  Signal processing played an important role in improving the quality of
communications over copper cables in earlier DSL technologies. Even more
powerful signal processing techniques are required to enable a gigabit per
second data rate in the upcoming G.fast standard. This new standard is
different from its predecessors in many respects. In particular, G.fast will
use a significantly higher bandwidth. At such a high bandwidth, crosstalk
between different lines in a binder will reach unprecedented levels, which are
beyond the capabilities of most efficient techniques for interference
mitigation. In this article, we survey the state of the art and research
challenges in the design of signal processing algorithms for the G.fast system,
with a focus on novel research approaches and design considerations for
efficient interference mitigation in G.fast systems. We also detail relevant
VDSL techniques and points out their strengths and limitations for the G.fast
system.
