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Coordinated sleep MAC for energy constraint networks

Betreuer: Markus Waelchli, Prof. Dr. Torsten Braun

Wireless sensor networks are strongly affected by the energy constraints off the participating nodes. Whenever possible, e.g. if no data is expected for a certain time, a node should be able to shutdown its radio interface in order to save energy. Thus, sleep modes may lead to longer network lifetime. On the other hand, sleep modes add additional complexity and problems. The network connectivity may be negatively affected, nodes may have to be synchronized, or additional control messages are necessary. An appropriate trade-off between these properties is searched.

In this diploma thesis two enhancements of SYNC-based MAC protocols are developed. The first improvement is a local adaptive clock assimilation scheme. This scheme achieves local consistency, while avoiding the drawbacks of virtual clustering. There is no need for the maintenance of multiple schedules causing increased energy consumption. The second improvement concerns the possibility to detect and disconnect redundant nodes for a certain amount of time. Coordinated sleeping is a task normally done on the routing layer. On the other hand periodic sleeping is done on the MAC layer. Furthermore, most MAC protocols following periodic sleep cycles have to exchange information in order to synchronize each other. Thus, these MAC protocols are inherently supported with information from their neighborhood. We propose to make advantage of this information and use it to maintain a distributed and coordinated sleep algorithm that turns-off redundant nodes for a given amount of time.

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