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Annales Des Télécommunications

, Volume 56, Issue 5–6, pp 291–305 | Cite as

Récepteurs en râteau pour les systèmes à étalement de spectre par séquences directes

  • Hatem BoujemÂa
  • Mohamed Siala
Article

Résumé

Cet article développe les structures des récepteurs en râteau à temps continu et à temps discret. Le premier récepteur est celui qu’on utilise ďhabitude et consiste à combiner les sorties de corrélateurs synchronisés sur les trajets les plus significatifs. Afin de pallier ľincapacité des dispositifs de synchronisation usuels à discerner des trajets à instants ľarrivée proches, nous proposons un algorithme ľacquisition au maximum de vraisemblance ainsi qu’ une boucle de poursuite améliorée. Le second récepteur, récemment proposé, fonctionne sans aucune connaissance du nombre de trajets et de leurs délais. Il est basé sur une estimation globale du produit de convolution des réponses impulsionnelles du canal de propagation et du filtre de mise en forme. La comparaison des performances des deux récepteurs est établie dans le cadre applicatif du mode fdd de la norme UMTS.

Mots clés

Spectre étalé séquence directe Récepteur optimal Circuit multicanal Systàme continu Systàme discret Estimation paramàtre Canal radioélectrique Propagation trajet multiple Filtre adapté Maximum vraisemblance Acquisition signal Poursuite Boucle verrouillage 

Rake receivers for direct sequence spread spectrum systems

Abstract

This paper investigates the structure of a continuous and a discrete time Rake receivers. The former receiver is the most used and consists on combining the output of correlators locked on the most significant paths. Since the conventional synchronisation module of this receiver is not able to distinguish closer paths, we propose a maximum likelihood acquisition algorithm and an enhanced tracking loop. The latter receiver was recently suggested and works without the knowledge of path delays and their number. It is based on a global estimation of the impulse response of the multipath channel convolutionned with the shaping filter. Performance comparison of the two receivers is established for the fdd mode of the umts interface.

Key words

Direct sequence spread spectrum Optimum receiver Multicanal circuit Continuous system Discrete system Parameter estimation Radio channel Multipath propagation Matched filter Maximum likehood Signal acquisition Tracking Locking loop 

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Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  1. 1.France Telecom r&d/dmr/iim—38-40France

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