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Abstract
A major constraint for long term sustainability of wireless sensor networks (WSN) and the Internet of Things (IoT) is the limitation of their energy resources. Most wireless sensors are low energy consuming devices which are, in general, designed to transmit sporadically, and various energy saving techniques have been proposed to reduce the power consumption. However, battery replacement in sensor nodes can be a prohibitively expensive exercise because of their abundance. Dedicated RF energy harvesting (R-EH) has emerged as a promising technique to improve the lifespan, reliability, and capacity of WSN and IoT networks. This work evaluates the potential benefit of using a combination of an omnidirectional RF energy transmitter for getting periodic information updates, and then beam steering, by physically rotating a directional RF energy transmitter, to achieve higher sampling rates from the areas of need. An information based scheme for steering directional RF energy transmitter is presented that is based on the number of alarms (an indication of abnormal events) received from the network. An energy harvesting development kit for wireless sensor network manufactured by Powercast Corporation is used for developing the proof of concept. This work is supported by extensive MATLAB simulations to analyze the proposed scheme performance in different network scenarios. The simulation results show that the proposed maximum alarm based directional transmitter rotation scheme performs significantly better than the sequential transmitter rotation in terms of total abnormal events detected and alarms received per abnormal event occurred.