Improved Block DFE Equalization for Mobile WiMAX OFDM Systems

In this paper an improved decision feedback equalizer (DFE) for mobile orthogonal frequency division modulation (OFDM) systems is presented. The time-varying nature of the channel, due to the Doppler effect, produces inter carrier interference (ICI) that may be counteracted by using a DFE frequency- domain OFDM symbol equalizer. The proposed algorithm is based on a recently proposed block DFE equalizer exploiting an LDL^H decomposition. The main novelty of this work is the idea to modify the backward filter in order to have a complete MMSE linear equalization before the decisions needed for the interference cancellation. Performance may be further improved by re-filtering the signal in an iterative algorithm which makes use of the proposed backward filter at the first iteration. The proposed scheme performance is evaluated by considering a mobile WiMAX IEEE 812.16e standard transceiver.