Noncausal and Bidirectional Soft Decision Feedback Equalizer for Turbo Equalization

The goal of this paper is to develop equalizers which can provide soft information to channel decoders for use in the initial stage of iteration, of equalization and decoding architectures. We propose an initial-stage equalization structure by combining noncausality, bidirectionality and soft processing for common non-initial type equalizers such as ML, MAP, or soft interference, which typically requires sufficiently accurate previous information to perform some type of soft cancellation, especially for hostile channel conditions which are hard to equalize.