Reliable Backscatter Video Streaming with Ambient WiFi

Recent research has advanced the transmission rate and quality of video streaming in backscatter communications. However, these studies often overlook the challenge of deploying such systems in environments without dedicated excitation signals. To address this, we propose VideoBack, a high-quality video backscatter system using ambient WiFi signals for easy monitoring. VideoBack employs JPEG compression on high-resolution images to reduce transmission payload, enabling adaptation to the lower rates of WiFi backscatter. We design a customized packet structure for tags to backscatter image data using multiple uncontrolled ambient WiFi packets. To ensure power efficiency, we incorporate envelope detection with energy harvesting. To enable single-receiver deployment, we design a pilot-subcarrier-based recovery method to reconstruct the original WiFi signal. Our system maintains video reliability through a low bit error rate (BER) decoding strategy that includes phase error tracking and self-correction with multi-subcarriers. We prototype VideoBack using a commercial WiFi adapter, achieving a transmission rate of nearly 250 kbps with a BER below 0.05% up to 9 meters. VideoBack can send one frame of an image after just 2 seconds of energy harvesting within 3 meters.