Reliable Communication using LoRaWAN for Industrial IoT devices

Abstract

The Internet of Things (IoT) area is growing by the minute, with more and more devices being connected to the internet. Long Range Wide Area Network (LoRaWAN) is one technology that makes this possible. It is made to deliver long-range coverage while at the same time using low power. However, with the increasing demand for low latency requirements on connected devices, the same requirements must be fulfilled for the network technology. In particular, the Industrial Internet of Things (IIoT) devices requires the network link to be of low latency and high reliability. This thesis aims to evaluate LoRaWAN in terms of reliability. This evaluation will be done by comparing the default reliability method against an alternative method. In order to evaluate reliability, latency, Packet Delivery Rate (PDR) and Packet Acknowledgment Rate (PAR) are important metrics to see how reliable the communication is. Furthermore, having concrete values on these metrics will help companies determine whether LoRaWAN is suitable for IIoT devices. The proposed alternative reliability method is one found in the literature. It alters the uplink and downlink windows of LoRaWAN by introducing a redundant retransmission scheme. This scheme utilizes the Time-on-Air (ToA) of the previous transmission for retransmissions instead of a static value LoRaWAN uses in the default protocol. It further adds a redundant retransmission step if the previous one failed. This thesis shows that the alternative reliability method provides a significant reduction in latency by 69%, an increase in PDR by 1.1% but at the cost of a slightly lower PAR by 3%. Lower PAR is an indication of more network traffic and power usage. This thesis concludes that there are pros and cons to both methods. The default method is better suited for dense networks with fewer requirements on latency and higher requirements on battery power. In contrast, the alternative method is better suited for less dense networks and higher latency requirements. These trade-offs are ones the manufacturers need to consider when analyzing whether or not LoRaWAN is suitable, that is, both in terms of the manufacturers’ environment requirements but also the IIoT device requirements.