Timing estimation in communication systems

1. A method of symbol timing estimation, the method including:

obtaining peak integration values from despread symbol samples of a received direct-sequence spread-spectrum signal;

selecting a set of peaks from the peak integration values by finding a maximum of the peak integration values and searching for further peaks within predetermined time windows in backward and forward directions in time;

using the set of peaks to select from the despread symbol samples a group of the despread symbol samples;

further processing the group of despread symbol samples;

applying curve fitting to the set of peaks; and

projecting results of the curve fitting backwards and forwards in time to obtain a group of sampling instants,

wherein using the set of peaks comprises using the group of sampling instants to select the group of despread symbol samples.

2. The method of claim 1 , wherein obtaining the peak integration values comprises:

performing non-coherent integration on at least a subset of the despread symbol samples to obtain integrated values; and

applying a threshold to the integrated values to obtain the peak integration values.

3. The method of claim 1 , wherein the curve fitting is polynomial curve fitting.

4. The method of claim 2 , further including computing the threshold based on at least a subset of the integrated values.

5. The method of claim 2 , wherein the threshold is a predetermined value.

6. The method of claim 4 , wherein computing the threshold comprises obtaining a mean of the at least a subset of the integrated values.

7. The method of claim 6 , wherein computing the threshold further comprises obtaining the threshold by performing a process selected from the group consisting of:

obtaining a standard deviation of the at least a subset of the integrated values and adding to the mean a multiple of the standard deviation; and

multiplying the mean by a predetermined factor.

8. A non-transitory computer readable medium having stored thereon executable instructions configured to result in the implementation of operations including:

obtaining peak integration values from despread symbol samples of a received direct-sequence spread-spectrum signal;

selecting a set of peaks from the peak integration values by finding a maximum of the peak integration values and searching for further peaks within predetermined time windows in backward and forward directions in time; and

using the set of peaks to select from the despread symbol samples a group of the despread symbol samples;

further processing the group of despread symbol samples;

applying curve fitting to the set of peaks; and

projecting results of the curve fitting backwards and forwards in time to obtain a group of sampling instants,

wherein using the set of peaks comprises using the group of sampling instants to select the group of despread symbol samples.

9. The non-transitory computer readable medium of claim 8 , wherein the operations further include:

performing non-coherent integration on at least a subset of the despread symbol samples to obtain integrated values; and

applying a threshold to the integrated values to obtain the peak integration values.

10. The non-transitory computer readable medium of claim 8 , wherein the curve fitting is polynomial curve fitting.

11. An apparatus to perform symbol timing synchronization, the apparatus including:

at least one processor; and

the non-transitory computer readable medium according to claim 8 .

12. The non-transitory computer readable medium of claim 9 , wherein the operations further include computing the threshold based on at least a subset of the integrated values.

13. The non-transitory computer readable medium of claim 9 , wherein the threshold is a predetermined value.

14. The non-transitory computer readable medium of claim 12 , wherein computing the threshold comprises obtaining a mean of the at least a subset of the integrated values.

15. The non-transitory computer readable medium of claim 14 , wherein computing the threshold further comprises obtaining the threshold by performing a process selected from the group consisting of:

obtaining a standard deviation of the at least a subset of the integrated values and adding to the mean a multiple of the standard deviation; and

multiplying the mean by a predetermined factor.

16. A symbol timing synchronization apparatus, including:

a non-coherent integrator coupled to receive despread symbol samples obtained from a received direct-sequence spread-spectrum signal and configured to output integrated values based on the despread symbol samples;

a thresholding device configured to apply a threshold to the integrated values to obtain peak integration values;

a peak selector configured to:

find a maximum of the peak integration values;

search for further peaks within predetermined time windows in backward and forward directions in time; and

select a set of peaks based on the maximum and the further peaks; and

a sample selector configured to receive the despread symbol samples and configured to select, based on timing instants derived from the set of peaks, a group of the despread symbol samples for further processing, and

the apparatus further including:

a curve fitter configured to apply curve fitting to the set of peaks; and

a projection module configured to project results of the curve fitting backwards and forwards in time to obtain a group of sampling instants and to provide the group of sampling instants to the sample selector.

17. The apparatus of claim 16 , wherein the thresholding device is configured to compute the threshold based on at least a subset of the integrated values.

18. The apparatus of claim 16 , wherein the threshold is a predetermined value.