Researchers at the University of California at San Diego (UCSD) have developed a new wake-up receiver for wireless devices which, they claim, could dramatically improve battery life of future Internet of Things (IoT) devices.

The wake-up chip measures just 4.55 square centimetres. (📷: David Baillot)

The UCSD team began researching possible solutions to one of the biggest problems for network-connected IoT devices: the power draw required to keep the radio and microcontroller ticking over. In particular, their focus was on devices which do not always need to be transmitting or receiving data — things like buttons which trigger product orders or personal health monitors which take readings only a few times a day.

"The problem now is that these devices do not know exactly when to synchronise with the network, so they periodically wake up to do this even when there's nothing to communicate. This ends up costing a lot of power," explains Professor Patrick Mercier. "By adding a wake-up receiver, we could improve the battery life of small IoT devices from months to years."

Prof. Mercier's team have what they say is a solution: an ultra-low-power receiver which does nothing more than listen for a wake-up transmission, and in doing so draws a mere 22.3 nanowatts — far less than the main transceiver on the device. Unlike previous attempts at a nanowatt-power wake-up receiver, the team's chip also works at a wide temperature range between -10°C and 40°C (14°F and 104°F) — much wider than previous best efforts, and good enough for indoor use.

The only downside: a lag of around 540 milliseconds between the wake-up signal being received and the device actually waking up.

The chip draws just 22.3 nanowatts of power. (📷: David Baillot)

"These numbers are pretty impressive in the field of wireless communications - power consumption that low, while still retaining temperature-robustness, all in a small, highly sensitive system — this will enable all sorts of new IoT applications," Prof. Mercier notes. "You don't need high-throughput, high-bandwidth communication when sending commands to your smart home or wearables devices, for example, so the trade-off of waiting for a mere half a second to get a 100,000x improvement in power is worth it."

The team's work has been published in the IEEE Journal of Solid-State Circuits.