Performances en probabilité d'erreur des modulations à grand nombre d'états en période d'évanouissements sélectifs

A comparison of high-level modulation techniques and their performance during selective fading periods is presented. In order to obtain precise results, the error rate was used as the quality criterion, thus avoiding the use of criteria such as the eye-opening approach. For this purpose, an error-rate evaluation method was developed; the flexibility and low computing cost of this method made it possible to investigate current coherent modulation techniques as well as techniques (characterized by hexagonal constellations) with low packing coefficient. Error rate was determined in the presence of intersymbol interference, and the signature analysis of digital transmission systems was considered. Specifically, the proposed approach was applied to calculate the relation between the spectrum efficiency and multipath robustness of 140 Mbit/s transmission systems.