The use of RF signals allows ultra-low power computing devices to function with no power source other than energy harvested from ambient radio frequencies from cellular, Wi-Fi, radio and similar sources.
Wireless sensor networks and other M2M networks use RF-powered computing where both low processing and low bandwidth requirements make it feasible. RF-powered environments require less maintenance and don’t consume batteries that will need to be replaced, as may be the case in other environments where wired connections are impractical.
A small, licensed AM radio station at 1kW can provide adequate energy for RF-powered devices at a distance of 1.2 miles. Additionally, low-power signals at closer ranges can be used in unregulated frequency bands without FCC licensing requirements.
While the power requirements for receiving data are low, traditionally the need for higher power came with the need to broadcast. Traditional Wi-Fi signals require more than 2.5 times the power that RF-powered devices can harvest in total. RF-powered computing and communication overcome this by using a technique called Wi-Fi backscattering.
Wi-Fi backscattering selectively mirrors ambient signals, resulting in small but detectable signal strength fluctuations. These fluctuations can be interpreted by specially tuned equipment as a separate data transmission.