Carrier frequency offset estimation scheme, for digital standards with MPSK modulated preamble

1. A receiver for reducing acquisition time of a Carrier Frequency Offset (CFO) of an input intermediate frequency (IF) signal with M-ary Phase Shift Keying (M-PSK) modulated preamble, said receiver comprising:

an analog to digital converter (ADC) that converts said input IF signal into a digital signal;

a down conversion unit that down converts said digital signal to a baseband complex signal; and

a CFO estimation block that estimates said CFO using spectral based analysis, wherein said CFO estimation block comprises:

a carrier harmonic generation unit that generates an output of a carrier Mth harmonic without modulation from said baseband complex signal;

a spectral mapping unit that spectrally maps said carrier Mth harmonic using a complex Fast Fourier Transform (FFT) and generates a spectrally mapped carrier Mth harmonic signal;

a spectral analysis unit that performs a peak search on said spectrally mapped carrier Mth harmonic signal to obtain a peak position (PPOS); and

a Carrier Frequency Offset (CFO) estimation unit that estimates the CFO based on said peak position (PPOS);

wherein said receiver is capable of supporting wire-line as well as wireless standards, and wherein an estimation of said CFO is carried out at said symbol rate to reduce implementation complexity.

2. A receiver for reducing acquisition time of a Carrier Frequency Offset (CFO) of an input intermediate frequency (IF) signal with M-ary Phase Shift Keying (M-PSK) modulated preamble, said receiver comprising:

an analog to digital converter (ADC) that converts said input IF signal into a digital signal;

a down conversion unit that down converts said digital signal to a baseband complex signal; and

a CFO estimation block that estimates said CFO using spectral based analysis, wherein said CFO estimation block comprises (a)-(d):

(a) a carrier harmonic generation unit that generates an output of a carrier Mth harmonic without modulation from said baseband complex signal;

(b) a spectral mapping unit that spectrally maps said carrier Mth harmonic using a complex Fast Fourier Transform (FFT) and generates a spectrally mapped carrier Mth harmonic signal;

(c) a spectral analysis unit that performs a peak search on said spectrally mapped carrier Mth harmonic signal to obtain a peak position (PPOS); and

(d) a Carrier Frequency Offset (CFO) estimation unit that estimates the CFO based on said peak position (PPOS);

wherein said receiver further comprises:

a signal conditioning filter that rejects unwanted out-of-band signals from said baseband complex signal;

a sample rate converter that converts said baseband complex signal to a symbol rate;

a numerically controlled oscillator (NCO) that generates a complex signal for a down conversion; and

a coherent demodulator connected to said sample rate converter, wherein said coherent demodulator demodulates said baseband complex signal.

3. A receiver for reducing acquisition time of a Carrier Frequency Offset (CFO), with constant phase M-ary Phase Shift Keying (M-PSK) modulated preamble of an input Intermediate Frequency (IF) signal, said receiver comprising:

a down conversion unit that down converts said input IF signal into a baseband complex signal; and

a CFO estimation block that comprises:

a data selection unit that selects a data p(n) based on at least constant phase M-PSK modulated preamble of said baseband complex signal;

a down-sampling unit that downsamples said baseband complex signal to obtain a downsampled signal;

an Mth power logic unit that processes said downsampled signal and generates a carrier Mth harmonic signal without modulation;

a spectral domain mapping unit that spectrally maps said carrier Mth harmonic signal by computing a complex Fast Fourier Transform (FFT) and generates a spectrally mapped signal;

a non-coherent averaging unit that generates an averaged spectrally mapped signal by averaging a magnitude of said spectrally mapped signal with a magnitude of signal that is previously spectrally mapped;

a spectral analysis unit that performs a peak search on said averaged spectrally mapped signal to detect Mth harmonic of said baseband complex signal and obtains a peak position (PPOS); and

a carrier frequency offset estimation unit that estimates said CFO based on said peak position.

4. The receiver of claim 3 , wherein a down-sampling of said baseband complex signal enables reliable CFO estimates in low SNR condition and strong multipath.

5. A method for reducing acquisition time of a Carrier Frequency Offset (CFO) of an input intermediate frequency (IF) signal, with Mth power of a phase M-ary Phase Shift Keying (M-PSK) modulated preamble of said input IF signal in a receiver, said method comprising:

performing a first set of operations when said phase of said M-PSK modulated preamble is constant, said first set of operations comprising (a)-(e):

(a) performing a data selection to output a selected signal p(n);

(b) down-sampling said selected signal p(n) to obtain better resolution for a spectral mapping;

(c) generating a carrier Mth harmonic without modulation of said selected signal p(n);

(d) spectrally mapping said carrier Mth harmonic by computing a complex Fast Fourier Transform to obtain a spectrally mapped signal; and

(e) performing a non-coherent averaging for said spectrally mapped signal to avoid affect of phase variation on CFO estimations to obtain an averaged spectrally mapped signal; and

performing a spectral analysis of said averaged spectrally mapped signal based on a peak search to obtain a peak position (PPOS); and

estimating said CFO based on said PPOS.

6. The method of claim 5 , further comprising:

setting a number of iterations j to a value N before performing said first set of operation;

decrementing a value of said j after said non-coherent averaging is performed; and

performing said spectral analysis only when said j is 0;

wherein said first set of operations are performed again when said value of j is greater than 0.

7. The method of claim 5 , further comprising:

performing a second set of operations when said phase of said M-PSK modulated preamble is variable, said second set of operations comprising (f)-(i):

(f) performing a data selection to output a selected signal p(n),

(g) generating a carrier Mth harmonic signal without modulation of said selected signal p(n),

(h) spectrally mapping of said carrier Mth harmonic signal of said selected signal by computing a complex Fast Fourier Transform to obtain a spectrally mapped signal, and

(i) performing a spectral analysis of said spectrally mapped signal based on a peak search to detect Mth harmonic of said selected signal and to obtain a peak position (PPOS); and

estimating said CFO based on said PPOS.

8. The method of claim 7 , further comprising:

setting a number of iterations j to a value N before performing said data selection to output said selected signal p(n);

decrementing a value of said j after performing said spectral analysis; and

estimating said CFO based on said PPOS only when j is 0;

wherein said second set of operations are performed again when said value of j is greater than 0.

9. The method of claim 2 wherein:

said receiver is capable of supporting wire-line as well as wireless standards; and

an estimation of said CFO is carried out at said symbol rate to reduce implementation complexity.