System and method for maximizing efficiency in a time division duplex system employing dynamic asymmetry

• US 6,597,668 B1
• Filed: 06/27/2000
• Issued: 07/22/2003
• Est. Priority Date: 11/07/1996
• Status: Expired due to Fees

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Broadband Wireless Access Incorporated
• Inventors: Foster, Robert B., Schafer, David C., McMeekin, M. Sue
• Primary Examiner(s): Hsu, Alpus H.
• Assistant Examiner(s): Nguyen, Toan
• Application Number:
  US09/604,437
• Time in Patent Office: 1,120 Days
• Field of Search: 370/229, 370/230, 370/235, 370/252, 370/280, 370/281, 370/294, 370/295, 370/321, 375/326, 375/346, 375/348, 375/349, 375/240, 455/450, 455/464
• US Class Current: 370/280
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04J 3/1694 Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers Passive Optical Networks H04Q11/0062
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 72/52 based on load
• CPC Class Codes: H04W 72/56 based on priority criteria

Abstract

Systems and methods for efficiently utilizing spectrum in a time division duplex system are shown. In the preferred embodiment fractions of a time division duplex frame are asymmetrically adjusted as forward and reverse channels according to communication demands/requests. Particular groups of resources for which independent asynchronous operation would result in undesired consequences are preferably operated in lockstep to thereby avoid the undesired consequences. Accordingly, a most preferred embodiment of the present invention provides for lockstep asymmetric adaptive time division duplexing among multiple carriers of a hub and multiple node wireless communication system.

Claims

1. A time division duplex, fixed frame with dynamically variable data density, point-to-multipoint communications system with at least one hub each having at least one modem and plural directional antennas and a plurality of nodes each having a highly directional antenna comprising a traffic scheduler operable to dynamically establish a forward link fraction and a reverse link fraction of at least one carrier, wherein said traffic scheduler comprises:

a traffic determination system; and

an allocation system operable to dynamically establish a forward link fraction and a reverse link fraction based on information from said traffic determination system and to allocate said forward link fraction and said reverse link fraction to traffic sources according to a predetermined set of operational procedures.

2. The traffic scheduler of claim 1, wherein said allocation system comprises:

a traffic congestion portion operable according to said predetermined set of operational procedures to distribute a capacity deficit among ones of said traffic sources if information provided by said traffic determination system indicates traffic in excess of an available capacity provided at least in part by said at least one carrier.

3. The traffic scheduler of claim 2, wherein the predetermined set of operational procedures provide substantially equal distribution of said capacity deficit among ones of said traffic sources.

4. The traffic scheduler of claim 2, wherein the predetermined set of operational procedures provide a weighted distribution of said capacity deficit among ones of said traffic sources.

5. The traffic scheduler of claim 4, wherein said weighted distribution is based at least in part on a transmission priority associated with a particular traffic source.

6. The traffic scheduler of claim 4, wherein said weighted distribution is based at least in part on a minimum bandwidth guarantee associated with a particular traffic source.

7. The traffic scheduler of claim 4, wherein said weighted distribution is based at least in part on historical deficit information with respect to a particular traffic source.

8. The traffic scheduler of claim 1, wherein said allocation system comprises:

an excess bandwidth portion operable according to said predetermined set of operational procedures to distribute a capacity excess among ones of said traffic sources if information provided by said traffic determination system indicates a surplus of available capacity provided at least in part by said at least one carrier.

9. The traffic scheduler of claim 8, wherein the predetermined set of operational procedures provide substantially equal capacity excess among ones of said traffic sources.

10. The traffic scheduler of claim 8, wherein the predetermined set of operational procedures provide weighted distribution of capacity excess among ones of said traffic sources.

11. The traffic scheduler of claim 10, wherein said weighted distribution is based at least n part on a transmission priority associated with a particular traffic source.

12. The traffic scheduler of claim 10, wherein said weighted distribution is based at least in part on a minimum bandwidth guarantee associated with a particular traffic source.

13. The traffic scheduler of claim 1, wherein said allocation system comprises:

a carrier assignment system operable to dynamically assign carriers to said traffic sources.

14. The traffic scheduler of claim 13, wherein assignment of said carriers is performed in combination with said allocation of said forward link fraction and said reverse link fraction to said traffic sources to optimize utilization communication capacity.

15. The traffic scheduler of claim 10, wherein said weighted distribution is based at least in part on historical deficiency information with respect to a particular traffic source.

16. The traffic scheduler of claim 1, wherein said traffic determination system utilizes information regarding current traffic demands/requests in determining traffic.

17. The traffic scheduler of claim 1, wherein said traffic determination system utilizes historical traffic information.

18. The traffic scheduler of claim 1, wherein said traffic determination system operates to determine instantaneous traffic utilization.

19. The traffic scheduler of claim 1, wherein said at least one carrier comprises a plurality of carriers.

20. The traffic scheduler of claim 19, wherein operation of said allocation system establishes a forward link fraction and a reverse link fraction of a first carrier of said plurality of carriers different than a forward link fraction and a reverse link fraction of a second carrier of said plurality of carriers.

21. A traffic scheduler operable to dynamically establish a forward link fraction and a reverse link fraction of at least one carrier, wherein said traffic scheduler comprises:

a traffic determination system; and

an allocation system operable to dynamically establish a forward link fraction and a reverse link fraction based on information from said traffic determination system and to allocate said forward link fraction and said reverse link fraction to traffic sources according to a predetermined set of operational procedures,

wherein said at least one carrier comprises a plurality of carriers,

wherein operation of said allocation system establishes a forward link fraction and a reverse link fraction of a first carrier of said plurality of carriers different than a forward link fraction and a reverse link fraction of a second carrier of said plurality of carriers,

wherein said first carrier is a carrier of an interference group, and

wherein said interference group includes a plurality of carriers which are operated with a same forward link fraction and a seam reverse link fraction.

22. A time division duplex, fixed frame with dynamically variable data density, point-to-multipoint communications system with at least one hub each having at least one modem and plural directional antennas and a plurality of nodes each having a highly directional antenna comprising:

a plurality of carriers, and

a traffic scheduler operable to dynamically establish a directional link channel fraction of communication capacity for carriers of said plurality of carriers, wherein said traffic scheduler comprises;

an allocation system operable to allocate said directional link channel fraction to traffic sources according to a predetermined set of operational procedures, wherein a directional link channel fraction of a first carrier of said plurality of carriers is different than a corresponding directional link channel fraction of a second carrier of said plurality of carriers.

23. The communication system of claim 22, wherein said traffic scheduler further comprises:

a carrier assignment system operable to dynamically assign traffic sources to carriers of said plurality of carriers according to said predetermined set of operational procedures.

24. The communication system of claim 23, wherein said carrier assignment system and said allocation system operating according to said predetermined set of operational procedures minimize an amount of capacity deficit experienced by said communication system.

30. The communication system of claim 22, wherein said allocation system comprises:

a congestion system operable to determine a capacity deficit, wherein said allocation operates to allocate said directional link channel fraction responsive to said capacity deficit.

31. The communication system of claim 30, wherein said allocation of said directional link channel fraction responsive to said capacity deficit distributes said deficit substantially equally among ones of said traffic sources.

32. The communication system of claim 30, wherein said allocation of said directional link channel fraction responsive to said capacity deficit distributes said deficit substantially equally among ones of said carriers.

33. The communication system of claim 30, wherein said allocation of said directional link channel fraction responsive to said capacity deficit distributes said deficit differently among ones of said traffic sources.

34. The communication system of claim 33, wherein said distribution of said deficit is based at least in part on historical deficits associated with ones of said traffic sources.

35. The communication system of claim 33, wherein said distribution of said deficit is based at least in part on a priority of service associated with ones of said traffic sources.

36. The communication system of claim 33, wherein said distribution of said deficit is based at least in part on a guarantee of bandwidth associated with ones of said traffic sources.

37. The communication system of claim 33, wherein said distribution of said deficit is based at least in part on historical deficits associated with ones of said carriers.

38. The communication system of claim 22, wherein said allocation system comprises:

an excess bandwidth system operable to determine a capacity surplus, wherein said allocation operates to allocate said directional link channel fraction responsive to said capacity surplus.

39. The communication system of claim 38, wherein said allocation of said directional link channel fraction responsive to said capacity surplus distributes said surplus substantially equally among ones of said traffic sources.

40. The communication system of claim 38, wherein said allocation of said directional link channel fraction responsive to said capacity surplus distributes said surplus substantially equally among ones of said carriers.

41. The communication system of claim 38, wherein said allocation of said directional link channel fraction responsive to said capacity surplus distributes said surplus differently among ones of said traffic sources.

42. The communication system of claim 41, wherein said distribution of said surplus is based at least in part on historical deficits associated with ones of said traffic sources.

43. The communication system of claim 41, wherein said distribution of said surplus is based at least in part on a priority of service associated with ones of said traffic sources.

44. The communication system of claim 41, wherein said distribution of said surplus is based at least in part on a guarantee of bandwidth associated with ones of said traffic sources.

45. The communication system of claim 41, wherein said distribution of said surplus is based at east in part on historical deficits associated with ones of said carriers.

46. The communication system of claim 22, wherein said directional link channel fraction is a forward link channel fraction.

47. The communication system of claim 22, wherein said directional link channel fraction is a reverse link channel fraction.

25. A communication system for providing adaptive time division duplexing, said communication system comprising:

a plurality of carriers, and

a traffic scheduler operable to dynamically establish a directional link channel fraction of communication capacity for carriers of said plurality of carriers, wherein said traffic scheduler comprises;

an allocation system operable to allocate said directional link channel fraction to traffic sources according to a predetermined set of operational procedures, wherein a directional link channel fraction of a first carrier of said plurality of carriers is different than a corresponding directional link channel fraction of a second carrier of said plurality of carriers,

wherein said plurality of carriers includes a first group of carriers determined to cause undesired interference when operated in at least one configuration.

26. The communication system of claim 25, wherein said at least one configuration includes carriers of said first group simultaneously operating with a same communication interface.

27. The communication system of claim 26, wherein said same communication interface is an antenna element.

28. The communication system of claim 25, wherein said at least one configuration includes a carrier of said first group operating in a forward link simultaneously with another carrier of said first group operating in a reverse link.

29. The communication system of claim 25, wherein said first group comprises said first carrier and not said second carrier.

48. A communication system for providing adaptive time division duplexing, said communication system comprising:

a plurality of carriers, and

a traffic scheduler operable to dynamically establish a directional link channel fraction of communication capacity for carriers of said plurality of carriers, wherein said traffic scheduler comprises;

an allocation system operable to allocate said directional link channel fraction to traffic sources according to a predetermined set of operational procedures, wherein a directional link channel fraction of a first carrier of said plurality of carriers is different than a corresponding directional link channel fraction of a second carrier of said plurality of carriers,

wherein said plurality of carriers are microwave carriers.

49. The communication system of claim 48, wherein said microwave carriers are in the range of 10-60 GHz.

50. A method for providing communication capacity optimization in a time division duplex, fixed frame with dynamically variable data density, point-to-multipoint communications system with at least one hub each having at least one modem and plural directional antennas and a plurality of nodes each having a highly directional antenna, said method comprising the steps of:

providing a plurality of carriers;

determining a level of communication desired by traffic sources communicating via said plurality of carriers; and

determining a portion of carrier capacity to be utilized in at least one of a forward and a reverse channel responsive to said determined level of communication desired by said traffic sources.

57. The method of claim 50, further comprising the step of:

determining a desired capacity deficit resulting from said determined portion of carrier capacity to be utilized in at least one of a forward and a reverse channel.

58. The method of claim 57, further comprising the step of:

allocating said capacity deficit substantially equally among ones of said traffic sources.

59. The method of claim 57, further comprising the step of:

allocating said capacity deficit according to historical deficit determinations.

60. The method of claim 57, further comprising the step of:

allocating said capacity deficit according to a priority of service.

61. The method of claim 57, further comprising the step of:

allocating said capacity deficit according to a desired quality of service.

62. The method of claim 50, further comprising the step of:

determining a capacity excess resulting from said determined portion of carrier capacity to be utilized in at least one of a forward and a reverse channel.

63. The method of claim 62, further comprising the step of:

allocating said capacity excess substantially equally among ones of said traffic sources.

64. The method of claim 62, further comprising the step of:

allocating said capacity excess according to a priority of service.

65. The method of claim 62, further comprising the step of:

allocating said capacity excess according to a desired quality of service.

51. A method for providing communication capacity optimization, said method comprising the steps of:

providing a plurality of carriers;

determining a level of communication desired by traffic sources communicating via said plurality of carriers;

determining a portion of carrier capacity to be utilized in at least one of a forward and a reverse channel responsive to said determined level of communication desired by said traffic sources; and

identifying ones of said carriers as a lockstep group of carriers, wherein determination of a portion of said carrier capacity to be utilized in at least one of a forward and a reverse channel of each carrier of said lockstep group is the same.

52. The method of claim 51, wherein said step of identifying a lockstep group of carriers comprises the step of:

determining ones of said plurality of carriers for which insufficient isolation is provided between other ones of said carriers to provide simultaneous utilization in a forward link of said ones of said plurality of carriers and a reverse link of said other ones of said carriers.

53. The method of claim 51, wherein said step of identifying a lockstep group of carriers comprises the step of:

determining communication system resources for which a non-lockstep use configuration of ones of said plurality of carriers provide undesired results.

54. The method of claim 53, wherein said communication system resources comprise ones of said traffic sources.

55. The method of claim 53, wherein said communication system resources comprise antenna systems.

56. A method for providing communication capacity optimization, said method comprising the steps of:

providing a plurality of carriers;

determining a level of communication desired by traffic sources communicating via said plurality of carriers; and

determining a portion of carrier capacity to be utilized in at least one of a forward and a reverse channel responsive to said determined level of communication desired by said traffic sources,

wherein said step of determining a portion of carrier capacity to be utilized in at least one of a forward and a reverse channel provides a forward channel of a first carrier overlapping a reverse channel of a second carrier.

66. A system for providing communication capacity optimization, said system comprising:

means for determining a level of communication desired by traffic sources communicating via a plurality of carriers;

means for determining a portion of carrier capacity to be utilized in at least one of a forward and a reverse channel responsive to said determined level of communication desired by said traffic sources; and

means for identifying ones of said carriers as a first lockstep group of carriers, wherein determination of a portion of said carrier capacity to be utilized in at least one of a forward and a reverse channel of each carrier of said first lockstep group is the same.

67. The system of claim 66, further comprising:

means for identifying ones of said carriers as a second lockstep group of carriers, wherein determination of a portion of said carrier capacity to be utilized in at lest one of a forward and a reverse channel of each carrier of said second lockstep group is the same, and wherein said portion of said carrier capacity of said first group and said second group are different.

68. The system of claim 66, wherein said means for determining a portion of carrier capacity is operable every communication frame of a carrier.

69. The system of claim 66, wherein said means for determining a portion of carrier capacity is operable every superframe of a carrier, wherein said superframe is a predetermined plurality of communication frames of a carrier.

70. The system of claim 66, wherein said means for determining a portion of carrier capacity is operable upon the occurrence of an event.

71. The system of claim 70, wherein said event is a determination that a communication data queue has reached a predetermined threshold.

72. The system of claim 71, wherein said threshold is a queued amount of data.

73. The system of claim 71, wherein said threshold is an age of queued data.

74. The system of claim 70, wherein said event is a predetermined amount of time.