  Long Range (LoRa) is a modem technology for wireless communication in the
Internet of Things (IoT), which trades off low data-rate for low power
consumption. Long Range Wide Area Network (LoRaWAN) has an open specification
that determines the Medium Access Control (MAC) protocol for LoRa networks.
This paper contributes a simulation module in Network Simulator 3 (ns-3) to
evaluate the limitation of LoRaWAN in various metrics. The result shows the
performance of LoRaWAN in a simulation environment and a large scale scenario,
indicating the feature of flexible propagation range on physical layer, and
limited channel capacity on the data-link layer. The feasibility of optimized
multi-hop in LoRaWAN is analyzed. Based on the simulation result, a multi-hop
mechanism driven by spreading factor is proposed, not only to extend the
network coverage but to reduce the channel load. The novel approach takes
benefit of the dynamic feature of LoRa and estimates optimized forwarding hops
with parameter configuration. The result shows that Time on Air can be
significantly decreased.
