Codec supporting PCM modem communications over a universal digital loop carrier

摘要

A codec supports PCM modem communications (e.g., V.90, X2, or K56flex protocols) over a universal digital loop carrier (UDLC) having an analog interface to the central office (CO). The codec includes an analog- to- digital converter (ADC) that is synchronized to the CO clock, and an equalizer that has been trained to provide a transfer function to compensate for the distortion introduced by the CO line interface reconstruction filter and connecting circuits, to minimize resampling error. The features allow the codec to output a PCM stream that accurately reproduces the PCM data at the central office, at data rates sufficient to support PCM modem communications, as well as voice and conventional modem communications.