In this paper, the authors present BackFi, a novel communication system that enables high throughput, long range communication between very low power backscatter IoT sensors and Wi-Fi APs using ambient Wi-Fi transmissions as the excitation signal. Specifically, they show that it is possible to design IoT sensors and Wi-Fi APs such that the Wi-Fi AP in the process of transmitting data to normal Wi-Fi clients can decode backscatter signals which the IoT sensors generate by modulating information on to the ambient Wi-Fi transmission. They show via prototypes and experiments that it is possible to achieve communication rates of up to 5 Mbps at a range of 1 m and 1 Mbps at a range of 5 meters.