The
researchers tested the ambient backscatter technique with credit card-sized
prototype devices placed within several feet of each other. 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. It’s also
feasible to build this technology into devices that do rely on batteries, such
as smartphones. It could be configured so that when the battery dies, the phone
could still send text messages by leveraging power from an ambient TV signal.
