OFDM signal acquisition

1. A method comprising

receiving an OFDM signal;

determining a fractional frequency offset of the OFDM signal, wherein the determining includes performing a time domain cyclic prefix auto correlation (TDCPAC) of symbols within a frame of the OFDM signal;

selecting a frequency domain associated with the fractional frequency offset;

determining a coarse location for a preamble of the OFDM signal, wherein the determining includes performing a frequency domain differential correlation (FDDC) on possible preambles;

determining downlink portion of a frame of the OFDM signal based on the course location of the preamble;

aligning a frame start with the course location of the preamble;

determining a symbol boundary, wherein the determining includes performing a TDCPAC of symbols within the downlink portion of a frame of the OFDM signal;

aligning a frame start with the symbol boundary;

determining preamble location, wherein the determining includes performing a FDDC on possible preambles within the course location of the preamble;

aligning a frame start with the preamble location; and

determining preamble sequence and integer frequency offset.

2. The method of claim 1 , wherein the determining a fractional frequency offset further includes summating the auto correlations, and finding peak of the summation, wherein phase of the peak is the fractional frequency offset.

3. The method of claim 1 , wherein the determining a coarse location further includes performing the FDDC of possible preambles over multiple frames and averaging the FDDCs.

4. The method of claim 1 , wherein the course location of the preamble is a range of symbols.

5. The method of claim 1 , wherein the determining a symbol boundary further includes summating the auto correlations, and finding peak of the summation, wherein the peak is the symbol boundary.

6. The method of claim 1 , wherein the determining preamble sequence and integer frequency offset includes performing a FDDC for possible preamble sequences.

7. The method of claim 1 , wherein the determining preamble sequence and integer frequency offset includes performing a cross correlation (XCORR) between the received signal preamble and possible preamble sequences.

8. The method of claim 1 , wherein the determining preamble sequence and integer frequency offset includes performing a FDDC and XCORR.

9. An apparatus including

at least one antenna to receive OFDM signals;

a detector to perform calculations on the received OFDM signals;

a processor to control operations of the detector, wherein for signal acquisition the processor is to instruct the detector to perform a cyclic prefix auto correlation (CP AutoCorr) to determine fractional frequency offset, to perform an averaging frequency domain differential correlation (AFDDC) to determine preamble location within a range of symbols, to perform a CP AutoCorr to determine symbol start, to perform a FDDC to determine preamble location, and to perform a FDDC to identify preamble index.

10. The apparatus of claim 9 , wherein the detector includes a time domain detector to perform calculations in the time domain and a frequency domain detector to perform calculations in the frequency domain.

11. The apparatus of claim 9 , wherein the processor further instructs the detector to perform cross correlations (XCORR) to identify the preamble index.

12. A method comprising

receiving an OFDM signal;

performing a time domain cyclic prefix auto correlation (TDCPAC) of symbols within a frame to determine a fractional frequency offset of the OFDM signal, wherein the fractional frequency offset of the received signal provides an OFDM sub-carrier utilized to transmit the OFDM signal;

performing an averaging frequency domain differential correlation (AFDDC) over several frames to estimate preamble location within the OFDM sub-carrier, wherein the estimated preamble location is within a range of symbols;

performing a TDCPAC on downlink portion of a frame to determine symbol start, wherein the downlink portion is determined based on the estimated preamble location;

performing an FDDC on the range of symbols aligned in time to the symbol start to determine preamble location, wherein the preamble location is the selected symbol; and

determining preamble sequence and integer frequency offset based on the preamble location.

13. The method of claim 12 , further comprising summating the TDCPAC for the symbols within the frame and finding a peak of the summation, wherein the fractional frequency offset is determined from phase of the peak.

14. The method of claim 12 , further comprising summating the TDCPAC for the symbols within the downlink portion of the frame and finding a peak of the summation, wherein the peak is the symbol start.

15. The method of claim 12 , wherein the determining preamble sequence and integer frequency offset includes performing an FDDC of possible preamble sequences based on the preamble location.

16. The method of claim 12 , wherein the determining preamble sequence and integer frequency offset includes performing a cross correlation (XCORR) to possible preamble sequences.

17. The method of claim 12 , wherein the determining preamble sequence and integer frequency offset includes performing an FDDC of and a cross correlation (XCORR) to possible preamble sequences.

18. The method of claim 12 , further comprising determining total frequency offset by adding integer frequency offset and fractional frequency offset.

19. The method of claim 18 , further comprising:

setting the preamble sequence and the total offset frequency;

entering normal receive mode; and

verifying signal acquisition.

20. The method of claim 19 , wherein the verifying signal acquisition includes receiving a downlink map signal with correct error coding.