Exploiting the common-mode signal in xDSL

Communication over the copper twisted-pair channel is performed by transmitting and receiving differential-mode (DM) signals. In this paper, we extend the conventional DM receive scheme by incorporating the common-mode (CM) signal, which can be extracted at the end of every wire pair. We assess the potential of this idea for digital subscriber line systems (xDSL) in terms of channel capacity using channel measurement data. We show that especially those scenarios that suffer strong interference benefit most from joint DM-CM processing, since the interference at the DM port is strongly correlated with the interference at the CM port in these cases. Numerical evaluation of VDSL example scenarios shows that the capacity of the twisted-pair channel when using also the CM signal can exceed the capacity of the conventional DM channel by a factor of up to three.