Cyclic Prefixed Orthogonal Frequency Division Multiplexing (CP-OFDM)
is viewed as an attractive transmission scheme for wired and wireless
high-speed communications. Its bit error rate performance, however,
can be very sensitive to impairments like frequency offset and
timing mismatch. In this paper it is shown that using long modulating
windows with overlap in time and good spectral containment offers
significantly higher robustness to impairments and ingress than 
CP-OFDM transmissions. Further, the effect of the manner in which
redundancy inserted into an OFDM system onto its robustness is considered.
Redundant OFDM transmissions based on long modulating windows and without
channel coding are shown to offer a higher robustness to impairments
than coded CP-OFDM transmissions.