Ambient Backscatter Technique Lets Wireless Devices Go Battery-Free

University of Washington engineers have created a new communication technique, called ambient backscatter, that takes advantage of ambient TV and cellular transmissions. Two devices communicate with each other by detecting, harnessing, and reflecting the existing RF signals to exchange information. For each battery-free device, the researchers built antennas into circuit boards that flash an LED light when receiving a communication signal from another device. The receiving devices pick up a signal from their transmitting counterparts at a rate of 1 kilobit per second when up to 2.5 feet apart outdoors and 1.5 feet apart indoors - enough to send information like text messages and a sensor reading. "We can repurpose wireless signals that are already around us into both a source of power and a communication medium," said Shyam Gollakota, a UW assistant professor of computer science and engineering. "It's hopefully going to have applications in a number of areas including wearable computing, smart homes, and self-sustaining sensor networks."