21.08.13

Unpowered devices connect using ambient RF

Researchers have created prototype devices without a power source that can connect wirelessly using the ambient radio waves in the atmosphere. The development could mean that a network of devices and sensors could in future communicate with no power source or human attention needed. It could also enable devices to continue to operate on a basic level in the event of a power failure or allow malfunctioning equipment to contact monitoring stations. 

Called ambient backscatter, the technology developed by researchers at the University of Washington relies on two or more devices absorbing or reflecting TV signals to communicate with each other. So far, the project has seen information rates of 1kbps over distances of up to two-and-a-half feet – both indoors and outdoors.

“Our devices form a network out of thin air,” said Joshua Smith, a UW associate professor of computer science and engineering and of electrical engineering. “You can reflect these signals slightly to create a Morse code of communication between battery-free devices.”

To demonstrate possible new forms of payment technology, the researchers transferred virtual money from one credit card sized device to another by pushing a button.

“We can repurpose wireless signals that are already around us into both a source of power and a communication medium,” said lead researcher 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.”

Smart sensors could be built and placed permanently inside nearly any structure, then set to communicate with each other. For example, sensors placed in a bridge could monitor the health of the concrete and steel, then send an alert if one of the sensors picks up a hairline crack. The technology can also be used for communication – text messages and emails, for example – in wearable devices, without requiring battery consumption.