Reduced complexity sequence detection for nonminimum phase intersymbol interference channels

Controlled intersymbol interference may be used to design bandwidth efficient coded modulation schemes. The performance of the optimum receiver depends only on the free distance of the code and is independent of its phase. Large reductions in receiver complexity are obtained by using reduced search detection techniques like the M-algorithm (MA). However, we show that MA detector performance depends critically on phase, and is characterized by the partial energy of the encoder or channel. The minimum phase encoder needs by far the least detector searching. We propose modifications to the receiver, so that the reduced search can operate on all nonminimum phase channels at this same low complexity.