DELTA-THETA FREQUENCY ESTIMATION

• US 20100159861A1
• Filed: 12/18/2009
• Published: 06/24/2010
• Est. Priority Date: 12/18/2008
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Thesling, William H., Becker, Donald W., Nimon, Matthew D.
• Granted Patent: US 8,683,283 B2
• Time in Patent Office: Days
• US Class Current: 455/205
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04L 7/0029 interpolation of received data signal

Abstract

Systems, devices, processors, and methods are described which may be used for the reception of a wireless broadband signal at a user terminal from a gateway via satellite. A physical layer header may be identified, the header including a number of subcode blocks. A phase may be estimated for each of the subcode blocks, and intra-header phase differences may be calculated. The intra-header phase differences may be used to calculate a frequency error, which may be corrected. Frequency errors may be monitored and, when such errors fall below a threshold level, an alternative inter-frame frequency error tracking method may be used.

Claims

1. A method of frequency estimation comprising:

identifying a physical layer header including a plurality of subcode blocks;

estimating a phase for each of at least a subset of the plurality of subcode blocks;

calculating a first phase difference between a first two of the subcode block phase estimates;

calculating a second phase difference between a second two of the subcode block phase estimates;

utilizing the first phase difference and the second phase difference to calculate a frequency error; and

correcting a frequency for receiving a wireless signal utilizing the calculated frequency error.

2. The method of claim 1, further comprising:

decoding each of the subset of subcode blocks, wherein the phase for each of the subset of subcode blocks is estimated using the decoded data.

3. The method of claim 1, wherein utilizing the first phase difference and the second phase difference to calculate a frequency error comprises:

calculating average between the first phase difference and the second phase difference.

4. The method of claim 1, further comprising:

calculating, for each of a plurality of additional physical layer headers, a frequency error utilizing two or more phase difference measurements in each of the additional physical layer headers; and

correcting a frequency error for a received wireless signal utilizing at least a subset of the calculated frequency errors for the additional physical layer headers.

5. The method of claim 4, further comprising:

averaging the calculated frequency errors for at least a subset of the additional physical layer headers; and

continuing to correct the signal utilizing the calculated frequency errors for the additional physical layer headers until the average frequency error falls below a threshold.

6. The method of claim 1, wherein the plurality of subcode blocks in the physical layer header comprises three subcode blocks.

7. The method of claim 6, wherein the three subcode blocks each comprise a Walsh code block.

8. A device for frequency estimation comprising:

a frame synchronization module configured to identify a physical layer header including a plurality of subcode blocks in a digitized wireless signal;

a phase estimation module, communicatively coupled with the frame synchronization module, and configured to estimate a phase for each of at least a subset of the plurality of subcode blocks in the identified physical layer header;

a phase differential calculation module, communicatively coupled with the phase estimation module, and configured to;

calculate a first phase difference between a first two of the subcode block phase estimates; and

calculate a second phase difference between a second two of the subcode block phase estimates; and

a frequency error estimation module, communicatively coupled with the phase differential calculation module, and configured to utilize the first phase difference and the second phase difference to calculate a frequency error.

9. The device of claim 8, further comprising a header decoder module, communicatively coupled with the phase estimation module, and configured to decode each of the subset of subcode blocks, wherein the phase for each of the subset of subcode blocks is estimated using the decoded data.

10. The device of claim 8, further comprising a frequency error correction module, communicatively coupled with the frequency error estimation module, and configured to correct a frequency for receiving a wireless signal utilizing the calculated frequency error.

11. The device of claim 8, wherein the frequency error estimation module is further configured to calculate, for each of a plurality of additional physical layer headers, a frequency error utilizing two or more phase difference measurements in each of the additional physical layer headers.

12. The device of claim 11, further comprising a frequency error correction module, communicatively coupled with the frequency error estimation module, configured to correct a frequency error for a received wireless signal utilizing the calculated frequency errors for the additional physical layer headers.

13. The device of claim 12, further comprising:

a threshold comparator module, communicatively coupled with the frequency error estimation module, and configured to monitor the calculated frequency errors for at least a subset of the additional physical layer headers to determine when the monitored frequency errors fall below a threshold,

wherein the frequency error correction module continues to iteratively correct the frequency error for the received wireless signal utilizing calculated frequency errors for the additional physical layer headers until the monitored frequency errors fall below the threshold.

14. The device of claim 13, further comprising an inter-header module, communicatively coupled with the frequency error estimation module, and configured to monitor an inter-header phase difference to determine whether an acquired wireless signal is lost.

15. The device of claim 8, wherein,

the first phase difference comprises a difference measurement between a first subcode and a second subcode;

and

the second phase difference comprises a difference measurement between the second subcode and a third subcode.

16. The device of claim 8, wherein the plurality of subcode blocks comprises three adjacent Walsh code blocks.

17. A method of frequency estimation comprising:

identifying a plurality of physical layer headers in a digitized wireless signal, each identified physical layer header including a substantially same code structure including a plurality of subcode blocks;

estimating, for each of the identified physical layer headers, a phase for each of at least a subset of the plurality of subcode blocks;

calculating, for each of the identified physical layer headers, a first phase difference between a first two of the subcode block phase estimates;

calculating, for each of the identified physical layer headers, a second phase difference between a second two of the subcode block phase estimates;

calculating, for each of the identified physical layer headers, a frequency error utilizing the first phase difference and the second phase difference for each respective physical layer header; and

correcting a frequency error for the wireless signal utilizing the calculated frequency errors.

18. The method of claim 17, further comprising:

monitoring the calculated frequency errors to determine when a set of one or more of the calculated frequency errors falls below a threshold level; and

generating a carrier lock signal when there is a determination that the set of one or more of the calculated frequency errors falls below the threshold level.

19. The method of claim 18, wherein the threshold level is programmable.

20. The method of claim 17, further comprising:

determining that a set of one or more of the calculated frequency errors falls below a threshold level; and

calculating, responsive to the determination, an inter-header phase difference between a phase estimate associated with a first physical layer header of the plurality of physical layer headers and a phase estimate associated with a second physical layer header of the plurality of physical layer headers.

21. The method of claim 20, further comprising:

generating a carrier lock lost signal responsive to a determination that an inter-header phase difference measurement exceeds a second threshold level.

22. A device for frequency estimation comprising:

an intra-header module configured to estimate, for each of a plurality of physical layer headers of a received wireless signal, an intra-header frequency error utilizing intra-header phase difference measurements; and

a frequency error correction module, communicatively coupled with the intra-header module, and configured to iteratively correct a frequency error for the received wireless signal utilizing the calculated frequency errors;

a threshold comparator module, communicatively coupled with the frequency correction module, and configured to signal the frequency error correction module to suspend the intra-header corrections when intra-header frequency errors fall below a threshold and signal for activation of an inter-frame module when intra-header frequency errors fall below the threshold; and

the inter-frame module, communicatively coupled with the threshold comparator module, and configured to track a frequency error for the received wireless signal utilizing inter-frame phase difference measurements when signaled by the threshold comparator module.

23. The device of claim 22, wherein a threshold comparator module is further configured to signal to reactivate the intra-header module when the inter-frame-phase difference measurements exceed a second threshold level and signal to suspend the inter-frame module when the inter-frame- phase difference measurements exceed the second threshold level.

24. The device of claim 22, wherein the intra-header module comprises a phase estimation module, a phase differential calculation module, and a frequency error estimation module, and is configured to calculate intra-header frequency errors by calculating a difference measurement between a first phase difference and a second phase difference in each of the physical layer headers.