Method for tracking location of a mobile unit

• US 20050014497A1
• Filed: 05/24/2004
• Published: 01/20/2005
• Est. Priority Date: 05/23/2003
• Status: Active Grant

• Current Assignee: Extreme Networks, Inc.
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Goren, David P.
• Granted Patent: US 7,424,300 B2
• Time in Patent Office: Days
• US Class Current: 455/423
• 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

Location of a mobile unit is determined by a combined probability, derived from a first probability for possible locations based on a current sample of radio signal characteristics and a second probability that a unit has moved from a prior location or probable location to each possible location.

Claims

1. A method for locating within an area a mobile unit arranged for a wireless radio communications with fixed devices, wherein location is determined by comparing radio signal characteristics between said mobile unit and said fixed devices to a database relating said radio signal characteristics to location within said area, comprising;

taking sequential samples of said radio signal characteristics;

for each sample of said radio signal characteristics determining two or more possible locations for said mobile unit and assigning a first probability that said mobile unit is at each of said possible locations;

for each possible location determined using a sample after an initial sample, determining a second probability that a mobile unit has moved from each possible location for one or more prior samples to said possible location, said second probability being derived from proximity of said possible location for said one or more prior samples and said possible locations for said current sample; and

selecting a location for said mobile unit as the most probable location for said current sample based on a combination of said first and second probabilities.

2. A method as specified in claim 1 wherein said first probability is assigned according to a comparison of said sampled radio signal to radio signal characteristics for said location in said database.

3. A method as specified in claim 1 wherein said database includes data characterizing quality of radio signal characteristics for locations within said area and wherein said first probability is assigned according to said quality characterizing data.

4. A method as specified in claim 1 wherein said second probability is determined by comparing distance between said locations to expected distance for movement of said mobile unit in a time period between said samples.

5. A method as specified in claim 1 wherein said second probability is modified by factors constituting a barrier to movement between said possible location for said one or more prior samples and said possible location for a current sample.

6. A method for locating within an area a mobile unit arranged for a wireless radio communications with fixed devices, wherein location is determined by comparing radio signal characteristics between said mobile unit and said fixed devices to a database relating said radio signal characteristics to location within said area, comprising;

taking sequential samples of said radio signal characteristics;

for each sample of said radio signal characteristics determining two or more possible locations for said mobile unit and assigning a first probability that said mobile unit is at each of said possible locations;

for each possible location determined using a sample after an initial sample, determining a second probability that a mobile unit has moved from a selected location determined for one or more prior samples to said possible location, said second probability being derived from proximity of said possible location for said one or more prior samples and said possible locations for said current sample; and

selecting a location for said mobile unit as the most probable location for said current sample based on a combination of said first and second probabilities.

7. A method as specified in claim 6 wherein said first probability is assigned according to a comparison of said sampled radio signal to radio signal characteristics for said location in said database.

8. A method as specified in claim 6 wherein said database includes data characterizing quality of radio signal characteristics for locations within said area and wherein said first probability is assigned according to said quality characterizing data.

9. A method as specified in claim 6 wherein said second probability is determined by comparing distance between said locations to expected distance for movement of said mobile unit in a time period between said samples.

10. A method as specified in claim 6 wherein said second probability is modified by factors constituting a barrier to movement between said possible location for said one or more prior samples and said possible location for a current sample.