Passive Wi-Fi is even 1,000 times more energy efficient than Bluetooth

Wi-Fi that uses 10 000 times less power developed

Wi-Fi chips that consume 10,000 times less power than their traditional counterparts could replace Bluetooth as the low-power wireless transmission method of choice, according to a US study.

The new ‘Passive Wi-Fi’ system even consumes 1,000 times less power than existing energy-efficient wireless communication platforms, which includes Bluetooth Low Energy and ZigBee.

Researchers at the University of Washington say Passive Wi-Fi can transmit signals at bit rates of up to 11 megabits per second and is expected to work on all modern devices with wireless connectivity.

Although the speeds are lower than the maximum that current Wi-Fi can achieve, it is still about 11 times higher than Bluetooth.

Aside from saving battery life on today's devices, wireless communication that uses almost no power will help enable an ‘Internet of Things’ reality where household devices and wearable sensors can communicate using Wi-Fi without worrying about power.

"We wanted to see if we could achieve Wi-Fi transmissions using almost no power at all," said co-author of the study Shyam Gollakota, who works at the University of Washington.

"That's basically what Passive Wi-Fi delivers. We can get Wi-Fi for 10,000 times less power than the best thing that's out there."

To achieve such low-power Wi-Fi transmissions, the team decoupled the digital and analogue operations involved in radio transmissions. While the digital side has progressively drawn less power over the years to become extremely energy efficient, the analogue components still consume a lot of power.

The Passive Wi-Fi architecture assigns the analogue, power-intensive functions, like producing a signal at a specific frequency, to a single device in the network that is plugged into the wall.

An array of sensors produces Wi-Fi packets of information using very little power by reflecting and absorbing that signal using a digital switch. In real-world conditions the team found the passive Wi-Fi sensors and a smartphone can communicate even at distances of 30 metres.

"All the networking, heavy-lifting and power-consuming pieces are done by the one plugged-in device," said co-author Vamsi Talla. "The passive devices are only reflecting to generate the Wi-Fi packets, which is a really energy-efficient way to communicate."

Because the sensors are creating actual Wi-Fi packets, they can communicate with any Wi-Fi enabled device right out of the box.

The team believes their system could be used for Internet-of-Things (IoT) devices that typically rely on low power operations to communicate.

In November, the same team demonstrated a router that can wirelessly power electronic devices which could also benefit IoT devices.

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