Wireless Tracking System And Method With Multipath Error Mitigation

• US 20090219210A1
• Filed: 05/10/2009
• Published: 09/03/2009
• Est. Priority Date: 10/22/2003
• Status: Abandoned Application

• Current Assignee: Clinical Patents, LLC (Halma PLC)
• Original Assignee: Awarepoint Corporation
• Inventors: Caliri, Dyami, Smith, Derek
• Application Number:
  US12/463,411
• Publication Number:
  US 20090219210A1
• Time in Patent Office: Days
• US Class Current: 342/451
• 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 location of an object within a predetermined environment, the method comprising:

transmitting a plurality of radiofrequency signals for a wireless tracking device to a positioning engine, each of the plurality of radiofrequency signals corresponding to a signal transmitter within the environment;

processing each of the plurality of radiofrequency signals to determine the location of the signal transmitter for each of the plurality of radiofrequency signals;

determining a probable region of the object based on the location of a of the signal transmitter for each of the plurality of radiofrequency signals;

weighting any of the plurality of radiofrequency signals corresponding from a fixed signal transmitter located outside of the probable region of the object; and

calculating the position of the object within the predetermined environment using only the plurality of radiofrequency signals corresponding to a fixed signal transmitter within the probable region of the object.

2. The method according to claim 1 wherein the predetermined environment is a hospital and the probable region of the object is a room in the hospital.

3. The method according to claim 1 wherein transmitting a plurality of radio frequency signals for a wireless tracking device to a positioning engine comprises:

transmitting radio frequency signals from the wireless tracking device comprising signal strength, link quality, time of transmission and identification of the wireless tracking device;

receiving the radio frequency signals at a plurality of stationary sensors positioned within the predetermined environment; and

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

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

5. The method according to claim 1 further comprising comparing the calculated location of the object within the predetermined environment to a previously calculated location for the object.

6. The method according to claim 5 further comprising monitoring the motion state of the object to confirm movement of the object from the previously calculated location to the location of the object within the predetermined environment.

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

a mapped space of a physical environment of the indoor facility; and

a processor comprising

means for updating the mapped space in response to received measurements of the physical environment from one or more stationary sensors located within the indoor facility,

means for generating a plurality of location hypotheses for a non-stationary object within the physical environment, at least one of the location hypotheses computed in response to measurement received from the non-stationary object and the mapped space, and

means for generating a location estimate based on one or more of the plurality of location hypotheses, wherein one or more of the plurality of location hypotheses are selected based on a probability associated respectively therewith, and wherein a probability is computed in association with a plurality of known barriers in the physical space.

8. The system according to claim 7 wherein the indoor facility is a hospital.

9. The system according to claim 7 wherein the measurement from the object is generated from a radiofrequency signal from a tag.

10. The system according to claim 9 wherein the radiofrequency signal from a tag comprises signal strength, link quality, time and identification of the tag.

11. The system according to claim 10 wherein the processor is located at a remote server in communication with the plurality of stationary sensors through at least one bridge device.

12. The system according to claim 9 wherein the tag transmits a radiofrequency signal of approximately 2.48 GigaHertz, and each of the plurality of stationary sensors communicates utilizing a 802.15.4 protocol.

13. 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;

a mapped space of a physical environment of the indoor facility;

a processor comprising

means for updating the mapped space in response to received measurements of the physical environment from one or more stationary sensors located within the indoor facility,

means for generating a plurality of location hypotheses for each of the plurality of non-stationary objects located within the physical environment, at least one of the location hypotheses computed in response to measurement received from a non-stationary object of the plurality of non-stationary objects and the mapped space, and

means for generating a location estimate based on one or more of the plurality of location hypotheses, wherein one or more of the plurality of location hypotheses are selected based on a probability associated respectively therewith, and wherein a probability is computed in association with a plurality of known barriers in the physical space.

14. The system according to claim 13 wherein the indoor facility is a hospital.

15. The system according to claim 13 wherein the measurement from the object is generated from a radiofrequency signal from the tag.

16. The system according to claim 15 wherein the radiofrequency signal from a tag comprises signal strength, link quality, time and identification of the tag.

17. The system according to claim 13 wherein the processor is located at a remote server in communication with the plurality of stationary sensors through at least one bridge device.

18. The system according to claim 15 wherein the tag transmits a radiofrequency signal of approximately 2.48 GigaHertz, and each of the plurality of stationary sensors communicates utilizing a 802.15.4 protocol.

19. The system according to claim 13 wherein a radial basis function is utilized by the processor in generating a location estimate.

20. The system according to claim 13 wherein the processor further comprises means for determining if the calculated location is consistent with a previous location.