LMMSE detection of OFDM signals in time-varying channels with partial whitening of intercarrier interference and soft decision feedback

The transmission performance of orthogonal frequency-division multiplexing (OFDM) in time-varying channels can be adversely affected by intercarrier interference (ICI). Typical ICI countermeasures address a few dominant ICI terms only, yielding an error floor due to the residual ICI. We have shown in a previous work that the residual ICI has high normalized autocorrelation and that this autocorrelation is insensitive to a variety of system and channel conditions. Consequently, the residual disturbance (consisting of residual ICI plus noise) can be whitened and reduced in a nearly channel-independent manner, benefiting signal detection. In this work, we consider linear minimum mean-square error (LMMSE) and iterative LMMSE detection with the above partial whitening of additive disturbance, together with soft decision feedback. The method is shown to provide good performance-complexity tradeoff compared to other ICI countermeasures.