Disney Research’s Wireless Systems group demonstrates IoT technology powered by radio waves.
Radio waves are used by many IoT devices to connect to the wider internet and send back data, but this process often uses a lot of energy. Researchers at Disney Research, the R&D arm of The Walt Disney Company, have come up with a way for devices to use ambient radio waves to send data.
Alanson Sample, associate lab director and leader of Disney Research’s Wireless Systems group, has devised 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.
“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,” Sample said.
This substantially lowers the power requirements of sensor nodes, because it is the generation of radio waves that consumes most of their battery power. The researchers revealed that they could meet the tiny bit of power demand that remained by using solar cells optimised for low-light conditions.
They demonstrated their ultra-wideband (UWB) ambient backscatter system in an indoor office environment, using ambient signals from 14 radio towers, as well as two mobile phones.
Backscatter communication is already used in passive RFID tags. In that case, a RFID reader transmits radio frequency power to the battery-free RFID tag; the tag sends data to the reader by reflecting, or backscattering, the carrier wave back to the reader. These systems have limited range, however, which makes them impractical for some IoT systems.
Other researchers have shown systems that require even less power by using ambient radio waves from a single source, such as a TV station. But, again, the range is limited to a few meters unless the power of the ambient signals is boosted to high levels.
Sample said that using ultra-wideband, which backscatters all ambient sources, has some advantages. Using multiple backscatter channels boosts the signal-to-noise ratio, substantially improving the sensitivity of the backscatter reader and decreasing dead zones.
He added that this enables the system to operate on real-world ambient sources and substantially extends the range – up to 22 metres when using ambient signals from broadcast towers, and 50 metres when using ambient signals generated by mobile phone uplink traffic.
He added that the nodes are simple and require the backscatter reader to do the heavy lifting for the system. The reader must receive the backscatter signals, decode and combine multiple backscatter carriers to recover the data from each sensor. The reader uses four software-defined radio receivers – one for the FM radio band, another to cover most of the cellular uplink and downlink bands, and two for digital TV bands.
The hardware doesn’t need to be tuned to any frequency band and thus such devices can be used in almost any metropolitan area. Unlike other experimental systems that leverage ambient radio waves, the Disney system doesn’t focus on a single-signal source, but uses all available ambient radio sources, from FM radio broadcasts to digital TV signals to transmissions to and from cellular phones.
More information on the research, conducted by a team at Disney Research’s Pittsburgh lab, can be found here.