RETURN LINK POWER CONTROL

• US 20090296629A1
• Filed: 05/27/2009
• Published: 12/03/2009
• Est. Priority Date: 05/27/2008
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Mo, Fan, Lincoln, Andrew
• Granted Patent: US 8,259,604 B2
• Time in Patent Office: Days
• US Class Current: 370/321
• CPC Class Codes: H04B 7/18589 Arrangements for controlling an end to end session, i.e. for initialising, synchronising or terminating an end to end link

Abstract

Satellite communication methods and systems are disclosed. Various embodiments employ dummy bursts to monitor the communication channel between a user terminal and a hub. In some embodiments, dynamic link adaptation can also be employed to optimize channel performance. In some embodiments, the link margin can be estimated based on the signal quality of a traffic or dummy burst that is received at the hub and compared with a threshold value. If the link margin is less than a first/low threshold then the hub can instruct the terminal to change any of various communication parameters according to a predetermined algorithm to mitigate channel fading. If the link margin is greater than a second/high threshold then the hub can instruct the terminal to change any of various communication parameters according to a predetermined algorithm to reduce overcompensation for channel fading.

Claims

1. A satellite communication method comprising:

receiving signals at a hub from a plurality of terminals through a satellite, each of the signals being segmented into a plurality of timeslots;

receiving a burst from a terminal within one of the plurality of timeslots, wherein the burst comprise a dummy burst or a traffic burst;

estimating a received signal quality of the burst at the hub; and

when the received signal quality is less than a first signal quality value, communicating an indication to the terminal to change at least one communication parameter.

2. The satellite communication method according to claim 1, further comprising when the received signal quality is greater than a second signal quality value, communicating an indication to the terminal to change at least one communication parameter.

3. The satellite communication method according to claim 1, wherein the received signals are segmented into one of a plurality of carrier frequencies.

4. The satellite communication method according to claim 1, wherein the signal quality is estimated by estimating the link margin of the signal.

5. The satellite communication method according to claim 4, wherein the link margin is calculated as the difference between the received signal quality and the expected signal quality.

6. The satellite communication method according to claim 1, wherein the received signal quality can be indicated by at least one of the group consisting of the estimated power of the received signal, the estimated signal-to-noise ratio of the received signal, the estimated link margin of the received signal, the estimated decoded BER of the received signal, the estimated packet error rate (PER) of the received signal, and the estimated channel BER of the received signal.

7. The satellite communication method according to claim 1, wherein the east one communication parameter includes a communication parameter selected from the group consisting of transmission power, modulation format, code rate, carrier frequency, and symbol rate of the burst.

8. The satellite communication method according to claim 1, wherein the at least one communication parameter is communicated from the hub to a terminal using a burst time plan or other control message.

9. The satellite communication method according to claim 1 further comprising sending a burst time plan from the hub to the terminal, wherein the burst time plan includes an indication specifying a timeslot within which the burst should be sent.

10. The satellite communication method according to claim 1 further comprising sending a burst time plan from the hub to the terminal, wherein the burst time plan includes an indication specifying a carrier frequency within which the burst should be sent.

11. The satellite communication method according to claim 1, wherein the dummy burst includes data selected from the group consisting of:

random data, system data, terminal diagnostic data, network data, and communication data.

12. A satellite communication method comprising:

receiving a control message at a terminal from a hub through a satellite;

sending a burst to the hub through the satellite during a timeslot specified by the control message, wherein the burst is transmitted from the terminal using an antenna, and the burst includes either a dummy burst or a traffic burst;

receiving a second control message at the terminal from the hub through the satellite, the second control message including information indicating changes to at least one communication parameter selected from the group consisting of transmission power, carrier frequency, modulation, code rate, and symbol rate; and

communicating with the hub using changes to the at least one communication parameter indicated in the second control message.

13. The satellite communication method according to claim 12, wherein the burst is sent using a carrier frequency specified by the control message.

14. The satellite communication method according to claim 12, wherein the communication parameter is selected from the group consisting of transmission power, modulation, code rate, carrier frequency, and symbol rate.

15. A satellite communication hub comprising:

a satellite dish configured to transmit signals to and receive signals from one or more terminals through one or more satellites;

a controller coupled with the satellite dish, the controller being configured to;

estimate the signal quality of traffic, control, and dummy burst(s) received at the satellite dish from a terminal,

when the estimated signal quality is less than a first threshold signal quality value, communicate an indication to the terminal to change at least one communication parameter.

16. The satellite communication hub according to claim 15, wherein the controller is configured to communicate an indication to the terminal to change at least one communication parameter when the estimated link margin is higher than a second threshold signal quality value

17. The satellite communication hub according to claim 15, wherein the controller is configured to estimate the signal quality by estimating at least one of the group consisting of the estimated power of the received signal, the estimated signal-to-noise ratio of the received signal, the estimated link margin of the received signal, the estimated decoded BER of the received signal, the estimated packet error rate (PER) of the received signal, and the estimated channel BER of the received signal.

18. The satellite communication hub according to claim 17, wherein the link margin is calculated as the difference between the received signal quality and the expected signal quality.

19. The satellite communication hub according to claim 15, wherein the communicating an indication to the terminal to change at least one communication parameter includes communicating the at least one communication parameter as part of a control message.

20. The satellite communication hub according to claim 15 further comprising communicating a control message using the satellite dish, wherein the control message indicates a timeslot within which the terminal should send the dummy burst.

21. The satellite communication hub according to claim 15 further comprising communicating a control message using the satellite dish, wherein the control message indicates a carrier frequency within which the terminal should send the dummy burst.

22. The satellite communication hub according to claim 15, wherein the communication parameter is selected from the group consisting of transmission power, modulation, code rate, carrier frequency, and symbol rate.

23. The satellite communication hub according to claim 15, wherein the controller is further configured to determine which of the one or more terminals should send a dummy burst.

24. A satellite communication terminal comprising:

a satellite antenna configured to transmit signals to and receive signals from a hub through one or more satellites;

a controller coupled with the satellite antenna, the controller being configured to;

receive a first control message from the hub using the satellite antenna;

transmit at least one burst to the hub using the satellite antenna, wherein the at least one burst comprises either or both a dummy burst or a traffic burst and the burst is transmitted during at least one timeslot specified by the first control message, and the at least one burst is transmitted using a first set of communication parameters;

receive a second control message from the hub using the satellite antenna, the second control message includes a second set of communication parameters, wherein at least one communication parameter in the second set of communication parameters is different from a corresponding communication parameter in the first set of communication parameters; and

thereinafter communicate with the hub using the second set of communication parameters.

25. The satellite communication terminal according to claim 24, wherein the communication parameters include parameters selected from the group consisting of transmission power, carrier frequency, modulation, code rate, and symbol rate.

26. The satellite communication terminal according to claim 24, wherein the control message comprises a burst time plan.

27. A satellite communication hub comprising:

reception means for receiving signals from one or more terminals through one or more satellites, wherein the signals include a received burst from at least one of the terminals;

processing means for determining whether the link margin estimated from received burst is below a first threshold; and

transmission means for transmitting an indication to the terminal to change at least one communication parameter when the link margin is below the first threshold.

28. The satellite communication hub according to claim 27, wherein the transmission means transmits an indication to the terminal to change at least one communication parameter when the link margin is above a second threshold.

29. The satellite communication hub according to claim 27, wherein the transmission means transmits a burst time plan that includes the indication to change at least one communication parameter.

30. The satellite communication hub according to claim 27, wherein the transmission means transmits a burst time plan that specifies either or both a timeslot or a carrier frequency within which a terminal should send a dummy burst.

31. The satellite communication hub according to claim 27, wherein the processing means determines which terminals of the one or more terminals should send a dummy burst.

32. A satellite communication terminal comprising:

receiving means for receiving a first control message from a hub and a second control message from the hub, wherein the first control message indicates a timeslot within which a first burst should be transmitted to the hub and indicating a first set of communication parameters, and wherein the second control message indicates a timeslot within which a second burst should be transmitted to the hub and indicating a second set of communication parameters; and

transmitting means for sending the first burst to the hub as specified by the first control message using a first set of communication parameters, and for sending a second burst as specified by the second control message using the second set of communication parameters, wherein the value of at least one parameter in the first set of communication parameters differs from the value of a corresponding parameter in the second set of communication parameters.

33. The satellite communication terminal according to claim 32, wherein the burst comprises either a dummy burst or a traffic burst.

34. The satellite communication terminal according to claim 32, wherein the receiving means includes an antenna.

35. The satellite communication terminal according to claim 32, wherein the transmitting means includes an antenna.

36. A satellite communication method comprising:

receiving a burst at a hub from a terminal through a satellite;

estimating the link margin of the burst;

when the link margin is not within threshold values, then;

determining a power correction for the terminal;

determining whether the power correction would result in a transmit power at the terminal that is within the power threshold values; and

when the power correction is within the power threshold values, sending the power correction to the terminal; and

when the power correction is not within the power threshold values, sending the power correction to the terminal along with changes to either or both of the modulation and code rate.

37. The satellite communication method according to claim 36, wherein the burst comprises either a dummy burst or a traffic burst.

38. The satellite communication method according to claim 36, wherein when the power correction is not within the power threshold values, sending the power correction to the terminal along with changes to the symbol rate.