University of Washington engineers have designed a clever new communication system called Wi-Fi backscatter that uses ambient radio frequency signals as a power source for battery-free devices (such as temperature sensors or wearable technology) and also reuses the existing Wi-Fi infrastructure to provide Internet connectivity for these devices.
“If Internet of Things devices are going to take off, we must provide connectivity to the potentially billions of battery-free devices that will be embedded in everyday objects,” said Shyam Gollakota, a UW assistant professor of computer science and engineering.
“We now have the ability to enable Wi-Fi connectivity for devices while consuming orders of magnitude less power than what Wi-Fi typically requires.”
To supply power to the devices, the system uses an “ambient backscatter” scheme previously developed by the UW group, which allows two devices to communicate with each other by harvesting ambient radio, TV, and cellular transmissions, as KurzweilAI described last year.
So the new research takes that a step further by also connecting each individual device to the Internet. But but even low-power Wi-Fi consumes 1000 to 10,000 times more power than can be harvested in these wireless signals. Instead, the new system uses an ultra-low-power “tag” with an antenna and circuitry that can talk to Wi-Fi-enabled laptops or smartphones while consuming negligible power (less than 10 microwatts).
These tags work by essentially “looking” for Wi-Fi signals moving between the router and a laptop or smartphone. The tags encode data in real time by either reflecting or not reflecting the Wi-Fi router’s signals, thus slightly changing the wireless signal. Wi-Fi-enabled devices like laptops and smartphones would detect these minute changes (by analyzing changes in reflected signals) and receive data from the tag.
So far, the UW’s Wi-Fi backscatter tag has communicated with a Wi-Fi device at rates of 1 kilobit per second with about 2 meters between the devices. The researchers plan to extend the range to about 20 meters and have files patents on the technology.
The “Internet of Things” would extend connectivity to perhaps billions of devices. Battery-free sensors could be embedded in everyday objects to help monitor and track everything from the structural safety of bridges to the health of your heart. For example, your smart watch could upload your workout data onto a Google spreadsheet.
Or sensors embedded around your home could track minute-by-minute temperature changes and send that information to your thermostat to help conserve energy.
The researchers will publish their results at the Association for Computing Machinery’s Special Interest Group on Data Communication‘s annual conference this month in Chicago. The team also plans to start a company based on the technology.