  In this paper we propose a novel transmit signal structure and an adjusted
and optimized receiver for OFDM (orthogonal frequency division multiplexing).
Instead of the conventional cyclic prefix we use a deterministic sequence,
which we call unique word (UW), as guard interval. We show how unique words,
which are already well investigated for single carrier systems with frequency
domain equalization (SC/FDE), can also be introduced in OFDM symbols. Since
unique words represent known sequences, they can advantageously be used for
synchronization and channel estimation purposes. Furthermore, the proposed
approach introduces a complex number Reed-Solomon (RS-) code structure within
the sequence of subcarriers. This allows for RS-decoding or to apply a highly
efficient Wiener smoother succeeding a zero forcing stage at the receiver. We
present simulation results in an indoor multipath environment to highlight the
advantageous properties of the proposed scheme.
