CN101478820A - Wireless positioning method for sensor network - Google Patents

Abstract

The invention relates to a method for wirelessly locating sensor network, which is concretely: signals transmitted from an unknown node are received respectively by a plurality of wireless sensors which constitute the sensor network; thereafter, signals of the obtained unknown node are conveyed to an information desk server by each wireless sensor through a tree network; based on the distance from each sensor to the unknown node or the strength of the received signals, as well as abscissa and vertical axis of each sensor, abscissa and vertical axis of the unknown nodes are obtained by the information desk server, thus the position information of the unknown node is acquired and the coordinate of the unknown node is matched on a preset locating area; if the unknown node enters an illegal area or an illegal operation is carried out, an alarming order is started by the information desk server. The method of the invention is handy and easy to be handled; the positioning speed is fast; besides, the positioning accuracy is good; the method is suitable for a real-time application to various embedded systems which have high demands for positioning speed but not strict demand for positioning accuracy.

Description

The wireless location method of sensor network

Technical field

The present invention relates to a kind of localization method that is applied to sensor network, be specifically related to a kind of wireless location method of sensor network.

Background technology

In sensor network, positional information is most important to the monitoring of sensor network, position that incident takes place or the node location that obtains information are the important informations that is comprised in the sensor node supervisory messages, do not have the supervisory messages of positional information often meaningless.Therefore, the node location of determining the position that incident takes place or obtaining message is one of basic functions of sensor network, the sensor network effectiveness of application is played a part crucial.

In wireless sensor network, adopt trilateration and centroid method to carry out the measurement of unknown node positional information usually at present based on TDOA (Time Different of Arrival).Wherein, trilateration is three node A, B, C with three known sensor, and unknown node S coordinate is labeled as (x, y), unknown node is da, db, dc, then da to the range mark of 3 of A, B, C, db, the length of dc can be measured by the TDOA method, that is:

$\left\{\begin{array}{c}S=C_1{T}_1\left(1\right)\\ S=C_2{T}_2\left(2\right)\end{array}\right.\⇒\left\{\begin{array}{c}{C}_{2}S=C_2{C}_1{T}_1\left(1\right)\\ C_{1}S=C_1{C}_2{T}_2\left(2\right)\end{array}\right.$

(2)-(1)

C ₁S-C ₂S＝C ₁C ₂T ₂-C ₁C ₂T ₁

$S=\frac{C_1{C}_2}{C_1-C_2}(T_2-T_1)$

∴ S=k (T ₂-T ₁)=k Δ T and C ₁≠ C ₂

Wherein, C ₁With C ₂Be the transmission speed of different media, T ₁With T ₂For from the unknown node to the beaconing nodes with C ₁With C ₂Speed is transmitted the needed time,

Then $\left\{\begin{array}{c}\sqrt{{(x-x_a)}^2+{(y-y_a)}^2}=\mathrm{da}\\ \sqrt{{(x-x_b)}^2+{(y-y_b)}^2}=\mathrm{db}\\ \sqrt{{(x-x_c)}^2+{(y-y_c)}^2}=\mathrm{dc}\end{array}\right.$

$\left[\begin{array}{c}x\\ y\end{array}\right]={\left[\begin{array}{cc}2(x_a-x_c)& 2(y_a-y_c)\\ 2(x_b-x_c)& 2(y_b-y_c)\end{array}\right]}^{-1}\left[\begin{array}{c}{x_a}^2-{x_c}^2+{y_a}^2-{y_c}^2+{d_c}^2-{d_a}^2\\ {x_a}^2-{x_c}^2+{y_b}^2-{y_c}^2+{d_c}^2-{d_b}^2\end{array}\right]$

As from the foregoing, if adopt trilateration, then know the coordinate that A point, B point and C are ordered except needs, also need to know length and the time T of da, db, dc, though the length of da, db, dc can be measured by the TDOA method, but because in wireless system, the transmission speed of radio signals is identical with the light velocity, thus time T usually difficulty obtain.For overcoming such problem, and obtain precise time, then must in wireless system, increase the related hardware facility, thereby the production cost of the system of increasing is unfavorable for the extensive use of sensor network.

And if adopt centroid method, then be with each transducer in the sensor network as polygonal summit, thereby make up simple polygon, and make unknown node and polygonal geometric center, i.e. its center of mass point coincidence then, is calculated each polygonal head coordinate (x _i, y _i) mean value, with the coordinate A as unknown node _i(X _i, Y _i), promptly

A _i(x _i，y _i)，i＝1，2，...n $(x,y)=(\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{x}_i}{n},\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{y}_i}{n})$

Though this method is simple and easy to do, the unknown node coordinate that is obtained generally has than mistake with the unknown node coordinate of reality, that is, the positioning accuracy of sensor network is relatively poor.

Summary of the invention

The objective of the invention is to propose a kind of simple and easy to do, locating speed is fast, and positioning accuracy sensor wireless localization method preferably, to overcome deficiency of the prior art.

For achieving the above object, the present invention has adopted following technical scheme:

A kind of wireless location method of sensor network, it is characterized in that, this method is: a plurality of wireless sensers that constitute sensor network receive the signal that unknown node is sent respectively, then each wireless senser is communicated to total station server with the signal of the unknown node that obtains by tree network respectively, total station server is handled by following formula these signals, that is:

A _i(x _i，y _i)，i＝1，2，...n

$(x,y)=(\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(M-\mathrm{LQ}{I}_i)\·x_i}{(M-\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I})\·n},\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(M-\mathrm{LQ}{I}_i)\·y_i}{(M-\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I})\·n})$

$\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{LQ}{I}_i$

Wherein, M is a constant, can adjust according to the transmitting power and the antenna number of degrees of application scheme radio frequency chip, and n receives the transducer number that unknown node is sent wireless signal, LQI _iIndicate the wireless signal strength that transducer receives, x _i, y _iBe the coordinate of each transducer, thereby obtain current unknown node coordinate A _i(x _i, y _i), this unknown node coordinate is matched on the default locating area, if this unknown node enters illegal zone or carries out illegal operation, then total station server starts alert program.

Particularly, in this method, the wireless signal strength that each transducer receives is that (B is a signal receiving strength for LQI/2) dBm, LQI=20*lg B wherein.

Adopt 8bit to deposit LQI in the described transducer, the maximum of LQI is M, and M is a constant, according to the transmitting power and the antenna number of degrees of the radio frequency chip of application scheme, does corresponding adjustment.

Described M=190.

Among the present invention, carrying out barycenter weight method by the framing signal that the unknown node of being obtained by a plurality of wireless sensers is sent handles, thereby when having overcome the available technology adopting trilateration, the problem that time is difficult to obtain, or when adopting centroid method, replace the too rough problem of coordinate of unknown node with the center of mass point coordinate.Principle of the present invention is, the wireless senser known by a plurality of coordinates receives the framing signal that unknown node is sent respectively, then the framing signal that will obtain separately of each transducer is sent to total station server by tree network respectively, by total station server these framing signals being carried out the barycenter weight by following formula handles, obtain current unknown node coordinate, that is:

$(x,y)=(\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(M-\mathrm{LQ}{I}_i)\·x_i}{(M-\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I})\·n},\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(M-\mathrm{LQ}{I}_i)\·y_i}{(M-\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I})\·n})$

Wherein n receives the transducer number that unknown node is sent signal, LQI _iI=1,2 ... n is used to indicate the wireless signal strength that each transducer receives, and $\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{LQ}{I}_i.$ Furthermore, the signal strength expression that each transducer receives is that (B is a signal receiving strength for LQI/2) dBm, LQI=20*lg B wherein.The LQI value is more little, and the wireless signal strength that representative receives is good more, and unknown node is near more apart from sensor distance, and this parameter is provided by each transducer, if adopt 8bit to deposit this parameter in transducer, then the maximum of LQI is M.According to law of conservation of energy, the antenna number of degrees and M value are monotonic increases, and transmitting power and M value are monotone decreasings.With the LQI of each transducer as a weight coefficient, react each transducer to the distance of unknown node distance or the power of received signal, the LQI that the abscissa of each transducer and ordinate multiply by respectively separately sues for peace again, average then as the abscissa and the ordinate of unknown node, can realize more accurately locating, thereby avoid relatively poor problem of the precision in the centroid method and the unhandy problem of trilateration.After utilizing method of the present invention to obtain the locating information of unknown node, again it is matched on the default locating area, the course of this unknown node of real-time tracking if enter illegal zone, or has illegal operation, and then total station server starts alert program.

Compared with prior art, beneficial effect of the present invention is: this sensor wireless localization method is simple and easy to do, and locating speed is fast, and positioning accuracy is better, be suitable for locating speed being had relatively high expectations various, and the real-time application of the very not strict embedded system of positioning accuracy request.

Description of drawings

Below in conjunction with the drawings and specific embodiments, technical scheme of the present invention is further elaborated.

Fig. 1 is the structural representation of building sensing monitoring system in the specific embodiment of the invention.

Embodiment

Be a building sensing monitoring system as shown in Figure 1, it is a tree structure.These tree structure the superiors are total station server, can finish functions such as computing and instruction manipulation; The intermediate layer is a router, is used to be implemented in the signal transmission between total station server and transducer; Orlop is a plurality of wireless sensers that are distributed in each floor, and it constitutes a sensor network, and these transducers can transmit and receive the radiofrequency signal with fixed frequency.If one can launch the object with above-mentioned radiofrequency signal, be that unknown node enters building, then a plurality of wireless sensers receive the signal that unknown node is sent respectively, then each wireless senser is communicated to the signal of the unknown node that obtains total station server on upper strata respectively by a plurality of routers, total station server is handled by following formula the signal from each transducer, that is:

A _i(x _i，y _i)，i＝1，2，...n

$(x,y)=(\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(M-\mathrm{LQ}{I}_i)\·x_i}{(M-\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I})\·n},\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(M-\mathrm{LQ}{I}_i)\·y_i}{(M-\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I})\·n})$

$\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{LQ}{I}_i$

Wherein M is for being preferably 190 according to the transmitting power of the radio frequency chip of application scheme and the constant that the antenna number of degrees adjust accordingly, and n receives the transducer number that unknown node is sent signal, LQI _iI=1,2 ... n is used to indicate the wireless signal strength that each transducer receives, and $\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{LQ}{I}_i.$ Furthermore, the signal strength expression that each transducer receives is that (B is a signal receiving strength for LQI/2) dBm, LQI=20*lg B wherein.LQI is low more, and then the wireless signal strength of Jie Shouing is high more, and unknown node is near more apart from sensor distance.LQI is provided by each transducer, and each transducer all adopts 8bit to deposit this parameter, and the maximum of LQI is M, and promptly 190.With the LQI of each transducer as a weight coefficient, react each transducer to the distance of unknown node distance or the power of received signal, the abscissa of each transducer and ordinate multiply by LQI summation separately respectively, average then as the abscissa and the ordinate of unknown node, can obtain the locating information of this unknown node, this locating information is matched on the locating area that is preset in total station server, then can realize real-time tracking to this node, if object enters illegal zone, or illegal operation arranged, then total station server program start alert program.

Certainly, method of the present invention also can be applicable to the sensor network such as formations such as infrared ray sensors, or such as in the navigation systems such as gps system.So, above embodiment is only for the usefulness that the present invention is described, but not limitation of the present invention, under the situation that does not break away from the spirit and scope of the present invention, various distortion that the common engineers and technicians of this area make and improvement all should belong to category of the present invention, and are limited by every claim of the present invention.

Claims (4)

1. the wireless location method of a sensor network, it is characterized in that, this method is: a plurality of wireless sensers that constitute sensor network receive the signal that unknown node is sent respectively, then each wireless senser is communicated to total station server with the signal of the unknown node that obtains by tree network respectively, total station server is handled by following formula these signals, that is:

A _i(x _i，y _i)，i＝1，2，...n

$(x,y)=(\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(M-{\mathrm{LQI}}_i)\·x_i}{(M-\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I})\·n},\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(M-{\mathrm{LQI}}_i)\·y_i}{(M-\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I})\·n})$

$\stackrel{\‾}{L}\stackrel{\‾}{Q}\stackrel{\‾}{I}=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{LQI}}_i,$

Wherein, M is a constant, and the transmitting power and the antenna number of degrees of the radio frequency chip that can adopt according to application scheme are adjusted, and n receives the transducer number that unknown node is sent wireless signal, LQI _iIndicate the wireless signal strength that transducer receives, x _i, y _iBe the coordinate of each transducer, thereby obtain current unknown node coordinate A _i(x _i, y _i), this unknown node coordinate is matched on the default locating area, if this unknown node enters illegal zone or carries out illegal operation, then total station server starts alert program.

2. the wireless location method of sensor network according to claim 1 is characterized in that, in this method, the wireless signal strength that each transducer receives is that (B is a signal receiving strength for LQI/2) dBm, LQI=20*1gB wherein.

3. the wireless location method of sensor network according to claim 2, it is characterized in that, adopt 8bit to deposit LQI in the described transducer, the maximum of LQI is M, the constant of M for adjusting according to the transmitting power and the antenna number of degrees of application scheme radio frequency chip.

4. the wireless location method of sensor network according to claim 3 is characterized in that, described M=190.

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