Unique word prefix in SC/FDE and OFDM: A comparison

Abstract

The concept of using unique word (UW) prefixes instead of cyclic prefixes (CPs) is already well investigated for single carrier systems with frequency domain equalization (SC/FDE). In OFDM (orthogonal frequency division multiplexing), where the data symbols are specified in frequency domain, the introduction of UWs — which are specified in time domain — is not that straight forward. In this paper we show how unique words can also be introduced in OFDM symbols. In OFDM our proposed method introduces correlations between subcarrier symbols. This allows to apply a highly efficient LMMSE (linear minimum mean square error) receiver. Throughout this paper we discuss the similarities and differences of UW-SC/FDE and UW-OFDM transmitter/receiver processing, and we present simulation results in indoor multipath environments.