A set of ultra-low power Wi-Fi radios integrated in small chips, each measuring 1.5 square millimeters in area (grain of rice shown for scale). (Credit: David Baillot/UC San Diego Jacobs School of Engineering)

More portable, fully wireless smart home setups; lower power wearables; batteryless smart devices, could all be made possible with this new ultra-low power Wi-Fi radio. It is housed in a chip smaller than a grain of rice, which was developed by electrical engineers at the University of California San Diego.

The device enables Internet of Things (IoT) devices to communicate with existing Wi-Fi networks using 5000 times less power than today’s Wi-Fi radios — just 28 microwatts. And it does so while transmitting data at a rate of 2 megabits per second, a connection fast enough to stream music and most YouTube videos.

“You can connect your phone, your smart devices, even small cameras or various sensors to this chip, and it can directly send data from these devices to a Wi-Fi access point near you. You don’t need to buy anything else. And it could last for years on a single coin cell battery,” said Dinesh Bharadia, a professor of electrical and computer engineering at the UC San Diego Jacobs School of Engineering.

Commercial Wi-Fi radios typically consume hundreds of milliwatts to connect IoT devices with Wi-Fi transceivers. As a result, Wi-Fi compatible devices need either large batteries, frequent recharging or external power sources to run.

This Wi-Fi radio runs on low enough power that we can now start thinking about new application spaces where you no longer need to plug IoT devices into the wall. This could unleash smaller, fully wireless IoT setups. For example, a portable Google Home device that you can take around the house and can last for years instead of just hours when unplugged.

The Wi-Fi radio runs on extremely low power by transmitting data via a technique called backscattering. It takes incoming Wi-Fi signals from a nearby device (like a smartphone) or a Wi-Fi access point, modifies the signals and encodes its own data onto them, and then reflects the new signals onto a different Wi-Fi channel to another device or access point.

The researchers accomplished this by building in a component called a wake-up receiver. This “wakes up” the Wi-Fi radio only when it needs to communicate with Wi-Fi signals, so it can stay in low-power sleep mode the rest of the time, during which it consumes only 3 microwatts. It also features a custom integrated circuit for backscattering data, which makes the whole system smaller and more efficient, and thus enables the Wi-Fi radio to operate over a communication range of up to 21 meters. This is a practical distance for operating in a smart home environment, the researchers said.