Location determination using RF fingerprinting

• US 6,269,246 B1
• Filed: 09/22/1998
• Issued: 07/31/2001
• Est. Priority Date: 09/22/1998
• Status: Expired due to Term

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: PNM Incorporated (Union Pacific Corporation)
• Inventors: Rao, Padmanabha R., Siccardo, Paolo L.
• Primary Examiner(s): BANKS HAROLD, MARSHA DENISE
• Application Number:
  US09/158,296
• Time in Patent Office: 1,043 Days
• Field of Search: 455/410, 455/440, 455/456, 455/454, 455/186.1, 455/FOR.100, 342/457
• US Class Current: 455/456.3
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The location of a mobile unit (MU) in a wireless communication system 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 the fly.

Claims

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

capturing a first fingerprint of the RF spectrum in the mobile unit and storing therewith a time of capture;

comparing said first fingerprint with a multiplicity of fingerprints, each of said multiplicity of fingerprints having an associated location, wherein said multiplicity of fingerprints is designed, by including for at least some fingerprints of said multiplicity of fingerprints respective indications of time of capture to take into account a dynamic, but predetermined, change in signal power as a function of time for some signal frequencies in the RF spectrum;

selecting a second fingerprint from said multiplicity of fingerprints as the closest matching fingerprint to said first fingerprint, wherein said closest matching fingerprint is selected based on the combination of said indications of time of capture for said multiplicity of fingerprints and said time of capture for said first fingerprint so as to account for said dynamic, but predetermined change in signal power as a function of time for some signal frequencies in the RF spectrum; and

assigning a location corresponding to said second fingerprint to said mobile unit.

2. The method of claim 1 wherein said first and second fingerprints are generated using a predetermined portion of the RF spectrum.

3. The method of claim 2 wherein said predetermined portion of the RF spectrum overlaps with the portion of the RF spectrum utilized by the wireless communication network.

4. The method of claim 2 wherein said predetermined portion of the RF spectrum overlaps with the portion of the spectrum utilized by commercial FM radio broadcasting stations.

5. The method of claim 1 wherein said first and second fingerprints are generated using a predetermined set of signal parameters.

6. The method of claim 1 wherein said multiplicity of fingerprints is stored in the mobile unit.

7. The method of claim 6 wherein said location assignment is performed by the mobile unit.

8. The method of claim 1 wherein said multiplicity of fingerprints is stored in an Other Party that is linked to the mobile unit via the wireless communication network.

9. The method of claim 8 wherein said first fingerprint is processed and transmitted over the wireless communication network to the Other Party.

10. The method of claim 9 wherein said location assignment is performed by the Other Party.

11. A method for locating the position of a mobile unit in a wireless communication network, said method comprising the following steps:

capturing a first fingerprint of the RF spectrum in the mobile unit and storing therewith a time of capture;

comparing said first fingerprint with a fingerprint database, each entry in said fingerprint database having an associated location, wherein said fingerprint database is designed, by including for at least some of the entries in the fingerprint database respective indications of time of capture to take into account a dynamic, but predetermined, change in signal power as a function of time for at least some signal frequencies in the RF spectrum;

selecting a second fingerprint from said fingerprint database as the closest matching fingerprint to said first fingerprint, wherein said closest matching fingerprint is selected based on the combination of said indications of time of capture for each entry stored in said fingerprint database and said time of capture for said first fingerprint so as to account for said dynamic, but predetermined change in signal power as a function of time for at least some signal frequencies in the RF spectrum; and

assigning a location corresponding to said second fingerprint to said mobile unit.

12. The method of claim 11 wherein said first and second fingerprints are generated using a predetermined portion of the RF spectrum.

13. The method of claim 11 wherein said multiplicity of fingerprints is stored in the mobile unit.

14. The method of claim 13 wherein said location assignment is preformed by the mobiled unit.

15. The method of claim 11 wherein said multiplicity of fingerprints is stored in an Other Party that is linked to the mobile unit via the wireless communication network.

16. The method of claim 15 wherein said first fingerprint is processed and transmitted over the wireless communication network to the Other Party.

17. The method of claim 16 wherein said location assignment is performed by the Other Party.

18. The method of claim 11 wherein said predetermined portion of the RF spectrum overlaps with the portion of the RF spectrum utilized by the wireless communication network.

19. The method of claim 11 wherein said predetermined portion of the RF spectrum overlap with the portion of the spectrum utilized commercial FM radio broadcasting stations.