A Novel Time-Slotted LoRa MAC Protocol for Scalable IoT Networks

Long Range (LoRa) networks provide long range, cost-effective and energy-efficient communications by utilising the free unlicensed ISM band, which makes them appealing for Internet of Things (IoT) applications. However, in high density networks, reliable performance might be hard to achieve due to the nodes’ random-access method. Furthermore, the duty cycle restrictions that are imposed on nodes and gateways transmissions can limit the scalability of the network. More importantly, the duty cycle restrictions that are imposed on the downlink communication from the server to nodes can impose further challenges. Consequently, the server in high density networks might not be able to communicate with all network nodes due to its limited duty cycle. Besides, the server might not be able to send individual controlling packets from server to nodes. One way to mitigate such a limit is to allow nodes autonomously determine their transmission parameters without the need for any downlink transmission from the server. Thus, this paper presents the Sector-Based Time Slotted SBTS-LoRa MAC protocol that allows nodes to determine their transmission parameters autonomously based on their location to the gateway. SBTS-LoRa is targeting large scale networks. Simulation results show that our proposed protocol significantly enhances the scalability and outperforms its counterparts by maximizing throughput without compromising the energy efficiency. Specifically, the average throughput for dense networks was enhanced 14 times compared to the Adaptive Data Rate ADRLoRaWAN