Quadrature vestigial sideband digital communications method and system with correlated noise removal
A quadrature vestigial-sideband (QVSB) method and system with correlated noise removal are embodied in a QVSB receiver with a correlated-noise estimator-subtractor configured to obtain I/Q channel correlated noise estimates for receive-filtered I/Q signals in the QVSB receiver, and to subtract the I/Q channel correlated noise estimates from the receive-filtered I/Q signals to whiten noises entering a quadrature-crosstalk, maximum-likelihood-sequence-estimator (QC-MLSE) of the QVSB receiver.
1. A communications method with correlated noise removal in a demodulator system, the method comprising the steps of:
translating a quadrature vestigial-sideband (QVSB) signal to inphase and quadrature (I/Q) baseband components, r T iq and r T qi ;
filtering the baseband components to generate I and Q channel cross-coupled filtering outputs;
estimating transmitted data content of the I and Q channel cross-coupled filtering outputs;
employing the estimated data content to reconstruct originally transmitted I/Q signals, {tilde over (s)} T iq and {tilde over (s)} T qi ;
processing the reconstructed signal components and the inphase and quadrature (I/Q) baseband components to generate correlated-noise estimates, {circumflex over (n)} i and {circumflex over (n)} q ;
subtracting the correlated-noise estimates, {circumflex over (n)} i and {circumflex over (n)} q , from the cross-coupled filtering outputs to yield receive-filtered I/Q signals in white noise, r iq and r qi ; and
procesing the receive-filtered I/Q signals in white noise to provide optimal data estimates, {circumflex over (m)}.
2. The communications method with correlated noise removal of claim 1 , wherein the step of filtering the baseband components comprises:
employing a set of cross-coupled, matched data filters to filter the baseband components.
3. The communications method with correlated noise removal of claim 1 , wherein the step of estimating transmitted data content of the I and Q channel cross-coupled filtering outputs comprises:
employing a quadrature-crosstalk, maximum-likelihood-sequence-estimator (QC-MLSE) adapted from a Viterbi algorithm.
4. The communications method with correlated noise removal of claim 1 , wherein the step of employing the estimated data content to reconstruct originally transmitted I/Q signals comprises:
waveshaping the estimated data content with filters.
5. The communications method with correlated noise removal of claim 1 , wherein the step of employing the estimated data content to reconstruct originally transmitted I/Q signals comprises:
waveshaping the estimated data content with a lookup table.
6. The communications method with correlated noise removal of claim 1 , wherein the step of processing the reconstructed signal components and the inphase and quadrature (I/Q) baseband components to generate correlated-noise estimates comprises:
subtracting the reconstructed signal components from the inphase and quadrature (I/Q) baseband components to generate uncorrelated white noise processes; and
cross-couple filtering the uncorrelated white noise processes.
7. The communications method with correlated noise removal of claim 1 , wherein the step of processing the receive-filtered I/Q signals in white noise to provide optimal data estimates comprises:
employing a quadrature-crosstalk, maximum-likelihood-sequence-estimator (QC-MLSE) to create preliminary, hypothetical data estimates.
8. A quadrature vestigial-sideband (QVSB) demodulator system with correlated noise removal, comprising:
a demodulator front-end for translating an incoming signal to inphase and quadrature (I/Q) baseband components, r T iq and r T qi :
a set of cross-coupled, matched data filters for filtering the baseband components to generate I and Q channel cross-coupled filtering outputs;
an initial quadrature-crosstalk,maximum-likelihood-sequence-estimator (QC-MLSE) for estimating transmitted data content of the I and Q channel cross-coupled filtering outputs;
a transmit waveform reconstructor for employing the estimated data content to reconstruct originally transmitted I/Q signals, {tilde over (s)} T iq and {tilde over (s)} T qi ;
a correlated-noise estimator-subtractor for processing the reconstructed signal components and the inphase and quadrature (I/Q) baseband components to generate correlated-noise estimates, {circumflex over (n)} i and {circumflex over (n)} q , and for subtracting the correlated-noise estimates, {circumflex over (n)} i and {circumflex over (n)} q , from the cross-coupled filtering outputs to yield receive-filtered I/Q signals in white noise, r iq and r qi ; and
a final QC-MLSE for processing the whitened I/Q inputs to provide optimal data estimates, {circumflex over (m)}.
9. The quadrature vestigial-sideband (QVSB) demodulator system with correlated noise removal of claim 8 , wherein:
the transmit waveform reconstructor comprises data filters.
10. The quadrature vestigial-sideband (QVSB) demodulator system with correlated noise removal of claim 8 , wherein:
the transmit waveform reconstructor comprises cross-coupled data filtering.
11. The quadrature vestigial-sideband (QVSB) demodulator system with correlated noise removal of claim 8 , wherein:
the transmit waveform reconstructor comprises data filters with finite impulse-response (FIR) realizations.
12. The quadrature vestigial-sideband (QVSB) demodulator system with correlated noise removal of claim 8 , wherein:
the transmit waveform reconstructor comprises a lookup table.
13. The quadrature vestigial-sideband (QVSB) demodulator system with correlated noise removal of claim 8 , wherein:
the correlated-noise estimator-subtractor includes filters that are the same as filters in the set of cross-coupled, matched data filters.