Abstract
A new multiuser detector (MUD) exploiting the MAP algorithm is proposed for channels affected by severe multipath and is then suitable for time-division duplexing (TDD)-CDMA receivers. After coherent combining the received multipaths, a multidimensional MAP non-linearity is employed to compute step-by-step the a posteriori probabilities (APPS) of the transmitted data for each user separately and then their expected values conditional to the available observations. These are then employed for soft ISI and MAI removal from the received sequences so that the APPS can be more reliably re-computed. The procedure is iterated in a multistage structure until final decisions are taken. From the comparison with other existing techniques (interference cancellation, zero-forcing) the proposed reduced MAP-MUD receiver exhibits better performance and equal or minor complexity.
Résumé
L’article propose un nouveau détection multiutilisa-teur exploitant un algorithme de probabilité a posteriori maximale (MAP) pour des canaux fortement dégradés par des trajets multiples. Ce détecteur convient donc aux récepteurs à accès multiple par répartition en code et à duplexage temporel. Après combinaison cohérente des signaux provenant des différents trajets, on calcule pas à pas les probabilités (APP) des données transmises, séparément pour chaque utilisateur, en employant une non-linéarité MAP multklimensionnelle, puis leurs espérance mathématiques conditionnelles étant donné les observations disponibles. Ces valeurs servent ensuite à éliminer de façon « soft » des séquences reçues l’interférence intersymbole et le brouillage d’accès multiple de façon à permettre de recalculer les APP de façon plus fiable. La procédure est itérée dans une structure multi-étage jusqu’aux décisions finales. La comparaison avec d’autres techniques existantes (annulation des brouillages, forçage de zéro) montre que le récepteur réduit proposé présente de meilleures performances et une complexité équivalente ou plus faible.
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Cusani, R., Mattila, J. & Felice, M.D. MAP multiuser detection with soft interference cancellation for UTRA-TDD receivers. Ann. Télécommun. 54, 359–364 (1999). https://doi.org/10.1007/BF02997758
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DOI: https://doi.org/10.1007/BF02997758
Key words
- Mobile radiocommunication
- Optimal receiver
- UMTS
- Signal detection
- Complex signal
- A posteriori probability
- Multipath propagation
- Code division multiple access
- Signal interference
- Inter-symbol interference