Robust burst detection and acquisition system and method
View Patent ↗A method of parameter estimation in a shared channel communications system includes the steps of receiving a preamble including a first sequence corresponding to a sequence having zero autocorrelation, a second sequence having zero autocorrelation, and a third sequence having zero autocorrelation, performing a coarse carrier frequency estimate based on the first sequence, and performing a fine carrier frequency estimate based on the second and third sequences.
1. A system for ranging a receiver in a shared communications channel, comprising:
a filter that receives a signal from the shared communications channel and outputs a Nyquist sample, wherein said signal includes:
a ranging preamble containing a first sequence whose derivative is a zero autocorrelation sequence,
a second sequence corresponding to a truncated first sequence, and
a third sequence corresponding to said truncated first sequence;
a preamble processor/ranging subsystem that receives said Nyquist sample from said filter, provides a first carrier frequency estimate based on said first sequence, and refines said first carrier frequency estimate to provide a second carrier frequency estimate, wherein said refining is based on said second sequence and said third sequence, wherein said first carrier frequency estimate is of a first accuracy, wherein said second carrier frequency estimate is of a second accuracy that is greater than said first accuracy; and
a tracking subsystem that extracts data from said signal based on said second carrier frequency estimate.
2. The system of claim 1 , wherein a derivative of said first sequence is a constant-amplitude zero autocorrelation sequence.
3. The system of claim 1 , wherein said preamble processor/ranging subsystem estimates a channel signal-to-noise ratio based on said ranging preamble.
4. The system of claim 1 , wherein said preamble processor/ranging subsystem estimates a carrier phase based on said ranging preamble.
5. The system of claim 1 , wherein said preamble processor/ranging subsystem estimates a gain of said signal based on said ranging preamble.
6. The system of claim 1 , wherein said preamble processor/ranging subsystem estimates a symbol rate based on said ranging preamble.
7. The system of claim 1 , wherein said preamble processor/ranging subsystem estimates said first carrier frequency using a phase of a differential correlation peak of said first sequence.
8. The system of claim 1 , wherein said preamble processor/ranging subsystem comprises a first derotator and wherein said filter outputs said Nyquist sample to said first derotator.
9. The system of claim 1 , wherein said tracking subsystem corrects a gain of said signal based on said second carrier frequency estimate.
10. The system of claim 1 , wherein said tracking subsystem determines a correction factor from a table based on an error of said second carrier frequency estimate.
11. The system of claim 1 , wherein said tracking subsystem tracks a burst during a payload when said system receives said burst comprising both the ranging preamble and said payload.
12. The system of claim 11 , wherein said burst includes at least one zero autocorrelation sequence outside said ranging preamble.
13. A system for parameter estimation in a shared channel communications system, comprising:
means for receiving a preamble comprising:
a first sequence corresponding to a sequence having zero autocorrelation,
a second sequence corresponding to a truncated first sequence, and
a third sequence corresponding to said truncated first sequence;
means for performing a first carrier frequency estimate based on said first sequence; and
means for performing a second carrier frequency estimate based on said second sequence and said third sequence.
14. The system of claim 13 , further comprising means for differentiating said first sequence.
15. The system of claim 13 , further comprising means for estimating a channel signal-to-noise ratio based on said preamble.
16. The system of claim 13 , further comprising means for estimating a carrier phase based on said preamble.
17. The system of claim 13 , further comprising means for estimating a gain of said preamble based on said preamble.
18. The system of claim 13 , further comprising means for estimating a symbol timing based on said preamble.
19. The system of claim 13 , further comprising means for estimating a channel signal-to-noise ratio based on information provided by a modem coupled to a channel of the shared channel communication system.
20. The system of claim 13 , further comprising means for estimating a channel signal-to-noise ratio based on a spectral analysis of said preamble.
21. The system of claim 13 , wherein said means for performing said first frequency estimate uses a phase of a differential correlation peak of said first sequence.
22. The system of claim 13 , further comprising means for derotating said first sequence prior to said means for performing a first carrier frequency estimate.
23. The system of claim 13 , further comprising means for comparing a phase of a first correlation vector corresponding to said second sequence to a phase of a second correlation vector corresponding to said third sequence wherein said first correlation vector and said second correlation vector are consecutive.
24. The system of claim 13 , further comprising means for correcting a gain of said preamble based on said second carrier frequency estimate.
25. The system of claim 13 , further comprising means for determining a correction factor based on an error of said second carrier frequency estimate.
26. The system of claim 13 , further comprising:
means for receiving a burst that includes the preamble and data; and
means for tracking a burst parameter during reception of said data.
27. A system for ranging in a shared channel communications system, comprising:
means for receiving a ranging preamble comprising:
a first sequence having a derivative that is a zero autocorrelation sequence,
a second sequence that corresponds to an integral of said zero autocorrelation sequence, wherein said second sequence follows said first sequence, and
a third sequence that corresponds to an integral of said zero autocorrelation sequence, wherein said third sequence follows said first sequence;
means for performing a first carrier frequency estimate based on said derivative of said first sequence; and
means for performing a second carrier frequency estimate based on a derivative of said second sequence and a derivative of said third sequence.
28. The system of claim 27 , further comprising means for estimating a channel signal-to-noise ratio based on said ranging preamble.
29. The system of claim 27 , further comprising means for estimating a carrier phase based on said ranging preamble.
30. The system of claim 27 , further comprising means for estimating a gain based on said ranging preamble.
31. The system of claim 27 , further comprising means for estimating a symbol rate based on said ranging preamble.
32. The system of claim 27 , further comprising means for estimating a channel signal-to-noise ratio based on information provided by a modem operating on a channel in the shared channel communication system.
33. The system of claim 27 , further comprising means for estimating a channel signal-to-noise ratio based on a spectral analysis of said ranging preamble.
34. The system of claim 27 , further comprising means for derotating said first sequence prior to said performing said first frequency estimate.
35. The system of claim 27 , further comprising means for comparing a phase of a first correlation vector corresponding to said second sequence to a phase of a second correlation vector corresponding to said third sequence.
36. The system of claim 27 , further comprising means for gain correction based on said second carrier frequency estimate.
37. The system of claim 27 , further comprising means for determining a correction factor based on an error of said second carrier frequency estimate.