LoRa Synchronized Energy-Efficient LPWAN

This work addresses the need for low-power wide-area networks (LPWANs) that remain energy efficient even when scaled to cover large geographic areas without power delivery infrastructure. LoRaWAN is a widely used LPWAN that requires a star (or star-of-stars) topology in which only leaf nodes are energy efficient enough to be powered by compact and inexpensive batteries. We describe the design of LoRa Synchronized Energy-Efficient LPWAN (SEEL), a novel protocol for multi-hop LoRa networks that allows battery-powered nodes to forward messages to difficult-to-access locations. SEEL performs link-quality-aware, dynamic formation of a tree topology network enabling nodes to deliver their packets to a central gateway while minimizing node energy consumption. We evaluate SEEL via a month-long deployment in an outdoor, real-world environment covering 9.0 km
²
and analyze its delivery rates and energy efficiency; we find SEEL nodes, on average, function 6.6× as long as always-on nodes would in the same deployment setting. We conduct a follow-up deployment of SEEL to compare its dynamic network formation protocol with a static network formation protocol; the SEEL network drops 16% fewer node-to-node packets than would a static topology network, even in near-ideal circumstances for a static topology network.