A wireless sensor network (WSN) are spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data through the network to a main location(sink).
The modern networks are bi-directional, also enabling control of sensor activity. The development of wireless sensor networks was motivated by military applications such as battlefield surveillance; today such networks are used in many industrial and consumer applications, such as industrial process monitoring and control, machine health monitoring, and so on.
The promise of wireless sensors lies in their reduced susceptibility to failure, reduced weight and configuration flexibility compared with conventional wired sensors. However, because they are wireless, such sensors must include a self-contained power source.
Batteries provide the current solution to this problem, but they are subject to well-known challenges such as limited lifetime. For example, in an environment where access to sensor nodes may be limited or not possible, routine maintenance to replace batteries becomes both time-consuming and expensive. Energy harvesting technologies that convert ambient energy (e.g., solar, GSM Band signals, TV signals, RF, etc.) into electrical energy represent one means of providing long lived power for inaccessible wireless sensors life time.
Energy harvesting devices depend on a constant, high quality source of ambient energy to deliver continuous power. In our study we consider a sensor network where the nodes near the sink node will be deployed with energy-harvester (EH) enabled sensors and the rest of the nodes will be traditional battery powered. In this work we use Powercast device for the harvesting energy from radio frequency. It is more efficient than the other harvesting device. So we use this device for better energy for our proposed network for increasing the network life time