Method and apparatus for an X-DSL modem supporting multiple X-DSL line codes

An X-DSL modem supporting both a discrete multi-tone (DMT) line code and a carrierless amplitude and phase modulated (CAP) line code, and the modem comprising:

• a plurality of discrete components coupled to one another to form a transmit path and a receive path for processing data associated with at least one communication channel which exhibits either a DMT line code or a CAP line code;
• and the components including:
• an encoder component coupled to the transmit path for encoding data associated with the at least one communication channel exhibiting the CAP line code into QAM symbols and encoding data associated with the at least one communication channel exhibiting the DMT line code into DMT sub-symbols;
• a Fourier transform component with an input coupled to the encoder component on the transmit path for transforming DMT sub-symbols associated with the at least one communication channel exhibiting the DMT line code from a frequency-to-time domain and transforming QAM symbols associated with the at least one communication channel exhibiting the CAP line code from the time-to-frequency domain followed by a filtering step in the frequency domain and a subsequent transformation back from the frequency-to-time domain to effect a pulse shaping function on transmitted data associated with the at least one communication channel exhibiting the CAP line code without requiring a discrete pulse shaping component in the transmit path.