  We show that spatially coupled low-density parity-check (LDPC) codes yield
robust performance over changing intersymbol interfere (ISI) channels with
optimal and suboptimal detectors. We compare the performance with classical
LDPC code design which involves optimizing the degree distribution for a given
(known) channel. We demonstrate that these classical schemes, despite working
very good when designed for a given channel, can perform poorly if the channel
is exchanged. With spatially coupled LDPC codes, however, we get performances
close to the symmetric information rates with just a single code, without the
need to know the channel and adapt to it at the transmitter. We also
investigate threshold saturation with the linear minimum mean square error
(LMMSE) detector and show that with spatial coupling its performance can get
remarkably close to that of an optimal detector for regular LDPC codes.
