RF-Energy Harvesting from Moving Vehicles: Mathematical Modeling and Selection Protocol

Wireless energy transfer can extend the lifetime of wireless sensor networks deployed in hard-to-reach and/or harsh environments. A number of works have proposed using dedicated mobile chargers (e.g., robots, drones, or vehicles) to transmit Radio Frequency (RF) energy to sensor nodes, which, despite optimal route selection, remains an expensive approach. In this article, we consider a scenario where sensor nodes could be recharged by passing vehicles. This could be the case of a wireless sensor network deployed to monitor the health of a bridge or a dam. We provide exact mathematical modeling of the harvested energy from a moving vehicle over $T$ seconds and over a trip time. This model captures the effect of the vehicle's speed and location. Then, we extend the discussion to the case of multiple vehicles and propose a multi vehicle harvesting protocol. This protocol allows the sensor node to maximize its energy intake by proactively selecting the source vehicle. This work paves the ground for accurate designs of energy harvesting protocols that leverage surrounding sources of RF energy. The accuracy of the derived results is verified using computer simulations.