Long Modulating Windows and Data Redundancy for Robust OFDM Transmissions

Cyclic Prefixed Orthogonal Frequency Division Multiplexing (CP-OFDM) is viewed as an attractive transmissions system 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 as well as ingress and impulse noise. In this paper it is shown that using long modulating windows with overlap in time and good spectral containment offers significantly higher robustness to these effects compared to CP-OFDM transmissions. Further, the effect of the manner in which redundancy is inserted into an OFDM system onto its robustness is considered. If the level of impairments exceeds a specific amount, redundant OFDM transmissions based on long modulating windows and without channel coding are shown to offer a higher robustness than coded CP-OFDM transmissions.