Low-Power Wide-Area Network Over White Spaces

As a key technology driving the Internet-of-Things, low-power wide-area networks (LPWANs) are evolving to overcome the range limits and scalability challenges in traditional wireless sensor networks. This paper proposes a new LPWAN architecture called sensor network over white spaces (SNOW) by exploiting the TV white spaces. The SNOW is the first highly scalable LPWAN over TV white spaces that enable asynchronous, bi-directional, and massively concurrent communication between numerous sensors and a base station. This is achieved through a set of novel techniques. The SNOW has a new OFDM-based physical layer that allows the base station using a single antenna-radio: 1) to send different data to different nodes concurrently and 2) to receive concurrent transmissions made by the sensor nodes asynchronously. It has a lightweight media access control protocol that: 1) efficiently implements per-transmission acknowledgments of the asynchronous transmissions by exploiting the adopted OFDM design and 2) combines CSMA/CA and location-aware spectrum allocation for mitigating hidden terminal effects, thus enhancing the flexibility of the nodes in transmitting asynchronously. We implement the SNOW in GNU radio using universal software radio peripheral devices. Experiments through deployments in three radio environments—a large metropolitan city, a rural area, and an indoor environment—as well as large-scale simulations demonstrated that the SNOW drastically enhances the scalability of a sensor network and outperforms existing techniques in terms of scalability, energy, and latency.