Location caching and extrapolation based on speed

• US 7,532,897 B2
• Filed: 08/03/2007
• Issued: 05/12/2009
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: McNamara, Justin, Cenciarelli, Fulvio, Mikan, Jeffrey Clinton
• Primary Examiner(s): Taylor, Barry W
• Application Number:
  US11/833,751
• Publication Number:
  US 20080020784A1
• Time in Patent Office: 648 Days
• Field of Search: 455/456.1, 455/456.2
• US Class Current: 455/456.1
• CPC Class Codes: G08G 1/127 to a central station ; Indicators in a central station
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination

Abstract

A system for locating a device in a wireless network that caches a known location and estimates a location at a given time based on a speed at which the device is moving. The system initially determines plural locations and determines the speed from location. The speed and location information is stored in a cache. The system also includes a mechanism to query the cache. The system extrapolates an estimated location of the device based on the time of the query and speed of the device. Route information may be factored into the determination to account for traffic, transit or travel itinerary.

Claims

1. A method of caching location data associated with a location of a moving mobile device, comprising:

determining a first location of said mobile device;

determining whether said first location is a special location;

determining a speed of said mobile device;

determining a granularity of a geographic area corresponding to said location data to be cached;

determining a first granularity variable, the first granularity variable comprising a time value corresponding to a time period needed to leave the geographic area corresponding to the location data to be cached; and

storing said first location in a cache database together with a first expiration time value for said first location if said first location is not said special location, said first expiration time being based on at least one of said first location of said mobile device, said speed, and said first granularity variable.

2. The method of caching location data according to claim 1, wherein the first location is a present location of the mobile device.

3. The method of caching location data according to claim 1, wherein said special location is one of a plurality of predetermined locations within said geographic area.

4. The method of caching location data according to claim 1, further comprising:

determining a plurality of actual locations of said mobile device, each actual location being associated with a time; and

determining said speed of said mobile device based on said plurality of actual locations and said associated times.

5. The method of caching location data according to claim 4, further comprising:

comparing said actual locations with route data to determine a route on which the mobile device is moving;

receiving route information regarding said route; and

adjusting said determined speed of said mobile device in accordance with said route information.

6. The method caching location data according to claim 5, wherein said route information includes at least one of traffic data, transit data, and travel data.

7. The method of caching location data according to claim 1, further comprising:

determining if said first location matches a previously cached location in the cache database; and

determining a second expiration time of the cached location, the second expiration time being based on the first expiration time and a number of times said first location matches the previously cached location in the cache database.

8. The method of caching location data according to claim 1, further comprising:

determining whether a second granularity variable is associated with said special location;

determining whether said second granularity variable has a granularity restriction, said granularity restriction preventing use of previously cached location data to determine the present location of said mobile device; and

updating said cached location data based on one of said present location, said second granularity variable, and said granularity restriction.

9. The method of caching location data according to claim 8, further comprising:

linking to an external location determining system to determine said present location of the mobile device if the granularity restriction prevents the use of said cached location data; and

updating said cached location data based on information in said external location determining system.

10. The method of caching location data according to claim 1, further comprising:

comparing said first location and said speed with route data to determine a route on which the mobile device is moving;

receiving route information regarding said route; and

adjusting said cached location data in accordance with said route information.

11. The method of caching location data according to claim 10, wherein said route information includes at least one of traffic data, transit data, and travel data.

12. A method of querying a cached location database for a location of a mobile device, comprising:

determining a cached location of a mobile device;

determining a time of a query of a cached location database;

determining a desired granularity of a location associated with the query, the desired granularity corresponding to a size of a geographic area;

determining a granularity variable, the granularity variable corresponding to a time period needed to leave the geographic area corresponding to the desired granularity;

determining an adjusted time of the query, the adjusted time being based on the time of the query and the granularity variable; and

determining whether the cached location in the cached location database has expired, said determination being based on said desired granularity, said granularity variable, and said adjusted time.

13. The method of querying a cached location database according to claim 12, further comprising:

determining whether said cached location is a special location;

determining whether said cached location is associated with a granularity restriction; and

determining a location of said mobile device in accordance with said cached location and said granularity restriction.

14. The method of querying a cached location database according to claim 13, wherein said special location is one of a plurality of predetermined locations within said geographic area.

15. The method of querying a cached location database according to claim 12, further comprising:

determining an actual location of said mobile device if said cached location has expired.

16. The method of querying a cached location database according to claim 15, further comprising linking to an external location determining system to determine said actual location of the mobile device.

17. The method of querying a cached location database according to claim 12, further comprising:

determining a speed associated with said cached location;

comparing said cached location and speed to determine a route on which the mobile device is moving;

receiving route information regarding said route; and

determining whether the cached location in the cached location database has expired further according to said route information.