Wireless Medical Devices Go Battery-Free

A new communication technique allows devices to interact with each other without relying on batteries or wires for power.

Developed by researchers at the University of Washington (Seattle, USA), the ambient backscatter communication (ABC) technique takes advantage of commonplace TV and cellular transmissions. The technology could enable devices and sensors to communicate with no power source using small, battery-free devices with antennas that can detect, harness, and reflect a TV signal, which then is picked up by other similar devices that communicate with each other by reflecting the existing signals to exchange information.

The researchers tested the ABC technique with credit card-sized prototype devices placed within several feet of each other. For each device, the researchers built antennas into ordinary circuit boards that flash an LED light when receiving a communication signal from another device. Groups of the devices were tested in a variety of settings in the Seattle (WA) area, including inside an apartment building, on a street corner, and on the top level of a parking garage, ranging from less than 800 meters away from a TV tower to about 10 kilometers away.

They found that the devices were able to communicate continuously with each other, even with the ones farthest from a TV tower. The receiving devices picked up a signal from their transmitting counterparts at a rate of 1 kilobit per second when up to 60 cm apart outdoors, and 40 cm apart indoors. These transmission speeds are sufficient to send information such as a sensor reading, text messages, and contact information over a network.

The researchers added that it is also feasible to build the technology into devices that do rely on batteries, such as smartphones; when the battery dies, the phone could still send text messages by leveraging power from an ambient TV signal. The study was presented at the Association for Computing Machinery’s Special Interest Group on Data Communication conference, held during August 2013 in Hong Kong.

“We can repurpose wireless signals that are already around us into both a source of power and a communication medium,” said study presenter Shyam Gollakota, PhD, 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.”

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