Location tracking system and method

• US 20060082457A1
• Filed: 10/17/2005
• Published: 04/20/2006
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group)
• Original Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group)
• Inventors: Koo, Ji-hun, Park, Kyung-ho, Kang, Woo-shik, Koo, Si-gyoung, Artem, Moutchkaev, Dehaut, Pierre
• Granted Patent: US 7,417,544 B2
• Time in Patent Office: Days
• US Class Current: 340/572.100
• CPC Class Codes: G06Q 10/06 Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00

Abstract

A location tracking system and method are provided. The location tracking system includes a plurality of tags which receive a read signal and which output tag signals, a reader which transmits the read signal to the tags, receives the tag signals, and identifies tag IDs from the tag signals, and a data processing system which stores location information of the tags and determines the location of the reader by using the tag IDs received from the reader based on the location information.

Claims

1. A location tracking system comprising:

a plurality of tags which receive a read signal and output tag signals;

a reader which transmits the read signal to the tags, receives the tag signals, and identifies tag identifiers (Ids) from the tag signals; and

a data processing system which stores location information of the tags and determines a location of the reader by using the tag IDs that are received from the reader based on the location information.

2. The system according to claim 1, wherein the plurality of tags are provided at an indoor zenith in a lattice shape with a predetermined spacing interval.

3. The system according to claim 1, wherein the reader adjusts a strength of the read signal according to a specified adjusting signal and outputs an adjusted read signal.

4. The system according to claim 3, wherein the data processing system calculates the location of the reader based on a strength of the read signal and tag IDs of tags which output tag signals according to the strength of the read signal.

5. The system according to claim 4, wherein the location of the reader is calculated using:

[x, y]=Σ

W_i(P_m−

P_n, P_m)Cⁱ_x,y

wherein i is an index of a read tag, w_i is a weight, (P_m−

P_n) is a difference between minimum strengths of the read signal by which an m^th tag and an n^th tag can be read, and Cⁱ_x,y is a location (x, y) of an i^th tag.

6. The system according to claim 4, wherein the location of the reader is calculated using:

$\begin{array}{c}{x}_{\mathrm{reader}}=\frac{1}{N}<br><br>\underset{i=1}{\overset{N}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>w_{m,n}<br><br>x_i^{\mathrm{tag}}\\ y_{\mathrm{reader}}=\frac{1}{N}<br><br>\underset{i=1}{\overset{N}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>w_{m,n}<br><br>y_i^{\mathrm{tag}}\end{array}$

where x_reader and y_reader are coordinates (x, y) of the reader, x^tag and y^tag are coordinates (x, y) of an i^th tag, N is a total number of read tags, and w_m,n is a weight.

7. The system according to claim 6, wherein the weight is inversely proportional to a difference between a minimum strength of a read signal that detects an m^th tag and a minimum strength of a read signal that detects an n^th tag.

8. The system according to claim 3, wherein the reader further comprises a tag signal measuring unit which measures strengths of the tag signals.

9. The system according to claim 8, wherein the data processing system estimates a distance from directly beneath a central tag, which corresponds to a strongest tag signal measured by the tag signal measuring unit.

10. The system according to claim 9, wherein the data processing system previously stores a distance directly beneath each of the plurality of tags and corresponding strengths of the tag signals.

11. The system according to claim 8, wherein the data processing system calculates an angle φ

, between a line connecting a central tag and the reader and a line extending directly downward from the central tag, using strengths of signals output from tags closest to the central tag as;

$\underset{\mathrm{\phi <br><br>}}{\min }<br><br>\left[{\left(\frac{P_{\mathrm{BS}<br><br>\text{\hspace{1em}<br><br>}<br><br>1}}{P_e}-G_1<br><br>\left(\mathrm{\phi <br><br>}\right)\right)}^2+{\left(\frac{P_{\mathrm{BS}<br><br>\text{\hspace{1em}<br><br>}<br><br>2}}{P_e}-G_2<br><br>\left(\mathrm{\phi <br><br>}\right)\right)}^2\right]$

wherein, P_BS1 and P_BS2 are measured strengths of a first tag signal and a second tag signal, respectively, P_e is a maximum strength of the read signal, and G₁ and G₂ are antenna gains of a first tag and a second tag, respectively, and

wherein the location of the reader is corrected using the calculated angle.

12. The system according to claim 8, wherein the reader is internally or externally assembled in a movable terminal.

13. A method of tracking a location of a reader using a plurality of tags with which the reader can communicate and which are provided at an indoor zenith, the method comprising:

outputting a read signal by the reader;

receiving first tag signals generated as a result of the read signal and identifying tag identifiers (IDs) of tags by using the first tag signals;

adjusting the strength of the read signal and outputting an adjusted read signal by the reader;

receiving second tag signals generated as a result of the adjusted read signal and identifying tag IDs of tags by using the received second tag signals; and

calculating the location of the reader by using a strength of the read signal, a strength of the adjusted read signal, and tag IDs which correspond to the strength of the read signal and the strength of adjusted read signal.

14. The method according to claim 13, wherein adjusting the strength of the read signal and outputting an adjusted read signal, and receiving second tag signals and identifying tag IDs is repeated until a specified number of tags output tag signals.

15. The method according to claim 13, further comprising:

before calculating the location of the reader, storing identified tag IDs and location information regarding the identified tag IDs.

16. The method according to claim 13, wherein the location of the reader is calculated using:

[x, y]=ρ

w_i(P_m−

P_n, P_m)Cⁱ_w,y

wherein i is a read tag index, w_i is a weight, (P_m−

P_n) is a difference between minimum strengths of the read signal by which an m^th tag and an n^th tag can be read, and Cⁱ_x,y is a location (x, y) of an i^th tag.

17. The method according to claim 13, wherein the location of the reader is calculated using:

$\begin{array}{c}{x}_{\mathrm{reader}}=\frac{1}{N}<br><br>\underset{i=1}{\overset{N}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>w_{m,n}<br><br>x_i^{\mathrm{tag}}\\ y_{\mathrm{reader}}=\frac{1}{N}<br><br>\underset{i=1}{\overset{N}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>w_{m,n}<br><br>y_i^{\mathrm{tag}}\end{array}$

wherein x_reader and y_reader are coordinates (x, y) of the reader, x^tag and y^tag are coordinates (x, y) of the i^th tag, N is a total number of read tags, and w_m,n is a weight.

18. The method according to claim 17, wherein the weight is inversely proportional to a difference between a minimum strength of a read signal that detects an m^th tag and a minimum strength of a read signal that detects an n^th tag.

19. The method according to claim 13, further comprising:

after receiving the first tag signals, measuring strengths of the first tag signals; and

after receiving the second tag signals, measuring strengths of the second tag signals.

20. The method according to claim 19, further comprising correcting the location of the reader by estimating a distance from directly beneath a central tag, which corresponds to a strongest measured tag signal.

21. The method according to claim 20, further comprising previously storing a strength of a corresponding tag signal at a distance directly beneath each of the plurality of tags.

22. The method according to claim 21, further comprising calculating an angle φ

, between a line connecting the central tag and the reader and a line extending directly downward from the central tag, using strengths of signals output from tags closest to the central tag using the expression;

$\underset{\mathrm{\phi <br><br>}}{\min }<br><br>\left[{\left(\frac{P_{\mathrm{BS}<br><br>\text{\hspace{1em}<br><br>}<br><br>1}}{P_e}-G_1<br><br>\left(\mathrm{\phi <br><br>}\right)\right)}^2+{\left(\frac{P_{\mathrm{BS}<br><br>\text{\hspace{1em}<br><br>}<br><br>2}}{P_e}-G_2<br><br>\left(\mathrm{\phi <br><br>}\right)\right)}^2\right]$

wherein, P_BS1 and P_BS2 are measured strengths of a first tag signal and a second tag signal, respectively, P_e is a maximum strength of the read signal, and G₁ and G₂ are antenna gains of a first tag and a second tag, respectively, and

wherein the location of the reader is corrected using the calculated angle.