Master terminal synchronization for mesh satellite communications

• US 8,675,635 B2
• Filed: 10/06/2009
• Issued: 03/18/2014
• Est. Priority Date: 10/06/2008
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Agarwal, Anil
• Primary Examiner(s): Nguyen, Steven H
• Assistant Examiner(s): Waqas, Saad A
• Application Number:
  US12/574,068
• Publication Number:
  US 20100085909A1
• Time in Patent Office: 1,624 Days
• Field of Search: 370/350
• US Class Current: 370/350
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/2125 Synchronisation

Abstract

Methods, systems, and devices are described for synchronization in mesh satellite communications. The arrival time of the gateway signal may be used to set a start of receive frame time for a terminal. A received control signal from the gateway may then be used to set a start of transmit frame time for the user terminal. The distance between the satellite and the gateway may change. Ephemeris data, various collections of terminal measurements, or terminal sync bursts may be used to modify start of transmit frame or start of receive frame settings for the terminal or gateway.

Claims

1. A system for synchronizing timing for mesh satellite communications, the system comprising:

a gateway configured to;

transmit a first set of signals to set a first start of receive frame timing for a user terminal for communications from the gateway; and

transmit a second set of signals to set a start of transmit frame timing for the user terminal for communications to the gateway and communications to other user terminals;

the user terminal, in communication with the gateway via satellite, configured to;

receive the first set of signals to set the first start of receive frame timing for communications received at the user terminal from the gateway, the first start of receive frame timing set based on a reception time of the first set of signals at the user terminal;

receive the second set of signals to set a start of transmit frame timing for the user terminal for communications to the gateway and communications to other user terminals via the satellite; and

receive a third set of signals from a master user terminal to set a second start of receive frame timing for communications received at the user terminal from other user terminals via the satellite, the second start of receive frame timing set based on a reception time of the third set of signals at the user terminal; and

the master user terminal, in communication with the user terminal via satellite, and configured to;

transmit the third set of signals comprising a broadcast burst signal received by the user terminal and other user terminals to set start of receive frame timing for mesh communications.

2. The system of claim 1, wherein the third set of signals set start of receive frame timing at one or more of the other user terminals for mesh communications transmitted from the user terminal via the satellite.

3. The system of claim 1, wherein the user terminal comprises a master user terminal.

4. The system of claim 1, wherein the user terminal is further configured to transmit the third set of signals to itself to set the second start of receive frame timing based on a reception time of the third set of signals transmitted to itself.

5. The system of claim 1, wherein, when the distance between the gateway and the satellite decreases, the gateway is configured to:

transmit the second set of signals to adjust start of transmit frame timing for the user terminal in response to a fourth set of signals transmitted from the user terminal; and

maintain transmission timing for the first set of signals used to set the first start of receive frame timing for the user terminal for communications from the gateway.

6. The system of claim 1, wherein,

the communications by the user terminal to the gateway and the communications from the gateway to the user terminal comprise a portion of a star communications link;

and

the communications by the user terminal to other user terminals and the communications from the other user terminals to the user terminal comprise mesh communications links.

7. A user terminal for synchronizing timing for mesh satellite communications, the user terminal comprising:

a receiver module configured to;

receive a first set of signals from a master user terminal, configured to transmit the first set of signals, the first set of signals comprising a broadcast burst signal received by the user terminal and other user terminals to set start of receive frame timing for mesh communications;

a frame synchronization module, communicatively coupled with the receiver module, configured to;

use the first set of signals from the master user terminal to identify a first start of receive frame timing for communications received at the user terminal via satellite from other user terminals, the first start of receive frame timing identified based on a reception time of the first set of signals at the user terminal; and

use a second set of signals to identify a second start of receive frame timing for communications received at the user terminal via satellite from a gateway, the second start of receive frame timing identified based on a reception time of the second set of signals at the user terminal;

a star receiver module, communicatively coupled with the frame synchronization module, and configured to receive communications from the gateway via satellite according to the second start of receive frame timing; and

a mesh receiver module, communicatively coupled with the frame synchronization module, and configured to receive communications from the other user terminals according to the first start of receive frame timing.

8. The user terminal of claim 7, wherein the receiver module is further configured to:

receive the second set of signals transmitted from the gateway; and

receive a third set of signals transmitted from the gateway, the third set of signals used by the frame synchronization module to set a start of transmit frame timing for the user terminal for communications to the gateway and communications to other user terminals.

9. The user terminal of claim 7, wherein the user terminal comprises a master user terminal.

10. The user terminal of claim 7, further comprising:

a transmission module configured to transmit the first set of signals to set the first start of receive frame timing at the user terminal for mesh communications.

11. The user terminal of claim 7, wherein,

the communications from the user terminal to the gateway and the communications from the gateway to the user terminal comprise star communications links;

and

the communications by the user terminal to other user terminals and the communications from the other user terminals to the user terminal comprise mesh communications links.

12. A method for synchronizing timing for mesh satellite communications, the method comprising:

using a first set of signals received from a gateway to set a first start of receive frame timing for communications received from the gateway, the first start of receive frame timing set based on a reception time of the first set of signals;

using a second set of signals received from a first user terminal of a plurality of user terminals, the first user terminal comprising a master user terminal configured to transmit the second set of signals, the second set of signals comprising a broadcast burst signal received by each of the plurality of user terminals to set a second start of receive frame timing for mesh communications received from one or more of the plurality of user terminals, the second start of receive frame timing set based on a reception time of the second set of signals; and

using a third set of signals received from the gateway to set start of transmit frame timing for both communications to the gateway and communications to the one or more of the plurality of user terminals.

13. The method of claim 12, further comprising:

transmitting the second set of signals to set the second start of receive frame timing for mesh communications, wherein the method is performed by the first user terminal.

14. The method of claim 12, wherein the method is performed by the master user terminal.

15. The method of claim 12, wherein the method is performed by a second user terminal of the plurality of user terminals.

16. A device for synchronizing timing for mesh satellite communications, the device comprising:

means for using a first set of received signals to identify a first start of receive frame timing for communications received at the device via satellite from a gateway, the first start of receive frame timing identified based on a reception time of the first set of received signals at the device;

means for using a second set of received signals from a user terminal comprising a master user terminal, the second set of received signals comprising a broadcast burst signal received by the device and user terminals to identify a second start of receive frame timing for communications received at the device via satellite from user terminals, the second start of receive frame timing identified based on a reception time of the second set of received signals at the device;

means for receiving communications from the gateway via satellite according to the first start of receive frame timing; and

means for receiving communications from the user terminals according to the second start of receive frame timing.