The paper introduces a LoRaWAN simulation model implemented for the Riverbed Modeler (former OPNET modeler suite). First, the key components of the developed simulator solution are detailed. Then, the results of the simulator’s validation for several test scenarios are presented. The developed simulator is used to investigate the effect of collision models on the results of LoRaWAN performance simulation. Specifically, the three models are studied: a baseline — implying loss off all colliding packets, an intra spreading factor (SF) with capture effect, and intra/inter SF with capture effect. The simulations verify that the results of the baseline model are in line with that for pure Aloha, while the two other demonstrate up to two-three fold higher delivery ratio. The obtained results illustrate the substantial impact of the collision model on the accuracy of simulations and motivate the need for further practical studies for the collision and interference mechanisms within a LoRaWAN network. Based on the results obtained through simulations, several drawbacks related to the use of strictly periodic traffic in LoRaWAN networks are noted.