MMSE-DFE equalizer design for OFDM systems with insufficient cyclic prefix

Abstract

In orthogonal frequency division multiplexing (OFDM) systems, the transmitter inserts a cyclic prefix (CP) at the head of each symbol, in order to avoid inter-symbol interference (ISI) and inter-channel interference. However, since the CP does not carry useful data, this approach causes a loss in the OFDM system efficiency. To solve this problem, one can use a CP of insufficient length and decrease ISI- and ICI power by a decision feedback equalizer (DFE), presented in (J Zhu et al, Proc. Int. Conf. on Comm., p.948-952, 1992). In this paper, we introduce new techniques to improve the performance of this equalizer. Feedback error elimination by forward error correction and designing the equalizer with a minimum mean square error (MMSE) criterion are proposed here.