Earth tiling system for providing regional based service in a mobile satellite communication network

• US 6,389,289 B1
• Filed: 04/12/1999
• Issued: 05/14/2002
• Est. Priority Date: 05/07/1998
• Status: Expired due to Term

• Current Assignee: Hughes Network Systems LLC (Echostar Corporation)
• Original Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Inventors: Fry, John, Mohebbi, Matthew, Mehrotra, Asha, Voce, Daniel A.
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US09/290,487
• Time in Patent Office: 1,128 Days
• Field of Search: 455/427, 455/428, 455/429, 455/430, 455/431, 455/446, 455/448, 455/12.1, 455/13.1, 455/13.2, 455/13.3, 455/517, 455/456.7, 345/428, 283/34, 283/35, 434/150
• US Class Current: 455/456.5
• CPC Class Codes: H04B 7/18547 for geolocalisation of a station position fixing by direction or distance determination G01S5/00

Abstract

A method and apparatus for determining the proper satellite communications service to be provided to a subscriber unit that may be integrated with the geographically defined service areas used in terrestrial cellular communications systems. The pre-existing geographically defined service areas are subdivided into quadrilateral tiles wherein each tile corresponds to a single service area. In addition, the tiles are mapped to a grid having a plurality of regularly spaced grid locations. A lookup table is created that references each grid location to the tiles that overlap the grid locations. The position of the subscriber unit and an approximated region of error within which the subscriber unit is likely to be located are used as input. The approximated region of error is mapped to the grid to identify the grid locations that align with the approximated region of error. Thereafter, the lookup table is accessed to identify the tiles associated with the aligning grid locations and the identified tiles are then used to identify the service area in which the subscriber unit is located so that the proper communications service may be provided. If necessary, geometrical point in polygon inclusion methods and ellipse and polygon intersection methods are used to more accurately identify the tiles of interest.

Claims

1. A method for determining a geographical region within which a target is located, the target being positioned at a target location, using a map of a plurality of geographical regions on the surface of the earth, wherein an estimate of the target location has been previously determined, and wherein the estimate of the target location comprises a region of error, the method comprising the steps of:

determining at least one target grid square, wherein at least a portion of the error region is intersected by the at least one target grid square;

identifying a first set of tiles that intersect the at least one target grid square;

identifying a first set of the geographical regions, the first set of geographical regions comprising the geographical regions that are associated with the tiles in the first set of tiles;

wherein a south polar tile comprises a geographical region that is centered at the south pole and that is bounded by a first line of latitude and wherein a north polar tile comprises a geographical region that is centered at the north pole and that is bounded by a second line of latitude, and further wherein the error region is bounded by an upper boundary and a lower boundary;

comparing the upper boundary of the error region to the second line of latitude; and

comparing the lower boundary of the error region to the first line of latitude; and

if the upper boundary is positioned at or above the second line of latitude, then adding the north polar tile to the first set of tiles; and

if the lower boundary is positioned at or below the first line of latitude, then adding the south polar tile to the first set of tiles.