The existence of a coordinate system can often improve the routing in a wireless sensor network. While most coordinate systems correspond to the geometrical or geographical coordinates, in recent years researchers had proposed the use of virtual coordinates. Virtual coordinates depend only on the topology of the network as defined by the connectivity of the nodes, without requiring geographical information. The work in this thesis extends the use of virtual coordinates to scenarios where the wireless sensor network has a mobile sink. One reason to use a mobile sink is to distribute the energy consumption more evenly among the sensor nodes and thus extend the life-time of the network. We developed two algorithms, MS-DVCR and CU-DVCR which perform routing towards a mobile sink using virtual coordinates. In contrast to the baseline virtual coordinate routing MS-DVCR limits routing updates triggered by the sink movement to a local area around the sink. In contrast, CU-DVCR limits the route updates to a circular area on the boundary of the local area. We describe the design justification and the implementation of these algorithms. Using a set of experimental studies, we show that MS-DVCR and CU-DVCR achieve a lower energy consumption compared to the baseline virtual coordinate routing without any noticeable impact on routing performance. In addition, CU-DVCR provides a lower energy consumption than MS-DVCR for the case of a fast moving sink.

Wireless Sensor Networks (WSNs) are composed of a large number of battery-powered sensor nodes that have the ability to sense the physical environment, compute the obtained information and communicate using the radio interfaces. Because sensor nodes are generally deployed on a large and wild area, they are powered by embedded battery. And it is difficult to change or recharge the battery, thus to reduce the energy consumption when sensors and protocols are designed is very important and can extend the lifetime of WSNs. So sensor nodes transmit packets with a lower transmission power (e.g. OdBm). With this transmission power, a packet can only be transmitted dozens of meters away. Therefore, when a sensor detects an event, a packet is sent in a multi-hop, ad-hoc manner (without fixed infrastructure and each sensor is able to relay the packet) to the sink (specific node which gathers information and reacts to the network situation). In this thesis, we first give an elaborate state of the art of WSNs. Then the impacts of duty-cycle and unreliable links or the performances of routing layer are analyzed. Based on the analytical results, we then propose three new simple yet effective methods to construct virtual coordinates under unreliable links in WSNs. By further taking the duty-cycle and real-time constraints into consideration we propose two cross-layer forwarding protocols which can have a greater delivery ratio and satisfy the deadline requirements. In order to have protocols for the WSNs that have dynamic topology, we then propose a robust forwarding protocol which can adapt its parameters when the topology changes. At last, we conclude this thesis and give some perspectives.

Les réseaux de capteurs sans fils (WSN) sont composés d'un très grand nombre de capteurs, capables de mesurer des paramètres physiques de l'environnement, de mettre en forme l'information obtenue et de la communiquer aux autres capteurs grâce à une interface radio. Les capteurs étant en général déployés sur de très grandes étendues géographiques, l'énergie nécessaire pour les faire fonctionner est fournie par une batterie embarquée sur le capteur. En général, il est difficile de recharger les batteries une fois les capteurs déployés. Economiser l'énergie est donc une préoccupation constante lors de la conception des capteurs et des protocoles de communication utilisés, de manière à prolonger la durée de vie du réseau. Dans ce but, les capteurs transmettent leurs données avec des puissances d'émission très faibles. Avec de telles puissances d'émission, un message ne peut être transmis que sur quelques dizaine de mètres. De ce fait, lorsqu'un capteur détecte un événement, le message est transmis en mode ad-hoc multisauts jusqu'au puits, un nœud spécifique du réseau, qui récolte toutes les informations et est capable de réagir de manière adéquate. Dans cette thèse, nous donnons d'abord un état de l'art avancé sur les WSN. Ensuite nous analysons l'impact du cycle d'endormissement et des liens non fiable sur la couche de routage. A partir des résultats analytiques, nous proposons trois méthodes originales, simples et efficaces pour construire des coordonnées virtuelles en prenant en compte la non fiabilité des liens dans les WSN. En prenant en compte le cycle d'endormissement et les contraintes temps-réel, nous proposons deux protocoles cross-layer qui ont de bons taux de livraison et qui permettent de respecter des contraintes temporelles. Pour pallier à la dynamicité des réseaux de capteurs sans fil, nous proposons un protocole de routage robuste qui adapte ses paramètres quand la topologie change. Enfin, nous concluons et donnons quelques perspectives. / Wireless Sensor Networks (WSNs) are composed of a large number of battery-powered sensor nodes that have the ability to sense the physical environment, compute the obtained information and communicate using the radio interfaces. Because sensor nodes are generally deployed on a large and wild area, they are powered by embedded battery. And it is difficult to change or recharge the battery, thus to reduce the energy consumption when sensors and protocols are designed is very important and can extend the lifetime of WSNs. So sensor nodes transmit packets with a lower transmission power (e.g. OdBm). With this transmission power, a packet can only be transmitted dozens of meters away. Therefore, when a sensor detects an event, a packet is sent in a multi-hop, ad-hoc manner (without fixed infrastructure and each sensor is able to relay the packet) to the sink (specific node which gathers information and reacts to the network situation). In this thesis, we first give an elaborate state of the art of WSNs. Then the impacts of duty-cycle and unreliable links or the performances of routing layer are analyzed. Based on the analytical results, we then propose three new simple yet effective methods to construct virtual coordinates under unreliable links in WSNs. By further taking the duty-cycle and real-time constraints into consideration we propose two cross-layer forwarding protocols which can have a greater delivery ratio and satisfy the deadline requirements. In order to have protocols for the WSNs that have dynamic topology, we then propose a robust forwarding protocol which can adapt its parameters when the topology changes. At last, we conclude this thesis and give some perspectives.