Έλεγχος Ισχύος Και Εξοικονόμηση Ενέργειας Σε Ασύρματα Δίκτυα Αισθητήρων

Abstract

Energy saving is a valuable commodity for wireless networks due to the limited battery of the portable devices. The energy conservation problem becomes harder in ad hoc wireless sensor networks (WSNs) due to their limitations arising from their nature. Wakeup schemes that turn off the sensors' transceiver whenever communication is not needful contribute considerably in energy saving. However, the various proposed schemes have only paid little attention to reducing the end-to-end packet delay while retaining the energy-saving capability, and, moreover, to apply the most appropriate route selection strategy that may have an impact on the network lifetime. The present thesis proposes three basic schemes to give solutions to these important problems. Since a long delay can be harmful for either large or small WSNs, the first proposed scheme, is a TDMA (Time-Division Multiple Access)-based wakeup intervals scheduling scheme that helps to manage the balance between energy saving and end-to-end delay. It achieves the reduction of the end-to-end delay caused by the sleep mode operation while maximizing the energy savings. The second scheme, proposed in this thesis, is a lifetime prolonging route selection strategy for WSNs. This scheme tries to avoid the least-energy nodes, while maintaining, at the same time, low energy consumption for each transmission. The third scheme introduces a new metric which contributes to the optimization of the second proposed algorithm. It is based on the MBCR (Minimum Battery Cost Routing) strategy and tries to improve the battery cost function, and thus, increasing further the network lifetime. Simulation results confirm the superiority of the proposed schemes in terms of node lifetime and network connectivity in comparison with some other relevant schemes.