Housed in a chip smaller than a grain of rice, a new ultra-low-power WiFi radio enables Internet of Things (IoT) devices to communicate with existing WiFi networks using 5,000 times less power than today’s WiFi radios. It consumes just 28 microwatts of power and does so while transmitting data at a rate of 2 megabits per second (a connection fast enough to stream music and most YouTube videos) over a range of up to 21 meters.

Phones, smart devices, and small cameras or various sensors can be connected to the chip, which directly sends data from these devices to a WiFi access point. The radio could last for years on a single coin cell battery. Commercial WiFi radios typically consume hundreds of milliwatts to connect IoT devices with Wi-Fi transceivers. As a result, WiFi-compatible devices need large batteries, frequent recharging, or other external power sources to run.

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

The PCB onto which the WiFi radio is mounted (component underneath the black blob). (Photo: David Baillot/UC San Diego Jacobs School of Engineering)

This work builds on low-power WiFi radio technology that builds in a component called a wake-up receiver. This “wakes up” the WiFi radio only when it needs to communicate with WiFi signals, so it can stay in low-power sleep mode the rest of the time, during which it consumes only 3 microwatts of power.

The new radio also features a custom integrated circuit for backscattering data, which makes the whole system smaller and more efficient and enables the WiFi radio to operate over a longer communication range (21 meters).

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