Wireless Tracking System And Method Utilizing Tags With Variable Power Level Transmissions

• US 20080278327A1
• Filed: 05/02/2008
• Published: 11/13/2008
• 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.
• Granted Patent: US 7,884,712 B2
• Time in Patent Office: Days
• US Class Current: 340/572.1
• 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 a first energy level, a second reading set from a secondary plurality of sensor readings transmitted from a tag at a second energy level and a third reading set from a tertiary plurality of sensor readings transmitted from a tag at a third energy level, the tag attached to the object;

sorting each of the first, second and third reading sets by a plurality of physical regions;

selecting a first physical region of the plurality of physical regions for each of the first, second and third energy levels, the first physical region composed of a first plurality of sensor readings having the highest average signal strength for each of the first, second and third energy levels;

sorting the first plurality of sensor readings into a second plurality of sensor readings for each of the first, second and third energy levels, each of the second plurality of sensor readings corresponding to a zone within the first physical region;

selecting a selected zone having the highest average reading for each of the first, second and third energy levels;

calculating a real-time location of the object from a plurality of the highest sensor readings from the second plurality of sensor readings corresponding to the selected zone for each of the first, second and third energy levels; and

comparing each of the real-time locations for each of the first, second and third energy levels to determine a new real-time location of the object.

2. The method according to claim 1 wherein the first, second and third reading sets comprise signal strength, link quality, time and identification of the tag.

3. The method according to claim 1 further comprising displaying the new real-time location of the object on a graphical user interface.

4. The method according to claim 1 further comprising comparing the calculated real-time location of the object for each of the first, second and third energy levels to a previously calculated location for the object.

5. The method according to claim 4 further comprising monitoring the motion state of the object to confirm movement of the object from the previously calculated location to the true real-time location.

6. The method according to claim 1 wherein the indoor facility is a hospital, each of the plurality of physical regions is a floor of the hospital, and the selected zone is a group of rooms on a floor of the hospital.

7. The method according to claim 1 wherein the plurality of sensor readings of the reading set comprises at least one sensor reading for the tag, and each of the plurality of sensor readings originates from a single stationary sensor positioned within the indoor facility.

8. The method according to claim 1 wherein each of the plurality of sensor readings is a radio frequency transmission from the tag.

9. The method according to claim 1 wherein obtaining a plurality of sensor readings from a tag attached to the object comprises:

transmitting a radio frequency transmission from the tag;

receiving the radio frequency transmission at a plurality of stationary sensors positioned within the indoor facility; and

transmitting a signal strength, a link quality, a time of transmission and a identification of the tag from each of the plurality of stationary sensors to a server for processing.

10. A system for providing real-time location information for a plurality of non-stationary objects within an indoor facility, the system comprising:

a plurality of stationary sensors, each of the plurality of stationary sensors positioned within the indoor facility;

a plurality of tags, each of the plurality of tags attached to one of the plurality of non-stationary objects, each of the plurality of tags having means for wirelessly transmitting radiofrequency transmissions to each of the plurality of stationary sensors wherein each of the plurality of stationary sensors obtain tag specific data at least three different energy levels from the radiofrequency transmissions; and

means for processing the tag specific data at each of the three different energy levels to obtain a real-time first plurality of sensor readings for the tag at a first energy level, a real-time second plurality of sensor readings for the tag at a second energy level, and a real-time third plurality of sensor readings for the tag at a third energy level, to select a physical region within the indoor facility having sensor readings from each of the first plurality of sensor readings, second plurality of sensor readings and third plurality of sensor readings, and to calculate the position of an object from the sensor readings positioned within the selected physical region.

11. The system according to claim 10 wherein the tag specific data comprises signal strength, link quality, time and identification of the tag.

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

calculating a first preliminary location of the object from a first plurality of sensor readings generated at a first power level;

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.

13. The method according to claim 12 wherein the second power level is 50% of the first power level.

14. The method according to claim 12 wherein calculating the first preliminary location comprises:

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; and

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.

15. The method according to claim 14 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.

16. The method according to claim 12 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.

17. The method according to claim 12 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 comprises:

determining a zone within the indoor facility that contains the first preliminary location of the object and the second preliminary location of the object; and

calculating the real-time location of the object from the position of sensors within the zone utilizing a radial basis function.

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

calculating a plurality of preliminary locations of the object, each of the plurality of preliminary locations generated from a plurality of sensor readings set at a unique power level; and

analyzing each of the plurality of preliminary locations of the object to determine a real-time location of the object within the indoor facility.

19. The method according to claim 18 wherein the plurality of preliminary locations ranges from two to ten, and the unique power levels range from two to ten, and each unique power level is at least 10% different than any other unique power level.

20. The method according to claim 18 wherein analyzing each of the plurality of preliminary locations of the object to determine a real-time location of the object within the indoor facility comprises:

determining a zone within the indoor facility that contains each of the plurality of locations of the object; and

calculating the real-time location of the object from a position of a plurality of sensors within the zone utilizing a radial basis function.