Method and apparatus for packet acquisition
Certain aspects of the present disclosure relate to a method for acquisition of a received spread spectrum signal transmitted over a wired or wireless medium.
1. A method for synchronizing a received signal comprising a spread sync field, comprising:
correlating the received signal to produce a filtered signal;
performing differential detection of the filtered signal to produce detector outputs;
accumulating the detector outputs to produce accumulated detector outputs;
storing the accumulated detector outputs in a memory component; and
deriving a timing estimate based on a location in the memory component of at least one of the accumulated detector outputs.
2. The method of claim 1 , wherein correlating comprises employing a function selected from the group consisting of an efficient serial Golay correlation, an efficient parallel Golay correlation, an efficient generalized serial Golay correlation, and an efficient generalized parallel Golay correlation.
3. The method of claim 1 , wherein the sync field comprises a sequence selected from the group consisting of a sequence of ones spread with a spreading sequence, and a sequence of alternating ones and minus-ones spread with a spreading sequence.
4. The method of claim 3 , wherein the spreading sequence comprises a sequence selected from the group consisting of a Golay sequence and a generalized Golay sequence.
5. The method of claim 4 , wherein performing differential detection comprises employing a differential detector with a memory component of N memory cells, where N denotes length of the spreading sequence.
6. The method of claim 4 , wherein storing comprises employing a memory component of N memory cells for storing the accumulated detector outputs, where N denotes length of the spreading sequence.
7. The method of claim 6 , wherein deriving the timing estimate comprises deriving the timing estimate from the location within the memory component of one of the accumulated detector outputs having a maximum magnitude.
8. The method of claim 7 , further comprising deriving a frequency offset estimate from the angle of the accumulated detector output's complex value at the timing estimate.
9. The method of claim 1 , wherein correlating comprises filtering using mismatched filtering.
10. The method of claim 1 , wherein accumulating comprises employing an Infinite Impulse Response filter.
11. The method of claim 1 , further comprising comparing the accumulated detector outputs to a threshold value.
12. An apparatus for synchronizing a received signal comprising a spread sync field, comprising:
a correlator configured for filtering the received signal to produce a filtered signal;
a differential detector for performing differential detection of the filtered signal to produce detector outputs;
an accumulator for accumulating outputs of the differential detector and producing accumulated detector outputs;
a memory component for storing the accumulated detector outputs; and
a timing estimator for deriving a timing estimate based on a location in the memory component of at least one of the accumulated detector outputs.
13. The apparatus of claim 12 , wherein the correlator comprises a correlator selected from the group consisting of an efficient serial Golay correlator, an efficient parallel Golay correlator, an efficient generalized serial Golay correlator, and an efficient generalized parallel Golay correlator.
14. The apparatus of claim 12 , wherein the sync field comprises a sequence selected from the group consisting of a sequence of ones spread with a spreading sequence, and a sequence of alternating ones and minus-ones spread with a spreading sequence.
15. The apparatus of claim 14 , wherein the spreading sequence comprises a sequence selected from the group consisting of a Golay sequence and a generalized Golay sequence.
16. The apparatus of claim 15 , wherein the differential detector comprises a memory component of N memory cells, where N denotes length of the spreading sequence.
17. The apparatus of claim 15 , wherein the memory component comprises N memory cells for storing the accumulated detector outputs, where N denotes length of the spreading sequence.
18. The apparatus of claim 17 , wherein the timing estimator is configured for deriving the timing estimate from the location within the memory component of one of the accumulated detector outputs having a maximum magnitude.
19. The apparatus of claim 18 , further configured for deriving a frequency offset estimate from the angle of the accumulated detector output's complex value at the timing estimate.
20. The apparatus of claim 12 , wherein the correlator comprises a mismatched filter.
21. The apparatus of claim 12 , wherein the accumulator comprises an Infinite Impulse Response filter.
22. The apparatus of claim 12 , further comprising a hypothesis testing device for comparing the accumulated detector outputs to a threshold value.
23. A machine-readable medium comprising instructions encoded thereon and executable to:
correlate the received signal to produce a filtered signal;
perform differential detection of the filtered signal to produce detector outputs;
accumulate the detector outputs to produce accumulated detector outputs;
store the accumulated detector outputs in a memory component; and
derive a timing estimate based on a location in the memory component of at least one of the accumulated detector outputs.