Adaptive beam forming with multi-user detection and interference reduction in satellite communication systems and methods

• US 20070135051A1
• Filed: 01/03/2006
• Published: 06/14/2007
• Est. Priority Date: 01/05/2005
• Status: Active Grant

• Current Assignee: ATC Technology Corporation (FedEx Corporation)
• Original Assignee: ATC Technology Corporation (FedEx Corporation)
• Inventors: Zheng, Dunmin, Karabinis, Peter
• Granted Patent: US 7,813,700 B2
• Time in Patent Office: Days
• US Class Current: 455/63.100
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/18563 Arrangements for interconnecting multiple systems data switching networks H04L12/00

Abstract

Satellite communications methods include receiving communications signals including co-channel interference at a space-based component from a plurality of wireless terminals in a satellite footprint over a satellite frequency band and reducing interference in the communication signals by (a) performing co-channel interference reduction on the communications signals to generate a plurality of interference reduced signals and (b) performing multiple access interference cancellation on the interference reduced signals. An interference reducing detector for a satellite communications system includes an interference reducer configured to perform co-channel interference reduction on communications signals to generate a plurality of interference reduced signals, and a detector configured to perform multiple access interference cancellation on the interference reduced signals. Satellite communications systems and satellite gateways including interference reducing detectors are also disclosed.

Claims

1. A communications method comprising:

receiving at a space-based component over a space-based component frequency band a plurality of signals including interference that is dependent on transmissions of a plurality of terminals communicating with the space-based component over a geographic area and interference that is independent of the transmissions of the plurality of terminals communicating with the space-based component over the geographic area; and

reducing interference of the plurality of signals sequentially by first reducing the interference that is independent of the transmissions of the plurality of terminals communicating with the space-based component over the geographic area and then reducing the interference that is dependent on the transmissions of the plurality of terminals communicating with the space-based component over the geographic area.

2. The method of claim 1 wherein the interference that is independent of the transmissions of the plurality of terminals communicating with the space-based component over the geographic area comprises interference that is dependent on transmissions by an ancillary terrestrial network and/or by one or more terminals communicating with the ancillary terrestrial network, and wherein the ancillary terrestrial network and/or the one or more terminals communicating therewith use at least some frequencies of the space-based component.

3. The method of claim 1, wherein receiving at the space-based component comprises receiving using a plurality of antenna feed elements.

4. The method of claim 3, wherein reducing interference of the plurality of signals sequentially comprises processing pilot signals and determining weights for the plurality of antenna feed elements based on the processing of the pilot signals.

5. The method of claim 4, further comprising generating at least one pilot signal error based on the processing.

6. The method of claim 5, wherein the weights for the antenna feed elements are selected to reduce a mean squared measure of the at least one pilot signal error.

7. The method of claim 4, further comprising applying the weights to signals received by the antenna feed elements to obtain interference reduced signals.

8. The method of claim 7, wherein reducing the interference that is dependent on the transmissions of the plurality of terminals communicating with the space-based component over the geographic area comprises determining a set of channel estimates based on the interference reduced signals, generating a set of bit estimates from the interference reduced signals, and performing interference reduction on the interference reduced signals using the set of channel estimates and the bit estimates.

9. The method of claim 8, wherein performing interference reduction on the interference reduced signals using the channel estimates and the bit estimates comprises generating second interference reduced signals, and wherein the method further comprises determining a set of second channel estimates based on the second interference reduced signals, generating a set of second bit estimates from the second interference reduced signals, and performing interference reduction on the second interference reduced signals using the second channel estimates and the second bit estimates.

10. The method of claim 1, wherein receiving at the space-based component comprises receiving at the space-based component using at least two antenna patterns that differ in at least a polarization orientation.

11. The method of claim 8, wherein generating a set of bit estimates from the interference reduced signals comprises correlating an interference reduced signal with a spreading code.

12. The method of claim 1, wherein reducing the interference that is dependent on transmissions of a plurality of terminals communicating with the space-based component over a geographic area comprises generating bit estimates, and the method further comprises performing interference reduction using the generated bit estimates.

13. The method of claim 1, further comprising transmitting at least some of the plurality of signals to at least one satellite gateway, wherein reducing interference of the plurality of signals is performed at the at least one satellite gateway.

14. The method of claim 13, wherein the at least one satellite gateway is terrestrially based.

15. The method of claim 1, wherein reducing interference of the plurality of signals is performed at least partially at the space-based component and at least partially at a satellite gateway that is terrestrially based.

72. The method of claim 1, further comprising repeatedly reducing the interference that is dependent on the transmissions of the plurality of terminals communicating with the space-based component over the geographic area until a predetermined criterion is met.

73. The method of claim 72, wherein the predetermined criterion comprises a bit error rate.

16. A system comprising:

a plurality of terminals that are configured to transmit a plurality of multiple access signals over a space-based component frequency band in a space-based component footprint;

a space-based component that is configured to receive the plurality of multiple access signals over the space-based component frequency band, the space-based component also receiving interference along with the plurality of multiple access signals in the space-based component frequency band, the interference comprising a component that is dependent on the plurality of multiple access signals and a component that is independent of the plurality of multiple access signals; and

an interference reducing element that is responsive to the space-based component, and that is configured to sequentially perform interference reduction of the interference that is independent of the plurality of multiple access signals and the interference that is dependent on the plurality of multiple access signals.

17. The system of claim 16, further comprising:

an ancillary terrestrial network including a plurality of transmitters configured to transmit a plurality of waveforms over at least some of the space-based component frequency band, and wherein the interference that is independent of the plurality of multiple access signals comprises a component that is dependent on the plurality of waveforms.

18. The system of claim 16, wherein the space-based component includes an antenna having a plurality of antenna feed elements, and the space-based component is configured to receive the plurality of multiple access signals using the antenna having the plurality of antenna feed elements.

19. The system of claim 18, wherein the interference reducing element is further configured to perform interference reduction on a plurality of multiple access signals by processing pilot signals transmitted by a plurality of terminals and determining a set of weights for the antenna feed elements based on the processing of the pilot signals.

20. The system of claim 19, wherein the processing generates at least one pilot signal error.

21. The system of claim 20, wherein the interference reducing element is further configured to select a set of weights for the antenna feed elements to reduce a mean squared measure of the at least one pilot signal error.

22. The system of claim 21, wherein the interference reducing element is further configured to apply the set of weights to signals received by the plurality of antenna feed elements to obtain interference reduced signals.

23. The system of claim 22, wherein the interference reducing element is further configured to determine a set of channel estimates based on the interference reduced signals, generate a set of bit estimates from the interference reduced signals, and perform interference reduction on the interference reduced signals using the set of channel estimates and the set of bit estimates to thereby generate second interference reduced signals.

24. The system of claim 23, wherein the interference reducing element is further configured to determine a set of second channel estimates based on the second interference reduced signals, to generate a set of second bit estimates from the second interference reduced signals, and to perform interference reduction on the second interference reduced signals using the set of second channel estimates and the set of second bit estimates.

25. The system of claim 16, wherein the space-based component receives the plurality of multiple access signals using at least two antenna patterns that differ in at least a polarization orientation.

26. The system of claim 22, wherein the interference reducing element is further configured to generate a plurality of interference reduced bit estimates from the interference reduced signals, and to perform interference reduction using the plurality of interference reduced bit estimates.

27. The system of claim 16, wherein the space-based component is further configured to re-transmit the multiple access signals to a satellite gateway, and wherein the interference reducing element is located at the satellite gateway.

28. The system of claim 27, wherein the satellite gateway is terrestrially-based.

29. A system comprising:

a space-based component that is configured to receive multiple access signals from a plurality of terminals in a satellite footprint over a satellite frequency band;

an interference reducer that is responsive to the space-based component and is configured to perform co-channel interference reduction on the multiple access signals to generate a plurality of interference reduced signals; and

a detector that is responsive to the interference reducer and is configured to perform multiple access interference reduction on the interference reduced signals.

30. The system of claim 29, further comprising:

an ancillary terrestrial network including a plurality of transmitters configured to transmit a plurality of wireless communications signals using at least some frequencies of the satellite frequency band in the satellite footprint;

wherein the space-based component also receives the wireless communications signals from the transmitters in the ancillary terrestrial network in the satellite footprint over the at least some frequencies of the satellite frequency band as interference along with the multiple access signals.

31. The system of claim 29, wherein the space-based component includes an antenna having a plurality of antenna feed elements, and the space-based component is configured to receive the multiple access signals using the antenna having the plurality of antenna feed elements.

32. The system of claim 31, wherein the interference reducer is further configured to perform co-channel interference reduction on the multiple access signals by processing pilot signals transmitted by the plurality of terminals and determining a set of weights for the antenna feed elements based on the processing of the pilot signals.

33. The system of claim 32, wherein the processing generates at least one pilot signal error.

34. The system of claim 33, wherein the interference reducer is further configured to select a set of weights for the antenna feed elements to reduce a mean squared measure of the pilot signal error.

35. The system of claim 34, wherein the interference reducer is further configured to apply the set of weights to signals received by the plurality of antenna feed elements to obtain the plurality of interference reduced signals.

36. The system of claim 35, wherein the detector is further configured to determine a set of channel estimates based on the interference reduced signals, to generate a set of bit estimates from the interference reduced signals, and to perform multiple access interference reduction on the interference reduced signals using the set of channel estimates and the set of bit estimates to thereby generate second interference reduced signals.

37. The system of claim 36, wherein the detector is further configured to determine a set of second channel estimates based on the second interference reduced signals, to generate a set of second bit estimates from the second interference reduced signals, and to perform multiple access interference reduction on the second interference reduced signals using the set of second channel estimates and the set of second bit estimates.

38. The system of claim 36, wherein the space-based component is configured to receive the multiple access signals using at least two antenna patterns that differ in at least a polarization orientation.

39. The system of claim 35, wherein the detector is further configured to generate a plurality of bit estimates from the interference reduced signals, and to perform multiple access interference reduction using the plurality of bit estimates.

40. The system of claim 29, wherein the space-based component is further configured to re-transmit the multiple access signals to a satellite gateway, and wherein the interference reducer and/or the detector is/are located at the satellite gateway.

41. The system of claim 40, wherein the satellite gateway is terrestrially-based.

42. The system of claim 29, further comprising at least one satellite gateway, and wherein the interference reducer is located at the space-based component, the detector is located at the at least one satellite gateway, and the space-based component is further configured to transmit the interference reduced signals to the at least one satellite gateway.

43. An interference reducing detector for a satellite communications system that includes a space-based component that is configured to receive multiple access wireless communication signals including co-channel interference from a plurality of wireless terminals in a satellite footprint over a satellite frequency band, the interference reducing detector comprising:

an interference reducer that is responsive to the space-based component and that is configured to perform co-channel interference reduction on the multiple access wireless communication signals to generate a plurality of interference reduced signals; and

a detector that is configured to perform multiple access interference cancellation on the interference reduced signals.

44. The interference reducing detector of claim 43, wherein the interference reducer is further configured to perform co-channel interference reduction on the multiple access wireless communications signals by processing pilot signals transmitted by the plurality of wireless terminals and determining a set of weights for a set of antenna feed elements of the space-based component based on the processing of the pilot signals.

45. The interference reducing detector of claim 44, wherein the interference reducer is further configured to generate at least one pilot signal error.

46. The interference reducing detector of claim 45, wherein the interference reducer is further configured to select a set of weights for the antenna feed elements to reduce a mean squared measure of the at least one pilot signal error.

47. The interference reducing detector of claim 46, wherein the interference reducer is further configured to apply the set of weights to signals received by the antenna feed elements to obtain the plurality of interference reduced signals.

48. The interference reducing detector of claim 46, wherein the detector is further configured to determine a set of channel estimates based on the interference reduced signals, generate a set of received bit estimates from the interference reduced signals, and perform multiple access interference cancellation on the interference reduced signals using the set of channel estimates and the set of received bit estimates to thereby generate second interference reduced signals.

49. The interference reducing detector of claim 48, wherein the detector is further configured to determine a set of second channel estimates based on the second interference reduced signals, generate a set of second received bit estimates from the second interference reduced signals, and perform multiple access interference cancellation on the second interference reduced signals using the set of second channel estimates and the set of second received bit estimates.

50. The interference reducing detector of claim 43, wherein the space-based component receives the multiple access wireless communication signals including co-channel interference using at least two antenna patterns that differ in at least a polarization orientation.

51. The interference reducing detector of claim 43, wherein the detector is further configured to generate a plurality of interference reduced bit estimates from the interference reduced signals, and to perform multiple access interference cancellation using the plurality of interference reduced bit estimates.

52. The interference reducing detector of claim 43, wherein the space-based component is further configured to re-transmit the multiple access wireless communication signals to at least one satellite gateway, and wherein the interference reducer is located at the at least one satellite gateway.

53. The interference reducing detector of claim 52, wherein the at least one satellite gateway is terrestrially-based.

54. The interference reducing detector of claim 43, wherein the interference reducer is located at the space-based component and the detector is located remotely from the space-based component.

55. A gateway for a satellite wireless terminal system that includes a space-based component that is configured to receive multiple access wireless communication signals from a plurality of wireless terminals in a satellite footprint over a satellite frequency band, the gateway comprising:

an interference reducer that is responsive to the space-based component and that is configured to perform co-channel interference reduction on the multiple access wireless communication signals to generate a plurality of interference reduced signals; and

a detector that is configured to perform multiple access interference cancellation on the interference reduced signals.

56. The gateway of claim 55, wherein the interference reducer is further configured to perform co-channel interference reduction on the multiple access wireless communication signals by processing pilot signals transmitted by the plurality of wireless terminals and determining a set of weights for a set of antenna feed elements of the space-based component based on the processing of the pilot signals.

57. The gateway of claim 56, wherein the interference reducer is further configured to generate at least one pilot signal error.

58. The gateway of claim 57, wherein the interference reducer is further configured to select a set of signal weights for the feed elements to reduce a mean squared measure of the pilot signal error.

59. The gateway of claim 58, wherein the interference reducer is further configured to apply the set of signal weights to signals received by a plurality of antenna feed elements to obtain the plurality of interference reduced signals.

60. The gateway of claim 58, wherein the detector is further configured to determine a set of channel estimates based on the interference reduced signals, generate a set of received bit estimates from the interference reduced signals, and perform multiple access interference cancellation on the interference reduced signals using the set of channel estimates and the set of received bit estimates to thereby generate second interference reduced signals.

61. The gateway of claim 60, wherein the detector is further configured to determine a set of second channel estimates based on the second interference reduced signals, generate a set of second received bit estimates from the second interference reduced signals, and perform multiple access interference cancellation on the second interference reduced signals using the set of second channel estimates and the set of second received bit estimates.

62. The gateway of claim 55, wherein the space-based component receives the multiple access wireless communication signals using at least two antenna patterns that differ in at least a polarization orientation.

63. The gateway of claim 55, wherein the detector is further configured to generate a plurality of interference reduced bit estimates from the interference reduced signals, and to perform multiple access interference cancellation using the plurality of interference reduced bit estimates.

64. The gateway of claim 55, wherein the interference reducer performs co-channel interference reduction on the multiple access wireless communications signals by processing at least two signals that have been provided to the interference reducer by the space-based component wherein the space-based component has received the at least two signals using at least two antenna patterns that differ in at least a polarization orientation.

65. The gateway of claim 64 wherein the at least two antenna patterns are a substantially Left Hand Circularly Polarized (LHCP) antenna pattern and a substantially Right Hand Circularly Polarized (RHCP) antenna pattern.

66. An interference reducer for a space-based component that is configured to receive components of a signal using at least first and second antenna patterns that differ in a spatial orientation and a polarization orientation, wherein the space-based component is configured to provide the components of the signal to the interference reducer and the interference reducer is configured to process the components of the signal to reduce a level of interference of the signal.

67. A transmitter for a space-based component configured to communicate with a radioterminal by transmitting to the radioterminal a first signal over a first antenna pattern and at least one second signal over at least a second antenna pattern, wherein the at least one second signal differs from the first signal by at least a time delay value.

68. A radioterminal configured to communicate with a space-based component by receiving a first signal over a first antenna pattern of the space-based component and at least one second signal over at least a second antenna pattern of the space-based component, wherein the at least one second signal differs from the first signal by at least a time delay value;

the radioterminal configured to process the first signal and the at least one second signal to improve at least one communications performance measure.

69. A wireless communications system comprising a space-based component and an ancillary terrestrial network, wherein the ancillary terrestrial network provides control channel and traffic channel communications to a plurality of first radioterminals by using a first set of frequencies authorized for use by the space-based component to provide control channel and/or traffic channel communications more than a second set of frequencies authorized for use by the space-based component to provide control channel and/or traffic channel communications;

wherein the second set of frequencies is used preferentially by the space-based component to provide control channel and traffic channel communications to a plurality of second radioterminals within a geographic area.

70. The wireless communications system of claim 69, wherein the ancillary terrestrial network does not use the second set of frequencies.

71. An interference reducer for a space-based component that is configured to receive waveforms from radioterminals including interference that is dependent on the waveforms from the radioterminals and interference that is independent of the waveforms from the radioterminals, wherein the interference reducer is configured to reduce the interference that is independent of the waveforms from the radioterminals and to reduce the interference that is dependent on the waveforms from the radioterminals;

and wherein the interference reducer is configured to reduce the interference that is dependent on the waveforms from the radioterminals repeatedly until a predetermined criterion is met.

74. A method of reducing interference, comprising:

receiving, at a space-based component, components of a signal using at least first and second antenna patterns that differ in a spatial orientation and a polarization orientation;

providing the components of the signal to an interference reducer; and

processing the components of the signal at the interference reducer to reduce a level of interference of the signal.

75. A method of communicating between a space-based component and a radioterminal, comprising:

transmitting a signal to the radioterminal as a first signal over a first antenna pattern; and

transmitting the signal to the radioterminal as a second signal over at least a second antenna pattern, wherein the second signal differs from the first signal by at least a time delay value.

76. The method of claim 75, wherein the first antenna pattern differs from the second antenna pattern by a spatial orientation and/or a polarization orientation.

77. The method of claim 75, wherein the first antenna pattern spans a first geographic service area and the second antenna pattern spans a second geographic service area that at least partially overlaps the first geographic service area.

78. The method of claim 77, further comprising:

transmitting the signal to the radioterminal as a third signal over at least a third antenna pattern, wherein the time delay value comprises a first time delay value, and wherein the third signal differs from the second signal by at least a second time delay value.

79. A method of communicating between a space-based component and a radioterminal, comprising:

transmitting a signal to the radioterminal as a first signal over a first antenna pattern; and

transmitting the signal to the radioterminal as a second signal over at least a second antenna pattern, wherein the second signal differs from the first signal by a unique characteristic.

80. The method of claim 79, wherein the unique characteristic comprises a time delay value, a pilot signal, a bit sequence, a mid-amble, a pre-amble, and/or a spreading code of the signal.

81. A method of communicating with a space-based component, comprising:

receiving a first signal over a first antenna pattern of the space-based component and at least one second signal over at least a second antenna pattern of the space-based component, wherein the at least one second signal differs from the first signal by at least a time delay value; and

processing the first signal and the at least one second signal to improve at least one communications performance measure.

82. A communications method for a wireless communications system comprising a space-based component and an ancillary terrestrial network, the method comprising:

providing control channel and traffic channel communications from the ancillary terrestrial network to a plurality of first radioterminals using a first set of frequencies authorized for use by the space-based component to provide control channel and/or traffic channel communications more than a second set of frequencies authorized for use by the space-based component to provide control channel and/or traffic channel communications; and

providing control channel and traffic channel communications from the space-based component to a plurality of second radioterminals within a geographic area using the second set of frequencies.

83. The method of claim 82, wherein the ancillary terrestrial network does not use the second set of frequencies.

84. A method of reducing interference, comprising:

receiving, at a space-based component, a plurality of components of a signal using a respective plurality of different antenna patterns;

selecting a subset of the received signal components for processing;

providing the selected subset of the received signal components to an interference reducer; and

processing the selected subset of the received signal components at the interference reducer to reduce a level of interference of the signal.

85. The method of claim 84, wherein the antenna patterns differ in a spatial orientation and/or a polarization orientation

86. The method of claim 84, wherein selecting the subset of the received signal components comprises selecting the subset of the received signal components based on a characteristic of the signal.

87. The method of claim 86, wherein the characteristic of the signal comprises a geographic location associated with the signal, a signal strength associated with the signal, or a signal quality associated with the signal.

88. The method of claim 84, wherein the signal comprises a return link control channel signal.

89. The method of claim 84, further comprising:

determining a geographic location of a source of the signal;

wherein selecting a subset of the received signal components for processing comprises selecting a subset of the received signal components such that, for the determined geographic location, an improved performance measure is provided for the signal.

90. The method of claim 89, wherein the performance measure comprises a signal to interference ratio and/or a signal to noise ratio.