WSN Design for Unlimited Lifetime

Wireless sensor networks (WSNs) are among the most natural applications of energy harvesting techniques. Sensor nodes, in fact, are usually deployed in harsh environments with no infrastructured power supply and they are often scattered over wide areas where human intervention is difficult and expensive, if not impossible at all. As a consequence, their actual lifetime is limited by the duration of their batteries, so that most of the research efforts in the field of WSNs have been devoted so far to lifetime maximization by means of the joint application of low-power design, dynamic power management, and energy-aware routing algorithms. The capability of harvesting renewable power from the environment provides the opportunity of granting unbounded lifetime to sensor nodes, thus overcoming the limitations of battery-operated WSNs. In order to optimally exploit the potential of energy-harvesting WSNs (hereafter denoted by EH-WSNs) a paradigm shift is required from energy-constrained lifetime maximization (typical of battery-operated systems) to power-constrained workload maximization. As long as the average workload at each node can be sustained by the average power it takes from the environment (and environmental power variations are suitably filtered-out by its onboard energy buffer) the node can keepworking for an unlimited amount of time. Hence, the main design goal for an EH-WSN becomes the maximization of its sustainable workload, which is strongly affected by the routing algorithm adopted.