Reliable Battery-free Backscatter Video Transmission for Ubiquitous Vision-based Sensing

Past decades have witnessed the rapid development of battery-free backscatter-based cameras, opening up promising long-term and sustainable surveillance applications by harvesting wireless energy. However, limited by the fluctuations of the ambient energy, existing backscatter systems suffer from unreliability issues, e.g., stalls and frame losses in video transmission. To tackle this problem, we propose EATag, the first energy-aware backscatter system that can provide reliable battery-free video frame transmission through adaptation. EATag provides hardware and software co-designs to achieve energy budgeting, prediction, capacity estimation, and adaptation for reliable video transmission. By leveraging the reader to monitor the operation duty cycles and estimate the channel fluctuation, the tag only needs to consume a little energy to achieve efficient adaptation. We implement the EATag system with off-the-shelf components. We conduct extensive experiments to evaluate the performance of EATag. Results demonstrate that EATag can achieve a stalling rate reduction of 57.3%-89.2% when compared to the existing battery-free video systems. We also present an IC schematic design of the tag with TSMC 90 nm standard cells. Circuit simulation results show that it can potentially consume only 58  μ W to provide reliable battery-free video transmission.