Location determination using RF fingerprints

• US 20050037776A1
• Filed: 08/23/2004
• Published: 02/17/2005
• 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 7,725,111 B2
• Time in Patent Office: Days
• US Class Current: 455/456.100
• 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 comprising:

receiving a first RF fingerprint for a first signal that traverses a first path between a mobile unit and a base station; and

estimating the location of said mobile unit based on said first RF fingerprint.

2. The method of claim 1 wherein said mobile unit generates said first RF fingerprint.

3. The method of claim 1 wherein said base station generates said first RF fingerprint.

4. The method of claim 1 wherein said first RF fingerprint comprises a signal-strength measurement.

5. The method of claim 1 wherein said first RF fingerprint comprises phase information of said first signal.

6. The method of claim 1 wherein said first RF fingerprint is generated at a first time, and further comprising:

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

7. The method of claim 6 further comprising:

receiving a second RF fingerprint for said first signal, wherein said second RF fingerprint is generated at a second time; and

generating a second probability distribution for the location of said mobile unit based on said second RF fingerprint; and

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

8. A method comprising:

receiving (i) a first RF fingerprint for a first signal that traverses a first path between a mobile unit and base station and (ii) a first estimate of the location of said mobile unit based on the global positioning system; and

generating a second estimate of the location of said mobile unit based on (i) said first RF fingerprint and (ii) said first estimate of the location of said mobile unit.

9. The method of claim 8 wherein said first RF fingerprint comprises a signal-strength measurement.

10. The method of claim 8 wherein said first RF fingerprint comprises phase information of said first signal.

11. The method of claim 8 wherein the generation of said second estimate comprises comparing said first RF fingerprint to a reference database containing RF fingerprints to various locations.

12. The method of claim 8 wherein said mobile unit records said first RF fingerprint.

13. The method of claim 8 wherein said base station records said first RF fingerprint.

14. The method of claim 8 further comprising receiving (iii) a second RF fingerprint for a second signal that traverses a second path between a mobile unit and base station, and

wherein the generation of said second estimate of the location of said mobile unit is also based on (iii) said second RF fingerprint.