  The boom of the Internet of Things has revolutionized people's lives, but it
has also resulted in massive resource consumption and environmental pollution.
Recently, Green IoT (GIoT) has become a worldwide consensus to address this
issue. In this paper, we propose EEWScatter, an energy-efficient WiFi
backscatter communication system to pursue the goal of GIoT. Unlike previous
backscatter systems that solely focus on tags, our approach offers a
comprehensive system-wide view on energy conservation. Specifically, we reuse
ambient signals as carriers and utilize an ultra-low-power and battery-free
design for tag nodes by backscatter. Further, we design a new CRC-based
algorithm that enables the demodulation of both ambient and tag data by only a
single receiver while using ambient carriers. Such a design eliminates system
reliance on redundant transceivers with high power consumption. Results
demonstrate that EEWScatter achieves the lowest overall system power
consumption and saves at least half of the energy. What's more, the power
consumption of our tag is only 1/1000 of that of active radio. We believe that
EEWScatter is a critical step towards a sustainable future.
