WiFi Backscatter

The future of wearable Health Tech is all about data: collecting it, distributing it, analyzing it, and using it to drive better choices about our personal activities and treatment of health conditions including heart disease, diabetes, and more. One of the big questions is how to get the power to transmit this information to a controller that can package the data and send it on its way for processing. Wired connections are inconvenient (or impractical) but it takes significant power to send data wirelessly using standard systems such as WiFi. Advances in battery technology can help to some extent, and there are all sorts of interesting energy harvesting systems available and under development, but researchers at the University of Washington have come up with an extremely clever solution to the problem that they call “WiFi Backscatter.”

Imagine that you are located between a street light and an observer at night. You could signal the observer by putting something between the light and observer to block the light. By blocking and allowing the light to pass, you could use something like Morse Code to convey information. That’s similar to the idea of the WiFI Backscatter approach. Using special antennas to absorb or reflect WiFi signals from a standard router, a WiFi-enabled device like a computer or smartphone can detect differences in the WiFi signal strength. By alternating between absorbing and reflecting, the antennas can convey information to the receiving device without actually having to broadcast any radio signal.

As a result, a sensor can send data to a WiFi-enabled device using less than 10 microWatts of power, which can be harvested from the passing radio frequency waves or using a small solar cell. The UW research team has already 1 Kbit/second using this technology, and hopes to extend the distance between devices from the current six feet to about 60 feet. This wireless communication system could make gathering data from low-power sensors practical, and transform the possibilities for wearable Health Tech devices.