Demonstrating Passive WiFi.
Separating Analog from Digital
The system achieves its low-power transmissions by separating the analog and digital functions needed for wireless communication. Analog operations, such as frequency synthesis and power amplification, consume the majority of power in Wi-Fi systems. Digital operations, such as coding and modulation, are much more power efficient. Decoupling the two is the key to low power utilization.
This separation is achieved through two stages. The first stage involves placing the power-intensive analog components in a single device that remains plugged into a wall outlet. In the second stage, digital sensors use reflections from the first stage to generate Wi-Fi packets, consuming very little energy themselves.
“We wanted to see if we could achieve Wi-Fi transmissions using almost no power at all,” said UW assistant professor of computer science and engineering, Shyam Gollakota.
A World of Communication
The new Wi-Fi system not only outperforms current Wi-Fi, it also uses 10,000 times less power than current energy-efficient wireless platforms such as Bluetooth. This means Wi-Fi could for the first time be a viable contender in smart home applications utilizing interconnected sensors, such as smart thermostats or lighting systems. Currently, these systems typically use their own communication platforms instead of Wi-Fi, in order to save power.
With low cost and low power Wi-Fi sensors, almost any physical household device can theoretically be connected to a network, a system becoming known as the Internet of Things.
Joshua Smith, an associate professor at the University of Washington involved in the research, believes the sky is the limit. “Now that we can achieve Wi-Fi for tens of microwatts of power and can do much better than both Bluetooth and ZigBee, you could now imagine using Wi-Fi for everything.”
A paper detailing the research was presented at the 13th USENIX Symposium on Networked Systems Design and Implementation.
To learn more about this technology, visit the project site at the University of Washington .