Long-Range Time-Synchronisation Methods in LoRaWAN-based IoT

LoRa (Long-Range) is an LPWAN (low-power wide-area network) protocol that is part of the IoT family that focusses on long-range communication of up to 14km, albeit with delay-inherent transmissions. Three IoT-based time synchronisation methodologies are analysed, and their efficacy measured through a systematic critical literature review. These include a GNSS-based method, an off-the-shelf GPS hardware resampling method, and the LongShoT method, within the context of vehicular ad-hoc networks (VANET), wireless sensor networks (WSN), and long-range wide area network (LoRaWAN) respectively. Although two of the three methods are not LoRaWAN-specific, the findings obtained from the research are applied to the context of LoRa in the proposed methodology. A methodology for selecting a time synchronisation methodology with regards to LoRa specifically is posited, whereby each requirement of synchronisation objective, energy consumption and costs, scenario and security analysis, application requirements, microcontroller requirements and transceiver requirements are taken into consideration. These are then followed by a fine-grain approach to the selection of a particular time-sync method. The resultant methodology may not only have implications in the field of research, where practitioners may adopt this literature review as a baseline understanding of time synchronisation methods and obstacles encountered toward LoRa, however developers of applications for the LoRaWAN may adapt the analysed methods outlined within.