. Dans-le-contexte-de-la, les utilisateurs secondaires peuvent générer des interférences sur le primaire au cours de collisions qui peuvent survenir soit si l'utilisateur du primairé emet lors d'une utilisation du secondaire, soit si le secondaire utilise la bande après un mauvais sondage de canal. Dans ce cadre, la mise en place de mécanismes Hybrid-ARQ a une utilité additionnellè a son utilité classique, ` a savoir détecter et pallier aux effets de collision. Cependant, dans ce cas les mécanismes peuvent entrer en compétition : en effet l'Hybrid-ARQ du secondaire doit garantir la fiabilité du secondaire sans pour

L. De-même and . Grande, secondaire peut rendre difficile l'utilisation de mécanismes classiques tels que les modulations codées adaptatives qui nécessitent une bonne connaissance des conditions de propagation. Ainsi, l'Hybrid-ARQ appara??tappara??t comme un moyen simple de s'adapter dynamiquement sans connaissance a priori du canal et avec une voie de retour limitée. Dans le contexte de la radio cognitive avec un accès partagé du spectre, les mécanismes HARQ permettraient de garantir la fiabilité malgré la variabilité des conditions de transmission induite par l

. Si-on-considère-enfin and . Qu, une coopération est possible au sein des systèmes primaire et secondaire, alors l'´ etude des techniques d'alignement d'interférences semble très prometteuse

. La-transmission-robuste, L'idée initialé etait de capitaliser sur nos expertises respectives. A. Revel possède l'expertise des système multi-agents (SMA) et il a déjàdéjàévalué l'apport de ces systèmes dans un contexte de télécommunications filaires Il a montré la capacité des SMAàSMAà s'adapteràadapterà une structure changeante de la topologie du réseau. Pour ma part, je m'intéresse aux aspects de robustesse au niveau transport ou applicatif et aux techniques de codage canal afférentes. Cette thématique est riche et intéressante sur de nombreux portuniste. Ainsi, je souhaiterais m'intéresserintéresserà différents aspects en se basant sur les différentes expériences et expertises que j'ai eues. Parmi les différentes voies de recherche, on peut citer ? Systèmes de codage pour les communications coopératives : AMC flexible pour les systèmes coopératifs pour le " half " et " full duplex, Le but est de proposer un système de codage au rendement adaptatifàadaptatifà l'´ emetteur et au relai qui permet d'avoir un codage efficace et adapté aux topologies variables existantes en relais coopératifs. C'est un travail que je vais commencer en collaboration avec P. Piantanida (Supélec) et I. Andriyanova (ETIS)

@. Codage-de-réseaux-sur-la-couche-physique, comment avoir une stratégie de codage pratique sur la couche physique permettant d'opérer au niveau paquet? Le codage réseau est avant tout défini pour la couche réseau. Cependant, dans un environnement sans fil, les stratégies usuelles sont peu pratiques dûdûà la propagation d'erreurs possibles. Une stratégie alternative est de concevoir le codage de réseau directement sur la couche physique avec une combinaison des paquets au niveau signal

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