Delta-theta frequency estimation

• US 8,683,283 B2
• Filed: 12/18/2009
• Issued: 03/25/2014
• Est. Priority Date: 12/18/2008
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Becker, Donald W., Nimon, Matthew D., Thesling, William H.
• Primary Examiner(s): Decady, Albert
• Assistant Examiner(s): KABIR, ENAMUL MD
• Application Number:
  US12/641,537
• Publication Number:
  US 20100159861A1
• Time in Patent Office: 1,558 Days
• Field of Search: None
• US Class Current: 714/746
• 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 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;

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.

2. The device of claim 1, wherein the 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.

3. The device of claim 1, 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 the 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.

4. The device of claim 3, wherein the frequency error correction module is further configured to correct the frequency for receiving the wireless signal utilizing the intra-header frequency errors when the intra-header frequency errors are above the threshold.

5. The device of claim 3, wherein the intra-header module is further configured to calculate the intra-header frequency errors by averaging the first phase difference and the second phase difference.

6. The device of claim 3, wherein the intra-header module is further configured to generate the first phase difference and the second phase difference in each of the physical layer headers by estimating phases of decoded subcode data of each of a plurality of subcode blocks of the physical layer headers.

7. The device of claim 6, wherein the plurality of subcode blocks of the physical layer headers comprise at least three subcode blocks.

8. The device of claim 7, wherein the at least three subcode blocks each comprise a Walsh code block.

9. The device of claim 1, wherein the intra-header module is further configured to identify one or more of the plurality of physical layer headers by performing a frequency search of the received wireless signal.

10. The device of claim 9, wherein the frequency search comprises a random frequency search.

11. The device of claim 9, wherein the intra-header module is further configured to identify the one or more physical layer headers using a unique word correlation.

12. A method for frequency estimation comprising:

estimating, 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;

iteratively correcting a frequency error for the received wireless signal utilizing the estimated intra-header frequency errors; and

activating inter-frame frequency error correction when the intra-header frequency errors fall below a threshold, the activating comprising;

suspending the intra-header corrections utilizing the estimated intra-header frequency errors; and

tracking a frequency error for the received wireless signal utilizing inter-frame phase difference measurements.

13. The method of claim 12, further comprising:

reactivating intra-header frequency error correction utilizing the estimated intra-header frequency errors when the inter-frame-phase difference measurements exceed a second threshold level; and

suspending the tracking the frequency error utilizing the inter-frame phase difference measurements when the inter-frame phase difference measurements exceed the second threshold level.

14. The method of claim 12, further comprising:

calculating the 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.

15. The method of claim 14, further comprising:

correcting the frequency for receiving the wireless signal utilizing the intra-header frequency errors when the intra-header frequency errors are above the threshold.

16. The method of claim 14, wherein utilizing the first phase difference and the second phase difference to calculate the intra-header frequency error comprises averaging the first phase difference and the second phase difference.

17. The method of claim 14, wherein calculating the intra-header frequency errors comprises:

generating the first phase difference and the second phase difference in each of the physical layer headers by estimating phases of decoded subcode data of each of a plurality of subcode blocks of the physical layer headers.

18. The method of claim 17, wherein the plurality of subcode blocks of the physical layer headers comprise at least three subcode blocks.

19. The method of claim 18, wherein the at least three subcode blocks each comprise a Walsh code block.

20. The method of claim 12, further comprising:

identifying one or more of the plurality of physical layer headers by performing a frequency search of the received wireless signal.

21. The method of claim 20, wherein the frequency search comprises a random frequency search.

22. The method of claim 20, wherein identifying one or more of the plurality of physical layer headers is performed using a unique word correlation.