Now, power-free Wi-Fi connectivity near you

How about a world where you do not require power to access your smartphone or tablet or even an eye-wearable device like Google Glass?

Led by an Indian-origin engineer, a team at University of Washington has designed a unique communication system that uses radio frequency signals as a power source and reuses existing Wi-Fi infrastructure to provide internet connectivity to these devices.

Called Wi-Fi backscatter, this technology is the first that can connect battery-free devices to Wi-Fi infrastructure.

"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, an assistant professor of computer science and engineering at University of Washington.

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, he added.

This work builds upon previous research that showed how low-powered devices such as temperature sensors or wearable technology could run without batteries or cords by harnessing energy from existing radio, TV and wireless signals in the air.

This work takes a step further by connecting each individual device to the internet, which previously was not possible.

The researchers developed an ultra-low power tag prototype with an antenna and circuitry that can talk to Wi-Fi-enabled laptops or smartphones while consuming negligible power.

These tags work by essentially "looking" for Wi-Fi signals moving between the router and a laptop or smartphone.

They encode data by either reflecting or not reflecting the Wi-Fi router's signals, slightly changing the wireless signal.

"Wi-Fi-enabled devices like laptops and smartphones would detect these minute changes and receive data from the tag," Gollakota said.

In this way, your "smart" watch could download e-mails or offload your workout data onto a Google spreadsheet.

The Wi-Fi backscatter tag has communicated with a Wi-Fi device at rates of 1 kilobit per second with about two metres between the devices.

They plan to extend the range to about 20 metres and have patents filed on the technology.

The researchers will publish results at the Association for Computing Machinery's Special Interest Group on Data Communication's annual conference this month in Chicago.