LoRa is popular in the Internet of Things (IoT) domain as a Low Power,Wide Area Network (LPWAN) radio technology, providing low-power and long-range communication in the sub-GHz band. Most often, LoRa is used as part of the LoRaWAN architecture with a star-of-stars topology, but it can also be operated standalone. This paper presents and evaluates a minimalistic Routing Protocol (RP) for building LoRa networks with a more flexible mesh network topology. We propose a Time on Air (ToA) metric that, when used in heterogeneous network topologies, can take better advantage of LoRa’s multiple Spreading Factors (SFs), and their trade-off between transmission distance and bit rate, and their quasi-orthogonality property. We evaluate the routing protocol with the FLoRa framework and OMNeT++ and compare it with other common routing strategies. Our experiments provide a comprehensive understanding of the routing protocol performance concerning the scalability, throughput, and latency in several topology and network traffic scenarios. When using the ToA metric, we observed in LoRa mesh networks formed by random topologies and heterogeneous links the positive impact of a more balanced Packet Delivery Ratio (PDR) among the nodes with different network centrality, suggesting hence the multi-SF ToA metric to be used for improved PDR in conditions that are expected to occur in real-world systems. Regarding goodput, we observed that using multiple SF simultaneously had a limited impact on low to high traffic loads but dramatically improved throughput and goodput in traffic saturation scenarios. This suggests that multi-SF operation would be preferred to maximize network performance.We observed the best latency performance with multi-SF ToA for low and medium traffic loads, especially for the random topology, where the metric can again take advantage of the node and link heterogeneity.

This work was supported in part by Spanish State Research Agency under Grant PDC2023-145809-I00/AEI/10.13039/501100011033, in part by the Recovery and Resilience Mechanism of European Union, and in part by European Union-NextGenerationEU.

Peer Reviewed