Exploiting RF-EH to Power FSO Communications: a Vehicular Network Scenario

In this paper, we investigate the potential of exploiting Free Space Optical (FSO) transmissions over short links to relay data from vehicular communications to a dedicated Access Point (AP). In the envisioned scenario, a small device capable of Energy Harvesting (EH) from radio frequency signals is placed alongside the road. Using the Simultaneous Wireless Information and Power Transfer (SWIPT) principle, the device obtains both data and energy from passing vehicles. The scavenged energy is then used to power a small optical transmitter and relay the received data to the AP. We address the problem of finding the optimal fraction of incoming energy to be reserved for EH, taking into account the stochastic losses over the optical link. A theoretical expression is derived, and a suitable approximation for some parameters setup is shown. The results, obtained through extensive Monte Carlo simulations, confirm the validity of the analysis, and show how the optimal harvesting range depends on the vehicular traffic characteristics as well as on the implemented schemes for transmissions collision avoidance.