Adapting LoRaWAN Relay Specification for Battery-Sustainable Subterranean LoRa Mesh Networks
Traditional IoT technologies such as LoRaWAN, Sigfox, and NB-IoT rely on single-hop star topologies, requiring many gateways to cover large areas. In subterranean environments where cellular coverage and grid power may be unavailable, such deployments are often impractical. This paper presents a novel LoRa mesh network designed for such environments, capable of operating for years on battery power. While the recent LoRaWAN relay specification supports two-hop communication via an intermediate relay between an end device and a gateway, our work is the first to extend this specification for on-demand multi-hop communication across multiple LoRa repeaters, adapting its sleep mechanism. Our proposed sleep mechanism combines an on-demand cascaded repeater wakeup process with a repeater synchronization strategy, minimizing the power consumption. Moreover, our network architecture integrates existing packet routing and collision recovery mechanisms and is highly scalable and general-purpose, enabling a wide range of applications. Network simulations demonstrate that the proposed design operates reliably, sustaining years on battery power, while the repeater synchronization strategy further reduces average energy consumption by up to 50%. [Code: https://bit.ly/4nALuNX]