Now, wireless devices that communicate sans batteries

The new communication technique, which the researchers call `ambient backscatter,` takes advantage of the TV and cellular transmissions that already surround us around the clock.

Updated: Aug 14, 2013, 14:14 PM IST

Washington: Engineers including an Indian-origin have developed a new wireless communication system which allows devices to interact with each other without relying on batteries or wires for power.

The new communication technique, which the researchers call `ambient backscatter,` takes advantage of the TV and cellular transmissions that already surround us around the clock.

Two devices communicate with each other by reflecting the existing signals to exchange information. The researchers built small, battery-free devices with antennas that can detect, harness and reflect a TV signal, which then is picked up by other similar devices.

The technology could enable a network of devices and sensors to communicate with no power source or human attention needed.

Lead researcher Shyam Gollakota, a UW assistant professor of computer science and engineering, said that they are hoping that it is going to have applications in a number of areas including wearable computing, smart homes and self-sustaining sensor networks.

Joshua Smith, a UW associate professor of computer science and engineering and of electrical engineering, said that their devices form a network out of thin air.

He said that people can reflect these signals slightly to create a Morse code of communication between battery-free devices.

The researchers tested the ambient backscatter 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 area, including inside an apartment building, on a street corner and on the top level of a parking garage. These locations ranged from less than half a mile away from a TV tower to about 6.5 miles away.

They found that the devices were able to communicate with each other, even 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 2.5 feet apart outdoors and 1.5 feet apart indoors. This is enough to send information such as a sensor reading, text messages and contact information.

The findings have been published in the Association for Computing Machinery`s Special Interest Group.

ANI