Full reach high-speed digital subscriber loops via power control

The theoretical performance of the next generation high-speed digital subscriber loops (HDSL2) is calculated under the limited latency constraint in the presence of near end crosstalk (NEXT). The concept of having different up-stream and down-stream power spectral densities is highlighted. The noise margin at the central office HDSL terminal unit (HTU-C) can be enhanced by boosting the power output of the remote user HDSL terminal unit (HTU-R). Further improvement in performance can be achieved by reducing the HTU-C NEXT interference, similar to the power control used in wireless systems. The preemphasis/deemphasis can also be used to further reduce the interference levels, and in the mean time cut the power consumption. Combining the techniques leads to at least a 6 dB SNR margin improvement for the full reach carrier serving area (CSA) loops.