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 shared-channel communication receiver, comprising:
means for performing a gain estimate based on a burst preamble;
means for tracking a burst with an equalizer having a main tap coefficient; and
means for adjusting said gain estimate based on said main tap coefficient.
2. The receiver of claim 1 , wherein said equalizer uses a portion of a burst payload to derive said main tap coefficient.
3. The receiver of claim 1 , further comprising:
means for acquiring said burst having said burst preamble and a payload; and
means for extracting symbols from said burst.
4. The receiver of claim 3 , wherein said equalizer uses said payload to derive said main tap coefficient.
5. The receiver of claim 1 , wherein said gain estimate is adjusted based on a plurality of taps of said equalizer.
6. The receiver of claim 1 , further comprising means for estimating a channel signal-to-noise ratio based on said burst preamble.
7. The receiver of claim 1 , further comprising means for estimating a carrier phase based on said burst preamble.
8. The receiver of claim 1 , further comprising means for looking-up a correction factor in a look-up table, wherein said look-up table is based on a frequency error.
9. The receiver of claim 1 , wherein said burst preamble includes a constant-amplitude zero autocorrelation sequence and a cyclic continuation prior to said constant-amplitude zero autocorrelation sequence.
10. The receiver of claim 9 , wherein said burst preamble includes a second cyclic continuation after said constant-amplitude zero autocorrelation sequence.
11. The receiver of claim 1 , wherein said burst preamble includes:
two back-to-back zero autocorrelation sequences;
a first cyclic continuation that includes two symbols prior to said two back-to-back zero autocorrelation sequences; and
a second cyclic continuation that includes two symbols after said two back-to-back zero autocorrelation sequences.
12. The receiver of claim 1 , wherein said burst preamble includes:
three back-to-back zero autocorrelation sequences;
a first cyclic continuation having two symbols prior to said three back-to-back zero autocorrelation sequences; and
a second cyclic continuation having two symbols after said three back-to-back zero autocorrelation sequences.
13. The receiver of claim 3 , wherein said burst includes at least one constant-amplitude zero autocorrelation sequence outside of said burst preamble.
14. The receiver of claim 3 , further comprising means for pre-filtering said burst.
15. The receiver of claim 3 , wherein said means for extracting symbols further includes means for adjusting a gain based on said main tap coefficient.
16. A system for receiving communications over a shared communications channel, comprising:
a feed forward equalizer having a main equalizer tap;
a decision feedback equalizer that adjusts a gain of a phase-adjusted sample based on said main equalizer tap;
wherein said feed forward eciualizer outputs a forward equalized sample; and
a tracking loop, including a derotator, that receives said forward eciualized sample and outputs a phase-adjusted symbol sample having a phase, wherein said phase is adjusted by said derotator;
wherein said decision feedback eciualizer receives said phase-adjusted symbol sample and outputs an eciualized sample.
17. The system of claim 16 , further comprising:
a filter that receives a digital signal from the shared communications channel and outputs a sampled signal;
a preamble correlator that correlates a portion of said sampled signal with a local replica of a preamble to generate a correlation vector and a start of packet signal;
a parameter estimator that receives said correlation vector and said start of packet signal and outputs a frequency estimate, an estimated gain, an estimated carrier phase and a symbol timing estimate;
a second derotator that receives said sampled signal and outputs a second derotated signal;
a buffer that receives said second derotated signal and outputs a buffered second derotated signal;
a third derotator that receives said buffered second derotated signal multiplied by said estimated gain, and outputs a third derotated signal; and
a symbol timing subsystem that receives said symbol timing estimate and said third derotated signal and outputs a timed symbol sample;
wherein said feed forward equalizer receives said timed symbol sample.
18. The system of claim 17 , wherein a derivative of said sampled signal has at least one of a zero autocorrelation sequence and a constant-amplitude zero autocorrelation sequence.
19. The system of claim 17 , wherein said parameter estimator compares phases of two consecutive correlation vectors corresponding to zero autocorrelation sequences to produce said frequency estimate.