CN101349746A - Wireless radio frequency positioning method based on virtual reference label algorithm - Google Patents

Abstract

A wireless radio frequency positioning method based on virtual reference label algorism comprises the steps of: arranging reader at the boundary of an object region, distributing the reference labels as a rectangular grid type in the indoor object region; arranging an object with a radio frequency label in the object region, using each reader to reach the radio frequency signal intensity of each reference label and object label to be transmitted to a host computer to be processed to attain the coordinates of the object. The invention is characterized in that the host computer builds a virtual reference label in calculation, uses the virtual reference label as substrate to induce the concept of similar map; the host computer preliminarily finds the positioning region of the object on the similar map corresponding to each reader; the similar maps are intersected to reduce the positioning region of the object; the residual weighting algorism between the possible positions and the position information of the virtual reference label are used to attain the position coordinate of the object. The method has the advantages of low power consumption and high positioning accuracy.

Description

A kind of wireless radio frequency positioning method based on virtual reference label algorithm

Technical field

The present invention relates to a kind of wireless pinpoint method, particularly a kind of in the indoor accurate position field, based on the wireless radio frequency positioning method of virtual reference label algorithm.

Background technology

Wireless location technology is by special algorithm electromagnetic some parameter that receives to be handled, and infers the position of object to be measured with this.Measurement parameter comprise test signal transmission time, amplitude, phase place, reach angle and signal intensity etc.At present, along with wireless technology, mobile computing device and and the continuous development of internet, the indoor positioning service system more and more attracts much attention.Indoor wireless location technology commonly used has:

(1) indoor GPS location technology: GPS is the location technology that is most widely used at present.But when GPS receiver during in office work, because signal is subjected to the influence of buildings and big high attenuation, its bearing accuracy is very low, and locating speed is also relatively slow, and the cost of steady arm terminal is higher.

(2) cellular localization technology: cellular networks such as GSM, CDMA are all supported location technology, but factors such as non-line-of-sight propagation, multipath effect and multiple access interference have reduced its bearing accuracy, and relate to user's privacy concern, make its popularization be subjected to certain limitation.

(3) infrared technique: the active label based on the infrared technique of loosing can be used for indoor positioning, but it requires the object to be measured must be in alignment with the infrared ray reader, and orientation distance is too near, thereby the having little significance of practical application.

(4) based on the location technology of WLAN (wireless local area network): in certain zone, an amount of wireless base station is installed, the relevant information of the object to be measured that obtains according to these base stations, and in conjunction with the topological structure of base station, analysis-by-synthesis, thereby the particular location of definite object.The system that uses this type of technology sets up easily, but measuring accuracy is barely satisfactory, remains further to be improved.

(5) ultrasonic technology: successfully use this technology can obtain high orientation precision really at present, but need a large amount of infrastructure supports, the cost costliness can't large tracts of land be promoted.

Compare with above-mentioned positioning system, RFID tag RFID technology has non line of sight and non-contacting advantage.It can be with outstanding speed operation, and bigger transmission range and high performance-price ratio also are the advantage places of RFID.

Radio-frequency (RF) identification claims electronic tag again, is a kind of contactless automatic identification technology, is called for short RFID, and it is by the automatic recognition objective object of radiofrequency signal and obtain related data, and identification work need not manual intervention, can work in various rugged surroundings.RFID application the earliest can be traced back to " enemy and we's identification " system that is used to distinguish allied forces and Nazi's aircraft in the World War II.Along with development of technology, the RFID application enlarges day by day, has now related to the various aspects of people's daily life, and will become the basic technology that following information society is built.The RFID technology has been widely used in medical monitoring, numerous areas such as prison convict management, main equipment fixed capital management, highway tolling system, aviation logistics identification.

Along with the continuous development of chip technology and production technology, increase, the reduction in processing time of the reduction of label cost, the raising of reading/writing distance, memory capacity will become possibility, and the kind of RFID product will be more and more abundanter, use also more and more widely.

Basic rfid system is made up of three parts:

1.RFID label.The RFID label is made up of coupling element and chip, and each label has unique electronic code.Label contains built-in aerial, be used for and radio-frequency antenna between communicate.The RFID label is according to the mode difference that sends radiofrequency signal, is divided into active and two kinds of passive types.Active tag initiatively sends radiofrequency signal to read write line, by the internal battery power supply, is called active label again usually; Passive label is charged pool not, is called passive label again, the electromagnetic wave that its emission electric wave and internal processor operation institute energy requirement all produce from reader.Passive label is converted into the part electromagnetic energy energy of working for own after receiving the electromagnetic wave signal that reader sends.Wherein active tag has farther communication distance usually, and its price is higher relatively, is mainly used in applications such as the remote detection of valuables.Passive label has low-cost advantage, but its operating distance, memory capacity etc. are subjected to the restriction of energy source.

The RFID label according to the different mining of factors such as application scenario, shape, frequency of operation and operating distance with dissimilar antennas.A RFID label comprises one or more antennas usually.Employed frequency is called the RFID frequency of operation when RFID label and reader work.The frequency of RFID use is at present crossed over a plurality of frequency ranges such as low frequency, high frequency, ultrahigh frequency, microwave.The selection of RFID frequency influences the distance, speed of signal transmission etc., also is subjected to the national laws regulation limitations simultaneously.

2.RFID reader.The main task of RFID reader is that the control radio-frequency module reads signal to the label emission, and receives replying of label, and the object id information of label is decoded, and other related information transmission on the related label of object id information is arrived main frame for processing.Different according to using, reader can be a hand-held or fixed.Current reader cost is higher, and mostly can only be in the work of single-frequency point.The price of following reader will significantly reduce, and support a plurality of Frequency points, can discern the label information of different frequency automatically.

3. antenna.Antenna is used for transmitting radiofrequency signal between label and reader.The groundwork flow process of system is: reader produces induction current by the radiofrequency signal of emitting antenna transmission certain frequency when radio-frequency (RF) tag enters the emitting antenna perform region, radio-frequency (RF) tag obtains energy and is activated; Radio-frequency (RF) tag sends information such as self coding by blocking built-in transmitting antenna; System's receiving antenna receives the carrier signal of sending from radio-frequency (RF) tag, is sent to reader through the antenna adjustments device, and reader carries out the demodulation sign indicating number to the signal that receives and delivers to the backstage main system then and carry out relevant treatment; Main system is judged the legitimacy of this card according to logical operation, makes corresponding processing and control at different settings, sends the action of command signal control executing mechanism.

In the application of RFID, consideration for the power consumption aspect, electronic tag can not become the masters of location, so adopt based on network method, promptly need be at the receiving trap of fixed position deploy radiofrequency signal, and gather the information of sending attached to the electronic tag on the object to be measured by these devices, by Wireless/wired network information is mail to control center then and further process.

Therefore, in wireless positioning field, improve the precision and the reliability of RFID location technology, the cost that reduces positioning system is that problem to be solved is arranged in the prior art.

Summary of the invention

The problem that the present invention need solve provides a kind of technology of novel wireless radio frequency positioning method.Based on this technology, the precision and the unfailing performance of locating information improve effectively, and the power consumption of system also can further reduce.

Designed a kind of wireless radio frequency positioning method based on RFID tag according to the above-mentioned problem that needs to solve, implementation step is:

(1) reader is positioned over zone boundary to be monitored;

(2) reference label is distributed in indoor zone to be monitored with the rectangular node form, and each reader and reference label position and distance each other separately is known;

(3) place when zone to be monitored when the object to be measured that has radio-frequency (RF) tag, the electromagnetic wave of antenna detection each radio-frequency (RF) tag of each reader by separately reaches host computer with the reference label that measures and the radio-frequency (RF) signal strength value of object tag to be measured;

(4) host computer is set up the virtual reference label, described virtual reference label n the point in the rectangular node that per four true reference label constitute that promptly evenly be equally spaced, the coordinate Calculation of the radio-frequency (RF) signal strength value by each reference label of recording and each known reference label goes out the coordinate and the radio-frequency (RF) signal strength value of each virtual reference label;

(5) host computer is set up close map for each reader, described close map is about to the equal-sized zone (R) that whole indoor area dividing to be monitored becomes some, each zone is the center with a virtual reference label all, and the virtual reference population of tags that obtains like this is called close map;

(6) absolute difference of the radio-frequency (RF) signal strength of host computer each virtual reference label of comparison and object tag to be measured is tentatively determined effective locating area of object to be measured with near the nearest reference label definite object to be measured on the close map of each reader;

(7) host computer is eliminated some impossible position by the close map of each reader being got occur simultaneously, and further dwindles the effective locating area of object to be measured;

(8), obtain the position coordinates of object to be measured according to the positional information of residual error weighting algorithm between the different possible positions and virtual reference label.

The present invention has three main advantages:

(1) compare with existing location technology, this programme does not need to increase extra reader and reference label, but can reach better precision;

(2) dynamic that can more easily conform.Because reference label and object to be measured are in the same environment, so many environmental factors of the variation of identification range that causes can be cancelled, therefore, in the identification range based on reference label, we are the reference information of real-time update about searching dynamically;

(3) positional information of object to be measured is more accurately with reliable.In case after nearest reference label was chosen, traditional scheme was the coordinate that simply calculates object to be measured by the position of nearest reference label and their weight factor; This programme is then eliminated some impossible position by virtual reference label algorithm, effectively raises bearing accuracy.

Description of drawings

Fig. 1 is a positioning system hardware arrangement synoptic diagram of the present invention;

Fig. 2 is the virtual label synoptic diagram;

Fig. 3 gets to occur simultaneously for close map and eliminates impossible position view.

Embodiment

Purport of the present invention is technical scheme of design so that when utilizing radio RF recognition technology to carry out indoor accurate position, can effectively improve the precision and the reliability of measurement under the condition that does not increase hardware cost.Be elaborated with reference to accompanying drawing below in conjunction with embodiment, so that the technical characterictic and the advantage of the inventive method are carried out more deep annotation.

Hardware arrangement of the present invention is as shown in Figure 1: reader is positioned over zone boundary to be monitored; Reference label is distributed in indoor zone to be monitored with the rectangular node form, and each reader and reference label position and distance each other separately is known.

When the object to be measured that has radio-frequency (RF) tag places zone to be monitored, each reader receives the electromagnetic wave that each radio-frequency (RF) tag is initiatively sent by antenna separately, the reference label that measures and the radio-frequency (RF) signal strength value of object tag to be measured are reached host computer by transmission control protocol and Internet protocol, and described host computer is a computer processor.

Host computer is set up the virtual reference label, as shown in Figure 2.Described virtual reference label n the point (shown in circle among the figure) in the rectangular node that per four true reference label (shown in black lattice among the figure) constitute that promptly evenly be equally spaced, the coordinate Calculation of the radio-frequency (RF) signal strength value by each reference label of recording and each known reference label goes out the coordinate and the radio-frequency (RF) signal strength value of each virtual reference label.

The virtual reference label can obtain by the linear interpolation algorithm computation to the signal strength values (being called for short the RSSI value) of each reader:

For example, with n-1 equidistant being placed between two adjacent true labels of virtual reference label, the true grid of each that obtains all can comprise (n+1) like this ²-4 virtual reference labels and 4 true reference label.

The RSSI value of the virtual label on these horizontal lines can calculate by formula (a), and the RSSI value of the virtual label on the perpendicular line can calculate by formula (b):

$S_K\left(T_{p,b}\right)=S_K\left(T_{a,b}\right)+p\×\frac{S_K\left(T_{a+n,b}\right)-S_K\left(T_{a,b}\right)}{n+1}$

$=\frac{p\×S_K\left(T_{a+n,b}\right)+(n+1-p)\×S_K\left(T_{a,b}\right)}{n+1}......\left(a\right)$

$S_K\left(T_{a,q}\right)=S_K\left(T_{a,b}\right)+q\×\frac{S_K\left(T_{a,b+n}\right)-S_K\left(T_{a,b}\right)}{n+1}$

$=\frac{q\×S_K\left(T_{a,b+n}\right)+(n+1-q)\×S_K\left(T_{a,b}\right)}{n+1}......\left(b\right)$

Here, S _k(T _{I, j}) denotation coordination (i, j) the virtual reference label on is to the RSSI value of k reader; $a=\left[\frac{i}{n}\right];$ $b=\left[\frac{j}{n}\right];$ 0≤p＝i?mod?n≤n-1；0≤q＝j?mod?n≤n-1。

The virtual reference label is the same with true reference label like this, and its position coordinates and RSSI value all become known conditions, are equivalent to set up several true reference label.And when true reference label took place to change, the virtual reference label position also can real-time update.

Host computer is the notion that close map is set up on the basis with the virtual reference label then, and described close map as shown in Figure 2.Close map is about to equal-sized zone that whole indoor area dividing to be monitored becomes some shown in R among the figure, and each zone is the center with a virtual reference label all, and the virtual reference population of tags that obtains like this is called close map.

Suppose to have four readers, the absolute difference of the object tag to be measured that host computer is read by each reader and the RSSI value of reference label is determined near the nearest reference label the object to be measured, be depicted on the close map of each reader, as black entity zonule among Fig. 3, so just obtain four close maps.

The absolute difference of the RSSI value of object tag to be measured described here and reference label calculates by following formula:

$E_j=\sqrt{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{({\mathrm{\θ}}_i-S_i)}^2}$

Wherein, n is the reader number, S _iBe the radio-frequency (RF) signal strength value of object tag to be measured on reader i, θ _iBe the radio-frequency (RF) signal strength value of reference label j on reader i; The E value is used for characterizing signal distance relation between reference label and the object tag to be measured, and more little expression reference label of E and object tag to be measured are separated by near more.

Described nearest reference label is meant and calculates the zonule of back E value less than the capping value.The capping value is the important design parameter of this programme; In order to reduce search coverage, should use less higher limit.

Because the error that factors such as measurement, calculating, environment cause, make that the nearest reference label zone of the object to be measured depicted on the close map of each reader correspondence is different, each close map is got common factor, just can obtain the zonule that those have maximum likelihood, shown in Fig. 3 center section.We claim this process for eliminating the process of impossible position.

Object's position to be measured is locked in so littler accurate more scope, and last host computer is obtained the position coordinates of object to be measured by the positional information of residual error weighting algorithm between the different possible positions and virtual reference label.

In order to improve the bearing accuracy of system, introduce two kinds of weight factor: W during calculating _1iAnd W _2i

Weight factor W _1iLay particular emphasis on the RSSI difference of selected virtual reference label and label that object to be measured is tied up, decide according to different RSSI values, formula is as follows:

$W_{1i}={\mathrm{\Σ}}_{k=1}^K\frac{|S_k\left(T_i\right)-S_k\left(R\right)|}{K\×S_k\left(T_i\right)}$

Weight factor W _2iRelevant with the density of the virtual reference label of selecting.We use P _iBe illustrated in the ratio of the Probability Area that connects in the whole indoor regional extent to be monitored, formula is as follows:

$W_{2i}=\frac{p_i}{{\mathrm{\Σ}}_{i=1}^{n_a}{p}_i}=\frac{n_{\mathrm{ci}}}{{\mathrm{\Σ}}_{i=1}^{n_a}{n}_{\mathrm{ci}}}$

Here, n _CiThe quantity of expression join domain, n _aThe quantity of representing the whole Probability Areas in the whole indoor zone to be monitored.

At the coordinate time that calculates object to be measured, consider above-mentioned two kinds of weight factors, i.e. W simultaneously _i=W _1i* W _2i, the coordinates computed formula is:

$(x,y)={\mathrm{\Σ}}_{i=1}^{n_a}{W}_i(x_i,y_i)$

In a word, the various changes that can carry out the wireless radio frequency positioning method among the present invention of those skilled in the art and distortion and do not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims (8)

1, a kind of wireless radio frequency positioning method based on virtual reference label algorithm, implementation step is:

(1) reader is positioned over zone boundary to be monitored;

(2) reference label is distributed in indoor zone to be monitored with the rectangular node form, and reader and reference label position and distance each other separately is known;

(3) place when zone to be monitored when the object to be measured that has radio-frequency (RF) tag, the electromagnetic wave that reader sends by the antenna detection radio-frequency (RF) tag of self reaches host computer with the reference label that measures and the radio-frequency (RF) signal strength value of object tag to be measured;

(4) host computer is set up the virtual reference label, described virtual reference label evenly is equally spaced on the point in the rectangular node that per four true reference label constitute, and the coordinate Calculation of radio-frequency (RF) signal strength value by the reference label that records and known reference label goes out the coordinate and the radio-frequency (RF) signal strength value of each virtual reference label;

(5) host computer is that reader is set up close map, and described close map is the equal-sized zone (R) that whole indoor area dividing to be monitored is become some, and each zone is the center with a virtual reference label all;

(6) host computer relatively between the virtual reference label with the absolute difference of the radio-frequency (RF) signal strength of object tag to be measured to determine near the nearest reference label the object to be measured, preliminary effective locating area of determining object to be measured on the close map of reader;

(7) host computer is eliminated error by the close map of reader being got occur simultaneously, and further dwindles the effective locating area of object to be measured;

(8) again according to the positional information of residual error weighted calculation between the possible position and virtual reference label, obtain the position coordinates of object to be measured.

2, the wireless radio frequency positioning method based on virtual reference label algorithm according to claim 1 is characterized in that: the numerical value of the described rectangular node mid point of step (4) is determined by positioning accuracy request.

3, the wireless radio frequency positioning method based on virtual reference label algorithm according to claim 2 is characterized in that: the virtual reference label radio-frequency (RF) signal strength value of the described rectangular node mid point of step (4) is calculated according to following formula:

$\begin{array}{c}{S}_K\left(T_{p,b}\right)=S_K\left(T_{a,b}\right)+p\×\frac{S_K\left(T_{a+n,b}\right)-S_K\left(T_{a,b}\right)}{n+1}\\ =\frac{p\×S_K\left(T_{a+n,b}\right)+(n+1-p)\×S_K\left(T_{a,b}\right)}{n+1}..........\left(a\right)\end{array}$

$\begin{array}{c}{S}_K\left(T_{a,q}\right)=S_K\left(T_{a,b}\right)+q\×\frac{S_K\left(T_{a,b+n}\right)-S_K\left(T_{a,b}\right)}{n+1}\\ =\frac{q\×S_K\left(T_{a,b+n}\right)+(n+1-q)\×S_K\left(T_{a,b}\right)}{n+1}..........\left(b\right)\end{array}$

Wherein, the virtual label RSSI value on the horizontal line is calculated by formula (a), and the virtual label RSSI value on the perpendicular line is calculated by formula (b); S _k(T _{I, j}) denotation coordination (i, j) the virtual reference label on is to the radio-frequency (RF) signal strength value of k reader; $a=\left[\frac{i}{n}\right];$ $b=\left[\frac{j}{n}\right];$ 0≤p=i mod n≤n-1; 0≤q=j mod n≤n-1, the wherein number of n representative point.

4, the wireless radio frequency positioning method based on virtual reference label algorithm according to claim 3 is characterized in that: the absolute difference of the described radio-frequency (RF) signal strength of step (6) calculates according to following formula:

$E_j=\sqrt{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{({\mathrm{\θ}}_i-S_i)}^2}$

Wherein, n is the reader number, S _iBe the radio-frequency (RF) signal strength value of object tag to be measured on reader i, θ _iBe the radio-frequency (RF) signal strength value of reference label j on reader i; The E value is used for characterizing signal distance relation between reference label and the object tag to be measured, and more little expression reference label of E and object tag to be measured are separated by near more.

5, the wireless radio frequency positioning method based on virtual reference label algorithm according to claim 4 is characterized in that: the position coordinates of the described object to be measured of step (8) calculates according to following formula:

$(x,y)={\mathrm{\Σ}}_{i=1}^{n_a}{W}_i(x_i,y_i)$

W wherein _iBe weight factor W _1iAnd W _2iProduct, described W _1iLay particular emphasis on the radio-frequency (RF) signal strength difference of selected virtual reference label and label that object to be measured is tied up, W _2iRelevant with the density of the virtual reference label of selecting, its computing formula is respectively:

$W_{1i}={\mathrm{\Σ}}_{k=1}^K\frac{|S_k\left(T_i\right)-S_k\left(R\right)|}{K\×S_k\left(T_i\right)},$ $W_{2i}=\frac{p_i}{{\mathrm{\Σ}}_{i=1}^{n_a}{p}_i}=\frac{n_{\mathrm{ci}}}{{\mathrm{\Σ}}_{i=1}^{n_a}{n}_{\mathrm{ci}}}$

K is the reader number, P _iBe illustrated in the ratio of the Probability Area that connects in the whole indoor regional extent to be monitored, n _CiThe quantity of expression join domain, n _aThe quantity of representing the whole Probability Areas in the whole indoor zone to be monitored.

6, according to any described wireless radio frequency positioning method based on virtual reference label algorithm in the claim 1 to 4, it is characterized in that: described reader reaches host computer to the radio-frequency (RF) signal strength value by transmission control protocol and Internet protocol.

7, the wireless radio frequency positioning method based on virtual reference label algorithm according to claim 6 is characterized in that: described radio-frequency (RF) tag can be on one's own initiative to the reader launching electromagnetic wave.

8, the wireless radio frequency positioning method based on virtual reference label algorithm according to claim 7, it is characterized in that: described host computer is a computer processor.

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