Autonomous Collision-Free Scheduling for LoRa-Based Industrial Internet of Things

LoRa-based transmissions suffer from extensive collisions even for low node numbers due to unregulated access to the medium. In order to tackle this problem, we propose a collision-free time-slotted scheduling approach where each node autonomously decides when to transmit a packet based on its unique identifier which is converted to a slot number using a modulo operation. We report through simulations and real experiments that this approach can provide very high reliability when the nodes are synchronized. Moreover, it does not require any additional communication overhead apart from a broadcast packet emitted by the gateway. Our comparison with the native LoRa, as well as to a slotted-LoRa version, shows significant performance gains in terms of packet delivery ratio, especially in the case of low node populations.