An enhanced MMSE per subchannel equalizer for highly frequency selective channels for FBMC/OQAM systems

In this paper the problem of equalization for filter bank multicarrier modulation based on offset OQAM (FBMC/OQAM) is investigated. Existing equalizers for FBMC/OQAM do not completely cancel intercarrier interference (ICI) and hence some ICI remains even after equalization. To cope more efficiently with ICI, we propose a two stage MMSE (TS-MMSE) equalizer. The first stage consists in applying an MMSE equalizer and taking some preliminary decisions, then subsequetly using these decisions to remove the term corresponding to ICI from the received signal for each subchannel. The resulting signal from the first stage has its ICI practically removed (up to channel estimation errors and decision errors) and is therefore corrupted only by intersymbol interference (ISI) and additive noise. In the second stage we apply an MMSE equalizer which copes only with ISI. The proposed two stage MMSE equalizer has shown better performance compared to the classical MMSE one. Some simulation results are provided to illustrate the effectiveness of the proposed equalizer.