Wireless tracking system and method utilizing tags with variable power level transmissions

• US 7,884,712 B2
• Filed: 05/02/2008
• Issued: 02/08/2011
• Est. Priority Date: 05/08/2007
• Status: Active Grant

• Current Assignee: Centrak Incorporated (Halma PLC)
• Original Assignee: Awarepoint Corporation
• Inventors: Caliri, Dyami, Nierenberg, Nicolas C
• Primary Examiner(s): Bugg; George A
• Assistant Examiner(s): LAI, ANNE VIET NGA
• Application Number:
  US12/114,740
• Publication Number:
  US 20080278327A1
• Time in Patent Office: 1,012 Days
• Field of Search: 340/10.1, 340/10.3, 340/10.4, 340/539.13, 340/825.49, 340/572.1, 340/572.4, 340/573.1, 340/573.3, 340/573.4, 340/539.11, 34053921-53923, 340/539.32, 342/357.01, 342/463, 455/456.1
• US Class Current: 340/539.13
• CPC Class Codes: G08C 21/00 Systems for transmitting the position of an object with respect to a predetermined reference system, e.g. tele-autographic system

Abstract

The present invention provides a solution to mistaken location calculations based on multipath effects. The present invention utilizes tags attached to objects that transmit signals at various power levels for reception by sensors stationed throughout a facility. Sensor readings at the various power levels are utilized to determine the location of the tagged object.

Claims

1. A method for determining a real-time location of an object within an indoor facility, the method comprising:

generating a first reading set from a primary plurality of sensor readings transmitted from a tag at the first energy level, the tag attached to the object;

sorting the first reading set by a plurality of primary physical regions;

selecting a first primary physical region of the plurality of primary physical regions, the first physical region composed of a first plurality of sensor readings having a highest average signal strength from the first reading set;

sorting the first plurality of sensor readings into a second plurality of sensor readings, the second plurality of sensor readings corresponding to a zone within the first primary physical region;

selecting a selected primary zone having the highest average reading from the second plurality of sensor readings;

calculating the first preliminary location of the object from a plurality of the highest sensor readings from the second plurality of sensor readings corresponding to the selected primary zone;

calculating a second preliminary location of the object from a second plurality of sensor readings generated at a second power level, the second power level less than the first power level; and

analyzing the first preliminary location of the object and the second preliminary location of the object to determine a real-time location of the object within the indoor facility.

2. The method according to claim 1 wherein the second power level is 50% of the first power level.

3. The method according to claim 1 wherein calculating the second preliminary location comprises:

generating a second reading set from a secondary plurality of sensor readings transmitted from the tag at the second energy level;

sorting the second reading set by a plurality of secondary physical regions;

selecting a first secondary physical region of the plurality of secondary physical regions, the first secondary physical region composed of a first plurality of sensor readings having a highest average signal strength from the second reading set;

sorting the first plurality of sensor readings into a second plurality of sensor readings, the second plurality of sensor readings corresponding to a zone within the first secondary physical region;

selecting a selected secondary zone having the highest average reading from the second plurality of sensor readings; and

calculating the second preliminary location of the object from a plurality of the highest sensor readings from the second plurality of sensor readings corresponding to the selected secondary zone.

4. The method according to claim 1 wherein the first power level is 1 milli-Watt, the second power level is 0.5 milli-Watt, and third power level is 0.25 milli-Watt.