Digital technology has made us more dependent on our electronic devices, and it has made us hungrier 
for power.


Recognizing the need for a more energy-efficient way to connect with our devices, researchers at the University of Washington (UW) have developed something they call “passive Wi-Fi.” In February, university computer scientists and engineers announced they had generated transmissions using 10,000 times less power than conventional methods.


The passive Wi-Fi system also consumes 1,000 times less power than existing energy-efficient wireless communication platforms, such as Bluetooth low energy and Zigbee.


“We wanted to see if we could achieve Wi-Fi transmissions using almost no power at all,” said Shyam Gollakota, co-author and UW assistant professor of computer science and engineering.


Passive Wi-Fi can transmit wireless signals at bit rates of up to 11 megabits per second. These speeds are lower than the maximum Wi-Fi speeds but 11 times higher than Bluetooth. To achieve such low-power Wi-Fi transmissions, the team decoupled the digital and analog operations involved in radio transmissions.


The architecture assigns the power-intensive, analog functions to a single device that is plugged into the wall. A sensor array produces Wi-Fi packets of information using very little power by simply reflecting and absorbing that signal with a digital switch.


Because the sensors are creating actual Wi-Fi packets, they can communicate with any device that has Wi-Fi connectivity.


Aside from saving battery life, passive Wi-Fi could also help enable the Internet of Things, where household devices and wearable sensors communicate with very little power usage. The technology could enable entirely new types of communication that have not been possible because energy demands have outstripped available power supplies.