CN103068039A - Wireless fidelity (WIFI) signal-based locating method for received signal strength indicator (RSSI) values - Google Patents

Abstract

The invention discloses a wireless fidelity (WIFI) signal-based locating method for received signal strength indicator (RSSI) values. WIFI signal RSSI values of each known position in the field to be located are collected repeatedly, the WIFI signal RSSI values are uploaded to a server, the collected values are calculated to get an average value (avg) and a standard deviation (dev) by the server , and the average value (avg) and the standard deviation (dev) are saved in a data base. The WIFI signal RSSI value of a position to be located is collected, the WIFI signal RSSI value is uploaded to the server, the WIFI signal RSSI value of the position to be located is matched up with an expected value by adopting the fingerprint verification algorithm, information of three most probable positions is obtained, weighted average is calculated according to the probability, and a coordinate of the position being located is obtained. Compared with the prior art, by means of the WIFI signal-based locating method for RSSI values, the locating accuracy is improved, the locating accuracy can be as accurate as 2 meters, and the requirement of indoor locating can be met.

Description

A kind of localization method of the RSSI value based on the WiFi signal

Technical field

The present invention relates to indoor WiFi location technology, particularly the localization method of a kind of RSSI value based on the WiFi signal (signal receiving strength value).

Background technology

At present, general WiFi indoor positioning technology is based on the signal strength signal intensity location technology of the wireless lan (wlan) of IEEE802.11b/g agreement mostly.Location technology basic principle based on signal strength signal intensity is according to the intensity reckoning signal receiver of the signal that receives and the distance between the signal source, mainly is divided into two classes: triangle intensity algorithm and location fingerprint recognizer.Wherein triangle intensity arithmetic accuracy is low, is difficult to satisfy the indoor positioning requirement; And common algorithm for recognizing fingerprint exists receiving equipment different and so that receive the defective that there is error in signal.

Summary of the invention

Above-mentioned shortcoming and deficiency in order to overcome prior art the object of the present invention is to provide a kind of localization method based on WiFi signal RSSI value, have improved positioning accuracy.

Purpose of the present invention is achieved through the following technical solutions:

A kind of localization method of the RSSI value based on the WiFi signal may further comprise the steps:

(1) a plurality of WiFi focuses is set in place to be positioned, use handheld terminal to each the known location point in the place to be positioned, the RSSI value of multi collect WiFi signal, and upload onto the server, server is deposited to database the data that collect average avg and standard deviation dev;

(2) use handheld terminal to gather the RSSI value of the WiFi signal in site undetermined, and upload onto the server;

(3) to the normal state distribution formula

$f\left(x\right)=\frac{1}{\mathrm{\σ}\sqrt{2\mathrm{\π}}}{e}^{-\frac{{(x-\mathrm{\μ})}^2}{2{\mathrm{\σ}}^2}}$

Make μ=avg, σ=dev, the x with in the RSSI value substitution normal distribution formula of the WiFi signal in site undetermined obtains probability P _Mn, wherein m represents the sequence number of known location point, n represents the sequence number of WiFi focus;

P _m=P _m1·P _m2...P _mn；

(4) in database, seek out corresponding P _MnThree known location points that value is maximum are established its coordinate and are respectively (x ₁, y ₁), (x ₂, y ₂), (x ₃, y ₃), corresponding P _MnValue is respectively P ₁, P ₂, P ₃Tried to achieve the initial coordinate in site undetermined by following formula:

$(x,y)=\frac{P_1}{P_1+P_2{+P}_3}(x_1,y_1)+\frac{P_2}{P_1{+P}_2+P_3}(x_2,y_2)+\frac{P_3}{P_1+P_2+P_3}(x_3,y_3)$

(5) in fact the gap of probability, is revised so probability taken the logarithm because above-mentioned formula maximum probability point has almost accounted for all weights generally at 10 more than the order of magnitude, obtains the correction coordinate in site undetermined:

$(x^{,},y^{,})=(-1g\frac{P_1+P_2+P_3}{P_1})(x_1,y_1)+(-1g\frac{P_1+P_2+P_3}{P_2})(x_2,y_2)+(-1g\frac{P_1+P_2+P_3}{P_3})(x_3,y_3).$

The described use handheld terminal of step (2) gathers the WiFi signal RSSI value in site undetermined, and uploads onto the server, and is specially:

The user at first is being provided with the known location spot scan two-dimension code of two-dimension code, handheld terminal is uploaded onto the server the RSSI value of current location and the WiFi signal surveyed, the WiFi signal RSSI value that server will measure this moment is as the origin reference location data of current handheld terminal, the RSSI value of the WiFi signal of current location in this value and the database is compared, then subtract each other, be averaged, obtain side-play amount Offset, upload onto the server after during the location RSSI value of the WiFi signal surveyed being deducted side-play amount Offset.

The localization method of above-mentioned RSSI value based on the WiFi signal, also carry out following steps:

Two handheld terminals are bound, and server calculates the distance of two handheld terminals, report to the police when distance surpasses threshold value.

The putting of described a plurality of WiFi focuses is broken line " it " word and puts.

Compared with prior art, the present invention has the following advantages and beneficial effect:

(1) the present invention can be accurate to positioning accuracy 2 meters by traditional method based on fingerprint location is improved, and can satisfy the requirement of indoor positioning fully.

(2) the present invention is by arranging two-dimension code at the known location point, and handheld terminal scans two-dimension code before the location, and the WiFi signal RSSI value that handheld terminal records is proofreaied and correct, and what solved the multiple terminals obtains the different problem of RSSI value difference at same position.

(3) putting of WAP (wireless access point) of the present invention is broken line " it " word and puts, and locating effect is better.

Description of drawings

Fig. 1 is the workflow diagram of the handheld terminal of embodiments of the invention.

Fig. 2 is the workflow diagram of the server of embodiments of the invention.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited to this.

Embodiment

The system based on the localization method of the RSSI value of WiFi signal that present embodiment be used for to be realized comprises handheld terminal, WAP (wireless access point) and server.

Present embodiment may further comprise the steps based on the localization method of the RSSI value of WiFi signal:

(1) a plurality of WiFi focuses is set in the megastore; Be to improve positioning accuracy, the putting of a plurality of WiFi focuses is broken line " it " word and puts; Use handheld terminal to each the known location point in the place to be positioned, multi collect WiFi signal RSSI value, and uploading onto the server, server is deposited to database the data that collect average avg and standard deviation dev.

(2) use handheld terminal to gather the WiFi signal RSSI value in site undetermined, and upload onto the server, be specially:

The user at first is being provided with the known location spot scan two-dimension code of two-dimension code, handheld terminal is uploaded onto the server the RSSI value of current location and the WiFi signal surveyed, the WiFi signal RSSI value that server will measure this moment is as the origin reference location data of current handheld terminal, the RSSI value of the WiFi signal of current location in this value and the database is compared, then subtract each other, be averaged, obtain side-play amount Offset, upload onto the server after during the location RSSI value of the WiFi signal surveyed being deducted side-play amount Offset.

(3) to the normal state distribution formula

$f\left(x\right)=\frac{1}{\mathrm{\σ}\sqrt{2\mathrm{\π}}}{e}^{-\frac{{(x-\mathrm{\μ})}^2}{2{\mathrm{\σ}}^2}}$

Make μ=avg, σ=dev, the x with in the RSSI value substitution normal distribution formula of the WiFi signal in site undetermined obtains probability P _Mn, wherein m represents the sequence number of known location point, n represents the sequence number of WiFi focus;

P _m=P _m1·P _m2...P _mn。

(4) in database, seek out corresponding P _MnThree known location points that value is maximum are established its coordinate and are respectively (x ₁, y ₁), (x ₂, y ₂), (x ₃, y ₃), corresponding P _MnValue is respectively P ₁, P ₂, P ₃Tried to achieve the initial coordinate in site undetermined by following formula:

$(x,y)=\frac{P_1}{P_1+P_2{+P}_3}(x_1,y_1)+\frac{P_2}{P_1{+P}_2+P_3}(x_2,y_2)+\frac{P_3}{P_1+P_2+P_3}(x_3,y_3).$

(5) in fact the gap of probability, is revised so probability taken the logarithm because above-mentioned formula maximum probability point has almost accounted for all weights generally at 10 more than the order of magnitude, obtains the correction coordinate in site undetermined:

$(x^{,},y^{,})=(-1g\frac{P_1+P_2+P_3}{P_1})(x_1,y_1)+(-1g\frac{P_1+P_2+P_3}{P_2})(x_2,y_2)+(-1g\frac{P_1+P_2+P_3}{P_3})(x_3,y_3).$

The principle of step (4) is: according to Bayesian formula: D1, and D2 ..., Dn is the division of sample space S, if the probability that occurs with P (Di) presentation of events Di, and P (Di)＞0 (i=1,2 ..., n).For any one event x, P (x)＞0 then has:

Wherein, the RSS intensity level that P (A) is collected at certain point as terminal equals the probability of certain value, and P (B) is that terminal is at the probability of some points.The probability that the user appears at each point is identical, so to a definite system equations the right, except P (A|B _i) all be definite value, so if P is (AB _i) P (AB _j), P (B is then arranged _i| A)〉P (B _j| A).So, as long as find out max{P _mCorresponding point, be exactly most probable position, site undetermined.

As shown in Figure 1, the course of work of handheld terminal is as follows: after the startup, initialization is finished when the interface, sends log-on message to server, and server returns the ID client; Terminal is obtained after the ID address, hangs three process operations.Process one: the RSSI value of WIFI sent to server near handheld terminal was collected always; Process two: when handheld terminal detects the positional information that server returns, show current location.Process three: when detecting the consumer process button operation, if searching request then sends to server, by server return the search target coordinate and navigation way, handheld terminal with the show navigator route until the user arrives the target location; If recall request, send the request to equally server, return just now walking path by server, the user can be returned along former road.If the user carries out parent-offspring's binding, then can show the customer position information of active user and its binding on the handheld terminal, when both positional distances surpassed secure threshold, then head of a family's terminal can give the alarm, until the user contacts alarm voluntarily.

As shown in Figure 2, monitor UDP information after the server work, when the RSSI value of receiving that the user sends always, mean value avg and standard deviation dev with the RSSI value, mate according to above-mentioned localization method and the coordinate in the database, upgrade obtaining customer position information, the broadcasting coordinate data; When obtaining navigation request, carry out coordinates of targets search, obtain in ground node of graph file, carrying out route searching behind the coordinates of targets, near the path of destination and return; Obtain recalling request, from routing database, obtain user's travel path before, return the nearest path of user; When receiving two-dimension code control information (comprising the current coordinate position of user) and current RSSI value, server compares the benchmark RSSI value of same point in these data and the database, calculate deviation from linearity, server data is revised, return simultaneously user's current location information.

Above-described embodiment is the better execution mode of the present invention; but embodiments of the present invention are not limited by the examples; other any do not deviate from change, the modification done under Spirit Essence of the present invention and the principle, substitutes, combination, simplify; all should be the substitute mode of equivalence, be included within protection scope of the present invention.

Claims (4)

1. the localization method based on the RSSI value of WiFi signal is characterized in that, may further comprise the steps:

(1) a plurality of WiFi focuses is set in place to be positioned, use handheld terminal to each the known location point in the place to be positioned, the RSSI value of multi collect WiFi signal, and upload onto the server, server is deposited to database the data that collect average avg and standard deviation dev;

(2) use handheld terminal to gather the RSSI value of the WiFi signal in site undetermined, and upload onto the server;

(3) to the normal state distribution formula

$f\left(x\right)=\frac{1}{\mathrm{\σ}\sqrt{2\mathrm{\π}}}{e}^{-\frac{{(x-\mathrm{\μ})}^2}{2{\mathrm{\σ}}^2}}$

Make μ=avg, σ=dev, the x with in the RSSI value substitution normal distribution formula of the WiFi signal in site undetermined obtains probability P _Mn, wherein m represents the sequence number of known location point, n represents the sequence number of WiFi focus;

P _m=P _m1·P _m2...P _mn；

(4) in database, seek out corresponding P _MnThree known location points that value is maximum are established its coordinate and are respectively (x ₁, y ₁), (x ₂, y ₂), (x ₃, y ₃), corresponding P _MnValue is respectively P ₁, P ₂, P ₃Tried to achieve the initial coordinate in site undetermined by following formula:

$(x,y)=\frac{P_1}{P_1+P_2{+P}_3}(x_1,y_1)+\frac{P_2}{P_1{+P}_2+P_3}(x_2,y_2)+\frac{P_3}{P_1+P_2+P_3}(x_3,y_3)$

(5) probability taken the logarithm revise, obtain the correction coordinate in site undetermined:

$(x^{,},y^{,})=(-1g\frac{P_1+P_2+P_3}{P_1})(x_1,y_1)+(-1g\frac{P_1+P_2+P_3}{P_2})(x_2,y_2)+(-1g\frac{P_1+P_2+P_3}{P_3})(x_3,y_3).$

2. the localization method of the RSSI value based on the WiFi signal according to claim 1 is characterized in that the described use handheld terminal of step (2) gathers the RSSI value of the WiFi signal in site undetermined, and uploads onto the server, and is specially:

The user at first is being provided with the known location spot scan two-dimension code of two-dimension code, handheld terminal is uploaded onto the server the RSSI value of current location and the WiFi signal that measures, server is with the RSSI value of the WiFi signal that the measures origin reference location data as current handheld terminal, the RSSI value of the WiFi signal of current location in this value and the database is compared, then subtract each other, be averaged, obtain side-play amount Offset, upload onto the server after during the location RSSI value of the WiFi signal surveyed being deducted side-play amount Offset.

3. the localization method of the RSSI value based on the WiFi signal according to claim 1 is characterized in that, also carries out following steps:

Two handheld terminals are bound, and server calculates the distance of two handheld terminals, report to the police when distance surpasses threshold value.

4. the localization method of the RSSI value based on the WiFi signal according to claim 1 is characterized in that, the putting of described a plurality of WiFi focuses is broken line " it " word and puts.

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