An asynchronous scheduler to minimize energy consumption in wireless sensor networks

Energy efficiency is one of the main issues in the design and optimization of Wireless Sensor Networks (WSN) since each node is typically subject to a hard battery limitation. Taking into account that the most energy-consuming component of a WSN node is the radio, the design of energyefficient routing and MAC protocols is certainly a valid approach to face the problem. Minimizing the energy consumption allows to increase the lifetime of nodes and so of the overall network. This paper deals with a novel low power Medium Access Control (MAC) protocol compliant with the ZigBee standard. In particular, a new algorithm to tune the duty cycle of a node, i.e., the cycling between an awake and a sleep state of the radio transceiver, is proposed. The basic idea of this solution is that neighboring nodes exchange information about their transmission time, so that each one knows in advance when it is supposed to be awake to receive a message and when it can switch off its radio. Low requirements in terms of processing and storage capacity characterize this solution. Furthermore, it is able to react effectively both to network topology changes and to clock desynchronization. The effectiveness of the defined schema has been evaluated, in terms of delay and power consumption, by means of simulations. The simulation results have highlighted substantial improvements of the proposed solution