| Narrowband communication systems are widely employed in mobile services, but fading severely degrades system performances. Because phase tracking is difficult in fading channels, differential demodulation is used. Equalizers should then be used to mitigate the non-linear inter-symbol interference induced by the fading channel. Linear equalizers are simple, but decision feedback equalizers (DFE) generally provide better performances, especially in channels with non-linear interference or spectral nulls. However, DFE's for differential detectors do not perform as well as optimal equalizers.; Our goal is to improve the performance of a differential DFE. We investigated the use of soft decision, multiple feedback structures, and Viterbi algorithms using Euclidean distance and correlation based metric measures. However, they provide no significant improvement in our fading models. We then investigated the use of linear block codes and fractionally spaced linear equalizer front-end. They are shown to provide significant performance gains. |
