In this thesis, centralized routing methods for wireless sensor networks studied. The goal has been to extend the network's lifetime by reducing energy consumption for sensornodernas communication. Wireless sensor networks are becoming an increasingly common application where information from many sensors need to be collected and processed. The use of wireless sensor network increases the network exibility, and costs for wiring can be avoided. Wireless sensor networks can consist of hundreds or even up to thousands of small units, equipped with one or your sensors (eg, sound, light, movement and visual), that form a wireless network. Each sensor node in the network collects information from its environment, which it then sends to the base station either from sensor node to sensor node, called multihop, or directly to the base station, known singelhop.
We have done simulations show that asymmetric communication with multihop increases the longevity of large wireless sensor networks . We have also investigated the usefulness of maintaining a minimum distance between cluster heads in a cluster-based sensor networks. The results show that our wireless sensor network performs up to 150% better when a minimum distance between cluster heads are used, measured in number of messages received at the base station. The simulations have also shown that the minimum distance between cluster heads that generates the lowest energy consumption of the network varies with the number of clusters. We have also made a first study where we studied how to choose a path
through the network to maximize the lifetime of a sparse sensor networks. The study has been done to see how different heuristic algorithms influence the energy consumption of individual nodes, and hence the entire wireless seniiisornätverkets life. We also compared the maximum lifetime of the heuristic algorithms with the maximum lifetime of an optimal solution. The simulations have shown that for certain types of applications, the choice of heuristic algorithm is more important for the network's lifetime, than for other types of applications.