Satellite communication system

• US 7,480,506 B2
• Filed: 01/16/2007
• Issued: 01/20/2009
• Est. Priority Date: 03/27/2000
• Status: Expired due to Fees

• Current Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Wang, Arthur W.
• Primary Examiner(s): Nguyen; David Q
• Application Number:
  US11/653,516
• Publication Number:
  US 20070117509A1
• Time in Patent Office: 735 Days
• Field of Search: 455/11.2, 455/12.1, 455/13.1, 455/427, 455/428, 455/429, 455/430, 455/431
• US Class Current: 455/427
• CPC Class Codes: H04B 7/195 Non-synchronous stations

Abstract

A communication system has a plurality of ground stations and a plurality of satellites located in a first orbit with respect to the earth. The satellites generate a plurality of beams corresponding to a respective plurality of cell. The plurality of beams has widths that vary relative to position in the orbit to maintain a cell size of the plurality of cells. A plurality of user terminals within the cells receives communication signals from the satellite.

Claims

1. A communications system comprising:

a plurality of ground stations;

a plurality of satellites located in a first orbit with respect to the earth, said satellites generating a plurality of beams corresponding to a respective plurality of cells, said plurality of beams having widths that vary relative to position in the orbit to maintain a cell size of the plurality of cells; and

a plurality of user terminals within the cells receiving communication signals from the satellite.

2. A system as recited in claim 1 wherein the plurality of ground stations is coupled to one selected from the group consisting of an internet service provider, a broadcast television center and a corporate internet.

3. A communications system as recited in claim 1 wherein the plurality of cells are substantially fixed within a service area.

4. A communications system as recited in claim 1 wherein said plurality of beams provide equal capacity density to said cell size.

5. A communications system as recited in claim 1 wherein said first plurality of satellites are disabled when coextensive with a geostationary orbit.

6. A communications system as recited in claim 1 wherein within said plurality of satellites maintain an elevation greater than 30°

relative to the user terminal.

7. A communications system as recited in claim 1 wherein said plurality of satellites operate using a frequency of a GSO satellite.

8. A communications system as recited in claim 1 wherein said first satellite and said second satellite are disabled when coextensive with a geostationary orbit.

9. A method of providing a system of satellites above the earth, the method comprising:

defining at least one geographic service area within which satellite coverage is to be provided;

defining a first orbit having a first satellite and a second orbit having a second satellite therein;

operating said first satellite above a minimum elevation angle above the service area to generate a plurality of fixed cells relative to the earth by varying first beamwidths of first beams generated during operation in a first active arc of the first orbit, said first beamwidths varying relative to position in the first orbit;

handing over operation from the first satellite to the second satellite to maintain at least the minimum elevation angle; and

operating said second satellite to generate the plurality of fixed cells by varying second beamwidths of second beams generated during operation in a second active arc of the second orbit, said second beamwidths varying relative to position in the second orbit.

10. A method as recited in claim 9 wherein said first orbit is an inclined eccentric sub-geosynchronous orbit.

11. A method as recited in claim 9 wherein said second orbit is an inclined eccentric sub-geosynchronous orbit.

12. A method as recited in claim 9 wherein said first orbit is an inclined sub-geosynchronous orbit.

13. A method as recited in claim 9 wherein said second orbit is an inclined sub-geosynchronous orbit.

14. A communications system as recited in claim 9 wherein said first satellite and said second satellite maintain an elevation greater than 30°

relative to the user terminal.

15. A communications system as recited in claim 9 wherein said plurality of satellites operate using a frequency of a GSO satellite.

16. A method of operating a system satellites comprising:

operating said first satellite above a minimum elevation angle for a service area to generate a first plurality of beams corresponding to a plurality of fixed cells relative to the earth by varying first beamwidths of the first plurality of beams generated during operation in a first active arc of a first orbit, said first beamwidths varying relative to position in the first orbit;

handing over operation from the first satellite to a second satellite to maintain at least the minimum elevation angle for the service area; and

operating said second satellite to generate a second plurality of beams corresponding to the plurality of fixed cells by varying second beamwidths of the second plurality of beams generated during operation in a second active arc of a second orbit, said second beamwidths varying relative to position in the second orbit.

17. A method as recited in claim 16 wherein said first orbit is an inclined eccentric sub-geosynchronous orbit.

18. A method as recited in claim 16 wherein said second orbit is an inclined eccentric sub-geosynchronous orbit.

19. A method as recited in claim 16 wherein said first orbit is an inclined sub-geosynchronous orbit.

20. A method as recited in claim 16 wherein said second orbit is an inclined sub-geosynchronous orbit.

21. A method as recited in claim 16 wherein said first satellite and said second satellite are disabled when coextensive with a geostationary orbit.

22. A method as recited in claim 16 wherein said first satellite and said second satellite maintain an elevation greater than 30°

relative to the user terminal.

23. A method as recited in claim 16 wherein said plurality of satellites operate using a frequency of a GSO satellite.