Method and apparatus for sample frequency offset correction OFDM and single carrier frequency domain equalized receiver systems
View Patent ↗Methods and apparatuses of the invention are directed to correcting errors caused by frequency offsets between clocks in a communication system, for example SFO. According to certain aspects, embodiments of the invention provide for resampling data samples corresponding to a received data symbol immediately prior to performing an FFT. According to certain additional aspects, the resampler operates only on the data samples of a cyclic data block, with a known (and minimized) sample timing error to correct.
1. An apparatus comprising:
an analog-to-digital converter configured to produce samples of a wireless signal;
a time domain processing block configured to operate on the samples and determine a sampling time drift;
a resampler configured to adjust the samples in accordance with the sampling time drift; and
an FFT configured to transform the adjusted samples to a frequency domain representation of the wireless signal.
2. The apparatus of claim 1 , wherein the resampler comprises a filter with a plurality of taps having corresponding coefficients.
3. The apparatus of claim 2 , further comprising logic configured to determine the coefficients using the sampling time drift.
4. The apparatus of claim 3 , further comprising a table including a plurality of sets of corresponding coefficients, each set associated with a value of the sampling time drift.
5. The apparatus of claim 1 , wherein the time domain processing block is further configured to perform carrier frequency offset correction on the samples.
6. The apparatus of claim 1 , further comprising a synchronization block configured to direct the resampler to operate on samples within a single data block.
7. The apparatus of claim 6 , wherein the single data block corresponds to a data symbol.
8. The apparatus of claim 7 , wherein the data symbol is an OFDM symbol.
9. The apparatus of claim 1 , wherein the sampling time drift is less than 50 ppm.
10. A method comprising:
obtaining samples of a wireless signal;
operating on the samples to determine a sampling time drift;
adjusting the samples in accordance with the sampling time drift; and
transforming the adjusted samples to a frequency domain representation of the wireless signal.
11. The method of claim 10 , wherein adjusting the samples includes filtering the samples with a plurality of taps having corresponding coefficients.
12. The method of claim 11 , further comprising determining the corresponding coefficients using the sampling time drift.
13. The method of claim 12 , further comprising selecting the corresponding coefficients from a plurality of sets of coefficients, each set associated with a value of the sampling time drift.
14. The method of claim 10 , further comprising, before the adjusting, performing carrier frequency offset correction on the samples.
15. The method of claim 10 , wherein adjusting the samples comprises operating on samples within a single data block.
16. The method of claim 15 , wherein the single data block corresponds to a data symbol.
17. The method of claim 16 , wherein the data symbol is an OFDM symbol.
18. The method of claim 10 , wherein the sampling time drift is less than 50 ppm.