Nonlinear equalization of multipath fading channels with differentially coherent demodulation

A nonlinear decision-based adaptive equalizer compatible with differentially coherent PSK is proposed for frequency selective fading channels. This equalization scheme is appropriate whenever conventional equalizers are not able to track channel phase variations. A nonlinear processor before the equalizer generates the needed nonlinear terms which are weighted and summed in the equalizer. Nonlinear intersymbol interference at the output of the differential demodulator is dealt with by minimizing an error signal between the output of the equalizer and the detected data. Our simulation results indicate that, for channels with spectral nulls, equalization will be achieved successfully with the proposed scheme, whereas linear equalizers, either with coherent or non-coherent detection, fail