People repurpose all manner of things, but engineers have created a battery-free communication technique that repurposes wireless signals that already surround us. This new wireless communication system seems like "magic," since it "provides connectivity between computers out of what is essentially thin air." It takes us a step closer to an Internet of Things reality as it lets devices talk to each other without relying on batteries or wires for power. Instead, it taps into already existing ambient Wi-Fi, TV or cellular signals to exchange information.
University of Washington researchers call it "ambient backscatter;" it's so revolutionary that when engineers presented their work [pdf] at the Association for Computing Machinery's Special Interest Group on Data Communication 2013 conference in Hong Kong, they won the "best paper" award.
"Ambient Backscatter: Wireless Communication Out of Thin Air" [pdf] states:
In this technique, TV signals and other source of RF signals serve as both the source of power and the means of communication. Because ambient backscatter avoids the maintenance-heavy batteries and dedicated power infrastructure of other forms of low-power communication (e.g., RFID and NFC), it enables a bevy of new applications that were previously impossible or at least impractical. We believe that ambient backscatter provides a key building block that enables ubiquitous communication (with no restrictions except the existence of ambient RF signals) among pervasive devices which are cheap and have near-zero maintenance.
"Two devices communicate with each other by reflecting the existing signals to exchange information," reported The University of Washington. "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."
Please take three minutes to watch the video that explains more about ambient backscatter "transforming existing ambient RF signals into a source of power and a communication medium." It gives an example of everyday objects like keys, wallets and sunglasses that are enabled with ambient backscatter tags that "exchange information by reflecting or absorbing pre-existing radio signals. These tiny battery-free devices can leverage ambient Wi-Fi, TV or cellular signals to communicate with each other and localize themselves."
If a person who had tagged their items later "lost" their keys, such as by accidentally leaving them on the couch, then the "couch can use the ambient backscatter to communicate with the lost keys" and send a text alert the user's smartphone.
The researchers used credit card-sized prototype devices to test the ambient backscatter technique. "For each device the researchers built antennas into ordinary circuit boards that flash an LED light when receiving a communication signal from another device." Using ambient RF signals for both power and communication, they showed how "one payment card can transfer funds to another card."
During "range" testing, the tags were located anywhere from a half mile to about 6.5 miles away from a TV tower; they were still able to communicate with each other. "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."
They believe that this technology could be added to smartphones so that when the battery dies, "the phone could still send text messages by leveraging power from an ambient TV signal."
The researchers claim this tech will enable smart homes, smart cities and the Internet of Things. The tags could be embedded in concrete walls, floors or roofs, and since they require no batteries, they would last "forever" and will require no maintenance.
A Google Faculty Research Award and the National Science Foundation's Research Center for Sensorimotor Neural Engineering helped fund this University of Washington research.
Hopefully this technology breakthrough won't also be used as yet another surveillance tool to spy on us.