utilize the electromagnetic transmission range of ionization meter of signal exactly.And search out the position of target according to these transmission ranges.Electromagnetic wave can experience the decay of energy in communication process.Decay will be carried out with certain rules.Indoor locating system is exactly to go the distance of judging that oppositely signal is passed by according to the signal energy after the decay.Then according to these counter positions of releasing target of distance.But the method for sort signal intensity is in indoor environment, and error is very big.This mainly also is because the influence of multipath effect.Because, the reason of various reflectings surface, the transmission of straight line signal will be divided into the transmission of a lot of roads.Last these paths are superimposed at receiving end, and the energy of signal will change greatly.The energy localization method that the basis signal energy is found range will be very inaccurate.This causes, and seldom has indoor locating system to use this method.But, the energy localization method has original advantage, and this is because the energy localization method only utilizes the energy of signal, and hardware is not had special requirement.The wifi system of laying has been enough to satisfy its hardware requirement at present.

Summary of the invention

The present invention is directed to existing carrying out in the indoor orientation method based on electromagnetism intensity owing to exist multipath to disturb, and the problem that can't accurately locate, and a kind of method that multipath disturbs of eliminating is provided.This method can overcome in the indoor environment, and the interference that the stack that the signal of reflection paths causes the direct projection path signal brings improves the degree of accuracy of carrying out indoor positioning based on electromagnetism intensity greatly.

In order to achieve the above object, the present invention adopts following technical scheme:

Be applied to the multipath interference elimination method based on the signal intensity indoor positioning, this method comprises the steps:

(1) utilizes the anchor node of three known own positions, carry out the signal receiving end of the positioning system of indoor positioning based on signal intensity and set up direct projection path under the different wave length and the vector stack model of many reflection pathss according to the corresponding signal intensity of different frequencies;

(2) in positioning system, the model of setting up according to step (1) at one above the anchor node, utilizes the corresponding signal intensity of different frequencies to make up corresponding relation equation group;

(3) signal receiving end of positioning system is found the solution the nonlinear equation group model accordingly according to setting up at the system of equations of setting up;

(4) signal receiving end of positioning system detect corresponding signal emissive porwer, the product value between gain and the gain acceptance in three takes place;

(5) quantity of reflection paths during the signal receiving end of positioning system estimates;

(6) signal receiving end of positioning system is set corresponding initial value and scope at the unknown quantity of finding the solution in the nonlinear equation group model, and carries out interative computation to finding the solution Nonlinear System of Equations accordingly;

(7) equal 0 when the first order derivative of finding the solution Nonlinear System of Equations, second derivative is greater than 0 the time, and this direct projection path values of finding the solution the Nonlinear System of Equations correspondence is final direct projection path values.

In the preferred embodiment of this programme, the quantity of the reflection paths of determining in the described step (5) is less than 5.

Further, between the d1+1m, reflection paths di finds the solution scope at d1＜di＜2d1 to the scope of finding the solution of setting direct projection path d1 in the described step (6) at d1-1m, and the scope of finding the solution of reflection coefficient is less than 0.3.

Can overcome in the indoor environment by the present invention, the direct projection path can be accurately determined in the interference that the stack that the signal of reflection paths causes the direct projection path signal brings, and can improve the degree of accuracy of carrying out indoor positioning based on electromagnetism intensity greatly thus.

Should invent based on the receiving end energy and carry out indoor positioning, not only utilize based on the energy location to the less characteristics of hardware requirement but also solved problem based on ENERGY METHOD accuracy deficiency.

Description of drawings

Further specify the present invention below in conjunction with the drawings and specific embodiments.

Fig. 1 is the schematic diagram of the indoor locating system that relates among the present invention;

Fig. 2 is the invention process principle flow chart;

Fig. 3 is the three-point fix synoptic diagram.

Embodiment

For technological means, creation characteristic that the present invention is realized, reach purpose and effect is easy to understand, below in conjunction with concrete diagram, further set forth the present invention.

Multipath interference elimination method provided by the invention is implemented based on the positioning system of utilizing signal intensity realization indoor positioning.

This positioning system mainly is made up of signal transmitting terminal and signal receiving end, wherein comprises following three parts (as shown in Figure 1) in the signal receiving end:

First is identification and the measure portion 101 of antenna power, gain, and this part is used for identification and measures emissive power, received power and the antenna gain of antenna.This part is mainly by obtaining relevant information by three aspects: the 1st, and the hardware description book; The 2nd, the result compares with other hardware; The 3rd, in inhaling the ripple environment, measure.

Second portion is signal strength measurement part 102, carries out the frequency hopping measure signal intensity.This part is carried out the measurement of signal intensity by changing signal.

Third part is that the signal intensity after measuring is integrated and corresponding calculating.This part mainly is the measurement result that obtains according to second portion, form corresponding and battle-sight range, the Nonlinear System of Equations of being correlated with between reflective distance and the reflection coefficient is found the solution it, and form the triangle location according to solving result, and positioning result is shown.

Based on above-mentioned positioning system, multipath interference elimination method provided by the invention has been set up corresponding model by the overlapping system in the positioning system, and sets up a solving equation group thus and find the solution in the indoor positioning true transmitting terminal to the distance of receiving end.

Based on above-mentioned principle, concrete enforcement of the present invention is as follows:

(1) in positioning system, utilize the anchor node of three known own positions, make the signal receiving end of positioning system utilize the corresponding signal intensity of different frequencies to set up direct projection path under the different wave length and the vector stack model of many reflection pathss.

(2) model of setting up according to step (1) utilizes the corresponding signal intensity of different frequencies to make up corresponding relation equation group at one above the anchor node, and this system of equations is as follows:

$\left\{\begin{array}{c}Q(x,{\mathrm{\λ}}_1)=\left|\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{q}_i(\stackrel{\→}{x},{\mathrm{\λ}}_1)\right|\\ Q(x,{\mathrm{\λ}}_2)=\left|\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{q}_i(\stackrel{\→}{x},{\mathrm{\λ}}_2)\right|\\ \·\·\·\\ Q(x,{\mathrm{\λ}}_n)=\left|\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{q}_i(\stackrel{\→}{x},{\mathrm{\λ}}_n)\right|\end{array}\right.---\left(1\right)$

Wherein, Q (x, λ ₁) be that anchor node is in wavelength X ₁Condition under received signal energy value; X is the unknown number that comprises battle-sight range, reflective distance and reflection coefficient.And

Be respectively in direct projection path 1, reflection paths 2,3 ... m accepts energy value; Can obtain to solve by these energy values and include battle-sight range, the unknown quantity x of reflective distance and reflection coefficient.

(3) signal receiving end of positioning system is found the solution the nonlinear equation group model accordingly according to setting up at the system of equations of setting up; Namely formula (1) is set up and found the solution nonlinear equation group model such as formula (2) and formula (3), wherein P in the formula 3 _jThe signal strength values that under j wavelength, receives for system.

${\min }_{x\∈R^{2n}}y\left(x\right)=\frac{1}{2}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\mathrm{wj}{\left(x\right)}^2---\left(2\right)$

w _j(x)=Q(x,λ _j)-Q _j,j=1,...,m （3）

Then by to the finding the solution of formula (2), just can remove battle-sight range d.

(4) in the quantity of unknown number less than in 2 times of equation quantity, will have exact solution according to the Newton method Nonlinear System of Equations.Below will provide the preliminary way of finding the solution.

$\▿y\left(x\right)={[\frac{\∂y}{\∂x_i}\left(x\right),...,\frac{\∂y}{\∂x_{2n+1}}\left(x\right)]}^T---\left(4\right)$

Here

It here is the single order partial derivative of function y.Parameters such as x are to represent battle-sight range, the unknown number of reflective distance and reflection coefficient.

And

I≤2n+1, j≤2n+1 is the second-order partial differential coefficient of y.

When first order derivative and two partial derivatives all satisfy formula (5), w(x) will obtain minimum value, just the deviation minimum of Shi Ji acquisition value and system of equations functional value.X at this time is optimum solution.

$\▿y\left(x\right)=0$ （5）

$\▿y^2\left(x\right)>0$

(5) search the status number of equation, check the reliability of equation optimum solution.

The first order derivative of function y is:

$\▿y=[{{\mathrm{\λ}}_j}^2{d_1}^2-2c{{\mathrm{\λ}}_j}^2{d_1}^{-3}]---\left(6\right)$

In formula (6), c is emissive power * transmitter antenna gain (dBi) * accept antenna gain, and d1 is transmitting terminal and receiving end battle-sight range length, λ _jWavelength for the transmission signal.

The status number of equation is obtained by the second derivative of y

$H={\▿}^{2}y=\left[\begin{array}{cc}0& -2{{\mathrm{\λ}}_j}^2{d_1}^{-3}\\ -2{{\mathrm{\λ}}_j}^2{d_1}^{-3}& 6c{{\mathrm{\λ}}_j}^2{d_1}^{-4}\end{array}\right]---\left(7\right)$

And, second-order partial differential coefficient H invert for

H ^-1=adj(H)/det(H) (8)

Two norms of H are:

${\left|\right|H\left|\right|}_2={\left(\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{\left(h_{\mathrm{ij}}\right)}^2\right)}^{\frac{1}{2}}---\left(9\right)$

At last by solving the status number of Nonlinear System of Equations:

$\mathrm{Cond}\left(H\right)={\left|\right|H\left|\right|}_2{\left|\right|H^{-1}\left|\right|}_2$

$=\det {\left(H\right)}^{-2}{\left({\left|\right|H\left|\right|}_2\right)}^2---\left(10\right)$

$={(9\frac{c^2}{d^2}+2)}^{}$

By this parameter, as seen work as

In the time of very high, the state value of Nonlinear System of Equations also can be very high.At this moment system of equations is exactly the system of equations of a morbid state, and in the time of the input end subtle change, acute variation will take place solution of equations.So, in order to reach a stable solution, below step will come battle-sight range d is found the solution by three measures.

Measure 1 is by the c unknown quantity in definite system of equations.Unknown quantity c has represented the gain of gain * receiving antenna of the transmitted power * transmitting antenna of transmitting antenna.The value of c will be estimated or determine to this patent by 3 kinds of methods, to replace finding the solution in Nonlinear System of Equations:

First method is to utilize the instructions of hardware.A lot of hardware have the instructions parameter of standard, such as emissive power, and the gain of transmitting antenna gain and receiving antenna.Utilize these data above instructions just can obtain a comparatively accurately c value, to alleviate the solution procedure of Nonlinear System of Equations.

The second method utilization is tested hardware below the environment of microwave.Because do not have the path of emission, so according to the frequency of transmission range and transmission and the signal intensity of acceptance, this value of gain * receiving antenna that has represented transmitted power * transmitting antenna will be easy to find the solution out.

The third method is utilized in physical condition, utilizes known d, brings into and solves corresponding c parameter in the system of equations.

Measure 2 is by reducing the reflection paths number of model.The more many numbers of Nonlinear System of Equations unknown number that will cause of reflection paths are more many.This will cause Nonlinear System of Equations to be difficult to more find the solution.This patent will come system of equations is simplified by the unknown number number that reduces model.This patent hypothesis only has the signal that is lower than 5 reflection pathss to participate in stack at receiving end in a common indoor environment.Because, so decay has to a great extent also taken place at reflection paths itself owing to length and the emission ratio of reflection paths in signal, so the signal above most of reflection paths can be ignored at last.So think that it is rational having only 5 reflection pathss.

Measure 3: by the scope of the unknown number in the Nonlinear System of Equations solution procedure is set, stablize solution of equations.When the unknown number initial value that gives system of equations more close to the solution of Newton method the time, the unknown number that utilizes newton's solution to solve will become more accurate.So this patent is set at the scope of direct projection path distance d in 1 meter scope of initial value.And the scope of reflection paths will be greater than d less than 2d.Emission ratio will increase this Nonlinear System of Equations stability of solution greatly for so limiting less than 0.3..

Utilize such scheme to realize that the specific implementation process of indoor accurate position is as follows:

1, sets up model according to the system of equations (1) of setting up of such scheme in the information receiving end of indoor locating system.

$\left\{\begin{array}{c}Q(x,{\mathrm{\λ}}_1)=\left|\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{q}_i(\stackrel{\→}{x},{\mathrm{\λ}}_1)\right|\\ Q(x,{\mathrm{\λ}}_2)=\left|\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{q}_i(\stackrel{\→}{x},{\mathrm{\λ}}_2)\right|\\ \·\·\·\\ Q(x,{\mathrm{\λ}}_n)=\left|\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{q}_i(\stackrel{\→}{x},{\mathrm{\λ}}_n)\right|\end{array}\right.---\left(1\right)$

Set up solving model (2)

${\min }_{x\∈R^{2n}}y\left(x\right)=\frac{1}{2}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\mathrm{wj}{\left(x\right)}^2---\left(2\right)$

w _j(x)=Q(x,λ _j)-Q _j,j=1,...,m （3）

Wherein x comprises a lot of unknown numbers such as emissive power * antenna transmitting gain * antenna gain acceptance in c, direct projection path d1, reflection paths di and reflection coefficient.

2, the signal receiving end of positioning system detect corresponding signal emissive porwer, the product value between gain and the gain acceptance in three takes place; Specifically can utilize the hardware description book method in the declaratives, absorber lined chamber method and the actual method of bringing into estimate emissive power * antenna transmitting gain * antenna gain acceptance in c.

3, in the signal receiving end of positioning system the reflection paths in the model is reduced to 5.

4, the signal receiving end of positioning system set direct projection path d1 the scope of finding the solution between d1-1 and d1+1, reflection paths is found the solution scope at d1＜di＜2d1, the scope of finding the solution of reflection coefficient is less than 0.3.

5, beginning iterative equation/equal 0 when the first order derivative of y, second derivative record the value of d1 at that time greater than 0 the time.And it is separated as final.

6, utilize traditional three-point positioning method among Fig. 3, finally solve the position of impact point.

More than show and described ultimate principle of the present invention, principal character and advantage of the present invention.The technician of the industry should understand; the present invention is not restricted to the described embodiments; that describes in above-described embodiment and the instructions just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.The claimed scope of the present invention is defined by appending claims and equivalent thereof.

Claims (3)

1. be applied to the multipath interference elimination method based on the signal intensity indoor positioning, it is characterized in that, described method comprises the steps:

(1) utilizes the anchor node of three known own positions, carry out the signal receiving end of the positioning system of indoor positioning based on signal intensity and set up direct projection path under the different wave length and the vector stack model of many reflection pathss according to the corresponding signal intensity of different frequencies;

(2) in positioning system, the model of setting up according to step (1) at one above the anchor node, utilizes the corresponding signal intensity of different frequencies to make up corresponding relation equation group;

(3) signal receiving end of positioning system is found the solution the nonlinear equation group model accordingly according to setting up at the system of equations of setting up;

(4) signal receiving end of positioning system detect corresponding signal emissive porwer, the product value between gain and the gain acceptance in three takes place;

(5) quantity of reflection paths during the signal receiving end of positioning system estimates;

(6) signal receiving end of positioning system is set corresponding initial value and scope at the unknown quantity of finding the solution in the nonlinear equation group model, and carries out interative computation to finding the solution Nonlinear System of Equations accordingly;

(7) equal 0 when the first order derivative of finding the solution Nonlinear System of Equations, second derivative is greater than 0 the time, and this direct projection path values of finding the solution the Nonlinear System of Equations correspondence is final direct projection path values.

2. the multipath interference elimination method that is applied to based on the signal intensity indoor positioning according to claim 1 is characterized in that, the quantity of the reflection paths of determining in the described step (5) is less than 5.

3. the multipath interference elimination method that is applied to based on the signal intensity indoor positioning according to claim 1, it is characterized in that, the scope of finding the solution of setting direct projection path d1 in the described step (6) at d1-1m between the d1+1m, reflection paths di finds the solution scope at d1＜di＜2d1, and the scope of finding the solution of reflection coefficient is less than 0.3.

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