Location determination using RF fingerprints

• US 20040259575A1
• Filed: 08/03/2004
• Published: 12/23/2004
• Est. Priority Date: 09/22/1998
• Status: Active Grant

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: Polaris Wireless Incorporated
• Inventors: Rao, Padmanabha R., Siccardo, Paolo, Dressler, Robert M., Spain, David S., Perez-Breva, Luis, Chong, Chee-Yee
• Granted Patent: US 7,167,714 B2
• Time in Patent Office: Days
• US Class Current: 455/456.5
• CPC Class Codes: G01S 5/0236 Assistance data, e.g. base station almanac
• CPC Class Codes: G01S 5/02526 using non-dedicated equipment, e.g. user equipment or crowd-sourcing
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method for determining the location of a mobile unit (MU) in a wireless communication system and presenting it to a remote party. The location of a remote MU is determined by comparing a snapshot of a predefined portion of the radio-frequency (RF) spectrum taken by the MU to a reference database containing multiple snapshots taken at various locations. The result of the comparison is used to determine if the MU is at a specific location. The comparison may be made in the MU, or at some other location situated remotely from the MU. In the latter case, sufficient information regarding the captured fingerprint is transmitted from the MU to the remote location. The database may be pre-compiled or generated on-line.

Claims

1. A method for locating a position of a mobile unit in a wireless communication network, said method comprising:

receiving a first RF fingerprint from said mobile unit, wherein said first RF fingerprint is indicative of a portion of the RF spectrum at said mobile unit at a first time;

generating a first probability distribution for said position of said mobile unit based on said first fingerprint;

receiving a second RF fingerprint from said mobile unit, wherein said second RF fingerprint is indicative of said portion of the RF spectrum at said mobile unit at a second time that is after said first time; and

generating a second probability distribution for said position of said mobile unit based on a combination of said first probability distribution and said second fingerprint.

2. The method of claim 1 further comprising generating a filtered estimate of said position of said mobile unit at said second time based on said second probability distribution.

3. The method of claim 1 further comprising generating a smoothed estimate of said position of said mobile unit said first time based on said second probability distribution.

4. The method of claim 1 further comprising modifying said first probability distribution based on at least one possible motion of said mobile unit between said first time and said second time.

5. The method of claim 1 further comprising generating an estimate of said position of said mobile unit at said first time based on said second probability distribution and the expected location of said mobile unit.

6. The method of claim 1 further comprising generating an estimate of said position of said mobile unit at said first time based on said second probability distribution and the most probable location of said mobile unit.

7. A method comprising:

receiving a first RF fingerprint that is indicative of the signal attenuation between a mobile unit and at least one base station at a first time;

generating a first probability distribution for a location of said mobile unit based on said first RF fingerprint;

receiving a second RF fingerprint that is indicative of the signal attenuation between said mobile unit and at least one base station at a second time that is after said first time; and

generating a second probability distribution for a location of said mobile unit based on a combination of said first probability distribution and said second fingerprint.

8. The method of claim 7 further comprising generating a filtered estimate of said position of said mobile unit at said second time based on said second probability distribution.

9. The method of claim 7 further comprising generating a smoothed estimate of said position of said mobile unit said first time based on said second probability distribution.

10. The method of claim 7 further comprising modifying said first probability distribution based on at least one possible motion of said mobile unit between said first time and said second time.

11. The method of claim 7 further comprising generating an estimate of said position of said mobile unit at said first time based on said second probability distribution and the expected location of said mobile unit.

12. The method of claim 7 further comprising generating an estimate of said position of said mobile unit at said first time based on said second probability distribution and the most probable location of said mobile unit.

13. A method comprising:

receiving a first RF fingerprint and a second RF fingerprint for a mobile unit, wherein said first RF fingerprint is taken at a first time, and wherein said second RF fingerprint is taken at a second time;

estimating the location of said mobile unit at said second time based on said first RF fingerprint and said second RF fingerprint.

14. The method of claim 13 further comprising estimating the location of said mobile unit at said first time based on said first RF fingerprint.

15. The method of claim 13 wherein said first RF fingerprint is indicative of the signal attenuation between said mobile unit and at least one base station.