D. Contents,

.. .. Le,

. , 3.1 Les méthodes d'estimation d'un canal variant dans le temps pour un signal OFDM 55 4.3.2 Méthode proposée

. .. Résultats, , p.61

, Impact d'une mauvaise estimation du signal de référence sur la détection, p.66

. .. Complexité-de-la-détection, 94 6.2.1 Perturbations limitant les capacités de détection

. Conséquences and . .. De-référence, 99 6.3.2 Réjection du trajet direct et des échos proches

. , 123 (a) Signal focalisé-RSBT D = 6.5 dB-RSBLS = 25.5 dB (b) Signal décodé-RSBT D = 16.9 dB-RSBLS = 32 dB FIGURE 6.8-Réjection du TD à partir des signaux de référence décodé et focalisé-Fichier M190 (a) Signal focalisé-RSBT D = 16.8 dB-RSBLS = 28 dB (b) Signal décodé-RSBT D = 0 dB-RSBLS = 35

, Il se focalise sur le trajet direct. Les différences de niveaux résiduels de lobes secondaires ont été évaluées en fonction du critère MER proposé pour la mesure de la qualité de l'estimation de la constellation, masque de réjection est plus restreint

, Cependant, il est complexe d'établir quantitativement l'impact de cet aspect d'autant plus que les résultats analysés concernent des fichiers différents avec des fouillis plus ou moins importants. (a) Fichier V357-MER = 26.6 dB-RSBLS = 36 dB (b) Fichier V488-MER = 18.7 dB-RSBLS = 44.2 dB FIGURE 6.13-Comparaison de la réjection du TD-Signaux de référence BIEN et MAL décodésEmetteur A-MtV (a) 8 symboles/bloc-RSBLS = 21 dB (b) 10 symboles/bloc-RSBLS = 20.9 dB FIGURE 6.15-Rejection par bloc signal de référence décodé-8 et 10 symboles/bloc-Fichier M190 (a) 16 symboles/bloc-RSBLS = 21 dB (b) 20 symboles/bloc-RSBLS = 21 dB FIGURE 6.16-Rejection par bloc signal de référence décodé-16 et 20 symboles/bloc-Fichier M190 6.4. Méthode de réjection par bloc (a) 32 symboles/bloc-RSBLS = 21.1 dB FIGURE 6.17-Rejection par bloc signal de référence décodé-32 symboles/bloc-Fichier, La table Tab.6.8 rassemble les valeurs observées. Les figures Fig.6.13 et Fig.6.14 confirment que, qualitativement, la réjection est d'autant meilleure que le décodage semble de qualité (au regard du niveau de lobes secondaires

, FIGURE 6.19-Etalement Doppler des principaux échos de fouillis après réjection standard-Signal de référence décodé-Fichier M190

, permet aussi de décorréler la durée nécessaire à la caractérisation du fouillis (sur la durée totale du bloc),de la durée de mise à jour des coefficients (mis à jour sur la partie centrale du bloc seulement)

, Le schéma Fig.6.20 explicite le principe

T. Le-tableau, 11 montre les résultats obtenus avec la méthode par bloc glissant, vol.6

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