Noise compensation in satellite communications

• US 20040131028A1
• Filed: 07/22/2003
• Published: 07/08/2004
• Est. Priority Date: 07/23/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Schiff, Leonard N., Miller, David S.
• Granted Patent: US 8,121,536 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 7/18532 Arrangements for managing transmission, i.e. for transporting data or a signalling message
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A quality measure, such as a signal-to-noise ratio, of a signal arriving at a gateway for a return link is used to adjust a data rate for the link. The return link is transferred from a terminal to the gateway through a satellite, and shared by a number of user terminals at any given time, including the terminal for which the data rate is adjusted. The terminals sharing the link have a certain interference relationship. Adjusting a data rate for a message sent from one or more terminals through the return link in the presence of signal degradation or power loss does not appreciably change the interference relationship among the plurality of terminals.

Claims

1. A method comprising:

identifying a change in a return link signal quality at a gateway for a return link from a terminal communicatively coupled to the gateway through a satellite, said return link being shared by a plurality of terminals having an interference relationship; and

adjusting a data rate for a message sent from the terminal through the return link based on the change in the return link signal quality without changing the interference relationship among the plurality of terminals.

2. The method of claim 1 wherein identifying the change and adjusting the data rate are performed substantially at the same time by both a transmitter of the message and a receiver of the message.

3. The method of claim 1 wherein identifying the change in signal quality comprises identifying a change in a signal-to-noise ratio for the return link from the terminal.

4. The method of claim 3 wherein the return link signal-to-noise ratio includes both thermal noise and interference.

5. The method of claim 3 wherein identifying the change in the return link signal-to-noise ratio comprises:

receiving a feedback signal at the terminal from the gateway, said feedback signal indicating at least one of the return link signal-to-noise ratio as measured at the gateway and the change in the return link signal-to-noise ratio as measured at the gateway .

6. The method of claim 3 wherein identifying the change in the return link signal-to-noise ratio comprises:

measuring a forward link signal-to-noise ratio at the terminal for a forward link from the gateway through the satellite to the terminal; and

approximating the return link signal-to-noise ratio at the gateway based on the forward link signal-to-noise ratio.

7. The method of claim 3 wherein adjusting the data rate comprises:

reducing the data rate if the return link signal-to-noise ratio has fallen below a first threshold; and

increasing the data rate if the return link signal-to-noise ratio has risen above a second threshold.

8. The method of claim 3 wherein adjusting the data rate comprises:

transmitting a bit of the message for a longer duration of time to reduce the data rate; and

transmitting a bit of the message for a shorter duration of time to increase the data rate.

9. The method of claim 3 wherein adjusting the data rate comprises adjusting the data rate to one of a set of discrete data-rate-to-carrier-bandwidth ratios.

10. The method of claim 1 wherein adjusting the data rate comprises:

transmitting a bit of the message for a longer duration of time to reduce the data rate; and

transmitting a bit of the message for a shorter duration of time to increase the data rate.

11. The method of claim 1 wherein adjusting the data rate comprises:

applying a higher coding rate to bits of the message to increase the data rate; and

applying a lower coding rate to bits of the message to reduce the data rate.

12. The method of claim 11 wherein adjusting the data rate further comprises:

transmitting a bit of the message for a longer duration of time to further reduce the data rate; and

transmitting a bit of the message for a shorter duration of time to further increase the data rate.

13. The method of claim 1 wherein adjusting the data rate comprises adjusting the data rate to one of a set of discrete data-rate-to-carrier-bandwidth ratios.

14. The method of claim 1 wherein said return link comprises a code division multiple access (CDMA) channel.

15. The method of claim 1 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, the method further comprising:

suspending the message if a current messaging time slot in a current time frame expires before the message is complete; and

resuming the message in a subsequent messaging time slot in a subsequent time frame.

16. The method of claim 15 wherein resuming the message comprises resuming the message at a beginning of the subsequent messaging time slot in the subsequent time frame.

17. The method of claim 1 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, the method further comprising initiating the message at a random point within a particular messaging time slot.

18. The method of claim 1 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, the method further comprising:

determining that the message will span more than a particular number of durations of the messaging time slot; and

transmitting the message beyond an end of a messaging time slot in a particular frame until the message is complete.

19. The method of claim 18 wherein determining that the message will span more than a particular number of durations of the messaging time slot comprises:

comparing a duration of the message at the current data rate to a length threshold, said length threshold comprising the particular number of durations.

20. The method of claim 18 wherein determining that the message will span more than a particular number of durations of the messaging time slot comprises:

comparing a current data-rate-to-bandwidth ratio for the message to a threshold data-rate-to-bandwidth ratio.

21. Apparatus comprising:

means for identifying a change in a return link signal quality at a gateway for a return link between a terminal and a gateway, said return link being shared by a plurality of terminals having an interference relationship; and

means for adjusting a data rate for a message sent from the terminal through the return link based on the change in the return link signal quality without changing the interference relationship among the plurality of terminals.

22. The apparatus of claim 21 wherein the means for identifying a change in a return link signal quality further comprises means for identifying a change in a signal-to-noise ratio for the return link from the terminal.

23. The apparatus of claim 22 wherein the means for identifying the change in the return link signal-to-noise ratio comprises:

means for receiving a feedback signal at the terminal from the gateway, said feedback signal indicating at least one of the return link signal-to-noise ratio as measured at the gateway and the change in the return link signal-to-noise ratio as measured at the gateway.

24. The apparatus of claim 22 wherein the means for identifying the change in the return link signal-to-noise ratio comprises:

means for measuring a forward link signal-to-noise ratio at the terminal for a forward link from the gateway through the satellite to the terminal; and

means for approximating the return link signal-to-noise ratio at the gateway based on the forward link signal-to-noise ratio.

25. The apparatus of claim 21 wherein the means for adjusting the data rate comprises:

means for reducing the data rate if the return link signal-to-noise ratio has fallen below a first threshold; and

means for increasing the data rate if the return link signal-to-noise ratio has risen above a second threshold.

26. The apparatus of claim 21 wherein the means for adjusting the data rate comprises:

means for transmitting a bit of the message for a longer duration of time to reduce the data rate; and

means for transmitting a bit of the message for a shorter duration of time to increase the data rate.

27. The apparatus of claim 21 wherein the means for adjusting the data rate comprises:

means for applying a higher coding rate to bits of the message to increase the data rate; and

means for applying a lower coding rate to bits of the message to reduce the data rate.

28. The apparatus of claim 27 wherein the means for adjusting the data rate further comprises:

means for transmitting a bit of the message for a longer duration of time to further reduce the data rate; and

means for transmitting a bit of the message for a shorter duration of time to further increase the data rate.

29. The apparatus of claim 21 wherein the means for adjusting the data rate comprises means for adjusting the data rate to one of a set of discrete data-rate-to-carrier-bandwidth ratios.

30. The apparatus of claim 21 wherein the means for adjusting the data rate comprises:

means for transmitting a bit of the message for a longer duration of time to reduce the data rate; and

means for transmitting a bit of the message for a shorter duration of time to increase the data rate.

31. The apparatus of claim 21 wherein the means for adjusting the data rate comprises means for adjusting the data rate to one of a set of discrete data-rate-to-carrier-bandwidth ratios.

32. The apparatus of claim 21 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, further comprising:

means for suspending the message if a current messaging time slot in a current time frame expires before the message is complete; and

means for resuming the message in a subsequent messaging time slot in a subsequent time frame.

33. The apparatus of claim 32 wherein the means for resuming the message comprises means for resuming the message at a beginning of the subsequent messaging time slot in the subsequent time frame.

34. The apparatus of claim 21 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, the apparatus further comprising means for initiating the message at a random point within a particular messaging time slot.

35. The apparatus of claim 21 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, the apparatus further comprising:

means for determining that the message will span more than a particular number of durations of the messaging time slot; and

means for transmitting the message beyond an end of a messaging time slot in a particular frame until the message is complete.

36. The apparatus of claim 35 wherein the means for determining that the message will span more than a particular number of durations of the messaging time slot comprises:

means for comparing a duration of the message at the current data rate to a length threshold, said length threshold comprising the particular number of durations.

37. The apparatus of claim 35 wherein the means for determining that the message will span more than a particular number of durations of the messaging time slot comprises:

means for comparing a current data-rate-to-bandwidth ratio for the message to a threshold data-rate-to-bandwidth ratio.

38. Apparatus comprising:

a comparator to identify a change in a return link signal quality at a gateway for a return link from a terminal communicatively coupled to the gateway through a satellite, said return link being shared by a plurality of terminals, said plurality of terminals having an interference relationship; and

a data rate generator to adjust a data rate for a message sent from the terminal through the return link based on the change in the return link signal-to-noise ratio without changing the interference relationship among the plurality of terminals.

39. The apparatus of claim 38 wherein the comparator is configured to identify a change in a signal-to-noise ratio for the return link from the terminal as the change in signal quality.

40. The apparatus of claim 39 wherein the comparator comprises:

a feedback input to receive a feedback signal from the gateway, said feedback signal indicating at least one of the return link signal-to-noise ratio as measured at the gateway and the change in the return link signal-to-noise ratio as measured at the gateway .

41. The apparatus of claim 39 wherein the comparator comprises:

a signal-to-noise detector to measure a forward link signal-to-noise ratio at the terminal for a forward link from the gateway through the satellite to the terminal; and

a logic block to approximate the return link signal-to-noise ratio at the gateway based on the forward link signal-to-noise ratio.

42. The apparatus of claim 39 wherein the data rate generator is to reduce the data rate if the return link signal-to-noise ratio has fallen below a first threshold, and increase the data rate if the return link signal-to-noise ratio has risen above a second threshold.

43. The apparatus of claim 38 wherein the data rate generator is to transmit a bit of the message for a longer duration of time to reduce the data rate, and transmit a bit of the message for a shorter duration of time to increase the data rate.

44. The apparatus of claim 38 wherein the data rate generator is to encode a bit of the message at a higher code rate to reduce the data rate, and encode a bit of the message at a lower code rate to increase the data rate.

45. The apparatus of claim 38 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, and wherein the data rate generator is to suspend the message if a current messaging time slot in a current time frame expires before the message is complete, and resume the message in a subsequent messaging time slot in a subsequent time frame.

46. The apparatus of claim 38 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, and wherein the data rate generator is to determine that the message will span more than a particular number of durations of the messaging time slot, and transmit the message beyond an end of a messaging time slot in a particular frame until the message is complete.

47. The apparatus of claim 38 wherein the data rate generator comprises:

a threshold comparator to compare a duration of the message at the current data rate to a length threshold, said length threshold comprising the particular number of durations.

48. The apparatus of claim 38 wherein the data rate generator comprises:

a threshold comparator to compare a current data-rate-to-bandwidth ratio for the message to a threshold data-rate-to-bandwidth ratio.

49. A machine readable medium having stored thereon machine executable instructions that when executed implement a method comprising:

identifying a change in a return link signal quality at a gateway for a return link from a terminal communicatively coupled to the gateway through a satellite, said return link being shared by a plurality of terminals having an interference relationship; and

adjusting a data rate for a message sent from the terminal through the return link based on the change in the return link signal quality without changing the interference relationship among the plurality of terminals.

50. The machine readable medium of claim 49 wherein the instructions, when executed to implement the step of identifying the change in signal quality further cause identifying a change in a signal-to-noise ratio for the return link from the terminal.

51. The machine readable medium of claim 50 wherein the instructions, when executed, to identify the change in the return link signal-to-noise ratio implement a method comprising:

receiving a feedback signal at the terminal from the gateway, said feedback signal indicating at least one of the return link signal-to-noise ratio as measured at the gateway and the change in the return link signal-to-noise ratio as measured at the gateway .

52. The machine readable medium of claim 50 herein the instructions, when executed, implement a method comprising

measuring a forward link signal-to-noise ratio at the terminal for a forward link from the gateway through the satellite to the terminal;

and

approximating the return link signal-to-noise ratio at the gateway based on the forward link signal-to-noise ratio.

53. The machine readable medium of claim 50 herein the instructions, when executed, implement a method adjusting the data rate comprising:

reducing the data rate if the return link signal-to-noise ratio has fallen below a first threshold; and

increasing the data rate if the return link signal-to-noise ratio has risen above a second threshold.

54. The machine readable medium of claim 50 wherein the instructions, when executed, implement a method adjusting the data rate comprising:

transmitting a bit of the message for a longer duration of time to reduce the data rate; and

transmitting a bit of the message for a shorter duration of time to increase the data rate.

55. The machine readable medium of claim 49 wherein the instructions, when executed, implement a method adjusting the data rate comprising:

transmitting a bit of the message for a longer duration of time to reduce the data rate; and

transmitting a bit of the message for a shorter duration of time to increase the data rate.

56. The machine readable medium of claim 49 wherein the instructions, when executed, implement a method comprising adjusting the data rate to one of a set of discrete data-rate-to-carrier-bandwidth ratios.

57. The machine readable medium of claim 49 wherein the return link comprises a messaging time slot among a plurality of time slots in each of a series of time frames, and wherein the instructions, when executed, implement a method comprising:

suspending the message if a current messaging time slot in a current time frame expires before the message is complete; and

resuming the message in a subsequent messaging time slot in a subsequent time frame.

58. The machine readable medium of claim 57 wherein the instructions, when executed, implement a method comprising resuming the message at a beginning of the subsequent messaging time slot in the subsequent time frame.

59. The machine readable medium of claim 49 wherein the instructions, when executed, implement a method comprising:

determining that the message will span more than a particular number of durations of a messaging time slot in the return link among a plurality of time slots in each of a series of time frames forming the return link; and

transmitting the message beyond an end of a messaging time slot in a particular frame until the message is complete.