LOCALIZATION APPARATUS FOR RECOGNIZING LOCATION OF NODE IN SENSOR NETWORK AND METHOD THEREOF

• US 20080080441A1
• Filed: 09/06/2007
• Published: 04/03/2008
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Sun-Joong, Chae, Jong-Suk, Pyo, Cheol-Sig, Lee, Jong-Oh, Park, Jong-Jun
• Granted Patent: US 7,969,913 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

Provided are a localization apparatus for recognizing a location of a node in a sensor network and a method thereof. The method includes the steps of: a) selecting reference nodes from a plurality of anchor nodes to be used for triangulation; and b) obtaining location information of a target node by performing triangulation using the selected reference node, wherein in the step a), the reference nodes are selected by removing anchor nodes having obstacle factor from a plurality of the anchor nodes where the obstacle factor causes error in a distance measured by the target node.

Claims

1. A method for obtaining location information of a node in a sensor network, comprising the steps of:

a) selecting reference nodes from a plurality of anchor nodes to be used for triangulation; and

b) obtaining location information of a target node by performing triangulation using the selected reference node,

wherein in the step a), the reference nodes are selected by removing anchor nodes having obstacle factor from a plurality of the anchor nodes where the obstacle factor causes error in a distance measured by the target node.

2. The method of claim 1, wherein the step a) includes the steps of:

a-1) selecting a test node from a plurality of the anchor nodes;

a-2) selecting a representative reference node for determining whether the selected test node is added as a reference node or not;

a-3) calculating a first distance between the test node and the representative reference node using location information of the test node and the representative reference node;

a-4) measuring a second distance between the test node and the representative reference node; and

a-5) adding the test node as a reference node if a difference of the first distance and the second distance is in an allowable error range.

3. The method of claim 2, wherein the second distance between the test node and the representative node is measured using a received signal strength (RSS) method.

4. The method of claim 2, wherein in the step a-2), the representative reference node is a reference node that forms a triangle having the smallest result of subtracting a longest line from a sum of shorter lines among triangles formed of a plurality of previously selected reference nodes, the test node, and the target node.

5. The method of claim 4, wherein the shorter two lines are a measured distance between the target node and the reference node and a measured distance between the target node and the test node, and the longest line is a calculated distance between the reference node and the test node, which is estimated using location information of the reference node and the test node.

6. The method of claim 2, wherein the step a) further includes the step of:

a-6) selecting an anchor node having the closest calculated distance from the target node among a plurality of the anchor nodes as an initial reference node.

7. The method of claim 2, wherein in the a-5), the test node is not added as a reference node if a result of subtracting the first distance from a sum of a measured distance between the target node and the reference node and a measured distance between the target node and the test node is larger than a threshold value.

8. The method of claim 5, wherein the measured distance between the target node and the reference node and the measured distance between the target node and the test node are measured using a received signal strength (RSS) method.

9. A node apparatus for selecting reference nodes for triangulation to obtain location information of a target node, comprising:

a storing unit for storing location information of the node apparatus;

a distance measuring unit for measuring a first distance to a neighbor node; and

a reference node selecting unit for determining whether the neighbor node is added as a reference node or not,

wherein the reference node selecting unit calculates a second distance to the neighbor node using the stored location information and location information of the neighbor node and selects the neighbor node as a reference node to be used for triangulation if a difference of the measured first distance and the calculated second distance is in an allowable error range.

10. The node apparatus of claim 9, wherein the distance measuring unit uses a received signal strength (RSS) method to measure the first distance to the neighbor node.

11. The node apparatus of claim 9, wherein the allowable error range is a value equivalent to two times of an average value of measured distances measured in an environment having no obstacle between the target node and the neighbor node.

12. The node apparatus of claim 9, further comprising:

a transmitting unit for transmitting the calculated second distance to the target node if the neighbor node is selected as a reference for triangulation.

13. A node apparatus for obtaining location information of a target node using triangulation in a sensor network, comprising:

a location information obtaining unit for obtaining a target node by performing triangulation using reference nodes selected from neighbor nodes of the target node; and

a representative reference node selecting unit for selecting one having a most similar line of sight (LoS) characteristic between the target node and oneself comparing to a LoS characteristic between the target node and the test node from the reference nodes as a representative reference node,

wherein the location information obtaining unit adds the test node as a new reference node to be used for triangulation if the selected representative reference node informs the location information obtaining unit that a measured distance between the test node and the representative reference node is in an allowable error range.

14. The node apparatus of claim 13, wherein the representative reference node selecting unit selects a reference node having a smallest result of subtracting a third distance between the test node and a reference node from a sum of a first measured distance between the target node and a reference node and a second measured distance between the target node and the test node as a representative reference node.

15. The node apparatus of claim 14, wherein the third distance between the test node and the reference node is calculated using location information of the test node and the reference node.

16. The node apparatus of claim 15, wherein the first measured distance between the target node and a reference node and the second measured distance between the target node and the test node are calculated using a received signal strength (RSS) method.