Exploiting localization systems for LoRaWAN transmission scheduling in industrial applications

The Internet of Things (IoT) paradigm contaminated the industrial world. Wireless communications seem to be particularly attracting, especially when complement indoor and outdoor Real Time Location Systems (RTLS) for geo-referencing smart objects (e.g. for asset tracking). In this paper, the LoRaWAN solution is considered for long range transmission of RTLS data (LoRaWAN is an example of Low Power Wide Area Network). Given that the RTLSs use time synchronization, this work proposes to opportunistically obtain LoRaWAN Class A node time synchronization using the RTLS ranging devices. Once a common sense of time is shared in the LoRaWAN network, more efficient scheduled medium access strategies can be implemented. The experimental testbed, based on commercially available solutions, demonstrates the affordability and feasibility of the proposed approach. When low-cost GPS (outdoor) and UWB (indoor) ranging devices are considered, synchronization error of few microseconds can be easily obtained. The experimental results show the that time reference pulses disciplined by GPS have a maximum jitter of 180 ns and a standard deviation of 40 ns whereas, if time reference pulses disciplined by UWB are considered, the maximum jitter is 3.3 μs and the standard deviation is 0.7 μs.