Method and apparatus for increased system capacity using antenna beamforming

• US 6,195,037 B1
• Filed: 06/01/1999
• Issued: 02/27/2001
• Est. Priority Date: 06/01/1999
• Status: Expired due to Term

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Emmons, Thomas Peter Jr., Gross, Jonathan H., Erlick, John Richard
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/323,349
• Time in Patent Office: 637 Days
• Field of Search: 342/357.01, 342/352, 342/354, 455/12.1, 455/13.1
• US Class Current: 342/354
• CPC Class Codes: H04B 7/2041 Spot beam multiple access
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

In a satellite communications system (100), system capacity is improved using a satellite (110 and 120) that includes a main mission antenna (MMA) (310 FIG. 3), antenna subsystem (320), and controller (350). Antenna subsystem (320) comprises a beamformer and associated software to optimize the beam shape and cell position with respect to the satellite'"'"'s location. In one example, beam optimization is performed using a location based on latitude. Satellite (110 and 120) determines its spatial position and determines its latitudinal location based on this position information. The satellite determines the number of cells, the cell sizes, and the beam steering angles required at this latitudinal location. In other cases, beam optimization is performed using a location based on latitude and longitude, system loading, and satellite health and status.

Claims

1. A method for increasing system capacity in a satellite communications system comprising a plurality of communications satellites, wherein a satellite comprises an array antenna and beamformer for providing a plurality of beams, said method comprising the steps of:

(a) determining a location for said satellite, said location being determined using latitude, said latitude being an angular distance measured in degrees from an equator;

(b) establishing said plurality of beams based on said location;

(b1) identifying a first beam in said plurality of beams;

(b2) determining whether said first beam requires modification based on said location for said satellite;

(b2a) determining whether cell size modification is required for said first beam; and

(b2b) modifying a cell diameter to accomplish said cell size modification.

2. The method as claimed in claim 1, wherein said method further comprises the step of:

(c) determining said location of the satellite using longitude, said longitude being an angular distance established in degrees at said equator.

3. The method as claimed in claim 1, wherein step (b2) further comprises the steps of:

(b2a) determining whether beam steering angle modification is required for said first beam; and

(b2b) modifying distance between cell centers to accomplish said beam steering angle modification.

4. The method as claimed in claim 1, wherein step (b2) further comprises the steps of:

(b2a) determining whether cell size modification is required for said first beam; and

(b2b) modifying a minor axis of a cell to accomplish said cell size modification.

5. The method as claimed in claim 1, wherein step (b2) further comprises the steps of:

(b2a) determining whether beam steering angle modification is required for said first beam; and

(b2b) modifying distance between cell focal points to accomplish said beam steering angle modification.

6. The method as claimed in claim 1, wherein step (b) further comprises the steps of:

(b3) identifying a second beam in said plurality of beams; and

(b4) determining whether said second beam requires modification based on said location of said satellite.

7. The method as claimed in claim 1, wherein step (b) further comprises the steps of:

(b3) identifying a second beam in said plurality of beams;

(b4) identifying a location of a second cell associated with said second beam; and

(b5) determining whether said second beam requires modification based on said location of said satellite and said location of said second cell.

8. The method as claimed in claim 1, wherein step (b2) further comprises the steps of:

(b2a) identifying a location of a first cell associated with said first beam; and

(b2b) determining whether said first beam requires modification based on said location of said satellite and said location of said first cell.

9. The method as claimed in claim 1, wherein step (b2) further comprises the steps of:

(b2a) identifying a location of a first cell associated with said first beam; and

(b2b) determining whether said first beam requires modification based on said location of said satellite and a time of day at said location of said satellite.

10. The method as claimed in claim 1, wherein step (b) further comprises the steps of:

(b1) identifying a first set of beams in said plurality of beams; and

(b2) determining whether said first set of beams requires modification based on said location for said satellite.

11. The method as claimed in claim 1, wherein step (b) further comprises the steps of:

(b1) identifying a first set of beams in said plurality of beams;

(b2) identifying a location of a first set of cells associated with said first set of beams; and

(b3) determining whether said first set of beams requires modification based on said location of said satellite and said location of said first set of cells.

12. The method as claimed in claim 11, wherein step (b) further comprises the steps of:

(b4) identifying a second set of beams in said plurality of beams;

(b5) identifying a location of a second set of cells associated with said second set of beams; and

(b6) determining whether said second set of beams requires modification based on said location of said satellite and said location of said second set of cells.

13. The method as claimed in claim 12, wherein said first set of beams and said second set of beams are identified using a table stored in said satellite.

14. The method as claimed in claim 12, wherein said first set of beams and said second set of beams are identified using a ring-like groups of cells.

15. The method as claimed in claim 12, wherein said first set of beams and said second set of beams are identified using a rows of cells.

16. The method as claimed in claim 11, wherein step (b3) further comprises the steps of:

(b3a) determining whether cell size modifications are required for said first set of cells;

(b3b) modifying cell diameters to accomplish said cell size modifications;

(b3c) determining whether beam steering angle modifications are required for said first set of beams; and

(b3d) modifying distances between cell centers to accomplish said beam steering angle modifications.

17. The method as claimed in claim 11, wherein step (b3) further comprises the steps of:

(b3a) determining whether cell size modifications are required for said first set of cells;

(b3b) modifying minor axes of cells to accomplish said cell size modifications;

(b3c) determining whether beam steering angle modifications are required for said first set of beams; and

(b3d) modifying distances between cell focal points to accomplish said beam steering angle modifications.

18. The method as claimed in claim 11, wherein step (b) further comprises the steps of:

(b4) identifying a second set of beams in said plurality of beams;

(b5) identifying a location of a second set of cells associated with said second set of beams; and

(b6) determining whether said second set of beams requires modification based on said location of said satellite and the operational status of said first set of beams.

19. In a communications system having a plurality of subscriber units (SUs), and a plurality of communications satellites, a satellite for performing location-based beamforming procedures, said satellite comprising:

a main mission antenna (MMA) for establishing a plurality of beams, said beams providing communications links with at least one of said plurality of SUs;

an antenna subsystem coupled to said MMA;

an earth link transceiver for providing a link to a terrestrial-based communications device;

a crosslink transceiver for providing crosslinks to other satellites;

a controller coupled to said antenna subsystem, to said earth link transceiver, and to said crosslink transceiver, said controller for determining a latitudinal location for said satellite, for processing said plurality of beams, for determining cell sizes and beam steering angles using said latitudinal location;

means for modifying a cell'"'"'s size diameter, said means for modifying coupled to the controller and MMA; and

means for modifying a beam steering angle coupled to the controller and MMA.

20. The satellite as claimed in claim 19, wherein said satellite further comprises:

means for modifying cell sizes for a set of cells; and

means for modifying beam steering angles for said set of cells.