Satellite communication service with non-congruent sub-beam coverage

• US 6,301,476 B1
• Filed: 08/07/2000
• Issued: 10/09/2001
• Est. Priority Date: 10/09/1997
• Status: Expired due to Term

• Current Assignee: Globalstar Incorporated
• Original Assignee: Globalstar Incorporated
• Inventors: Hirshfield, Edward, Monte, Paul A
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US09/633,694
• Time in Patent Office: 428 Days
• Field of Search: 455/11.1, 455/12.1, 455/13.2, 455/13.3, 455/427, 455/429, 455/430, 455/422, 455/450, 455/452, 455/454, 370/310, 370/315, 370/316, 370/319, 370/347, 370/348, 370/320-337
• US Class Current: 455/427
• CPC Class Codes: H04B 7/18539 Arrangements for managing radio, resources, i.e. for establishing or releasing a connection
• CPC Class Codes: H04B 7/2041 Spot beam multiple access

Abstract

A method for use in a satellite communications system (20) of a type that has at least one satellite (22) having forward and reverse beams each comprised of sub-beams for relaying user communications between a ground station (24) and user terminals (30). In a first embodiment forward and reverse antenna systems are separately optimized for their intended applications without regard for maintaining congruence between antenna beam sub-beams at the surface of the earth. In a second embodiment a method optimizes signal flow between the ground station and the user terminals and includes the steps of: (a) determining user terminal RF signal conditions within the sub-beams of at least one of the forward and reverse beams; and (b) in response to the determined RF signal conditions, re-allocating sub-beams of at least one of the forward and reverse beams such that the totality of the sub-beams of the forward beam are non-congruent with the totality of the sub-beams of the reverse beam, at the surface of the earth, while maintaining the forward beam substantially congruent with the reverse beam, at the surface of the earth. The step of determining includes a step of maintaining a database that stores a map of the sub-beams. In one embodiment of this invention the steps of determining and maintaining are executed at the ground station, while in another embodiment the steps of determining and maintaining are executed on-board the satellite.

Claims

1. A satellite communications system comprising:

at least one satellite having a forward beam and a reverse beam that move across the surface of the earth, said forward beam being substantially congruent with said reverse beam at the surface of the earth, each of said beams being comprised of M sub-beams for relaying user communications between a ground station and user terminals, wherein X sub-beams of said forward beam are disposed along an outer perimeter of said forward beam and wherein Y sub beams of said reverse beam are distributed along an outer perimeter of said reverse beam, and further wherein Y is greater than X and less than M.

2. A satellite communications system according to claim 1, wherein M is equal to 16.

3. A satellite communications system according to claim 1, wherein X is equal to 9.

4. A satellite communications system according to claim 1, wherein Y is equal to 15.

5. A satellite communications system according to claim 1, wherein M is equal to 16, X is equal to 9 and Y is equal to 15.

6. A method of operating a satellite communications system comprising the steps of:

providing at least one satellite in earth orbit; and

transmitting a forward beam to the surface of the earth and receiving a reverse beam from the surface of the earth, said forward beam being substantially congruent with said reverse beam at the surface of the earth, each of said beams being comprised of M sub-beams for relaying user communications between a ground station and user terminals, wherein X sub-beams of said forward beam are disposed along an outer perimeter of said forward beam and wherein Y sub beams of said reverse beam are distributed along an outer perimeter of said reverse beam, and further wherein Y is greater than X and less than M.

7. A method of operating a satellite communications system according to claim 6, wherein M is equal to 16.

8. A method of operating a satellite communications system according to claim 6, wherein X is equal to 9.

9. A method of operating a satellite communications system according to claim 6, wherein Y is equal to 15.

10. A method of operating a satellite communications system according to claim 6, wherein M is equal to 16, X is equal to 9 and Y is equal to 15.

11. A method of operating a satellite communications system according to claim 6, wherein said satellite is a non-geosynchronous orbit satellite.