Building ubiquitous backscatter IoT: From sensors to networks and to applications

Energy efficiency has long been a big concern for large-scale wireless networking and Internet of Things (IoT) deployment. Backscatter communication conveys information through reflecting ambient electromagnetic waves, enabling battery-free communications for sensor nodes. It has been advocated as a key building block for the next generation IoT that involve billions of sensors. Building practical backscatter sensors however faces a series of fundamental challenges. The IoT vision for ubiquitous interconnection, in practice, demands compatibility with such existing wireless technologies as WiFi, connectivity for large-scale and highly dynamic network topologies, and capability of supporting such advanced applications as multimedia sensing and communication. In this thesis, we will describe our works towards building practical ubiquitous backscatter systems from these three dimensions. We start from an innovative WiFi-compatible backscatter design and implementation via spatial multiplexing, which has been the cornerstone for advanced WiFi (802.11n and beyond). Using this higher-throughput and longer-distance solution, we for the first time demonstrated multi-hop backscatter networking, a fire-new architecture with backscatter sensors relaying for each other to achieve not only robustness but also scalable topology. Driven by advanced acoustic sensing applications, we further demonstrate a microphone array backscatter sensor to explore super lightweight multi-track multimedia streaming, potentially to empower ubiquitous self-sustainable 360-degree audio/video and immersive applications. We will also discuss important future directions in this field, such as using these designs in micro-robots, and connecting this IoT frontend to the AI-based data hub.