Patent ID: 6052412
Filing Date: 2000-04-18
Classification: H04B,H04L

Abstract:
A codec supporting quantization level sampling (QLS) communications with a PCM modem over a digital loop carrier (DLC) having an analog connection to a central office (CO) line interface; said CO line interface having a digital-to-analog converter (DAC), a clock controlling the DAC, and a reconstruction filter; said codec also being switchably connected over the CO line interface to a training unit transmitting a predetermined sequence of training signals to said codec; said codec comprising:an analog-to-digital converter (ADC) synchronized to the CO clock for converting analog signals from the CO line interface into corresponding digital signals;an equalizer having an operational mode in which said equalizer receives said digital signals from said ADC and provides a transfer function to substantially compensate for distortions introduced by said CO line interface reconstruction filter and the signal path from said CO line interface reconstruction filter to said ADC; said equalizer also having a training mode in which said equalizer is connected to the training unit, receives the training signals, and adjusts predetermined equalizer parameters to more accurately compensate for said distortions; anda PCM converter converting the output of said equalizer to output digital data over said DLC that reproduces the digital data entering the CO line interface.