PITTSBURGH—Disney Researchers are harvesting energy from ambient radio waves generated by TV, radio and cellphones to power the networks that support the so-called “Internet of Things,” or IoT.
“This is accomplished through ultra-wideband backscatter techniques that leverage the breath of commercial broadcast signals in the 80 MHz to 900 MHz range from FM radios, digital TVs, and cellular networks,” a trio of Disney researchers said in a paper entitled, “Riding the Airways: Ultra-Wideband Ambient Backscatter via Commercial Broadcast Systems.”
According to Disney, researchers led by Alanson Sample, associate lab director and leader of the Disney Research Wireless Systems group, created an “ultra-low-power system of sensors that transmit data to a central receiver by reflecting the ambient radio waves from commercial broadcasting systems that already bathe most office environments.”
The system is enabled by the use of universal backscatter readers that power “a network of ultra-low power nodes to operate on ambient carriers as low as -80 dBm, which is typical for indoor home and office environments. For the first time, we demonstrate the simultaneous use of 17 ambient signal sources to achieve node-to-reader communication distances of 50 meters, with data rates up to 1 kbps,” the paper states.
Simply put, Sample said, “Our idea is to reuse all the radio signals that are around us as a medium for transmitting data, much like sending ripples across a pond.”
The approach is said to “radically” reduce power requirements for the sensor nodes because generating radio waves is what consumes most of their battery power. The researchers filled the remaining “tiny bit of power demand” in their experiment “using solar cells optimized for low-light conditions.”
Sample, along with Disney’s Chouchang Yang and Jeremy Gummeson, presented details of system at the IEEE Conference on Computer Communication, INFOCOM 2017, in Atlanta, Ga. Disney said the team “demonstrated the system in an indoor office environment, using ambient signals from 14 radio towers as well as two mobile phones. ”
“The promise of the Internet of Things is that wireless sensors will be ubiquitous, allowing devices to sense their environments and talk to each other,”said Markus Gross, vice president at Disney Research. “As we move towards connecting the next billion wireless devices to the internet, however, the use of batteries to power these devices will become unworkable. UWB ambient backscatter systems, which potentially could be deployed in any metropolitan area, hold great potential for solving this dilemma.”
Backscatter communication is now employed in in passive RFID tags, but the limited range makes it “impractical for IoT systems,” Disney said. The same was true of using a single source for ambient RF, such as a TV station.
Image of the ultra-wideband ambient backscatter node with solar cell for energy autonomous sensing and computing. Sample said the multiple-source approach boosted the signal-to-noise ratio, “substantially improving the sensitivity of the backscatter reader and decreasing dead zones.” This was said to enable the system to operate on “real-world ambient sources” at a range of up to 22 meters on broadcast sources and up to 50 meters on cellular uplink traffic.
Sample also said the ultra-low-power sensor nodes are simple, and that the backscatter readers do “the heavy lifting” by decoding and combining multiple backscatter carriers to recover data from each sensor using four software-defined receivers—one each for FM and cellular and two for digital TV. Since the hardware is not tuned to specific frequencies, it can be deployed in“almost any metropolitan area,” he said.