A novel type of wireless device sends and receives data without a battery or other conventional power source. Instead, the devices harvest the energy they need from the radio waves that are all around us from TV, radio, and Wi-Fi broadcasts.
These seemingly impossible devices could lead to a slew of new uses of computing, from better contactless payments to the spread of small, cheap sensors just about everywhere.
“Traditionally wireless communication has been about devices that generate radio frequency signals,” says Shyam Gollakota, one of the University of Washington researchers who led the project. “But you have so many radio signals around you from TV, Wi-Fi, and cellular networks. Why not use them?”
Gollakota and colleagues have created several prototypes to test the idea of using ambient radio waves to communicate. In one test, two credit-card-sized devices—albeit with relatively bulky antennas attached—were used to show how the technique could enable new forms of payment technology. Pressing a button on one card caused it to connect with and transfer virtual money to a similar card, all without any battery or external power source.
In the tests, the devices were able to transfer data at a rate of one kilobit per second, sufficient to share sensor readings, information required to verify a device’s identity, or other simple tidbits. So far the longest links made between devices are around 2.5 feet, but the University of Washington team could extend that to as much as 20 feet with some relatively straightforward upgrades to the prototypes. The researchers also say the antennas of backscatter devices could be made smaller than those in the prototypes.
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