Method and apparatus for extending the frequency range of multi-tone modems

A method for modulating and demodulating data on a communication medium in accordance with a proscribed band plan including frequency division multiplexed transmit and receive bands;

• and the method comprising:
• sampling received portions of the band plan including at least one relatively higher frequency received band at a rate which generates a spectral replication of the at least one received band at a relatively lower frequency range with overlaps with a gap in remaining received portions of the band plan;
• performing a time-to-frequency transform of the spectral replication of the at least one relatively higher frequency received band along with time-to-frequency transform of any remaining non selected received bands;
• selecting for at least one relatively higher frequency transmit band, a spectrally compatible lower frequency gap in a transmit portion of the band plan;
• performing a frequency-to-time transform of a lower frequency image of the selected transmit band concurrently with frequency-to-time transforms of any remaining non-selected transmit bands;
• upconverting all time domain resultants to generate both base band images as well as replications thereof with an amount of the upconversion required determined by a requirement that the transformed image of the selected transmit band overlap with the selected transmit band on the communication medium;
• and
• filtering out the undesired images, either baseband or higher frequency replications thereof and passing remaining mix onto the communication medium.

A method for modulating and demodulating data on a communication medium in accordance with a proscribed band plan including frequency division multiplexed transmit and receive bands;

• and the method comprising:
• sampling received portions of the band plan including at least one relatively higher frequency received band at a rate which generates a spectral replication of the at least one received band at a relatively lower frequency range with overlaps with a gap in remaining received portions of the band plan;
• performing a time-to-frequency transform of the spectral replication of the at least one relatively higher frequency received band along with time-to-frequency transform of any remaining non selected received bands;
• and
• reversing Hermietian symmetry of the spectral replication of the at least one received band at the relatively lower frequency range.

An apparatus for modulating and demodulating data on a communication medium in accordance with a proscribed band plan including frequency division multiplexed transmit and receive bands;

• and the apparatus comprising:
• a hybrid downconverter for sampling received portions of the band plan including at least one relatively hither frequency received band at a rate which generates a spectral replication of the at least one received band at a relatively lower frequency range with overlaps with a gap in remaining received portions of the band plan;
• a discrete Fourier transform module for performing a time-to-frequency transform of the spectral replication of the at least one relatively higher frequency received band along with time-to-frequency transform of any remaining non selected received bands;
• a hybrid encoder for selecting for at least one relatively higher frequency transmit band, a spectrally compatible lower frequency gap in a transmit portion of the band plan;
• an inverse discrete Fourier transform module for performing a frequency-to-time transform of a lower frequency image of the selected transmit band concurrently with frequency-to-time transforms of any remaining non-selected transmit bands;
• and
• a hybrid upconverter for upconverting all time domain resultants to generate both base band images as well as replications thereof with an amount of the interpolation required determined by a requirement that the transformed image of the selected transmit band overlap with the selected transmit band on the communication medium, and for filtering out the undesired images, either baseband or higher frequency replications thereof and passing remaining mix onto the communication medium.

An apparatus for modulating and demodulating data on a communication medium in accordance with a proscribed band plan including frequency division multiplexed transmit and receive bands;

• and the apparatus comprising:
• a hybrid downconverter for sampling received portions of the band plan including at least one relatively higher frequency received band at a rate which generates a spectral replication of the at least one received band at a relatively lower frequency range with overlaps with a gap in remaining received portions of the band plan;
• a discrete Fourier transform module for performing a time-to-frequency transform of the spectral replication of the at least one relatively higher frequency received band along with time-to-frequency transform of any remaining non selected received bands;
• and
• a hybrid decoder for reversing Hermetian symmetry of the spectral replication of the at least one received band at the relatively lower frequency range.