METHOD AND APPARATUS FOR EFFICIENT DATA TRANSMISSIONS IN HALF-DUPLEX COMMUNICATION SYSTEMS WITH LARGE PROPAGATION DELAYS

• US 20170005741A1
• Filed: 06/23/2016
• Published: 01/05/2017
• Est. Priority Date: 07/02/2015
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: WU, Qiang, BLACK, Peter John, DAMNJANOVIC, Jelena
• Granted Patent: US 10,693,574 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 17/364 Delay profiles
• CPC Class Codes: H04B 7/185 Space-based or airborne stations; Stations for satellite systemsH04B7/204 takes precedence
• CPC Class Codes: H04B 7/2041 Spot beam multiple access
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic

Abstract

Methods and apparatus for efficient transmission of data by half-duplex transceivers in satellite communication systems are provided. Time reference for the return link is skewed or time-lagged relative to the time reference for the forward link to reduce the amount of guard time required to separate return link transmission from forward link reception by the half-duplex transceiver of a user terminal. The guard time is determined based on a maximum differential round-trip propagation delay and transition times of the half-duplexer transceiver to switch between transmit and receive modes. In a satellite communication system in which a large number of active user terminals are present in a beam coverage, random time offsets are applied to spread approximately equal traffic loads across the time offsets.

Claims

1. A method of determining a time lag of a return link time reference relative to a forward link time reference in a satellite communication system, the method comprising:

determining a minimum round-trip propagation delay of signals between a ground station and a satellite;

determining a transition time for a half-duplex transceiver of the ground station to switch between a transmit mode and a receive mode;

determining a system parameter based on the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode; and

determining the time lag of the return link time reference relative to the forward link time reference based on the minimum round-trip propagation delay and the system parameter.

2. The method of claim 1, further comprising determining a guard time between reception and transmission in the half-duplex transceiver.

3. The method of claim 2, wherein determining the guard time between reception and transmission in the half-duplex transceiver comprises:

determining a maximum round-trip propagation delay of signals between the ground station and the satellite;

determining a maximum differential round-trip propagation delay based on the maximum round-trip propagation delay and the minimum round-trip propagation delay; and

determining the guard time based on the maximum differential round-trip propagation delay and the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode.

4. The method of claim 1, wherein the ground station comprises a user terminal.

5. The method of claim 1, wherein the satellite comprises a non-geosynchronous satellite.

6. An apparatus configured to determine a time lag of a return link time reference relative to a forward link time reference in a satellite communication system, the apparatus comprising:

at least one processor; and

at least one memory coupled to the at least one processor, the at least one processor and the at least one memory being configured to;

determine a minimum round-trip propagation delay of signals between a ground station and a satellite;

determine a transition time for a half-duplex transceiver of the ground station to switch between a transmit mode and a receive mode;

determine a system parameter based on the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode; and

determine the time lag of the return link time reference relative to the forward link time reference based on the minimum round-trip propagation delay and the system parameter.

7. An apparatus for determining a time lag of a return link time reference relative to a forward link time reference in a satellite communication system, the apparatus comprising:

means for determining a minimum round-trip propagation delay of signals between a ground station and a satellite;

means for determining a transition time for a half-duplex transceiver at the ground station to switch between a transmit mode and a receive mode;

means for determining a system parameter based on the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode; and

means for determining the time lag of the return link time reference relative to the forward link time reference based on the minimum round-trip propagation delay and the system parameter.

8. A computer-readable medium comprising at least one instruction for causing a computer or processor to perform a method to determine a time lag of a return link time reference relative to a forward link time reference in a satellite communication system, the at least one instruction comprising instructions to:

determine a minimum round-trip propagation delay of signals between a ground station and a satellite;

determine a transition time for a half-duplex transceiver of the ground station to switch between a transmit mode and a receive mode;

determine a system parameter based on the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode; and

determine the time lag of the return link time reference relative to the forward link time reference based on the minimum round-trip propagation delay and the system parameter.

9. A method of determining a guard time between reception and transmission in a half-duplex transceiver, the method comprising:

determining a maximum round-trip propagation delay of signals between the half-duplex transceiver and a satellite;

determining a minimum round-trip propagation delay of signals between the half-duplex transceiver and the satellite;

determining a maximum differential round-trip propagation delay based on the maximum round-trip propagation delay and the minimum round-trip propagation delay;

determining a transition time for the half-duplex transceiver to switch between a transmit mode and a receive mode; and

determining the guard time based on the maximum differential round-trip propagation delay and the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode.

10. The method of claim 9, wherein the half-duplex transceiver comprises a transceiver of a user terminal.

11. The method of claim 9, wherein the satellite comprises a non-geosynchronous satellite.

12. An apparatus configured to determine a guard time between reception and transmission in a half-duplex transceiver, the apparatus comprising:

at least one processor; and

at least one memory coupled to the at least one processor, the at least one processor and the at least one memory being configured to;

determine a maximum round-trip propagation delay of signals between the half-duplex transceiver and a satellite;

determine a minimum round-trip propagation delay of signals between the half-duplex transceiver and the satellite;

determine a maximum differential round-trip propagation delay based on the maximum round-trip propagation delay and the minimum round-trip propagation delay;

determine a transition time for the half-duplex transceiver to switch between a transmit mode and a receive mode; and

determine the guard time based on the maximum differential round-trip propagation delay and the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode.

13. An apparatus for determining a guard time between reception and transmission in a half-duplex transceiver, the apparatus comprising:

means for determining a maximum round-trip propagation delay of signals between the half-duplex transceiver and a satellite;

means for determining a minimum round-trip propagation delay of signals between the half-duplex transceiver and the satellite;

means for determining a maximum differential round-trip propagation delay based on the maximum round-trip propagation delay and the minimum round-trip propagation delay;

means for determining a transition time for the half-duplex transceiver to switch between a transmit mode and a receive mode; and

means for determining the guard time based on the maximum differential round-trip propagation delay and the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode.

14. A computer-readable medium comprising at least one instruction for causing a computer or processor to perform a method to determine a guard time between reception and transmission in a half-duplex transceiver, the at least one instruction comprising instructions to:

determine a maximum round-trip propagation delay of signals between the half-duplex transceiver and a satellite;

determine a minimum round-trip propagation delay of signals between the half-duplex transceiver and the satellite;

determine a maximum differential round-trip propagation delay based on the maximum round-trip propagation delay and the minimum round-trip propagation delay;

determine a transition time for the half-duplex transceiver to switch between a transmit mode and a receive mode; and

determine the guard time based on the maximum differential round-trip propagation delay and the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode.

15. A method of determining a forward link time duration and a guard time duration in a half-duplex frame in a satellite communication system, the method comprising:

allocating a forward link time segment in a special subframe of the half-duplex frame;

allocating a guard time segment in the special subframe;

determining the forward link time duration in the half-duplex frame based on the forward link time segment in the special subframe; and

determining the guard time duration in the half-duplex frame based on the guard time segment in the special subframe.

16. The method of claim 15, wherein the half-duplex frame further comprises a forward link subframe preceding the special subframe and a guard subframe succeeding the special subframe.

17. The method of claim 16, wherein determining the forward link time duration in the half-duplex frame comprises adding the forward link time segment in the special subframe to the forward link subframe.

18. The method of claim 16, wherein determining the guard time duration in the half-duplex frame comprises adding the guard time segment in the special subframe to the guard subframe.

19. The method of claim 15, wherein the method is performed by an adaptive special subframe (SSF) scheduler.

20. The method of claim 19, wherein the adaptive SSF scheduler is in a gateway.

21. The method of claim 15, wherein the satellite communication system includes at least one ground station.

22. The method of claim 15, wherein the satellite communication system includes a satellite that is a non-geosynchronous satellite.

23. An apparatus configured to determine a forward link time duration and a guard time duration in a half-duplex frame in a satellite communication system, the apparatus comprising:

at least one processor; and

at least one memory coupled to the at least one processor, the at least one processor and the at least one memory being configured to;

allocate a forward link time segment in a special subframe of the half-duplex frame;

allocate a guard time segment in the special subframe;

determine the forward link time duration in the half-duplex frame based on the forward link time segment in the special subframe; and

determine the guard time duration in the half-duplex frame based on the guard time segment in the special subframe.

24. An apparatus for determining a forward link time duration and a guard time duration in a half-duplex frame in a satellite communication system, the apparatus comprising:

means for allocating a forward link time segment in a special subframe of the half-duplex frame;

means for allocating a guard time segment in the special subframe;

means for determining the forward link time duration in the half-duplex frame based on the forward link time segment in the special subframe; and

means for determining the guard time duration in the half-duplex frame based on the guard time segment in the special subframe.

25. A computer-readable medium comprising at least one instruction for causing a computer or processor to perform a method to determine a forward link time duration and a guard time duration in a half-duplex frame in a satellite communication system, the at least one instruction comprising instructions to:

allocate a forward link time segment in a special subframe of the half-duplex frame;

allocate a guard time segment in the special subframe;

determine the forward link time duration in the half-duplex frame based on the forward link time segment in the special subframe; and

determine the guard time duration in the half-duplex frame based on the guard time segment in the special subframe.

26. A method of scheduling time offsets of a plurality of user terminals in a beam coverage of a satellite in a satellite communication system, the method comprising:

determining a number of time offsets based on a number of active user terminals in the beam coverage;

assigning equally spaced time offsets based on the number of time offsets;

determining whether aggregate patterns for the active user terminals in the beam coverage have random offsets; and

spreading approximately equal traffic loads across times for the active user terminals.

27. The method of claim 26, wherein the method is performed by a random offset scheduler.

28. The method of claim 27, wherein the random offset scheduler is in a gateway.

29. The method of claim 26, wherein the satellite comprises a non-geosynchronous satellite.

30. An apparatus configured to schedule time offsets of a plurality of user terminals in a beam coverage of a satellite in a satellite communication system, the apparatus comprising:

at least one processor; and

at least one memory coupled to the at least one processor, the at least one processor and the at least one memory being configured to;

determine a number of time offsets based on a number of active user terminals in the beam coverage;

assign equally spaced time offsets based on the number of time offsets;

determine whether aggregate patterns for the active user terminals in the beam coverage have random offsets; and

spread approximately equal traffic loads across times for the active user terminals.

31. An apparatus for scheduling time offsets of a plurality of user terminals in a beam coverage of a satellite in a satellite communication system, the apparatus comprising:

means for determining a number of time offsets based on a number of active user terminals in the beam coverage;

means for assigning equally spaced time offsets based on the number of time offsets;

means for determining whether aggregate patterns for the active user terminals in the beam coverage have random offsets; and

means for spreading approximately equal traffic loads across times for the active user terminals.

32. A computer-readable medium comprising at least one instruction for causing a computer or processor to perform a method to schedule time offsets of a plurality of user terminals in a beam coverage of a satellite in a satellite communication system, the at least one instruction comprising instructions to:

determine a number of time offsets based on a number of active user terminals in the beam coverage;

assign equally spaced time offsets based on the number of time offsets;

determine whether aggregate patterns for the active user terminals in the beam coverage have random offsets; and

spread approximately equal traffic loads across times for the active user terminals.