Abstract
LoRaWAN is a widely used protocol for low power Internet of Things devices targeting ubiquitous applications. It is mainly designed for unconfirmed traffic where no acknowledgements need to be sent back to the reporting devices. Nevertheless, there are multiple applications where acknowledgments are required for the nature of the measurements (e.g., healthcare applications). It is commonly known that LoRaWAN does not scale well in the presence of confirmed traffic even when multiple gateways are deployed. Because the gateways are resource constrained devices, the decision making of selecting or not a gateway to send an acknowledgement becomes an important part of the system. This paper examines and proposes a number of downlink policies with the main goal to improve the downlink fairness among the end-devices. Other performance parameters such as the packet delivery ratio and the energy consumption are taken into account as well. Using simulations, we show that considering factors such as the retransmission count and the number of acknowledgements per end-device in the decision making, the downlink fairness increases up to 47% compared to other approaches.