MRT-LoRa: A multi-hop real-time communication protocol for industrial IoT applications over LoRa networks

Recent literature proposed MAC protocols running on top of LoRa that are able to offer real-time communications for Industrial Internet of Things (IIoT) applications. However, such solutions work over single-hop star topologies and therefore, to reach a wide coverage through a single hop, they require to configure the LoRa radio parameters in a way that reduces the maximum supported bit rate, thus increasing the message time on air. Consequently, to comply with the maximum duty cycle constraints imposed on LoRa devices by the current regulations, the maximum number of messages that can be sent per hour is also reduced. However, industrial environments typically cover very large areas and require bit rate values in the order of a few thousands of bits per second for LoRa-based networks. To cope with both coverage and bit rate requirements of IIoT, a multi-hop protocol able to provide bounded delays to the real-time flows typical of industrial applications is a better solution than a single-hop approach. For this reason, this paper proposes MRT-LoRa, a multi-hop communication protocol running on top of LoRa that provides support for real-time flows. The MRT-LoRa protocol enables long-range communications while maintaining shorter time on air at each hop, thus lowering the impact on the duty cycle of each node. The paper describes the MRT-LoRa design and configuration, and discusses the performance obtained through OMNeT++ simulations in realistic industrial IoT scenarios.