CN104931925A - Self-adaptive method based on reference label RFID positioning - Google Patents

Abstract

The invention discloses a self-adaptive method based on reference label RFID positioning. The self-adaptive method comprises the steps that 1) an equation of environmental parameters is set; 2) the environmental parameters in a single area are determined; and 3) a self-adaptive RFID positioning system is designed. Thus, the environmental parameters in a positioning space can be calculated in a self-adaptive manner, the environment can be dynamically adapted to in real time, the positioning method can adapted to environmental change in real time, and calculation and positioning can be more accurate; and compared with traditional methods, the problems, such as movement of people may obstruct signal spreading and sudden landslide may change the signal spreading intensity, that positioning is inaccurate due to dynamic environment change is solved.

Description

A kind of adaptive approach based on reference label RFID location

Technical field

The present invention relates to a kind of localization method, particularly relate to a kind of adaptive approach based on reference label RFID location.

Background technology

Terminological interpretation:

RFID: radio-frequency (RF) identification is (English: Radio Frequency IDentification, abbreviation: RFID) be a kind of wireless communication technology, related data can be read and write by radio signals identification specific objective, and without the need to setting up machinery or optical contact between recognition system and specific objective.

RSSI:RSSI (Received Signal Strength Indicator) is the intensity instruction of Received signal strength, and its realization is carried out after backward channel Baseband Receiver wave filter.

Adopt several fixed labels and label communication to be positioned to be positioned based on reference label RFID localization method, label to be positioned is by detecting and the signal intensity of fixed labels (RSSI).The distance with label to be positioned is calculated according to signal intensity.RFID reader can gather the signal intensity of label to be positioned to be positioned and all fixed reference labels, and is uploaded to host computer.According to the data that reader collection exports, host computer can handle accordingly to obtain label point to be positioned to be positioned to the ranging information of reference label node.

Detect according to current label node to be positioned the received signal strength RSSI numerical value coming from reference label node, try to achieve distance according to formula (3).

$d={10}^{\frac{RSSI\left(d\right)-A}{-10n}}---\left(3\right)$

Wherein: the signal intensity of A representative when distance one meter; RSSI (d) represents the signal intensity between distance d;

The loss of n delegated path, also namely environment to the attenuation coefficient of signal, depending on specific environment.

According to signal intensity, formula (3) calculates distance.The result of having found range when there being this, can utilize the coordinate position of some location algorithm location Calculation label to be positioned.Formula (3) source signal path loss principle, exist under various circumstances, its parameter A is different with n.Will adopt artificial method setup parameter exactly at present, recycling formula (3) goes range finding, thus compute location coordinate.

The range finding formula of formula (3) is as shown in the formula (1) from the classical signals propagation model (path-loss formula) based on RSSI

$RSSI\left(d\right)=RSSI\left(d_0\right)-10\·n\·log\frac{d}{d_0}+X_{\mathrm{\σ}}---\left(1\right)$

Wherein, n represents path loss index, and d is the distance of target range read write line, d0 is closely reference distance, what RSSI (d) and RSSI (d0) represented that read write line reads respectively arrives with it apart from the tag signal strength being d and d0 place, x σ → (0, σ ²) represent noise, meet Gaussian distribution.

Traditional based in the localization method of signal propagation model, path loss severally can provide an estimated value according to ideal space, and remains unchanged in a lot of environment.In actual applications, be difficult to reach ideal space conditions Ambient, the factors such as the temperature in real space, humidity, air and suspension, can make pair signals decay in various degree, especially in actual location space, the movement of personnel also can produce obstacle.So path loss system estimation value can cause positioning precision error very large usually.

Summary of the invention

A kind of adaptive approach based on reference label RFID location is the invention provides for solving the problem.The present invention reduces range finding based on RSSI formula by the impact of environment, improve positioning precision, range measurement parameters of formula of finding range with environmental change is adaptively changed, under the change of environment occurrence dynamics, distance accuracy can remain unchanged, and makes the tag location system of RFID can conform dynamic change like this.

For reaching above-mentioned technique effect, technical scheme of the present invention is:

Based on an adaptive approach for reference label RFID location, comprise the steps:

Step one) environmental parameter equation is set:

The classical signals propagation model of RSSI is as shown in the formula (1):

$RSSI\left(d\right)=RSSI\left(d_0\right)-10\·n\·log\frac{d}{d_0}+X_{\mathrm{\σ}}---\left(1\right)$

Wherein, n represents path loss index, and d is the distance of target range read write line, d ₀for closely reference distance, RSSI (d) for read write line read to being the tag signal strength at d place with its distance, RSSI (d ₀) arriving and its d for read write line reading ₀the tag signal strength at place, X _σrepresent environmental interference, meet Gaussian distribution X _σ(0, σ ²);

According to formula (2) push type (3):

$d=d_0\·{10}^{\frac{RSSI\left(d_0\right)-RSSI\left(d\right)-x_{\mathrm{\σ}}}{10n}}---\left(2\right)$

D ₀for the distance of read write line and label to be positioned; RSSI (d ₀) for read write line and tag distances to be positioned be d ₀and signal is the signal intensity when free-space propagation; x _σrepresent environmental interference, meet Gaussian distribution x _σ(0, σ ²); N is the loss parameter that in environment, signal is propagated; Make A=RSSI (d ₀)+x _σ, then A meets Gaussian distribution (RSSI (d0), σ ²), then there is formula (3):

$d={10}^{\frac{RSSI\left(d\right)-A}{-10n}}---\left(3\right)$

In the plane at read write line and label place to be positioned, fix four position reference labels, four position reference labels form a quadrilateral, and four position reference tag coordinates are respectively T ₁(x ₁, y ₁), T ₂(x ₂, y ₂), T ₃(x ₃, y ₃), T ₄(x ₄, y ₄); Arrange a parameter reference label, coordinate is RT (x ₀, y ₀);

If P _it(d _i) be position reference label T _ipass to the signal intensity of parameter reference label RT at time t, d _ifor reference label T _iwith the actual range of parameter reference label RT; Gather m signal intensity, recording signal intensity if actual is P ₁=(P ₁₁, P ₁₂..., P _1m), then within the time interval gathering m signal intensity, parameter reference label receives the average signal strength P that position reference label transmits _ishown in (4):

${\stackrel{\‾}{P}}_i=\underset{t=1}{\overset{m}{\Σ}}{P}_{it}\left(d_i\right)---\left(4\right)$

Will substitute into (3), then calculate

If T _icoordinate be (x _i, y _i), then RT and T _idistance d _ishown in (5):

$d_i=\sqrt{{(x_0-x_i)}^2+{(y_0-y_i)}^2}---\left(5\right)$

To two different position reference label T _ivalue, then can form system of equations about parameter n and A as shown in the formula (6):

$\{\begin{array}{c}{d}_1={10}^{\frac{{\stackrel{\‾}{p}}_1-A}{-10n}}\\ d_2={10}^{\frac{{\stackrel{\‾}{p}}_2-A}{-10n}}\end{array}---\left(6\right)$

Environmental parameter n and A can be tried to achieve according to formula (6);

Step 2) environmental parameter in single region determines:

Two neighboring reference labels and parameter reference label RT form a delta-shaped region; Signal is passed to parameter reference label RT and is obtained two signal P by described two neighboring reference labels ₁and P ₂, then the computation process of this Delta Region environment parameter is as following algorithm:

2.1) within a set time, parameter reference label gathers signal intensity m time that two position reference labels propagate, then: P ₁=(P ₁₁, P ₁₂..., P _1m), P ₂=(P ₂₁, P ₂₂..., P _2m);

2.2) the average signal strength P of two positioning labels propagation is calculated by formula (4) ₁and P ₂;

2.3) by formula (5) calculating parameter reference label respectively with the distance d of two position reference labels ₁and d ₂;

2.4) environmental parameter A and the n of the delta-shaped region that two position reference labels and parameter reference label RT are formed is tried to achieve by formula (6);

Step 3) design of self-adaptation RFID location system:

3.2) label to be positioned enters the quadrilateral area that four position reference labels are formed;

3.2) data of the signal intensity acquisition of reader acquisition parameter reference label, according to step 2), calculate environmental parameter n and the A of each Delta Region in real time;

3.3) reader is according to the position of label to be positioned, collect the signal intensity of the position reference label of corresponding Delta Region, utilize the environmental parameter calculated in real time, calculate the distance of label to be positioned and four position reference labels according to formula (3);

3.4) according to the distance of label to be positioned and position reference label, the coordinate figure of label to be positioned is calculated.

Advantage of the present invention:

The technology of the present invention can the environmental parameter in compute location space adaptively, and can conform real-time dynamicly, and then the change that localization method can be made to conform in real time, more can accurate Calculation location.Compared with past method, solve because environment dynamic change may cause the coarse problem in location.Such as, the movement of personnel self, may hinder the propagation of signal, and unexpected landslide may make signal transmission intensity change to cause accurate positioning to reduce.

Accompanying drawing explanation

Fig. 1 is plane RFID location model schematic diagram.

Embodiment

A kind of adaptive approach based on reference label RFID location as shown in Figure 1, comprises the steps:

Step one) environmental parameter equation is set:

The classical signals propagation model of RSSI is as shown in the formula (1):

$RSSI\left(d\right)=RSSI\left(d_0\right)-10\·n\·log\frac{d}{d_0}+X_{\mathrm{\σ}}---\left(1\right)$

Wherein, n represents path loss index, and d is the distance of target range read write line, d ₀for closely reference distance, RSSI (d) for read write line read to being the tag signal strength at d place with its distance, RSSI (d ₀) arriving and its d for read write line reading ₀the tag signal strength at place, X _σrepresent environmental interference, meet Gaussian distribution X _σ(0, σ ²);

According to formula (1) push type (2):

$d=d_0\·{10}^{\frac{RSSI\left(d_0\right)-RSSI\left(d\right)-x_{\mathrm{\σ}}}{10n}}---\left(2\right)$

D ₀for the distance of read write line and label to be positioned; RSSI (d ₀) for read write line and tag distances to be positioned be d ₀and signal is the signal intensity when free-space propagation; x _σrepresent environmental interference, meet Gaussian distribution x _σ(0, σ ²); N is the loss parameter that in environment, signal is propagated; Make A=RSSI (d ₀)+x _σ, then A meets Gaussian distribution (RSSI (d0), σ ²), then there is formula (3):

$d={10}^{\frac{RSSI\left(d\right)-A}{-10n}}---\left(3\right)$

In the plane at read write line and label place to be positioned, fix four position reference labels, four position reference labels form a quadrilateral, and four position reference tag coordinates are respectively T ₁(x ₁, y ₁), T ₂(x ₂, y ₂), T ₃(x ₃, y ₃), T ₄(x ₄, y ₄); Arrange a parameter reference label, coordinate is RT (x ₀, y ₀);

If P _it(d _i) be position reference label T _ipass to the signal intensity of parameter reference label RT at time t, d _ifor reference label T _iwith the actual range of parameter reference label RT; Gather m signal intensity, recording signal intensity if actual is P ₁=(P ₁₁, P ₁₂..., P _1m), then within the time interval gathering m signal intensity, parameter reference label receives the average signal strength P that position reference label transmits _ishown in (4):

${\stackrel{\‾}{P}}_i=\underset{t=1}{\overset{m}{\Σ}}{P}_{it}\left(d_i\right)---\left(4\right)$

Will substitute into (3), then calculate

If T _icoordinate be (x _i, y _i), then RT and T _idistance d _ias shown in Equation 6:

$d_i=\sqrt{{(x_0-x_i)}^2+{(y_0-y_i)}^2}---\left(5\right)$

To two different position reference label T _ivalue, then can form system of equations about parameter n and A as shown in the formula (6):

$\{\begin{array}{c}{d}_1={10}^{\frac{{\stackrel{\‾}{p}}_1-A}{-10n}}\\ d_2={10}^{\frac{{\stackrel{\‾}{p}}_2-A}{-10n}}\end{array}---\left(6\right)$

Environmental parameter n and A can be tried to achieve according to formula 7;

Step 2) environmental parameter in single region determines:

Two neighboring reference labels and parameter reference label RT form a delta-shaped region; Signal is passed to parameter reference label RT and is obtained two signal P by described two neighboring reference labels ₁and P ₂, then the computation process of this Delta Region environment parameter is as following algorithm:

2.1) within a set time, parameter reference label gathers signal intensity m time that two position reference labels propagate, then: P ₁=(P ₁₁, P ₁₂..., P _1m), P ₂=(P ₂₁, P ₂₂..., P _2m);

2.2) average signal strength of two positioning labels propagation is calculated by formula (4) with

2.3) by formula (5) calculating parameter reference label respectively with the distance d of two position reference labels ₁and d ₂;

2.4) environmental parameter A and the n of the delta-shaped region that two position reference labels and parameter reference label RT are formed is tried to achieve by formula (6);

Step 3) design of self-adaptation RFID location system:

3.3) label to be positioned enters the quadrilateral area that four position reference labels are formed;

3.2) data of the signal intensity acquisition of reader acquisition parameter reference label, according to step 2), calculate environmental parameter n and the A of each Delta Region in real time;

3.3) reader is according to the position of label to be positioned, collect the signal intensity of the position reference label of corresponding Delta Region, utilize the environmental parameter calculated in real time, calculate the distance of label to be positioned and four position reference labels according to formula (3);

3.4) according to the distance of label to be positioned and position reference label, the coordinate figure of label to be positioned is calculated.

The explanation of above example just understands core concept of the present invention for helping; Meanwhile, for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.

Claims (1)

1., based on an adaptive approach for reference label RFID location, it is characterized in that, comprise the steps:

Step one) environmental parameter equation is set:

The classical signals propagation model of RSSI is:

$RSSI\left(d\right)=RSSI\left(d_0\right)-10\·n\·log\frac{d}{d_0}+X_{\mathrm{\σ}}---\left(1\right)$

Wherein, n represents path loss index, and d is the distance of target range read write line, d ₀for closely reference distance, RSSI (d) for read write line read to being the tag signal strength at d place with its distance, RSSI (d ₀) arriving and its d for read write line reading ₀the tag signal strength at place, X _σrepresent environmental interference, meet Gaussian distribution X _σ(0, σ ²);

According to formula (1) push type (2):

$d=d_0\·{10}^{\frac{RSSI\left(d_0\right)-RSSI\left(d\right)-x_{\mathrm{\σ}}}{10n}}---\left(2\right)$

D ₀for the distance of read write line and label to be positioned; RSSI (d ₀) for read write line and tag distances to be positioned be d ₀and signal is the signal intensity when free-space propagation; x _σrepresent environmental interference, meet Gaussian distribution x _σ(0, σ ²); N is the loss parameter that in environment, signal is propagated; Make A=RSSI (d ₀)+x _σ, then A meets Gaussian distribution (RSSI (d0), σ ²), then there is formula (3):

$d={10}^{\frac{RSSI\left(d\right)-A}{-10n}}---\left(3\right)$

In the plane at read write line and label place to be positioned, fix four position reference labels, four position reference labels form a quadrilateral, and four position reference tag coordinates are respectively T ₁(x ₁, y ₁), T ₂(x ₂, y ₂), T ₃(x ₃, y ₃), T ₄(x ₄, y ₄); Arrange a parameter reference label RT, coordinate is RT (x ₀, y ₀);

If P _it(d _i) be position reference label T _ipass to the signal intensity of parameter reference label RT at time t, d _ifor reference label T _iwith the actual range of parameter reference label RT; Gather m signal intensity, recording signal intensity if actual is P ₁=(P ₁₁, P ₁₂..., P _1m), then within the time interval gathering m signal intensity, parameter reference label receives the average signal strength P that position reference label transmits _ibe expressed as formula (4):

$\stackrel{\‾}{P_i}=\underset{t=1}{\overset{m}{\Σ}}{P}_{it}\left(d_i\right)---\left(4\right)$

Will substitution formula (3), then calculate

If T _icoordinate be (x _i, y _i), then RT and T _idistance d _ibe expressed as formula (5):

$d_i=\sqrt{{(x_0-x_i)}^2+{(y_0-y_i)}^2}---\left(5\right)$

To two different position reference label T _ivalue, then the system of equations that can form about parameter n and A is formula (6):

$\left\{\begin{array}{c}{d}_1={10}^{\frac{{\stackrel{\‾}{p}}_1-A}{-10n}}\\ d_2={10}^{\frac{{\stackrel{\‾}{p}}_2-A}{-10n}}\end{array}\right.---\left(6\right)$

Environmental parameter n and A can be tried to achieve according to formula (6);

Step 2) environmental parameter in single region determines:

Two neighboring reference labels and parameter reference label RT form a delta-shaped region; Signal is passed to parameter reference label RT and is obtained two signal P by described two neighboring reference labels ₁and P ₂, then the computation process of this Delta Region environment parameter is as following algorithmic procedure:

2.1) within a set time, parameter reference label gathers signal intensity m time that two position reference labels propagate, then: P ₁=(P ₁₁, P ₁₂..., P _1m), P ₂=(P ₂₁, P ₂₂..., P _2m);

2.2) average signal strength of two positioning labels propagation is calculated by formula (4) with

2.3) by formula (5) calculating parameter reference label respectively with the distance d of two position reference labels ₁and d ₂;

2.4) environmental parameter A and the n of the delta-shaped region that two position reference labels and parameter reference label RT are formed is tried to achieve by formula (6);

Step 3) design of self-adaptation RFID location system:

3.1) label to be positioned enters the quadrilateral area that four position reference labels are formed;

3.2) data of the signal intensity acquisition of reader acquisition parameter reference label, according to step 2), calculate environmental parameter n and the A of each Delta Region in real time;

3.3) reader is according to the position of label to be positioned, collect the signal intensity of the position reference label of corresponding Delta Region, utilize the environmental parameter calculated in real time, calculate the distance of label to be positioned and four position reference labels according to formula (3);

3.4) according to the distance of label to be positioned and position reference label, the coordinate figure of label to be positioned is calculated.