ADVANCED MODULATION TECHNIQUES FOR V-FAST

An overview is provided of the modulation techniques that are being co nsidered for a new voiceband modem Recommendation, nicknamed V.fast. T hese techniques include adaptive bandwidth operation for automatically selecting the transmission band, multi-dimensional trollis coded modu lation for higher coding gain, constellation shaping for higher shapin g gain, precoding and pre-emphasis for advanced equalization, and warp ing for resistance against signal-dependent impairments. Simulation re sults are presented to illustrate performance. By adaptively selecting an appropriate combination of these modulation techniques based on li ne conditions, V.fast modems are expected to double the maximum data r ate of standard modems.