System and method for minimizing guard time in a time division duplex communication system

• US 20030026215A1
• Filed: 06/28/2002
• Published: 02/06/2003
• Est. Priority Date: 11/07/1996
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Schafer, David C.
• Granted Patent: US 7,031,295 B2
• Time in Patent Office: Days
• US Class Current: 370/280
• CPC Class Codes: H04B 7/2656 for structure of frame, burst
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• 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 56/003 Arrangements to increase tolerance to errors in transmission or reception timing
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time
• CPC Class Codes: H04W 72/52 based on load
• CPC Class Codes: H04W 72/56 based on priority criteria

Abstract

Disclosed is a system and method for optimizing capacity in a multi-user time division duplex (“TDD”) communication system such as a broadband wireless radio frequency communication system. More specifically the invention minimizes guard time in duplexed signals to thereby allow for higher data throughput which results in an increase in system communication capacity. Depending upon instantaneous traffic load associated with the subscribers using a particular TDD carrier, guard times may be adjusted to provide a desired level of throughput. As traffic loads demand, the order of assignment of burst periods in either or both the transmit and receive frames of a TDD carrier with respect to the subscriber systems operable thereon are adjusted to accommodate desired guard times.

Claims

1. A system for controlling scheduling of information communication in a time division duplex communication environment, said system comprising:

a memory storing propagation delay information for a plurality of nodes in communication with a hub; and

a controller in communication with said memory and operable under control of an instruction set to determine a communication resource implementation to be implemented in said time division duplex communication environment to minimize a guard time thereof through reference to said stored propagation delay information.

2. The system of claim 1, wherein said communication resource implementation determined by said controller includes a determination of an order of ones of said plurality of nodes to be provided communications in a communication frame.

3. The system of claim 2, wherein said order of ones of said plurality of nodes is determined at least in part from a hierarchy of said stored propagation delay information.

4. The system of claim 3, wherein minimization of said guard time by said controller includes determining said communication resource implementation based at least in part on the greatest of a first guard time determined from a propagation delay associated with a first node of said determined order and guard times determined from a propagation delay minus the sum of any preceding time slot durations associated with each succeeding nodes of said determined order.

5. The system of claim 3, wherein said ordering of at least one of said ones of said remote communication system is further based upon an additional communication attribute associated with at least one node.

6. The system of claim 5, wherein said additional communication attribute is selected from the group consisting of a signal strength indicator, a signal to noise ratio, and a carrier to interference ratio.

7. The system of claim 5, wherein said additional communication attribute is selected from the group consisting of a minimum capacity to be provided to said at least one remote communication system and a quality of service to be maintained with respect to said at least one remote communication system.

8. The system of claim 2, wherein said determination of said order includes assigning at least one node of said plurality of nodes to an alternate antenna element of said hub.

9. The system of claim 2, wherein said determination of said order includes assigning at least one node of said plurality of nodes to an alternate frequency available at said hub.

10. The system of claim 2, wherein said determination of said order includes assigning at least one node of said plurality of nodes to an alternate time division multiple access frame.

11. The system of claim 1, wherein said communication resource implementation determined by said controller includes a determination of an instantaneous traffic demand associated with ones of said plurality of nodes.

12. A method for controlling the scheduling of information communication in a time division duplex communication environment, comprising the steps of:

(a) storing propagation delay information with respect to a plurality of nodes in communication with a hub;

(b) monitoring instantaneous traffic demand associated with ones of said plurality of nodes; and

(c) determining a communication resource implementation to be implemented in said time division duplex communication environment to minimize a guard time thereof through reference to said stored propagation delay information and said instantaneous traffic demand,

thereby controlling the scheduling of information communication in a time division duplex communication environment.

13. The method of claim 12, wherein determining a communication resource implementation comprises the step of:

determining an order of ones of said plurality of nodes to be provided communications in a time division multiple access frame portion.

14. The method of claim 13, wherein determining an order of ones of said plurality of nodes comprises the step of:

determining a hierarchy of said ones of said plurality of nodes based upon said stored propagation delay information.

15. The method of claim 13, wherein determining a communication resource implementation further comprises the steps of:

(a) calculating a first guard time from a propagation delay associated with a first node of said determined order;

(b) calculating additional guard times for each node of said plurality of nodes except said first nodes from a respective propagation delay minus any preceding burst period durations of said time division multiple access frame portion associated with other nodes of said plurality of nodes; and

(c) setting a calculated guard time to zero if the calculated guard time is negative.

16. The method of claim 12, further comprising the steps of:

monitoring at least one communication attribute associated with ones of said plurality of nodes; and

assigning at least one node of said plurality of nodes to an alternate available resource based at least in part on said at least one monitored communication attribute.

17. The method of claim 16, wherein said alternative available resource is selected from the group consisting of an antenna element of said hub, an alternate frequency available at said hub, and an alternate time division multiple access frame.

18. The method of claim 16, wherein said monitored at least one communication attribute includes a communication attribute selected from the group consisting of a signal strength indicator, a signal to noise ratio, and a carrier to interference ratio.

19. The method of claim 12, further comprising:

storing communication link information associated with ones of said plurality of nodes; and

assigning at least one node of said plurality of nodes to an alternative available resource.

20. The method of claim 19, wherein said alternative available resource is selected from the group consisting of an antenna element of said hub, an alternate frequency available at said hub, and an alternate time division multiple access frame.

21. The method of claim 19, wherein said stored communication link information includes communication link information selected from the group consisting of a minimum capacity to be provided to said at least one remote communication method, and a quality of service to be maintained with respect to said at least one remote communication method.

22. A system for providing information communication between a centralized communication system and a plurality of remote communication systems, said system comprising:

a processor based traffic scheduler in communication with said centralized communication system and monitoring instantaneous traffic demand associated with ones of said plurality of remote communication systems, wherein said traffic scheduler determines an assignment of resources for providing said information communication between said centralized communication system and ones of said plurality of remote communication systems as a function of said monitored instantaneous traffic demand.

23. The system of claim 22, wherein said assignment of resources includes an ordering of said ones of said remote communication systems in a time division multiple access frame utilized in providing said information communication between said centralized communication system and said ones of said plurality of remote communication systems.

24. The system of claim 23, wherein said ordering of said ones of said remote communication systems is selected to minimize a guard time implemented in said time division multiple access frame.

25. The system of claim 24, wherein said information communication between said centralized communication system and said ones of said plurality of remote communication systems further implements time division duplexing, and wherein said guard time minimized is a guard time between a forward link and a reverse link as referenced at said centralized communication system.

26. The system of claim 25, wherein said guard time is dynamically determined through reference to a propagation delay associated with each remote communication system of said ones of said plurality of remote communication systems.

27. The system of claim 26, wherein said guard time is dynamically determined from the greatest of a first guard time determined from a propagation delay associated with a first remote communication system of said determined order and guard times determined from a propagation delay minus the sum of any preceding time slot durations associated with each succeeding remote communication systems of said determined order.

28. The system of claim 23, wherein said ordering of said ones of said remote communication systems is based at least in part upon a propagation delay associated with respective ones of said plurality of remote communication systems being ordered.

29. The system of claim 28, wherein said ordering of at least one of said ones of said remote communication system is further based upon an additional communication attribute associated with said at least one remote communication system.

30. The system of claim 29, wherein said additional communication attribute includes a communication quality attribute.

31. The system of claim 30, wherein said communication quality attribute is selected from the group consisting of a signal strength indicator, a signal to noise ratio, and a carrier to interference ratio.

32. The system of claim 28, wherein said ordering of at least one of said ones of said remote communication system is further based upon additional communication information associated with said at least one remote communication system.

33. The system of claim 32, wherein said additional communication information includes information selected from the group consisting of a minimum capacity to be provided to said at least one remote communication system, and a quality of service to be maintained with respect to said at least one remote communication system.

34. The system of claim 32, wherein said ordering of said ones of said remote communication system using said additional communication information includes assigning at least one remote communication system of said ones of said remote communication systems to an alternative antenna element.

35. The system of claim 32, wherein said ordering of said ones of said remote communication system using said additional communication information includes assigning at least one remote communication system of said ones of said remote communication systems to an alternative frequency assignment.

36. The system of claim 32, wherein said ordering of said ones of said remote communication system using said additional communication information includes assigning at least one remote communication system of said ones of said remote communication systems to an alternative time division multiple access frame.

37. The system of claim 22, wherein said traffic scheduler further monitors communication attribute information associated with said information communication between said centralized communication system and said plurality of remote communication systems.

38. The system of claim 37, wherein said communication attribute information includes information for determining a timing advance for a particular remote communication system of said plurality of remote communication systems.

39. The system of claim 37, wherein said communication attribute information includes information with respect to particular antenna beams available at said centralized communication system for providing said information communication between said centralized communication system and a particular remote communication system of said plurality of remote communication systems.

40. The system of claim 37, wherein said communication attribute information includes information with respect to particular carrier channels available at said centralized communication system for providing said information communication between said centralized communication system and a particular remote communication system of said plurality of remote communication systems.

41. The system of claim 37, wherein said communication attribute information includes information with respect to particular burst periods available at said centralized communication system and a particular remote communication system of said plurality of remote communication systems.

42. The system of claim 22, wherein said traffic scheduler compiles historical communication information with respect to ones of said plurality of remote communication systems.

43. The system of claim 42, wherein said historical communication information includes historical traffic demands associated with particular remote communication systems of said plurality of remote communication systems.

44. In a time division duplex communication system comprising a centralized communication system and a plurality of remote communications systems and a guard time to prevent simultaneous communications, the improvement comprising the determination of a guard time for each remote communications system as a function of the propagation delay associated with each remote communications system.

45. In a method of time division duplex communication between a centralized communication system and a plurality of remote communications systems, the improvement comprising the minimizing of guard time delay for a particular remote communications system as a function of both propagation delay for that remote communications system and the instantaneous traffic demand of that remote communications system.

46. In a communication system with scheduled communication between a centralized communication system and a plurality of remote communications systems each having variable communications transmissions, the improvement wherein the communication scheduler assigns communication system resources as a function of the instantaneous remote system transmission demands.

47. In a method of scheduling communication between a centralized communication system and a plurality of remote communications systems, each of the remote communications systems having variable communications transmissions, the improvement wherein the communication system resources are scheduled as a function of the instantaneous transmission demands of the remote communications systems.