Non-coherent combining detection with reduced buffering requirements

1. A method for detecting a primary synchronization sequence, comprising:

obtaining samples of a received signal across one or more reference pilot intervals;

for each reference pilot interval, evaluating a plurality of timing hypotheses for one or more primary synchronization sequences, based on the samples, and storing a limited number of samples corresponding to a subset of the evaluated timing hypotheses in a buffer, the subset determined based on the evaluation; and

performing primary synchronization sequence detection based on an analysis of the limited number of samples stored in the buffer.

2. The method of claim 1 , wherein:

the obtaining comprises obtaining samples of the received signal across at least two reference pilot intervals; and

performing the primary synchronization sequence detection comprises non-coherent combining of samples corresponding to the subset of hypotheses for the at least two reference pilot intervals.

3. The method of claim 2 , wherein:

the non-coherent combining is performed over a number of half-frames following an initial half-frame for which the limited number of samples are stored.

4. The method of claim 1 , wherein the evaluation is performed only after a threshold number of samples have been stored in the buffer.

5. The method of claim 1 , wherein storing a limited number of samples comprises:

storing samples corresponding to a limited number of strongest hypotheses.

6. The method of claim 5 , wherein the storing comprises:

overwriting samples corresponding to weak hypotheses.

7. The method of claim 5 , wherein storing a limited number of samples comprises:

sorting samples in the buffer, based on strength of corresponding hypotheses.

8. The method of claim 7 , wherein storing a limited number of samples further comprises:

obtaining a set of new samples;

evaluating one or more hypotheses based on the new samples;

sorting samples in the buffer and the new samples, based on the evaluation; and

storing only samples corresponding the strongest hypotheses.

9. The method of claim 1 , wherein the reference pilot interval is greater than an interval corresponding to a half radio frame.

10. The method of claim 1 , wherein the one or more primary synchronization sequences comprise at least three primary synchronization sequences.

11. The method of claim 1 , wherein, for each pilot reference interval, samples corresponding to no more than 256 timing hypotheses are stored.

12. The method of claim 1 , wherein storing a limited number of samples comprises storing timing indices corresponding to the limited number of samples.

13. An apparatus for detecting a primary synchronization sequence, comprising:

means for obtaining samples of a received signal across one or more reference pilot intervals;

means for evaluating, for each reference pilot interval, a plurality of timing hypotheses for one or more primary synchronization sequences, based on the samples, and storing a limited number of samples corresponding to a subset of the evaluated timing hypotheses in a buffer, the subset determined based on the evaluation; and

means for performing primary synchronization sequence detection based on an analysis of the limited number of samples stored in the buffer.

14. The apparatus of claim 13 , wherein:

the obtaining comprises obtaining samples of the received signal across at least two reference pilot intervals; and

performing the primary synchronization sequence detection comprises non-coherent combining of samples corresponding to the subset of hypotheses for the at least two reference pilot intervals.

15. The apparatus of claim 14 , wherein:

the non-coherent combining is performed over a number of half-frames following an initial half-frame for which the limited number of samples are stored.

16. The apparatus of claim 13 , wherein the evaluation is performed only after a threshold number of samples have been stored in the buffer.

17. The apparatus of claim 13 , wherein storing a limited number of samples comprises:

storing samples corresponding to a limited number of strongest hypotheses.

18. The apparatus of claim 17 , wherein the storing comprises:

overwriting samples corresponding to weak hypotheses.

19. The apparatus of claim 17 , wherein storing a limited number of samples comprises:

sorting samples in the buffer, based on strength of corresponding hypotheses.

20. The apparatus of claim 19 , wherein storing a limited number of samples further comprises:

obtaining a set of new samples;

evaluating one or more hypotheses based on the new samples;

sorting samples in the buffer and the new samples, based on the evaluation; and

storing only samples corresponding the strongest hypotheses.

21. The apparatus of claim 13 , wherein the reference pilot interval is greater than an interval corresponding to a half radio frame.

22. The apparatus of claim 13 , wherein the one or more primary synchronization sequences comprise at least three primary synchronization sequences.

23. The apparatus of claim 13 , wherein, for each pilot reference interval, samples corresponding to no more than 256 timing hypotheses are stored.

24. The apparatus of claim 13 , wherein storing a limited number of samples comprises storing timing indices corresponding to the limited number of samples.

25. An apparatus for detecting a primary synchronization sequence, comprising:

at least one processor configured to obtain samples of a received signal across one or more reference pilot intervals, evaluate, for each reference pilot interval, a plurality of timing hypotheses for one or more primary synchronization sequences, based on the samples, and store a limited number of samples corresponding to a subset of the evaluated timing hypotheses in a buffer, the subset determined based on the evaluation, and perform primary synchronization sequence detection based on an analysis of the limited number of samples stored in the buffer; and

a memory coupled with the at least one processor.

26. A computer program product comprising a non-transitory computer readable medium having instructions stored thereon, the instructions executable by one or more processors for:

obtaining samples of a received signal across one or more reference pilot intervals;

for each reference pilot interval, evaluating a plurality of timing hypotheses for one or more primary synchronization sequences, based on the samples, and storing a limited number of samples corresponding to a subset of the evaluated timing hypotheses in a buffer, the subset determined based on the evaluation; and

performing primary synchronization sequence detection based on an analysis of the limited number of samples stored in the buffer.