Assessing the cost of deploying and maintaining indoor wireless sensor networks with RF-power harvesting properties

Since Wireless Sensor Networks (WSNs) consist of nodes with limited power resources, methods that extend their energy lifespan are always in the spotlight. A potential method is the use of RF-power harvesting antennas which can absorb energy from radio frequency (RF) signals and transform a part of it into electricity. Dedicated energy transmitters (ETs) are used to emit power to the nodes. In this paper, we model the amount of harvesting energy as a function of several parameters such as the received power, the efficiency of the harvesting module and the transmission time. We consider a simple communication model that separates the ETs' transmissions with the node data transmissions to avoid interference whilst we allow multi-hop energy transfer between the nodes when it is achievable. However, the ultimate purpose of this paper is to examine whether the cost of the investment of using energy harvesting nodes can be covered by achieving a lower operation cost; that is longer and cheaper operation times and, thus, less frequent maintenance. We consider several scenarios with different node densities and transmitter populations. Simulation results show that the use of RF-energy harvesting nodes can save a significant amount of energy, while the cost of the investment can be (theoretically) covered in less than 7 years for dense networks.