Stratospheric platforms based mobile communications architecture

• US 6,756,937 B1
• Filed: 06/06/2000
• Issued: 06/29/2004
• Est. Priority Date: 06/06/2000
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Cha, Alan, Yung, Kar W., Hagen, Frank A., Chang, Donald C. D., Chang, Ming U., Feria, Ying, Wang, Weizheng
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US09/588,395
• Time in Patent Office: 1,484 Days
• Field of Search: 342/354, 455/13.3, 455/429, 455/431
• US Class Current: 342/354
• CPC Class Codes: H04B 7/18504 Aircraft used as relay or high altitude atmospheric platform
• CPC Class Codes: H04B 7/2041 Spot beam multiple access

Abstract

A communication system including a first transceiver located on a first platform at a predetermined altitude. A first antenna is located on the first platform and connected to the first transceiver. A second antenna is connected to the other end of the first transceiver. A second transceiver is located on a ground hub physically and independent of the first platform. A third antenna is located on the ground hub and connected to the second transceiver. The third antenna is adapted to communicate with the second antenna. The first platform is maintained in a stratospheric orbit. A beamforming system is connected to the second transceiver and mounted on the ground hub. The beamforming system provides a beamformed signal from the second transceiver to the first transceiver effective to drive the first array antenna to radiate multiple beams to a surface, whereby the multiple beams create time varying and dissimilar footprints thereon. A second antenna is mounted on the first platform to receive the beamformed signal from the ground hub. The beamforming system is adapted to drive the first antenna to generate plural beams on the earth'"'"'s surface, each beam providing a respective footprint or cell. Each beam tracks a respective user located at a center of each cell. The system allows for narrow beams to be created which, in turn, enables frequency reuse. A code is assigned to each beam and a mechanism is provided for preventing a user from receiving more than one beam with a given code. This mechanism is adapted to anticipate a condition by which a user will move to a location at which the user would receive more than one beam with a given code. The mechanism will quickly assign a second code to at least one beam prior to the arrival of the user at that position.

Claims

1. A communication system, comprising:

a first transceiver located on a first platform at a predetermined altitude;

a first antenna located on said first platform and connected to said first transceiver;

a second transceiver located on a second platform physically independent of said first platform;

a second antenna located on said second platform, said second antenna being adapted to communicate with said first transceiver and being connected to said second transceiver; and

a beamforming system connected to said second transceiver and mounted on said second platform generating a beamforming signal from said second transceiver to said first transceiver effective to drive said first antenna to radiate a plurality of beams having dissimilar size and shape over a coverage area of a surface, whereby said plurality of beams create dissimilar footprints having a corresponding cell size thereon;

said beamforming system driving said first antenna to direct a portion of said plurality of beams that are narrower in size to radiate near a center of said coverage area, wherein said cell size varies directly as a function of a distance of a scan angle from nadir, said beamforming system moving at least one of the plurality of beams to follow a movement of a user.

2. The invention of claim 1 wherein said first platform is mobile.

3. The invention of claim 2 wherein said first platform is maintained in a predetermined orbit.

4. The invention of claim 3 wherein said orbit is in a stratosphere.

5. The invention of claim 1, further comprising a third antenna, said third antenna being mounted on said first platform.

6. The invention of claim 5 wherein said third antenna is adapted to receive said beamforming signal from said first antenna.

7. The invention of claim 1, wherein said surface is a surface of earth.

8. The invention of claim 7 wherein said second platform is located on the earth.

9. The invention of claim 1, wherein said beamforming system generates said plurality of beams, each of said plurality of beams having a respective footprint.

10. The invention of claim 9, wherein each said respective footprint is a cell.

11. The invention of claim 10, wherein each of said plurality of beams is directed to a respective user located at a center of each cell.

12. The invention of claim 11, wherein said beamforming system assigns a code to each of said plurality of beams.

13. The invention of claim 12, wherein said beamforming system prevents a user from receiving more than one of said plurality of beams with a given code.

14. The invention of claim 13, wherein said beamforming system anticipates a condition by which a user moves to a position at which the user receives more than one of said plurality of beams with a given code and assigns a second code to at least one of said plurality of beams prior to arrival of the user at said position.

15. A communication system, comprising:

a first transceiver located on a first platform, said first platform being maintained in a stratospheric orbit;

a first antenna located on said first platform and connected to said first transceiver;

a second antenna located on said first platform and connected to said first transceiver;

a second transceiver located on earth;

a third antenna being connected to said second transceiver, said third antenna being adapted to communicate with said second antenna; and

a beamforming system connected to said second transceiver and generating a beamforming signal from said second transceiver to said first transceiver effective to drive said first antenna to radiate a plurality of beams having dissimilar size and shape over a coverage area of a surface on earth, each of said plurality of beams having a respective footprint, at least two of said plurality of beams creating dissimilar footprints thereon, each footprint having a cell, and each of said plurality of beams being directed to a respective user location at a center of each cell, said beamforming system comprising;

a digital beamforming network for scanning at least one of said plurality of beams to follow a movement of a user and to generate an assigned code for each of said plurality of beams, said digital beam forming network preventing the user from receiving more than one beam with a given code;

said beamforming system driving said first antenna to direct a portion of said plurality of beams that are narrower in size to radiate near a center of said coverage area, wherein a size of said cell varies directly as a function of a distance of a scan angle from nadir.

16. The invention of claim 15, wherein said beamforming system anticipates a condition by which the user moves to a position at which the user receives more than one beam with a given code and assigns a second code to at least one of said plurality of beams prior to the arrival of the user at said position.

17. A method for communicating, comprising:

providing a first transceiver on a first platform at a predetermined altitude;

connecting a first antenna to said first transceiver;

providing a second transceiver on a second platform physically independent of said first platform;

connecting a second antenna to said second transceiver, said second antenna being adapted to communicate with said first antenna;

generating a beamforming signal from said second transceiver to said first transceiver effective to drive said first antenna to radiate a plurality of beams having dissimilar size and shape over a coverage area of a surface, whereby said plurality of beams create dissimilar footprints having a corresponding cell size thereon;

driving said first antenna to direct a portion of said plurality of beams that are narrower in size to radiate near a center of said coverage area, wherein said cell size varies directly as a function of a distance of a scan angle from nadir, and

moving at least one of the plurality of beams to follow a movement of a user.

18. A communication system, comprising:

a first transceiver located on a first platform at a predetermined altitude;

a first antenna located on said first platform and connected to said first transceiver;

a second transceiver located at a ground hub, said ground hub being physically independent of said first platform;

a second antenna located on said ground hub, said second antenna being adapted to communicate with said first platform; and

a beamforming system connected to said second transceiver and located at said ground hub generating a beamforming signal from said second transceiver to said first transceiver effective to drive said first antenna to radiate a plurality of individual beams having dissimilar size and shape to a surface, whereby at least two of said plurality of individual beams create dissimilar footprints having a corresponding cell size on said surface in time and space;

said beamforming system driving said first antenna to direct a portion of said plurality of beams that are narrower in size to radiate near a center of said coverage area, wherein said cell size varies directly as a function of a distance of a scan angle from nadir, said beamforming system moving at least one of the plurality of beams to follow a movement of a user.

19. A communication system, comprising:

a first antenna coupled to a first platform at a predetermined altitude;

a second antenna coupled to a second platform that is physically independent of said first platform; and

a beamforming system coupled to said second antenna and generating a beamforming signal to drive said first antenna to radiate a plurality of beams having dissimilar size and shape to a surface, said plurality of beams each having a corresponding cell size;

said beamforming system driving said first antenna to direct a portion of said plurality of beams that are narrower in size to radiate near a center of said coverage area and to increase said cell size of said plurality of beams as a function of a scan angle, said beamforming system moving at least one of the plurality of beams to follow a movement of a user.

20. The system of claim 19, wherein said beamforming system drives said first antenna to alter cell shape with an increase in a scan angle.

21. The system of claim 19, wherein said beamforming system drives said first antenna to elongate cell shape with an increase in a scan angle.

22. The system of claim 19, wherein said plurality of beams create dissimilar footprints on the surface and said footprints have dissimilar cells.

23. The system of claim 19, wherein said plurality of beams have surrounding exclusion regions.

24. The system of claim 23, wherein said surrounding exclusion regions have bounded contours each of which has a magnitude of approximately 20 dB.

25. The system of claim 24, wherein said bounded contours vary in size and shape.

26. The system of claim 19, wherein said beamforming system assigns color codes to respective users, including at least one independent color code.

27. The system of claim 19, wherein said beamforming system determines whether a sidelobe criterion is satisfied when a new user having a selected color code is added.

28. The system of claim 19, wherein said first platform is mobile.

29. The system of claim 19, wherein said first platform is maintained in a predetermined orbit.

30. The system of claim 29, wherein said orbit is in a stratosphere.

31. The system of claim 19, further comprising:

a third antenna, said third antenna being mounted on said first platform.

32. The system of claim 31, wherein said third antenna is adapted to receive said beamforming signal from said second antenna.

33. The system of claim 19, wherein said surface is a surface of earth.

34. The system of claim 19, wherein said second platform is earth based.

35. The system of claim 19, wherein each one of said plurality of beams creates a footprint on the surface and each footprint is a cell.

36. The system of claim 35, wherein each of said beams in said plurality of beams is directed to a respective user located at a center of each cell.

37. The system of claim 36, wherein said beamforming system assigns a code to each of said beams in said plurality of beams.

38. The system of claim 37, wherein said beamforming system prevents a user from receiving more than one beam with a particular code.

39. The system of claim 38, wherein said beamforming system alters the code of at least one beam of said plurality of beams to prevent a user from receiving more than one beam with a particular code.

40. A method of operating a communications system having a plurality of mobile users and a stratospheric platform, comprising:

generating a plurality of beams from the stratospheric platform, each of said plurality of beams associated with a respective one of the plurality of users;

moving the plurality of beams with the plurality of users; and

increasing a size of the plurality of beams as a distance of a center of the plurality of beams from a nadir of the stratospheric platform increases.

41. The method of claim 40, wherein generating comprises generating a plurality of beams so that a respective one of the plurality of users is at a center of a respective one of the plurality of beams.

42. The method of claim 41, wherein generating comprises generating a plurality of non-interfering beams.

43. The method of claim 42, wherein a plurality of codes are assigned to the non-interfering beams.

44. The method of claim 43, further comprising:

reusing the plurality of codes.

45. The method of claim 41, further comprising:

generating a broad beam; and

identifying new users with the broad beam.

46. The method of claim 41, further comprising:

upon detecting a potential interference in said plurality of beams, reassigning a beam code in response to detecting.

47. The method of claim 40, wherein prior to generating, receiving a beamforming signal from a ground hub.

48. A method for communicating with a plurality of users, comprising:

receiving a beamforming signal;

generating a plurality of beams from a stratospheric platform in response to the beamforming signal, said plurality of beams having dissimilar size and shape and a corresponding cell size over a coverage area, whereby said beams create dissimilar footprints thereon so that beams that are narrower in size radiate near a center of said coverage area, wherein said cell size varies directly as a function of a distance of a scan angle from nadir; and

moving the plurality of beams with the plurality of users.

49. The method of claim 48, further comprising:

detecting a new user with a broad beam.

50. The method of claim 48, wherein receiving comprises receiving a beamforming signal from a ground hub.

51. A communication system, comprising:

a stratospheric platform generating a plurality of individual beams having dissimilar sizes and shapes and a corresponding cell size, whereby at least two of said plurality of individual beams create dissimilar footprints on said surface in time and space so that beams that are smaller in cell size radiate near a center of said coverage area and so that the plurality of individual beams move to follow a movement of a corresponding user.

52. The communication system of claim 51, wherein said stratospheric platform generates a broad beam where no individual beams are present to detect new users.

53. The communication system of claim 51, further comprising:

a ground hub transmitting a beamforming signal to said stratospheric platform, said plurality of individual beams being generated as a function of the beam forming signal.

54. A method of operating a communication system, comprising:

generating a first beam for a first user having a first beam size at or near a nadir of the stratospheric platform;

locating the user at a center of the beam having a corresponding cell size to define a beam scan angle;

repositioning the beam as the user moves to maintain the user in the center of the beam; and

increasing the cell size at the platform as a function of the scan angle.

55. The method of claim 54, further comprising:

generating a second beam having a dissimilar size and shape for a second user.

56. The method of claim 55, wherein the second user is positioned outside the first beam, said first beam and said second beam having a first code.

57. The method of claim 56, further comprising:

changing the second user to a second code when a potential interference between said first beam and said second beam is detected.

58. The method of claim 54, wherein increasing the cell size comprises elongating the beam in a first direction.