A 1.6 MBPS DIGITAL-QAM SYSTEM FOR DSL TRANSMISSION

An all digital-QAM system is studied here for highspeed data transmiss ion on digital subscriber loops. All elements of the system have been fully investigated and their effects on overall system performance doc umented. In particular, the following issues have been explicitly addr essed: utility of an adaptive error-prediction (noise-prediction) filt er; equalizer size and convergence; blind equalization; choice of cons tellation size and center frequency; combined timing/carrier recovery; and the oversampling requirements of a numerically-controlled-oscilla tor (NCO) for potential use in the timing and carrier recovery loop. T he paper relies on simulation results to investigate and quantify the overall interactions of the various blocks. Throughout the paper empha sis has been placed on reducing the complexity of the system for imple mentation on an integrated circuit (IC). It is expected that the infor mation provided here will serve as a good starting point for an IC des igner to start the implementation of a transceiver ASIC.