Wireless tracking system and method with multipath error mitigation

• US 7,545,326 B2
• Filed: 02/07/2007
• Issued: 06/09/2009
• Est. Priority Date: 10/22/2003
• Status: Active Grant

• Current Assignee: Centrak Incorporated (Halma PLC)
• Original Assignee: Awarepoint Corporation
• Inventors: Caliri, Dyami, Smith, Derek
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US11/672,047
• Publication Number:
  US 20080012767A1
• Time in Patent Office: 853 Days
• Field of Search: 342/463, 342/465, 342/450
• US Class Current: 342/465
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A system (50) and method (300) for providing multipath error mitigation for real-time wireless tracking of an object (100) is disclosed herein. A plurality of sensor readings are obtained from a tag (60) attached to an object (100) within an indoor facility (70). A plurality of reading sets are generated and sorted by zones. A zone with the highest average reading is preferably selected and the location of the object (100) is calculated based on the selected zone readings. In this manner, faulty position readings are eliminated from the location calculation thereby allowing for more accurate tracking of the object (100) within the indoor facility (70).

Claims

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

obtaining a plurality of sensor readings from a tag attached to the object;

generating a reading set comprising the plurality of sensor readings;

sorting the reading set by a plurality of physical regions;

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

sorting the first plurality of sensor readings into a second plurality of sensor readings, 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; and

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.

2. The method according to claim 1 wherein the sensor readings comprise signal strength, link quality, time and identification of the tag.

3. The method according to claim 1 further comprising displaying the 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 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 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 room on a floor of the hospital.

7. The method according to claim 1 wherein the plurality of sensor readings of the reading set comprises from eight to thirty sensor readings 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 comprising signal strength, link quality, time of transmission and identification of the tag;

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

transmitting the signal strength, the link quality, the time of transmission and the 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 to each of the plurality of stationary sensors tag specific data; and

means for processing the tag specific data to obtain a real-time reading set for the tag, to process the reading set to determine a first plurality of sensor readings with the highest average reading, to select a physical region within the indoor facility having the highest average reading, to select a zone within the physical region having the highest average reading, and to calculate the position of an object from the sensor readings positioned within the selected zone.

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

12. The system according to claim 10 wherein the indoor facility is a hospital, the physical region is a floor of the hospital, and the selected zone is a room on a floor of the hospital.

13. The system according to claim 10 wherein the processing means is a server in communication with the plurality of stationary sensors through at least one bridge.

14. The system according to claim 10 wherein each of the plurality of tags transmits a radiofrequency transmission of approximately 2.48 GigaHertz, and each of the plurality of stationary sensors communicates utilizing a 802.15.4 protocol.

15. The system according to claim 10 further comprising means for eliminating sensor readings not associated with the selected zone.