I am proposing an IoT adoption model for Higher Education Institutes as my Master's research work. I need to simulate the model proposed and validate it.
Well, one of the simulation tools I can recommend is OMNet++ (https://omnetpp.org/download/).
Chapter Internet of Things Simulation Using OMNeT++ and Hardware in the Loop
Mind you in fairness, you would explicitly need to model everything for your use case (Hubs, Switches, RE motes etc.). Also, if you only want to model the RE motes and simulate the motes individually, you can use Contiki NG (https://github.com/contiki-ng/contiki-ng). I hope this answers your query.